EPA/600/R-11/088 | August 2011 | www.epa.gov /nrmrl
United States
Environmental Protection
Agency
Principles of Design and Operations
of Wastewater Treatment Pond Systems
for Plant Operators, Engineers, and Managers
Office of Research and Development
National Risk Management Research Laboratory - Land Remediation and Pollution Control Division
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Principles of Design and Operations of Wastewater
Treatment Pond Systems for Plant Operators, Engineers,
and Managers
Land Remediation and Pollution Control Division
National Risk Management Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio
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Notice
This document has been reviewed in accordance with U.S. Environmental Protection Agency
policy and approved for publication. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
11
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Foreword
The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the
Nation's land, air, and water resources. Under a mandate of national environmental laws, the
Agency strives to formulate and implement actions leading to a compatible balance between
human activities and the ability of natural systems to support and nurture life. To meet this
mandate, EPA's research program is providing data and technical support for solving
environmental problems today and building a science knowledge base necessary to manage our
ecological resources wisely, understand how pollutants affect our health, and prevent or reduce
environmental risks in the future.
The National Risk Management Research Laboratory (NRMRL) is the Agency's center for
investigation of technological and management approaches for preventing and reducing risks
from pollution that threaten human health and the environment. The focus of the Laboratory's
research program is on methods and their cost-effectiveness for prevention and control of
pollution to air, land, water, and subsurface resources; protection of water quality in public water
systems; remediation of contaminated sites, sediments and ground water; prevention and control
of indoor air pollution; and restoration of ecosystems. NRMRL collaborates with both public
and private sector partners to foster technologies that reduce the cost of compliance and to
anticipate emerging problems. NRMRL's research provides solutions to environmental
scientific and engineering information to support regulatory and policy decisions; and providing
the technical support and information transfer to ensure implementation of environmental
regulations and strategies at the national, state, and community levels.
This publication has been produced as part of the Laboratory's strategic long-term research plan.
It is published and made available by EPA's Office of Research and Development to assist the
user community and to link researches with their clients.
Sally Gutierrez, Director
National Risk Management Research Laboratory
in
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Abstract
Principles of Design and Operations of
Wastewater Treatment Pond Systems for Plant Operators, Engineers, and Managers
Wastewater pond systems provide reliable, low cost, and relatively low maintenance treatment
for municipal and industrial discharges. However, they do have certain design, operations, and
maintenance requirements. While the basic models have not changed in the 30-odd years since
EPA published the last ponds manual, there have been some innovations and improved
understanding of the complex biological processes at work in these systems. Additionally, new
water quality requirements are either in place or about to be put in place throughout the United
States, particularly relating to nutrient concentrations, that were not factored into the design
specifications when many of the existing ponds were constructed. This updated version of the
wastewater treatment ponds manual includes basic design recommendations, discusses the
innovations in design that have been made in new, expanded or modified systems, as well as the
additional processes that have been added to address nutrient requirements. An emphasis is
placed on the importance of operations and maintenance, which is demonstrated in the
troubleshooting section and appendices from several states, directed at providing training for
operators.
IV
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Contents
Notice ii
Foreword iii
Abstract iv
Contents v
Figures List viii
Tables List xii
Conversion Factors, Physical Properties of Water, and DO Solubility xiv
Glossary xviii
Acknowledgments xxii
Preface xxv
Chapter 1 Introduction 1-1
1.1 Background 1-1
1.2 Pond Nomenclature 1-3
1.3 Elements of Pond Processes 1-5
Chapter 2 Planning, Feasibility Assessment and Site Selection 2-1
2.1 Introduction 2-1
2.2 Concept Evaluation 2-1
2.3 Resources Required 2-1
2.4 Site Identification 2.2
2.5 Site Evaluation 2-3
2.6 Site and Process Selection 2-5
2.7 Design Criteria of Municipal Wastewater Treatment Ponds 2-6
2.8 State Design Standards 2-6
Chapter 3 Design of Municipal Wastewater Treatment Ponds 3-1
3.1 Introduction 3-1
3.2 Anaerobic Ponds 3-1
3.3 Facultative Ponds 3-7
3.4 Aerated Pond Systems 3-11
Chapter 4 Physical Design and Construction 4-1
4.1 Introduction 4-1
4.2 Dike Construction 4-1
4.3 Pond Sealing 4-3
4.4 Pond Hydraulics 4-14
4.5 Pond Recirculation and Configuration 4-16
Chapter 5 Advances in Pond Design 5-1
5.1 Introduction 5-1
5.2 Advanced Integrated Wastewater Pond Systems® (AIWPS®) 5-1
5.3 Systems with Deep Sludge Cells 5-20
5.4 High-Performance Aerated Pond System (RICH DESIGN) 5-33
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5.5 Biolac Process (Activated Sludge in Earthen Ponds) 5-39
5.6 Lemna Systems 5-53
5.7 LAS International, Ltd., Accel-o-Fac® and Aero-Fac® Systems 5-64
5.8 Oxygen Addition Systems 5-65
Chapter 6 Nutrient Removal 6-1
6.1 Introduction 6-1
6.2 Facultative Ponds 6-1
6.3 Aerobic Ponds 6-9
6.4 Commercial Products 6-19
6.5 Removal of Phosphorus 6-27
Chapter 7 Upgrading Pond Effluents 7-1
7.1 Introduction 7-1
7.2 Solids Removal Methods 7-1
7.3 Operations Modifications and Additions 7-28
7.4 Control of Algae and Design of Settling Basins 7-30
7.5 Comparison of Various Design Procedures 7-34
7.6 Operational Modifications to Facultative Ponds 7-34
7.7 Combined Systems 7-37
7.8 Performance Comparisons with Other Removal Methods 7-37
Chapter 8 Cost and Energy Requirements 8-1
8.1 Introduction 8-1
8.2 Capital Cost 8-1
8.3 Updating Costs 8-4
8.4 Cost Data for Upgrading Methods 8-4
8.5 Energy Requirements 8-11
Chapter 9 Operation and Maintenance 9-1
9.1 Introduction 9-1
9.2 Terminology 9-1
9.3 Control Testing Information 9-2
9.4 Operation and Maintenance for Ponds 9-11
9.5 Safety around Ponds 9-20
9.6 Troubleshooting 9-22
Appendices
A State Design Criteria for Wastewater Ponds A-l
B Summary of Pond Characteristics B-l
C Design Examples C-l
D Case Studies D-1
vi
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E Troubleshooting E-l
F Study Guides for Pond Operators F-l
F-l Introduction F-2
F-2 Advanced F-29
G Discharge Guidance G-l
H Guidance for Deploying Barley Straw H-l
References R-l
vn
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Figures
Number Page
1-1 The Nitrogen Cycle in Wastewater Pond System 1-9
1 -2 Relationship between pH and Alkalinity 1-11
1-3 Changes Occurring in Forms of Nitrogen Present in a Pond Environment under 1-14
Aerobic Conditions
3-1 Method of Creating a Digestion Chamber in the Bottom of an Anaerobic Pond 3-7
3-2A Static Tube, Brush and Aspirating Aerators 3-15
3-2B Floating Pump, Pier-Mounted Impeller with Draft Tube and Pier-Mounted 3-16
Impeller
3-3 Floating Aerators in Summer and Winter Operation 3-16
4-1 An Example of Eroded Dike Slopes 4-2
4-2 Evidence of Burrowing at the Edge of a Treatment Pond 4-3
4-3 Common Pond Configurations and Recirculati on Systems 4-16
4-4 Cross-Sectional View of a Typical Recirculati on Pumping Station 4-19
5-1 AIWPS Facilities over Time Showing the Design Trend of Increasing Primary 5-2
Pond Depth in Meters and Decreasing Footprint Area per Treatment Capacity in
Hectares Per Million Liters Per Day (MLD) of Capacity
5-2 Type 1 Advanced Integrated Wastewater Pond System® 5-3
5-3 Schematic Cross-Section of Primary Facultative Pond of an Advanced Integrated 5-4
Wastewater Pond System®
5-4 Schematic of Raceway to Cultivate Microalgae for C>2 Production 5-5
5-5 Plan View of St. Helena, CA, AIWPS 5-10
5-6 St. Helena, CA Biochemical Oxygen Demand 5-11
5-7 St Helena, CA Total Suspended Solids 5-11
5-8 Performance of AIWPS® Type 1: Annual Means at St. Helena, CA 5-12
5-9A Configuration of the St. Helena AIWPS® 5-13
5-9B Configuration of Pond IB (as of 1994) 5-14
5-10 A. Delhi, CA AIWPS®; B. Hilmar, CA AIWPS™ 5-15
5-11 Delhi AIWPS® BOD/TSS Study, 1 A) August 2009, IB) January 2010 5-16
5-12 Delhi AIWPS® Coliform Study, A. Summer, B. Winter 5-17
5-13 Bolinas AWIPS® 5-19
5-14 Bolinas AIWPS®BOD5 through the System, 2010 5-20
5-15 Cross-Sectional View of the Facultative Cell at the Dove Creek, CO WWTP 5-21
5-16 Plan View of Dove Creek, CO Fermentation Pit 5-22
5-17 Flow Rate Performance Data for Dove Creek, CO January 31, 2000 to October 5-24
31,2006
5-18 BOD5 Performance data for Dove Creek, CO January 31, 2000 to October 31, 5-25
2006
5-19 TSS Performance Data for Dove Creek, CO January 31, 2000 to October 31, 5-25
2006
5-20 Fecal Coliform Performance Data for Dove Creek, CO January 31, 2000 to 5-26
October 31,2006
5-21 Fisherman Bay, Washington. Anaerobic cell with Recirculation Manifold Using 5-29
an Aerated Cap of Polishing Cell Effluent to Provide Odor Control
viii
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5-22 Fisherman Bay. Flow Rate Data for October 28, 2003 through August 29, 2006 5-30
5-23 Fisherman Bay. BOD5 Performance Data for October 28, 2003 through August 5-30
29, 2006
5-24 Fisher Bay. NH3 Performance Data for October 28, 2003 through August 29, 5-31
2006
5-25 Fisherman Bay. TSS Performance Data for October 28, 2003 through August 5-32
29, 2006
5-26 Fisherman Bay. Fecal Coliform and pH Performance Data for October 28, 2003 5-33
through August 29, 2006
5-27 Flow Diagrams of DPMC Aerated Pond System. A) Two Basins in Series 5-34
Utilizing Floating Baffles in Settling Cells. B) A Single Basin Using Floating
Baffles to Divide Various Unit Processes.
5-28 Performance of DPMC Aerated Pond System in Berkley County, SC, with 5-35
Aerators Operating Continuously
5-29 Effluent TSS and BOD5 from a DPMC Aerated Pond System, Aerators 5-35
Operating Intermittently
5-30 Monthly Average BOD5 and TSS from Ocean Drive, North Myrtle Beach 5-36
5-31 Sketch of a DPMC Aerated Pond-Intermittent Sand Filter System at North 5-37
Myrtle Beach, SC
5-32 Monthly Average Effluent BOD5 and TSS at Crescent Beach, North Myrtle 5-37
Beach
5-33 Flow Diagram of BIOLAC® -R System 5-40
5-34 Wave-Oxidation Modification of the BIOLAC®-R System 5-41
5-35 Detail of the BIOLAC® Aeration Chain Element 5-43
5-36 Cross-Section View of the Integral BIOLAC® -R Clarifier 5-45
5-37 Flow Rate for Alamosa BIOLAC® Facility 5-48
5-38 BOD5 for Alamosa BIOLAC® Facility 5-48
5-39 TSS for Alamosa BIOLAC® Facility 5-49
5-40 NH3 for Alamosa BIOLAC® Facility 5-49
5-41 DO, pH and Fecal Coliform for Alamosa BIOLAC® Facility 5-50
5-42 Flow Rate for Tri-Lakes, Colorado BIOLAC® Facility 5-51
5-43 BOD5 for Tri-Lakes BIOLAC® Facility 5-51
5-44 TSS for Tri-Lakes BIOLAC® Facility 5-52
5-45 NH3 and Inorganic TV for Tri-Lakes BIOLAC® Facility 5-52
5-46 Fecal Coliform for Tri-Lakes BIOLAC® Facility 5-53
5-47 Flow Diagram for Typical Lemna System 5-55
5-48 Diagram of Rayne, Louisiana Wastewater Treatment Ponds 5-56
5-49 Lemna System, Rayne 5-56
5-50 LemTec1™ Biological Treatment Process 5-57
5-51 Site Plan for LemTec System in Jackson, Indiana 5-58
5-52 LemTec System, Jackson 5-58
5-53 A. (BOD5) B. (TSS) and C. (NH3). Compliance data for Rayne 5-59
5-54 A. (BOD5) B. (TSS) and C. (NH3). Compliance data for Jackson 5-62
5-55 Photograph of Lemna Harvesting Equipment and Floating Barrier Grid 5-63
5-56 Praxair® In-Situ Oxygenation (ISO™) System 5-66
5-57 Photograph of the Laboratory Experiment Used to Develop the Concept of the 5-67
IX
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Speece Cone
6-1 Generalized N Pathways in Wastewater Ponds 6-2
6-2 Predicted Versus Actual Effluent N, Peterborough, New Hampshire 6-6
6-3 Verification of Design Models 6-8
6-4 Schematic Diagram of Nitrification Filter Bed 6-16
6-5 Benton Performance Data for Pond + Wetland + NFB 6-17
6-6 Benton Performance Data for Pond + Wetland + NFB 6-18
6-7 EDI ATLAS - IS Internal Pond Settler 6-21
6-8 CLEAR™ Process 6-22
6-9 The Quincy SBR System 6-23
6-10 The AquaMat® Process 6-24
6-11 A MBBR™ "Wheel" 6-25
6-12 Schematic of a Poo-Gloo Device Cross-Section 6-25
7-1 Cross-sectional and Plan Views of a Typical Intermittent Sand Filter 7-3
7-2 Rock Filter at Veneta, Oregon 7-11
7-3 State of Illinois Rock Filters Configurations 7-12
7-4 Nitrogen Species in Veneta Wastewater Treatment Rock Filter 7-14
7-5 Cross-Sectional View of Paeroa, New Zealand Rock Filter 7-17
7-6 Types of Dissolved Air Flotation Systems 7-24
7-7 TSS Removal from Pond Effluent in Dissolved Air Flotation with Alum 7-26
7-8 Concentration and Percent TSS Removal from Pond Effluent in Dissolved Air 7-27
Flotation with Alum Addition
7-9 Dissolved Air Floatation Thickening (DAFT) at the Stockton, CA Wastewater 7-27
Treatment Facility
7-10 Photograph of Shading for Control of Algal Growth in Naturita, Colorado 7-31
7-11 A Barley Straw Boom in Cell 3, New Baden, Illinois Wastewater Pond System 7-32
7-12 Change in Chlorophyll over Time under Different Treatment Conditions 7-34
8-1 Construction Costs vs. Design Flow Rate for Flow-Through Ponds (Facultative), 8-2
Kansas City, 2006. (DFR<500,000 L/d [0.130 MOD]
8-2 Data Bid Tabulations: Construction Costs vs. DFR for Flow-Through Ponds, 8-2
Kansas City, 2006
8-3 Construction Costs vs. DFR for Nondischarging Ponds, Kansas City, 2006 8-3
8-4 Construction Costs vs. DFR for Aerated Ponds Kansas City, 2006 - Q = 0 to 1.2 8-3
8-5 Center Pivot Sprinkling Costs, ENR CCI = 6076. (a) Capital Cost; (b) Operation 8-5
and Maintenance Cost
8-6 Solid Set Sprinkling (buried) Costs. ENR CCI=6076. (a) Capital Cost; (b) 8-6
Operation and Maintenance Cost
8-7 Gated Pipe - Overland Flow or Ridge-and-Furrow Slow Rate Costs, ENR 8-7
CCI=6076. (a) Capital Cost; (b) Operation and Maintenance Cost
8-8 Rapid Infiltration Basin Costs, ENR CCI = 6076. (a) Capital Cost; (b) Operation 8-8
and Maintenance Cost
8-9 Mixed-Media Filtration Capital Cost, ENR CCI = 6076 8-9
8-10 Mixed-Media Filtration O&M Costs, ENR CCI = 6076 8-9
8-11 Dissolved Air Flotation Capital Costs, ENR CCI = 6076 8-10
8-12 Dissolved Air Flotation Capital Costs, ENR CCI = 6076 8-10
8-13 Sequencing Batch Reactor Capital Costs, ENR CCI = 6076 8-11
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9-1 Sampling Grid System 9-6
9-2 Diurnal O2 Curve 9-7
XI
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Tables
Number Page
1-1 Basic Wastewater Pond Specifications 1-3
2-1 Land Area Estimates for 3,785 m3/d (1 mgd) Systems 2-2
2-2 Sequence of Field Testing, Typical Order [reading from left to right] 2-5
3-1 Ideal Operating Ranges for Methane Fermentation 3-3
3-2 Concentrations of Inhibitory Substances 3-3
3-3 BODs Reduction as a Function of Detention Time for Temperatures Greater than 3-4
Twenty Degrees Celsius
3-4 BODs Reduction as a Function of Detention Time and Temperature 3-5
3-5 Design and Operational Parameters for Anaerobic Ponds Treating Municipal 3-6
Wastewater
3-6 Design and Performance Data from U.S. EPA Pond Studies 3-9
4-1 Reported Seepage Rates from Pond Systems 4-5
4-2 Seepage Rates for Various Liners 4-7
4-3 Classification of the Principal Failure Mechanisms for Cut-and-Fill Reservoirs 4-13
5-1 Evolution of the Design of Selected AIWPS® Wastewater Treatment Facilities 5-1
1965 to present
5-2 AIWPS® Types I and II with Treatment Areas (acres) 5-7
5-3 Type I Advanced Integrated Wastewater Pond Systems (AIWPS®) 5-8
5-4 Type II AIWPS® 5-18
5-5 Design Criteria for Pond Systems with Deep Sludge Cells (from Hotchkiss, CO 5-23
Wastewater Ponds Treatment System).
5-6 Performance of DMPC Aerated Pond at North Myrtle Beach, SC 5-36
5-7 Comparison of Pond-Intermittent Sand Filter Systems with Carousel-Extended 5-38
Aeration Systems
5-8 Typical Manufacturer's Design Criteria for BIOLAC Systems versus 5-44
Conventional Extended Aeration Systems
5-9 Description of Alamosa, CO BIOLAC® Facility 5-46
5-10 Effluent Requirements for the Alamosa, CO BIOLAC® Facility 5-47
6-1 Annual Values from EPA Facultative Wastewater Pond Studies 6-3
6-2 Model 1, TV Removal in Facultative Ponds - Plug Flow Model 6-7
6-3 Model 2, TV Removal in Facultative Ponds - Complete Mix Model 6-7
6-4 Wastewater Characteristics and Operating Conditions for Five Aerated Ponds 6-9
6-5 TV Removal in Aerated Ponds 6-10
6-6 Comparisons of Various Equations to Predict NHs and TKN Removal in 6-11
Diffused-Air Aerated Ponds
6-7 Average Values for Batch Test in Pond 4 at Dickinson, North Dakota Area=l 1.7 6-14
Ha (29 acres), No Inflow
6-8 Benton, Kentucky Recirculating Gravel Filter/Constructed Wetland 6-17
6-9 Data for the Quincy, Washington SBR System 6-22
6-10 Nelson AquaMat® Biomass Carrier, Larchmont, Georgia 6-24
6-11 Phosphorus Removal in Ponds 6-27
7-1 Design and Performance of Early Massachusetts Intermittent Sand Filters 7-2
7-2 Intermittent Sand Filter Performance Treating Pond Effluents 7-5
xii
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7-3 Mean Performance Data for Three Full-Scale Pond-Intermittent Sand Filter 7-6
Systems
7-4 Design Characteristics and Performance of Facultative Pond-Intermittent Sand 7-7
Filter Systems
7-5 Performance of Aerated Pond-Intermittent Sand Filter, New Hamburg Plant 7-8
7-6 Mean and Range of Performance Data for Veneta, OR Wastewater Treatment 7-13
Plant-- 1994
7-7 Performance of Rock Filters 7-16
7-8 Summary of Removal Efficiency in the First Run 7-17
7-9 Design Parameters for Rock Filter Systems in the US 7-18
7-10 Design Parameters and Performance of New Zealand Rock Filters 7-19
7-11 BOD, TSS and Ammonia-N Concentrations in the Effluents of the Facultative 7-20
Pond, Aerated Rock Filter and Constructed Wetlands
7-12 Summary of Direct Filtration with Rapid Sand Filters 7-21
7-13 Summary of Typical Dissolved Air Flotation Performance 7-23
7-14 List of Chemicals Produced by Decomposing Straw 7-32
7-15 Hydrograph Controlled Release Pond Design Basics Used in U.S. 7-37
8-1 Total Annual Energy for Typical 1 mgd System Including Electrical plus Fuel, 8-14
Expressed as 1000 kwh/yr
9-1 TSS:BOD5 Ratios as Problem Indicators 9-8
9-2 Problems Associated with Types of Solids 9-9
9-3 Important Indicators in Pond Troubleshooting 9-10
9-4 Example Operation and Maintenance Checklist 9-13
Xlll
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Conversion Table, Physical Properties of Water, and DO Solubility (Reed et al., 1995)
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w
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15
3
ws
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si o
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S s.
M
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•^
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o
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1
3
p
C
s
U
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4-»
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6
w'
IS
p
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_c
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xv
-------
Table 3. Physical Properties of Water
Temperature
(°C)
0
5
10
15
20
25
30
40
50
60
70
80
90
100
Density
(kg/m3)
999.8
1000.0
999.7
999.1
998.2
997.0
995.7
992.2
988.0
983.2
977.8
971.8
965.3
958.4
Dynamic viscosity
x 103
(N • s/m2)
1.781
1.518
1.307
1.139
1.002
0.890
0.798
0.653
0.547
0.466
0.404
0.354
0.315
0.282
Kinematic viseoity (y)
x 106
(mz/s)
1.785
1.519
1.306
1.139
1.003
0.893
0.800
0.658
0.553
0.474
0.413
0.364
0.326
0.294
XVI
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Table 4. Dissolved Oxygen Solubility in Fresh Water*
Temperature (°C) Dissolved oxygen solubility (mg/L)
0
1
2
3
4
5
6
7
8
i
10
11
12
13
14
15
16
n
18
li
20
21
22
23
24
25
26
2?
28
29
30
14,62
14.23
13,84
13.48
13.13
12,80
12A8
12,17
11.87
11.59
11.33
11.08
10.83
10.60
10.37
10,15
9,95
9.74
9.54
9.35
9.17
8.99
8.S3
8,68
8.53
8,38
8.22
8.07
7.02
7,77
7.63
'Saturation values of dissolved oxygen when exposed to dry air containing
20.90% oxygen under a totaj pressure of 760 mmHg.
xvn
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Glossary
Abate®
AFP
AIWPS
AMTA
AMIS
ASP
ATLAS-IS
AWT
BIOLAC® Process
BOD
BOD5
Bti
CAPM
CBOD
CFID
CLEAR™
COD
CWT
DAF
DFR
DMR
DO
DPMC
larvicide
advanced facultative pond
Advanced Integrated Wastewater Pond System®
Activated Membrane Technology Associations
Advanced Microbial Treatment System
algae settling pond
Advanced Technology Lagoon Aeration System with
Internal Separator
activated waste treatment
activated sludge in earthen ponds
biochemical oxygen demand
5 day biochemical oxygen demand
Bacillus thuringiemis israelemis (larvicide)
Centre for Aquatic Plant Management
carbonaceous biochemical oxygen demand
continuous feed, intermittent discharge
Cyclical Lagoon Extended Aeration Reactor
chemical oxygen demand
Centralized Waste Treatment
dissolved air flotation
design flow rate
discharge monitoring reports
dissolved oxygen
Dual-power, multi-cellular system
xvin
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DPMC-IS
e.s.
EDI
ENRCCI
FC
F/M
FWS
GIS
gpm
HCR
HLT
HP APS
HRP
HRT
IPDs
I&I
JTU
Lagoon-ISF
M
MBBR™
MCRT
mgd
MLSS
MLVSS
MPN
MSL
Dual-power, multi-cellular intermittent sand filter
system
effective size
Environmental Dynamics, Inc.
Engineering News Record Construction Cost Index
fecal coliform(s)
food/mi croorgani sm
free water surface
Geographic Information System
gallons per minute
hydrogen controlled release
high level transfer
high-performance aerated pond system
high rate pond
hydraulic residence time/hydraulic retention time
in-pond digesters
Inflow & Infiltration
Jackson Turbidity Unit
Lagoon Intermittent Sand filter
metal ion
Moving Bed Biofilm Reactor
mean cell resident time
million gallons per day
mixed liquor suspended solids
mixed liquor volatile suspended solids
most probable number
mean sea level
xix
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NEIWPCC
NFB
NH4-N
NOAA
NPDES
NRCS
OD
O&M
%
POTWs
RAS
RO
SAR
SBR
SCBOD5
scfm
sf
SF, SSF
SFP
ss
STEP
TFCC
TKN
TP
TSS
TVSS
New England Interstate Water Pollution Control
Commission
nitrification filter bed
ammonia-N, ammonia nitrogen
National Oceanic and Atmospheric Administration
National Pollutant Discharge Elimination System
National Resources Conservation Services
oxygen demand
operation and maintenance
percent
publicly owned treatment works
return activated sludge
reverse osmosis
sodium adsorption ratio
sequencing batch reactor
soluble carbonaceous BODs
standard cubic feet per minute
square foot
subsurface flow
secondary facultative pond
suspended solids
septic tank effluent pumping system
total fecal coliform count
total Kjeldahl nitrogen
total phosphorus
total suspended solids
total volatile suspended solids
XX
-------
U.C., u.c.
UF
USGS
vss
WAS
WHO
WTCost
uniformity coefficient
ultrafiltration
U. S. Geological Society
volatile suspended solids
waste activated sludge
World Health Organization
a CD-Rom for estimating plant membrane treatment
costs
xxi
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Acknowledgments
This document, an up-to-date revision of the Municipal Wastewater Stabilization Ponds design
manual published by USEPA in 1983, is the result of the interest and commitment of many
contributors, who are listed below in alphabetical order.
Editors*
Eugenia McNaughton, USEPA, Region 9, San Francisco, CA
James E. Smith, Jr., retired, formerly with USEPA, NRMRL, Cincinnati, OH
Sally Stoll, USEPA, NRMRL, Cincinnati, OH
Contracted Authors*
Richard H. Bowman, R.H. Bowman and Associates
E. Joe Middlebrooks, Consultant
Contributing Writer
Laurel J. Staley, USEPA, NRMRL, Cincinnati, OH
Special Contributions, Technical Assistance and Review
Robert K. Bastian, USEPA, OWM, Washington, DC
Robert B. Brobst, USEPA, Region 8, Denver, CO
David Chin, USEPA, Region 1, Boston, MA
Ronald W. Crites, consultant
Wayne Daugherty, City of St. Helena CA Public Works
Steve Duerre, MN Pollution Control Agency
Gene Erickson, MN Pollution Control Agency
F. Bailey Green, consultant
Geoffrey Holmes, Fisherman Bay Sewer District, Lopez Island, WA
Peter Husby, USEPA, Region 9 Laboratory, Richmond, CA
Craig Johnson, University of Utah
Thomas Konner, USEPA, Region 9
Russell Martin, USEPA, Region 5, Chicago, IL
Larry Parlin, City of Stockton CA Public Works
Charles Pycha, USEPA, Region 5
Wes Ripple, NH Department of Environmental Services
Robert Rubin, North Carolina State University
Michael Sample, City of St. Helena CA Public Works
Amy Wagner, USEPA, Region 9 Laboratory
Jianpeng Zhou, Southern Illinois University at Edwardsville
Technical Reviewers
Don Albert, retired, formerly with ME Department of Environmental Protection
Edwin Earth, USEPA, NRMRL
Charles Corley, IL Environmental Protection Agency
John Hamilton, Indian Health Service, USEPA Region 9
xxii
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Paul Krauth, UT Department of Environmental Quality
Tryg Lundquist, California State University at San Luis Obispo
Paul Olander, retired, formerly with VT Department of Environmental Conservation
Syed Shahriyar, USEPA, Region 6, Dallas, TX
Editing and Production:
Jan Byers, contractor USEPA, Region 9
Jean Dye, USEPA, ORD, Cincinnati, OH
Katherine Loizos, contractor, USEPA
Patricia Louis, USEPA, ORD, Cincinnati, OH
The authors wish to dedicate this manual to the memory of Dr. William J. Oswald, whose vision
of using design principles respecting and modeled after natural processes has come to be
understood as basic to our survival as a species: reducing energy consumption, reimagining
"waste products" as resources, and building sustainable projects, in order to solve some of
civilization's most complicated and persistent problems. Dr. Oswald continues to be an
inspiration to generations of his students, in and out of universities, and throughout the world.
*In 2000, USEPA Office of Wastewater Management (OWM) underwrote a needs assessment to
determine whether a revised and updated edition of the 1983 Wastewater Stabilization Ponds
Design Manual was needed. The answer was affirmative and OWM, working with ORD
NRMRL, Cincinnati, hired a consultant, E. Joe Middlebrooks to conduct the work. Several of
the Regions contributed funding to complete the project: Regions 5, 8 and 9 applied for Regional
Applied Research Effort (RARE) funds; Region 6 contributed funds from its Tribal program;
Region 1 funds were from RARE as well as general funding. Gajindar Singh, Office of Water
has been a tireless supporter of pond technology. The final product represents the work of the
consultant and his subcontractor and many USEPA staff, who share the belief that the benefits of
wastewater pond technology should be more widely known and accepted among the community
of design engineers, city and community managers, and that information about them should be
more readily available, especially to the plant operators, who work with them every day.
Cover Picture is of a modified AIWPS treating wastewater from Pine Ridge, South Dakota on
the Pine Ridge Reservation, home the Oglala Sioux (Lakota) Tribe. Startup was in 2009 treating
wastewater from the 5,500 residents of the village. The Treatment works consist of AIWPS®
primary Pond with fermentation pits, followed by secondary cells, followed by a wetland for
final treatment prior to discharge. The design was based on the Tribe's desire for something
other than a conventional lagoon system and the need to keep operation and maintenance to a
minimum. The Treatment area is surrounded by pasture lands and can be expected to stay remote
for the foreseeable future. Each of the primary ponds will contain two Oswald type fermentation
pits that are conservatively designed. The outer pond is oversized to compensate for lack of
aerators. The secondary cells have been sized for holding during the winter with a total detention
xxiii
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of 150 days. The wetland design is based on 25,000 gpd/ac which was recommended by the State
of South Dakota. The facility will discharge 725,000 gallons per day at design capacity. For
additional information contact Anthony Kathol, P.E. at Anthony.Kathol@ihs.gov.
xxiv
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Preface
Eugenia McNaughton (U.S. EPA Region 9), James E. Smith, Jr. (U.S. EPA ORD NRMRL,
retired), Sally Stoll (ORD NRMRL)
January 21,2011
Stabilization ponds have been used for treatment of wastewater for over 3,000 years. The first
recorded construction of a pond system in the U.S. was at San Antonio, Texas, in 1901. Today,
over 8,000 wastewater treatment ponds are in place, involving more than 50% of the wastewater
treatment facilities in the U.S. (CWNS, 2000). Facultative ponds account for 62%, aerated ponds
25%, anaerobic 0.04% and total containment 12% of the pond treatment systems. They treat a
variety of wastewaters from domestic wastewater to complex industrial wastes, and they function
under a wide range of weather conditions, from tropical to arctic. Ponds can be used alone or in
combination with other wastewater treatment processes. As our understanding of pond operating
mechanisms has increased, different types of ponds have been developed for application in
specific types of wastewater under local environmental conditions. This manual focuses on
municipal wastewater treatment pond systems.
We should note here that we will use the word "treatment" in place of "stabilization," which has
come to have a much more specific meaning since the first manual was published. We will also
refer to "ponds" versus "lagoons," for consistency in the manual, though we recognize that in
this case either term is acceptable.
The U.S. Environmental Protection Agency (EPA) last published a Wastewater Stabilization
Ponds Design Manual in 1983 under the Technology Transfer Program, which was developed
"to describe technological advances and present new information." EPA support for pond
systems as options for municipal wastewater treatment was most welcome, particularly for small
communities that could not afford to match even the generous construction grants that were
offered at that time to bring communities of all sizes some level of wastewater treatment.
While the tendency in the U.S. has been for smaller communities to build ponds, in other parts of
the world, including Australia, New Zealand, Mexico and Latin America, Asia and Africa,
treatment ponds have been built for large cities. As a result, our understanding of the biological,
biochemical, physical and climatic factors that interact to transform the organic compounds,
nutrients and pathogenic organisms found in sewage into less harmful chemicals and unviable
organisms (i.e., dead or sterile) has grown since 1983. A wealth of experience has been built up
as civil, sanitary or environmental engineers, operators, public works managers and public health
and environmental agencies have gained more experience with these systems. While some of
this information makes its way into technical journals and text books, there is a need for a less
formal presentation of the subject for those working in the field every day.
In gathering the information for this revision, we interviewed state regulators, local operators,
engineers, consultants, and academics. We read as much of the literature as we could find,
always searching for case histories illustrating new performance achievements and associated
xxv
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design details that might be employed in other systems. We found that there has been some
evolution of design, such as in the AIWPS™, but many improvements have included, for
example, the addition of more aerators, moving the systems closer to activated sludge with the
attendant high energy and sludge removal costs. Much recent work has focused on pond
hydraulics and we understand now that for consistent performance, the design and placement of
inlet and outlet structures to avoid short circuiting and loss of solids is critical, and that
redundancy must be built into the system to allow for flexibility in operation and maintenance.
Some additions have been necessary to meet nutrient requirements that were not in place when
the systems were built. Overall, however, pond systems still offer an alternative that is lower in
capital outlay, operations, and maintenance costs. Appropriately designed ponds are capable of
meeting strict environmental standards with minimal biosolids management requirements and
reasonable energy costs.
Looking to the future, what has been the most problematic element for stabilization ponds, the
growth and persistence of algae throughout the system, is lately coming to be seen as a potential
asset. It may soon be time to talk about enhancing the growth of algae for use as biofuel or
livestock food supplements to replace irrigated feed crops and conventional energy sources.
Opportunities to install solar power collectors, either to supply the entire system's energy needs
or to run aerators, may make an already low energy use system effectively carbon neutral or net-
energy positive. The cost to add elements that treat wastewater to reduce nutrient discharge
would be less challenging for a community that has a system that is already a low energy
consumer.
In the spirit of the times, we acknowledge that another book isn't necessarily the way to get
information out these days. This version of the manual is instead a compendium organized
around the topics related to design, operation, and maintenance of wastewater stabilization ponds
that must meet ever more stringent discharge requirements. It will be available on the web in its
entirety chapter by chapter. It is our hope that this will be a resource to which you will return
many times over the course of your involvement with wastewater ponds. And we look forward
to hearing from you about improvements to existing text or other information that we might
include to make the manual an evolving and dynamic document, attesting to the importance of
this wastewater treatment process and to the continued enthusiasm for it that inspired us to make
this effort to bring it to you.
xxvi
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CHAPTER 1
INTRODUCTION
1.1 BACKGROUND
1.1.1 History
Treatment ponds have been employed for treatment of wastewater for over 3,000 years. The first
recorded construction of a pond system in the U.S. was in San Antonio, Texas, in 1901 (Gloyna,
1971). Today, over 8,000 wastewater treatment ponds, comprising more than 50 percent of the
wastewater treatment facilities in the United States, are in place (Bastian, pers. comm., 2010).
Ponds are used to treat wastewater generated by small communities in Europe. Larger pond
systems are in place in New Zealand, Australia and Africa (Mara, 2003). They are used to treat a
variety of wastewaters, from domestic to complex industrial effluent, and they function under a
wide range of climatic conditions, from tropical to arctic. Ponds can be used alone or in
combination with other wastewater treatment processes. As understanding of pond operating
mechanisms has improved, different types of ponds have been developed to meet specific
conditions. Ponds generally require less energy than other treatment systems and have lower
operation and maintenance costs.
1.1.2 Trends
The basic elements of pond system design have remained unchanged in the 25 years since the
publication of the EPA manual (Design Manual: Municipal Wastewater Stabilization Ponds,
EPA-625/1-83-015, 1983a). Aspects of the basic pond designs have evolved and several
modifications have been developed. These have been in response to increasingly stringent water
quality regulatory requirements for point source discharges.
The major procedures, processes and design methods relevant to wastewater treatment ponds that
will be discussed in this manual are:
Basic Processes (flow through basins)
• Anaerobic
• Facultative
• Aerobic
In-Pond Design Evolution and Enhancements
• AIWPS® (Oswald)
• Deep Fermentation Pits
• High Performance Shallow Ponds
Oxygen Addition
• LAS International, Ltd.
• PRAXAIR, Inc.
Modifications that Require Energy
• Partial Mix
• Complete Mix
1-1
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• High-Performance Aerated Ponds (Rich)
• BIOLAC™
Nutrient Removal
• Nitrogen
o In pond
o Modified high performance aerated systems for nitrification/denitrification
o In pond with wetlands and gravel bed filters
• Phosphorus
Effluent TSS (Algae) Removal
• Lemna
• Algae settling basins
• Barley straw
1.1.3 Manual Objective and Scope
This manual provides an overview of wastewater treatment pond systems through the discussion
of factors affecting treatment, process design principles and applications, aspects of physical
design and construction, effluent total suspended solids (TSS), algae, nutrient removal
alternatives, and cost and energy requirements. In this chapter, the biological, physical and
chemical processes that occur in wastewater treatment ponds are discussed.
Chapter 2 describes a sequential approach to the development of a wastewater management
project. This approach determines feasibility of the process itself and the land area required for
treatment, and identifies possible sites. These sites are evaluated based on technical and cost-
effective alternatives.
Chapter 3 includes design for the basic types of treatment ponds.
Chapter 4 discusses the physical design and construction criteria that define effective pond
performance, regardless of the design equation employed, and must be considered in the facility
design process.
Chapter 5 describes the evolution and enhancement of the basic designs within ponds over the
last 30 years.
Chapter 6 presents a discussion of the capability of conventional facultative and aerated lagoons
to reduce nutrient concentrations, including commercial products for nitrogen (TV) and
phosphorus (P) removal.
Chapter 7 presents alternatives for control and removal of algae-derived TSS.
Chapter 8 covers cost and energy requirements.
Chapter 9 includes information on the operation, maintenance and troubleshooting of treatment
ponds.
1-2
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Appendix A lists the state criteria for wastewater treatment ponds. A summary of pond design
methods is presented in Appendix B. Design models and examples are presented in Appendix C.
Case studies are found in Appendix D. Appendix E is a troubleshooting guide; Appendix F
contains study guides for operators from the state of Wisconsin; discharge guidance from the
state of Minnesota is in Appendix G. Appendix H presents guidance for the use of barley straw
to reduce algal TSS from the state of Illinois. Appendix I contains the glossary, and Appendix J
contains a conversion table and other general information.
1.2 POND NOMENCLATURE
Ponds are designed to enhance the growth of natural ecosystems that are either anaerobic
(providing conditions for bacteria that grow in the absence of oxygen [02] environments),
aerobic (promoting the growth of 02 producing and/or requiring organisms, such as algae and
bacteria), or facultative, which is a combination of the two. Ponds are managed to reduce
concentrations of biochemical oxygen demand (BOD), TSS and coliform numbers (fecal or total)
to meet water quality requirements. Table 1-1 summarizes information on pond application,
loading, and size of wastewater treatment ponds.
Table 1.1. Basic Wastewater Pond Specifications (adapted from Curi and Eckenfelder
1980).
Pond
Anaerobic
Application
Industrial
Typical
Loading
(BOD5r
280-4500
kg/
Typical
Detention
Time (d)
5-50
Typical
Depth (m)
2.5-4.5
Comments
Subsequent
wastewater
lOOOrrf/d
treatment normally
required.
Facultative
22-56 kg/
7-50
0.9-2.4
lOOOrrr/d
Aerobic
112-225 kg/ 2-6
1000m2/d
0.18-0.3
Most commonly used
wastewater treatment
pond. May be aerobic
through entire depth if
lightly loaded.
Maximizes algae
production and, if
algae are harvested,
nutrient removal.
Raw municipal
wastewater. Effluent
from primary
treatment, trickling
filters, aerated
ponds, or anaerobic
ponds.
Generally used to
treat effluent from
other processes.
Produces effluent
low in soluble BOD5
and high in algal
solids.
*BOD5 = Biochemical Oxygen Demand measured over 5 days
1.2.1 Anaerobic Ponds
Anaerobic ponds receive such a heavy organic loading that there is no aerobic zone. They are
usually 2.5 - 4.5 m in depth and have detention times of 5 - 50 days. The predominant
biological treatment reactions are bacterial acid formation and methane fermentation.
Anaerobic ponds are usually used for treatment of strong industrial and agricultural (food
processing) wastes, as a pretreatment step in municipal systems, or where an industry is a
1-3
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significant contributor to a municipal system. The biochemical reactions in an anaerobic pond
produce hydrogen sulfide (7/2-5) and other odorous compounds. To reduce odors, the common
practice is to recirculate water from a downstream facultative or aerated pond. This provides a
thin aerobic layer at the surface of the anaerobic pond, which prevents odors from escaping into
the air. A cover may also be used to contain odors. The effluent from anaerobic ponds usually
requires further treatment prior to discharge.
1.2.2 Facultative Ponds
The most common type of pond is the facultative pond, which may also be called an oxidation or
photosynthetic pond. Facultative ponds are usually 0.9 - 2.4 m deep or deeper, with an aerobic
layer overlying an anaerobic layer. Recommended detention times vary from 5-50 days in warm
climates and 90 - 180 days in colder climates (New England Interstate Water Pollution Control
Commission [NEIWPCC], 1998, heretofore referred to as TR-16). Aerobic treatment processes
in the upper layer provide odor control, nutrient and BOD removal. Anaerobic fermentation
processes, such as sludge digestion, denitrification and some BOD removal, occur in the lower
layer. The key to successful operation of this type of pond is 02 production by photosynthetic
algae and/or re-aeration at the surface.
Facultative ponds are used to treat raw municipal wastewater in small communities and for
primary or secondary effluent treatment for small or large cities. They are also used in industrial
applications, usually in the process line after aerated or anaerobic ponds, to provide additional
treatment prior to discharge. Commonly achieved effluent BOD values, as measured in the
BODs test, range from 20 - 60 mg/L, and TSS levels may range from 30 - 150 mg/L. The size of
the pond needed to treat BOD loadings depends on specific conditions and regulatory
requirements.
Facultative ponds overloaded due to unplanned additional sewage volume or higher strength
influent from a new industrial connection may be modified by the addition of mechanical
aeration. Ponds originally designed for mechanical aeration are generally 2 - 6 m deep with
detention times of 3 - 10 days. For colder climates, TR-16 suggests 20 - 40 days. Mechanically
aerated ponds require less land area but have greater energy requirements.
1.2.3 Aerobic Ponds
Aerobic ponds, also known as oxidation ponds or high-rate aerobic ponds, maintain dissolved
oxygen (DO) throughout their entire depth. They are usually 30 - 45 cm deep, which allows
light to penetrate throughout the pond. Mixing is often provided, keeping algae at the surface
to maintain maximum rates of photosynthesis and 02 production and to prevent algae from
settling and producing an anaerobic bottom layer. The rate of photosynthetic production of 02
may be enhanced by surface re-aeration; 02 and aerobic bacteria biochemically stabilize the
waste. Detention time is typically two to six days.
These ponds are appropriate for treatment in warm, sunny climates. They are used where a high
degree of BODs removal is desired but land area is limited. The chief advantage of these ponds
is that they produce a stable effluent during short detention times with low land and energy
requirements. However, their operation is somewhat more complex than that of facultative
ponds and, unless the algae are removed, the effluent will contain high TSS. While the shallow
1-4
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depths allow penetration of ultra-violet (UV) light that may reduce pathogens, shorter detention
times may work against effective coliform and parasite die-off Since they are shallow, bottom
paving or covering is usually necessary to prevent aquatic plants from colonizing the ponds. The
Advanced Integrated Wastewater Pond System® (AIWPS®) uses the high-rate pond to maximize
the growth of microalgae using a low-energy paddle-wheel. This use of the high-rate pond will
be discussed in Chapter 5.
1.3 ELEMENTS OF POND PROCESSES
1.3.1 The Organisms
Although our understanding of wastewater pond ecology is far from complete, general
observations about the interactions of macro- and microorganisms in these biologically driven
systems support our ability to design, operate and maintain them.
1.3.1.1 Bacteria
In this section, we discuss other types of bacteria found in the pond; these organisms help to
decompose complex, organic constituents in the influent to simple, non-toxic compounds.
Certain pathogenic bacteria and other microbial organisms (viruses, protozoa) associated with
human waste enter into the system with the influent; the wastewater treatment process is
designed so that their numbers will be reduced adequately to meet public health standards. Their
fate in wastewater ponds will be discussed in Chapters 5 and 9.
1.3.1.1.1 Aerobic Bacteria
Bacteria found in the aerobic zone of a wastewater pond are primarily the same type as those
found in an activated sludge process or in the zoogleal mass of a trickling filter. The most
frequently isolated bacteria include Beggiatoa alba, Sphaerotilus natans, Achromobacter,
Alcaligenes, Flavobacterium, Pseudomonas and Zoogoea spp. (Lynch and Poole, 1979; Pearson,
2005). These organisms decompose the organic materials present in the aerobic zone into
oxidized end products.
1.3.1.1.2 Anaerobic Bacteria
Hydrolytic bacteria convert complex organic material into simple alcohols and acids, primarily
amino acids, glucose, fatty acid and glycerols (Brockett, 1976; Pearson, 2005; Paterson and
Curtis, 2005). Acidogenic bacteria convert the sugars and amino acids into propionic, acetic and
butyric acids. Acetogenic bacteria convert these organic acids into acetate, ammonia (Aff/?),
hydrogen (H), and carbon dioxide (CO2). Methanogenic bacteria break down these products
further to methane (CH4) and CO2 (Gallert and Winter, 2005).
1.3.1.1.3 Cyanobacteria
Cyanobacteria, formerly classified as blue-green algae, are autotrophic organisms that are able to
synthesize organic compounds using CO^as the major carbon source. Cyanobacteria produce 02
as a by-product of photosynthesis, providing an 02 source for other organisms in the ponds.
They are found in very large numbers as blooms when environmental conditions are suitable
(Gaudy and Gaudy, 1980). Commonly encountered Cyanobacteria include Oscillatoria,
Arthrospira, Spirulina, andMicrocystis (Vasconcelos and Pereira, 2001).
1-5
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1.3.1.1.4 Purple Sulfur Bacteria
Purple sulfur bacteria (Chromatiaceae) may grow in any aquatic environment to which light of
the required wavelength penetrates, provided that C02, nitrogen (TV), and a reduced form of
sulfur (S) or H are available. Purple sulfur bacteria occupy the anaerobic layer below the algae,
cyanobacteria, and other aerobic bacteria in a pond. They are commonly found at a specific
depth, in a thin layer where light and nutrient conditions are at an optimum (Gaudy and Gaudy,
1980; Pearson, 2005). Their biochemical conversion of odorous sulfide compounds to elemental
S or sulfate (SO4) helps to control odor in facultative and anaerobic ponds.
1.3.2 Algae
Algae constitute a group of aquatic organisms that may be unicellular or multicellular, motile or
immotile, and, depending on the phylogenetic family, have different combinations of photo-
synthetic pigments. As autotrophs, algae need only inorganic nutrients, such as N, phosphorus
(P) and a suite of microelements, to fix CC^and grow in the presence of sunlight. Algae do not
fix atmospheric N; they require an external source of inorganic TV in the form of nitrate (NO3) or
NHs. Some algal species are able to use amino acids and other organic TV compounds. Oxygen is
a by-product of these reactions.
Algae are generally divided into three major groups, based on the color reflected from the cells
by the chlorophyll and other pigments involved in photosynthesis. Green and brown algae are
common to wastewater ponds; red algae occur infrequently. The algal species that is dominant at
any particular time is thought to be primarily a function of temperature, although the effects of
predation, nutrient availability, and toxins are also important.
Green algae (Chlorophyta) include unicellular, filamentous, and colonial forms. Some green
algal genera commonly found in facultative and aerobic ponds are Euglena, Phacus,
Chlamydomonas, Ankistrodesmus, Chlorella, Micractinium, Scenedesmus, Selenastrum,
Dictyosphaerium and Volvox.
Chrysophytes, or brown algae, are unicellular and may be flagellated, and include the diatoms.
Certain brown algae are responsible for toxic red blooms. Brown algae found in wastewater
ponds include the diatoms Navicula and Cyclotella.
Red algae (Rhodophyta) include a few unicellular forms, but are primarily filamentous (Gaudy
and Gaudy, 1980; Pearson, 2005).
1.3.2.1 Importance of Interactions between Bacteria and Algae
It is generally accepted that the presence of both algae and bacteria is essential for the
proper functioning of a treatment pond. Bacteria break down the complex organic waste
components found in anaerobic and aerobic pond environments into simple compounds,
which are then available for uptake by the algae. Algae, in turn, produce the 02 necessary
for the survival of aerobic bacteria.
In the process of pond reactions of biodegradation and mineralization of waste material by
bacteria and the synthesis of new organic compounds in the form of algal cells, a pond
effluent might contain a higher than acceptable TSS. Although this form of TSS does not
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contain the same constituents as the influent TSS, it does contribute to turbidity and needs
to be removed before the effluent is discharged. Once concentrated and removed,
depending on regulatory requirements, algal TSS may be used as a nutrient for use in
agriculture or as a feed supplement (Grolund, 2002).
1.3.3 Invertebrates
Although bacteria and algae are the primary organisms through which waste stabilization is
accomplished, predator life forms do play a role in wastewater pond ecology. It has been
suggested that the planktonic invertebrate Cladocera spp. and the benthic invertebrate family
Chironomidae are the most significant fauna in the pond community in terms of stabilizing
organic matter. The cladocerans feed on the algae and promote flocculation and settling of
particulate matter. This in turn results in better light penetration and algal growth at greater
depths. Settled matter is further broken down and stabilized by the benthic feeding
Chironomidae. Predators, such as rotifers, often control the population levels of certain of the
smaller life forms in the pond, thereby influencing the succession of species throughout the
seasons.
Mosquitoes can present a problem in some ponds. Aside from their nuisance characteristics,
certain mosquitoes are also vectors for such diseases as encephalitis, malaria, and yellow fever,
and constitute a hazard to public health which must be controlled. Gambusia, commonly called
mosquito fish, have been introduced to eliminate mosquito problems in some ponds in warm
climates (Ullrich, 1967; Pipes, 1961; Pearson, 2005), but their introduction has been problematic
as they can out-compete native fish that also feed on mosquito larvae. There are also
biochemical controls, such as the larvicides Bacillus thuringiensis israelensis (Bti), and Abate ,
which may be effective if the product is applied directly to the area containing mosquito larvae.
The most effective means of control of mosquitoes in ponds is the control of emergent
vegetation.
1.3.4 Biochemistry in a Pond
1.3.4.1 Photosynthesis
Photosynthesis is the process whereby organisms use solar energy to fix CO2 and obtain the
reducing power to convert it to organic compounds. In wastewater ponds, the dominant
photosynthetic organisms include algae, cyanobacteria, and purple sulfur bacteria (Pipes, 1961;
Pearson, 2005).
Photosynthesis may be classified as oxygenic or anoxygenic, depending on the source of
reducing power used by a particular organism. In oxygenic photosynthesis, water serves as the
source of reducing power, with O2 as a by-product. The equation representing oxygenic
photosynthesis is:
H2O + sunlight — » 1/2O2 + 2H* + 2e (1-1)
Oxygenic photosynthetic algae and cyanobacteria convert CO2 to organic compounds, which
serve as the major source of chemical energy for other aerobic organisms. Aerobic bacteria need
the C>2 produced to function in their role as primary consumers in degrading complex organic
1-7
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waste material.
Anoxygenic photosynthesis does not produce 02 and, in fact, occurs in the complete absence of
02. The bacteria involved in anoxygenic photosynthesis are largely strict anaerobes, unable to
function in the presence of 02- They obtain energy by reducing inorganic compounds. Many
photosynthetic bacteria utilize reduced S compounds or elemental S in anoxygenic
photosynthesis according to the following equation:
H2S —> S° + 2H+ + 2e (1-2)
1.3.4.2 Respiration
Respiration is a physiological process by which organic compounds are oxidized into C02 and
water. Respiration is also an indicator of cell material synthesis. It is a complex process that
consists of many interrelated biochemical reactions (Stanier et al., 1963; Pearson, 2005).
Aerobic respiration, common to species of bacteria, algae, protozoa, invertebrates and higher
plants and animals, may be represented by the following equation:
C2HnO6 + 6O2 + enzymes -^6CO2 + 6H2O + new cells (1-3)
The bacteria involved in aerobic respiration are primarily responsible for degradation of waste
products.
In the presence of light, respiration and photosynthesis can occur simultaneously in algae.
However, the respiration rate is low compared to the photosynthesis rate, which results in a net
consumption of C02 and production of 02. In the absence of light, on the other hand, algal
respiration continues while photosynthesis stops, resulting in a net consumption of 02 and
production ofCO2.
1.3.4.3 Nitrogen Cycle
The N cycle occurring in a wastewater treatment pond consists of a number of biochemical
reactions mediated by bacteria. A schematic representation of the changes in N speciation in
wastewater ponds over a year is represented by Figure 1-1. See Chapter 6 for a more detailed
discussion of the cycling of TV species in ponds.
1-8
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volatilization
volatilization
oxidation
i mechanical)
effluent
lag
spring
or
Algal Growth
declining
summer
fail
stationary
winter
Figure 1-1. The nitrogen cycle in wastewater pond system.
Organic TV and NHs enter with the influent wastewater. Organic TV in fecal matter and other
organic materials undergo conversion toNHs and ammonium ion NH^ by microbial activity.
The NHs may volatilize into the atmosphere. The rate of gaseous NH3 losses to the atmosphere
is primarily a function of pH., surface to volume ratio, temperature, and the mixing conditions.
An alkaline pH. shifts the equilibrium ofNH3 gas and NH4+ towards gaseous NH3 production,
while the mixing conditions affect the magnitude of the mass transfer coefficient.
Ammonium is nitrified to nitrite (7V02 ) by the bacterium Nitrosomonas and then to MVby
Nitrobacter. The overall nitrification reaction is:
NH4+
NOi + 2H+ + H2O
(1-4)
The NOi produced in the nitrification process, as well as a portion of the NH4+produced from
ammonification, can be assimilated by organisms to produce cell protein and other TV-containing
compounds. The NO3' may also be denitrified to form NO^ and then TV gas. Several species of
bacteria may be involved in the denitrification process, including Pseudomonas, Micrococcus,
Achromobacter, and Bacillus. The overall denitrification reaction is
6NOi
3N2 + 5CO2 + 7H2O + 6OR
(1-5)
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Nitrogen gas may be fixed by certain species of cyanobacteria when TV is limited. This may
occur in TV-poor industrial ponds, but rarely in municipal or agricultural ponds (U.S. EPA, 1975a,
1993).
Nitrogen removal in facultative wastewater ponds can occur through any of the following
processes: (1) gaseous NHs stripping to the atmosphere, (2) NH^ assimilation in algal biomass,
(3) NO3' uptake by floating vascular plants and algae, and (4) biological nitrification-
denitrification. The removal of TV is discussed in detail in Chapter 6. Whether NH^ is
assimilated into algal biomass depends on the biological activity in the system and is affected by
several factors such as temperature, organic load, detention time, and wastewater characteristics.
1.3.4.4 Dissolved Oxygen (DO)
Oxygen is a partially soluble gas. Its solubility varies in direct proportion to the atmospheric
pressure at any given temperature. DO concentrations of approximately 8 mg/L are generally
considered to be the maximum available under local ambient conditions. In mechanically aerated
ponds, the limited solubility of O2 determines its absorption rate (Sawyer et al., 1994).
The natural sources of DO in ponds are photo synthetic oxygenation and surface re-aeration. In
areas of low wind activity, surface re-aeration may be relatively unimportant, depending on the
water depth. Where surface turbulence is created by excessive wind activity, surface re-aeration
can be significant. Experiments have shown that DO in wastewater ponds varies almost directly
with the level of photosynthetic activity, which is low at night and early morning
and rises during daylight hours to a peak in the early afternoon. At increased depth,
the effects of photosynthetic oxygenation and surface re-aeration decrease, as the
distance from the water-atmosphere interface increases and light penetration
decreases. This can result in the establishment of a vertical gradient. The microorganisms in the
pond will segregate along the gradient.
1.3.4.5 />H and Alkalinity
In wastewater ponds, the Hion concentration, expressed as/>H, is controlled through the
carbonate buffering system represented by the following equations:
where:
CO2 + H2O <-> H2CO3 <-> HCOi + tT (1-6)
HCOi^COi2 + H+ (1-7)
COi2 + H2O <-> HCOi + OH~ (1-8)
OH~ + H+^H2O (1-9)
The equilibrium of this system is affected by the rate of algal photosynthesis. In photosynthetic
metabolism, CO2 is removed from the dissolved phase, forcing the equilibrium of the first
expression (1-6) to the left. This tends to decrease the hydrogen ion (tT) concentration and the
bicarbonate (HCOi) alkalinity. The effect of the decrease in HCOi concentration is to force the
third equation (1-8) to the left and the fourth (1-9) to the right, both of which decrease total
alkalinity. Figure 1-2 shows atypical relationship betweenpR, CO2, HCOi', COi2, and OH.
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The decreased alkalinity associated with photosynthesis will simultaneously reduce the carbonate
hardness present in the waste. Because of the close correlation between pH and photosynthetic
activity, there is a diurnal fluctuation mpR when respiration is the dominant metabolic activity.
9.5 10 10.5 11
Figure 1-2. Relationship between pH and alkalinity (Sawyer et al., 1994).
1.3.5 Physical Factors
1.3.5.1 Light
The intensity and spectral composition of light penetrating a pond surface significantly affect all
resident microbial activity. In general, activity increases with increasing light intensity until the
photosynthetic system becomes light saturated. The rate at which photosynthesis increases in
proportion to an increase in light intensity, as well as the level at which an organism's
photosynthetic system becomes light saturated, depends upon the particular biochemistry of the
species (Lynch and Poole, 1979; Pearson, 2005). In ponds, photosynthetic 02 production has
been shown to be relatively constant within the range of 5,380 to 53,800 lumens/m2 light
intensity with a reduction occurring at higher and lower intensities (Pipes, 1961; Paterson and
Curtis, 2005).
The spectral composition of available light is also crucial in determining photosynthetic activity.
1-11
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The ability of photosynthetic organisms to utilize available light energy depends primarily upon
their ability to absorb the available wavelengths. This absorption ability is determined by the
specific photosynthetic pigment of the organism. The main photosynthetic pigments are
chlorophylls and phycobilins. Bacterial chlorophyll differs from algal chlorophyll in both
chemical structure and absorption capacity. These differences allow the photosynthetic bacteria
to live below dense algal layers where they can utilize light not absorbed by the algae (Lynch
and Poole, 1979; Pearson, 2005).
The quality and quantity of light penetrating the pond surface to any depth depend on the
presence of dissolved and particulate matter as well as the water absorption characteristics. The
organisms themselves contribute to water turbidity, further limiting the depth of light
penetration. Given the light penetration interferences, photosynthesis is significant only in the
upper pond layers. This region of net photosynthetic activity is called the euphotic zone (Lynch
and Poole, 1979; Pearson, 2005).
Light intensity from solar radiation varies with the time of day and difference in latitudes. In cold
climates, light penetration can be reduced during the winter by ice and snow cover.
Supplementing the treatment ponds with mechanical aeration may be necessary in these regions
during that time of year.
1.3.5.2 Temperature
Temperature at or near the surface of the aerobic environment of a pond determines the
succession of predominant species of algae, bacteria, and other aquatic organisms. Algae can
survive at temperatures of 5 - 40 C. Green algae show most efficient growth and activity at
temperatures of 30 - 35 C. Aerobic bacteria are viable within a temperature range of 10 - 40 C;
35 - 40 C is optimum for cyanobacteria (Anderson and Zweig, 1962; Gloyna et al., 1976;
Paterson and Curtis, 2005; Crites et al., 2006).
As the major source of heat for these systems is solar radiation, a temperature gradient can
develop in a pond with depth. This will influence the rate of anaerobic decomposition of solids
that have settled at the bottom of the pond. The bacteria responsible for anaerobic degradation
are active in temperatures from 15 - 65 C. When they are exposed to lower temperatures, their
activity is reduced.
The other major source of heat is the influent water. In sewerage systems with no major inflow
or infiltration problems, the influent temperature is higher than that of the pond contents. Cooling
influences are exerted by evaporation, contact with cooler groundwater and wind action.
The overall effect of temperature in combination with light intensity is reflected in the fact that
nearly all investigators report improved performance during summer and autumn months when
both temperature and light are at their maximum. The maximum practical temperature of
wastewater ponds is likely less than 30 C, indicating that most ponds operate at less than
optimum temperature for anaerobic activity (Oswald, 1968b; Oswald, 1996; Paterson and Curtis,
2005; Crites et al., 2006).
During certain times of the year, cooler, denser water remains at depth, while the warmer water
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stays at the surface. Water temperature differences may cause ponds to stratify throughout their
depth. As the temperature decreases during the fall and the surface water cools, stratification
decreases and the deeper water mixes with the cooling surface water. This phenomenon is called
mixis, or pond overturn. As the density of water decreases and the temperature falls below 4 C,
winter stratification can develop. When the ice cover breaks up and the water warms, a spring
overturn can also occur.
Pond overturn, which releases odorous compounds into the atmosphere, can generate complaints
from property owners living downwind of the pond. The potential for pond overturn during
certain times of the year is the reason why regulations may specify that ponds be located
downwind, based on prevailing winds during overturn periods, and away from dwellings.
1.3.5.3 Wind
Prevailing and storm-generated winds should be factored into pond design and siting as they
influence performance and maintenance in several significant ways:
• Oxygen transfer and dispersal: By producing circulatory flows, winds provide the
mixing needed for 02 transfer and diffusion below the surface of facultative ponds. This
mixing action also helps disperse microorganisms and augments the movement of algae,
particularly green algae.
• Prevention of short circuiting and reduction of odor events: Care must be taken during
design to position the pond inlet/outlet axis perpendicular to the direction of prevailing
winds to reduce short circuiting, which is the most common cause of poor performance.
Consideration must also be made for the transport and fate of odors generated by
treatment by-products in anaerobic and facultative ponds.
• Disturbance of pond integrity: Waves generated by strong prevailing or storm winds are
capable of eroding or overtopping embankments. Some protective material should
extend one or more feet above and below the water level to stabilize earthen berms.
• A study by Wong and Lloyd (2004) indicates that wind effects can reduce hydraulic
retention time.
1.3.6 Pond Nutritional Requirements
In order to function as designed, the wastewater pond must provide sufficient macro- and
micronutrients for the microorganisms to grow and populate the system adequately. It should be
understood that a treatment pond system should be neither overloaded nor underloaded with
wastewater nutrients.
1.3.6.1 Nitrogen
Nitrogen can be a limiting nutrient for primary productivity in a pond. Figure 1-3 represents the
various forms that TV typically takes overtime in these systems. The conversion of organic TV to
various other TV forms results in a total net loss (Assenzo and Reid, 1966; Pano and
Middlebrooks, 1982; Middlebrooks et al. 1982; Middlebrooks and Pano, 1983; Craggs, 2005).
This TV loss may be due to algal uptake or bacterial action. It is likely that both mechanisms
contribute to the overall total TV reduction. Another factor contributing to the reduction of total N
is the removal of gaseous NHs under favorable environmental conditions. Regardless of the
specific removal mechanism involved, NH^ removal in facultative wastewater ponds have been
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observed at levels greater than 90 percent, with the major removal occurring in the primary cell
of a multicell pond system (Middlebrooks et al., 1982; Shilton, 2005; Crites et al., 2006).
Time, days
Figure 1-3. Changes occurring in forms of N present in a pond environment under aerobic
conditions (Sawyer et al., 1994).
1.3.6.2 Phosphorus
Phosphorus (P) is most often the growth-limiting nutrient in aquatic environments. Municipal
wastewater in the United States is normally enriched in P even though restrictions on P-
containing compounds in laundry detergents in some states have resulted in reduced
concentrations since the 1970s. As of 1999, 27 states and the District of Columbia had passed
laws prohibiting the manufacture and use of laundry detergents containing P. However,
phosphate (PO4 ) content limits in automatic dishwashing detergents and other household
cleaning agents containing P remain unchanged in most states. With a contribution of
approximately 15 percent, the concentration of P from wastewater treatment plants is still
adequate to promote growth in aquatic organisms (Canadian Environmental Protection Act,
2009).
In aquatic environments, P occurs in three forms: (1) particulate P, (2) soluble organic P, and (3)
inorganic P. Inorganic P, primarily in the form of orthophosphate (OP (OR) 3), is readily utilized
by aquatic organisms. Some organisms may store excess P as polyphosphate. At the same time,
some PO4 is continuously lost to sediments, where it is locked up in insoluble precipitates
(Lynch and Poole, 1979; Craggs, 2005; Crites et al., 2006).
Phosphorus removal in ponds occurs via physical mechanisms such as adsorption, coagulation,
and precipitation. The uptake ofP by organisms in metabolic functions as well as for storage can
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also contribute to its removal. Removal in wastewater ponds has been reported to range from 30
- 95 percent (Assenzo and Reid, 1966; Pearson, 2005; Crites et al., 2006).
Algae discharged in the final effluent may introduce organic P to receiving waters. Excessive
algal "afterblooms" observed in waters receiving effluents have, in some cases, been attributed to
N and P compounds remaining in the treated wastewater.
1.3.6.3 Sulfur
Sulfur (S) is a required nutrient for microorganisms, and it is usually present in sufficient
concentration in natural waters. Because ^is rarely limiting, its removal from wastewater is
usually not considered necessary. Ecologically, S compounds such as hydrogen sulfide (H2S and
sulfuric acid (Ł[2804) are toxic, while the oxidation of certain S compounds is an important
energy source for some aquatic bacteria (Lynch and Poole, 1979; Pearson, 2005).
1.3.6.4 Carbon
The decomposable organic C content of a waste is traditionally measured in terms of its BODs,
or the amount of 02 required under standardized conditions for the aerobic biological stabili-
zation of the organic matter over a certain period of time. Since complete treatment by biological
oxidation can take several weeks, depending on the organic material and the organisms present,
standard practice is to use the BODs as an index of the organic carbon content or organic
strength of a waste. The removal of BODs is a primary criterion by which treatment efficiency is
evaluated.
BODs reduction in wastewater ponds ranging from 50 - 95 percent has been reported in the
literature. Various factors affect the rate of reduction of BODs. A very rapid reduction occurs in
a wastewater pond during the first five to seven days. Subsequent reductions take place at a
sharply reduced rate. BOD5 removals are generally much lower during winter and early spring
than in summer and early fall. Many regulatory agencies recommend that pond operations do not
include discharge during cold periods.
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CHAPTER 2
PLANNING, FEASIBILITY ASSESSMENT AND SITE SELECTION
2.1 INTRODUCTION
During the early planning stages of a wastewater management project, it is prudent to consider as
many alternatives as possible in order to select the technically appropriate and most cost
effective process. The feasibility of using pond systems described in this manual depends
significantly on site conditions, climate, and related factors. This chapter describes a sequential
approach that first determines potential feasibility, land area requirements for treatment and
potential sites. The second step is to evaluate these sites, based on technical and economic
factors, and to select one or more for detailed investigation. The final step involves detailed field
investigations, identification of the most cost-effective alternative and development of the
criteria needed for final design. Additional information can be found in Borowitzka &
Borowitzka (1988a, b), Crites et al., (2006), Reed et al., (1995) and Shilton (2005).
2.2 CONCEPT EVALUATION
Once the decision to use pond technology has been made, a further review of the types of ponds
appropriate to the site should be undertaken. A number of factors must be considered, including
but not limited to, required effluent quality, effluent discharge point, site topography, soils,
geology, climate and groundwater conditions. Specific information is needed related to
geotechnical characteristics, such as surface and groundwater hydrology, proximity to surface
water for discharge, site permeability and lining requirements, feasibility of siting the ponds
within or outside a flood plain, and presence of bedrock or groundwater within the depth of
excavation (Crites et al., 2006).
2.3 RESOURCES REQUIRED
The identification of potential sites is made using the information contained in publicly available
sources, such as existing maps and other published documents. Climate data, for example, can
be obtained from the National Oceanic and Atmospheric Administration (NOAA)
(http://www.noaa.gov/climate.html), at Worldclimate (http://www.worldclimate.com), and at
Weather Base (http://www.weatherbase.com). Solar maps can be found at the National
Renewable Energy Resources website (http://www.nrel.gov/gis/solar.html). Local or community
maps should indicate such features as topographical features, water features such as ponds and
streams, flood hazard zones, community layout and land use (e.g., residential, commercial,
industrial, agricultural, forest), existing water supply and sewage systems, anticipated areas of
growth and expansion, and soil types within the community and adjacent areas. Sources for these
maps include the U.S. Geological Survey (USGS) (http://www.usgs.gov/pubprod/), the Natural
Resources Conservation Service (NRCS) (http://www.soils.usda.gov/), state agencies, as well as
local planning and zoning agencies. Much of this work can now be done using the Geographical
Information System (GIS) and most of the layers are now available either for free or at low cost
(http://www.gis.com).
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2.3.1 Estimating Land Area Required for Treatment Ponds
The area estimate for a pond system will depend on the effluent quality required, the type of
pond system proposed and the geographic location. A facultative pond or an integrated system of
wastewater ponds in the southern United States will require less area than the same pond or
integrated pond system in the northern states. The pond areas given in Table 2-1 are for total
project area and include an allowance for dikes, roads and unused portions of the site (after Reed
et al., 1995 andF.B. Green, pers. comm.).
The land area required for a community wastewater flow of 3,785 m3/d (1 mgd) is estimated
below for three types of locations: a cold climate, a temperate climate (the mid-Atlantic states),
and a warm climate (the southern states). Allowances are made for any preliminary treatment
that might be required and for unused portions of the general site area.
Table 2-1. Land Area Estimates for 3,785 m3/d (1 mgd) Systems.
Treatment System
Aerobic
Facultative
Controlled Discharge
Partial-Mix Aerated
Complete-Mix Aeratec
AIWPS®***
North (ha*)
NA**
67
Mid-Atlantic (ha*)
NA**
44
South (ha*)
13
20
12
* 1 ha = 2.471 ac
** NA = not applicable
***See discussion of land requirements in Chapter 4.
2.4 SITE IDENTIFICATION
The information collected should be used in conjunction with current maps of the community
area to determine if there are potential sites for wastewater treatment within a reasonable
distance to the source. The potential sites should be plotted on the community maps. Local
knowledge regarding land use commitments and costs and a technical ranking procedure should
be brought into the decision-making process. Critical factors at this point are how close the site
is to the wastewater source and whether there is access to a reuse site (e.g., agricultural fields for
use as irrigation supply) or to surface water for final discharge. Characterization of the site soils
should be undertaken if percolation to groundwater is a disposal option.
2.4.1 Potential for Floods
Locating a wastewater system within a flood plain can be either an asset or a liability, depending
on the approach used for planning and design. Flood-prone areas may be undesirable because of
variable drainage characteristics and potential flood damage to the structural components of the
system. On the other hand, flood plains and similar terrain may be the only deep soils in the area
and the only location low enough to permit conveyance by gravity. If permitted by the
regulatory authorities, utilization of such sites for wastewater or sludge storage can be an integral
part of a flood-plain management plan. Off-site storage of wastewater or sludge should be
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included as a design feature if the site is to be flooded on an as-needed basis. An example of a
design of a wastewater treatment system located in a floodplain can be found in Chapter 4.
Maps of flood-prone areas have been produced by the USGS for many areas of the UnitedStates
as part of the Uniform National Program for Managing Flood Losses. The maps are based on the
standard 7.5' USGS topographic sheets. They identify areas with a potential of a l-in-100
chance of flooding in a given year. The hydrologic maps can be obtained from USGS
(http://edc2.usgs.gov/pubslists/booklets/usgsmaps/usgsmaps.php). Other detailed flood
information is available from local offices of the U.S. Army Corps of Engineers and flood-
control districts. If the screening process identifies potential sites in flood-prone areas, local
authorities must be consulted to identify regulatory requirements before beginning any detailed
site investigation. At the very least, in designing a system within a flood plain, incorporated tank
walls, structural openings, motor drives and pumps should be raised so that they are above the
100-year flood level.
2.4.2 Water Rights
Riparian water laws, primarily in states east of the Mississippi River, protect the rights of
landowners to use the water along a watercourse. Appropriative water rights laws in the western
states protect the rights of prior users of the water basin. Adoption of any of the pond concepts
for wastewater treatment can have a direct impact on water rights concerns:
• Site drainage, both quantity and quality, may be affected.
• A zero discharge system, or a new discharge location, will affect the quantity of flow in a
body of water where the discharge previously existed.
• Operational considerations for land treatment systems may alter the pattern and the
quality of discharges to a water body.
In addition to surface waters in well-defined channels or basins, many states also regulate or
control other superficial waters and the groundwater beneath the surface. State and local
discharge requirements for the proposed project should be determined prior to the development
of the design. If the project has the potential to generate legal questions, a water rights attorney
should be consulted.
2.5 SITE EVALUATION
The next phase of the site and system selection process involves developing field surveys to
confirm map data and field testing in order to provide the data needed for design. It also includes
making an estimate of capital and operation and maintenance costs so that the sites identified can
be compared. A design concept and a site are selected for final design based on these results.
Each site evaluation must include the following information:
• Property ownership, physical dimensions of the site, current and future land use
• Surface and groundwater conditions: location and depth of water supply wells and
injection wells, surface water flooding or surface water bodies within one mile of the
proposed site, fluctuation in groundwater levels, other potential drainage problems
• Quality and use of groundwater, e.g., is area designated as a wellhead protection area or
other critical recharge zone?
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• Characterization of the soil profile to the depth of the first limiting condition such as the
seasonal high water table, aquitard, or bedrock, or bottom of the excavation, whichever is
deeper
• Reclamation of the site describing the existing vegetation, historical causes for distur-
bance, previous reclamation efforts, historical site contamination from anthropogenic or
natural sources, need for grading or other terrain modification
• Current and future land use of adj acent properties
• Environmental impact and habitat evaluation
2.5.1 Soil and Groundwater Characterization
Table 2-2 presents a sequential approach to field testing to define the physical and chemical
characteristics of the on-site soils. In addition to the on-site test pits and borings, exposed soil
profiles in road cuts, borrow pits, and plowed fields on or near the site should be examined and a
preliminary geotechnical investigation of the highest ranked potential sites should be undertaken.
Backhoe test pits to a 3 m depth, or to 6 - 8 m for deeper ponds, such as AIWPS® Advanced
Facultative Pond with stable methane fermentation zones (Oswald and Green, 2000), are
recommended, where soil conditions permit, in each of the major soil types on the site. These
samples should be reserved for future testing. The walls of the test pit should be carefully
examined to define the characteristics of the soil (Reed and Crites, 1984a; U.S. EPA, 1980c; U.S.
EPA, 1984; Silva-Tulla and Flores-Berrones, 2005; Crites et al., 2006). The test pit should be
left open long enough to determine if there is groundwater seepage and the highest level attained
should be recorded. Equally important is the observation of any indication of seasonally high
groundwater, most typically demonstrated by mottled or hydric soils (Vasilas et al., 2010).
Soil borings should penetrate to below the groundwater table if it is within 10 - 15 m of the
surface. At least one boring should be located in every major soil type on the site. If generally
uniform conditions prevail, one boring for every 1 - 2 ha is recommended for large-scale
systems. For small systems (<5 ha), three to five shallow borings spaced over the entire site
should be sufficient.
Groundwater encountered during test borings should be analyzed for general chemistry (pH,
conductivity, nitrate, metals, and major ions using drinking water methods (see
http://www.epa.gov/ogwdw/methods/methods inorganic.pdf or 40 CFR 141) to establish
background conditions. Seeps, perched saturated zones, depth of mottled zones, and depth to the
seasonal high water table should be recorded on the site plan.
2.5.2 Buffer Zones
Prior to the site investigation, state and local requirements for buffer zones or setback distances
should be researched to ensure that there is adequate area on site or that additional acreage can
be obtained. Most requirements for buffer zones or separation distances are based on aesthetic
considerations and to avoid potential complaints. A number of studies have been conducted at
both conventional and land treatment facilities on aerosols and the results indicate that there is
very little, if any, health risk to adjacent populations (Sorber et al., 1976; Reed, 1979; Sorber et
al., 1984). Therefore, designing extensive buffer zones for aerosol containment is not
2-4
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recommended.
Most wastewater ponds and natural lakes are holo- or dimictic, overturning for a period during
the spring and fall, which brings deeper anaerobic or anoxic water and bacterial solids to the
surface, releasing volatile, odiferous compounds into the atmosphere. A typical requirement in
these cases is to locate such ponds at least 0.4 km from human habitations.
Table 2-2. Sequence of Field Testing, Typical Order, reading from left to right (Crites in Asano and
Pettygrove, 1984)
Comments
Type of Test
Data needed
Estimate
Then test for
Estimate
Number of
tests
Test Pits
Backhoe pit,
inspect road
cuts
Depth of profile,
texture,
structure,
restriction layers
Need for
hydraulic
conductivity
tests
Hydraulic
conductivity, if
needed
Loading rates
3-5/site, more
for large sites,
lack of soil
uniformity
Soil Borings
Drill or auger log
review of local
wells for soil
data and water
level
Depth to ground
water, depth to
barrier
Infiltration Soil Chemistry13
Tests3
Basin method0 if NRCSd
possible Surveyed
Infiltration rate Nitrogen,
phosphorus,
metals, other
potential site
specific
Groundwater
flow direction
Horizontal
conductivity, if
needed
Groundwater
mounding,
drainage needs
3-5/site, more
for lack of soil
uniformity
^ contaminants
Soil
capacity amendments,
crop limitations
Quality of any
percolate
Depends on
site, soil
uniformity,
character of
waste
2/site, more for
large site or lack
of soil uniformity
"Required only for land application of wastewater; some definition of subsurface permeability
needed for pond and sludge systems
bTypically needed for land application of sludges or wastewaters
cCritesetal., 2006
Natural Resources Conservation Service
2.6 SITE AND PROCESS SELECTION
At this point, the evaluation procedure will have identified potential sites for a particular
treatment alternative and field investigations will have been conducted to obtain data for the
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feasibility determination. Evaluation of the field data will determine whether the site
requirements are adequate. If site conditions are favorable, it can be concluded that the site is at
least a candidate for the intended concept. If only one site and related treatment concept emerge
from this screening process, the focus can shift to final design and perhaps additional detailed
field tests to support the design process. If more than one site for a particular concept, and/or
more than one concept remains technically viable after the screening process, it will be necessary
to do a preliminary analysis to identify the most cost-effective alternative.
The design criteria presented in later chapters should be used to develop the preliminary design
of the concept. The design should then be used as the basis for a preliminary cost estimate for
capital and operation/maintenance that should include the cost of purchasing the land as well as
pumping or transport costs to move the wastes from sources to the site. In many cases the final
selection of process or type of pond system will also be influenced by the social and institutional
acceptability of the proposed site and treatment facility to be developed on it.
2.7 DESIGN CRITERIA OF MUNICIPAL WASTEWATER TREATMENT PONDS
Most states have design criteria for wastewater treatment ponds, but the depth of detail provided
by each state varies widely (see Appendix A). Detailed sets of criteria are provided for the State
of Nebraska, and the State of Iowa as examples. The Recommended Standards for Wastewater
Facilities, known as the 10 States Standards, published by The Great Lakes-Upper Mississippi
River Board of State and Provincial Public Health and Environmental Managers (Health
Research, Inc., 2004), or a modification of these standards, is often cited as a reference.
2.8 STATE DESIGN STANDARDS
2.8.1 10 States Standards
The 10 States Standards recommend a minimum separation of 1.2 m between the bottom of the
pond and the maximum groundwater elevation and a minimum separation of 3 m between the
pond bottom and any bedrock formation. For a conventional facultative treatment pond system
design, an average five day biochemical oxygen demand (BODs) loading from 17-40 kg/ha/d
for the primary pond(s) with a detention time of 90 - 120 d is recommended. Controlled
discharge facultative treatment pond systems have different requirements (see Chapter 7).
For the development of final design parameters for aerated treatment pond systems, it is recommended
that actual experimental data be developed; however, the minimum detention time may be estimated
using the following formula applied separately to each aerated cell:
t= E/f2.3ki x(100-E)] (2-1)
where: t = detention time in days; E = percent of BODs to be removed in an aerated pond; and
kj = reaction coefficient, aerated pond, base 10. For normal domestic wastewater, the kj value
may be assumed to be 0.12/d at 20 °C and 0.06/day at 1 °C.
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Additional storage volume should be considered for sludge, and in northern climates, for ice
cover. If aeration equipment is used, it should be capable of maintaining a minimum dissolved
oxygen (DO) level of 2 mg/L in the ponds at all times (Health Research, Inc., 2004).
The 10 States Standards recommend that, at a minimum, a wastewater treatment pond system
consist of three cells designed to facilitate both series and parallel operations. The maximum size
of a conventional pond cell should be 16 ha. Two-cell systems may be utilized in very small
installations. Guidance is also provided on pond construction details.
2.8.2 Summary of Other Criteria
Other criteria to be considered are briefly discussed here.
Freeboard: The minimum and maximum recommended freeboard varies from 0.6 - 0.9
m. Some states allow a 0.3 m freeboard for small systems, while others specify 0.6 m.
Pond Bottom: The majority of the states include a detailed description of the materials
that are acceptable for sealing the pond bottom and sides of the dikes. Permissible seepage rate
or hydraulic conductivity is specified in all pond criteria; an emphasis is placed on groundwater
protection. Natural earth, bentonite, asphalt, concrete and synthetic liners are acceptable in most
cases.
Flow Distribution: Design of structures split hydraulic and organic loads effectively
between two primary cells is a common requirement. This is frequently expanded to include
multiple inlet points to accomplish even distribution of the flow. Most states allow one
discharge point from secondary cells, but frequently recommend multiple outlets from primary
cells.
Influent Discharge Apron: A common requirement for the influent discharge to a
primary cell is that the flow should enter a shallow, saucer-shaped depression and that the end of
the discharge line rest on a concrete apron large enough to prevent soil erosion.
Piping and Pipe Connections: In most states, the acceptable type of piping materials is
specified, such as ductile iron, plastic or lined pipes. Where pipes penetrate the pond seal, anti-
seep collars or similar devices should be used to prevent leaks around the pipes.
Hydraulic capacity frequently is specified as 250 percent of the design maximum day
flow rate of the system. Most states specify that the piping must allow for parallel and series
operation of multi-cell systems, and that provisions for by-passing each cell be provided.
Provisions for draining each cell are also usually required.
Settling Ponds: Settling ponds may sometimes be referred to as polishing ponds, but
they are not synonymous. A polishing pond is any pond in the treatment train that follows the
facultative pond. A settling pond is usually placed at the beginning of the treatment series, but
may also be a pond at the end of the system. The amount of time that effluent is retained in a
settling pond can vary from 24 hours to some proportion of the time it takes the water to move
through entire system. This can result in a hydraulic residence time (HRT) greater than 10-15
d. Most state standards distinguish between the two, but may not provide an explanation of the
need for a correctly designed settling pond to help control algae in the effluent before it is
discharged (Green, 2009). An HRT of 2 days at average design flow rate will provide better
control.
