600282001d
EPA-600/8-80-042d
TREATABILITY MANUAL
VOLUME IV. Cost Estimating
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
July 1980
Fur suit1 li.v the Siiporliiti'iiilciit of l>nc innmts, ('.s. <;»vi>nmi")it 1'rln.lim <
Wiishiii^ti.ii. H.C LM>40a
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PREFACE
In January, 1979, EPA's Office of Enforcement and Office of
Water and Waste Management requested help from the Office of
Research and Development in compiling wastwater treatment per-
formance data into a "Treatability Manual". This Manual was to
be used in developing NPDES permit limitations for facilities
which, at the time of permit issuance, were not fully covered
by promulgated, industry-specific effluent guidelines authorized
under Sections 301, 304, 306, 307, and 501 of the CWA.
A planning group was set up to manage the treatability program
under the chairmanship of William Cawley, Deputy Director,
Industrial Environmental Research Laboratory - Cincinnati. The
group includes participants from: 1) the Industrial Environmen-
tal Research Laboratory - Cincinnati, 2) Effluent Guidelines
Division, Office of Water and Waste Management; 3) Permits
Division, Office of Enforcement; 4) Municipal Environmental
Research Laboratory - Cincinnati; 5) R. S. Kerr, Environmental
Research Laboratory - Ada; 6) Industrial Environmental Research
Laboratory - Research Triangle Park; 7) Monsanto Research Corpo-
ration; and 8) Aerospace Corporation.
The objectives of the treatability program are:
• To provide readily accessible data and information on
treatability of industrial and municipal waste streams
for use by NPDES permit writers, enforcement personnel,
and by industrial or municipal permit holders;
• To provide a basis for research planning by identifying
gaps in knowledge of the treatability of certain pollut-
ants and wastestreams;
• To set up a system allowing rapid response to program
office requirements for generation of treatability data.
The primary output from this program is a five-volume Treat-
ability Manual. The individual volumes are named as follows:
Volume I - Treatability Data
Volume II - Industrial Descriptions
Volume III - Technologies
Volume IV - Cost Estimating
Volume V - Summary
Date: 6/23/80
11
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ACKNOWLEDGEMENT
The sheer size and comprehensiveness of this document should make it
obvious that this had to be the effort of a large number of people. It
is the collection of contributions from throughout the Environmental
Protection Agency, particularly from the Office of Enforcement, Office of
Water and Hazardous Materials and the Office of Research and Development.
Equally important to its success were the efforts of the employees of the
Aerospace Corporation, MATHTECH, INC., and the Monsanto Research Corporation
who participated in this operation.
No list of the names of everyone who took part in the effort would in
any way adequately acknowledge the effort which those involved in preparing
this Manual made toward its development. Equally difficult would be an
attempt to name the people who have made the most significant contributions
both because there have been too many and because it would be impossible to
adequately define the term "significant." This document exists because of
major contributions by the contractor's staff and by members of the following:
Effluent Guidelines Division
Office of Water and Waste Management
Permits Division
Office of Water Enforcement
National Enforcement Investigation Center
Office of Enforcement
Center for Environmental Research Information
Municipal Environmental Research Laboratory
Robert S. Kerr Environmental Research Laboratory
Industrial Environmental Research Laboratory
Research Triangle Park, NC
Industrial Environmental Research Laboratory
Cincinnati, OH
Office of Research and Development
The purpose of this acknowledgement is to express my thanks as Committee
Chairman and the thanks of the Agency to the Committee Members and others who
contributed to the success of this effort.
William A. C3v7ley, Deputy Director, lERL-Ci
Chairman, Treatability Coordination Committee
iii
Date: 6/23/80
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VOLUME IV
CONTENTS
IV. 1 Introduction IV.1-1
IV.2 Wastewater Conditioning IV.2.1-1
IV.2.1 Screening IV.2.1-1
IV.2.2 Grit Removal IV.2.2-1
IV.2.3 Flow Equalization IV.2.3-1
IV.2.4 Neutralization IV.2.4-1
IV.3 Primary Wastewater Treatment IV.3.1-1
IV.3.1 Gravity Oil Separation IV.3.1-1
IV.3.2 Clarification/Sedimentation IV.3.2-1
IV.3.3 Sedimentation with Chemical Addition IV.3.3-1
IV.3.4 Gas Flotation IV.3.4-1
IV.3.5 Gas Flotation with Chemical Addition IV.3.5-1
IV.3.6 Granular Media Filtration IV.3.6-1
IV.3.7 Ultrafiltration IV.3.7-1
IV.4 Secondary Wastewater Treatment IV.4.1-1
IV.4.1 Activated Sludge IV.4.1-1
IV.4.2 Trickling Filters IV.4.2-1
IV.4.3 Lagoons IV.4.3-1
IV.4.4 Rotating Biological Contactors IV.4.4-1
IV.4.5 Steam Stripping IV.4.5-1
IV.4.6 Solvent Extraction IV.4.6-1
IV.5 Tertiary Wastewater Treatment IV.5.1-1
IV.5.1 Granular Activated Carbon Adsorption IV.5.1-1
IV.5.2 Powdered Activated Carbon Adsorption IV.5.2-1
IV.5.3 Chemical Oxidation IV.5.3-1
IV.5.4 Air Stripping IV.5.4-1
IV.5.5 Nitrification IV.5.5-1
IV.5.6 Dentrification IV.5.6-1
IV.5.7 Ion Exchange IV.5.7-1
IV.5.8 Polymeric (Resin) Adsorption IV.5.8-1
IV.5.9 Reverse Osmosis IV.5.9-1
IV.5.10 Electrodialysis IV.5.10-1
IV.5.11 Distillation IV.5.11-1
IV.5.12 Chlorination IV.5.12-1
Date: 6/23/80
v
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CONTENTS (continued)
IV.5.13 Dechlorination IV.5.13-1
IV.5.14 Ozonation IV.5.14-1
IV.5.15 Chemical Reduction IV.5.15-1
IV.6.1 Gravity Thickening IV.6.2-1
IV.6.2 Flotation Thickening IV.6.2-1
IV.6.3 Centrifugal Thickening IV.6.3-1
IV.6.4 Aerobic Digestion IV.6.4-1
IV.6.5 Anaerobic Digestion IV.6.5-1
IV.6.6 Chemical Conditioning IV.6.6-1
IV.6.7 Thermal Conditioning IV.6.7-1
IV.6.8 Disinfection IV.6.8-1
IV.6.9 Vacuum Filtration IV.6.9-1
IV.6.10 Filter Press Dewatering IV.6.10-1
IV.6.11 Belt Filter Dewatering IV.6.11-1
IV.6.12 Centrifugal Dewatering IV.6.12-1
IV.6.13 Thermal Drying IV.6.13-1
IV.6.14 Drying Beds IV.6.14-1
IV.6.15 Lagoons IV.6.15-1
IV.7 Disposal IV.7.1-1
IV.7.1 Incineration IV.7.1-1
IV.7.2 Starved Air Combustion IV.7.2-1
IV.7.3 Landfilling - Area Fill IV.7.3-1
IV.7.4 Landfilling - Sludge Trenching IV.7.4-1
IV.7.5 Land Application IV.7.5-1
IV.7.6 Composting IV.7.6-1
IV.7.7 Deep Well Injection IV.7.7-1
IV.8 Bibliography IV.8-1
Appendix A - Economic Assumptions IV.A-1
Date: 6/23/80
VI
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GLOSSARY
AAP: Army Ammunitions Plant.
AN: Ammonium Nitrate.
ANFO: Ammonium Nitrate/Fuel Oil.
BATEA: Best Available Technology Economically Achievable.
BAT: Best Applicable Technology.
BDL: Below Detection Limit.
BEJ: Best Engineering Judgement.
BOD: Biochemical Oxygen Demand.
clarification: Process by which a suspension is clarified to give
a "clear" supernatant.
cryolite: A mineral consisting of sodium-aluminum fluoride.
CWA: Clean Water Act.
cyanidation process: Gold and/or silver are extracted from finely
crushed ores, concentrates, tailings, and low-grade mine-run
rock in dilute, weakly alkaline solutions of potassium or
sodium cyanide.
comminutor: Mechanical devices that cut up material normally
removed in the screening process.
effluent: A waste product discharged from a process.
EGD: Effluent Guidelines Division.
elutriation: The process of washing and separating suspended
particles by decantation.
extraction: The process of separating the active constituents of
drugs by suitable methods.
fermentation: A chemical change of organic matter brought about
by the action of an enzyme or ferment.
Date: 6/23/80
VII
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flocculation: The coalescence of a finely-divided precipitate.
fumigant: A gaseous or readily volatilizable chemical used as a
disinfectant or pesticide.
GAC: Granular Activated Carbon.
gravity concentration: A process which uses the differences in
density to separate ore minerals from gangue.
gravity separation/settling: A process which removes suspended
solids by natural gravitational forces.
grit removal: Preliminary treatment that removes large objects,
in order to prevent damage to subsequent treatment and
process equipment.
influent: A process stream entering the treatment system.
intake: Water, such as tap or well water, that is used as makeup
water in the process.
lagoon: A shallow artificial pond for the natural oxidation of
sewage or ultimate drying of the sludge.
LAP: Loading Assembly and Packing operations.
MGD: Million Gallons per Day.
MHF: Multiple Hearth Furnace.
NA: Not Analyzed.
ND: Not Detected.
neutralization: The process of adjusting either an acidic or a
basic wastestream to a pH near seven.
NPDES: National Pollutant Discharge Elimination System.
NRDC: National Resources Defense Council.
NSPS: New Source Performance Standards.
photolysis: Chemical decomposition or dissociation by the action
of radiant energy.
PCB: PolyChlorinated Biphenyl.
POTW: Publicly Owned Treatment Works.
Date: 6/23/80
viii
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PSES: Pretreatment Standards for Existing Sources.
purged: Removed by a process of cleaning; take off or out.
screening process: A process used to remove coarse and/or gross
solids from untreated wastewater before subsequent treatment.
SIC: Standard Industrial Classification.
SS:. Suspended Solids.
SRT: Solids Retention Time.
starved air combustion: Used for the volumetric and organic re-
duction of sludge solids.
terpene: Any of a class of isomeric hydrocarbons.
thermal drying: Process in which the moisture in sludge is re-
duced by evaporation using hot air, without the solids being
combusted.
TKN: Total Kjeldahl Nitrogen.
TOC: Total Organic Carbon.
trickling filter: Process in which wastes are sprayed through
the air to absorb oxygen and allowed to trickle through a
bed of rock or synthetic media coated with a slime of micro-
bial growth to removed dissolved and collodial biodegradable
organics.
TSS: Total Suspended Solids.
vacuum filtration: Process employed to dewater sludges so that a
is produced having the physical handling characteristics
and contents required for processing.
VSS: Volatile Suspended Solids.
WQC: Water Quality Criterion.
Date: 6/23/80
IX
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IV.1 INTRODUCTION
This manual presents total capital investment and annual operating
cost curves for wastewater treatment technologies. The cost
curves, which generally show costs in millions of dollars versus
wastewater flowrate, are presented for 78 technologies grouped
into the following six classifications: wastewater conditioning,
primary wastewater treatment, secondary wastewater treatment,
tertiary wastewater treatment, sludge treatment, and disposal.
Each technology is described in terms of a general overview, dis-
cussion of common modifications and typical equipment, and a flow
diagram. Design criteria are briefly discussed and cost assump-
tions for each technology are presented. As discussed in Appen-
dix A-Economic Assumptions, all costs are indexed to September
1979 (corresponding to an Engineering News Record index of 3119)
unless noted.
Cost data presented in this manual are generalized rather than
site specific, and are intended primarily for comparative analy-
sis. The user of this manual is cautioned against treating any
cost estimates based on the data contained herein as absolute.
These estimates are valid only for comparison purposes, and even
these comparisons must be performed with caution because of the
possible differences in the reliability of the performance and
cost information from various sources. Further, there may be
considerable difference between cost estimates for comparative
purposes and the actual total capital investment for the
facilities.
Cost data presented in this manual have been derived from EPA
publications, open literature, construction grant files, and manu-
facturers' information and have been indexed to 1979. These data
exhibit a level of accuracy dependent upon the degree of usage of
the process. Higher reliability costs generally occur where a
large amount of historical data exists, such as clarifiers and
activated sludge. Those processes with few examples beyond the
demonstration stage must be considered as individual cases with
the potential for wider variation in costs when applied in a
generalized fashion. It can generally be said that the data on
a specific control alternative are sufficient only to establish
a relationship as expressed by a table of data or a single curve
or family of curves (± approximately 30%).
Date: 6/23/80 IV.1-1
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A large number of the cost curves developed for this manual have
been obtained or derived from the Areawide Assessment Procedures
Manual (EPA-600/9-76-014) and Innovative and Alternative Tech-
nology Assessment Manual (EPA-430/9-78-009). This information
is the result of cost estimates developed over a period of years
by several contractors from detailed conceptual designs, process
and equipment layouts in accordance with standard estimating
techniques, plus verification using normalized "as built" costs
where available. Processes having limited "as built" cost data
bases contain single or multiple case history costs as available.
In some cases, costs have been tabulated rather than displayed
graphically.
Land costs, except in land application and landfill, are not in-
cluded in the cost curves. Land costs are highly dependent on
local conditions and should be developed on a case-by-case basis.
It should be noted, however, that land costs (except for land
application and land disposal of sludge) may not be necessary
for comparison purposes.
Cost components included in the estimation of the total capital
investment are shown below. Cost components included in the
estimation of total annual operating costs are shown on the
following page. A more detailed discussion of economic assump-
tions is presented in Appendix A.
BREAKDOWN OF TOTAL CAPITAL INVESTMENT
FIXED CAPITAL INVESTMENT
Direct cost components:
• Purchased equipment and installation
• Instrumentation and controls
• Piping
• Electrical equipment and materials
• Buildings
• Yard improvements
• Service facilities
Indirect cost components:
• Engineering and supervision
• Construction expenses
• Contractors fee
• Contingency
WORKING CAPITAL
Date: 6/23/80 IV.1-2
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BREAKDOWN OF ANNUAL OPERATING COST
TOTAL ANNUAL OPERATING COST:
Total direct operating cost:
Labor
Materials
Chemicals
Power
Fuel
Total indirect operating cost:
Plant overhead
Taxes and insurance
General and administrative expenses
Depreciation
Interest on working capital
Date: 6/23/80
IV.1-3
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IV.2 WASTEWATER CONDITIONING
IV.2.1 SCREENING
IV.2.1.1 Horizontal Rotary Shaft Screen [I]
Description. A horizontal rotary-shaft screen is an inter-
mittently or continuously rotating drum covered with a plastic or
stainless-steel screen of uniform-sized openings, installed and
partially submerged in a chamber. The chamber is designed to
permit entry of wastewater to the interior of the drum and col-
lection of filtered (or screened) wastewater from the exterior
side of the drum. With each revolution, the solids are flushed
by sprays from the exposed screen surface into a collecting
trough. Different types of screen are used. Coarse screens have
openings of 1/4 inch or more; fine screens have openings less
than 1/4 inch; screens with openings of 20 to 70 ym are called
microscreens or microstrainers. Drum diameters are usually 3 to
5 feet; lengths are 4 to 12 feet. The most common modifications
for horizontal rotary shaft screen are the following:
Tile chambers; reinforced concrete chamber; steel chamber
Variable-speed drive for drum
Addition of backwash storage and pumping facilities
Addition of ultraviolet light slime-growth control equipment
Addition of chlorinating equipment
Equipment normally associated with the horizontal rotary-shaft
screen process includes screens and mechanical components. A
flow diagram of a horizontal rotary-shaft screen is presented
below.
DRIVE UNIT-
SCREENING
^FABRIC
i 'j»j
JETS
EFFLUENT WEIR
SCREENING
WASTEWATER
DISCHARGE
EFFLUENT CHAMBER
INFLUENT CHAMBER
Date: 6/23/80
IV.2.1-1
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Typical design criteria. Typical design criteria of horizon-
tal rotary-shaft screen are shown below.
Design criterion Value
Screen submergence 70 - 80%
Loading rate 2-10 gpm/ft2 of submerged area, depending
on pretreatment and mesh size
Screen openings 150 ym - 0.4 in. for pretreatment;
20 - 70 ym for tertiary treatment
Drum rotation 0-7 revolutions/min
Screen materials Stainless steel or plastic cloth
Washwater quantity 2 - 5% of flow being treated
Performance of fine Varies considerably depending on influent
screen device solids type, concentration and loading
patterns, mesh size, hydraulic head, and
degree of biological conditioning of
solids
Costs. Purchased equipment and installation cost for esti-
mation of total capital investment includes tanks, drums, screens,
backwash equipment, drive motors, and building. Instrumentation
for automatic operation is also included. The following operat-
ing characteristics were assumed for cost estimation:
Operating characteristic Assumed value ~
Hydraulic load 2.5 gpm/ft2 at average flow
Screen mesh 25 y
Peripheral drum speed 15 ft/min at 3-in. head loss
Backwash 3% of throughput at 35 psi
References. '-
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.2.1-2
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TOTAL CAPITAL INVESTMENT
10
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FLOW, 1,000 m3/d
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TOTAL CAPITAL
INVESTMENT.
PURCHASED AND
INSTALLED EQUIPMENT
ENR INDEX • 3119
. .1.11
1.0 10
ROW, Mgal/d
100
Date: 6/23/80
IV.2.1-3
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ANNUAL OPERATING COST
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Date: 6/23/80
IV.2.1-4
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IV.2.1.2 Wedge-wire Screen [1]
Description. A wedge-wire screen is a device onto which
wastewater is directed across an inclined stationary screen or a
drum screen of uniform-sized openings. Solids are trapped on the
screen surface while the wastewater flows through the openings.
The solids are moved either by gravity (stationary) or by mechan-
ical means (rotating drum) to a collecting area for discharge.
Stationary screens introduce the wastewater as a thin film flow-
ing downward with a minimum of turbulence across the wedge-wire
screens, which are generally in three sections of progressively
flatter slope. The drum screen employs the same type of wedge
wire wound around its periphery. Wastewater is introduced as a
thin film near the top of the drum and flows through the hollow
drum and out the bottom. The solids retained by the peripheral
screen follow the drum rotation until removed by a doctor blade
located at about 120° from the introduction point.
Wedge-wire spacing can be varied to best suit the application.
For municipal wastewater applications, spacings are generally
between 0.01 and 0.06 inches (0.25 to 1.5 mm). Inclined screens
can be housed in stainless steel or fiberglass; wedge-wires may
be curved or straight; the screen face may be a single multi-angle
unit, three separate multi-angle pieces, or a single curved unit.
Rotary screens can have a single rotation speed drive or a
variable speed drive.
Equipment normally associated with this technology includes
screen systems. A flow diagram of a wedge-wire screen system is
shown below.
FEED
WATER LEVEL .
SLUDGE
s
INFLUENT —*• f| \
I I \ROTATINGDRUMj
SOLIDS
EFFLUENT / (SEE
SECTION
IV.7)
EFFLUENT
(SEE SECTION IV.7)
Date: 6/23/80
IV.2.1-5
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Typical design criteria. Typical design criteria of a
wedge-wire screen based on screening of raw wastewater at
0.05 - 36 Mgal/d are shown below.
Design criterion Stationary screen Rotary drum screen
Screen opening
Head required
Space required
Motor size
0.01 -
4 -
10 -
™"
0.06 in.
7 ft
750 ft2
0.01 -
2.5 -
10 -
0.5 -
0.06 in.
4.5 ft
100 ft2
3 hp
Costs. Purchased equipment and installation cost for esti-
mation of total capital investment includes wedge-wire stainless-
steel screen with 0.06 in. opening, electrical provisions, and
equipment that provides suitable weirs for flow control. Flumes,
piping for effluent or sludge, and pumping equipment are not
included. Annual operating costs are based on the pumping head
of 4.5 ft for a stationary screen.
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.2.1-6
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TOTAL CAPITAL INVESTMENT
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TOTAL CAPITAL
INVESTMENT
(ROTARY SCREEN)
FLOW, Mgal/d
Date: 6/23/80
IV.2.1-7
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IV.2.2 GRIT REMOVAL (PRELIMINARY TREATMENT) [1]
IV.2.2.1 Description
Preliminary treatment usually consists of two separate and dis-
tinct unit operations: bar screening and grit removal. There
are two types of bar screens (or racks). The most commonly
used, and oldest technology, consists of hand-cleaned bar racks,
which are generally used in smaller treatment plants. The
second type of bar screen is the type that is mechanically
cleaned, which is commonly used in larger facilities.
Grit is most commonly removed in chambers that are capable of
settling out high density solid materials, such as sand, gravel,
and cinders. There are two types of grit chambers: horizontal
flow, and aerated; in both types the settleables collect at the
bottom of the unit. Horizontal units are designed to maintain a
relatively constant velocity by use of proportional weirs or
flumes in order to prevent settling of organic solids, while
simultaneously obtaining relatively complete removal of inor-
ganic particles (grit). Aerated grit chambers produces spiral
action whereby the heavier particles remain at the bottom of the
tank to be removed, while organic particles are maintained in
suspension by rising air bubbles. One main advantage of aerated
units is that the amount of air can be regulated to control the
grit/organic solids separation, and less offensive odors are
generated. The aeration process also facilitates cleaning of
the grit. Grit removed from horizontal flow units usually needs
additional cleaning steps prior to disposal.
Some plants also use comminutors, which are mechanical devices
that cut up the material normally removed in the screening
process. Therefore, these solids remain in the wastewater to be
removed in downstream unit operations, rather than being removed
immediately from the wastewater. In recent years, the use of
static or rotating wedge-wire screens has increased to remove
large organic particulates just prior to degritting. These units
have been found to be superior to comrainutors in that they
remove the material immediately from the waste instead of creat-
ing additional loads downstream. Other grit chamber designs are
available including swirl concentrators and square tanks.
Equipment normally associated with preliminary treatment includes
screens, grinders, comminutors, sedimentation equipment, and
wedge-wire screens. A flow diagram for preliminary treatment in-
cluding grit removal is shown below.
_- METERING
INFUJENT "
LARGE SOLIDS
(SEE SECTION IV.7) GRIT
(SEE SECTION IV.7)
Date: 6/23/80 IV.2.2-1
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IV.2.2.2 Typical Design Criteria
Typical design criteria for screening and grit chambers are shown
below.
Design criterion
Value
Bar screens
Bar size
Spacing
Slope from vertical
Velocity
Wedge-wire screens
Grit chambers
Horizontal velocities
Length
Weir crest position
1/4 - 5/8 in. width by 1 - 3 in. depth
3/4 - 3 in.
0 - 45°
1.5-3 ft/s
See Section IV.2.1
1/2 - 1.25 ft/s
Units are sufficiently long to settle
lightest and smallest (usually 0.2 mm)
grit particles with an additional
factor of safety (up to 50%)
Generally set 4 - 12 in. above bottom
IV.2.2.3 Costs
Purchased equipment and installation cost includes flow channels
and superstructures, bar screens (mechanical), horizontal grit
chamber with mechanical grit handling equipment, Parshall flume,
and flow-recording equipment. Total annual costs do not include
cost for grit disposal. Screenings 1 to 3 ft3 of suspended
material/Mgal. Grit 2 to 5 ft3 of grit/Mgal.
IV.2.2.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80
IV.2.2-2
-------
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-------
ANNUAL OPERATING COST
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TOTAL ANNUAL
OPERATING COST
TOTAL DIRECT
OPERATING COST
ENR INDEX =3119
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FLOW, Mgal/d
Date: 6/23/80
IV.2.2-4
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IV.2.3 FLOW EQUALIZATION [1]
IV.2.3.1 Description
Wastewater flows into treatment facilities are subjected to fluc-
tuation in water quality and quantity. Most waste treatment proc-
esses are sensitive to such changes. An equalization basin
serves to balance the extreme quality and quantity of these fluc-
tuations to allow normal contact time in the treatment facility.
This section only addresses equalization basins that are used to
equalize flow; however, equalization of the quality of wastewater
will also occur to a degree.
Equalization basins may be designed as either in-line or side-
line units. In the in-line design, the basin recieves the waste-
water directly from the collection system, and the discharge from
the basin through the treatment plant is kept essentially at con-
stant rate. In the side-line design, flows in excess of the
average are diverted to the equalization basin and, when the plant
flow falls below the average, wastewater from the basin is dis-
charged to the plant to increase the flow to the average level.
The basins are sufficiently sized to hold the peak flows and dis-
charge at constant rate.
Pump stations may or may not be required to discharge into or out
of the equalization basin, depending upon the available head.
Where pumping is found necessary, the energy requirements are
based on total flow for in-line basins and on excess flow for
side-line basins.
Aeration of the wastewater in the equalization basin is normally
required for mixing and maintaining aerobic conditions.
There are various methods of aeration, pumping, and flow control.
Tanks or basins can be manufactured from steel or concrete •, or
they can be excavated and of the lined or unlined earthen variety.
Equipment normally associated with flow equalization includes lift
pumps, air compressors, basin liners, flow controllers, and aera-
tors. Flow diagrams for in-line and side-line flow equalization
are shown below.
SECTION 1V.7)
SLuocf-ntoassiNG
KCYCU FLOWS
(SEE SECTION IV.7}
Date: 6/23/80
IV.2.3-1
-------
IV.2.3.2 Typical Design Criteria
The design of an equalization basin is highly site specific and
dependent upon the type and magnitude of the input flow variations
and facility configurations. Typical design criteria and their
dependencies are shown below for flow equalization.
Design criteria Value
Pumping/flow control mode, Dependent upon size and site
aeration, mixing, and conditions
flushing methods
Grit removal Should be provided upstream of
basin
Mechanical mixing3 20 - 40 hp/Mgal of storage
Aerationa 1.25 - 2 ft3/min/l,000 gal of
storage13
_
Mechanical aerators will supply both mixing and aeration.
Dependent upon IOD and BOD.
IV.2.3.3 Costs
Purchased equipment and installation cost is based on a concrete
basin for design flows less than 1 Mgal/d and 6-in. concrete-lined
earthen basin for design flows greater than 1 Mgal/d. Detention
time equals 1.0 day. Capital costs include mixers. Operating
costs are based on mechanical mixing at 20 hp/Mg and pumping at
10 ft TDK.
IV.2.3.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.2.3-2
-------
TOTAL CAPITAL INVESTMENT
100 r
CO
0£
1
o
u.
o
to
o
10
a 1.0
0.1
0.1
CAPACITY, 1,000 m3/d
1.0 10
100
ENR INDEX-3119
. . t . . ..
1.0 10
CAPACITY, Mgal/d
100
Date: 6/23/80
IV.2.3-3
-------
a
(0
rt
(D
MILLIONS OF DOLLARS/YEAR
to
OJ
00
o
to
•
OJ
I
O
8
o
o
O
-a
m
50
O
o
o
to
-------
IV.2.4 NEUTRALIZATION [1]
IV.2.4.1 Description
Neutralization is the process of adjusting either an acidic or a
basic wastestream to a pH in the range of seven. Since many man-
ufacturing and processing operations produce effluents that are
acidic or alkaline in nature, neutralization of an excessively
acidic or basic waste stream is necessary in a variety of situa-
tions. For example it is required: (1) to prevent metal corro-
sion and/or damage to other construction materials; (2) to protect
aquatic life and human welfare; (3) as a preliminary treatment
allowing effective operation of biological treatment processes,
and (4) to provide neutral pH water for recycle, either as proc-
ess water or as boiler feed. Treatment to adjust pH may also be
desirable to break emulsions, to insolubilize certain chemical
species, or to control chemical reaction rates, e.g., chlorination,
Although natural waters may differ widely in pH, changes in a par-
ticular pH level could produce deterimental effects on the environ-
ment. To minimize any undesirable consequences, the effluent
limitations guidelines for industrial sources set the pH limits
for most industries between 6.0 and 9.0 for 1977 and 1983.
Simply, the process of neutralization is the interaction of an
acid with a base. The typical properties exhibited by acids in
solution are due to the hydrogen ion, (H+). Similarly, alkaline
(or basic) properties are a result of the hydroxyl ion, (OH~).
In aqueous solutions, acidity and alkalinity are defined with
respect to pH, where pH = - log (H+) and, at room temperature,
pH = 14 + log (OH~). In the strict sense, neutralization is the
adjustment of pH to 7, the level at which the concentrations of
hydrogen and hydroxyl ions are equal. Solution with excess
hydroxyl ion concentration (pH >7) are said to be basic, solu-
tions with excess hydrogen ions (pH <7) are acidic. Since
adjustment of the pH to 7 is not often practical or even desir-
able in waste treatment, the term "neutralization" is sometimes
used to describe adjustment of pH to values other than 7.
The actual process of neutralization is accomplished by the addi-
tion of an alkaline to an acidic material or by adding an acidic
to an alkaline material, as determined by the required final pH.
The primary products of the reaction are a salt and water. A
simple example of acid-base neutralization is the reaction be-
tween hydrochloric acid and sodium hydroxide:
HC1 + NaOH -» H20 + NaCl
The product, sodium chloride in aqueous solution, is a neutral
with pH = 7.0.
Date: 6/23/80 IV.2.4-1
-------
Required equipment may be as varied as the reactions that can be
classified as neutralizations. However, the most commonly occur-
ring scheme for neutralization is the addition of a chemical, in
either liquid or solid form, directly into a wastewater stream.
The required equipment for this treatment is simple, i.e.,
storage and reaction tanks with accessory agitators, and delivery
systems. The tanks may be of any shape, round or square, but must
be properly baffled to allow adequate mixing and prevent "short-
circuiting." Frequently the neutralization is carried out in a
series of reactors to provide better control of the final pH.
Such a system with three units is shown in the flow diagram below.
There are two addition points for neutralizing agent, controlled
by pH monitors. Most of the neutralization occurs in the first
reactor, adjustment to the final desired pH takes place just
before discharge. In large-scale operations the tanks are often
built below ground level and constructed of concrete.
NEUTRALIZING CHEMICAL
RED SYSTEM
INCOMING WATER
pH METER CONTROLLER.
pH ROW CELLS
SAMPLE PUMPS
r
NEUTRALIZING CHEMICAL
FEED SYSTEM
V.
J*
=
1
ea
t
I
^
\
9
\
(
S
a
a
NEUTRALIZED WAI
IV.2.4.2 Typical Design Criteria
The design of a neutralization system is highly specific. The
following design criteria is based on the requirements for lime
neutralization of sulfuric acid waste stream and is discussed in
the following section.
IV.2.4-2
-------
Design criteria
Value
Basis
Equipment
Three reactors (with mixers)
Slaking tank (with mixer)
Lime slurry tank (with mixer)
Water storage tank
Lime/silo
Clarifier
Rotary filter
Lime screw feeder
Pumps
P-l
P-2
P-3
P-4
Two pH recorder/controllers
(with sample pumps)
Chemicals
Quicklime
Power
Electricity (annual basis)
Labor
1 Mgal/d; 1% H2SCu (by vol);
350 day/yr operation
7,500 gal each
1,000 gal
5,000 gal
200,000 gal
2,000 ft3
250,000 gal
11,250 Ib/hr dry solids
(filter cake 50-60%
solids)
3,700 Ib/hr
70 gpm
70 gpm
35 gpm
70 gpm
44 ton/d
675,000 kWh
32 man-hr/d
Due to possible acidic conditions, reactors should be lead-
or rubber-lined; agitator shafts and blades should be
rubber-coated.
IV.2.4.3 Costs
The capital investment for neutralization depends on the specific
treatment process selected and the size of the stream to be
treated, and it can result in differences in capital costs of
orders of magnitude. For example, a 1971 study of limestone
treatment of acid mine drainage (sulfuric acid) estimated that
capital costs for treating a stream of about 900 gpm could range
from $352,000 to $1,238,000, depending on the composition of the
stream. High levels of iron, aluminum, and sulfate contribute
to larger capital investment, particularly in the area of sludge
handling equipment. For the same reason the estimated cost of
operation ranged from $0.35 to $3.76 per 1,000 gal (including
Date: 6/23/80
IV.2.4-3
-------
sludge disposal). This example indicates the potentially large
variation in investment and operating costs in the same process
operating on different quality wastes. It would be inappropri-
ate to draw conclusions concerning investment capital for neutral-
ization without some knowledge of the system. Materials of
construction and the need for sludge-handling equipment are just
two additional factors that can drastically alter an economic
analysis. With regard to operating costs, similar considerations,
such as sludge disposal costs, may be critical.
To provide a general understanding of the economics of a neutral-
ization process a "simulated" sample system is illustrated in
the figure below. This design, along with the description in
the following table, represents a common scheme for lime neutral-
ization of a waste stream containing sulfuric acid. An economic
analysis for the treatment process also is shown below.
WASTE ACID
1 RECYCLE
EFRUENT
SOLIDS
Placing the exact price on the sludge disposal is difficult. The
chemical composition of the material will influence the choice of
disposal method. A sludge containing large quantities of heavy
metals may not be suitable for landfill, due to the possibility
of leaching, and a more costly method may have to be devised.
Conversely, a relatively pure sludge of calcium sulfate might be
sold as a by product and count as a credit.
Fixed capital cost based on an ENR index of 3119 is estimated to
be $1,420,000. Similarly, total capital cost is estimated to be
$1,504,000. Estimation of annual operating cost is presented in
the following table.
Date: 6/23/80
IV. 2.4-4
-------
ESTIMATE OF ANNUAL OPERATING COST FOR LIME
NEUTRALIZATION OF SULFURIC ACID WASTE STREAM
Cost item
Direct operating cost
Labor
Operating
Maintenance
Chemicals
Lime
Coagulant aids
Annual
quantity
11,200 man-hr
15,400 tons
3,000 Ib
Cost per unit
quantity
$16/hr
$35/ton
$2.00/lb
Annual
180,000
28,000
539,000
6,000
cost, $
208,000
Materials -
Maintenance
Power
Total
Total indirect
operating cost
Total annual
operating cost
675,000 kWh
$0.035/kWh
545,000
29,000
23,600
806,000
389,000
1,200,000
Costs have not been included for sludge disposal or, conversely for gypsum
credit, if the gypsum is saleable.
Cost curves were developed for total capital investment and annual
operating cost using the cost data shown above and the following
exponential scaling factors, which were used to determine costs at
varying capacities:
Cost item
Exponential
factor
Total capital investment
Labor
Materials, power and chemicals
0.7
0.3
1.0
Date: 6/23/80
IV.2.4-5
-------
IV.2.4.4 References
1. Physical, Chemical, and Biological Treatment Techniques for
Industrial Wastes, PB 275 287, U.S. Environmental Protection
Agency, Washington, D.C., November 1976. pp. 34-1 to 34-20.
Date: 6/23/80 IV.2.4-6
-------
MILLIONS OF DOLLARS
I-- K- •
o 5 8
0.1
TOTAL CAPITAL INVESTMENT
FLOW, 1,000 m3/d
1.0 10 100
i
-
* ^^^
: /
-/'
\
A
i i i i 1 1 11
i
TOTAL CAPITAL
INVESTMENT
ENR INDEX • 3119
0.1
1.0 10
FLOW, Mgal/d
100
Date: 6/23/80
IV.2.4-7
-------
ANNUAL OPERATING COST
FLOW, 1,000 m3/d
10 100
ENR INDEX • 3119
, . i ,
to
o
1C
o
QC
UJ
O
Q_
l
CO
1.0 10
FLOW, Mgal/d
Date: 6/23/80
IV.2.4-8
-------
IV.3 PRIMARY WASTEWATER TREATMENT
IV.3.1 GRAVITY OIL SEPARATION
IV.3.1.1 Description
Gravity oil separation is used for the removal of floatable oil
and grease.
A gravity oil separator (skimming tank) is a chamber so arranged
that floating matter rises and remains on the surface of the
wastewater until removed, while the liquid flows out continuously
through deep outlets or under partitions, curtain walls, or deep
scum boards. This may be accomplished in a separate tank or com-
bined with primary sedimentation, depending on the process and
nature of the wastewater.
The objective of skimming tanks is the separation from the waste-
water of the lighter floating substances. The material collected
on the surface of skimming tanks, whence it can be removed, may
include oil, grease, soap, pieces of cork and wood, vegetable
debris, and fruit skins. The outlet, which is submerged, is
opposite the inlet and at a lower elevation to assist in flota-
tion and to remove any solids that may settle.
Gravity-type separators are the most common devices employed in
oily waste treatment. The effectiveness of a gravity separator
depends upon proper hydraulic design, and the design period of
wastewater retention. Longer retention times allow better
separation of the floatable oils from the water. Short detention
times of less than 20 minutes result in less than 50% oil-water
separation, while more extended holding periods improve oil
separation from the waste stream.
Gravity separators are equally effective in removing both greases
and nonemulsified oils. The standard unit in refinery waste
treatment is the API separator, based upon design standards pub-
lished by the American Petroleum Institute. Separators used for
metal and food processing oily wastes operate upon the same prin-
ciple of floating the oil, and many are designed in a similar
fashion to the API process insofar as skimming, retention time,
etc. Separators may be operated as batch vats, or as continuous
flow-through basins, depending upon the volume of waste to be
treated.
Date: 6/23/80 IV.3.1-1
-------
IV.3.1.2 Typical Design Criteria
Design criteria Value
Surface loading9 <700 gpm/ft2
Wastewater depth 6-7 ft
Detention time 1-2 hr
Many states require the surface
loading to be <700 gpm/ft2.
To adjust costs for alternative surface overflow rate, calculate
the effective flow (Q ) using the following equation:
800 gpd/ft2
X.
E Design new design surface overflow rate
IV.3.1.3 Costs. Purchased equipment and installation cost for
estimation of the total capital investment includes primary sludge
pumps and separator. The following operating characteristics were
assumed for cost estimation.
Operating characteristic Assumed value
Service life 50 yr
Surface overlow rate 800 gpd/ft2 (based on average flow)
Sludge concentration 4% solids
Pump head 10 ft TDK
IV.3.1.4 References
1. Patterson, J. W. Wastewater Treatment Technology.
Ann Arbor Science Publishers, Inc., Ann Arbor, Michigan,
1975. pp. 179-185.
2. Azad, H. S. Industrial Wastewater Management Handbook,
McGraw Hill Book Company, New York, 1976. p. 5-28.
Date: 6/23/80 IV.3.1-2
-------
TOTAL CAPITAL INVESTMENT
00
o
o
u.
o
co
z
o
0.001
Mgal/d
Date: 6/23/80
IV.3.1-3
-------
ANNUAL OPERATING COST
1.0 r
o
Q_
0.001
o.ooiai
0.0001
ROW, Mgal/d
Date: 6/23/80
IV.3.1-4
-------
IV.3.2 CLARIFICATION/SEDIMENTATION
IV.3.2.1 Primary Circular Clarification [1]
Description. Primary circular clarification involves a rel-
atively long period of quiescence in a basin (depths of 10 to 15
feet) where most of the settleable solids fall out of suspension
by gravity; a chemical coagulant may be added. The solids are
mechanically collected on the bottom and pumped as a sludge
underflow.
The conical bottom (one inch per foot of slope) is equipped with
a rotating mechanical scraper that plows sludge to a center hop-
per. An influent feed well located in the center distributes the
influent radially, and a peripheral weir overflow system carries
the effluent. Floating scum is trapped inside a peripheral scum
baffle and squeegeed into a scum discharge box. The unit con-
tains a center motor-driven turntable drive supported by a bridge
spanning the top of the tank, or supported by a vertical steel
center pier. The turntable gear rotates a vertical cage or torque
tube, which in turn rotates the truss arms (preferably two long
arms). The truss arms carry multiple flights (plows) on the
bottom chord that are set at a 30° angle of attack and literally
"plow" heavy fractions of sludge and grit along the bottom slope
toward the center blowdown hopper. An inner diffusion chamber
receives influent flow and distributes it (by means of about a
four-inch water head loss) inside of the large diameter feedwell
skirt.
Approximately three percent of the clarifer surface area is used
for the feed-well. The depth of the feed-wells is generally
about one-half of the tank depth. The center sludge hopper should
be less than two feet deep and less than four square feet in cross
section.
Two short auxiliary scraper arms are added perpendicular to the
two long arms on medium-to-large tanks. This makes practicable
the use of deep spiral flights, which aid in center region plowing
where ordinary shallow straight plows (30° angle of attack) are
nearly useless. Peripheral feed systems are sometimes used in
lieu of central feed. Also, central effluent weirs are sometimes
used. Flocculating feed wells also may be provided if coagulants
are to be added to assist sedimentation.
Equipment normally associated with primary circular clarification
includes a clarifier and sludge pumps. A flow diagram for primary
circular clarification is shown on the following page.
Date: 6/23/80 IV.3.2-1
-------
SCUM TROUGH
SCUM PIT
DRIVE UNIT
SKIMMER
BLADE/ ,SCUM BAFFLE
WEIR
EFFLUENT
SIDE WATER DEPTH
SLUDGE
DRAW-OFF PIPE
(SEE SECTION IV.7)
^SCRAPER BLADES
INFLUENT PIPE
Typical design criteria. Typical design criteria for a pri-
mary circular clarification system are tabulated below.
Design criteria
Value
Surface loading
Detention time
Weir loading
Sludge pumping rate
Domestic scum handling
requirement
Sludge collector tip speed
600 - 1,200 gpd/ft2
1.5 - 3.0 hr
10,000 - 70,000 gpd/linear ft
2,500 - 20,000 gpd/Mgal
6 ft3/Mgal decant water
10 - 15 ft/min
Depends on chemical addition and service.
Additionally, heads of 2 to 3 ft H20 are required to overcome
losses at inlet and effluent controls and in connecting pipes.
Forward velocity should be less than 9 to 15 times the particle
settling velocity to avoid scour.
Costs. Purchased equipment and installation cost for estima-
tion of the total capital investment includes primary sludge pumps
and clarifiers. The following operating characteristics were
assumed for cost estimation:
Operating characteristic
Assumed value
Service life
Surface overflow rate
Sludge concentration
Pump head
50 yr
800 gpd/ft2 (based on average flow)
4% solids
10 ft TDK
To adjust costs for alternative surface overflow rate, calculate
the effective flow (Q.,) using the following equation:
LJ
0=o x 800 gpd/ft2
E Design new design surface overflow rate
Date: 6/23/80
IV.3.2-2
-------
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.3.2-3
-------
TOTAL CAPITAL INVESTMENT
0.1
FLOW, 1,000 m3/d
1.0 10
100
1.0 10
FLOW, Mgal/d
100
Date: 6/23/80
IV.3.2-4
-------
o
DJ
ft
(D
CTi
to
U)
00
o
ISJ
i
UI
g
UQ
MILLIONS OF DOLLARS/YEAR
TOTAL- MATERIALS
>
c:
O
-o
s
GO
POWER - LABOR
-------
IV.3.2.2 Primary Rectangular Clarification [1]
Description. Primary rectangular clarification involves a
relatively long period of quiescence in a basin (depths of 10 to
15 feet) where most of the settleable solids in the wastewater
fall out of suspension by gravity. The solids are mechanically
transported along the bottom of the tank by a scraper mechanism
and" pumped as a sludge underflow.
The maximum length of rectangular tanks has been approximately
300 feet. Where widths greater than 20 feet are required, mul-
tiple bays with individual cleaning equipment may be employed,
thus permitting tank widths up to 80 feet or more. Influent chan-
nels and effluent channels should be located at opposite ends of
the tank.
Sludge removal equipment usually consists of a pair of endless
conveyor chains. Attached to the chains at about 10 foot inter-
vals are wooden crosspieces or flights, extending the full width
of the tank or bay. Linear conveyor speeds of 2 to 4 ft/min are
common. The settled solids are scraped to sludge hoppers in small
tanks and to transverse troughs in large tanks. The troughs, in
turn, are equipped with cross collectors, usually of the same
type as the longitudinal collectors, which convey solids to one
or more sludge hoppers. Screw conveyors have been used for the
cross collectors.
Scum is usually collected at the effluent end of rectangular
tanks by the flights returning at the liquid surface. The scum
is moved by the flights to a point where it is trapped by baffles
before removal, or it can be moved along the surface by water
sprays. The scum is then scraped manually up an inclined apron,
or it can be removed hydraulically or mechanically, and for this
process a number of means have been developed (rotating slotted
pipe, transverse" rotating helical wiper, chain and flight col-
lectors, scum rakes).
Tanks may be cleaned by a bridge-type mechanism which travels up
and down the tank on rails supported on the sidewalls. Scraper
blades are suspended from the bridge and are lifted clear of the
sludge on the return travel. Chemical coagulants may be added to
improve BODs and suspended solid removals and to remove phos-
phorus ion.
Equipment normally associated with primary rectangular clarifica-
tion includes clarifiers and sludge pumps. A flow diagram for
primary rectangular clarification is shown on the following page.
Date: 6/23/80 IV.3.2-6
-------
ADJUSTABLE WE IRS
INFLUENT
SLUDGE *
(SEE
SECTION
IV.7)
! , TRAVEL
'SLUDGE HOPPER
Typical design criteria. Typical design criteria for a pri-
mary rectangular clarification system are tabulated below.