Miscellaneous: All of the criteria specify that some type of fencing be put in place to
limit access and discourage trespassing. Some states require only a fence with a few strands of
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barbed wire to prevent animals from entering the site. Others are more conservative and specify
that a chain-link fence with barbed wire strands at the top be installed to discourage access.
Gates should be of sufficient width to allow maintenance vehicles to enter the facility and should
be provided with a lock.
An all-weather road to the pond site should be built and maintained to allow year-round access
for operation and maintenance. The requirement that permanent warning signs are to be placed
conspicuously around the site designating the nature of the facility is included in all the state
criteria. Signs should be posted every 150 m along the perimeter of the facility.
Flow measurement parameters vary, but in all cases, some type of flow measuring device is
recommended or required. Groundwater monitoring wells are required by most states. Pond
level gauges are specified by most states. A service building that contains a laboratory and space
for storage and maintenance of equipment is required in most criteria.
2.8.3 Criteria for Types of Ponds
As shown in Appendix A, many state guidances do not indicate what criteria are specific to the
type and proposed operation schedule of a pond system (e.g., anaerobic, partial-mix, complete-
mix, controlled discharge or hydrographically controlled). When seeking advice as to the factors
that need to be considered in a specific pond design, it is advisable to consult with the relevant
state regulatory agency. For general guidance, the Minnesota, Nebraska, South Dakota,
Montana, Wyoming, Tennessee and several other state criteria provide sufficiently detailed
information that can be used to develop an appropriate design.
2-8
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CHAPTER 3
DESIGN OF MUNICIPAL WASTEWATER TREATMENT PONDS
3.1 INTRODUCTION
Wastewater treatment ponds existed and provided adequate treatment long before they were
acknowledged as an "alternative" technology to mechanical plants in the United States. With
legislative mandates to provide treatment to meet certain water quality standards, engineering
specifications designed to meet those standards were developed, published and used by
practitioners. The basic designs of the various pond types are presented in this chapter. Design
equations and examples are found in the Appendix C.
3.2 ANAEROBIC PONDS
An anaerobic pond is a deep impoundment, essentially free of DO. The biochemical processes
take place in deep basins, and such ponds are often used as preliminary treatment systems.
Anaerobic ponds are not aerated, heated or mixed.
Anaerobic ponds are typically more than eight feet deep. At such depths, the effects of oxygen
(02) diffusion from the surface are minimized, allowing anaerobic conditions to dominate. The
process is analogous to that of a single-stage unheated anaerobic digester. Preliminary treatment
in an anaerobic pond includes separation of settleable solids, digestion of solids and treatment of
the liquid portion. They are conventionally used to treat high strength industrial wastewater or to
provide the first stage of treatment in municipal wastewater pond treatment systems.
Anaerobic ponds have been especially effective in treating high strength organic wastewater.
Applications include industrial wastewater and rural community wastewater treatment systems
that have a significant organic load from industrial sources. BOD5 removals may reach 60
percent. The effluent cannot be discharged due to the high level of BODs that remains.
Anaerobic ponds are not an appropriate design for locations that do not have sufficient land
available. The potential to give off odors, if not properly managed, makes them less a reliable
choice for municipal wastewater treatment. Finally, the anaerobic process may require long
retention times, especially in cold climates, as anaerobic bacteria are inactive below 15° C. As a
result, anaerobic ponds are not widely used for municipal wastewater treatment in the northern
United States.
Because anaerobic ponds are deep and generally have a relatively longer hydraulic residence
time (HRT), so solids settle, retained sludge is digested, and BODs concentration is reduced.
Raw wastewater enters near the bottom of the pond and mixes with the active microbial mass in
the sludge blanket. Anaerobic conditions prevail except for a shallow surface layer in which
excess undigested grease and scum are concentrated. Sometimes aeration is provided at the
surface to control odors. An impervious crust that retains heat and odors will develop if surface
aeration is not provided. The discharge is located near the side opposite the influent. Anaerobic
ponds are usually followed by aerobic or facultative ponds to provide additional treatment.
3-1
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The anaerobic pond is usually preceded by a bar screen and a Parshall flume with a flow recorder
to determine the inflow. A cover can be provided to trap and collect CH^ a by-product of the
process, for use elsewhere.
3.2.1 Microbiology
Anaerobic microorganisms convert organic materials into stable products, such as CO2 and CH.4.
The degradation process involves two separate but interrelated phases: acid formation and
methane production. During the acid phase, bacteria convert complex organic compounds
(carbohydrates, fats, and proteins) to simple organic compounds, mainly short-chain volatile
organic acids (acetic, propionic, and lactic acids). The anaerobic bacteria involved in this phase
are called "acid formers," and are classified as non-methanogenic microorganisms. During this
phase, the chemical oxygen demand (COD) is low and BODs reduction occurs, because the
short-chain fatty acids, alcohols, and other organic compounds can be used by many aerobic
microorganisms.
The methane production phase involves an intermediate step. First, bacteria convert the short-
chain organic acids to acetate, hydrogen gas (#2), and CO2. This intermediate process is referred
to as acetogenesis. Subsequently, several species of strictly anaerobic bacteria called "methane
formers" convert the acetate, H2, and CC>2 into CH4 through one of two major pathways. This
process is referred to as methanogenesis. During this phase, waste stabilization occurs, indicated
by the formation of CH.4. The two major pathways of methane formation are
1) the breakdown of acetic acid to form methane and carbon dioxide:
CH3COOH -> CH4 + CO2 (3-1)
and
2) the reduction of carbon dioxide by hydrogen gas to form methane:
CO2 + 4H2 -> CH4 + 2 H2O. (3-2)
3.2.2 Equilibrium
When the system is working properly, the two phases of degradation occur simultaneously in
dynamic equilibrium. The volatile organic acids are converted to methane at the same rate that
they are formed from the more complex organic molecules. The growth rate and metabolism of
the methanogenic bacteria can be adversely affected by small fluctuations in/?H substrate
concentrations and temperature, but the performance of acid-forming bacteria is more tolerant of
a wide range of conditions. When anaerobic ponds are stressed by shock loads or temperature
fluctuations, CH4 bacteria activity occurs more slowly than the acid formation and an imbalance
occurs. Intermediate volatile organic acids accumulate and the/>H drops. The methanogens are
further inhibited and the process eventually fails without corrective action. For this reason, the
CH4 formation phase is the rate-limiting step and must not be inhibited. For an anaerobic pond to
function properly, the design must incorporate the limiting characteristics of these methanogens.
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3.2.3 Establishing and Maintaining Equilibrium
The system must operate at conditions favorable for the performance of methanogenic bacteria.
Ideally, temperatures should be maintained within the range of 25 to 40° C. Anaerobic activity
decreases rapidly at temperatures below 15° C, and virtually ceases when water temperature
drops below freezing (0° C). The/>H value should range from 6.6 to 7.6, and should not drop
below 6.2 as CH.4 bacteria cannot function below this level. Sudden fluctuations ofpH will upset
methanogenic activity and inhibit pond performance. Alkalinity should range from 1,000 to
5,000 mg/L.
Volatile acid concentration is an indicator of process performance. Ideally, volatile acid
concentrations will be low if the pond system is working properly and dynamic equilibrium
between acid formation and consumption is maintained. As a general rule, concentrations should
be less than 250 mg/L. Inhibition occurs at volatile acid concentrations in excess of 2,000 mg/L.
Table 3-1 presents optimum and extreme operating ranges for CH.4 formation. The rate of C//4
formation drops dramatically outside these ranges. In addition to adhering to these guidelines,
sufficient nutrients, such as N and P must be available. Concentrations of inhibitory substances,
including NHs and calcium, should be kept to a minimum. High concentrations of these
inhibitors will reduce biological activity. Concentration of free NHs in excess of 1,540 mg/L will
result in severe toxicity, but concentrations ofNH4+ must be greater than 3,000 mg/L to produce
the same effect. Maintaining apH of 7.2 or below will ensure that most NHs will be in the form
ofNH4+, so that higher concentrations can be tolerated with little effect. Table 3-2 provides
guidelines for acceptable ranges of other inhibitory substances.
Table 3-1. Ideal Operating Ranges for Methane Fermentation.
Variable
Temperature, °C
PH
Oxidation-Reduction
Potential, MV
Volatile Acids, mg/L as Acetic
Alkalinity, mg/L as CaCO3
Optimal
30-35
6.8-7.4
-520 to -530
50-500
2000-3000
Extreme
25-40
6.2-7.8
-490 to -550
2000
1000-5000
Table 3-2. Concentrations of Inhibitory Substances (Parkin and Owen, 1986.)
Substance
Sodium
Potassium
Calcium
Magnesium
Sulfides
Moderately Inhibitory (mg/L)
3,500-5,500
2,500-4,500
2,500-4,500
1,000-1,500
200
Strongly Inhibitory (mg/L)
8,000
12,000
8,000
3,000
>200
Anaerobic ponds produce undesirable odors unless provisions are made to oxidize the escaping
gases. Gas production must be minimized (sulfate [SOi2]) concentration must be reduced to less
3-3
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than 100 mg/L) or aeration should be provided at the surface of the pond to oxidize the escaping
gases. Aerators must not introduce DO to depths below the top 0.6 - 0.9 m (2 - 3 ft) so that
anaerobic activity at depth is not inhibited.
Another option is to locate the pond in a remote area. A relatively long detention time is required
for organic stabilization due to the slow growth rate of the CH.4 formers and sludge digestion.
Wastewater seepage into the groundwater may be a problem. Providing a liner for the pond can
help avoid this problem.
Advantages and Disadvantages
The advantages of anaerobic ponds are several: sludge removal is infrequently needed; 80-90
percent BODs removal can be expected; the energy requirements to run the plant are low or
none; and operation and maintenance (O&M) is relatively uncomplicated.
On the other hand, they are not designed to produce effluent that can be discharged; the ponds
can emit unpleasant odors; and the rate of treatment is dependent on climate and season.
3.2.4 Design Criteria
The design of anaerobic ponds is not well defined and a widely accepted overall design equation
does not exist. Design is often based on organic loading rates, surface or volumetric loading rates
and HRT derived from pilot plant studies and observations of existing operating systems. States
in which ponds are commonly used often have regulations governing their design, installation,
and management. For example, state regulations may require specific organic loading rates,
detention times, embankment slope ratio of 1 to 3 to 1 to 4, and maximum allowable seepage of
1 to 6 mm/d.
3.2.5 Performance
System performance depends on loading, temperature, and whether thepR is maintained within
the optimum range. Tables 3-3 and 3-4 show expected removal efficiencies for municipal
wastewaters. In cold climates, detention times as great as 50 days and volumetric loading rates as
low as 0.04 kg BOD5/m3/d may be required to achieve 50 percent reduction in BODs. Effluent
TSS will range between 80 and 160 mg/L. The effluent is not suitable for direct discharge to
receiving waters. Pond contents that are black indicate that it is functioning properly.
Table 3-3. BODs Reduction as a Function of Detention Time for Temperatures Greater
than 20 °C (World Health Organization, 1987)
Detention Time
(Days)
1
2.5
5
BODs Reduction
(Percent)
50
60
70
3-4
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Table 3-4. BODs Reduction as a Function of Detention Time and Temperature (World
Health Organization, 1987)
Temperature
(°Celsius)
10
10-15
15-20
20-25
25-30
Detention Time
(Days)
5
4-5
2-3
1-2
1-2
BOD5 Reduction
(Percent)
0-10
30-40
40-50
40-60
60-80
3.2.6 Operation and Maintenance
Operation and maintenance requirements of an anaerobic pond are minimal. A daily grab sample
of influent and effluent should be taken and analyzed to ensure proper operation. Aside from
sampling, analysis, and general upkeep, the system is virtually maintenance-free. Solids
accumulate in the pond bottom and require removal infrequently (5-10 years), depending on the
amount of inert material in the influent and the temperature. Sludge depth should be measured
annually.
3.2. Costs
The primary costs associated with constructing an anaerobic pond are the cost of the land,
building earthwork appurtenances, constructing the required service facilities, and excavation.
Costs for forming the embankment, compacting, lining, service road and fencing, and piping and
pumps must also be considered. Operating costs and energy requirements are minimal.
3.2.8 Design Models and Example Calculations
Anaerobic treatment ponds are typically designed on the basis of volumetric loading rate and
HRT. Although often done, it is probably inaccurate to design on the basis of surface loading
rate. Design should be based on the volumetric loading rate, temperature of the liquid, and the
HRT. Areal loading rates that have been used around the world are shown in Table 3-5. It is
possible to approximate the volumetric loading rates by dividing by the average depth of the
ponds and converting to the proper set of units.
In climates where the temperature exceeds 22 °C, the following design criteria should yield a
BOD5 removal of 50 percent or better (World Health Organization, 1987).
Volumetric loading up to 300 g BOD5/m /d
HRT of approximately 5 d
Depth between 2.5 and 5 m
In cold climates, detention times as great as 50 d and volumetric loading rates as low as 40 g
BOD5/m /d may be required to achieve 50 percent reduction in BODs
3-5
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Table 3-5. Design and Operational Parameters for Anaerobic Ponds Treating Municipal
Wastewater (See p. xiv for Conversion Table)
ALR BOD5
Ibs/ac/d
Summer
360
280
100
170
560
400
900-
1200
220-600
500
Winter
400
100
675
Est. VLR
lbs/1000ft3
Summer
2.34
1.84
0.66
1.11
3.67
5.17-6.89
Winter
2.62
3.88
0.51-
1.38
1.15
Removal
Percent
Summer
75
65
86
52
89
70
60-70
70
Winter
60
Depth
Ft
3-4
3-4
3-4
3-4
3-4
3-5
8-10
8-12
8-12
HRT
D
2-5
30-50
15-160
5
2(s)
5(w)
Refs.
Parker,
1970
Parker,
1970
Parker,
1970
Parker,
1970
Parker,
1970
Oswald,
1968b
Parker et
al., 1959
Eckenfelder,
1961
Cooper,
1968
Oswald et
al., 1967
Malina and
Rios, 1976
ALR = areal loading rate
VLR = volumetric loading rate
See p. xiv for conversion table.
An example of an approach to the design of anaerobic ponds has been presented by Oswald
(1996) (Figure 3-1). In his Advanced Integrated Wastewater Pond System® (see Chapter 4),
Oswald incorporates a deep anaerobic pond within a facultative pond. The anaerobic pond
design is based on organic loading rates that vary with water temperature in the pond, and the
design is checked by determining the volume of anaerobic pond provided per capita, which is
one of the methods used for the design of separate anaerobic digesters. An example of this
design approach is presented in Appendix C (Example C-3-1), along with another example using
volumetric loading or detention times (see Example C-3-2) (Crites et al., 2006).
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Figure lO-t. Methods of"t;rei»tinK a DIE**""" Chamber in
Bottom of an Anaerobic I.agoon (Oswald,
Figure 3-1. Method of creating a digestion chamber in the bottom of an anaerobic pond
(Oswald, 1968).
3.3 FACULTATIVE PONDS
3.3.1 Description
The technology associated with conventional facultative ponds to treat municipal and industrial
wastewater has been in widespread use in the United States for 100 years. These ponds are
usually 1.2 - 2.4 m in depth and are not mechanically mixed or aerated. The layer of water near
the surface contains sufficient DO from atmospheric re-aeration and photo synthetic oxygenation
by microalgae growing in the photic zone to support the growth of aerobic and facultative
bacteria that oxidize and stabilize wastewater organics. The bottom layer of a conventional
facultative pond includes sludge deposits that are decomposed by anaerobic bacteria. These
shallow ponds tend to integrate carbon and primary solids undergoing acetogenic fermentation
but only intermittent methane fermentation. The intermediate anoxic layer, called the
facultative zone, ranges from aerobic near the top to anaerobic at the bottom. These three strata
or layers may remain stable for months due to temperature-induced water density differentials,
but normally twice a year during the spring and fall seasons, conventional facultative ponds will
overturn, and the three strata will mix bottom to top, top to bottom. This dimictic overturn
inhibits CH.4 fermentation by 02 intrusion into the bottom anaerobic stratum, and, as a result, C is
integrated rather than being converted into biogas (Oswald et al., 1994).
The presence of algae, which release 02 as they disassociate water molecules photochemically to
assimilate hydrogen during photosynthesis, is essential to the successful performance of
conventional, as well as advanced, facultative ponds. On warm, sunny days, the 02 concentration
in the aerobic zone can exceed saturation levels. As the algae take up C02, thepR of the near-
surface water can exceed 10, creating conditions favorable for ammonia removal via
volatilization (see Chapter 5). At night, when the algae are not photosynthesizing, 02 levels
decrease. Oxygen andpH levels shift together from a maximum in daylight hours to a minimum
at night. The 02 in the upper layers of the facultative pond is used by aerobic and facultative
bacteria to stabilize organic material. Anaerobic fermentation, which takes place in the absence
of 02, is the dominant activity in the bottom layer of the pond. In cold climates, both
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oxygenation and fermentation reaction rates are significantly slower during the winter and early
spring so that effluent quality may be reduced to the equivalent of primary effluent when an ice
cover persists on the water surface. As a result, northern United States and Canadian provinces
prohibit discharge from facultative ponds in the winter months.
3.3.2 Applicability
Conceptually, conventional facultative ponds are well suited for rural communities and industries
where land costs are not a limiting factor. Conventional facultative ponds have been used to treat
raw, screened, or primary settled municipal wastewater as well as higher strength biodegradable
industrial wastewater. They represent a reliable and easy-to-operate process that is cost effective.
3.3.3 Advantages and Disadvantages
The advantages of facultative ponds include infrequent need for sludge removal; effective
removal of settleable solids, BOD5, pathogens, fecal coliform, and, to a limited extent, NH3.
They are easy to operate and require little energy, particularly if designed to operate with gravity
flow.
The disadvantages include higher sludge accumulation in shallow ponds or in cold climates and
variable seasonal NHs levels in the effluent. Emergent vegetation must be controlled to avoid
creating breeding areas for mosquitoes and other vectors. Shallow ponds require relatively large
areas. During spring and fall dimictic turnover, odors can be an intermittent problem.
3.3.4 Design Criteria
Facultative pond systems may be relatively simple mechanically, but the biological and chemical
reactions taking place within them are more complex than those in conventional mechanical
wastewater treatment systems. Typical design features needed to operate facultative ponds
include the use of linings to control seepage to groundwater and emergent plant growth; proper
design and location of inlet and outlet structures; and hydraulic controls, floating dividers, and
baffles.
Many existing conventional facultative ponds are large, single-cell systems with inlets located
near the center of the cell. This configuration can result in short-circuiting and ineffective use of
the system design volume. A multiple-cell system with at least four cells in series, with
appropriate inlet and outlet structures, is strongly recommended (Mara and Cairncross, 1989).
Most states have design criteria that specify the areal or surface organic loading rate expressed in
kg/ha/d or Ibs/ac/d and/or the hydraulic loading rate expressed in m/d or ft/d residence time.
Typical organic loading values range from 15-80 kg/ha/d. Detention times range from 20 - 180
days, and can approach 200 days in northern climates where discharge restrictions prevail.
Effluent BODs < 30 mg/L can usually be achieved, while effluent TSS may range from < 30
mg/L to more than 100 mg/L, depending on the algal concentrations and discharge structure
design.
A number of empirical and rational models exist for the design of simple conventional and in-
series facultative ponds. These include first order plug flow, first order complete mix, and
models proposed by Gloyna (1976), Marais (1961), Oswald (1968b), and Thirumurthi (1974).
3-8
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All provide reasonable designs, as long as the basis for the formula is understood, appropriate
parameters are selected, and the hydraulic detention and sludge retention characteristics of the
system are known. This last element is of critical importance because short-circuiting in a poorly
designed cell can result in detention time of 50 percent or less than the theoretical design value.
3.3.5 Design Methods
3.3.5.1 Areal Loading Rate Method
A series of detailed evaluations of facultative pond systems conducted by EPA remains a useful
data set for pond systems performance in the United States (U.S. EPA, 1975). Studies of
systems in other countries bring the literature up to date (Racault and Boutin, 2001; Kotsovinos
et al., 2004; Oliveira and von Sperling, 2008; von Sperling and Oliveira, 2009). A comparison
of the state design criteria for each location and actual design values for organic loading and
HRT for four facultative pond systems evaluated by the EPA (Middlebrooks et al., 1982) are
presented in Table 3-6. Many of the design flaws in the systems referenced in Table 3-6 have
been corrected since 1983.
The following surface organic loading rates for various climatic conditions are recommended for
use in designing facultative pond systems. For average winter air temperatures above 15 °C, a
BODs loading rate range of 45 - 90 kg/ha/d is recommended. When the average winter air
temperature ranges between 0 - 15 °C the organic loading rate should range between 22 - 45
kg/ha/d. For average winter temperatures below 0 °C the organic loading rates should range
from 11 - 22 kg/ha/d.
A review of design standards in 2006 showed that most states have design criteria for organic
loading and/or HRT for facultative ponds with many now incorporating NH4 conversion and P
removal requirements. The principal changes since a survey by Canter and Englande (1970) are
the nutrient removal requirements.
Table 3-6. Design and Performance Data from U.S. EPA Pond Studies (Middlebrooks et
al., 1982).
Location
P'borough1
Kilmichael2
Eudora3
Corinne4
Organic Load (kg BOD5/ha/d)
State
Design
39.3
56.2
38.1
45.0*
Design
19.6
43.0
38.1
36.2
Actual
16.2
17.5
18.8
29.7*
14.6**
Theoretical Detention Time
State
Design
None
None
None
180
Design
57
79
47
180
Actual
107
214
231
70
88***
Month 30
mg/L
exceeded
10,2,3,4
11, 7
3,4, 8
None
1New Hampshire; Mississippi; 3Kansas; "Utah.
*Primary cell; ** Entire system; ***Estimated from dye study.
The BODs loading rate in the first cell is usually limited to 40 kg/ha/d or less, and the total FtRT
in the system is 120 - 180 days in climates where the average winter air temperature is below 0
3-9
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°C. In mild climates, where the winter temperature is greater than 15 °C, loadings on the
primary cell can be 100 kg/ha/d (see Example C-3-3 in Appendix C).
3.3.5.2 Comparison of Facultative Pond Design Models
Because there are many possible approaches to the design of facultative ponds and given the lack
of adequate performance data for the latest designs, it is not possible to recommend one approach
over the others. An evaluation of the design methods presented above, with operational data
referenced in Table 3-6 did not indicate that any of the models are superior to the others in
predicting performance (Middlebrooks, 1987). Other reviews of facultative pond systems based
on more limited data sets have reached similar conclusions (Pearson and Green, 1995). Each of
the models was used to design a facultative pond for the conditions presented in Example C-3-3;
the results are summarized at the end of the example (see Appendix C).
While it is difficult to make direct comparisons, an examination of the HRTs and total volume
requirements calculated by all of the methods show considerable consistency if the reaction rates
are selected carefully. The major limitation of all these methods is the selection of a reaction rate
constant or other factors in the equations. Appropriate reaction rates must be selected, but if the
pond hydraulic system is designed and constructed so that the theoretical HRT is approached,
reasonable success can be assured with all of the design methods. Short-circuiting is the greatest
deterrent to consistent pond performance. The importance of the hydraulic design of a pond
system cannot be overemphasized.
The surface loading rate approach to design requires a minimum of input data, and is based on
operational experiences in various geographical areas of the United States. It is probably the
most conservative of the design methods, but the hydraulic design should be included as well.
The Gloyna loading design method achieves 80 to 90 percent BOD5 removal efficiency, and it
assumes that solar energy for photosynthesis is above the saturation level. Provisions for
removal outside this range are not anticipated; however, adjustments for other solar conditions
can be calculated. Mara (1975) provides a detailed critique of the method.
3.3.6 Performance
Overall, facultative pond systems are simple to operate, but may be variable in performance;
BODs removal can range up to 75 percent; TSS may exceed 150 mg/L; NHs removal can be
significant (up to 90 percent) depending on temperature, pH and detention time in the system,
except in winter; approximately 50 percent/1 removal can be expected under high/>H conditions;
and pathogens and coliform removal is effective, depending on temperature and detention time.
Limitations to be considered include the fact that algae in the effluent may increase TSS above
the 30 mg/L limit for TSS; low temperatures and ice formation will limit process efficiency; and
odors may be a problem in the spring and fall.
3.3.7 Operation and Maintenance
Most facultative ponds are designed to operate by gravity flow. The system requires less
maintenance and has lower associated energy costs because pumps and other electrically
powered devices may not be required. Although some analysis is essential to ensure proper
3-10
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operation, an extensive sampling and monitoring program is usually not necessary. Regular
observation of impoundment earth works must be performed to monitor for excavation by
burrowing animals. See Chapter 9 for more details on operation and maintenance.
3.3.8 Common Modifications
A common modification to facultative ponds is to operate them in the controlled discharge mode,
where discharge is prohibited during the winter months in cold climates and/or during peak algal
growth periods in the summer. In this approach, each cell in the system is isolated and
discharged sequentially. A similar modification, the hydrograph controlled release (HCR),
retains treated wastewater in the pond until flow volume and conditions in the receiving stream
are adequate for discharge. A recently developed physical modification uses plastic curtains,
supported by floats and anchored to the bottom, to divide ponds into multiple cells and/or to
serve as baffles to improve hydraulic conditions. Another modification uses a floating plastic
grid to support the growth of duckweed (Lemna spp.) on the surface of the final cell in the pond
system, which restricts light penetration and reduces algal growth (with sufficient detention time,
>20 d), improving the final effluent quality. These types of modifications are discussed in detail
in Chapter 7.
3.3.9 Costs
Cost information for facultative ponds varies significantly. Construction costs include land
purchase, excavation, grading, berm construction, and inlet and outlet structures. If the soil is
permeable, an additional cost for lining should be considered. See Chapter 8 for discussion of
costs associated with construction of pond systems.
3.4 AERATED POND SYSTEMS
3.4.1 Partial Mix Aerated Ponds
Aerobic ponds are classified by the amount and source of 02 supplied. In aerated systems, 02 is
supplied mainly through mechanical or diffused aeration rather than by algal photosynthesis. The
submerged systems can include perforated tubing or piping, with a variety of diffusers attached.
A partial mix system provides only enough aeration to satisfy the 02 requirements of the system.
It does not provide energy to keep all solids in suspension. In some cases, the initial cell in a
system might be a complete mix unit followed by partial mix and settling cells. A complete mix
system requires about 10 times the amount of energy needed for a similarly sized partial mix
system.
Some solids in partial mix ponds are kept in suspension to contribute to overall treatment. This
allows for anaerobic fermentation of the settled sludges. Partial mix ponds are also called
facultative aerated ponds and are generally designed with at least three cells in series; total
detention time depends on water temperature. The ponds are constructed to have a water depth of
up to 6 m to ensure maximum 02 transfer efficiency. In most systems, aeration is not applied
uniformly over the entire system.
Typically, the most intense aeration (up to 50 percent of the total required) is used in the first
cell. The final cell may have little or no aeration to allow settling to occur. In some cases, a small
separate settling pond is provided after the final cell. Diffused aeration equipment typically
3-11
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provides about 3.7 - 4 kg 02/kW/hr and mechanical surface aerators are rated at 1.5 - 2.1 kg
02/kW/hr. Consequently, diffused systems are somewhat more efficient than non-aerated ponds,
but also require a significantly greater installation and maintenance effort.
Aerobic ponds can reliably produce an effluent to achieve BODs and TSS < 30 mg/L if a settling
pond is in place at the end of the system. Additionally, significant nitrification will occur during
the summer if there is adequate DO. Many systems designed only for BOD5 removal fail to meet
discharge standards during the summer because of a shortage of DO. Both nitrification of NHs
and BODs removal require 02. To achieve regulatory limits for the two parameters in heavily
loaded systems, pond volume and aeration capacity beyond that provided for BODs removal
alone are required. It is generally assumed that 1.5 kg of 02 will treat 1 kg of BOD5. About 5 kg
of 02 are theoretically required to convert 1 kg of NHs to NO3'.
3.4.1.1 Applicability
Aerated ponds are well suited for small communities and industries and require less land. They
are usually designed with a shorter retention time. They have been used to treat raw, screened or
primary settled municipal wastewater, as well as higher strength biodegradable industrial
wastewater. The process is reliable, relatively easy to operate and cost effective.
3.4.1.2 Advantages and Disadvantages
The advantages include reliable BODs removal; significant nitrification ofNHs possible with
sufficient mean cell resident time; treatment of influent with higher BODs in less space; and
reduced potential for unpleasant odors.
Aerated ponds are more complicated to design and construct, which increases capital and O&M
costs. A larger staff is needed for whom training must be provided on a regular basis. Finally,
sludge removal is more frequent and requires secondary treatment for disposal off-site.
3.4.1.3 Design Methods
The basic approach to the design of partial mix aerobic ponds has not changed since the early
1980's. The most notable innovations have been the placement of floating plastic partitions in
the ponds to improve the hydraulic characteristics and the development of a wider selection of
more efficient aeration equipment (Water Environment Federation, 2001). Given the importance
of the hydraulic characteristics, retaining redundancy in the design of aerobic pond systems is
still strongly encouraged. Operation and maintenance costs associated with aerobic pond
systems often are not included when communities compare system options. The initial cost of a
system built without redundancy is lower in the short term. Systems that include flexibility in
operation in the long run, however, greatly reduce the actual cost to the environment and the
owner.
In partial mix systems, the aeration serves to provide only an adequate 02 supply, and there is no
attempt to keep all of the solids in suspension. Although some of the solids are suspended,
anaerobic degradation of the organic matter that settles does occur.
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3.4.1.4 Partial Mix Design Model
Although the pond is partially mixed, it is conventional to estimate the BODs removal using a
complete mix model and first order reaction kinetics. Studies by Middlebrooks et al. (1982) have
shown that a plug flow model and first order kinetics more closely predict the performance of
these ponds when either surface or diffused aeration is used. However, most of the ponds
evaluated in this study were lightly loaded and the calculated reaction rates are very
conservative, as it seems that the rate decreases as the organic loading decreases (Neel et al.,
1961). Without additional data to support theoretical design reaction rates, it is necessary to
design partial mix ponds using complete mix kinetics.
The design model using first order kinetics and operating n number of equal sized cells in series
is given by Equation 3-3 (Middlebrooks et al. 1982; 10 States Standards, 2004; Water
Environment Federation, 2001; Crites et al., 2006).
Ce= I (3-3)
Co [1 + (kt/n) ]"
Where:
Cn = effluent BODs concentration in cell n, mg/L
C0 = influent BOD5 concentration, mg/L
k = first order reaction rate constant /d
= 0.276 day"1 at 20° C (assumed to be constant in all cells)
t = total hydraulic residence time in pond system, d
n = number of cells in the series
If other than a series of equal volume ponds are to be employed and varying reaction rates
are expected, the following general equation should be used:
where hi, k2,...kn are the reaction rates in cells 1 through n (all usually assumed to be equal
without additional data) and tj, t2,...tn are the hydraulic residence times in the respective cells.
Mara (1975) has shown that a number of equal volume reactors in series is more efficient than
unequal volumes; however, due to site topography or other factors, there may be sites where it is
necessary to construct cells of unequal volume.
3.4.1.5 Temperature Effects
The influence of temperature on the reaction rate is defined by Equation 3-5.
K/j' — 20
(3-5)
Where:
hi = reaction rate at temperature T/d
&2o = reaction rate at 20° C/d
3-13
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Q = temperature coefficient = 1.036
o
Tw = temperature of pond water, C
The pond water temperature (Tw) can be estimated using the following equation developed by
Mancini and Barnhart (1976).
Tv,=AfT+QTL (3-6)
Af+Q
Where:
o
Tw = pond water temperature, C
Ta = ambient air temperature, C
A = surface area of pond, m2
/ = proportionality factor = 0.5
Q = waste water flow rate, m3/d
An estimate of the surface area is made based on Equation 3-4, corrected for temperature, and
the temperature is calculated using Equation 3-6. After several iterations, when the water
temperature used to correct the reaction rate coefficient agrees with the value calculated with
Equation 3-6, the detention time in the system can be determined.
3.4.1.6 Selection of Reaction Rate Constants
The selection of ak value is the critical decision in the design of any pond system. A design
value of 0.12 /d at 20 °C and 0.06/d at 1 °C is recommended by the 10 States Standards (2004).
Studies of systems in Texas have empirically derived the value of the temperature coefficient, 0,
for soluble organic removal in complete mix ponds to be 1.03-1.04 (Wang and Pereira, 1986.)
3.4.1.7 Influence of Number of Cells
When using the partial mix design model, the number of cells in series has a pronounced effect
on the size of the pond system required to achieve the specified degree of treatment. The effect
can be demonstrated by rearranging Equation 3-1 and solving for t:
f =
n
C.
o
— 1
^c~.
All terms in this equation have been defined previously.
(3-7)
3.4.1.8 Pond Configuration
The ideal configuration of a pond designed on the basis of complete mix hydraulics is a circular
or square pond. However, even though partial mix ponds are designed using the complete mix
model, it is recommended that the cells be configured with a length-to-width ratio of 3:1 or 4:1.
This is because it is recognized that the hydraulic flow pattern in partial mix systems more
closely resembles the plug flow condition. The dimensions of the cells can be calculated using
Equation 3-8.
3-14
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V = [LW+(L- 2sd)(W- 2sd) + 4(L - sd)(W- sd)]d (3-8)
6
Where:
V= volume of pond or cell, m3
L = length of pond or cell at water surface, m
W= width of pond or cell at water surface, m
s = slope factor (e.g., with 3:1 slope, s = 3)
d = depth of pond, m
3.4.1.9 Mixing and Aeration
The O2 requirements control the energy input required for partial mix pond systems. There are
several rational equations available to estimate the 02 requirements for pond systems; these can
be found in Benefield and Randall (1980), Gloyna (1976, 1971), and Metcalf and Eddy (1991,
2003). In most cases, partial mix system design is based on the strength of the BODs entering
the system. After calculating the required rate of 02 transfer, information contained in
equipment manufacturers' catalogs should be consulted to determine the zone of complete 02
dispersion by surface, helical, or air gun aerators or the proper spacing of perforated tubing.
Schematic sketches of several of the various types of aerators used in pond systems are shown in
Figure 3-2A and B. Photographs of installed aeration equipment are shown in Figure 3-3.
Stabc
ft »-. •. • • ... • RiiUliug Drui
, ". + >• ^
P(M _... _.. ',.' , ,. •--.__
Figure 3-2A. Static Tube, Brush and Aspirating Aerators. (Reynolds and Richards, 1996).
3-15
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Elrclnr Motor
(b) Pier Mounfni Impeller with linn Tube
HI I Vt Mounted Impeller
Figure 3-2B. Floating pump, pier-mounted impeller with draft tube and pier-mounted
impeller (Reynolds and Richards, 1996).
See Appendix C for mixer and diffuser design calculations.
Surface aeration equipment is subject to potential icing problems in cold climates, but there are
many options available to avoid this problem (see Figure 3.3 and Chapter 4). Improvements have
been made in fine bubble perforated tubing, but a diligent maintenance program is still the best
policy. In the past, a number of systems experienced clogging of the perforations, particularly in
hard water areas, and corrective action required purging with HCl gas.
Figure 3-3. Floating aerators in summer and winter operation.
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The final element recommended in this partial mix aerobic pond system is a settling cell with a 2
d HRT at the average design flow rate.
3.4.1.10 Performance
Reliable BODs removal up to 95 percent can be expected. Effluent TSS can range from 20 to 60
mg/L, depending on the design of the settling basin and the concentration of algae in the effluent.
Removal of NHs is less effective due to shorter detention times, but nitrification of NHs can
occur in aerated ponds if the system is designed for that purpose. Phosphorus removal is only 15
- 25 percent. Removal of total and fecal coliform depends on length of detention time and
temperature. If effluent limits are < 200 MPN/100 mL, disinfection may be needed.
3.4.1.11 Limitations and Operation and Maintenance
Depending upon the rate of aeration and the environment, ice may form on the surface of aerobic
ponds during cold weather. Rates of biological activity slow down during cold weather. If
properly designed, a system will continue to function and produce acceptable effluents under
these conditions. The potential for ice formation on floating aerators may encourage the use of
submerged diffused aeration in very cold climates.
The use of submerged perforated tubing for diffused aeration requires maintenance and cleaning
on a routine basis to maintain design rates. There are numerous types of submerged aeration
equipment that can be used in warm or cold climates, and these should be considered for all
designs. In submerged diffused aeration, the routine application of hydrochloric acid (HCJ) gas
in the system is used to dissolve accumulated material on the diffuser units. Any earthen
structures used as impoundments must be periodically inspected. Typically, operation occurs by
gravity flow. Energy is required for the aeration devices, the amount depending on the intensity
of mixing desired. Partial mix systems require between 1-2 W/m3 capacity, depending on the
depth and configuration of the system. See design example C-3-7 in Appendix C for a method of
calculating the energy requirements for partial mix systems.
3.4.1.12 Modifications
One physical modification to an aerobic pond is the use of plastic curtains supported by floats
and anchored to the bottom to divide existing ponds into multiple cells and/or serve as baffles to
improve hydraulic conditions. A recently developed approach suspends a row of submerged
diffusers from flexible floating booms, which move in a cyclic pattern during aeration activity.
This treats a larger volume with each aeration line. Effluent is periodically recycled within the
system to improve performance. If there is sufficient depth for effective 02 transfer, aeration is
used to upgrade existing facultative ponds and is sometimes used on a seasonal basis during
periods of peak wastewater discharge (e.g., seasonal food processing wastes) to the pond.
3.4.1.13 Costs
Construction costs associated with partially mixed aerobic ponds include cost of the land,
excavation, and inlet and outlet structures. If the soil where the system is constructed is
permeable, there will be an additional cost for lining. Excavation costs vary, depending on
whether soil must be added or removed. Operating costs of partial mix ponds include operation
and maintenance of surface or diffused aeration equipment.
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3.4.2 Complete Mix Aerated Ponds (Subset of Aerated Pond System)
Complete mix systems rely on mechanical aeration to introduce enough 02 to completely
degrade all BODs. In addition to that, however, the additional mixing suspends the solid
material to enhance biodegradation.
3.4.2.1 Applicability
See Section 3.4.1.1.
3.4.2.2 Advantages/Disadvantages
See Section 3.4.1.2.
3.4.2.3 Design models and example calculations
Complete mix ponds are smaller than partial mix ponds and all solids in the aeration cell are kept
in suspension. The system is designed using first order kinetics and a complete mix model.
Most states specify the formulation shown in Equation 3-7 and used in the design example to
size the aeration cell and specify the size of the settling cell. Typically a plastic, clay or other
impervious lining is required to protect groundwater. A multiple cell system with at least three
cells in series is recommended, with appropriate inlet and outlet structures to maximize
effectiveness of the design volume. Hydraulic residence times are generally are less than 3 d
except where high strength wastewaters are treated. An HRT range of 2 - 4 d is recommended so
that the microbial community has sufficient time to grow (von Sperling and de Lemos
Chernicharo, 2005).
3.4.2.4 Design Equation
The design model using first order kinetics and operating n number of equal sized cells in series
is given in Section 3.4 by Equation 3-3 and if a series of non-equal volume ponds or ponds with
varying reaction rates are to be designed, use Equation 3-4.
3.4.2.5 Temperature Effects
See Section 3.4.1.5.
3.4.2.6 Selection of Reaction Rate Parameters
See Section 3.4.1.6.
3.4.2.7 Influence of Number of Cells
See Section 3.4.1.7. An example (C-3-4) can be found in Appendix C.
3.4.2.8 Pond Configuration
The ideal configuration of a pond designed on the basis of complete mix hydraulics is a circular
or a square pond; however, it is recommended that the cells be configured with a length to width
ratio of 3:1 or 4:1 because the hydraulic flow pattern in complete mix systems actually more
closely resembles the plug flow model. The dimensions of the cells can be calculated using
Equation 3-8 in Section 3.4.1.8.
3.4.2.9 Mixing and Aeration
The mixing requirements usually control the energy input required for complete mix pond
systems. There are several rational equations available to estimate the 02 requirements for pond
3-18
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systems (see Section 3.4.1.9 for references). Complete mix systems are designed by estimating
the strength of the BODs entering the system and then calculated to ensure that adequate energy
is available to provide complete mixing. Once the required rate of 02 transfer is known, the
equipment manufacturers' catalogs should be consulted to determine the zone of complete
mixing and 02 dispersion. The aerators used in complete mix systems are the same as those used
in partial mix systems.
Equation 3-9 is used to estimate 02 transfer rates.
(l.025)(
where
N = equivalent 02 transfer to tap water at standard conditions, kg/hr
Na = 02 required to treat the wastewater, kg/hr (usually taken as 1.5 x the
organic loading entering the cell)
a = (02 transfer in wastewater)/(02 transfer in tap water) = 0.9
CL = minimum DO concentration to be maintained in the wastewater,
assume 2 mg/L
Cs = 02 saturation value of tap water at 20 C and one atmosphere
pressure = 9.17 mg/L
Tw = wastewater temperature, C
Csw = ^(Css)P = 02 saturation value of the waste, mg/L
P = (wastewater saturation value)/(tap water 02 saturation value)
Css = tap water 02 saturation value at temperature Tw
P = ratio of barometric pressure at the pond site to barometric pressure at sea
level, assume 1.0 for an elevation of 100 m
Equation 3-6 can be used to estimate the water temperature in the pond during the summer
months, which is the most active period of biological activity. However, as energy to provide
complete mixing is assumed to be available, DO should be at adequate levels throughout the
year. The complete mix design procedure is illustrated in Example 3-5 found in Appendix C.
The four-cell system can be simulated by using floating plastic partitions (see Chapter 4).
3.4.2.10 Performance
See Section 3.4.1.10.
3.4.2.11 Modifications
There are many configurations of complete mix pond systems. Examples that will be discussed
/R\
in Chapter 4 include the High-Performance Aerated Pond Systems and the BIOLAC Process.
An examination of Example C-3-3 (Appendix C) will show the similarity between the design for
the High-Performance Aerated Pond System and the complete mix design when the final three
cells of the complete mix design are supplied with only enough DO to meet the BOD5. This is
not to imply that the designs are identical, but only to point out that they have some common
features.
3.4.2.12 Costs
See Section 3.4.1.12.
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CHAPTER 4
PHYSICAL DESIGN AND CONSTRUCTION
4.1 INTRODUCTION
No matter how carefully coefficients are evaluated and biological or kinetic models reviewed, if
sufficient consideration is not given to optimization of the pond layout and construction, the
actual efficiency of the system may be far less than the calculated efficiency. The biological
factors affecting wastewater pond performance must be understood so that a reasonable estimate
of the hydraulic residence time required to achieve a specified efficiency is incorporated into the
design. But it is the physical factors, such as length to width ratio, placement of inlet and outlet
structures and redundancy in design that determine the actual treatment efficiency that can be
achieved (Crites et al., 2006; Shilton, 2005).
The danger of groundwater contamination frequently imposes seepage restrictions, necessitating
lining or sealing the pond. Reuse of the pond effluent in dry areas where all water losses are to be
avoided may also dictate the use of linings. Layout and construction criteria should be
established to reduce dike erosion from wave action, weather and burrowing animals. Transfer
structure placement and size affect flow patterns within the pond and determine operational
ability to control the water level and discharge rate. These important physical design
considerations are discussed in the following sections.
4.2 DIKE CONSTRUCTION
Dike stability is most often affected by erosion caused by wind-driven wave action or rain and
rain-induced weathering. Dikes may also be destroyed by burrowing animals. A good design
with proper maintenance, will anticipate these problems and provide a stable, reliable system.
4.2.1 Wave Protection
Erosion protection should be provided on all slopes; however, if winds are predominantly from
one direction, protection should be enhanced for those areas that receive the full force of the
wind-driven waves. Protection should always extend from at least 0.3 m below the minimum
water surface to at least 0.3 m above the maximum water surface (U.S. EPA, 1977b; Kays, 1986;
U.S. Department of Interior [USD I], 2001). Wave height is a function of wind velocity and fetch
(the distance over which the wind acts on the water). The size of riprap needed depends on the
fetch length (Uhte, 1974; Kays, 1986). Riprap varies from river run rocks that are 15 - 20 cm to
quarry boulders that are 7 - 14 kg. Uniformly graded river run material, when used for riprap, can
be quite unstable. River run rocks, if not properly mixed with smaller material and carefully
placed, can be loosened by wave action and slip down the steep sloped dikes. Broken concrete
pavement can often be used for riprap but can make mechanical weed control difficult.
Asphalt, concrete, fabric, and low grasses can also be used to provide protection from wave
action. When riprap is used for wave protection, the designer must take into consideration its
effect on weed and animal control and routine dike maintenance.
4.2.2 Weather Protection
Dike slopes must be protected from weather induced erosion as much as from wave erosion in
4-1
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many areas of the country. The most common method of weather erosion protection employs
grass when large dike areas are involved. Because variations in depth develop in total
containment ponds, they often have large sloped dike areas that cannot be protected in a more
cost-effective way. Ponds that have only minimum freeboard and constant water depth may be
protected more cost-effectively if the riprap is carried right to the top of the slope where it can
serve as wave and weather protection.
In some cases climate and soil conditions are suitable for completely bare dike slopes without
major weather erosion problems. Figure 4-1 shows the erosion effects on the bare slopes of a
treatment pond.
Weather caused erosion, unlike wave erosion, can also affect the top and outside slopes of the
pond diking system. The designer should make sure that the all-weather road system for the top
of the dike is of sufficient width to allow traffic to pass over every part of the surface. Too
narrow a road will result in ruts that can create runoff erosion problems in areas of high rain
intensity. Final grading should be specified to minimize rutting and frequent maintenance should
be required to control surface runoff and erosion.
It is also necessary to protect the exterior surface of dikes. A thin layer of gravel may be used;
placement of topsoil and seeding for native groundcover is recommended. Local highway
department experience on erosion control for cut-and-fill slopes should be used as a guide.
Figure 4-1 An example of eroded dike slopes.
4.2.3 Animal Protection
If a treatment pond is located in an area that supports burrowing animals, such as muskrats and
nutria, design elements can be put in place to control this threat to dike stability. Broken concrete
or other riprap that does not completely cover the dike soil can become a home for burrowing
animals. Riprap design and placement should emphasize limiting the creation of voids that allow
them to burrow near the water surface (Crites et al., 2006).
Varying pond water depth can discourage muskrat infestation (U.S.EPA, 1977b; Crites et al.,
2006). Muskrats prefer a partially submerged tunnel, so design provisions to vary the water level
over a several-week period will discourage them from burrowing in the dike. Such provisions
will often add to the expense of riprap placement for wave protection, but can greatly reduce
operation and maintenance expenses.
4-2
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Figure 4.2 Evidence of burrowing at the edge of a treatment pond (Mayo et al., 2010).
4.2.4 Seepage
Dikes should be designed and constructed to minimize seepage. Vegetation and porous soils
should be removed and the embankment should be well compacted. Use of conventional
construction equipment is usually suitable for this purpose.
Seepage collars should be provided around any pipes penetrating the dike (Kays, 1986; Thomas
et al., 1966). The seepage collars should extend a minimum of 0.6 m from the pipe. Proper
installation of transfer pipes can be assured by building up the dike above the pipe elevation,
digging a trench for the pipe and seepage collar, backfilling the trench, and compacting the
backfill.
In some circumstances it may be necessary to control seepage and ensure bank stability at the
exterior toe. A filter blanket material can be used (Middlebrooks, et al. 1978; Kays, 1986).
Another method of preventing seepage where embankment material cannot be adequately
compacted is placement of an impervious core in the levee with imported material.
4.3 POND SEALING
4.3.1 Introduction
The need for a well-sealed treatment pond has impacted modern pond design, construction, and
maintenance, and sealing is required in most design situations. The primary motive for sealing
ponds is to prevent seepage. Seepage affects treatment capabilities by causing fluctuation in the
water depth and can cause pollution of groundwater. Although many types of pond sealers exist,
they can be classified into three major categories: (1) synthetic and rubber liners, (2) earthen and
cement liners, and (3) natural and chemical treatment sealers. Within each category there exists a
wide variety of application characteristics. Choosing the appropriate lining for a specific site is a
critical issue in pond design and seepage control. Detailed information is available from other
publications (Kays, 1986; Middlebrooks et al., 1978; USDA, 1997; USDI, 2001, Koerner and
Koerner, 2009).
4.3.2 Seepage Rates
Most regulatory agencies limit the amount of seepage from ponds, so it may be important to be
able to estimate seepage rates. Stander et al. (1970) presented a summary of information (Table
-------
4.1) on measured seepage rates in wastewater treatment ponds. Seepage rates in irrigation
channels can be found in U.S. DI (1991). Seepage is a function of a number of variables; it is
difficult to anticipate or predict rates even with extensive soil tests. Careful evaluations must be
conducted along with a review of manufacturers' information to determine whether a lining is
required and which type. This should be done before the ponds are constructed.
The Minnesota Pollution Control Agency (Hannaman et al., 1978) initiated an intensive study to
evaluate the effects of treatment pond seepage from five municipal systems. The five
communities were selected for study on the basis of geologic setting, age of the system, and past
operating history of the pond. The selected ponds were representative of the major geomorphic
regions in the state, and the age of the systems ranged from 3 to 17 years.
Estimates of seepage were calculated by two independent methods for each of the five pond
systems. Water balances were calculated by taking the difference between the recorded inflows
and outflows, and pond seepage was determined by conducting in-place field permeability tests
of the bottom soils at each location. Good correlation was obtained with both techniques.
Table 4-1. Reported Seepage Rates From Pond Systems (from Stander et al., 1970)a.
Location
Mojave1
Kearney215
Filer City3
Pretoria40
Pond
Base
Desert
soil
(sandy
soil)
Sand
and
gravel
Sandy
soil
Clay
loam
and
shale
Initial
Seepage
Rate
cm/d
(m3/m2/d)
22.4
(0.19)
14.0
(0.12)
(0.13)
Hydraulic
Load
Seepage
Rate as
percent
of
Hydraulic
Load
Settling-in
Period
m3/m2/d
0
0
0
30
13
05
63
90
Exceeded
inflow rate
9 mo
1 yr
Average
over 5 yr
Approx. 1 yr
Eventual
Seepage
Rate
cm/d
(m3/m2/d)
0.9
(0.007)
1.5
(0.013)
0.9
(0.007)
0.8
(0.006)
Hydraulic
Load
m3/m2/d
0.36
0.04
0.009
0.05
Seepage
Rate as
percent
of
Hydraulic
Load
2
29
84
13
California; 2Nebraska; 3Michigan; 4South Africa
"Courtesy of Ann Arbor Science Publishers, Inc., Ann Arbor, Ml.
bEvaporation and rainfall effects apparently not corrected for. Seepage losses also
influenced at times by a high water table.
Constructed in sandy soil for the express purpose of seeping away Paper Mill NSSC
liquor.
Field permeability tests indicated that the additional sealing from the sludge blanket was
insignificant in locations where impermeable soils were used in the construction process. In the
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case of more permeable soils, it appeared that the sludge blanket reduced the permeability of the
bottom soil from an initial level of 10~4 or 10~5 cm/sec to the order of 10~6 cm/sec. At all five
systems evaluated, the treatment pond was in contact with the local groundwater table. Local
groundwater fluctuations had a significant impact on seepage rates. Reducing the groundwater
gradient resulted in a reduction of seepage losses at three of the sites. Contact with groundwater
possibly explains the reduction in seepage rates in many ponds; in the past this reduction in
seepage rates has been attributed totally to a sludge buildup. (Stander, et al.)
In an area underlain by permeable material where little groundwater mounding occurs, there is
probably little influence from the water table on seepage rates. The buildup of sludge on the
bottom of a pond appears to improve the quality of the seepage water leaving the pond. Sludge
accumulation apparently increases the cation exchange capacity of the bottom of the pond.
Groundwater samples obtained from monitoring wells did not show any appreciable increases in
N, P, or fecal coliform over the background levels after 17 years of operation. The seepage from
the ponds did show an increase in soluble salts as great as 20 times over background levels.
Concentrations of 25 mg/L to 527 mg/L of chloride were observed.
A comparison of observed seepage rates for various types of liner material is presented in Table
4.2 (Kays, 1986). If an impermeable liner is required, one of the synthetic materials must be
used. The East Bay Municipal Utility District, Oakland California, developed the following
formula for leakage tolerance, which can be modified by inserting more stringent factors in the
denominator, e.g., 100, 200 and so forth. The equation is empirical and its use must be based on
experience:
(4-1)
80
Where:
Q = maximum permissible leakage tolerance, L/min
A = lining area, m2
H = maximum water depth, m
4.3.3 Natural and Chemical Treatment Sealing
The most complex techniques of pond sealing, either separately or in combination, are natural
pond sealing and chemical treatment sealing (Thomas et al., 1966; Bhagat and Proctor, 1969;
Seepage Control, Inc., 2005).
Natural sealing of ponds occurs via three mechanisms: (1) physical clogging of soil pores by
settled solids; (2) chemical clogging of soil pores by ionic exchange; and (3) biological and
organic clogging caused by microbial growth at the pond lining. Which mechanism should be
used depends on the characteristics of the wastewater being treated.
Infiltration characteristics of anaerobic ponds were studied in New Zealand (Hill, 1976). Certain
soil additives were employed (bentonite, sodium carbonate, sodium triphosphate) in 12 pilot
ponds with varying water depth, soil type and compacted bottom soil thickness. It was found that
chemical sealing was effective for soils with a minimum clay content of 8 percent and a silt
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content of 10 percent. Effectiveness increased with clay and silt content.
Four different soil columns were placed at the bottom of an animal wastewater pond to study
physical and chemical properties of soil and sealing of ponds (Chang et al., 1974; U.S. DA,
1972). It was discovered that the initial sealing which occurred in the top 5 cm of the soil
columns was caused by the trapping of suspended matter in the soil pores. This was followed by
a secondary mechanism of microbial growth that completely sealed off the soil from water
intrusion.
A similar study performed in Arizona (Wilson et al., 1973) also found this double mechanism of
physical and biological sealing. Physical sealing of the pond was enhanced by the use of an
organic polymer mixed with bentonite clay. This additive could have been applied with the pond
full or empty, although it was more effective when the pond was empty.
Table 4-2. Seepage Rates for Various Liners3 (Kays, 1986)b.
Liner Material
Open sand and gravel
Loose earth
Loose earth plus chemical treatment
Loose earth plus bentonite
Earth in cut
Soil cement (continuously wetted)
Gunite
Asphalt concrete
Un-reinforced concrete
Compacted earth
Exposed prefabricated asphalt panels
Exposed synthetic membranes
Thickness
(cm)
NA
NA
NA
NA
NA
10.2
3.8
10.2
10.2
91
1.3
0.11
Minimum Expected
Seepage Rate at
6 m of Water Depth
After 1 Yr of Service (cm/d)
244
122
30.5
25.4
30.5
10.2
7.6
3.8
3.8
0.76
0.08
0.003
NA = not available
aThe data are based on actual installation experience. The chemical and bentonite treatments
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depend on seepage rates, and in the table loose earth values are assumed.
bCourtesy of John Wiley & Sons, Inc., New York, NY.
An experiment was performed in South Dakota (Matthew and Harms, 1969) in an effort to relate
the sodium adsorption ratio (SAR) of the in situ soil to the sealing mechanism of treatment
ponds. The general observation was made that the equilibrium permeability ratio decreases by a
factor of 10 as SAR varies from 10 to 80. Polymeric sealants have been used to seal both filled
and unfilled ponds (Rosene and Parks, 1973; Seepage Control, Inc., 2005). Unfilled ponds have
been sealed by admixing a blend of bentonite and the polymer directly into the soil lining. Filled
ponds have been sealed by spraying the fluid surface with alternate slurries of the polymer and
bentonite. It has been recommended that the spraying take place in three subsequent layers: (1)
polymer, (2) bentonite, and (3) polymer. The efficiency of the sealant has been found to be
significantly affected by the characteristics of the impounded water. Most importantly, calcium
ions in the water exchange with sodium ions in the bentonite and cause failure of the compacted
bentonite linings.
Davis et al., (1973) found that for liquid dairy waste, the biological clogging mechanism
predominated. In a San Diego County study site located on sandy loam, the infiltration rate of a
virgin pond was measured. A clean water infiltration rate for the pond was 122 cm/d. After two
weeks of manure water addition, infiltration averaged 5.8 cm/d; after four months, 0.5 cm/d.
A study performed in southern California (Robinson, 1973) showed similar results. After waste
material was placed in the unlined pond in an alluvial silty soil, the seepage rate was reduced.
The initial 11.2 cm/d seepage rate dropped to 0.56 cm/d after three months, and to 0.30 cm/d
after six months.
4.3.4 Design and Construction Practice
4.3.4.1 Lining Materials
Information about current commercial sources of lining materials is available elsewhere (see
Section 4.3.1). Design and construction methods are available from these sources. A general
presentation of recommended pond sealing design and construction procedures is presented
below. The methods are divided into two categories: (1) bentonite, asphalt, and soil cement
liners, and (2) thin membrane liners. Although there are major differences between the two
application techniques, there are some similarities between the application of asphalt panels and
elastomer liners.
Regardless of the difference between the type of material selected, there are many common
design, specification, and construction practices. A summary of the effective design practices in
cut-and-fill reservoirs is given below. Most of these practices are common sense observations,
yet experience shows that these practices are very often ignored.
Summary of Effective Design Practices for Placing Linings
in Cut-and-Fill Reservoirs
• Lining must be placed on a stable soil foundation or structure.
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• Facility design and inspection should be the responsibility of professionals with
backgrounds in liner applications and experience in geotechnical engineering.
• A continuous underdrain of perforated piping or other configuration to collect
groundwater below the lining that operates at atmospheric pressure should be put in
place.
• A leakage tolerance should be included in the specifications.
• Continuous, thin, impermeable-type linings should be placed on a smooth surface of
concrete, earth, gunite, or asphalt concrete.
• Except for asphalt panels, all field joints should be made perpendicular to the toe of the
slope. Some materials can run in any direction, but generally joints run perpendicular to
the toe of the slope.
• Formal or informal anchors may be used at the top of the slope.
• Inlet and outlet structures must be sealed properly.
• All lining punctures and cracks in the support structure should be sealed.
• Emergency discharge quick-release devices should be provided in large reservoirs.
• Wind problems with exposed thin membrane liners can be controlled by
installing vents so that they are built into the lining.
• Adequate protective fencing must be installed to control vandalism.
Bentonite, Asphalt, and Soil Cement
The application of bentonite, asphalt, and soil cement as lining materials for reservoirs and
wastewater ponds has a long history (Kays, 1986). The following summary includes
consideration of the materials, costs, evaluations of durability, and effectiveness in limiting
seepage. The cost analysis is somewhat arbitrary, since it depends primarily on the availability of
the materials. Most states have developed standards relating to the application of these types of
materials, and detailed discussions of these materials are presented elsewhere (Middlebrooks et
al., 1978; Koerner and Koerner, 2009).
Bentonite
Bentonite is a sodium montmorillonite clay that exhibits a high degree of swelling,
imperviousness, and low hydraulic conductivity. The variety of ways in which bentonite may be
used to line ponds are listed below:
• A suspension of bentonite in water (with a bentonite concentration of approximately 0.5
percent of the water weight) is placed over the area to be lined. The bentonite settles to
the soil surface, forming a thin blanket.
• The same procedure as above, except frequent harrowing of the surface produces a
uniform soil-bentonite mixture on the surface of the soil. The amount of bentonite used in
this procedure is approximately 4.5 kg/m2.
• A gravel bed approximately 15 cm deep is first prepared and the bentonite application
performed as in the first method. The bentonite will settle through the gravel layer and
seal the void spaces.
• Bentonite is spread as a membrane 2.5 - 5 cm thick and covered with a 20 - 30 cm
4-8
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blanket of soil and gravel to protect the membrane. A mixture of soil and gravel is more
satisfactory than soil alone, because the stability is increased and there is greater
resistance to erosion.
• Bentonite is mixed with a sand ratio of approximately 1:8. A layer 5 - 10 cm in thickness
is placed on the reservoir bottom and covered with a protective cover of sand or soil. This
method takes about 13.5 kg/m of bentonite.
In the last two methods listed above, the following construction practices are recommended:
• The section must be over-excavated (30 cm) with drag lines or graders.
• Side slopes should not be steeper than two horizontal to one vertical.
• The sub-grade surface should be dragged to remove large rocks and sharp angles.
Usually two passes with adequate equipment are sufficient to smooth the sub-grade.
• Sub-grade should be rolled with a smooth steel roller.
• The sub-grade should be sprinkled to eliminate dust problems. The bentonite or soil-
bentonite membrane should then be applied.
• The protective cover should contain sand and small gravel, in addition to cohesive, fine
grained material, so that it will be erosion resistant and stable.
The performance of bentonite linings is greatly affected by the quality of the bentonite. Some
natural bentonite deposits may contain quantities of sand, silt and clay impurities. Poor quality
bentonite deteriorates rapidly in the presence of hard water, and tends to erode in the presence of
currents or waves. Bentonite linings must often be put in place manually, which can add
considerably to the cost. Wyoming-type bentonite, which is a high-swelling sodium
montmorillonite clay, has been found to be satisfactory.
Fine-ground bentonite is generally more suitable for the lining than pit-run bentonite. If the
bentonite is finer than a No. 30 sieve, it may be used without specifying size gradation. But if the
material is coarser than the No. 30 sieve, it should be well graded. Bentonite should contain a
moisture content of less than 20 percent. This is especially important for thin membranes. Some
disturbance, and possibly cracking of the membranes, may take place during the first year after
construction due to settling of the sub-grade upon saturation. A proper maintenance program,
especially at the end of the first year, is a necessity.
Sodium bentonite linings may be effective if they have an adequate amount of exchangeable
sodium. Deterioration of the linings has been observed to occur in cases where magnesium or
calcium has replaced sodium as the adsorbed ions. A thin layer, less than 15 cm, of bentonite on
the soil surface tends to crack if allowed to dry. Because of this, a bentonite soil mixture with a
cover of fine grained soil on top, or a thicker bentonite layer, is recommended (Dedrick, 1975).
Surface bentonite cannot be expected to be effective longer than two to four years. A buried
bentonite blanket may last from 8 to 15 years (U.S. EPA, 1978; U.S. DA, Natural Resources
Conservation Services, 2010).
O r\
Seepage losses through buried bentonite blankets are approximately 0.2 - 0.25 m /m /d. This
figure is for thin blankets and represents about a 60 percent improvement over ponds with no
lining.
4-9
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Asphalt
Asphalt linings may be buried on the surface and may be composed of fresh asphalt or a
prefabricated asphalt. Some variations include:
• An asphalt membrane is produced by spraying asphalt at high temperatures. This lining
may be either on the surface or buried. Special equipment is needed for installation. A
useful life of 18 years or greater has been observed when these membranes are carefully
applied and covered with an adequate layer of fine grained soil.
• Buried Asphaltic Membrane. This is similar to the first asphalt membrane, except that a
gravel-sand cover is applied over the asphaltic membrane. This cover is usually more
expensive and less effective in discouraging plant growth.
• Built-up Linings. These include several different types of materials. One type could be a
fiberglass matting, which is applied over a sprayed asphalt layer and then sprayed or
swept over with a sealed coat of asphalt or clay. A 280 g jute burlap has also been used as
the interior layer between two hot-sprayed asphalt layers. In this case, the total asphalt
application should be about 11.3 L/m2. The prefabricated lining may be on the surface or
buried. If it is buried, it could be covered with a layer of soil or, in some cases, a
geotextile coating.
• Prefabricated Linings. These linings consist of a fiber or paper material coated with
asphalt. This type of liner can be exposed or covered with soil. Joints between the
material are sealed with asphaltic mastic. When the asphaltic material is covered, it is
more effective and durable. When it is exposed, it should be coated with aluminized paint
every three to four years to retard degradation. This is especially necessary above the
water line. Joints also have to be maintained if they are not covered with fine-grained
soil. Prefabricated asphalt membrane lining is approximately 0.32 - 0.64 cm thick. It may
be handled in much the same way as rolled roofing, with lapped and cemented joints.
Cover for this material is generally soil and gravel, although shot-crete and macadam
may also be used.
Installation procedures for prefabricated asphalt membrane linings and for buried asphalt linings
are similar to those for buried bentonite linings (U.S. DI, 2001). The preparation of the sub-grade
is important; it should be stable and adequately smooth before the lining is put in place. Linings
of bentonite and asphalt are sometimes unsuitable in areas of high weed growth, since weeds and
tree roots readily puncture the membranes ). Many lining failures occur as a result of rodent and
crayfish holes in embankments. Asphalt membrane lining tends to decrease the damage, but, in
some cases, harder surface linings are necessary to prevent water loss from embankment failures.
Linings of hot applied buried asphalt membrane provide one of the tightest linings available.
These linings last longer than other flexible membrane linings. Asphalt linings composed of
prefabricated buried materials are best for small jobs, since there is a minimum amount of special
equipment and labor connected with installation. For larger jobs sprayed asphalt is more
economical. When fibers and filler composed of organic materials are used in building asphalt
membranes, the membranes have a shorter lifetime. Inorganic fibers are, therefore,
recommended. Typical seepage volume through one buried asphalt membrane after 10 years of
service was consistently 0.02 m3/m2/d (2.3 x 10"7 cm/s). Asphalt membrane linings can be
4-10
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constructed at any time of the year, but fall and winter installation may dictate the use of the
buried asphalt membrane lining.
Buried asphalt membranes usually perform satisfactorily for more than 15 years. When these
linings fail, it is generally due to one or more of the following causes:
• Placement of lining on unstable side slopes
• Inadequate protection of the membrane
• Weed growth
• Surface runoff
• Type of sub-grade material
• Cleaning operations
• Scour of cover material Membrane puncture
Soil Cement
The best results are obtained with soil cement when the soil mixed with the cement is sandy and
well graded to a maximum thickness of about 2 cm. Soil cement should not be laid down in cold
weather. It should be cured for about seven days after placement. Some variations of the soil
cement lining are listed below.
• Standard soil cement is compacted using a water content of the optimum moisture
content of the soil. (Moisture content is expressed in percent dry weight at which a given
soil can be compacted to its maximum density by means of a standard method of
compaction.) The mixing process is accomplished by traveling mixing machines and can
be handled satisfactorily in slopes up to 4:1. Standard soil cement may be on the surface
or buried.
• Plastic soil cement (surface or buried) is a mixture of soil and cement with a consistency
comparable to that of Portland cement concrete. This requires the addition of a
considerable amount of water. Plastic soil cement contains from three to six sacks of
cement per cubic meter and is approximately 7.5 cm thick.
• Cement modified soil contains two to six percent volume of cement. This may be used
with plastic fine grained soils. The treatment stabilizes the soil in sections subject to
erosion. The lining is constructed by spreading cement on top of loose soil layers by a
fertilizer-type spreader. The cement is then mixed with loose soil by a rotary traveling
mixer and compacted with a sheeps-foot roller. A 7-day curing period is necessary for a
cement modified soil. Soil cement has been used successfully in some cases in mild
climates. Where wetting or drying is a factor, or if freezing-thawing cycles are present,
the lining will deteriorate rapidly (U.S. DI, 2001).
Thin Membrane Liners
Plastic and elastomeric membranes are popular in applications requiring essentially zero
permeability. These materials are economical, resistant to most chemicals if selected and
installed properly, available in large sheets simplifying installation, and essentially
impermeable. As environmental standards become more stringent, the application of plastic and
elastomeric membranes will increase because of the need to guarantee protection against
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seepage. This is particularly true for sealing ponds containing toxic wastewaters or the sealing
of landfills containing toxic solids.
Most regulatory agencies have general standards for the application of liners, as do most
manufacturers. Searching the Internet using key words such as "liners," "plastic liners,"
"seepage prevention," "sealing," "water proofing," or "membranes" will yield the most current
information. Detailed drawings showing the correct method for the application of linings are
presented in Kays (1986) and manufacturer's literature. These sources of information should be
consulted before designing a liner.
The most difficult design problem encountered in liner application involves placing a liner in an
existing pond. Effective design practices are essentially the same as those used in new systems,
but the evaluation of the existing structure must be done carefully to achieve the required results.
Lining materials must be selected for their compatibility with the existing structure. For
example, if a badly cracked concrete lining is to be covered with a flexible synthetic material, it
must be properly sealed and the flexible material placed in such a way so that any movement will
not destroy the integrity of the new liner. Sealing around existing columns and footings must also
be considered.
Protection of a thin membrane lining is essential. Kays (1986) recommends that a fence at least 2
m high be placed on the outside berm slope with the top of the fence below the top elevation of
the dike to keep the membrane out of sight.
There are many firms specializing in the installation of lining materials. Most installation
companies and manufacturers publish specifications and installation instructions and design
details. The manufacturers' and installers' recommendations are similar, but there are differences
worthy of consideration when designing a system requiring a liner. For details, consult the
Internet for manufacturers using the key words "Pond Liners".
New products are always being developed, and with each new material the options available to
designers expand. If the liners are chosen and installed with care, control of seepage and
associated pollution should become a minor operation and maintenance element.
4.3.4.2 Mechanisms of Failure
Kays (1986) classified the principal types of failures observed in cut-and-fill reservoirs (Table 4-
3). The list is extensive and case histories involving all of the categories are available; however,
the most frequently observed failure mechanisms were the lack of integrity in the lining support
structure and abuse of the liner. For example, exposed thin membrane liners must be protected
from aerator damage, contact with sharp objects, and excess foot traffic. In general, unless a
protective cover is provided, it is advisable to use reinforced membranes or thick materials
recommended for exposure to the elements.
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Table 4-3. Classification of the Principal Failure Mechanisms for Cut-and-Fill Reservoirs
(Kays, 1986) a.
Supporting Structure
Underd rains
Substrate
Compaction
Texture
Voids
Subsidence
Holes and cracks
Groundwater
Expansive clays
Out gassing
Sloughing
Slope anchor stability
Mud
Frozen ground and ice
Operations
Cavitation
Impingement
Lack of regular cleaning
Reverse hydrostatic uplift
Vandalism
Seismic activity
Lining
Mechanical
Field seams
Fish moughtsb
Structure seals
Bridging
Porosity
Holes and pinholes
Tear strength
Tensile strength
Extursion and extension
Animals including burrowing birds
Insects
Weeds
Weather
General weathering
Wind
Wave erosion
Ozone
aCourtesy of John Wiley and Sons, Inc.
bSeparation of butyl-type cured sheets
., New York, NY.
at the joint due to unequal tension between the sheets.
4.3.4.3 Cover Material
The cost of linings for ponds vary with the type and the quality required to ensure against
seepage problems. Contacting individual suppliers will yield accurate and up-to-date cost
information.
Placing cover material over buried membranes is the most expensive part of the procedure. The
cover material should, therefore, be as thin as possible, while still providing adequate protection
for the membrane. If a significant hydraulic current is present in the pond, the depth of coverage
should be greater than 25 cm, and this minimum depth should only be used when the material is
erosion resistant and cohesive. Such a material as a clay gravel is suitable. If the material is not
cohesive, or if it is fine grained, a higher amount of cover is needed.
Maintenance costs for different types of linings are difficult to estimate. Maintenance should
include repair of holes, cracks, and deterioration and damage caused by animals and pond
cleaning, as well as weed control expenses. Climate, type of operation, type of terrain, and
surface conditions also influence maintenance costs.
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Synthetic liners are most practical where zero or minimum seepage regulations are in effect, a
facility is treating industrial waste that might degrade concrete or earthen liners and/or there are
extremes in climatic conditions
4.4 POND HYDRAULICS
4.4.1 Inlet and Outlet Configuration
In the past, the majority of ponds were designed to receive influent wastewater through a single
pipe, usually located toward the center of the pond. Hydraulic and performance studies
(Mangelson, 1971; Ewald, 1973; Mangelson and Walters, 1972; Finney and Middlebrooks,
1980; Middlebrooks et al., 1982; Shilton, 2005; Crites et al., 2006) have shown that the use of
centralized inlet structures is an inefficient method of introducing wastewater to a pond, often
resulting in less than ideal residence time. Multiple inlet arrangements are preferred, even in
small ponds (<0.5 ha) and preferably by means of a long splitter box with multiple outlets large
enough to avoid plugging by influent solids. The splitter box should be located at approximately
mid-depth above the sludge blanket. Outlets should be located as far as possible from the inlets.
The inlets and outlets should be placed so that flow through the pond has a uniform velocity
profile between the next inlet and outlet.
Single inlets can be used successfully if the inlet is located at the greatest distance possible from
the outlet structure and baffled or the flow directed to avoid currents and short circuiting. Outlet
structures should be designed for multiple depth withdrawal, and all withdrawals should be a
minimum of 0.6 m below the water surface.
4.4.1.1 Pond Transfer Inlets and Outlets
Pond transfer inlets and outlets should be constructed to minimize head loss at peak recirculation
rates, assure uniform distribution to all pond areas at all recirculation rates, and maintain water-
surface continuity between the supply channel, the ponds, and the return channel. See Section
4.5 for further discussion of recirculation.
Transfer pipes should be numerous and large enough to limit peak head loss to about 7-10 cm
with the pipes flowing about two-thirds to three-quarters full. Supply- and return-channel sizing
should assure that the total channel loss is no more than one-tenth of the transfer-pipe losses.
When such a ratio is maintained, uniform distribution is assured.
By operating with the transfer pipes less than full, unobstructed water surface is maintained
between the channels and ponds and scum does not build up in any one area. If the first cell is
designed to remove scum, then the transfer pipes must be submerged.
Transfer inlets and outlets usually are made of plastic pipe or bitumastic-coated, corrugated
metal pipe, and have seepage collars located near the midpoint. These types of pipe are
inexpensive, but strong enough to allow for the differential settlement often encountered in pond-
dike construction.
4-14
-------
Specially made fiberglass plugs can be provided to close the pipes. The plugs may be installed
from a boat. Such plugs permit any pipe to be closed without expensive construction of sluice
gates and access platforms at each transfer point. Launching ramps into each pond and channel
are recommended to assure easy boat access for sampling, aquatic plant control and pond
maintenance.
4.4.2 Baffling
Better treatment is obtained when the flow is guided through the pond. Treatment efficiency,
economics and esthetics play an important role in deciding whether or not baffling is desirable.
Because there is little horizontal force on baffling except that caused by wave action, the baffle
structure need not be particularly strong. The lateral spacing and length of the baffle should be
specified so that the cross-sectional area of the flow is as close to a constant as possible.
It may also be placed below the pond surface to help overcome esthetic objections. A typical
type of baffle might be a submerged fence attached to posts driven into the pond bottom and
covered with a flexible, heavy plastic membrane. Commercial float-supported plastic baffling for
ponds also is available.
Baffling has additional advantages. The spiral action induced when flow occurs around the end
of the baffles enhances mixing and tends to break up or prevent any stratification or tendency to
stratify. Reynolds et al. (1975) and Polprasert and Agarwalla (1995) have discussed the
advantages of biomass distribution and attachment to baffles leading to improved pond
efficiency. It should be mentioned that winter ice can damage or destroy baffles in cold climates.
4.4.3 Wind Effects
Wind generates a circulatory flow in bodies of water. To minimize short circuiting due to wind,
the pond inlet-outlet axis should be aligned perpendicular to the prevailing wind direction. If for
some reason the inlet-outlet axis cannot be oriented properly, baffling can be used to control, to
some extent, the wind-induced circulation. Where the pond depth is constant, the surface current
is in the direction of the wind and the return flow is in the upwind direction along the bottom.
4.4.4 Stratified Ponds
Ponds that are stratified because of temperature differences between the inflow and the pond
contents tend to behave differently in winter and summer. In summer, the inflow is generally
colder than the pond water. It sinks to the pond bottom and flows toward the outlet. In the winter,
the reverse is true. The inflow rises to the surface and flows toward the outlet. A likely
consequence of this is that the effective volume of the pond is reduced to that of the stratified
inflow layer (density current). The result can be a drastic decrease in detention time and an
unacceptable level of treatment.
One strategy is to use selective pond outlets positioned vertically so that outflow is drawn from
the layer with density different from that of the inflow. For example, under summer conditions,
the inflow will occur along the pond bottom. Hence, the outlets should draw from water near the
pond surface.
Another approach is to premix the inflow with pond water while in the pipe or diffuser system,
4-15
-------
thereby decreasing the density difference. This could be accomplished by regularly constricting
the submerged inflow diffuser pipe and locating openings in the pipe at the constrictions. The
low pressure at the pipe constrictions would draw in pond water and mix it with the inflow to
alter the density. However, in this case, clogging of openings with solid material could be a
problem.
4.5 POND RECIRCULATION AND CONFIGURATION
Pond recirculation involves inter- and intra-pond recirculation as opposed to mechanical mixing
in the pond cell. The effluents from pond cells are mixed with the influent to the cells. In intra-
pond recirculation, effluent from a single cell is returned to the influent to that cell. In inter-pond
recirculation, effluent from another pond is returned and mixed with influent to the pond (Figure
4-3).
Pump
I
i
Series
Figure 4-3. Common pond configurations and recirculation systems.
Both methods return active algal cells to the feed area to provide photo synthetic oxygen that can
treat some of the organic load. The principal benefit is to control odors and anaerobic conditions
in that area of the pond. Inter- and intra-pond recirculation can also affect stratification in ponds.
Pond recirculation, however, is not as efficient as mechanical mixing in facultative ponds.
Excessive organic loading of primary ponds and the associated odors can be mitigated by
recirculating treated effluent to the overloaded ponds. Recirculation dilutes high BODs
concentrations and essentially pushes BOD5 into downstream ponds, spreading the load over a
4-16
-------
greater pond surface area in a shorter time than influent flow could do alone. If the recirculated
water originates in ponds with high DO, some of this DO mass is brought into the overloaded
ponds. However, conventional aeration is likely to be a more energy efficient means of
providing DO mass than pumping recirculation water.
Another effect of recirculation is inoculation of primary ponds with microalgae and other
organisms from downstream ponds. Inoculation may help maintain algal populations in primary
ponds, leading to increased photosynthetic DO and odor control. To promote photosynthesis,
water should be recirculated to the surface of the primary ponds in an attempt to form a cap of
algae-rich water. Ideally, this recirculated water is warmer than the bulk of the water in the
primary ponds. In this way, a surface layer of recirculated water is promoted. However, such a
surface cap may be short-lived if night time cooling of the surface allows the surface water to
cool and sink. Three common types of inter-pond recirculation systems (series, parallel, and
parallel series) are shown in Figure 4-3.
Recirculation in series
Recirculating wastewater through the pond series dilutes the organic mass in the first cell by
increasing the flow rate. Neither the mass of material entering the cell nor the surface loading
rate (mass/unit area/d) is reduced by this configuration. Intra-cell recirculation does reduce the
HRT of the water in the cell receiving the recirculated flow, but not the overall HRT of the
system. The method attempts to flush the influent through the pond system faster than it would
travel without recirculation, thereby reducing the concentration in the reactor. The reduction in
HRT might offset any advantages gained other than odor control. This reduction in the first-pass
HRT of the influent and recycled mixture in the first, most heavily loaded, pond in the series
system is:
t= V (4-2)
(1 + r)Q
Where:
V= the volume of pond cell
Q = the influent flow rate
r = the recycle flow rate
r/Q = the recycle ratio
Another effect of recirculation in the series configuration is to reduce the BODs in the mixture
entering the pond, and is given by the expression:
S.
e _ in ,
Where:
Sm = the BOD5 of the mixture
Se = the effluent BOD5 from the third cell
S^ = the influent BOD5
r = recycle flow rate
4-17
-------
Sm would be only 20 percent of Sin with a 4:1 recyle ratio, as Se would be negligible in almost all
cases. Thus, the application of organic load in the pond is spread more evenly throughout the
ponds, and organic loading and odor generation near the feed points are reduced. Recirculation in
series has been used to reduce odors in those cases where the first pond is anaerobic. The
recirculation ratio is selected based on the loading rate applied to the cell that will not cause a
nuisance.
Recirculation in parallel
The parallel configuration more effectively reduces pond loadings than does the series
configuration, because the mixture of influent is spread evenly across all ponds instead of the
first pond. For example, consider three ponds, either in series or parallel. In the parallel
configuration, the surface loading (kg BODs/ha/d) on the three ponds is one-third that of the first
pond in the series configuration. The parallel configuration, therefore, is less likely to produce
odors than the series configuration. However, the hydraulic improvements in design using a
series configuration generally will offset the benefits of reduced loading in parallel
configuration.
Based upon the analyses of performance data from selected aerated and facultative ponds, four
ponds in series give the best BODs and fecal coliform removals for ponds designed as plug flow
systems. Good performance can be obtained with a smaller number of ponds if baffles or dikes
are used to optimize the hydraulic characteristics of the system.
Recirculation usually is accomplished with high-volume, low-head propeller pumps. Figure 4-4
presents a simplified cross-section of such an installation. In this design, the cost and
maintenance problems associated with large discharge flap gates are eliminated by the siphon
discharge. An auxiliary pump with an air eductor maintains the siphon. Siphon breaks are
provided to ensure positive backflow protection.
Pumping stations of this type can be designed to maintain full capacity with minimal increase in
horsepower even when the inlet and discharge surface levels fluctuate over a range of 1.0 - 1.2
m. Multiple- and/or variable-speed pumps are used to adjust the recirculation rate to seasonal
load changes.
4-18
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4-
-------
CHAPTER 5
ADVANCES IN POND DESIGN
5.1 INTRODUCTION
In Chapter 3, the basic design of wastewater treatment ponds was described. In this chapter, we
discuss design innovations that have come about through a better understanding of the biological
processes occurring in these systems and experience building them under different
environmental conditions. Many of these innovations have allowed communities to retain their
pond system with modifications rather than abandoning them in favor of mechanized systems.
Examples include fermentation pits in facultative ponds to protect anaerobic digestion,
streamlined footprints, improved aerators or mixers and additions of covers to retard algal
growth in polishing ponds.
5.2 ADVANCED INTEGRATED WASTEWATER POND SYSTEMS® (AIWPS®)
5.2.1 Description
The AIWPS Technology (Oswald, 1977; Oswald and Green, 2000) has evolved over a 50-year
period of research by Dr. William J. Oswald at the University of California, Berkeley and other
locations. The majority of the research and operations experience has involved facilities in areas
with moderate climates. Certain aspects of the process are currently patent-protected, with new
patents pending. The salient features of the patent reflect the evolution of the design, including a
smaller land footprint, an increased depth in the primary pond, and appropriately sized aperture
for the in-pond digesters (IPDs). The evolution of AIWPS design vs. size is demonstrated in
Table 5-1 and shown in Figure 5-1.
Table 5-1. Evolution of the Design of Selected AIWPSR Wastewater Treatment Facilities
1965 to present.
AIWPS® WWTF Location, Type,
and Design Date
Design
Capacity in
MLD
Treatment
Area in
hectares
Treatment Area/ Design
Capacity
ha/MLD
Type 1
St Helena, CA1965
Hollister, CA1977
Varanasi, Sota, INDIA 1997
Delhi, CA1998
Hilmar, CA1999
Wanganui, NEW ZEALAND
2002
Rosamond, CA 2009
Varanasi, Ramana, INDIA
1.1
7.6
200
5.7
3.8
23
7.6
40
9.3
19.2
220
7.9
7.7
49
16.7
45
8.1
2.5
1.1
1.4
1.9
2.1
2.2
1.1
5-1
-------
2010
Type II
Napa, CA1966
Bolinas, CA 1973
Ridgemark Estates, CA 1975
45.4
0.2
0.5
142.5
2.2
1.7
3.1
3.7
3.4
See p.xiv for conversion table.
^Treatment area/MLD
• Primary Pond Depth
0
0
1960 1965 1970 1975 1980
1985 1990
Design Date
1995 2000 2005 2010 2015
Figure 5-1. AIWPSR Facilities over time showing the design trend of increasing primary
pond depth in meters and decreasing footprint area per treatment capacity in hectares per
million liters per day (MLD) of capacity.
Typically, the AIWPS technology consists of compacted earthen dikes, such as those used in
conventional pond systems, with a minimum of four types of ponds in series. These separate
unit processes in the treatment scheme reduce the impact of short-circuiting in the ponds and
provide for depth control in areas where evaporation exceeds precipitation. While the unit
processes in the AIWPS® do not differ from those in conventional wastewater treatment pond
systems (i.e., primary sedimentation, flotation, anaerobic digestion, methane fermentation,
aeration, photosynthetic oxygenation, nutrient removal, secondary sedimentation, nutrient
removal, storage and final disposal or reclamation and reuse), their application and some
patented design features do differ from those in most conventional pond systems. Figure 5-2 is a
plan view and a schematic profile of a Type 1 AIWPS facility. This is followed by a
description of the functions of the individual ponds.
5-2
-------
City
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r
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md
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entrateL^
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Ci
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u1
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Remove
•
LL
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_^
3
I
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r
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* Lar
i
d
Disposal
Primary
Fermentation
LLT-Lo*
/Level Tra
Photos ynthctk
Oxygenation
J
T
V
nsfer
Sedimentation
Note:
Parasite Ova. BOO,
Nutrients. Heavy Metals
andVOCsWilBeLow
MPN Will Be Less Than
1000/100 mL Dissolved
AirFkutfonandUV
Disinfection May Be
Required for Contact lisa
PLAN VIEW
tin
Is
i.
n
ed
Jsa
Figure 5-2. Type I Advanced Integrated Wastewater Pond System15.
The first pond in the series is an Advanced Facultative Pond (AFP) that contains one of the
unique features of an AIWPS Facility. The AFP contains deep anaerobic digestion and methane
fermentation pits with a minimum depth of 6 - 8m through which all of the influent wastewater
upflows. Figure 5-3 shows a schematic cross section of the AFP. The great depth and certain
design elements prevent DO from entering the fermentation pit or IPD, thereby improving
methane fermentation and reducing solids transfer to subsequent ponds. Most settleable solids
are retained in the pit and undergo anaerobic digestion and methane fermentation. The overflow
velocity is limited to less than 2.0 m/d to optimize sedimentation and to prevent most helminth
5-3
-------
ova and ova cysts from leaving the fermentation pit. Sludge fermentation has been shown to be
sufficiently complete to essentially eliminate sludge handling in moderate climates for many
decades. A public works budget should maintain a line item for removal activities against the
time when it will be necessary to remove sludge and a plan should be in place to compost it,
preferably on site.
ClflMM »
11-j.h K.lr h-x.<
(1) Aerobic Oxidation
(2) Photosynthesis
(3) Organic Acid formation (Putrefaction)
(4) Methane formation
(5) Carbon dioxide reduction
Figure 5-3. Schematic Cross-section of primary facultative pond of an Advanced
(S)
Integrated Wastewater Pond System (Oswald, 1996).
Limited data are available for cold climate operation, but indications are that fermentation occurs
in areas with weather as severe as that in the high country of the Rocky Mountains. Floatables
are collected on a down-wind concrete scum ramp and removed periodically. An AFP will
reportedly remove at least 60 percent of the influent BODs and a greater percentage of TSS. In
the southwestern United States, removals up to 80 percent have been observed. Outlets from the
AFP are located 1 - 1.3 m below the surface to prevent discharge of floatables into the secondary
pond. Recirculation with algal-laden waters with levels of 02 and supplementary mechanical
aeration controls odors.
The second pond in series may be a Secondary Facultative Pond (SFP) or a High Rate Pond
(HRP), depending on the desired level of treatment. Figure 5-4 shows a schematic drawing of
the raceway in the HRP. The HRP is used to produce high concentrations of algae and DO.
With recirculation, the DO can be used for odor control at the surface of the AFP. The algae
remove nutrients and can also serve useful purposes (Woertz et al., 2009). HRP systems are
usually less than one meter in depth and mixed with low-speed paddle wheel mixers (brush
5-4
-------
aerators in Figure 5-2) at a mean surface velocity of approximately 15 cm per second. The
elevated/>H in the HRP along with the intensity of the sunlight it receives contributes to
maintaining high kill rates of bacteria present in the influent. These high/?H values and
temperature in the summer contribute to NHs removal from the wastewater by volatilization,
although this is not the only NHs removal mechanism. Effluent from the HRP is withdrawn from
the surface to obtain the highest quality water with high DO concentrations and high/>H values.
Channel
Width
w
Dividers or
Inside Walls
.Levels or Channel Walls
or Outside Walls
./
Channel Lining
Note:
Length A to B by
V\fery of Channel is
Termed Channel
length L
Mixing Station
or System
PLAN VIEW
Figure 5-4. Schematic of raceway to cultivate microalgae for #2 production. (Oswald,
1996).
5-5
-------
Oswald does not recommend chlorination of the effluent from AIWPS systems because of low
MPN counts in the effluent and the fact that chlorine doses above 10 mg/L are required to kill
algae, potentially releasing their nutrients and BODs back into the water column. However, it is
likely that many states will still require chemical disinfection of these effluents, and if such a
requirement is set, Oswald recommends that algae should be removed prior to chlorination.
Algae can tolerate ozone disinfection.
The third pond is used for algal sedimentation and collection for drying, while the fourth is for
storage, further disinfection and TSS removal. In areas where advanced treatment may not be
feasible and human contact is expected, deep maturation ponds with detention times of 10 - 20
days following treatment in AFP, HRP and Algae Settling Pond (ASP) in series will provide
reliable control of pathogenic microorganisms of human origin.
5.2.2 Modifications
The Type 2 AIWPS® modification provides supplementary aeration to replace algae as the
source of DO in the primary pond surface. The primary pond (AFP) is designed exactly as the
primary pond in the AIWPS® Type 1. In Type 2 AIWPS® facilities has less land, but more
energy for mechanical aeration is required.
5.2.3 Applicability
Where land costs are not a limiting factor, the concept is well suited for the treatment of
municipal wastewater and biodegradable industrial and agricultural wastewaters. New
configurations of the design have reduced the footprint and thus the land requirements (Table 5-
2).
5-6
-------
Table 5-2. AIWPS® Types I and II with Treatment Areas (in acres)1.
AIWPS® WWTF
St. Helena CA Type 1)
NapaCA(Typell)2
Ridgemark Estates CA (Type II)
Bolinas CA (Type II)
Varanasi Uttar Pradesh India
Delhi CA
HilmarCA
Wanganui New Zealand
Melbourne Australia 25 W
Melbourne Australia 55E
Ramana2 Uttar Pradesh India
Design Flow
(MGD)
0.3-3.0
12
0.13
0.05-0.12
54
1.5
1.0
6.2
10
Total
Treatment
Wet Surface
Area (not
including
roads)
(acres)
30.86
342.2
4.1
5.44
566.70
19.86
17.8
117.87
586.26
505.5
91.9
Total
Treatment
Wet
Surface
Area/MGD
design
capacity
(acres/MG
D)
10.3
28.5
31.5
45.3
10.5
13.2
17.8
19
9
1See p. xiv for conversion to hectares.
2From Napa to Ramana, the treatment system footprint has decreased by 200 percent, from
Napa to Delhi, by 100 percent.
5.2.4 Advantages and Disadvantages
The advantages of the AIWPS® technology are reliable treatment, much reduced need for sludge
disposal, lower energy and land requirements, which result in considerable cost reduction for
operation and maintenance. Additional information about the process and operational data are
available in the following sources (Oswald, 1990a; 1990b, 1995, 1996, 2003; Oswald et al.,
1994; Nurdogan and Oswald, 1995; Green et al., 1995a; Green et al., 1995b; Green et al., 1996;
Green et al., 2003; U.S. EPA, 2000a; Downing et al., 2002).
Another advantage of the AIWPS® technology is the ability of the sludge blanket to retain
parasite eggs (ova), adsorb toxic materials, and convert organic TV into .A/2. Toxicity tests
conducted over forty years demonstrate that the AIWPS® is able to produce an effluent from
municipal/industrial wastewaters that will satisfy most regulatory requirements.
One disadvantage of the AIWPS® technology is that land is required for disposal of the effluent
at certain times of the year to remove algae from the effluent. If there is no recirculation of the
settling pond effluent, odors may be present in the advanced facultative pond. The use of surface
mechanical aeration in the primary pond at those times will correct the situation.
5.2.5 Design Criteria
5-7
-------
Design criteria can be obtained in "A Syllabus on Advanced Integrated Pond Systems" (Oswald,
1996). Further information can be found in Crites et al., 2006. The exact number of operating
AIWPS systems is unknown, but many are in operation around the world. Four complete full-
scale AIWPS® units have been closely studied in California, and large-scale pilot units have been
built and studied in the Philippines, Australia, Tunisia, Kuwait, South Africa, France, Indonesia,
Thailand, Morocco, and Spain.
5.2.6 Performance
Some examples of Type I systems are listed in Table 5-3. More detailed descriptions of
AIWPS include St. Helena, Bolinas, Delhi and Hilmar, all in California.
Table 5-3. Type I Advanced Integrated Wastewater Pond Systems (AIWPS R).
Name of Site
Location in CA
Climate
Population Served
Date Commissioned
Type
Design Capacity
Influent
Characteristics
Present Flow
BOD5
Type
Effluent Disposal
Total WWTF Area
Residual Solids
Disposal
St. Helena
Napa County, Napa
Valley, adjacent to
Napa River
3-28° C
5,000
1967
1st Type I AIWPS®
0.3 MGD
0.5 MGD
430 mg/L
Municipal with two
small seasonal
wineries
Beneficial Reuse for
irrigation adjacent to
Napa River
124 acres incl. 90 for
irrigation reuse
No removal to date
Delhi
Merced County, San
Joaquin Valley,
Merced River Basin
3 - 35° C
7,000
1998
Type I AIWPS®
1.2 MGD
0.67 MGD
200 mg/L
Municipal
Percolation disposal
and beneficial reuse
for agricultural
irrigation
37 acres including 9
for effluent percolation
No accumulation to
date
Hilmar
Merced County, San
Joaquin Valley,
Merced River Basin
3 - 35° C
5,000
2004
Type I AIWPS®
1.0 MGD
0.45 MGD
240 mg/L
Municipal with
seasonal FOG
Percolation disposal
40 acres including 12
for effluent
percolation
No accumulation to
date
Pond Design
Treatment Wet
Surface Area
Advanced Facultative
Pond(s)
High Rate Pond(s)
Algae Settling
31 acres
Yes (1 with baffle-
protected
fermentation crib)
Yes (1 serpentine)
Yes (1)
20 acres
Yes (2 operated in
parallel each with one
fermentation pit)
Yes (2 peripheral)
Yes (2 in parallel)
1 8 acres
Yes (2 operated in
parallel each with two
In-Pond Digesters)
Yes (2 peripheral)
Yes (2 in parallel)
5-8
-------
Pond(s)
Maturation Pond(s)
Algae Drying Beds
Operators
Yes (2 in series)
None
2
Yes (3 in series)
Yes (4)
2 (part-time)
Yes (2 in series)
Yes (4)
2 (part-time)
5.2.6.1 St. Helena, California
The St. Helena, California system was the first full-scale Type 1 AIWPS Facility designed and
constructed under the supervision of Dr. Oswald. It has been in operation for over 40 years. The
site includes a spray irrigation and secondary reclamation field for land application for use
during the dry season (May to October). The system discharges to the Napa River intermittently
during the winter.
Figure 5-5 shows a plan view of the St. Helena system, not including the irrigated pasture
adjacent to the treatment facility. Table 5-3 summarizes the characteristics of the facility. The
wastewater treatment system serves about 6,000 people (2000 Census) at an average flow rate of
1.5-1.9 ML/d (400 - 500, 000 g/d) on about 6 ha. There are approximately 36 ha of grassland
available for summer time use.
5-9
-------
24" Bypass Q-
to Ditch
24" Influent
Sewer Control Building
OSampling Point
Figure 5-5. Plan view of St. Helena, California, AIWPS^ (Oswald, 1996)
5-10
-------
St Helena 2009-10
BOD5 mg/L
500
100
sept oct nov dec jan feb mar apr may jun jul aug
—^BODmg/LInf -^BODmg/LEff
Figure 5-6. St. Helena biochemical oxygen demand.
St Helena 2009-10
TSS mg/L
700
100
sept oct nov dec jan feb mar apr may jun jul aug
—^TSS mg/L Inf ^^TSS mg/L Eff
Figure 5-7. St. Helena total suspended solids.
Figures 5-6 and 5-7 present the BODs and TSS performance data for the St. Helena system.
Figure 5-8 presents a summary of annual means for total P, total N and BODs (Meron, 1970) for
the various stages of the St. Helena system.
5-11
-------
Performance of AIWPS® Type 1
Annual Means at St. Helena, CA
_, 45
O) 40
Ł 35
• 30
Q. 9c
I- 25
•O 20
C 15
10
iiM
0)
!
o
co
il _
1
0>
i
r-
J)
250
D Total P
D Total N
• BOD
200
150
100
- 50
-Zl Ct
^1 o
O) C
C 0
1 I
v> 3
x Ł
O)
E
Q
O
Figure 5-8. Performance of AIWPSR Type 1: annual means at St. Helena (Meron, 1970).
5-12
-------
City at Si Helena
\
]
Figure 5-9A. Configuration of the St. Helena AIWPSR. Pond 4 has been divided into IB
and 4. IB was designed to treat seasonal industrial waste from small winery operations.
Currently all influent is sent to IB.
5-13
-------
FACULTATIVE1 POND
AIPS TYPE II
OMAftMUAl. AenATOff
Figure 5-9B. Configuration of Pond IB (as of 1994).
The effluent quality can vary depending on whether growth conditions are favorable for algae in
the HRP and ASP, but the data for 2010 show consistently acceptable water quality. When the
effluent is discharged to land, TSS is not a compliance parameter, though the high concentration
of algae can reduce the effectiveness of the disinfection process. Based upon published data, the
process can produce excellent quality effluent if algae are removed before the effluent is
disinfected and discharged to land or ambient water.
5-14
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5.2.6.2. Delhi and Hilmar, California
Delhi and Hilmar are two small towns (populations of 10,000 and 8,000, respectively) in the
Central Valley, a large ancient marine lake bed that lies between the Coast Range and the Sierra
Nevada. It is the site of industrial-scale agricultural enterprises that include poultry and dairy
operations. Nitrogen infiltration of groundwater is a valley-wide problem. The temperature
ranges from 3 °C in winter to 35 °C in summer. Rain fall is low (highly variable average: 150
mm) and is limited to the winter months. Both towns had outgrown their original treatment
systems and decided to replace them with AIWPS®. Figure 5-10A and B show the plans for the
Delhi and Hilmar systems.
Figure 5-10A and B. A. Delhi, California AIWPS®; B. Hilmar, California AIWPS
(AFP=Advanced Facultative Pond, FP= Fermentation Pit, HRP=High Rate Pond,
ASP=Algal Settling Pond, ADB-Algal Drying Bed, MP=Maturation Pond, PB=Percolation
Bed).
5-15
-------
In 2009-10, the EPA Region 9 Laboratory, Richmond, California, conducted a study at Delhi
comparing dry (August) and wet (January) season treatment throughout the system. BOD5 and
TSS removal are presented in Figures 5-11A and B. Total coliform and E. coli results, are
presented in Figures 5 - 12A and B.
Delhi BOD5 and TSS (mg/L)
August 12-27, 2009
300
250
200
I BOD
I TSS
Influent AFP-1 AFP-2 HRP ASP-1 ASP-2 MP-1 MP-2 MP-3
B.
Delhi BOD5 and TSS (mg/L)
January 12-28, 2010
I Total BOD
I TSS
„
-------
Delhi AIWPS Bacterial Values
August 12-27, 2009
i Total Coliforms
I Ł. CQI'I
<*
&
&
B
Delhi AIWPS Bacterial Values
January 12 - 28, 2010
l.OE+8
1.0 E+7
1.0 E+6
1.0 E+5
1.0 E+4
1.0 E+3
1.0 E+2
1.0 E+l
1.0 E+0
f i i
ii i • n •
i Total
Co I if or rr.
I f. coli
'V
Figure 5 - 12A and B. Delhi AIWPS Coliform Study. A. Summer, B. Winter.
(AFP=Advanced Facultative Pond, HRP=High Rate Pond, ASP=Algal Settling Pond,
MP=Maturation Pond).
5-17
-------
5.2.6.3 Type II AIWPS®
A variation on the AIWPS® design, Type II, does not include the high rate pond or algae settling
basin. Details of these systems are presented in Table 5-4.
Table 5-4. Type II AIWPSg
Location in California
Climate
Population served
Date commissioned
Type
Design Capacity
Influent
Characteristics
Present Flow
BOD5
Type
Effluent disposal
and/or reuse
Total WWTF Area
Residual Solids
Disposal
Napa
Napa County adjacent
to the Napa River
near San Francisco
Bay
3-28° C
77,000
1968
II (4 ponds operated
in series)
12MGD
12MGD
320 mg/L
Municipal
Discharge to Napa
River and beneficial
irrigation reuse
360 acres
None
Bolinas
Marin County, Pacific
Coast in the Bolinas
Bay watershed
6 - 29° C
500
1973
II (3 ponds operated
in series)
0.03 MGD
0.03 MGD
160 mg/L
Municipal
On-site disposal by
spray irrigation to land
and wetlands
40 acres including 34
acres of on-site
disposal
Land application of
residual solids
removed from Pond
1A in 2005
Ridgemark Estates
San Benito County
near the City of
Hollister
6-29°C
1,000
1973
II (4 ponds operated
in series)
0.1 MGD
0.1 MGD
220 mg/L
Municipal
Beneficial reuse for
landscape irrigation
6 acres
None
Pond Design
Treatment Wet
Surface Area
Primary Facultative
Pond(s)
Secondary Facultative
Pond(s)
Algae Settling Ponds
Maturation Pond(s)
Algae Drying Beds
Operators
340 acres
Yes (1) with internal
fermentation trenches
Yes (1)
None
Yes (2 in series)
None
4 (part-time)
5.4 acres
Yes (2) with baffle-
protected
fermentation pit
(Ponds 1Aand 1Bare
operated in parallel)
Yes (1)
None
Yes (1)
None
2 (part-time)
4.1 acres
Yes (1)
Yes (1)
None
Yes (2 in series)
None
1 (part-time)
5-18
-------
5.2.6.3.1 Bolinas, California
The Bolinas Type IIAWIPS® has been in operation since 1973. The system consists of four
ponds (2 facultative; 1 maturation; and 1 storage) (Figure 5-13) that occupies 1.6 ha of a 35.6 ha
community-owned area. Treated effluent is land applied during the dry season (May - October)
and stored in Pond 3 during the winter. Figure 5-14 shows the treatment of BODs throughout
the treatment system in 2010. The population served is approximately 500, as only part of the
town is connected to the system. Restrictions on additional water connections, as well as a
strong voluntary water conservation program, postponed the need to design for increased
capacity indefinitely and improvements to the collection system have reduced inflow and
infiltration (I&I). The plant accepts septage from the rest of the community. Pond 1A was
dewatered and accumulated biosolids were treated on adjacent community-owned land in 2001.
Plans are being developed to remove biosolids from Pond IB. In 2008, solar panels were
installed near the ponds system laboratory in a shade-free area facing southeast to southwest.
The installation generates power to run the spray field pumps and the aerator in Pond IB. It has
been generating more energy than it uses and is expected to be paid off in 16 years.
Figure 5-13. Bolinas, California AWIPSR with adjacent spray fields, including seasonal
wetlands, depressions worked into the surrounding area providing habitat for birds during
the rainy season. Operation rotates the area being sprayed over the dry season.
Maintenance includes monitoring condition of pipes, pumps, valves and sprinklers and
harvesting emergent vegetation.
5-19
-------
Bolinas BOD5 (mg/L)
300 -C
250 -\
200
i Influent
HA
I IB
12
3
Jan Feb March April May June July Aug
Figure 5-14. Bolinas AIWPS BOD5 through the system, 2010.
(1A, IB = primary; 2 = maturation pond; 3 = storage pond.)
5.2.7 Limitations
Limited data are available for cold climates.
5.2.8 Operation and Maintenance
Operation and maintenance for the AIWPS® are basically the same as that for other types of
ponds. The system is not maintenance intensive and energy costs are comparable to those of a
partial mix pond. Analytical work is essential to ensure proper operation, but extensive sampling
and monitoring is usually not necessary. Inspection of earthen dikes is necessary to control
rodent damage. See Chapter 9 for details on operation and maintenance of pond systems.
5.2.9 Costs
Costs to construct and operate the AIWPS® are lower than conventional wastewater treatment
processes. Green, et al. (1995a) reported, "The overall energy savings of photosynthetic
oxygenation in paddle wheel mixed HRPs are significant when compared with the energy
requirements of mechanical aeration in activated sludge and extended aeration systems."
Construction costs include cost of land, excavation, grading, berm construction, sealing, and inlet
and outlet structures. Construction methods used are the same as with other pond systems.
5.3 SYSTEMS WITH DEEP SLUDGE CELLS
The wastewater treatment facilities presented in this section are similar to a Type II AIWPS®
system, that is, they do not include the high rate algal growth and settling ponds in the system.
5-20
-------
5.3.1 Dove Creek, Colorado
5.3.1.1 Description
Dove Creek is located approximately 48.1 km north of Cortez, CO, at an elevation of 2.1 km
above sea level. Air temperatures range from -18 C to greater than 32 C. The wastewater
treatment plant serves approximately 700 people with an average design flow rate of 173.4
L/min. The system is permitted for a design flow of 302.3 L/m and 130.6 kg of BODs/day.
The system has an anaerobic pond preceding the aerated cells followed by a free water surface
wetland. The fermentation pit is shown in plan and cross sectional view in Figures 5-15 and 5-
16, respectively. The fermentation pit has a total volume of 905 m3.
Figure 5-15. Cross-sectional view of the facultative cell at the Dove Creek, Colorado
WWTP.
5-21
-------
Aerated Pond on This Side of Anaerobic Pit
Elevation 53.1
Elevation = 56.0
Inlet Pipe
Figure 5-16. Plan view of Dove Creek Fermentation Pit (Fagan, pers. comm.).
5.3.1.2 Common Modifications
The only modification that has been made is that a wetland has been constructed after the pond
system to polish the effluent.
5.3.1.3 Applicability
The system is well suited for small communities located in practically any climate. The system
is effective in removing TSS, BODs, fecal coliform and nitrification ofNHs during the warmer
months of the year.
5.3.1.4 Advantages and Disadvantages
The primary advantage of the system is that it combines the benefits of both anaerobic and
aerobic processes. By preceding the aerobic cell with an anaerobic cell, solids production is
reduced and less-frequent cleaning of the settling cell is required.
One disadvantage of the system is that biological activity slows down during cold weather.
Mosquito and similar insect vectors can be a problem if vegetation on the dikes and berms is not
properly managed. Sludge accumulation rates will be higher in cold climates because low
temperatures inhibit anaerobic reactions. Energy input is required.
5-22
-------
5.3.1.5 Design Criteria
Systems with deep sludge cells are designed with the same criteria as those for anaerobic and
aerated cells. The design criteria shown in Table 5-5 are acceptable for most environmental
conditions.
Table 5-5. Design Criteria for Pond Systems with Deep Sludge Cells (from Hotchkiss,
Colorado Wastewater Ponds Treatment System).
Unit Processes
Lagoon #1
Aeration
Lagoon #2
Aeration
Polishing Pond
Recirculation
Chlorination
Chlorine contact
chamber
Effluent Flow
Measuring
Irrigation
Pumping
Dechlorination
Unit Process Features Description
Anaerobic portion: Vol. = 1.75 MG,
Depth=18.5-21.5ft.
t=3.5 days; Aerobic portion: Vol. =2. 9 MG,
Depth=13ft.
t=5.9 days.
2-5 hp and 1 -1 0 hp surface aerators,
FTR=1.40lbs02/hp-hr
Vol. =5.0 MG, Depth=13 ft., t=10.0 days
1 -5 hp and 1 -1 0 hp surface aerators, 1 -5 hp
aspirating aerator. FTR=1.46 Ibs C^/hp-hr
Vol=1 .74 MG, Depth=12 ft., t=3.5 days
0.5 hp pump rates at 100 gpm
2-150 Ib. Gas cylinders, 0 to 4 Ibs/day and 0
to 1 0 Ibs/day.
Regulators: 2.5 mg/L maximum dosage
Serpentine Basin, Length=190ft, Width=3.5
ft, 54:1 length to width ratio. Vol. =34,800
gallons, t=30 minutes
450 V-notch weir, h=15 inches
A pump of undetermined size will be used to
pump a portion of the effluent to an irrigation
ditch supplying 70 acres of farm land
502 gas, same equipment as gas chlorination
equipment
Capacity,
Hydraulic/Organic
315lbsBOD5/day
0.494 mgd
1.67 mgd
0.494 mgd
See p. xiv for conversion factors.
5.3.1.6 Performance
Performance data from January 31, 2000 to October 31, 2006 are shown in Figures 5-17 through
5-20. At the time, the system was receiving only 44 percent of the permitted flow rate. After an
initial excursion, the BODs removal tended to stabilize, but on occasion still exceeded the
5-23
-------
effluent standard of 30 mg/L. The effluent TSS concentrations varied rather widely. Both BODs
and TSS were measured in the constructed wetland following the pond system. Data were not
available for the intermediate or pond system effluent.
Developing a sustainable plant crop proved to be more complicated than was expected.
Therefore, it is difficult to access the performance of the various components of the system. It is
reasonable to assume that the water quality exceedances were attributable to the variability
encountered in the management of the constructed wetland.
Oov« Cf««k CO. Performance DHa
0.12
01
•*• Avfl Inf Flow Rat*
» MM Inf Row Rat*
Avg B1 Row Rat*
iiiii
SSMCM
Figure 5-17. Flow rate performance data for Dove Creek, January 31, 2000 to October 31,
2006 (Colorado Department of Public Health and Environment (CDPHE), 2006).
5-24
-------
Dove Creek, CO, Performance Data
Dale
Figure 5-18. BOD5 performance data for Dove Creek, January 31, 2000 to October 31, 2006
(CDPHE, 2006).
Dove Creek.CO, Performance Data
Date
Figure 5-19. TSS performance data for Dove Creek, January 31, 2000 to October 31,
2006 (CDPHE, 2006).
5-25
-------
10*
10'
10>
o
10
j i i i J i i i
10 •
12/31/99 12/31/00 12/31/01 12/31/02 12/31/03 12/31/04 12/31/05 12/31/06
Date
Figure 5-20. Fecal coliform performance data for Dove Creek, January 31, 2000 to October 31,
2006 (CDPHE, 2006).
5.3.1.7 Limitations
Depending upon the rate of aeration and the local climate, aerated ponds may experience ice
formation on the water surface during cold weather periods. Reduced rates of biological activity
also occur during cold weather. If properly designed, a system will continue to function and
produce acceptable effluents under these conditions. The potential for ice formation on floating
aerators may encourage the use of submerged diffused aeration in very cold climates (see
Chapter 3 for a discussion of maintenance of submerged aeration devices). Any earthen
structures used as impoundments must be periodically inspected as rodent damage can cause
severe weakening of pond embankments.
5.3.1.8 Energy
Typically, systems are designed to flow by gravity from one pond to the next, otherwise energy
will be required to keep the system flowing. Energy is also required for the aeration devices, the
amount depending on the intensity of the mixing. Partial mix systems require between 1-2
W/m3 per MG of capacity, depending on the depth and configuration of the system. See the
5-26
-------
design example 3-7 (#9) in Appendix C for a method of calculating the energy requirements for
partial mix systems.
5.3.1.9 Costs
Construction costs associated with deep sludge ponds are similar to those with partially or
completely mixed aerated ponds and include cost of the land, excavation, and inlet and outlet
structures. Costs are similar to building an anaerobic pond. If the soil where the pond is
constructed is permeable, an additional cost for lining should be included. Excavation costs vary,
depending on whether soil must be added or removed. Compacting and synthetic lining material
should be included in cost estimates. Operating costs of partially aerated ponds include electrical
surface or diffused aeration equipment and maintenance of these units.
5.3.2 Fisherman Bay, Washington
5.3.2.1 Description
Fisherman Bay is located on Lopez Island in San Juan County, Washington, approximately 161
km northwest of Seattle at an elevation slightly above sea level. Influent water temperatures
range from 7 C in the winter to 22 C in the summer.
The community has a septic tank effluent pumping (STEP) system that serves residences and
small community commercial sites near an enclosed salt water bay with generally poor soil
conditions. The system is currently rated for about 139.3 L/m.
The wastewater treatment plant, built in 1979 with a single 946.4 m3 aerated pond was upgraded
in 1995 with a second 1703.4 m3 aerated pond operated in series with the original basin. The
upgrade did not provide consistent treatment at the level needed for compliance. Since there is
considerable treatment of wastewater in local septic tanks, the influent coming to the plant is low
in BODs and TSS, but has a high NHs concentration, averaging 57 mg/L (Li et al., 2006).
In 2000 Sear Brown Engineering (now Stantec) performed a plant evaluation that recommended
upgrading the pond system to an AlWPS-like based on research and process theory published by
Dr. Oswald (see Section 5.2) and Dr. Michael Richards. In 2003, an anaerobic cell was built to
pretreat the STEP system influent with an anaerobic methane bacteria process. This reduced the
carbon load to the larger aerated pond, which was partitioned into three cells to provide a settling
cell. The fermentation pit has a total volume of 314 m3 and a depth of 4.57 m. Within the 4.57
m depth is a manhole pit at the bottom 1.5m deep and 1.8 m in diameter from which the influent
enters the pond (Figure 5-21). The original, smaller, shallower pond was taken offline, re-
excavated and relined as a storage and surge pond for future water reuse.
Since these modifications were made, the district has not had violations but there were still
problems dealing with the seasonal algae and biomass blooms that made disinfection difficult.
5-27
-------
The last part of the system, the constructed wetland, was built to use the nutrients in the pond
effluent. The effluent quality is now consistently high year round, including low bacteria
residuals. Future plans include reusing the plant effluent (Geoffrey Holmes, pers. comm., 2010).
5.3.2.2 Modifications
The modification to this system was to add the anaerobic pond with the deep sludge pit to an
existing system of two ponds. Other modifications to the existing ponds were included in the
2003 up-grade of the system. In 2006, a wetland was constructed through which the effluent
from the last pond flows.
5.3.2.3 Applicability
The system is well suited for small communities located in practically any climate. The system
is effective in removing TSS, BODs, fecal coliform and nitrification ofNHj during the warmer
months of the year.
5.3.2.4 Advantages and Disadvantages
See Section 5.3.1.4.
5.3.2.5 Design Criteria
Systems with deep sludge cells are designed using the same criteria for anaerobic and aerated
cells. The design criteria shown in Table 5-5 are valid for most environmental conditions.
5 .3.2.6 Performance
The system has functioned well, as shown in Figures 5-22 through 5-26. The average flow rate
entering the plant in the years 2003 - 2006 was 45.5 L/m (0.0173 mgd), approximately 50
percent of the design flow of 89.3 L/m (0.034 mgd). In this period, BODs removal has averaged
86.5 percent, CBOD5 removal 88.9 percent, TSS removal 34.8 percent (Max = 69.3, Min = 6.3),
and NHs removal 56.0 percent (Max = 76.0, Min = 25.2). Ammonia removal is positively
correlated with the effluent water temperature. The plant CBODs removal failed to achieve 85
percent removal six times out of the 86 samples analyzed; whereas BODs removal failed 32 out
of 113 samples. This satisfied the standard of 85 percent removal 93.0 percent of the time, while
the BODs removal satisfied the standard only 71.6 percent of the time. The failure to meet the
85 percent removal standard can be attributed to the weak sewage entering the facility from on-
site septic systems. The addition of a constructed wetland using a substrate of tire crumbs and
gravel in 2007 has reduced CBOD5 by 79 percent, TSS by 88 percent, fecal coliform by 97
percent and total residual chlorine below 0.75 mg/L consistently and below 0.25 mg/L the
majority of the time (Li and Holmes, 2010).
5-28
-------
Figure 5-21. Fisherman Bay, Washington. Anaerobic cell with recirculation manifold using
an aerated cap of polishing cell effluent to provide odor control.
5-29
-------
Fisherman Bay, WA, Performance Data
60000
50000
40000
Q.
O)
~ 30000
OL
^
u. 20000
10000
8
a
C!
00000
00000
CM CM CM CM CM
0000
0000
CM CM CM CM
CO h- T- tD
CM CM
° ° °
5
CO
00 O) O T-
CO
CM
CM CM CM CM CM CM CM
CO (D CM (D O"> O"> T—
S 3 ^ ^ ^ C! S
r- oo o> T-
Date
Figure 5-22. Fisherman Bay, Washington flow rate data for October 28, 2003 through
August 29, 2006 (Li et al., 2006).
Fisherman Bay Performance Data
- Influent
-Anaer Eff
- Plant Eff
- Plant Eff CBOD
Date
Figure 5-23. Fisherman Bay. BOD5 performance data for October 28, 2003 through
August 29, 2006 (Li et al., 2006).
5-30
-------
Fisherman Bay Performance Data
CO CO
8888888
in in
8888888
00 CM CD O CD
Q c* ^ z: z:
o T- CM co
in
Q
in
~
00 55 O
00
inininininininto
88888888
00 O5
Date
Figure 5-24. Fisherman Bay. NHs performance data for October 28, 2003 through August
29, 2006 (Li et al., 2006).
5-31
-------
Fisherman Bay, WA, Performance Data
O)
100
90
80
70
60
50
40
30
20
10
0
•InfTSS
-Anaer Lagoon Eff
• Lagoon 2 Eff
Plant Eff
Date
Figure 5-25. Fisherman Bay. TSS performance data for October 28, 2003 through August
29, 2006 (Li et al., 2006).
5-32
-------
PH
KC
• 100 ml
i
10'
' * *» * J*f . /\*»"^V *•**"'
. U
*•%*•. '
* '
;.
. t-ri •
• i
1 n Jli 1 iiwll '
Ł 10'
• 'iii & •
• • • • • • •
• •
'.. B*J .
1. .-.-.. r r
10 ;
_i L
a
9/3(W)3
9/30/04
9 3006
Date
Figure 5-26. Fisherman Bay. Fecal coliform and/jH performance data for October 8, 2003
through August 29, 2006 (Li et al., 2006).
5.3.2.7 Limitations
See "Limitations," Section 5.3.1.7.
5.3.2.8 Energy
See "Energy," Section 5.3.1.8.
5.3.2.9 Costs
See "Costs," Section 5.3.1.9.
5.4 HIGH-PERFORMANCE AERATED POND SYSTEM (RICH DESIGN)
The high-performance aerated pond system (HPAPS) described by Rich (1999) has been referred
to in the literature as dual-power, multi-cell systems (DPMC). The system consists of two
aerated basin in series. Screens to remove large solids precede the system. A reactor basin for
bioconversion and flocculation is followed by a settling basin dedicated to sedimentation, solids
stabilization and sludge storage. Algal growth is controlled by limited hydraulic retention time
and division of the settling basin into cells in series. Disinfection facilities follow the settling
basin (Figure 5-27).
5-33
-------
Reactof Basin
Settling Basin
Reaclor Cell
Settling Calls
Figure 5-27A and B. Flow diagrams of DPMC Aerated Pond System. A. Two basins in
series utilizing floating baffles in settling cells. B. A single basin using floating baffles to
divide various unit processes. (Rich, 1999)
Design procedures are available for the HP APS system and are illustrated in Example 3-6
(Appendix C).
5.4.1 Performance
Several sets of performance data for the HP APS systems are available; all are for locations in
mild climates, such as South Carolina and Georgia.
Performance data for the DPMC system in Berkeley County, South Carolina are presented in
Figure 5-28. Data are for six years of operation; the system appears to be functioning as
designed. Sludge removal data were not available.
Continuous operation of the aeration system is essential to obtain maximum efficiency as
illustrated by Figure 5-29. The Berkeley County performance data were taken from a system
using continuous aeration, while the data for the performance of a similar system in South
Carolina from a system using aeration 50 percent of the time. Results in the second case were
improved by about 50 percent by changing to a continuous aeration operation.
A DPMC system (design flow = 12,870 m3/d) followed by an intermittent sand filter located at
the Ocean Drive plant in North Myrtle Beach, South Carolina has been in service for over twelve
years and has performed very well, (Figure 5-30). A flow diagram for the system is shown in
Figure 5-31. Final effluent TSS concentrations have not exceeded 15 mg/L. In October 1997,
EPA, Region 4 collected two 24-hr composite samples from the DPMC aerated ponds. The data
from this evaluation are presented in Table 5-6 (Rich, 1999). A similar plant, the Crescent
Beach plant at Myrtle Beach, also performed well as shown in Figure 5-32.
5-34
-------
mmummumimmi
MONTHS
Figure 5-28. Performance of DPMC Aerated Pond System in Berkley
County, South Carolina, aerators operating continuously (Rich, 1999).
60
•!*
O 20
10
i 1 I
m m
§ s
I
Date
Figure 5-29. Effluent TSS and BOD5 from a DPMC Aerated Pond
System, aerators operating intermittently (Rich, 1999).
5-35
-------
Table 5-6. Performance of DPMC Aerated Pond at North Myrtle Beach (Rich, Bowden,
and Henry unpublished data, personal comm.).
Influent
Parameter
(mg/L)
BOD5
CBOD5
SCBODs
TSS
Alkalinity
NH3
N03
TK/V
TP
Chi a
160
165
62
185
195
25
0.07
37
5,9
-
Effluent
Aerated
Reactor A1
21
16
5
79
190
25
0.05
35
2.8
-
Aerated
Reactor A2
23
20
5
77
190
28
0.05
40
3,3
-
Settling
Pond A4
10
8
4
8
210
31
0.09
34
0.6
0.036
Settling
Pond B4
12
6
4
4
220
30
0.44
33
1.2
0.043
Intermittent
Sand Filter
2
1
1
4
17
1
32
2
0.8
-
CBOD5= Carbonaceous BOD5
SCBODs = Soluble CBOD5
DM
Figure 5-30. Monthly Average BOD5 and TSS from Ocean Drive,
North Myrtle Beach (Rich 1999).
5-36
-------
Influent
Headworks
DPMC Aerated
Lagoon
i/
f
1
\
DPMC Aerated
Lagoon
\
B1
1
B4
Intermittent
Sand Filters
Effluent
IE h.
Figure 5-31. Sketch of a DPMC Aerated Pond-Intermittent Sand Filter System at
North Myrtle Beach (Rich et al., pers. comm.).
O5 O> W ffl O>
h- O ^ ^ N-
n n cj
2? 2? 2?
*3 ^ |Q
Date
Figure 5-32. Monthly average effluent BODs and TSS at Crescent Beach, North Myrtle
Beach (Rich, 1999).
Having collected 36 months of data, Rich and Rich (2005) compared the performance of three
DPMC-Intermittent Sand Filter systems with three carousel-extended aeration type systems
(Table 5-7). The performance of the DPMC-intermittent sand filter (-IS) systems approached
that of the carousel-extended aeration type systems with tertiary rapid sand filtration. Ammonia
removal permit requirements were met in the intermittent sand filter facility in winter and
summer, but the carousel systems reduced the concentration to less than 1 mg/L at the 90
percentile value. The DPMC-IS systems effluent 90 percentile value ranged from 1.66 to 1.81
mg/L. Capital and operational costs of the DPMC-IS systems were approximately 74 and 61
percent, respectively, less than the costs of the carousel-type systems.
5-37
-------
Table 5-7. Comparison of Pond-Intermittent Sand Filter Systems with Carousel-Extended
Aeration Systems (Rich and Rich, 2005).
Flow, mgd
Mode
Max
Permit
Max/Permit
TSS, mg/L
50°/c/
90%J
Permit
90%/Permit
BOD5, mg/L
50%
90%
Permit
90%/Permit
NH3-N, mg/L
50%
90%
Permit
Violations
DPMC-lntermittent Sand Filter
Systems
Ocean Drive
2001-2004
1.4
3.1
3.4
0.91
1.66
5.84
30
0.19
2.06
3.33
10
0.33
0.67
1.81
W10, S24
0
Crescent
Beach
2001-
2004
1.1
1.8
2.1
0.86
1.35
3.20
30
0.11
2.34
3.98
10
0.40
0.44
1.66
6
0
Hampton
2002-
2005
0.8
1.3
2.0
0.65
1
1
30
0.03
2.6
3.85
10
0.38
1.70
1.88
W4.2,
SI
0
Carousel-Extended Aeration Systems
Page
Creek
2001-
2004
0.4
0.6
1.0
0.60
8.81
13.82
30
0.46
3.31
4.86
30
0.16
0.02
0.11
20
0
Yellow
River
2001-
2004
8.6
11
12.0
0.92
1.69
2.56
10
0.26
1.27
1.95
30
0.06
0.15
0.28
1
0
Jackson
Creek
2001-
2004
2.9
3
3.0
1.00
1.84
2.55
20
0.13
2.05
3.34
10
0.33
0.15
0.31
2
0
Beaver
Run
2001-
2004
4.1
4.5
4.5
1.00
2.19
3.90
20
0.20
1.54
2.64
10
0.26
0.13
0.25
2
0
11mgd=3,785m3d
250 percentile value
390 percentile value
4W-winter value, S=summer value
5.4.2 Limitations
The only performance data for the HP APS systems available are for locations in mild climates.
5.4.3 Operation and Maintenance
As with most ponds systems, the HP APS is not maintenance intensive, but more maintenance is
required than for facultative ponds. Operation and maintenance is similar to that required for
other complete mix systems. See Chapter 9 for operation and maintenance requirements.
5-38
-------
5.4.4 Costs
Cost information for all pond systems varies widely (see Chapter 8).
5.5 BIOLAC® PROCESS (ACTIVATED SLUDGE IN EARTHEN PONDS)
5.5.1 Description
EPA published an excellent summary of the status of the BIOLAC® processes in the U.S. (U.S.
EPA, 1990). Information from that report is presented in this section. Additional information
was provided by the Parkson Corporation (2004) (http://www.parkson.com/main.aspx).
There are several variations of the BIOLAC® process. Basically, the processes are extended
aeration activated sludge systems with and without recirculation of solids. There are three basic
systems: (1) BIOLAC-R, an extended aeration process with recycle of solids; (2) BIOLAC®-L,
an aerated pond system without recycle of solids; and (3) BIOLAC® Wave Oxidation
Modification (WOM) used to nitrify and denitrify wastewater. In addition to these systems,
floating aeration chains have been installed to upgrade existing pond systems.
The BIOLAC -R system is shown in Figure 5.33. It is an extended aeration process operating
within earthen embankments or other types of structures.
5-39
-------
Waste Activated Sludge
Grrt
Chamber
* (Optional)
Figure 5-33. Flow diagram of BIOLAC -R System (Parkson Corp., 2004).
5.5.2 Common Modifications
5.5.2.1 BIOLAC®-L System
The BIOLAC -L system is a typical flow-through aerated pond without recycle of solids and a
waste sludge pond. The flow diagram is the same as that shown in Figure 5-33 minus the
clarifier and sludge pond. Sludge storage and decomposition occur in the polishing pond.
5.5.2.2 Wave Oxidation Modification
Carbon oxidation and nitrification-denitrification occur in the Wave Oxidation Modification
system (Figure 5-34). This is a BIOLAC®-R system operated at low DO concentrations and
automatic control of the airflow rate in each aeration chain. Airflow is alternated such that
several moving oxic and anoxic zones are created in the aeration basin. This modification has
been used successfully for TV removal.
5-40
-------
Influent
Time: t= 0 minutes
Return Activated Sludge
I WAS
Effluent
Anoxic| Oxic |Anoxic| Oxic |Anoxic|
Influent
^| ,
Time: t= 15 minutes
Return Activated Sludge
WAS
Effluent
Oxic |Anoxic | Oxic |Anoxic| Oxic
-vS,
Figure 5-34. Wave-Oxidation modification of the BIOLAC -R System (Parkson Corp.,
2004).
5.5.2.3 Other Applications
BIOLAC floating aeration chains are used as retrofits for existing ponds and installed as
original aeration equipment. Several operations around the country are using BIOLAC® aeration
equipment.
5-41
-------
5.5.2.4 Applicability
The concepts are suited to any size of system, depending upon the requirements for the
municipality or industry. When used as a conventional partial mix or complete mix pond
system, the concept is generally limited by the same constraints imposed on other aerated pond
systems. The processes are very flexible and are applicable at any location where activated
sludge, partial mix or complete mix ponds are acceptable.
5.5.3. Advantages and Disadvantages
The advantage of the BIOLAC® systems is that they are very flexible and can be designed as a
typical partial mix or complete mix pond system to achieve BODs removal using the patented
aeration system. The system can also be designed to operate as an extended aeration activated
sludge system to nitrify NHs or to achieve nitrification and denitrification.
The disadvantages of the BIOLAC® systems are that operation and maintenance are more
complex, but no more than that required for conventional extended aeration activated sludge
entails when nitrification or denitrification are required. Sludge bulking occurred, but was
corrected by inserting a selector section (anoxic section) at the head of the aeration tank.
5.5.4 Design Criteria
Recommended design criteria are shown in Table 5-8. Conservative design parameters are used,
and loadings typically are 0.11 - 0.16 kg/d/m3 BODs in the aeration pond with food to
microorganism ratios of 0.014 - 0.045 kg/kg of mixed liquor suspended solids (MLSS). The
average loading rate for 25 BIOLAC®-R plants reported (U.S. EPA, 1990) was 0.12 kg
BODs/m3. The average relationship between the aeration basin volume and the number of
diffusers used for the 25 BIOLAC -R plants was 385 diffusers/mg with an airflow rate of 0.01
scm/min/m3. The actual operating hp at the 25 BIOLAC®-R plants averaged 34 kW/MG for
fully nitrified effluent. The average kW usage is not significantly different from other complete
mix systems.
HRTs range from 24 - 48 hours with solids retention times of 30 - 70 days. Preliminary and
primary treatment is normally not provided, but screening of the influent is desirable. Depths in
the aeration ponds range from 2.5 -6.1m. Because sludge production is expected to be low, a
relatively small waste sludge tank is provided.
Design of the BIOLAC -L system is based on HRT, with values ranging from 6-20 days.
Equivalent loadings of 0.008 to 0.029 kg BOD5/m3/d are used. A polishing pond is required for
the BIOLAC®-L system and has a HRT of 2 - 4 days. Sludge storage and decomposition occur
in the polishing pond.
5-42
-------
Float f,'.'."«-\'\-t
FICURF, 3. B101.AR AFWTII1N ClinlU DF.TAII..
Figure 5-35. Detail of the BIOLACR aeration chain element.
5-43
-------
Table 5-8. Typical Manufacturer's Design Criteria for BIOLACR-R Systems versus
Conventional Extended Aeration Systems (Parkson Corp., 2004).
Parameter
HRT, h
SRT, d
F/M Ibs BODs/d-lb MLVSS
Volumetric Loading,
LbsBOD5/d-1000ft3
MLSS, mg/L
Basin Mixing, hp/mg
Extended Aeration
18-36
20-30
0.05-0.15
10-25
3000 - 6000
80-150
BIOLAC®-R
24-48
30-70
0.03-0.1
7- 12
1500-5000
12- 15
HRT - hydraulic retention time, hrs
SRT - solids retention time, days
F/M - food/ microorganism
MLVSS - mixed liquor volatile suspended solids
MLSS - mixed liquor suspended solids
See p.xiv for conversion factors.
Sludge storage for up to one to two decades is provided in the quiescent zone of the polishing or
settling basin. Further sludge degradation of 40 - 60 percent occurs under anaerobic conditions
in the settling basin.
The unique feature of the BIOLAC® systems is the floating aeration chain system (Figure 5-35).
Fine bubble diffusers are suspended from a floating aeration chain that carries air to the diffusers.
The floating aeration chain is attached to an anchor on the embankment, and allowed to move in
a controlled way to create the oxic and anoxic zones. Each diffuser assembly can support from
2- 5 diffusers. Each diffuser is rated at 2 - 10 scfrn and normally operates at an airflow rate of 6
scfm. Diffuser membranes are expected to last about 5-8 years.
Continuous service positive displacement rotary blowers are generally used. In larger systems,
multistage centrifugal blowers may be more economical. Most systems use three blowers, each
capable of providing 50 percent of the required airflow, one unit being a spare.
An integral clarifier is used with the BIOLAC®-R system although conventional clarifiers are
used on occasion. BIOLAC®-L systems require that a polishing basin be installed for solids
separation and storage. A cross-sectional view of the integral clarifier is shown in Figure 5-36.
The integral clarifier is constructed in the aeration basin but is separated from the aeration zone
by a concrete partition wall. Flow enters the clarifier along the bottom over the entire length of
the partition wall to minimize short-circuiting. A flocculating rake moves the length of the
clarifier sludge trough to concentrate and distribute the sludge. Sludge return and waste is
removed with an air-lift pump.
5-44
-------
Waste
Activated
Sludge
Return Activated Sludge
Effluent
Concrete Wall for
Aeration Basin/Clarfflcation
Zone Separation
FlocculationRake
Mechanism for Sludge
Distribution and
Concentration
Rear Watt of Aeration Basin
C la rifler Influent
Sludge Hopper
Sludge Suction Pipe - PVC Pipe Located
Along the Length of the Clarifier Hopper
Bottom
Figure 5-36. Cross-section view of the Integral BIOLAC®-R Clarifier (Parkson Corp.,
2004).
5.5.5 Performance
Over 600 BIOLAC® systems have been installed in the United States and throughout the world.
The results from two installations in Colorado are presented in this section.
5-45
-------
5.5.5.1 Colorado BIOLAC Facilities
The Alamosa and Tri-Lakes, Colorado BIOLAC Systems have similar flow diagrams. A
description of the Alamosa facility is shown in Table 5-9; the effluent standards are presented in
Table 5-10. The systems have met the effluent standards established by the State of Colorado
(Figures 5-37 through 5-41).
Table 5-9. Description of Alamosa BIOLAC® Facility (CDPHE 2007).
Unit Process
Influent Flow
Measuring
Lifts Pumps
Bar Screen
Grit Removal
Aeration Basins
Aeration
Clarifier
UV Light
UV Contact
Chamber
Measuring
Unit Process
Features/Description
Alamosa - 12" Parshall flume with recorder.
East Alamosa - 8" Electromagnetic meter with
recorder.
3-48" diameter screw pumps each rated at
2,900 gpm @ 24' head. Return sludge is by
gravity to bottom of screw pumps.
One mechanical unit, 2.5' wide, 3/16" bars, %"
spacing.
One aerated vortex grit chamber, 10' diameter
at top, volume = 3,000 gallons, Minimum td =
30 seconds at peak flow .
2 Basins, 150' x 196' x 12.75' deep with 2:1
inside sloops, Volume= 1 ,730,000 gallons
each, td = 32 hours.
3 - 1 00 hp blowers each rated @ 1 965 scfm
at 6.6 psi, 10 air laterals per basin, hanging
diffuser assemblies per lateral.
2 center feed octagon basins 58' inside
diameter, 14' diameter center well, SWD =
12', Volume = 213,000 gallons, SOR = 515
gpd/ft2 , td = 4 hours.
2 UV channels, 2 UV modules per channel,
lamps per module, 20,000 uWs/cm2/module.
2 channels, 25' long, 3' wide.
12" Parshall flume recorder.
Capacity
Hydraulic/Organic
0.23 to 7.37 MGD
Recommended Range
8.3 MGD (Peak)
9.25 MGD (Peak)
8.3 MGD (Peak)
2.571 MGD
3,110lbsBOD5/day
2.571 MGD
2.571 MGD
2.571 MGD
0.23 to 7.27 MGD
Recommended Range
5-46
-------
Table 5-10. Effluent Requirements for the Alamosa BIOLAC® Facility (CDPHE, 2007).
Effluent Parameter
(maximum)
Flow, mgd (reported)
BOD5 mg/L
TSS mg/L
DO mg/L
Fecal coliform
(MPN/100mL
pH units
A/H3mg/L
Jan
Feb
Mar
Apr
May
June
July
Aug
Sept
Oct
Nov
Dec
Discharge Limitations (maximum)
30-D Average
2.57
30
30
NA
288
NA
6.0
4.2
2.4
2.7
2.3
1.4
1.6
2.5
1.8
2.5
2.1
4.3
7-D Average
NA
45
45
NA
576
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Daily
NA
NA
NA
5
NA
6.5-9.0
13
10
7.9
11
12
9
12
15
10
11
7
10
5-47
-------
Alamosa, CO, Performance Data
Date
Figure 5-37. Flow rate for Alamosa BIOLAC facility.
350
Alamosa, CO, Performance Data
Maximum Influent
BOD
Average Effluent
BOD
Maximum Effluent
BOD
Date
Figure 5-38. BODs for Alamosa BIOLACR facility, (upper lines =influent; lower lines
effluent).
5-48
-------
Alamosa, CO, Performance Data
300
erage
TSS
Maximum Influent
TSS
Average Effluent
TSS
Maximum Effluent
TSS
Date
Figure 5-39. TSS for Alamosa BIOLAC facility.
0.7
0.6
0.5
. 0.4
m
| °-3
I 0.2
0.1
0
Alamosa, CO, Performance Data
- Minimum Effluent NH3-
N
Average Effluent NH3-
N
Date
Figure 5-40. NH3 for Alamosa BIOLAC^ facility.
5-49
-------
• DO. moil A MinpH « MaicpH
AvgFC T ManFC
• >100roL »/100mL
8
7
5. 6
•g
5
3
2
1
,;:,:,,::::,:;;,f;:.
• .''
1 i I
11/1/01
11/1/02
11/1/03 11/1/04
Date
11/1/05
11,'1/06
Figure 5-41. DO,/>H and fecal coliform for Alamosa BIOLACR facility.
The Tri-Lakes, Colorado facility is similar to the typical BIOLAC -R system shown in Figure 5-
33 except that there are a modified entrance to the aeration tank and a separate clarifier in place
of the intra-pond settling section. The system has performed well for over five years as shown in
Figures 5-42 through 5-46. Influent BODs averaged 271 mg/L and the effluent averaged 3.4
mg/L, and the TSS influent averaged 288 mg/L with an effluent concentration of 4.4 mg/L.
Effluent NHs was measured during 2005 and 2006, and the average for the two years was 1.73
mg/L, with values ranging from 0.4 to 7.1 mg/L. The maximum effluent concentration reported
was less than 5 mg/L throughout the two years with only two exceptions. In those instances, the
concentrations were 5.12 and 7.1 mg/L.
5-50
-------
Performance Data for Tri-Lakes BIOLAC Facility
•o
ra
E
&
TO
a:
5
Date
Figure 5-42. Flow rate for Tri-Lakes, Colorado BIOLAC facility.
Performance Data for Tri-Lakes BIOLAC Facility
0)
E
cf
o
m
HI
3
E
400
350
300
250
200
150
100
Date
Figure 5-43. BOD5 for Tri-Lakes BIOLAC^ facility.
5-51
-------
Performance Data for Tri-Lakes, CO, BIOLAC Facility
Date
Figure 5-44. TSS for Tri-Lakes BIOLAC^ facility.
Performance Data for Tri-Lakes, CO, BIOLAC Facility
Ul
c~
HI
ra
2
o
<
08
c
re
P
Date
Figure 5-45. NH3 and inorganic N (NO2~, NO3~) for Tri-Lakes BIOLAC facility.
5-52
-------
A MlnpH
• U..pH
AvgFC
•HOOmL
V M»FC
•itOOmL
10'
10'
i
i 10'
I
0 10
o
10 •
•.,..**'.•.« ».• •
•«*»««*«• •
i»».44
: •• .. V . : ' \ • . . >'• :•< •• nj
..,-•:,.. ;" :-.: V:- v^y" H^
10 •
9/30/01
9/30/02
9J30/03
I
9/JO/04
Date
3
9/30/06
.0?
Figure 5-46. Fecal coliform for Tri-Lakes BIOLAC facility.
5.5.5.2 Limitations
Depending upon the rate of aeration and the environment, BIOLAC® systems may not be cost-
competitive when compared with conventional aerated pond systems.
5.5.5.3 Operation and Maintenance
In U.S. EPA (1990) there is a summary of the problems encountered at various BIOLAC®
facilities. The difficulties were typical mechanical failures and excessive debris and floating
sludges, with excessive oil and grease in the clarifier. Most of the problems appear to be
correctable with routine maintenance.
5.5.5.4 Energy
See Section 5.3.1.8.
5.5.5.5 Costs. See Section 5.3.1.9. The operating costs of BIOLAC®-R and aerated ponds
include aeration equipment and maintenance of these units. Solids production, treatment and
handling in the BIOLAC®-R system will be higher than those with conventional aerated ponds
depending upon the system used.
5.6 LEMNA SYSTEMS
5.6.1 Description
5-53
-------
There are numerous references to the use of duckweed (Lemna spp.) in pond wastewater
treatment systems dating back to the early 1970's. The present discussion, however, is limited to
the application of proprietary processes produced by Lemna Technologies, Inc. (Culley and
Epps, 1973; Wolverton and McDonald, 1979; Zirschky and Reed, 1988; Reed et al., 1995; Crites
et al., 2006).
Lemna Technologies, Inc. offers two basic duckweed-based systems for wastewater treatment:
the Lemna Duckweed System with floating partitions used to keep the plants evenly distributed
over the surface of the pond, and the LemTec™ Biological Treatment Process. In addition to
these two basic units, the company produces LemTec™ Modular Cover Systems, Lemna
Polishing Reactor™, LemTec™ C-4 Chlorine Contact Chamber-Cleaner, LemTec™ Anaerobic
Pond System, and the LemTec™ Gas Collection Cover.
Lemna Technologies, Inc. has installed approximately 370 projects worldwide. While the
majority of the covered systems are located primarily in the United States they have been
installed in Afghanistan, Mexico, Chile, and Poland. The typical client for the covered
wastewater treatment system is small municipality. Gas collection cover systems have been
placed exclusively in industrial treatment systems
(http://www.lemnatechnologies.com/index.htm).
5.6.2 Modifications and Processes Available
5.6.2.1 Lemna Duckweed System
The Lemna System can be used to retrofit an existing facultative or aerated pond system or can
be an original design. An original design consists of a regular facultative or aerated pond
followed in series by Lemna System components including the floating barrier grid to prevent
clumping of the duckweed and baffles to improve the hydraulics of the system. The treatment
processes are followed by disinfection, if required, and reaeration of the effluent beneath the
duckweed cover that is anaerobic. A diagram of the flow scheme for a typical Lemna System
design is shown in Figure 5-47 (Lemna Technologies, Inc., 1999a and b). The Lemna System in
Rayne, Louisiana is shown in Figures 5-48 and 5-49.
5-54
-------
Primary and Secondary
Treatment Stage
Polishing/Tertiary
Treatment Stage
Figure 5-47. Flow diagram for typical Lemna System (Lemna Technologies, Inc., 1999a
and 1999b, www.lemtechtechnologies.com).
5-55
-------
Figure 5-48. Diagram of Rayne, Louisiana wastewater treatment ponds. Green-hatched
area is the Lemna System. Influent comes into the aeration pond to the left.
Figure 5-49. Lemna System, Rayne.
5-56
-------
5.6.2.2 LemTec™ Biological Treatment Process
The Lemtec™ Biological Treatment Process uses the Lemtec™ Modular Cover to completely
cover the system rather than a mat to retain duckweed (Figure 5-50). The process is still a pond-
based treatment composed of a series of aerobic cells followed by an anaerobic settling pond.
Cells in series consist of a complete mix aerated reactor, a partial mix aerated reactor, a covered
anaerobic settling pond, and a Lemma polishing reactor. The polishing reactor is aerated and has
submerged, attached-growth media modules to supplement BOD5 and NH3 reduction. Sludge
removal from the settling pond is expected to be required about every 5 to 12 years. Frequency
of cleaning will vary with climate and strength of the wastewater. The Lemtec™ System in
Jackson Indiana is shown in Figures 5-51 and 5-52 .
LemTec™ Biological Treament Process
Influent
Mechanical
Mixers
Polishing
Reactor
Aeration Diffusers
TM
Figure 5-50. LemTec Biological treatment process (Lemna Technologies, 1999a and b,
www.lemtechtechnologies.com).
5-57
-------
Figure 5-51. Site plan for LemTec™ System in Jackson, Indiana. The covered pond with
crosswalks is on the left.
Figure 5-52. LemTec™ System, Jackson.
5-58
-------
5.6.3 Applicability
The treatment process is suitable for areas where land costs are not a limiting factor. The
systems can be used to treat raw, screened, or primary settled municipal or biodegradable
industrial wastewaters. The process has been used to remove BODs, TSS, NH^ and total N.
5.6.4 Advantages and Disadvantages
Both the Lemna Duckweed System and the LemTec™ Biological Treatment Process are
effective in removing TSS, BODs, fecal coliform and
On the other hand, both are susceptible to system impacts from toxic substance inputs, as are
most biological systems. Harvesting, treatment and disposal of the duckweed can be time
consuming and expensive (see Appendix D). Both systems may require increased maintenance,
and aeration, therefore, increased operating costs.
5.6.5 Design Criteria
Design criteria for Lem
not provided by the manufacturer.
Design criteria for Lemna Duckweed and the LemTec™ Biological Treatment processes were
5.6.6 Performance Data for Lemna Systems
Performance data summary reported by Lemna are shown in Figures 5-53 A, B, and C (Rayne,
Louisiana , the Lemna System) and Figures 5-54 A, B and C (Jackson, Indiana, the LemTec™
System).
A.
.'
20
BOOi.MGA
•Lflii1. = ID mjfl
0 •
OATI
5-59
-------
B.
9999
1 I i S
DATf
c.
•NH3. IT^/I
•Ult>< " S mt/t
Figures 5-53 A. (BOD5), B. (TSS) and C. (NH3). Compliance data for Rayne (U.S. EPA
Enforcement and Compliance History Online [ECHO] Database).
5-60
-------
A.
•Umrt = 10 T»f*
o»n
B.
i I
'• i
5-61
-------
c.
-MM.MG/1
- •
Figures 5-54 A (CBOD5) B. (TSS) and C. (NH3). Compliance data for Jackson (U.S. EPA
ECHO Database).
5-62
-------
5.6.7 Limitations
The Lemna systems have been used in both warm and cold climates. It is necessary to aerate the
anoxic/anaerobic effluent from the Lemna covered cell to meet discharge requirements of 5 to 6
mg/L of DO.
5.6.8 Operation and Maintenance
For the Lemna System to function properly, it may be necessary to harvest the duckweed on a
regular basis. Lemna Technologies markets a harvester for use in ponds with the floating barrier
grid used to ensure distribution of the duckweed (Figure 5-55). The harvesters operate by
depressing the floating barrier and removing the duckweed from the water surface. Biomass
harvested from the Lemna System can be managed via land application, composting the
duckweed or producing pelletized feedstuff. Other than land application, these management
methods can be expensive, and data are needed to evaluate the economic feasibility of these two
options. Other operation and maintenance procedures are the same as with other pond systems.
Figure 5-55. Photograph of Lemna harvesting equipment and floating barrier grid
(Lemna Technologies, www.lemtechtechnologies.com).
5-63
-------
5.6.9 Costs
Cost information was not available for either of the two Lemna Technologies processes, but
costs are probably higher for these processes given the need for special equipment, such as the
floating barrier grid for the Lemna systems and the cover for the LemTec™ Biological
Treatment Process. Costs other than the special equipment would be the same as for facultative
ponds or aerated ponds.
5.7 LAS International, Ltd., Accel-o-Fac and Aero-Fac Systems
5.7.1 Description
Accel-o-Fac and Aero-Fac® systems are offered as upgrades and original installations. The
Accel-o-Fac is a facultative pond with wind-driven aerators, and the Aero-Fac is a partial mix
aerated pond with an Aero-Fac® diffused air bridge and LAS Mark 3 wind and electric aerators.
Systems have been installed in several countries including the United Kingdom, Canada and the
United States, but the only information that could be found on the web was related to
installations in LaPine, Oregon and Holkham, Norfolk, United Kingdom (http://www.water-
technol ogy . net/proj ects/accel of ac/accel of ac8 . html ) .
5.7.2 Applicability
The systems are appropriate for any aerated pond system.
5.7.3 Advantages and Disadvantages
The primary advantage of the processes is a savings in energy costs if adequate wind velocity is
available.
A disadvantage is the lack of control of the aeration process.
5.7.4 Design Criteria
The systems are designed using the same approach as that used in the partial mix and complete
mix design examples (see Chapter 3, Section 3.4 and Appendix C).
5.7.5 Performance
Performance data are limited and are mostly drawn from operation during warm months of the
year. Winter performance data are needed to evaluate the processes fully. It is expected that the
systems will perform essentially as other partial mix pond systems with equivalent aeration.
5.7.6 Limitations
Depending upon the rate of aeration and the environment, aerated ponds may experience ice
formation on the water surface during cold weather.
5.7.7 Operation and Maintenance
Operation and maintenance are essentially the same as for aerated ponds.
5-64
-------
5.7.8 Energy
See Section 5.3.1.8. The use of wind power should reduce the cost of energy, depending on
climatic conditions.
5.7.9 Costs
See Section 5.3.1.9. Operating costs for the LAS aerated ponds include stand-by aeration
equipment and maintenance of these units in addition to the wind driven aerators.
5.8 OXYGEN ADDITION SYSTEMS
5.8.1 Pure Oxygen Aeration System for Wastewater Treatment
While there are no ponds with these systems, they may have application in the future as
efficiency and costs data become available (Agent: Holme Roberts & Owen LLP - Denver, CO,
US. Inventor: Jai-Hun Lee. US Patent and Trademark Office [USPTO] Applicaton #:
20090008311 - Class: 210194 (1/8/2009).
5.8.2 PRAXAIR, INC., I-SO SYSTEM™
The Praxair® In-Situ Oxygenation (I-SO)™ Systems have been installed in over 100 locations
throughout the world (Figure 5-56). The company states that the units are capable of transferring
109 kg/hr of Oi per unit. Praxair® has reported that the total energy required to operate the I-
SO System, including the generation of 02, is as much as 60 percent less than the air systems
the system replaced. Plants located near an oxygen pipeline can decrease power costs by as
much as 90 percent (www.praxair.com).
5-65
-------
G«armotor
Assembly
Oxygen Inlot
Float
Assembly
••• • • a9**
• • o . TA&'l
. • .«•:•:•
• • $ • *••
• • * • f* *•'
^ " ~L -^^
• • •• ]« r -« T^f • r«.
. • •• V^TV- L-^=F^ »i?$r-
. -.5 - ^ /•>;• Jcvy.**
..• • '"k* I /T^ I s*j • • • • •
• • *«*•••* ••** •*••.•
••••.*• • • *•*" /*V ** . * *• • • •*•
V. \:.:Jk^L>yx><.'- •• •;
Figure 5-56. Praxair In-Situ Oxygenation (I-SO) System (Yoon et al., 2010).
5.8.3 ECO2 SUPER-OXYGENATION SYSTEM
ECO2 SuperOxygenation systems for water and wastewater treatment are designed and produced
by Eco-Oxygen Technologies, LLC, based on the work of Dr. Richard Speece, who invented the
Speece Cone, a device originally used to add oxygen to the bottom of lakes to enhance
downstream fisheries (Speece, 2007). Photographs of the laboratory experiment used to develop
the concept are shown in Figure 5-57. The ECO2 SuperOxygenation method is a simple process
based upon the scientific principle of Henry's Law. No chemicals, other than O2, and no moving
parts other than standard municipal wastewater pumps are used.
5-66
-------
Figure 5-57. Photograph of the laboratory experiment used to develop the concept of the
Speece Cone (Dominick and DeNatale, 2009).
Downliow
Iniei
5-67
-------
CHAPTER 6
NUTRIENT REMOVAL
6.1 INTRODUCTION
While the reliability of pond systems to remove BOD5 and suspended solids is well-documented,
the N and P removal capability of wastewater ponds has been given little consideration in any type
of system design until recently. As more stringent nutrient standards are adopted, nutrient
removal processes must be included in design for new systems and added to existing systems.
Nitrogen removal can be critical in many situations since NHs, even at low concentrations, can
adversely affect aquatic life in receiving waters, and the addition of NO3 to surface waters is a
major contributor to eutrophication. Nitrate'is often the controlling parameter for design of land
treatment systems. Any TV removal in the primary pond units can result in very significant savings
in acreage required for final land treatment. Phosphorus, which is limiting for algal growth, is
present at concentrations in municipal wastewater that stimulate that growth and must be reduced
to control eutrophi cation.
The dominant forms of TV coming into a conventional facultative wastewater treatment pond
system are referred to as the Total Kjeldahl Nitrogen (TKN), which is the sum of the organic N,
NHs and ammonium ions (NH4+). In biological systems, such as aerobic ponds, where thepH is
usually less than 8.0, the majority of the NHs is in the ionic form. TKN can be reduced through
several processes, including gaseous NHs stripping to the atmosphere, NHs assimilation into the
biomass, biological nitrification/denitrification and sedimentation of insoluble organic TV. These
processes are affected by temperature, DO concentration, pR value, retention time and wastewater
characteristics. Within bottom sediments under anoxic conditions in facultative ponds,
denitrification can take place. Temperature, redox potential and sediment characteristics affect the
rate of denitrification. In well-designed aerated ponds with good mixing conditions and
distribution of DO, however, the effect on the rate of denitrification will be negligible.
The capacity of conventional facultative and aerated ponds to convert NHs is discussed in the
following sections. Several commercial processes that have been developed for TV removal are
also described. There is, however, little operational data available to demonstrate the
effectiveness of the commercial units.
6.2 FACULTATIVE PONDS
6.2.1 Removal Mechanisms
Nitrogen loss from streams, lakes, impoundments, and wastewater ponds has been observed for
many years. Data on TV losses in pond systems were not sufficient to conduct a comprehensive
analysis until the early 1980's, and even then there was no agreement as to the mechanisms of
removal. Investigators have suggested algal uptake, sludge deposition, adsorption by bottom
soils, nitrification, denitrification, and loss ofNH3 as a gas to the atmosphere (volatilization).
Evaluations by Pano and Middlebrooks (1982), Reed (1984b) and Reed et al. (1995) indicate that
a combination of factors may be responsible. The dominant mechanism, under favorable
6-1
-------
conditions, is thought to be loss by volatilization to the atmosphere. The several mechanisms are
depicted in Figure 6-1.
volatilization
•4 - '•]
Algal growth stag*
SUIT rr ~f tall
Figure 6-1. Generalized TV pathways in wastewater ponds.
6. 2.2 Performance
EPA undertook a number of studies of facultative wastewater pond systems in the late 1970's
(Bowen, 1977; Hill and Shindala, 1977; McKinney, 1977 and Reynolds et al., 1977). The results
verified the hypothesis that significant TV removal occurs in pond systems. Their findings from
those studies are summarized in Table 6-1. Nitrogen removal is related topR, detention time,
and temperature. pR fluctuation resulting from the interaction of algae and HCOi changes the
alkalinity and is an important parameter to monitor. Under ideal conditions, up to 90 percent
NHs removal can be achieved in facultative wastewater treatment ponds.
6-2
-------
Table 6-1. Annual Values from EPA Facultative Wastewater Pond Studies
Location
Peterborough
3 cells
Kilmichael
3 cells
Eudora
3 cells
Corinne
First 3 cells
HRT(d)
107
214
231
42
Temp (°C)
Ave. range
-7-20
4.5-26
1.1 -27
-3.9-23
pH (median)
7.1
8.2
8.4
9.4
Alkalinity
(mg/L)
85
116
284
555
N Removal
(percent)
43
80
82
46
Several studies of TV removal have been completed more recently, but the quantity of data is still
limited. A study of 178 facultative ponds in France showed an average TV removal of 60 to 70
percent (Racault et al., 1995). Wrigley and Toerien (1990) studied four small-scale facultative
ponds in series for 21 months and observed an 82 percent reduction in NH3.
Shilton (1995) quantified the removal ofNH3 from a facultative pond treating piggery
wastewater, and found that the rate of volatilization varied from 355 to 1534 mg/m2/d (0.07 -
0.314 lb/1000 ft2/d). The rate of volatilization increased at higher concentrations ofNH3 and
TKN.
Scares et al., (1995) monitored NH3 removal in a wastewater treatment pond complex of
different geometries and depths in Brazil, and found that the NH3 concentrations were lowered to
5 mg/L in the maturation ponds so that the effluent could be discharged to surface waters. The
NH3 removal in the facultative and maturation ponds could be modeled by the equations based
on the volatilization mechanism proposed by Pano and Middlebrooks (1982).
Using 757V-labelled NH3, Camargo Valero and Mara (2007) demonstrated the uptake ofNH3 by
the algal biomass in the pond, followed by assimilation into the suspended organic fraction (85
percent in the effluent), and movement into the pond benthos by sedimentation. A study of
ponds in Kansas (Tate et al., 2002) showed increased NH3 in August, which would tend to
confirm that it is taken up by algae, and its movement to the benthos, from which it is released
under late summer conditions.
6.2.3 Theoretical Considerations
It is hypothesized that NHs removal in facultative wastewater treatment ponds occurs via three
mechanisms: gaseous NH3 stripping to the atmosphere, NH3 assimilation in algal biomass and
biological nitrification.
The low concentrations ofNOi and 7V02 measured in pond effluents indicate that nitrification
generally does not account for a significant portion ofNH3 removal. Ammonia assimilation in
algal biomass depends on the biological activity in the system and is affected by temperature,
organic load, detention time, and wastewater characteristics. The rate of gaseous NH3 losses to
6-3
-------
the atmosphere depends mainly on the/?H value, temperature, and the mixing conditions in the
pond. Alkaline pH shifts the equilibrium equation NHs^ + H2O NH4+ + OH~ toward gaseous
NHs, whereas the mixing conditions affect the magnitude of the mass transfer coefficient.
Temperature affects both the equilibrium constant and mass transfer coefficient.
At low temperatures, when biological activity decreases and the pond contents are generally well
mixed due to wind effects, stripping will be the major process for NHs removal in facultative
wastewater treatment ponds. The NHs stripping process in ponds may be expressed by assuming
a first-order reaction (Stratton, 1968; 1969). The mass balance equation will be:
VdC/dt = Q(C0- Ce) - kA (NH3) (6-1)
where:
Q = flow rate, m3/d
C0 = influent concentration of(NH4+ + NHs), mg/L as N
Ce = effluent concentration of(NH4+ +NHs), mg/L as N
C = average pond contents concentration of (NH4+ + NHs), mg/L as N
V = volume of the pond, m3
k = mass transfer coefficient, m/d
A = surface area of the pond, m3
t = time, d
The equilibrium equation for NHs dissociation may be expressed as
Kb = rNHSirOHJ (6-2)
where:
Kb = NHs dissociation constant.
By modifying Equation 6-2, gaseous NHs concentration may be expressed as a function of the
pR value and total NHs concentration (NH4+ + NHs) as follows:
KK^ (6-3)
[Off]
C = NH4+ + NH3 (6 - 4)
NH3 + C (6 - 5)
1 -
where:
pKw = -l
PKb = -logK
6-4
-------
Assuming steady-state conditions and a completely mixed pond where Ce = C, Equations 6-4
and 6-5 will yield the following relationship:
Cf = I (6-6)
C0 l+AK [ - L - ]
ft 1 + WpKw -pKb-pH
This relationship emphasizes the effect of/>H, temperature (pKw andpKb are functions of
temperature) and hydraulic loading rate on NHs removal.
Experiments on NH3 stripping conducted by Stratton (1968, 1969) showed that the NH3 loss-rate
constant was dependent on the/?H value and temperature (T = C) as shown in the following
relationships:
NH3 loss rate constant oc eL57(pH-8'5) (6 - 7)
NH3 loss rate constant oc e°-13(T-2°) (6 - 8)
King (1978) reported that only four percent TV removal was achieved by harvesting floating
Cladophora fracta from the first pond in a series of four receiving secondary effluents. The
major TV removal in the ponds was attributable to NHs gas stripping. The removal of total TV was
described by first-order kinetics, using a plug flow model (Nt = No e~°'03t where Nt = total N
concentration, mg/L, NO = initial total TV concentration, mg/L and t = time, d).
During windy seasons, or large-scale facultative steady-state conditions, will well-designed
ponds approach completely mixed conditions. Moreover, when NHs removal through biological
activity becomes significant, or NHs is released from anaerobic activity at the bottom of the
pond, the expressions for NHs removal in the system must include these factors along with the
theoretical consideration ofNHj stripping. A mathematical relationship for total TV removal based
on the performance of three full-scale facultative wastewater treatment ponds is developed here
that considers the theoretical approach and incorporates temperature, pR value, and hydraulic
loading rate as variables. In this case, Equation 6-9 for TKN removal in facultative ponds is
substituted for the theoretical expression for NHs stripping:
Ce = _ 1 (6 - 9)
C0
Q
where:
K = removal rate coefficient (L/t)
f(pH) = function ofpH.
The K values are considered to be a function of temperature and mixing conditions. For a similar
pond configuration and climatic region, the lvalues may be expressed as a function of
temperature only. The function of/?H, which is considered to be dependent on temperature,
affects thepK, andpKb values, as well as the biological activity. Based on a statistical analysis
of the data when incorporated into the equation, the/>H function was found to describe an
6-5
-------
exponential relationship. As many reaction rate and temperature relationships are described by
exponential functions, such as the Van't Hoff-Arrhenius equation, it is not unreasonable to
assume that such a relationship would apply to the application of the theoretical equation to a
practical problem.
6.2.4 Design Models
Data were collected on a frequent schedule from every cell in the pond system listed in Table 6-1
for at least a full annual cycle. A quantitative analysis of all major variables was performed and
several design models were developed. Both plug flow and complete mixing models were useful
in predicting TV removal in facultative pond systems (Tables 6-2 and 6-3). They are first-order
models that depend on/?H, temperature and HRT. They have been validated using data from
other sources. Further validation of the models can be found in Crites et al. (2006), Reed et al.
(1995), Reed (1985), and Reed (1984b).
Both models assume that volatilization ofNH3 is the major pathway of TV removal from
wastewater treatment ponds. The application of the models is shown in Figure 6-2, and the
predicted total TV in the effluent is compared to the actual monthly average values measured at
the Peterborough, New Hampshire ponds. The models are expressed in terms of total N, and
should not be confused with the equations reported by Pano and Middlebrooks (1982) that are
limited to the NHs fraction.
Measured
—•--Model 1
—•-Model 2
Dec Feb Apr Jun
Month
Aug
Oct
Dec
Figure 6-2. Predicted versus actual effluent N, Peterborough, New Hampshire.
6-6
-------
Table 6-2. Model 1, TV Removal in Facultative Ponds - Plug Flow Model (Reed, 1985)
Ne = No6-^+ 60.6(^-6.6)} (6_1Q)
where:
Ne = effluent total nitrogen, mg/L
NO = influent total nitrogen, mg/L
KT = temperature dependent rate constant
v -v //}) (T-20)
KT-K2o(t>)
K20 = rate constant at 20°C = 0.0064
0 = 1.039
t = detention time in system, d
pH =pH of near surface bulk liquid
See Reed (1984b) for typical pH values or estimate with:
pH = 7.3eaooo5ALK
Use the Mancini and Barnhart Equation (1976) for pond water temperature determination.
where:
ALK = expected influent alkalinity, mg/L [derived from data in U.S. EPA (1983 a) and
Reed(1984b)l
0.5A + Q
where:
r\
A = surface area of pond, m
Ta = ambient air temperature, °C
Ti= influent temperature, °C
Q = influent flow rate, m3 / d
A high rate ofNHs removal by air stripping in advanced wastewater treatment depends on a high
(> 10) chemically adjusted pH. The algae-carbonate interactions in wastewater ponds can
elevate the/>H to similar levels for brief periods during the day. At other times, at lower pH
levels, the rate of removal may be slower, but the long detention time results in lower TV
concentrations in the effluent.
Table 6-3. Model 2, N Removal in Facultative Ponds - Complete Mix Model
(Middlebrooks, 1985).
N
~
6-7
-------
where:
Ne = effluent total nitrogen, mg/L
N0 = influent total nitrogen, mg/L
t = detention time, d
T = temperature of pond water, °C
=pH of near surface bulk liquid
Use the Mancini and Barnhart (1976) Equation (Table 6-2) to determine pond water temperature.
Figure 6-3 (Crites, 2006) illustrates the validation of both models using data from pond systems
from other sources. The diagonal line represents the best fit of predicted versus actual values.
The close fit and consistent trend demonstrate that either model can be used to estimate N
removal. In addition, the models have been used in the design of several ponds systems and
have been found to work as predicted. It is nevertheless likely that other removal mechanisms are
at work (Camargo Valero and Mara, 2007) and therefore this model should be used only as a first
step in designing for NH3 removal in ponds.
so
re
g30
0>
o
Ł 20
2
ai
110
Ł
• Model 1
A Model 2
0 10 20 30 40 50
Measured Effuent Nitrogen (Total N, mg/l)
Figure 6-3. Verification of design models.
6.2.5 Applicability
Nitrogen removal occurs in facultative wastewater treatment ponds, and may be reasonably
predicted for design purposes with either of the two models. Nitrogen removal in ponds may be
more cost-effective than other alternatives for removal and/or NH^ conversion. These models
should be useful for new or existing wastewater ponds when TV removal and/or NHs conversion is
required. The design of new systems would typically base detention time on the BOD5 removal
requirements. The TV removal that will occur during that time can then be calculated with either
model. It is prudent to assume that the remaining TV in the effluent will be NHs and to design any
6-8
-------
further removal/conversion for that amount. A final step would be to compare the cost of
additional detention time in an expanded pond system for TV removal with other removal
alternatives.
Use of these models is particularly important when ponds are used as a component in land
treatment systems, since total TV is often the controlling design parameter. A reduction in pond
effluent TV will often permit a significant reduction in the area needed for land treatment.
6.2.6 Limitations
Other than the requirement for sufficient pond acreage, the facultative pond system can be
expected to provide maximum NHs conversion during the summer months, occasionally
exceeding 90 percent. This level of treatment cannot be expected during winter months.
6.2.7 Operation and Maintenance
Operation and maintenance are the same as for facultative ponds designed to remove BOD5.
6.3 AEROBIC PONDS
6.3.1 Introduction
The same conditions that apply to push the equilibrium ofNH4+ to NHs in conventional facultative
pond systems applies to aerobic ponds.
6.3.2 Performance
EPA sponsored comprehensive studies of aerated pond systems between 1978 and 1980 that
provided information about TV removal (Tables 6-4 and 6-5). The results verify the consensus of
previous investigators that TV removal is related to/>H, detention time and temperature in the
pond system.
Table 6-4. Wastewater Characteristics and Operating Conditions for Five Aerated Ponds
(Earnest et al., 1978; Englande, 1980; Gurnham et al., 1979; Polkowski, 1979; Reid and
Streebin, 1979; Russell et al., 1980)
See p.xiv for conversion table.