Design criteria
Values
Surface loading
Detention time
Weir loading
Length/width ratio ,
Sludge pumping rate
Scum handling requirement
600 - 1,200 gpd/ft2
1.5 - 3.0 hr
10,000 - 30,000 gpd/linear ft
At least 4/1 per day
2,500 - 20,000 gpd/Mgal
6 ft3/Mgal decant water
Average for untreated wastewater. If chemicals are
used, the ranges are 360 to 600 gpd/ft2 for alum,
540 to 800 gpd/ft2 for iron, and 1600 gpd/ft2 for lime.
Depends on chemical addition and service.
Additionally, forward velocities should be less than 9 to 15 times
the settling velocity to avoid scour.
Costs. Purchased equipment and installation costs for esti-
mation of the total capital investment includes primary sludge
pumps and clarifiers. The following operating characteristics
were, assumed for cost estimation:
Operating characteristic Assumed value
Service life
Sludge concentration
Surface overflow rate
Pump head
50 yr
4% solids
800 gpd/ft2
10 ft TDK
Date: 6/23/80
IV.3.2-7
-------
To adjust for alternative surface overflow rate, calculate the
effective flow (Q_) using the following equation:
Ci
O = o „ 800 gpd/ft'
E Design new design surface overflow rate
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.3.2-8
-------
TOTAL CAPITAL INVESTMENT
1,000 m3/d
10
ENR INDEX • 3119
i i i I
1.0 10
FLOW, Mgal/d
100
Date: 6/23/80
IV.3.2-9
-------
o
pi
t+
(D
MILLIONS OF DOLLARS/YEAR
(TOTAL-LABOR-MATERIALS)
(Ti
K)
U»
00
O
to
I
0)
8
>
I—
o
O i—
V*
oT
O
o
o
-8
(POWER)
-------
IV.3.2.3 Secondary Circular Clarification [1]
Description. Secondary circular clarifiers have been con-
structed with diameters ranging from 12 to 200 feet with depths
of 12 to 15 feet. There are two basic types: the center-feed
and the rim-feed. Both utilize a revolving mechanism to trans-
port and remove the sludge from the bottom of the clarifier.
Mechanisms are of two types: those that scrape or plow the
sludge to a center hopper similar to the types used in primary
sedimentation tanks, and those that remove the sludge directly
from the tank bottom through suction orifices that serve the en-
tire bottom of the tank in each revolution. In one of the
latter, the suction is maintained by reduced static head on the
individual drawoff pipes. In another patented suction system,
sludge is removed through a manifold either hydrostatically or
by pumping.
Secondary circular clarifiers are made with effluent overflow
weirs located near the center or near the perimeter of the tank.
Skimming facilities are required on all federally funded projects.
While the design is similar to primary clarifiers, the large
volume of flocculent solids in the mixed liquor requires that
special consideration be given to the design of activated sludge
clarifiers. The sludge pump capacity and the size of the set-
tling tank are larger. Further, the mixed liquor, on entering
the tank, has a tendency to flow as a density current interfering
with the separation of the solids and the thickening of the
sludge. To cope successfully with these characteristics, the
following factors must be considered in the design of these
tanks: type of tank to be used, surface loading rate, solids
loading rate, flow-through velocities, weir placement and loading
rates, and scum removal.
Multiple inlets are used with balanced flow at various spacings
with target baffles to reduce velocity of streams. Hydraulic
balancing is used between parallel clarifier units. Wind effects
on water surface are controlled. Sludge hopper collection sys-
tems and flocculation inlet structures are used. Traveling
bridge sludge collectors and skimmers are used an an alternate
to chain and flight systems.
Equipment normally associated with secondary circular clarifica-
tion includes clarifiers and sludge pumps. Flow diagrams of
secondary circular clarification systems are shown on the next
page.
Date: 6/23/80 IV.3.2-11
-------
ACTIVATED SLUDGE
OARIFIER EFFLUENT INFLUENT
TRICKLING FILTER
CLAHIFial EFFLUENT
WASTE
(SEE SECTION IV.7)
I SLUDGE
(SEE SECTION IV.7)
Typical design criteria. Typical design criteria for a sec-
ondary circular clarification system are tabulated below.
Deaign criteria
Hydraulic loading (average)
Hydraulic loading (peak)
Solida loading (average)
Solid, loading (peak)
Depth
Inlet baffle dlaieter
Heir loading rate
nmt""^ upflow velocity
in vicinity of weir
circular
clarification air
activated aludge*
400-800
700 - 1,200
14 - 28
JO - 4»
12 - 15
-
10,000 - 30,000
12 - M
Trickling
filtration
400-600
1,000 - 1,200
-
-
10 - 12
IS - 20
10,000 - 10,000
12 - M
air
activated
aludge
400 - 800
1,000 - 2,000
20-10
SO
12 - 15
15 - 20
10,000 - 10,000
12 - M
Extended
aeration
200 - 400
800
20 - 10
50
12 - 15
15 - 20
10,000 - 10,000
11 - M
Secondary
clarification
following oxygen
activated aludae
400-800
1,000 - 1,200
25 - IS
50
12 - 15
15 - 20
10,000 - 10,000
12 - 24
Unite
9pd/ft«
gpd/ft"
tt/d/ft"
lb/d/ft*
ft
Percent of
tank diajfttter
gpd/linaai ft
ft/hi
Excluding •zt.Hk.tod Mration.
Costs. Purchased equipment and installation cost for esti-
mation of the total capital investment includes sludge return and
waste pumps. Spare pumps (nonclog centrifugal) are included as
necessary. The following operating characteristics were assumed
for cost estimation.
Operating characteristic
Assumed value
Service life
Clarifier type
Overflow rate
Sludge concentration
Pump head
Pump capacity
Maximum clarifier diameter 200 ft
40 yr
Flocculator-type
600 gpd/ft2
1% solids
10 ft TDK
350 gpm/Mgpd of plant capacity
To adjust costs for an alternative overflow rate, calculate the
effective flow (Q ) using the following equation:
fcj
O = 0 x 600 gpd/fta
E Design new design overflow rate
Date: 6/23/80
IV.3.2-12
-------
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 ' IV.3.2-13
-------
a 1.0
0.1
TOTAL CAPITAL INVESTMENT
FLOW, 1,000 m3/d
1.0 10
1.0 10
FLOW, Mgal/d
100
Date: 6/23/80
IV.3.2-14
-------
ANNUAL OPERATING COST
25-
DC a:
i
u.
CO
0.01
ROW, 1,000 m3/d
10 100
TOTAL ANNUAL
OPERATING COST
O
o_
0.001
0.001
0.0001
0.1
1.0 10
FLOW, Mgal/d
100
Date: 6/23/80
IV.3.2-15
-------
IV.3.2.4 Secondary Rectangular Clarification [1]
Description. The design of secondary rectangular clarifiers
is similar to that of primary rectangular clarifiers except that
the large volume of flocculent solids in the mixed liquor must be
considered during the design of activated sludge clarifiers and
in sizing the sludge pumps. Further, the mixed liquor, on enter,-
ing the tank, has a tendency to flow as a density current inter-
fering with the separation of the solids and the thickening of
the sludge. To cope successfully with these characteristics, the
following factors must be considered in the design of these tanks:
(1) type of tank to be used, (2) surface loading rate, (3) solids
loading rate, (4) flowthrough velocities, (5) weir placement and
loading rates, and (6) scum removal.
In rectangular tanks, the flow enters at one end, passes a baffle
arrangement, and traverses the length of the tank to the effluent
weirs. The maximum length of rectangular tanks has been approxi-
mately 300 feet with depths fo 12 to 15 feet. Where widths
greater than 20 feet are required, multiple bays with individual
cleaning equipment may be employed, thus permitting tank widths
up to 80 feet or more.
Sludge removal equipment usually consists of a pair of endless
conveyor chains. Attached to the chains at 10 foot intervals are
2-inch thick wooden crosspieces or flights, 6 to 8 inches deep,
extending the full width of the tank or bay. Linear conveyor
speeds of 2 to 4 ft/min are common. The settled solids are
scraped to sludge hoppers in small tanks and to transverse
troughs in large tanks. The troughs, in turn, are equipped with
cross collectors, usually of the same type as the longitudinal
collectors, which convey solids to one or more sludge hoppers.
Conveyors also have been used for the cross collection.
Tanks also may be cleaned by a bridge-type mechanism that travels
up and down the tank on rails supported on the sidewalls. Scraper
blades are suspended from the bridge and are lifted clear of the
sludge on the return travel. For very long tanks, it is desirable
to use two sets of chains and flights in tandem with a central
hopper to receive the sludge. Tanks in which mechanisms that
move the sludge toward the effluent end in the same direction as
the density current have shown superior performance in some
instances.
Scum is usually collected at the effluent end of rectangular
tanks by the flights returning at the liquid surface. The scum
is moved by the flights to a point where it is trapped by baffles
before removal, or it can be moved along the surface by water
sprays. The scum is then scraped manually up an inclined apron,
or it can be removed hydraulically or mechanically, and for this
process a number of means have been developed (rotating slotted
Date: 6/23/80 IV.3.2-16
-------
pipe, transverse rotating helical wiper, chain and flight collec-
tors, scum rakes).
Common modifications of secondary rectangular clarification in-
clude multiple inlets with balanced flow at various spacings with
target baffles to reduce velocity of streams; hydraulic balancing
between parallel clarifier units; control of wind effects on
water surfaces; sludge hopper collection systems; flocculation
inlet structures; use of traveling bridge sludge collectors and
skimmers as an alternate to chain and flight systems; use of
steeply inclined tube settlers to enhance suspended solids re-
moval in either new or rehabilitated clarifiers; use of wedge
wire settler panels at peak hydraulic loading of less than
800 gpd/fta for improved suspended solids removal.
A flow diagram of secondary rectangular clarification is shown
below.
PRIMARY EFFLUENT
1
\ «r j
• • • AERATION •.';
'• '. TANK ..'•'
SECONDARY
LCLARIFIW
RECYCLE
SLUDC
SECONDARY EFFLUENT
;E
WASTE
(SEE SECTION IV.7)
Typical design criteria. Typical design criteria for sec-
ondary rectangular clarification are shown below.
Design criteria
Value
Average hydraulic loading'
Peak hydraulic loading
Average solids loading3
Peak solids loading
Depth
Weir loading rate
Maximum upflow velocity
in vincinity of weir
400 - 800 gpd/ft2
700 - 1,200 gpd/ft2
14 - 29 lb/d/ft2
30 - 48 lb/d/ft2
12 - 15 ft
10,000 - 30,000 gpd/linear ft
12 - 24 ft/hr
In activated sludge systems.
Costs. The cost for rectangular clarifiers are the same as
those for circular. Purchased equipment and installation cost
for estimation of the total capital investment includes sludge
return and waste pumps. Spare pumps (nonclog centrifugal) are
also included as necessary. The following operating character-
istics were assumed for cost estimation:
Date: 6/23/80
IV.3.2-17
-------
Operating characteristic
Assumed value
Service life
Overflow rate of flocculator-type clarifier
Concentration of sludge
Pump head
40 yr
600 gpd/ft2
1% solids
10 ft TDK
To adjust costs for an alternative overflow rate, calculate the
effective flow (Q_) using the following equation:
i.
QT, = Q
600 gpd/ff
_
Design new design overflow rate
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80
IV.3.2-18
-------
TOTAL CAPITAL INVESTMENT
10 c
to
ce
o
o
o
CO
O
1.0
ri 0.1
0.01
0.1
1.0
FLOW, 1,000 m3/d
10
100
ENR INDEX-3119
i i i i i 11
1.0 10
ROW, Mgal/d
100
Date: 6/23/80
IV.3,2-19
-------
ANNUAL OPERATING COST
1.0 c
u-8
0<
-------
IV.3.3 CLARIFICATION/SEDIMENTATION WITH CHEMICAL ADDITION
Clarification/sedimentation with chemical addition is utilized
to remove collodial solids, and for phosphate removal. Sedi-
mentation with chemical addition of alum, ferric chloride, lime,
and polymer are discussed in Sections IV.3.3.1 through IV.3.3.4,
respectively. The sedimentation process (assumed to be circular
primary clarification for cost estimation purposes) was discussed
in detail in Section IV.3.2.1.
IV.3.3.1 Alum Addition [1]
Description. Alum or filter alum [A12(SCM 3«14H20] is a
coagulant which, when added to wastewater, initially forms hydro-
metal complexes which are readily adsorbed by colloids to de-
stabilize them causing flocculation, and finally forms an
aluminum hydroxide precipitate. Phosphorus will also be precipi-
tated as the aluminum salt prior to colloid destabilization. The
reaction is pH dependent with the minimum solubility occurring at
a pH of approximately 6. Since alum acts as an acid, alkalinity
will be destroyed after addition to wastewater.
Alum is an off-white crystal which when dissolved in water pro-
duces acidic conditions. As a solid, alum may be supplied in
lumps, or in ground, rice, or powdered form. Shipments may be in
small bags (100 Ib), in drums, or in bulk quantities (over
40,000 Ib). In liquid form, alum is commonly supplied as a 50
percent solution delivered in minimum loads of 4,000 gallons.
The choice between liquid or dry alum use is dependent on factors
such as availability of storage space, method of feeding, and
economics. In general, purchase of liquid alum is justified only
when the supplier is close enough to make differences in trans-
portation costs negligible. Dry alum is stored in mild steel or
concrete bins with appropriate dust collection equipment. Be-
cause dry alum is slightly hydroscopic, provisions are made to
avoid moisture, which could cause caking and corrosive conditions.
Before addition to wastewater, dry alum must be dissolved, form-
ing a concentrated solution. Bulk-stored or hopper-filled alum
is transported to a feeder mechanism by bucket elevator, screw
conveyor or a pneumatic device. Three basic' types of feeders are
in common use: volumetric, belt gravimetric, and loss-in-weight
gravimetric. The feeder supplies a controlled quantity of dry
alum (accuracy ranges from about 1% to 7%) to a mixed dissolver
vessel. Because alum solubility is temperature dependent, the
quantity supplied depends on the concentrate strength desired
and the temperature.
Date: 6/23/80 IV.3.3-1
-------
Because alum solution is corrosive, the dissolving chamber as
well as the following storage tanks, pumps, piping and surfaces
that may come in contact with the solution or generated fumes
must be constructed of resistant materials such as type 316
stainless steel, fiberglass reinforced plastic (FRP), or plastics,
Rubber or saran-lined pipes are commonly used. Liquid alum,
which crystallizes at about 30°F and freezes at about 18°F, is
stored and shipped in insulated type 316 stainless steel or
rubber-lined vessels. Feeding of liquid alum (purchased or made
up on site) to wastewater treatment unit processes may be accom-
plished by gravity, pumping, or using a roto-dip feeder. Dia-
phragm pumps and valves are common.
Equipment normally associated with alum addition includes bins,
hoppers, conveyors and elevators, liquid storage tanks, dry and
wet feeders, and pH instrumentation. A flow diagram of an alum
addition process is shown below.
DRY ALUM
STORAGE
V'
/MIXER
CONVEYOR
FEEDER
<4
DISSOLVER
HOLDING
TANK
METERING
PUMP
fe
POINT OF
APPLICATION
LIQUID ALUM
DRY ALUM
Typical design criteria. Typical design criteria for primary
circular clarification are described in Section IV.3.2.1. Typical
design criteria for alum addition are shown below.
Design criteria
Value
Dosage, determined by Generally 5-20 mg/L as
jar testing aluminum as an average
for most industrial
waste
In mixing,
In flocculation,
Gt
GCt
In sedimentation,
Overflow rate
Alum unit cost
Approximately 300/s
<30 s
Approximately 10s
Approximately 100
500 - 600 gpd/fta average,
800 - 900 gpd/ft2 (peak)
$185/ton
Measure of mean velocity gradient.
DTime.
Date: 6/23/80
IV.3.3-2
-------
Costs. Purchased equipment and installation cost for esti-
mation of the total capital investment includes primary sludge
pumps, clarifiers, liquid alum, chemical feed equipment sized for
twice the average feed rate and storage for at least 15 days,
building (except for plants with a capacity less than 1 Mgal/d),
rapid mix tank (includes stainless steel mixer), and basins. The
rapid mix tank is constructed of concrete, and multiple basins are
used for volumes greater than 1500 ft3. Costs are based on the
addition of alum into the primary circular clarification system.
An alum dosage of 200 mg/L as Ala (S0<») 3»14HaO was assumed for cost
estimation.
To adjust costs at the effective flow (Q_,) for different alum dos-
ages, use the following equation:
n - n v Alum dosage
UE " "Design 200 mg/L
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.3.3-3
-------
TOTAL CAPITAL INVESTMENT
100 c
10
O
u.
o
CO
O
0.1
i i i i 1111
i i i i 1111
ENR INDEX • 3119
i i i i i i ii
0.1
1.0 10
ROW, Mgal/d
100
Date: 6/23/80
IV.3.3-4
-------
o
0)
ft
(D
MILLIONS OF DOLLARS/YEAR
U)
oo
o
8
I
Ul
I I I
§
D)
8
I I I
O
-o
m
O
O
o
to
-------
IV.3.3.2 Ferric Chloride Addition [1]
Description. Ferric chloride (FeCl3) is a chemical coagu-
lant which, when added to wastewater destabilizes colloids and
reacts with alkalinity and phosphates, similar to alum, forming
insoluble iron salts. The colloidal particle size of insoluble
ferric phosphate is small, requiring excess dosages of ferric
chloride to produce a well flocculated iron hydroxide precipitate,
which carries the phosphate precipitate. Large excesses of
ferric chloride, and corresponding quantities of alkalinity, are
required to assure phosphate removal. Exact ferric chloride
dosages are usually best determined using jar tests and full-scale
evaluations.
Ferric chloride is available in either dry (hydrated or anhydrous)
or liquid form. Liquid ferric chloride is a dark brown oil-
appearing solution supplied in concentrations ranging between
35 and 45 percent ferric chloride. Because higher concentrations
of ferric chloride have higher freezing points, lower concentra-
tions are supplied during winter. Liquid ferric chloride is
shipped in 3,000- to 4,000-gallon bulk truckload lots, in 4,000-
to 10,000-gallon carloads, and in 5- to 13-gallon carboys. Ferric
chloride solution stains surfaces which it contacts and is
highly corrosive (a one percent solution has a pH of 2.0); con-
sequently, it must be stored and handled with care. Storage
tanks are equipped with vents and vacuum relief valves. Tanks
are constructed of fiberglass reinforced plastic, rubber-lined
steel and plastic-lined steel. Because of freezing potential,
ferric chloride solutions are either stored in heated areas or in
heated and insulated vessels in northern climates.
Ferric chloride solution should not be diluted because of possi-
ble unwanted hydrolysis. Consequently, feeding at the concentra-
tion of the delivered product is common. The stored solution is
transferred to a day tank using graphite or rubber-lined self-
priming centrifugal pumps with corrosion resistant Teflon seals.
From the day tank, controlled quantities are fed to the unit
process using Rotodip feeders or diaphragm metering pumps. Roto-
meters are not used for ferric chloride flow measurement because
the material tends to deposit on and stain the glass tubes. All
pipes, valves, or surfaces that come in contact with ferric chlo-
ride must be made of corrosion-resistant materials such as rubber
or Saran lining, Teflon, or vinyl. Similar treatment results are
obtainable by substituting ferrous chloride, ferric sulfate,
ferrous sulfate, or spent pickle liquor for ferric chloride.
Details of storage feeding and control for these materials are
similar to those for ferric chloride. Dry ferric chloride may
also be dissolved on site before use in treatment.
Equipment normally associated with the ferric chloride addition
process includes liquid storage tanks, dry and wet feeders, and
Date: 6/23/80 IV.3.3-6
-------
pH instrumentation. A flow diagram of a ferric chloride addi-
tion process is shown below.
FERRIC
CHLORIDE
SOLUTION
STORAGE ,
J-r.
CP
DAY TANK
DIAPHRAGM
METERING PUMP
CP
POINT OF
APPLICATION
RUBBER-LINED. SELF-PRIMING
CENTRIFUGAL PUMP
WITH TEFLON SEALS
Typical design criteria. Typical design criteria for primary
circular clarification are described in Section IV.3.2.1.2. Typi-
cal design criteria for ferric chloride addition are shown below.
Design criterion
Value
Dosage, determined by jar testing 20 - 100 mg FeCla/L are common
for most industrial wastes
In mixing,
G
t
FeCla unit cost
Approximately 300/s
<30 s
$38/ton
Costs. Purchased equipment and installation cost for esti-
mation of the total capital investment includes primary sludge
pumps, clarifiers, liquid ferric chloride, chemical feed equip-
ment sized for twice the average feed rate, storage for at least
15 days, rapid mix tank, stainless steel mixer, and building
(except for plants with a capacity less than 1 Mgal/d). The
rapid mix tank is constructed of concrete, and multiple basins
are used for volumes greater than 1,500 ft3. Costs are based on
primary circular clarification with ferric chloride addition.
A ferric chloride dosage of 100 mg/L was assumed for cost
estimation.
To adjust costs at the effective flow (QF) for different
dosages, use the following equation:
QE = QDesign x
FeCl3 dosage
100 mg/L
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80
IV.3.3-7
-------
TOTAL CAPITAL INVESTMENT
CO
O£
1
u_
O
to
O
100 r
10
1.0
0.1
0.1
ENR INDEX • 3119
i i i i i 111
1.0 10
FLOW, Mgal/d
100
Date: 6/23/80
IV.3.3-8
-------
o
QJ
(1-
(D
to
oo
oo
o
MILLIONS OF DOLLARS/YEAR
CO
•
CO
I
vo
p
8
g
O)
O
8
CO
-------
IV.3.3.3 Lime Addition (Primary) [1]
Description. Lime clarification of raw wastewater removes
suspended solids as well as phosphates. There are two basic
processes: the low-lime system and the high-lime system. The
low-lime process consists of the addition of lime to obtain a pH
of approximately 9 to 10. Generally, a subsequent biological
treatment system is capable of readjusting the pH through natural
recarbonation. The high-lime process consists of the addition of
lime to obtain a pH of approximately 11 or more. In this case,
the pH generally requires readjusting with carbon dioxide or acid
to be acceptable to the secondary treatment system.
Lime can be purchased in many forms; quicklime (CaO) and hydrated
lime [Ca(OH)2] are the most prevalent forms. In either case,
lime is usually purchased in the dry state, in bags, or in bulk.
Bulk lime can be (1) shipped by trucks that are generally equip-
ped with pneumatic unloading equipment; or (2) shipped by rail
cars that consist of covered hoppers. The rail cars are emptied
by opening a discharge gate, which discharges to a screw conveyor.
The bulk lime is then transferred by the screw conveyor to a
bucket elevator, which empties into the elevated storage tank.
Bulk storage usually consists of steel or concrete bins. Storage
vessels should be water- and air-tight to prevent the lime from
"slaking".
Lime is generally made into a wet suspension or slurry before
being introduced into the treatment system. The precise steps
involved in converting from the dry to the wet stage will vary
according to the size of operation and type and form of lime used
In the smallest plants, bagged hydrated lime is often charged
manually into a batch mixing tank with the resulting "milk-of-
lime" (or slurry) being fed by means of a so-called solution
feeder to the process. Where bulk hydrate is used, some type of
dry feeder charges the lime continuously to either a batch or
continuous mixer, then, by means of solution feeder, to the point
of application. With bulk quicklime, a dry feeder is also used
to feed a slaking device, where the oxides are converted to
hydroxides, producing a paste or slurry. The slurry is then
further diluted to milk-of-lime before being piped by gravity
or pumped to the process. Dry feeders can be of the volumetric
or gravimetric type.
Equipment normally associated with the lime clarification process
includes bins, hoppers, conveyors and elevators, liquid storage
tanks, dry and wet feeders, lime slakers, and pH instrumentation
A flow diagram of a lime clarification process is shown on the
next page.
Date: 6/23/80 IV.3.3-10
-------
PRIMARY
CLARIFIER
TO SECONDARY
TREATMENT
MIXER
LIME
FEED
LIME
STORAGE
Typical design criteria. Typical design criteria for pri-
mary circular clarification are described in Section IV.3.2.1.2.
The lime requirements of a lime clarification system are tabu-
lated below.
Feed water alkalinity,
mg/L (as CaC03)
Clarifier pH
Approximate lime dose,
mg/L (as CaO)
300
300
400
400
9.5
10.5
9.5
10.5
185
270
230
380
Costs. Purchased equipment and installation cost for esti-
mation of the total capital investment includes primary sludge
pumps, clarifiers, chemical storage and feeding equipment, and
hydrated lime for 0.1 to 10 Mgal/d plants or pebble quicklime
for 10 to 100 Mgal/d plants. Piping and buildings to house the
feeding equipment are not included. Costs are based on primary
circular clarification with lime addition. The following lime
addition operating characteristics were additionally assumed for
cost estimation:
Operating characteristic
Assumed value
Lime dosage
Storage
CaO
150 mg/L
150 days minimum
$54.00/ton
1.
References.
Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80
IV.3.3-11
-------
TOTAL CAPITAL INVESTMENT
0.1
1.0
FLOW, 1,000 m3/d
10
100
1.0 10
FLOW, Mgal/d
100
Date: 6/23/80
IV.3.3-12
-------
rt
(D
10
U)
00
o
H
u>
u>
MILLIONS OF DOLLARS/YEAR
(TOTAL - LABOR)
O
-D
m
o
o
(MATERIALS-POWER)
-------
IV.3.3.4 Polymer Addition [1]
Description. Polymers or polyelectrolytes are high-molecular-
weight compounds (usually synthetic) which, when added to waste-
water, can be used as coagulants, coagulant aids, filter aids, or
sludge conditioners. In solution, polymers may carry either a
positive, negative, or neutral charge and, as such, they are
characterized as cationic, anionic, or nonionic. As a coagulant
or coagulant aid, polymers act as bridges, reducing charge repul-
sion between colloidal and dispersed floe particles, and increas-
ing settling velocities. As a filter aid, polymers strengthen
fragile floe particles, controlling filter penetration and reducing
particle breakthrough. Filterability and dewatering character-
istics of sludges may similarly be improved through the use of
polyelectrolytes.
Polymers are available in predissolved liquid or dry form. Dry
polymers are supplied in relatively small quantities (up to about
100-lb bags or barrels) and must be dissolved on site prior to
use. A stock solution, usually about 0.2 to 2.0 percent concen-
tration, is made up for subsequent feeding to the treatment
process. Preparation involves automatic or batch wetting, mixing,
and aging. Stock polymer solutions may be very viscous.
Surfaces coming in contact with the polymer stock solution should
be constructed of resistant materials such as type 316 stainless
steel, fiberglass-reinforced plastic or other plastic lining
materials. Polymers may be supplied as a prepared stock solution
ready for feeding to the treatment process. Many competing poly-
mer formulations with different characteristics are available,
requiring somewhat differing handling procedures. Manufacturers
should be consulted for optimum practices. Polymer stock solu-
tions are generally fed to unit processes using equipment similar
to that commonly in service for dissolved coagulant addition.
Because of the high viscosity of stock solutions, special atten-
tion should be paid to the diameter and slopes of pipes, as well
as the size of orifices used in the feed systems.
Equipment normally associated with the polymer addition process
includes bins, hoppers, liquid storage tanks, and dry and wet
feeders. A flow diagram of a polymer addition process is shown
below.
DRY FEEDER
WATER SUPPLY——
DISPERSER MIXER ^ ^ saUTION
I
X
y TANK
4
/
1
« • • " — x —
POINT OF
APPLICATION
Date: 6/23/80 IV.3.3-14
-------
Typical design criteria. Typical design criteria for pri-
mary circular clarification are described in Section IV.3.2.1.2,
Typical design criteria for polymer addition are shown below.
Design criteria Value
Dosage Determined by jar testing
Materials contacting Type 316 stainless steel,
polymer solutions FRP or plastic
Storage conditions Cool and dry; storage period
should be minimized
Viscosity Must be considered in feed-
ing system design
Costs. Purchased equipment and installation cost for esti-
mation of the total capital investment includes primary sludge
pumps; clarifier; chemical storage, chemical feeding, and rapid
mixing tanks; piping and building to house the feeding equipment;
and bag storage. Cost varies according to the plant size as
shown below.
Plant size Factors affecting costs
0.1 Mgpd Manual operation of feeder, mix tank, solu-
tion feeder, and holding tank are included
in cost estimation; no separate building is
required.
1 Mgpd and smaller Manual procedures are applied; two systems of
tanks and feeders are included in cost
estimation.
10 Mgpd Cost estimate includes feeders and mixing
tanks, one day tank, and two solution
feeders.
100 Mgpd Cost estimate includes four feeders and mix-
ing tanks, two holding tanks, and 10 solu-
tion feeders; rapid mix tank is concrete
and equipped with stainless steel mixer and
handrails.
This cost assumption is based on primary circular clarification
with polymer addition at a dosage of 1.0 mg/L and a cost of
$1.50/lb.
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978.
Date: 6/23/80 IV.3.3-15
-------
TOTAL CAPITAL INVESTMENT
10 c
1.0 10
ROW, Mgal/d
Date: 6/23/80
IV.3.3-16
-------
a
0)
rt
MILLIONS OF DOLLARS/YEAR
OJ
00
o
O
o1-1
H
<
•
to
•
U)
(O
O)
O
•o
O
O
O
to
-------
IV.3.4 DISSOLVED AIR FLOTATION (GAS FLOTATION)
IV.'3. 4.1 Description
Dissolved air flotation (DAF) is used to remove suspended solids
by using highly pressurized air to form bubbles. DAF consists of
saturating a portion or all of the wastewater feed, or a portion
of recycled effluent, with air at a pressure of 25 to 70 lb/in2
(gage). The pressurized wastewater is held at this pressure for
0.5 to 3.0 minutes in a retention tank and then released to the
flotation chamber. The sudden reduction in pressure results in
the release of microscopic air bubbles in the flotation chamber,
which attach themselves to oil and suspended particles in the
wastewater. This results in agglomeration which, due to the
entrained air, results in greatly increased vertical rise rates
of about 0.5 to 2.0 ft/min. The floated materials rise to the
surface to form a froth layer. Specially designed flight scrapers
or other skimming devices continuously remove the froth. The
retention time in the flotation chamber is usually about 20 to
60 minutes. The effectiveness of dissolved air flotation depends
on the attachment of bubbles to the suspended oil and other par-
ticles that are to be removed from the waste stream. The attrac-
tion between the air bubble and particle is primarily a result of
the particle surface charges and bubble-size distribution.
The more uniform the distribution of water and microbubbles, the
shallower the flotation unit can be. Generally, the depth of
effective flotation units is between 4 and 9 feet.
In certain cases, the surface sludge layer can attain a thickness
of many inches and can be relatively stable for a short period.
The layer thickens with time, but undue delays in removal will
cause a release of particulates back to the liquid.
DAF units can be round, square, or rectangular. In addition,
gases other than air can be used. The petroleum industry has
used nitrogen, with closed vessels, to reduce the possibilities
of fire. Chemical addition is normally used for coagulation
colloidal solids and for breaking emulsions.
Common modifications include chemical additions such as alum,
ferric chloride, lime and polymer. The chemicals can be added
to aid in the coagulation process prior to the actual flotation
step. Capital cost will be greater for gas flotation with chemi-
cal addition than for gas flotation alone. This is due to addi-
tional equipment and installation costs. Such equipment will
include chemical feed equipment, rapid mix tank, chemical storage
and a stainless steel mixer.
Date: 6/23/80 IV.3.4-1
-------
Equipment normally associated with gas flotation system includes
dissolved air flotation units, air compressors, and skimmers.
A flow diagram of a gas flotation system is shown below.
SLUDGE REMOVAL MECHANISM
' •
EFFLUENT -!j'1 -- — •.--—•7—"'•' i-~ SLUDGE (SEE SECTION IV.7)
"FLOW ZONE p^T"72
RECIRCULATION Q RECYCLE FLOW INftUENT
PUMP
DISCHARGE
A.RFEED -x^-_ ^ ^CYOE-FUW
REAERATION PUMP-1 RETENTION TANK
AIR DISSOLUTION
IV.3.4.2 Typical design criteria
design criteria for gas flotation systems are as follows:
Design criteria Values
Pressure 25 - 70 lb/in.2a
Air-to-solids ratio 0.01 - 0.1 Ib/lb
Float detention 20 - 60 min
Surface hydraulic loading 500 - 8,000 gpd/ft2
Recycle (where employed) 5 - 120%
Pressure in psig.
IV.3.4.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes the DAF unit and equipment to
feed in coagulants if needed. The following design character-
istics were assumed for cost estimation:
Operating
characteristic Assumed value
Air injection 1.25 ft3/!,000 gal
Recycle 33%
Float detention time 25 min
Surface hydraulic loading 500 - 8,000 gpd/ft2
IV.3.4.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.3.4-2
-------
10 c
CO
OS
O
O
U.
O
CO
O
1.0
3 O.l
0.01
TOTAL CAPITAL INVESTMENT
FLOW, 1,000 m3/d
1.0 10
TOTAL CAPITAL
INVESTMENT
PURCHASED AND
INSTALLED EQUIPMENT
ENR INDEX-3119
i i i I
0.01
0.1 1.0
aOW, Mgal/d
10
Date: 6/23/80
IV.3.4-3
-------
ft
(D
ro
CD
o
H
<
•
u>
•
•C^
I
MILLIONS OF DOLLARS/YEAR
>
I—
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O
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O
-------
IV.3.5 DISSOLVED AIR FLOTATION WITH CHEMICAL ADDITION
Gas flotation is used to remove lighter suspended materials whose
specific gravity is only slightly in excess of 1.0. It is usually
used to remove oil and grease materials; the process is also used
when existing clarifiers are overloaded hydraulically because of
its lower surface area requirement. Alum (A12 (SO**) 3*14 H2O) ,
ferric chloride (FeCl3), and polymers can be added to aid in the
coagulation process prior to the actual flotation step. The
basic gas flotation system is described in Section IV.3.4. The
typical design criteria and descriptions of chemical addition
(alum, ferric chloride, lime and polymer) are presented in Section
IV.3.3.1 through IV.3.3.4. Costs are estimated for the combina-
tion of gas flotation with chemical addition. The exact chemical
costs are broken down in Section IV.3.4 and dosages indicated.
IV.3.5.1 Alum Addition in Gas Flotation [1]
Description. Alum or filter alum [A12 (S0<*) 3*14H20] is a
coagulant which, when added to wastewater, reacts with available
alkalinity (carbonate, bicarbonate and hydroxide) and phosphate
to form insoluble aluminum salts. The combination of alum with
alkalinity or phosphate are competing reactions that are pH
dependent.
Alum is an off-white crystal which when dissolved in water pro-
duces acidic conditions. As a solid, alum may be supplied in
lumps, or in ground, rice, or powdered form. Shipments may be
in small bags (100 Ib), in drums or in bulk quantities (over
40,000 Ib). In liquid form, alum is commonly supplied as a 50
percent solution delivered in minimum loads of 4,000 gallons.
The choice between liquid or dry alum use is dependent on factors
such as availability of storage space, method of feeding, and
economics. In general, purchase of liquid alum is justified only
when the supplier is close enough to make differences in trans-
portation costs negligible. Dry alum is stored in mild steel or
concrete bins with appropriate dust collection equipment. Because
dry alum is slightly hydroscopic, provisions are made to avoid
moisture, which could cause caking and corrosive conditions.
Before addition to wastewater, dry alum must be dissolved, form-
ing a concentrated solution. Bulk-stored or hopper-filled alum
is transported to a feeder mechansim by bucket elevator, screw
conveyor, or a pneumatic device. Three basic types of feeders
are in common use: volumetric, belt gravimetric, and loss-in-
weight gravimetric. The feeder supplies a controlled quantity of
dry alum (accuracy ranges from about 1% to 7%) to a mixed dis-
solver vessel. Because alum solubility is temperature-dependent,
the quantity supplied depends on the concentrate strength desired
and the temperature.
Date: 6/23/80 IV.3.5-1
-------
Because alum solution is corrosive, the dissolving chamber as
well as the following storage tanks, pumps, piping, and surfaces
that may come in contact with the solution or generated fumes
must be constructed of resistant materials such as type 316
stainless steel, fiberglass reinforced plastic (FRP), or plastic.
Rubber or saran-lined pipes are commonly used. Liquid alum,
which crystallizes at about 30°F and freezes at about 18°F, is
stored and shipped in insulated type 316 stainless steel or
rubber-lined vessels. Feeding of liquid alum (purchased or made
up on site) to wastewater treatment unit processes may be
accomplished by gravity, pumping, or using roto-dip type feeder.
Diaphragm pumps and valves are common.
Equipment normally associated with alum addition includes bins,
hoppers, conveyors and elevators, liquid storage tanks, dry and
wet feeders, and pH instrumentation.
Typical design criteria. Typical design criteria for dis-
solved air flotation are discussed in Section IV.4.3.2. Typical
design criteria for alum addition are shown below.
Design criteria Value ~
Dosage, determined Generally 5-20 mg/L as aluminum
by jar testing
In mixing,
G? Approximately 300/s
tD <30 s
In flocculation,
GCt Approximately 100
Gt Approximately 10s
Costs. Purchased equipment and installation cost for esti-
mation of the total capital investment includes the DAF unit,
liquid alum (8.3% Ala03), chemical feed equipment sized for twice
the average feed rate, storage of at least 15 days, building
(except for plants with a capacity less than 1 Mgpd), rapid mix
tank, stainless steel mixer, and multiple basins with volumes
greater than 1,500 ft3. The following operating characteristics
were assumed for cost estimation:
Operating characteristic Assumed value
Alum dosage 200 mg/L
Air injection 1.25 ft3/!,000 gal
Recycle 33%
Detention time 25 min
Area flow rate 2-3 gpm/ft2
Date: 6/23/80 IV.3.5-2
-------
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency,. Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.3.5-3
-------
TOTAL CAPITAL INVESTMENT
100
10
o
to
O
3 1.0
O.I
0.1
1.0
1,000 m3/d
10
100
TOTAL CAPITAL
INVESTMENT
PURCHASED AND
NSTALLED EQUIPMENT
ENR INDEX • 3119
. .i.ii
1.0 10
FLOW, Mgal/d
100
Date: 6/23/80
IV.3.5-4
-------
D
£U
rt
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U)
00
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H
Ul
I
Ul
UD
Q>
MILLIONS OF DOLLARS/YEAR
8
3>
>
m
O
O
o
to
-------
IV.3.5.2 Ferric Chloride Addition in Gas Flotation System [1]
Description. Ferric chloride (FeCl3) is a chemical coagulant
which, when added to wastewater, reacts with alkalinity and phos-
phates, forming insoluble iron salts. The colloidal particle size
of insoluble ferric phosphate is small, requiring excess dosages
of ferric chloride to produce a well flocculated iron hydroxide
precipitate, which carries the phosphate precipitate. Large ex-
cesses of ferric chloride, and corresponding quantities of alka-
linity, are required to assure phosphate removal. Exact ferric
chloride dosages are usually best determined using jar tests and
full-scale evaluations.
Ferric chloride is available in either dry (hydrated or anhydrous)
or liquid form. Liquid ferric chloride is a dark borwn oil-
appearing solution supplied in concentrations ranging between 35
and 45 percent ferric chloride. Because higher concentrations of
ferric chloride have higher freezing points, lower concentrations
are supplied during winter. Liquid ferric chloride is shipped in
3,000- to 4,000-gallon bulk truckload lots, in 4,000- to 10,000-
gallon carloads, and in 5- to 13-gallon carboys. Ferric chloride
solution stains surfaces which it contacts and is highly corros-
ive (a one percent solution has a pH of 2.0); consequently, it
must be stored and handled with care. Storage tanks are equipped
with vents and vacuum relief valves. Tanks are constructed of
fiberglass reinforced plastic, rubber-lined steel and plastic-
lined steel. Because of freezing potential, ferric chloride solu-
tions are either stored in heated areas or in heated and insulated
vessels in northern climates.
Ferric chloride solution should not be diluted because of possible
unwanted hydrolysis. Consequently, feeding at the concentration
of the delivered product is common. The stored solution is trans-
ferred to a day tank using graphite or rubber-lined self-priming
centrifugal pumps with corrosion resistant Teflon seals. From
the day tank, controlled quantities are fed to the unit process
using Rotodip feeders or diaphragm metering pumps. Rotometers
are not used for ferric chloride flow measurement because the
material tends to deposit on and stain the glass tubes. All
pipes, valves, or surfaces that come in contact with ferric chlo-
ride must be made of corrosion-resistant materials such as
rubber or Saran lining, Teflon, or vinyl. Similar treatment
results are obtainable by substituting ferrous chloride, ferric
sulfate, ferrous sulfate, or spent pickle liquor for ferric chlo-
ride. Details of storage feeding and control for these materials
are similar to those for ferric chloride. Dry ferric chloride
may also be dissolved on site before use in treatment.
Equipment normally associated with the ferric chloride addition
process includes liquid storage tanks, dry and wet feeders, and
pH instrumentation.
Date: 6/23/80 IV.3.5-6
-------
Typical design criteria. Typical design criteria for dis-
solved air flotation are discussed in Section IV.4.3.2. Typical
design criteria for ferric chloride addition is shown below.
Design criterion Value
Dosage, determined by jar testing 20 - 100 mg FeCl3/L are common
In mixing,
G* Approximately 300/s
tD £30 s
Measure of mean velocity gradient.
Time.
Costs. Purchased equipment and installation cost for estima-
tion of the total capital investment includes the DAF unit,
liquid ferric chloride, chemical feed equipment sized for twice
the average feed rate, storage of at least 15 days, building
(except for plants with a capacity less than 1 Mgpd), rapid mix
tanks, multiple basins with volumes greater than 1,500 ft3, and
stainless steel mixer. The following operating characteristics
were assumed for cost estimation:
Operating characteristic Assumed value
Fed3 100 mg/L
Air injection 1.25 ft3/100 gal
Recycle 33%
Detention time 25 min
Area flow rate 2.3 gpm/ft3
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.3;.5-7
-------
TOTAL CAPITAL INVESTMENT
10,000 F
1,000
on
_j
O
o
u_
O
O
100
10
1.0
0.1
0.1
1.0
10
100
FLOW, Mgal/d
Date: 6/23/80
IV.3.5-8
-------
ANNUAL OPERATING COST
1,000 F
O£
S
O
I—I
2
ENR INDEX • 3119
i i i i 11 n
FLOW, Mgal/d
Date: 6/23/80
IV.3.5-9
-------
IV.3.5.3 Lime Addition [1]
Description. Lime clarification of raw wastewater removes
suspended solids as well as phosphates. There are two basic
processes: the low-lime system and the high-lime system. The
low-lime process consists of the addition of lime to obtain a pH
of approximately 9 to 10. Generally, a subsequent biological
treatment system is capable of readjusting the pH through natural
recarbonation. The high-lime process consists of the addition of
lime to obtain a pH of approximately 11 or more. In this case,
the pH generally requires readjusting with carbon dioxide or acid
to be acceptable to the secondary treatment system.
Lime can be purchased in many forms; quicklime (CaO) and hydrated
lime [Ca(OH)2] are the most prevalent forms. In either case, lime
is usually purchased in the dry state, in bags, or in bulk. Bulk
lime can be (1) shipped by trucks that are generally equipped
with pneumatic unloading equipment; or (2) shipped by rail cars
that consist of covered hoppers. The rail cars are emptied by
opening a discharge gate, which discharges to a screw conveyor.
The bulk lime is then transferred by the screw conveyor to a
bucket elevator, which empties into the elevated storage tank.
Bulk storage usually consists of steel or concrete bins. Storage
vessels should be water- and air-tight to prevent the lime from
"slaking."
Lime is generally made into a wet suspension or slurry before
introduced into the treatment system. The precise steps involved
in converting from the dry to the wet stage will vary according
to the size of operation and type and form of limes used. In the
smallest plants, bagged hydrated lime is often charged manually
into a batch mixing tank with the resulting "milk-of-lime" (or
slurry) being fed by means of a so-called solution feeder to the
process. Where bulk hydrate is used, some type of dry feeder
charges the lime continuously to either a batch or continuous
mixer, then, by means of solution feeder, to the point of appli-
cation. With bulk quicklime, a dry feeder is also used to feed
a slaking device, where the oxides are converted to hydroxides,
producing a paste or slurry. The slurry is then further diluted
to milk-of-lime before being piped by gravity or pumped to the
process. Dry feeders can be of the volumetric or gravimetric
type.
Equipment normally associated with the lime clarification process
includes bins, hoppers, conveyors and elevators, liquid storage
tanks, dry and wet feeders, lime slakers, and pH instrumentation.
Typical design criteria. Typical design criteria for dis-
solved air flotation are discussed in Section IV.4.3.2. Typical
lime requirements of a lime addition system are tabulated on the
following page.