Parameter
BOD, mg/L
COD, mg/L
TKN mg/L
NH3-N mg/L
Alkalinity mg/L
PH
Hydraulic loading rate
mgd
Pawnee3
473
1026
51.41
26.32
242
6.8-7.4
0.0213
Bixby"
368
635
45.04
29.58
154
6.1-7.1
0.0285
Koshkonong0
85
196
15.3
10.04
397
7.2-7.4
0.0423
Windber"
173
424
24.33
22.85
67
5.6-6.9
0.0663
North Gulfport6
178
338
26.5
15.7
144
6.7- 7.5
0.0873
6-9
-------
Parameter
Organic loading rate
kg BOD5/ha/d
Detention time, d
Pawnee3
151
143
Bixby"
161
107
Koshkonong0
87
72
Windber"
285
46
North Gulfport6
486
22
Illinois; "Oklahoma; cWisconsin; "Pennsylvania; eMississippi
Table 6-5. TV Removal in Aerated Ponds (adapted from U.S. EPA 1983a)
Location
Parameter,
mg/L
TKN
NH3
NOi
NO2=
Alkalinity
pR
Temp °C
DO
Pawnee, Illinois
Influent
51.4
26.3
-
-
242
6.8-7.4
-
-
Effluent
5.0
1.3
0.8
0.1
161
7.8-9.3
3-22
1.9-16.0
Bixby, Oklahoma
Influent
45.0
29.6
-
-
154
6.1-7.1
-
-
Effluent
8.4
3.5
-
-
70
6.7-9.2
5-29
3.9-13.5
Koshkonong, Wisconsin
Influent
15.3
10.0
1.7
0.1
397
7.2-7.4-7.9
-
-
Effluent
7.6
5.3
4.4
-
382
1-25
7.6-15.3
Location
Parameter,
mg/L
TKN
Range
NH3
NOi
NO2=
Alkalinity
pH.
Temp, °C
DO
Windber, Pennsylvania
Influent
24.3
13.2-46.0
22.9
-
-
67
5.6-6.9
-
-
Effluent
23.6
14.4-34.1
22.9
0.72
0.2
82
6.8-8.5
2-24
5.7-15.0
N. Gulfport, Mississippi
Influent
26.5
20.6-30.9
15.7
-
-
144
6.7-7.5
-
Effluent
10.8
7.2-13.3
5.1
2.36
0.6
102
6.8-7.5
11-29
0.8-9.3
Mt. Shasta, California
Influent
15.7
10.1-20.9
10.3
0.3
0.2
93
6.5-7.6
-
-
Effluent
11.1
6.8-14.2
5.4
0.7
0.5
74
7.4-9.7
2-27
10.9-14.0
6.3.3 Empirical Design Equations
Table 6-6 contains a summary of selected equations developed to predict NH3 and TKN removal
in diffused air aerated ponds (Middlebrooks and Pano, 1983). All of the equations draw values
from the same database. Different combinations of data were chosen and combined to develop
several of the equations. The "system" column in Table 6-6 indicates which ponds or series of
ponds were used to develop each equation. These data were analyzed statistically and the
equations were selected based upon the best statistical fit for the various combinations. It should
be noted that the combinations of data sets are not directly comparable.
6-10
-------
An examination of the HRT calculated using the various formulas for TKN removal show that
the greatest difference between the maximum and minimum detention times calculated from the
equation is 14 percent. In view of the variation in methods used, this variability is reasonable.
All of the relationships are statistically significant at levels higher than one percent. As a result,
any of them may be applied to estimate TKN removal in an aerated pond design. Given the
simplicity of the plug flow model and the fraction removed model, it is recommended that one or
both be used along with the theoretical models to verify that there will be adequate removal in
the event that unusual BODs loading rates are encountered.
Table 6-6. Comparisons of Various Equations to Predict NHs and TKN Removal in
Diffused-Air Aerated Ponds (Middlebrooks and Pano, 1983).
Equation Used to Estimate
HRTor Effluent Concentration
TKN Removal
In Ce/C0 = 0.0129(Detention Time)
TKN Removal Rate
TKNrr = 0.809(TKN Loading Rate)
TKN Removal Rate
TKNrr = 0.0946(BOD5 Loading Rate)
TKN Fraction Removed
TKNfr =0.0062(Detention Time)
NH3 Removal
lnCe/CO=-0.0205(Detention Time)
NH3 Removal Rate
NH3rr = 0.869(NH3-N Loading Rate)
NH3 Removal Rate
NH3rr = 0.0606(BOD5 Loading Rate)
NH3 Fraction Removed
A/H3fr = 0.0066(Detention Time)
Correlation
Coefficient
0.911
0.983
0.967
0.959
0.798
0.968
0.932
0.936
HRT, d
125
132
113
129
79
92
132
121
Compared w
MaxRT
% Difference
5.3
0
14.4
2.3
40.2
30.3
0
8.3
System
Ponds 1, 2 and 3
Mean Monthly Data
Total System
Mean Monthly Data
Total System
Ponds 1, 2 and 3
Mean Monthly Data
All Data
Mean Monthly Data
Total System
Mean Monthly Data
Total System
Mean Monthly Data
Ponds 1, 2 and 3
Mean Monthly Data
6-11
-------
Using any of the above expressions will result in an estimate of the TKN removal that is likely to
occur in diffused-air aerated ponds. Unfortunately, data are not available to develop similar
relationships for surface aerated ponds.
While the relationships developed to predict NHs removal are significant for all of the equations
presented in Table 6-6, the agreement between the calculated HRT for NHs removal differed
significantly from that observed for the TKN data. This is not surprising in view of the variety
of mechanisms involved in NHs production and removal in wastewater ponds, but it does
complicate the use of the equations to estimate NHs removal in aerated ponds.
Statistically, any of the expressions may be used to calculate the HRT required to achieve a
certain percent reduction in NHs. Perhaps the best equation to use in designing NHs removal is
the relationship between the fraction removed and the HRT. The correlation coefficient for this
relationship is higher than the correlation coefficient for the plug flow model, and both equations
are relatively straightforward to use.
6.3.4 Nitrogen Removal in Continuous Feed Intermittent Discharge (CFID) Basins
6.3.4.1 Description
Rich (1996, 1999) has proposed CFID basins for use in aerated pond systems for nitrification and
denitrification. The systems are designed to use in-basin sedimentation to uncouple the solids
retention time from the HRT. The influent flow is continuous. A single basin has a dividing
baffle to prevent short-circuiting.
6.3.4.2 Applicability of CFID
Some CFID systems have experienced major operational problems with short-circuiting and
sludge bulking; however, by minimizing these problems with design changes the systems can be
made to function properly. CFID design modifications can be made to overcome most
difficulties and details are presented by Rich (1999).
6.3.4.3 Advantages and Disadvantages
When designed and built correctly, the system is capable of producing an effluent in a pond
system comparable with activated sludge systems designed for nitrification/denitrification.
Experience with the system, however, is limited.
6.3.4.4 Design Criteria
The basic CFID system consists of a single reactor basin divided into two cells with a floating
baffle. The two cells are referred to as the influent (Cell 1) and effluent cell (Cell 2). Mixed
liquor is recycled from Cell 2 to the head-works to provide a high ratio of soluble biodegradable
organics to organisms and the ft source is primarily NOi. This approach is used to control
bulking. Although some nitrification will occur in the influent cell, the system is designed for
nitrification to occur in the effluent cell. Further details of the operation of the CFID systems, see
Rich (1999).
6.3.4.5 Performance
6-12
-------
Performance data were not available.
6.3.4.6 Limitations
There is little proven design information and operational difficulties have been encountered.
6.3.4.7 Operation and Maintenance
It is expected that maintenance would be the same as that required for other aerobic ponds.
6.3.4.8 Costs
Construction costs would be the same as those for conventional aerobic pond systems.
Considerable savings would accrue when comparing the cost to produce an effluent quality with
a CFID system with an equivalent effluent produced by an activated sludge system designed for
nitrifi cati on/denitrifi cati on.
6.3.4.9 General Applicability
The Rich (1999) method is a design for nitrification in an aerobic pond. The equations in Table
6-6 are empirical and may or may not apply to a general design. That said, they show what might
be expected in terms of TV removal. Designing a pond system to nitrify wastewater is not
difficult if the water temperature and detention time are adequate to support nitrifiers and
sufficient DO is supplied. Recycling of the mixed liquor is a significant benefit. As with all
treatment methods, an economic analysis should be performed to determine whether this system
is cost effective.
6.3.5 Nitrification Using Fixed Film Media
In addition to the proprietary systems described later in this chapter, Reynolds et al., (1975),
Polprasert and Agarwalla, (1995), and Ripple (2002) have conducted studies using baffles and
suspended materials as media for attached growth for nitrifying organisms. Nitrification is a
function of temperature, and where temperature was a factor in the studies, there was a
significant decline in nitrification. It is not clear that the impact of winter temperatures can be
overcome when the water temperature drops below IOC.
6.3.6 Pump Systems, Inc. Batch Study
6.3.6.1 Description
In 1998, a solar-powered circulator (equivalent to the SolarBee Model SB2500) was installed in
an 11.7 ha pond with a depth of 4.5 m at Dickinson, North Dakota with no incoming wastewater.
The circulator flow rate was 9463 L (2500 G) per minute. The NHs concentration at the
beginning of the experiment was approximately 20 mg/L. Dissolved oxygen, /?H, BODs, TSS,
NHs, water temperature and other parameters were measured over a 90-day period at various
locations and depths. Over 1500 samples were collected over the test period. Average data for
the various locations and depths are shown in Table 6-7. The average water temperature was
20.5 °C. DO was present throughout the pond at all depths, but on occasion dropped to 0.4 mg/L
at the bottom. These occasional low DO concentrations may have had an adverse effect on the
results presented below, but they do provide some guidance as to how to estimate the expected
conversion ofNHj in a partial mix aerobic pond system (see Equation 6.9).
6-13
-------
Table 6-7. Average Values for Batch Test in Pond 4 at Dickinson,
North Dakota Area = 11.7 Ha (29 Ac), No Inflow. (Pump Systems, Inc., 2004).
Days
0
1
7
12
13
19
26
29
36
42
48
50
57
62
70
76
84
90
Ln
Ce/Co
0
0.15
0.21
0.16
0.11
-0.06
-0.36
-0.36
-0.6
-0.67
-0.79
-0.82
-0.76
-0.75
-0.48
-0.62
-0.74
-0.91
PH
7.7
7.7
7.7
8
8.1
8.4
8.8
8.7
8.8
8.6
8.5
8.5
7.7
8
8.1
8
7.8
8.1
C0 = influent concentration of (A//-// + NH3), mg/L as N
Ce = effluent concentration of (A//-// + NH3), mg/L as N
The reduction in 7W/4+with time was directly related to the variation inpH value (Table 6-7).
When thepH exceeded 8.0, the reduction in NH4+ increased, implying a greater loss of the NHs
to the atmosphere.
The results of this experiment show the low reaction rate for nitrification that occurs in partial
r-M-, °
mix aerobic ponds. The reaction rate of 0.0107/d obtained at an average temperature of 20.5 C
in the Dickinson experiments agrees with results obtained with data collected in an aerobic pond
located in Wisconsin (Middlebrooks et al., 1982). At 1 C, the NHs conversion reaction rate for
the Wisconsin partial mix pond ranged between 0.0035 and 0.0070/ d. Using the average value
o o
of 0.005/d at 1 C and the value of 0.0107/d obtained at Dickinson at 20.5 C, an approximate
value of 1.04 can be inserted into the 6 in the classic temperature correction equation: kT =
&2o(1.04)(r~20). Example C-6-1 in Appendix C illustrates the effects of reaction rates and
temperature on the performance of partial mix pond systems.
6-14
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6.3.7 Nitrogen Removal in Ponds with Wetlands and Gravel Nitrification Filters
The nitrification filter bed (NFB) was developed by Sherwood C. Reed, and the following
material was extracted from Reed et al. (1995). The NFB has been installed at three locations in
the United States. The system was developed as a retrofit for existing free water surface (FWS)
and subsurface flow (SF) wetland systems having trouble meeting NHs effluent standards.
Schematic diagrams of both FWS and SF wetlands fitted with NFBs are shown in Figure 6-5.
The NFB is a vertical-flow gravel filter bed located on top of existing wetlands. When applied to
the FWS wetland, the fine gravel bed is supported on a coarse gravel layer to ensure aerobic
conditions in the NFB.
NFB units can be located at the front or near the end of the wetland where wetland effluent is
pumped to the top of the NFB and distributed evenly over the surface. Introducing the wetland
effluent to the NFB at the head of the system has the advantage of mixing the influent
wastewater with the highly nitrified NFB, effluent which results in denitrification and removal of
nitrogen from the system. In addition the BODs is reduced, and some of the alkalinity lost
during nitrification will be recovered. If the NFB is placed at the end of the wetland, nitrification
will occur, but denitrification will be limited and the NOi will pass out of the system. This will
require less pumping capacity, but the advantages of denitrification could easily offset the cost of
pumping.
Although similar to a recirculating sand filter, the NFB uses gravel rather than sand and can
process a much higher hydraulic loading rate than the sand filter. Hydraulic loading rates,
including a 3 : 1 recycle ratio, for a NFB located in Kentucky is 4 m3/m2/d (100 G/ft /d), in
contrast to loadings on recirculating sand filters of 0.2 m3/m2/d (5 G/ft2/d).
Trickling filter and rotating biological contactor attached-growth concepts were used to develop
a design relationship for the NFB (Equation 6-12). The relationship in Equation 6-12 was
derived from curve fitting performance data and should be used with caution. The equation
should give reasonable estimates of the specific surface area to produce effluent NH3
concentrations between 0 and 6 mg/L. Equation 6-12 has been verified at a 2 MGD system in
Mandeville, Louisiana (Reed et al., 2003).
Av = 2713 - 1 115(0 + 204(C.) - 12(Ca)
" kr " (6-12)
where:
Av = specific surface area, m2/kg NHs/
Ce = desired NFB effluent NH3, mg/L
kf = temperature-dependent coefficient
6(NH4+)= 1.15
At temperatures > 10 ' C, kT= 1(1.048) (r"20)
6-15
-------
At temperatures 1-10 ° C, Ł7= 0.626(1.15)
(T-10)
The following conditions are necessary for good nitrification performance:
• BODs:TKN ratio must be less than one
• Sufficient oxygen must be present
• Surface must be moist at all times
• Sufficient alkalinity must be available to support nitrification (approximately lOg
of alkalinity per gram of NH3)
The NFB bed depth ranges from 0.3 - 0.6 m and the bed extends across the entire width of the
wetland cell to ensure mixing with the influent wastewater (Fig 6-4). Sprinklers are used to
distribute the wetland effluent over the surface of the NFB. In cold climates it may be necessary
to enclose the NFB to prevent freezing.
Coarse gravel
Recycle
Fine gravel
Figure 6-4. Schematic diagram of nitrification filter bed (Reed et al., 1995).
The Benton, Kentucky NFB has been operating successfully at a hydraulic design flow of 3.79 x
106 L/d (1 MGD) per day with a wetland input of 20 mg/L NHs and an output of 2 mg/L.
Performance data for approximately three years for the Benton facility are shown in Table 6-8
(Reed, 2000). Pond influent carbonaceous BOD5 and NFB effluent carbonaceous BOD5 are
shown in Figure 6-6. The very large concentration values are probably analytical errors because
the TSS concentrations for these days were very low. NFB effluent carbonaceous BODs, TSS
and NHs concentration variability are shown in Figure 6-7. Ammonia effluent concentrations
were well below 5 mg/L with very few exceptions.
6-16
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Table 6-8. Benton, Kentucky Recirculating Gravel Filter / Constructed Wetland
Operational Data (Reed, 2000).
Date
April 92
May
June
July
August
September
October
November
December
January 93
February
March
April
May
Carbonaceous BOD5 (mg/L)
Influent
137(3)a
180(4)
160(4)
208 (5)
202 (4)
270 (5)
153(3)
99(4)
216(3)
173(4)
115(4)
73(5)
178(4)
174(5)
Effluent
4.2 (3)
2.6 (4)
4.6 (4)
6.7 (5)
4(4)
4.9 (5)
5.7 (3)
18(4)
54.5 (4)
5(4)
5.5 (4)
3.8 (5)
6.3 (4)
7.4 (5)
TSS(mg/L)
Influent
89(4)
273 (4)
124(4)
113(5)
144(4)
164(5)
131 (3)
195(4)
124(4)
148(4)
129(4)
170(5)
158(4)
212(5)
Effluent
4.5 (4)
2.8 (4)
7(4)
13.8(5)
4.5 (4)
5.6 (5)
2.7 (3)
9(4)
2.5 (4)
4(4)
7(4)
5(5)
6.8 (4)
4.8 (5)
NH3 (mg/L)
Effluent
1.5(4)
2(4)
1.5(4)
1.9(5)
1.3(4)
1.4(5)
0.7 (3)
0.5 (4)
0.9 (4)
6.8 (4)
1 (4)
3.7 (5)
3.8 (4)
1.1(5)
aBOD and TSS averages from April 1992 - May 1993.
Number in parentheses = number of samples.
450
Date - March 1992-December 1994
Figure 6-5. Benton performance data for pond + wetland + NFB (Reed, 2000).
6-17
-------
35
30
E 25
t 20
! 15
8 10
l^LzZ
B^u^'vuv^kkMnA^>/Ji
^
Date - March 1992-December 1994
Figure 6-6. Benton performance data for pond + wetland + NFB (Reed, 2000).
When retrofitting an existing pond-wetland system for nitrification and TV removal, the NFB
appears to have economic advantages and simplicity of construction and operation. It also is
likely that the NFB would be a viable alternative for N removal in the initial design of a pond-
wetland system.
6.4 COMMERCIAL PRODUCTS
There are numerous products and processes that are offered as a means to improve pond
performance and remove N. Several options are presented below (Burnett et al., 2004).
6.4.1 Description of Options
6.4.1.1 Add Solids Recycle
Adding solids recycle can be a reliable method of producing an effluent that can meet stringent
NHs limits. With the addition of solids recycle, a pond is converted to a low-mixed liquor
suspended solids (low-MLSS) activated sludge system. This can be accomplished using an
external clarifier and adding a pump to return solids to the headworks. The BIOLAC® process
uses an internal clarifier. Effluent from the clarifier is discharged to disinfection or routed
through the subsequent cells of the pond system.
Successful operation of low-MLSS activated sludge system requires that the recycled solids be
kept in suspension. The aerobic pond must be kept completely mixed. In most cases, a portion of
the existing pond is partitioned into a complete mix cell because the energy required to mix the
cell is far greater than that required to reduce the BOD5 or nitrify the NH3. The remaining
portion of the system is used for polishing the effluent or storing the water before discharge.
Because the recycle system is an activated sludge variation, it can be designed and operated with
traditional activated sludge design methods. Floating baffle curtains with exit ports are
6-18
-------
frequently used for cell partitioning. Excess sludge wasting can be accomplished in a separate
holding pond, or downstream cells of the existing pond can be used to store and treat sludge for
disposal.
A complete mix section can be located anywhere in the flow train of an aerobic pond system. If
the complete mix cell is placed near the end of the flow train nitrification occurs after
carbonaceous BOD5 has been removed. With the complete mix zone first in the process, sludge
can easily be returned to a manhole or other suitable location upstream of the plant influent. By
recycling sludge to the headworks, anoxic conditions and a high food-to-microorganism ratio
will help control sludge bulking, provide some denitrification, and recover alkalinity.
6.4.1.2 Converting to a Sequencing Batch Reactor (SBR) Operation
Converting an aerobic pond to an activated sludge system can be accomplished by operating the
aerobic pond as an SBR. A portion of the aerobic pond is partitioned into two or more complete
mix SBR zones.
SBRs operate in a sequence of fill, react, settle, and decant. In a single-train SBR, flow into the
basin will continue through all four cycles. Where parallel systems exist, the SBR can be
operated as a typical SBR system; however, the construction costs will be higher. Rich (1999)
has referred to this operation as a CFID process, but it is the same as the commercial SBR
system marketed by Austgen-Biojet.
In SBR mode, aeration is used intermittently, and a decanting process transports the settled
wastewater to downstream facultative cells or to a disinfection chamber before discharge.
Decanting is accomplished with pumps, surface weirs, or floating decanting devices. A portion
of the low-MLSS must be wasted during the reaction (mixing and aeration) phase to keep the
process in balance. Rich (1999) suggests adding a recycle pump station with mixed liquor
returned to the influent sewer to provide an anoxic environment for control of sludge bulking.
6.4.1.3 Install Biomass Carrier Elements
The addition of baffles and suspended fabrics for attached growth to accumulate and reduce
pollutants has been suggested for many years (Reynolds et al., 1975; Polprasert and Agarwalla,
1995). The availability of commercial fabrics for the removal ofNH^ is a relatively new
development. The carriers are plastic ribbons or wheels that are installed in the aerated zone to
provide surface area for the growth of microorganisms. Provided that there is adequate surface
area, nitrifying microorganisms can grow and multiply on the plastic surfaces and achieve NHs
removal. The aerated cell does not have to be completely mixed, which is required in the recycle
and SBR approaches, but the increased 02 demand of the attached microorganisms must be met.
Solids that drop from the biomass carriers settle or pass to next pond cells. Sludge buildup will
increase, but will be reduced by anaerobic digestion, which will minimally affect the frequency
at which sludge will need to be removed.
6.4.1.4 Commercial Pond Nitrification Systems
The following is a partial list of pond nitrification systems offered commercially:
1. ATLAS IS™ - Internal clarifier system by Environmental Dynamics, Inc.
6-19
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2. CLEAR™ Process - SBR variant by Environmental Dynamics, Inc.
3. Ashbrook SBR - SBR system by Ashbrook Corporation
4. AquaMat® Process - Plastic biomass carrier ribbons by Nelson Environmental, Inc.
5. MBBR™ Process - Plastic biomass carrier elements by Kaldnes North America, Inc.
6. Poo-Gloo™ - Wastewater Compliance Systems, Inc.
6.4.1.5 Applicability of Commercial Systems
Experience with all of the systems mentioned above is limited, and it is difficult at this time to
predict the applicability and performance.
6.4.1.6 Advantages and Disadvantages
Until more design and operational data become available, it is difficult to delineate differences in
the various commercial systems.
6.4.1.7 Design Criteria
Although design criteria were not available, the SBR systems would be designed the same way
as a typical SBR. The quantities of plastic biomass required apparently are proprietary
information. The design of the MBBR™ process is proprietary, as is the Poo-Gloo™ system.
6.4.1.8 Performance
The limited performance data are presented with the descriptions of the individual processes.
6.4.1.9 Limitations
Because of the limited experience and associated data, it is difficult to assess the effectiveness of
the various processes.
6.4.1.10 Operation and Maintenance
With the addition of any of these treatments, it is expected that there will be more operation and
maintenance time.
6.4.1.11 Costs
It is expected that the base costs associated with the type of pond into which the commercial
equipment was placed in would continue. Additional costs would include the commercial
product and any associated operation and maintenance.
6.4.1.12 ATLAS-IS™
Description
The Advanced Technology Pond Aeration System with Internal Separator (ATLAS-IS™) is
offered by Environmental Dynamics, Inc. (EDI). It is designed to provide a high level of
treatment with minimal operation and maintenance requirements. The process consists of a fine
bubble floating lateral aeration system that contains a series of internal clarifiers or settlers. The
settlers are constructed of a plastic material and may contain lamellate baffles. The units are
installed within a complete mix zone of the aerated pond system. Mixed liquor enters the settling
chamber through the bottom. A slight concentration of the low-MLSS takes place in the settler as
the mixed liquor rises and spills over a weir into an effluent pipe. No return activated sludge
6-20
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(RAS) or waste activated sludge (WAS) is required. Over time the low-MLSS will build up to a
level adequate to grow nitrifying microorganisms. Some solids are carried downstream so no
separate sludge wasting is necessary.
6.4.1.12.1 Performance
The ATLAS-IS™ system has been tested at Ashland, Missouri and has been successful in
building up low-MLSS and in achieving nitrification. A schematic of the system is shown on
Figure 6-8.
6.4.1.13 CLEAR™ Process
EDI also offers an SBR variant known as the Cyclical Pond Extended Aeration Reactor
(CLEAR™). A completely mixed aerated pond cell is partitioned into three zones using floating
baffle curtains. Influent is fed to each of the three zones in sequence. Aeration is applied to the
zone receiving influent wastewater and, for part of this cycle, one of the other two zones. While
the inflowing zone is aerated, the other two zones cycle between settling and decanting. WAS is
removed using airlift pumps, either to downstream facultative ponds for storage or for further
processing and disposal. A control system is provided to operate the motorized wastewater
influent valves and decanters. There are currently no full-scale installations of the CLEAR™
process. A depiction of the process is shown in Figure 6-9.
Floating IS Module
AIR LATERAL
rn i ITI m rn i n i ri' i rri rn tri i rr
HI ii mi in iiiiiiii HI ii in
J i JJ 1 U, 1 LJJ LLJ I.IJ LU 1 11 1 UJ UJ
EFFLUENTS WAS
OPTIONAL
VERTICAL MEDIA
Figure 6-7. EDI ATLAS - IS Internal Pond Settler.
6-21
-------
Figure 6.8. CLEAR™ Process.
6.4.1.14 Ashbrook Sequencing Batch Reactor
Description
Ashbrook Corporation (Houston, Texas) Sequencing Batch Reactor (SBR) system consists of
decanters, motorized valves, and a control system. A facility has been installed in a pond system
in Quincy, Washington. The aerated pond was portioned into sections and air was provided for
complete mixing in two or more SBR cells. Operation is similar to a conventional SBR process,
and the system in Quincy has been working well. Performance data are presented in Table 6.9.
Figure 6-10 is a photograph of the system.
Table 6.9. Data for the Quincy, Washington SBR System (Ashbrook Corporation).
2002-2003 Average Influent/Effluent Data
Flow, MGD = 0.78
Influent
Effluent
BOD, mg/L
145
14
TSS, mg/L
159
6
NH3, mg/L
19
1.7
6-22
-------
Figure 6-9. The Quincy SBR System.
®
6.4.1.15 AquaMat Process Description
AquaMat®is a biomass carrier system marketed by Nelson Environmental, Inc., Winnipeg,
Manitoba. Plastic ribbons slightly more dense than water are connected to a plastic float, and
ribbons extend into the waste stream three feet or more and provide additional surface area for
bacteria to grow. When used with pond systems, the application is referred to as the Advanced
Microbial Treatment System (AMTS).
6.4.1.15.1 Performance
Year-round nitrification has been achieved in an aerated pond in Laurelville, Ohio, and in
Canada. Performance data are shown in Table 6-10 and two views of the AquaMat® are shown
in Figure 6-11.
6-23
-------
Figure 6-10. The AquaMatR Process
,38
Table 6-10. Nelson AquaMat Biomass Carrier, Larchmont, Georgia (Burnett et al., 2004).
Reported Average Effluent Quality
BOD5 (mg/L)
TSS (mg/L)
NH3 (mg/L)
6.4.1.16 Moving Bed Biofilm Reactor™ Process
6
10
0.1
6.4.1.16.1 Description
The Moving Bed Biofilm Reactor™ (MBBR™) is marketed by AnoxKaldnes North America,
Inc., Providence, Rhode Island. The process is similar to the AquaMat except that thousands of
small polyethylene wheels are suspended in the pond (Figure 6-12). With a sufficient number of
the "wheels", adequate surface area is provided for growth of nitrifiers. An aerated pond in
Johnstown, Colorado has been successfully upgraded using the MBBR™.
6-24
-------
Figure 6-11. A MBBR™ "wheel."
6.4.1.17 Poo-Gloo™ (Wastewater Compliance Systems, Inc.)
This patented device, developed at the University of Utah, consists of several concentrically
nested domes that provide substrate for bacteria. They are placed on the bottom of a pond,
creating a dark environment with robust air and wastewater mixing which removes contaminants
from the water. Figure 6-13 shows a diagram of the device.
Airin
. Water Surface
Water Movement
Bubble Distribution Tube*
Bottom of L>f oof
Figure 6-12. Schematic of a Poo-Gloo device cross-section.
6.4.2 Other Processes
Partial denitrification has been achieved by most of the systems described above, although the
nitrogen removal pathways are not well understood. Several other commercial SBR systems and
biomass carrier systems are available. Their use in ponds appears to be limited. The principle is
the same and it appears reasonable to expect these proprietary systems would work. The
manufacturers of the products have unique experience working with pond systems. In addition to
the products, the companies have experience with floating baffle curtains for partitioning,
installation of equipment without removing existing ponds from service, cost-effective and
6-25
-------
efficient aeration systems for large surface area installations, and optimizing complete mix and
partial mix aeration regimes.
6.5 REMOVAL OF PHOSPHORUS
In general, removal of phosphorus (P) has not been required for wastewaters that receive pond
treatment, but there are a number of exceptions for systems in the north central United States
and Canada. It is expected that P removal will become a nation-wide requirement. The
following sections present what has been done to control the discharge of P from wastewater
treatment ponds.
6.5.1 Batch Chemical Treatment
In order to meet a P requirement of 1 mg/L for discharge to the Great Lakes, an approach
using in-pond chemical treatment in controlled-discharge ponds was developed in Canada.
Alum, ferric chloride and lime were tested using a motorboat for distribution and mixing of the
chemical. A typical alum dosage might be 150 mg/L to produce an effluent from the
controlled-discharge pond that contains less than 1 mg/L of P and less than 20 mg/L BODs
and TSS. The sludge buildup from the additional chemicals is insignificant and would allow
years of operation before requiring cleaning. The costs for this method were very reasonable
and much less than conventional P removal methods. It has been applied successfully in several
Mid-western states (U.S. EPA, 1992). The procedure does require a long-term management
plan that includes calibrating applications to minimize use and monitoring of sludge quality.
6.5.2 Continuous-Overflow Chemical Treatment
Studies of in-pond precipitation of P, BOD5, and TSS were conducted in Ontario, Canada.
The primary objective of the chemical dosing process was to test for the removal ofP with ferric
chloride (Fed3), alum and lime. Ferric chloride doses of 20 mg/L and alum doses of 225 mg/L,
when added continuously to the pond influent, effectively maintained pond effluent P levels
below 1 mg/L over a 2-year period. Hydrated lime at dosages up to 400 mg/L was not effective
in consistently reducing P below 1 mg/L (1-3 mg/L was achieved), and yielded no BODs
reduction, while slightly increasing the TSS concentration. Ferric chloride reduced effluent
BODs from 17 to 11 mg/L and TSS from 28 to 21 mg/L; alum produced no BODs reduction and a
slight TSS reduction (from 43 to 28-34 mg/L). Direct chemical addition appears to be effective
only forP removal.
A six-cell pond system located in Waldorf, Maryland, was modified to operate as two three-cell
units in parallel. Alum was added one system, while the other was the control. Each system
contained an aerated first cell. Alum addition to the third cell of the system proved to be
more efficient in removing total P, BODs, and TSS than alum addition to the first cell. Total P
reduction averaged 81 percent when alum was added to the inlet to the third cell and 60
percent when alum was added to the inlet of the first cell. Total P removal in the control ponds
averaged 37 percent. When alum was added to the third cell, the effluent total P
concentration averaged 2.5 mg/L, with the control units averaging 8.3 mg/L. Improvements
in BODs and TSS removal by alum addition were more difficult to detect, and at times
increases in effluent concentrations were observed.
6-26
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Thirty-seven pond systems in Michigan and Minnesota using chemical treatment to remove P
were studied (U.S. EPA, 1992). In Minnesota liquid alum was added to the secondary cells of
eleven facultative ponds using a motorboat. These ponds were designed with a hydraulic
residence time of 180 days and discharge in the spring and fall. The system used is essentially
the same as that developed in Ontario, Canada to achieve a total P effluent concentration of 1.0
mg/L. Influent concentrations ranged from 1.5 - 6.0 mg/L and averaged approximately 3.3
mg/L. In general, the facilities satisfied the requirement for 1.0 mg/L with several minor
excursions outside the limit by 10 percent. In 2010, 38 percent of the treatment ponds in
Minnesota were treating the wastewater for P removal (Steve Duerre, pers. comm., 2010). The
majority use alum, although other chemicals, such as potassium permanganate, are being
evaluated as possible substitutes. All of the ponds are able to meet the P limit. The chemical is
applied twice a year, prior to the seasonal spring and fall discharges.
The State of Michigan evaluated 26 ponds that had been in operation ranging from 1 to 20 years.
Both facultative and aerated ponds were evaluated. Discharge was seasonal (once or twice a
year) or continuous, (varying from 24 hours/day, 7 days/week to 8 hours/day, 5 days/week). The
chemicals were added to a clarifier following the pond system. None of the systems applied the
chemicals by boat. The influent total P concentration in the Michigan systems ranged from 0.5 to
15 mg/L, with an average of 4.1 mg/L. By 2010, more than 300 ponds in Michigan have or will
have aP limit of 1 mg/L (Dan Holmquist, pers. comm.). Phosphorus removal has been
successful as long as the chemical flocculant is added at the appropriate rate at the end of the
pond system, i.e., the clarifier or the maturation pond.
A description of the facilities and the influent and effluent P concentrations is shown in Table 6-
11.
Table 6-11. Phosphorus Removal in Ponds (from U.S. EPA, 1992).
Location
Belding3
Bessemer3
Coopersville3
Kalamazoo
Lake3
Elk Rapids3
Carson City3
Fowlerville3
Remus3
Serpent
Lakeb
Grand
Portageb
Discharge
schedule
Continuous
Continuous
Continuous
Continuous
Continuous
Seasonal
Seasonal
Seasonal
Seasonal
Seasonal
Chemical
treatment
Alum
Alum polymer
FeC/s
FeC/3
polymer
FeC/s
Alum
FeC/3
FeC/s
Alum
Alum
Facility
description
5-cell pond
3-cell pond
with clarifier
4-cell pond
3-cell pond
3-cell pond
with clarifier
5-celll pond
6-cell pond
4-cell pond
3-cell pond
2-cell pond
Phosphorus (mg/L)
Influent
4.0
1.8-2.0
5.0
6.0-7.0
3.2-4.3
6.0-7.0
2.5-3.5
4.7
1.8-2.8
2.9-3.3
Effluent
0.6-0.7
0.6-0.9
0.3
0.5-0.6
0.6-0.7
4.0
0.8
0.4-1.0
0.6-0.7
0.3-1.2
aMichigan, bMinnesota
6-27
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CHAPTER 7
UPGRADING POND EFFLUENTS
7.1 INTRODUCTION
There are two general ways to upgrade pond effluents: adding a solids removal step or
making modifications to the pond process. The selection of the appropriate method to
achieve a desired effluent quality depends upon the design conditions and effluent limits
imposed on the facility. The various methods are discussed in the following sections:
Solids Removal Methods and Operation Modifications and Additions to Typical Designs.
7.2 SOLIDS REMOVAL METHODS
The occasional high concentration of TSS in the effluent, which can exceed 100 mg/L,
has been a major operational challenge to pond systems. The solids are composed
primarily of algae and other pond detritus, not wastewater solids. These high
concentrations usually occur, during the summer months. Solids removal mechanisms
include the use of intermittent sand filters, recirculating sand filters, rock filters,
coagulation-flocculation and dissolved air flotation. Nolte & Associates (1992)
conducted a review of the literature covering recirculating sand filters and intermittent
sand filters.
7.2.1 Intermittent Sand Filtration
Intermittent sand filtration applies pond effluent to a sand filter bed on a periodic or
intermittent basis. The use of intermittent sand filters has a long and successful history of
treating wastewaters (Massachusetts Board of Health, 1912; Grantham et al., 1949;
Furman et al., 1955). A summary of the design characteristics and performance of
several systems employed in Massachusetts around 1900 is presented in Table 7-1.
These systems were treating raw or primary effluent wastewater and producing an
excellent effluent. A typical intermittent sand filter is shown in Figure 7-1.
7-1
-------
Table 7-1. Design and Performance of Early Massachusetts Intermittent Sand
Filters (Mass. Board of Health, 1912; Mancl and Peeples, 1991).
Location
Andover
Brockton
Concord
Farmington
Gardner
Leicester
Natick
Spencer
Year
Started
1902
-
1899
-
1891
-
-
1897
Loading
Rate
(gal/d/ac)
3500
-
83,000
-
122,000
-
-
61,000
Filter
Depth
(in)
48-60
-
-
70
60
-
-
48
Sand
Size
(mm)
0.15-
0.2
-
-
0.06-
0.12
0.12-
0.18
-
-
0.18-
0.34
Ammonia
Removal
Influent
(mg/L)
-
40.7
-
27.3
21.2
-
12.4
16
Effluent
(mg/L)
-
1.5
-
2.7
7.5
-
2.3
2.1
BOD5 Removal
Influent
(mg/L)
-
314
-
-
139
321
-
116
Effluent
(mg/L)
-
6.2
-
-
9.5
13.1
-
6.9
See p. xiv for conversion table.
7-2
-------
.5"Dia.Rock
"Dta. Rock
.5" Did. Rock
Section 2-2
Sand and gravel placement
buppiy
line
1
t
\ "
X
/
j
1
!
i
\
\ i
v
>r and Filter bed T
\ l
Seal between
^^~ liner and pipe
X
1
1
1
I
1
\
1
AlIS
^
\
\
\
\
\c«
^ lin
al between
erand Dice
1
t
plan view
Drain
Drain Pipe
Seal between drain pipe and
liner with suitable material
Figure 7-1. Cross-sectional and plan views of a typical intermittent sand filter (U.S.
EPA, 1983a).
7-3
-------
Intermittent sand filtration is capable of polishing pond effluents at relatively low cost
and is similar to the practice of slow sand filtration in potable water treatment. As the
wastewater passes through the bed, TSS and other organic matter are removed through a
combination of physical straining and biological degradation processes. The particulate
matter collects in the top 5 - 8 cm (2 - 3 in) of the filter bed. This accumulation eventually
clogs the surface and prevents effective infiltration of additional effluent. At that time,
the bed is taken out of service, the top layer of clogged sand removed, and the unit is put
back into service. The removed sand can be washed and reused or discarded.
7.2.1.1 Summary of Performance
Summaries of the performance of intermittent sand filters treating pond effluents
conducted during the 1970's and 1980's are presented in Tables 7-2 and 7-3. Table 7-2 is
a summary of studies reported in the literature and EPA documents, and Table 7-3 is a
summary of results from field investigations at three full-scale systems consisting of
ponds followed by intermittent sand filters. These are the most extensive studies
conducted in the US. Though there are some effluent concentration above the 30/30
(TSS/BODs mg/L) limit, on the whole, the results demonstrate that it is possible to
produce an effluent with TSS and BODs less than 15 mg/L from anaerobic, facultative
and aerated ponds followed by intermittent sand filters with effective sizes less than or
equal to 0.3 mm.
It should be noted that Mt. Shasta Wastewater Treatment Plant retired the intermittent
sand filter bed and has been using dissolved air flotation to remove algae since 2000
(see Section 7.2.5). The treatment process consists of headworks, four oxidation
ponds, ballast lagoon dosing basin, dissolved air flotation system, intermittent
backwash filter, chlorine contact chamber, declorination system and discharge line.
The treated wastewater can be discharged to any of three locations, depending on water
quality and time of year: the Sacramento River, a leach field located adjacent to
Highway 89, or the Mt. Shasta Resort Golf Course (http://ci.mt-
shasta.ca.us/publicworks/wastewater.php). The intermittent sand filter bed was
determined to be too labor intensive, although it worked fairly well (Jackie Brown,
pers. comm., 2010).
7-4
-------
Table 7-2. Intermittent Sand Filter Performance Treating Pond Effluents".
Pond
Type
Facultative c
Facultative
Facultative
Facultative c
Aerated
Anaerobic
Facultative
ucb
5.8
9.74
6.2
9.73
9.73
NA
9.7
Load
ing
Rate
mgd/
ac
0.1
0.2
0.31
0.2
0.4
0.6
0.8
1.0
0.5
1.0
1.5
0.25
1.0
0.5
1.0
0.1
0.35
0.5
0.2
0.4
TSS
Inf.
mg/L
13.7
13.7
13.7
30.0
30.1
34.0
23.9
28.5
32.4
32.4
32.4
70.7
68.7
158
68.7
353
208
194
23.0
20.8
TSS
Eff.
mg/L
4.0
4.8
6.0
3.5
2.9
5.9
4.7
5.1
8.6
7.8
6.4
10.1
32.9
52.5
32.9
45.5
46.5
45.1
2.7
3.5
TSS
Rem.
%
71
65
56
88
90
83
80
82
74
76
80
86
52
67
52
87
78
77
88
83
vss
Inf.
mg/L
9.2
9.2
9.2
23.0
22.5
25.9
15.2
21.5
21.9
21.9
21.9
38.8
36.6
71.1
36.6
264
162
175
17.8
18.5
VSS
Eff.
mg/L
2.0
21
2.3
1.3
1.3
3.1
1.2
2.5
3.3
3.2
3.3
6.5
11.3
13.2
11.3
28.1
35.3
35.7
1.0
2.3
VSS
Rem.
%
78
77
75
94
94
88
92
88
85
85
85
83
69
81
69
84
78
80
95
88
BOD
Inf.
mg/L
6.3
6.3
6.3
19.5
19.5
25.6
2.8
13.5
10.7
10.7
10.7
20.2
19.6
34.4
19.6
123
108
107
10.9
11.5
BOD
Eff.
mg/L
1.2
1.3
2.0
1.9
1.9
4.2
1.8
2.6
1.8
2.0
2.3
6.6
11.7
5.1
11.7
19.5
43.7
67.6
1.1
2.6
BOD
Rem.
%
82
80
69
90
90
84
36
81
83
82
79
67
40
85
40
84
60
37
90
77
Reference
Marshall and
Middlebrooks
1974
Earnest et al.,
1978
Hilletal.,
1977
Bishop et al.,
1977
Bishop et al.,
1977
Messinger,
1976
Tupyi et al.,
1979
TSS = Total suspended solids; VSS =
demand
aResults for best overall performing 0.
bU.C. = Uniformity constant
cDairy waste
Volatile suspended Solids; BOD = Biochemical oxygen
17 mm effective size (e.s.) filters
7-5
-------
Table 7-3. Mean Performance Data for Three Full-Scale Pond-Intermittent Sand
Filter Systems (Russel et al., 1979 in Crites, 2006).
Parameter
BOD5 (mg/L)
Soluble
BOD5 (mg/L)
TSS (mg/L)
VSS (mg/L)
FC
(col/1 00ml)
pH
DO (mg/L)
COD (mg/L)
Soluble COD
(mg/L)
Akl (mg/L as
CaCO3)
TP (mg-P/L)
TKN (mg-
N/L)
NH3 (mg-
N/L)
Org-N (mg
N/L)
NO2~ (mg-
N/L)
NO3~ (mg-
N/L)
Total Algal
Count
Flow (mgd)
Mt. Shasta CA
Pond
Eff
22
7
49
34
292
87
12.4
100
71
75
3.88
11.1
5.56
56
0.56
0.78
4x1 05
NA
Filter
Eff
11
4
18
13
30
68
5.5
87
64
51
3.09
7.5
1.83
5.7
7.7
43
1x105
NA
Facility
Eff
8
5
16
10
<2
66
5.3
68
50
42
2.72
5.2
1.76
3.4
0.020
45
1x105
0.488
Moriarty NM
Pond
Eff
30
17
81
64
290
8.9
10.9
84
67
293
4.02
22
16
5.7
159
0.09
8x1 05
NA
Filter
Eff
17
16
13
9
18
8.0
8.3
43
34
260
2.8
121
9.16
3.3
1.66
4.09
3x1 04
0.046
Facility
Eff
17
16
13
9
34
8.0
8.3
43
34
260
2.8
121
9.16
3.3
1.66
4.09
3x1 04
NA
Alley GA
Pond
Effluent
22
10
43
32
55
8.9
10.2
57
41
84
3.10
7.3
0.658
6.7
0.56
349,175
NA
Filter
Effluent
8
6
15
8
8
7.1
7.4
32
23
76
2.67
4.1
0.402
3.8
77
21583
NA
Facility
Effluent
6
5
13
6
<1
6.8
7.9
25
16
69
2.45
2.2
0.31
1.9
0.020
29360
0.070
NA = Not Available
Rich and Wahlberg (1990) evaluated the performance of five facultative pond-
intermittent sand filter systems located in South Carolina and Georgia. A summary of the
design characteristics and performance of these systems is shown in Table 7-4. The
systems provided superior performance when compared with ten aerated pond systems
7-6
-------
not using intermittent sand filtration. Six of the 10 aerated pond systems consisted of one
aerated cell followed by a polishing pond; three were designed as dual-power (aeration
reduced in succeeding cells), multi-cellular systems, and one was a single cell dual-power
system. Using data reported by Niku et al. (1981), the performance of the facultative
pond-intermittent sand filter systems compared favorably with activated sludge plants.
Table 7-4. Design Characteristics and Performance of Facultative Pond-
Intermittent Sand Filter Systems (Rich and Wahlberg, 1990).
Design
Flow
m3/L
303
303
568
378
568
Present
Flow
%of
Design
56
79
48
66
37
HRT
d
93
70
59
52
55
Filter
Dosing3
m3/m2/d
0.03
0.37
0.47
0.37
0.31
BOD5
gm/
m3
50%
9
6
7
9
6
gm/
m3
95%
28
22
17
21
17
TSS
gm/
m3
50%
12
7
11
11
6
gm/
m3
95%
41
29
30
25
16
NH3
gm/
m3
50%
0.9
0.4
-
0.9
1.3
gm/
m3
95%
4
1.2
-
2.4
5.4
Based on design flow rate
Truax and Shindala (1994) reported the results of an extensive evaluation of facultative
pond-intermittent sand filter systems using four grades of sand with effective sizes of
0.18 - 0.70 mm and uniformity coefficients ranging from 1.4 - 7.0 (Appendix C, Tables
C-7-1 and C-7-2). Performance was directly related to the effective size of the sand and
hydraulic loading rate. With effective size sands of 0.37 mm or less and hydraulic
loading rates of 0.2 m3/m2/d, effluents with BODs and TSS of less than 15 mg/L were
obtained. TKN concentrations were reduced from 11.6 mg/L to 4.3 mg/L at the 0.2
m3/m2/d loading rate. The experiments were conducted in a mild climate, and it is not
known whether similar N removal rates would be achieved during cold months in more
severe climates.
Melcer et al. (1995) reported the performance of a full-scale aerated pond-intermittent
system located in New Hamburg, Ontario, that had been in operation since 1980. Results
for 1990 and for January to August of 1991 are presented in Table 7-5. Surface loading
rates for both periods were 3.24 m3/m2/d, with influent BOD5, TSS and TKN
concentrations of 12, 16 and 19 mg/L, respectively. Filter effluent quality exceeded
requirements with BODs, TSS and TKN concentrations being less than 2 mg/L.
7-7
-------
Table 7-5. Performance of Aerated Pond-Intermittent Sand Filter, New Hamburg,
Ontario Plant (Melcer et al., 1995).
Location in System
Parameter
1990
1991 (Jan-Aug)
Influent
Average Flow Rate
(m3/d)
Max Flow Rate (nrVd)
BOD5, mg/L
TSS, mg/L
TKN, mg/L
TP, mg/L
1676
4530
186
314
45
9.3
1673
3990
120
171
44
9.5
Aerated Cell
Aerated Cell Effluent
HRT (d)
BOD5 Loading
(kg/m3/d)
BOD5, mg/L
TSS, mg/L
TP, mg/L
7
0.03
34
44
6
7
0.02
36
44
5
Facultative Pond
HRT (d)
Avg. BOD5 loading
(kg/1 000 m2/d)
165
0.51
165
0.55
Cell 2 Effluent
BOD5, mg/L
TSS, mg/L
TKN, mg/L
NH3, mg/L
T/V, mg/L
TP, mg/L
12
16
19
15
1.1
1.2
11
18
18
14
0.8
0.7
Filter
Annual Surface
Loading, m3/m2
Surface Loading,
L/m2/d
195
3240
153
3240
Filter Effluent
BOD5, mg/L
TSS, mg/L
TKN, mg/L
/VH3, mg/L
T/V, mg/L
TP, mg/L
Mar-Dec
2
1.7
2
1.2
7
0.5
Mar-Aug
2
1.1
1.1
0.6
9
0.4
7.2.1.2 Operating Periods
The length of filter run is a function of the effective size of the sand and the quantity of
solids deposited on the surface of the filter. EPA (1983a) and several publications
(Marshall and Middlebrooks, 1974; Messinger, 1976; Earnest et al., 1978; Hill et al.,
1977; Bishop et al., 1977; Tupyi et al., 1979; Russel et al., 1983) contain extensive
7-8
-------
information on the relationship between solids deposited on the surface of a filter and the
length of run time. Truax and Shindala (1994) also reported similar run times.
7.2.1.3 Maintenance Requirements
Maintenance is directly related to the quantity of solids applied to the surface of the filter,
and this is related to the concentration of solids in the influent to the filter and the
hydraulic loading rate. Filters with low hydraulic loading rates tend to operate for
extended periods. With such extended operating periods, maintenance consists of routine
inspection of the filter, removing weeds, and an occasional cleaning by removing the top
5 - 8 cm of sand after allowing the filter to dry out. Early control of weeds is the key to
good maintenance. The use of chemicals is not advised. In Wisconsin, where there are
many sand filters, the O&M manuals advise that the sand beds can be tilled if the weeds
are very small. Once they have grown, however, they need to be removed manually (Jack
Saltes, Wisconsin Department of Natural Resources, pers. comm., 2010).
7.2.1.4 Hydraulic Loading Rates
Typical hydraulic loading rates on a single-stage filter range from 0.37 - 0.56 m3/m2/d. If
the TSS in the influent to the filter routinely exceeds 50 mg/L, the hydraulic loading rate
should be reduced to 0.19 - 0.37 m3/m3/d to increase the filter run. In cold weather
locations, the lower end of the range is recommended to avoid having to clean the filter
during the winter months.
7.2.1.5 Design of Intermittent Sand Filters
Algae removal from pond effluent is almost totally a function of the sand size used. With
a required BODs and TSS below 30 mg/L, a single-stage filter with medium sand
(effective size = 0.3 mm) will produce a reasonable filter run. If better effluent quality is
required, finer sand (effective size = 0.15 - 0.2 mm) or a two-stage filtration system with
the finer sand in the second stage should be used.
The total filter area required for a single-stage operation is calculated by dividing the
expected influent flow rate by the hydraulic loading rate selected for the system. One
spare filter unit should be included to permit continuous operation, since the cleaning
process may require several days. An alternate approach is to provide temporary storage
in the pond units. Three filter beds are the preferred arrangement to permit maximum
flexibility. In small systems that depend on manual cleaning, the individual bed should
not be bigger than about 90 m2. Larger systems with mechanical cleaning equipment
could have individual filter beds up to 5000 m .
The design depth of sand in the bed should be at least 45 cm with a sufficient depth for at
least one year of cleaning cycles. A single cleaning operation may remove 2.5 - 5 cm of
sand. A 30-day filter run would then require an additional 30 cm of sand. In the typical
case, an initial bed depth of about 90 cm of sand is usually provided. A graded gravel
layer 30 - 45 cm separates the sand layer from the under drains. The bottom layer is
graded so that its effective size is four times as great as the openings in the under-drain
piping. The successive layers of gravel are progressively finer to prevent intrusion of
sand. An alternative is to use gravel around the underdrain piping and then a permeable
7-9
-------
geo-textile membrane to separate the sand from the gravel. Further details on design and
performance are presented in the U.S. EPA (1983a), Reed et al. (1995) and Crites et al.
(2006). A design example for an intermittent sand filter treating a pond effluent is
presented in Example C-7-1 in Appendix C.
7.2.2 Rock Filters
A rock filter operates by allowing pond effluent to travel through a submerged porous
rock bed, causing algae to settle out on the rock surfaces as the liquid flows through the
void spaces. The accumulated algae are then biologically degraded. Algae removal with
rock filters has been studied extensively at Eudora, Kansas; California, Missouri; and
Veneta, Oregon (USEPA, 1983a). Rock filters have been installed throughout the United
States and the world, and performance has varied (USEPA, 1983a; Middlebrooks, 1988;
and Saidam et al., 1995). A diagram of the Veneta rock filter is shown in Figure 7-2.
The West Monroe, Louisiana rock filters were essentially the same as the one in Veneta,
but the filters received higher loading rates. Several rock filters of various designs have
been constructed in Illinois with varied success. Many of the Illinois filters produced an
excellent effluent, but the designs varied widely (Menninga, pers. comm., 1986). Figure
7-3 contains diagrams of the various types of rock filters in use in Illinois. Snider (pers.
comm., 1998) designed a rock filter for Prineville, Oregon and knew of one built at
Harrisburg, Oregon. Performance and design detail are not available, but Snider
indicated that the systems were designed using information from the Veneta system.
7-10
-------
Effluent
Effluent
„„_.
Influent xf
\
36,9 m
"" 7,3 m
Influent
pipe
V
36,9 m
73m
'/
73 m"
S2.4m
J
73m
Effluent
Weir
Plan
Influent
pipe
Profile
Figure 7-2. Rock filter at Veneta, Oregon (Swanson and Williamson, 1980).
7-11
-------
Influent
Effluent
. Collection Pipe
* Effluent
Figure 7-3. State of Illinois rock filter configurations (Menninga, pers.
comm.,1986).
The principal advantages of the rock filter are the relatively low construction cost and
simple operation. Odor problems can occur, and the design life for the filters and the
cleaning procedures has not yet been firmly established. Several units have been
operating successfully for over 20 years.
Archer and O'Brien (2005) have used inter-pond rock filters to improve suspended solids
and nitrogen removal. Rock embankments across the ponds provide filtering, reduced
short-circuiting, and increased surface area to grow nitrifying bacteria.
7-12
-------
7.2.2.1 Performance of Rock Filters
7.2.2.2 Veneta, Oregon
Based on data from filter systems in place in Veneta, it can be concluded that rock filter
performance is mixed. Forms of TV in the effluent from a study by Swanson and
Williamson (1980) for the Veneta system are shown in Figure 7-4. Performance data for
1994 are shown in Table 7-6. After approximately 20 years of operation, the system was
producing an effluent meeting secondary standards with regard to BODs, TSS and fecal
coliform. Ammonia data were not collected routinely as it was not included in the
discharge permit. Ammonia data were only collected on a regular basis during the winter
months of the Swanson and Williamson (1980) study, and high NHs concentrations were
observed in the effluent as shown in Figure 7-4. Occasional NH^ measurements were
made after the Swanson and Williamson study, and higher concentrations were observed
during the winter, indicating that the process may not be suitable if a discharge must meet
effluent limits.
Table 7-6. Mean and Range of Performance Data for Veneta Wastewater
Treatment Plant, 1994.
FC
Constituent
BOD5, mg/L
TSS, mg/L
MPN/100mg/L
Flow, mgd
Influent
138(50-238)
124(50-202)
Not available
0.251 (0.159-0.452)
Effluent
17(5-30)
9 (2-27)
<10(<10-20)
0.309 (0.079-0.526)
7-13
-------
=
=
I
r.
•9
u
I Iota IN
I Nitrate-N
lOrg-N
INH4-N
Inf Eff Inf Eff Inf Eff Inf Eff Inf Eff Inf Eff
Figure 7-4. Nitrogen species in Veneta wastewater treatment rock filter. Nov-77;
Jan, Feb, Mar, Apr and May-78 (Swanson and Williamson, 1980).
7.2.2.3 West Monroe, Louisiana
Stamberg et al. (1984) presented performance results for the two rock filters operating in
West Monroe, Louisiana. The systems were loaded at higher hydraulic loading rates than
that used for the Veneta facility (<0.3 m3 of wastewater/d per rock m3), and the TSS
removals were less than those reported for the Veneta system. In general, the West
Monroe systems produced effluent BODs and TSS concentrations less than 30 mg/L, but
while there were occasional exceedances of BODs to 40 mg/L and TSS to 50 mg/L, only
12 out of over 100 samples exceeded 30 mg/L for either parameter. The design flow
rates on the West and East filter were 3.5 and 1.8 mgd, respectively, and the flow rates
frequently exceeded the design rate by a factor of 2 to 3. This resulted in an increase in
the loading rate by a factor of 2 to 3, which greatly exceeded the Veneta loading rate.
7-14
-------
7.2.2.4 Jordan Rock Filters
Saidam et al. (1995) performed a series of studies of rock filters treating pond effluent in
Assram, Jordan. The filters were arranged in three trains, the first train consisting of two
filters in series, with the first filter containing rock and having an average diameter of 18
cm followed by a filter containing local gravel (wadi gravel) with an average diameter of
11.6 cm. The second train contained the same rock as used in the first filter, but with an
average diameter of 2.4 cm. The wadi gravel was used in the first filter of the third train,
and the second filter contained an aggregate with an average diameter of 1.27 cm. The
filters in the three trains were operated in series, and the characteristics of the wastewater,
hydraulic loading rates, and the characteristics of the effluents from the various filters are
shown in Table 7-7. The removal efficiencies obtained in the first run for the various
filters and the trains are summarized in Table 7-8. Even though the rock sizes of several
of the filters were similar to what was used at Veneta and West Monroe, the hydraulic
loading rates exceeded the maximum recommended value of 0.3 m3/m3/d and the quality
of the effluents was much lower. There was insufficient DO in the influent to oxidize
NHs, and considering the temperature of the influent wastewater and the H2$ in the
effluent, it is likely that the filters were anaerobic. On the other hand, TSS was lowered
by 60 percent and fecal coliform levels met WHO guidelines for unrestricted use of the
effluent for agricultural purposes (WHO, 2003).
7-15
-------
Table 7-7. Performance of Rock Filters (Saidam et al., 1995).
Unit
INFLUENT
FIRST TRAIN
Rock Filter 1
Avg. Diameter- 18 cm
Voids=49%
Surface Area =17 m^nf
Wadi Gravel Filter 1
Avg. Diameter=1 1 .6 cm
Voids=41%
Surface Area =25 z/mj
SECOND TRAIN
Rock Filter 2
Avg. Diameter = 18 cm
Voids=49%
Surface Area =17 m^nf
Coarse Aggregate Filter 2
Avg. Diameter=2.4 cm
Voids=40%
Surface Area =150 z/mj
THIRD TRAIN
Wadi Gravel Filter 3
Avg. Diameter=1 1 .6 cm
Voids=41%
Surface Area =25 z/mj
Medium Aggregate Filter 3
Avg. Diameter=1 .27 cm
Voids=28%
Surface Area =327 z/mj
Hydraulic
Loading
Rate
m3/m3-d
0.498
0.634
0.5 to .58
0.5 to .58
0.386
0.634
0.5 to .58
0.5 to .58
0.311
0.634
0.5 to .58
0.5 to .58
0.333
0.634
0.5 to .58
0.5 to .58
0.274
0.634
0.5 to .58
0.5 to .58
0.442
0.634
0.5 to .58
0.5 to .58
Run
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
T
°C
25.7
21
14.0
15.0
25.1
20.0
13.4
13.0
25.2
13.4
13.0
25.3
19.7
13.3
13.7
25.6
19.9
13.3
15.0
25.7
20.2
13.3
15.0
25.9
19.7
13.4
13.0
DO
mg/L
3.2
4.8
4.0
3.5
1.2
1.5
1.0
2.1
1.9
1.0
1.9
1.1
1.4
1.0
1.9
1.7
1.4
1.0
1.9
1.6
1.4
1.0
1.9
2.0
1.5
1.0
1.9
TSS
mg/L
201
234
213
101
131
200
156
76
78
161
129
66
130
203
164
88
102
154
134
60
109
206
150
81
79
121
108
45
BOD5
mg/L
95
105
122
108
61
81
100
77
36
66
77
74
53
79
87
92
51
65
73
87
48
76
86
76
42
72
66
59
TFCC
mpn/
100mg/L
1.10E+04
6.3E+04
9.6+05
1 .6W+04
2.2E+03
5.7E+04
8.1E+05
1.4E+04
1.00E+03
4.2E+04
4.7E+05
1.10E+04
1.9E+03
5.00E+04
8.6E+05
1.00E+04
1.5E+03
E
3.2E+04
5.4E+05
6.5E+03
1.6E+03
6.8E+04
3.2E+05
6.3E+03
6.4E+02
3.3E+04
4.4E+05
3.3E+03
NH4-N
mg/L
85
93
97
71
89
96
96
72
91
97
71
89
98
98
71
89
98
97
71
91
96
97
71
92
96
100
71
7-16
-------
Table 7-8. Summary of Removal Efficiency in the First Run (Saidam et al., 1995).
Parameter
TSS
BOD5
COD
Total P
Total FC
Color
HLR
m3/m3/d
Percent Removal of Individual Filters
Rock
Filter
1
34
36
19
9
80
25
0.498
Wadi
Gravel
Filter
1
41
41
18
15
55
34
0.386
Rock
Filter
2
35
44
21
9
83
28
0.311
Coarse
Aggregate
Filter
2
22
4
15
30
21
20
0.333
Wadi
Gravel
Filter
3
46
49
24
18
85
30
0.274
Medium
Aggregate
Filter
3
25
13
25
33
60
36
0.442
% Removal Per Train
1st
Train
61
62
33
24
90
51
-
«nd
Train
49
46
33
35
86
42
-
3rd
Train
59
56
44
46
94
55
-
7.2.2.5 New Zealand Rock Filters
Rock filters have been used in New Zealand for removing high concentrations of algae
from pond effluents (Middlebrooks et al,2005). The systems were developed from sub-
surface flow wetlands without plants. The rock ranged from 12 - 24 cm in diameter, with
the coarser rocks at the inlet and outlet to distribute the flow evenly. A cross-section of
the rock filter at Paeroa, New Zealand is shown in Figure 7-5.
Distribution Inlet Pipes
20-50mm
/~Melter Slag
Level Floor. 300mm Fall
Across First Third of Bed
10-20mm
Melter Slag
20-50mm
Melter Slag
1.2m
20.0m
1.0m
\ Outlet Perforated
^— Pipes to Level
Control Chamber
Figure 7-5. Cross-sectional view of Paeroa, New Zealand rock filter (Middlebrooks
et al., 2005).
7-17
-------
The rock filters are generally anoxic and there is little nitrification, however, there can be
denitrification. The effluent is anaerobic and does emit H2$ on occasion. If the influent
contains high concentrations of algae, organic TV will increase in the effluent.
Three systems in New Zealand used steel slag, which has a high porosity and produces
less H2S. Some phosphorus removal was observed for the first years of operation. The
filters followed partial mix aerated ponds, and have consistently produced TSS effluent
concentrations less than 25 mg/L. Average removals have been less than 12 mg/L, even
when influent solids were 100 mg/L or greater.
7.2.2.6 Design of Rock Filters
Rock filters have been designed using a number of parameters. A summary of the design
parameters used for several locations is shown in Table 7-9. The parameters shown for
the state of Illinois are the current standards and were not necessarily used to design the
systems diagrammed in Figure 7-3. The critical factor in the design of rock filters
appears to be the hydraulic loading rate. Rates less than 0.3 m3/mVd give the best results
with rocks in the range of 8 - 20 cm and a depth of 2 m with the water applied in an up
flow pattern. Design parameters and performance of some rock filters in New Zealand
are shown in Table 7-10.
Table 7-9. Design Parameters for Rock Filter Systems in the United States (Oregon:
Swanson and Williamson, 1980; Louisiana: Stamberg et al., 1984; Kansas and
Missouri: U.S. EPA, 1983a).
Parameter
Hydraulic
Loading
Rate
m3/m2/d
Rock cm
Aeration
Depth, m
Disinfection
Veneta
0.3
7.5-20
None
2
Yes
W. Monroe
0.36
5-13
None
1.8
Yes
State of Illinois
0.8
8-15
Free of fines
Soft weathering
stone , and no
flat rock
Post-aeration
ability necessary
Rock media
must extend 0.3
m above water
surface
Chlorination of
post-aeration cell
encouraged
Eudora
Up to 1.2 in
the summer.
0.4 in winter &
spring
2.5
None
1.5
Not Applicable
California
0.4
6-13
None
1.68
Yes
7-18
-------
Table 7-10. Design Parameters and Performance of New Zealand Rock Filters
(Middlebrooks, 2005).
Design flow (average)
Current flow (average)
Width
Length
No. of beds
Total rock filter area
Rock size
Rock type
Rock depth
Rock filter loading rate
(average)
Rock filter loading rate
(average)
Average water depth
Hydraulic retention time
(average)
Year constructed
mj/day
m3/day
m
m
m2
1 mm
m
1 mm/day
m3/m3 day
1 m
days
Waluku
3,000
1,800
29.6
97.4
10
28,868
20/10
slag
0.5
'62
0.14
0.45
3.3
1993
Paeroa
2,067
2,100
22
131
8
23,056
20/10
slag
0.5-0.8
91
0.20
0.45
2.2
2000
Ngatea
460
250
26.3
136.0
2
7,154
20/10
slag
0.5-0.8
35
0.08
0.45
5.8
2002
Clarks
V^ICXI i\O
Beach
375
290
32
62
2
3,875
20/10
greywacke
0.5-0.65
75
0.17
0.45
1.5
1998
Average water quality (mg/L)
CBOD5
Suspended Solids
NH3
Total N
average
95 percentile
average
95 percentile
average
95 percentile
average
95 percentile
6
11
12
24
5
24
8
20
5
19
9
17
7
12
10
17
3
6
6
9
15
27
19
36
7.2.2.7 Aerated Rock Filter
To address the lack ofNHs removal in rock filters, Mara and Johnson (2006) constructed
an aerated rock filter with perforated pipe placed in the underdrain. They operated the
aerated rock filter in parallel with a non-aerated control over an 18-month period.
Facultative pond effluent containing approximately 10 mg/L ofNHs was applied to the
filters at a hydraulic rate of 150 L/m2/d during the first eight months of operation and at
300 L/m2/d thereafter. Ammonia concentrations in the aerated filter effluent were less
than 3 mg/L, and NO3' concentrations were approximately 5 mg/L, while the control filter
N concentrations were approximately 7 mg/L. Ammonia removal did not occur in the
non-aerated control, and there was a statistically significant increase in the mean NHs
concentration between the influent and effluent. Fecal coliform concentrations were
reduced in the aerated filter from 103 to 104 per lOOmL to a geometric mean count of 65
per 100 mL. BODs and TSS removals were much higher in the aerated filter. The 95
percentile effluent concentrations in the aerated filter were 9 and 10 mg/L, respectively,
while the effluent concentrations from the control were 38 and 43 mg/L.
r\
Increasing the hydraulic loading rate from 150 to 300 L /m /d did not negatively affect
the mean percentage BOD5, NH3 and fecal coliform removals. There was a slight
reduction in the TSS removals. It was concluded that the use of aerated rock filters
7-19
-------
eliminates the need for maturation ponds to remove NHs, and reduces the surface area
required for maturation ponds at a flow rate of 200 L/person/d from approximately 5
m2/person to 1.3 m2/person with an aerated rock filter 0.5 m deep and loaded at 300
L/m2/d. In winter, the facultative pond DO concentration was approximately 2 mg/L and
approximately 8 mg/L in the aerated filter effluent. The control non-aerated filter effluent
DO concentration was approximately 1 mg/L.
In a follow-up study Johnson and Mara (2007) conducted studies comparing a pilot-scale
subsurface horizontal flow constructed wetland, a non-aerated rock filter and an aerated
rock filter receiving effluent from a facultative pond loaded at 79 kg/ha/d. BODs, TSS
and NHs concentrations were lower in the effluent from the aerated rock filter when
compared with the non-aerated rock filter and the constructed wetland. A summary of
the results are shown in Table 7-11.
Table 7-11. BOD5, TSS and NH3 Concentrations in the Effluents of the Facultative
Pond, Aerated Rock Filter and Constructed Wetlands (Johnson and Mara, 2007).
Period
Summer3
Winter"
Parameter
BOD5 (mg/L)
Mean
S.D°
95%°
TSS (mg/L)
Mean
S.D.
95%
NH3 (mg/L)
Mean
S.D.
95%
BOD5
Mean
S.D.
95%
TSS
Mean
S.D.
95%
Ammonia
Mean
S.D.
95%
Facultative
Pond
39
9
53
58
27
99
3.8
1.6
6
41
14
58
78
21
113
10
1.4
12
Aerated
Rock Filter
4.5
1.5
6
4
2
7
1.7
0.2
2
4.2
2.7
8.1
4.9
2.9
9
4.7
2.4
8
Constructed
Wetland
20
7
29
26
19
52
2
1.5
4.4
21
8
32
30
6
35
9
1
10
B June-August 2004,b December 2004-February 2005. ° Standard Deviation,d 95 percentile value
7.2.3 Normal Granular Media Filtration
Granular media filtration (rapid sand filters) separates liquids and solids. The simple
design and operation process makes it applicable to wastewater streams containing up to
200 mg/L suspended solids. The process can be automated based on easily measured
parameters with minimum operation and maintenance costs. On the other hand, regular
granular media filtration is not as efficient for removing algae unless coagulants or
flocculants have been added prior to filtration. Table 7-12 contains a summary of the
results with direct granular media filtration.
7-20
-------
Table 7-12. Summary of Direct Filtration with Rapid Sand Filters (dso = diameter
of 50 percent of sand).
Investigator
Borchardt
and O'Melia
(1961)
Coagulant
none
Fe 7 mg/L
Filter
Loading
gpm/sf
0.2-2
2.1
Filter
Depth
cm
61
61
Sand
Size
mm
dso = 0.32
dso = 0.40
Findings
Removal declines to
21 -45% after 1 5 hr
50% algae removal
Davis and
Borchardt
(1966)
none
none
none
none
Fe
0.49
0.49
1.9
1.9
NA
NA
NA
dso = 0.75
dso = 0.29
dso = 0.75
dso = 0.29
dso = 0.75
22% algae removal
34% algae removal
10% algae removal
2% algae removal
45% algae removal
Foss and
Borchardt
(1969)
none
2
91
dso = 0.71
pH 2.5, 90% removal
Lynam et al.
(1969)
none
1.1
28
dso = 0.55
62% TSS removal
Kormanik
and Cravens
(1978)
none
-
-
-
11 -45% TSS removal
Diatomateous earth filtration is capable of producing a high-quality effluent when
treating wastewater treatment pond water, but the filter cycles are generally less than 3
hours. This results in excessive usage of backwash water and diatomateous earth, which
increases costs and eliminates this method of filtration as an alternative for polishing
wastewater treatment pond effluents.
7.2.4 Coagulation-Flocculation
Coagulation followed by sedimentation has been applied extensively for the removal of
suspended and colloidal materials from water. Lime, alum and ferric salts are the most
commonly used coagulating agents. Floe formation is sensitive to parameters such as/?H,
alkalinity, turbidity and temperature. Most of these variables have been studied, and their
effects on the removal of water supply turbidity have been evaluated. In the case of the
chemical treatment of wastewater treatment pond effluents, however, the data are not
comprehensive.
Shindala and Stewart (1971) investigated chemical treatment of treatment pond effluents
as a post-treatment process to remove the algae and to improve the quality of the effluent.
They found that the optimum dosage for best removal of the parameters studied was 75-
100 mg/L of alum. When this dosage was used, the removal of phosphate was 90 percent
and the BOD 5 was 70 percent.
7-21
-------
Tenney (1968) has shown that at apH range of 2 to 4, algal flocculation was effective
when a constant concentration of a cationic polyelectrolyte (10 mg/L of C-31) was used.
Golueke and Oswald (1965) conducted a series of experiments to investigate the relation
of hydrogen ion concentrations to algal flocculation. In this study, only H2SO4 was used,
and only to lower the/?H. Golueke and Oswald found that flocculation was most
extensive at apR value of 3, which agrees with Tenney's results and reported algal
removals of about 80-90 percent. Algal removal efficiencies by cationic polyelectrolytes
were not affected in thepH range of 6-10.
The California Department of Water Resources (1971) reported that of 60
polyelectrolytes tested, 17 compounds were effective with regard to coagulation of algae
and were economically competitive when compared to mineral coagulation used alone.
Generally, a dose of less than 10 mg/L of the polyelectrolytes was required for effective
coagulation. A daily addition of 1 mg/L ofFeCls to the algal growth pond resulted in
significant reductions in the required dosage of both organic and inorganic coagulants.
McGarry (1970) studied the coagulation of algae in treatment pond effluents and reported
the results of a complete factorial designed experiment using the common jar test. Tests
were performed to determine the economic feasibility of using polyelectrolytes as
primary coagulants alone or in combination with alum. McGarry also investigated some
of the independent variables that affected the flocculation process, such as concentration
of alum, flocculation turbulence, concentration of polyelectrolytes, pR after the addition
of coagulants, chemical dispersal conditions, and high rate oxidation pond suspension
characteristics. Alum was found to be effective for coagulation of algae from high rate
oxidation pond effluent. The lowest cost per unit algal removal was obtained with alum
alone (75-100 mg/L).
Al-Layla and Middlebrooks (1975) evaluated the effects of temperature on algae removal
using coagulation-flocculation-sedimentation. Removal at a given alum dosage
decreased as the temperature increased. Maximum algae removal generally occurred at
an alum dosage of approximately 300 mg/L at 10 °C. At higher temperatures, alum
dosages as high as 600 mg/L did not produce removals equivalent to the results obtained
at 10 °C with 300 mg/L of alum. The settling time required to achieve significant
removals, flocculation time, organic carbon removal, total P removal, and turbidity
removal were found to vary inversely as the temperature of the wastewater increased.
Dryden and Stern (1968) and Parker (1976) reported on the performance and operating
costs of a coagulation-flocculation system followed by sedimentation, filtration, and
chlorination, with discharge to recreational lakes. This system, in Lancaster, California,
probably has the longest operating record of any coagulation-flocculation system treating
wastewater treatment pond effluent. The TSS concentrations of influent coming to the
plant have ranged from about 120 to 175 mg/L, and the plant has produced an effluent
with a turbidity of less than 1 Jackson turbidity unit (JTU) most of the time. Aluminum
sulfate [Al2(SO4)3] dosages have ranged from 200 to 360 mg/L. The design capacity is
1893m3/d(0.5mgd).
7-22
-------
Coagulation-flocculation is not easily controlled and requires expert operating personnel
at all times. A large volume of sludge may be produced, which can introduce an
additional operating cost.
7.2.5 Dissolved Air Flotation
Several studies have shown the dissolved air flotation process to be an efficient and a
cost-effective means of algae removal from wastewater treatment pond effluents. The
performance obtained in several of these studies is summarized in Table 7-13.
Table 7-13. Summary of Typical Dissolved Air Flotation Performance.
Location and
Reference
Stockton n
Parker (1976)
Lubbock^
Ort (1972)
Eldorado"
Komline-
Sanderson
Engineering
(1972)
Logan4
Bare (1971)
Sunnyvale1
Stone et al.,
(1975)
Stockton1
Parker (1976)
Lubbock^
Ort (1972)
Eldorado"
Komline-
Sanderson
Engineering
(1972)
Logan4
Bare (1971)
Sunnyvale1
Stone et al.,
(1975)
Coagulant and
Dose (mg/L)
Alum, 225 Acid
added to pH 6.4
Limec, 150
Alum, 200
Alum, 300
Alum, 175 Acid
added to pH 6.0 to
6.3
Alum, 225 Acid
added to pH 6.4
Limec, 150
Alum, 200
Alum, 300
Alum, 175 Acid
added to pH 6.0 to
6.3
Overflow
Rate
(gpm/sf)
2.7a
NA
4.0C
1.3-2.4d
2.0e
2.7a
NA
4.0C
1.3-2.4d
2.0e
Detention
Time
(minutes)
17a
12b
8C
NA
11e
17a
12b
8C
NA
11e
BOD5
Influent
(mg/L)
46
280-
450
93
NA
NA
104
240-
360
450
100
150
Effluent
(mg/L)
5
1.3
<3
NA
NA
20
0-50
36
4
30
%
Removed
89
>99
<97
NA
NA
81
>79
92
96
80
California, Texas, Arizona, 4Utah
3 33% pressurized (35-60 psi) recycle
b30% pressurized (50 psi) recycle
c 100% pressurized recycle
d 25% pressurized (45 psi) recycle
e 27% pressurized (55-70 psi) recycle
Three basic types of dissolved air flotation are employed to treat wastewaters: total,
partial and recycle pressurization. These three types are illustrated by flow diagrams in
7-23
-------
Figure 7-6. In the total pressurization system, the entire wastewater stream is injected
with air, pressurized and held in a retention tank before entering the flotation cell. The
flow is direct, and all recycled effluent is repressurized. In partial pressurization, only
part of the wastewater stream is pressurized, and the remainder of the flow bypasses the
air dissolution system and enters the separator directly. Recycling serves to protect the
pump during periods of low flow, but it does load the separator hydraulically. Partial
pressurization requires a smaller pump and a smaller pressurization system. In recycle
pressurization, clarified effluent is recycled for the purpose of adding air and then is
injected into the raw wastewater. Approximately 20-50 percent of the effluent is
pressurized in this system. The recycle flow is blended with the raw water flow in the
flotation cell or in an inlet manifold.
Full Flow Pressunsation
Partial Pressurisation
Cfflypnl
Rfcycle Pressurisation
>-
Figure 7-6. Types of dissolved air flotation systems (Snider, 1976).
Important parameters in the design of a flotation system are hydraulic loading rate
(including recycle), concentration of TSS contained within the flow, coagulant dosage,
and the air-to-solids ratio required to achieve efficient removal. Pilot-plant studies by
Stone et al. (1975), Bare (1971) and Snider (1976) have shown the maximum hydraulic
loading rate to range between 81.5 - 101.8 L/min/m2. The most efficient air-to-solids
ratio was found to be 0.019 - 1.0 (Bare 1971). Solids concentrations during Bare's
7-24
-------
studies were 125 mg/L. Experimental results with the removal of algae indicate that
lower hydraulic rates and air-to-solids ratios than those recommended by the
manufacturers of industrial equipment should be employed when attempting to remove
algae.
In combined sedimentation flotation pilot-plant studies at Windhoek, Namibia, van
Vuuren and van Duuren (1965) reported effective hydraulic loading rates to range
between 11.2 and 30.5 L/min/m2, with flotation provided by the naturally dissolved
gases. Because air was not added, air-solids ratios were not reported. They also noted that
it was necessary to use from 125 - 175 mg/L of Al2(SO4)3 to flocculate the effluent
containing from 25 - 40 mg/L of algae. Subsequent reports on a total flotation system by
van Vuuren et al. (1965) stated that a dose of 400 mg/L of A^SO/Os was required to
flocculate a 110 mg/L algal suspension sufficiently to obtain a removal that was
satisfactory for consumptive reuse of the water. Based on data provided by Parker et al.
(1973), Stone et al. (1975), Bare (1971), and Snider (1976), it appears that a much lower
dose of alum can be applied to produce an effluent that will meet present discharge
standards.
Dissolved air flotation with the application of coagulants performs essentially the same
function as coagulation-flocculation-sedimentation, except that a much smaller system is
required with the flotation device. Flotation will occur in shallow tanks with hydraulic
residence times of 7-20 min, compared with hours in deep sedimentation tanks.
Overflow rates can be as high as 81.5-101.8 L/min-m2 with flotation; whereas, a value of
less than 40.7 L/min-m2 is recommended with sedimentation. However, it must be
pointed out that the sedimentation process is much simpler to operate and maintain than
the flotation process, and when applied to small systems, consideration must be given to
this factor.
The flotation process does not require a separate flocculation unit, and this has definite
advantages. It has been shown that it is best to add alum at the point of pressure release
where mixing occurs so that the chemicals are well dispersed. Brown and Caldwell
(1976) designed two tertiary treatment plants that employ flotation, and have developed
design considerations that should be applied when employing flotation. These features
are not included in standard flotation units and should be incorporated to ensure good
algae removal (Parker, 1976).
In addition to incorporating various mechanical improvements, Brown and Caldwell
recommended that the tank surface be protected from excessive wind currents to prevent
float movement to one side of the tank. It was also recommended that the flotation tank
be covered in rainy climates to prevent the breakdown of the floe. Another proposed
alternative is to store the wastewater in treatment ponds during the rainy season and then
operate the flotation process at a higher rate during dry weather.
Dissolved air flotation thickening (DAFT) has been used at the Stockton, California
regional wastewater treatment facility for many years to remove algae from the treatment
ponds ahead of the tertiary filtration process. Performance results for the period June -
7-25
-------
October 2005 are shown in Figures 7-7 and 7-8. Average pond influent TSS
concentrations averaged 74 mg/L (range: 20 - 223). Effluent concentrations averaged 34
mg/L, (range: 15 - 105). The percentage removal averaged 50 percent. In 2009-2010,
the DAFT process tanks and internal equipment underwent major rehabilitation.
Additional skimmer arms were added to improve removal of floating algae, and the initial
results indicate improved performance (Figure 7-9).
DAFT influent is secondary effluent that has received further treatment in facultative
ponds, then flows through a constructed wetlands that was put in service in 2007. Alum is
fed to the DAFT influent for chemical conditioning of the algae solids. Performance
results available for 2010 show the influent TSS concentrations average 70 mg/L and
effluent TSS concentrations average 17 mg/L, for an average removal efficiency of 76
percent (Larry Parlin, pers. comm. 2010).
TSS Removal in DAF at Stockton, CA
—*—Pond Eff & DAF Inf
175 T _ n,^m, . ~ Inf =2146223
Influent
TSS, mg/L
Ja.. Fe.. M..
O..
Date
Figure 7-7. TSS removal from pond effluent in dissolved air flotation with alum
addition (Middlebrooks, 2005).
7-26
-------
DAF Data for Stockton, CA
R
e
m
o
V
T e
S d
s
• Concentration Removed
% Removal
-40.00
Date
Figure 7-8. Concentration and percent TSS removal from pond effluent in dissolved
air flotation with alum addition (Middlebrooks, 2005).
Figure 7-9 Dissolved air floatation thickening (DAFT) at the Stockton, California
wastewater treatment facility (Parlin, pers. comm. 2010).
Alum-algae sludge was returned to the wastewater treatment ponds for over three years at
Sunnyvale, California with no apparent detrimental effect (Farnham, pers. comm., 1981).
No sludge banks, floating mats of material, or increased TSS concentrations in the pond
effluent have been observed. Returning the float to the pond system is an operational
option, at least for a few years. Most estimates of a period of time that sludge can be
returned range from 10 to 20 years.
7-27
-------
Sludge disposal from a dissolved air flotation system can present considerable challenges.
Alum-algae sludge is very difficult to dewater and discard. Centrifugation and vacuum
filtration of raw alum-algae sludge have produced marginal results. Indications are that
lime coagulation may prove to be as effective as alum to produce sludge that is more
easily dewatered.
Brown and Caldwell (1976) evaluated heat treatment of alum-algae sludges using the
Porteous, Zimpro® low-oxidation, and Zimpro® high-oxidation processes without great
effect. The Purifa process, using chlorine to stabilize the sludge, produced a sludge that
was dewaterable on sand beds or in a pond. If algae are killed before entering an
anaerobic digester, the proportion of volatile matter destruction and dewatering can
provide more useful results. But, as with the other sludge treatment and disposal
processes, additional operations and costs are incurred, which may make the option of
dissolved air flotation less competitive financially.