Date: 6/23/80 IV.3.5-10
-------
Feed water alkalinity, Approximate lime dose,
mg/L (as CaC03) pH mg/L (as CaO)
300
300
400
400
9.5
10.5
9.5
10.5
185
270
230
380
Costs. Purchased equipment and installation cost for esti-
mation of the total capital investment includes the DAF unit,
chemical feeding equipment, chemical storage for at least 15
days at the average rate, hydrated lime for 0.1 to 10 Mgpd plants
or pebble quicklime for 10 to 100 Mgpd plants. The depreciation
of equipment, piping, and buildings to house the feeding equip-
ment are not included in the purchased and installed equipment
cost. The following operating characteristics were assumed for
cost estimation:
Operating characteristic Assumed value
Dosage of lime .150 mg/L
Air injection 1.25 ft3/!,000 gal
Recycle 33%
Detention time 25 min
Air flow rate 2.3 gpm/ft2
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.3.5-11
-------
TOTAL CAPITAL INVESTMENT
100
i/s
10
o
to
O
1.0
0.1
FLOW, 1,000 m3/d
1.0 10
100
TOTAL CAPITAL
INVESTMENT
PURCHASED AND
INSTALLED EQUIPMENT
ENR INDEX-3119
i i i I i 11
1.0 10
, Mgal/d
100
Date: 6/23/80
IV.3.5-12
-------
1.0
ANNUAL OPERATING COST
FLOW, 1,000 rn^/d
10
- TOTAL DIRECT
• OPERATING COST
1.0 10
FLOW, Mgal/d
100
Date: 6/23/80
IV.3.5-13
-------
IV.3.5.4 Polymer Addition [1]
Description. Polymers or polyelectrolytes are high-molecular-
weight compounds (usually synthetic) which, when added to waste-
water, can be used as coagulants, coagulant aids, filter aids, or
sludge conditioners. In solution, polymers may carry either a
positive, negative, or neutral charge and, as such, they are
characterized as cationic, anionic, or nonionic. As a coagulant
or coagulant aid, polymers act as bridges, reducing charge repul-
sion between colloidal and dispersed floe particles, and increas-
ing settling velocities. As a filter aid, polymers strengthen
fragile floe particles, controlling filter penetration and
reducing particle breakthrough. Filterability and dewatering
characteristics of sludges may similarly be improved through the
use of polyelectrolytes.
Polymers are available in predissolved liquid or dry form. Dry
polymers are supplied in relatively small quantities (up to about
100-lb bags or barrels) and must be dissolved on site prior to
use. A stock solution, usually about 0.2 to 2.0 percent concen-
tration, is made up for subsequent feeding to the treatment proc-
ess. Preparation involves automatic or batch wetting, mixing, and
aging. Stock polymer solutions may be very viscous.
Surfaces coming in contact with the polymer stock solution should
be constructed of resistant materials such as type 316 stainless
steel, fiberglass-reinforced plastic, or other plastic lining
materials. Polymers may be supplied as a prepared stock solution
ready for feeding to the treatment process. Many competing poly-
mer formulations with differing characteristics are available,
requiring somewhat differing handling procedures. Manufacturers
should be consulted for optimum practices. Polymer stock solu-
tions are generally fed to unit processes using equipment similar
to that commonly in service for dissolved coagulant addition.
Because of the high viscosity of stock solutions, special atten-
tion should be paid to the diameter and slopes of pipes, as well
as the size of orifices used in the feed systems.
Equipment normally associated with polymer addition process
includes bins, hoppers, liquid storage tanks, and dry and wet
feeders.
Typical design criteria. Typical design criteria for dis-
solved air flotation are discussed in Section IV.4.3.2. Typical
design criteria for polymer addition are shown on the next page.
Date : 6/23/80 TV. ? , S- 1. 4
-------
Design criterion Value
Dosage Determined by jar testing
Materials contacting Type 316 stainless steel,
polymer solutions FRP or plastic
Storage conditions Cool and dry; storage period
should be minimized
Viscosity Must be considered in feed-
ing system design
Costs. Purchased equipment and installation cost for estimat-
ing the total capital investment includes the DAF unit, chemical
storage, chemical feeding, rapid mix tank, polymer solution
(0.25% solution), piping and building to house the feeding equip-
ment, and bag storage. Costs vary according to the plant size as
shown below.
Plant size Factors affecting costs
0.1 Mgpd Cost estimation consists of manual operation feeder,
mix tank, solution feeder, and holding tank; no
separate building is required.
1 Mgpd and Manual procedures are applied; two systems of tanks
smaller and feeders are included in cost estimation.
10 Mgpd Cost includes feeders and mixing tanks, two holding
tanks, and 10 solution feeders; the rapid mix tank
is concrete, and equipped with stainless steel mix-
er and handrails.
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.3.5-15
-------
TOTAL CAPITAL INVESTMENT
100
10
o
o
u_
o
o
I—I
ri
0.1
0.1
1.0
FLOW, 1,000 m3/d
10
100
TOTAL CAPITAL
INVESTMENT
PURCHASED AND
INSTALLED EQUIPMENT
ENR INDEX-3119
i i i I 111
1.0 10
ROW, Mgal/d
100
Date: 6/23/80
IV.3.5-16
-------
D
P>
rt
(D
CTl
\
to
oo
o
Ul
I
MILLIONS OF DOLLARS/YEAR
i 111
o
TJ
O
O
o
-------
IV.3.6 GRANULAR MEDIA FILTRATION [1, 2]
IV.3.6.1 Description
Granular media filtration, which is used to remove suspended
solids from a liquid wastestream, is one of the oldest and most
widely applied types of filtration. It utilizes a bed of gran-
ular particles (typically sand or sand with coal) as the filter
medium. The bed is typically contained within a basin or tank
and is supported by an underdrain system which allows the filtered
liquid to be drawn off while retaining the filter medium in place.
The underdrain system typically consists of metal or plastic
strainers located at intervals on the bottom of the filter.
As suspended particle-laden water passes through the bed of the
filter medium, particles are trapped on top of and within the
bed, thus reducing its porous nature and either reducing the
filtration rate at constant pressure or increasing the amount of
pressure needed to force the water through the filter. If left
to continue in this manner, the filter would eventually plug up
with solids; the solids, therefore, must be removed. This is
done by forcing a wash water stream up through the bed of gran-
ular particles. The washwater is sent through the bed at a
velocity sufficiently high so that the filter bed becomes fluid-
ized and turbulent. In this turbulent condition, the solids are
dislodged from the granular particles and are discharged in the
spent washwater. Air may be used initially during the backwash
cycle to provide a greater surface shear force for separation of
filtered particles from the granular media. This whole process
is referred to as "backwashing." When the backwashing cycle is
completed, the filter is returned to service.
The spent backwash water contains the suspended solids removed
from the liquid, and, therefore, presents a liquid disposal prob-
lem in itself. The volume of the backwash water stream, however,
is normally only a small fraction (1% to 4%) of the volume of the
liquid being filtered. Consequently, the suspended solids con-
centration of the backwash water is far greater than that of the
liquid filtered. Granular media filtration essentially removes
suspended solids from one liquid stream and concentrates them in
another, but much smaller, liquid stream. Depending on the spec-
ific process configuration, backwash water itself can be treated
to remove suspended solids by flocculation and/or sedimentation
or by returning it to the portion of the process from whence the
liquid stream subjected to filtration originated.
Dual-media filtration involves the use of both sand and anthracite
as filter media, with anthracite being placed on top of the sand.
This provides a large pore size near the filter surface allowing
a large degree of solids capture with a relatively low head loss.
The smaller pores in the lower sand media act as a polishing unit
to remove the smaller sized particles from the wastewater. For
Date: 6/23/80 IV.3.6-1
-------
wastewater filtration involving relatively high suspended solids
concentrations compared to potable water treatment, a gradation
in media pore size from large to small in the direction of flow is
required to provide a feasible length of filter run prior to back-
washing. Dual-media, multimedia and upflow immedium filters serve
this purpose.
Filtration systems can be constructed of concrete or steel, with
single or multiple compartment units. Steel units can be either
horizontal or vertical and are generally used for pressure filters.
Systems can be manually or automatically operated.
Backwash sequences can include air scour or surface wash steps.
Backwash water can be stored separately or in chambers that are
integral parts of the filter unit. Backwash water can be pumped
through the unit or can be supplied through gravity head tanks.
Equipment normally associated with the dual-media filtration proc-
ess includes dual-media filters, blowers, and controls. A flow
diagram of a dual-media filtration system is shown below.
INFLUENT
SPENT BACKWASH
TO HEAD WORKS
OR LAGOON
OPERATING
BACKWASH
ANTHRACITE
SAND
UNDERDRAIN
EFFLUENT
BACKWASH
BACKWASH STORAGE
PUMP
IV.3.6.2 Typical Design Criteria
Typical design criteria for a dual-media filtration system are
tabulated below.
Design criteria
Value
Filtration rate
Bed depth
Depth ratio
Backwash rate
Air scour rate
Filter run length
Terminal head loss
2 to 8 gpm/ft2
24 to 48 in.
1.1: to 1:4 (sand to anthracite)
15 to 25 gpm/ft2
3 to 5 standard ft3/min/ft2
8 to 48 hr
6 to 15 ft
Note: Multi-media filtration utilizes similar cri-
teria; however, the depth ratio will differ.
Date: 6/23/80
IV.3.6-2
-------
IV.3.6.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes facilities for backwash stor-
age, all feed and backwash pumps, piping, and building. The
following operating characteristics were assumed for cost estima-
tion of a dual-media filtration system:
Operating characteristic
Assumed value
Gravity filters
TDK for backwash and feed pumps
Run length
Pump efficiency
Motor efficiency
Centrifugal pumps
Backwash holding tank
4 gpm/ft2
14 ft
12 hr; 15 min backwash at
15 gpm/ft2
70%
93%
Capacity of two backwash
cycles
IV.3.6.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
2. Physical, Chemical, and Biological Treatment Techniques for
Industrial Wastes, PB 275 287, U.S. Environmental Protection
Agency, Washington, D.C., November 1976. pp. 22-1-22-25.
Date: 6/23/80
IV.3.6-3
-------
TOTAL CAPITAL INVESTMENT
100 r
CO
10
O
CO
O
0.1
I I I I I 11
0.1
I I I I i I I I
ENR INDEX - 3119
i i i i i iit
1.0 10
FLOW, Mgal/d
100
Date: 6/23/80
IV.3.6-4
-------
rt
(D
MILLIONS OF DOLLARS/YEAR
a\
u>
00
o
M
cr>
I
en
ua
O)
>
I—
o
O
o
o
CO
-------
IV.3.7 ULTRAFILTRATION [1,2]
IV.3.7.1 Description
Ultrafiltration is a membrane filtration process that separates
high-molecular-weight solutes or colloids from a solution or
suspension. The process has been successfully applied for both
homogeneous solutions and colloidal suspensions, which are
difficult to separate practically by other techniques. To
date, commercial applications have been entirely focused on
aqueous media.
The basic principle of operation of ultrafiltration can be .ex-
plained as follows: Flowing by a porous membrane is a solution
containing two solutes: one solute has a molecular size too
small to be retained by the membrane, and the other has a larger
size that allows 100% retention. A hydrostatic pressure, typi-
cally 10 to 100 psig, is applied to the upstream side of the
supported membrane, and the large-molecule solute or colloid is
retained (rejected) by the membrane. A fluid concentrated in
the retained solute is collected as a product from the upstream
side; a solution of small-molecule solute and solvent is col-
lected from the downstream side of the membrane. Of course,
where only a single solute is present and is rejected by the
membrane, the liquid collected downstream is (ideally) pure
solvent.
Retained solute (or particle) size is one characteristic distin-
guishing Ultrafiltration from other filtration processes.
Viewed on a spectrum of membrane separation processes, Ultrafil-
tration is only one of a series of membrane methods that can be
used. For example, reverse osmosis, a membrane process capable
of separating dissolved ionic species from water, falls further
down the same scale of separated particle size.
Ultrafiltration membranes are asymmetric structures, possessing
an extremely thin selective layer (0.1- to 1.0-ym thick) sup-
ported on a thicker spongy substructure. Controlled variation
of fabrication methods can produce membranes with desirable
retentitive characteristics for a number of separation appli-
cations. It has become possible to tailor membranes with a wide
range of selective properties. For example, tight membranes can
retain organic solutes of 500 to 1,000 molecular weight while
allowing passage of most inorganic salts; conversely, loose
membranes can discriminate between solutes of 1,000,000 versus
250,000 molecular weight.
Ultrafiltration membranes are different from so-called "solution-
diffusion" membranes, which have been studied for a wide variety
of gas and liquid-phase separations. The latter group possesses
a permselective structure that is nonporous, and separation is
Date: 6/23/80 IV.3.7-1
-------
effected on the basis of differences in solubility and molecular
diffusivity within the actual polymer matrix. Reverse osmosis
membranes generally fall into this category.
Membranes can be made from various synthetic or natural polymeric
materials. These range from hydrophilic polymers, such as cellu-
lose, to very hydrophobic materials, such as fluorinated polymers,
Polyarylsulfones and inorganic materials have been introduced to
deal with high temperatures and pH values.
Membranes of this type are in many respects similar to reverse
osmosis membranes except for the openness of their pores. Other
forms and materials are available as well, including porous
zirconia deposited on a porous carbon substrate and on a porous
ceramic tube. The latter two systems, while more expensive than
the former, are capable of use to very high pH values and
temperatures.
A flow diagram of an ultrafiltration process is shown below.
I
PRESSURIZED SOLUTION OF lAI.IBI
CONCENTRATED (A)
. MEMBRANE
IV.3.7.2
" SOLUTION OF IB)
Typical Design Criteria
Design criteria
Value
Membrane:
Material
Water permeability
Molecular weight
Retentivity
Maximum operating temperature
Driving force
Most organic polymers
7-290 gpd per sq ft at 30 psi
340-45,000
60-100 percent
50-120°C
Approximately 25 psi
Date: 6/23/80
IV.3.7-2
-------
IV.3.7.3 Costs
Capital and operating costs for ultrafiltration are strongly
dependent on the specific application and the capacity of the
system; there is no typical model. For the purpose of cost
estimation, data are generated for sulfide recovery by the ultra-
filtration method. Design basis for economic projection of
sulfide recovery by ultrafiltration are shown on the next page.
Category
Tannery
operation
Ultraf iltration
system
Item
Tannery output
Discharge treated
Volume treated
Hair burn liquor
Operating period
Membrane flux
Water recovery
Membrane life
Basis
50,000 Ib of hide/d
First dump only
3,000 gpd (25,000 Ib water)
3% sulf hydrate
1% sulfide flakes
4% lime
(percentages based on hide weight)
260 d/yr
40 gal/ft2-d
80% (2,400 gpd)
3 yr
A flow diagram of sulfide recovery by ultrafiltration, including
operating characteristics, is shown below.
MAKEUP 100%
SULFIDES3,OOOgal
UNHAI RING BATH
20% CONSUMED
in or cvrrcc IKI
FIRST DUMP
50%SULFIDES
3, 000 gal
UURAFILTRATION
SYSTEM
HIDES TO BE
REMOVED BY
WASHES
CONCENTRATE TO
VACUUM FILTER
10%SULFIDES
600 gal
PERMEATE FOR REUSE
40%SULFIDES
2,400 gal
Fixed capital cost is approximately $136,000 for a daily feed
volume of 0.003 Mgpd. Total capital cost is estimated to be
$144,000. Estimation of annual operating cost is presented in
the following table, found on the next page.
Date: 6/23/80
IV.3.7-3
-------
Annual Cost per unit
Cost item quantity quantity Annual cost, $
Direct operating cost
Labor
Operating 520 man-hr $10/hr 5,200
Maintenance 52 man-hr $12/hr 620
b 5,820
Chemicals (cleaning) 430
Membrane replacement 900
Maintenance 1,250
2,150
Power 18,200 kWh $0.035/kWh 640
Total direct
operating cost 9,040
Total indirect
operating cost 23,100
Total annual
operating cost 32,100
Design basis included 260 d/yr, 3,000 gpd, 80% water recovery, 60-ft2
membrane area, and $40,000 purchased equipment cost.
200 gal/wk x 8.33 Ib/gal x 0.5% chemicals x $1/113*5 d/wk x 260 d/yr.
Cost curves were developed for total capital investment and an-
nual operating cost using the cost data shown above and the follow-
ing exponential scaling factors, which were used to determine costs
at varying flowrates:
Cost item
Total capital investment
Labor
Chemicals, power and materials
Exponential
factor
0.7
0.3
1.0
References
1. Abcor, Inc. A New Approach for Treatment of Spent Tannery
Liquors, Massachusetts 1979.
2. Physical, Chemical, and Biological Treatment Techniques for
Industrial Wastes, PB 275 287, U.S. Environmental Protection
Agency, Washington, D.C., November 1976. pp. 33-1 to 33-13,
Date: 6/23/80 IV.3.7-4
-------
TOTAL CAPITAL INVESTMENT
10
1.0
o
CO
O
0.1
0.01
0.001
FLOW, 1,000 m3/d
1.0 10
100
. 1
•
»
•
•
X
• X"
•
I J 1 I 1 1 1 1
1
/ TOTAL CAPIT
X
1 1 1 } I 1 1 1
1
*L INVESTMENT
ENR INDEX • 3119
, ,l,iii
0.01 0.1
FLOW, Mgal/d
1.0
Date: 6/23/80
IV.3.7-5
-------
rt
(D
MILLIONS OF DOLLARS/YEAR
00
o
I
cr>
O
8
.o
8
o
o
o
O
g
O)
o i—
O
•o
m
TO
O
O
O
t/>
-------
IV.4 SECONDARY WASTEWATER TREATMENT
IV.4.1 ACTIVATED SLUDGE
IV.4.1.1 Conventional Activated Sludge (Diffused Aeration) [1]
Description. In the conventional activated sludge plant,
the wastewater is commonly aerated in a plug-flow hydraulic mode.
Diffusers are employed to transfer oxygen from air to wastewater.
Compressors are used to supply air to the submerged systems, nor-
mally through a network of diffusers, although newer submerged
devices which do not come under the general category of diffusers
(e.g., static aerators and jet aerators) are being developed and
applied.
Diffused air systems may be classified as fine bubble or coarse
bubble. Diffusers commonly used in activated sludge service in-
clude^ the following: porous ceramic plates laid in the basin
bottom (fine bubble), porous ceramic domes or ceramic or plastic
tubes connected to a pipe header and lateral system (fine bubble),
tubes covered with synthetic fabric or wound filaments (fine or
coarse bubble), and specially designed spargers with multiple
openings (coarse bubble).
Common modifications include step aeration, contact stabilization,
and complete mix flow regimes. Aluminum or ferric chloride is
sometimes added to the tank for phosphorus removal.
Equipment normally associated with diffused air, activated sludge
systems includes air diffusers and compressors. A flow diagram
for conventional activated sludge with diffused aeration is shown
below.
PR I MARY EFFLUENT
AERATION TANK
TO FINAL CLARIFIER
RETURN SLUGDE
SLUDGE FROM FINAL CLARIFIER
EXCESS SLUDGE
(SEE SECTION IV.7)
Date: 6/23/80 IV.4.1-1
-------
Typical design criteria. A partial listing of typical de-
sign criteria for the conventional activated sludge process is
summarized below.
Design criteria Value
Mixed liquor suspended solids (MLSS) 1,500-3,000 mg/L
Food-to-microorganism (F/M) ratio 0.25-0.5 Ib BODs/d/lb MLSS
Air required 800-1,500 standard ft3/lb BODs removed
Sludge retention time 5-10 d
Costs. Purchased equipment and installation cost for esti-
mation of the total capital investment includes aeration basins,
air supply and dissolution equipment and piping, and blower build-
ing. Clarifier and recycle pumps are not included in the pur-
chased and installed equipment cost. The following operating
characteristics were assumed for cost estimation:
Operating characteristic Assumed value
Organic loading 1,300 mg/L BODs
Service life 40 yr
Oxygen requirement 1.1 Ib Oz supplied/lb BODs removed
MLSS 2,000 mg/L
F/M ratio 0.25 lb/BOD5/d/lb MLSS
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.4.1-2
-------
TOTAL CAPITAL INVESTMENT
l.OOOp
CO
Q£
g
o
o
u_
o
uo
100 r
LOADING, Ib/dayBOD
5
Date: 6/23/80
IV.4.1-3
-------
o
pj
CTi
u>
oo
o
H
o
o
,°
^
CL
O)
CO
O
MILLIONS OF DOLLARS/YEAR
(TOTAL DIRECT OPERATING COST - TOTAL ANNUAL OPERATING COST)
3>
O
m
o
o
o
to
LABOR - MATERIALS - POWER
-------
IV.4.1.2 Conventional Activated Sludge (Mechanical Aeration) [1]
Description. Mechanical aeration methods include the surface-
type mechanical entrainment aerators and the submerged turbine
with compressed air spargers (agitator/sparger system). The
surface-type aerators entrain atmospheric air by producing a
region of intense turbulence at the surface around their periph-
ery. They are designed to pump large quantities of liquid, thus
dispersing the entrained air and agitating and mixing the basin
contents. The agitator/sparger system consists of a radial-flow
turbine located below the mid-depth of the basin with compressed
air supplied to the turbine through a sparger. Volatile compounds
are removed to a certain extent in the aeration process. Metals
will also be partially removed, with accumulation in the sludge.
The submerged turbine aeration system affords a convenient and
relatively economical method for sludge plants that have high
capacity input per unit volume. To attain optimum flexibility of
oxygen input, the surface aerator can be combined with the sub-
merged turbine aerator. Several manufacturers supply such equip-
ment, with both aerators mounted on the same vertical shaft.
Such an arrangement might be advantageous if space limitations
require the use of deep aeration basins. In addition, mechanical
aerators may be either the floating or fixed installation type.
Diagrams for activated sludge sytems containing mechanical surface
aerators or submerged turbine aerators are shown below.
DRIVE
DRIVE
COMPRESSOR
i
•i
™
TURBINE ^-^.
SPARGER £
1 1?
-.
»
IAIR :
. a ,.9
MECHANICAL SURFACE AERATOR
SUBMERGED TURBINE AERATOR
Date: 6/23/80
IV.4.1-5
-------
Typical design criteria. A partial listing of typical de-
sign criteria for the conventional activated sludge process is
summarized below.
Design criteria Value
Mixed liquor suspended solids (MLSS) 1,500-3,000 mg/L
Food-to-microorganism (F/M) ratio 0.25-0.5 Ib BOD5/d/lb MLSS
Sludge age 5-10 d
The mixing equipment for aeration or oxygen transfer must be
sized to keep the solids in uniform suspension at all times. De-
pending on basin shape and depth, 4,000 mg/L of MLSS require about
0.75 to 1.0 hp/1,000 ft3 (0.02 to 0.03 kW/m3) of basin volume to
prevent settling if mechanical aerators are employed. However,
the power required to transfer the necessary oxygen will usually
equal or exceed this value.
Costs. Purchased equipment and installation cost for esti-
mation of the total capital investment includes aeration basins.
Clarifier and recycle pumps are not included. The following op-
erating characteristics were assumed for cost estimation:
Operating characteristic Assumed value
Organic loading 1,200 mg/L BODs
Oxygen requirement 1.1 Ib 02 supplies/lb BOD5 removed
MLSS 2,000 mg/L
F/M 0.25 Ib BODs/d/lb MLSS
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.4.1-6
-------
TOTAL CAPITAL INVESTMENT
100 r
in
5 10
g
O
u_
O
m
O
S 1.0
0.1
ENR INDEX - 3119
—i—i—i l i i i
10'
2
10" 10'
LOADING, Ib/day BOD,
10"
IV.4.1-7
-------
ANNUAL OPERATING COST
1.0 c
TOTAL ANNUAL
OPERATING COST
ENR INDEX • 3119
i i i I i t 1 1
i
0.001
0.01
10
Mr 10
LOADING, Ib/dayBOD,
IV.4.1-8
-------
IV.4.1.3 High-rate Activated Sludge-Diffused Aeration [1]
Description. A description of the activated sludge process
in general is presented in Section IV.4.1.1. Activated sludge
systems have traditionally been classified as high-rate, conven-
tional, or extended aeration based on organic loading.
High-rate air-activated sludge systems are designed with a food-
to microorganisms (F/M) loadings in the range of 0.75 to 1.5 Ib
BODs/d/lb MLVSS (mixed liquor volatile suspended solids). More-
over, they are usually characterized by mixed liquor suspended
solids - not necessarily (MLSS) concentrations, short aeration
detention times, high volumetric loadings, low air usage rates,
and intermediate levels of BOD5 and suspended solids removal
efficiencies. Prior to enactment of nationwide secondary treat-
ment regulations, this technology was utilized as an independent
treatment system for plants where BOD5 removals of 50 to 70 per-
cent would suffice. With present-day treatment requirements, it
no longer qualifies as a "stand-alone" activated sludge option.
These systems are normally designed to operate in either complete-
mix or plug-flow hydraulic configurations. Either surface or
submerged aeration systems can be employed to transfer oxygen
from air to wastewater, although submerged equipment is specified
more frequently for this process. Compressors are used to supply
air to submerged aeration systems.
Due primarily to rapidly escalating power costs, interest has
been recently expressed in the development of high-rate, diffused
aeration systems that would produce a high quality secondary
effluent. The key to development of efficient high-rate air
systems is the availability of submerged aeration equipment that
could satisfy the high oxygen demand rates that accompany high
MLSS levels. New innovations in fine bubble diffuser and jet
aeration technology offer potential for uniting high-efficiency
oxygen transfer with high-rate, air-activated sludge-flow regimes
to achieve acceptable secondary treatment as independent "stand-
alone" processes. Research evaluations and field studies cur
rently underway should provide performance and cost data on this
subject in the next several years.
Equipment normally associated with high-rate activated sludge
systems include air diffusers and compressors. A flow diagram of
the high-rate activated sludge system is shown on the next page.
Date; 6/23/80 IV.4.1-9
-------
SCREENED AND DEC KITTED
RAW WASTEWATER OR PRIMARY
EFFLUENT FEED
1 1 t
COMPLETE MIX
*!»»»»
"""" * I I 1 1 *
AERATION TANK
i
Tri
TO FINAL CLARIFIER
FROM FINAL CLARIFIER
1 . WASTE SLUDGE
RETURN SLUDGE
(SEE SECTION IV.7)
Typical design criteria. A partial listing of typical de-
sign criteria for the modified aeration process and the high-
solids, high-rate aeration process is summarized below.
Design criteria
Mixed liquor suspended solids (MLSS)
Food-to-microorganism (F/M) ratio
Air required
Oxygen required
Sludge age
Recycle ratio
Volatile fraction of MLSS
Units
mg/L
Ib BODs/d/lb MLVSSb
standard ft3 air/lb BODS removed
Ib Oa/lb BOD5 removed
days
Modification
800 - 2,000
0.75 - 1.5
400 - 800
0.4 - 0.7
0.75 - 2
0.25 - 1.0
0.7 - 0.85
High solids,
high-rate aeration
3,000 - 5,000
0.4 - 0.8
800 - 1,200
0.9 - 1.2
2-5
1.0 - 5.0
0.7 - 0.8
Tentative.
MLVSS = mixed liquor volatile suspended solids.
Costs. Purchased equipment and installation cost for esti-
mation of the total capital investment includes aeration basins,
air supply equipment and piping, and a blower building. Clarifier
and recycle pumps are not included in the purchased and installed
equipment cost. Basins are sized with 50% recycle flow. The
following operating characteristics were assumed for cost
estimation:
Operating characteristics
Assumed value
Organic loading
F/M
Oxygen requirement
MLVSS
Service life
1,300 mg/L BOD5
1.0 Ib BOD5/d/lb MLVSS
0.7 Ib BOD5 removed
1,050 mg/L
40 yr
References.
Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Metcalf & Eddy, Inc., Wastewater Engineering, Collection
Treatment Disposal, McGraw-Hill Publishing Co., New York,
New York, 1972. 782 pp.
Date: 6/23/80
IV.4.1-10
-------
TOTAL CAPITAL INVESTMENT
l,000c
to
oc
o
o
u.
O
to
100
LOADING, Ib/dayBOD,
Date: 6/23/80
IV.4.1-11
-------
ft
(D
ON.
NJ
MILLIONS OF DOLLARS/YEAR
00
O
NJ
8
p
O
Q
O
o
DO
O
O
vn
\ji
1 1 1 1 1 1 1 1
- o
- SZ
_ I
- VA>
_ i—•
i—•
Z >o
1 1 1 1 1 1 1
1 1 1 1 1 1 I
S3
5O CJ
il
§1
1 1 1 1 1 Ml
1 1 1 1 1 II
O
tJ
o
o
-------
IV.4.1.4 Pure Oxygen Activated Sludge, Covered [1]
Description. The use of pure oxygen for activated sludge
treatment has become competitive with the use of air due to the
development of efficient oxygen dissolution systems. The covered
oxygen system may be a high-rate activated sludge system. The
rain benefits cited for the process include reduced power re-
quirements for dissolving oxygen in the wastewater, reduced
aeration tank volume requirements, and improved biokinetics of
the activated sludge system. In the covered system, oxygenation
is performed in a staged, covered reactor in which oxygen gas is
recirculated within the system until it reaches a reduced level
of purity and a decreased undissolved mass at which it can no
longer be used and is vented to the atmosphere. High-purity
oxygen gas (90 to 100 percent volume) either from direct on-site
aeneration, off-site generation combined with pipeline delivery,
or trucked-in and on-site stored liquid oxygen followed by vapor-
ization enters the first stage of the system and flows concurrent-
ly with the wastewater being treated through the aeration basin.
Pressure under the tank covers is essentially atmospheric, being
held at 2 to 4 inches water column, sufficient to maintain oxygen
gas feed control and prevent backmixing from stage to stage.
Affluent mixed liquor is separated in conventional gravity clari-
fiers, and the thickened sludge is recycled to the first stage
for contact with influent wastewater.
Mass transfer and mixing within each stage are accomplished either
with surface aerators or with a submerged-turbine rotating-sparge
system. In the first case, mass transfer occurs in the gas phase;
in the latter, oxygen is sparged into the mixed liquor where mass
transfer occurs from the oxygen bubbles to the bulk liquid. In
both cases, the mass-transfer process is enhanced by the high
oxygen partial pressure maintained under the tank covers in each
stage.
The UNOX® and OASES® processes are examples of patented and
licensed systems, respectively, for pure oxygen activated sludge
based on the description presented here.
Although flexibility is claimed to permit operation in any of the
normally used flow regimes, i.e., plug flow, complete mix, step
aeration, and contact stabilization, the method of oxygen contact
employed favors the plug-flow mode.
Equipment normally associated with covered pure-oxygen activated
sludge systems include the aeration basin, oxygen generators,
liquid oxygen storage tank (for standby and peak load capacity),
and aerators. A diagram of the covered pure-oxygen activated
sludge process is shown on the next page.
Date: 6/23/80 IV.4.1-13
-------
OXYGEN FEED GAS
SCREENED AND DEGRITTED
RAW WASTEWATER OR PRIMARY -a£
EFFLUENT FEED
RETURN SLUDGE
AERATION _
TANK COVER
n
SURFACE AERATOR
DRIVE
,— aunrnist MC.KMIUK
\ / rMIXER DR
\ n / n ' r=-~
EXHAUST GAS
MIXED LIQUOR
TOCLARIFIER
SUBMERGED PROPELLER (OPTIONAL)
Typical design criteria. Typical design criteria for a
covered pure-oxygen activated sludge system are listed below,
Design criteria
Value
Food-to-microorganism (F/M) ratio
Mixed liquor suspended solids (MLSS)
Mixed liquor dissolved oxygen
Oxygen required
0.5 - 1.0 Ib BOD5/d/lb MLVSS
3,000 - 6,000 mg/L
4-8 mg/L
1.2 Ib 02/lb BOD5 removed
Costs. Purchased equipment and installation cost for
estimation of the total capital investment includes oxygenation
basins and covers, dissolution equipment, oxygen generators and
liquid oxygen feed, storage facilities, instrumentation, and li-
censing fees. The operating characteristics shown in the table
below were assumed for cost estimation on the assumptions that
(1) oxygen is delivered as liquid oxygen for plants ranging in
size from 0.1 to 1 Mgpd, and (2) oxygen is generated on site
for plants ranging in size from 1.0 to 100 Mgpd.
Operating characteristic
Assumed value
Organic loading
Oxygen supplied
MLVSSa
F/M
1,200 mg/L EOD5
1.2 Ib 02/lb BOD5 removed
3,000 mg/L
0.5 Ib BODs/d/lb MLVSS
Mixed liquor volatile suspended solids.
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80
IV.4.1-14
-------
TOTAL CAPITAL INVESTMENT
1,000
00
Of,
o
o
LU
O
*/)
100
10
1.0
0.1
0.01
I ] I J 1111
1 1 1J Ji
ENR INDEX = 3119
J J 1 1 M I L
10
10
LOADING, Ib/dayBOD,
Date: 6/23/80
IV.4.1-15
-------
D
0)
ti-
ro
to
u>
00
o
H
•
iU
•
I-1
I
MILLIONS OF DOLLARS/YEAR
(TOTAL ANNUAL OPERATING COST)
c:
>
o
o
o
to
TOTAL DIRECT OPERATING COST - OXYGEN
-------
IV.4.1.5 Pure-Oxygen Activated Sludge (Uncovered) [1]
Description. In the uncovered system, oxygenation is per-
formed in an open reactor in which extremely fine porous diffus-
ers are utilized to develop small oxygen gas bubbles that are
completely dissolved before breaking surface in normal-depth
tanks. The principles that apply in the transfer of oxygen in
conventional diffused air systems also apply to the open-tank,
pure-oxygen system.
The pure-oxygen, open-tank system currently available is the FMC
system (formerly referred to as the "Marox" system) in which
ultrafine bubbles are produced, with a correspondingly high gas-
surface area. These ultrafine bubbles are of micron size, where-
as "fine bubbles" normally produced in diffused air systems are
in millimeter sizes. The complete oxygenation system is composed
of an oxygen dissolution system comprised of rotating diffusers;
a source of high-purity oxygen gas (normally, an on-site oxygen
generator); and an oxygen control system, which balances oxygen
supply with oxygen demand through use of basin-located dissolved-
oxygen probes and control valves.
The influent to the system enters the oxygenation tank and is
pixed with .return activated sludge. The mixed liquor is contin-
uously and thoroughly mixed using low-energy mechanical agitation
near the bottom of the tank. Mixing is produced by radial tur-
bine impellers located on both surfaces (top and bottom) of the
rotating diffusion discs. Pure-oxygen gas in the form of micron-
size bubbles is simultaneously introduced into the tank to accom-
plish oxygen transfer. The rotating diffuser is a gear-driven
disc-shaped device equipped with a porous medium to assist in the
diffusion process. As the diffuser rotates at constant speed in
the mixed liquor, hydraulic shear wipes bubbles from the medium
before they have an opportunity to .coalesce and enlarge.
Operation in any of the normally-used flow regimes (i.e., plug
flow, complete rdx, step aeration and contact stabilization) can
be used as conditions dictate because the method of oxygen con-
tact employed does not favor one particular operating mode.
A flow diagram of the uncovered pure-oxygen activated sludge proc-
ess is shown on the next page.
Date: 6/23/80 IV.4.1-17
-------
INFLUENT RAW
WASTEWATER
OR PRIMARY
EFFLUENT
MOTOR/GEAR
OXYGEN GENERATOR
D.O. ANALYZER
TYPICAL OPEN BASIN
j f '
Iw"!
/ ) ^
V.D.O. PROBE V.
i» v ^
"" 0? DIFFUSIONS
" i ,
..*..•* '•.•'.•*. '.•:*•••• /:•.-. . < ' *'
:MIXED LIQUOR TO CLAIRIFIER
STORAGE
(STAND-BY)
VAPORIZER
Typical design criteria. Typical design criteria for the
uncovered pure-oxygen activated sludge system are shown in the
following table.
Design criteria
Value
Food-to-microorganism (F/M) ratio
Mixed liquor dissolved oxygen
Mixed liquor suspended solids (MLSS)
0.5 - 1.0 Ib BODs/d/lb MLVSS
2-6 mg/L
3,000 - 6,000 mg/L
Costs. Purchased equipment and installation cost for esti-
mation of the total capital investment includes oxygenation
basins, dissolution equipment, oxygen generators and liquid
oxygen feed, storage facilities, instrumentation (where appli-
cable) and licensing fees. The operating characteristics shown
in the table below were assumed for cost estimation on the as-
sumptions that (1) oxygen is delivered as liquid oxygen for
plants with loads up to about 1.1 x 103 Ib/d BOD, and (2) oxygen
is generated on site for plants treating loads greater than
1.1 x 103 Ib/d BOD.
Operating characteristic
Assumed value
Organic loading
Oxygen supplied
MLVSS3
F/M
1,200 mg/L BOD5
1.2 Ib 02/lb BOD5 removed
3,000 mg/L
0.5 Ib EODs/d/lb MLVSS
Mixed liquior volatile suspended solids.
Date: 6/23/80
IV.4.1-18
-------
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.4.1-19
-------
TOTAL CAPITAL INVESTMENT
lOOOp
to
o
u-
O
to
10
LOADING, lb/dayBOD(
Date: 6/23/80
IV.4.1-20
-------
ANNUAL OPERATING COST
1,000 F
100
zs
CO
10
o
CO
1.0
0.1
0.01
TOTAL ANNUAL
OPERATING COST
i i i i i i ii
10'
10
ENR INDEX - 3119
i i i i 11 ii
105
10"
LOADING, Ib/dayBOD,
Date: 6/23/80
IV.4.1-21
-------
IV.4.1.6 Contact Stabilization, Diffused Aeration [1]
Description. Contact stabilization is a modification of the
activated sludge process. In this modification, the adsorptive
capacity of the floe is utilized in the contact tank to adsorb
suspended, colloidal, and some dissolved organics. The hydraulic
detention time in the contact tank is only 30 to 60 minutes
(domestic). After the biological sludge is separated from the
wastewater in the secondary clarifier, the concentrated sludge is
separately aerated in the stabilization tank with a detention
time of 2 to 6 hours (domestic). The adsorbed organics undergo
oxidation in the stabilization tank and are synthesized into
microbial cells. If the detention time is long enough in the
stabilization tank, endogenous respiration will occur, along with
a concomitant decrease in excess biological sludge production.
Following stabilization, the reaerated sludge is mixed with
incoming wastewater in the contact tank, and the cycle starts
anew.
This process requires smaller total aeration volume than the con-
ventional activated sludge process. It also can handle greater
organic shock and toxic loadings because of the biological buffer-
ing capacity of the stabilization tank and the fact that at any
given time the majority of the activated sludge is isolated from
the main stream of the plant flow. Generally, the total aeration
basin volume (contact plus stabilization basins) is only 50% to
75% of that required in the conventional activated sludge system.
Equipment normally associated with the contact stabilization proc-
ess includes air diffusers, compressors, clarifier, contact basin,
and stabilization basin. A flow diagram of a contact stabiliza-
tion system is shown below.
SCREENED AND DEGRITTED
RAW WASTEWATER OR
PRIMARY EFFLUENT
-—CONTACT TANK
-+• TO FINAL CLARIFIER
FROM FINAL CLARIFIER
ALTERNATE EXCESS
SLUDGE DRAW-OFF
POINT
(SEE SECTION IV.7)
STABILIZATION
TANK
RETURN SLUDGE
(SEE SECTION IV.7)
Date: 6/23/80
IV.4.1-22
-------
Typical design criteria. A partial listing of typical de-
sign criteria for the contact stabilization process is summarized
below.
Design criteria
Value
Organic loading
Food-to-microorganism (F/M) ratio
Mixed liquor suspended solids (MLSS)
Sludge retention time
Recycle ratio
Oxygen required
Volatile fraction of MLSS
1,200 mg/L BOD5
0.2 - 0.6 Ib BODs/d/lb MLSS
1,000 - 2,500 mg/L for contact tank;
4,000 - 10,000 mg/L for stabiliza-
tion tank.
5 - 10 d
0.25 - 1.0
0.7 - 1.0 Ib 02/lb BODs removed
0.6 - 0.8
Costs. Purchased equipment and installation cost for estima-
tion of the total capital investment includes aeration basin,
clarifier, chlorine contact chamber, aerobic digester, and chlo-
rine feed facility. An organic loading of 1,200 mg/L BOD5 was
nsed.
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80
IV.4.1-23
-------
TOTAL CAPITAL INVESTMENT
1,000 F
100
00
o
o
u_
o
CO
10
1.0
0.1
0.01
TOTAL CAPITAL
-INVESTMENT-
PURCHASED AND
INSTALLED
EQUIPMENT
ENR INDEX = 3119
i i i i i 111
10'
10'
10
10"
LOADING, Ib/dayBOD
5
Date: 6/23/80
IV.4.1-24
-------
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IV.4.1.7 Extended Aeration, Mechanical and Diffused Aeration [1]
Description. Extended aeration is the "low-rate" modification
of the activated sludge process. The food-to-microorganism (F/M)
loading is in the range of 0.05 to 0.15 Ib EOD5/d/lb MLVSS. The
extended aeration system operates in the endogenous respiration
phase of the bacterial growth cycle, because of the low BOD5
loading. The organisms are starved and forced to undergo partial
auto-oxidation.
In the complete mix version of the extended aeration process, all
portions of the aeration basin are essentially homogeneous, re-
sulting in a uniform oxygen demand throughout the aeration tank.
This condition can be accomplished fairly simply in a symmetrical
(square or circular) basin with a single mechanical aerator or by
diffused aeration. The raw wastewater and return sludge enter at
a point (e.g., under a mechanical aerator) where they are quickly
dispersed throughout the basin. In rectangular basins with
mechanical aerators or diffused air, the incoming waste and
return sludge may be distributed along one side of the basin, and
the mixed liquor is withdrawn from the opposite side.
Common modifications include step aeration, contact stabilization,
and plug flow regimes.
Equipment normally associated with the extended aeration process
includes aerators, aeration tanks, clarifier, air diffusers, and
compressors. A flow diagram of an extended aeration system is
shown below.
SCREENED AND
DEGRITTEDRAW'
WASTEWATER
COMPLETE MIX
AERATION TANK
•* TO FINAL CLARIFIER
FROM FINAL CLARIFIER
1
RETURN SLUDGE
EXCESS SLUDGE
(SEE SECTION IV.7)
Date: 6/23/80
IV.4.1-26
-------
Typical design criteria. A partial listing of typical de-
sign criteria for the extended aeration activated sludge process
is summarized below.
Design criteria
Value
Mixed liquor suspended solids (MLSS)
Food-to-microorganism (F/M) ratio
Oxygen required
Sludge age
Recycle ratio
Volatile fraction of MLSS
3,000-6,000 mg/L
0.05-0.15 Ib BODs/d/lb MLVSS
2.0-2.5 Ib 02/lb BOD5
on 1.5 Ib 02/lb BODs removed and
4.6 Ib 02/lb NH/+-N removed)
20-40 d
0.75-1.5
0.6-0.7
Costs. Construction cost includes coiraninutor, aeration
basin, clarifier, chlorine contact chamber, aerobic digester,
and chlorine feed facility. Detention time: 24 hours (based on
average daily flow). An organic loading of 1,200 mg/L BOD5 was
used.
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80
IV.4.1-27
-------
TOTAL CAPITAL INVESTMENT
1,000F
to
01
o
O
100
10
1.0
0.1
0.01
i i i i 1111
TOTAL CAPITAL
INVESTMENT
PURCHASED AND
INSTALLED EQUIPMENT-
i i 1111
ENR INDEX = 3119
i i i
10'
10'
io5
LOADING, Ib/dayBOD
5
Date: 6/23/80
IV.4.1-28
-------
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IV.4.1.8 Oxidation Ditch [I]
Description. An oxidation ditch is an activated sludge
biological treatment process, which is commonly operated in the
extended aeration mode, although conventional activated sludge
treatment is also possible. Typical oxidation ditch treatment
systems consist of a single or closed loop channel, 4 to 6 feet
deep, with 45° sloping sidewalls.
Some form of preliminary treatment such as screening, comminution
or grit removal may precede the process After pretreatment the
wastewater is aerated in the ditch using mechanical aerators that
are mounted across the channel. Horizontal brush, cage, or disc-
type aerators, as well as jet aerators, specially designed for
oxidation ditch applications, are normally used. The aerators
provide mixing and circulation in the ditch, as well as suffi-
cient oxygen transfer. Mixing in the channels is uniform, but
zones of low dissolved oxygen concentration can develop. Aera-
tors operate in the 60 to 110 rpm range and provide sufficient
velocity to maintain solids in suspension. A high degree of
nitrification may occur in the process without special modifi-
cation when high solid retention times (10 to 50 days) are
utilized. Secondary settling of the aeration ditch effluent
is provided in a separate clarifier.
Ditches may be constructed of various materials, including con-
crete, gunite, asphalt, or impervious membranes; concrete is the
most common. Ditch loops may be oval or circular in shape.
"Ell" and "horseshoe" configurations have been constructed to
maximize land usage. Conventional activated sludge treatment,
in contrast to extended aeration, may be practiced. Oxidation
ditch systems with depths of 10 feet or more with vertical side-
walls and vertical shaft aerators may also be used.
Equipment normally associated with an oxidation ditch system in-
cludes hydraulic controls and brush aerators. A flow diagram of
the oxidation ditch process is shown below.
RAW
WASTEWATER
FINAL) EFFLUENT
CLARIFIER
RETURN SLUDGE
EXCESS SLUDGE
(SEE SECTION IV.7)
Date: 6/23/80
IV.4.1-30
-------
Typical design criteria. Typical design criteria for an
oxidation ditch system operated in the extended aeration mode
are listed below.
Design criteria Value
Organic loading 1,200 mg/L BODs
Sludge age 10-50 d
Channel depth 4-6 ft
Channel geometry 45° or vertical side-
walls
Aeration channel detention Depends on waste
time strength
Costs. Purchased equipment and installation cost for esti-
mation of the total capital investment includes building, labo-
ratory, and outdoor sludge drying beds.
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.4.1-31
-------
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-------
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1 "
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en
§ 0.1
0.01
0.001
• "«** A
103
ANNUAL OPERATING COST
TOTAL ANNUAL
OPERATING COST
i 111
ENR INDEX - 3119
i 111 i iii
10
II?
10
LOADING, Ib/dayBOD,
Date: 6/23/80
IV.4.1-33
-------
IV.4.2 TRICKLING FILTERS
Trickling filters are applicable to the same industrial waste
streams as the activated sludge treatment process. In the trick-
ling filter process, wastes are'sprayed through the air to absorb
oxygen and allowed to trickle through a bed of rock or synthetic
media coated with a slime of microbial growth. The microbial
slime is capable of decomposing organic matter in the waste
stream. Process modifications employ various types and depths
of media to retain the microorganisms under varying hydraulic
conditions [1].
Trickling filters provide media for the support of biomass,
rather than have suspended biomass as do activated sludge treat-
ment processes. The wastewater is trickled through the media and
collected underneath in a drain. Suspended solids, including
microbial slime that has sloughed off the media, are clarified
from the underflow, which may be either recycled to the trickling
filter head or sent to following treatment units. Hydraulic
loading rates for trickling filters are generally less than 0.5
gpm/ft2; however, loadings up to 4 gpm/ft* have been employed.
Rock media used to pack the filters typically allow depths of 3
to 8 ft. The use of synthetic media allows deep filters because
of their lessened tendency to clog and become anaerobic. Also,
the comparative light weight of synthetic media allows higher
packings. Filter packings up to 40-ft in depth are reasonable
where synthetic media are employed [1].
Trickling filtration is classified as low rate, using rock media.
and high rate, using rock, plastic and wood media. Plastic media,
high-rate rock media, and low-rate rock media trickling filters
are discussed in Sections IV.4.2.1 through IV.4.2.3, respectively.
IV.4.2.1 Plastic Media Trickling Filter [2]
Description. The process consists of a fixed bed of plastic
media over which wastewater is applied for aerobic biological
treatment. Zoogleal slimes form on the media which assimilate
and oxidize substances in the wastewater. The bed is dosed by
a distributor system, and the treated wastewater is collected by
an underdrain system. Primary treatment is normally required to
optimize trickling filter performance, whereas post-treatment is
generally not required to meet secondary standards.
The rotary distributor has become the standard because of its
reliability and ease of maintenance, however, fixed nozzles are
often used in roughing filters. Plastic media is comparatively
light with a specific weight of 10 to 30 times less than rock
media. Its high void space (approximately 95 percent) promotes
better oxygen transfer during passage of the liquid through the
Date: 6/23/80 IV.4.2-1
-------
filter than rock media with its approximate 50 percent void space.
Because of its light weight, plastic media containment structures
are normally constructed as elevated towers 20 to 30 feet high.
Excavated containment structures for rock media can sometimes
serve as a foundation for elevated towers for converting an exist-
ing facility to plastic media.
Plastic media trickling filters can be employed to provide inde-
pendent secondary treatment or roughing ahead of a second-stage
biological process. When used for secondary treatment, the media
bed is generally circular in plan and dosed by a rotary distribu-
tor. Roughing applications often utilize rectangular media beds
with fixed nozzles for distribution.
The organic material present in the wastewater is degraded by a
population of microorganisms attached to the filter media. As
the microorganisms grow, the thickness of the slime layer in-
creases. Periodically, the liquid will wash some slime off the
media, and a new slime layer will start to grow. This phenomenon
of losing the slime layer is called sloughing and is primarily a
function of the organic and hydraulic loadings on the filter.
Filter effluent recirculation is vital with plastic media trick-
ling filters to ensure proper wetting of the media and to promote
effective sloughing control compatible with the high organic
loadings employed.
Modifications common to all types of trickling filtration include
addition of recirculation, multistaging, electrically powered
distributors, forced ventilation, filter covers, and use of
various methods of pretreatment and post-treatment of wastewater.
Equipment normally associated with plastic media trickling fil-
ters includes underdrains, distributors, filter covers, and
plastic media. A flow diagram for a plastic media trickling
filtration system is shown below.
RECIRCULATION
PUM
RAW WASTEWATER
P STATION — NS
PRIMARY
CLARIFIER
1
^
?-
PLASTIC
MEDIA
TRICKLING
FILTER
I ' '
i
i
FINAL
CLARIFIER
1
WASTE SLUDGE
EFFLUENT
(SEE SECTION IV.7)
RECIRCULATION (SEE SECTION IV.7)
Date: 6/23/80
IV.4.2-2
-------
Typical design criteria. Typical design criteria for
plastic media trickling filters include hydraulic loading and
organic loading as noted below.
Design criteria
Value
Hydraulic loading (with recirculation)
Secondary treatment
Roughing
Recirculation ratio
Dosing interval
Sloughing
Organic loading
Secondary treatment
Roughing
Bed depth
Power requirement
Underdrain minimum slope
30-60 Mgal/acre/d; 700-1,400 gpd/ft2
100-200 Mgal/acre/d; 2,300-4,600
gpd/ft2
0.5:1 to 5:1
Not more than 15 s (continuous)
Continuous
450-2,200 Ib BODs/d/acre ft;
10-50 Ib BOD5/d/l,000 ft3
4,500-22,000 Ib BOD5/d/acre ft;
100-500 Ib BOD5/d/l,000 ft3
20-30 ft
20-200 hp/Mgal
1%
Costs. Purchased equipment and installation cost for esti-
mation of the total capital investment includes plastic media,
underdrains, distributors, and tower containment structures.
Clarifiers and recirculation equipment are not included in the
purchased and installed equipment cost. Annual operating costs
include labor and materials; energy costs are not included. The
following operating characteristics were assumed for cost
estimation:
Operating
characteristics
Assumed value
Organic loading
Bed depth
BOD5 loading
Recirculation rates
1,200 mg/L BOD5
•21 ft
11 Ib BODs/d/1,000 ft3
4.5 (based on average daily flow) to
0.6 (based on peak daily flow,
assumed to be 3.5 times daily
average flow)
Date: 6/23/80
IV.4.2-3
-------
References.
1. Physical, Chemical, and Biological Treatment Techniques for
Industrial Wastes, PB 275 287, U.S. Environmental Protection
Agency, Washington, D.C., November 1976. pp. 41-1 through
41-15.
2. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.4.2-4
-------
TOTAL CAPITAL INVESTMENT
l.OOOc
to
O
o
u_
o
to
100
10
1.0
0.1
0.01
/
i i 11111
ENR INDEX = 3119
i i i i 1111
10
105
10
LOADING, Ib/dayBOD
5
Date: 6/23/80
IV.4.2-5
-------
ANNUAL OPERATING COST
10 P
tr
S
t/>
on
g
d
o
u_
O
CO
O
ENR INDEX • 3119
i i i 11 it
0.001 =
0.0001
10
LOADING, Ib/dayBOD,
Date; 6/23/80
IV.4.2-6
-------
IV.4.2.2 Rock Media Trickling Filter - High Rate [1]
Description. The process consists of a fixed bed of rock
media over which wastewater is applied for aerobic biological
treatment. Zoogleal slimes form on the media which assimilate
and oxidize substances in the wastewater. The bed is dosed by a
distributor system, and the treated wastewater is collected by
an underdrain system. A primary clarifier is normally used to
optimize trickling filter performance, and final treatment is
often necessary to meet secondary standards or water quality
limitations.
The rotary distributor has become the standard because of its
reliability and ease of maintenance. It consists of two or more
arms that are mounted on a pivot in the center of the filter.
Nozzles distribute the wastewater as the arms rotate due to the
dynamic action of the incoming wastewater. Continuous recircula-
tion of filter effluent may be used to maintain a constant hy-
draulic loading to the distributor arms.
Underdrains are manufactured from specially designed vitrified-
clay blocks that support the filter media and pass the filtered
solids sewage to a collection sump for transfer to the final
clarifier.
The filter media consists of 1- to 5-inch stone. The high rate
trickling filter media bed generally is circular in plan, with a
depth of 3 to 6 feet. Containment structures are normally made
of reinforced concrete and installed in the ground to support the
weight of the media.
The organic material present in the wastewater is degraded by a
population of microorganisms attached to the filter media. As
the microorganisms grow, the thickness of the slime layer in-
creases. As the slime layer increases in thickness, the absorbed
organic matter or oxygen is utilized before it can reach the
microorganisms near the media face. As a result, the microorgan-
isms near the media face enter into either an endogenous phase
or anaerobic phase of growth depending on whether organic
matter or oxygen is limiting. In this phase, the microorganims
lose the media surface. The liquid then washes the slime off
the media, and a new slime layer will start to grow. This
phenomenon of losing the slime layer is called sloughing and is
primarily a function of the organic and hydraulic loadings on
the filter. Filter effluent recirculation is vital with high
rate trickling filters to promote the flushing action necessary
for effective sloughing control, without which media clogging
and anaerobic conditions could develop due to the high organic
loading rates employed.
Date: 6/23/80 IV.4.2-7
-------
Common modifications include various recirculation methods, rates
of recirculation, multistaging, electrically powered distributors,
forced ventilation, and filter covers.
Equipment normally associated with high rate, rock media trick-
ling filters includes underdrains and distributors. A flow dia-
gram of a high rate, rock media trickling filtration system is
shown below.
PUMP STATION
RAW WASTEWATER
PRIMARY
CLARIFIER
i
RAW SLUDGE
RECIRCULATION
^
J *
HIGH RATE,
ROCK MEDIA
TRICKLING
FILTER
i
FINAL
CLARIFIER
i
1
UACIT cinnr.F
•» ccci i irniT
RECIRCULATION
. |
Typical design criteria. Typical design criteria for high
rate, rock media trickling filters are shown below.
Design criteria
Value
Hydraulic loading (with recirculation)
Recirculation ratio
Dosing interval
Sloughing
Media
Organic loading
Bed depth
Power requirements
Underdrain minimum slope
10-40 Mgal/acre/d; 230-900 gpd/ft2
0.5:1 to 4:1
Not more than 15 s (continuous)
Continuous
Rock; 1-5 in.
900-2,600 Ib BODs/d/acre ft;
20-60 Ib BODs/d/1,000 ft3
3-6 ft
10-50 hp/Mgal
1%
Costs. Purchased equipment and installation cost for esti-
mation of the total capital investment includes rock media,
underdrains, distributors, and reinforced concrete containment
structures. Clarifier and recirculation equipment are not
included in the purchased and installed equipment cost. Energy
costs are also not included in the annual operating costs. The
following operating characteristics were assumed for cost
estimation:
Date: 6/23/80
IV.4.2-8
-------
Operating characteristic Assumed value
Organic loading 1,200 mg/L BOD5
Bed depth 5 ft
BOD5 loading 20 Ib BOD5/d/l,000 ft3*
Hydraulic loading 0.3 gpm/ft2
Recirculation ratio 4.0 (based on average daily flow) to
0.4 (based on peak daily flow
assumed to be 3.5 tiroes average
daily flow)
aTo attain an effluent BOD5 of 45 mg/L for a domestic sewage
influent of 130 mg/L. Based on raw load only.
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.4.2-9
-------
TOTAL CAPITAL INVESTMENT
l.OOOp
o
o
u_
O
O
ENR INDEX:3119
i i i i M
0.1 =
0.01
LOADING, Ib/dayBOD,
Date: 6/23/80
IV.4.2-10
-------
o
Q)
ri-
en
\
to
U)
\
00
o
NJ
I
o
51
Q.
Q)
*<
CD
O
O
MILLIONS OF DOLLARS/YEAR
S •=• =
O
•o
o
o
-------
IV.4.2.3 Rock Media Trickling Filter - Low Rate [1]
Description. This process also consists of a fixed bed of
rock media over which wastewater is applied for aerobic biolog-
ical treatment. Zoogleal slimes form on the media which assimi-
late and oxidize substances in the wastewater. The bed is dosed
by a distributor system, and the treated wastewater .is collected
by an underdrain system.
The rotary distributor has become the standard because of its
reliability and ease of maintenance. In contrast to the high
rate trickling filter which may uses continuous recirculation of
filter effluent to maintain a constant hydraulic loading to the
distributor arms, either a suction-level controlled pump or a
dosing siphon is employed for that purpose with a low rate
filter. Nevertheless, programmed rest periods may be necessary
at times because of inadequate influent flow.
Underdrains are manufactured from specially designed vitrified-
clay blocks that support the filter media and pass the filtered
solids to a collection sump for transfer to the final clarifier.
The filter media consists of 1- to 5-inch stone. Containment
structures are normally made of reinforced concrete and installed
in the ground to support the weight of the media.
The low rate trickling filter media bed generally is circular in
plan, with a depth of 5 to 10 feet. Although filter effluent
recirculation is generally not utilized, it can be provided as a
standby tool to keep filter media wet during low flow periods.
The organic material present in the wastewater is degraded by a
population of microorganisms attached to the filter media. As
the microorganisms grow, the thickness of the slime layer in-
creases. Periodically, wastewater washes the slime off the
media, and a new slime layer will start to grow. This phenomenon
of losing the slime layer is called sloughing and is primarily a
function of the organic and hydraulic loadings on the filter.
Equipment normally associated with low rate, rock media trickling
filters includes underdrains, distributors, and filter covers. A
flow diagram of a low rate, rock media trickling filtration system
is shown below.
RAW
WASTEWATER
PRIMARY
CLARIFIER
TRICKLING
FILTER
FINAL
CLARIFIER
EFFLUENT
RAW SLUDGE WASTE SLUDGE
(SEE SECTION IV.7) (SEE SECTION IV.7)
Date: 6/23/80 IV.4.2-12
-------
Typical design criteria. Typical design criteria for low
rate rock media trickling filtration are listed below.
Design criteria Assumed value
Hydraulic loading 1-4 Mgal/acre/d; 25-90 gpd/ft2
Organic loading 200-900 Ib BOD5/d/acre ft; 5-20 Ib
BODs/d/1,000 ft3
Dosing interval Continuous for majority of daily operat-
ing schedule, but may become intermit-
tent (not more than 5 min) during low
flow periods
Effluent channel minimum velocity 2 ft/s at average daily flow
Media Rock; 1-5 in., must meet sodium sulfate
soundness test
Depth 5-10 ft
Underdrain minimum slope 1%
Costs. Purchased equipment and installation cost for esti-
mation of the total capital investment includes reinforced con-
crete containment structures, rotating distributors, rock media,
and underdrains. Clarifiers and recirculation equipment are not
included in the purchased and installed equipment cost. Energy
costs are not included in the annual operating cost. The follow-
ing operating characteristics were assumed for cost estimation:
Operating
characteristic Assumed value
Organic layer 1,300 mg/L BOD5
Bed depth 8 ft
BOD5 loading 10 Ib BODs/d/1,000 ft3
Hydraulic loading 75 gpd/ft2
aTo attain an effluent BOD5 of 25 mg/L at an
influent of 1,300 mg/L.
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.4.2-13
-------
TOTAL CAPITAL INVESTMENT
1,000F
en
oc.
g
o
o
u_
O
oo
LOADING, Ib/dayBOD
5
Date: 6/23/80
IV.4.2-14
-------
o
0)
ft
(D
U>
OO
O
H
<
MILLIONS OF DOLLARS/YEAR
>
r—
O
m
50
—t
HH
O
O
O
CO
-------
IV.4.3 LAGOONS
Lagooning (stabilization ponding) is used to remove dissolved and
collodial biodegradable organics, and suspended solids. A lagoon
is a relatively shallow body of water contained in an earthen
basin of controlled shape, which is designed for the purpose of
treating wastewater. The term "oxidation pond," often used, is
synonymous. Ponds have become popular because their low con-
struction and operating costs offer a significant financial ad-
vantage over other recognized treatment methods. Ponds are used
extensively for the treatment of industrial wastes and mixtures
of industrial wastes and domestic sewage that are amenable to
biological treatment.
Sections 4.3.1 through 4.3.3, respectively, include of discus-
sions on the following modifications of lagoons: aerated
lagoons, anaerobic lagoons, and facultative lagoons.
IV.4.3.1 Aerated Lagoons [1]
Description. Aerated lagoons are medium-depth basins
designed for the biological treatment of wastewater on a con-
tinuous basis. In contrast to stabilization ponds, which obtain
oxygen from photosynthesis and surface reaeration, aerated
lagoons employ aeration devices that supply supplemental oxygen
to the system. The aeration devices may be a mechanical (i.e.,
surface aerator) or diffused air system. Surface aerators are
divided into two types: horizontal aerators, and the more common
turbine and vertical shaft aerators. The many diffused air
systems utilized in lagoons consist of plastic pipes supported
near the bottom of the cells with regularly spaced sparger holes
drilled in the tops of the pipes.
Because aerated lagoons are normally designed to achieve partial
mixing only, aerobic-anaerobic stratification will occur, and a
large fraction of the incoming solids and a large fraction of
the biological solids produced from waste conversion settle to
the bottom of the lagoon cells. As the solids begin to build
up, a portion will undergo anaerobic decomposition. Volatile
toxics can potentially be removed by the aeration process, and
incidental removal of other toxics can be expected to be similar
to an activated sludge system. Several smaller aerated lagoon
cells in series are more effective than one large cell. Taper-
ing aeration intensity downward in the direction of flow pro-
motes settling out of solids in the last cell. A nonaerated
polishing cell following the last aerated cell is an optional,
but recommended, design technique to enhance suspended solids
removal prior to discharge.
Lagoons may be lined with concrete or an impervious flexible lin-
ing, depending on soil conditions and environmental regulations.
Date: 6/23/80 IV.4.3-1
-------
Equipment normally associated with aerated lagoons includes
lining systems, aerators, and hydraulic controls. A flow
diagram for aerated lagooning is shown below.
INFLUENT
AERATED
LAGOON(S)
TO POLISHING POND
Typical design criteria. Typical design criteria for aer-
ated lagoons consist of operation and energy requirements. The
operation requires one or more aerated cells, followed by a set-
tling (unaerated) cell. Additional operational criteria are
provided below.
Design criteria
Value
Depth
pH
Water temperature range
Optimum water temperature
Oxygen requirement
Organic loading
Operation
6-20 ft
6.5-8.0
0-40>*C
20^0
0.7-1.4 times the amount of BODs removed
10-300 Ib BODs/acre/d
One or more cells
Costs. Purchased equipment and installation cost for esti-
mation of the total capital investment includes excavation, em-
bankment, seeding of lagoons/slopes (three cells), service road,
fencing rirap embankment protection, hydraulic control works,
aeration equipment, and electrical equipment. An organic load-
ing of 2,100 mg/L was assumed for cost estimation.
To adjust purchased and installed equipments cost for other de-
tention times, calculate the effective flow (Q ) using the fol-
lowing equation:
QT, =
QDesign X
new design detection time
7 days
References.
1.
Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80
IV.4.3-2
-------
TOTAL CAPITAL INVESTMENT
100 F
o
0
u_
O
on
10
LOADING, Ib/dayBOD,
Date: 6/23/80
IV.4.3-3
-------
ANNUAL OPERATING COST
100 F
CO
0,001
0.001
0.0001
FLOW, Mgal/d
Date: 6/23/80
IV.4.3-4
-------
IV.4.3.2 Anaerobic Lagoons [1]
Description. Anaerobic lagoons are relatively deep (up to
20 ft) ponds with steep sidewalls in which anaerobic conditions
are maintained by keeping loading so high that complete deoxy-
genation is prevalent. Although some oxygenation is possible
in a shallow surface zone, once greases form an impervious
surface layer, complete anaerobic conditions develop. Treatment
or stabilization results from thermophilic anaerobic digestion
of organic wastes. The treatment process is analogous to that
occurring in the single-stage untreated anaerobic digestion of
sludge in which acid-forming bacteria break down organics. The
resultant acids are then converted to carbon dioxide, methane,
cells, and other end products.
In the typical anaerobic lagoon, raw wastewater enters near the
bottom of the pond (often at the center) and mixes with the
active microbial mass in the sludge blanket, which is usually
about 6 feet deep. The discharge is located near one of the
sides of the pond, submerged below the liquid surface. Excess
undigested grease floats to the top, forming a heat-retaining
and relatively air-tight cover. Wasteflow flow equalization and
heating are generally not practiced. Excess sludge is washed
out with the effluent. Recirculation of waste sludge is not
required. '
Anaerobic lagoons are capable of providing treatment of high
strength wastewaters and are resistant to shock loads.
Anaerobic lagoons are customarily contained within earthen dikes.
Depending on soil characteristics, lining with various impervious
materials such as rubber, plastic or clay may be necessary. Pond
geometry may vary, but surface-area-to-volume ratios are mini-
mized to enhance heat retention.
Typical equipment includes lining systems and hydraulic controls.
A flow diagram for anaerobic lagooning is shown below.
INLET
GREASE LAYER
8 TO 20 ft
SLUDGE BLANKET
3 OUTLET
LINER (IF NECESSARY)
Date: 6/23/80
IV.4.3-5
-------
Typical design criteria. Typical design criteria for
anaerobic lagoons are shown below.
Design criteria
Value
Operation
Detention time
Depth
PH
Water temperature range
Optimum water temperature
Organic loading
Parallel
1-50 d
8-20 ft
6.8-7.2
43-120°F
86°F
220-2,200 Ib BODs/acre/d
Costs. Purchased equipment and installation cost for esti-
mation of the total capital investment includes excavating,
grading, other earth work, and service roads. These costs do
not include land and pumping. Anaerobic lagoons are operated by
gravity flow and, therefore, have no energy requirements other
than any pumping that may be necessary to lift the influent
wastewater into the lagoons. Liner cost is not included in the
estimation. An average detention time of 35 days was assumed
for cost estimation.
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80
IV.4.3-6
-------
TOTAL CAPITAL INVESTMENT
1,000F
100 r
CO
o:
o
o
on
O
10
10
LOADING, Ib/dayBOD,
Date: 6/23/80
IV.4.3-7
-------
o
fa
rt
(D
CT>
U>
\
CD
O
to
I
CO
MILLIONS OF DOLLARS/YEAR
>
I—
o
m
50
-<
i—i
O
O
o
en
-------
IV.4.3.3 Facultative Lagoons [1]
Description. Facultative lagoons are intermediate depth
(3 to 8 feet) ponds in which the wastewater is stratified into
three zones. These zones consist of an anaerobic bottom layer,
an aerobic surface layer, and an intermediate zone. Strati-
fication is a result of solids settling and temperature-water
density variations. Oxygen in the surface stabilization zone is
provided by reaeration and photosynthesis. This is in contrast
to aerated lagoons in which mechanical aeration is used to
create aerobic surface conditions. In general, the aerobic
surface layer serves to reduce odors while providing treatment
of soluble organic byproducts of the anaerobic process operat-
ing at the bottom.
Sludge at the bottom of facultative lagoons will undergo anaer-
obic digestion producing carbon dioxide, methane, and cells. The
photosynthetic activity at the lagoon surface produces oxygen
diurnally, increasing the dissolved oxygen during daylight hours,
while surface oxygen is depleted at night.
Facultative lagoons are often, and for optimum performance, should
be, operated in series. When three or more cells are linked, the
effluent from either the second or third cell may be recirculated
to the first. Recirculation rates of 0.5 to 2.0 times the plant
flow have been used to improve overall performance.
Facultative lagoons are customarily contained within earthen
dikes. Depending on soil characteristics, lining with various
impervious materials such as rubber, plastic or clay may be nec-
essary. Use of supplemental top-layer aeration can improve
overall treatment capacity, particularly in northern climates
where icing over of facultative lagoons is common in the winter.
Typical equipment includes lining systems and hydraulic controls.
A flow diagram for a facultative lagoon is shown below.
EFFLUENT DISCHARGE SUMP WITH
MULTIPLE DRAWOFF LEVEL DISCHARGE
CAPABILITY (TO MINIMIZE ALGAE
CONCENTRATIONS IN DISCHARGE)
..TRANSFER PIPE TO
-> SECONDARY CELL
LINER (IF NECESSARY)
INLET (TYPICALLY NEAR 1/3 ^ SLUDG£ STORAGE Z(M (FQR
PRIMARY CELLS ONLY WITHOUT
PRIOR PRIMARY SEDIMENTATION)
Date: 6/23/80
IV.4.3-9
-------
Typical design criteria. Typical design criteria for facul-
tative lagoons are shown below.
Design criteria
Value
Operation
Detention time
Depth
pH
Water temperature range
Optimum water temperature
Organic loading
At least three cells in series are required;
parallel trains of cells may be used for larger
systems
20-180 d
3-8 ft, although a portion of the anaerobic zone
of the first cell may be up to 12 ft deep to
accommodate large initial solids deposition
6.5-9.0
35-90°P for municipal applications
68°F
10-100 Ib BODs/acre/d
Costs. Purchased equipment and installation cost for esti-
mation of the total capital investment includes excavating,
grading, and other earth work required for normal subgrade
preparation, and service roads. These costs do not include land,
pumping, and liner. Facultative lagoons are operated by gravity,
and, therefore, have no energy requirements other than any pump-
ing that may be necessary to lift the influent wastewater into
the lagoons. The following operating and wastewater character-
istics were assumed for cost estimation:
Operating/wastewater
characteristic
Assumed value
Lagoon loading
Water depth
BODs
COD
TSS
Total-P
NH3-N
40 Ib BOD5/acre/d in warm climate;
20 Ib BODs/acre/d in cool climate
4 ft
30 mg/L effluent
100 mg/L effluent
210 mg/L influent;
400 mg/L influent;
230 mg/L influent;
11 mg/L influent;
20 mg/L influent;
60 mg/L effluent
8 mg/L effluent
15 mg/L effluent
in cool climate
and 15 mg/L in
warm climate
To adjust costs for loadings other than those above, calculate
the effective flow (0_) using the following equations:
For warn, climate Q£ - QDesign *
For COM
QE - QDes.gn x
Date: 6/23/80
fv.4.3-10
-------
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.4.3-11
-------
TOTAL CAPITAL INVESTMENT
l.OOOp
CO
o:
3
o
O
u_
O
oo
100 r
ENR INDEX = 3119
i i M i
0.01
LOADING, Ib/dayBOD
5
Date: 6/23/80
IV.4.3-12
-------
ANNUAL OPERATING COST
100 p
o
Q_
o
00
0.001
0.0001
0.001
0.00001
10
10
LOADING, Ib/dayBOD,
Date: 6/23/80
IV.4.3-13
-------
IV.4.4 ROTATING BIOLOGICAL CONTACTORS [1]
IV.4.4.1 Description
Rotating biological contactors (RBC) are used to remove dissolved
and collodial biodegradable organics. The process utilizes a
fixed-film biological reactor consisting of plastic media mounted
on a horizontal shaft and placed in a tank. Common media forms
are a disc-type made of styrofoam and a denser lattice-type made
of polyethylene. While wastewater flows through the tank, the
media are slowly rotated, about 40% immersed, for contact with
the wastewater to remove organic matter by the biological film
that develops on the media. Rotation results in exposure of the
film to the atmosphere as a means of aeration. Excess biomass
on the media is stripped off by rotational shear forces, and the
stripped solids are maintained in suspension by the mixing action
of the rotating media. Multiple staging of RBC's increases treat-
ment efficiency and could aid in achieving nitrification year
round. A complete system could consist of two or more parallel
trains, each consisting of multiple stages in series. Common
modifications of RBC's include the following: multiple staging;
use of dense media for latter stages in train; use of molded
covers or housing of units; various methods of pretreatment and
after treatment of wastewater; use in combination with trickling
filter or activated sludge processes; use of air driven system
in lieu of mechanically driven system; addition of air to the
tanks; addition of chemicals for pH control; and sludge recycle
to enhance nitrification.
Equipment normally associated with rotating biological contactors
includes rotating disc systems. A flow diagram of a typical
staged rotating biological contactor configuration is shown below,
TYPICAL STAGED RBC CONFIGURATION
„ SHAFT DRIVE
RAW WASTEWATER
\
•
—
*,
SHAFT
ORIE
STATIC
PRIMARY SLUDGE
SECONDARY
EFFLUENT
WASTE SLUDGE
(SEE SECTION IV.6) -ALTERNATE SHAROR.ENTAT.ON IS PARALLEL TO (SEE SECTION IV'6)
DIRECTION OF FLOW WITH A COMMON DRIVE FOR ALL
THE STAGES IN A SINGLE TRAIN.
IV.4.4.2 Typical Design Criteria
Typical design criteria of rotating biological contactors are
tabulated on the following page.
Date: 6/23/80
IV.4.4-1
-------
Design criteria
Value
Organic loading
T >55*F
Hydraulic loading
Number of stages/
train
Number of
parallel trains
Rotational velocity
Media surface area
Media submerged
Tank volume
Detention time
Secondary clarifier
overflow rate
Power
Without nitrification: 4-5 - 60 Ib BODs/1.000 ft* of media/day
With nitrification: 1.5-3.0 Ib BODs/1/000 ft* of media
Without nitrification: 1.5-3 gpd/fta of media surface area
With nitrification: 0.9-2 gpd/fta of media surface area
At least 4
At least 2
60 ft/min (peripheral, mechanical drive)
Disc type: 20 - 25 fta/ft3
Lattice type: 30 - 35 fta/ft*
40*
0.12 gal/fta of disc area
Without nitrification: 55 - 120 min (based on 0.12 gal/fta)
With nitrification: 80 - 190 min (based on 0.12 gal/fta)
500 - 700 gpd/fta
7-20 hp/25 ft shaft
IV.4.4.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes RBC shafts (standard media,
100,000 fta/shaft), motor drives (5 hp/shaft), molded fiberglass
covers, and reinforced concrete basins. Final clarifiers are not
included in the purchased and installed equipment cost. Cost is
based on organic loading rate of 2,800 mg/L.
Q = Q x 1.0 gpd/fta
*E ^Design Actual hydraulic loading (gpd/ft2)
IV.4.4.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80
IV.4.4-2
-------
TOTAL CAPITAL INVESTMENT
l,000p
0.01
LOADING, Ib/dayBOD,
Date: 6/23/80
IV.4.4-3
-------
ANNUAL OPERATING COST
10 P
IS
CO
o
o
u_
o
CO
O
TOTAL
0 DIRECT
iPERATING
COST —
ENR INDEX - 3119
i i i i 1111
0.001 =
0.0001
10V
LOADING, Ib/dayBOD,
Date: 6/23/80
IV.4.4-4
-------
IV.4.5 STEAM STRIPPING [1]
IV.4.5.1 Description
Steam stripping is essentially a fractional distillation of vola-
tile compounds from a wastewater stream. The volatile component
may be a gas or volatile organic compound with solubility in the
wastewater stream. In most instances, the volatile component,
such as methanol or ammonia, is quite water soluble.
Steam stripping is usually conducted as a continuous operation
in a packed tower or conventional fractionating distillation
column (bubble cap or sieve tray) with more than one stage of
vapor/liquid contact. The preheated wastewater from the heat
exchanger enters near the top of the distillation column and
then flows by gravity countercurrent to the steam and organic
vapors (or gas) rising up from the bottom of the column. As tne
wastewater passes down through the column, it contacts the vapors
rising from the bottom of the column that contain progressively
less volatile organic compound or gas. When the wastewater
reaches the bottom of the column, it is heated by the incoming
steam to reduce the concentration of volatile component(s) to
their final concentration. Much of the heat in the wastewater
discharged from the bottom of the column is recovered in pre-
heating the feed to the column.
Reflux (i.e., condensing a portion of the vapors from the top of
the column and returning it to the column) may or may not be
practiced depending on the composition of the vapor stream that
is desired. Although many of the steam strippers in industrial
use introduce the wastewater at the top of the stripper, there
are advantages to introducing the feed to a tray below the top
tray when reflux is used.
Introducing the feed at a lower tray (while still using the same
number of trays in the stripper) will have the effect of either
reducing steam requirements (due to the need for less reflux) or
yielding a vapor stream richer in volatile component). The com-
bination of using reflux and introducing the feed at a lower tray
will increase the concentration of the volatile organic component.
beyond that obtainable by reflux alone.
Equipment for steam stripping is nearly the same as that required
for conventional fractional distillation (i.e., packed column or
tray tower, reboiler, reflux condenser and feed tanks, and pumps).
However, a heat exchanger is used for heating feed entering column
and cooling stripped wastewater leaving column; the reboiler is
often an integral part of the tower body rather than a separate
vessel; materials of construction depend on operating pH and
presence (or absence) of corrosive ions (i.e., sulfides, chlo-
rides); in a single-column sour-water steam stripper, the high
pH (from the presence of ammonia) allows use of mild steel; if
Date: 6/23/80 IV.4.5-1
-------
sour water is stripped in two columns (H2S removed in one and NH3
removed in other), alloy steel or alloy-clad steel should be used
in unit in which H2S is removed.
IV.4.5.2 Typical Design Criteria
Design criteria
Value
Wastewater feed
Steam feed rate
Volumetric flowrate:
overhead
bottoms
Temperature feed
overhead
bottoms
Column height
Column diameter
250 ml/min; 3.8 L/m
design
59.7 mL/min
4.3 mL/min
305 mL/min
104°C
104°C
3.67 m
5.08 cm
IV.-4.5.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes feed pumps (130-ft head and
60-ft head), feed heat exchanger (800 ft2), distillation column
(24 trays, 6-ft diameter x 60 ft), condenser (400 ft2), and con-
densate tank (1,000 gal). The following operating characteris-
tics were assumed for cost estimation.
Operating characteristic
Assumed value
Wastestream
Operation
0.288 Mgpd sour water containing 5%
(NHit)2S (by wt)
350 d/yr, 24 hr/d
Date: 6/23/90
IV.4.5-2
-------
Cost per
Cost item unit quantity Annual cost, $
Direct operating cost
Labor
Operating $16/man-hr 33,600
Maintenance 28,000
51,600
Materials 29,500
Steam $5/1,000 Ib 1,008,000
Cooling water $0.043/1,000 gal 26,000
Power $0.035/kWh 6,000
Total 1,121,000
Total indirect operating cost 198,000
Total annual operating cost 1,320,000
Cost curves were developed for total capital investment and
annual operating cost using the cost data shown above and the
following exponential scaling factors, which were used to deter-
mine costs at varying flowrates:
Exponential
Cost item factor
Total capital investment
Labor
Materials, power, and chemicals
0.7
0.3
1.0
The capital cost for 106 MM gal/yr (0.286 Mgal/d) is $850,000.
IV.4.5.4 References
1. Physical, Chemical, and Biological Treatment Techniques for
Industrial Wastes, PB 275 287, U.S. Environmental Protection
Agency, Washington, D.C., November 1976.
Date: 6/23/80 IV.4.5-3
-------
TOTAL CAPITAL INVESTMENT
10 c
to
1.0
o
o
o
3 0.1
0.01
0.1
FLOW, 1,000 m3/d
1.0 10
X
X
X
J I III
X
X
X
100
TOTAL CAPITAL
INVESTMENT
ENR INDEX - 3119
. .i.ii
1.0 10
FLOW, Mgal/d
100
Date: 6/23/80
IV.4.5-4
-------
ANNUAL OPERATING COST
10
1.0
FLOW, 1,000 m3/d
10
100
to
^ 1.0
o -f
2 E 0.1
0.01
TOTAL ANNUAL
OPERATING COST
TOTAL DIRECT
OPERATING COST
WATER
STEAM
- POWER
ENR INDEX - 3119
0.1
0.01
u^
»—I
a:
LU
<
0.001
Of:
0.0001
0.01
0.1 10
FLOW, Mgal/d
10
Date: 6/23/80
IV.4.5-5
-------
IV.4.6 SOLVENT EXTRACTION [1]
IV.4.6.1 Description
Liquid-liquid solvent extraction, hereinafter referred to as
solvent extraction, is the separation of the constituents of a
liquid solution by contact with another immiscible liquid. If
the substances comprising the original solution distribute them-
selves differently between the two liquid phases, a certain
degree of separation will result, and this may be enhanced by
use of multiple contacts.
The solvent extraction process is shown schematically below.
The diagram shows a single solvent extraction unit operating on
an aqueous stream, in practice this unit might consist of (1) a
single-stage mixing and settling unit, (2) several mixers and
settlers (single-stage unit) in series, or (3) a multi-stage
unit operating by countercurrent flows in one device (e.g., a
column or differential centrifuge).
UNTREATED
WASTE WATER
SOLVENT
EXTRACTION
TREATED
•WATER
RAFTINATE
WATER*
SOLVENT
SOLVENT + SOLUTE
SOLVENT
SOLVENT
RECOVERY
SOLUTE
•SOLVENT
MAKE-UP
As indicated in the diagram, reuse of the extracting solvent
(following solute removal) and recovery of that portion of the
extracting solvent that dissolves in the extracted phase are
usually necessary aspects of the solvent extraction process.
Solvent reuse is necessary for economic reasons; the cost of
the solvent is generally too high to consider disposal after
use. Only in a very few cases may solvent reuse be eliminated;
these cases arise when an industrial chemical feed stream can be
used as the solvent and then sent on for normal processing, or
where water is the solvent. Solvent recovery from extracted
water may be eliminated in cases when the concentration in the
water to be discharged is not harmful, and when the solvent loss
does not incur a high cost.
Date: 6/23/80
IV.4.6-1
-------
The end result of solvent extraction is to separate the original
solution into two streams: a treated stream (the raffinate),
and a recovered solute stream (which may contain small amounts
of water and solvent). Solvent extraction may thus be considered
a recovery process since the solute chemicals are generally re-
covered for reuse, resale, or further treatment and disposal.
A process for solvent extracting a solution will typically in-
clude three basic steps: the actual extraction, solute removal
from the extracting solvent, and solvent recovery from the raffi-
nate (treated stream). The process may be operated continuously.
The first step, extraction, brings the two liquid phases (feed
and solvent) into intimate contact to allow solute transfer
either by forced mixing or by countercurrent flow caused by
density differences. The extractor will also have provisions to
allow separation of the two phases after mixing. One output
stream from the extractor is the solute-laden solvent; some
water may also be present. Solute removal may be via a second
solvent extraction step, distillation, or some other process.
For example, a second extraction, with caustic, is sometimes
used to extract phenol from light oil, which is used as the
primary solvent in diphenolizing coke plant wastewaters. Distil-
lation will usually be more common, except when problems with
azeotropes are present. In certain cases, it may be possible to
use the solute-laden solvent as a feed stream in some industrial
process, thus eliminating solute recovery. This is apparently
the case at some refineries where crude or light oil can be used
as a solvent (for phenol removal from water) and later processed
with the solute in it. Other similar applications probably
exist and are particularly attractive because they eliminate one
costly step. Solvent recovery from the treated stream may be
required if solvent losses would otherwise add significantly to
the cost of the process, or cause a problem with the discharge
of the raffinate. Solvent recovery may be accomplished by
stripping, distillation, adsorption, or other suitable processes.
There are two major categories of equipment for liquid extrac-
tion: single-stage and multi-stage equipment.
In single-stage equipment, the fluids are mixed, extraction
occurs, and the insoluble liquids are settled and separated. A
cascade of such stages may then be arranged. A single-stage
must provide facilities for mixing the insoluble liquids and for
settling and decanting the emulsion or dispersion which results.
In batch operation, mixing together with settling and decanting
may take place in the same or in separate vessels. In continu-
ous operation, different vessels are required.
In multi-stage equipment, the equivalent of many stages may be
incorporated into a single device or apparatus. Countercurrent
Date: 6/23/80 IV.4.6-2
-------
flow is produced by virtue of the difference in densities of the
liquids, and with few exceptions the equipment takes the form of
a vertical tower which may or may not contain internal devices
to influence the flow pattern. Other forms include centrifuges,
rotating discs, and rotating buckets. Depending upon the nature
of the internal structure, the equipment may be of the stagewise
or continuous-contact type.
IV.4.6.2 Typical Design Criteria
Design criteria
Value
Column diameter
Column length (glass pipe)
Solvent flow rate
Wastewater flowrate
0.0762 m
1.22 m
0.457 m/hr
3.60 m/hr
IV.4.6.3 Costs
It is quite difficult to generalize about the costs of solvent
extraction because of the wide variety of systems, feed streams,
and equipment that may be involved. In order to present a gen-
eralized cost estimate, however, data are generated for a speci-
fic application; i.e., the removal of phenol from water with
toluene by solvent extraction. A flow diagram of this system
and its operating characteristics are shown below.
10-HP MOTOR
F"l TOLUENE/PHENOL
TOLUENE
WATER/PHENOL
PUMP
TOLUENE
STILL
1
CRUDE PHENOL
ADDITIONAL
PURIFICATION
(e.g., fUSH
VACUUM)
"PURE" |
PHENOL '
TANK
D SOME WATER
Y/S//,
^S^
h—
O
K
WATER AND TRACE OF TOLUENE
WA
m AND SOMEI TOLUENE
STEAM STRIPPER
DISCH
* WA
TOLUENE
Date: 6/23/80
IV.4.6-3
-------
Operating characteristics
Value
Water/phenol/feed
Toluene feed
Discharge water
Extraction column
Loss of toluene/cycle
Electrical requirements
(column only)
Operation
45,000 Ib/hr containing 1.5% phenol (by wt);
temperature is 110°F.
45,000 Ib/hr (containing ^20 ppm phenol from
recycle)
Contains 75 ppm phenol
Rotating disc type; 6-ft diameter, 60 ft high;
made from carbon steel; contains 50 compart-
ments and equivalent of about 5 theoretical
stages. (Equilibrium distribution coefficient
of phenol between toluene and water is about 2.)
Approximately 0.1%/cycle
One 10 hp electric motor
330 d/yr; 24 hr/d
Fixed capital costs based on an ENR index of 3119 are estimated
to be $1,100,000. Similarly, total capital cost is estimated to
be $1,150,000. Estimation of annual operating cost is presented
in the following table.
Cost item
Direct operating cost
Labor
Operating
Maintenance
Chemicals - Toluene
Materials
Steam
Power
Total
Total indirect
operating cost
Total annual
a
operating cost
Annual Cost per unit
quantity quantity
12,000 man-hr $16/hr
15,000 gal $1.15/gal
33 x 106 Ib $5/1,000 Ib
150,000 kWh $0.035/kWh
Annual cost, $
192,000
16,000
208,000
17,300
16,700
165,000
5,300
412,000
350,000
762,000
Excludes annual credit for phenol recovery.
Date: 6/23/80
IV.4.6-4
-------
Cost curves were developed for total capital investment and annual
operating cost using the cost data shown on the previous page and
the following exponential scaling factors, which were used to de-
termine cost at varying capacities:
Exponential
Cost item factor
Total capital investment
Labor
Power, materials, steam and chemicals
0.7
0.3
1.0
IV.4.6.4 References
1. Physical, Chemical, and Biological Treatment Techniques for
Industrial Wastes, PB 275 287, U.S. Environmental Protection
Agency, Washington, D.C. November 1976. pp. 32-1 through
30-26.
Date: 6/23/80 IV.4.6-5
-------
TOTAL CAPITAL INVESTMENT
10
to
1.0
o
CO
O
0.1
0.01
0.1
«
•
X
I I I I I I
TOTAL CAPITAL
INVESTMENT
ENR INDEX • 3119
lilt
1.0 10
FLOW,Mlb/d OF WATER/PHENOL FEED
100
Date: 6/23/80
IV.4.6-6
-------
ANNUAL OPERATING COST
O
CO
I
GO
—I
O
O
i
O
Q_
0.001
1.0 10
FLOW, Mlb/d OF WATER PHENOL FEED
100
Date: 6/23/80
IV.4.6-7
-------
IV.5 TERTIARY WASTEWATER TREATMENT
IV.5.1 GRANULAR ACTIVATED CARBON ADSORPTION II]
IV.5.1.1 Description
Activated carbon adsorption is used for the removal of dissolved
organics and control of such wastewater parameters as COB, TOG,
BOD5, TOD, and specific soluble organic materials. In most cases,
activated carbon is used as an individual stream pretreatnient
process; however, in other cases activated carbon treatment is
used as a final treatment process following biological treatment.