7.3 OPERATIONS MODIFICATIONS AND ADDITIONS
7.3.1 Autoflocculation and Phase Isolation
Autoflocculation of algae (natural settling under specific environmental conditions) has
been observed in some studies (Golueke and Oswald, 1965; McGriff and McKinney,
1971; McKinney, 1971; Hill et al., 1977). Chlorella was the predominant alga occurring
in most of the cultures. Laboratory-scale continuous experiments with mixtures of
activated sludge and algae have produced large bacteria-algae floes with good settling
characteristics (Hill et al., 1977; Hill and Shindala, 1977). Floating algal blankets have
been reported in the presence of chemical coagulants in some cases (Shindala and
Stewart, 1971; van Vuuren and van Duuren, 1965). This may be caused by the
entrapment of gas bubbles produced during metabolism or by the fact that, at a particular
stage in the growth cycle, algae have neutral buoyancy. In an 11,355 L/hr (3000 g/h)
pilotplant that combined flocculation and sedimentation, a floating algal blanket was
formed with alum doses of 125 -170 mg/L. About 50 percent of the algae was able to be
skimmed from the surface (van Vuuren and van Duuren, 1965). Given the unpredictable
occurrence of conditions necessary for autoflocculation, it can not be considered a
reliable method for removing algae from wastewater treatment ponds.
Phase isolation is defined as the operation of a pond system to create natural conditions
favorable to settling of algae and some success has been reported based on this
phenomenon to remove algae from pond effluents. The results of a study by McGriff
(1981) of a full-scale operation of a phase isolation system were not consistent.
Oswald and Green, (2000), enhanced algal growth is in a high rate pond with a raceway
configuration and a slow-moving paddle wheel to keep algae suspended. This
concentrated algal slurry is sent to a settling basin, where the algae can be concentrated
further and sent to a drying bed. There is potential to use the algal slurry for feed
supplement, soil fertilization and amendment and, most recently, for biofuel production
(Woertz et al., 2009, Brune et al., 2009).
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7.3.2 Baffles and Attached Growth
The enhancement of attached microbial growth in oxidation ponds is an apparently
practical solution for maintaining biological populations while still obtaining the
treatment desired. Although baffles are considered useful primarily to ensure good
mixing and to eliminate the problem of short-circuiting, they provide a substrate for
bacteria, algae, and other microorganisms to grow (Reynolds et al., 1975; Polprasert and
Agarwalla, 1995). In general, attached growth surpasses suspended growth if sufficient
surface area is available. In anaerobic or facultative ponds with baffling or biological
disks, the microbiological community consists of a gradient of algae to photosynthetic,
chromogenic bacteria and, finally, to nonphotosynthetic, nonchromogenic bacteria
(Reynolds et al., 1975). In these experiments, the microbial growth associated with the
baffled system was identified as the mechanism that produced a more effective treatment.
Simple fixed baffles constructed of wood or plastic, floating plastic baffles used to
improve hydraulic characteristics, or, indeed, any surface can provide a substrate on
which microbial growth can take place.
Polprasert and Agarwalla (1995) demonstrated the significance of biofilm biomass
growing on the side walls and bottoms of ponds and presented a model for substrate
utilization in facultative ponds using first-order reactions for both suspended and biofilm
biomass.
7.3.3 Land Application
The design and operation of land treatment systems is described in detail in Reed et al.,
(1995), Crites et al., (2000) and U.S. EPA (2006). These publications should be
consulted before designing a land application system to polish a pond effluent. Ecological
conditions will dictate whether this is as an option that should be considered.
7.3.4 Macrophyte and Animal Systems
Various macrophytic floating plans have been used to reduce algal concentrations and
TSS in maturation ponds. Rittman and McCarty (2001). Detailed design information can
be obtained in Reed et al., (1995), Pearson and Green (1995), Mara et al. (1996), Pearson
et al. (2000) and Shilton (2005).
7.3.4.1 Floating Plants
Water hyacinths (Eichhornia crassipes), duckweed (Lemna spp), pennywort (Centella
asiatica), and water ferns (Azolla spp.) appear to offer the greatest potential for
wastewater treatment. Each has its own environmental requirements, and hyacinths,
pennywort, and duckweeds are the only floating plants that have been evaluated in pilot -
or full-scale systems. Detailed design considerations are presented in Reed et al. (1995).
Information about the use of these plants to improve wastewater quality for reuse can be
found in Rose (1999).
7.3.4.2 Submerged Plants
Submerged aquatic macrophytes for treatment of wastewaters have been studied
extensively in the laboratory, greenhouses, a pilot study by McNabb (1976), and in large
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scale wetland storm water treatment systems designed to remove P to less than 20 mg/L
(South Florida Water Management District, 2003).
7.3.4.3 Daphnia and Brine Shrimp
Daphnia spp. are filter feeders and their main contribution to wastewater treatment is the
removal of suspended solids, particularly algae (U.S. EPA, 2002). Daphnia is sensitive
to the concentration ofNHs in wastewater which is toxic to invertebrates. To be
effective, shading is required to prevent the growth of algae that will result in high/?H
values during the daytime. The addition of acid and gentle aeration may be necessary.
7.3.4.4 Fish
Fish have been grown in treated wastewaters for centuries, and, where toxics are not
encountered, the process has been successful. Many species offish have been used in
wastewater treatment, but fish activity is temperature dependent. Most grow successfully
in warm water. Catfish and minnows are exceptions. Dissolved oxygen concentrations
are critical and the presence ofNHs is toxic to the young of the species. Detailed studies
offish in wastewater treatment ponds have been conducted by Coleman (1974) and
Henderson (1979). Numerous studies offish culture have been conducted around the
world. Polprasert and Koottatep (2005) presented an excellent summary of the use of
algae eating fish in pond systems.
7.4 CONTROL OF ALGAE AND DESIGN OF SETTLING BASINS
Control of algae in wastewater treatment pond effluents has been a major concern
throughout the history of the use of these systems. Algae grow in maturation and
polishing ponds following all types of treatment processes, which increases the TSS in
the effluent. State design standards requiring long detention times in the final cell in a
pond system have inadvertently exacerbated the problem. In recognition of the difference
between the source of the TSS in the influent and the effluent, the state of Minnesota has
mandated a higher TSS limit of 45 mg/L for ponds. (Steve Duerre, pers. comm.)
It has been established that few, if any, of the solids in pond effluents are fecal matter or
material entering the pond system. This has led to much discussion about the necessity to
remove algae from pond effluents. Although the concern that the TSS might harbor
human pathogens may not be realistic, when the algae die, settle out and decay, they do
create some 02 demand on the receiving stream. The concern about decay and 02
consumption has led to investigations of the most effective methods to remove algae and
how to design systems to minimize growth in the settling basins. Toms et al. (1975)
studied algal growth rates in polishing ponds receiving activated sludge effluents for 18
months. They concluded that growth rates for the dominant species were less than 0.48
/d, and if the HRT was less than two days, algal growth would not be a problem. At HRT
less than 2.5 days, the effluent TSS decreased. Uhlmann (1971) reported no algal growth
in hyper-fertilized ponds when the detention times were less than 2.5 days. Toms et al.
(1975) evaluated one- and four-cell polishing ponds and found that for HRT beyond 2.5
days the TSS increased in both ponds, but significant growth did not occur until after 4 -
5 days in the four-cell pond.
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Algae require light to grow, and as light penetration is reduced with increasing depth, it
might be hypothesized that increasing the depth of a maturation or polishing pond would
help to reduce algal growth. As most pond cells are trapezoidal, there is little to be gained
by increasing the depth beyond three to four meters. Without mechanical mixing,
thermal stratification occurs in ponds, providing an excellent environment for algae to
grow. Disturbing stratification will reduce algal growth. Rich (1999) recommends some
degree of aeration for pond cells to control algae. The higher aeration rate will suspend
more solids. The resulting reduction in light transmission helps to reduce the rate of algal
growth.
7.4.1 Control of Algal Growth by Shading, Barley Straw and Ultra Sound
7.4.1.1 Dyes have been applied to small ponds to control algal growth. However, EPA
has not approved dyes for use in municipal or industrial wastewater ponds. Aquashade®,
a mixture of blue and yellow dyes, is marketed as a means of controlling algae in
backyard garden pools and large business park and residential development ponds. The
product is registered with EPA for these uses.
7.4.1.2 Fabric Structures
Operators of ponds in Colorado and other locations have constructed structures
suspending opaque greenhouse fabrics to reduce or eliminate light transmittance in small
wastewater ponds. A partially covered pond using a fabric located in Naturita, Colorado
is shown in Figure 7-10.
Figure 7-10. Photograph of shading for control of algal growth in Naturita,
Colorado (R. Bowman, pers. comm., 2000).
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The screening effect has been successful, but in some cases fabrics were not fastened
adequately and they were damaged by the wind. Covering the final pond with adequate
protection from the wind should reduce or eliminate algal growth. With full coverage of
the surface, anaerobic conditions may develop and aeration of the effluent may be
necessary to meet discharge standards. Partial shading in correct proportions should
reduce the possibility of creating anaerobic conditions.
7.4.1.3 Barley Straw
In 1980 it was observed that the addition of barley straw to a lake reduced the algal
concentration. Placing barley straw in ponds has been proposed as a means of controlling
algal growth. Details for the application of barley straw is given in lACR-Centre for
Aquatic Plant Management (1999) and the state of Illinois guidance for application and
discussion of how to classify barley straw in this application is found in Appendix H.
Figure 7-11 shows a barley straw application in the final cell in an aerated pond system in
New Baden, Illinois (Zhou et al., 2005).
During decomposition, the chemicals listed in Table 7-11 are released to the water and
inhibit the growth of algae (Everall and Lees, 1997). The acceptability of this method of
algal control by regulatory agencies has not been resolved.
Figure 7-11. A barley straw boom in cell 3, New Baden, Illinois wastewater pond
system.
Table 7-14. List of Chemicals Produced by Decomposing Straw (Everall and Lees,
1997).
Acetic Acid
3-Methylbutanoic Acid
2-Methylbutanonic Acid
Hexanoic Acid
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Octanoic Acid
Nonanoic Acid
Decanoic Acid
Dodecanoic Acid
Tetradecanoic Acid
Hexadecanoic Acid
1 -Methylnaphthalene
2-(1,1-Dimethlyethyl Phenol)
2,6-Dimethoxy-4-(2-propenyl) Phenol
2,3-Dihydrobenzofuron
5,6,7,7A-Tetrahydro-4,4,7A-trimethyl-2(4H) benzofuranone
1,1,4,4-Tetramethyl-2,6-bis(methylene) cyclohexone
1-Hexacosene
11 Unidentified
7.4.1.4 Ultra Sound
Ultra sound devices have been used for algal control in golf course ponds, large
residential area ponds, and water treatment storage ponds, but limited data are available
for municipal pond systems. A microcosm study at the Centre for Aquatic Plant
Management (CAPM) in Reading, Berkshire, United Kingdom evaluated the efficacy of
several treatment options to control algae (Clarke, 2004). Methods included an ultrasonic
device, a recirculating pump, bacteria, barley straw, Aquavantage (electromagnet
treatment), EcoFlow (fixed magnet) and a control. The results of the experiments are
summarized in Figure 7-12.
According to Clarke (2004), none of the treatments appeared to remove the algae to a
level that would meet water quality requirements. Differences in the level of algae could
be seen, but some of the four replicate tanks in all treatments remained turbid and green.
The only tanks that were clear were found to be populated by Daphnia spp., an
invertebrate herbivore. Clarke reported that no significant differences could be found
between treatments. The variability and experimental challenges made it difficult to
draw conclusions as to the possible causes of either growth or inhibition of growth.
The CAPM investigated the mode of action of ultrasound on algae. Clarke reported
Spirogyra and Selenastrum were damaged irreversibly by the treatment.
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Effect of treatments on total chlorophyll level over time
I
o
1600
1400
1200
1000
800
600
400
200
77
28
56 84 112
Time (days)
140
168
Figure 7-12. Change in chlorophyll over time under different treatment
conditions (Clarke, 2004).
7.5 COMPARISON OF VARIOUS DESIGN PROCEDURES
The variety of configurations and objectives of the design approaches for nutrient
removal make it difficult to make direct comparisons to determine which will be the most
effective for a given site. Reasonable reaction rates must be selected, but if the pond
hydraulic system is designed and constructed so that the theoretical HRT is approached,
reasonable success can be assured with all of the design methods. Short-circuiting is the
greatest deterrent to successful pond performance, barring any toxic effects. The
importance of the hydraulic design of a pond system to achieve water quality objectives
cannot be overemphasized.
7.6 OPERATIONAL MODIFICATIONS TO FACULTATIVE PONDS
7.6.1 Controlled Discharge Ponds
No rational or empirical design model exists specifically for the design of controlled
discharge wastewater ponds. The unique features of controlled discharge ponds are long-
term retention and periodic, controlled discharge usually once or twice a year. Rational
and empirical design models applied to facultative pond design may also be applied to the
design of controlled discharge ponds, provided allowance is made for the required larger
storage volumes. Application of the ideal plug flow model developed for facultative
ponds can be applied to controlled discharge ponds if HRTs of less than 120 days are
considered. A study of 49 controlled discharge ponds in Michigan indicated that
discharge periods vary from less than 5 days to more than 31 days, and residence times
were 120 days or greater (Pierce, 1974). Ponds of this type have operated satisfactorily in
the north-central United States using the following design criteria:
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• Overall organic loading: 22-28 kg BOD5/ha/d (20-25 Ib BOD5/ac/d)
• Liquid depth: Not more than 2 m (6 ft) for the first cell, not more than 2.5 m (8 ft)
for subsequent cells
• Hydraulic detention: At least 6 months of storage above the 0.6 m (2 ft) liquid
level (including precipitation), but not less than the period of ice cover
• Number of cells: At least 3 for reliability, with piping flexibility for parallel or
series operation
The design of the controlled discharge pond must include an analysis showing that
receiving stream water quality standards will be maintained during discharge intervals,
and that the receiving watercourses can accommodate the discharge rate from the pond.
The design must also include a recommended discharge schedule.
Selecting the optimum day and hour for release of the pond contents is critical to the
success of this method. The operation and maintenance manual must include instructions
on how to correlate pond discharge with effluent and stream quality. The pond contents
and stream must be carefully monitored before and during the release of the pond
contents.
In a typical program, discharge of effluents follows a consistent pattern for all ponds. The
following steps are usually taken:
• Isolate the cell to be discharged, usually the final one in the series, by shutting off
the valve on the inlet line from the preceding cell.
• Arrange to analyze samples for BOD5, TSS, VSS, />H, and other parameters
which may be required for a particular location.
• Plan work so as to be able to spend full time on control of the discharge
throughout the period.
• Sample contents of the cell to be discharged for DO, noting turbidity, color, and
any unusual conditions.
• Monitor conditions in the stream to receive the effluent.
• Notify the state regulatory agency of results of these observations and plans for
discharge and obtain approval.
• If discharge is approved, commence discharge, and continue so long as weather is
favorable, DO is near or above saturation values, and turbidity is not excessive
following the prearranged discharge flow pattern among the cells.
o Draw down the last 2 cells in the series (if there are 3 or more) to about 46
- 60 cm (18 - 24 in) after isolation, interrupting the discharge for a week or
7-35
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more to divert raw waste to a cell that has been drawn down, and resting
the initial cell before its discharge.
o When the first cell is drawn down to about 60 cm (24 in) depth, the usual
series flow pattern, without discharge, is resumed.
o During discharge to the receiving waters, samples should be taken at least
3 times each day near the discharge pipe for immediate DO analysis.
Additional testing may be required for TSS.
Experience with these ponds is limited to northern states with seasonal and climatic
influences on algal growth. See Appendix G for step-by-step instructions for controlled
discharge operation (Minnesota Pollution Control Authority). The process will be quite
effective for BODs removal in any location and will also work with a more frequent
discharge cycle than semi-annually, depending on receiving water conditions and
requirements. Operating the isolation cell on a fill-and-draw batch basis is similar to the
"phase isolation" technique.
7.6.2 Complete Retention Ponds
In areas of the United States where the moisture deficit (evaporation minus rainfall)
exceeds 75 cm (30 in) annually, a complete retention wastewater pond may prove to be
the most economical method of disposal. Complete retention ponds must be sized to
provide the necessary surface area to evaporate the total annual wastewater volume plus
the precipitation that would fall on the pond. The system should be designed for the
maximum wet year and minimum evaporation year of record if overflow is not
permissible under any circumstances. Less-stringent design standards may be appropriate
in situations where occasional overflow is acceptable or an alternative disposal area is
available under emergency conditions.
Monthly evaporation and precipitation rates must be known to properly size the system.
Complete retention ponds usually require large land areas, and these areas may not be
productive once they have been committed to this type of system. Land for this system
must be naturally flat or be shaped to provide ponds that are uniform in depth, and have
large surface areas. The design procedure for a complete retention wastewater pond
system is presented in the following example.
7.6.2.1 Design Conditions
See Appendix C, Example C-7-3.
7.6.3 Hydrograph Controlled Release
The hydrograph controlled release (HCR) pond is a variation of the controlled discharge
pond. This management practice was first put into practice in the southern United States,
but can be used successfully in most areas of the world. In this case the discharge periods
are controlled by a gauging station in the receiving stream and are allowed to occur
during high flow periods. During low flow periods, the effluent is stored in the HCR
pond.
7-36
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The process design uses conventional facultative or aerated ponds for the basic treatment,
followed by the HCR cell for storage and/or discharge. No treatment allowances are
made during design for the residence time in the HCR cell; its sole function is storage.
Depending on stream flow conditions, storage needs may range from 30 - 120 days. The
design maximum water level in the HCR cell is typically about 2.4 m (8 ft), with the
minimum water level at 0.6 m (2 ft). Other physical elements are similar to conventional
pond systems. The major advantage of the HCR system is the possibility of utilizing
lower discharge standards during high flow conditions as compared to a system designed
for very stringent low flow requirements operated on a continuous basis. A summary of
the design approach is shown in Appendix B.
Table 7-15. Hydrograph Controlled Release Pond Design Basics Used in United
States.
a. Basic Principle: At critical low river flow, BOD5 and TSS loadings are reduced by restricting
effluent discharge rates rather than decreasing concentration of pollutants. Zirschsky and
Thomas (1987).
b. Pond system must be sized to retain wastewater during low flow (Q10/7). Use existing ponds
or build storage ponds.
Q10/7 = once-in-10-year low flow rate for 7-day period. Zirschsky and Thomas (1987).
c. Assimilative capacity of receiving stream must be established by studying historical data or
estimated using techniques such as that proposed by Hill and Zitta (1982).
Zirschsky and Thomas (1987) performed a nationwide assessment of HCR systems,
which showed that they are effective, economical and simple to operate. HCR systems
were also found to be an effective means of upgrading a pond effluent.
7.7 COMBINED SYSTEMS
In certain situations it is desirable to design pond systems in combinations, i.e., an
anaerobic or an aerated pond (Li et al., 2006) followed by a facultative or a polishing
pond. These combinations use the same design as the individual ponds. For example, the
aerated pond would be designed as described in Chapter 3, Section 3.4, and the predicted
effluent quality from this unit would be the influent quality for the facultative pond,
which would be designed as described in Chapter 3, Section 3.3. Many of the proprietary
systems described in Chapter 4 are combinations of various types of ponds.
7.8 PERFORMANCE COMPARISONS WITH OTHER REMOVAL METHODS
Designers and owners of small systems are strongly encouraged to use as simple a
technology as feasible. Experience has shown that small communities or larger
municipalities without properly trained operating personnel and access to spare parts,
inevitably encounter serious maintenance problems using sophisticated technology and
frequently fail to meet effluent standards. Methods discussed in this chapter that require
good maintenance and operator skills are dissolved air flotation, centrifugation,
coagulation-flocculation, and granular media filtration (rapid sand or mixed-media filters
with chemical addition). At locations where operation and maintenance are available,
these processes can be made to work well.
In summary, there are many methods of removing or controlling algae concentrations in
pond effluents. Selection of the proper method for a particular site is dependent on many
7-37
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variables. Small communities with limited resources and untrained operating personnel
should select as simple a system as is suitable to the site situation.
In rural areas with adequate land, ponds such as controlled discharge ponds or
hydrograph controlled release ponds are an appropriate choice. In arid areas, the total
containment pond should be considered. Performance by these types of treatment is
controlled by selecting the time of discharge and can be managed to produce an effluent
(BODs and TSS < 30 mg/L) that meets compliance standards.
Where land is limited and resources and personnel are not available, it is best to utilize
relatively simple methods to control algae in effluents. Intermittent sand filters,
application of effluent to farmlands, overland flow, rapid infiltration, constructed
wetlands, and rock filters are reasonable choices. Intermittent sand filters with low
application rates and a warm climate will provide nitrification. Application to farm land
will reduce both TV and P, while producing a satisfactory effluent.
7-38
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CHAPTER 8
COST AND ENERGY REQUIREMENTS
8.1 INTRODUCTION
Costs associated with wastewater treatment facilities fall under one of two categories: capital
costs and operations and maintenance (O&M) costs. The price of energy makes up a significant
portion of O&M costs for most wastewater treatment facilities. Although O&M cost data for
many of the pond types and polishing methods are relatively limited, it is understood that these
costs are generally lower than for conventional systems. Data presented in the following sections
vary widely, but are thought to be reasonable estimates to serve as guides in budgeting for the
costs associated with a treatment system. It should be kept in mind, however, that the data have
different constraints that may be applicable to a specific design. Conventional estimating
procedures should be used during final design.
8.2 CAPITAL COSTS
Construction cost data presented in this section were extracted from EPA reports (U. S. EPA,
1980c; U.S. EPA, 1999, 2000a, 2006) and bid Summary Sheets provided by the various EPA
regions (R8: Brobst, 2007; R5: Martin, 2007; R9: McNaughton, 2007; Oklahoma: Rajaraman,
2007). The costs extracted from the EPA report (1980c) were indexed to Kansas City/St. Joseph,
Missouri during the fourth quarter of 1978. These data were projected for Kansas City to 2006
and the bid sheets corrected to Kansas City as a baseline using the ENR CC Indices
(www.enr.com), which are available by subscription. General information about construction
costs is available in Fact Sheet 5: Treatment Series, Lagoons, Performance and Cost of
Decentralized Unit Processes (werf.org/AM/Template). To compare costs of ponds with other
types of treatment, it is suggested that the engineer consult relevant references for her/his region.
Construction costs only are represented in Figures 8-1 through 8-4. Associated costs include
administration/legal, preliminary, land, structures, right-of-way, mobilization, architect/engineer
(A/E) basic fees, other A/E fees, project inspection costs, land development, relocation,
demolition and removal, bond interest, indirect costs, miscellaneous, equipment, and
contingencies. These represent approximately 50 percent of the construction costs.
Figure 8-1 contains both the 1978 corrected data and the data from the bid summary sheets for
flow through ponds (facultative). Figure 8-2 contains data extracted from the low bid on the bid
summary sheets for flow through ponds. Predicted construction costs using the equations of best
fit from Figure 8-1 and 8-2 result in similar estimates, but the estimates deviate considerably
from individual construction cost values.
The low flow rates presented in the bid summary sheet data are lumped together with several
other data points that does not seem to influence the fit of the data. With one exception, the R
of the bid summary sheet data is = 0.705, a relatively good fit. Therefore, with low-flow systems,
it is probably prudent to use the bid sheet projection equations with the best coefficient of
determination (R ) to estimate the cost of a flow-through pond.
8-1
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Insufficient data were available for the non-discharging and aerated ponds, therefore they could
not be compared to the bid summary sheet data combined with the updated Kansas City data.
The data points from the bid sheets agreed reasonably well with the up dated information.
1.2
0.8
• Unknown 1978
y=6.7026x
R2 = 0.2014
Updated
South Dakota
0.04 0.06 0.08 0.1
Design Flow Rate, mgd
Figure 8-1. Construction costs vs. DFR for flow-through ponds (facultative), Kansas City,
2006. (DFR < 500,000 L/d [0.130 MGD]) . See p. xiv for conversion table.
10
o
s
o
u
o
u
flow not known, not
used in curve fits
Design Flow Rate, mgd
Figure 8-2. Data bid tabulations: construction costs vs. DFR for flow-through ponds,
Kansas City, 2006.
8-2
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DOS 0,1 0.15 0.2 025
Design Flow Rate, mgd
03
0 35
M.1
Figure 8-3. Construction costs vs. DFR for nondischarging ponds, Kansas City, 2006.
y=3.349x
R* = -0.
2.7983^°
R2 = 0.1758
Upgrade
—
0.2 0,4 0,6 0,8
1,4 1.6 1,8
Design Flow Rate, mgd
Figure 8-4. Construction costs vs. DFR for aerated ponds, Kansas City, 2006 - Q = 0 to 1.2
MGD.
8-3
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8.3 UPDATING COSTS
Costs may be up dated to other cities by using the ratio of the 2006 ENR CC Index for Kansas
City to the ENR CC index for the location of interest as shown in the following equation:
Updated Construction Costs = ENR CC Index for City of Choice
ENRCC Index for Kansas City (12/2006)
8.4 COST DATA FOR UPGRADING METHODS
There are many options for the upgrading of pond systems, but accurate cost data for all of the
systems are not available. Wetlands, land application, granular media filtration, dissolved air
flotation, and sequencing batch reactors cost data are relatively expensive as is shown in the
following sections. Data for rock filters, intermittent sand filters, fish production, hyacinth
systems and other plant applications are limited. General cost estimation techniques are
presented for the systems with limited data.
8.4.1 Wetlands
8.4.1.1 Free Water Surface Wetlands (FWS) Cost Estimation
The available cost data for FWS constructed wetlands are difficult to interpret given the number
of design constraints placed on the various systems. The size required and resulting costs will
vary depending upon whether the systems are designed to remove BODs, TSS, NH^ or total N.
Further information about costs for FWS constructed wetlands can be found in U.S. EPA,
(2000b) and Crites et al. (2006).
8.4.1.2 Subsurface Flow (SSF)
Available cost data for SSF constructed wetlands are hard to interpret because of design
constraints that may be placed on the particular system. It is not clear what the design
parameters were for most of the systems. Further information about costs for SSF wetlands can
be obtained in U.S. EPA (2000b) and Crites et al. (2006).
8.4.2 Land Application Cost Estimation
A detailed discussion of the various types of land application treatment of wastewaters can be
found in U.S. EPA (2006), Shilton (2005) and Crites et al. (2006). There are three basic land
application methods: slow rate, overland flow, and soil aquifer treatment or rapid infiltration.
Capital costs and labor costs were compiled in U.S. EPA 2006 for an ENR CCI of 6076.
Construction costs and labor, materials and energy costs for center pivot irrigation, solid set
irrigation, gated pipe overland flow and rapid infiltration are shown in Figures 8-5 through 8-8.
Land application systems should only be designed by an engineer who has first-hand experience
or has studied the above references.
8-4
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20,000
10.000
Q>
b
o
O
o
15
3
C
100 1000
Field Area, Acres (a)
10,000
500
100
100 1000
Field Area, Acres (b)
10,000
Figure 8-5. Center pivot sprinkling costs, ENR CCI = 6076: (A) capital cost; (B) operation
and maintenance cost (U.S. EPA, 2006).
8-5
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10,000
Slow rate (SR)
• Overland Flow (OF)
100
Field Area, Acres (a)
1000
10,000
100 1000
Field Area, Acres (b)
10,000
Figure 8-6. Solid set sprinkling (buried) costs, ENR CCI = 6076: (A) capital cost; (B)
operation and maintenance cost (U.S. EPA, 2006).
8-6
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10,000
to
T3
03
V)
o
w
O
o
a.
CD
O
1000
100
100 1000
Field Area, Acres (a)
10,000
1000
03
Q)
2
o
(0
en
o
o
75
3
100
100 1000
Field Area, Acres (b)
10,000
Figure 8-7. Gated pipe - overland flow or ridge-and-furrow slow rate costs, ENR CCI
6076: (A) capital cost; (B) operation and maintenance cost (U.S. EPA, 2006).
8-7
-------
10,000
10 100
Field Area, Acres (a)
1000
1000
03
0)
o
CT3
S/5
O
o
15
_j
c
c
100
10
10 100
Field Area, Acres (b)
1000
Figure 8-8. Rapid infiltration basin costs, ENR CCI = 6076.: (a) capital cost; (b) operation
and maintenance cost (U.S. EPA, 2006).
8-8
-------
8.4.3 Granular Media Filtration Cost Estimation
The relationships shown in Figures 8-9 and 8-10 were taken from the U.S. EPA (2000a)
concerning the Centralized Waste Treatment (CWT) point source category. The data may not be
totally accurate for pond systems, but are reasonable enough to provide guidance with regard to
preliminary designs.
1,000,000;
lA
CO
jq 100,0001
O
Q.
OJ
1Q,Qt»
0.001 0.01 0.1 1 10
Figure 8-9. Mixed-media filtration capital costs, ENR CCI = 6076 (U.S. EPA, 2000a).
1 .OOO.OQOr-
100,000
o
o
o
10,000
0,001
0.01
0.1
flow (mgd)
10
Figure 8-10. Mixed-media filtration O&M costs, ENR CCI = 6076 (U.S. EPA, 2000a).
8-9
-------
8.4.4 Dissolved Air Flotation (DAF) Cost Estimation
The relationships shown in Figures 8-11 and 8-12 were taken from the U.S. EPA (2000a)
concerning the CWT point source category. Again, the data may not be totally accurate for pond
systems, but are reasonable enough to provide guidance with regard to preliminary design.
10,000.000
e>
CO
a
u
,000,000
10,1X30
0,01
0.1
10
Flow {mgd}
Figure 8-11. Dissolved air flotation capital costs, ENR CCI = 6076 (U.S. EPA, 2000a).
IG.QOQ.QOO
IF
Si,
-------
8.4.5 Sequencing Batch Reactor (SBR) Cost Estimation
The relationships shown in Figure 8-1 were taken from the U.S. EPA (2000a) concerning the
CWT point source category. The data may not be totally accurate for pond systems, but are
reasonable enough to provide guidance with regard to preliminary design.
10,000 000
1,000,000
u
100,000
0,0001
0-001
0.01 0,1
Flow {mgd>
10
Figure 8-13. Sequencing batch reactor capital costs, ENR CCI = 6076 (U.S. EPA, 2000a).
8.4.6 Intermittent Sand Filter Cost Estimation
Given the limited cost data for intermittent sand filtration, a spreadsheet and tables were
developed to assist design engineers in estimating costs associated with this polishing technique
(Appendix C).
8.4.7 Intermittent Rock Filter Cost Estimation Procedure
See Section 8.4.6.
8.5 ENERGY REQUIREMENTS
Energy consumption is a major factor in the operation of wastewater treatment facilities. Many
of the plans for water pollution management in the United States were developed before the cost
of energy and the limitations of energy resources had to be taken into consideration. As
wastewater treatment facilities are built to incorporate current treatment technology and to meet
regulatory performance standards, the cost of the energy to run the processes must be considered
more carefully in the designing and planning of the facilities. Planners and designers should
seek out the most recent information on energy requirements so as to develop a system that
incorporates the most efficient and affordable type and use of energy to treat wastewater to meet
regulatory requirements consistently and reliably. Wherever possible, self-sustaining elements,
8-11
-------
such as alternative energy sources, capture and use of energy produced (i.e., C//^), and uses of
by-products (e.g., algae) should be considered.
8.5.1 Effluent Quality and Energy Requirements
Expected effluent quality and energy requirements for various wastewater treatment processes
are shown in Table 8-3. Energy requirements and effluent quality are not directly related.
Facultative ponds and land application processes can produce excellent quality effluent with
smaller energy budgets. The same is true for several other combinations.
Table 8-1. Total Annual Energy for Typical 1 mgd System Including Electrical plus Fuel,
expressed as 1000 kwh/yr (Middlebrooks et al., 1981).
TREATMENT SYSTEM
EFFLUENT QUALITY, mg/L
BOD5
Rapid infiltration (facultative pond)
Slow rate, ridge & furrow (facultative pond)
Overland flow (facultative pond)
Facultative pond + intermittent sand filter
Facultative pond + microscreens
Aerated pond + intermittent sand filter
Extended aeration + sludge drying
Extended aeration + intermittent sand filter
Trickling filter + anaerobic digestion
RBC + anaerobic digestion
Trickling filter + gravity filtration
Trickling filter + N removal + filter
Activated sludge + anaerobic digestion
Activated sludge + anaerobic digestion +
filter
Activated sludge + nitrification + filter
Activated sludge + sludge incineration
Activated sludge + AWT
Physical chemical advanced secondary
5
1
5
15
30
15
20
15
30
30
20
20
20
15
15
20
<10
30
rss
1
1
5
15
30
15
20
15
30
30
10
10
20
10
10
20
5
10
P
2
0.1
5
-
-
-
-
-
-
-
-
-
-
< 1
1
N
10
3
3
10
15
20
-
-
-
5
-
-
-
-
<1
-
ENERGY
(1000
KwH/YR)
150
181
226
241
281
506
683
708
783
794
805
838
889
911
1,051
1,440
3,809
4,464
8-12
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CHAPTER 9
OPERATION AND MAINTENANCE
9.1 INTRODUCTION
The information presented in this chapter covers various topics related to operations and
maintenance, including control testing, safety, troubleshooting and optimizing operations of a
pond system. Much that has been written on these topics in the past 30 years remains valuable,
but may not be readily available. This chapter summarizes much of that information and brings
it up to date. It introduces the basic tools used to monitor an operating pond treatment system
and provides guidance when the system does not seem to be functioning as designed. See also
Appendices E (Troubleshooting) and F (Wisconsin Department of Natural Resources Study
Guide Introduction to Advanced Stabilization Ponds and Aerated Lagoons
(www.dnr.wigov/org/es/science/opert/doc).
9.2 TERMINOLOGY
9.2.1 Basic Nomenclature
A pond system is typically a number of earthen basins connected together to treat raw
wastewater.
9.2.2 Types of Pond Systems
9.2.2.1 Anaerobic Ponds
Anaerobic pond cells receive such a heavy organic loading that there is no aerobic zone.
9.2.2.2 Facultative Ponds
Facultative pond cells are 1.2-2.4 m (4 - 8 ft) deep with an aerobic surface layer and an anaerobic
bottom layer.
9.2.2.3 Aerated Ponds
The O2 in the aerated pond cells is supplied or supplemented by surface mechanical or diffused
aeration equipment.
9.2.3 Flow Configuration
Pond systems can be operated either in series or parallel.
9.2.3.1 Series
In series operation the influent wastewater flows into the primary cell, then to the secondary cell
and finally to the polishing cell before being discharged.
9.2.3.2 Parallel
In parallel operation, the operator has the option of splitting the flow. This is usually done in
equal parts between the first two cells. Facultative ponds are commonly operated in parallel
under winter conditions. As water temperatures drop, biological activity is reduced and the
primary cell of a facultative pond system can become organically overloaded. To prevent this,
9-1
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the flow is sent to the first two cells at the same time, which reduces the organic load to each
one. As water temperatures warm up in spring, biological activity increases, and the flow regime
can return to series operations.
9.2.3.3 Recirculation
The operational flexibility to recirculate wastewater in a treatment plant or pump back treated
wastewater from the end of the process to the first series of cells can be used to great advantage.
The operator can introduce treated wastewater with a higher dissolved 02 concentration into the
first series of cells that have a higher organic loading. Recirculation also tends to smooth out the
performance of the system. Entering flow varies significantly over 24 hours, and recirculation
can create a more uniform flow rate.
9.3 CONTROL TESTING INFORMATION
For a facility to be consistently in compliance with discharge permit requirements, adequate
process controls must be in place. The influent quantity and quality should be monitored on a
regular schedule to provide the information needed to treat the wastewater stream adequately and
operate the facility properly. It is also necessary to monitor the processes within the system in
order to solve any effluent water quality problems. The influent, the internal pond processes and
the plant effluent should be evaluated on a regular basis.
The wastewater must be analyzed for a number of water quality parameters. Typical tests and
measurements include flow, temperature, pR, DO, BOD5, soluble BOD5 (SBOD5), CBOD5, TSS,
NHs, P, coliform (fecal or total) and chlorine (CT) residual. The results of these tests are used to
determine whether the treatment process is reducing the wastewater contaminants and to predict
the impact of potential operational changes. Some of the tests can be performed with basic
equipment (flow, temperature, pH, DO and CT residual) and some require more time, specialized
equipment and technical expertise (BOD5, SBOD5, CBOD5, TSS, NH3 and coliform). The
operator of a small pond system may elect to collect samples for these tests and have a
commercial lab complete some of the analyses. (U.S. EPA, 1977'a).
All system operators will need to review the facility discharge permit to determine sample
parameters to be tested, sample type, location and frequency needed to meet permit compliance.
Operators of systems that have a controlled discharge will need to perform tests during the
period prior to and during discharge as required by the regulatory agency. Those systems
operating on a hydrograph controlled release discharge basis must monitor the treatment plant
process and the quantity and quality of both the effluent and the receiving stream.
9.3.1 Sample Collection
Samples collected for analysis must be representative of the water being tested, which requires
that they be taken at a location where the wastewater is well mixed and not subject to short
circuiting. If the sample is to be stored before testing, it must be refrigerated. Sample containers
must always be cleaned to method specifications before sampling to avoid confounding the
results with background contamination. Temperature, /?H, CT residual and DO should always be
taken in the field to prevent false readings and should be taken at the same time each day. These
parameters should be measured at other times of the day from time to time to gain an
understanding of the changes that occur throughout the day.
9-2
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9.3.2 Types of Samples
9.3.2.1 Grab
Grab samples, taken at no set time or flow, are used to measure temperature, pH, DO, fecal and
total coliform and CT residual. As raw sewage flow varies in content, as well as volume, over the
course of the day, samples taken at sunrise and in mid-afternoon and analyzed separately will
yield the most information. Grab samples of effluent from controlled discharge ponds should be
taken during discharge, perhaps one sample every two hours, but then should be combined into
one composite sample (see Section 9.3.2.2). The operator should review state guidelines for
specific information.
9.3.2.2 Composite Samples
9.3.2.2.1 Volumetric Composite
A volumetric sample is taken by collecting individual predetermined sample volumes at regular
intervals over a selected period of time, usually using a sampling device designed for this
purpose (see Section 9.3.3). The samples must be refrigerated. They are then mixed together and
considered to be a representative sample for whatever analysis is being performed.
9.3.2.2.2 Flow Proportional Composite
A flow proportional composite is taken by collecting individual samples at regular intervals over
a selected period of time. A flow measurement is taken and recorded at the time the individual
sample is collected. All samples must be refrigerated. At the end of the sampling period, each
sample is stirred and an amount that is proportional to the flow at the time the sample was taken
is poured into the composite container.
9.3.2.2.3 Automatic Samplers
There are numerous types of automatic samplers on the market. Some are self-contained with
battery packs while others must have an external power source. They take samples at chosen
intervals, some as frequently as every 10 minutes, and composite the samples as they are
collected. The samplers can be connected to existing flow measuring devices or may have built-
in flumes that deliver flow-proportional composite samples. This equipment is most useful for
sampling raw wastewater flow, but can be used for effluent as well.
9.3.3 Handling and Preservation of Samples
Sewage samples rapidly undergo biochemical changes if they are subjected to summer
temperatures or freezing temperatures or if exposed to sunlight. Thus, collected samples should
be transferred as soon as possible to a refrigerator. Keeping samples at a temperature of 4 °C
reduces post-collection biochemical changes for 24 hours. Samples taken for bacterial analyses
should be collected separately and analyzed or sent to a laboratory for analysis within 30 hours
of collection (http://www.epa.gov/OGWDW/methods/methods.html).
Containers used for sample storage should be as clean as required for the specified method
analysis. Stoppered glass bottles or wide-mouthed jars are preferred and are easiest to use for
mixing and cleaning. Bacterial samples should be collected in sterile containers.
9-3
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9.3.4 Sample Point Locations
9.3.4.1 Pond Influent
Samples of the raw wastewater can be collected at the wet well of the influent pump station, a
manhole at the inlet diversion control structure, or the influent headworks.
9.3.4.2 In Pond
Pond composite samples should consist of four equal portions taken from four corners of the
pond. The sample should be collected 2.4 m out from the water's edge and 0.3 m below the
water surface or at the transfer structures between the cells if these are present. Care should be
taken to avoid stirring up material from the pond bottom and should not be taken near
mechanical aerators or during or immediately after high wind or strong storms, as these
processes may stir solids into the water column.
9.3.4.3 Effluent
Effluent samples can be collected from the final cell outlet structure or at a well-mixed location
in the outfall channel prior to mixing with any dilution waters such as the receiving stream
waters.
9.3.5 Tests and Measurements
Test results, along with visual indicators, are used by the operator to evaluate whether the pond is
in discharge permit compliance. The following sections describe the tests.
9.3.5.1 Temperature
The temperature of the influent wastewater can be used to detect inflow and infiltration (I&I) and
some industrial wastes. A sudden increase in temperature may indicate the presence of warm
industrial wastes. On the other hand, influent temperatures may cool rapidly in late fall and early
winter. In one case, an investigation of the collection system revealed that owners of poorly
insulated homes were bleeding their internal plumbing systems to prevent freezing of the pipes.
This cold water diluted the influent sewage strength and cooled the temperature, which reduced
the ability of the system to treat the waste.
Temperature can also be used to predict treatment efficiency and mode of operation (parallel or
series) and estimate the necessary HRT. As influent water temperature cools, a facultative pond
system may need to be changed from series to parallel operation to reduce organic loading to
each cell. A mechanically aerated pond system subject to cooler ambient temperature may need
to have all cells in series operation to obtain the correct HRT for continuous permit compliance.
Conversely, as influent water temperature increases, a facultative pond system may need to be
changed from parallel to series operation. The operator of a mechanically aerated pond system
may choose to remove an individual cell from operation to reduce the overall HRT and prevent a
possible algal overgrowth condition.
9.3.5.2 Flow
Keeping a record of accurate flow measurements is essential for successful operation and control
and troubleshooting pond systems. Influent flow measurement can be used to detect I&I
9-4
-------
problems, determine the HRT of a cell, calculate the organic loading to a cell, provide data for
determining mode of operation and calculate appropriate chemical dosages. Effluent flow
measurement is a requirement of the discharge permit and can be used to calculate chemical
dosage needed for disinfection. Most states require both influent and effluent flow measurement
to determine the extent of infiltration and/or exfiltration from the cells, depending on the distance
of the system to groundwater.
9.3.5.3 />H Value
Large fluxes in influentpH may signal an industrial and/or septic waste problem. The range of
pH for normal domestic influent waste is 6.8 - 7.5, depending on alkalinity and hardness of the
water. The/>H is a good indicator of the health of the pond system. Pond cells that have a dark
green color generally have a high number of green algae and a corresponding higher pR. Algae
take up C02 in the photosynthetic process. If C02 is not available, the algae will utilize a carbon
source from the HCOi alkalinity, which drives up thepH to 9.5 or above. At night, both the
algae and aerobic bacteria utilize 02 and produce C02. The C02 in solution forms carbonic acid
(H2COs) and drives thepR down. These diurnal pR patterns are indicators of internal pond
conditions. Pond cells that appear black or gray in color and have a decreasingpH value (< 6.8)
may be septic or moving toward a septic condition.
9.3.5.4 Dissolved Oxygen
Dissolved oxygen is an essential indicator of aerobic biological activity. The DO test is
performed on a grab sample and must be performed immediately. The easiest method for
analyzing for DO is with a portable meter. The test should be performed at sunrise and again
around 2-3 p.m. Large fluctuations in the primary cell may signal problems with the influent,
such as shock loading or toxic waste problems. Some fluctuation in day-to-day DO in the pond
system is expected. The operator should plot daily readings and identify trends in concentrations.
A decreasing trend in DO in the early morning test may indicate an increasing organic load, a
developing short-circuiting problem or an algal overgrowth problem. All measures should be
taken to avoid the DO concentration dropping to zero. This will cause incomplete treatment of
the wastewater and will result in discharge permit violations. The operator may have to take
corrective action, such as increasing aerator running time or aeration capacity or switching to
parallel operation. An increasing trend in the DO concentration, on the other hand, may allow
the operator to decrease aerator running time or switch from parallel to series operation.
9.3.5.5 Dissolved Oxygen Profile
A DO profile is developed by taking a series of DO measurements at 0.3 m increments from top
to bottom on an individual cell. An informal grid system is established to ensure uniform
coverage of the cell (Figure 9-1). This test is best performed by two people for safety reasons
and data recording needs. A boat and a portable temperature-compensating DO meter with a
long probe are required. The probe should be marked off in 0.3 m increments from the tip of the
probe to a length that will allow the operator to have the probe touch the bottom of the cell from
the boat. The water depth at which the probe goes slack should be recorded.
9-5
-------
4-
D
fj
6—0
Figure 9-1. Sampling grid system (Richard and Bowman, 1991). Sampling points are
located where lines with letters and numerals intersect.
This test allows the operator to determine if there is a DO deficit during evening hours when 02
depletion is greatest due to biological activity. The test will also indicate if the pond is
completely mixed or stratified; identify areas of low DO or dead spots; draw attention to short
circuiting; and help define bottom pond contours and areas of possible sludge build-up. The test
should be performed just as it is getting light. As is seen in Figure 9-2, the lowest 02 reading is
noted just prior to sunrise. Once it is daylight, the algae photosynthesize, which may become a
supersaturated DO condition in early afternoon. As light intensity lessens and photosynthetic
activity diminishes, 02 is depleted. During the night, if the DO level in the ponds drops to zero,
aerobic decomposition of organic matter stops, causing incomplete treatment. This can lead to
BOD5 permit violations.
9-6
-------
30_
Ap 9f% 11 n 1*0 BOO
Illtlil Oxygen D»fldt
3CCX
20
10
0
/=^ ^ -A
P. ^ yCZ =\ ,001
/ \ /= — x
/ 5 /= -\
/— — \ / V loot
j|7 ^i|||jf NUI
0
Mghr
12
18
24
Nghl
12
IB
Day
24
Mght
Figure Diurnal Oxygen Concontrotlon in o Lagoon.
NOTEi Tho graph Intfcaloc thai the to wo it duclved oxygen levels occur oarly In tho morning djo to tlw oarcblc boclerlo
end dgaa iriUxlng oxygen during the nlghl, Tho Hghoit duowed oxygen larol li kit* In the oftornoon due to dgd
phofotynttwdi, .1 It lk»;y tho oorotor* muit run more at idght to cwrp«n*at« for tlw dgo» m*tobolUlng oxygon. R li
Vrtxxtani *o heuro propor oarator oporotlon during the day for adequate irJxlng end to olrrtnato pofwtld lirolineatlon.
Figure 9-2. Diurnal O2 curve ( Richard and Bowman, 1997).
9.3.5.6 Chlorine Residual
The Cr residual test determines the amount of Cl present after the detention time for disinfection
(to destroy fecal coliform) has been met. The general rule is that there should be 0.5 mg/L
remaining after a contact time of 1 hour. This grab sample must be tested immediately. The
operator should review the National Pollution Discharge Elimination System (NPDES) permit,
as some states may not require disinfection. Some states may designate a prescribed coliform
minimum, and some may require dechlorination after disinfection.
9.3.5.7 BOD5
The BODs test measures the amount of 02 used (depleted) by the microorganisms in
metabolizing the organic material in a sample of wastewater. It is an indirect measurement of the
relative organic strength of a sample. The test is performed over five days in a controlled
environment. The sample is placed in an incubator at 20 C with no light or additional 02- The
test is used to determine the influent wastes organic strength, calculate the organic loading to the
pond system or an individual cell, make decisions about operational changes and determine
whether the effluent is in compliance with the discharge permit.
The BODs test can be misleading if there is a high concentration of algae in the effluent
discharge. The BODs test is an 02 depletion test that is run in the dark. When algae are in the
dark for long periods of time they cannot photosynthesize and will instead use 02. The up take
by the algae also reduces the 02 concentration at the end of the five-day period. The result is a
calculated BODs value that is higher than it would be if it measured the organic loading from
wastewater alone.
9-7
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9.3.5.8 Soluble BOD5
For this test, the BOD5 sample is filtered using a 0.45 ji filter before the test is run. The filter
should be observed for any obvious change and the color noted. The filtrate is then prepared in
the same way and run at 20 °C, in the dark. It is recommended that a standard BODs test and a
soluble (filtered) BODs test be run at the same time and the results compared. This is a valuable
troubleshooting tool that will be discussed in Section 9.3.6.
9.3.5.9 Carbonaceous BOD5 (CBOD5)
It has long been recognized that ponds will nitrify (convert NHs to NOi) under certain
conditions. This process uses approximately 1.8 kg 02 per 453 g ofNH3 converted to NOi and
approximately 4.1 kg of alkalinity per 453 g NHs converted NO3' (see Section 1.3.4.5 for a
discussion of alkalinity). The nitrification process will continue in the BODs bottle causing a
higher BODs test result. To compensate for this nitrogenous BOD in effluent BODs testing, a
CBOD5 test can be substituted for the BOD5 test. A CBOD5 test is a BOD5 test with inhibitor
added to prevent ft depletion due to nitrification. To compensate for nitrification effects,
regulatory agencies may allow operators to amend the discharge permit to substitute a CBODs
effluent limit for the BODs parameter.
9.3.5.10 Suspended Solids
The suspended solids (TSS) test measures the dry weight of solids retained on a glass fiber or
Millipore™ filter and is expressed in mg/L. Equipment required for this test includes a drying
oven, a desiccator and a weighing balance. Tests must always be run on composited samples
from both the influent and effluent.
Suspended solids removal is as important as BODs removal in preventing stream pollution. In
normal domestic sewage, the concentration of TSS and BOD5 are similar. The origin of the
suspended solids in the influent is not the same as in the effluent, however, as the former comes
from the sewage, while the latter from algae growing in the final pond. As a result, the TSS may
be higher than the BODs in the effluent from pond systems.
9.3.5.11 TSS to BOD5 Ratio
Effluent BODs violations are often accompanied by high effluent TSS concentrations. Table 9-1
presents TSS to BODs ratios that may indicate the cause of violations.
Table 9-1. TSS to BOD5 Ratios as Problem Indicators (Richard and Bowman , 1997).
TSS to BOD5 Ratio
<1
1
1.5
2.0-3.0
Cause(s)
old sludge solubilization and release of soluble BOD5
nitrification in the BOD5 test bottle
poor treatment or short circuiting with untreated wastewater mixing
with the effluent
normal for most pond systems
algal overgrowth
loss of old sludge particles
9-8
-------
9.3.5.12 Microscopic Solids Analysis
The microscopic solids analysis is a test performed with samples from each pond cell taken at the
transfer point and the final effluent before chlorination (Richard and Bowman, 1991). This
requires the microscopic examination of fresh pond samples using a phase contrast microscope
capable of achieving a total magnification of 1000X. Solids types present and their relative
abundance are measured. Solids type categories include: (1) raw wastewater or sludge solids; (2)
treatment solids (bacterial floes); (3) filamentous bacteria; (4) sulfur bacteria; and (5) algae.
These solids types are easily recognized with a little experience (Richard and Bowman 1997).
The significance of these solids types is listed in Table 9-2.
Table 9-2. Problems Associated with Types of Solids (Richard and Bowman 1997).
Solids Type Present
Raw wastewater solids
Old sludge particles
Treatment solids (bacterial floes)
Filamentous bacteria
Sulfur bacteria
Algae
Indicated Problem (s)
short-circuiting
poor aeration and improper waste stabilization
sludge buildup and need for sludge removal
organic overloading or sludge accumulation
indicators of low oxygen conditions orsepticity
anaerobic conditions and sulfides
algal overgrowth
9.3.5.13 Soluble and Total BOD5
The difference between these two values is the amount of particulate BODs present. A typical
domestic wastewater contains 40 percent soluble and 60 percent parti culate BODs. The soluble
BOD5 is rapidly removed in wastewater treatment and it is unusual to see a soluble BOD5 in the
effluent that is greater than 20 percent of the total. A paniculate BODs value greater than 70
percent of the total BODs in the effluent indicates a solids loss problem. The microscopic
examination is then used to identify the types of solids being lost (Richard and Bowman, 1997).
9.3.5.14 Microbial Tests
The coliform and other microbial tests (total and fecal coliform, E. coli and enterococci) indicate
the possible presence or absence of pathogens (human disease-causing organisms). The sources
of this group of organisms are the excreta of man, mammals, and birds. Tests are always run on
grab samples collected in a sterile container. Recent regulations regarding which test method
may be used for a particular discharge requirement may be found in the [Federal Register notice
of 3/26, 2007 (http://www.epa.gov/fedrgstr/EPA-WATER/2007/March/Day-26/wl455.htm)].
9.3.5.15 Nitrogen
Wastewater contains organic N (protein) and NH^. Organic TV is converted to NH^ by bacteria as
protein is broken down. The NHs is further oxidized to 7V02 and then to NOi by nitrifying
bacteria. This latter step is called nitrification. In some cases, it is necessary to remove NOi in
9-9
-------
order to control algal growth. Oxygen is removed under anaerobic conditions (NOi is a source
of O2 for the anaerobic bacteria), and NOi is reduced to nitrogen gas (A/2). This is the
denitrification step.
Ponds will nitrify and produce low effluent NHs concentrations under certain conditions,
particularly in the warmer months of the year. As wintertime cools the wastewater temperatures,
longer HRTs are required to reduce both CBOD5 and nitrogenous BOD5. Ultimately,
nitrification will cease at approximately 5-8 C. In colder climates, ponds cease to nitrify and
will actually produce NHs in the wintertime and early spring. Installation of floating insulated
covers may extend the period of time a pond system will nitrify NHs.
Low DO and low alkalinity can also limit nitrification. Typically, DO levels of 2.0 mg/L are
required to optimize nitrification. Total carbonate (CO/') alkalinity of less than 60 mg/L usually
limits nitrification. Nitrification can be increased or prolonged by raising the DO level in the
pond and increasing the alkalinity by adding an inorganic C source such as lime.
9.3.6 Important Visual and Olfactory Observations
Operators' visual and olfactory observations are important pond troubleshooting tools. Color
and odor can be important indicators of pond health and ability to meet discharge permit
standards (Table 9-3).
Table 9-3. Important Indicators in Pond Troubleshooting (after Richard and Bowman,
1991).
Pond
Appearance
Clear
Brown
Grey-black floating
sludge gas bubbles
on pond surface
Green
Floating mats of
blue-green algae
Red streaks
Entirely red or pink
Odor
None
Earthy
Septic-sewage
Grassy or earthy
Fishy
None or septic
Septic (rotten egg
odor)
Microscopic
Observation
Little suspended
material
Small bacterial
floes
Precipitated
sulfides in floes;
often filamentous
sulfur bacteria
Green algal bloom
Blue-green
bacterial bloom
High amounts of
Daphnia
Sulfur bacteria
(Chromatium spp.)
Problem
None
None; usually good
operation
Organic
overloading; low
dissolved oxygen;
influent sludge
short circuiting
Algal bloom, pH
often >9; long
detention time;
organic under-
loading
See above
Daphnia
overgrowth, often
after algal bloom
Anaerobic; gross
organic
overloading and
under aeration.
Solution
None
None
Increase aeration capacity,
add baffles or additional
cells, improve inlet-outlet
design recirculation,
remove sludge
accumulation
Recirculate; addition of a
settling pond, land
discharge
Remove cells from
operation, decrease water
depth to decrease HRT;
CAUTION: MAY
INCREASE ALGAL
BLOOM
Increase aerator running
time, recirculate
Increase aerator running
time or increase aeration
capacity, recirculate
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9.3.7 Other Data
9.3.7.1 Weather
Weather plays a major role in an operator's ability to meet discharge permit requirements for a
pond system consistently. The operator should keep a daily journal or log of periods of sunshine,
cloudiness, air and pond temperature, precipitation (rain or snow levels should be recorded), and
percentage of the individual cells that are ice covered. Prolonged periods of cloudiness may
increase the effluent BODs and require the operator to make a change from series to parallel
operation in a facultative pond system. In an aerated pond system, the operator may be required
to increase aerator running time to insure discharge permit compliance.
9.4 OPERATION AND MAINTENANCE FOR PONDS
The following sections are summaries from the Operations Manual: Stabilization Ponds, 1977,
Office of Water Program Operations, U.S. EPA, Washington D.C. Another source of
information about O&M for ponds is the Office of Water Programs at California State
University, Sacramento, which offers training manuals and distance education courses for
operators and managers on the safe operation and maintenance of wastewater collection systems,
wastewater treatment plants, and utility management. Operations and maintenance of
wastewater treatment ponds is found in Operation of Wastewater Treatment Plants., Volume 1,
Chapter 9 (Kerri, 2002). To obtain more information about the program or to order the training
manual, which is available in English and Spanish, go to the website at www.owp.csus.edu.
9.4.1 Operation and Maintenance Guidelines for Anaerobic Ponds
9.4.1.1 Anaerobic Ponds
A well-operating anaerobic pond is covered entirely with a dense scum blanket which helps to
keep the pond anaerobic and minimizes foul odors.
9.4.1.2 Important Operation Considerations
• Keep the pondpH at or near neutral (pH = 7).
• Control odors by maintaining zero mg/L DO and a heavy scum blanket.
• Keep records of flow, HRT, pH, BOD5 and TSS.
• Include information on volatile acids, scum and sludge depth.
9.4.1.3 On-site Attendance
Maintaining an aerobic pond in good condition requires full-time operator attention. These
activities should be performed on a daily basis, on a regular schedule and as needed:
• Maintain mechanical equipment
• Keep pipelines, diversion boxes and screens clean
• Collecting samples
• Run lab tests
• Perform housekeeping
9.4.2 Operation and Maintenance Goals for Facultative Ponds
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9.4.2.1 Pond Effluent Compliance Conditions
The pond effluent should:
• Meet the NPDES or other regulatory permit levels for BOD5 and TSS for continuous
flow systems.
• Discharge when the effluent has the best quality and will least affect the receiving stream.
• Have a deep green sparkling color in the primary pond.
• Have high DOs in the secondary or final cells.
9.4.2.2 Wave Action
The surface water should have wave action when wind is blowing. The absence of good wave
action may indicate anaerobic conditions or an oily surface.
9.4.2.3 Maintenance
General maintenance guidelines:
• To maintain wave action, a pond should be free of weeds in the water or tall weeds on the
banks.
• Dikes should be well seeded with grasses above the water line. Grass should be mowed
regularly to prevent soil erosion and insect problems.
• Riprap, broken concrete rubble or a poured concrete erosion pad should be placed at the
water's edge to prevent erosion of dikes.
• Inlet and outlet structures should be cleaned regularly to remove any floating debris,
caked scum, or other trash that might produce odors or be unsightly.
• Mechanical equipment should be maintained according to a regular schedule.
Maintenance records should be kept and be readily accessible.
• All pond operations should be listed on a posted schedule. The plant records should
include weather data and basic test results such as flow,/>H, DO, BODs, TSS and
chlorine residuals.
9.4.3 Operation and Maintenance Goals for Aerated Ponds
In the past, many of the facultative pond systems were converted to aerated pond systems by the
addition of mechanical aeration. This allowed the hydraulic and organic loading rates to
increase, but caused many operational problems. Cell depths remain shallow (1.2 - 1.8m and
HRTs were typically lower than those used in facultative ponds, but greater than those used in
aerated pond systems. Some problems were caused by the surface aerators mixing too deeply
and scouring the bottom of the cells, compromising the integrity of the liners. The shallow
depths and longer HRTs promoted algal overgrowth, making it difficult to meet discharge permit
requirements in the summer months.
Aerated ponds require the same daily inspections and maintenance as any other treatment ponds.
In addition, special attention must be paid to the aeration equipment. The following are minimal
guidelines:
• Maintain a minimum of 1 mg/L DO throughout the pond at heaviest loading periods.
• Run the system so that surface mechanical aerators produce good turbulence and a light
amount of froth.
• Monitor DO at aerated cell outlet daily.
• Keep large objects out of the pond to prevent damage to the aerator.
9-12
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For diffused air systems that use a blower and pipelines to diffuse air over entire bottom of pond:
• Check the blower daily.
• Visually inspect the aeration pattern for dead spots or dead lines.
• Check for ruptures and repair them if necessary to maintain even distribution of air.
• Measure DO at several locations in the pond weekly and adjust air to maintain even
distribution.
Periodic maintenance, such as lubrication, adjustment and replacement of parts, must be
performed on a regular basis. A checklist of maintenance tasks and frequency, taken from the
manufacturer's instructions bulletins, should be available and activities relating to maintenance
recorded in a log book.
9.4.4. Pond System Checklist
A checklist is a handy tool for the operator to schedule activities. Most of the items are visual
observations or maintenance needs that take little time if performed according to a regular
schedule. Over time, the operator will develop ways to combine some of the duties. In many
installations that are overseen regularly by a conscientious operator, the scheduled tasks can be
accomplished in one to two hours a day, allowing the balance of the time to be used to complete
laboratory work and other duties.
Table 9-4 is a sample O&M checklist for pond operation. Although it is not a complete list of
everything the operator should be observing, it will serve as a guide for setting up a regular
schedule and as a daily reminder. The schedule will help the operator organize work in a step-by-
step fashion, which will also help operators coming on in relief during an emergency or new
personnel who are not familiar with the system. The design engineer should develop a checklist
for the system that is included in the O&M manual.
Table 9-4 Example Operation and Maintenance Checklist.
Operation and
Maintenance
Frequency
Daily
Weekly
Monthly
3 mos.
6 mos.
Yearly
As Needed
Plant Survey
Drive around perimeters of ponds taking note of the following conditions:
Any buildup of scum on
pond surface and
discharge outlet boxes
Signs of burrowing
animals
X
X
9-13
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Operation and
Maintenance
Anaerobic conditions:
noted by odor and
black color, floating
sludge, large number
of gas bubbles
Water-grown weeds
Evidence of dike erosion
Dike leakage
Fence damage
Ice buildup in winter
Evidence of short-
circuiting
Frequency
Daily
X
X
X
X
X
X
Weekly
Monthly
3 mos.
6 mos.
Yearly
X
As Needed
X
A review of the information obtained from the observations should be included in the next
year's planning activities.
Plan, schedule, and
correct problems
found. Use
troubleshooting
section of this manual
for information.
X
Pretreatment
Clean inlet and screens,
and properly dispose
of trash.
Check inlet flow meter
and float well.
X
X
If discharge is once or twice per year, the discharge permit may require observations of the
following:
Odor
Aquatic plant coverage
of pond
Pond depth
Dike condition
Ice cover
X
X
X
X
X
9-14
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Operation and
Maintenance
Flow (influent)
Rainfall (or snowfall)
Frequency
Daily
X
X
Weekly
Monthly
3 mos.
6 mos.
Yearly
As Needed
Note:
Each state has requirements for data collected prior to and during discharge that are defined in
the pond system discharge permit.
If discharge is continuous, the discharge permit may require the following information:
Weather
Flow
Condition of all cells
Depth of all cells
Pond effluent:
DO and pH grab
sample
Cf residual
BOD5 and TSS run on
composited sampled
Microbial tests
kg (Ib) of Cf used and
remaining
X
X
X
X
X
X
X
X
X
X
Other tests and frequency information will be defined in the individual permit.
Mechanical Equipment
Check mechanical equipment and perform scheduled preventive maintenance on
the following pieces of equipment according to the manufacturer's recommendations:
Pump stations:
Remove debris
Check pump operation
Run emergency
generator
Log running times
X
X
X
X
9-15
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Operation and
Maintenance
Clean floats, bubblers,
or other control
devices
Lubricate
Comminuting devices:
Check cutters
Lubricate
Aerators:
Log running time
Check amperage
Chlorinators:
Check feed rate
Change cylinders
Flow measuring devices:
Check and clean
floats, etc.
Verify accuracy
Valves and gates:
Check to see if set
correctly
Open and close to be
sure they are
operational
Frequency
Daily
X
X
X
X
Weekly
X
X
X
X
X
Monthly
3 mos.
6 mos.
Yearly
As Needed
X
X
X
9.4.5 Flexible Design to Improve Operation
9.4.5.1 Flow Regulation
Flow regulation is one of the most helpful operational tools. Without the flexibility to move
water around where it is needed, the operator would be severely limited in his or her ability to
troubleshoot and solve pond system problems. The following sections enumerate these options.
9.4.5.1.1 Single Cell Ponds
The only flexibility an operator has with a single cell pond is depth control. The water level may
have to be varied seasonally or to control weeds and mosquitoes.
9-16
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9.4.5.1.2 Multiple Cell Ponds
Multiple cell pond systems may be operated to optimize a number of different parameters. They
may be operated so as to:
• Hold wastewater in the primary cell, especially during seasonal discharge operation.
• Move water from cell to cell to correct an 02 deficiency problem.
• Control liquid depth to eliminate weeds or mosquitoes.
• Isolate a cell that has become anaerobic or to hold a toxic waste.
• Take advantage of both series and parallel operation to regulate loading.
• Rest a cell temporarily for recovery.
• Recirculate water from the last cell to the first cell, at a minimum. This allows the
operator to increase the DO and to seed the first cell with algae. Remove an individual
cell from operation which varies the HRT of the system, particularly in summer.
9.4.5.2 Baffles and Screens
Screens, often custom-made, are used around pond surface outlets to keep windblown weed and
surface trash from entering a pipe.
Baffles may consist of pilings (5 by 24 cm) driven into the pond bottom. They are commonly
used for a large variety of purposes, for example:
• Direct the flow of water, especially around inlets.
• Reduce or eliminate short circuiting.
• Allow selection of depth for pond draw-off and to keep surface scum and trash from
entering.
• Provide a quiet zone ahead of a flow measuring device.
• Reduce the force of a pump discharge.
9.4.5.3 Inlet and Outlet Design
Submerged outlets should be used to prevent the discharge and/or transfer of floating material
between ponds.
Variable depth draw-off is especially useful in parts of the country where algal overgrowth is a
problem. The effluent should be able to be drawn from any depth in the pond cell, giving the
operator the choice of transferring or discharging the best quality water. Variable depth
discharge works best with surface mechanical aeration. Low discharge approach velocities are
required to minimize the area of influence adjacent to the discharge structure.
There are numerous discharge structure designs that allow the operator to draw effluent in the
area under the algal layer while staying 0.6 - 0.9 m above the benthic sludge layer. At a
minimum, the pond should be designed with three draw-off points: the first below the algae
layer, the second in approximately the mid-depth, and the third above the bottom of the pond.
The use of properly designed inlet and outlet manifolds may aid in the distribution and collection
of wastewater flows and minimize short-circuiting.
9-17
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Transverse perforated collection pipes may reduce approach velocities, increase the discharge
collection area of influence and also help minimize short circuiting.
Having multiple inlets and outlets in the system design gives the operator greater flexibility to
match the loading and discharge of a pond system more closely to environmental conditions.
9.4.5.4 Dike Erosion
Dike erosion from wave action can be prevented by using riprap in the form of rocks 8 - 48 cm
laid along the water's edge. One unusual method employed was to sink 5 by 15 cm uprights into
the pond floor extending above the water surface to dissipate the waves. In another case, the
pond operator filled bags with a dry mix of sand, gravel and cement. These were laid side by
side and stacked to form a system of riprap protection. Riprap should extend 0.3 m above and
below extreme operating levels. Other forms of riprap or bank stabilization include cribbing
(snow fence) laid on the bank and reed canary grass. Canary grass is effective in ponds that are
deep, have steep slopes and a stable water level. If sod is used it should be at least 7.5 cm (3 in)
square and placed not more than 1 m apart.
9.4.6 Pond Cleaning
When it becomes necessary to clean a pond, the operator should first contact the regulatory
agency to find out about any special requirements. In most cases the operator and/or consulting
engineer are required to develop a plan outlining the method of sludge removal, steps to be taken
to ensure pond liner integrity, test of the sludge to be removed for volatile solids and metals, and
describe the plan for ultimate disposal of the sludge. A separate permit may be required when
land application of the sludge is selected for ultimate disposal. The regulatory agency may
require site geological information (e.g., type of soil, slope of ground, depth to groundwater),
type of crop grown and agronomic uptake rate of metals and nutrients of that crop, sludge
testing, method of application, method of solids incorporation into the soil, irrigation practices,
runoff control and disposal, and if applicable, vector control and monitoring requirements.
The most common method of sludge removal is to employ some type of sludge pumping
equipment. Care should be taken to maintain the integrity of the pond liner. Damage to a pond
liner may require repair or replacement, or at a minimum, increased monitoring and testing to
ensure the pond is not adversely affecting surface water, groundwater and/or public health.
9.4.7 Procedures for Startup
9.4.7.1 Primary Cell
Spring or early summer is the best time for startup to avoid low temperatures and possible
freezing. Fill primary cell(s) with water from a river or municipal system, if available, to the 0.6
m level. Begin to add the wastewater, keeping thepR above 9.5 and checking the DO daily (see
Appendix G.) Algal blooms should appear in 7-14 d.
A good biological community will be established in about 60 d or less. The color will be a
definite green, not blue or yellow-green. This procedure tends to avoid odorous anaerobic
conditions and weed growth during the start-up phase.
9-18
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If is it necessary to start in late fall or winter, the water level should be brought to 0.75 -1m and
not discharged until late spring.
9.4.7.2 Filling Successive Ponds
• Begin filling when the water level in the first pond reaches a depth of 1 m.
• Add fresh water to a depth of 0.6 m.
• Begin adding water from previous pond observing the following:
o Use top draw-off to achieve good transfer. Do not draw off from a level below
the bottom 45 cm.
o Do not allow the water depth in the previous pond(s) to fall below 1 m.
o Equalize water depths in all ponds. This should be done in the following manner:
Hold the discharge until all ponds are filled.
Use effluent box with gates or valves to allow pumping of the effluent to any
pond in the system if it is designed with this capability.
Recycle the effluent continuously to the ponds with low water levels.
Repeat the operation using 15 cm increments until ponds are at their operating
depth.
Finally, start continuous or intermittent discharge, according to the system design.
9.4.8 Discharge Control Program for Seasonal Discharges
9.4.8.1 Preparation
• Make a note of conditions in the stream to receive discharge.
• Estimate duration of discharge and expected volume.
• Obtain state regulatory agency approval.
• Isolate cell to be discharged. Allow it to rest for at least one month, if possible.
• Arrange for daily sample analysis of BODs, TSS,/?H, coliform and nutrients (if required).
• Plan other work so as to be able to devote full attention to control of discharge throughout
the period.
• Sample contents of cell and analyze for DO; note and record turbidity, color and any
unusual conditions.
9.4.8.2 Discharge Procedures
Ponds in a number of northern states are permitted to discharge effluent seasonally. Three or
four weeks after ice break-up, the ponds generally return to normal operating conditions.
Wastewater in the cells is tested and results are reported to the state. If the wastewater is of a
quality suitable for discharging, the operator follows state guidelines for discharging. The
NPDES permit contains information about the discharge quality.
The quality of the receiving stream is usually determined by the state water quality control
agency as part of the discharge approval program. When discharge approval is obtained, proceed
as follows:
• Begin the discharge program with the last cell in series.
• Draw off the discharge from the best level at a time when the discharge is acceptable.
• Stop the discharge when ponds are upset.
9-19
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• Follow testing procedures outlined by the state regulatory agency.
9.5 SAFETY AROUND PONDS
9.5.1 Public Health
Operators and others conducting activities around treatment ponds must proceed with caution
and make safety and public health a priority. Treatment ponds must be utilized for their
designed purpose only, not for public recreation. The relative amount of water surface of
treatment ponds is insignificant compared to the many natural bodies of open water in most
localities. In some areas, however, treatment ponds represent the only sizeable body of water
and have been sources of attraction for recreation purposes. Incidents of boating, ice skating,
waterfowl hunting and even swimming in ponds have been reported. Recreational use should be
discouraged and safety practices encouraged for several important reasons. Even though the
efficiency of bacterial removal as measured by the MPN method is very high, the possibility of
contamination or infection from pathogenic organisms does exist when a person comes in
contact with wastewater in a treatment pond.
People can drown in treatment ponds. Clay and synthetic liners used in sealing ponds become
very sticky when water is added. Should a person fall into a pond, the presence of liners would
make it extremely difficult to get out. To discourage use of the ponds for recreation, the entire
area should be fenced and warning signs displayed.
Another factor to be considered is the presence of mosquitoes. In a well-maintained pond system,
mosquitoes usually are not a nuisance. According to studies by the U.S. Public Health Service,
the density of the mosquito population is directly proportional to the extent of weed growth in a
pond. Where weed growth in the ponds and along the water line of the dikes is negligible and
where wind action on the pond is not unduly restricted, the likelihood of mosquitoes breeding is
low.
9.5.2 Personal Hygiene
In the interest of the health of those who work around wastewater treatment ponds and their
families, this list of Do's and Don't 's for personal hygiene is presented.
• Never eat or put anything into your mouth without first washing your hands.
• Refrain from smoking while working in manholes.
• Wear gloves when working on pumps or other parts of the operation where hands may
become contaminated.
• Don't wear work coveralls or rubber boots in the car or at home.
• Always clean any equipment, such as safety belts, harnesses, face masks, or gloves after
use.
• Keep fingernails cut short and clean.
9.5.3 Safety
9.5.3.1 Sewer Maintenance Safety Precautions
• Remove and replace heavy manhole covers carefully and only with the proper tools.
• Descend into any manhole slowly and cautiously.
9-20
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• Use the buddy system; do not enter without a spotter present.
See Section 9.5.3.4 for information regarding noxious gases that may be found in sewers.
9.5.3.2 Pumping Station and Treatment Pond Safety Precautions
• Maintain a high level of housekeeping. Keep floors, walls and equipment free from dirt,
grease and debris. Keep tools properly stored when not in use.
• Keep walkways clean and free of slippery substances. If ice forms on walks, apply salt or
sand or cover with earth or ashes that can be removed later.
• Be especially cautious when working with an electrical distribution system and related
facilities. Never work on electrical equipment and wire with wet hands or in wet clothes
or shoes. Always wear appropriate safety gloves for electrical work. Never use a
switchbox as anything other than a switchbox.
• Keep all personnel safety conscious by providing training at regular intervals. Have
specific safety instructions posted in appropriate places. Such instructions should include
information as to how to contact the nearest medical center and fire station, rescue
techniques, resuscitation and first aid techniques.
• Make certain that a sufficient number of trained and experienced personnel with proper
equipment are assigned and present whenever it is necessary to perform any hazardous
work.
• Staff should have boating safety training. Life preservers must be used whenever
personnel are in a boat on treatment ponds. At least two people should work together
around the ponds because of the danger of drowning and other accidents. Safety training
for a pond operator should include life saving skills, including the ability to swim at least
30 m in normal work clothing.
• Sufficient fire extinguishers (Underwriter's Laboratories Approved) should be placed in
readily accessible locations.
9.5.3.3 Body Infection and Disease Safety Precautions
Treat all cuts, skin abrasions and similar injuries promptly. When working with wastewater, the
smallest cut or scratch is potentially dangerous and should be cleaned and treated immediately
with a 2 percent solution of tincture of iodine. In addition, personnel should:
• Receive medical attention for all injuries.
• Be given first aid training.
• Be inoculated for waterborne diseases, particularly typhoid and para-typhoid fever.
• Keep a record of all immunizations in an employee health record.
• Review records annually for necessary boosters and new immunizations.
In the laboratory, always use appropriate laboratory equipment and supplies, and avoid any
contamination by mouth. Don't take laboratory glassware for personal use. Paper cups should
be provided in laboratories for drinking purposes. Never prepare or eat food in a laboratory.
9-21
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9.5.3.4 Noxious Gases, Explosive Mixtures and Oxygen Deficiency
The principal air hazards associated with wastewater treatment are accumulations of sewer gas
and its mixture with other gases or air, which may cause death or injury through explosion or
asphyxiation as a result of 02 deficiency. The term "sewer gas" is generally applied to the
mixture of gases in sewers and manholes containing high percentages of CO2, varying amounts
of CH4, H2, H2S, and low percentages of 02. Such mixtures sometimes accumulate in sewers and
manholes where organic matter has been deposited and has undergone decomposition. The
actual hazards from sewer gas are the result of the explosive amount of CH^ H2S or in 02
deficiency. Hydrogen sulfide is toxic at very low concentrations and a person's sensitivity to the
odor is quickly deadened.
Chlorine gas, which is irritating to the eyes, respiratory tract and other mucous membranes, may
settle in low-lying, still areas. The gas forms an acid in the presence of moisture. The gas may
leak from cylinders and feed lines and diffuse and settle into these places.
9.5.3.5 Safety Equipment
A wastewater facility should have the following types of safety equipment:
• Detection equipment (for gases and 02 deficiencies)
• Respirators (self-contained SCBA packs for 02 deficiencies)
• Safety harnesses, lines and hoists
• Proper protective clothing, footwear and head gear
• Ventilation equipment
• Non sparking tools
• Communications equipment
• Portable air blower
• Explosion-proof lantern and other safe illumination
• Warning signs and barriers
• Emergency first aid kits
• Proper fire extinguishers
• Eye wash and shower stations in laboratory areas
• Safety goggles for work in laboratories and other dangerous areas
9.6 TROUBLESHOOTING
An operator or engineer must have a thorough understanding of the treatment process and tests
required to diagnose problems affecting effluent quality (see Appendices E and F). This expertise
must be brought to bear to achieve the highest level of process performance from a pond system
and stay within the agency's budget. Prior to visiting the site, the following documents should
be reviewed:
• Past inspection reports.
• The discharge permit.
• Discharge monitoring reports (DMRs) and plant performance records for a three-year
period.
• Any noncompliance correspondence to compare to plant operation records and DMRs to
look for trends.
• Plans and specifications to verify that they reflect current plant conditions.
9-22
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• Current plant records to verify that it is operating within required parameters.
• Organic loading rates, surface loading rates and aeration capacity to determine whether
the ponds are organically overloaded.
• O&M Manual to determine if the plant is being operated within the engineers'
recommendations.
Once on site, the following items should be observed and reviewed:
• Plant appearance and maintenance, including weed control, dike vegetation, dike erosion
and stability, fencing and out-building conditions.
• Individual cells: Note any floating material, such as grease, sludge, floating vegetation,
or mats of blue-green algae; water depth; freeboard height; cell color; odor problems;
septic conditions; sludge buildup.
• Influent and effluent flows for infiltration/inflow problems, influent septicity or odors,
and unusually high effluent solids, and/or floating material.
• Plant influent and effluent parameters.
• Plant operation and maintenance and equipment records.
• Plant staffing for operations and maintenance.
• Safety equipment and procedures.
• Sampling locations, methods, frequency and weather records.
9.6.1 Common Causes of Pond Effluent Noncompliance
Pond effluent violations can be caused by organic overloading, short-circuiting, algal overgrowth
conditions, sludge accumulation and nitrification, or partial nitrification. The following sections
will describe some of the causes of effluent violation, troubleshooting tests and results, and
present possible solutions to the problem.
9.6.1.1 Organic Overload
Organic overload is normally caused by influent organic shock loads or increased organic load
with no corresponding increase in treatment plant capacity. This condition causes low dissolved
O2 concentrations (< 1.0 mg/L) and inhibits treatment. This can be verified by calculating the
organic loading (BODs/d) and comparing it to design capacity. A DO test and DO profiles
should be run at various times of the day to verify whether there is a continuous low DO
condition.
The diagnostic troubleshooting tests will demonstrate high BODs, high CBODs, high soluble
BODs, low DO, a low TSS to BODs ratio and high NH^. The immediate solution is to increase
organic treatment capacity by increasing aeration. In the long term, a pretreatment program with
collection system monitoring of those areas suspected of introducing high organic shock loads
should be developed and implemented.
9.6.1.2 Short-circuiting
Short-circuiting normally occurs when untreated or partially treated wastewater does not have
adequate detention time in the system for complete treatment. This can be caused by
temperature stratification in the cells, poor inlet and/or outlet design, inadequate cell length-to -
width ratio or cell shape, or poor mixing and improper aerator placement. Performing a DO
profile test on an established grid system while recording both DO and temperatures in 0.3 m
9-23
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increments from the surface to the bottom should verify a short circuiting condition. The
operator will note variations in DO and temperature indicating temperature stratification and or
poor mixing. The diagnostic trouble shooting test will indicate high BOD5, high soluble BOD5,
moderate TSS and high NHs levels. This condition should be verified with a microscopic
examination of the effluent.
Possible solutions are relocating aerators, addition of directional aerators or mixers, adding
baffles, recirculating to enhance mixing, and redesigning inlet and outlet structures to include
manifolds or relocating structures.
9.6.1.3 Algal Overgrowth
Algal overgrowth is prevalent in the areas where there is a high number of sunny days during the
year. This condition occurs predominantly in the spring and summer. Long detention times,
shallow pond depths (1.2 - 1.8 m), abundant nutrients, warm water and sunshine promote algal
growth. The diagnostic troubleshooting test results indicate high/?H, high BOD5, low CBOD5,
low soluble BODs, high TSS, a high TSS to BODs ratio, low DO (early morning) and moderate-
to-high NHs concentrations.
During the night, algae and aerobic bacteria will utilize 02, potentially depleting the DO in the
cells prior to sunrise. Lack of 02 will cause incomplete treatment, possibly resulting in permit
violation. A DO profile test run at sunrise will normally verify the lack of 02 in the cells. A
microscopic examination of the effluent and count of the algae will confirm the overgrowth
condition.
Possible solutions include increasing the aerator running time at night. The operator may choose
to reduce aerator running time during the day, allowing the algae to concentrate on the surface of
the cells. The high concentration of algae at the surface will reduce sunlight penetration and may
slow the algal growth rate. Drawing off the effluent from variable depths below the surface will
also keep the algae in the cells, while allowing for the discharge of high quality water. The
addition of floating covers will block the sunlight and, with the maintenance of adequate in-cell
DO levels, produce a higher quality effluent. The addition of physical shade such as greenhouse
fabric suspended above the surface of the cells, or chemicals such as Aquashade® or photo blue,
used in accordance with EPA registry instructions
(http://www.epa.gov/oppsrrdl/REDs/aquashade_red.pdf) may also prove effective in controlling
algal growth.
9.6.1.4 Sludge Accumulation in Ponds
Sludge will accumulate in the bottom of pond cells over years of operation. Soluble organics are
released from these benthic sludges and have the largest effect on ponds in the spring of the year.
Diagnostic troubleshooting test results will indicate high CBODs, high soluble BODs, low to
moderate TSS, a low TSS to BODs ratio, low DO and high NH^ concentrations. This condition
can be verified with a microscopic examination. Increasing aerator running times may offer a
temporary solution. Ultimately removal of the sludge from the bottom of the pond cells will be
necessary. The operator must comply with all state and federal regulations and must take care to
protect the pond liner during the process.
9-24
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9.6.1.5 Nitrification or Partial Nitrification
Nitrification in ponds will occur under proper environmental conditions (in warmer water
temperatures and adequate DO) and is most prevalent in late spring and summer. Complete
nitrification would be indicated by low BODs, low CBODs, low to moderate TSS, moderate DO,
low NHs and moderate NOi levels.
Partial nitrification is common in ponds in late spring and summer when adequate DO levels are
not maintained for complete treatment. Troubleshooting diagnostic tests will show high BODs,
low CBOD5, low soluble BOD5, low to moderate TSS, a low TSS to BOD5 ratio, low DO and
moderate NHs concentrations.
Increased aeration (aerator running times) or, in some cases, increased aeration capacity may
increase nitrification.
9-25
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R-20
-------
APPENDIX A
State Design Criteria for Wastewater Ponds
-------
APPENDIX A
STATE DESIGN CRITERIA FOR WASTEWATER STABILIZATION PONDS
Table A-1 Minimum Hydraulic Residence Time and Depth Requirements
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Minimum Hydraulic Residence Time (HRT)
Controlled
Discharge and
Non -discharge
Each design evaluate
Stabilization alone do
Facultative
Flow-Through
days
d on a case-by-case basis.
es not meet state water quality re
Aerated
days
quirements for sewage treatment
Depth Requirements
Facultative
Cell
ft
acility. New facilities must meet "
Controlled
Discharge
ft
Best Available Demonstrated Cor
Technology" treatment standards. Exceptions require demonstrations unique site-specific characteristics and environmental factors. Economic hardship
is not a listed criterior
Ten State
All criteria controlled
NA
TR-16
See end of table
Case by Case
Analysis
Ten State
for exception to BADCT.