Granular carbon systems generally consist of vessels in which the
carbon is placed, forming a "filter" bed. These systems can also
include carbon storage vessels and thermal regeneration facili-
ties. Vessels are usually circular for pressure systems or rec-
tantular for gravity flow systems. Once the carbon adsorptive
capacity has been fully utilized, the carbon must be disposed of
or regenerated. Usually multiple carbon vessels are used to
allow continuous operation. Columns can be operated in a series
or parallel mode. All vessels must be equipped with carbon
removal and loading mechanisms to allow for the removal of spent
carbon and the addition of new material. Flow can be either up-
ward or downward through the carbon bed. Vessels are backwashed
periodically. Surface wash and air scour systems can also be
used as part of the backwash cycle.
Small systems usually dispose of spent carbon or regenerate it
off site. Systems using above about 1,000 Ib/d usually provide
on-site regeneration of carbon for economic reasons.
Equipment normally associated with granular activated carbon
adsorption systems includes activated carbon material and granu-
lar carbon systems. A flow diagram of the activated carbon
adsorption process is shown below.
SPENT BACKWASH
j TO HEADWORKS
SECONDARY
EFFLUENT
ACTIVATED
CARBON
A
BACK-
WASH
TANK
1
EFFLUENT
BACKWASH PUMP
Date: 6/23/80
IV.5.1-1
-------
IV.5.1.2 Typical Design Criteria
Typical design criteria for an granular activated carbon adsorp-
tion process are shown below.
Design criterion Value
Vessel size 2 - 12 ft diameter commonly used
Area loading 2-10 gpm/ft2
Organic loading 0.1 - 0.3 Ib BOD5(or COD)/lb carbon
Backwash 12 - 20 gpm/ft2
Air scour 3-5 ft3/min/ft
Bed depth 5 - 30 ft
Contact time 10 - 50 min
Land area Minimal
IV.5.1.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes vessels, media, pumps, carbon
storage tanks, controls, and operations building. Disposal costs
are not included. No regeneration is included; therefore, above
3 Mgal/d cost curves are extrapolated. The following operating
characteristics were assumed for cost estimation.
Operating characteristic Assumed value
Loading rate 30 Ib/Mgal
Contact time 30 min
IV.5.1.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.5.1-2
-------
TOTAL CAPITAL INVESTMENT
100 c
o
en
O
10 r
0.1
1.0 10
FLOW, Mgal/d
100
Date: 6/23/80
IV.5.1-3
-------
ft
(D
NJ
CO
00
O
8
MILLIONS OF DOLLARS/YEAR
'
en
O)
i- S
- \J»
3
1 1 1 II
\
I Mill I I I I I I II
O
o
o
-------
ANNUAL OPERATING COST
ac
s
£
to
ec
to
o
ENR INDEX =3119
i i i i i 111
FLOW, Mgal/d
Date: 6/23/80
IV.5.1-5
-------
IV.5.2 POWDERED ACTIVATED CARBON ADSORPTION [1]
IV.5.2.1 Description
Powdered activation carbon is used in wastewater facilities to
absorb soluble organic materials and to aid in the clarification
process.
Powdered carbon is fed to a treatment system using chemical feed
equipment similar to that used for other chemicals that are pur-
chased in dry form. The spent carbon is removed with the sludge
and then discarded or regenerated. Regeneration can be accom-
plished in a furnace or wet air oxidation system.
Powdered carbon can be fed to primary clarifiers directly, or to
a separate sludge recirculation-type clarifier that enhances the
contact between the carbon and the wastewater. Powdered carbon
can also be fed to tertiary clarifiers to remove additional
amounts of soluble organics. Powdered carbon, when added to a
sludge recirculation-type clarifier, has been shown to be capable
of achieving secondary removal efficiencies.
Powdered carbon can be fed in the dry state using volumetric or
gravimetric feeders or it can be fed in slurry form.
A new technology has been developed over the past several years
that consists of the addition of powdered activated carbon to the
aeration basins of biological systems. This application is capa-
ble of the following: high BOD5 and COD reduction, despite hy-
draulic and organic overloading; aiding solids settling in the
clarifiers; a high degree of nitrification due to extended sludge
age; a substantial reduction in phosphorus; adsorbing coloring
materials such as dyes and toxic compounds; and adsorbing deter-
gents and reducing foam.
Equipment normally associated with powdered activated carbon ad-
sorption includes powdered carbon, volumetric and gravimetric
feeders, and slurry feeders. A flow diagram of a powdered
activated carbon adsorption system is shown below.
POWDERED x—v
CARBON FEED f \
TREATED EFFLUENT
MIXER
SLUDGE TO DISPOSAL
OR REGENERATION
(SEE SECTION IV.7)
Date: 6/23/80 IV.5.2-1
-------
IV.5.2.2 Typical Design Criteria
The amount of powdered carbon fed to a system greatly depends on
the characteristics of the wastewater and the desired effluent
quality; however, powdered carbon will generally be fed at a rate
between 50 and 300 mg/L.
IV.5.2.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes carbon feeding and storage
equipment only. The following operating characteristics were
assumed for cost estimation:
Operating characteristic Assumed value
Carbon dosage 80 mg/L
Carbon feed concentration 1 Ib/gal slurry
IV.5.2.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.5.2-2
-------
TOTAL CAPITAL INVESTMENT
LU
£
o
o
u.
o
0.01
FLOW, Mgal/d
Date: 6/23/80
IV.5.2-3
-------
o
0)
ft
(D
MILLIONS OF DOLLARS/YEAR
10
u>
00
o
p
o
to
I
id
o>
O
-O
8
-------
IV. 5. 3 CHEMICAL OXIDATION [1]
IV. 5. 3.1 Description
The chemical oxidation process involves the chemical rather than
the biological oxidation of dissolved organics in wastewater.
The processes discussed here are based on chemical oxidation as
differentiated from thermal, electrolytic, and biological oxida-
tion. Ozonation, a commonly used chemical method of oxidation
for waste treatment, and another oxidation process, chlorination,
are discussed elsewhere in this volume. The oxidation reactions
discussed here should be distinguished from the higher tempera-
ture, and typically pressurized, wet oxidation processes, such
as the Zimpro process, which are also discussed in a separate
section of this volume.
Oxidation-reduction or "redox" reactions are those in which the
oxidation state of at least one reactant is raised while that of
another is lowered. In reaction (1) in alkaline solution:
2MnOa + CN- + 20H-
-------
WASTE TREATMENT APPLICATIONS OF
OXIDATION IDENTIFIED
Oxidant
Waste
Ozone
Air (atmospheric oxygen)
Chlorine gas
. b
Chlorine and gas caustic
Chlorine dioxide
Sodium hypochlorite
Calcium hypochlorite
Potassium permanganate
Trace quantities only
Permanganate
Hydrogen peroxide
Nitrous acid
Sulfites (SQ3 )
Sulfides (S )
Ferrous iron (Fe++) (very slow)
Sulfide
Mercaptans
Cyanide (CN~)
Cyanide
Diquat
Paraquat
Cyanide
Lead
Cyanide
Cyanide (organic odors)
Lead
Phenol
Diquat
Paraquat
Organic sulfur compounds
Rotenone
Formaldehyde
Manganese
Phenol
Cyanide
Sulfur compounds
Lead
Benzidene
^Discussed in another section of this volume.
Alkaline chlorination.
The first step of the chemical oxidation process is the adjust-
ment of the pH of the solution to be treated. In the use of
chlorine gas to treat cyanides, for instance, this adjustment is
required because acid pH has the effect of producing hydrogen
cyanide and/or cyanogen chloride, both of which are poisonous
gases. The pH adjutment is done with an appropriate Alkali
(e.g., sodium hydroxide). This is followed by the addition of
the oxidizing agent. Mixing is provided to contact the oxi-
dizing agent and the waste. Because some heat is often liber-
ated, more concentrated solutions will require cooling. The
agent can be in the form of a gas (chlorine gas), a solution
(hydrogen peroxide) or perhaps a solid if there is adequate
mixing. Reaction times vary but are in the order of seconds and
minutes for most of the commercial-scale installations. Addi-
tional time is allowed to ensure complete mixing and oxidation.
Date: 6/23/80
IV.5.3-2
-------
At this point, additional oxidation may be desired and, as with
cyanide destruction, often requires the readjustment of the pH
followed by the addition of more oxidant. Once reacted, this
final oxidized solution is then generally subjected to some form
of treatment to settle or precipitate any insoluble oxidized
material, metals, and other residues. A treatment for the re-
moval of what remains of the oxidizing agent (both reacted and
unreacted) may be required. A product of potassium permanganate
oxidation is manganese dioxide (Mn02) which is insoluble and can
be settled or filtered for removal.
The characteristics of a number of common oxidizing agents are
described in the following paragraphs.
• Potassium Permanganate. Potassium permanganate (KMnCU)
has been used for destruction of organic residues in wastewater
and in potable water. Its usual reduced form, manganese dioxide
(Mn02) , can be removed by filtration. KMnCU reacts with alde-
hydes, mercaptans, phenols, and unsaturated acids. It is con-
sidered as a relatively powerful oxidizing agent.
• Hydrogen Peroxide. Hydrogen peroxide (H^Oa) has been used
for the separation of metal ions by selective oxidation. In this
way it helps remove iron from combined streams by oxidizing the
ferrous ion to ferric, which is then precipitated by the addition
of the appropriate base. In dilute solution (<30%) , the decompo-
sition of hydrogen peroxide is accelerated by the presence of
metal ion contaminants. At higher concentrations of hydrogen
peroxide, these contaminants can catalyze its violent decomposi-
tion. Hydrogen peroxides should be added slowly to the solution
with good mixing. This caution relates to other oxidants as
well. If the follow-on treatment involves distillation or crys-
tallization, the absence of all unspent peroxides must be con-
firmed since these techniques tend to concentrate the unused
reagent. Hydrogen peroxide has also been used as an "anti-chlor"
to remove residual chlorine following chlorination treatment.
• Chromic Acid. Chromium trioxide (CrO3) commercially called
chromic acid, is used as an oxidizing agent in the preparation
of organic compounds. It is often regenerated afterward by
electrolytic oxidation. In the oxidation of organic compounds,
chromic acid in a solution of sulfuric acid is reduced and forms
chromium sulfate [Cr2 (804)3].
Only very simple equipment is required for chemical oxidation.
This includes storage vessels for the oxidizing agents and per-
haps for the wastes, metering equipment for both streams, and
contact vessels with agitators to provide suitable contact of
oxidant and waste. Some instrumentation is required to deter-
mine the concentration and pH of the water and the degree of
completion of the oxidation reaction. The oxidation process
may be monitored by an oxidation-reduction potential (ORP)
Date: 6/23/80 IV.5.3-3
-------
electrode. This electrode is generally a piece of noble metal
(often platinum) that is exposed to the reaction medium, and
which produces an EMF output that is empirically related to the
reaction conditon by revealing the ratio of the oxidized to the
reduced constituents.
A flow diagram of chemical oxidation process is shown below.
MOT INCLUDED IN CYANIDE TREATMENT)
IA1CM
»Asn CON:rwTRATTD erAMDt WASH
7 Btpr- COPPE* CYANIDE
1 OOC pet SODIJM CYANIDE
»ASTT PROCESSING CAPACHY: 1 OBpl/l!
OPERATING PEHIOD ?C Vr
Ihr/d
SUMWARY:
J.JOO 91 I/O COOLING WATTS
»A* MATERIALS
« Ut MtW
277 Me M.MINE
IV.5.3.2 Typical Design Criteria'
Design criterion
Value
Tower temperature (top)
Feed
Air flow
Detention time
Pressure (top)
185-250°F
1.4-11.7 Ib sulfide/min
7.3-12.2 Ib air/lb sulfide oxidized
1.1-7.9 hr
50-79 psia
Design criteria based on sulfide oxidation.
Date: 6/23/80
IV.5.3-4
-------
IV.5.3.3 Costs
The cost of treatment at individual plant locations and on indi-
vidual wastes varies greatly. Capital costs depend upon such
factors as the type, volume, and composition of the waste; degree
of treatment required; treatment process selected; availability
of required services; and the specific material to be recovered
(i.e., metals, chemicals, or water). For the purpose of cost
estimating, data are generated for the chemical oxidation of cop-
per cyanide and sodium cyanide waste from a plating operation
using sodium hydroxide and chlorine treatment. A flow diagram
was presented in Section IV.5.3.1.
Cost item
Annual
quantity
Cost per unit
quantity
Annual cost, $
Direct operating cost
Labor
Operating
Maintenance
Chemicals
Sodium hydroxide
Chlorine
Power
Materials
Total
Total indirect
operating cost
Total annual
operating cost
2,500 man-hr $16/hr
22.9 tons
54.5 tons
35,000 kWh
$160/ton
$160/ton
$0.035/kWh
40,000
4,700
3,699
8,717
44,700
12,365
1,200
4,900
147,665
IV.5.3.4 References
1. Physical,•Chemical, and Biological Treatment Techniques for
Industrial Wastes, PB 275 287, U.S. Environmental Protection
Agency, Washington, D.C., November 1976. pp. 35-1 through
35-19.
Date: 6/23/80
IV.5.3-5
-------
TOTAL CAPITAL INVESTMENT
CO
Of.
i
o
fc
CO
ENR INDEX=3119
i i i i i i i i
0.001
0.01 0.1
FLOW, Mgal/d
Date: 6/23/80
IV.5.3-6
-------
ANNUAL OPERATING COST
10
Q£
<
UJ
§?
ENR INDEX=3119
i iii
0.01
0.001
0.01
001
FLOW, Mgal/d
Date: 6/23/80
IV.5,3-7
-------
IV.5.4 AIR STRIPPING [1, 2]
IV.5.4.1 Description
Air stripping of wastewater removes the ammonia nitrogen from the
wastewater and discharges it to the air.
Ammonia is quite soluble in water, but this solubility is temper-
ature-dependent. The relationship between temperature and the
solubility of ammonia for dilute ammonia solution is expressed by
Henry's Law:
y = MX
where y = mole fraction NHa in the vapor
x = mole fraction NH3 in the liquid
M = Henry's constant
Henry's constant is a function of temperature. By raising the
temperature of the wastewater the vapor pressure of the ammonia
is increased, and ammonia removal efficiency increased.
Another factor in ammonia removal efficiency is the pH of the
wastewater. A portion of the ammonia dissolved in the water
reacts with the water to give the following equilibrium:
NH3 + H20 ^ NH4+ + OH- (1)
By increasing the pH (concentration of OH~), the equilibirum is
shifted to the left, reducing the concentration of NHt» + and in-
creasing the concentration of free dissolved ammonia.
In air stripping of ammonia from dilute wastewater, the air tem-
perature limits the effectiveness of heating the wastewater.
Ammonia removal efficiency is enhanced instead by increasing the
pH, usually by the addition of lime. The ammonia-containing
wastewater and the lime slurry are fed to a rapid mix tank. Fol-
lowing the rapid mix tank are flocculators and a settling basin,
where calcium phosphate precipitates and recirculated calcium
carbonate settles out. The clarified, lime-treated, wastewater is
pumped to the top of packed towers. In each tower, fans draw
air up through the tower countercurrent to the falling wastewater.
The "packing" in the tower may be slats or a series of bundles of
pipe with the pipe sections spaced 2 to 3 inches on center. The
pipe sections are horizontal, and the direction of each row
alternates.
After the wastewater has been air stripped of ammonia, it flows
into the recarbonation basin where compressed carbon dioxide rich
gas from the lime recalcining furnace is bubbled through it to
precipitate calcium carbonate. Some of the calcium carbonate
Date: 6/23/80 IV.5.4-1
-------
sludge is returned to the rapid mix tank to enhance flocculation
while the remainder of the calcium carbonate sludge and the phos-
phate sludge from the settling basins are sent to centrifuges.
The sludges can be fractionally centrifuged to yield two dewatered
sludges, one rich in calcium carbonate and one containing phosphate,
Equipment normally associated with the air stripping process
includes the stripping tower, which closely resembles a con-
ventional cooling tower. A flow diagram of the air stripping
process is shown below.
4 AIR
I OUTLET
DRIFT
ELIMINATORS
WATER INLET
AIR INLET
OUTLET
DISTRIBUTION
SYSTEM
AIR INLET
WATER COLLECTING
BASIN
COUNTERCURRENT TOWER
IV.5.4.2 Typical Design Criteria
Typical design criteria for an air stripping system are listed
below.
Design criterion
Value
Wastewater loading
Stripping air flow rate
Packing depth
pH of wastewater
Air pressure drop
Packing material
Packing spacing
Provisions required
Land requirement
1-2 gpm/ft2
300 - 500 ftVgal
20 - 25 ft
10.8 - 11.5
0.015 - 0.019 in. of water/ft
Plastic or wood
Approximately 2 in. horizontal and
vertical
Uniform water distribution, and scale
removal and cleanup
Small
Date: 6/23/80
IV.5.4-2
-------
IV.5.4.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes tower, piping, and pump. The
following operating characteristics were assumed for cost
estimation:
Operating characteristic Assumed value
Pump total discharge head 50 ft
Loading 1 gpm/ft3
Air flow 400 ft3/gal
Ammonia concentration 18 mg/L influent;
3 mg/L effluent
pH 11-11.5
Tower height 20 ft
Indicate line dosage Typical
The tower is packed with 1/2-inch diameter Schedule-80 PVC pipes.
The distances between these pipes is 3 inches in horizontal rows
and 2 inches in vertical columns.
IV.5.4.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati/ Ohio, 1978. 252 pp.
2. Physical, Chemical, and Biological Treatment Techniques for
Industrial Wastes, PB 275 287, U.S. Environmental Protection
Agency, Washington, DC, November 1976. pp. 41-1 through
41-15.
Date: 6/23/80 IV.5.4-3
-------
TOTAi CAPITAL INVESTMENT
100 c
GO
O
CO
O
0
1.0 10
ROW, Mgal/d
Date: 6/23/80
IV.5.4-4
-------
o
(U
rt
(D
U)
00
o
I
Ul
MILLIONS OF DOLLARS/YEAR
(TOTAL DIRECT OPERATING COST - TOTAL ANNUAL OPERATING COST)
•"•* £2
• t—• o
O CD O
m
TO
O
8
MATERIALS - LABOR - CHEMICALS - POWER
-------
IV.5.5 NITRIFICATION [1,2]
IV.5.5.1 Description
Nitrification is used for the biological oxidation of ammonia to
nitrates and nitrites. This process is called single-stage
nitrification, because ammonia and carbonaceous materials are
oxidized in the same aeration unit. As in any aerobic biological
process, carbonaceous materials are oxidized by heterotrophic
aerobes. In addition, a special group of autotrophic aerobic
organisms called nitrifiers oxidize ammonia in two stages:
Nitrosomonas baceteria convert ammonia to nitrate, and Nitrobacter
bacteria convert nitrite to nitrate. The optimal conditions for
nitrification, in general, include a temperature of about 30°C,
pH of about 7.2 to 8.5, F/M of about .10 to .20, relatively long
aeration detention times (as nitrifiers have a lower growth rate
than other aerobes), and sludge retention times of about 25 to 20
days, depending upon temperature.
The degree of nitrification depends on a number of factors:
sludge retention time (SRT) as a function of temperature, mixed
liquor DO concentration, pH, and the absence of inhibitors. If
the sludge is wasted at a rate that is too high, the nitrifiers
will be eliminated from the system. The aeration system is de-
signed to provide the additional oxygen. Alkalinity is destroyed
during nitrification (7.15 mg A' N as CaC03/mg N03-N) and thus
alkalinity addition may be required for high TNN (Total Niedahl
Nitrogen) low buffer capacity wastewaters.
The conventional and high-rate modifications of the activated
sludge process do not provide the necessary hydraulic and sludge
detention times; in addition, the F/M ratio is higher. As a
result, single-stage nitrification is not normally achieved in
these configurations, although they effect a small reduction
(about 20 percent) in ammonia due to incorporation into microbial
cells.
Any low-rate modification of the activated sludge process such as
extended aeration and the oxidation ditch can be used. In addi-
tion, the use of powdered activated carbon has the potential of
providing consistent ammonia removal, although its application is
in a state of infancy and costs are relatively high.
Another modification involves the use of separate stage nitrifi-
cation. In this modification, carbonaceous oxidation and nitro-
genous oxidation are treated in two separate aeration basin and
clarifier systems. This provides some degree of production to
the nitrification system when inhibiting organics present in the
raw wastewater removed in the first carbonaceous stage.
Date: 6/23/80 IV.5.5-1
-------
Equipment normally associated with a nitrifying system includes air
diffusers, aeration tanks, clarifier equipment, controls, and in-
strumentation. A flow diagram of the nitrification system is shown
below.
PRIMARY
EFFLUENT
(SINGLE STAGE)
1
AERATION
TANK
FINAL
CLARIFIER
EFFLUENT
RETURN SLUDGE |
(SEE SECTION IV.7)
IV.5.5.2 Typical Design Criteria
Typical design criteria are tabularized below.
Design criterion Value
Type of reactor Plug-flow
Aeration system Oxygen or air
Mean cell residence time 10 - 20 d
MLVSSa 1,000 - 2,000 mg/L
pH 7.2-8.5
aMixed liquor volatile suspended solids.
IV.5.5.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes nitrification tanks, aeration
devices, clarifiers, and sludge recycle and waste pumps. Facili-
ties for pH adjustment are not included. The system is designed
to follow a high-rate activated sludge system. The following
operating characteristics were assumed for cost estimation:
Date: 6/23/80 IV.5.5-2
-------
Operating characteristic Assumed value
Nitrogen loading 1800 mg/L NH3-N
Sludge age Design parameter
Oxygen requirement 1.5 Ib 02/lb BODs removed; plus
4.6 Ib Oa/lb NH4-N (oxidized)
Final clarifier overflow rate 600 gpd/ft2 (30 Ib/ft2/d)
Sludge return pumps sized for 100% recycle and operated at 50%
recycle.
IV.5.5.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
2. Metcalf and Eddy. Wastewater Engineering: Collection, Treat-
ment, Disposal. McGraw-Hill Book Co., New York, New York,
1972. pp. 662-667.
Date: 6/23/80 IV.5.5-3
-------
TOTAL CAPITAL INVESTMENT
ce
o
o
u_
O
CO
100 F
10
1.0
0.1
0.01
0.001
I I III
ENR INDEX = 3119
_L I I I II I I
10'
10
10
NITROGEN LOAD, Ib/dayNH^N
Date: 6/23/80
IV.5.5-4
-------
0
p>
rt
CTl
co
oo
o
Ol
•
en
I
en
MILLIONS OF DOLLARS/YEAR
p
8
•so
8
§
O
t m
V*}
o
m
-------
IV.5.6 DENITRIFICATION [1]
IV.5.6.1 Description
Denitrification is used for the reduction of nitrates and nitrites
to nitrogen gas through the action of facultative heterotrophic
bacteria. In suspended-growth, separate-stage denitrification
processes, nitrified wastewater containing primarily nitrates is
passed through a mixed anaerobic vessel containing denitrifying
bacteria. Because the nitrified feedwater contains very little
carbonaceous material, a supplemental source of carbon is re-
quired to maintain the denitrifying biomass. This supplemental
energy is provided by feeding methanol to the biological reactor
along with the nitrified wastewater. Mixing in the anaerobic
denitrification reaction vessel may be accomplished using low
speed paddles analogous to standard flocculation equipment. Fol-
lowing the reactor, the denitrified effluent is aerated for a
short period (5 to 10 min) to strip out gaseous nitrogen formed
in the previous step that might otherwise inhibit sludge settling.
Clarification follows the stripping step with the collected sludge
being either returned to the head end of the denitrification
system or wasted.
Common modifications include the use of alternate energy sources
such as sugars, acetic acid, ethanol or other compounds. Nitrogen-
deficient materials, such as brewery wastewater, may also be used.
An intermediate aeration step for stabilization (about 50 min)
between the denitrification reactor and the stripping step may be
used to guard against carryover of carbonaceous materials. The
denitrification reactor may be covered but not air tight to assure
anaerobic conditions by minimizing surface reaeration.
Additional modification include the use of anaerobic-aerobic zones
in a nitrifying reactor to promote dentrification using the raw
waste carbonaceous BOD such as used in the Caroucel Process. This
may also be accomplished by effluent recycle from the nitrifying
reactor to the lead of the aeration task which is maintained in
an anaerobic condition as practiced in the Bardenpho process. For
high rate dentrification requiring minimal land area, fluidized
bed processes have recently been developed.
Equipment normally associated with the denitrification process
includes clarifier equipment, controls, air diffuser, aeration
tanks, instrumentation, chemical feed equipment, and flocculators.
A flow diagram of a denitrification system is shown below.
METHANOL
— »
ANAEROBIC MIXED
DENITRIFICATION
REACTOR
_
I m AD
AERATED NITROGEN \
STRIPPING CHANNEL X^
T«5min
NITRIFIED
EFFLUENT _ _.. ^ ^
^" """ WASTE
RETURN SLUDGE (SEE SECTION IV.7)
Date: 6/23/80 IV.5.6-1
-------
IV.5.6.2 Typical Design Criteria
Typical design criteria for denitrification are listed below.
Criteria
Value
Flow scheme
Optimum pH
Mixed liquor volatile suspended solids
Mixer power requirement
Clarifer surface loading rate
Solids loading
Return sludge rate
Sludge generation
Hydraulic detention time
Mean cell .residence time
Plug flow (preferable)
6.5 - 7.5
1,000 - 3,000 mg/L
0.25 - 0.5 hp/1,000 ft3
400 - 600 gpd/ft2
20 - 30 lb/d/ft2
50 - 100*
0.2 Ib/lb CH3OH
or 0.7 Ib/lb NO3-N
reduced
0.2 - 2 hr
1 - 5 d
IV.5.6.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes denitrification tanks (uncovered),
mixers, methanol feed, clarifiers, and sludge recycle and waste
pumps. The reaeration facility is not included. The operating
characteristics shown below were assumed for cost estimation.
Operating characteristic
Assumed value
Detention time
MLVSSa
Final clarifier overflow rate
Methanol requirement
Methanol storage
Denitrification recycle pumps
NO3-N concentration
2 hr in denitrification tank
2,000 mg/L
600 gpd/ft2
3 Ib methanol/lb nitrate nitrogen
removed
30 d supply with a minimum tank
size of 500 gal
Sized for 100* recycle but
operated at 50* recycle
18 mg/L influent
Mixed liquor volatile suspended solids.
Date; 6/23/80
IV.5,6-2
-------
IV.5.6.4 Referances
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-73-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.5.6-3
-------
TOTAL CAPITAL INVESTMENT
l,000p
CO
ce
o
u_
o
CO
NITROGEN LOAD, f NO^N/day
Date: 6/23/80
IV.5.6-4
-------
rt
(D
N>
U>
00
o
P
8
MILLIONS OF DOLLARS/YEAR
p
o
Ui
I
en
O
>
O
s:
Q.
D)
*<
00
O
O
TJ
m
PD
O
O
to
-------
IV.5.7 ION EXCHANGE [1]
IV,5.7.1 Description
In simplest terms, ion exchange may be thought of as the revers-
ible interchange of ions between an insoluble, solid salt (the
"ion exchanger") and a solution of electrolyte in contact with
that solid.
In the customary mode of usage, the ion exchanger is contacted
with the solution containing the ion to be removed until the
active sites in the exchanger are partially or completely used
up ("exhausted") by that ion. The exchanger is then contacted
v-i th a sufficiently concentrated solution of the ion originally
ass.iated with it for conversion ("regeneration") back to its
origin;;! form.
Tlve .icn exchange process works well with cations (including, of
course, the hydrogen ion) and anions, both inorganic and organic.
However, the organic species frequently interact with the
exchangers (particularly the organic resins) via both absorption
and ion exchange reactions, often necessitating the use of
extremely high regenerant concentrations and/or the use of
organic solvents to remove the organics. Consequently, most of
the applications of ion exchange of interest have involved inor-
ganic species.
There are a variety of different cation and anion exchangers
that forn salts of more or less different stabilities with a
particular ion. Thus, knowledgeable choice of a particular ion
exchange material will often allow selective separation of one
ion in solution from another, and afford selective removal of an
undesirable ion from a number of innocuous ones. As a general
rule, ions with a higher charge will form more stable salts with
the exchanger than those with a lower charge, and hence polyva-
lent species can frequently be selectively removed from a solu-
tion of monovalent ones.
In carrying out ion exchange reactions in a column or bed opera-
tion (as opposed to a stirred batch operation which is occasion-
ally used in chemical processing), there are four operations
carried out in a complete cycle: service (exhaustion), back-
wash, regeneration, and rinse. The service and regeneration
steps have been described above. The backwash step is one in
which the bed is washed (generally in water) in reverse direc-
tion to the service cycle in order to expand and resettle the
resin bed. This step eliminates channeling which might have
occurred during service and removes fines or other material that
may be clogging the bed. The rinse step removes the excess
regeneration solution prior to the next service step.
Date: 6/23/80 IV.5.7-1
-------
There are three principal operating modes in use today: cocur-
rent fixed-bed, countercurrent fixed-bed, and continuous counter-
current. A comparison summary is presented in the following
table.
COMPARISON OF ION EXCHANGE OPERATING MODES
Operating characteristic Concurrent fixed bad
Capacity for high feed
flow and concentration
Effluent quality
Regenerant and rinse
requirements
Equipment complexity
Equipment for continuous
operation
Relative costs (per unit
volume)
Investment
Materials/labor
Least
Fluctuates with bed
exhaustion
Highest
Simplest; can use
manual operation
Multiple beds, single
regeneration
equipment
Least
Highest chemicals and
labor needs, high-
est resin inventory
Countercurrent fixed bed Countercurrent continuous
Middle
High with minor
fluctuations
Somewhat less than
concurrent
More complex; auto-
matic controls for
regeneration
Multiple beds, single
regeneration
equipment
Middle
Less chemicals, water
and labor than
cocurrent
Highest
High
Least, yields most concen-
tration regenerant waste
Most complex; completely
automated
Provides continuous
service
Highest
Least chemicals, and
and labor needs, lowest
resin inventory
Most ion exchange installations in use today are of the fixed-
bed type, with countercurrent operation coming more into favor,
especially for removal (polishing) of traces of hazardous species
from the stream prior to reuse or discharge.
In order to minimize regeneration chemical requirements (i.e.,
to make most efficient use of regenerant), many fixed-bed instal-
lations use a technique termed "staged," or "proportional,"
regeneration. The first part of the regeneration solution to
exit from the ion exchange bed is the most enriched in the
component being removed; the concentration of that component
decreases in succeeding portions of the exiting regeneration
solution. In staged regeneration, the solution is divided
(generally in separate tanks) into two or more portions. The
first portion through the bed is "discarded" (i.e., sent for
subsequent treatment), while the second and succeeding portions
(less rich in the species being removed) are retained. On the
next regeneration cycle, the second portion from the preceding
cycle is passed through the bed first (and then "discarded"),
followed by the succeeding portions, the last of which is a
portion of fresh regenerant. In this way, regenerant utilization
can be maximized.
Fixed-bed ion exchange operations are straightforward systems,
requiring a cylindrical ion exchange bed, tanks for solution
storage, and pumps. The choice of materials is governed by the
chemical environment. Continuous ion exchange systems are much
more complex, requiring solids handling equipment and more
Date: 6/23/80
IV.5.7-2
-------
intricate control systems. Apparently only one company (Chemical
Separations Corp.) has been truly successful in the design and
fabrication of continuous ion exchange systems, and it should be
consulted if the use of such a system is contemplated.
A flow diagram of ion exchange systems is shown below.
eoamm ran n mew g
snvictw
_J,
"I tana our
SERVICE STEP
( (UBOMNTOUT
REGENERATION STEP
COMDICMIOIT 'Dm KI MOK
£_
aeeaaun
OUT
T soviet our
SERVICE STEP
I KCOCIAOT IN
REGENERATION STEP
COUKTOreUMOd CMTMWK MOM
MtiCINS QONNKOW TVKI
WASH TO KMOVE FIHtS
WSE coounon uaiON
Date: 6/23/80
IV.5.7-3
-------
IV.5.7.2 Typical Design Criteria
Design criterion
Value
Clinoptilolite size
Bed height
Wastewater suspended
solids
Wastewater loading
rate
Pressure drop
Cycle time
20 x
4 to
50 mesh
6 ft
35 mg/L max
7.5 to 20 bed volume/h
8.4 in of water/ft
100 to 150 bed volumes for one 6 ft bed;
200 to 250 bed volumes for two 6 ft
beds in series
Ion exchange for ammonia removal.
IV.5.7.3 Costs
Ion exchange is frequently incorporated into systems with other
treatment processes, such as reverse osmosis. In most cases,
separate cost data are not available solely for ion exchange.
In addition, many practitioners are reluctant to divulge treat-
ment cost data. Additionally, costs vary widely and depend
primarily upon the stream size and composition. Care should be
exercised in comparing costs for different processes because the
product streams are rarely the same.
For the purpose of cost estimating, data are generated for a
dilute mixed acid waste stream (80,000 gpd) from a metal finish-
ing operation. Treatment is based on the following wastewater
characteristics shown below. Product streams were clean water,
metal cations, chromium, and cyanide.
Pollutant
Concentration
Feed stream to process Effluent
Zinc
Copper
Cyanide (total)
Chromium
pH
15 mg/L <1 mg/L
0.5 mg/L <0.3 mg/L
19 mg/L <0.3 mg/L
22 mg/L (mostly Cr+6) <0.3 mg/L
M.O 6 - 8.5
Design basis for the above operation included a three-bed system,
in duplicate for regeneration; a 24 hr, 350 d/yr operation;
and a 24-hr loading time.
Date: 6/23/80
IV.5.7-4
-------
Fixed capital costs based on an ENR index of 3119 are estimated
to be $540,000. Similarly, total capital cost is estimated to be
$570,000. Estimation of annual operating cost is presented in
the following table.
Cost item
Annual
quantity
Cost per unit
quantity
Annual co»t, $
Direct operating cost
Labor
Chemicals
2,200/man-hr
S16/hr
35,200
NaOH (70%)
HaSO* (98%)
Resin replacement
Power (electricity)
Total
Total indirect operating
cost
Total annual operating
cost
175 tons $160/ton
48 tons 555/ton
20%
75,000 kWh $0.035/kWh
28,000
2,600
3,200
33,800
2,600
71,600
103,600
175,200
Cost curves were developed for total capital investment and annual
operating cost using the cost data shown on the previous page and
the following exponential scaling factors, which were used to
determine costs at varying flowrates:
Cost item
Exponential
factor
Total capital investment
Labor
Power and chemicals
0.7
0.3
1.0
IV.5.7.4 References
1. Physical, Chemical, and Biological Treatment Techniques for
Industrial Wastesr PB 275 287, U.S. Environmental Protection
Agency, Washington, D.C., November 1976. pp. 30-1 through
30-26.
Date: 6/23/80
IV.5.7-5
-------
TOTAL CAPITAL INVESTMENT
100
10
00
i i-o
o
o
u_
O
oo
O
I "-1
0.01
n nm
-
- •
- ^o
- /
r"
-
i-
-
?S
\ \ i 1 1 1 1 1
X
ENR INDEX: 3119
i i i i i 1 1 1
0.1
1.0
10
100
FLOW, Mgal/d
Date: 6/23/80
IV.5.7-6
-------
o
0)
ft
(D
to
OJ
00
o
Ul
.<=>
8
g
cO
Qi
MILLIONS OF DOLLARS/YEAR
O
TJ
o
o
-------
IV.5.8 POLYMERIC (RESIN) ADSORPTION [1]
IV.5.8.1 Description
Adsorption on synthetic resins is considered here primarily as a
process for the removal of organic chemicals from liquid waste
streams. Waste treatment by resin adsorption involves two basic
steps: (1) contacting the liquid waste stream with the resins
and allowing the resins to adsorb the solutes from the solution;
and, (2) subsequently regenerating the resins by removing the
adsorbed chemicals, often effected by simply washing with the
proper solvent.
The chemical nature of the various commercially available resins
can be quite different; perhaps the most important variable in
this respect is the degree of their hydrophilicity. The adsorp-
tion of a nonpolar molecule on to a hydrophobic resin (e.g., a
styrene-divinyl benzene based resin) results primarily from ef-
fect of van der Waal's forces. In other cases, other types of
interactions such as dipole-dipole interaction and hydrogen
bonding are also important. In a few cases, an ion-exchange
mechanism may be involved; this is thought to be true, for
example, in the adsorption of alkylbenzene sulfonates from
aqueous solution onto weakly basic resins; e.g., a phenol-
formaldehyde-amine based resin.
Resin adsorbents are used in much the same way as granular carbon.
Commonly, a typical system for treating low volume waste streams
will consist of two fixed beds of resin. One bed will be on
stream for adsorption while the second is being regenerated. In
cases where the adsorption time is very much longer than the
regeneration time (e.g., when solute concentrations are very
low), one resin bed plus a hold-up storage tank could suffice.
The adsorption bed is usually fed downflow at flow rates in the
range of 0.25 to 2 gpm per cubic foot of resin; this is equivalent
to 2 to 16 bed volumes/hr, and thus contact times are in the range
of 3 to 30 minutes. Linear flow rates are in the range of 1 to
10 gpm/ft2. Adsorption is stopped when the bed is fully loaded
and/or the concentration in the effluent rises above a certain
level.
Regeneration of the resin bed is performed in situ; basic, acidic,
and salt solutions or regenerable nonaqueous solvents are most
commonly used. Basic solutions may be used for the removal
of weakly acidic solutes, and acidic solutions for the removal
of weakly basic solutes; hot water or steam could be used for
volatile solutes; methanol and acetone are often used for the
removal of nonionic organic solutes. A prerinse and/or a post-
rinse with water will be required in some cases. As a rule,
about three bed volumes of regenerant will be required for resin
regeneration; as little as one-and-a-half bed volumes may suffice
in certain applications.
Date: 6/23/80 IV.5.8-1
-------
Solvent regeneration will be required unless (1) the solute-laden
solvent can be used as a feed stream in some industrial process
at the plant, or (2) the cost of the solvent is low enough so
that it may be disposed of after a single use. Solvent recovery,
usually by distillation, is thus most common when organic sol-
vents are used. Distillation will allow solute recovery for
reuse if such is desired.
Resin lifetimes may vary considerably depending on the nature of
the feed and regenerant streams. Regeneration with caustic is
estimated to cause a loss of 0.1 ro 1% of the resin per cycle;
replacement of resins at such installations may be necessary
every two to five years. Regeneration with hot water, steam, or
organic solvent should not affect the resins, and, in this case,
lifetimes will be limited by slow fouling or oxidation resulting
in a loss of capacity; actual experience indicates that lifetimes
of more than five years are obtainable.
Equipment for resin adsorption systems is relatively simple. The
system will generally consist of two or more steel tanks (stain-
less or rubber-lined) with associated piping, pumps, and (perhaps)
influent hold-up tank. Regeneration takes place in the same
tanks, and thus the extra equipment needed for regeneration will
consist only of such items as solvent storage tanks, associated
solvent piping and pumps, and solvent (and perhaps solute) recov-
ery equipment; e.g., a still. Up to three stills may be required
in some systems.
A flow diagram of a polymeric adsorption system is shown below.
Date: 6/23/80
IV,5.8-2
-------
IV.5.8.2 Typical Design Criteria
Design criterion
Value
Flow rates (downflow)
Contact time
Suspended solid
Surface areas of resin adsorbents
0.25 to 2 gpm/foot of resin
3 to 30 min
<50 ppm
800-1,200 m2/g
IV.5.8.3 Costs
Costs of wastewater treatment by polymeric adsorption can vary
widely depending on the nature of waste being treated and the
system design. As with carbon adsorption systems, two primary
variables in the process economics are: (1) the polymer exhaus-
tion rate (i.e., the amount of polymer required to treat a given
volume of liquid), and (2) the superficial liquid retention time
(i.e., the time that the liquid takes to fill the volume of the
polymer bed). For a given flow, influent concentration, and
polymer, the capital and operating costs depend almost entirely
on these two variables. The operating costs are determined
primarily by the polymer exhaustion rate because this v/ill set
the frequency of regeneration required. Total capital costs will
be determined primarily by the superficial liquid retention time
because this will set the size (or number) of the resin beds
required.
For the purpose of cost estimating, data are generated for a
phenol removal and recovery system. A flow diagram of this
system and its operating characteristics follow.
COUMN »> union wm mmr tint PWNCH is KOJIDED
Date: 6/23/80
IV.5.8-3
-------
MATERIAL BALANCE FOR PHENOL REMOVAL AND RECOVERY SYSTEM
(lb/hr)
Material
Phenol
Water
Acetone
Total
1
264
21,736
22,000
Stream
2
1,480
1,480
in flow diagram
3 4
264
9
4
4 273
5 plus 6
<10 ppm
23,207
4
23,211
The design basis for the recovery system included the following:
(1) 1.2% phenol in water; (2) 330 d/yr operation, and (3) recov-
ered pehnol of 2.08 x 106 Ib/yr.
Fixed capital costs based on an ENR index of 3119 are estimated
to be $1,060,000. Similarly, total capital cost is estimated to
be $1,120,000. Estimation of annual operating cost is presented
in the following table.
Cost item
Direct operating cost
Labor
Operating
Maintenance
Power
Steam
Water
Makeup water
Cooling water
Materials
Chemicals
Resin replacement
Acetone replacement
Annual
quantity
4,500 man-hr
150 x 103 kWh
42 x 106 Ib
125 x 106 gal
250 x 10s gal
100 ft3
35,000 Ib
Cost per unit
quantity
$16/hr
$0.03/kWh
$5/MM Btu
$0.57/1,000 gal
$0.04/1,000 gal
$175/ft3
$0.24/lb
Annual cost, $
72,000
21,000
71,000
11,000
17,500
8,400
93,000
4,500
210,000
82,000
21,500
25,900
Total
Total indirect operating
cost
Total annual operating
cost
437,000
355,000
792,000
Excludes annual credit based on selling phenol.
Date: 6/23/8
IV.5.8-4
-------
Cost curves were developed for total capital investment and
annual operating cost using the cost data shown above and the
following exponential scaling factors, which were used to deter-
mine costs at varying flowrates.
Exponential
Cost item factor
Total capital investment
Labor
Power, chemicals, materials, steam and water
<**
0.7
0.3
1.0
IV.5.8.4 References
1. Physical, Chemical, and Biological Treatment Techniques for
Industrial Wastes, PB 275 287, U.S. Environmental Protection
Agency, Washington, D.C., November 1976. pp. 2-1 to 2-26.
Date: 6/23/80 IV.5.8-5
-------
o
OJ
rt
(D
MILLIONS OF DOLLARS
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K)
LO
00
O
CD
I
8
—i
1C
o
oo
cr
O
-n
j—«
ro
ro
o
8
1 1 1 1 1 ^1 1
\
-
—
_
—
-
-
-
-
•
•
z
. 50
i— i
Z
- O
_ I
t— •
1— •
•o
1 1 1 1 1 1 I 1
\
\
\
\
\
\
\
\
\
\
\
1 1 ijllll
\
\
— 0
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m i—
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ft
(D
MILLIONS OF DOLLARS/YEAR
00
o
8
Ul
•
00
-J
g
IS3
a.
Q)
O
TJ
m
O
O
O
WATER
-------
IV.5.9. REVERSE OSMOSIS [1]
IV.5.9.1 Description
Reverse osmosis is used for the removal of dissolved organic and
inorganic materials and control of such wastewater parameters as
soluble metals, TDS, and TOC.
Reverse osmosis (RO) separates dissolved materials in solution by
filtration through a semipermeable membrane at a pressure greater
than the osmotic pressure caused by the dissolved materials in
the wastewater. With existing membranes and equipment, operating
pressures vary from atmospheric to 1,500 psi. Products from the
process are (1) the permeate or product stream with dissolved
material removed, and (2) concentrate stream containing all
removed material. Removal levels obtainable are dependent on
membrane type, operating pressure, and the specific pollutant
of concern. Removal of multicharged cations and anions is
normally very high, while most low molecular weight dissolved
organics are not removed or are only partially removed.
Typical equipment includes: membrane modules; feed, product,
concentrate tanks; high pressure pump; prefilter plus pump;
stainless steel piping; heat exchanger; flow and pressure in-
strumentation. An overall flow diagram of an RO system is
shown below.
PPFTPFATFD
OPTIONAL RECYCLE
r •
i
• —__—_— ^^____
INFLUENT - - H MEMBRANE MODULE | - *— ^-CONCENTRATE
PRODUCT (PERMEATE)
IV. 5. 9. 2 Typical Design Criteria
Typical design criteria for the reverse osmosis process are sum-
marized on the next page.
Date: 6/23/80 IV.5.9-1
-------
Design criteria
Value
Membrane type
Flux (product) rate at 600 psi,
5,000 ppm NaCl solution, and
25°C
Rejection at 600 psi, 5,000 ppm
NaCl solution, and 25°C
Operating pressure
Membrane configuration
Water recovery
Cellulose acetate (also di- and tri-
acetate ), polyamide, and polysulfone
6 to 10 gpd/ft2 membrane or 25 to 100
gpd/ft3 module
70% to 99% depending on membrane
specification
250 to 1,500 psi
Plate, tubular, spiral or hollow
fiber
50% to 85% depending on minimum
solubility
IV.5.9.3 Costs
Costs of reverse osmosis plants are strong functions of the
purified-water output capacity. They vary considerably with
size of plant and model chosen. Hence, the reader is cautioned
against generalization of the associated cost curves.
For the purpose of cost estimating, data are generated for an RO
unit which is used on cascaded rinses of an acid nickel plating
line. A flow diagram of the unit and its operating character-
istics are shown below.
l.OOOg/hr
NICKa DRAG-OUT
PLATE TANK
FIRST RINSE
2,250 ppm
(2.25 gA.)
CASCADE
SECOND RINSE
ML/hr
34 g/l
ROl
97% RE
SOOL/hr
JNIT
470L/hr
20 ppm
33X103 gpd
•ASSUME LIQUID VOLUME OF DRAG-IN EQUALS DRAG-OUT.
Date: 6/23/80
IV.5.9-2
-------
The design basis for reverse osmosis included 24-hr/d, 330-d/yr
operation; pumps and filter, and cellulose acetate membranes in
a spiral configuration.
Fixed capital costs based on an ENR index of 3119 are estimated
to be $16,000. Similarly, total capital cost is estimated to be
$17,000. Estimation of annual operating cost is presented in
the following table based on a flowrate of 3,300 gal/d.
Cost item Annual cost, $
Direct operating cost
Labor 1,320 (1/4-hr/d §$16/hr)
Membrane replacement 436 (replaced @2.5 yr)
Power 375 ($0.035/kWh)
Total 2,131
Annual operating cost 5,491
Cost curves were developed for total capital investment and
annual operating cost using the cost data shown above and the
following exponential scaling factors, which were used to deter-
mine costs- at varying flowrates:
Exponential
Cost item factor
Total capital investment
Labor
Power and chemicals
0.7
0.3
1.0
IV.5.9.4 References
1. Physical, Chemical, and Biological Treatment Techniques for
Industrial Wastes, PB 275 287, U.S. Environmental Protection
Agency, Washington, D.C., November 1976. pp. 39-1 to 39-19.
Date: 6/23/80 IV.5.9-3
-------
TOTAL CAPITAL INVESTMENT
CO
a:
<
_j
O
o
u_
O
CO
1,UUU
100
10
1.0
0.1
n m
-
„
—
-
_
-
<
- x
- x
^xx
-
-
1 1 1 1 M I 1
<#
$^'
1 1 1 1 M 1 1
1
si
5
X
X
jf
s'
ENR INDEX = 3119
1 1 Mill!
0.1
1.0
10
100
FLOW, Mgal/d
Date: 6/23/80
IV.5.9-4
-------
o
PI
rt
(D
o\
\
10
u>
\
00
o
Ol
•
vo
Ol
g
MILLIONS OF DOLLARS/YEAR
(POWER - MATERIALS - TOTAL)
P
o
O
TJ
O
O
O
LABOR
-------
IV.5.10 ELECTRODIALYSIS [1]
IV.5.10.1 Description
The general function of electrodialysis is the separation of an
aqueous stream under the action of an electric field into two
streams: an enriched stream (more concentrated in electrolyte
than the original), and a depleted stream. Success of the proc-
ess depends on special synthetic membranes, usually based on
ion exchange resins, which are permeable only to a single charge
type of ion. Cation exchange membranes permit passage only of
positive ions under the influence of the electric field; anion
exchange membranes permit passage only of negatively charged ions.
In the electrodialysis process, feed water passes through com-
partments formed by the spaces between alternating cation-
permeable and anion-permeable membranes held in a stack. At
each end of the stack is an electrode that has the same area as
the membranes. A dc potential applied across the stack causes
the positive and negative ions to migrate in opposite directions.
Because of the semipermeability of the membranes, a given ion
will either migrate to the adjacent compartment or be confined
to its original compartment, depending on whether or not the
first membrane it encounters is permeable to it. As a result,
salts are concentrated or diluted in alternate compartments.
To achieve high throughput, electrodialysis cells in practice are
made very thin and assembled in stacks of cells in series. Each
stack often consists of more than 100 cells. Feed material is
first filtered to remove suspended particulate matter that could
clog the system or foul the membrane and, if required, is given
a pretreatment to remove oxidizing materials and ferrous or man-
ganous ions, which would damage the membranes. Very high organic
levels may also lead to membrane fouling. The catholyte stream
is commonly acidified to offset the increase in pH that would
normally occur within the cell., and an antiscaling additive may
be required as well. An operating plant usually contains many
recirculation, feedback, and control loops and pumps to optimize
the concentrations and pH's at different points and thus maximize
the overall efficiency. Although a certain amount of water
transfer (electroosmosis) does occur, the process can be catego-
rized with ion exchange, solvent extraction, or adsorbent proc-
esses as one in which solutes are removed from the solvent,
rather than with distillation, freezing, or reverse osmosis in
which the solvent is transported.
All ionized species are not removed in proportion to their con-
centration because of different mobilities and equilibrium con-
centrations within the membrane. Therefore, a solution partially
deionized or concentrated by electrodialysis may contain signifi-
cantly different proportions of ionized species than does the
original feed.
Date: 6/23/80 IV.5.10-1
-------
Many colloids and polyanions have a net negative charge. For
this reason they may collect upon or foul anion exchange mem-
branes because of their positively charged functional groups.
This problem may be avoided to some extent using an electrodialy-
sis cell that consists of alternating cation and "neutral" mem-
branes. Such systems utilizing a porous "neutral" membrane to
avoid convective flow or mixing/ frequently perform very well
from a separation standpoint although they are not common commer-
cially because of their higher electrical power requirements.
Generally, electrodialysis works best on acidic streams con-
taining a single principal metal ion (such as acid nickel baths).
At alkaline pH's, membrane life may diminish, but the system has
been reported useable up to pH 14 under special circumstances.
Mixed metals may not be concentrated in the same ratio as that
in the feed, leading to problems in recycle. In addition,
although a sodium and copper cyanide stream may perform as ex-
pected under electrodialysis, the presence of zinc (a common ,
occurrence, especially in brass plating) can foul the anion mem-
brane by the (ZnCl)~ ion and partially convert that membrane to
the cation form, with significant loss in system performance. If
strongly alkaline, the feed streams are generally neutralized or
rendered slightly acidic to prevent degradation of the anion
membrane, which usually contains quaternary ammonium groups.
Iron and manganese in the feed water also degrade most common
membranes and must be removed if their total concentration in the
feed water is greater than about 0.3 mg/L.
Calcium sulfate scale can also accumulate if the calcium concen-
tration in the concentrated stream is allowed to exceed about
400 mg/L. Addition of a sequestering agent to the feed permits
operation to a higher calcium concentration, but generally not
above 900 mg/L. For this reason, the brine rarely constitutes
less than 10 to 15% of the feed water volume (a concentration
factor of 6 to 10).
Because the process depends on electrolytic conductance through
the various liquid streams, it is rarely practical to produce
product water of less than about 250 ppm total dissolved solids.
For the same reason, it is often desirable to operate an electro-
dialysis system at a slightly elevated temperature. As a rule
of thumb, a temperature increase of 17°C reduces the power con-
sumption by 1%.
Membrane life, although dependent upon service conditions, is
frequently five years. Other conponents are generally long lived,
because the system, although somewhat corrosive perhaps, operates
at a modest or ambient temperatures and pressures, and abrasives
and particulates normally will have been removed from the feed
water.
Date: 6/23/80 IV.5.10-2
-------
A flQW diagram of one electrodialysis system is shown below.
• SuHm ind CMoridl
IS Nickil
O.Ji/lMekil
0.15 IA«
IV.5.10.2 Typical Design Criteria
Design criterion
Value
Flow rate
Brine stream
Membrane thickness
Plastic spacers
Temperature
Max 10 MGD
10%-25% of feed stream
0.005 to 0.025 in
0.04 in thick
<100°F
Date: 6/23/80
IV.5.10.3
-------
IV.5.10.3 Costs
The costs for electrodialysis systems are dependent not only on
the volume of water to be treated but also the amount of salts
to be removed. The contributions of various economic factors is
illustrated in the cost estimation for a cooling tower circuit
with side stream electrodialysis. A flow diagram of this system
and its operating characteristics are shown below.
EVAPORATION
2,000 gpm
MAKEUP
2,000 gpm '
1,000 mgA
IZton/d SALT
ED PRODUCT
500 gpm
5300 mg/L
RECIRCLILATION
100,000 gpm
10,000 mgA
S1DESTREAM
500 gpm
10,000 mgA.
ED BRINE
13 gpm
150,000 mgA.
12 ton/a SALT
The design basis for the electrodialysis system includes the side
stream electrodialysis of cooling tower water in a single stage
with 300 d/yr operation.
Fixed capital costs based on an ENR index of 3119 are estimated
to be $610,000. Similarly, total capital cost is estimated to be
$646,000. Estimation of annual operating cost is presented in
the following table.
Cost item
Annual
quantity
Cost per unit
quantity
Annual cost, $
Direct operating cost
Labor
Operating
Maintenance
Chemicals
Materials
Membrane replacement
Maintenance
9,240 man-hr
$16/hr
150,000
12,000
162,000
10,000
9,700
12,500
Power 6,000,000 kWh $0.035 AH"
Total
Total indirect operating cost
Total annual operating cost
22,200
210,000
404,200
240,000
644,000
Date: 6/23/80
IV.5.10-4
-------
Cost curves were developed for total capital investment and
annual operating cost using the operating and the cost data shown
on the previous page and the following exponential scaling fac-
tors, which are used to determine costs at varying flowrates:
IV.
1.
Total
Labor
Power
5.10.4
Physic.
Cost item
capital investment
, materials and chemicals
References
al, Chemical, and Biologies
Exponential
0.7
0.3
1.0
il Treatment 1
factor
'echniqi
Industrial Wastes, PB 275 287, U.S. Environmental Protection
Agency, Washington, D.C., November 1976. pp. 18-1 throuah
18-14.
2. R.L. Gulp; Wesner, G.M.; Gulp, G.L. Handbook of Advanced
Wastewater Treatment. Van Nostrand Reinhold Co. 1978 by
Litton Educational Publishing Inc. New York, New York,
632 pp.
Date: 6/23/80 IV.5.10-5
-------
TOTAL CAPITAL INVESTMENT
10 c
1.0
FLOW, 1,000 m3/d
10
100
to
1.0
u.
O
O
S 0.1
0.01
rX
X
X
X
1 1 1 1 1
1 1
X
X
*
X
ENR INDEX - 3119
. .1.11
0.01
0.1 1.0
ROW, Mgal/d
10
Date: 6/23/80
IV.5.10-6
-------
G
V
rt
to
u>
CD
H
U1
O
I
.<=>
8
(O
ca
i i TI1111
:B
MILLIONS OF DOLLARSA'EAR
I I 111
8
I I III
I I I
O
TJ
m
O
o
o
00
-------
IV.5.11 - DISTILLATION [1]
IV.5.11.1 Description
Distillation is the boiling of a liquid solution and condensation
of the vapor for the purpose of separating the components. In the
distillation process, there are two phases: the liquid phase and
the vapor phase. The components that are to be separated by dis-
tillation are present in both phases but in different concentra-
tions. If there are only two components in the liquid, one
concentrates in the condensed vapor (condensate) and the other
in the residual liquid. If there are more than two components,
the less volatile components concentrate in the residual liquid
and the more volatile in the vapor or vapor condensate. The ease
with which a component is vaporized is called its volatility, and
the relative volatilities (ratio of equilibrium ratios) of the
components determine their vapor-liquid equilibrium relationships.
There are five general types of distillation, and a general de-
scription of each type is provided below.
• Batch Distillation. The simplest form of distillation is a
single equilibrium stage operation. It is carried out in a "still"
in which the reboiler equivalent consists of a steam jacket or a
heating coil. The liquid is "boiled"; the vapor is driven off,
condensed, and collected in an accumulator (a condensed vapor col-
lector) until the desired concentration of the "product" has been
reached. As the remaining liquid becomes leaner in the volatile
component and richer in the less volatile component, its volume
diminishes. If the residual liquid is the product, then "bottoms"
concentration will be the controlling parameter. The batch still,
as previously described, consists of a vessel that provides one
equilibrium stage. By adding a condenser and recycling some of
the condensed vapor, a second vapor-liquid equilibrium stage is
added, and the separation is improved.
• Continuous Fractional Distillation. In continuous fractional
distillation,a steady stream feed enters the column, which con-
tains plates or packing (packing is normally used only in small-
scale equipment) that provide additional vapor-liquid contact
(equilibrium) stages. Overhead vapors and bottoms are continuously
withdrawn. Vapor from the top plate is condensed and collected
in a vessel known as an accumulator. Some of the liquid in the
accumulator is continuously returned to the top plate of the col-
umn as reflux while the remainder of the liquid is continuously
withdrawn as the overhead product stream. At the bottom of the
column, the liquid collects in the reboiler, where it is heated
by steam coils or a steam jacket. The function of the reboiler
is to receive the liquid overflow from the lowest plate and re-
turn a portion of this as a vapor stream, while the remainder is
withdrawn continuously as a liquid bottom product.
Date: 6/23/80 IV.5.11-1
-------
• Azeotropic Distillation. An azeotrope is a liquid mixture
that maintains a constant boiling point and produces a vapor of
the same composition as the mixture when boiled. Because the com-
position of the vapor produced from an azeotrope is the same as
that of the liquid, an azeotrope may be boiled away at a constant
pressure, without change in concentration in either liquid or
vapor. Since the temperature cannot vary under these conditions,
azeotropes are also called constant boiling mixtures.
An azeotrope cannot be separated by constant pressure distillation
into its components. Furthermore, a mixture on one side of the
azeotrope composition cannot be transformed by distillation to a
mixture on the other side of the azeotrope. If the total pressure
is changed, the azeotropic composition is usually shifted. Some-
times this principle can be applied to obtain separations under
pressure or vacuum that cannot be obtained under atmospheric
pressure conditions. Most often, however, a third component -
an additive, sometimes called an entrainer - is added to the bi-
nary (two-component) mixture to form a new boiling-point azeotrope
with one of the original constituents. The volatility of the new
azeotrope is such that it may be easily separated from the other
original constituents.
• Extractive Distillation. Extractive distillation is a multi-
component rectification method of distillation. A solvent is added
to a binary mixture that is difficult or impossible to separate
by ordinary means. This solvent alters the relative volatility
of the original constituents, thus permitting separation. The
added solvent is of low volatility and is not appreciably vapor-
ized in the fractionator.
• Molecular Distillation. Molecular distillation is a form of
a very low pressure distillation conducted at absolute pressures
in the order of 0.003 mm of mercury that is suitable for heat-
sensitive substances. Ordinarily, the net rate of evaporation is
very low owing to the fact the evaporated molecules are reflected
back to the liquid after collisions occurring in the vapor. By
reducing the absolute pressure to values used in the molecular
distillation, the mean free path of the molecules becomes very
large (in the order of 1 cm). If the condensing surface is then
placed at a distance not exceeding a few centimeters from the
vaporing liquid surface, very few molecules will return to the
liquid, and the net rate of evaporation is substantially improved.
A flow diagram of a distillation process is shown on the next
page.
Date: 6/23/80 IV.5.11-2
-------
FEED
ACCUMULATOR
BOHOMS
PRODUCT
PUMP
OVERHEAD PRODUCT
STEAM
COMPENSATE
IV.5.11.2 Typical Design Criteria
Typical Design Criteria is discussed in the Cost Section,
Date: 6/23/80
IV.5.11-3
-------
IV.5.11.3 Costs
To illustrate (but not typify) the economics of distillation, an
economic analysis was performed on an "all purpose" utility dis-
tillation system. This type of system is most likely to be in-
stalled when there is a high probability that many different types
of organic liquid waste streams will be treated. Because of the
high degree of flexibility, the utility column is not designed for
optimum operation with any particular stream or flow rate.
For the purpose of cost estimating, data are generated for the
distillation of 20% acetone in a water waste stream. A flow
diagram of this distillation system showing the equipment and
operating characteristics assumed is presented below.
Operating characteristic
Value
Column
Diameter
Height
Packing
Liquid redistribution plates
Reboiler
Condenser
Pumps
Material of construction
Conditions at equilibrium:
3 ft
80 ft
Berl saddles; 1 1/2-in. stone
Located every 4 ft
375 ft2
100 ft2
Centrifugal; 5 gpm ratio and 1/2 hp
motor
Stainless steel
Concentration,
Stream
Peed (F)
Overheads (0)
Reflux (R)
Product heads (H)
Bottom (B)
Flow rate, Ib/hr
1,000
812
609
203
797
Temperature, °C
21
59
59
59
100
Acetone
20
98.5
98.5
98.5
0
Water
90
1.5
1.5
1.5
100
aColumn operates under slight positive pressure; reflux ratio = 3.1.
Letter in ( ) corresponds to those on flow diagram.
Date: 6/23/80
IV.5.11-4
-------
The design basis for distillation included 8,000 Ib waste/d;
125 d/yr, 8 hr/d operation, and 50% of utility column utilization
(actual system).
Fixed capital costs based on an ENR index of 3119 are estimated
to be $312,000. Similarly, total capital cost is estimated to be
$330,000. Estimation of annual operating cost is presented in the
following table.
Cost item
Annual
quantity
Cost/unit
Annual cost, $
Direct operating cost
Labor
Operating
Maintenance
Water
Makeup
Cooling
Steam
Materials
Power
Total
Total indirect
operating cost
Total annual
operating cost
375 man-hr
16/hr
6,000
2,300
6,000 gal $0.57/1,000 gal
535,000 gal $0.04/1,000 gal
1,000 MM Btu $5/MM Btu
290 kWh $0.035/kWh
3
23
8,300
26
5,000
2,400
9
16,000
47,900
64,000
Date: 6/23/80
IV.5.11-5
-------
FEED (F)
OVERHEAD
(0)
DIAMETER 3rt
HEIGHT 80ft -H
-8—r
P-i I
«n
CONDENSER
DIAMETER 2ft
[ACCUMULATOR] LENGTH4n
PROOUQ HEATER (H)
REBOILER
i
i STEAM
• CONDENSATE
BOTTOMS (B)
P-3
Cost curves were developed for total capital investment and annual
operating cost using the cost data shown above and the following
exponential scaling factors, which were used to determine costs
at varying flowrates.
Cost item
Exponential factor
Total capital investment
Labor
Power, chemicals, water and steam
1.2
0.3
1.0
IV.5.11.4 References
1. Physical, Chemical, and Biological Treatment Techniques for
Industrial Wastes, PB 275 287, U.S. Environmental Protection
Agency, Washington, D.C., November 1976. pp. 17-1 to 17-35.
Date: 6/23/80
IV.5.11-6
-------
TOTAL CAPITAL INVESTMENT
100
10
CO
1 1.0
0
0
u_
O
CO
O
^ 0.1
0.01
n nm
-
-
-
<$>
.s
/
-s
\ I 1 1 1 1 1 1
^r
^^
s
\ 1 1 1 1 1 1 1
X
ENR INDEX = 31 19
j i i i 1 1 1 1
0.1
1.0
10
100
WASTE, 10,000 Ibs/day
Date: 6/23/80
IV.5.11-7
-------
ANNUAL OPERATING COST
100 cr
10
CE
UJ
O
o
2 0.1
0.01
0.001
\ 1 i i 1 1 n
ENR INDEX • 3119
i i i i 11 n
0.1
1.0 10
WASTE, 10,000 Ibs/day
100
Date: 6/23/80
IV.5.11-8
-------
IV.5.12 CHLORINATION (DISINFECTION) [1]
IV.5.12.1 Description
Chlorination is the most commonly used disinfection process; it
is especially used for the removal of pathogens and other disease
causing organisms. Chlorination involves the addition of elemen-
tal chlorine or hypochlorites to the wastewater. Chlorine com-
bines with water to form hypochlorous (HOC1) and hydrochloric
(HC1) acids. Hydrolysis goes virtually to completion at pH val-
ues and concentrations normally experienced in municipal waste-
water applications. Hypochlorous acid will ionize to hypochlorite
(OC1) ion significantly above a pH of 7.5. Both are considered
free residual chlorine with hypochlorous acid having the greater
disinfecting power in water. In wastewater, the primary disinfec-
tant species is monochloromine.
The amount of chlorine added is determined by cylinder weight
loss. Chlorine demand is determined by the difference between
the chlorine added and the measured residual concentration after
a certain period has passed from the time of addition; this is
usually 15-30 minutes. The chlorine or hypochlorite is rapidly
mixed with the wastewater, after which it passes through a deten-
tion tank,'which normally contains baffled zones to prevent short
circuiting of wastewater.
Chlorine is also used as an oxidizing agent for taste and odor
control in wastewater treatment plants and for cyanide destruction
in industrial applications. One of the major problems with the
use of chlorine for disinfection, taste, and odor control is the
formation of chlorinated organics, many of them priority pollut-
ants.
Chlorine or hypochlorite salts can be used. The two most common
hypochlorite salts are calcium and sodium hypochlorite. Dechlo-
rination may be used; this generally involves the addition of
sulfur dioxide, aeration, or even activated carbon, when chlorine
residual standards are strict.
Equipment normally associated with the Chlorination process in-
cludes chlorine analyzers, pH controllers, chemical feeders, and
mixers. A flow diagram of a Chlorination system is shown
on the next page.
Date: 6/23/80 IV.5.12-1
-------
CHLORINATOR
CHLORINE GAS
SOLUTION HATER
CHLORINE
EDUCTOR
INFLUENT
EFFLUENT
MIXING TANK
(OPTIONAL)
CONTACT TANK
IV.5.12.2 Typical Design Criteria
Generally a contact period of 15 to 30 minutes at peak flow is
required. Detention tanks should be designed to prevent short
circuiting; this usually involves the use of baffling. Baffles
can either be the over-and-under or the end-around varieties.
Residuals of at least 0.5 mg/L are generally required. The fol-
lowing table presents typical dosages for disinfection:
Effluent source
Dosage range,
mg/L
Untreated wastewater (prechlorination) 6-25
Primary sedimentation 5-20
Chemical-precipitation plant 3-10
Trickling-filter plant 3-10
Activated-sludge plant 2-8
Multimedia filter following activated-sludge plant 1-5
IV.5.12.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes chlorine supply, chlorinator,
and contact chamber. Chlorine cost is assumed to be $160/ton.
The operating characteristics shown below were assumed for cost
estimation.
Operating characteristic Assumed value
Service life
Dosage
Contact time
15 yr
10 mg/L
30 min
Date: 6/23/80
IV.5.12-2
-------
IV 5.12.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.5.12-3
-------
a
f»
rt
u>
oo
o
<
•
Ul
N)
I
•fc.
.0
o
ta
0)
8
MILLIONS OF DOLLARS
O
>
-o
O
o.
co
-------
o
(U
ft
(D
to
U)
00
o
MILLIONS OF DOLLARS/YEAR
(TOTAL - CHEMICALS - LABOR)
to
I
Ul
g
g
>
G
O
TJ
m
o
o
o
to
(MATERIALS - POWER)
-------
IV.5.13 DECHLORINATION [1]
IV.5.13.1 Description
Dechlorination is used to remove free and combined chlorine from
effluents in order to reduce the toxic effects of chlorinated
effluents. Both free chlorine and chloramine residuals are toxic
to fish and other aquatic organisms.
Therefore, dechlorination involves the addition of sulfur dioxide
to wastewater, whereby the following reactions occur:
SO2 + HOCl + H20 = SO
-------
IV.5.13.2 Typical Design Criteria
Typical design criteria for a dechlorination system are shown
below.
~~ Design criterion Value
Contact time 1-5 min
Sulfur dioxide feed rate 1.1 Ib/lb residual chlorine
Sodium sulfite feed rate 0.57 Ib/lb chlorine
Sodium bisulfite feed rate 0.68 Ib/lb chlorine
Sodium thiosulfate feed rate 1.43 Ib/lb chlorine
IV.5.13.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes S02 feed facilities, reaction
tank (1-min detention time), mixer, and storage facilities.
Building space and control instrumentation are not included. SO2
costs were based on 20 Ib/Mgal (1.1 mg/L of S02 required per mg/L
of chlorine, residual).
IV.5.13.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.5.13-2
-------
TOTAL CAPITAL INVESTMENT
1.0
co
on
o
o
o
CO
o
0.1
3 0.01
0.001
0.1
FLOW, 1,000 m3/d
1.0 10
100
ENR INDEX - 3119
i , I i 1
1.0 10
, Mgal/d
100
Date: 6/23/80
IV.5.13-3
-------
ANNUAL OPERATING COST
ROW, 1,000 m3/d
10
CO
<
O
o:
UJ
o
a.
0.001 =
CO
<
oe:
0.001
0001
0.1
1.0 10
FLOW, Mgal/d
100
Date: 6/23/80
IV.5.13-4
-------
IV.5.14 OZONATION [1]
IV.5.14.1 Description
Ozone (03) is a very strong oxidant, which may be used, at dosages
of 10 to 300 mg/L, to remove residual dissolved organics from sec-
ondary effluent. Ozone has also been experimentally used to treat
raw wastewater and wastewater after various stages of treatment.
The rate of oxidation is both temperature- and pH-dependent.
Reaction rates increase with increasing temperature. The optimum
pH range is 6 to 8. Because there is a wide range of ozone
reactivity with the diverse organic content of wastewater, both
the required ozone dose and reaction time are dependent on the
quality of the influent to the ozonation process. Generally,
higher doses and longer contact times are required for ozone
oxidation reactions than are required for wastewater disinfection
using ozone.
Systems have been designed to utilize staged contactors (injec-
tion type) with recycle of the ozone/oxygen off-gas. On these
systems, provision must be made for the removal of nitrogen gas
from the influent wastewater stream and for the removal of
reaction-produced carbon dioxide from the off-gas stream in those
situations that warrant it. Ozone tertiary treatment may elimi-
nate the need for a final disinfection step.
Ozone breaks down to elemental oxygen in a relatively short period
of time (half life about 20 minutes). Consequently, it must be
generated on site using either air or oxygen as the feed gas.
Ozone generation utilizes a silent electric arc or corona through
which air or oxygen passes, and yields ozone in an air/oxygen
mixture. The percentage of ozone formed is a function of voltage,
frequency, gas flow rate, and moisture. Automatic devices are
commonly applied to control and adjust the ozone generation rate.
Equipment normally associated with the ozone oxidation process in-
cludes oxygen generator, columns-towers, ozone auxiliary equipment,
and ozone generator. A flow diagram of the ozone oxidation sys-
tem is shown below.
PURGE
WASTEWATER _J.
INFLUENT
CATALYTIC
"OZONE DECOMP.
RECYCLE GAS
—EFFLUENT
STAGED CONTACTOR
DEAERATOR
Date: 6/23/80
IV.5.14-1
-------
IV.5.14.2 Typical Design Criteria
Typical design criteria for an ozone oxidation system are shown
below.
Design criterion Value
Contact time 1-90 min
Dosage rate 10 - 300 mg/L
Ozone production 4.5 kWh/lb from oxygen
7.5 kWh/lb from air
pH range 5-11 (6-8 optimum)
IV.5.14.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes deaerators, process pump, in-
jector", mixers, reactors, holding tanks, oxygen compressors,
dryers, ozone generators, sumps and draws, ozone decomposer, and
ozone Dosage of 55 mg/L derived from an oxygen feed.
IV.5.14.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.5.14-2
-------
TOTAL CAPITAL INVESTMENT
10,000 F
1,000 r
CO
o
o
u_
o
CO
100 r
OZONE LOAD, #/day
Date: 6/23/80
IV.5.14-3
-------
o
p>
ft
O\
\
ro
MILLIONS OF DOLLARS/YEAR
00
o
en
O
O
-------
iv.5.is CHEM'ICAL REDUCTION [i]
IV.5.15.1 Description
Chemical reduction is used to reduce metals to less toxic oxida-
tion states. Reduction-oxidation or "redox" reactions are those
in which the oxidation state of at least one reactant is raised
while that of another is lowered. In the reaction
2H2CrOu + 3S02 + 3H20 - Cr2 (SO*)3 + 5H20 (1)
the oxidation state of Cr changes from 6+ to 3+ (Cr is reduced);
the oxidation state of S increases from 2+ to 3+ (S is oxidized).
This change of oxidation state implies that an electron was trans-
ferred from S to Cr(Vl). The decrease in the positive valence
(or increase in the negative valence) with reduction takes place
simultaneously with oxidation in chemically equivalent ratios.
Reduction is used to treat wastes in such a way that the reducing
agent lowers the oxidation state of a substance in order to reduce
its toxicity, reduce its solubility, or transform it into a form
that can be more easily handled.
The base metals are good reducing agents, as evidenced by the use
of iron, aluminum, zinc, and sodium compounds for reduction treat-
ments. In addition, sulfur compounds also appear among the more
common reducing agents.
Liquids are the primary waste form treatable by chemical reduction.
The most powerful reductants are relatively nonselective; there-
fore, any easily reducible material in the waste stream will be
treated. For example, in reducing heavy metals to remove them
from a waste oil, quantities of esters large enough to cause odor
problems may also be formed by the reduction.
Gases such as chlorine dioxide and chlorine have been treated by
reducing solutions for the small-scale disposal of gas in labor-
atories. For reduction of fluorine, instead of a solution, a
scrubber filled with solid bicarbonate, soda lime or granulated
carbon is recommended. Reduction has limited application to slur-
ries, tars, and sludges, because of the difficulties of achieving
intimate contact between the reducing agent and the hazardous con-
stituent; consequently, the reduction process would be very
inefficient.
In general, hazardous materials occurring as powders or other solids
usually have to be solubilized prior to chemical reduction. The
first step of the chemical reduction process is usually the adjust-
ment of the pH of the solution to be treated. With sulfur dioxide
treatment of chromium (VI), for instance, the reaction requires a
pH in the range of 2 to 3. The pH adjustment is done with the
appropriate acid (e.g., sulfuric). This is followed by addition of
the reducing agent. Mixing is provided to improve contact between
Date: 6/23/80 IV.5.15-1
-------
the reducing agent and the waste. The agent can be in the form
of a gas (sulfur dioxide) or solution (sodium borohydride) or per-
haps finely divided powder if there is adequate mixing. Reaction
times vary for different wastes, reducing agents, temperatures,
pH, and concentration. For commercial-scale operations for treat-
ing chromium wastes, reaction times are in the order of minutes.
Additional time is usually allowed to ensure complete mixing and
reduction. Once reacted, the reduced solution is generally sub-
jected to some form of treatment to settle or precipitate the re-
duced material. A treatment for the removal of what remains of
the reducing agent may be included. This can be unused reducing
agent or the reducing agent in its oxidized state. Unused alkali
metal hydrides are decomposed by the addition of a small quantity
of acid. The pH of the reaction medium is typically increased so
that the reduced material will precipitate out of solution.
Filters or clarifiers are often used to improve separation.
While some stream components may be added or removed, the output
stream from a chemical reduction treatment is not very different
from the input stream. Reducing agents, such as sodium borohyride
and zinc, introduce to the reaction mixture ions that are not easily
separable from the product streams. The effluent solution is typ-
ically acidic and must be neutralized prior to discharge with mate-
rials such as hydrated lime, caustic soda, or soda ash.
Equipment normally associated with chemical reduction processes
includes storage and contact vessels, metering equipment, agitators,
and instrumentation for determination of pH and degree of comple-
tion of the reduction reaction. A flow diagram of a chemical re-
duction system is shown below.
500 gel
ACID STORAGE
2,500 gal
TREATMENT TANK
1 t
-Q-
ROTARY FILTER
(50 ft»)
J,
-Q-
POLISHING
FILTER (50 ft')
i
0-i( *Vm V^
EFFLUENT
BACK FLUSH
FILTER CAKE Vft SOLIDS
(SEE SECTION IV.7)
TREATMENT: BATCH
HASTE: CONCENTRATED CHROME WASTE
100,000 ppm CrOj; B5J is Cr
IN 20tH,SO.
WASTE PROCESSING CAPACITY:
OPERATING PERIOD:
+3
2,000 gal/sMft
240 days/yr
8 hours/day
RAW MATERIALS:
240 Ib/day SO,
2,065 Ib/day line
Date: 6/23/80
IV.5.15-2
-------
IV.5.15.2 Typical Design Criteria
The design parameters for a chemical reduction treatment process
are dependent on a variety of factors, such as the flow rate,
and the utilized reductant. For instance, with sulfur dioxide
treatment of chromium (VI) the reaction requires a pH of 2 to 3.
A typical chromium (VI) treatment process using sulfur dioxide
needs 240 Ib/day of sulfur dioxide and 2,065 Ib/day of lime based
on a waste processing capacity of 2,000 gal per shift. In gen-
eral, contact times range from 1 to 5 minutes.
IV.5.15.3 Costs
The cost of treatment at individual plant locations and on indi-
vidual wastes varies greatly. Capital costs depend upon such
factors as the type, volume, and composition of the waste; degree
of treatment required; treatment process selected; availability
of required services; and the specific material to be recovered
(i.e., metals, chemicals, or water). For the purpose of cost
estimating, data are generated for the chemical reduction of chro-
mium waste from a plating operation using sulfur dioxide treatment.
A flow diagram of this system and its operating characteristics
was presented in Section IV.5.15.1.
Cost item
Direct operating cost
Labor
Operating
Maintenance
Annual
quantity
2 , 500 man-hr
Cost per unit
quantity
$16/hr
Annual cost, $
40,000
4,700
44,700
Chemicals
Sulfur dioxide 29 tons $158/ton 4,600
Lime 250 tons $33.5/ton 8,400
13,000
Power 35,000 kWh S0.035/kWh 1,200
Materials 4,900
Total 63,800
Total indirect
operating cost 84,500
Total annual
operating cost 193,000
Date: 6/23/80 IV.5.15-3
-------
Cost curves were developed for the total capital investment and
annual operating cost using the cost data shown on the previous
page and the following exponential scaling factors, which were
used to determine costs at varying flowrates:
Cost item Exponential factor
Total capital investment 0.7
Labor 0.3
Power and chemicals 1.0
IV.5.15.4 References
1. Physical, Chemical, and Biological Treatment Techniques for
Industrial Wastes, PB 275 287, U.S. Environmental Protection
Agency, Washington, D.C., November 1976. pp. 38-1 to 38-13.
Date: 6/23/80 IV.5.15-4
-------
TOTAL CAPITAL INVESTMENT
o
oo
o
in .
1U
i n
1. U
Om
. UI
0.1
-
r •
i i i i 1 1 n
301 0.
K«*
<£$s
•d^x ~>J
^Jjx t^y
i i i 1 1 1 1 1
01 0.
X
ENR INDEX • 3119
i i i i i 1 1 1
1 1(
Cr03LOAD, Cr03#/day
Date: 6/23/80
IV.5.15-5
-------
D
(D
ft
NJ
CO
00
o
H
Ul
I
cr>
MILLIONS OF DOLLARS/YEAR
(TOTAL - LABOR)
o
o
O
-T
O
J^
OL
CO
>
o
m
—j
O
O
o
to
MATERIALS - CHEMICALS - POWER - MATERIALS
-------
IV.6 SLUDGE TREATMENT
IV.6.1 GRAVITY THICKENING [1]
IV.6.1.1 Description
Thickening of sludge consists of the removal of supernatant,
thereby reducing the volume of sludge that requires disposal or
further treatment. Gravity thickening takes advantage of the
difference in specific gravity between the solids and water.
A gravity thickener normally consists of two truss-type steel
scraper arms mounted on a hollow pipe shaft keyed to a motorized
hoist mechanism. A truss-type bridge is fastened to the tank
walls or to steel or concrete columns. The bridge spans the tank
and supports the entire mechanism. The thickener resembles a
conventional circular clarifier with the exception of having a
greater bottom slope.
Sludge enters at the middle of the thickener, and the solids
settle into a sludge blanket at the bottom. The concentrated
sludge is very gently agitated by the moving rake, which dis-
lodges gas bubbles and prevents bridging of the sludge solids.
It also keeps the sludge moving toward the center well from which
it is removed. Supernatant liquor passes over an effluent weir
around the circumference of the thickener. In the operation of
gravity thickeners, it is desirable to keep a sufficiently high
flow of fresh liquid entering the concentrator to prevent the
development of septic conditions and resulting odors.
Gravity thickening is characterized by zone settling. The four
basic settling zones in a thickener are:
• The clarification zone at the top containing the relatively
clear supernatant
• The hindered settling zone where the suspension moves down-
ward at a constant rate and a layer of settled solids begins
building from the bottom of the zone.
• The transition zone characterized by a decreasing solids
settling rate
• The compression zone where consolidation of sludge results
solely from liquid being forced upward around the solids
Date: 6/23/80 IV.6.1-1
-------
Gravity thickener tanks can be square or round; the round variety
is much more prevalent. Tanks can be manufactured of concrete or
steel. Chemicals can be added to aid in the sludge dewatering.
Equipment normally associated with gravity thickening systems in-
cludes sedimentation units and chemical feed equipment. A flow
diagram of a gravity thickener is shown below.
WATER LEVEL
INFLUENT
EFFLUENT
WEIR
RAISED POSITION
OF TRUSS ARM
HOPPER PLOW
IV.6.1.2 Typical Design Criteria
UNDERFLOW
(SEE SECTION IV.7)
SCRAPER BLADES
Detention times of one to three days are generally used. Sludge
blankets at least three feet deep are common. Side water depths
are at least ten feet in general practice. The following tabula-
tion represents a performance summary with no chemical conditioning,
Type of sludge
Solids surface
loading,
lb/d/ft2
Thickened sludge
solids
concentration, %
Primary
Waste activated
Trickling filter
Limed tertiary
Primary and activated
Primary and trickling filter
Limed primary
20
5
8
6
10
20
- 30
- 6
- 10
60
- 10
- 12
- 25
8
2.5
7
12
4
7
7
- 10
- 3
- 9
- '15
_ *j
- 9
- 12
IV.6.1.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes the thickener and all related
mechanical equipment. Pumps are not included. Total annual
operating costs do not include polymer addition. The following
operating characteristics were assumed for cost estimation:
Date: 6/23/80
IV.6.1-2
-------
Operating characteristic Assumed value
Thickening of secondary sludge 820 Ib/Mgal
Loading 6 Ib/ft2/d
To adjust costs for alternative sludge quantities, concentrations,
and thickening properties, calculate the effective sludge load,
L , using the following equation:
_ 6 Ib/ft2/d new design sludge mass
e Design x new design mass loading x 820 Ib/Mgal
IV.6.1.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.6.1-3
-------
TOTAL CAPITAL INVESTMENT
l.OOOp
CO
oc
o
o
u-
O
CO
100
10
1.0
ENR INDEX = 3119
i i i i 1111
10
SLUDGE LOAD, Tons of DRY SOLIDS/day
Date: 6/23/80
IV.6.1-4
-------
o
0)
ft
(D
MILLIONS OF DOLLARS/YEAR
OJ
CO
o
I
ui
CO
I—
o
m
i—
O
O
o
O
t/>
Si
D)
er> i
O
TJ
O
o
o
CO
-------
IV.6.2 FLOTATION THICKENING [1]
IV.6.2.1 Description
Flotation (dissolved air flotation) thickening utilizes air to
float sludge to the surface of the thickener, thereby reducing
the water content and volume of the sludge.
In a dissolved air flotation (DAF) system, a recycled subnatant
flow is pressurized from 30 to 70 lb/in.2 (gage) and then satu-
rated with air in a pressure tank. The pressurized effluent is
then mixed with the influent sludge and subsequently released into
the flotation tank. The excess dissolved air then separates from
solution, which is now under atmospheric pressure, and the minute
(average diameter 80 ym) rising gas bubbles attach themselves to
particles that form the floating sludge blanket. The thickened
blanket is skimmed off and pumped to the downstream sludge hand-
ling facilities while the subnatant is returned to the plant.
Polyelectrolytes are frequently used as flotation aids to enhance
performance and create a thicker sludge blanket. A description
of the DAF process in general is presented in Section IV.3.4.
Equipment normally associated with a flotation thickening system
includes dissolved air flotation units and air compressors. A
flow diagram for a flotation thickening system is shown below.
SKIMMER MECHANISM
PRESSURE TANK
(
LIBNATANT |~"
RECYCLED _
JSUBNATANT~
n J >>>
/RKFynwF^ [THICKENED
'RISE ZONE W. j
k. ^BOTTOM > \— —,
T~ rni i FPTOP v. '
"^^j
RECYCLEU
SUBNATANT
1 — INFLUENT
ci \\nr.f
AUXILIARY
" RECYCLE
IV.6.2.2 Typical Design Criteria
Typical design criteria for flotation thickening are shown on
the next page.
Date: 6/23/80
IV.6.2-1
-------
Design criteria
Value
Pressure
Effluent recycle ratio
Air-to-solids ratio
Solids loading
Polyelectrolyte addition
(when used)
Solids capture
Total solids in
unthickened sludge
Total solids in
thickened sludge
Hydraulic loading
30 - 70 lb/in.2 gage
30 - 150% of influent flow
0.005 -0.06 Ib air/lb
solids
5-55 Ib/ft2/d (depending
on sludge type and
whether flotation aids
are used)
5-10 Ib/ton of dry solids
70 - 98+%
0.3 - 2.0%
3 - 12%
0.4 - 2.0 gpm/ft2
Conditions for specific sludge types are shown below.
Sludge type
Primary + WAS*
Primary + (WAS + FeCl3)
(Primary + FeCla) + WAS
WAS
WAS + FeCls
Digested primary + WAS
Digested primary + (WAS + FeCl3)
Tertiary, alum
Feed
solids
concentra-
tion, %
2.0
1.5
1.8
1.0
1.0
4.0
4.0
1.0
Typical loading
rate without
polymer ,
Ib/ftVd
20
15
15
10
10
20
15
8
Typical loading
rate with
polymer.
Ib/ftVd
60
45
45
30
30
60
45
24
Float
solids
concentra-
tion, %
5.5
3.5
4.0
3.0
2.5
10.0
8.0
2.0
*Waste activated sludge.
IV.6.2.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes the flotation chamber (2 hr
detention time based on sludge flow), pressure tanks (60 lb/in.2
gage), and recycle pumps (100% recycle). The following operating
characteristics were assumed for cost estimation.
Operating characteristic
Assumed value
Thickening of secondary sludge
Loading rate
Operating hours
820 Ib/Mgal
2 Ib/ft2/hr
0.1 and 1 Mgal/d =40 hr/wk
10 Mgal/d =100 hr/wk;
100 Mgal/d =168 hr/wk
Date: 6/23/80
IV.6.2-2
-------
To determine costs at loading rates or sludge quantities other
than those specified on the previous page, calculate the effec-
tive flow using the following equation:
_ 2 Ib/ft2/hr new design sludge mass
E Design new design mass loading rate 820 Ib/d/Mgal
IV.6.2.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.6.2-3
-------
TOTAL CAPITAL INVESTMENT
100 F
10
oc.
o
Q
LL.
O
CO
O
1.0
0.1
0.01
0.001
i i i i 1111
j i i i 11 j i
ENR INDEX = 3119
j i l i i 11
0.01
0.1
1.0
10
SLUDGE LOAD, Tons of DRY SOLIDS/day
Date: 6/23/80
IV.6.2-4
-------
o
p»
rt
MILLIONS OF DOLLARS/YEAR
ro
to
oo
o
10
I
U1
00
o
m
5
o
o
5D
CO
O
Ol
P
8
o
CD
o
o
CO
-------
IV.6.3 CENTRIFUGAL THICKENING [1]
IV.6.3.1 Description
Centrifugal thickening is the thickening of sludges using disc,
basket, or solid-bowl centrifuges.
Centrifuges may be used to thicken sludges by the use of centri-
fugal force to increase the sedimentation rate of sludge solids.
The three most common types of units are the continuous solid-bowl
type, the disc type, and the basket type. Refer to Section
IV.6.12 for unit descriptions.
Equipment normally associated with a centrifugal thickening sys-
tems includes the centrifuge, sludge feed pump, solids conveyor,
and concentrate pumps. A flow diagram of a centrifugal thicken-
ing system is shown below.
PRIMARY
EFFLUENT
RETURN ACTIVATED SLUDGE
AERATOR
OVERFLOW
SLUDGE
JL
CENTRIFUGE
SECONDARY
CLARIFIER
SLUDGE
UNDERFLOW
DEGRITTING
AND SCREENING
EFFLUENT
REQUIRED FOR DISC
TYPE CENTRIFUGES
ONLY
TO DISPOSAL (SEE SECTION IV.7)
IV.6.3.2 Typical Design Criteria
Installation of centrifugal thickening systems is site-specific
and dependent upon a manufacturer's product line. Maximum capac-
ities of about 100 tons/hr of dry solids are available in solid-
bowl units with diameters up to 54 in. and power requirements up
to 175 hp. Disc units are also available with capacities up to
400 gpm of concentrate.