Second cell of two cell system
two cell system
must be designed
at same loading
rate as primary with
min HRT of 30 days.
Cells following
primary of 3 or more
cells will have
combined HRT of
30 days. Final cell
designed for settling.
3y Regional Board
180
TR-16
See end of table
Ten State
t = HRT, d
E = % BOD5 removed
k, = reaction rate, d "1
kT = 0.12/dat20 °C
kT = 0.06/d at 1 °C
12-30
Polishing
Pond 2-5
at avg flow
TR-16
See end of table
Ten State
Ten State
5
TR-16
See end of table
Ten State
Ten State
NA
TR-16
See end of table
Ten State
Aerated
Cell
ft
trol
Ten State
8-20
Polishing
pond 8-12
but as great
as practical.
TR-16
See end of table
Ten State
Anaerobic
Cell
NA
NA
TR-16
See end of table
NA
NA= Not available
-------
A-l (Corrt)
State
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Minimum Hydraulic Residence Time (HRT)
Controlled
Discharge and
Non-discharge
Must be considered
with regard to
environmental
conditions.
Ten State
90
180
Design to be based
on wettest 180
consecutive days
Ten State
Based on storage
required.
NA
Facultative
Flow-Through
days
Must be considered
with regard to
environmental
conditions.
Ten State
90
Not acceptable for secondary
treatment
Primary cell must
have minimum hydaulic
residence time of
90 days
Design standards in TR-16, Ten
State Standards or other
published literature accepted
by DEP or EPA are to be
considered.
Recirculation required.
60
Aerated
days
Must be considered
with regard to
environmental
conditions.
Ten State
Ten State
Partial Mix 180
Design to be based
on wettest 30
consecutive days
Ten State
Also based on organic
loading rate of 150 Ibs
per acre-day
Design standards in TR-16, Ten
State Standards or other
published literature accepted
by DEP or EPA are to be
considered.
Recirculation required.
30
Depth Requirements
Facultative
Cell
ft
Must be considered
with regard to
environmental
conditions.
Minimum operating
depth is 2 ft.
Not less than 5
Min Operating
2
5
Not acceptable for secondary
treatment
Ten State
Design standards in TR-16, Ten
State Standards or other
published literature accepted
by DEP or EPA are to be
considered.
Recirculation required.
Minimum 3ft
Maximum 5ft
Controlled
Discharge
ft
Must be considered
with regard to
environmental
conditions.
Minimum operating
depth is 2 ft.
10 State
5
Primary Cells Max 6
Secondary Max 8
Ten State
Design standards in TR-16, Ten
State Standards or other
published literature accepted
by DEP or EPA are to be
considered.
Recirculation required.
NA
Aerated
Cell
ft
Must be considered
with regard to
environmental
conditions.
Minimum operating
depth is 2 ft.
10-15
Ten State
Ten State
Partial Mix
Minimum 10ft
15
Anaerobic
Cell
Must be considered
with regard to
environmental
conditions.
Minimum operating
depth is 2 ft.
NA
NA
NA
NA
Design standards in TR-16, Ten
State Standards or other
published literature accepted
by DEP or EPA are to be
considered.
Recirculation required.
NA
NA= Not available
-------
A-l (Corrt)
State
Massachusetts
Michigan
Minnesota
54 pg document
with details for
all aspects of
lagoon systems.
Mississippi
Missouri
Montana
Minimum Hydraulic Residence Time (HRT)
Controlled
Discharge and
Non -discharge
TR-16
See end of table
Ten State
Ten State
Hydrograph
controlled release
minimum storage
90 days
Primary
40-80
Based on volume
between 2 ft and
maximum depth.
Secondary
Based on volume
between 1 ft and
maximum depth.
Facultative
Flow-Through
days
TR-16
See end of table
Ten State
180-210
1 80 d between two
and a max. depth
of 6 feet
30 days at 4 ft. operating depth.
Primary
40-80
Based on volume
between 2 ft and
maximum depth.
Secondary
Based on volume
between 1 ft and
maximum depth.
Aerated
days
TR-16
See end of table
Ten State
Varies with
design
E
~ 2.3t,(lOO- E)
Eq. used for
each cell.
Total HRT
must equal
min of 25 d
to meet BOD
of 25 mg/L.
Total HRT
must equal
min of 35 d
to meet BOD
of 15 mg/L.
t = HRT, d
E = % BOD5 removed
k, = reaction rate, d "1
kT = 0.12/dat20 °C
kT = 0.06/dat0.5 °C
Partial Mix 18 days plus settling
area of 1 day.
Complete Mix not specified.
Partial Mix
Min 20 days under
aeration
t = HRT, d
E = % BOD5 removed
k, = reaction rate, d "1
kT = 0.12/dat20 °C
Depth Requirements
Facultative
Cell
ft
TR-16
See end of table
Ten State
Max 6
6
Secondary
Cells 8
Controlled
Discharge
ft
TR-16
See end of table
Ten State
NA
15
Max for storage cell 20
Secondary
Cells 8
Aerated
Cell
ft
TR-16
See end of table
Ten State
10-15
10-15
10-15
Anaerobic
Cell
TR-16
See end of table
NA
NA
20 Day HRT
8-20 Water Depth
NA
NA= Not available
-------
A-l (Corrt)
State
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Minimum Hydraulic Residence Time (HRT)
Controlled
Discharge and
Non -discharge
Discharge limited
to once or
twice per year. Half
or all of average
flow must be stored.
NA
TR-16
See end of table
Each design evaluate
Ten State and
TR-16
NA
Facultative
Flow-Through
days
Primary cells must
have minimum HRT of
60 days and entire
volume must have a
minimum of HRT of
120 days. Area of initial
cell should not be greater
than approx. 2/3 of the
total area.
c k
C0~~
t = HRT
kp = kP2D(1 .09)(T-20)
e = base natural log
Ce = eff BOD
C0 = inf BOD
kP2o= varies with load
0.045to 0.096 d'1
TR-16
See end of table
d on a case-by-case basis.
Ten State and TR-16
Primary Cells
180
One-half of total
Aerated
days
kT = 0.06/d at 0 °C
Partial Mix
BOD removal 30-60
Ammonia-N 80-90
TKN 100-120
Complete Mix
1.5 to 2.0 for 85% BOD
removal. HRT of 7 to 10
for complete nitrification.
c „ i
c° [K^H"
t = HRT
kPUT= kPU2[(1.036)(T-20)
Ce = eff BOD
C0 = inf BOD
n = no. cells in series
Same equation for
partial mix and
complete mix.
kPM20= 0.276 d'1
kCM20 = 2.5 d'1
TR-16
See end of table
Ten State and TR-16
Can be reduced from
180 days with
addition of
Depth Requirements
Facultative
Cell
ft
Primary 4-6
Final cells max. 8.
4-10
TR-16
See end of table
Ten State and TR-16
5
Min operating
2
Controlled
Discharge
ft
NA
NA
TR-16
See end of table
Ten State and TR-16
NA
Aerated
Cell
ft
Partial Mix
7-14
Complete Mix
10-20
6-20
TR-16
See end of table
10 State and TR-16
NA
Anaerobic
Cell
As deep as possible.
Not less than
10-1 5 ft.
NA
TR-16
See end of table
NA
NA
NA= Not available
-------
A-l (Corrt)
State
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Minimum Hydraulic Residence Time (HRT)
Controlled
Discharge and
Non -discharge
Based on calculated
loading rates.
Ten States
NA
90 days between
2 foot and max.
operating depth.
Mean oprating
depth is max.
operating depth plus
minimum divided
by two.
TR-16
See end of table
No Specific Criteria. E
Surface Area for
total retention,
A=I/WL.
Summr or yr around,
A = I/(H+WL)
Winter months,
Facultative
Flow-Through
days
surface area.
180 days based on
total hydraulic loading.
Based on calculated
loading rates.
Ten States
NA
90-120
TR-16
See end of table
Ivaluated on a case by case.
Primary Cell should
be approx. 50-60%
of total surface area.
1 80 d between two
and a max. depth
of 5 feet.
Aerated
days
aeration.
NA
NA
E
2.3^(1 00 -E)
t = HRT, d
E = % BOD5 removed
k, = reaction rate, d "1
kT = 0.20/d at 20 °C
kT = 0.06/d at 0 °C
TR-16
See end of table
t E
2.3^(1 00 -E)
t = HRT, d
E = % BOD5 removed
k, = reaction rate, d "1
Depth Requirements
Facultative
Cell
ft
Max. 7
Min. Operating 1.5
3 to 5
Primary cells 6
Secondary ponds depth 8 ft.
TR-16
See end of table
5
Controlled
Discharge
ft
Max. 7
Min. Operating 1.5
NA
Primary cells 6
TR-16
See end of table
5
Aerated
Cell
ft
Ten State
8-10
10-15
TR-16
See end of table
Max. 20
Min. 10
Anaerobic
Cell
NA
NA
NA
TR-16
See end of table
NA
NA= Not available
-------
A-l (Corrt)
State
Tennessee
Texas
Utah
Vermont
Minimum Hydraulic Residence Time (HRT)
Controlled
Discharge and
Non -discharge
A = I/(H+S-P)
A = surface area, ac
1 = inflow, ac-ft
WL = net H 2O loss
S = seepage, ft
H = depth > 2 ft
P = precip., ft
NA
NA
NA
TR-16
See end of table
Facultative
Flow-Through
days
First secondry cell
max depth is 6.
Other following cells
may have depth 8.
Not specified.
Based on organic
loading rate
Exclusive of sludge
build-up, 120 on winter
flow at max operating
depth, or 60 on summer
flow and peak month I/I.
HRT shall not be less
than 150 at mean
operating depth without
chlorination. To meet
bact. standards, at least
5 cells required.
TR-16
See end of table
Aerated
days
kT = 0.20/d at 20 °C
kT = 0.08/d at 0 °C
k, = kT20(1 .47)(TJD)
t = 5-1 Od Warm
t = 8-20 d Cold
Settling Pond 5-7
Ce 1
C, l + 2.3(4,»)
t = HRT, d
Ce = eff BOD5, mg/L
C0 = inf BOD5, mg/L
k, = reaction rate, d ~1
k, = 1.097@20 °C
for complete mix.
k, = 0.12@20°C
for partial mix.
kT = k20(1.036)(T'20)
HRT in combined aerated
lagoon and secondary
pond system shall be a
minimum of 21 days.
Secondary ponds BOD5
removal calculated by
1
Where: E = efficiency of
CM without recycle.
K = removal rate constant
K = 0.5 day'1
V = volume, MG
Q = flow rate, mgd
Applies to Partial Mix
and complete aerated
cells.
~ [l + (2.3V)]
E = frac BOD5 remaining
t = HRT, d
k, = reaction rate, d "1
k, = 0.12/d@20 °C
k, = 0.06/d @ 1 °C
30 minimum
TR-16
See end of table
Depth Requirements
Facultative
Cell
ft
Primary
6
Greater depths
considered for
polishing and
last ponds in
series.
Approx. 25 % of Inlet
portion shall have a
10-1 2 ft depth for sludge
storage and anaerobic
treatment. Remainer of
pond 5 to 8 ft.
Primary
6
Greater depth
if aeration or
mixing is
incorporated.
Min operating
depth 3
Min of 18 in
for sludge.
TR-16
See end of table
Controlled
Discharge
ft
NA
NA
NA
TR-16
See end of table
Aerated
Cell
ft
Not less
than 7
Secondary aerated
ponds 3-5 ft
10-15
TR-16
See end of table
Anaerobic
Cell
NA
NA
NA
TR-16
See end of table
NA= Not available
-------
A-l (Corrt)
State
Virginia
Washington
West Virginia
Wsconsin
Wyoming
Ten-State Standards
1997 Edition
TR-16 Guides for
Design of Wastewater
Treatment Works
1998 Edition
Minimum Hydraulic Residence Time (HRT)
Controlled
Discharge and
Non -discharge
NA
NA
Ten State
NA
Atleast180d
between 2' depth
and max depth
180
Between 2-foot
and maximum
operating depth.
Facultative
Flow-Through
days
45 based on 4-ft
operational level.
Sludge storage based
20-year design life.
NA
150
180
90-120
90-120
Aerated
days
NA
NA
B
K(IOO-E)
t = HRT
E = BOD removal, %
K = reaction coef. Base e
K = 0.5 at 20 °C
KT = K20(1.07)(T-20)
Min settling = 6
Primary Cell
Complete Mix Not < 1.5
Partial Mix Not < 7
Secondary cells shall
increase overall HRT
to 30
E
2.3*,(100- E)
t = HRT, d
E = % BOD5 removed
k, = reaction rate, d "1
kT = 0.12/dat20 °C
kT = 0.06/d at 1 °C
Partial Mix
E
1 /I f\f\ J-1 ~\
K e i^i. uu — h, )
t = HRT, d
E = % BOD removed
ke = reaction rate, base e, d "1
kT = 0.28/d at 20 °C
kT = 0.14/dat10 °C
For three cell facility suggested
Depth Requirements
Facultative
Cell
ft
Min operating
depth 2
Max operating
depth 5
excluding sludge
storage.
NA
Max 6
Min Operting 2
6
Max 6' Primary
Min 2'
Greater Depths
allowed in
subsequent
cells
3 ft minimum oprating depth.
5ft maximum
Controlled
Discharge
ft
NA
NA
Ten State
NA
Max 6' Primary
Min 2'
Greater Depths
allowed in
subsequent
cells
3 ft minimum oprating depth.
5ft maximum
Aerated
Cell
ft
NA
NA
15
Minimum
Operating 6
4-15
10-15
Partial Mix
10-20
Anaerobic
Cell
NA
NA
NA
NA
NA
NA
NA= Not available
-------
A-l (Corrt)
State
Minimum Hydraulic Residence Time (HRT)
Controlled
Discharge and
Non-discharge
Facultative
Flow-Through
days
Aerated
days
keat10°C
First cell -0.1 4
Second cell - 0.06
Third cell - 0.02
Complete Mix
7-20
Depth Requirements
Facultative
Cell
ft
Controlled
Discharge
ft
Aerated
Cell
ft
Anaerobic
Cell
NA= Not available
-------
Table A-2. Sealing, Point of Discharge, N-Removed, P. Removal, Drawoff, Multi-level Required, Comments
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Pond Bottom
Sealing
Ten State
Required
seepage must
not exceed 1/32
in/d. If not obtained
in natural soil, must
use native clays,
soil cement,
asphalt or
synthetic liners.
Point of Discharge
Primary
Ten State
NA
Aerated
Ten State
NA
Nitrogen
Removal
Required
Ten State
Where
applicable
Phosphorus
Removal
Required
Ten State
No
Multi-level
Drawoff
Required
NA
Required
Comments
NA = Not applicable
A-9
-------
Table A-2 (cont)
State
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Minnesota
54 pg document
with details for
all aspects of
lagoon systems.
Mississippi
Pond Bottom
Sealing
TR-16
See end of table
Ten State
Required
Maximum seepage rate
must not exceed
500 gallons per acre
per day. Sensitive
aquifers or near TMDL
streams may require
considerably lower
seepage rate.
After 4/1 5/07, rate
shall be no more than
0.125 inches/day.
Testing required after
five years of operation.
Required
Required
Water loss shall not
exceed 500 gpd/ac at
head equal to max
operating depth.
Point of Discharge
Primary
TR-16
See end of table
Ten State
NA
Primary Cells
Influent Line
terminates
at midpoint
of width and
approx. 2/3 length
from outlet
Primary cells
terminate near center
of cell.
Aerated
TR-16
See end of
table
Ten State
NA
Multiple
inlets
required
Distribute
flow and load
in mixing zone.
Nitrogen
Removal
Required
TR-16
See end of
table
Ten State
Where
applicable
Ten State
NA
Phosphorus
Removal
Required
TR-16
See end of
table
NA
Where
applicable
NA
NA
Multi-level
Drawoff
Required
TR-16
See end of table
Ten State
NA
Required
Recommended
Comments
TR-16
See end of table
Controlled discharge lagoons
allowed.
NA = Not applicable
A-10
-------
Table A-2 (cont)
State
Missouri
Montana
Nebraska
Nevada
Pond Bottom
Sealing
Required
Max seepage
6 in/year
Required
Maximum seepage rate
must not exceed
1/8in./d
Required
Point of Discharge
Primary
Midpoint of width, at
approx. 1 0 ft from toe
of dike and as far as
possible from outlet
structure.
Inlets to regular shaped
cells terminate at center
of cell. Rectangular cells
inlets terminate at approx.
one-third the length from
upstream end of cell.
Cells without outlet
discharge at center of
cell. Multiple inlets
should be considered
for large cells.
Multiple inlets
and outlets
recommended
Aerated
Distribute load
within mixing
zone.
NA
Multiple inlets
and outlets
recommended
Nitrogen
Removal
Required
NA
See HRT
Where
applicable
Phosphorus
Removal
Required
NA
NA
NA
Multi-level
Drawoff
Required
Must
Consider
Recommended
Recommended
Comments
Total Retention Ponds
1 primary, 15-35 Ibs/ac-d,
max depth 6 ft, t = 40-80 d,
1 secondary, max depth 8 ft,
Complete retention lagoons
allowed. A minimum of two
cells must be provided with at
least one pond having capacity
to assure adequate depth.
Lemna ponds considered for
final pond.
NA = Not applicable
A-ll
-------
Table A-2 (cont)
State
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Pond Bottom
Sealing
TR-16
See end of table
Required
Required
compacted clay,
bentonite, or other
approved material.
Point of Discharge
Primary
TR-16
See end of table
Multiple inlets
and outlets
encouraged
Primary Cells
Essentially center of
cell.
Aerated
TR-16
See end of
table
Multiple inlets
and outlets
encouraged
NA
Nitrogen
Removal
Required
TR-16
See end of
table
NA
NA
Phosphorus
Removal
Required
TR-16
See end of
table
NA
NA
Multi-level
Drawoff
Required
TR-16
See end of table
Multiple
outlets
encouraged
NA
Comments
TR-16
See end of table
Hydrograph control release
lagoons permissible
L:W, 3:1 Facultative
NA = Not applicable
A-12
-------
Table A-2 (cont)
State
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Pond Bottom
Sealing
Ten State
Average seepage rate
less than 1/8 per day,
corrected for evaporation
and precipitation.
Required
On-site soils, bentonite,
or other synthetic liners.
Coefficient of permeability
of sides and bottom will
not exceed 1 x 1 07
centimeters per second.
Flexible membrane liners
shall have a minimum
thickness of 0.030 in.
TR-16
See end of table
Required
Seepage rate for
primary cell shall not
exceed 1/16 in/d.
Allowable seepage
1/8 in/d for cells in
series following
Point of Discharge
Primary
Ten State
Primary cells inlets
located near center of
lagoon.
Secondary cells inlets
located at or near
shoreline.
At mid-point of width
and at approximately
two-thirds of length away
from outlet structure.
Multi-influent discharge
points for primary cells
20 acres or larger
TR-16
See end of table
Influent line should
terminate at approx.
1/3 of length upstream
end of cell.
At approx. mid-point
in cells without outlet.
Aerated
Ten State
NA
Distribute load
within mixing
zone.
TR-16
See end of
table
To active
mixing
Nitrogen
Removal
Required
Ten State
NA
TR-16
See end of
table
NA
Phosphorus
Removal
Required
Ten State
NA
TR-16
See end of
table
NA
Multi-level
Drawoff
Required
Required
Outlet provide
for surface or
subsurface
withdrawals
Surface skimming
baffles shall be
provided ahead
of surface
overflow structures.
Recommended for
deep ponds where
stratification may
occur. A minimum
of three discharge
points are required.
TR-16
See end of table
Recomended
Comments
Aerobic ponds 12 to 18 in. deep.
Algae production main function.
Rectangular ponds with L:W
3:1 most desirable.
TR-16
See end of table
NA = Not applicable
A-13
-------
Table A-2 (cont)
State
Tennessee
Texas
Utah
Pond Bottom
Sealing
primary.
Required
Earth liners, bentonite,
synthetic membrane
liners. Seepage rate
shall not be greater
than 1/4in/d.
Required
Clay soils meeting certain
specifications are
allowable.
Membrane lining
minimum thichness
20 mils
Required
Earth liners, bentonite,
synthetic membrane
liners. Seepage rate
shall not be greater
than 1.0 x 1 06 cm/sec.
Point of Discharge
Primary
NA
NA
In center of round or
square cell or at
third point farthest
from outlet structure in
rectangular cell.
Aerated
NA
NA
At point where
load is
distributed
within mixing
zone.
Multiple inlets
considered in
diffused air
system.
Nitrogen
Removal
Required
NA
NA
NA
Phosphorus
Removal
Required
NA
NA
NA
Multi-level
Drawoff
Required
Multiple inlets
for ponds larger
than 10 ac.
Required
multiple inlets
and outlets with
baffling.
Multiple inlets
to primary cell of
20 ac
Comments
Hydrograph controlled
release lagoons allowed.
Recirculation should be
considered.
L:W of ponds 3:1 or 4:1
Total containment lagoons
allowed. Same requirements
for facultative apply with
exception of discharge.
NA = Not applicable
A-14
-------
Table A-2 (cont)
State
Vermont
Virginia
Washington
West Virginia
Wisconsin
Pond Bottom
Sealing
TR-16
See end of table
Required
Natural soil, enhanced
soil (bentonite, cement,
etc., synthetic materials.
Seepage rate <3 cm/yr.
Required
Double liner with leak
detection required, and
single liner with leak
detection required.
Required
Natural soil, enhanced
soil (bentonite, cement,
etc.,) synthetic materials.
Seepage rate
1 000 gal/ac-d
Point of Discharge
Primary
TR-16
See end of table
Round or square
ponds acceptable, but
rectangular with
LWup to 10:1 most
desirable.
Influent and effluent
shall be located as far
apart as possible
along flow path.
NA
Round, square or
rectangular allowed.
Length not to exceed
3 times width.
Circular lagoons
discharge to center.
Rectangular or square
discharge to first one
third of lagoon length.
Aerated
TR-16
See end of
table
NA
NA
NA
Nitrogen
Removal
Required
TR-16
See end of
table
NA
Aeration
must be
provided for
nitrification.
NA
Phosphorus
Removal
Required
TR-16
See end of
table
NA
NA
NA
Multi-level
Drawoff
Required
TR-16
See end of table
Withdrawal points
located at 0.75 ft
to 2 ft below water
irrespective of
pond depth.
Lowest draw-off
shall be 12 in.
off bottom.
NA
Required
Multi-valved
drawoff lines.
Comments
TR-16
See end of table
Total containment lagoons
allowed. Design case is "wet"
year (1 year in 10 recurrence
interval).
NA = Not applicable
A-15
-------
Table A-2 (cont)
State
Wyoming
Ten-State Standards
1997 Edition
TR-16 Guides for
Design of Wastewater
Treatment Works
1998 Edition
Pond Bottom
Sealing
Must guarantee no
threat to groundwater.
Permeability of
1 0"7 cm/sec or less
required without
guarantee.
Required
soils, bentonite
or synthetic
liners
Required
Soils, bentonite
or Synthetic
Liners
Leakage should be
less than 500 gpd/ac.
Sealed so that seepage
loss is as low as
possible.
Point of Discharge
Primary
Fac Primary Cell
Inlet shall terminate from
outlet at least equal to
greater than 2/3 the
longest dimension.
Primary Cells
Influent line
terminates
at midpoint
of width and
approx. 2/3 length
from outlet.
NA
Aerated
Aerated inlet
shall terminate
in mixing
zone.
Distribute
load within
mixing
zone.
Distribute
load within
mixing
zone.
Nitrogen
Removal
Required
Facultative
t = 1 80 days
Aerated
t = 1 60 days
NA
NA
Phosphorus
Removal
Required
Chemical
treatment
required.
NA
NA
Multi-level
Drawoff
Required
Required in final
cell. At least one
located at
two-foot level.
NA
Should be
provided.
In deeper ponds
minimum of three
withdrawal pipes
at different
elevations should
be installed.
Comments
Total containment lagoons
allowed. BOD5 loading shall
not exceed 14lb/ac-d.
Rectangular cells shall have a
maximum L:Wof5:1.
NA
Screening and/or comminution
should precede wastewater
treatment ponds.
Hydrograph release allowed.
Treated effluent should be
recirculated to primary cell.
Anaerobic lagoons typical
HRT 20-50 days.
NA = Not applicable
A-16
-------
APPENDIX B
Summary of Pond Characteristics
-------
APPENDIX B
Summary of Pond Characteristics
Description
Common
Modifications
FACULTATIVE
Earthen impoundment less
than 2.5m deep. O2"
saturated water at surface
supports aerobic
biodegradation. Aerobic and
anaerobic degradation
processes occur mid-depth.
Bottom anaerobic water
supports methanogenesis.
Performance depends on O2
from algae.
Controlled Discharge -
during winter or peak algal
growth periods in summer
Hydrograph Controlled
Release - discharge when
conditions in the receiving
stream are suitable.
Plastic Curtains - used as
baffles to divide lagoon into
cells.
Floating Plastic Grids -
supporting the Growth of
plants to reduce algal growth.
AEROBIC
Partial Mix
Earthen
impoundment in
which aeration
(mechanical surface
mixing or submerged
diffusion) is used to
meet O2 needs. No
solids suspended.
Performance
depends on aeration.
Plastic curtains -
with floats, anchored
to bottom dividing
lagoons into multiple
cells to improve
hydraulic conditions.
Submerged
diffusers -
suspended from
flexible floating
booms which move in
a cyclic pattern
during aeration
activity. Treats a
larger volume with
Complete Mix
Earthen
impoundment in
which mechanical
mixing introduces
air for BOD removal
and to suspend
solids.
Performance
depends on
aeration.
High Performance
BIOLAC™
Nitrogen Removal
Nitrification and de-
nitrification.
High Performance
Dual-power, multi-
cellular systems
(DPMC) designed for
maximum BOD
conversion efficiency.
None known at this
time.
ANAEROBIC
A deep earthen basin not
mixed or aerated. The
organic load exceeds any
naturally occurring
dissolved O2 Degradation
takes place anaerobically.
Placement - in front of
facultative lagoon as part
of design or retrofitted to
existing system.
B-l
-------
Performance
Costs
FACULTATIVE
BOD: to <30mg/L 95% of the
time.
TSS:to<100mg/L.
NH3: up to 90% removal in
summer.
P: up to 50% removal.
Pathogen and fecal
coliform removal: varies
with temperature and
detention time.
See Ch. 8
each aeration line.
Effluent
recirculation -within
the system to
enhance oxygen
levels.
AEROBIC
Partial Mix
BOD: to <30 mg/L
95% of the time with
settling at end of
system.
TSS: to < 60 mg/L.
NH 3: nitrified during
summer.
See Ch. 8
Complete Mix
Not available.
See Ch. 8
High Performance
TSS:to<15mg/L.
NH3: 90%removal.
See Ch. 8
ANAEROBIC
BOD: reduced by 60%;
less in cold climates.
See Ch. 8
B-2
-------
FACULTATIVE
AEROBIC
Partial Mix
Complete Mix
High Performance
ANAEROBIC
Applicability
Raw municipal wastewater
effluent from
Primary treatment
Trickling filters
Aerated ponds
Anaerobic ponds
Biodegradable
industrial
wastewater
Municipal and industrial
wastewaters of low to
medium strength.
Municipal and
industrial applications
where space is limited.
Raw, screened or
primary settled
municipal wastewater.
Biodegradable
industrial wastewaters.
Screened municipal
and industrial
wastewater in areas
where space is
limited.
Pretreatment of
municipal and
industrial wastewater
with high organic
loading.
Advantages
Removes BOD, TSS,
bacteria and NH3
Low energy requirements.
Easy to operate.
Smaller plant footprint
than facultative ponds.
Discharge acceptable
under all climatic
conditions.
Small footprint.
Discharge acceptable
under all conditions.
No ice formation in
cold weather.
Small footprint
Removes BOD,
TSS and bacteria
when used with a
settling basin
Effective at
converting NH3 to
N03-.
Treats high organic
loadings.
Produces methane for
energy recovery.
Produces less sludge
than other processes.
Low energy
requirements.
Disadvantages
Higher sludge accumulation
in cold climates; removal
required.
Mosquitoes, other insect
vectors, and burrowing
animals may be a problem.
Odors can occur with spring
and fall pond turnover.
Larger footprint.
Difficult to control or predict
ammonia levels in winter.
Requires energy input.
Not as effective at
removing N and P as
facultative ponds.
Ice formation.
Mosquitoes and other
vectors.
Sludge removal
required.
Routine maintenance
and cleaning required to
maintain design aeration
rates.
Agitation must be
sufficient to suspend
all solids.
High energy
requirement for
aeration and solids
suspension.
Increased solids
disposal.
Settling basin needed
to facilitate solids
separation.
Solids removal is
greater than other
options.
High energy
requirements.
Relatively little
experience with this
type of system.
Large footprint.
Odors.
Long retention times.
Process may not be
effective in colder
climates.
B-3
-------
Design
Considerations
and Criteria
FACULTATIVE
Systems with at least three cell in
series are recommended.
Inlet and outlet structure design
should maximize volume to avoid
short circuiting.
Typical criteria:
Loading Rate
22-67kg BOD5/ha-d
Detention Time
25-1 80 d.
Depth 1.5m -2. 5m.
Surface Area 4-60 ha.
Average organic loading rate and
detention time relative
temperature:
T,°C BOD,
kg/ha/d
>15 18-36
0-10 9-18
<0 4.5-9
to ambient
tdet,d
?
?
120-180
Maximum loading rate for the 1st
cell in multi-cell systems relative to
temperature:
T, °C BOD,
kg/ha/d
>15 40
<0 16
Lining may be required.
AEROBIC
Partial Mix
1 .8 - 6 m (6 to 20 ft), 3
m(10ft).
Submerged diffusion 3.7
to 4 kg O2/kW-hour (6 to
6.5 Ibs O2/hphour).
Mechanical surface
aerators 1.5 to 2.1 kg
02/kW-hour (2.5 to 3.5
Ibs O2/hp-hour).
System should have at
least three lined cells in
series depending on soil
conditions.
Detention Times 10 -
30d [20 days most
common].
The design of aerated
lagoons for BOD
removal is based on
first-order kinetics and
the complete mix
hydraulics model. Even
though the system is not
completely mixed.
p
rectangular with a 3:1 or
4:1 length to width ratio
Complete Mix
Three cell systems
are recommended.
Agitation must be
sufficient to
suspend all solids.
Detention time: 1.5
<3d.
The design for
BOD removal is
based on first-
order kinetics and
the complete mix
hydraulics model.
High
Performance
> 6W/mJ needed
for primary basin,
1 .8W/m3 for
settling basin.
Detention Time
<1.5d.
Not appropriate
for
CBOD5<100mg/L
ANAEROBIC
BOD loading rate:
0.04 -0.30 kg/m3/d
(2.5- 18.7lb/103
ft3/d).
Detention time: 1-
50d.
Depth: 2.4-6m
[Deeper is better.]
Surface area: 0.2-0.8
ha.
Minimum freeboard:
0.9m.
Liners recommended
to prevent seepage.
Surface runoff should
be diverted from
lagoon surface.
B-4
-------
FACULTATIVE
AEROBIC
Partial Mix
Complete Mix
ANAEROBIC
Design Models
and Equations
[See Appendix
C for example
calculations]
Areal Loading Rate Method -
Simple to use when impoundment
will not be mixed.
Gloyna Model -Assumes a BOD5
removal efficiency of 89-90%.
Complete Mix Kinetics - Marias
and Shaw model (also assumes first
order degradation kinetics).
[NOTE: This model is not widely
accepted as a complete mix kinetic
model; assumptions have not
proven to be valid for facultative
ponds.]
Plug Flow
Intermediate Flow (between
complete mix and plug flow) -
Wehner-Wilhlem Equation accounts
for both biodegradation kinetics and
dispersion.
Use complete mix
kinetic model.
Use complete
mix kinetics
model.
Design based on
volumetric loading
rate, water
temperature and
hydraulic detention
time.
See Advanced
Integrated Pond
System Design
(Oswald 1999).
B-5
-------
APPENDIX C
Design Examples
C-1
-------
APPENDIX C
DESIGN EXAMPLES
FROM CHAPTER 3 DESIGN OF MUNICIPAL WASTEWATER POND SYSTEMS
Example 3-1. Design of Anaerobic Pond Based on Volume and Per Capita (Oswald, 1996)
Design Flow Rate = 947 m3/d
Influent Ultimate BOD5 (Co) = 400 mg/L
Effluent Ultimate BOD5 (Q = 50 mg/L
Sewered Population = 6000 people
Maximum Bottom Temperature in Local Waters = 20 °C
Temperature of Pond Water at Bottom of Pond = 10 °C
1. Calculate the BOD5 Loading
BOD5 Loading = Influent BOD5 x Flow Rate/1000 378.8 kg/d
2. Design the Anaerobic Pond (Fermentation Pits)
Except for systems with flows less than 200m3/day, always use two ponds so that one will be
available for removing sludge when pond is filled. Surface area of anaerobic pond should be
limited to 1000 m2 and made as deep as possible to avoid turnover with oxygen intrusion.
Minimum pit depth should be 4 m.
Number of Anaerobic Ponds in Parallel = minimum of two ponds = 2
BOD5 Loading on Single Pond = 189.4 kg/d
First Size Pond on Basis of Load per Unit Volume
Load per Unit Volume (varies with temperature of water) 0.189 kg/m3/d
Volume in One Pond = 1002.7 m3
HRT in Ponds = 2.12 d
Pond Depth = minimum of four meters = 4m
Pond Surface Area (assuming vertical walls) = 250.7 m2
Maximum Pond Surface Area = 1000 m2; No. of Ponds = 0.25
Round to Next Largest Number of Ponds = 1
Overflow Rate in Ponds = total surface area/total flow rate = 1.89 m/day
Overflow rates of less than 1.5 m/day should retain parasite eggs and other particles as small as
20 |i, which includes all but the smallest parasite eggs (ova). Size of pond should be increased
to reduce overflow rate to 1.5 m/day.
Check Pond Volume per Capita
C-2
-------
Total Volume in Ponds = total BOD5 loading/loading rate 2005 m3
Pond Volume/Capita = total volume/population 0.33 nrVcap
Pond Volume/Capita should be greater than 0.0566 nrVperson as used in conventional separate
digesters. When pit volume/capita exceeds that amount, fermentation can go to completion
with only grit and refractory organics left to accumulate.
Example 3-2. Anaerobic Pond Design Based on Volumetric Loading or Detention Times
(Crites et al., 2006)
Based on Volumetric Loading or HRT(WHO, 1987).
Design Based on Volumetric Loading, HRT and Climate Temperature.
Temperature, °C
10
10- 15
15-20
20-25
25-30
Detention Time, day
5
4-5
2-3
1 -2
1 -2
BOD5 Reduction, %
0- 10
30-40
40-50
40-60
60-80
Climates with temperatures exceeding 22 °C:
Volumetric Loading BOD5/m3/d
HRT approximately
Depth
Cold Climates : 50 percent estimated reduction in BOD5
Volumetric Loading BOD5/m3/d
HRT approximately
Design
Input
Flow, m3/day
Influent BOD5, mg/L
Temperature, °C
Depth, m
Length to Width Ratio,
Volumetric Loading, BODs/mVd
HRT, d
Slope
Output-Volumetric Loading
Volume, m3
Length, m
Width, m
Output-Detention Time
18925
250
10
3
1
60
5
3
78854
171
171
up to 300 g
5 days
2.5-5m
as low as 40g
50 days
C-3
-------
Volume, m3 94625
Length, m 187
Width, m 187
Detention Time, days 5
Example 3-3. Design of Facultative Pond with Frequently Used Formulations
Wehner-Wilhelm Equation
The Wehner-Wilhelm Equation is used when designing for conditions between ideal plug flow
and complete mix.
Ce = 4ae1/(2D)_
Co (l+a)2(e a/2D) - (1-a)2 (e -a/2D)
where:
Co = influent BOD concentration, mg/L
Ce = effluent BOD concentration, mg/L
e = base of natural logarithms, 2.7183
a = (1 + 4M))°'5
k = 1 st order reaction rate constant/d
t = HRT, d
D = dimensionless dispersion number
D = H/vL = Ht/L2
H= axial dispersion coefficient, area per unit time
v = fluid velocity, length per unit time
L = length of travel path of a typical particle
Dispersion numbers measured in wastewater ponds range from 0.1 to 2.0 with most values less
than 1 .0. The selection of a value for D can dramatically affect the detention time required to
produce a given quality effluent. The selection of a design value for k can have an equal effect.
A modified form of the chart prepared by Thirumurthi (1974) is shown to facilitate solving for
D:
(LdJ4S
where:
D = dimensionless dispersion number
t =HRT, d
v = kinematic viscosity, m2/d
d = liquid depth of pond, m
W= width of pond, m
L = length of pond, m
C-4
-------
0 4-
kt
Wehner-Wilhelm Equation (modified from Thirumuthi, 1974
The variation of the reaction rate constant k with the water temperature is determined by the
equation:
T-20
where:
= k20(1.09)
kT = reaction rate at water temperature T/d
20
= reaction rate at 20 C = 0.1 5/d
T= operating water temperature, C
Design a facultative pond system using the (1) Wehner-Wilhelm Equation surface loading
method; (2) the complete mix equation developed in South Africa; (3) and the plug flow
equation for the following environmental conditions and wastewater characteristics.
Flow rate = Q =
Influent BOD5, C0 =
Required effluent BODs, Ce=
Operating water temperature =
Reaction Rate kT at 20 °C =
Calculate kt= reaction rate at water temperature T I/day.
First Iteration: Solve for "a" first.
tj= Assumed HRT =
D = Assumed dimensionless dispersion # =
3785 m3/d (1MGD)
200 mg/L
30mg/L
5°C
0.15/d
Ł,= 0.04118
53.9 d
0.1
C-5
-------
or7=1.37399
Solve the Wehner-Wilhelm equation to determine if the two sides are equal.
Calculate the dimensions of the pond.
LtoW= 3
v = Kinematic Viscosity = 0.1312 m2/day
t = Optimum HRT (final iteration) 53.9 days
d = Liquid depth of pond = 2.45 m (8.0379 ft
Volume = 204012 m3 (53.9 MG)
Divide the flow into streams.
Number of Streams = 1
Volume in one stream = 204012m3
Divide volume into 3 equal volumes
Volume in one pond is = 68004 m3 (18.0 MG)
Surface Area of each is = 2.78 m2 (6.9 acres)
Theoretical HRT in each pond is = 53.9 days
Surface Area = L x W
W= 96.2m2(315.6ft2)
L = 288.6 m2 (946.7 ft2)
Approximately measured HRT is a value of 1/2 the theoretical value id = 26.95 days.
The following equation was developed by Polprasert and Bhattarai (1985) to improve D value
accuracy for the Wehner-Wilhelm Equation based on a measured HRT.
With measured HRT (assumed to be 1/2) and dimensions of one cell, the accurate dispersion
number is
td= 26.95 d
D = [0.184 ((txv (fF+2d))0'489 x W1-511] / (Lx a)1'489
Z> = 0.185
With theoretical detention time, the dispersion number is
td= 53.9 d
D = 0.2597
The dimensions of each cell using theoretical HRT and initial dispersion number
C-6
-------
L to W= 3
W= 96.19m (315.6 ft)
L = 288.57 m (946.7 ft)
Calculate the effluent BOD5 concentration using the theoretical HRT as the Wehner-Wilhelm
Equation was developed based on the theoretical value. Total HRT is used because the equation
represents the entire system.
D = 0.2597
03=1374
Ce = [4 a x e l/(2D)] I [ (1 + a )2 ( O -(1 - a)2 (e^20) ] / C0
Ce=30mg/L
Organic Loading Method
Depth = 2.45 m (8.04 ft)
Organic Load = BOD5 x g/1000 = 757 kg/d (1669 Ibs/d)
Organic Loading Rate = kg/ha (lbs/ac)/d = 27(60) 18(40) 14(30) 5(10)
Area Required = ha (ac) = 11(28) 17(42) 23(56) 68(167)
Volume = m3= 275774 413660 551547 1654641
Area or volume divided into three or four cells in series.
Complete Mix Model
n
t = —
Flow rate = Q = 3785 m3/d (1.00 MOD)
Influent BOD5 = 200 mg/L
Effluent BOD5 = 30 mg/L
Influent SS = 150 mg/L
No. of cells in series = 3
Water temperature = 5 °C
Reaction rate at 35 °C 0.5/d
Temp. corr. coef. 1.085/ d
Kt = rate @ t 0.043/d
HRT= 61.17d
Volume = 231533m3 (61.16 MG)
Depth = 2.45 m (8 ft)
Surface Area = 9.45 ha (23.4 ac)
Gloyna Method
V= 0.035g (BOD5) (
C-7
-------
where:
Q = Flow Rate = 3785 m3/d (0.999360 MG/D
BOD5 = 200 mg/L
LIGHT= 200Langleys
Temp. coef. = 1.099
Temperature = 5 °C
Volume = 255334 m3 (67.45 MG)
Predicted Effluent BOD5 = 80 to 90 percent reduction = 20-40 mg/L
Total volume will be divided into three or four equal cells.
Plug Flow Model
C^_e , = lnfe-U_
c0 exp p (CO)KP
where:
C0 = Influent BOD5 = 200 mg/L
Ce = Effluent BOD5 = 30 mg/L
kp20 = Plug flow reaction rate at 20 °C = 0.07 /d
HRT = 98.7 d
0 = Temperature Correction Factor = 1.09
T = Water temperature = 50 °C
kpT = Plug flow reaction rate at T°C = 0.01922 /d
With Influent and Effluent specified calculate HRT.
t= 98.7 d
With Influent and hydraulic detention time specified calculate Effluent.
Ce = 30 mg/L
Volume = Q x t = 373646 m3 (98 MG)
Surface Area = F/depth = 152508 m2 (37.7ac)
Summary of Results
Method
Wehner-Wilhelm
Surface Area*
Complete mix
Gloyna
Plug flow
HRT
d
53.9
145.7
61.2
67.5
98.7
Volume
m3
204012
551547
231533
255334
373646
Surface area
m2
83270
225124
94503
104218
152508
* Values based on surface loading rate of (34 kg/ha/d (30 Ibs/ac/d). At 66 kg/ha/d (60 Ibs/ac/d),
the results would be close to the others but a reliable effluent BOD5 of 30 mg/L might not be as
attainable.
C-8
-------
Example 3-4. Detention Times in Partial Mix Aerated Ponds
Compare detention times for the same BODs removal levels in partial mix aerated ponds having
one to
five cells.
Assume
C0 = 200 mg/L
Ł = 0.28/d
Tw = 20 °C
1. Solve the equation for a single cell system:
cn
t = -
1
0.28
f = 20.2d
'200V
^o"J
2. Similarly, when:
n = 2
n = 3
n = 4
n = 5
t = 11 days
t = 9.4 days
t= 8.7 days
t= 8.2 days
3. Continuing to increase n will result in the HRT being equal to the HRT in a plug flow reactor.
It can be seen from the tabulation above that the advantages diminish after the third or fourth
cell.
Example 3-5. Design a Four-Cell Partial Mix Aerated Pond having Two Trains for BODs
Removal
Design a four-cell partial mix aerated pond with two trains to remove BODs for the following
environmental conditions and wastewater characteristics:
Q =
c0 =
Ce from fourth cell
k20 = 0.276 d
Temperature =
Elevation =
Depth =
Solution:
Flow Rate = Q =
Influent BOD5 =
568 m7d
220 mg/L
1136m7d(0.3MGD)
220 mg/L
30mg/L
8 °C (winter), = 25
50m (164 ft)
4m (13.1 ft)
'C (summer)
C-9
-------
Influent TSS = 200 mg/L
Total N = 30 mg/L
Total P= 10 mg/L
Reaction rate at 20 °C = 0.276/d
Influent temperature °C = 15 °C
Summer air temp. °C = Ta 25 °C
Winter air temp: °C = Ta 8 °C
Temperature correction coef. = 1.09
Surface Elevation = 50m
Minimum DO = 2 mg/L
Depth = 4m
Length to Width Ratio = 2
Side slope = 3
1 . Start solution by assuming winter pond temperature and determine volume of Cell 1 in the
pond system.
Assume influent temperature 12.06 °C
Correct reaction rate for temperature kT = k2d(l .036)(r"20)
HRTinCelll= 3.60 d
Effluent BOD5 in Cell 1 = C0/(l + kt) 125.69 mg/L
Volume in Cell 1= 2044.80 m3
2. Calculate dimensions of Cell 1 at water surface and the surface area.
Depth = 4m
Width = 24.51m
Length = 49.02 m
Surface area in Cell 1 = 1201.61 m2 (0.134 ac)
3. Check pond temperature using cell area calculated above and equation shown below.
Cell 1 Tw = (AfTa + QTi)l(Af+ Q) 11.4 °C
If calculated Tw differs from assumed water temperature, iteration is necessary.
Add a freeboard 0.90 m
Dimensions at top of dike in Cell 1
W top of dike = 29.91m
L top of dike = 54.42 m
4. For second cell
Influent temperature 1 1 .4 °C
Correct reaction rate for temperature: fa = #20(1 .09)(r"20)
C-10
-------
kT = 0.20/d
Influent BOD5 in Cell 2 = 125.69 mg/L
HRTinCell2= 3.50 d
Effluent BOD5 Cell 2 = 73.39 mg/L
Volume in Cell 2 = 1988.00m3
Calculate dimensions of Cell 2 at water surface and the surface area.
Depth = 4.00 m
Width = 24.28 m
Length = 48.56m
Area= 1179.11 m2 (0.134 ac)
Cell 2 Tw = (AjTa + QT,)/(Af+ Q) 9.67 °C
Add a freeboard 0.9 m
Dimensions at top of dike in Cell 2
W top of dike = 29.68m
L top of dike = 53.96m
5. For third cell
Influent temperature 9.7 °C
kT = 0.l9/d
Influent BOD5 to Cell 3 = 73.39 mg/L
HRT in Cell 3 = 3d
Effluent BOD5 in Cell 3 = 46.61 mg/L
Volume in Cell 3 = 1704.00 m3
Calculate dimensions of Cell 3 at water surface and the surface area.
Depth = 4.00 m
Width = 23.07m
Length = 46.14m
Area= 1064.56 m2 (0.134 ac)
Cell 3 Tw = (AjTa + QT,y(Af+ Q) 8.86 °C
Add a freeboard 0.90 m
Dimensions at top of dike in Cell 3
W top of dike = 28.47m
L top of dike = 51.54m
6. For fourth cell influent temperature 8.86°C
kT = 0.l9/d
Influent BOD5 to Cell 4 = 46.61 mg/L
HRT in Cell 4 = 3d
Effluent BOD5 in Cell 4 = 29.91 mg/L
Volume in Cell 4 = 1704.00m3
Calculate dimensions of Cell 4 at water surface and the surface area.
C-11
-------
Depth = 4.00 m
Width = 23.07m
Length = 46.14m
Area = 1064.56 m2(0.134 ac)
Cell 4 Tw = (AJTa + QT,)/(Af+ Q) 8.44 °C
Add a freeboard 0.90 m
Dimensions at top of dike
W top of dike = 28.47m
L top of dike = 51.54m
7. Determine the oxygen requirements for pond system based on organic loading and Water
Temperature. Maximum oxygen requirements will occur during the summer months.
Tw Cell 1 = (AJTa + QTj)/(Af+ Q) 20.1 °C
Tw Cell 2 = 22.6 °C
TwCell3= 23.8°C
Tw Cell 4 = 24.4 °C
Organic load (OL) in the influent wastewater
OL on Cell 1 = C0 x Q 5.21 kg/hr
(Calculate effluent BOD5 from first cell using equations below at Tw for summer.)
kTw = k20 x (temp. coef)(rw"20) 0.28/d
Ci= Co/[(kt) + 1] 110.08 mg/L
Winter = 125.69 mg/L
OL on Cell 2 = Q x d 2.61 kg/hr
kTw = k20 x (temp. coef.)(Tw-20) 0.30/d
C2 = Cil[(kt) + 1] 53.45 mg/L
Winter = 73.39 mg/L
OL on Cell 3 = C2 x Q 1.26 kg/hr
*TV = k20 x (temp. coef.)(rw"20) 0.32 /d
Winter = 46.61 mg/L
OL on Cell 4 = C3*Q 0.65 kg/hr
kTw = k20 x (temp. coef.)(rw"20) 0.32/d
CĄ = C3l[(kf) + 1 ] 13.97 mg/L
Winter = 29.91 mg/L
DO is assumed to be a multiple of organic loading. Multiplication factor (MF) = 1.50
DO in Cell l = OLlxMF= 7.81 kg/hr
DO in Cell 2 = OL2 x MF = 3.91
DO in Cell 3 = OL3 x MF = 1.90
DO in Cell 4 = OL4 x MF = 0.97
C-12
-------
8. Use following equation to calculate equivalent 02 transfer.
N = NDO/a[(C,m-CLyCs\(tsmp factor)(rw-20))
NOD = DO in various cells
Csw = bx Css x P
6 = 0.90
P = ratio of barometric pressure at pond site to pressure at sea level = 0.80
Cell 1 Tap water O2 sat. value Css = 9.15 mg/L
Cell 2 = 8.74 mg/L
Cell 3 = 8.56 mg/L
Cell 4 = 8.46 mg/L
Cell 1 Csw = 6.59 mg/L
Cell 2 Csw = 6.29 mg/L
Cell3C™= 6.16 mg/L
Cell 4 C™ = 6.09 mg/L
a = O2 transfer in wastewater/ O2 transfer in tap water 0.90
CL = min. 02 cone, to be maintained in wastewater 2.00 mg/L
Cs = O2 sat. value of tap water at 20 °C and 1 atm. 9.17 mg/L
Temp, factor = 1.025
M= 17.29kg/hr
N2 = 8.70
N3 = 4.23
N4= 2.18
9. Evaluate surface and diffused air aeration equipment to satisfy oxygen requirement only.
Power for surface aerators (approx.) 1.90 kg 02/kWh
1.40
Power for diffused air (approx.) 2.70
2.00
Total power for surface aeration
Cell 1 9.10kW 12.35 hp
Cell 2 4.58 6.21
Cell 3 2.23 2.99
Cell 4 1.15 1.54
Total power for diffused aeration
Cell 1 6.40 kW 8.64 hp
Cell 2 3.22 4.35
Cell3 1.57 2.12
Cell 4 0.81 1.09
C-13
-------
These surface and diffused aerator power requirements must be corrected for gearing and
blower efficiency.
Gearing efficiency 0.90
Blower efficiency 0.90
Total power req. corrected for efficiency (surface aerators)
Celll
Cell 2
Cell3
Cell 4
Total Power - Surface aerators
lO.llkW
5.09
2.48
1.27
18.95
13.48hp
4.31
1.20
0.31
19.30
Power Cost/ kWhr:
Total Power Costs for Surface Aerators ($/yr)
Cell 1 - Diffused aeration
Cell 2
Cell3
Cell 4
Total Power
Power Cost/ kWhr:
Total Power Costs for Diffused Aerators ($/yr)
$ 0.06
9958.02
7.11 kW
3.58
1.74
0.90
13.33
9.49 hp
3.03
0.85
0.22
13.58
$ 0.06
7007.49/yr
These power requirements are approximate values and are used for the preliminary selection of
equipment.
Example 3-6. Detention Times in Complete Mix Aerated Ponds having One to Five Cells
Compare detention times for the same BOD5 removal levels in complete mix aerated ponds
having one to five cells. Assume
C0 = 200 mg/L
k=2.5/d
Tw = 20 °C
Solution
1. Solve the following equation for a single cell system:
t = -
1
2.5
= 2.7d
200V
-1
2. Similarly:
when
C-14
-------
n = 2 t= 1.04 days
n = 3 t = 0.35 days
n = 4 t = 0.24 days
3. Continuing to increase n will result in the detention time being equal to the detention time in a
plug flow reactor. It can be seen from the tabulation above that the advantages diminish after the
third cell. This advantage is lost because of the need for a hydraulic residence of time of
approximately one and one-half days for the biomass to develop.
Example 3-7. Design of a Four-Cell Complete Mix Aerated Pond having Two Trains for
BOD5 Removal
Design a four-cell complete mix aerated pond with two trains to remove BOD5 for the following
environmental conditions and wastewater characteristics:
Q= 1136m3/d(0.3MGD)
C0 = 220 mg/L
Ce from fourth cell = 10 mg/L
k20 = 2.5/d
Air temperature (winter) = 8 °C,
(summer) = 25 °C
Elevation = 50 m
DO = 2 mg/L in all cells
Depth = 4m (13.1ft).
Solution:
Flow Rate = Q= 568 m3/d
Influent BOD5 = 220 mg/L
Influent TSS = 200 mg/L
Total N = 30 mg/L
Total P= 10 mg/L
Reaction Rate at 20 °C = 2.5 d"1
Influent temperature °C = 15 °C
Winter air temp: °C = Ta = 8 °C
Summer temp. °C = Ta 25 °C
/= units conversion factor = 0.50
Temperature correc. coef. = 1.09
Surface Elevation = 50m
Minimum DO Cone. = 2 mg/L
Depth = 4m
Length to Width Ratio = 2
Side slope = 3
1. Start solution by assuming winter pond temperature and determine volume of a Cell 1 in the
pond system.
Assume water temperature: 12.7 °C
C-15
-------
Correct reaction rate for temperature: kT = k2d(l .09)(r~20)
fa=l.34/d
HRT in Cell 1 = Id
Effluent BOD5 in Cell 1 = 94.13 mg/L
Volume in Cell 1 = 568 m3
2. Calculate dimensions of Cell 1 at water surface and the surface area.
Depth = 4m
Width = 16.48m
Length = 32.97 m
Surface area in Cell 1 = 543.40 m2 (0.134 ac)
3. Check pond temperature using cell area calculated above and equation shown below:
Cell 1 Tw = (AfTa + QT,y(Af+ Q) 12.74 °C
If calculated Tw differs from assumed water temperature, iteration is necessary.
Add a freeboard 0.90 m
Dimensions at top of dike in Cell 1
W top of dike = 21.88m
L top of dike = 38.37m
4. For Cell 2, influent water temperature = 12.74 °C
Correct reaction rate for temperature: fa = #20(1.09)(r~20)
fa=l.34/d
Influent BOD5 = 94.13 mg/L
HRT= 1 d
Effluent BOD5 = 40.28 mg/L
Volume = 568 m3
Calculate dimensions at water surface and the surface area.
Depth = 4m
Width = 16.48m
Length = 32.97 m
Area= 543.40 m2 (0.134 ac)
Cell 2 Tw = (AfTa + QT,y(Af+ Q) 11.20 °C
Add a freeboard 0.90 m
Dimensions at top of dike 2
W top of dike = 21.88m
L top of dike = 38.37m
5. For Cell 3, influent temperature = 11.20 °C
fa= 1.17/d
Influent BOD5 = 40.28 mg/L
HRT= 1 d
C-16
-------
Effluent B OD5 = 18.55 mg/L
Volume = 568 m3
Calculate dimensions of Cell 3 at water surface and the surface area.
Depth = 4m
Width = 16.48m
Length = 32.97 m
Area = 543.40 m2 (0.134 ac)
Cell 3 Tw = (AfTa + QTl)l(Af+ Q) 10.17 °C
Add a freeboard 0.90 m
Dimensions at top of dike
W top of dike = 21.88m
L top of dike = 38.37m
6. For Cell 4, influent temperature = 10.17 °C
kT= 1.07/d
Influent BOD5 = 18.55 mg/L
HRT= 1 d
Effluent BOD5 = 8.96 mg/L
Volume = 568 m3
Calculate dimensions of Cell 4 at water surface and the surface area.
Depth = 4.00 m
Width = 16.48m
Length = 32.97 m
Area = 543.40 m2 (0.134 ac)
Cell 4 Tw = (AfTa + QTt)l(Af+ Q} 9.47 °C
Add a freeboard 0.90 m
Dimensions at top of dike
W top of dike = 21.88m
L top of dike = 38.37m
7. Determine the oxygen requirements for pond system based on organic loading and water
temperature. Maximum oxygen requirements will occur during the summer months. Use
Equation 3.14 to estimate pond temperature during the summer.
Tw Cell 1 = (AfTa + QT,y(Af+ Q) 18.2 °C
Tw Cell 2 = (AfTa + QT,)l(Af+ Q) 20.4 °C
Tw Cell 3 = (AfTa + QTt)/(Af+ Q) 21.9 °C
Tw Cell 4 = (AfTa + QT,)/(Af+ Q) 22.9 °C
OL in the influent wastewater
C-17
-------
OL on Cell 1 = C0 x Q 5.21 kg/hr
Calculate effluent BODs from first cell using equations below at Tw for summer.
kTw = k20 x (temp. coef)(rw"20) 2.13d'1
Ci = C0/[(kt)+l] 69.90 mg/L
Winter = 94.13 mg/L
OL on Cell 2 = Q x d 1.65 kg/hr
*TV = k20 x (temp. coef)(rw"20) 2.59/d
C2= Ci/[(kf) + 1 ] 19.45 mg/L
Winter = 40.28 mg/L
OL on Cell 3 = C2 x 0 0.46 kg/hr
*TV = Ł20 x (temp. coef.)(rw"20) 2.95/d
C3=C2/[(kf)+l] 4.93 mg/L
Winter = 18.55 mg/L
OL on Cell 4=C3*Q 0.12 kg/hr
*TV = k20 x (temp. coef.)(rw"20) 3.21/d
C4=C3l[(ki)+\] 1.17 mg/L
Winter = 8.96 mg/L
DO is assumed to be a multiple of organic loading
Multiplying factor (MF) 1.50
DO in Cell l = OLlxMF 7.81 kg/hr
DO in Cell 2 = OL2 x MF 2.48
DO in Cell 3 = OL3 x MF 0.69
DO in Cell 4 = OL4 x MF 0.18
8. Use following equation to calculate equivalent O2 transfer.
N = N0D/(a[(Csw-CL)/C&](temp factor)(rw-20))
NOD = DO in various cells
Csw = bx Css x P
6 = 0.90
P = ratio of barometric pressure at pond site to pressure at sea level 0.80
Cell 1 Tap water O2 sat. value Css = 9.49 mg/L
Cell 2= 9.10 mg/L
Cell 3 = 8.85 mg/L
Cell 4 = 8.69 mg/L
Cell 1 Csw = 6.84 mg/L
Cell 2 Csw = 6.55 mg/L
Cell 3 Csw = 6.37 mg/L
Cell 4 Csw = 6.26 mg/L
C-18
-------
a = O2 transfer in WW/02 transfer in tap water 0.90
CL = min. O2 cone, to be maintained in wastewater 2.00 mg/L
Cs = O2 sat. value of tap water at 20 °C and 1 atm. 9.17 mg/L
Temp, factor 1.025
7V7 = 17.19kg/hr
9. Evaluate surface and diffused air aeration equipment to satisfy O2 requirement only.
Power req. for surface aerators
Power req. for diffused air
Total power for surface aeration
Cell 1
Cell 2
Cell3
Cell 4
Total power for diffused aeration
Cell 1
Cell 2
Cell3
Cell 4
1.90kgO2/kWh
(1.40kgO2/hp-h)
2.70 kg O2/kWh
(2.00 kg O2/hp-h)
9.05 kW
2.89
0.81
0.21
6.37 kW
2.04
0.57
0.14
12.28 hp
3.93
1.10
0.28
8.60 hp
2.75
0.77
0.19
These surface and diffused aerator power requirements must be corrected for gearing and blower
efficiency.
Gearing efficiency 0.90
Blower efficiency 0.90
Total power req. corrected for efficiency
Cell 1 - Surface aerators 10.05 kW
Cell 2- 3.21 4.31
Cell3- 0.90 1.20
Cell 4- 0.23 0.31
Total Power- 14.39 19.30
13.48hp
Power Cost/kWhr: 0.06
Total Power Costs for Surface Aerators: $7564.74 /yr
Cell 1 - Diffused aeration 7.07 kW 9.49 hp
Cell 2- 2.26 3.03
Cell 3 - 0.63 0.85
Cell 4- 0.16 0.22
Total Power -
10.13kW13.58hp
C-19
-------
Power Cost/kWhr: 0.06
Total Power Costs for Diffused Aeration: $5323.33/yr
These power requirements are approximate values and should be used for the preliminary
selection of equipment.
10. Evaluation of power requirements for maintaining a complete mix reactor.
Power required to maintain solids suspension = 6.00 kW/1000 m3 (30.48 hp/MG)
Total power required in all Cells = 3.41 kW 4.57 hp
11. Total power required in system will be the sum of the maximum power required in each cell
as measured above.
Assuming that complete mixing is to occur in all cells, use the first set shown below. An
alternative is to use the power calculated for each cell to satisfy C>2 demand or a mixture of
complete mix and 02 requirements.
Power Required for Complete Mix in All Cells
All Cells = 3.41kW
Total = 13.63kW
Power Costs = $7164.98/year
Power Requirements for Each Cell Based on BODs removal
Celll= 10.05kW 13.48hp
Cell 2= 3.21 4.31
Cell 3= 0.90 1.20
Cell 4= 0.23 0.31
Total = 14.39 19.30
Power Costs = $7564.74/year
C-20
-------
The State of Minnesota Pollution Control Agency has prepared a graphic presentation on designing ponds that
provides a user-friendly overview of the entire process. We present it here for everyone's enlightenment, but
especially for public utility managers, who may find this version provides some insights into all the elements that
need to be addressed when a pond system is being considered for wastewater treatment.
Minnesota
Pollution
Control
Agency
DESIGN
C-21
-------
Minnesota
Pollution
Control
Agenc
Yearly Variations
Month
Algae ' ^
Bacterial
Activity
PH
BOD
Storage
Discharge Windows
C-22
-------
Minnesota
Pollution
Control
Agency
Basic Design Concepts
• How much "food" - organic load
• How much water - hydraulic load
CIIY OF CAHVEB
WASTEWATER
TREATMENT FACILITY
14025 COUNTY ROAD 40
C-23
-------
Minnesota
Pollution
Control
Agency
Area/Loading (Non- Aerated Pond)
Primary
Cell
Primary
Cell
22 Pounds of BOD/Day/Acre
or
approximately 100 people/acre
C-24
-------
Minnesota
Pollution
Control
Agency
Area/Loading (Aerated Pond)
0000
20 - 400 Pounds of BOD/Day/Acre
or
approximately 75 - 2350 people per acre
C-25
-------
Minnesota
Pollution
Control
Agency
Detention Times
Non - Aerated
minimum of 180 - 210 days
(210 days for spray irrigation)
Aerated
C-26
-------
Minnesota
Pollution
Control
Agency
Three-Cell System
C-27
-------
Minnesota
Pollution
Control
Agency
Two-Cell System
Primary
C-28
-------
Minnesota
Pollution
Control
Agency
Secondary Pond Size
• Volume of the secondary MUST BE at
least 1/3 the volume of the entire system
-Two cell system
Primary is twice the size of the
secondary
-Three cell system or larger
All cells are equal size
Why ?
10
C-29
-------
Minnesota
Pollution
Control
Agency
Secondary Volume Vs. Discharge Time
Secondary Volume
( As a % of total
volume)
20%
25%
33%
Actual Flow
( % of design)
25%
34
14
12
50%
62
40
36
75%
90
66
60
100%
115
92
66
C-30
-------
Total Days Needed To Discharge
Control
Agency
sota
on
j|
y
Transfer
Settle (after
transfer)
Test Results
Discharge
Days
Total Days
Number of Dischai
123
0
0
6
8
14
14
8
4
6
8
26
40
8
4
6
8
26
66
•ges Need eel *
4 5
8
4
6
8
26
92
8
4
6
8
26
118
* With four feet of elevation difference or a pump of sufficient size
12
C-31
-------
Minnesota
Pollution
Control
Agency
Typical Operating Levels
(Non - Aerated)
9 feet
3 feet freeboard
6 feet
4 feet (operating
depth)
2 feet
1:3 or 1:4
Slope
2 feet sludge storage
C-32
-------
Minnesota
Pollution
Control
Agency
Typical Operating Levels
(Aerated Pond)
3 feet freeboard
10 -15 feet
1:3 or 1:4
C-33
-------
Minnesota
Pollution
Control
Agency
ALLOWABLE SEEPAGE
CRITERIA
• Prior to 1975
3500 gallons per acre per day
• 1975 to present
500 gallons per acre per day
C-34
-------
Minnesota
Pollution
Control
Agency
Clay Liner
C-35
-------
Minnesota
Pollution
Control
Agency
Pond Sealed With Clay Liner
4" Topsoil and Grass
Minimum 6" Layer of Riprap
(to one foot above high water)
Minimum 12" Clay Liner
(to one foot above high water)
C-36
-------
Minnesota
Pollution
Control
Agency
Pond Sealed With Synthetic Liner
4" Topsail and Grass
Minimum 6" Layer of Riprap
(to one foot above high water)
Minimum 12" Fine
Textured Soil
6 Sand or
Clean Soil
Minimum 30 mil liner
18
C-37
-------
Minnesota
Pollution
Control
Agency
Installation of Synthetic Liner
19
C-38
-------
Minnesota
Pollution
Control
Agency
Joining of Liner Sheets
20
C-39
-------
Minnesota
Pollution
Control
Agency
Liner Cover Material
Min of 12 inches
C-33
C-40
-------
Minnesota
Pollution
Control
Agency
Conduct Water Balance
* To check for actual
seepage rate
4 Install barrels in pond
« Take depth
measurements in
barrels:
• pond depth
• rainfall
• evaporation
• four consecutive weeks
Do calculations
C-41
-------
Minnesota
Pollution
Control
Agency
Erosion Protection
Grass or Rock ?
Grass (inner dikes)
-Not recommended
Rock
-Durable (no sandstone, concrete)
-Clean (no fines) -.-M*
-Thickness (at least 6-9 inches)
-Size (majority 3-9 inches)
•• ^xS^^H
&f
C-42
-------
Control Structures
Minnesota
Pollution
Control
Agency
Mechanism to
regulate/transfer
water between pond
cells
Also provides a place
to measure depth
Slide gates and/or
valves
Shut off valve (outside
of structure)
C-43
-------
Minnesota
Pollution
Control
Agency
Control Structures
Telescoping Valve or Downward Sluice Sates
... i/.nmmii^MiimiumM
'iliminiinnin\r
/w///////i//iii»nimmum
m\\\\\\\\\\
w/////////iM!imwim\\
'linininiHim
IIBIIIlimm
II1IUI\\V
IIIIII1IU1
C-44
-------
Minnesota
Pollution
Control
Agency
Recommended Elevation
Difference
Primary
C-45
-------
Minnesota
Pollution
Control
Agency
Influent Line
Horizontal Vs. Vertical ?
• To avoid plugging
problems
Force main directly
into pond ?
Solids buildup
because of
vertical inlet
C-46
-------
Minnesota
Pollution
Control
Agency
Transfer Piping
• Two foot riser
• Allows for
transfer from
above; not bottom
Keeps
sludge/nutrients in
bottom of pond
C-47
-------
Minnesota
Pollution
Control
Agency
Entrance Road,
Gate, Fences, Signs
WARNING
WASTEWATER POND
NO TRESPASSING
C-48
-------
Minnesota
Pollution
Control
Agency
Flow Measurement
• Very important !
• Permit requirement
-daily flow
• Most have running time
meters
-must have three time
meters; both pumps run
together
• Must calibrate pumps
-at least once/year
C-49
-------
Minnesota
Pollution
Control
Agency
Depth Measurement
Permit requirement
- weekly
- nearest inch
• Measure actual
pond depth in control
structure
C-50
-------
Minnesota
Pollution
Control
Agency
Location
Recommended
(not a
requirement) !
- 1/2 mile
from the
nearest city
-1/4 mile
from the
nearest
resident
C-51
-------
FROM CHAPTER 6
NUTRIENT REMOVAL
Example C-6-1. NHs Conversion in a Partial Mix Pond
Estimate the expected NH3 conversion in a partial mix aerated pond receiving adequate DO and
alkalinity to nitrify an NH3 concentration of 20 mg/L at a water temperature of 10 °C. Determine
the effluent concentration at a detention time of 30 days and at a desired effluent concentration of
10 mg/L.
Temperature = 10 °C
Influent NH4+ = C0= 20 mg/L
0 = temp correction factor = 1 .04
Reaction Rate = k20 = 0.0107/d
HRT = 30 d
Effluent NH3= 10 mg/L
Solution:
1 . Correct reaction rate for temperature:
kT = k20(&f~20)= 0.005079/d
2. Determine the effluent concentration with known HRT:
/"> //"> -kt
Ce/Co = e
Ce=
17. 17 mg/L
3. Determine the detention time required to achieve effluent concentration:
t = (Ln(Ce/Co)l-k= 136.5 d
Example C-6-2. Design for Benthal Stabilization of Waste Solids
Input Data: Insert Design Values in Shaded Fields
BOD5
Flow Rate = Q =
Temperature = T=
Solids Retention Time =
Nonbiodegradable Solids = Xi =
Decay Factor = F}
Growth Yield = 7 =
Annual Average Stabilization Rate =
BM
Aerator Performance = N =
Unit Rate of Benthal Oxygen Demand
= B<92
Solids Fraction = X
Solution:
1000 mg/L
136.3 m3/d
35 °C
20 d
100 mg/L
0.427 (see Tables for Decay
Factors)
0.5gVSS/gBOD5
35.64gVSS/m2/d
1/25 kg 02/kWh
60 g 02/m2day
0.02
0.036 mgd
C-52
-------
1 . Calculate daily loading rate of
biomass:
Rxa = QY(S0+Xso)F1 =
2. Calculate surface area required for
stabilization:
A=RXJBM=
3. Calculate aeration power in terms of
sludge-water interface area:
P/A0 = 4.\6x \V'*B02/N =
4. Calculate volume of water column
so that aeration intensity will not
permit solids to settle by gravity =1.7
W/m3 (8.5 hp/MG);
F1/40=1000P/1.7 =
5. Estimate volume of sludge during
annual cycle:
Vs= 365 xQ xX/(Xx 106) =
6. Calculate required volume of basin:
v=vs + vw
29100.05 gVSS/d
816m2
0.001997 A0m*
1
1. 997^0 m3
249m3
8788 t2
0.065712
MG
Select a basin and operating depth that will provide a Vrequired using the following
equation:
Pond Depth =
W =
L =
Side Slope =
Volume =
V provided =
Surface Area =
V required =
4.62
10m
10m
0 Horizontal To Vertical
V= [LW+ (L-2 sd)(W+ 2sd) +
4(L-sd)(W-sd)]d/6
462m3
100m2
118m3
0.122MG
0.025 ac
0.118462
MG
7. Substitute values for length and width until V provided equals or exceeds V required.
8. For additional years of operation, use the following table. Substitute years and depths
in shaded fields.
Table C-6-1. Pond Volume and Area vs. Sludge Depth over Time
Years of
Operation
5
7
Volume
Required
m3
2242.138
3138.993
Area Required for Sludge Depth
Sludge Depth, m
1
2242.138
0.55
3138.993
0.78
2
1121.069
0.28
1569.496
0.39
3
747.3792
0.18
1046.331
0.26
4
560.5344
0.14
787.7481
0.19
5
448.4275
0.11
627.7985
0.16
6
373.6896
0.09
523.1654
0.13
m2
ac
m2
ac
C-53
-------
10
15
20
4484.275
6726.413
8968.55
4484.275
1.11
6726.413
1.66
8968.55
222
2242.138
0.55
3363.206
0.83
4484.275
1.11
1494.758
0.37
2242.138
0.55
2989.517
0.74
1121.069
0.28
1681.603
0.42
2242.138
0.55
896.855
0.22
1345.283
0.33
1793.71
0.44
747.3792
0.18
1121.069
0.28
1494.758
0.37
m2
ac
m2
ac
m2
ac
Table C-6-2. Annual Average Stabilization Rates
Month
Air Temp
(ave.)
Sludge
Temp.*
Bi**
L/m2/d (g)
B2***
L/m2/d (g)
B!+B2
L/m2/d (g)
Jan
Feb
Mar
Apr
May
June
July
Aug
Sept
Oct
Nov
Dec
Average
0.6
4
8.1
12
16.2
20.5
23.7
23.1
18
11.7
5.6
1.1
0.1
2
6.1
10
14.2
18.5
21.7
21.1
16
9.7
3.6
0.1
29.5 (7.81)
33.6(8.88)
44.3 (11. 71)
57.7 (15.25)
76.6 (20.26)
102.6(27. JO)
127.4(33.66)
122.3 (32.32)
86.6 (22.89)
56.5 (14.94)
37.4 (9.89)
29.6 (7.81)
553(17.71)
0.3 (0.07)
0.5 (0.13)
1.9(0.51)
7.0 (1.86)
28.0 (7.40)
115.5(30.51)
331.3 (87.52)
211.9(71.83)
50.7 (13.39)
6 A (1.68)
0.9 (0.23)
0.3 (0.07)
56.6(17.93)
29.9 (7.88)
34.1 (9.01)
46.2 (12.23)
64.7 (17.11)
104.6(27.67)
218.1 (57.62)
458.7 (121.17)
394.2(104.14)
137.3 (36.28)
62.9(16.63)
38.3 (10.12)
29.9 (7.88)
112 A (35.64)
* Sludge temperature assumed to be 2°C lower than average air temperature.
**Bi = aerobic stabilization rate
***B2 = anaerobic stabilization rate
C-54
-------
FROM CHAPTER 7
UPGRADING POND EFFLUENTS
Example C-7-1. Intermittent Sand Filter Design
DESIGN DATA AND ASSUMPTIONS
Design Flow = Q = 379 m3/d (0.1 mgd)
HRT = 0.29 m3/m3/d (0.310 mg/ac/d)
Minimum Number of filters = 2
Assum ptions:
Design to minimize operation and maintenance
Gravity flow
Topography and location satisfactory
Adequate land is available at reasonable cost
Filter sand is locally available
Filters are considered plugged when, by the end of the infiltration period, the water
from the previous dose has not dropped below the filter surface.
DESIGN
Determine dimensions of filters
Areas of each filter = Q/FILR
Area= 1306.9 m2 (0.32 ac)
L:W = 2:1
W = 25.56m (83.9 ft)
L = 51.1m (167.7 ft)
Minimum of 2 filters required
INFLUENT DISTRIBUTION SYSTEM
Design Assumptions:
Dosing siphon will be used to gravity feed filters.
Electronically activated valves may be used.
Loading sequence will be designed to deliver one-half the daily flow rate to one filter
unit/d in two equal doses.
More frequent dosing is acceptable.
Pipe sizes are selected to avoid clogging and to make cleaning convenient.
Hydraulics do not control the rate of treatment.
DOSING BASIN SIZING
No. of dosings/d = 2
Q = Design Q/# of dosings =189.5 m3/d (6,692 ft3)
Volume = 189.5 m3 (6,692 ft3)
Install overflow pipe to filters.
Distribution manifold from dosing siphon is designed to minimize velocity of water entering the
filter.
Use 25 cm (10 in) diameter pipe in this design.
Each of the outlets from the manifold will be spaced 30.5 cm (10 ft) from each end and 6.4 m (21
ft) on centers on the long side of the filter.
C-55
-------
Manifold outlets will discharge onto 91.4 cm by 91.4 cm (3 ft by 3 ft) splash pads constructed of
gravel 3.75 cm (1.5 in) in diameter.
FILTER CONTAINMENT
Filter may be contained in a reinforced concrete structure or a synthetic liner to prevent ground
water contamination. Slopes of filter bottom are dependent on slope of drainpipe configuration.
Use slope of 0.025 percent slope with lateral collection line 4.6 m (15 ft) on center.
Lateral collecting pipe (18 cm [6 in]) and 24 cm (8 in) collection manifolds will provide adequate
hydraulic capacity and ease of maintenance.
Minimum freeboard required for filters must be adequate to receive one dosing x safety factor.
Safety Factor = 3.
Water depth assuming no passage = 0.435 m (1.47 ft).
Example C-7-2. Design of a Controlled Discharge Pond Using a Minimum Discharge Period
Criterion
In areas of high evaporation rates or high rainfall, the volume of the pond should be adjusted to
compensate for the water loss or gain. In this example, it is assumed that rainfall is equal to
evaporation, producing no net change in volume. This example illustrates the design of a
controlled discharge pond using a minimum discharge period criterion.
Design Conditions:
Minimum discharge period = 30 d
Q = Design Flow Rate = 1893 m3/d (0.5 mgd)
C0 = Influent BOD5 =150 mg/L
Ce = Effluent BOD5 = 30 mg/L
kp2o = reaction rate for plug flow at 20°C = 0.1/d
Tw = water temperature during the critical period of the year = 2 °C
Requirements: Size a controlled discharge wastewater pond system to treat the wastewater and
specify the following parameters:
Detention time, t
Volume, V
Surface area, A
Depth, d
Length, L
Width, W
Solution: t = 365 d (minimum discharge period) = 365 d - 30 d = 335 d
Discharge can occur when the effluent quality satisfies standards or the receiving stream flow rate
is adequate to receive the effluent. Discharge periods more frequent than once a year can be
scheduled, but the performance of the system should be evaluated for the shorter hydraulic
residence times. The methods used to design facultative ponds can be used to estimate the
performance of a controlled discharge pond.
C-56
-------
Raw wastewater is not added to the pond being emptied. Raw wastewater inlets and effluent
withdrawal ports are provided in each cell of the system. The cells are connected in series to
facilitate operation and flexibility. Three cells are used in this example.
An effective depth (d') of 1.5 m (5 ft) and a total depth (d) of 2 m (6.6 ft) is used. This depth
allows for adequate light penetration to sustain photosynthetic oxygen production, providing an
aerobic environment through much of the pond contents. The aerobic environment enhances
treatment and reduces odor problems. Also, to control odors during discharge periods, the pond is
emptied to a minimum depth of 0.5 m (1.5 ft). Additional volume must be provided to compensate
for this minimum withdrawal depth.
effective volume _ Qt 1893 w3 (335 d)
n(effectivedepth) 3d' 3(\.5m) = 140,900 m2 (35 ac)
This area is used to calculate the total volume for the pond total depth:
d= 1.5 m + 0.5m = 2 m (6.6 ft)
F/cell = (Alcd\)(d) = (140,900 m2)(2 m) = 281,800 m3 (74.4 x 106 gal)
Significant volumes of wastewater may be lost through seepage if the pond bottom is not sealed.
For this example, seepage rates are considered minimal. The length to width ratio of the cells in a
controlled discharge pond has less effect on the performance of the system than in flow-through
systems. Dimensions for the cells are selected to avoid short-circuiting during discharge or
interbasin transfer. A length to width ratio of 2 to 1 was selected for this example.
Dimensions of Ponds
The dimensions of each pond with side slopes of 4 to 1 and a length to width ratio of 2 to 1 can be
calculated using the following formula:
V=(L*W) + (L- 2sd)(W- 2sd) + 4(L- sd)(W- sd)d/6 (7-1)
where:
Vi = volume of pond #1 = 281,800 m3
L = length of pond at water surface, m
W= width of pond at water surface, m
s = horizontal slope factor, e.g., 4 to 1 slope, s = 4
d= depth of pond = 2 m (6.6 ft)
(LxL/2} + (L - 2 x 4 x 2)(X/2 -2x4x2)
4 (L - 4 x 2)(L/2 - 4 x 2) = (281,800)(6/2)
3Z3-721 + 512 = 845,400
L2- 241 = 281,630
Solve the quadratic equation by completing the square:
C-57
-------
L2 - 24L + 144 = 281,630 + 144
(Z-12)2 = 281,774
1-12 = 530.8
L = 542.8 m (1780 ft)
W= 542.8/2 = 271.4 m (890 ft)
A freeboard of 0.6 m (2 ft) should be provided. The dimensions of each pond at the top of the
inside of the dike will be 547.6 by 276.2 m. The three ponds shall be interconnected by piping for
parallel and series operation.
Effluent Quality Prediction
In a pond with an HRT of over 300 days, it is obvious that an effluent with a BOD5 concentration
of less than 30 mg/L can be achieved. However, if it becomes necessary to discharge at shorter
intervals, some method of estimating the effluent quality is needed. Controlled discharge ponds
are basically facultative ponds, and the effluent quality can be predicted using the plug flow
model used to design a facultative pond in Appendix C.
f~<
where:
Ce = effluent BOD5 concentration, mg/L
C0 = influent BODs concentration, mg/L
e = base of natural logarithms, 2.7183
kp = plug flow first-order reaction rate/d
t = hydraulic residence time, d
kpT = reaction rate at minimum operating water temperature/d
kp20 = reaction rate at 20 °C = 0. 1/d
Tw = minimum operating water temperature, °C
Assume that it becomes necessary to discharge from the ponds after a mean HRT of 100 days
when the mean water temperature during the period is 2 °C. What would be the concentration of
BOD5 in the effluent?
V=0.1(1.09)(2-20)
= 0.02 1/d
Ce= 18 mg/L
The BOD5 concentration of 18 mg/L in the effluent will easily satisfy the standard of 30 mg/L.
TSS concentrations will have to be monitored on-site to ensure that the standards for discharge
are met. The guidelines presented at the beginning of this example must be followed in operating
the controlled discharge pond system.
Summary:
C-58
-------
V= 845,400m3
A = (542.8)(271.4)(3) = 441,950 m2
Example C-7-3. Complete Retention Ponds
Figure C-7-1 presents data from NOAA National Weather Service (2004) for estimating
evaporation and precipitation in southern Arizona. The air temperature and wind speed data
represent mean values over a 54- and 61 -year period, respectively. The precipitation data are the
mean of the 5 wettest years over a 60-year period. The pan evaporation data represent the year
with the lowest evaporation for a 10-year period. These values generally represent the worst case,
thus providing for a conservative design.
0,9
0,8
""I""!""!1'"!""!""!' "I'M °-9
ELEVATION* m. MSL
ELEVATION =3Q5M, ABOVE MSL
I !
10
20 30 0 10 20
PAN WATER TEMPERATURE, *C
Figure C-7-1. Portion of advected energy (into a Class A Pan) utilized for evaporation in
metric units (NOAA National Weather Service, 2004).
The difference between the surface water temperature and the air temperature is assumed to be 1
°C. The selection of this value can have a significant effect on the evaporation losses as shown in
Figure C-7-2; therefore, the value must be selected to reflect local conditions.
C-59
-------
220
Figure C-7-2. Shallow lake evaporation as a function of Class A Pan evaporation and heat
transfer through the Pan in metric units per day (NOAA National Weather Service, 2004).
Surface water temperature = T0= air temperature (Ta) minus 1°C
T - T = -1°C
Q = 950 m3/d (0.25 mgd)
Influent BOD5 = 150 mg/L
Seepage = 0.76 mm/d (0.2 in/wk).
Seepage is prohibited in some areas. State agency wastewater facility standards may require the
pond bottom be sealed with an impervious liner, reducing seepage to zero. Elevation = 300 m
(980 ft) above mean sea level (MSL).
Requirements:
C-60
-------
Size a complete retention wastewater pond with no overflow for the given geographic area.
Specify the following:
Area, A =
0 (365 d/vr)
d- (Annual Precip. - Annual Evap. - Annual Seepage)
Surface area, A
Depth, d
Length, L
Width, W
Solution
The design procedure consists of the following steps:
1. Using the data in Table C-7-1 with Figure C-7-1 (elevation = 305 m) and Figure C-7-2,
determine the mean monthly evaporation from the pond. The calculation of pond evaporation is
shown on the figures by dashed lines. The results are presented in Table C-7-2.