IV.6.3.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes the centrifuge, drive motor,
screens, strainer, pumps, and degritting system for a disc cen-
trifuge. For a solid-bowl centrifuge unit, these costs include
the centrifuge and drive motor only. All units are designed to
handle 820 Ib/Mgal of dry solids at 0.8% concentration. Polymer
costs are not included. Labor costs were assumed at $15/man-hour,
Date: 6/23/80
IV.6.3-1
-------
The total capital investment and total annual direct operating
costs for disc and solid-bowl centrifuges are shown below based
on an ENR Index of 3119. The following cost estimation was
based on a disc and solid-bowl type with a flow rate of
300-500 gpm.
Influent
Centrifuge sludge
Total capital
Annual operating and
maintenance cost, $
Total annual
direct
operating
type
Disc
Solid-bowl
flow,
100 -
150 -
300 -
50 -
up to
up to
gpm
150
300
550
60
150
400
investment, $
457,
687,
914,
413,
794,
1,484,
000
000
000
000
000
000
Power Material
11,
22,
40,
6,
14,
39,
000
000
400
000
900
700
2,300
3,500
6,900
2,100
4,000
7,500
Labor
13,
13,
13,
9,
9,
9,
000
000
000
200
200
200
cost, $
26
38
60
17
28
56
,300
,500
,300
,300
,100
,400
Power cost is based on maximum influent sludge flow return.
centrifuge drive requirements are considered.
IV.6.3.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Only
Date: 6/23/80
IV.6.3-2
-------
TOTAL CAPITAL INVESTMENT
(DISC)
100 F
to
o:
f
O
to
10 -
1.0 -
0.1 r
0.01 r
0.001
ENR INDEX = 3119
i i i M 11
0.1
1.0
10
100
FLOW, Mgal/d
Date: 6/23/80
IV.6.3-3
-------
ANNUAL OPERATING COST
(DISC)
100 p
10
on
zs
CO
1.0
o
o
U-
o
CO
§ 0.1
0.01
0.001
i i 11ii
ENR INDEX - 3119
i i i 11111
0.1
1.0
10
100
FLOW, Mgal/d
Date: 6/23/80
IV.6.3-4
-------
TOTAL CAPITAL INVESTMENT
(SOLID BOWL)
100 F
CO
O
O
u_
O
to
10 -
0.001
0.1
1.0
10
100
FLOW, Mgal/d
Date: 6/23/80
IV.6.3-5
-------
o
0)
rt
to
CO
00
o
U)
MILLIONS OF DOLLARS/YEAR
8
g
O
O
-------
IV.6.4 AEROBIC DIGESTION [1]
IV.6.4.1 Description
Aerobic digestion is a method of sludge stabilization in an open
tank that can be regarded as a modification of the activated
sludge process. In the aerobic digestion system, microbiological
activity beyond cell synthesis is stimulated by aeration, oxidiz-
ing both the biodegradable organic matter and some cellular mate-
rial into C02, H20, and N03. The oxidation of cellular matter is
called endogenous respiration and is normally the predominant
reaction occurring in aerobic digestion. Stabilization is not
complete until there has been an extended period of primarily
endogenous respiration (typically 15 to 20 days).
Major objectives of aerobic digestion include odor reduction,
reduction of biodegradable solids, and improved sludge dewater-
ability. Aerobic bacteria stabilize the sludge more rapidly than
anaerobic bacteria, although a less complete breakdown of cells
is usually achieved. Oxygen can be supplied by surface aerators
or by diffusers. Other equipment may include sludge recircula-
tion pumps and piping, mixers, and scum collection baffles.
Aerobic digesters are designed similar to rectangular aeration
tanks and use conventional aeration systems, or employ circular
tanks and use an eductor tube for deep tank aeration.
Both one- and two-tank systems are used. Small plants often use
a one-tank batch system with a complete mix cycle followed by
settling and decanting (to help thicken the sludge). Larger
plants may consider a separate sedimentation tank to allow con-
tinuous flow and facilitate decanting and thickening. Air may be
replaced with oxygen.
'•9
Typical equipment includes facilities for sludge handling, sludge
control, aeration, as well as pumps and mixers. A flow diagram of
an aerobic digestion system is shown below.
PRIMARY SLUDGE
EXCESS ACTIVATED OR
TRICKLING FILTER SLUDGE
i
"1
UJ
'• ** \*'~
•%^LJI«i'~ *> f ?• J*JUJ
il ,*-* "<#• •-- -X
.^••.VJL^^t^V^V
;>« V-4C.-., '^'^;''.'-V-^->;N% i
r ' o
C
C
MM
. ^r
CLEAR OXIDIZED
OVERFLOW TO PLANT
SETTLED SLUDGE RETURNED TO DIGESTER
(SEE SECTION IV.7)
Date: 6/23/80
IV.6.4-1
-------
IV.6.4.2 Typical Design Criteria
Typical design criteria for an aerobic digestion system are
listed below.
Design criteria
Value
Solids retention time for
40% reduction in volatile
suspended solids (VSS)
Volume allowance
VSS loading
Air requirements
Minimum dissolved oxygen
Energy for mechanical mixing
Oxygen requirements
18 - 20 d for mixed sludges from
activated sludge or trickling
filter plant; 10 - 16 d for waste
activated sludge only; 16 - 18 d
for activated sludge from plants
without primary settling
3-4 ftVcapita
0.02 - 0.4 Ib/ft3/d
20 - 60 ft3/min/l,000 ft3
1-2 mg/L
0.75 - 1.25 hp/1,000 ft3
2 Ib/lb of cell tissue destroyed
(includes nitrification demand);
1.6 - 1.9 Ib/lb of BOD removed in
primary sludge
IV.6.4.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes basins (20-day detention time),
sludge flow at 5,700 gal/Mgal (1,900 Ib/Mgal at 4% solids), and
floating mechanical aerators. In addition, power was determined
using 1.6 Ib 02/lb VSS destroyed (not including nitrification),
and 40% VSS destruction with mechanical aerators at 1.5 Ib O2/
hp IV.
To adjust costs for design factors different from those above,
calculate the effective flowrate (Q ) using the following
equation:
_ new design retention time new design sludge mass
QE ~ ^Design X 20 days X 1,900 Ib/Mgal X
4%
new design sludge concentration
IV.6.4.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80
IV.6.4-2
-------
TOTAL CAPITAL INVESTMENT
100 p
to
Q£
<
O
O
to
O
10 r
ENR INDEX = 3119
i i i i 111
0.001
SLUDGE LOAD, Ib/day
Date: 6/23/80
IV.6.4-3
-------
cri
tsj
OJ
CO
o
MILLIONS OF DOLLARS/YEAR
s
o
CD
C/l
o
o
o
o
DJ
o
TJ
O
o
o
CO
-------
IV.6.5 ANAEROBIC DIGESTION [1]
IV.6.5.1 Description
Anaerobic digestion is a process for the breakdown of sludge into
methane, carbon dioxide, unusable intermediate organics, and a
relatively small amount of cellular protoplasm.
The anaerobic digestion system consists of two vessels that are
used for sludge stabilization. The first tank, used for digestion,
is equipped with one or more of the following: heater, sludge
recirculation pumps, methane gas recirculation, mixers, and scum
breaking mechanisms. The second tank is used to store and concen-
trate the digested sludge and to form a supernatant.
The anaerobic digestion process consists of two distinct simul-
taneous stages of conversion of organic material by acid-forming
bacteria and gasification of the organic acids by methane-forming
bacteria. The methane-producing bacteria are very sensitive to
conditions of their environment and require careful control of
temperature, pH, excess concentrations of soluble salts, metal
cations, oxidizing compounds, and volatile acids. They also show
an extreme substrate specificity. The digester requires periodic
cleanout (from 1 to 2 years) due to buildup of sand and gravel on
the digester .bottom.
Typical equipment includes sludge handling and control units,
pumps, heating equipment, digestion tank equipment, and gas
holders. A flow diagram of the two-stage anaerobic digestion
system is shown below.
wnj
IM-LLTIJI. ^*- ~^\3I\
SLUDGE INLET _ Zx^- F
~j ^MIXING
ACTIVELY
IsDIGESTING^
j l\Ll-l_r\j
MIXED
LIQUOR
k ^
- SLUDGE -
DRAW/OFF
')^ GAS^^X
SUPERNATANT
DIGESTED SLUDGE
X^>
SUPERNATANT
REMOVAL
SLUDGE RETURN
(SEE SECTION IV.7)
IV.6.5.2 Typical Design Criteria
Typical design criteria for anaerobic digestion are shown on the
next page.
Date: 6/23/80
IV. 6.5-1
-------
Design criteria
Value
Solids retention time (SRT)
Tank size
Solids loading
PH
Depends on temperature; SRT in meso-
phitic range include 55 d @ 50°F;
40 d § 67°F; 30 d @ 75°F; 25 d @
85°F; and 20 d @ 95°F
20 - 115 ft diameter; 25 - 45 ft
depth; bottom vertical slope = 1
vertical/4 horizontal
0.04 - 0.40 Ib VSS/ft3/d
6.7 - 7.6
IV.6.5.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes the digester, heat exchanger,
gas collection equipment, and control building. The following
operating characteristics were assumed for cost estimation.
Operating characteristics
Assumed value
Service life
Feed to digester
(primary and secondary
are combined)
Effluent from digesters
Loading rate
Operating temperature
Gas utilization
50 yr
1,900 Ib/Mgal at 4% solids
(75% volatile)
900 Ib/Mgal at 2.5% solids
0.16 Ib/ft3/d
85 - 110°F
Digester gas utilized for
heating; excess not
utilized
IV.6.5.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80
IV. 6.5-2
-------
TOTAL CAPITAL INVESTMENT
l.OOOp
on
0£
g
o
es
2
O
100
10
1.0
0.1
0.01
I I I I I I 11 1 1 I I II
ENR INDEX = 3119
i i i i i 111
10
io5
SLUDGE LOAD ING, Ibs/day
Date: 6/23/80
IV. 6.5-3
-------
o
0)
rt
(D
to
oo
o
MILLIONS OF DOLLARS/YEAR
H
n
O
•u
m
O
O
O
en
-------
IV.6.6 CHEMICAL CONDITIONING [1]
IV.6.6.1 Description
Chemical conditioning is a process for coagulating sludge solids
and releasing absorbed water.
The use of chemicals to condition sludge for dewatering is econ-
omical because of the increased yields and greater flexibility
obtained.
Chemicals are most easily applied and metered in liquid form.
Dissolving tanks are needed if the chemicals are received as dry
powder. These tanks should be large enough for at least one-
day's supply of chemicals and should be furnished in duplicate.
They must be fabricated or lined with corrosion-resistant mate-
rial. Polyvinyl chloride, polyethylene, and rubber are suitable
materials for tank and pipe linings for handling acid solutions.
Metering pumps, which must be corrosion resistant, are generally
of the positive-displacement type with variable-speed or var-
iable-stroke drives to control the flowrate. Another metering
system consists of a constant-head tank supplied by a centrifugal
pump. A rotameter and throttling valve are used to meter the
flow.
The chemical dosage required for any sludge is determined in the
laboratory. Filter-leaf test kits are used to determine chemical
doses, filter yields, and the suitability of various filtering
media. These kits have several advantages over the Biichner fun-
nel procedure. In general, it has been observed that the type
and concentration of sludge has the greatest impact on the
quantity of chemical required. Sludges at less than 4 to 5%
solids and difficult-to-dewater sludges require larger doses of
chemicals and generally do not yield as dry a cake. Sludge
types, listed in the approximate order of increasing chemical
requirements for conditioning, are as follows:
Untreated (raw) primary sludge
Untreated mixed primary and trickling-filter sludge
Untreated mixed primary and waste activated sludge
Anaerobically digested primary sludge
Anaerobically digested mixed primary and waste activated
sludge
Aerobically digested sludge (normally dewatered on drying
beds without the use of chemicals for conditioning).
Intimate admixing of sludge and coagulant is essential for proper
conditioning. The mixing must not break the floe after it has
formed, and the detention is kept to a minimum so that sludge
reaches the filter as soon after conditioning as possible.
Mixing tanks are generally of the vertical type for small
plants and of the horizontal type for large plants. They are
Date: 6/23/80 IV.6.6-1
-------
ordinarily built of welded steel and lined with rubber or other
acid-proof coating.
A typical layout for a mixing or conditioning tank has a hor-
izontal agitator driven by a variable-speed motor to provide a,
shaft speed of 4 to 10 r/min. Overflow from the tank is adjus-
table to vary the detention period. Vertical cylindrical tanks
with propeller mixers are also used.
IV.6.6.2 Typical Design Criteria
The dosage of inorganic chemicals for various types of sludges
for vacuum filtration is shown below (conditioners are shown in
percentage of dry sludge). Due to ease of handling, both
cationic and anionic polymers are finding increased usage in
view of inorganic chemicals.
Fresh
solids
Type of sludge
Primary
Primary and
trickling filter
Primary and
activated
Activated (alone)
FeCl3
1-2
2-3
1.5-2.5
4-6
CaO
6-8
6-8
7-9
Digested
FeCl3
1.5-3.5
1.5-3.5
1.5-4
CaO
6-10
6-10
6-12
Elutriated,
digested
FeCl3 CaO
2-4
2-4
2-4
IV.6.6.3 Costs
Costs. Purchased equipment and installation cost for esti-
mation of the total capital investment includes primary sludge
pumps, clarifiers, liquid ferric chloride, chemical feed equip-
ment sized for twice the average feed rate, storage for at least
15 days, rapid mix tank, stainless steel mixer, and building
(except for plants with a capacity less than 1 Mgal/d). The
rapid mix tank is constructed of concrete, and multiple basins
are used for volumes greater than 1,500 ft3. Costs are based on
primary circular clarification with ferric chloride addition.
A ferric chloride dosage of 100 mg/L was assumed for cost esti-
mation. A dosage of 5% of ferric chloride was used as a per-
centage of dry primary sludge in deriving the chemical cost.
To adjust costs at the effective flow (Q ) for different FeCl3
dosages, use the following equation:
n = n v FeCl3dosage
UE ^Design 100 mg/L
Date: 6/23/80 IV.6.6-2
-------
IV.6.6.4 References
1. Metcalf and Eddy, Wastewater Engineering - Treatment, Dis-
posal, Reuse, McGraw-Hill, Inc., 1979. pp. 634-636.
Date: 6/23/80 IV.6.6-3
-------
TOTAL CAPITAL INVESTMENT
GO
on
d
o
u_
O
GO
100 p
10
1.0
0.1
0.01
0.001
J I I I 1 111
I I I I 1111
ENR INDEX = 3119
0.1
1.0
10
100
FLOW, Mgal/d
Date: 6/23/80
IV.6.6-4
-------
D
CU
ft
MILLIONS OF DOLLARS/YEAR
U)
CO
o
HI
<
•
CT>
I
Ul
ot
P
8
o
CD
r>
o
en
-------
IV.6.7 THERMAL CONDITIONING (HEAT TREATMENT OF SLUDGE) [1]
IV.6.7.1 Description
Heat treatment is essentially a conditioning process that pre-
pares sludge for dewatering on vacuum filters or filter presses
without the use of chemicals.
The heat treatment process involves heating sludge to 144°C to
210°C for short periods of time under pressure of 150 to
400 lb/in.2 gage. In addition, the sludge is sterilized and
generally stabilized and rendered inoffensive. Heat treatment
results in coagulation of solids, a breakdown in the cell struc-
ture of sludge, and a reduction of the water affinity of sludge
solids.
Several proprietary variations exist for heat treatment. In
these systems, sludge is passed through a heat exchanger into a
reactor vessel, where steam is injected directly into the sludge
to bring the temperature and pressure into the necessary ranges.
In one variation, air is also injected into the reactor vessel
with the sludge. The detention time in the reactor is approxi-
mately 30 minutes. After heat treatment, the sludge passes back
through the heat exchanger to recover heat, and then is dis-
charged to a thickener-decant tank. The thickened sludge may be
dewatered by filtration or centrifugation to a solids content of
30 to 50 percent. The sludge may be ground prior to heat treat-
ment. A small quantity ('^5% of that required for complete oxi-
dation may be introduced into the reaction to minimize reduced
sulfur type odor.
Complete heat treatment systems are generally proprietary, and
the most common systems are supplied by five manufacturers. The
major equipment common to these processes are grinders, sludge
feed pumps and handling equipment, heat exchangers, reactors,
boilers, and separators. A flow diagram of the heat treatment
system is shown below.
t
1
SLUDGE
GRINDER
fe
SLUDGE
STORAGE
' VAPOR
CONDITIONED SLUDGE
HEAT
EXCHANGER
DECANTER
FEED
WATER
0
REAC
i
2
TOR
STEAM
BOILER
(SEE SECTION IV.7)
Date: 6/23/80
IV.6.7-1
-------
IV.6.7.2 Typical Design Criteria
Typical design criteria for a heat treatment system are listed
below.
Design criteria Value
Temperature 140-210°C
Pressure 150-400 lb/in.2 gage
Detention time 30-90 min
Steam consumption 600 lb/1,000 gal of sludge
IV.6.7.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes sludge feed pumps, grinders,
heat exchangers, reactors, boilers, gas separators, and buildings,
Fuel costs are for steam generation. Sludge is assumed to be
4.5% solids with the system operating 3,000 hr/yr.
IV.6.7.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/30/80 IV.6.7-2
-------
TOTAL CAPITAL INVESTMENT
l.OOOp
o
o
u_
O
O
100 r
ENR INDEX = 3119
i i i i M 11
10
•SLUDGE LOAD, Ib/day
Date: 6/23/80
IV.6.7-3
-------
0
(o
rt
(D
cr>
to
U)
00
o
MILLIONS OF DOLLARS/YEAR
H
8
p
o
o
m
O
O
o
20
CL
01
O
•o
m
50
o
o
o
-------
IV.6.8 DISINFECTION (HEAT) [1]
IV.6.8.1 Description
Heating to pasteurization temperatures is a well known method of
destroying pathogenic organisms that has been applied success-
fully for disinfecting sludge. Pasteurization implies heating to
a specific temperature for a time period sufficient to destroy
undesirable organisms in sludge and to make sludge suitable for
land disposal on cropland. Usually heat is applied at 70 to 75°C
for 20 to 60 minutes. Treatment can be applied to raw liquid
sludge (thickened or unthickened), or stabilized or digested
sludge.
Pasteurization is usually a batch process, consisting of a re-
actor to hold sludge, a heat source, and heat exchange equipment,
pumping and piping, and instrumentation for automated operation.
Pasteurization has little effect on sludge composition or struc-
ture because the sludge is only heated to a relatively moderate
temperature.
Equipment normally associated with the heating process includes
sludge handling and control equipment, heating equipment, and
instrumentation. A flow diagram of the pasteurization system
is shown below.
FEED WATER
BOILER
STEAM
SLUDGE
HOLD ING TANK
PA5TURIZED SLUDGE
(SEE SECTION IV.7)
IV.6.8.2 Typical Design Criteria
Typical design criteria for a pasteurization process are shown
below.
Design criteria
Value
Temperature 70-75°C
Time 20-60 min
Heat required 4-6 x 106 Btu/ton of sludge solids
Operation Two units or more are usually designed
in parallel so that one unit can be
filling while the other is holding
sludge for the required time; units
can share a common boiler.
Date: 6/23/80
IV.6.8-1
-------
IV.6.8.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes steam boiler, pasteurization
tanks, sludge pumping, and automatic controls. The following
design characteristics were assumed for cost estimation:
Design characteristic
Assumed value
Sludge temperature
Sludge solids
Pasteurization temperature
Pasteurization time
Capacity
17°C
5%
70°C
1 hr
Single tank up to 10 tons
of sludge solids per
day; two tanks above.
IV.6.8.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80
IV.6.8-2
-------
TOTAL CAPITAL INVESTMENT
10
2
1.0
o
d
0.1
0.01
1.0
J I J 1 J I I I
I I I I I I I I
ENR INDEX-3119
l i I I I I I
10 100
SLUDGE LOAD, Tons of DRY SOLIDS/day
1,000
Date: 6/23/80
IV.6.8-3
-------
D
rt
cr\
fO
OJ
oo
o
MILLIONS OF DOLLARS/YEAR
00
I
p
8
O
>
o
o
o
o
I/)
(FUEL - LABOR)
-------
IV.6.9 VACUUM FILTRATION [1]
IV.6.9.1 Description
Vacuum filters are used to dewater sludges so as to produce a
cake having the physical handling characteristics and moisture
contents required for subsequent processing.
A rotary vacuum filter consists of a cylindrical drum rotating
partially submerged in a vat or pan of conditioned sludge. The
drum is divided radially into a number of sections, which are
connected through internal piping to ports in a valve body
(plate) at the hub. This plate rotates in contact with a fixed
valve plate with similar ports, which are connected to a vacuum
supply, a compressed air supply, and an atmospheric vent. As
the drum rotates, each section is thus connected to the appropri-
ate service. Various operating zones are encountered during a
complete revolution of the drum. In the pickup or form section,
vacuum is applied to draw liquid through the filter covering
(media) and form a cake of partially dewatered sludge. As the
drum rotates, the cake emerges from the liquid sludge pool, while
suction is maintained to promote further dewatering. A lower
level of vacuum often exists in the cake drying zone. A scraper
blade may be provided for sludge removal, followed by a waste-
water spray to clean the media.
The three principal types of rotary vacuum filters are the drum
type, coil type, and the belt type. The filters differ primarily
in the type of covering used and the cake discharge mechanism
employed. Cloth media are used on drum and belt types; stainless
steel springs are used on the coil type. Infrequently, a metal
media is used on belt types. The drum filter also differs from
the other two in that the cloth covering does not leave the drum
but is washed in place, when necessary. The design of the drum
filter provides considerable latitude in the amount of cycle
time devoted to cake formation, washing, and dewatering; the
design also minimizes inactive time.
The top feed drum filter is a variation of the conventional
drum filter. In this case, sludge is fed to the vacuum filter
through a hopper located above the filter. The potential advan-
tages of the top feed drum filter are that gravity aids in cake
formation; capital costs may be lower since the feed hopper is
smaller and no sludge agitator and related drive equipment are
required; and "blinding" of the media may be reduced.
The coil-type vacuum filter uses two layers of stainless steel
coils arranged in corduroy fashion around the drum. After a
dewatering cycle, the two layers of springs leave the drum and
are separated from each other so that the cake is lifted off the
lower layer of springs and discharged from the upper layer. Cake
release is essentially free of problems. The coils are then
Date: 6/23/80 IV.6.9-1
-------
washed and reapplied to the drum. The coil filter has been and
is widely used for all types of sludge. However, sludges with
particles that are both extremely fine and resistant to floccula-
tion dewater poorly on coil filters.
Solids loss during cake formation and during media washing pro-
duces high filtrate suspended solids for return to liquid treat-
ment processes.
Media on the belt-type filter leaves the drum surface at the end
of the drying zone and passes over a small diameter discharge
roll to facilitate cake discharge. Washing of the media next
occurs before it returns to the drum and to the vat for another
cycle. This type filter normally has a small diameter curved
bar between the point where the belt leaves the drum and the
discharge roll that aids in maintaining belt dimensional stabil-
ity. In practice, it is frequently used to insure adequate cake
discharge.
Many types of filter media are available for belt and drum
filters. There is some question whether increases in yield due
to operating vacuums greater than 15 inches of mercury are
justifiable. The cost of a greater filter area must be balanced
against the higher power costs for higher vacuums. An increase
from 15 to 20 inches of vacuum is reported to have provided about
10 percent greater yield in three full-scale installations.
Chemical conditioning is often employed to agglomerate a large
number of small particles. It is almost universally applied
with mixed sludges.
Equipment normally associated with the vacuum filtration process
includes the rotary vacuum filter, vacuum pump, filtrate re-
ceiver, filtrate pump, sludge conditioning apparatus, and sludge
conveyors. A flow diagram for a vacuum filtration system is
shown below.
SLUDGE
1
» 1
u
WATER-AIR
SEPARATOR
VACUUM
PUMP
DRUM
SLUDGE CAKE F"-TRATE
(SEE SECTION IV.7)
Date: 6/23/80
IV.6.9-2
-------
IV.6.9.2 Typical Design Criteria
Typical design criteria for vacuum filtration are shown below.
Design criterion
Value
Typical loading for raw
primary sludges
Typical loading for digested
primary sludges
Typical loading for mixed
digested sludges
7-15 Ib dry solids/hr/ft2
4-7 Ib dry solids/hr/ft2
3.5-5 Ib dry solids/hr/ft2
Loading is a function of feed solids concentrations, subsequent
processing requirements, and chemical preconditioning.
IV.6.9.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes pumps, internal piping and
electrical controls, mechanical equipment, conveyors, sludge
cake storage hopper, building, and chemical handling and storage
facilities. Costs are for dewatering of combined primary and
secondary digested sludge consisting of 900 Ib dry solids/Mgal
plant flow or lime sludge consisting of 4,500 Ib dry solids/Mgal
plant flow. The following operating characteristics were as-
sumed for cost estimation:
Operating characteristic
Assumed value
Filter yield
Operation time (excluding
down time for maintenance)
Chemical dosage
FeCl3
CaO
5 lb/ft2 for biological sludge;
8 lb/ft2 for lime sludge
6 hr/d for 1 Mgpd or less;
12 hr/d for 10 Mgpd
35 Ib/Mgal
90 Ib/Mgal
Date: 6/23/80
IV.6.9-3
-------
IV.6.9.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.6.9-4
-------
D
(o
rt
(D
MILLIONS OF DOLLARS/YEAR
N)
Ul
00
o
VO
o
-------
o
D>
rt
(D
N)
U)
vo
o
MILLIONS OF DOLLARS/YEAR
o
•
CD
vo
I
01
to
O
O
§
o
1/1
o
20
to
o
o
•O
m
O
O
O
O
to
-------
10 P
O
Q
u.
O
O1
2
O
0.01 r
0.001 r
ANNUAL OPERATING COST
(BIOLOGICAL SLUDGE)
0.0001
SLUDGE LOAD, Tons of DRY SOLIDS/day
Date: 6/23/80
IV.6.9-7
-------
IV.6.10 FILTER PRESS DEWATERING [1]
IV.6.10.1 Description
The diaphragm filter press is a recent extension of filter press
technology to increase the throughput of a press and provide a
higher solids content in wastewater filter cake. The press makes
use of a rubber diaphragm with pressurized water to provide a
high pressure on the partially dewatered sludge cake in the
press after conventional dewatering methods have been used. This
diaphragm provides the support for the filter cloth on one side
of the press cavity.
Filtration of the sludge is accomplished by charging the chambers
of the press with sludge under pump pressure in the conventional
manner, but at a generally lower pressure, and allowing a cake to
develop. The time alloted to this cycle is dependent upon the
characteristics of the sludge, but is scheduled to continue only
as long as high filtration rates are in progress. This cycle
usually is in the 10- to 30-minute range. The pump pressurizing
system is then turned off, and water pressure is applied inside
the diaphragm. This pressure, in the 200-psi range, applies a
uniform pressure over the cake and further reduces the water con-
tent. The squeezing cycle has been shown to substantially reduce
the overall cycle time for the press yet produce a low-moisture-
content cake. The filter cake produced is thinner than that
obtained in the conventional press but has a uniform moisture
content in contrast to the conventional press. The reduction in
operating time for the sludge pumps is reported to substantially
reduce wear and required maintenance. The pressurized water for
the diaphragm actuation is a closed recycle system; therefore,
components operate under predictable conditions and no effluent
is produced. Diaphragm presses are designed to make use of a
number of automation features to reduce labor and recycle time.
Common modifications include opening of the filter press to allow
simultaneous discharge of filter cake from all cavities, rejec-
tion of the sludge cake by physical movement of the filter cloth
from vibration or actual movement of the cloth in a forced re-
jection mode by partial withdrawal of the filter cloth loop,
automatic washing of filter cloths at each cycle or as conditions
dictate, air purging of feed and filtrate lines between cycles,
and full automation of press operation.
Equipment normally associated with the filter press dewatering
process includes diaphragm filter presses, sludge pumps, cake
conveyors, and sludge conditioning tanks. A flow diagram of
a filter press system is shown on the following page.
Date: 6/23/80 IV.6.10-1
-------
SLUDGE
•CONDITIONING TANK
CAKE (SEE SECTION IV.7)
FILTRATE
DRAIN
IV.6.10.2 Typical Design Criteria
Typical design criteria for a diaphragm filter press are shown
below.
Design criterion
Value
Filter areas
Cake thickness
Sludge yield
Total cycle time
5-40 ftVchamber
1/2-3/4 in.
0.4-0.8 lb/ft2 of filter area
20-50 min
IV.6.10.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes the chemical feed system, sludge
feed pump, dewatering unit with all necessary accessories, and a
conveyor system to transport cake to the next process.
A cost estimate has been derived for use of a diaphragm filter
press in a large multiple-press installation with a sludge cake
production of 250 dry tons/d. Sludge was assumed to be a mix of
2:1 secondary to primary with a feed solids of 5%. Sludge con-
ditioning was assumed to be lime at 20% and FeCl3 at 7% dry sludge
solids. Lime cost was assumed at $44/ton and FeCl3 at $130/ton.
Pricing is based on the largest size presses available. The total
number includes one spare. The capital cost (1978 dollars) in-
cludes the chemical feed system, sludge feed pumps, dewatering
unit with all necessary accessories, and a conveyor system to
transport cake to the next process. The total installation cost
was obtained by utilizing a multiplication factor of 3 which in-
cludes installation, piping, utilities, building, and engineering.
Labor is assumed at $21,000/manyear.
Date: 6/23/80
IV.6.10-2
-------
Item Cost
Cost suinmary
Capital cost $19,500,000
Lime system 1,000,000
FeCl3 system 500,000
Conveyors 2,000,000
Total $23,000,000
Annual costs
Amortization at 9% $ 2,070,000
Chemicals 1,633,000
Power at 66.7 kWh/ton and $0.04/kWh 243,000
Water 12 x 106 gallons 6,400
Labor - operation 504,000
Maintenance -
Cloth and diaphragm replacement-materials 312,000
Labor replacement 31,500
Equipment maintenance at 2% of purchase cost 153,000
Total annual costs $ 4,953,000
Unit cost/dry ton of sludge cake $ 54.28
Costs are in 1978 dollars.
IV.6.10.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.6.10-3
-------
TOTAL CAPITAL INVESTMENT
100 c
00
o
o
00
O
10 r
ENR INDEX-3119
i i i i i it
1.0 10
FLOW, Mgal/d
Date: 6/23/80
IV.6.10-4
-------
o
D)
rt
CO
NJ
U)
00
o
O
I
Ul
ua
O)
MILLIONS OF DOLLARS/YEAR
(TOTAL - POWER - CHEMICALS - LABOR - MATERIALS)
3>
O
S
CO
(WATER)
-------
IV.6.11 BELT FILTER DEWATERING [1]
IV.6.11.1 Description
Belt filter dewatering is the removal of water from sludge using
filtration in the form of rolling belts.
A belt filter consists of an endless filter belt that runs over a
drive and guide roller at each end like a conveyor belt. The
upper side of the filter belt is supported by several rollers.
Above the filter belt is a press belt that runs in the same di-
rection and at the same speed; its drive roller is coupled with
the drive roller of the filter belt. The press belt can be
pressed on the filter belt by means of a pressure roller system
whose rollers can be individually adjusted horizontally and
vertically. The sludge to be dewatered is fed on the upper face
of the filter belt and is continuously dewatered between the
filter and press belts. After having passed the pressure zone,
further dewatering in a reasonable time cannot be achieved by
only applying static pressures; however, a superimposition of
shear forces can effect this further dewatering. The supporting
rollers of the filter belt and the pressure rollers of the pres-
sure belt are adjusted in such a way that the belts and the
sludge between them describe an S-shaped curve. Thus, there is
a parallel displacement of the belt relative to each other due
to the differences in the radii. After further dewatering in
the shear zone, the sludge is removed by a scraper.
Some units consist of two states; the initial draining zone is
on the top level, followed by an additional lower section wherein
pressing and shearing occur. A significant feature of the belt
filter press is that it employs a coarse-mesh, relatively open
weave, metal-medium fabric. This is feasible because of the
rapid and complete cake formation obtainable when proper floc-
culation is achieved. Belt filters do not need vacuum systems
and do not have the sludge pickup problem occasionally exper-
ienced with rotary vacuum filters. The belt filter press system
includes auxiliaries such as polymer solution preparation equip-
ment and automatic process controls.
Some belt filters include the added feature of vacuum boxes in
the free drainage zone. To obtain higher cake solids, a vacuum
of about 6 in. Hg is applied. A "second generation" of belt
filters has extended shearing or pressure states that produce
substantial increases in cake solids but are more costly.
Equipment normally associated with belt filter dewatering process-
es includes the belt filter, chemical feed equipment, cake con-
veyors, and sludge pump. A flow diagram of a belt filter is
shown on the following page.
Date: 6/23/80 IV.6.11-1
-------
SLUDGE INLET PRESS BELT
PRESS ROLLS DRIVE ROLL
CAKE DISCHARGE,
(SEE SECTION IV.7)
DRIVE ROLL
FILTRATE
IV.6.11.2 Typical Design Criteria
The loadings shown below are based on active belt area:
Sludge type
Sludge loading,
gal/ft2/hr
Dry solids loading,
Ib/ft2/hr
Raw primary
Digested primary
Digested mixed/secondary
27-34
20-24
13-17
13.5-17
20.5-24
6.7-8.4
IV.6.11.3 Costs
Purchased equipment and installation cost for estimation of total
capital investment includes the belt filter press, sludge feed
pumps, polymer pumps, and control panels. The following operat-
ing characteristics were assumed for cost estimation:
Operating characteristic
Assumed value
Type of sludge
Sludge production
Dewatering operation
Chemicals polymer
Primary and secondary
(anaerobically digested)
5% solids concentration
7 d/wk
7 d/wk; 16 ur/d
$17,520/yr at 8 tons/day
IV.6.11.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80
IV.6.11-2
-------
TOTAL CAPITAL INVESTMENT
l.OOOp
CO
Q£
g
o
o
100
10
1.0
0.1
0.01
i i i i 11 ii
i i 1111
ENR INDEX = 3119
I I I I 111
1.0
10
100
1,000
Tons of DRY SOLIDS/day
Date: 6/23/80
IV.6.11-3
-------
ANNUAL OPERATING COST
10 P
en
ac
O
CO
O
0.0001
1.0 10 100 1,000
SLUDGE LOAD, Tons of DRY SOLIDS /day
Date: 6/23/80
IV.6.11-4
-------
IV.6.12 CENTRIFUGAL DEWATERING [1]
IV.6.12.1 Description
Centrifuges are used to dewater sludges using centrifugal force
to increase the sedimentation rate of sludge solids. The solid
bowl, the disc, and the basket are the three most common types
of units.
The solid-bowl continuous centrifuge assembly consists of a bowl
and conveyor joined through a planetary gear system, designed to
rotate the bowl and the conveyor at slightly different speeds.
The solid cylindrical bowl, or shell, is supported between two
sets of bearings and includes a conical section at one end.
This section forms the dewatering beach over which the helical
conveyor screw pushes the sludge solids to outlet ports and then
to a sludge cake discharge hopper. The opposite end of the bowl
is fitted with an adjustable outlet weir plate to regulate the
level of the sludge pool in the bowl. The centrate flows through
outlet ports either by gravity or by a centrate pump attached to
the shaft at one end of the bowl. Sludge slurry enters the unit
through a stationary feed pipe extending into the hollow shaft
of the rotating bowl and passes to a baffled, abrasion-protected
chamber for acceleration before discharge through the feed ports
in the rotating conveyor hub into the sludge pool. Due to the
centrifugal forces, the sludge pool takes the form of a concen-
tric annular ring on the inside of the bowl. Solids settle
through this ring to the wall of the bowl where they are picked
up by the conveyor scroll. Separate motor sheaves or a variable
speed drive can be used to adjust the bowl speed for optimum
performance.
Bowls and conveyors can be constructed from a large variety of
metals and alloys to suit special application. For dewatering
of wastewater sludges, mild steel or stainless steel has been
used normally. Because of the abrasive nature of many sludges,
hardfacing materials are applied to the leading edges and tips
of the conveyor blades, the discharge ports, and other wearing
surfaces. Such wearing surfaces may be replaced by welding when
required.
In the continuous concurrent solid-bowl centrifuge, incoming
sludge is carried by the feed pipe to the end of the bowl op-
posite the discharge. Centrate is skimmed off and cake proceeds
up the beach for removal. As a result, settled solids are not
disturbed by incoming feed.
In the disc-type centrifuge, the incoming stream is distributed
between a multitude of narrow channels formed by stacked conical
discs. Suspended particles have only a short distance to settle
so that small and low density particles are readily collected
and discharged continuously through fairly small orifices in the
Date: 6/23/80 IV.6.12-1
-------
bowl wall. The clarification capability and throughput range
are high, but sludge concentration is limited by the necessity
of discharging through orifices 0.050 in. to 0.100 in. in
diameter. Therefore, it is generally considered a thickener
rather than a dewatering device.
In the basket-type centrifuge, flow enters the machine at the
bottom and is directed toward the outer wall of the basket.
Cake continually builds up within the basket until the centrate,
which overflows a weir at the top of the unit, begins to increase
in solids. At that point, feed to the unit is shut off, the
machine decelerates, and a skimmer enters the bowl to remove the
liquid layer remaining in the unit. A knife is then moved into
the bowl to cut out the cake, which falls out of the open bottom
of the machine. The unit is a batch device with alternate
charging of feed sludge and discharging of dewatered cake.
Equipment normally associated with the centrifugal dewatering
process includes centrifuge, sludge feed pump, solids conveyor,
and centrate pumps. A flow diagram of a centrifugal dewatering
system is shown below.
DIFFERENTIAL
SPEED GEAR BOX
ROTATING
BOWL
COVER
MAIN DRIVE SHEAVE
CHEMICALS FOR CONDITIONING
'*^^V"? _ ^ 1
c
4
MCE
SHUTDOWN
FLUSH
y ,
1 1— »-4 SLUDGE
1 r^
! r^
1 ci unrc DIIMD
ROTATING
CONVEYOR
CENTRATE SLU
DISCHARGE DI
(SEE SECTION IV.7)
IV.6.12.2 Typical Design Criteria
Each installation is site specific and dependent upon a manu-
facturer's product line. Maximum capacities of about 100 tons/hr
of dry solids are available in solid-bowl units with diameters
up to 54 inches and power requirements up to 175 hp. Disc units
are available with capacities up to 400 gpm of concentrate.
IV.6.12.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes centrifuges (solid bowl), with
minimum of one spare; sludge pumps and piping; cake conveyors;
and internal electrical and building costs. Costs do not include
centrate handling. Cationic polymer cost is based on 10 Ib/ton
Date: 6/23/80
IV.6.12-2
-------
dry basis for biological sludge. The following operating charac-
teristics were assumed:
Operating characteristic Assumed value
Sludge quantity 4,500 Ib/Mgal at 10% solids
for lime sludge; 900 lb/
Mgal at 4% for digested
biological sludge
Operation 8 hr/d
IV.6.12.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.6.12-3
-------
TOTAL CAPITAL INVESTMENT
l.OOOp
CO
O
O
LL.
O
LO
ENR INDEX = 3119
i i i i 1
0.1
1.0
10
100
SLUDGE LOAD, Tons of DRY SOLIDS/day
Date: 6/23/80
IV.6.12-4
-------
rt
0>
MILLIONS OF DOLLARS/YEAR
ro
to
oo
o
ro
I
Ul
8
O
>
O
20
CO
O
O
CO
O
70
>
O
O
O
CO
-------
ft
ft)
CM
10
00
o
p
8
MILLIONS OF DOLLARS/YEAR
.<=>
o
o
O
O
>
o
2,
to
O
I/)
S;
O)
o
>
to
o
o
30
>
O
O
O
-------
IV.6.13 THERMAL DRYING [1]
IV.6.13.1 Description
Thermal drying is the process of reducing the moisture in sludge
by evaporation to 8 to 10 percent using hot air, without combus-
ting the solid materials. For economic reasons, the moisture
content of the sludge must be reduced as much as possible through
mechanical means prior to heat drying. The five available heat
treating techniques are flash, rotary, toroidal, multiple hearth
and atomizing spray.
Flash drying is the instantaneous vaporization of moisture from
solids by introducing the sludge into a hot gas stream. The
system is based on several distinct cycles that can be adjusted
for different drying arrangements. The wet sludge cake is first
blended with some previously dried sludge in a mixer to improve
pneumatic conveyance. Blended sludge and hot gases from the
furnace at about 1200°F to 1400°F (650 to 760°C) are mixed and
fed into a cage mill in which the mixture is agitated and the
water vapor flashed. Residence time in the cage mill is only a
matter of seconds. Dry sludge with eight-to-ten percent moisture
is separated from the spent drying gases in a cyclone, with part
of it recycled with incoming wet sludge cake and another part
screened and sent to storage.
A rotary dryer consists of a cylinder that is slightly inclined
from the horizontal and revolves at about five-to-eight r/min.
The inside of the dryer is equipped usually with flights or
baffles throughout its length to break up the sludge. Wet cake
is mixed with previously heat dried sludge in a pug mill. The
system may include cyclones for sludge and gas separation, dust
collection scrubbers, and a gas incineration step.
The toroidal dryer uses the jet mill principle, which has no
moving parts, dries, and classifies sludge solids simultaneously.
Dewatered sludge is pumped into a mixer where it is blended with
previously dried sludge. Blended material is fed into a doughnut-
shaped dryer, where it comes into contact with heated air at a
temperature of 800°F to 1100°F. Particles are dried, broken up
into fine pieces, and carried out of the dryer by the air stream.
The dried, powdered sludge is supplemented with nitrogen and
phosphorus and formed into briquettes, which are crushed and
screened to produce final products.
The multiple hearth furnace is adapted for heat drying of sludge
by incorporating fuel burners at the top and bottom hearths, plus
down draft of the gases. The dewatered sludge cake is mixed in a
pug mill with previously dried sludges before entering the fur-
nace. At the point of exit from the furnace, the solids temper-
ature is about 100°F, and the gas temperature is about 325°F.
Date: 6/23/80 IV.6.13-1
-------
Atomizing drying involves spraying liquid sludge in a vertical
tower through which hot gases pass downward. Dust carried with
hot gases is removed by a wet scrubber or dry dust collector.
A high-speed centrifugal bowl can also be used to atomize the
liquid sludge into fine particles and to spray them into the top
of the drying chamber where moisture is transferred to the hot
gases.
Complete heat drying systems are generally proprietary. The
major equipment includes mixers, furnaces, cyclones, sci ;
dryers, wet scrubbers, dust collectors, air blowers, heau -.. ,
spraying devices, sludge feed pumps, and handling equipment.
A flow diagram of the thermal drying process is shown below.
DEWATERED-
SLUDGE
IV.6.13.2 Typical Design Criteria
MIXER
DRYER
COLLECTOR
SCREEN
*•-DRIED SLUDGE
(See Section IV.7)
Approximately 1,400 Btu are needed to vaporize one pound of water,
based on a thermal efficiency of 72 percent. Less fuel would be
required with additional heat recovery. Chemical scrubbers are
used, or chemicals are added prior to heat drying. Excessive
drying tends to produce a sludge that is dusty or contains many
fine particles; this is less acceptable for marketing and should
be avoided. Wet scrubbers and/or solids collectors are needed.
Standby heat-drying equipment is needed for continuous operation.
IV.6.13.3 Costs
The costs of heat treatment are based upon the installation of a
Zimpro unit and include a complete oxidation unit, installation,
building and foundation and piping for the removal of effluent.
The equipment is sized to treat a three-percent solids content
sludge with a continuous 24-hour-per-day operation, allowing for
a 20-percent down time for maintenance.
IV.6.13.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80
IV.6.13-2
-------
TOTAL CAPITAL INVESTMENT
1,000
on
i
o
100
10
1.0
0.1
111
TOTAL CAPITAL
INVESTMENT
PURCHASED AND
INSTALLED EQUIPMENT
i i 11
ENR INDEX • 3119
i i i i 11
1.0 10
ROW, Mgal/d
100
Date: 6/23/80
IV.6.13-3
-------
ANNUAL OPERATING COST
to
oc
3
0.01 r
0.001
FLOW, Mgal/d
Date: 6/23/80
IV.6.13-4
-------
IV.6.14 DRYING BEDS [I]
IV.6.14.1 Description
Drying beds are used to dewater sludge both by drainage through
the sludge mass and by evaporation from the surface exposed to
the air. Collected filtrate is usually returned to the treatment
plant.
Drying beds usually consist of 4 to 9 inches of sand, which is
placed over 8 to 18 inches of graded gravel or stone. The sand
typically has an effective size of 0.3 to 1.2 mm and a uniformity
coefficient of less than 5.0. Gravel is normally graded from
1/8 to 1.0 inch. Drying beds have underdrains that are spaced
from 8 to 20 feet apart. Underdrain piping is often vitrified
clay laid with open joints and having a minimum diameter of
4 inches and a minimum slope of about 1 percent.