2. Using the data presented in Tables C-7-1 and C-7-2, calculate the area required for an assumed
mean depth for one year of operation under design conditions. The mean depth (d) may range
from 0.1 - 1.5 m (0.3 - 5.0 ft). The mean depth is usually near 1 m (3 ft).
3. Use the A value determined in step 2 to calculate the stage of the pond at the end of each month
of operation during the design year.
4. Calculate the monthly stage of the pond under average conditions. If the pond is designed so
that it never overflows, the average yearly evaporation and seepage must exceed the inflow and
precipitation entering the pond.
5. Repeat steps 2 and 3 until a satisfactory pond depth is obtained.
Table C-7-1. Climatological Data (National Climatic Data Center, 2004).
CLIMATOLOGICAL DATA FOR CALCULATING POND EVAPORATION AND PRECIPITATION
Month
(Days
in
Month)
Jan (31)
Feb (28)
Mar (31)
Apr (30)
May
(31)
Jun (30)
Mean
Precipitation
mm/month
12.3
12.1
10.1
4.2
2.9
2.2
Air
Temp.
°C
12.4
14.9
17.7
21.0
24.6
29.3
Wind
Speed
Kts,
day3
140.4
148.7
154.2
157.0
154.2
134.9
Minimum 10-Year
Pan Evaporation
mm/month
87.5
130.5
198.2
238.1
332.0
374.4
mm/day
2.82
4.66
6.39
7.94
10.71
12.48
Mean 10-
Year Pan
Evaporation
mm/month
1050
177.5
220.0
271.4
365.2
423.1
C-61
-------
CLIMATOLOGICAL DATA FOR CALCULATING POND EVAPORATION AND PRECIPITATION
Month
(Days
in
Month)
Jul (31)
Aug (31)
Sep (30)
Oct (31)
Nov (30)
Dec (31)
Total
Mean
Precipitation
mm/month
6.8
15.9
10.6
7.8
8.3
14.6
107.8
Air
Temp.
°C
32.8
32.4
29.1
22.6
16.8
12.9
Wind
Speed
Kts,
day3
140.4
134.9
115.6
110.1
126.6
143.2
Minimum 10-Year
Pan Evaporation
mm/month
416.0
347.8
278.5
210.4
137.4
95.2
2847.0
mm/day
13.42
11.22
9.28
6.82
4.58
3.07
Mean 10-
Year Pan
Evaporation
mm/month
449.3
389.5
323.1
219.9
163.5
131.4
3238.9
aKts = knots = total of nautical miles/hr of wind per day.
Use A = 142,259 m2 (35 ac) to calculate the stage of the pond at the end of each month of
operation. Table C-7-2 contains a summary of the results of this procedure for the design year of
operation, assuming the pond is empty at the beginning of the year.
An examination of the pond stage results in Table C-7-3 shows that the maximum depth of water
in the pond during the design year (conservative design data) would be 0.62 m (2 ft) plus the
depth at the beginning of the design year. The pond stage under average conditions is shown in
Table C-7-4. Average evaporation and seepage are within 5 percent of inflow and precipitation.
Assuming that several average years would occur in sequence, there would be a small
accumulation of water in the pond. Because of the imprecise methods available to predict the
sequence of occurrence of the design year, maximum and average years, the pond surface area of
142,259 m2 is large enough to prevent overflow of the pond.
The depth of complete retention ponds is limited only by ground water conditions, and
evaporation rates and cost. Generally maximum depths range from 1 to 3 m (3 to 10 ft) with a
freeboard of 0.6 m (2 ft). The maximum depth required will depend on the time of year that filling
of the pond begins and the initial depth of water in the pond. It is not possible to predict
accurately the water stage in the pond, therefore, it is necessary to exercise good judgment based
upon the constraints at particular locations. Estimates beyond the average- and design-year
conditions can be made by analyzing historical data for the site, but this is still no guarantee of
accuracy.
The water depth in the pond after one year of operation under design conditions will be equal to
the mean depth plus the depth of water at the beginning of the year. During certain months of the
year, the depth may exceed the mean depth when filling of the pond occurs at the beginning of the
wet season. Three different starting dates are shown in Table C-7-3 to illustrate this point. Using
the abovementioned procedure, it is possible for the design engineer to estimate the stage of the
pond under as many conditions as considered necessary.
A maximum depth of 1.2 m (4 ft) would be adequate to avoid overflow from the pond by
providing storage for 5 average years (Table C-7-3) and a design year in sequence. It is unlikely
that 5 average years of evaporation would preceed the design year. The pond L and lvalues are
C-62
-------
calculated from the surface area A No restrictions are imposed on the length to width ratio. Also,
the need to divide the pond volume to enhance hydraulic characteristics is eliminated. The most
economical design consists of a single pond, provided the system can be isolated enough to avoid
complaints about odors when solids decompose on exposed slopes.
A=LW
L = W = A(m)= 142,259 m(1/2) = 377 m (1,237 ft)
Summary:
2
A = 142259 m (35 ac)
W= 377m (1237 ft)
V= 170800 m2 (45 MG)
d= 1.2m (3. 9 ft)
C-63
-------
Table C-7-2. Calculated Pond Evaporation Data for Design and Average Conditions
Month
January
February
March
April
May
June
July
August
September
October
November
December
TOTAL
ap
0.58
0.62
0.64
0.66
0.71
0.74
0.77
0.77
0.73
0.58
0.62
0.58
Design Pond Evaporation
mm/day
1.7
3.0
4.1
5.2
7.2
8.4
9.0
7.4
6.2
4.4
2.9
1.8
mm/month
53
84
127
156
223
252
279
229
186
136
87
56
1868
Average
Pond
Evaporation
mm/month
61
110
141
174
259
313
323
300
235
127
101
76
2220
C-64
-------
Table C-7-3. Volume and Stage of Pond at Monthly Intervals for Design Conditions
and A = 142,259 m2/Month
No. Days
in Month
Starting Date 1
September 30
October 31
November 30
December 31
January 31
February 28
March 31
April 30
May 31
June 30
July 31
August 31
Total
Starting Date 2
January 31
February 28
March 31
April 30
May 31
June 30
July 31
August 31
September 30
October 31
November 30
December 31
Starting Date 3
December 31
January 31
February 28
March 31
April 30
May 31
June 30
July 31
August 31
September 30
October 31
November 30
Inflow +
Precipitation3
m3
29888
30436
29561
31403
31076
28209
30763
28977
29739
28693
30293
31588
360626
31076
28209
30763
28977
29739
28693
30293
31588
29888
30436
29561
31403
31403
31076
28209
30763
28977
29739
28693
30293
31588
29888
30436
29561
Evaporation
+Seepageb
m3
29704
22699
15620
11318
10891
14977
21419
25436
35075
39093
43042
35929
305202
10891
14977
21419
25436
35075
39093
43042
35929
29704
22699
15620
11318
11318
10891
14977
21419
25436
35075
39093
43042
35929
29704
22699
15620
Storage
Volume0
m3
184
7921
21862
41947
62131
75363
84708
88249
82912
72513
59764
55423
20184
33417
42761
46303
40966
30566
17817
13476
13661
21397
35338
55423
20085
40269
53502
62846
66387
61051
50651
37902
33561
33746
41482
55423
Pond
Staged
Depth
(m)
0
0.06
0.15
0.29
0.44
0.53
0.60
0.62
0.58
0.51
0.42
0.39
0.14
0.23
0.30
0.33
0.29
0.21
0.13
0.09
0.10
0.15
0.25
0.39
0.14
0.28
0.38
0.44
0.47
0.43
0.36
0.27
0.24
0.24
0.29
0.39
C-65
-------
a Inflow = Q(days/mo): precip. = (monthly precip)(X\)
b Seepage = 0.00076 m/d (days/mo)(A); evaporation = monthly evap.(X\)
c Storage V= cum. sum of (inflow + precip.) - (evap. + seepage)
d Pond Stage = storage V/A
C-66
-------
Table C-7-4. Volume and Stage of Pond at Monthly Intervals for Average Conditions and A
= 142,259 m2
Month
Average Year
September
October
November
December
January
February
March
April
May
June
July
August
Total
No. Days
in Month
30
31
30
31
31
28
31
30
31
30
31
31
Inflow +
Precipitation
(m3)
29888
30436
29561
31403
31076
28209
30763
28977
29739
28693
30293
31588
360626
Evaporation
+ Seepage
(m3)
36674
21561
17612
14192
12385
18690
23410
28708
40197
47771
50582
45887
357668
Storage
Volume
(m3)
6786
8875
20824
38035
56726
66245
73598
73868
63409
44332
24044
9744
Pond
Stage
Depth (m)
0
0.06
0.15
0.27
0.40
0.47
0.52
0.52
0.45
0.31
0.17
0.07
C-67
-------
FROM CHAPTER 8 COST ESTIMATES: Spread Sheets for Estimating the Cost of
Intermittent Sand and Rock Filters, Table 8-la, b and c; Intermittent Sand Filter Cost
Estimation Procedure, Table 8-2a, b and c; and Intermittent Rock Filter Cost Estimation
Procedure. Table 8-la. Spreadsheet for estimating costs. (Input Design Values are shaded)
j ., , . ., p, f,.-, Width of top of \
inside ana outside Slope oj dikes = * _ '
3HtolV= '
Design Flow Rate (DFR) =
0.3m
Design Loading Rate =
0.3 me/ac
Surface Area
-
Required/filter =
1 ac
At least one filter out of service for cleaning =
Total number of filters needed
Sand depth
Volume of sand/filter 119,050 cu ft
Surface area of sand required/filter =
LtoW=2tol =
Wwater surface =
Lwater surface =
1 ac
43 560 sq ft
2
147.58 ft
295.16ft
4,409 cu yd
Depth ofunderdrain graded gravel =
Volume of dike
Soil/Dike-ft =
Width to center of dike =
Length to center of dike =
191.2ft3/ftofdike
168.14ft
315.72ft
C-68
-------
Table 8-la (cont.)
If common walls are used, reduce number of widths or lengths (Input Design Values are
shaded)
Number of common dike I Dike widths to be reduced
Number of common dike I Dike lengths to be
lengths= Hfl reduced =
_ nn „
Total lengths to be reduced =
Corrected total lengths of dikes/filter =
Total Volume of dikes/filter =
Freeboard Volume 3 XDFR =
Wbottom =
Lbottom =
Surface Area of bottom of filter sand =
Volume of under 'drain graded grave I '=
Lateral Under Drain Piping Diameter =
336.29 ft
631.4ft
120,725.78 cu ft
4471. 33 cu yd
2.76
129.6 ft
277.2 ft
35914.6537 3sq ft
34,706 cu ft
1,285 cu yd
Center Drain Pipe Diameter =
Length of Center Drain Pipe=
Spacing of Laterals
Number of Laterals
Length of Laterals
Pump or dosing siphon sump
Valves/filter
Synthetic or soil liner /ft of dike
Total surface area of liner/filter
227ft
20 ft OC
14
1796ft
1
2
327.92
207,062
C-69
-------
Table 8-la (cont.)
COST SUMMARY Input values are shaded
Item
No.
Require
d per
filter
Quantit
y
Unit
Unit Cost
Total Cost
Filter Sand
4409
cuyd
Under drain Gravel
1285
cuyd
Dike Earth Work
4471.3
Lateral Pipe 10
Main Drain 12
Liner and protection
Hn\
? fit
ion
cuyd
1796
ft
277
ft
207,062
sqft
Valves 12 in
per
$66,138.88
$12,854.23
$8,942.65
$17,957.33
$4,711.74
$362,358.45
$2,000.00
Pump or dosing siphon
with sump
per
Total cost for one filter
$5,000.00
$479,963.00
Total cost for required
number of filters =
$1,439,890.00
Table 8-lb.
UPDATED COST FOR INTERMITTENT SAND FILTERS FROM 1983 EPA DESIGN MANUAL
Year
1975
1975
1975
1978
1976
Location
Huntington, UT
Alley, GA
Moriarty, NM
White Bird, ID
Mt. Shasta, CA
Design
Flow
0.300
0.080
0.200
0.030
0.700
Loading
Rate
300,000
600,000
300,000
400,000
700,000
ENRCC
Index
2508.98
2508.98
2508.98
3039.64
2687.10
ENRCC
Index for
2006
Kansas
City
8704.67
8704.67
8704.67
8704.67
8704.67
Capital Cost
418,745
62,093
94,033
21,160
512,315
Table 8-lc.
Location
Huntington, UT
Ailey, GA
Moriarty, NM
White Bird, ID
Mt. Shasta, CA
Capital Corrected
Costs
2006 US$
4,452,796
215,426
326,239
60,596
1,659,608
$/mgd
Year of
Construction
1,395,817
776,163
470,165
705,333
731,879
$/mgd
Corrected for
2006
4,842,655
2,692823
1,631,193
2,019,875
2,370,869
C-70
-------
C-71
-------
Table 8-2 a,b,c. Intermittent Rock Filter Cost Estimation Procedure
Table 8-2a. Spreadsheet for estimating costs. (Input Design Values are shaded)
Design Flow Rate (DFR)
10688 ft7d
0.08 mgd
0.4 ft3/ft3 Rock
Design Loading Rate =
Volume of Rock Required at WS = 26720 ft3
Top of Dike =
Inside and Outside Slopes of Dikes 3H to
1V =
Total number of filters needed =
Water Depth =
Trial and Error calculation ofL and W'must be completed before proceeding
Wwater surface=
Lwater surface =
When E56 and F56 agree, dimensions
are correct
Rock Depth above Water Surface
83.90 ft
83.90 ft
7039
Water Surface
Area
7054ft2 =
Design Flow Rate (DFR) =
Wwater surface
Lrock surface =
Rock Depth =
Volume of rock/filter =
Volume of Dike Soil/Dike-ft =
Width to Center of Dike =
Length to Center of Dike =
Total Length of Dikes =
Total Volume of Dikes =
89.90 ft
89.90 ft
7.00 ft
34,259 cu ft
l,269cuyd
203.0ft3/ftofdike
93.90ft
93.90ft
375.6ft
76,246. 80 cu ft
2,823.96yd3
C-72
-------
Table 8.2a (con't)
Lbottom =
Wbottom =
Surface Area of Bottom of Filter =
Central Influent Pipe Diameter =
Length of Center Drain Pipe=
Length of Two Effluent Channels :=
Pump or transfer structure =
Valves/filter =
Synthetic or Soil Liner /ft of Dike =
Total surface area of liner /filter =
47.90 ft
47.90 ft
2,294.41 ft2
48ft
95.8 ft
52.27 ft2
21,928 ft2
Table 8-2b.
CONSTRUCTION COST SUMMARY (INPUT VALUES ARE SHADED)
Item
Rock
Dike earthwork
Central influent pipe
12#
Effluent trough and
weir
Liner and protection
Valves 12 in
Pump with transfer
structure
No. Required per
filter
1
1
1
1
1
2
1
Total cost for one filter =
Total cost for required number of filters =
Quanti
ty
1,269
2,824
48
96
21,928
2
1
Uni
t
cu
yd
cu
yd
ft
ft
sqft
per
per
Unit
Cost
$10.00
$2.00
$10.00
$17.00
$1.75
$1,000.
00
$5,000.
00
Total
Cost
$2,688.6
9
$5,647.9
1
$479.00
$1,628.6
0
$38,373.
53
$2,000.0
0
$5,000.0
0
$65,818
$65,818
C-73
-------
Table 8-2b (cont.)
CONSTRUCTION COST SUMMARY (INPUT VALUES ARE SHAPED)
Item
Rock
Dike
earthwork
Central
influent
pipe 12#
Effluent
trough and
weir
Liner and
protection
Valves 12
in
Pump with
transfer
structure
No.
Required
per filter
1
1
1
1
1
2
1
Total cost for one filter
Total cost for required
number of filters =
Quantity
1,269
2,824
48
96
21,928
2
1
Unit
cuyd
cuyd
ft
ft
sqft
per
per
Unit Cost
$10.00
$2.00
$10.00
$17.00
$1.75
$1,000.00
$5,000.00
Total Cost
$2,688.69
$5,647.91
$479.00
$1,628.60
$38,373.53
$2,000.00
$5,000.00
$65,818
$65,818
C-74
-------
Table 8-2c.
UPDATED COST FOR ROCK FILTERS FROM 1983 EPA DESIGN MANUAL
Yea
r
197
4
197
4
197
6
197
5
Location
Wardell,
MO
Delta, CA
California,
MO
Luxembur
8,WI
Veneta,
OR
Wardell,
MO
Delta, CA
California,
MO
Luxembur
8,WI
Veneta,
OR
Design
Flow
Rate,
mgd
0.080
0.080
0.360
0.400
0.220
Loading
Rate
ft3/ft3 of
rock
0.40*
0.40*
0.40
0.40
0.27
Capital Costs
Connected to 2006
(US$)
$48,647.35
$57,434.04
$218,132.45
$151,307.26
$144,743.61
ENRCC
Index
2308.25
2308.25
2308.25
2687.10
2508.98
$/mgd
Year of
Constructi
on
161,250
190,375
160,675
116,770
189,636
ENRCC
Index for
2006 Kansas
City
8704.67
8704.67
8704.67
8704.67
8704.67
$/mgd 2006
608,092
717,926
605,923
378,268
657,926
Capital
Cost Year
of Const.
(US$)
12,900.00
15,230.00
57,843.00
46,708.00
41,720.00
65,818.00
65,818.00
165,032.00
178,659.00
154,190.00
C-75
-------
APPENDIX D
Case Studies
D-l
-------
Appendix D
CASE STUDIES
These studies are presented to provide a
sense of the range of challenges that
wastewater pond systems designers and
operators have faced over the years and
some of the solutions that have been put in
place. We include examples of systems
from different parts of the country, which
must comply with similar regulations though
they live in different environmental
conditions.
New Hampshire
Rockland
New Hampshire treatment ponds
generally operate with a permit to
discharge effluent to ambient water
during the winter months (November
1 through April 30) and spraying on
irrigation fields during the summer.
Ponds designed to meet BOD/TSS
are increasingly required to meet
NHs limits in the winter. Studies
measured the base level ofNH3
coming into the ponds and results
suggested that changing the
discharge schedule would reduce the
number of NHs limit violations.
Kansas
The Kansas Department of Health and
Environment published its Surface Water
Nutrient Reduction Plan in December 2004.
Referring to a study it conducted in 2002,
the KDHE reaffirmed its support of
wastewater treatment ponds as the only
feasible treatment technology for many
small Kansas towns and attested to their
effectiveness in removing nutrients (TTVby
65% and TP by 55%).
California
Los Banos
A small city (population 40,000) in
the Central Valley of California was
a candidate for a study using solar-
powered water circulators
(Solarbee®) to evaluate effectiveness
and potential savings in energy from
this source if new water quality
standards are added to its permit.
The study provided support for the
effectiveness of the treatment
system. Another study examined the
impact of the release of effluent on
agricultural fields over time.
Arkansas
The Wastewater Treatment Ponds in
Arkadelphia, AK have been in
operation since 1968. In 1994, with
the addition of a small Lem-Tech
duckweed system after the last pond,
the system consistently meets
discharge limits year round.
D-2
-------
New Hampshire
Meeting Ammonia Requirements by
Reviewing Nutrient Values against
Discharge Operation Schedules
Summary
A wastewater treatment pond system
consisting of two facultative ponds (2.6
MG) and one storage pond (18 MG) serving
a county jail and nursing home were
constructed in 1990 and designed to meet
BOD5/TSS of 30/30 mg/L. In 1996, NH3
limits of 6.1 mg/L monthly average with a
12.2 daily maximum. The storage pond was
permitted to discharge treated effluent to a
small stream from October to April. Total
Kjeldahl N(TKN) and NH3 in the influent
increased from 28 mg/L to 45 and 8 mg/L to
21, respectively from 1996 to 2010. Water
conservation and use of kitchen disposals is
thought to be the reason for the increase. An
operational decision to change the timing of
the initiation of discharge from January to
November brought the facility into
compliance for NH^.
Introduction
Rockingham County Complex, Brentwood,
New Hampshire operates a three-cell aerated
pond system dedicated to serving a county
jail and nursing home. The ponds were
constructed in 1990 and were designed to
meet typical secondary treatment standards
of 30/30 mg/1 for BOD5 and TSS. The plant
was originally designed to treat a flow of
0.67 ML/d (0.178 mg/D and a BOD5 load of
215 kg/d (475 Ibs/d). Current flow and
loadings are 0.26 ML/d (0.07 mg/d) and 73
kg/d (160 lbs)/d BOD5 (Table 1). No
expansions are anticipated and with water
conservation measures enacted over the
years, it is unlikely design conditions will be
met in the foreseeable future.
Table 1. Discharge Requirements,
Rockingham County Complex NH
Design
flow
0.67
ML/d
0.178
mg/d
Act.
flow
0.26
ML/
d
0.07
mg/
d
BOD/
TSS
(mg/L)
30/30
Discharge
season
October 1
to April 30
NH3 limit
(mg/L)
6.1 /mo.
ave.
12.2
max/d
The County has an NPDES permit that
allows discharge to a very small brook from
October 1st through April 30th at an implied
flow of 0.085 MGD. They also have a
groundwater discharge permit allowing
spray irrigation from May 1st through
October 31st. The majority of biological
treatment takes place in the first two ponds,
each having a volume of 2.6 MG. Treated
flow is then transferred to an 18 MG storage
pond, where it can be held until discharged
to the brook or spray irrigated. Due to the
design of the valving and piping
arrangements, the operator is limited to
holding and treating an entire week's worth
of flow in the first two ponds during the
week, and then transferring that volume of
water to the storage pond during the
weekend.
In 1997, the County's NPDES permit was
reissued with NHs limits to the brook from
October 1st through April 30th of 6.1 mg/1 as
a monthly average and 12.2 mg/1 for a max
day. This presented an immediate problem
as the system was not designed to remove
NHs. Eliminating discharge to the brook
altogether would require building another
large holding pond and expanding the spray
irrigation sites, neither of which was deemed
feasible at the time.
D-3
-------
Results
An initial one year study performed in '96
and '97 showed that the system was capable
of producing winter effluent concentrations
on the order of 5 mg/1 TKjVand 3.3 mg/1
NHs at water temperatures < 3°C. Summer
NHs levels would go as low as 0.2 mg/1.
Influent TKjV at the time averaged around
28 mg/1 and NH3 8 mg/1. Biological
nitrification was determined to be the
primary method for NHs reduction as
demonstrated by the production of NO3'.
Substantial nitrification occurred in the first
pond and was brought to completion in the
second pond. This continued throughout the
summer and well into the fall. The
unusually low winter effluent concentrations
are thought to be primarily due to dilution in
the storage pond.
By October 31st, the end of spray season, the
storage pond contained a volume of 4.8 MG
of fully nitrified effluent. The second pond
continued to support nitrification well into
December, until the temperatures decreased
to the level of nitrification inhibition and
NHs concentrations increased. As a more
NHs rich water is transferred to the holding
pond, the NHs concentration in the pond
and, ultimately, the final effluent, gradually
increases to a concentration potentially
exceeding 6.1 mg/1. That level was not
reached during the initial study.
The plant performed well for the first
several seasons under the new permit limits.
Beginning in the winter of 2001, however,
and lasting through 2005, winter monthly
average violations were experienced on a
regular basis. January, usually a good
month, averaged around 4.5 mg/1 NHs.
February, March and April averages ranged
from 6 to 11 mg/1. There were no violations
during the winters of '06 and '07. The
violations resumed, however, in '08 and '09.
Another study was undertaken to try to
determine the cause.
The study showed that the flow and
loadings remained the same but that the N
load had increased considerably. Influent
TKjVnow averages 45 mg/1, up from 28
mg/1, and influent NHs increased from an
average of 8 mg/1 in 1996 to 21 mg/1 in
2009. It is believed that water conservation
measures, in conjunction with the heavy use
of garbage disposals in the kitchen area,
have led to the increased TV loading of the
system (Table 2).
Table 2. TKW and NH3 in Pond Influent,
1996 and 2010
Influent
1996
2010
TK/V (mg/L)
28
45
NH3 (mg/L)
8
21
The new study showed that the ponds did
continue to nitrify, but that the process was
now confined to the second pond, and at a
slower rate and beginning much later in the
summer. As a result, the ponds were unable
to handle the increased TV load within the
system's detention time and resulted in the
passing ofNH3 to the storage pond and
effluent. Dissolved oxygen levels were also
found to be too low in the first pond (often <
0.2 mg/1). Insufficient aeration in the first
pond could lead to the passing of BOD5 to
the second pond, potentially delaying the
onset of nitrification. BODs must be
removed before nitrification can proceed. A
review of operational data pointed out the
fact that after spray season ends, the
operators held all flow for the entire months
of November and December and then
discharge to the brook in January, February
and March, precisely when NHs
concentrations would be expected to be the
highest.
D-4
-------
During the first year of operating under this plant operator is Mark Pettengill (603-679-
plan, discharge to the brook for the months 5335).
of November and December 2009 resulted
in average NHs concentrations of 1.77 and
1.29 mg/1, respectively. From January 2010
through April, all flow was held until the
start of spray season. Supplemental aeration
in the first pond has not yet been
implemented.
Discussion
The major recommendation of this study
was to maximize discharge to the brook,
within permit limits, during the months
when the NHs was expected to be low,
mainly November, December and the first
half of January, and rely on holding and
spray irrigation for the remainder of the
year. This plan, being weather dependent,
requires careful planning by the operator to
maximize the storage volume of the holding
pond to ensure there is adequate room for
storage from mid-January to the start of
spray season. The study also recommended
adding supplemental aeration to the first
pond in order to maximize BODs removal
there, which, in theory, should allow
nitrification to proceed faster and be of
longer duration in the second pond.
Conclusion
This case study illustrates the benefits of
system-wide monitoring, close evaluation of
flows and loadings, and assessing plant
operations to determine the potential for a
pond to nitrify. It is unlikely that a
continuous flow through pond would meet
limits of < 6 mg/1 in a cold climate without
further enhancements, but in an under-
loaded pond where the detention time and
discharge periods may be manipulated, this
may be possible. Further study of those
variables may be warranted.
Report by Wes JAipple, New Hampshire
Department of Environmental Services. The
D-5
-------
The State of Kansas
The Case for Ponds in Anticipation of More
Stringent Nutrient Limits for Wastewater
Treatment System Effluents
Given overall good, consistent treatment and
low cost, the Kansas Department of Health
and Environment has encouraged
communities to build ponds for wastewater
treatment. As a result, nearly 80% of all
municipal wastewater treatment in the State
of Kansas is provided by wastewater pond
systems.
In 1994, the Kansas Department of Health
and Environment adopted water quality
standards that were significantly increased
in scope and stringency. Language was
indicating that wastewater treatment ponds
would be able to meet these standards was
not approved by US EPA Region 5. In
1999, the KDHE adopted revised standards
that eliminated the reference to ponds and
spelled out how ponds would be addressed
in the NPDES permitting process. This
included a study of pond performance.
Effluent samples from eighteen facilities
built in accordance with KDHE's Minimum
Standards of Design for Water Pollution
Control Facilities were analyzed, including
BOD5, SBOD5, CBOD5, NH3, TKN, NO3,
TP, dissolved/1, fecal coliform and/?H.
Overall, the data indicated that pond systems
provide consistently good treatment for
CBODs, N and bacteria. Increase in total
BODs in late summer, correlating to
increase ofNH3 and organic N, is thought to
be due to increasing anaerobic conditions in
the sediment, leading to microorganism die-
off KDHE has been evaluating
maintenance options to reduce solids in
pond effluent.
Similarly, ponds are shown to provide good
quality year-round disinfection of
wastewater. During the recreation season,
-th
best fit curves indicated that fecal coliform
will be <200 MPN/100 mL 50% of the time,
with 100% of the samples <1700 MPN/100
mL. In the winter, 55% of the samples will
be <200 MPN/100 mL and 90% will be
<2000 MPN/100 mL. An increase in fecal
coliform seen in the late summer correlates
fairly well with the increase in N.
The issue of greatest concern for the
viability of the pond systems in Kansas is
the adoption of nutrient criteria by the EPA.
The Agency's approach is to develop criteria
by ecoregion; Kansas is located in five of
those regions. The EPA Region 7 Regional
Technical Advisory Group's task is to
identify rivers impacted by nutrients, collect
water quality data from those rivers, select
the upper 25th percentile of the nutrient
values as ecoregion reference conditions.
Where insufficient data exist, the lower 2511
percentile of the available data from all sites
will be used. RTAG recommended criteria
for all lakes and reservoirs in Kansas, Iowa,
Nebraska and Missouri are 0.70 mg/L (T7V);
35 |ig/L (TP); and 8 |ig/L (chl a). These
criteria, it is believed, will be of concern to
all types of wastewater treatment facilities,
not only pond systems.
The KDHE published the Surface Water
Nutrient Reduction Plan in December 2004.
It reaffirms its support of wastewater
treatment ponds as the only feasible
treatment technology for many small Kansas
towns and attests to their effectiveness in
removing nutrients (TTVby 65% and IP by
55%).
The information for this case study is taken
from Tate, M.B. et al. 2002 and the Kansas
Department of Health and Environment,
2004.
D-6
-------
Los Banos, CA
Looking at potential for reducing energy
costs and long-term impacts of irrigating
with pond effluent
Los Banos is community of 40,000 people
located in the Central Valley of California.
The wastewater treatment facility consists of
234 ha (354 ac) of treatment and storage
ponds (167.4 ha/ 354 ac) and spray fields
(67.2 ha/166 ac). Several studies have been
initiated to understand baseline conditions
before plans are developed for expansion.
Unfavorable economic conditions have
slowed the rate of growth, which affected at
least one of the studies.
Pacific Gas & Electric, working with the
California Wastewater Process Optimization
Program (CalPOP), asked the City of Los
Banos if it would participate in a study to
evaluate and document potential energy
savings using Solarbee technology.
Previous projects typically involved the
replacement of standard mechanical mixing
and aeration systems with Solarbee® units;
the Los Banos project involved the
introduction of the technology as an
alternative to introducing standard
mechanical mixing and aeration systems to a
large-scale facultative pond treatment
system. While the potential savings is
speculative, the deployment of the
Solarbee® aerators in one treatment and one
storage pond did demonstrate their
effectiveness in changing the
hydrodynamics (reducing stratification of
temperature and dissolved oxygen) and
provided water quality information.
Table 3. Los Banos Wastewater
Treatment System Process Features
Treatment
Process
Characteristics
Average Influent
Flow
Average Influent
BOD
Assumed Influent
NH3
Value
3.5 mg/d
535 mg/L
25 mg/L
Average Recycled
Flow (treatment
pond effluent) to
Plant Headworks
Average Recycled
BOD (treatment
pond effluent) to
Plant Headworks
Combined (Influent
+ recycled) BOD5
to Ponds
19.2 mg/d
70 mg/L
140 mg/L
Volume/Surface
Area
Treatment Pond
1&2
Treatment Pond 5
Treatment Pond 6
Storage Pond 3
Storage Pond 4
Storage Pond 7
Cm(K)/Ha
471/34.4
651/28.3
738/28. 3
307/12.9
609/36.4
723/27.1
(MG/Ac)
(124.5 /
85)
(1727
70)
(195 /
70)
(81 / 42)
(161 790)
(190.5 /
67)
The interpretation of water quality results
was complicated by the fact that the system
process includes constant effluent recycling
and redistribution to ponds, as well as
differences in pond depths, pond internal
loadings, and detention times. Project
analysis indicated that the Solarbee®s
operated according to their design
parameters and met specifications.
Specifically, the water column
D-7
-------
characteristics of temperature, DO,/>H, and
conductivity showed that the ponds with
Solarbee®s were better mixed, less stratified,
cooler, and had significantly better 02
profiles than the control ponds. It was
concluded that the installation of Solarbee®
aerators would be a reasonable alternative to
the mechanical aeration.
Table 3 provides a facility process summary
that presents applicable information
collected as part of the pre-project analysis
for the treatment facility. Based on influent
data from January 2007 to December 2007,
the current plant influent loading is 3.5 mgd
flow with a yearly average BODs
concentration is 535 mg/I. However, as is
common in plants with food processing
influent flows, there is a sustained peak of
600 mg/I influent BODs for two months
during the year.
Ponds 1 through 7 were monitored for DO,
BOD5, TSS, EC and temperature.
Supplemental testing included CBODs, NHs,
TKjV, NO2= and NOi (the results are not
presented here).
While the comparison of CBOD5 and BOD5
between ponds gave limited information, the
ratio of BODs to CBODs, an indicator of the
N and non-organic 02 demand portion, was
fairly consistent in all ponds. In addition, the
facility is achieving CBOD5 levels that are
non-detect in Ponds 6 and 7 (Table 4). ("The
non-detect CBOD results are outstanding for
any pond-based system anywhere in the
country. Most of the credit goes to a well-
maintained and well-operated system
operated by dedicated staff...")
Table 4. CBOD5 (mg/L) in Ponds with
Solarbee® Aerators vs. Control
Ave
Min
Max
Treatment
Ponds
Solar
Bee®
Pond
1
32
22
60
Control
Pond 2
26
13
35
Storage Ponds
Solar
Bee®
Pond
6
15
2.5*
35
Control
Pond 7
13
2.5*
24
*One/half the detection limit. Actual value
is non-detect.
Another study was conducted recently to
look at the effect of spraying fields with Los
Banos WWTP water (data not provided).
The consultant evaluated water level and EC
data from new and previously existing
monitoring wells around the WWTP, as well
as from a network of shallow piezometers
maintained by the Central California
Irrigation District. Results of this salinity
study indicate that (1) unlined irrigation
canals are likely influencing shallow
groundwater quality, masking the regional
salinity gradient, and (2) evapo-
concentration may be locally concentrating
salts in groundwater. The study also
included installation of additional
monitoring wells and quarterly sampling of
these wells. It is anticipated that these data
will be used to demonstrate that the City's
wastewater management practices are not
adversely impacting the groundwater.
This case study was prepared from Solar-Powered
Circulator Energy Assessment Project, Emerging
Technologies Program, Pacific Gas & Electric
(2008) Quantum Energy Services & Technologies,
Inc.; Six Months Report Reviewing Phase One
Solarbee® Pilot Program at the City of Los Banos
Wastewater Treatment Facility (2008)
(http://www.Solarbee.com) and Salinity Study for
Wastewater Treatment Facilities Expansion in City of
Los Banos EKI Consultants
(http://www.ekiconsult. com)
D-8
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Arkadelphia, Arkansas
The City of Arkadelphia, located on the
Ouachita River, with a current population of
11,000, put in a wastewater treatment pond
system in 1968. Arkadelphia's wastewater
treatment facility consists of 164 acres of
oxidation ponds, with the final eleven acres
in aquaculture (Lemna Process, see smallest
pond in Figure 1). Discharge NPDES limits
to the Ouachita River are 30 mg/L BODs
and 90 mg/L TSS. Average flow through the
system is 1.9 MGD with current capability
of treating 3.0 MOD.
Sludge was removed from the first pond in
1980. In 1994, a duck weed pond was
added to the treatment train to provide
consistent TSS, especially in the summer.
The operators were advised that they would
have to harvest the Lemna, using a harvester
to break up the clumps of vegetation. In
fact, they have never had to use the
harvester, as the Lemna breaks up in the fall
and decomposes, without causing a
significant build up of sludge. The Lemna
pond is partitioned into a grid system by a
series of plastic enclosures. The
infrastructure, including plastic sheeting,
stainless steel pins, has not needed to be
replaced in sixteen years of operation. An
added bonus is the number of species of
birds visiting the Lemna pond to eat the
insects that are found there.
Report based on interviews and website
information (www.cityorarkadelphia.com).
Figure 1. Arkadelphia Wastewater
Treatment Ponds with Lemna Process
(smallest pond).
D-9
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APPENDIX E
Troubleshooting
E-l
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APPENDIX E
TROUBLESHOOTING
Table 9-5. Common Problems in Wastewater Treatment Pond Operation (Richard and
Bowman 1991)
Problem
Odors
Poor BOD
Removal
High
Effluent
TSS
Poor Fecal
Coliform
Removal
High pH
Low pH
Possible Causes
Organic overload
Poor aeration or mixing
Previous ice-covered ponds
Duckweed growth
Excess weed growth on pond banks harboring flies,
and mosquitoes, trapping grease and organics.
Organic overloading
Short Circuiting
Ice-covered ponds
Recent reduction in pond temperature
Algal bloom
Algal bloom
Excess pond mixing or short circuiting
Spring or Fall turnover
Excessive solids buildup in bottoms of ponds
Chlorine residual too low or poor chlorine contact
chamber design
Increase in chlorine demanding substance in
effluent (H2 S, N02)
Water fowl contamination
Algal stripping of carbon dioxide and bicarbonate
alkalinity
Accumulation of organic sludge stuck in the "acid
phase"
Extensive nitrification
Organic overloading
Excessive daphnia growth
Possible Solutions
Increase aeration capacity.
After aerator run time, change or supplement type of aeration.
Increase aerator run time, change type of aerator to eliminate ice
over.
Increase aerator run time, chemical treatment (Diquat), physical
removal (harvest), add ducks or geese.
Physical removal by pulling, mowing, burning or chemical treatment
(Diquat). In winter, lower pond level and allow ice to freeze around
weed stem. Increase water level.
Increase aeration capacity.
Improve inlet-outlet conditions, add baffles, add recirculation to
improve mixing, add or improve aeration of ponds.
Change or add aerator.
Increase hydraulic detention time.
Increase mechanical mixing; add physical shade (Aquashade,
Photoblue), floating cover such as swimming pool cover, Styrofoam
sheets or balls, duckweed cover. Addition of algal predator such as
daphnia. Add chemicals (copper sulfate). Addition of constructed
wetlands to polish effluent.
See algal bloom solution above.
See short circuiting solution above.
Add different types of aeration to eliminate stratification or add
supplemental aeration, add recirculation.
Physically remove solids by pump or sludge barge; proper sludge
disposal in conformance with State and Federal regulations.
Increase chorine feed rate, provide 40:1 1:w ratio, provide a
minimum 30 minute detention time at peak flow.
Remove solids from chlorine contact chamber, increase chlorine
feed rate.
Increase chlorine feed rate.
See algal bloom solution above.
Physically remove sludge by pumping or sludge dredge.
Increase aerator run time, add recirculation.
Increase aeration capacity, add recirculation.
Increase aeration capacity or run time.
E-2
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Table 9-6. Troubleshooting Test and Probable Causes
(Richard and Bowman, 1991)
Probable Cause
Test
BOD5-high
CBOD5-high
TSS - moderate
Filtered BOD5 - high
Low DO
DO/DO Profile
Microscopic
Exam
TSS/BOD5 Ratio
BOD5-high
C BOD5 - low
TSS-high
pH-high
Low DO at night (Algae
overgrowth or nitrification)
Filtered BOD DO Profile (early
morning) Effluent Ammonia Test
TSS/BODs Ratio Microscopic Exam
BOD5-high
CBOD5-high
TSS - moderate
Filtered BOD - high
Low DO
Short circuiting
Sludge Buildup
(Soluble organics released
from sludges)
DO/DO Profile
Microscopic Exam TSS/BODs Ratio
Table 9-7. Troubleshooting Tables (USEPA, 1977)
How to Control Water Weeds (USEPA, 1977)
Indicators/Observations
Probable Cause
Solutions
Weeds provide for burrowing animals
cause short circuiting problems, stop wave
action so that scum can collect and make
a nice home for mosquitoes, and odors
develop in the still area. Duckweed stops
sunlight penetration and prevents wind
action thus reducing the oxygen in the
pond. Root penetration causes leaks in
pond seal.
Poor circulation, maintenance
insufficient water depth.
Pull weeds by hand if new growth.
Mow weeds with a sickle bar mower.
Lower water level to expose weeds, then
burn with gas burner. (Check with local
fire department prior to burning.)
Allow the surface to freeze at a low water
level, raise the water level and the
floating ice will pull the weeds as it rises.
(Large clumps of roots will leave holes in
pond bottom; best results are obtained
when weeds are young.)
Increase water depth to above tops of
weeds. Use riprap. Caution: If weeds get
started in the riprap they will be difficult
to remove but can be sprayed with EPA
approved herbicides.
To control duckweed, use rakes or push
a board with a boat, then physically
remove duckweed from pond.
E-3
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Table 9-7 (Cont.)
How to Control Burrowing Animals (USEPA 1977)
Indicators/Observations
Probable Cause
Solutions
Burrowing animals must be controlled
because of the damage they do to
dikes. Rodents such as muskrats
and nutria dig partially submerged
tunnels into dikes. If the water level
is raised, they will burrow further and
may go on out the top thus
weakening the dike.
Bank conditions that attract
animals. High population in area
adjacent to ponds.
Remove food supply such as cattails and
burr reed from ponds and adjacent areas.
Muskrats prefer a partially submerged
tunnel, if the water level is raised it will
extend the tunnel upward and if lowered
sufficiently, it may abandon the tunnel
completely. They may be discouraged by
raising and lowering the level 6-8 inches
over several weeks.
If problem persists, check with local game
commission officer for approved methods
of removal, such as live trapping, etc.
How to Control Dike Vegetation (Modified USEPA 1977)
Indicators/Observations
Probable Cause
Solutions
High weed growth, brush, trees and
other vegetation provide nesting
places for animals. This can cause
weakening of the dike and presents
an unsightly appearance. Also may
reduce wind action on the pond.
Poor maintenance.
Periodic mowing is the best method. Sow
dikes with a mixture of fescue and blue
grasses on the shore and short native
grasses elsewhere. It is desirable to select
a grass that will form a good sod and drive
out tall weeds by binding the soil and "out
compete" undesirable growth.
Spray with approved weed control
chemicals. Note: Be sure to check with
authorities. Some states do not allow
chemical usage. All others require that
chemicals be bio-degradable.
Some small animals, such as sheep, have
been used. May increase fecal coliform,
especially to the discharge cell. Not
recommended with pond systems utilizing
synthetic pond liner. Practice "rotation
grazing" to prevent destroying individual
species of grasses. An example schedule
for rotation grazing in a 3-pond system
would be: Graze each pond area for 2
months over a 6-month grazing season.
How to Control Scum (USEPA 1977)
Indicators/Observations
It is necessary to control sum
formations to prevent odor problems
and to eliminate breeding spots for
mosquitoes. Also, sizeable floating
rafts will reduce sunlight.
Probable Cause
Pond bottom is turning over
with sludge floating to the
surface. Poor circulation and
wind action. High amounts of
grease and oil in influent will
also cause scum.
Solutions
• Use rakes, a portable pump to get a water jet
or motor boats to break up scum formations.
Broken scum usually sinks.
Any remaining scum should be skimmed and
disposed of by burial or hauled to landfill with
approval of regulatory agency.
E-4
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Table 9-7 (Cont.)
How to Control Odors (Modified USEPA 1977)
Indicators/Observations
Probable Cause
Solutions
Low pH (less than 6.5) and dissolved
oxygen (less than 1 mg/L). Foul
odors develop when algae die off.
Blue-green algae is an indicator
of incomplete treatment,
overloading and/or poor nutrient
balance.
Refer to Common causes of pond effluent
noncompliance.
Apply chemical such as sodium nitrate.
Application rate: 5-15 percent of sodium nitrate
per pound of BOD on a pound for pound basis.
Or apply 200 pounds sodium nitrate per million
gallons. See literature for commercial products.
Repeat at a reduced rate on succeeding days.
Or use 100 pounds sodium nitrate per acre
(112kg/ha) for first day, then 50 pounds per acre
(56 kg/ha) per day thereafter if odors persist.
Apply in the wake of a motor boat.
Install supplementary aeration such as floating
aerators, caged aerators, or diffused aeration to
provide mixing and oxygen. Daily trips over the
pond area in a motor boat also helps. Note:
Stirring the pond may cause odors to be worse
for short periods but will reduce total length of
odorous period.
Recirculate pond effluent to the pond influent to
provide additional oxygen and to distribute the
solids concentration. Recirculate on a 1 to 6
ratio.
Eliminate septic or high-strength industrial
wastes.
How to Control Insects (Modified USEPA 1977)
Indicators/Observations
Insects present in area and larvae or
insects present in pond water.
Probable Cause
Solutions
Poor circulation and
maintenance.
• Keep pond clear of weeds and allow wave
action on bank to prevent mosquitoes from
hatching out.
• Keep pond free from scum.
• As for stocking fish, note that Gambusia do not
eat mosquito larvae any faster than other small
fish species.
• Spray with EPA approved larvacide as a last
resort. Check with state regulatory officials for
approved chemicals.
E-5
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Table 9-7 (Cont.)
How to Control Blue-Green Algae (Modified USEPA 1977)
Indicators/Observations
Probable Cause
Solutions
Low pH (less than 6.5) and dissolved
oxygen (less than 1mg/L). Foul odors
develop when algae die off.
Blue-green algae is an indicator
of incomplete treatment,
overloading and/or poor nutrient
balance.
• Refer to common causes of pond effluent
noncompliance. WARNING!: Prior to using
copper sulfate, see explanation below.
• Apply 3 applications of a solution of copper
sulfate.
> If the total alkalinity is above 50 mg/L
apply 1200 kg/m3 (10 Ibs/MG) of copper
sulfate per million gallons in cell.
> If alkalinity is below 50 mg/L reduce the
amount of copper sulfate to 600 kg/m3 (5
Ibs/MG.
Note: Some states do not approve the use of
copper sulfate since in concentrations greater than
1 mg/L it is toxic to certain organisms and fish.
• Break up algal blooms by motor boat or a
portable pump and hose. Motor boat motors
should be air cooled as algae may plug up
water cooled motors.
Important: In the past copper sulfate has been
used to control algae. It is recommended that the
operator check with the regulatory agency to
determine if a copper parameter must be added to
the discharge permit. It should also be noted that
prolonged use of copper sulfate may cause a
buildup of copper in the benthic sludges making it
difficult to dispose of the sludges when pond
cleaning becomes necessary.
How to Obtain Best Algae Removal In The Effluent (Modified USEPA 1977)
Indicators/Observations
Probable Cause
Solutions
Most of the suspended solids present
in a pond effluent are due to algae.
Because many single-celled algae
are motile and are also very small
they are difficult to remove.
Weather or temperature
conditions that favor particular
population of algae.
Draw off effluent from below the surface by
use of a good baffling arrangement or variable
depth draw off.
Use multiple ponds in series.
Check other chapters in the manual for latest
algae control methods.
In some cases, alum dosages of 20mg/L have
been used in final cells used for intermittent
discharge to improve effluent quality.
Dosages at or below this level are not toxic.
E-6
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Table 9-7 (Cont.)
How to Correct Lightly Loaded Ponds (USEPA 1977)
Indicators/Observations
Lightly loaded ponds may produce
filamentous algae and moss which
limits sunlight penetration. These
forms also tend to clog pond outlets.
Probable Cause
Overdesign, low seasonal flow.
Solutions
• Correct by increasing the loading by
reducing the number of cells in use.
• Use series operation.
How to Correct Overloading (Modified USEPA 1977)
Indicators/Observations
Probable Cause
Solutions
Overloading which results in
incomplete treatment of the waste.
Overloading problems can be
detected by offensive odors, a yellow
green or gray color. Lab tests
showing low pH, DO, and excessive
BOD loading per unit should also be
considered.
Short circuiting, industrial wastes,
poor design, infiltration, new
construction (service area
expansion), inadequate treatment
and weather conditions.
Bypass the cell and let it rest.
Use parallel operation.
Apply recirculation of pond effluent.
Look at possible short-circuiting.
Install supplementary aeration
equipment.
How to Correct A Decreasing Trend In pH (USEPA 1977)
Indicators/Observations
Probable Cause
Solutions
pH controls the environment of algae
types, as an example, the green
chlorella needs a pH from 9.0 to 8.4
pH should be on the alkaline side,
preferable about 8.0 to 8.4
Both pH and DO will vary throughout
the day with lowest reading at sunrise
and highest reading in the afternoon.
Measure pH same time each day and
plot on a graph.
A decreasing pH is followed by a
drop in DO as the green algae die
off. This is most often caused by
overloading, long periods of adverse
weather or higher animals, such as
Daphnia, feeding on the algae.
Bypass the cell and let it rest.
Use parallel operation.
Apply recirculation of pond effluent.
Check for possible short circuiting.
Install supplementary aeration equipment
if problem is persistent and due to
overloading.
Look for possible toxic or external
causes of algae die-off and correct at
source.
E-7
-------
Table 9-7 (Cont.)
How to Correct A Low Dissolved Oxygen (DO) (Modified USEPA 1977)
Indicators/Observations I Probable Cause I Solutions
A low, continued downward trend in DO
is indicative of possible impending
anaerobic conditions and the cause of
unpleasant odors. Treatment becomes
less efficient.
Poor light penetration, low
detention time, high BOD loading
or toxic industrial wastes.
(Daytime DO should drop below
1.0 mg/L during warm months.)
Increase aerator running time.
Remove weeds such as duckweed if
covering greater than 40 percent of the
pond.
Reduce organic loading to primary cell(s)
by going to parallel operation.
Add supplemental aeration (surface
aerators, diffusers and/or daily operation
of a motor boat).
Add recirculation by using a portable
pump to return final effluent to the head
works.
Apply sodium nitrate (see How to Control
Odors for rate).
Determine if overload is due to industrial
source and remove it.
How to Correct Short Circuiting (Modified USEPA 1977)
Indicators/Observations
Probable Cause
Solutions
Odor problems low DO in part of the
pond, anaerobic conditions and low pH
found by checking values from various
parts of the pond and noting on a plan of
the pond. Difference of 100 percent to
200 percent may indicate short
circuiting.
After recording the reading for each
location, the areas that are not receiving
good circulation become evident. These
areas are characterized by a low DO
and pH.
Poor wind action due to trees or
poor arrangement of inlet and
outlet locations. May also be due
to shape of pond, weed growth or
irregular bottom.
Cut trees and growth at least 150 m (500
ft) away from pond if in direction of
prevailing wind.
Install baffling around inlet location to
improve distribution.
Add recirculation to improve mixing.
Provide new inlet-outlet locations
including multiple inlets and manifolds.
Clean out weeds.
Fill in irregular bottoms.
Add directional surface mixers or
aerators to mix and retard flow.
E-8
-------
Table 9-7 (Cont.)
How to Correct Anaerobic Conditions (USEPA 1977)
Indicators/Observations
Probable Cause
Solutions
Facultative pond that turned anaerobic
resulting in high BOD, suspended solids
and scum in the effluent in continuous
discharge ponds. Unpleasant odors, the
present of filamentous bacteria and
yellowish-green or gray color and placid
surface indicate anaerobic conditions.
Overloading, short circuiting, poor
operation or toxic discharge.
Change from a series to parallel
operation to divide load. Helpful if
conditions exist at a certain time each
year and are not persistent.
Add supplemental aeration if pond is
continuously overloaded.
Change inlets and outlets to eliminate
short circuiting. See How to Correct
Short Circuiting.
Add recirculation (temporary use
portable pumps) to provide oxygen and
mixing.
In some cases temporary help can be
obtained by adding sodium nitrate at
rates described elsewhere in this
manual.
Eliminate sources of toxic discharges.
How to Correct Problems In Aerated Ponds (USEPA 1977)
Indicators/Observations
Probable Cause
Solutions
Fluctuating DO, fin pin floe in final cell
effluent, frothing and foaming, ice
interfering with operation.
Shock loading, over-aeration,
industrial wastes, floating ice.
• Control aeration system by using time
clock to allow operation during high load
periods, monitor DO to set up schedule
for even operation, holding
approximately 1 mg/L or more.
• Vary operation of aeration system to
obtain solids that flocculate or "clump"
together in the secondary cell but are not
torn apart by excessive aeration.
• Locate industrial wastes that may cause
foaming or frothing and eliminate or
pretreat wastes. Examples are slaughter
house, milk or some vegetable wastes.
• Operate units continuously during cold
weather to prevent freezing damage or
remove completely if not a type that will
prevent freeze-up.
E-9
-------
Table 9-7 (Cont.)
How to Correct A High BOD In The Effluent (Modified USEPA 1977)
Indicators/Observations
Probable Cause
Solutions
High BOD concentrations that are in
violation of NPDES or other
regulatory agency permit
requirements Visible dead algae.
Short detention times, poor inlet and
outlet placement, high organic or
hydraulic loads and possible toxic
compounds.
Refer to Common Causes of Lagoon
Effluent Noncompliance.
Check for collection system infiltration
and eliminate at source.
Use portable pumps to recirculate the
water.
Add new inlet and outlet locations.
Reduce loads due to industrial sources
if above design level.
Prevent toxic discharges.
How to Correct Problems In Anaerobic Ponds (USEPA 1977)
Indicators/Observations
Probable Cause
Solutions
Odors
Hydrogen sulfide, (rotten egg) odors
or other disagreeable conditions due
to sludge in septic condition.
LowpH
pH below 6.5 accompanied by odors
are the result of acid bacteria working
in the anaerobic condition.
Lack of cover over water surface and
insufficient load to have complete
activity which eventually forms scum
blanket.
Acid formers working faster than
methane formers in an acid
condition.
Use straw cast over the surface or
polystyrene plans as a temporary cover
until a good surface sludge blanket has
formed.
The pH can be raised by adding a lime
slurry of 580 kg dehydrated lime/200L
water (100 Ibs/ 50 gal) at a dosage rate
of 12 g/10,000 L (1 Ib/10,000 gal) in the
pond. The slurry should be mixed while
being added. The best place to put the
lime is in at the entrance to the lagoon
so that it is well mixed as it enters the
pond.
E-10
-------
APPENDIX F-1&F-2
Study Guides for Pond Operators
F-1
-------
TO
AND
D
WISCONSIN DEPARTMENT OF NATURAL
OF
http://dnr.wi.gov/org/es/science/opcert/
*
Note -As of Jan 2010, this study guide cont ains objectives plus key knowledges.
F-2
-------
ACKNOWLEDGEMENTS
Special appreciation is extended to the many individuals who
contributed to this effort.
Wastewater operators were represented by:
Mel Anderson - Spooner
Harold Bourassa - Iron River
Chester Bush - Weyerhaeuser
Jerry Chartraw - Cumberland
Dominic Ciatti - Montreal
Al Cusick - Spooner
Bruce Degerman - Barren
Mike Frey - Winter
Kenneth Grenawalt - Evansville
Dale Hager - Sauk City
Keith Johnson - Hollandale
Milo Kadlec - Hayward
Bob Kamke - Medford
Mike LaRose - Rice Lake
Mike Magee - Rice Lake
Joe McCarthy - Madeline Island
Jeff O'Donnell - Park Falls
Rod Peterson - Barren
Tim Powers - Minong
Ken Raymond - Cambridge
Bill Rogers - Stone Lake
George Siebert - Telemark
Don Silver - Pardeeville
Dennis Steinke - North Freedom
Wally Thorn - Rice Lake
Charles Walczak - Ridgeway
Dave Wardean - Webster
Jerry Wells - Browntown
VTAE and educational interests were represented by:
Glen Smeaton, VTAE Services District Consortium
Pat Gomez, Moraine Park Technical College
Steve Brand, Cooper Engineering, Rice Lake
DNR regional offices were represented by:
Bob Gothblad, Northern Region, Spooner
Jim Hansen, Northern Region, Park Falls
Janet Hopke, Northern Region, Spooner
Chuck Olson, Northern Region, Brule
Pete Prusack, Northern Region, Cumberland
Jack Saltes, South Central Region,Dodgeville
DNR central office was represented by:
Lori Eckrich, Madison
Rick Reichardt, Madison
Ron Wilhelm, Madison
Tom Kroehn, Madison
Tom Mickelson, Madison
F-3
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PREFACE
This operator's study guide represents the results of an
ambitious program. Operators of wastewater facilities,
regulators, educators and local officials, jointly prepared the
objectives and exam questions for this subclass.
The objectives in this study guide have been organized into
modules, and within each module they are grouped by major
concepts.
NOTE: As of January 2010, this study guide also includes key
knowledges.
HOW TO USE THESE OBJECTIVES WITH REFERENCES
In preparation for the exams, you should:
1. Read all of the key knowledges for each objective.
2. Use the resources listed at the end of the study guide for
additional information.
3. Review all key knowledges until you fully understand them
and know them by memory.
IT IS ADVISABLE THAT THE OPERATOR TAKE CLASSROOM OR ONLINE
TRAINING IN THIS PROCESS BEFORE ATTEMPTING THE CERTIFICATION
EXAM.
Choosing A Test Date
Before you choose a test date, consider the training
opportunities available in your area. A listing of training
opportunities and exam dates 1 s ava 1 1 abl e on the T)NP Operator
Certification home page http://dnr.wi.gov/org/es/science/opcert/
It can also be found in the annual DNR "Certified Operator" or by
contacting your DNR regional operator certification coordinator.
F-4
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TABLE OF CONTENTS
PAGE NO.
Acknowledgements 2
Preface 3
Table of Contents 4
Resources 27
MODULE A: PRINCIPLE, STRUCTURE AND FUNCTION
Concept: Principle of Ponds 5
Concept: Structure and Function 7
MODULE B: OPERATION AND MAINTENANCE
Concept: Operation 9
Concept: Maintenance 14
MODULE C: MONITORING AND TROUBLESHOOTING
Concept: Monitoring 17
Concept: Troubleshooting 19
MODULE D: SAFETY AND CALCULATIONS
Concept: Safety 23
Concept: Calculations 24
F-5
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INTRODUCTION TO THE OPERATION OF PONDS AND LAGOONS
MODULE A: PRINCIPLE, STRUCTURE AND FUNCTION
CONCEPT: PRINCIPLE OF PONDS
1. Explain the reasons for using Ponds to treat wastewater.
PONDS HAVE HISTORICALLY BEEN USED TO PROVIDE DETENTION TIME
FOR WASTEWATER TO ALLOW IT TO BE STABILIZED THROUGH NATURAL
PROCESSES. WASTEWATER IS TREATED BY THE ACTION OF BACTERIA
(BOTH AEROBIC AND ANAEROBIC), OTHER MICRO AND MACRO
ORGANISMS, ALGAE, AND BY THE PHYSICAL PROCESS OF GRAVITY
SETTLING. WHEN PROPERLY DESIGNED, PONDS ARE CAPABLE OF
PROVIDING THE EQUIVALENT OF SECONDARY TREATMENT FOR BOTH BOD
AND SUSPENDED SOLIDS.
2. Discuss the advantages and disadvantages of Pond systems as
compared to bio-mechanical systems for wastewater treatment.
ADVANTAGES DISADVANTAGES
* LOW CONSTRUCTION COST * LARGE LAND REQUIREMENTS
* LOW OPERATIONAL COST * POSSIBLE GROUNDWATER
* LOW ENERGY USAGE CONTAMINATION FROM LEAKAGE
* CAN ACCEPT SURGE LOADINGS * CLIMATIC CONDITIONS AFFECT
* LOW CHEMICAL USAGE TREATMENT
* FEWER MECHANICAL PROBLEMS * POSSIBLE SUSPENDED SOLIDS
* EASY OPERATION PROBLEMS (ALGAE)
* NO CONTINUOUS SLUDGE HANDLING * POSSIBLE SPRING ODOR
PROBLEMS (AFTER ICE-OUT)
* ANIMAL PROBLEMS (MUSKRATS,
TURTLES,ETC.)
* VEGETATION PROBLEMS (ROOTED
WEEDS,DUCKWEED,ALGAE)
* LOCALIZED SLUDGE PROBLEMS
(DEPOSITION NEAR INLET)
3. Describe the following types of ponds:
A. Areobic.
B. Anaerobic.
C. Aerated.
D. Facultative.
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A. AEROBIC: AN AEROBIC POND SYSTEM WOULD HAVE OXYGEN
DISTRIBUTED THROUGHOUT THE ENTIRE AREA. THIS WOULD
BE SIMILAR TO A CLEAN LAKE WITH ANAEROBIC
CONDITIONS OCCURRING ONLY IN BOTTOM SED-IMENTS.
THIS CONDITION WOULD PROBABLY ONLY OCCUR IN A
TREATMENT SYSTEM UPON INITIAL START-UP WHEN THE
POND WOULD BE FILLED WITH A CLEAR WATER SOURCE, OR
WHEN COMPLETELY MIXED WITH SUPPLEMENTAL AIR.
B. ANAEROBIC: AN ANAEROBIC POND WOULD BE DEVOID OF ALL OXYGEN
THROUGHOUT THE ENTIRE AREA. THIS TYPE OF POND
SYSTEM WOULD ONLY BE USED IN SPECIAL APPLICATIONS,
USUALLY FOR TREATING CERTAIN INDUSTRIAL WASTES. IF
A NORMAL POND SYSTEM IS TOTALLY ANAEROBIC, IT IS
ORGANICALLY OVERLOADED. THE ONLY EXCEPTION WOULD
BE UNDER ICE COVER FOR A FILL AND DRAW TYPE
FACILITY.
C. AERATED: AN AERATED POND SYSTEM WOULD HAVE SUPPLEMENTAL AIR
SOURCES TO PROVIDE DISSOLVED OXYGEN. THIS IS
USUALLY ACCOMPLISHED WITH SURFACE MECHANICAL
AERATORS AND MIXERS, OR BY VARIOUS FORMS OF
DIFFUSERS SUPPLIED WITH COMPRESSED AIR FROM
MECHANICAL BLOWERS OR COMPRESSORS. FOR EQUAL SIZED
PONDS, THE AERATED POND WOULD PROVIDE THE BEST
TREATMENT DUE TO THE MECHANICAL ADDITION OF OXYGEN,
AND FOR A GIVEN ORGANIC LOADING, WOULD REQUIRE THE
LEAST AMOUNT OF LAND AREA.
D. FACULTATIVE: MOST STABILIZATION POND FACILITIES ARE OF
THIS TYPE. THE POND CONTAINS AN AEROBIC
SURFACE ZONE, AN ANAEROBIC BOTTOM ZONE, AND A
TRANSITIONAL (FACULTATIVE) ZONE IN BETWEEN.
THIS ALLOWS AEROBIC ORGANISMS TO FUNCTION IN
THE UPPER AREA, ANAEROBIC ORGANISMS IN THE
LOWER AND SLUDGE AREA, AND FACULTATIVE
ORGANISMS IN THE MIDDLE AREA. A FACULATIVE
ORGANISM CAN USE DISSOLVED OXYGEN OR COMBINED
OXYGEN, BECAUSE THEY CAN ADAPT TO CHANGING
CONDITIONS. THEY CAN CONTINUE DECOMPOSITION
WHEN THE SYSTEM CHANGES FROM AEROBIC TO
ANAEROBIC, ORFROM ANAEROBIC TO AEROBIC.
4. Discuss the relationship between bacteria and algae in a
Pond system.
IN ANY WASTEWATER POND, TREATMENT IS ACCOMPLISHED BY A
COMPLEX COMMUNITY OF ORGANISMS. THEY WORK IN AN INTERACTION
WITH EACH OTHER WHICH IS MUTUALLY BENEFICIAL. ALGAE, LIKE
ALL GREEN GROWING MATTER, USES NUTRIENTS AND CARBON DIOXIDE
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IN THE PRESENCE OF SUNLIGHT TO PRODUCE OXYGEN IN A PROCESS
CALLED PHOTOSYNTHESIS. THE OXYGEN PRODUCED IS USED BY
BACTERIA TO ASSIMILATE ORGANIC MATTER, BREAKING IT DOWN INTO
SIMPLER MATERIALS AND RELEASING CARBON DIOXIDE TO BE USED BY
THE ALGAE.
CONCEPT: STRUCTURE AND FUNCTION
Draw line diagrams of three Ponds in Series and in Parallel
operation.
SERIES:
INCOMING > POND > POND > POND >DISCHARGE
WASTE #1 #2 #3 OF TREATED
STREAM EFFLUENT
PARALLEL:
PONDttl
INCOMING DISCHARGE
WASTE > > PONDttS > OF TREATED
STREAM EFFLUENT
POND#2
Explain the function of each part of the following parts of
a Pond system:
A. Dikes.
B. Pond Seal.
C. Inlet and Outlet Water Control.
D. Flow Meter/Weirs.
E. Headworks/Screening.
F. Rip Rap.
A. DIKES - THE POND SIDES WHICH GIVE THE POND IT'S DEPTH AND
STRUCTURE.
B. POND SEAL - A CLAY OR SYNTHETIC LINER THAT KEEPS
WASTEWATER FROM PERCOLATING INTO THE GROUNDWATER.
C. WATER CONTROL STRUCTURES:
1. INLET - THE PIPING ARRANGEMENT THROUGH WHICH
EASIEJ2ATER IS INTRODUCED INTO THE POND.
2. OUTLET - THE STRUCTURE TO MAINTAIN THE SELECTED POND
WATER LEVEL AND ALLOW TREATED WASTE TO FLOW OUT.
FLOW METER/WEIRS - DEVICES TO MEASURE INCOMING OR
DISCHARGED WASTEWATER FLOW RATES.
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E. HEADWORKS/SCREENING - SOMETIMES PROVIDED TO REMOVE RAGS
AND LARGE OBJECTS.
F. RIP RAP - ROCK OR STONE PLACED AT NORMAL POND OPERATING
LEVELS TO PREVENT EROSION OF THE DIKES THAT COULD OCCUR
FROM WIND ACTIONS.
7. Describe two common kinds of pond water level control
structures.
A. SUBMERGED PIPE OUTLET WITH WATER LEVEL CONTROL BOARDS
BOARDS ARE REMOVED OR ADDED TO RAISE OR LOWER THE POND LEVEL
(USUALLY IN A MANHOLE).
B. TELESCOPING VALVE - A TELESCOPING PIPE SECTION THAT CAN BE
RAISED OR LOWERED TO CONTROL WATER LEVELS (USUALLY IN A
MANHOLE-LIKE STRUCTURE).
8. State two important functions of an Aeration System.
A. IT ADDS DISSOLVED OXYGEN TO THE POND CONTENTS.
B. IT MIXES THE POND CONTENTS.
9. Describe the function of each of the following components of
a Pond Aeration System:
A. Compressors/Blowers.
B. Airlines.
C . Diffusers.
D. Mechanical Aeration.
A. COMPRESSORS/BLOWERS: USED TO PROVIDE LOW PRESSURE AIR
USED IN THE POND AERATION SYSTEM.
B. AIRLINES: A PIPING SYSTEM USED TO CONVEY COMPRESSED AIR
TO THE POINTS OF APPLICATION.
C. DIFFUSERS: VARIOUS TYPES OF EQUIPMENT USUALLY LOCATED
NEAR THE POND BOTTOM. USED TO FORM BUBBLES IN
THE POND LIQUID TO ENTRAIN OXYGEN AND PROVIDE
MIXING.
D. MECHANICAL AERATION: SEVERAL DIFFERENT TYPES OF
EQUIPMENT (USUALLY ON FLOATS)
THAT SPRAY THE WATER INTO THE AIR
TO ENTRAIN OXYGEN AND PROVIDE
MIXING.
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10. Discuss the purpose of a Blower Air Relief Valve in a Pond
Aeration System.
IN THE EVENT OF EXCESS PRESSURE (PLUGGED DIFFUSERS OR AIR
LINES) THE PRESSURE RELIEF VALVE WILL OPEN TO RELEASE EXCESS
PRESSURE AND PROTECT THE PIPING, DIFFUSERS, AND THE BLOWER.
11. Describe what is meant by the term "freeboard" in a Pond
system.
FREEBOARD IS THE DISTANCE BETWEEN THE NORMAL MAXIMUM
OPERATING WATER SURFACE OF THE POND, AND THE TOP OF THE
DIKE. FREEBOARD IS NORMALLY 3 FEET (MEANING THE WATER LEVEL
SHOULD BE KEPT WITHIN 3 FEET FROM THE DIKE TOP).
MODULE B: OPERATION AND MAINTENANCE
CONCEPT: OPERATION
12. Describe series and parallel modes of Pond operation, and
state conditions when each should be used.
A STABILIZATION POND SYSTEM IS USUALLY COMPOSED OF A NUMBER
OF INDIVIDUAL CELLS(PONDS) AND CAN BE OPERATED IN SEVERAL
MODES.
SERIES: IN THIS MODE THE FLOW GOES THROUGH EACH CELL(POND)
IN SUCCESSION (E.G. PRIMARY CELL TO SECONDARY CELL
TO TERTIARY CELL). THIS TYPE OF FLOW PATTERN
NORMALLY PROVIDES THE BEST DEGREE OF TREATMENT AND
MINIMIZES ALGAE IN THE EFFLUENT.
PARALLEL:IN THIS MODE OF OPERATION THE INFLUENT FLOW IS
DIVIDED INTO TWO OR MORE PRIMARY CELLS. PARALLEL
OPERATION IS NORMALLY USED WHEN LOADINGS EXCEED
DESIGN LEVELS, WHEN ORGANIC OVERLOADS ARE
EXPECTED,OR DURING WINTER CONDITIONS WHEN CLIMATIC
CONDITIONS REDUCE THE AMOUNT OF DISSOLVED OXYGEN.
13. Discuss why some Ponds have difficulty meeting suspended
solids limits.
THE MOST COMMON PROBLEM IN MEETING SUSPENDED SOLIDS LIMITS
IN POND SYSTEMS WOULD BE EXCESSIVE ALGAE GROWTH BEING
DISCHARGED WITH THE FINAL EFFLUENT. OTHER MINOR PROBLEMS
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THAT COULD CAUSE SUSPENDED SOLIDS EFFLUENT PROBLEMS ARE
RISING SLUDGE, AND SOMETIMES ABUNDANT ZOOPLANKTON (SUCH AS
DAPHNIA) .
14. Explain why an operator should prefer to have a Pond
dominated by green algae.
GREEN ALGAE IS THE PREFERRED SPECIES THAT INDICATES A
PROPERLY FUNCTIONING POND SYSTEM. IF BLUE-GREEN ALGAE TAKE
OVER (USUALLY INDICATING ORGANIC OVERLOADING), THEY CAN
CAUSE BLACK-GREEN FLOATING MATS. THIS CAN CAUSE OPERATIONAL
PROBLEMS SUCH AS SHORT-CIRCUITING, REDUCTION OF MIXING, POOR
LIGHT PENETRATION, MAT REMOVAL PROBLEMS, ODOR, AND GENERAL
UNSIGHTLINESS. SPRING TURN-OVER MAY CAUSE A BLUE-GREEN ALGAE
BLOOM.
15. List ways most Ponds gain Dissolved Oxygen.
A. PHOTOSYNTHESIS BY ALGAE WITHIN THE POND(MAIN SOURCE OF
OXYGEN IN MOST POND TYPE SYSTEMS, ESPECIALLY SHALLOW
PONDS IN THE 3-5 FOOT DEPTH RANGE).
B. DIFFUSION OF ATMOSPHERIC OXYGEN AT THE POND SURFACE WITH
THE ACTION OF THE WIND PROVIDING MIXING OF THE OXYGEN
RICH SURFACE LAYER WITH THE WATER BELOW.
C. THE USE OF COMPRESSED AIR SYSTEMS OR SURFACE MECHANICAL
AERATORS.
16. Explain why dissolved oxygen concentrations vary with Pond
depth.
OXYGEN LEVELS VARY WITH DEPTH FOR A NUMBER OF REASONS. THE
MAIN REASON IS THE RELATIONSHIP OF THE ORGANISMS WITHIN THE
POND. OTHER REASONS ARE THE PHYSICAL ACTIONS WITHIN THE
POND, AND THE LOADING TO THE POND.
THE RELATIONSHIP OF ORGANISMS INVOLVES THE GENERAL
INTERACTION BETWEEN ALGAE AND BACTERIA. THE ALGAE ARE THE
MAIN SOURCE OF OXYGEN IN A POND SYSTEM. ALGAE GROWTH IS
GREATEST NEAR THE SURFACE WHERE LIGHT PENETRATION AND
PHOTOSYNTHESIS IS THE GREAT- EST. OXYGEN LEVELS DECREASE
WITH DEPTH, DUE TO LESS LIGHT PENETRATION NEEDED FOR
PHOTOSYNTHESIS.
THE ALGAE USE CARBON DIOXIDE IN THE PROCESS OF
PHOTOSYNTHESIS AND PRODUCE OXYGEN. THE BACTERIA STABILIZE
ORGANIC MATTER USING THE OXYGEN AND PRODUCE CARBON DIOXIDE.
THE PHYSICAL DIFFUSION OF ATMOSPHERIC OXYGEN OCCURS AT THE
SURFACE OF PONDS AND IS MIXED IN THE UPPER LAYERS BY WIND
ACTION. THE AMOUNT OF MIXING IS LIMITED, SO THE OXYGEN
LEVELS DECREASE WITH DEPTH.
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THE FINAL FACTOR AFFECTING OXYGEN LEVELS IS THE ORGANIC
LOADING TO THE SYSTEM. IF ORGANIC LOADINGS ARE SMALL, THE
OXYGEN LEVELS WILL BE MAINTAINED AT GREATER DEPTHS. IF
ORGANIC OVERLOADING OCCURS, THE WHOLE POND COULD GO
ANAEROBIC.
17. List the steps to follow during start-up of a Pond system.
A. FILL WITH CLEAR WATER (RIVER OR WELL WATER) IF IT HAS A
PLASTIC LINING, PARTLY FULL IF IT HAS A CLAY SEAL. THIS
APPROACH PREVENTS WEEDS, DRYING OF THE POND, AND PREVENTS
ODORS WHEN SEWAGE IS ADDED.
B. CONDUCT LEAKAGE TESTS.
C. BEGIN ADDING RAW WASTEWATER.
18. Describe strategies to use when operating a Fill and Draw
Pond system.
FILL AND DRAW POND SYSTEMS ARE DESIGNED FOR INTERMITTENT
DIS-CHARGE. DISCHARGES ARE USUALLY IN THE SPRING AND FALL
WHEN STREAM FLOWS ARE HIGH AND TEMPERATURES LOW. LOW
TEMPERATURE ALLOWS MORE OXYGEN TO BE DISSOLVED IN WATER. IT
IS NECESSARY TO HAVE A HOLDING CAPACITY FOR A MINIMUM OF SIX
MONTHS FLOW. SAMPLING OF THE POND TO BE DISCHARGED IS
REQUIRED AND APPROVAL MUST BE OBTAINED FROM THE DNR.
19. Explain the conditions that indicate times to Drawdown and
to Fill a Pond.
A. DRAWDOWN:
A POND SHOULD BE DRAWN DOWN IN FALL AFTER THE FIRST FROST
AND WHEN THE ALGAE CONCENTRATION DROPS OFF, THE BOD IS STILL
LOW, AND WHEN THE RECEIVING STREAM TEMPERATURE IS LOW WITH
ACCOMPANYING HIGH DISSOLVED OXYGEN.
A POND SHOULD BE DRAWN DOWN IN SPRING BEFORE ALGAE
CONCENTRATION INCREASES, WHEN THE BOD LEVEL IS ACCEPTABLE,
AND WHEN THE RECEIV-ING STREAM FLOWS ARE HIGH (LOW
TEMPERATURE WITH HIGH DISSOLVED OXYGEN HELPS). DURING THE
ACTUAL DISCHARGE, THE EFFLUENT MUST BE SAMPLED FOR BOD,
SUSPENDED SOLIDS AND pH AT A FREQUENCY SPECIFIED IN THE
DISCHARGE PERMIT.
TO DRAW DOWN A POND, ISOLATE THE POND, IF POSSIBLE, ONE
MONTH BEFORE THE DISCHARGE PERIOD. BEGIN TESTING TO MONITOR
POND CONTENTS FOR BOD, SUSPENDED SOLIDS, AND pH. SEND
RESULTS TO THE DNR AND OBTAIN APPROVAL TO DISCHARGE.
CALCULATE WHAT VOLUME WILL BE NEEDED FOR STORAGE, AND
DISCHARGE AT LEAST THAT AMOUNT. DETERMINE FROM THE DISCHARGE
PERMIT DAILY DISCHARGE VOLUME, AND CALCULATE TOTAL DAYS
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REQUIRED FOR DISCHARGE. CALCULATE, OR USE A CHART PROVIDED
BY THE DESIGN ENGINEER, TO FIND WHAT LEVEL THE POND WILL BE
LOWERED AND HOW MANY INCHES/DAY IT WILL DROP. PONDS ARE
NEVER COMPLETELY DRAWN DOWN AS THIS COULD DRY OUT THE SEAL
AND CAUSE LEAKAGE.
B. FILL A POND:
ALWAYS LEAVE AT LEAST ONE OR TWO FEET OF TREATED WASTEWATER
IN A POND SO THE WASTEWATER WILL HAVE AN ACTIVE BACTERIAL
CONCENTR-ATION. THIS GREATLY AIDS IN MAINTAINING OXYGEN AND
PREVENTS ODORS OR ORGANIC UPSETS. IF POSSIBLE, FILL AS
SLOWLY AS POSSIBLE, STARTING WITH THE PRIMARY POND. IF THERE
ARE TWO OR MORE PRIMARIES, ALTERNATE FLOW TO EACH ON A DAILY
BASIS. CONTINUE FILLING THE PRIMARY UNTIL IT IS FULL. THIS
MAY TAKE SEVERAL MONTHS. ALLOW FLOW OF THE PRIMARY POND
CONTENTS TO THE SECONDARY POND.
20. List the reasons why an operator would vary Pond levels.
A. TO DRAW DOWN THE CELL.
B. TO HOLD CONTENTS LONGER AND ALLOW MORE TREATMENT AND
DETENTION TIME ( ESPECIALLY IN WINTER ).
C. TO REPAIR AERATION EQUIPMENT OR OTHER STRUCTURE.
D. TO REPAIR LEAKS.
E. TO CONTROL MUSKRATS.
F. TO CONTROL ROOTED WEEDS.
G. TO FLOOD CUT CATTAILS.
21. Describe the proper operation of Multiple Seepage Cells.
THE BEST OPERATION IS LOAD AND REST. DRYING OCCURS BETWEEN
LOAD-INGS SO AN AEROBIC ZONE IS MAINTAINED IN THE SOIL.
ALTERNATE EVERY THREE WEEKS, TO A MONTH. BEFORE DISCHARGING
TO A SEEPAGE CELL, THE POND CONTENTS MUST BE MONITORED FOR
BOD AND SUSPENDED SOLIDS. WHEN A DISCHARGE IS OCCURRING, A
DAILY CHECK FOR THE VOLUME TO THE SEEPAGE CELL AND THE DEPTH
OF WATER IN THE CELL IS APPROPRIATE. THE FLOW SHOULD BE
UNIFORMLY DISTRIBUTED ACROSS THE ENTIRE SEEPAGE CELL.
22. Discuss how to transfer liquid from cell to cell.
IN A 2-CELL SYSTEM, ISOLATE CELL#2, DRAW DOWN CELL#2 FIRST,
THEN REFILL CELL#2 FROM CELLttl. CONTROL VALVES BETWEEN CELLS
ARE REGULATED SO THE TRANSFERS ARE GRADUAL.
23. Describe how to check for efficient aeration of a Pond.
MONITOR POND DISSOLVED OXYGEN, WATCH SURFACE AERATION
PATTERNS FOR CHANGES, READ AIRLINE PRESSURE GAUGE, CHECK FOR
CHANGES IN EFFLUENT BOD, AND MONITOR ALL AERATION EQUIPMENT.
FOR PROPER TREATMENT, AN AERATED POND SHOULD HAVE AN
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ADEQUATE SUPPLY OF DISSOLVED OXYGEN. FOR PRACTICAL PURPOSES,
THE DISSOLVED OXYGEN IN THE SURFACE MIXED ZONE SHOULD
AVERAGE APPROXIMATELY 2 mg/L.
24. Explain why pH values vary in a Pond.
THE VARIATION IN pH IN A FACULTATIVE POND NORMALLY OCCURS IN
THE UPPER AEROBIC ZONE, WHILE THE ANAEROBIC AND FACULTATIVE
ZONES WILL BE RELATIVELY CONSTANT. THIS VARIATION HAPPENS
DUE TO THE CHANGES THAT OCCUR IN THE CONCENTRATION OF
DISSOLVED CARBON DIOXIDE. WHEN CARBON DIOXIDE IS DISSOLVED
IN WATER IT FORMS A WEAK CARBONIC ACID WHICH WOULD TEND TO
LOWER pH. THE RELATIONSHIP BETWEEN ALGAE AND BACTERIA AFFECT
THE CARBON DIOXIDE LEVELS. DURING INTENSE PHOTOSYNTHESIS,
ALGAE USE CARBON DIOXIDE AND PRODUCE OXYGEN TO BE USED BY
BACTERIA TO ASSIMILATE ORGANIC WASTES. THE ALGAE USE MUCH OF
THE CARBON DIOXIDE AND THE pH CAN RISE SIGNIFICANTLY(pH IN
THE 11 TO 12 RANGE IS NOT UNCOMMON).
DURING THE NIGHT OR DURING CLOUDY WEATHER, THE ALGAE RESPIRE
AND ACTIVE PHOTOSYNTHESIS DOES NOT OCCUR. THE BACTERIA
CONTINUE TO USE UP OXYGEN AND PRODUCE CARBON DIOXIDE. THIS
CAN CAUSE A SIGNIFICANT DROP IN THE POND pH, ESPECIALLY IF
THE INFLUENT WASTEWATER HAS LOW ALKALINITY. THIS SAME pH
SWING CAN OCCUR IN NATURAL PONDS, LAKES, AND STREAM
IMPOUNDMENTS. DURING PEAK SUMMER ALGAE ACTIVITY, THE
DISSOLVED OXYGEN OF STREAM IMPOUNDMENTS HAVE VARIED FROM
DAWN LEVELS OF LESS THAN 1 mg/L, TO LATE AFTERNOON VALUES OF
13-15 mg/L (SUPERSATURATION).
25. Describe the affects of seasonal changes on Pond treatment
efficiency.
WINTER: TREATMENT EFFICIENCY DECREASES IN THE WINTER WITH
COLDER TEMPERATURES AND LESS SUNLIGHT THROUGH THE
ICE COVER. SHORTER PERIODS OF SUNLIGHT AND ICE
COVER LIMITS THE AMOUNT OF PHOTOSYNTHESIS. THIS
REDUCES DISSOLVED OXYGEN IN THE POND. THE COLD
WATER ALSO SLOWS DOWN BACTERIAL ACTION, REDUCING
TREATMENT EFFICIENCY. IF SUFFICIENT ICE COVER IS
PRESENT,THE POND MAY GO ANAEROBIC. EMERGENT WEEDS
AND DUCKWEED DIE-OFF. DURING THIS PERIOD, FILL AND
DRAW PONDS ARE OPERATED BY STORING WASTEWATER FOR A
SPRING DISCHARGE.
SPRING: AFTER ICE-OUT, ODORS MAY OCCUR FOR SEVERAL DAYS
UNTIL DISSOLVED OXYGEN IS RESTORED. AS TEMPERATURES
INCREASE, BIOLOGICAL ACTIVITY INCREASES FOR BOTH
BACTERIA AND ALGAE. TREATMENT EFFICIENCY BEGINS TO
IMPROVE WITH INCREASING BIOLOGICAL ACTIVITY. AFTER
THE THE POND HAS STABILIZED, A SPRING DISCHARGE FOR
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FILL AND DRAW TYPE SYSTEMS IS USUALLY DONE PRIOR TO
ACTIVE ALGAE GROWTH.
SUMMER: THE LONG SUNNY DAYS PROVIDE MAXIMUM OXYGEN LEVELS
FROM ALGAE PHOTOSYNTHESIS. WARM WATER TEMPERATURES
INCREASE BACTERIA ACTION TO PROVIDE THE BEST
ENVIRONMENT FOR EFFICIENT TREATMENT. OPERATIONAL
PROBLEMS INCLUDE: CONTROLLING ROOTED EMERGENT
WEEDS, REMOVING DUCKWEED AND CONTROLLING ALGAE
BLOOMS. DURING THIS PERIOD, FILL AND DRAW POND
SYSTEMS ARE OPERATED BY STORING WASTEWATER FOR A
FALL DISCHARGE.
FALL: A TRANSITIONAL TIME, BUT IN REVERSE OF SPRING.
WATER TEMPERATURES BEGIN DROPPING, REDUCING
BACTERIAL ACTIVITY AND PHOTOSYNTHESIS AS THE DAYS
GET SHORTER. TREATMENT EFFICIENCIES BEGIN TO DROP
AS WINTER APPROACHES. WHEN THE ALGAE LEVELS DROP
AND THE BOD STABILIZES, FILL AND DRAW TYPE SYSTEMS
NORMALLY DISCHARGE.
26. Discuss the operating procedures for dealing with a spring
thaw.
PONDS WILL USUALLY FILL UP FAST DURING SPRING THAW AND
LEVELS MUST BE WATCHED SO DIKES DO NOT OVERFLOW. DISCHARGE
SHOULD BE CONTINUOUS UNTIL LEVELS STABILIZE. START SPRING
DRAW DOWN OF THE PONDS IF OPERATING ON FILL AND DRAW. THE
COLLECTION SYSTEM USUALLY HAS INFILTRATION, AND FLOW IS
QUITE LARGE DURING THE SPRING THAW. DRAW PONDS DOWN WHEN
STREAMS ARE COLD AND FLOWS HIGH.
CONCEPT:
MAINTENANCE
27. List some components of a maintenance management and
recordkeeping system.
A. MAINTENANCE INVENTORY OF PARTS AND OIL.
B. WEATHERIZATION OF PLANT AND EQUIPMENT.
C. INSURE O&M MANUAL IS BEING FOLLOWED.
D. MAINTAIN A MANAGEMENT CHECKLIST WHICH MIGHT INCLUDE:
1. EACH MAINTENANCE DUTY.
2. FREQUENCY OF MAINTENANCE.
3. INVENTORY OF PARTS NEEDED.
4. DETAILED DESCRIPTION OF PROPER METHODS OF MAINTENANCE
MAINTENANCE RECORD KEEPING IS THE USE OF VARIOUS FORMATS TO
RECORD THE PERFORMANCE OF ACTUAL MAINTENANCE. TYPICAL
EXAMPLES WOULD BE A FOLDER FILING SYSTEM (FILE CABINET). A
CARD SYSTEM FOR RECORDING INFORMATION, AND THE USE OF
MICROCOMPUTERS WITH APPROPRIATE SOFTWARE. ANY OF THESE
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SYSTEMS CAN BE USED FOR RECORD KEEPING AND PLANNING
MAINTENANCE.
28. Describe the meaning of air gauge readings on a blower.
HIGH READINGS OF AN AIR GAUGE ARE CAUSED BY PLUGGED AIRLINE,
ORIFICES, DIFFUSERS, OR ICE CAP. LOW READINGS OF AN AIR
GAUGE COULD BE CAUSED BY A FAULTY BLOWER, AN AIR LEAK, OR
CLOGGED BLOWER INLET FILTER.
IN EITHER CASE, THERE IS A POSSIBILITY THAT THE BLOWER COULD
OVERHEAT, CAUSING DAMAGE TO THE UNIT. A HOT BLOWER SHOULD BE
SHUT-DOWN AND CORRECTIVE ACTION TAKEN.
29. List the most common maintenance problems associated with
Pond systems.
A. WEED CONTROL - CATTAILS AND OTHER ROOTED AQUATIC PLANTS.
B. ALGAE CONTROL - BLUE-GREEN AND ASSOCIATED FLOATING ALGAE
MATS.
C. BURROWING ANIMALS - MUSKRATS AND TURTLES.
D. DUCKWEED CONTROL AND REMOVAL.
E. FLOATING SLUDGE MATS.
F. DIKE VEGETATION - MOWING AND REMOVING WOODY PLANTS.
G. DIKE EROSION - RIP RAP AND PROPER VEGETATION.
H. FENCE MAINTENANCE TO RESTRICT ACCESS.
I. MECHANICAL EQUIPMENT - PUMPS, BLOWERS ETC.
30. Discuss the maintenance of seepage cells.
RAKE THE DRY SURFACE WITH EQUIPMENT THAT WILL NOT COMPACT
SOIL. CONTROL WEEDS BY TILLING THE SOIL. KEEP LEVEL. SEEPAGE
CELL MAINTENANCE INVOLVES AERATING THE SOIL CRUST WHICH
BUILDS-UP AT THE SOIL-AIR INTERFACE. THIS CRUST IMPEDES
WATER AND OXYGEN PERCOLATION INTO THE SOIL. ANY SUITABLE
TILLING EQUIPMENT CAN BE USED. TILLING 6" TO 12" HELPS
CONTROL WEED GROWTH WHICH PROLIF-ERATES ON THE SURFACE.
AVOID UNNECESSARY SOIL COMPACTION.
31. Describe the ways to control aquatic vegetation.
ROOTED WEEDS CAN BE CONTROLLED BY PHYSICAL REMOVAL OF NEW
GROWTH BY HAND, OR MOWING WITH A SICKLE BAR AFTER ICE HAS
FORMED, RAISE WATER LEVEL ALLOWING THE ICE TO PULL THE WEEDS
OUT. BY INCREASING THE WATER LEVEL TO REDUCE LIGHT
PENETRATION TO STOP PHOTOSYNTHESIS. OTHER POSSIBLE WAYS
WOULD BE TO LOWER THE WATER LEVEL AND BURN THE WEEDS OR USE
AN APPROVED HERBICIDE.
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32. Explain how to remove duckweed from the Pond surface.
DUCKWEED MUST BE PHYSICALLY REMOVED WITH A RAKE, PUSHBOARD
OR BROOM. WITH SUFFICIENT WIND, THE DUCKWEED WILL BE PUSHED
TO ONE SIDE OR CORNER OF A POND. THIS IS AN IDEAL TIME TO
RAKE THEM OUT. IT IS IMPORTANT THAT DUCKWEED NOT BE ALLOWED
TO BECOME TOO ABUNDANT, AS IT REDUCES OXYGEN TRANSFER AT THE
WATER SURFACE, REDUCES LIGHT PENETRATION AND PHOTOSYNTHESIS,
AND UPON DECOMPOSING, CAN CAUSE BOTH ODOR AND BOD PROBLEMS.
33. Discuss how to deal with floating mats.
FLOATING MATS ON POND SYSTEMS ARE CAUSED BY FLOATING SLUDGE,
BLUE-GREEN ALGAE, OR OIL AND GREASE. THE MOST COMMON ARE THE
SLUDGE AND ALGAE MATS. THE FIRST ATTEMPT TO CORRECT THIS
WOULD BE TO TRY TO BREAK-UP THE SLUDGE OR ALGAE MATS,
ALLOWING THEM TO SETTLE TO THE BOTTOM. IF THIS DOES NOT
WORK, IT WILL BE NECESS-ARY TO RAKE THEM OUT AND DISPOSE OF
THEM. IF OIL AND GREASE ARE A PROBLEM, THE SOURCE OF THIS
MATERIAL SHOULD BE ELIMINATED TO PREVENT A RECURRENCE OF
THIS PROBLEM.
34. Describe how cattails are controlled without chemicals.
CATTAILS CAN BECOME ESTABLISHED IN THE SHALLOW WATER ALONG
THE DIKES. CONTROLLING CATTAILS IS A PROBLEM BECAUSE OF
THEIR EX-TENSIVE ROOT SYSTEMS. PHYSICAL REMOVAL HAS THE
POSSIBILITY OF DAMAGE TO THE POND LINER. WHEN CATTAILS ARE
YOUNG, PULLING THEM OUT IS VERY AFFECTIVE. ANOTHER AFFECTIVE
METHOD IS TO LOWER THE POND LEVEL, CUT THE CATTAILS, AND
THEN RAISE THE WATER THREE FEET OVER THE CATTAILS WHICH
EFFECTIVELY KILLS(DROWNS) THEM. ONE METHOD WOULD BE A BOAT
MOUNTED WEED CUTTER TO CUT THEM OFF BELOW THE WATERLINE.
35. Identify types of dike vegetation, and how to control grass
and other plant growths.
IT IS VERY IMPORTANT THAT DIKES HAVE A PROTECTIVE GRASS
COVER TO PREVENT EROSION FROM RUNOFF AND WAVE ACTION. THE
GRASSES USED SHOULD BE FAST GROWING, SPREADING, WITH
SHALLOW, BUT DENSE ROOT SYSTEMS(E.G. RYE, BROME AND QUACK).
MOWING SHOULD BE DONE PER-IODICALLY SO THAT THE DIKES CAN BE
OBSERVED AND TO REDUCE BREEDING AREAS FOR INSECTS.
NO LONG ROOTED PLANTS SHOULD BE ALLOWED ON DIKES(ALFALFA,
WILLOWS OR ANY WOODY SCRUBS) AS THEIR ROOT STRUCTURE COULD
CAUSE DIKE LEAKAGE, DAMAGE TO THE POND SEAL, OR STRUCTURAL
FAILURE TO THE DIKE. ALL WOODY PLANTS SHOULD BE REMOVED BY
PULLING OR MOWING, AND IN THE EVENT THEY BECOME ESTABLISHED,
IT WILL BE NECESSARY TO USE BRUSHING METHODS (EG. PRUNING,
CHAIN SAW, BRUSH SAW, WEED WACKER, ETC.). GRAZING ANIMALS
SHOULD NOT BE USED TO CONTROL DIKE VEGETATION AS THEY DAMAGE
DIKES AND INCREASE EROSION PROBLEMS.
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MODULE C: MONITORING AND TROUBLESHOOTING
CONCEPT: MONITORING
36. State the normal pressure reading range for the Discharge
Gauge in a blower unit.
5-14 PSI.
37. Describe what types of things that need monitoring usually
found in the discharge permit for influent and effluent from
a Pond system.
THE DISCHARGE PERMIT WILL SPECIFY THE TYPE OF SAMPLES(GRAB
OR COMPOSITE) REQUIRED, AND THE FREQUENCY OF SAMPLING.
NORMALLY, BOTH RAW WASTEWATER AND FINAL EFFLUENT WILL
REQUIRE SAMPLING FOR BOD, SUSPENDED SOLIDS, FECAL COLIFORM,
AND pH. OTHER PARAMETERS MAY BE SPECIFIED IN INDIVIDUAL
DISCHARGE PERMITS, SUCH AS, AMMONIA, TOTAL NITROGEN,
NITRATES, CHLORIDES, TOTAL DISSOLVED SOLIDS OR TOXICS.
38. List ways to measure the Dissolved Oxygen level of a Pond.
A. DISSOLVED OXYGEN METER.
B. WINKLER DISSOLVED OXYGEN DETERMINATION.
39. Define where samples should be taken on a Pond to monitor
the influent and effluent.
SAMPLES OF RAW WASTEWATER SHOULD BE TAKEN AT THE POINT WHERE
THE RAW WASTEWATER ENTERS THE WET WELL. SAMPLES OF FINAL
EFFLUENT SHOULD BE TAKEN WHERE THE FINAL EFFLUENT LEAVES THE
TREATMENT SYSTEM. USE THE LAST MANHOLE AFTER THE POND, JUST
BEFORE DIS-CHARGE INTO A STREAM OR RIVER.
THE MOST IMPORTANT FACTOR IN LOCATING AN INFLUENT SAMPLING
POINT WOULD BE TO ENSURE THAT IT IS WELL MIXED AND IS
REPRESENTATIVE OF THE RAW WASTEWATER. IF GRAB SAMPLES ARE
SPECIFIED, THEY SHOULD NOT BE COLLECTED DURING UNUSUAL FLOW
CONDITIONS, SUCH AS, VERĄ—LOW FLOW PERIODS ( EARLY MORNING,
LATE EVENING OR WEEKENDS), DURING A MAJOR STORM, POWER
OUTAGE, OR AN OBVIOUS SLUG LOADING. THE SAMPLE SHOULD BE
REPRESENTATIVE OF THE NORMAL LOADING. THE FINAL EFFLUENT
SAMPLE SHOULD BE AT A WELL-MIXED REPRESENTATIVE LOCATION.
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40. Describe how to take a representative sample of the contents
of a Pond.
OVERALL POND SAMPLING IS NORMALLY DONE FOR FILL AND DRAW
TYPE SYSTEMS TO BE SURE POND CONTENTS ARE SUITABLE FOR
DISCHARGE TO THE RECEIVING WATER COURSE. IT IS IMPORTANT
THAT THIS SAMPLING BE REPRESENTATIVE OF THE POND CONTENTS.
THIS WOULD MEAN THAT MULTIPLE SAMPLES SHOULD BE COLLECTED
AND THEN COMPOSITED PRIOR TO LABORATORY ANALYSIS. ONE
SUGGESTED METHOD WOULD BE TO TAKE SAMPLES AT FOUR LOCATIONS
AROUND THE POND AT LEAST 8 FEET FROM THE DIKE AND FROM BELOW
THE WATER SURFACE OF THE POND. MIX TOGETHER THOURGHLY PRIOR
TO ANALYSIS.
41. Explain how the following samples should be collected and
preserved for analysis:
A. BOD.
B. Fecal Coliform.
C. Suspended Solids.
D. Dissolved Oxygen.
E. pH.
A. BOD: SAMPLES SHOULD BE TAKEN AT PEAK FLOW
TIMES(I.E.,11:00AM, 12:00 NOON AND 1:OOPM),
COMPOSITED TOGETHER, MIXED WELL, PRESERVED WITH
ICE, AND SENT FOR ANALYSIS AS SOON AS POSSIBLE TO
PREVENT DEGRADATION WITHIN 48 HRS @ 3°C.
B. FECAL COLIFORM: THIS SAMPLE OF THE UNCHLORINATED
EFFLUENT MUST BE COLLECTED IN A
SEPARATE STERILIZED CONTAINER, PRESERVED
WITH ICE AND SENT FOR ANALYSIS AS SOON
AS POSSIBLE. IF SAMPLING A CHLORINATED
DISCHARGE, SODIUM THIOSULFATE MUST BE
ADDED AND NOTED ON THE LAB SLIP.
C. SUSPENDED SOLIDS: SAME AS FOR BOD.
D. DISSOLVED OXYGEN: MUST BE ANALYZED IMMEDIATELY AFTER
SAMPLING.
E. pH:MUST BE ANALYZED IMMEDIATELY AFTER SAMPLING.
42. Discuss how to collect a representative sample from a
groundwater monitoring well.
THE REQUIREMENTS FOR GROUND WATER SAMPLING POINTS AND
PARAMETERS TO BE TESTED WILL BE IN THE DISCHARGE PERMIT.
WHEN SAMPLING GROUND WATER, START WITH UP-GRADIENT WELLS
FIRST, AND THEN MOVE TO DOWN-GRADIENT WELLS. THE SEQUENCE
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OF PROCEDURES FOR OBTAIN-ING A REPRESENTATIVE SAMPLE WOULD
BE:
1. DETERMINE GROUND WATER ELEVATION USING PROPERLY CLEANED
AND RINSED EQUIPMENT (COPPER COATED TAPE, OR AN ELECTRIC
TAPE) .
2. SUBTRACT DEPTH TO WATER FROM REFERENCE POINT. USUALLY,
WELL TOP TO GET GROUND WATER ELEVATION.
3. DETERMINE DEPTH OF THE WELL FROM REFERENCE POINT TO GET
ELEV-ATION OF WELL BOTTOM.
4 . SUBTRACT BOTTOM OF WELL ELEVATION FROM GROUND WATER
ELEVATION TO OBTAIN DEPTH OF WATER IN THE WELL.
5. USE THE DEPTH OF WATER IN THE WELL AND THE INSIDE CASING
DIAMETER TO GET VOLUME OF WATER IN THE WELL.
6. BAIL FOUR VOLUMES OF WATER AS DETERMINED FROM ABOVE
VOLUME.
7. AFTER BAILING FOUR VOLUMES, COLLECT SAMPLE AND SEND TO
THE LABORATORY, FOLLOWING ANY INSTRUCTION OF THE
LABORATORY (E.G. PRE-FILTERING OR ANY PRESERVATION THAT
MAY BE REQUIRED).
CONCEPT: TROUBLESHOOTING
43. List the possible causes of low water levels in a Pond.
A. LEAKING LINER.
B. LEAKING CONTROL STRUCTURES.
C. UNDERLOADED FACILITY (OVER DESIGNED).
D. DIKE LEAKS CAUSED BY BURROWING ANIMALS.
E. IMPROPER SETTINGS OF CONTROL STRUCTURES.
44. List the causes and corrective actions for Seepage Cells
that do not seep.
CAUSE CORRECTIVE ACTION
A. COMPACTED CELL BOTTOM. REWORK CELL BOTTOM WITH
MECHANICAL EQUIPMENT TO LOOSEN
AND AERATE SOIL.
B. HYDRAULIC OVERLOAD. REDUCE OVERLOAD BY ALTERNATING
SEEPAGE CELL LOADING.
C. SLUDGE BUILD-UP. REMOVE SLUDGE FROM CELL.
CORRECT OPERATION OF TREATMENT
PONDS PRECEDING SEEPAGE CELLS.
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45. List some causes of Pond short-circuiting, and give
corrective action for each.
A. EXCESSIVE ROOTED WEED GROWTH.
B. HYDRAULIC OVERLOADING.
C. DESIGN RELATED PROBLEMS.
CAUSE CORRECTIVE ACTION
CONTROL WEED GROWTH TO
RESTORE NORMAL FLOW
PATTERNS AND DETENTION
TIME.
REDUCE HIGH LOADINGS BY
ELIMINATING EXCESS I/I IN
THE COLLECTION SYSTEM.
CHANGE INLET OR OUTLET
STRUG TURE LOCATION TO
STOP SHORT-CIRCUITING OR
ADD BAFFLES AS NEEDED.
46. Discuss the causes and corrective action for a Pond having a
suspended solids violation while meeting BOD limits.
THE MOST PROBABLE CAUSE OF THIS PROBLEM WOULD BE AN ALGAE
BLOOM. DEPENDING ON THE TYPE OF ALGAE PRESENT, THE
CORRECTION OF THE CAUSE OF THE BLOOM CAN BE:
IF, THE ALGAE IS OF THE NORMAL GREEN VARIETY, POSSIBLE
SOLUTIONS COULD INCLUDE:
A. DRAW OFF EFFLUENT FROM BELOW THE SURFACE TO TRY TO REDUCE
ALGAE CONCENTRATION.
B. CONSTRUCT BAFFLES TO GET A BETTER QUALITY EFFLUENT.
C. IF POSSIBLE, USE ANOTHER CELL AND LET THE OTHER "REST"
UNTIL THE BLOOM SUBSIDES.
D. CONSIDER USE OF A SAND FILTER FOR ALGAE REMOVAL.
E. SWITCH TO SERIES OPERATION OF PRIMARY CELLS IF YOU ARE
PRESENTLY OPERATING IN PARALLEL.
F. CONSIDERATION CAN BE GIVEN TO USE OF AN APPROVED
ALGICIDE.
G. IF OPERATIONAL CHANGES CANNOT CORRECT THE PROBLEM, AN
ALGAE PERMIT VARIANCE CAN BE PURSUED.
H. CHECK COLLECTION SYSTEM FOR EXCESS NUTRIENT LOADING
(ESPECIALLY PHOSPHORUS).
IF THE ALGAE PROBLEM IS CAUSED BY THE BLUE-GREEN VARIETY,
POSS-IBLE SOLUTIONS WOULD BE:
A. CORRECT THE OBVIOUS ORGANIC OVERLOADING THAT IS
OCCURRING.
B. IF ORGANIC LOADING CANNOT BE REDUCED, CONSIDERATION FOR
MECHANICAL SURFACE AERATION MUST BE CONSIDERED.
C. IF OPERATING PRIMARY CELLS IN SERIES, CONSIDER PARALLEL
OPERATION.
F-21
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D. IF SIGNIFICANT INDUSTRIAL LOADING IS PART OF THE RAW
WASTE-WATER, CHECK NUTRIENT BALANCE OF BOD TO NITROGEN TO
PHOS-PHORUS (THE RATE OF 100/5/1 SHOULD BE ADEQUATE FOR
AEROBIC TREATMENT). CHECK FOR LOW pH.
E. IF LOADING AND NUTRIENTS ARE IN THE ACCEPTABLE RANGE,
CON- SIDERATION CAN BE GIVEN TO AN APPROVED ALGICIDE.
F. IF OPERATIONAL CHANGES CANNOT CORRECT THE PROBLEM,
FACILITY RE-DESIGN IS PROBABLY REQUIRED.
47. Describe what might be done if a system has unacceptable
high effluent pH values.
IF HIGH EFFLUENT pH IS OCCURRING, IT WILL BE NECESSARY TO
DET-ERMINE THE CAUSE OF THIS PROBLEM. IF IT IS CAUSED BY
INFLUENT FLOWS, THE SOURCE OR SOURCES MUST BE FOUND AND
CORRECTIVE ACTION TAKEN. MOST LIKELY, IT WOULD BE AN
INDUSTRIAL SOURCE AND PRE-TREATMENT WOULD HAVE TO BE
INSTITUTED.
HIGH EFFLUENT pH ATTRIBUTED TO NORMAL ALGAE PHOTOSYNTHESIS
WOULD ALMOST BE IMPOSSIBLE TO CONTROL (RECIRCULATION COULD
BE TRIED, BUT IT WOULD NOT BE VERY AFFECTIVE). THE ONLY
OTHER ALTERNATIVE OF HIGH pH CAUSED BY ALGAE PHOTOSYNTHESIS
WOULD BE TO APPLY FOR AN ADJUSTMENT IN pH LIMITATIONS IN THE
DISCHARGE PERMIT.
48. Discuss the causes and corrective actions for a Pond with
odor problems.
WHEN PROPERLY OPERATED AND LOADED, POND SYSTEMS WILL
NORMALLY EXPERIENCE ODOR PROBLEMS ONLY IN THE SPRING, RIGHT
AFTER ICE-OUT. THIS ODOR IS CAUSED BECAUSE OF ANAEROBIC
CONDITIONS THAT OCCURRED UNDER THE ICE. IN MOST CASES, THIS
CONDITION MAY ONLY LAST FROM A FEW DAYS TO A WEEK, UNTIL
NORMAL AEROBIC CONDITIONS ARE RESTORED. WHEN A POND SYSTEM
IS NOT OPERATED PROPERLY; WHEN RECEIVING AN INDUSTRIAL SLUG
LOAD, OR, WHEN BEING OVERLOADED ORGANICALLY, ANAEROBIC
CONDITIONS CAN PERSIST FOR SOME TIME WITH SIGNIFICANT ODORS
FROM BOTH ANAEROBIC CONDITIONS AND THE DIE-OFF OF BLUE-GREEN
ALGAE DOMINATING THE SYSTEM. THE POND SYSTEM MAY HAVE BLUE-
GRAY APPEARANCE WITH THE ODOR.
TO CORRECT THIS SITUATION, THE OPERATOR SHOULD MAKE
OPERATIONAL CHANGES (EG. FROM SERIES TO PARALLEL OPERATION,
REDUCE ORGANIC OVERLOAD IF POSSIBLE, ISOLATE THE REST OF THE
PROBLEM CELL, OR CONTROL OF ALGAE AND DUCKWEED). POSSIBLE
CHEMICAL CONTROL FOR POND ODORS WOULD INCLUDE THE USE OF
HYDROGEN PEROXIDE, SODIUM NITRATE OR MASKING AGENTS. IT IS
ALWAYS BEST TO CORRECT ODOR PROBLEMS WITH OPERATIONAL
CHANGES BEFORE RESORTING TO CHEMICAL MEANS. IF THE
OPERATIONAL CHANGES CANNOT CORRECT THE PROBLEM, CHEMICALS
CAN BE USED UNTIL THE FACILITY CAN BE RECONSTRUCTED, OR
ADDITIONAL AERATION CAN BE PROVIDED.
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49. Describe the consequences of not controlling floating and
rooted weeds in a Pond system.
FLOATING WEED MATS COULD PREVENT SUNLIGHT FROM ENTERING THE
POND, CAUSING ANAEROBIC CONDITIONS. FLOATING DUCKWEED, IF
NOT REMOVED, WILL CONTINUE TO REPRODUCE AND MAKE THE PROBLEM
WORSE. THESE MATS WILL BLOCK SUNLIGHT FROM ENTERING THE POND
SLOWING ALGAE PHOTO-SYNTHESIS AND REDUCING OXYGEN
PRODUCTION. THE POND COULD GO ANAEROBIC. MATS ALSO BLOW INTO
DEAD ZONES OF THE POND AND REDUCE THE AFFECTIVE AREA OF THE
TREATMENT POND, AND WOULD HINDER SURFACE AERATION BY
REDUCING WIND TURBULENCE. ROOTED WEEDS COULD PIERCE THE POND
SEAL AND LEAD TO LEAKS. THIS IS ESPECIALLY TRUE FOR WOODY
VEGETATION. THE ROOTED WEEDS ARE FOOD AND COVER HABITAT FOR
MUSKRATS. MUSKRATS BUILD DENS INTO THE BANKS WHICH ALSO LEAD
TO SIGNIFICANT LEAKAGE. LARGE AMOUNTS OF ROOTED WEEDS IN THE
POND COULD ALSO CAUSE SHORT-CIRCUITING.
50. List some burrowing animals that cause damage to dikes, and
discuss control methods for each.
ANIMAL CONTROL
A. GOPHERS AND BADGERS. TRAPPING/SHOOTING (PERMIT
REQUIRED).
B. MUSKRATS. VARYING WATER LEVELS, REMOVE
FOOD SOURCES (ROOT WEEDS) OR
TRAPPING/ SHOOTING (PERMIT
REQUIRED).
C. TURTLES(MINOR PROBLEM). TRAPPING/SHOOTING (POSSIBLE
PERMIT).
51. Discuss how to legally remove burrowing animals from a Pond
system.
MUSKRATS, GOPHERS AND BADGERS, ARE FURBEARERS. THEIR REMOVAL
AND POSSESSION IS SUBJECT TO DNR FURBEARER REGULATIONS.
CONTACT SHOULD BE MADE WITH THE COUNTY DNR WARDEN FOR
SPECIFICS ON HOW TO REMOVE ANIMALS AND WHAT PROCEDURES TO
FOLLOW. THERE MAY BE A REQUIREMENT FOR SPECIAL DISPOSITION
OF THE HIDES AND CARCASSES.
DNR WARDENS AND WILDLIFE MANAGERS HAVE THE AUTHORITY TO GIVE
SPECIAL REMOVAL PERMITS. ASK FOR PERMISSION TO USE DEN SETS
AND GROUP SETS. SOME OF THESE TRAPS ARE ILLEGAL, BUT THE
POND OPERATOR CAN USE THEM TO SPEED REMOVAL. THE DNR CAN
ALSO ISSUE PERMITS TO SHOOT ILLEGAL RATS.
DO NOT USE POISON BAIT AROUND BERMS. ANIMALS OR EVEN HUMANS
MIGHT INGEST THE POISON. PREDATOR ANIMALS (HAWKS AND OWLS)
MIGHT FEED ON A POISONED ANIMAL AND COULD DIE.
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MODULE D: SAFETY AND CALCULATIONS
CONCEPT: SAFETY
52. Describe how a Pond could be judged an "Attractive
Nuisance."
THE TERM "ATTRACTIVE NUISANCE" IS A LEGAL EXPRESSION THAT
IMPLIES THE POND COULD BE ATTRACTIVE TO POTENTIAL USERS,
SUCH AS, DUCK HUNTERS, FISHERMAN OR PLAYING CHILDREN. SINCE
PONDS HAVE FAIRLY STEEP SLOPES, THE POTENTIAL FOR SOMEONE
FALLING-IN AND DROWNING IS A SIGNIFICANT LEGAL PROBLEM THAT
MUST BE A CONCERN. IT IS IMPORTANT THAT ADEQUATE FENCING AND
SIGNING BE PROVIDED.
53. Discuss reasonable Pond security precautions against
trespassing and vandalism.
SECURITY IS NECESSARY TO PROTECT THE AREA FROM UNAUTHORIZED
ACCESS AND TO PROTECT THOSE WHO ENTER THE FACILITY. THE
COMM-UNITY COULD BECOME SUBJECT TO LIABILITY AND LEGAL
ACTION IF IT FAILS TO MAKE A REASONABLE EFFORT TO RESTRICT
TRESPASSING.
REASONABLE FENCING INCLUDES:
A. GATES AND LOCKS WHICH ARE KEPT SECURE AT ALL TIMES. GATES
TO RESTRICT VEHICLES AND ATV'S. AT A MINIMUM, STEEL OR
ALUMINUM GATES WITH SOLID ANCHOR POSTS AND A SIGN ARE
REQUIRED.
B. FENCES INCLUDE A STURDY WIRE FENCE WITH SIGNS. FENCE
LINES SHOULD BE BRUSHED AND SIGNED AT SUITABLE INTERVALS.
C. REGULAR DRIVE-BY PATROL BY THE LOCAL POLICE IS
RECOMMENDED. WORK WITH ADJACENT PROPERTY OWNERS TO REPORT
SUSPICIOUS VEHICLES OR PEOPLE IN THE AREA.
54. List the personal safety precautions that should be
practiced by persons operating a Pond system.
A. DO NOT ENTER A MANHOLE ALONE, OR ANY CONFINED SPACE,
WITHOUT PROPER EQUIPMENT AND SOMEONE TO ASSIST YOU.
B. WEAR LIFE JACKETS WHEN WORKING AROUND PONDS.
C. LEARN TO SWIM.
D. WASH-UP AFTER CONTACT WITH SEWAGE.
E. LOCK-OUT ELECTRICAL CIRCUITS TO SHUT-DOWN AERATORS. (THIS
F-24
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REFERS TO THE TENDENCY OF AERATORS TO LOWER THE SPECIFIC
GRAVITY OF WATER. A PERSON WHO FALLS OVERBOARD COULD SINK
FASTER IF THE AERATORS WERE WORKING. OPERATORS HAVE BEEN
KNOWN TO DROWN EVEN WITH LIFE JACKETS ON).
F. NEVER PERFORM ANY HAZARDOUS TASK AROUND A POND WITHOUT
BEING ACCOMPANIED BY SOMEONE.
G. USE CARE WHEN MOWING OR TRIMMING GRASS AROUND BURIED
ELECTRIC CONDUITS.
55. Discuss the risks involved while walking on the ice of a
Pond to collect samples.
THE BIGGEST PROBLEM IN WALKING ON THE ICE OF A TREATMENT
POND WOULD BE THE POSSIBILITY OF THE ICE BREAKING AND
CAUSING A POTENTIAL DROWNING. INFLUENT WASTEWATER IS WARM
ENOUGH TO CAUSE POSSIBLE THIN ICE NEAR THE INFLUENT PIPING.
SAFETY PRECAUTIONS SHOULD BE USED WHEN GOING OUT ON THE ICE,
SUCH AS: FLOTATION EQUIPMENT, A ROPE CONNECTED TO SHORE,
LIFE JACKETS, AND ALWAYS BE ACCOMPANIED BY SOMEONE ELSE ( IT
WOULD ALSO BE ADVISABLE TO HAVE COMMUNICATION EQUIPMENT
AVAILABLE SUCH AS A RADIO OR MOBILE TELEPHONE IN CASE OF
EMERGENCY). ANOTHER RISK IS THE POSSIBILITY OF FALLING,
WHICH CAN BE REDUCED BY GOOD FOOTWEAR.
56. Discuss the safety precautions that should be practiced
while using grass cutting equipment around a Pond.
USE CAUTION WHEN CUTTING NEXT TO ELECTRICAL CABLES. USE CARE
WHEN SPRAYING WEEDS AROUND ELECTRICAL CABLES AND EQUIPMENT.
THE SPRAY COULD CONDUCT A CURRENT AND CAUSE ELECTRICAL
SHOCK.
BE CAREFUL OPERATING MOWING EQUIPMENT ON BANKS. STEEP BANKS
CAN BE VERY HAZARDOUS. ALL MOWERS SHOULD HAVE THROTTLE KILL-
SWITCHES. MAKE SURE THE MANUFACTURERS EQUIPMENT OPERATION
DIRECTIONS ARE UNDERSTOOD AND FOLLOWED.
CONCEPT: CALCULATIONS
57. Given data, calculate Pond surface area in acres
GIVEN: POND LENGTH = 400 FEET
POND WIDTH = 300 FEET
FORMULA:
(ONE ACRE = 43,500 SQUARE FEET)
AREA OF POND = LENGTH (FT) X WIDTH (FT)
(IN SQ.FT.)
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AREA OF POND = SURFACE AREA (SQ.FT.)
(IN ACRES) 1 ACRE (SQ.FT.)
AREA OF POND = LENGTH (FT) X WIDTH (FT)
= 400 X 300
= 120,000 SQUARE FEET
AREA OF POND = SURFACE AREA (SQ.FT.)
(IN ACRES) 1 ACRE (SQ.FT.)
= 120,000
= 43,560
=2.75 ACRES
58. Given data, calculate Pond volume in gallons.
GIVEN: POND WIDTH AT MID-DEPTH = 200 FEET
POND LENGTH AT MID-DEPTH = 500 FEET
POND DEPTH = 6 FEET
FORMULA:
AREA = LENGTH (FT) X WIDTH (FT)
(AT MID-DEPTH) (AT MID-DEPTH) (AT MID-DEPTH)
VOLUME = AREA (AT MID-DEPTH) X DEPTH
1 CUBIC FOOT =7.5 GALLONS
AREA = 200 X 500
= 100,000 SQ. FEET AT MID-DEPTH
VOLUME = 100,000 X 6
= 600,000 CU.FT.
GALLONS = 600,000 CU.FT.
7.5GAL/CU.FT.
= 4,500,000 (4.5) MILLION GALLONS
59. Given data, calculate the volume of water discharged in
gallons.
GIVEN: DRAWDOWN DEPTH =3.0 FEET
POND LENGTH = 675 FEET
POND WIDTH = 420 FEET
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FORMULA:
VOLUME = LENGTH (FT) X WIDTH (FT) X DRAWDOWN DEPTH (FT) X 7.5
(1 CUBIC FOOT =7.5 GALLONS)
VOLUME = 675 X 420 X 3.0 X 7.5
= 6,380,000 GALLONS
= 6.4 MILLION GALLONS
60. Given data, calculate a lagoons detention time in days.
GIVEN: SURFACE AREA = 4 ACRES
AVERAGE DEPTH = 4 FEET
AVERAGE DAILY FLOW = 60,000 GALLONS/DAY
FORMULA:
(1 CU.FT. = 7.5 GALLONS)
VOLUME = 43,560 X ACRES X DEPTH X 7.5
(GAL) (SQ.FT./ACRES)
= 43,560 X 4 X 4 7.5
= 5,227,200 GALLONS
DETENTION TIME = VOLUME (GAL)
(DAYS) AVG. DAILY FLOW (GAL/DAY)
= 5,227,200
60,000
= 87.12 DAYS
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RESOURCES
CONTROLLING WASTEWATER TREATMENT PROCESSES. (1984).
Cortinovis, Dan. Ridgeline Press, 1136 Orchard Road,
Lafayette, CA 94549.
2. GROUNDWATER SAMPLING PROCEDURES. Lindorff, David; Feld,
Jodi; and, Connelly, Jack. PUBL. WR-168-87 (1987).
Department of Natural Resources, Bureau of Water
Resources,P.O. Box 7921, Madison, WI 53707.
3. OPERATION OF MUNICIPAL WASTEWATER TREATMENT PLANTS. Manual
of Practice No.11 (MOP 11), 2nd Addition (1990), Volumes
I,II,andlll. Water Environment Federation (Old WPCF) ,
601 Wythe Street, Alexandria, VA 22314-1994. Phone (800)
666-0206. http://www.wef.org/
4. OPERATION OF WASTEWATER TREATMENT PLANTS. 3rd Edition
(1990), Volumes 1 and 2, Kenneth D. Kerri, California State
University, 6000 J Street, Sacramento, CA 95819-6025. Phone
(916) 278-6142. http://www.owp.csus.edu/training/
5. OPERATION OF WASTEWATER TREATMENT PLANTS. Manual of Practice
No.11 (MOP 11)(1976). Water Pollution Control Federation,
601 Wythe Street, Alexandria, VA 22314-1994.
Phone (800) 666-0206. (Probably Out-Of-Print, See Reference
Number 3).
6. OPERATIONS MANUAL:STABILIZATION PONDS. Zickenfoose,
Charles and Hayes, R.B.Joe EPA-430/9-77-012 (1977). U.S.
Environmantal Protection Agency, Office of Water Program
Operation, Washington, DC 20460.
7. STABILIZATION POND OPERATION AND MAINTENANCE MANUAL.
Sexauer, Willard and Karn, Roger (1979). Operator Training
Unit, Minnesota Pollution Control Agency, 1935 West County
Road B-2, Roseville, MN 55113. Phone (612) 296-7373.
F-28
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F-2
D
NATURAL
OF
OPERATOR CERTIFICATION
http://dnr.wi.gov/org/es/science/opcert/
*
* NOTE -As of Jan 2010, this study guide c ontains objectives plus key knowledges.
F-29
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ACKNOWLEDGEMENTS
Special appreciation is extended to the many individuals who
contributed to this effort.
Wastewater operators were represented by:
Mel Anderson - Spooner
Harold Bourassa - Iron River
Chester Bush - Weyerhaeuser
Jerry Chartraw - Cumberland
Dominic Ciatti - Montreal
Al Cusick - Spooner
Bruce Degerman - Barren
Mike Frey - Winter
Kenneth Grenawalt - Evansville
Dale Hager - Sauk City
Milo Kadlec - Hayward
Bob Kamke - Medford
Mike LaRose - Rice Lake
Mike Magee - Rice Lake
Mike Magee - Rice Lake
Joe McCarthy - Madeline Island
Jeff O'Donnell - Park Falls
Rod Peterson - Barren
Tim Powers - Minong
Ken Raymond - Cambridge
Bill Rogers - Stone Lake
George Siebert - Telemark
Don Silver - Pardeeville
Dennis Steinke - North Freedom
Wally Thorn - Rice Lake
Charles Walczak - Ridgeway
Dave Wardean - Webster
Jerry Wells - Browntown
VTAE and educational interests were represented by:
Glen Smeaton, VTAE Services District Consortium
Pat Gomez, Moraine Park Technical College
Steve Brand, Cooper Engineering, Rice Lake
DNR regional offices were represented by:
Bob Gothblad, Northwest District, Spooner
Jim Hansen, Northwest District, Park Falls
Janet Hopke, Northwest District, Spooner
Chuck Olson, Northwest District, Brule
Pete Prusack, Northwest District, Cumberland
Jack Saltes, Southern District,Dodgeville
DNR central office was represented by:
Lori Eckrich, Madison
Rick Reichardt, Madison
Ron Wilhelm, Madison
Tom Kroehn, Madison
Tom Mickelson, Madison
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PREFACE
This operator's study guide represents the results of an
ambitious program. Operators of wastewater facilities,
regulators, educators and local officials, jointly prepared the
objectives and exam questions for this subclass.
The objectives in this study guide have been organized into
modules, and within each module they are grouped by major
concepts.
NOTE: As of January 2010, this study guide also includes key
knowledges.
HOW TO USE THESE OBJECTIVES WITH REFERENCES
In preparation for the exams, you should:
1. Read all of the key knowledges for each objective.
2. Use the resources listed at the end of the study guide for
additional information.
3. Review all key knowledges until you fully understand them
and know them by memory.
IT IS ADVISABLE THAT THE OPERATOR TAKE CLASSROOM OR ONLINE
TRAINING IN THIS PROCESS BEFORE ATTEMPTING THE CERTIFICATION
EXAM.
Choosing A Test Date
Before you choose a test date, consider the training
opportunities available in your area. A listing of training
opportunities and exam dates is available on the DNR Operator
Certification home page http://dnr.wi.gov/org/es/science/opcert/
It can also be found in the annual DNR "Certified Operator" or by
contacting your DNR regional operator certification coordinator.
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TABLE OF CONTENTS
PAGE NO.
Acknowledgements 2
Preface 3
Table of Contents 4
Resources 17
MODULE A: PRINCIPLES, STRUCTURE AND FUNCTION
Concept: Principles of Ponds 5
Concept: Structure and Function 6
MODULE B: OPERATION AND MAINTENANCE
Concept: Operation 7
Concept: Maintenance 8
MODULE C: MONITORING AND TROUBLESHOOTING
Concept: Monitoring 10
Concept: Troubleshooting 11
MODULE D: SAFETY AND CALCULATIONS
Concept: Safety 14
Concept: Calculations 14
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ADVANCED OPERATION OF PONDS AND LAGOONS
MODULE A: PRINCIPLE, STRUCTURE AND FUNCTION
CONCEPT: PRINCIPLE OF PONDS
1. Describe how the stabilization of organic waste material
occurs in nature and in a wastewater treatment plant.
STABILIZATION OF ORGANIC WASTE IS ACCOMPLISHED BY BACTERIAL
DEGRADATION OF ORGANIC WASTE MATERIAL AEROBICALLY,
ANAEROBICALLY OR A COMBINATION OF THE TWO. THE AEROBIC
ORGANISMS ARE PROVIDED OXYGEN FROM PHOTOSYNTHESIS BY ALGAE.
2. Explain photosynthesis.
PHOTOSYNTHESIS IS THE CREATION OF PLANT CELL MASS USING
CARBON DIOXIDE, WATER, AND NUTRIENTS, WITH SUNLIGHT AS THE
ENERGY SOURCE AND CHLOROPHYLL AS A CATALYST. DURING THIS
PROCESS, FREE OXYGEN IS GIVEN-OFF.
3. Explain respiration.
RESPIRATION IS THE PROCESS BY WHICH AN ORGANISM (PLANT OR
ANIMAL) ASSIMILATES OXYGEN AND RELEASES CARBON DIOXIDE.
4. Relate photosynthesis and respiration to BOD removal.
THE OXYGEN PRODUCED BY PHOTOSYNTHESIS CAN BE USED BY
BACTERIA IN THEIR LIFE PROCESSES (RESPIRATION), THIS
INCLUDES DEGRADING ORGANIC MATERIAL, WHICH REDUCES BOD.
5. Relate pH, carbon dioxide, and dissolved oxygen
concentrations to photosynthesis and respiration.
DURING PHOTOSYNTHESIS, GREEN PLANTS USE CARBON DIOXIDE AND
PRODUCE OXYGEN. THIS CAUSES AN INCREASE IN DISSOLVED OXYGEN
AND pH (THE pH INCREASE IS DUE TO THE LOSS OF DISSOLVED
CARBON DIOXIDE WHICH WOULD NORMALLY FORM A WEAK CARBONIC
ACID).
DURING RESPIRATION, PLANTS OR ANIMALS USE DISSOLVED OXYGEN
TO ASSIMILATE ORGANIC MATERIAL AND GIVE OFF CARBON DIOXIDE.
THIS CAUSES A REDUCTION IN THE DISSOLVED OXYGEN AND pH (THE
pH DROP IS CAUSED BY THE INCREASE IN CARBON DIOXIDE, CAUSING
A WEAK CARBONIC ACID).
5
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Explain why a Pond may violate pH permit limits during
periods of intense photosynthesis.
INTENSE SUNLIGHT SPEEDS-UP ALGAE PHOTOSYNTHESIS. ALGAE USE
UP CARBON DIOXIDE WHICH RAISES pH TO VERY HIGH LEVELS (11 +
SU) .
Discuss some innovative uses of Aerated Lagoon Systems.
REARING MINNOWS OR OTHER FOOD FISH. MINNOWS THAT FORAGE ON
PLANKTONIC MATERIAL ARE A FOOD SOURCE FOR LARGER FISH.
THIS PROCESS WILL WORK PROVIDING THERE IS ENOUGH DISSOLVED
OXYGEN. A CONCERN WOULD BE POSSIBLE AMMONIA TOXICITY.
CONCEPT: STRUCTURE AND FUNCTION
8. Identify the valve action necessary to bypass a Pond cell.
CLOSE THE INLET AND OUTLET VALVES ON THE UNIT TO BE
BYPASSED. OPEN THE VALVE ON THE BYPASS LINE.
9. Discuss different flow patterns that are used in Multiple
Pond treatment systems.
THERE ARE VARIOUS WAYS TO ROUTE THE HYDRAULIC FLOW THROUGH
MULTI-PLE POND SYSTEMS. WITH PROPER VALVING, PONDS CAN BE
OPERATED IN EITHER SERIES OR PARALLEL MODES. IN MOST CASES,
MULTIPLE CELL TREATMENT IS DESIGNED AND OPERATED IN SERIES.
IN A THREE POND SYSTEM, SERIES OPERATIONS WILL MINIMIZE
ALGAE IN THE FINAL CELL. IF HIGH ORGANIC LOADING TO THE
PRIMARY CELL IS OCCURRING, (ESPECIALLY DURING WINTER MONTHS
AND ICE COVER), IT MAY BE DESIRABLE TO OPERATE THE CELLS IN
PARALLEL TO REDUCE THE AFFECT OF THIS OVER-LOADING. THIS
SHOULD BE CONSIDERED A SHORT TERM SOLUTION, AND IF
CONTINUOUS OVERLOADING OCCURS, ACTION NEEDS TO BE TAKEN TO
REDUCE THE OVERLOAD OR SYSTEM RE-DESIGN SHOULD BE EVALUATED.
10. Discuss the advantage of Helical Diffusers over Floating
Mechanical Aerators.
HELICAL DIFFUSERS ARE MUCH LESS AFFECTED BY ICE BUILD-UP
DURING WINTER WEATHER.
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MODULE B: OPERATION AND MAINTENANCE
CONCEPT: OPERATION
11. Explain the theory of isolation of a Pond cell which is
experiencing an algae bloom in a Series Pond System.
ISOLATION OF A POND CELL WHICH IS EXPERIENCING AN ALGAE
BLOOM GIVES THE CELL A CHANCE TO "REST" AND RECOVER.
12. Discuss the use of chemicals to control weeds.
IF CHEMICALS ARE USED FOR POND WEED CONTROL, THEY MUST BE
APPROVED FOR THAT SPECIFIC USE AND LABEL DIRECTIONS MUST BE
FOLLOWED PRECISELY. IT MAY BE NECESSARY TO PROVIDE
ADDITIONAL MONITORING FOR TOXICS. MANY TIMES, THE USE OF A
SURFACTANT IS RECOMMENDED TO IMPROVE THE "WETTING" ABILITY
OF THE MIXTURE SO IT ADHERES BETTER TO THE TREATED PLANTS.
13. Describe how Pond depth and bubble size affect aeration
efficiency.
THE DEEPER THE POND, THE LONGER THE CONTACT TIME BEFORE THE
BUBBLES REACH THE SURFACE. THE SMALLER THE BUBBLES, THE MORE
CONTACT SURFACE BETWEEN THE AIR AND WATER, WHICH INCREASES
THE TRANSFER RATE.
14. Explain how to balance aerators within and between Ponds.
BALANCING OF AERATION WITHIN AND BETWEEN PONDS IS
ACCOMPLISHED BY USING THE VALVES ON THE MANIFOLD TO GET AN
EVEN AGITATION PATTERN.
15. Discuss when Floating Aerators are used for temporary
additional aeration capacity.
FLOATING AERATORS ARE USED FOR ADDITIONAL AERATION CAPACITY
TO HANDLE LARGER THAN EXPECTED ORGANIC LOADS DURING THE
SUMMER MONTHS.
16. List the important issues to consider in developing a public
relations program for a Pond system.
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A. POST A NOTICE EXPLAINING THE PRINCIPLES OF OPERATION OF A
POND SYSTEM.
B. DEVELOP AN EDUCATIONAL PROGRAM FOR LOCAL ELECTED
OFFICIALS.
C. EXPLAIN TO THE PUBLIC HOW UNAUTHORIZED ENTRANCE AND USE
CAN JEOPARDIZE A PONDS AFFECTIVENESS.
D. EXPLAIN WHY CHILDREN SHOULD NOT BE ALLOWED IN THE AREA OF
THE PONDS "RAPID DEPTH".
E. EXPLAIN WHY YOU SHOULD STAY OFF THE ICE OF A POND AT ALL
TIMES.
F. ALL PUBLIC INFORMATION AND EDUCATION PROGRAMS COULD BE
DONE WITH PUBLIC NOTICE.
17. Explain why alternate discharges to seepage cells should be
practiced in a Multiple Seepage Cell system.
THE ALTERNATE LOADING/RESTING OF SEEPAGE CELLS IS DONE FOR A
NUMBER OF REASONS. ONE REASON IS TO ALLOW THE OPERATOR TO
PHYSICALLY WORK-UP (DISK,ROTOTILL,OR DRAG) AND CLEAN THE
CELL BOTTOM. IT ALSO ALLOWS THE OPERATOR TO CONTROL
VEGETATION WITHIN THE CELL. FINALLY, WITH THE NEW GROUND
WATER RULES, IT ALLOWS SPREADING THE LOAD OVER A LARGER AREA
TO PREVENT GROUND WATER EXCEEDANCES. THE NEW GROUND WATER
STANDARDS WILL CHANGE SEEPAGE CELL OPERATIONS TO MEET THESE
STANDARDS. THIS MAY MEAN MORE CELLS (LARGER AREA) OR EVEN
POSSIBLE DISCONTINUANCE OF SEEPAGE CELLS.
18. List the considerations a Pond operator would have to make
when considering accepting septic tank waste.
A. BOD CONCENTRATION OF HAULERS LOAD.
B. SOLIDS LOADING OF THE LOAD.
C. D.O. CAPACITY.
D. GRIT.
E. HYDRAULIC LOADING.
NORMALLY, PONDS AND AERATED LAGOONS ARE NOT DESIGNED WITH
HOLDING TANKS TO ACCEPT SEPTAGE
CONCEPT: MAINTENANCE
19. Identify the items to be included in a Preventive
Maintenance plan for a Pond system.
MONITOR ALL EQUIPMENT: BLOWERS, CHECK VALVES, AIR DIFFUSER
ORIFICES, DIKES, ALL PUMPS, CONTROL MANHOLES, AND SHEAR
GATES. MAINTAIN SEEPAGE CELLS. A PLANNED MAINTENANCE PROGRAM
WILL PRE-VENT PROBLEMS AND WILL IDENTIFY POTENTIAL CONCERNS
BEFORE THEY ACTUALLY BECOME PROBLEMS. MAINTENANCE AT A POND
SYSTEM INVOLVES SIMPLE HOUSEKEEPING ITEMS WHICH ARE CRITICAL
TO GOOD TREATMENT.
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GOOD HOUSEKEEPING ITEMS ARE:
A. REMOVE ANY SCUM WHICH IMPEDES OXYGEN TRANSFER AND CAUSES
ODORS.
B. MOW DIKES TO THE WATER LINE TO KEEP WEEDS DOWN,
DISCOURAGE BURROWING MUSKRATS, AND PROMOTE WIND MIXING.
C. MAINTAIN DIKES BY RESTORING ANY EROSION AND/OR FILL
MUSKRAT DENS.
D. SKIM FLOATING DUCKWEED REGULARLY.
E. CONTROL CATTAILS REGULARLY.
F. PERFORM PREVENTIVE MAINTENANCE ON ALL MECHANICAL
EQUIPMENT AS INSTRUCTED IN THE O&M MANUAL AND THE
EQUIPMENT MANUFACTURERS MANUALS.
G. EXERCISE VALVES IN THE SYSTEM ON A REGULAR BASIS.
20. List the maintenance items on Aeration Equipment.
A. PIPING: CHECK ALL AIR PIPING, INCLUDING VALVES AND
DIFFUSERS TO ENSURE THAT THERE ARE NO BLOCKAGES.
B. CENTRIFUGAL BLOWERS: CHECK OIL LEVELS, AIR FILTERS,
RELIEF VALVES, AND DRIVE MOTORS.
C. POSITIVE DISPLACEMENT BLOWERS: MAINTAIN OIL LEVELS, AIR
RELIEF VALVES, V-BELTS, AIR FILTERS, AND DRIVE MOTORS.
D. FLOATING AERATORS: MAINTAIN FLOATS, ELECTRIC LINES, CHECK
OIL LEVELS, ANCHORS, DRIVE MOTORS. MAKE SURE IMPELLERS
ARE NOT CLOGGED.
21. Explain how to clean clogged Air Diffusers.
CLEANING OF AIR DIFFUSERS IN POND SYSTEMS CAN BE DONE IN
SEVERAL WAYS. IF THE PLUGGING IS MINOR, THE AIR FLOW CAN BE
INCREASED BY SHUTTING DOWN SOME SECTIONS TO INCREASE THE AIR
TO THE REMAINING SECTIONS OR BY INCREASING BLOWER OUT-PUT
(IF POSSIBLE). ANOTHER CLEANING METHOD WOULD BE TO INTRODUCE
HYDROGEN CHLORIDE OR OXYGEN /OZONE GAS THROUGH THE AIR
LINES. IN SOME INSTANCES, DIVERS HAVE BEEN USED TO
MECHANICALLY CLEAN THE DIFFUSERS (ROLLING TUBING THROUGH A
FLEX TOOL OR OTHER METHODS). IF NONE OF THESE PROCEDURES
WORK, THE LAST OPTION WOULD BE TO DRAW THE POND DOWN TO
REPAIR/REPLACE DIFFUSERS.
22. Describe the function and maintenance of the Blower Inlet
Filter.
THE INLET AIR FILTER REMOVES PARTICULATES FROM THE AIR
BEFORE THE COMPRESSION STAGE SO DEBRIS DOES NOT GET INTO THE
AIR LINE AND PLUG DIFFUSER ORIFICES. IT IS ALSO ESSENTIAL TO
9
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PROTECT THE COMPRESSOR FROM ANY DAMAGE, ESPECIALLY FROM
GRITTY MATERIALS. THE MAIN MAINTENANCE REQUIREMENT IS TO
KEEP THE FILTER CLEAN. USUALLY, THIS IS DONE BY REMOVING THE
FILTER AND BLOWING IT OUT WITH COMPRESSED AIR. THE FREQUENCY
OF CLEANING IS DEPENDENT ON FILTER SIZE AND AMBIENT AIR
QUALITY. OTHER MAINTENANCE ACTIV-ITIES SHOULD BE SPECIFIED
BY THE MANUFACTURER OR AS LISTED IN THE O&M MANUAL. FAILURE
TO ADEQUATELY CLEAN FILTERS CAN CAUSE REDUCED BLOWER AIR
OUTPUT, AN OVERHEATED BLOWER, POSSIBLE DIFFUSER CLOGGING,
AND POSSIBLE DAMAGE TO BLOWER AND DRIVE MOTOR.
23. Explain methods of controlling dike erosion.
THE MAIN METHODS FOR PREVENTING DIKE EROSION ARE PROPER DIKE
VEGETATION AND THE USE OF RIP RAP AROUND THE NORMAL
OPERATING POND LEVELS TO PREVENT EROSION FROM WAVE ACTION.
24. Discuss how to prevent ice damage to floating aeration
equipment.
ICE DAMAGE OCCURS MOST OFTEN TO FLOATING AERATORS WHEN THEY
TIP OVER. THE MOTORS AND POWER CABLES CAN BE DAMAGED OR
BROKEN DURING TIPPING. THE BEST METHOD IS TO STABILIZE THEM
WITH ADEQUATE GUY CABLES. SINCE OXYGEN REQUIREMENTS ARE
LOWER IN THE WINTER, IT IS POSSIBLE TO PROTECT EQUIPMENT BY
REMOVING SOME OF THE AERATORS.
MODULE C: MONITORING AND TROUBLESHOOTING
CONCEPT: MONITORING
25. Set-up a sampling schedule for a Fill and Draw Pond system.
SAMPLING LOCATIONS SHOULD BE ABOUT EIGHT FEET FROM EACH
CORNER AND BELOW THE SURFACE OF THE POND. SAMPLES SHOULD BE
COLLECTED ABOUT A WEEK PRIOR TO PROPOSED DISCHARGE. DURING
THE ENTIRE DURATION OF DISCHARGE, CHECK THE POND LEVEL
DAILY. SAMPLE AT THE CONTROL MANHOLE ON THE FREQUENCY
SPECIFIED IN THE DISCHARGE PERMIT.
PRIOR TO DRAWING DOWN A POND, THE OPERATOR SHOULD SAMPLE THE
POND CONTENTS FOR pH, BOD, AND SUSPENDED SOLIDS. IT IS ALSO
NECESSARY TO DETERMINE THE VOLUME NEEDED TO HOLD FLOWS UNTIL
THE NEXT DRAW-DOWN (USUALLY 180 DAYS).
10
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26. Describe two ways to determine Dissolved Oxygen levels in a
Pond.
A. USE A DISSOLVED OXYGEN METER.
B. PERFORM A WINKLER DISSOLVED OXYGEN TEST.
27. Discuss the requirements for groundwater monitoring.
CHANGES IN STATE LAW HAVE ESTABLISHED REQUIREMENTS FOR
GROUND WATER (NR 140). THIS IS IMPORTANT FOR WASTEWATER
SYSTEMS, ESPEC- IALLY LAND DISPOSAL SEEPAGE FACILITIES AND
LAGOONS THAT MAY BE LEAKING. NORMALLY, UP-GRADIENT AND DOWN-
GRADIENT WELLS WILL BE LOCATED TO DETERMINE IF A SYSTEM IS
AFFECTING GROUND WATER. CONCERN AT MUNICIPAL TYPE TREATMENT
PLANTS WOULD BE TOTAL DISS-OLVED SOLIDS, CHLORIDES, AND
NITROGEN SERIES (AND MORE SPECIF-ICALLY, NITRATES). THESE
PARAMETERS WILL BE THE POTENTIAL AREAS THAT POND SYSTEMS
MIGHT EXPECT EXCEEDANCES OF THE GROUND WATER STANDARDS WHICH
WILL REQUIRE OPERATIONAL CHANGES, DISCHARGE LOCATION
CHANGES, OR FUTURE RECONSTRUCTION.
CONCEPT: TROUBLESHOOTING
28. Describe how to determine if a drop in Pond water levels is
caused by seepage or evaporation.
A. CALIBRATE THE FLOW METER TO DETERMINE IF THE TOTALIZER IS
WORKING PROPERLY.
B. CHECK THE RESULTS OF GROUNDWATER SAMPLES TO SEE IF DOWN-
GRADE WELLS SHOW SIGNIFICANT CHANGES IN WATER QUALITY.
CALIBRATE THE FLOW METER TO DETERMINE IF YOU HAVE ACCURATE
INFLUENT FLOW DATA. SET-UP A STAFF GAUGE TO ACCURATELY
MEASURE POND ELEVATION. BY FILLING A 55-GALLON DRUM, OR
SIMILAR HOLDING DEVICE WITH WATER, THIS CAN BE USED TO
DETERMINE THE AFFECTS OF PRECIPITATION AND EVAPORATION.
COLLECTING THIS DATA OVER A PERIOD OF TIME CAN BE USED TO
DETERMINE THE RATE OF POND SEEPAGE.
29. List the chemical and non-chemical controls for the
following Pond conditions:
A. Algae.
B. Rooted Weeds.
C. Duckweed.
D. Organic Overload.
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CONDITIONS CHEMICAL NON-CHEMICAL
A. ALGAE COPPER SULFATE FILTRATION
B. ROOTED WEEDS HERBICIDE CUTTING, PULLING
OR VARY POND LEVELS
C. DUCKWEED HERBICIDE WIND AND RAKE
D. ORGANIC OVERLOAD SODIUM NITRATE REDUCE LOAD AND
USE AERATION
NOTE: FOR CATTAIL CONTROL, HERBICIDES ARE USUALLY MOST
AFFECTIVE DURING DEVELOPMENT. CUTTING CATTAILS BELOW
THE WATER LINE IN FALL IS ALSO AN AFFECTIVE CONTROL
METHOD.
30. State the action to take if a polishing Pond produces worse
suspended solids effluent than its influent.
THIS SITUATION IS NORMALLY A PROBLEM ASSOCIATED WITH AN
ALGAE BLOOM. THE ALTERNATIVES TO CORRECT THIS PROBLEM WOULD
BE TO BY-PASS THE POLISHING POND, OR TO ATTEMPT TO WITHDRAW
EFFLUENT FROM A DIFFERENT ELEVATION.
31. List the conditions that might lead to solids build-up on
the bottom of a Pond.
A. HIGH INFLUENT TSS.
B. EXCESSIVE WEED GROWTH.
C. OVERLOADING.
D. POOR TREATMENT.
E. HIGH INFLUENT BOD.
F. INORGANIC SOLIDS.
32. List some possible consequences of exceeding the design
organic loading rate of a Pond system.
A. POOR TREATMENT.
B. HIGH EFFLUENT BOD.
C. INCREASE OF SLUDGE SOLIDS.
D. POTENTIAL FOR OBJECTIONABLE ODORS.
E. EXCESSIVE ALGAE (BLUE-GREEN FILAMENTOUS MATS).
33. Discuss the significance of long-term domination of a Pond
by blue-green algae.
BLUE-GREEN ALGAE DOMINANCE OF A POND SYSTEM IS AN INDICATION
OF INCOMPLETE OR POOR TREATMENT. THE PROBLEM WITH BLUE-GREEN
ALGAE HAPPENS WHEN THE ALGAE DIES-OFF AND FOUL ODORS OCCUR.
IF OPERATIONAL CHANGES CANNOT BE MADE TO ELIMINATE THE BLUE-
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GREEN ALGAE, THEN CONSIDERATIONS NEED TO BE GIVEN TO PLANT
RE-DESIGN.
34. Explain why a Pond receiving a white dairy waste might turn
red.
HIGH PROTEIN WASTE IS CAUSING RED ALGAE TO BLOOM.
35. Describe when and how to use copper sulfate to achieve
maximum control of algae.
USE COPPER SULFATE WHEN ALGAE BECOMES EXCESSIVE. USE LABEL
DIRECTIONS FOR MIXING AND APPLYING THIS CHEMICAL. ADDITIONAL
MONITORING FOR TOXICS MAY BE REQUIRED. A CONCERN THAT NEEDS
WATCHING WHEN TREATING THE ENTIRE POND IS THAT DISSOLVED
OXYGEN LEVELS CAN DECREASE DUE TO THE DIE-OFF AND
DECOMPOSITION OF ALGAE.
36. List some alternatives to using Copper Sulfate for algae
control.
A. INTRODUCTION OF FISH.
B. SPRAY THE PONDS WITH ANOTHER APPROVED ALGICIDE.
C. CHANGE OPERATIONAL MODE (IF POSSIBLE).
D. DISCHARGE EFFLUENT FROM A DIFFERENT POND LEVEL.
E. APPLY FOR AN ALGAE VARIANCE.
37. Describe short circuiting and possible causes and problems
it creates.
SHORT CIRCUITING IS A HYDRAULIC CONDITION WHICH MAY OCCUR IN
PARTS OF A POND WHEN THE FLOW PASSES THROUGH MORE QUICKLY
THAN THE THEORETICAL DETENTION. THIS TYPE OF FLOW PATTERN
REDUCES DETENTION TIME AS COMPARED WITH EVEN UNIFORM FLOW
THROUGH THE POND.
SHORT CIRCUITING CAN BE CAUSED BY POOR DESIGN AND/OR
CONSTRUCTION OF INLET AND OUTLET STRUCTURES, UNEVEN POND
BOTTOMS, SHAPE OF THE CELLS, PREVAILING WINDS, AND EXCESSIVE
GROWTH OF ROOTED WEEDS.
PROBLEMS ASSOCIATED WITH SHORT CIRCUITING INCLUDE: DEAD
SPOTS, UNEVEN OXYGEN LEVELS, SLUDGE BUILD-UP, ODOR PROBLEMS,
AND, A REDUCTION IN TREATMENT EFFICIENCY.
13
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MODULE D: SAFETY AND CALCULATIONS
CONCEPT: SAFETY
38. List the characteristics of an affective safety program.
A. RED CROSS FIRST AID TRAINING.
B. C.P.R. TRAINING.
C. PROPER EQUIPMENT OPERATION NEAR PONDS (MOWING, SNOW
REMOVAL FROM DIKES, ETC.).
D. WEARING PROPER APPAREL WHEN ENTERING CONTROL STRUCTURES,
E. CONFINED ENTRY TRAINING.
F. WATER SAFETY COURSE TRAINING.
G. UNDERSTANDING USAGE OF CHEMICALS.
39. List some Pond security measures.
A. FENCING TO PREVENT ANY UNAUTHORIZED ENTRY.
B. ERECTING SIGNS WITH PROPER MESSAGE.
C. PASSING AN ORDINANCE TO REGULATE USE OF THE AREA AND
PENALIZE VIOLATORS.
CONCEPT: CALCULATIONS
40. Given data, calculate pounds BOD per acre per day.
GIVEN: POND SURFACE = 6.2 ACRES
AVERAGE DAILY FLOW = 50,000 GPD
INFLUENT BOD5 = 220 mg/L
FORMULA:
SURFACE LOADING RATE = POUNDS OF BOD PER DAY
POND SURFACE AREA
POUNDS OF BOD/DAY = CONCENTRATION(mg/L) X FLOW(MG) X 8.34
= 220 X .05 X 8.34
= 91.7 Pounds BOD/DAY
SURFACE LOADING RATE = 91.7
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6.2
= 14.8 POUNDS BOD/ACRE/DAY
41. Given data, calculate the cost of a chemical ($/Pound)
needed to control Duckweed.
GIVEN: POND SURFACE AREA = 12.5 ACRES
APPLICATION RATE =2.1 PER ACRE
CHEMICAL COST = $8.75 PER ACRE
FORMULA:
COST = AREA X APPLICATION RATE X COST
($) (ACRES)
= 12.5 X 2.1 X 8.75
= $230
42. Given data, calculate the theoretical detention time of a
Pond.
GIVEN: VOLUME = 5.2 MGD
FLOW = .05 MGD
FORMULA:
DETENTION TIME = VOLUME (MGD)
FLOW RATE (MGD)
(FOR POND SYSTEMS, DETENTION TIME IS USUALLY EXPRESSED IN DAYS)
43. Given data, calculate a discharge flow rate to achieve a
given Pond draw-down.
GIVEN: POND DIMENSIONS = 200 FEET X 400 FEET
(AT MID-POINT OF DRAWDOWN)
DRAWDOWN DESIRED = 4 FEET
DURATION OF DRAWDOWN = 100 HOURS
(ONE CUBIC FOOT =7.5 GALLONS)
FORMULA:
FLOW RATE = VOLUME TO BE DISCHARGED
DURATION OF DRAW-DOWN
200 FT. X 400 FT. X 4 FT. X 7.5
100 HOURS X 60 MIN./HR.
= 400 GALLONS PER MINUTE
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44. Given data, for a Fill and Draw Pond system, calculate the
amount of draw-down required and the time required to
achieve draw-down.
GIVEN:
AMOUNT OF DRAW-DOWN REQ. = VOLUME REQ.FOR DESIRED STORAGE TIME
VOLUME PER FOOT OF DEPTH
TIME REQ. FOR DRAW-DOWN = VOLUME OF DRAW-DOWN NEEDED
MAXIMUM DRAW-DOWN RATE
(1 CUBIC FOOT =7.5 GALLONS)
A POND IS BEING OPERATED FILL AND DRAW WITH THE OPERATOR
DRAWING-DOWN A POND TO MEET A DESIRED DETENTION TIME OF 180
DAYS. THE POND DIMENSIONS ARE 400 FEET BY 600 FEET AT
AVERAGE DEPTH. THE MEASURED WATER DEPTH IS 6 FEET, WITH THE
MAXIMUM OPERATING DEPTH OF 6 FEET, AND THE MAXIMUM DRAW-DOWN
RATE OF 0.5 FEET PER DAY. THE INFLUENT FLOW TO THE SYSTEM IS
30,000 GPD. WHAT IS THE MINIMUM NUMBER OF DAYS THAT IT WILL
TAKE TO DRAW THE POND DOWN?
45. Given data, calculate the volume of water in a groundwater
monitoring well casing.
GIVEN: INSIDE WELL CASING DIAMETER = 2 INCHES
DEPTH OF WATER =15 FEET
FORMULA:
VOLUME (GALLONS) = 3.14 X R2 X DEPTH X 7.5
(1 CUBIC FOOT =7.5 GALLONS)
(1 CUBIC FOOT = 1728 CUBIC INCHES)
VOLUME = 3.14 X 1 X 1 X (15(FT) X 12(IN) X 7.5
1728
VOLUME =2.45 GALLONS
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RESOURCES
1. CONTROLLING WASTEWATER TREATMENT PROCESSES. (1984).
Cortinovis, Dan. Ridgeline Press, 1136 Orchard Road,
Lafayette, CA 94549.
2. GROUNDWATER SAMPLING PROCEDURES. Lindorff, David; Feld,
Jodi; and, Connelly, Jack. PUBL. WR-168-87 (1987).
Department of Natural Resources, Bureau of Water
Resources,P.O. Box 7921, Madison, WI 53707.
3. OPERATION OF MUNICIPAL WASTEWATER TREATMENT PLANTS. Manual
of Practice No.11 (MOP 11), 2nd Addition (1990), Volumes
I,II,andlll. Water Environment Federation (Old WPCF),
601 Wythe Street, Alexandria, VA 22314-1994.
Phone (800) 666-0206. http://www.wef.org/
4. OPERATION OF WASTEWATER TREATMENT PLANTS. 3rd Edition
(1990), Volumes 1 and 2, Kenneth D. Kerri, California State
University, 6000 J Street, Sacramento, CA 95819-6025. Phone
(916) 278-6142. http://www.owp.csus.edu/training/
5. OPERATION OF WASTEWATER TREATMENT PLANTS. Manual of Practice
No.11 (MOP 11)(1976). Water Pollution Control Federation,
601 Wythe Street, Alexandria, VA 22314-1994.
Phone (800) 666-0206. (Probably Out-Of-Print, See Reference
Number 3).
5. OPERATIONS MANUAL: STABILIZATION PONDS. Zickenfoose, Charles
and Hayes, R.B.Joe EPA-430/9-77-012 (1977). U.S.
Environmantal Protection Agency, Office of Water Program
Operation, Washington, DC 20460.
6. STABILIZATION POND OPERATION AND MAINTENANCE MANUAL.
Sexauer, Willard and Karn, Roger (1979). Operator Training
Unit, Minnesota Pollution Control Agency, 1935 West County
Road B-2, Roseville, MN 55113. Phone (612) 296-7373.
17
F-45
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APPENDIX G
Discharge Guidance
G-1
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Discharge
Guidance and
Procedure
Minnesota Pollution Control Agency
G-2
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Introduction
> Minimum detention time required
180 or 210 days
- Designed as a controlled discharge system
- Spring/Fall discharge
> Must avoid discharge during "Problem
Discharge Period"
Summer or Winter
Need adequate flow and reaeration capacity
of receiving waters
Changes to Acceptable
Discharge Periods
> Modified with permit re issuance
> Must continue with dates currently in
permit
> Spring - March 1 instead of April 1
> Fall - December 31 instead of
December 15
G-3
-------
Acceptable
Discharge Periods
> MPCA Regional > AAPCA Regional
Offices Offices
> Detroit Lakes, > Willmar/Marshall
Brainerd, Duluth st. Paul, and
> Spring Rochester
to June 30 > 5 jna
>Fall
- Sept 1
- Sept 15 to
AAPCA Regional Offices @ 800-657-3864
Detroit
Lakes
Bra i nerd
Municipal VT**tcw*tcr
CunpbiiKc «c Eutwiwuxnl Suff
—|tu,
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POND DISCHARGE PROCEDURE
1. Is discharge needed; if so how
much ?
2. Sampling prior to discharge
3. Is discharge notification required ?
4. Actual discharge
5. Sampling during discharge
6. Complete monthly report
Is Discharge Needed ?
If so, how much ?
What level are ponds at ?
How much wastewater will I receive ?
How many days do I provide storage for ?
Calculate discharge volume (in feet)
G-5
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Discharge Calculation
Worksheet
> Will determine amount of discharge in
feet
> Pond Discharge Calculation Worksheet
Master.xls
Sampling Prior to Discharge
Pre-discharge sampling required (Max. 2 weeks prior
to discharge;
CBOD, TSS, Fecal Coliform, DO, pH, Total
Phosphorus
Four-sided composite sample
CBOD, TSS, Total Phosphorus
Total phosphorus sample container
Special container
Separate sterilized grab sample for fecal col [form
Grab samples for dissolved oxygen and pH
- within 24 hours prior to discharge
G-6
-------
Is Discharge Notification Required ?
> Notification not required if
AJLsamples results meet permit limits
Within "Acceptable Discharge Period"
Notification required if
- One or more sample results do not meet
permit limits, or
Time between pre-discharge sample and
discharge exceeds two weeks, or
- If any of the discharge is in "Problem
Discharge Period", or
- If any of the discharge is to ice covered
receiving waters
Notification (if required) is to MPCA Regional
Actual Discharge
r Allowable discharge rate
- six inches per day
- Can exceed after discussion with MPCA
Regional office
*- Avoid discharge to ice covered receiving
waters
- If unavoidable, call MPCA Regional Office
G-7
-------
Sampling Required During
Discharge
> Grab sample from discharge control
structure
» CBOD, TSS, Fecal Coliform, DO, pH,
Total Phosphorus
• Fecal and phosphorus in special container
> Twice per week (once every 3-4 days)
Complete Monthly Reports
- Supplemental Monthly Report
-Record discharge results
-Do include pre-discharge results
> Discharge Monitoring Report (DMR)
-Summarize calculations
> Postmarked by 21st day of following month
G-8
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SUPPLEMENTAL DM \ anil COM.Ml-. \ / S
\\«-kl» ()liMT»aln.iiNf..i Stahili/tiliiin. \i-iiilni. Piilisliinj: nr Mvuirptinn Ponds
G-9
-------
Discharge Monitoring Report
Influent
...
..*. i*-. n*«
3-=-
•Ml* IllW»«tW^».rf«ll*fcfc
Discharge Monitoring Report
Effluent
•
.ft. m-t-
»•— —
* «
's !T "".-...-
G-10
-------
Discharge During Problem Discharge
Periods-Winter
> Winter (1/1 to 2/28)
^ Notification required
MPCA Regional Office 0 800-657-3864
r Ice covered receiving waters
-100% ice coverage from bank to bank
-Concern is adequate receiving waters DO
-Violation of permit; regardless of date and sample results
-If unavoidable, must have adequate dilution ratio
-If dilution is not available, receiving waters sampling is
required
-Can not begin until two weeks after ice cover has left
-Must complete Discharge Evaluation Report
Discharge During Problem Discharge
Periods-Summer
r Summer (7/1 to 8/31 or 6/16 to 9/14)
r Notification required (MPCA Regional Office)
> Pre-discharge samples permit limits
-Must calculate dilution ratio
-Receiving water flow Vs. discharge flow
-Discharge OK if adequate dilution is available
-Lack of dilution ratio
-receiving waters monitoring required (D.O.)
-could reduce discharge rate
-could discharge continuously (overflow at
maximum depth)
-Subject to enforcement action
-Complete Discharge Evaluation Report
G-11
-------
Discharge During Problem Discharge
Periods-Summer
Pre-discharge samples meet permit limits
-Resample and/or take corrective action
-Must calculate dilution ratio
-Lack of dilution ratio
-receiving waters monitoring required (D.O.)
-could reduce discharge rate
-could discharge continuously
-Adequate dilution ratio
-only effluent monitoring required
-Subject to enforcement action
-Complete Discharge Evaluation Report
CBOD Vs. Dilution Ratio
CBOD Concentration
(mg/L)
Less than 5
5-10
11 - 15
16- 20
21 - 25
Greater than 25
Dilution Ratio
Receiving waters Vs.
Discharge rate
No min. dilution ratio needed
3 : 1
5 : 1
7 : 1
10 : 1
Call MPCA Regional Office
G-12
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Dilution Ratio Worksheet
i. Calculate discharge rate in cubic feet per second (cfs)
- At 6 inches per day, take size of pond ( in acres)
divided by 4
z. Calculate flow rate in receiving waters in cfs
- Measure width, depth, and stream flow
- surface flow is typically 70% faster than actual flow
Example: Secondary pond is 16 acres.
Discharge rate of 6 inch per day is 16 acres/4 = 4 cfs
Receiving waters is 5 feet across, average depth is 2
feet and the time for an object to travel 20 feet was
5 seconds. Receiving water flow rate is:
5ftx2
eet/5 second x 07 = 28 cfs
Dilution Ratio Worksheet
Dilution Ratio = Stream flow
discharge flow
28 cfs
4 cfs
= 7:1
Prom dilution ratio chart, adequate dilution will
be available as long as CBOD is 20 mg/L or less
CBOD Concentration
(mg/L)
Less than 5
Dilution Ratio
Receiving waters Vs. Discharge
No min. dilution ratio needed
11-15
16-20
21 -25
Greater than 25
Call MFC A Regional Office
G-13
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Discharge Evaluation Report
> Facility Information
> Hydraulic Capacity Evaluation
> Organic Capacity Evaluation
> Discharge Evaluation
G-14
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APPENDIX H
Guidance for Deploying Barley Straw
H-l
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APPENDIX H
GUIDANCE FOR DEPLOYING BARLEY STRAW
Using Barley Straw to Reduce Algal Growth in Wastewater Treatment Pond Systems
Charles E. Corley, Illinois Environmental Protection Agency
Q: If you are not Anheuser Busch, what does one do with barley?
A: The days of filling a feedbag of a horse-drawn milk wagon being long gone, the sensible use
is float it, the straw portion at least, on your pond, ditch, impoundment or reservoir. Why? Well,
as some people have found from German Valley to Manchester, Illinois and England
respectively, your water will be clearer, cleaner and lower in suspended solids due to algae.
Studied in the UK, the decomposition of barley straw and the observed effects on algae has been
recorded since the late 1980's by multiple researchers including Dr. Jonathon Newman,
University of Bristol, Department of Agricultural Sciences, Reading, U.K. Over ten year's worth
of observations has distinguished "rotting barley straw" as an effective inhibitor of the color and
suspended solids attributed to various types of algae. The research was done in "impoundments",
slow moving "canals", and many other bodies of water; and has been confirmed by laboratory
studies. This has led researchers to propound: "Decomposing barley straw inhibits the growth of
both filamentous and blue-green algae species in all types of water bodies so far assessed".1
What causes barley to be so effective is not truly identified. Again, researchers have analyzed
many chemical constituents produced by rotting barley straw.2 No one chemical is predominant
and the combined effect appears to be the controlling factor. Not the presence of the straw, but
the decomposition products appears to provide the effect. Other straws and plant material have
been tested and dismissed in preference to barley.3 For example, green plant material like alfalfa
and hay impart an organic load on the system while wheat straw, corn and lavender stalks, two
quite common Illinois plant materials the latter less so, seem to have poorer effects and
longevity. Despite uncertainty of the exact mechanism or product that produces the benefit, a
benefit it is. One easily measured and observed, at that.
Transferring the technology, if one can refer to rotting barley straw as technology, to wastewater
systems at best would seem a stretch. Newman's own studies indicate that algae growth
continues with sufficient nutrient concentrations.4 Further, algae and fungi appear to be affected
while all other aquatic animal and plant life are not. Nor is dissolved oxygen. Therefore, no
detrimental conditions would be expected and, if any benefit accrues in wastewater systems, all
would be positive steps.
The application, of this truly natural and beneficial product, to water bodies of all types is
fundamentally simple. Bundle it, float it and watch it rot! No need to search for the "right" type
of barley straw or the vintage year, if there is one. Contact the nearest, cheapest and most readily
available source and have at it. A slight oversimplification perhaps, but the years of observation
have demonstrated these few basics. All confirmed by trials in Illinois communities and
industries.
H-2
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What few basics tenets have been displayed in use in Illinois include these: First, the straw must
be floating throughout the application period. When allowed to sink, the thought is that it
becomes a detrimental organic load. Secondly, since the original uses were in surface water
ponds and impoundments and not wastewater systems, repeated applications are necessary form
spring thru warm weather. Warm weather and wind action on the surface are two necessary
ingredients. Also, keeping the straw loosely packed inside a long open-web material such as
common snow fence is ideal and preferred to the more open-weave Christmas wrap where straws
can escape.
Success can be found in all corners of our state. From Gardner to Ohio and Sorrento to
Hudsonville barley straw decomposition abounds. Measurable and observable benefit without
any detrimental environmental effects abound. First used in Gardner at the wastewater pond
system, it reduced the use of copper sulfate while improving the effluent suspended solids for
weeks in the hottest part of the summer of 2000. The operator at Sorrento experienced similar
benefits during the summer of 2002 at the water plant where lower turbidity was demonstrated
and fewer applications of copper sulfate were needed. These two have a sided benefit of reduced
applications and reduced cost of an admittedly useful but hazardous material, copper sulfate.
Other wastewater applications include the ash pond treatment at the Amerens Hudsonville
Generating station. Barley straw here reduced the algae count in the effluent along with the
suspended solids while positively affecting the pH of the discharge to the Wabash River. Using
the straw at Ohio was done late in the summer in 2001. Not expecting a huge margin of success
as a result of sludge pockets in all pond cells, the floating barley straw booms were effective in
keeping the effluent suspended solids from exceeding the permitted limits for weeks.
These and others stories could be repeated throughout the Illinois with willing participants and
experimentation-minded communities.5 Who knows, the result might be cleaner, clearer ponds
with fewer green discharges to Illinois' surface waters. Better water quality. What a concept!6
Materials List and Cost:
Note: An application rate of 20 grams straw/m2 is the same as loz / sq yd.
Four to five forty-pound bales of barley straw for each acre @ $5 - $35
Two 100 ft. rolls of snow fence @ $20
Two rolls 350 Ib test polyethylene rope @ <$10
Two fence post @$ 1.89
Sixty one-gallon and half-gallon bottles
One tube silicon sealant @ $2.95
Nylon zip ties @ lowest cost
Two and a half hours on a sunny day.
Supplies and Method:
Flotation: Both gallon and half gallon bottles spaced 5 feet apart
Sealant: Silicon seal the inside of bottle caps
Configuration: Sausage Boom
Size: Two @ 95 ft. in series or parallel (or divide length as needed)
Location: Diagonally, upwind, in mixing pattern
Anchor: Double strands of poly rope tied to posts.
H-3
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Documentation:
Determine BOD and TSS loading on all cells and compare to the design
Sample early spring, before algae bloom starts or before first application
Sample treated cell influent and effluent TSS weekly
Compare results to same times in previous years
(Send your results to the Illinois EPA Rockford Regional Office or Charles Corley, 815 987-
7760.)
' Newman, Jonathon R and Barrett, P.R.F.; "Control of Microcystis aeruginosa by Decomposing Barley Straw".
1993, Aquatic Plant Management. 31: 203 - 206
' Newman, Jonathon (1999) "Information Sheet 3 - The Control of Algae Using Straw". Copyright ICAR-Centre
for Aquatic Plant Management.
3' ibid
4 ibid
' No conflict with the EPA Federal Insecticide Fungicide and Rodenticide Act (FIFRA) would be expected when
used in the privacy of one's own non-public water-body or pond; which the above were. In fact, barley straw has
been promoted without apparent conflict in the landscape pond industry for decades.
' Further information or a presentation of success stories in Illinois can be obtained from Charles Corley, Rockford
Region 815 987-7760 charles.corley@epa.state.il.us or from any Regional office.
H-4
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