Sludge is placed on the beds in an 8- to 12-inch layer. The
drying area is partitioned into individual beds, approximately
20 feet wide by 20 to 100 feet long, of a convenient size so
that one or two beds will be filled by a normal withdrawal of
sludge from the digesters. The interior partitions commonly
consist of two or three creosoted planks, one on top of the
other, to a height of 15 to 18 inches, stretching between slots
in precast concrete posts. The outer boundaries may be of simi-
lar construction or earthen embankments for open beds, but con-
crete foundation walls are required if the beds are to be
covered.
Piping to the sludge beds is generally made of cast iron and
designed for a minimum velocity of 2.5 feet/second. It is ar-
ranged to drain into the beds and provisions are made to flush
the lines and prevent freezing in cold climates. Distribution
boxes are provided to divert sludge flow to the selected bed.
Splash plates are used at the sludge inlets to distribute the
sludge over the bed and prevent erosion of the sand.
Sludge can be removed from the drying bed after it has drained
and dried sufficiently to be spadable. Sludge removal is ac-
complished by manual shoveling into wheelbarrows or trucks, or
by a scraper or front-end loader. Provisions should be made for
driving a truck onto or along the bed to facilitcite loading.
Mechanical devices can remove sludges of 20% to 30% solids while
cakes of 30% to 40% are generally required for hand removal.
Paved drying beds with limited drainage systems permit the use of
mechanical equipment for cleaning. Field experience indicates
that the use of paved drying beds results in shorter drying times
as well as more economical operation when compared with conven-
tional sandbeds because, as indicated above, the use of mechani-
cal equipment for cleaning permits the removal of sludge with a
Date: 6/23/80 IV.6.14-1
-------
higher moisture content than does hand cleaning. Paved beds have
worked successfully with anaerobically digested sludges but are
less desirable than sandbeds for aerobically digested activated
sludge.
Sandbeds can be enclosed by glass. Glass enclosures (1) protect
the drying sludge from rain, (2) control odors and insects,
(3) reduce the drying periods during cold weather, and (4) can
improve the appearance of a waste treatment plant.
Equipment normally associated with drying bed operations includes
front-end loaders and scrapers. A flow diagram of a drying bed
is shown below.
SLUDGE
6-in. FINE SAND
.3-in. COARSE SAND
3-in. FINE GRAVEL
, 3-in. MEDIUM GRAVEL ,
3 TO 6-in. COARSE GRAVEL
• PIPE COLUMN FOR
GLASS COVER
2-in. COARSE SAND
6-in. UNDERDRAW LAID
WITH OPEN JOINTS
IV.6.14.2 Typical Design Criteria
Area of drying beds
sq ft/capita
Type of sludge
Primary digested
Primary and humus digested
Primary and activated digested
Primary and chemically precipitated digested
Open beds
1.0 to 1.5
1.25 to 1.75
1.75 to 2.5
2.0 to 2.5
Covered beds
0.75 to 1.0
1.0 to 1.25
1.25 to 1.5
1.25 to 1.5
In the southern United States, reduced areas are often practical
because of more favorable climatic conditions.
Enclosed beds usually require 60% to 75% of the open bed area.
Solids loading rates vary from 10 to 28 Ib/ft2/yr for open beds
and 12 to 40 Ib/ft2/yr for closed beds. Sludge beds should be
located at least 200 feet from dwellings to avoid odor complaints
due to poorly digested sludges.
IV.6.14.3 Costs
Purchased equipment and installation cost for estimation of total
capital investment includes sand beds, sludge inlets, underdrains,
cell dividers, sludge piping, underdrain return, and other struc-
tural elements of the beds. The following operating character-
istics were assumed for cost estimation:
Date: 6/23/80
IV.6.14-2
-------
Operating characteristic Assumed value
Service life 20 yr
Bed loading 900 Ib sludge/Mgal;
20 Ib/ft2/yr
To adjust costs for alternative bed loading rates, sludge quanti-
ties, or characteristics, calculate the effective loading (L )
using the following equation:
L = L x 20 Ib/ftVyr
E Design new bed loading
IV.6.14.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.6.14-3
-------
TOTAL CAPITAL INVESTMENT
to
cr
3
o
O
LL.
O
to
0.0001
0.01
0.1
1.0
10
SLUDGE LOAD, Tons of DRY SOLIDS/day
Date: 6/23/80
IV.6.14-4
-------
ANNUAL OPERATING COST
10 F
1.0
IS)
o
o
IX.
O
tr>
O
0.1
3 0.01
0.001
0.0001
._ TOaLgfi
to*2
*&
$&
Cfi
i 11 n
MATERIALS
y
A
ENR INDEX - 3119
i i i i i 111
0.01 0.1 1.0 10
SLUDGE LOAD, Tons of DRY SOLIDS/day
Date: 6/23/80
IV.6.14-5
-------
IV.6.15 SLUDGE LAGOONS [1]
IV.6.15.1 Description
Digested sludge has often been applied to sludge lagoons adjacent
to or in the proximity of treatment facilities. These sludge
lagoons are primarily designed to accomplish long-term drying of
the digested sludge through the physical processes of percolation
and evaporation, primarily the latter.
This method of sludge processing has been extremely popular in
the U.S. due to its relatively low cost (when inexpensive land
is plentiful) and minimal operation and maintenance requirements,
especially at smaller wastewater treatment facilities. The proc-
ess is relatively simple, requiring periodic decanting of super-
natant back to the head of the plant and occasional mechanical
excavation of dewatered or dried sludge for transportation to its
ultimate disposal location. Lagoons can be a very useful process
step. Lagoon supernatant is far better (low SS) than supernatant
from a secondary digester or even a thickener. Ultimate disposal
of the product solids often is as a soil conditioner or landfill.
Sludge lagoons may also be used as contingency units at treatment
plants to store and/or process sludges when normal processing
units are either overloaded or out of service.
The drying time to 30% solids is generally quite lengthy and may
require years. Climatic conditions and pre-lagoon sludge process-
ing greatly influence lagoon performance. In warmer, drier
climates well-digested sludges are economically and satisfactor-
ily treated by sludge-drying lagoons because of their inherent
simplicity of operation and flexibility. Complete freezing
causes sludge to agglomerate; hence, when it thaws, the super-
natant decants or drains away easily. Well-digested sludges
minimize potential odor problems and are inherent in this type
of system. Multiple-cells are required for efficient operation.
Methods and patterns of loading, supernatant recycling tech-
niques, and mechanical cleaning techniques vary with location,
climate, and type of sludge to be processed.
Equipment normally associated with sludge lagooning includes
front-end loaders, bulldozers, and dragline. A flow diagram
of a sludge lagoon is shown below.
«m\\\m\Mm.
DIGESTED SLUDGE : ^ <
SUPERNATANT TO WET WELL
Date: 6/23/80 IV.6.15-1
-------
IV.6.15.2 Typical Design Criteria
Typical design criteria for sludge lagoons are shown below.
Design criteria
Value
Dikes
Depth
Bottom
Cells
Loading rates
Decant
Sludge removal
Slopes of 1:2 exterior and 1:3 interior are needed to
permit maintenance and mowing and to prevent erosion;
width must be sufficient to allow vehicle transport
during cleaning.
1.5 to 4.0 ft of sludge depth (depending on climate).
Separation from groundwater is dependent upon appli-
cation depths and soil characteristics, but should
not be less than 4 ft to prevent groundwater
contamination. An impermeable liner may be required.
A minimum of two cells is required.
2.2 to 2.4 Ib solids/yr/ft3 of capacity; 1.7 to 3.3 Ib
solids/ft2 of surface/30 days of bed use.
Single or multiple-level decant for periodic returning
supernatant to head of plant.
Approximately 1.5 to 3 yr intervals.
IV.6.15.3 Costs
Purchased equipment and installation cost for estimation of total
capital investment includes process piping, equipment, concrete,
steel, and excavation. The following operating characteristics
were assumed for cost estimation:
Operating characteristic
Assumed value
Sizing
Total annual direct
operating costs
75 tons/acre/yr; 1.5 ft depth of
sludge
Include materials, supplies, mainten-
ance, operation, and residuals
removal.
IV.6.15.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80
IV.6.15-2
-------
rt
(D
to
THOUSANDS OF DOLLARS
00
o
o
tl
m
to
-------
ANNUAL OPERATING COST
10 F
CO
O
CO
O
0.001 r
0.0001
10 10" 10" ior
SLUDGE LOAD, Tons of DRY SOLIDS/day
Date: 6/23/80
IV.6.15-4
-------
IV. 7. DISPOSAL
IV.7.1 INCINERATION
IV.7.1.1 Incineration of Sludge - Fluidized Bed Furnace (FBF) [1]
Description. Sludge incineration is a two-step process in-
volving drying and combustion after preliminary dewatering. A
typical sludge contains 75% water and 75% volatiles in dry solids.
Self-sustained combustion without supplementary fuel is often
possible with dewatered raw sludges having a solids concentration
greater than 30%.
The fluidized bed furnace (FBF) is a vertically oriented, cylin-
drically shaped, refractory-lined steel shell that contains a
sand bed and fluidizing air distributor. The FBF is normally
available in diameters of 9 to 25 feet and heights of 20 to 60
feet. There is one industrial unit operating with a diameter of
53 feet. The sand bed is approximately 2.5 feet thick and rests
on a refractory-lined air-distribution grid containing tuyeres
through which air is injected at a pressure of 3 to 5 psi to
fluidize the bed. Bed expansion is approximately 80% to 100%.
Bed temperature is controlled between 1,400°F and 1,500°F by
auxiliary burners and/or a water spray or heat removal system
above the bed. Ash is carried out the top of the furnace and
removed by air pollution control devices, usually wet venturi
scrubbers. Sand is lost by attrition at an approximate rate of
5% of the bed volume every 300 hours of operation. Furnace feed
can be introduced either above or directly into the bed depending
on the type of feed. Generally, sewage sludge is fed directly
into the bed.
Excess air requirements for the FBF vary from 20% to 40%. It
requires less supplementary fuel than a multiple hearth furnace.
An oxygen analyzer in the stack controls the air flow into the
reactor, and the auxiliary fuel feed rate is controlled by a bed-
temperature controller.
An air preheater is used in conjunction with a fluidized bed to
reduce fuel costs. Also, cooling tubes may be submerged in the
bed for energy recovery.
Date: 6/23/80 IV.7.1-1
-------
Equipment normally associated with sludge incineration includes
the FBF, screw pumps, air fans, gas scrubber, and ash handling
systems. A flow diagram of a fluidized bed furnace for incinera-
tion of sludge is shown on the next page.
FURNACE EXHAUST
BED COILS FOR
HEAT RECOVERY
1 GAS EXHAUST
-I , FAN
(NOT USED IN
THIS ANALYSIS)
RADIATION
SUPPLEMENTAL FUEL »
SLUDGE FEED
FLUID BED
FURNACE
X VENTURI
_ RECYCLE WATER
T»
« —
D
)H
MAKEUP WATER
WET SCRUBBER
SCRUBBER WATER
DRAIN
Typical Design Criteria. Design criteria for a FBF are
shown below. Concerning actual operations, some extensive main-
tenance problems have occurred with air preheaters. Scaling of
the venturi scrubbers has also been a problem. Screw feeds and
screw pump feeds are both subject to jamming because of either
overdrying of the sludge feed at the incinerator or because of
silt carried into the feed system with the sludge. Another
frequent problem has been the burnout of spray nozzles or thermo-
couples in the bed.
Design criteria
Value
Bed loading rate
Superficial bed velocity
Sand effective size
Operating temperature
Bed expansion
Sand loss
50 - 60 Ib wet solids/ft2/hr
0.4 - 0.6 ft/s
0.2 - 0.3 mm (uniformity coefficient = 1.8)
1,400 - 1,5QQ%F (normal); 2,200°F+ (maximum)
80 - 100%
5% of bed volume per 300 hr of operation
Costs. Purchased equipment and installation cost for estima-
tion of the total capital investment includes the reactor, air
blowers, accessories, preheaters, scrubbers, fuel pumps, and
building. Costs were based on undigested dewatered primary and
secondary sludge (1,900 Ib/M gal at 20% solids; 75% volatile).
Additionally, the following operating characteristics were
assumed.
Date: 6/23/80
IV.7.1-2
-------
Plant flow,
Mgal/d
0.1
1.0
10.0
100.0
Operation,
d/wk
1
7
7
7
Operation,
hr/d
20
20
20
20
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.7.1-3
-------
TOTAL CAPITAL INVESTMENT
o
fe
LO
o
d
0.1
1.0 10
SLUDGE LOAD, Tons of DRY SOLIDS/day
100
Date: 6/23/80
IV.7.1-4
-------
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ft
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(MATERIALS-LABOR)
-------
IV.7.1.2 Incineration of Sludge - Multiple Hearth
Furnace (MHF) [1]
Description. Sludge incineration is a two-step process in-
volving drying and combustion after preliminary dewatering. A
typical sludge is 80% water and has a dry solids volatility of
75%. Self-sustained combustion without supplementary fuel is
often possible with dewatered raw primary sludges, which can
frequently be dewatered to 30% solids.
The multiple hearth furnace (MHF) is a vertically oriented,
cylindrically shaped, refractory-lined steel shell having dia-
meters of 4 to 25 feet and containing 4 to 13 horizontal hearths
positioned one above the other. The hearths are constructed of
high heat duty fire brick and special fire brick shapes. Sludge
is raked radially across the hearths by rabble arms which are
supported by a central rotating shaft that runs the height of
the furnace. The cast iron shaft is motor driven with provision
for speed adjustment from 1/2 to 1-1/2 r/min. Sludge is fed to
the top hearth and proceeds downward through the furnace from
hearth to hearth. Inflow hearths have a central port through
which sludge passes to the next lower hearth. Outflow hearths
have ports.on their periphery that also tend to regulate gas
velocities. The central shaft contains internal concentric flow
passages through which air is routed to cool the shaft and
rabble arms. The flow of combustion air is countercurrent to
that of the sludge. Gas or oil burners are provided on some
hearths for start-up and/or supplemental use as required.
The rabble arms provide mixing action as well as movement to the
sludge so that a maximum sludge surface is exposed to the hot
furnace gases. Because of the irregular surface left by the
rabbling action, the surface area of sludge exposed to the hot
gases is as much as 130% of the hearth area. While there is
significant solids-gas contact time on the hearths, the overall
contact time is actually still greater, due to the fall of the
sludge from hearth to hearth through the countercurrent flow of
hot gases.
The various phases of the incineration process occur in three
zones of the MHF. The drying zone consists of the upper hearths,
the combustion zone consists of the central hearths, and the
lower hearths comprise the cooling zone. Temperatures in each
zone are shown on the following page.
Date: 6/23/80 IV.7.1-6
-------
Temperature/ °F
Zone
Drying
Burning
Cooling
Sludge
'v.lOO
^1,500
MOO
Air
^800
^1,500
^350
An afterburner, fired with oil or gas, is provided where required
by local air pollution regulations to eliminate unburned hydro-
carbons and other combustibles.
Equipment normally associated with multiple hearth furnace incin-
eration of sludge includes the multiple hearth furnace, flapgate
valves, cooling and combustion air fans, sludge conveyors, and
gas scrubber. A flow diagram of a multiple hearth furnace incin-
eration system is shown below:
GAS EXHAUST
SHAFT COOLING AIR NOT RETURNED'
SHAFT COOLING
AIR RETURN
FURNACE EXHAUST
SLUDGE FEED—e-
SUPPLEMENTALI
FUEL
WET SCRUBBER
SCRUBBER
WATER
COMBUSTION
AIR
DRAIN
SHAFT COOLING AIR
Typical design criteria.
are shown below.
Typical design criteria for MHF
Design criteria
Value
Maximum operating temperature
Hearth loading rate
Combustion air flow
Shaft cooling air flow
Excess air
1,700°F
6 - 10 Ib wet solids/ft2/hr with
a dry solids concentration of
20 to 40%
12 - 13 Ib/lb dry solids
1/3 - 1/2 of combustion air flow
75 - 100%
Date: 6/23/80
IV.7.1-7
-------
Costs. Purchased equipment and installation cost for esti-
mation of the total capital investment includes incinerator,
building, sludge, conveyor, ash handling equipment, and gas scrub-
bers. Costs were based on undigested dewatered primary and secon-
dary sludge (1,900 Ib/Mgal at 20% solids, 75% volatile). Fuel
requirements for warm-up and incineration are 4,500 x 10s Btu/yr/
Mgal/d.
Additionally, the following operating characteristics were
assumed:
Plant flow, Operation, Operation,
Mgal/d d/wk hr/d
0.1
1.0
10.0
100.0
1
7
7
7
20
20
20
20
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.7.1-8
-------
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TOTAL DIRECT OPERATING COST -
TOTAL ANNUAL OPERATING COST
-------
IV.7.2 STARVED AIR COMBUSTION (SAC) [1]
IV.7.2.1 Description
Starved air combustion is used for the volumetric and organic re-
duction of sludge solids. The process utilizes equipment and
process flows similar to incineration except that less than the
theoretical amount of air for complete combustion is supplied.
Autogenous starved air combustion (SAC) can be achieved with a
sludge solids concentration greater than 25%. For lower concen-
trations, an auxiliary fuel may be required, depending on the
percent volatiles in the solids. High temperatures decompose or
vaporize the solid components of this sludge. The gas phase re-
actions are pyrolytic or oxidative, depending on the concentra-
tion of oxygen remaining in the stream. Under proper control,
the gas leaving the vessel is a low-Btu fuel that can be burned
in an after burner to produce power and/or thermal energy. Some
processes utilize pure oxygen instead of air and thus produce a
higher-Btu fuel gas. The solid residue is a char with more or
less residual carbon, depending on how much combustion air had
to be supplied to reach the proper operating temperatures.
Because the process is neither purely pyrolytic or purely oxida-
tive, it is called starved-air combustion or thermal gasification,
rather than pyrolysis. Other processes still in the development
stage use indirect heating, rather than the partial combustion.
These are true pyrolysis processes. SAC reduces the sludge vol-
umes and sterilizes the end product. Unlike incineration, it
offers the potential advantages of producing useful by-products
and of reducing the volume of sludge without large amounts of
supplementary fuels. The gas that is produced has a heating
value of up to 130 Btu/standard dry cubic foot using air for com-
bustion and is suitable for use in local applications, such as
combustion in an afterburner or boiler or for fuel in another
furnace. SAC has a higher thermal efficiency than incineration
due to the lower quantity of air required for the process. In
addition, capital economies can be realized due to the smaller
gas handling requirements.
Furnaces may be operated in one of three modes resulting in sub-
stantially different heat generation and residue characteristics.
The low temperature char (LTC) mode only pyrolyzes the volatile
material thereby producing a charcoal-like residue with a high
ash content. The high temperature char (HTC) mode produces a
charcoal-like material converted to fixed carbon and ash. The
char burned (CB) mode reacts away all carbon and produces ash as
a residue. Heat recovered is maximum for the CB mode, less for
the HTC mode, and substantially less for the LTC mode of operation.
Equipment normally associated with the starved air combustion
process includes the SAC reactor, waste heat boiler, exhaust gas
scrubbers, sludge dewatering devices, and afterburners. A flow
diagram is shown on the following page.
Date: 6/23/80 IV.7.2-1
-------
SHAFT COOLING AIR
RETURNED TO FURNACE
SLUDGE DEWATERING
AND FEED SYSTEM
SLUDGE
FEED
GAS EXHAUST
SHAFT COOLING AIR NOT RETURNED
COMBUSTIOr
AIR
URNACE'
3(HAUSTt
ISHAFT COOLING AIR"
rTURNED TO AFTER-
BURNER
AFTERBURNER
AFTERBURNER r
3CHAUST f J
WASTE
HEAT
BOILER
MULTIPLE
HEARTH
PYROLYTIC
REACTOR
RECOVERABLE
HEAT
SUPPLEMENTAL FU&
RADIATION'
WET SCRUBBER
SCRUBBER
WATER
PRECOOLER AND VENTURI WATER
COMBUSTION
ASH AIR
_ CONNECTED POWER
SHAFT COOLING AIR
IV.7.2.2 Typical Design Criteria
In MHF systems, hearth loadings are 9 to 15 Ib wet (22%) solids/
ft2/h; for autogenous combustion, sludge solids content is 25% to
39% depending upon volatility. The off-gas heating value is de-
pendent upon operating mode.
IV.7.2.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes the multiple hearth furnace,
fans, motor controls, gas scrubber, external afterburner, ash
handling system, auxiliary fuel system, instrumentation, piping,
painting, initial operation, and test. The following operating
characteristics are assumed for cost estimation:
Operating characteristic
Assumed value
Design capacity
Annual throughput
324 ton/d at 40% dry solids
80,000 tons
Costs are based on third quarter 1979 dollars. Manpower costs
were assumed to be $17,500/yr average. Other cost assumptions
Date: 6/23/80
IV.7.2-2
-------
included: power at $0.02/kWh, fuel at $2.36/106 Btu, water and
sewer at $0.37/1,000 gal, and residue disposal at $5/ton.
Item Capital cost
Direct construction cost (DCC) $2,325,000
Design, construction management (20% DCC) 465,000
Land ($50,000/acre) 250,000
Legal fee (3% DCC) 69,750
Bond discount (3% total cost) 99,000
Total cost $3,325,000
Operating cost
Item
Manpower, 20 employees
Power, 210 kWh/hr
Water/sewer @ 385 gpm
Auxiliary fuel (250,000 gpy)
Maintenance (2.5% DCC)
Overhead (1% DCC)
Residual disposal
Total cost
Cost/ton^
$4.37
0.46
0.89
1.19
1.03
0.42
0.94
$9.30
Annual cost
$350,000
36,800
70,800
95,500
83,100
33,250
75,000
$744,450
aBased on 80,000 ton/yr throughput.
IV.7.2.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.7.2-3
-------
TOTAL CAPITAL INVESTMENT
100 c
to
10
o
CO
O
3 1-0
0.1
0.1
TOTAL CAPITAL
— INVESTMENT-
PURCHASED EQUIPMENT
AND INSTALLATION
ENR INDEX-3119
i i i I i 11
1.0 10
TonsOFDRYSOLIDS/d
100
Date: 6/23/80
IV.7.2-4
-------
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(D
MILLIONS OF DOLLARS/YEAR
(TOTAL - LABOR - FUEL - MATERIALS)
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IV.7.3 LANDFILLING - AREA FILL [1]
IV.7.3.1 Description
Landfilling is a sludge disposal operation in which sludge is
placed above the original earth cover and subsequently covered
with soil. To achieve stability and soil-bearing capacity, sludge
is mixed with a, bulking agent, usually soil. The soil absorbs
excess moisture from the sludge and increases its workability.
The large quantities of soil required may require hauling from
elsewhere. Provisions must be made to keep the stockpiled soil
dry. Installation of a liner is generally required for ground-
water control and provisions must be made for surface drainage
control, gas migration, dust, vectors and/or aesthetics. Area
fills are more specifically categorized as follows:
Area Fill Mound. In an area fill mound, sludge is mixed with
a bulking agent, usually soil, and the mixture is hauled to the
filling area where it is stacked in mounds approximately 6 feet
high. Cover material is then applied in a 3-foot thickness.
This cover thickness may be increased to 5 feet if additional
mounds are applied atop the first lift. The appropriate sludge/
soil bulking ratio and soil cover thickness depend upon the sol-
ids content of the sludge as received, the need for mound stabil-
ity, and the bearing capacity as dictated by the number of lifts
and equipment weight. Lightweight equipment with swamp pad
tracks is appropriate for area fill mound operations; heavier
wheel equipment is appropriate in transporting bulking material
to and from stockpiles. Construction of earthern containments
is useful to minimize mound slumping and for sloping sites.
Area Fill Layer. In an area fill layer, sludge is mixed
with soil on or off site and spread evenly in consecutive layers
0.5- to 3-feet thick. Interim cover between layers may be applied
to 0.5- to 1-foot thick applications. Layering may continue to
an indefinite height before final cover is applied. Lightweight
equipment with swamp pad tracks is appropriate for area fill
layer operations; heavier wheel equipment is appropriate for haul-
ing soil. Slopes should be relatively flat to prevent sludge
from flowing downhill. However, if sludge solids content is
high and/or sufficient bulking soil is used, the effect can be
prevented and layering performed on mildly sloping terrain.
Diked Containment. Dikes are constructed on level ground
around all four sides of a containment area. Alternatively, the
containment area may be placed at the toe of the hill so that the
steep slope can be utilized as containment on one or two sides.
Dikes are then constructed around the remaining sides. Access is
provided to the top of the dikes so that haul vehicles can dump
sludge directly into the containment. A 1- to 3-foot interim
cover may be applied at certain points during the filling; a 3-
to 5-foot thick final cover should be applied when filling is
Date: 6/23/80 IV.7.3-1
-------
discontinued. Cover material is applied either by a dragline,
based on solid ground atop the dikes, or by track dozers directly
on top of the sludge, depending upon sludge bearing capacity.
Usually, operations are conducted without the addition of soil
bulking agents, but occasionally soil bulking is added. Typical
dimensions are 50 to 100 feet wide, 100 to 200 feet long, 10 to
30 feet deep.
Equipment normally associated with landfilling processes includes
front-end loader, bulldozer, scraper, backhoe, dragline, and
grader. A flow diagram of landfilling system is shown below:
SLUDGE
-»• GAS, LEACHATE TO TREATMENT
IV. 7. 3.. 2 Typical Design Criteria .. _.„.. .........
Typical design criteria for a sludge landfilling system are
listed as follows:
Design criteria
value
Parameter
In area fill mound
In area fill layer
In diked containment
Sludge solids content
Sludge characteristics
Ground slopes
Bulking required
Bulking ratio of soil to sludge
Sludge application rate
Equipment
Greater than 20%
Stabilized
Mo limitation if
suitably prepared
Yes
0.5 to 2 parts soil
to 1 part sludge
3,000 to 14,000 yd3/
acre
Track loader; backhoe
with loader; track
dozer
Greater than 15%
Stabilized
Level ground
preferred
Yes
0.25 to 1 part soil
to 1 part sludge
2,000 to 9,000 yd3/
acre
Track dozert graderi
track loader
20 to 28% for land-
based equipment; Bore
than 28% for sludge-
based equipment
Stabilized or
unstabilized
Level ground or steep
terrain if suitably
prepared
Occasionally
0 to 0.5 part soil to
1 part sludge
4,800 to 15,000 yd3/
'acre
Dragline) track dozer;
scraper
IV.7.3.3 Costs
Costs are presented in 1978 dollars. Site and equipment costs
include land at $2,500/acre, site preparation (clearing, grubbing,
surface water control ditches and ponds, monitoring wells, soil
stockpiles, roads and facilities), equipment purchase, and
engineering. The actual fill area consumes 50% of the total site
area. Operating costs include labor (at $8/hr, including fringe,
overhead, and administration), equipment fuel, maintenance and
parts, utilities, laboratory analysis of water samples, supplies,
and materials. Actual costs vary considerably with specific
sludge and site conditions.
Date: 6/23/80
IV.7.3-2
-------
IV.7.3.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.7.3-3
-------
SITE AND EQUIPMENT COSTS
oo
oc
o
o
fc
00
o
O
50
40
30
20
15
10
5
4
3
10
DIKED CONTAINMENT
AREA FILL LAYER
20 30 4050
100
200 300 400 500
SLUDGE QUANTITY RECEIVED
(WETTons/d)
Date: 6/23/80
IV.7.3-4
-------
OPERATION AND MAINTENANCE COSTS
9©
O
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©
»~
I—
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•w-
50
40
30
20
15
10
5
4
3
•AREA FILL MOUND
DIKED CONTAINMENT
10
20 30 40 50
100
200 300 400 500
SLUDGE QUANTITY RECEIVED
(WETTons/d)
Date: 6/23/80
IV.7.3-5
-------
IV.7.4 LANDFILLING - SLUDGE TRENCHING [1]
IV.7.4.1 Description
Landfilling is the final disposal of sludge in evacuated trenches.
In landfilling, stabilized or unstabilized sludge is placed with-
in a subsurface excavation and covered with soil. Trench opera-
tions are more specifically categorized as narrow trench and wide
trench. Narrow trenches are defined as having widths less than
10 feet, while wide trenches are defined as having widths greater
than that value. The width of the trench is determined by the
solids content of the receiving sludge and its capability of sup-
porting cover material and equipment. Distances between trenches
should be large enough to provide sidewall stability, as well as
space for soil stockpiles, operating equipment, and haul vehicles.
Design considerations should include provisions to control leach-
ate and gas migration, dust, vectors, and/or aesthetics. Leachate
control measures include the maintenance of 2 to 5 feet of soil
thickness between the trench bottom and the highest groundwater
level or bedrock (2 feet for clay to 5 feet for sand), or membrane
liners and leachate collection and treatment system. Installation
of gas control facilities may be necessary if inhabited structures
are nearby.
In narrow trench operations, sludge is disposed in a single appli-
cation, and a single layer of cover soil is applied atop this
sludge. Trenches are usually excavated by equipment based on
solid ground adjacent to the trench; equipment does not enter the
excavation. Backhoes, excavators, and trenching machines are par-
ticularly useful. Excavated material is usually applied immedi-
ately as cover over an adjacent sludge-filled trench. Sludge is
placed in trenches either directly from haul vehicles, through a
chute extension, or by pumping. The main advantage of a 2- to
3-foot narrow trench is its ability to handle sludge with a rela-
tively low solids content (15% to 20%) . Instead of sinking to the
bottom of the sludge, the cover soil bridges over the trench,
supported from undisturbed soils along each side of the trench.
A 3- to 10-foot width is more appropriate for sludge with solids
content of 20% to 28%, which is high enough to support cover
soil.
Wide trench operations are usually excavated by equipment operat-
ing inside the trench. Track loaders, draglines, scrapers, and
track dozers are suitable. Excavated material is stockpiled on
solid ground adjacent to the trench for subsequent application as
cover materials. If sludge is incapable of supporting equipment,
cover is applied by equipment based on solid undisturbed ground
adjacent to the trench. A front-end loader is suitable for
trenches up to 10 feet wide; a dragline is suitable for trench
widths up to 50 feet. If sludge can support equipment, a track
dozer applies cover from within the trench. Sludge is placed in
trenches from haul vehicles directly entering the trench or from
Date: 6/23/80 IV.7.4-1
-------
haul vehicles dumping from the top of the trench. Dikes can be
used to confine sludge to a specific area in a continuous trench.
After maximum settlement has occurred, in approximately one year,
the area should be regraded to ensure proper drainage.
Equipment normally associated with the sludge trenching process
includes the front-end loader, bulldozer, scraper, backhoe, drag-
line, trencher, and grader. A flow diagram of a sludge trenching
system is shown below.
SLUDGE
GAS AND LEACHATE MAY BE
COLLECTED AND TREATED
IV.7.4.2 Typical Design Criteria
Typical design criteria for sludge trenching systems are listed
below.
Value
Design criteria
Narrow trench
Wide trench
Sludge solids content
Ground slopes
Cover soil thickness
Sludge application rate
Equipment
15% to 20% for 2- to 3-ft
widths; 20% to 28% for
3- to 10-ft widths
Less than 20%
2 to 3 ft for 2- to 3-ft
widths; 3 to 4 ft for
3- to 10-ft widths
1,200 to 5,600 yd3/acre
Backhoe with loader,
excavator, trenching
machine
20% to 28% for land-based
equipment; more than
28% for sludge-based
equipment
Less than 10%
3 to 4 ft for land-based
equipment; 4 to 5 ft
for sludge-based
equipment
3,200 to 14,500 yd3/acre
Track loader, dragline,
scraper, track dozer
IV.7.4.3 Costs
Site and equipment cost curves, and operation and maintenance
cost curves are based on 1978 costs. Site and equipment costs
include land at $2,500/acre, site preparation (clearing, grubbing,
surface water control ditches and ponds, monitoring wells, soil
stockpiles, roads, and facilities), equipment purchase, and engi-
neering. The actual fill area consumes 50% of the total site
area. Operating costs include labor (at $8/hr, including fringe,
overhead, and administration), equipment fuel, maintenance and
parts, utilities, laboratory analysis of water samples, supplies,
and materials. Actual cost vary considerably with specific
sludge and site conditions.
Date: 6/23/80
IV.7.4-2
-------
IV.7.4.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.7.4-3
-------
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ex.
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CO
o
o
50
40
30
20
15
10
5
4
3
2
10
SITE AND EQUIPMENT COSTS
NARROW TRENCH
WIDE TRENCH
20 30 4050
100
200 300 400 500
SLUDGE QUANTITY RECEIVED
(WETTons/d)
Date: 6/23/80
IV.7.4-4
-------
oo
o:
o
c
o
GO
o
50
40
30
20
15
10
5
4
3
10
OPERATION AND MAINTENANCE COSTS
NARROW TRENCH
WIDE TRENCH
20 30 40 50
100
200 300400500
SLUDGE QUANTITY RECEIVED
(WETTons/d)
Date: 6/23/80
IV.7.4-5
-------
IV.7.5 LAND APPLICATION [1]
IV.7.5.1 Description
Land application techniques for applying liquid sludge, dried
sludge, and sludge cake to the land include tank truck, injec-
tion, ridge and furrow spreading, and spray irrigation. Sludge
can be incorporated into the soil by plowing, discing, or similar
methods. Ridge and furrow methods involve spreading sludge in
the furrows and planting crops on the ridges. Utilization of
this technique is generally best suited to relatively flat land
and is well suited to certain row crops. Spray irrigation sys-
tems are more flexible, require less soil preparation, and can be
used with a wider variety of crops. High application rates are
commonly used to reclaim strip mine spoils or other low quality
land. Sludge spreading in forests has been limited; however, it
offers opportunities for improved soil fertility and increased
tree growth.
Farm equipment or tank trucks with standard tires can be adapted
for sludge application. However, specially-designed sludge appli-
cation equipment is now available with high flotation tires and
apparatus for applying liquid or dry sludge, or for subsurface
injection. This equipment has a 15 psi compaction factor with an
8-ton payload and does minimize rutting, compaction or crop damage
when sludge applications are made under proper soil moisture
conditions.
IV.7.5.2 Typical Design Criteria
Application rates depend on sludge composition, soil characteris-
tics (usually 3% nitrogen; 2% phosphorus; 0.25% potassium), cli-
mate, vegetation, and cropping practices. Annual application
rates have varied from 0.5 to more than 100 tons per acre. Apply-
ing sludge at a rate to support the nitrogen needs of a crop of
about 5 to 10 tons of digested solids in the liquid form, avoids
problems associated with overloading the soil. Rates based on
phosphorus needs are lower. A pH of 6.5 or greater will minimize
heavy metal uptake by most crops.
IV.7.5.3 Costs
Purchased equipment and installation cost for estimation of the
total capital investment includes storage lagoon, land prepara-
tion, monitoring wells, and service road. Costs for transport of
sludge to site and land are not included. The following operat-
ing characteristics were assumed for cost estimation.
Date: 6/23/80 IV.7.5-1
-------
Operating characteristic
Assumed value
Service life
Storage lagoon
Monitoring wells
Digested biological sludge
Sludge application rate
Sludge application
30 yr
6 wk
3 at 0.1 Mgpd
5 at 1 Mgpd
8 at 10 Mgpd
25 at 100 Mgpd
900 Ib/Mgal at 4% solids
10 ton (dry)/acre/yr
By subsurface injection;
unit attached to haul
truck
To adjust costs for different application rates, calculate the
effective (!,„) using the following equation:
Ci
_ 10 dry ton/acre/yr
E ~~ Design new design application rate
An additional example of costs for one project that uses high
flotation equipment is provided as follows [1]:
Equipment characteristic
Assumed value
Operation rate
Application rate
Compaction factor
Haul distance, sludge source to
spreading site
Fuel consumption, diesel
gas
Service life
50 wk/yr, 40 hr/wk or 2,000 hr/yr
8,000 gal/hr, 5% dry solids = 400
gal dry solids/hr x 8.34 Ib/gal
= 3,336 Ib/hr = 3,336 dry tons/yr
15 lb/in.2 for 8-ton payload
0.25 mi
6 gal/hr
9 gal/hr
10 yr
The estimated costs (1977 dollars) are shown on the following
page.
Date: 6/23/80
IV.7.5-2
-------
Estimated cost
Item
Maintenance and repair
Fuel cost, diesel @ 60^/gal
gas @ 65£/gal
Depreciation
Labor
Total Diesel
Gas
Cost/yr
$ 2,000
7,200
11,700
5,000
13,800
29,000
32,500
Cost ton
dry solids
$0.60
2.16
3.50
1.49
4.14
8.39
9.73
Prices as of November 1977
IV.7.5.4 References
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80
IV.7.5-3
-------
TOTAL CAPITAL INVESTMENT
t/i
O»
o
U_
o
0.01
0.001
1.0 10
SLUDGE LOAD, Tons of DRY SOLIDS/day
100
Date: 6/23/80
IV.7.5-4
-------
D
fu
rt
(D
MILLIONS OF DOLLARS/YEAR
8
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CO
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Ul
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VI
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00
R
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(MATERIALS-LABOR)
-------
IV.7.6 COMPOSTING
IV.7.6.1 Static Pile Composting Sludge [1]
Description. In static pile composting, sewage sludge is
converted to compost in approximately eight weeks in a four-step
process involving preparation, digestion, drying and screening,
and curing.
In the preparation step, sludge is mixed with a bulking material
such as wood chips or leaves to facilitate handling, provide the
necessary structure and porosity for aeration, and lower the
moisture content of the biomass to 60% or less. Following mix-
ing, the aerated pile is constructed and positioned over porous
pipe through which air is drawn. The pile is covered for
insulation.
In the digestion step, the aerated pile undergoes decomposition
by thermophilic organisms, whose activity generates a concomitant
elevation in temperature to 60°C (140°F) or more. Aerobic com-
posting conditions are maintained by drawing air through the pile
at a predetermined rate. The effluent air stream is conducted
into a small pile of screened, cured compost where odorous gases
are effectively absorbed. After about 21 days, the composting
rates and temperatures decline, and the pile is taken down, the
plastic pipe is discarded, and the compost is either dried or
cured depending upon weather conditions.
In the drying and screening step, drying to 40% to 45% moisture
facilitates clean separation of compost from wood chips, which
are recycled. The unscreened compost is spread out with a
front-end loader to a depth of 12 inches. Periodically a
tractor-drawn harrow is employed to facilitate drying. Screen-
ing is performed using a rotary screen.
In the curing step, the compost is stored in piles for about 30
days to assure that no offensive odors remain and to complete
stabilization. The compost is then ready for utilization as a
low-grade fertilizer, a soil amendment, or a material for land
reclamation.
Two common modifications of static pile composting sludge are
used: (1) extended high pile in which pile height is extended to
18 ft using a crane (still experimental), and (2) aerated extended
pile in which each day's pile is constructed against the shoulder
of the previous day's pile, forming a continuous or extended
pile. These modifications result in savings of space and materials,
Equipment normally associated with static pile composting sludge
includes the front-end loader or crane, 4-inch perforated plastic
pipe, blower, timer, tractor (drawn), narrow, and rotary screen.
Date: 6/23/80 IV.7.6-1
-------
A flow diagram of the static pile composting of sludge is shown
below.
SCREENED
COMPOST WOODCHIPS
AND SLUDGE
PERFORATED
PIPE
WATER TRAP FOR
CONDENSATES
FILTER PIPE
SCREENED COMPOST
Typical Design Criteria. Construction of the pile for a
10-dry-ton/d (43-wet-ton/d) operation involves the following
steps: (1) a 6-inch layer of unscreened compost for base;
(2) a 94-foot loop of 4-inch diameter perforated plastic pipe
placed on top (0.25-inch hole diameter); (3) a 6-inch layer of
unscreened compost or wood chips covering the pipe; (4) connec-
tion of the loop to a 1/3-hp blower using 15 feet of solid pipe
fitted with a water trap to collect condensate; (5) a timer set
for a cycle of 4 minutes on and 16 minutes off; (6) a blower
connected to a covered scrubber pile (2 yd3 wood chips covered
with 10 yd3 screened compost) using 16 feet of solid pipe;
(7) placement of a wet sludge-wood chip mixture, in a volumetric
ratio of 1:2.5, on a prepared base; and (8) placement of a 12-
inch layer of screened compost on top for insulation. Air flow
is 100 ft3/h/ton of sludge. Approximately 3.5 acres of land
area are required for processing 10 dry tons daily; the area
includes a runoff collection pond; bituminous surface for roads,
mixing, composting, drying, and storage; and an administration
area. Pile dimensions are 53 ft x 12 ft x 8 ft high.
Costs. The following operating characteristics are assumed
for the cost estimation presented in the tables on the following
page and related to graphical form using scaling factors.
Date: 6/23/80
IV.7.6-2
-------
Operating characteristic
Assumed value
Quantity processed
.>
Power for blower
Front-end loader size
Sewer line installation
Composting pad construction
Operation rate
Staff
Labor cost
Equipment maintenance
Estimated insurance
Fuel cost, gasoline
diesel
electricity
woodchips
10 dry tons/d (compost distribution will realize no
net revenues or costs to the industrial)
1/3 hp
3.5-yd3 bucket
400 ft of 8-in. sewer line 9 $35/ft
grading, 12 in. crushed stone, 4 in. asphalt
8 hr/d, 7 d/wk
1 superintendent @ $7.50/hr, 4 equipment operators
@ $6/hr
includes 5 wk off for paid sick leave, vacations,
holidays; $400/person health insurance; 6% FICA;
0.3 man-yr of overtime
6% purchase price
1% purchase price
57C gal, 1.1 gal/dry ton loading
41C/gal, 3.5 gal/dry ton loading
2*AWh, 17.3 kWh/dry ton loading
S3.50/yd3
CONSTRUCTION COST
OPERATION AND MAINTENANCE COST
Item
Construction cost
Cost
Site development
Asphalt pad (1.5 acre)
Roads, administration
Electrical work
Sewer
Pond, drainage
Equipment
Office trailer
Storage
Front-end loaders (2 pieces)
Screen
Tractor
Pickup
Blowers (33 pieces)
$ 83,800
13,000
20,000
14,000
28,000
5,000
1,500
106,000
16,300
4,700
4,700
2,500
$299,500
Item
Woodchips
Plastic pipe
Gasoline
Diesel
Electricity
Equipment maintenance
Equipment insurance
Pad, road maintenance
Water/sewer
Labor
Miscellaneous supplies
Total
Cost/yr
$ 35,000
12,200
2,300
5,300
1,500
8,400
1,400
1,200
500
77,500
4,400
$149,700
Cos t/dry ton
$ 9.60
3.34
0.63
1.45
0.41
2.30
0.44
0.33
0.14
21.23
1.20
$41.0la
OSM costs for a 50-dry-ton/d operation have
been estimated to amount to $28/dry ton.
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80
IV.7.6-3
-------
TOTAL CAPITAL INVESTMENT
1,000 F
o
Ik
o
0.01
1.0
10
100
1,000
SLUDGE LOAD, DRY Tons/d
Date: 6/23/80
IV.7.6-4
-------
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p>
ft
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IV.7.6.2 Windrow Composting Sludge [1]
Description. In windrow composting, the piles are turned
periodically to provide oxygen for the microorganisms to carry
out the stabilization and carry off the excess heat generated by
the process. When masses of solids are assembled, and conditions
of moisture, aeration, and nutrition are favorable for microbial
activity and growth, the temperature rises spontaneously. As a
result of biological self-heating, composting masses easily reach
60°C (140°F) and commonly exceed 70°C (150°F). Peak composting
temperatures approaching 90°C (194°F) have been recorded. Tem-
peratures of 140°F to 160°F serve to kill pathogens, insect larvae,
and weed seeds. Nuisances such as odors, insect breeding, and
vermin harborage are controlled through rapid destruction of
putrescible materials. Sequential steps involved in composting
are preparation, composting, curing, and finishing.
The preparation step involves adjusting the sludge properties in
order to permit composting. To be compostable, a waste must have
at least a minimally porous structure and a moisture content of
45% to 65%. Therefore, sewage sludge cake, which is usually
about 20% solids, cannot be composted by itself but must be com-
bined with a bulking agent, such as soil, sawdust, wood chips,
refuse, or* previously manufactured compost. Sludge and refuse
make an ideal process combination. Refuse brings porosity to the
mix, while sludge provides needed moisture and nitrogen; both are
converted synergistically to an end product amenable to resource
recovery. The sludge is suitably prepared and placed in piles or
windrows.
In the composting step, the composting period is characterized by
rapid decomposition. Air is supplied by periodic turnings. The
reaction is exothermic, and wastes reach temperatures of 140°F to
160°F or higher. Pathogen kill and the inactivation of insect
larvae and weed seeds are possible at these temperatures. The
period of digestion is normally about six weeks.
Curing is characterized by a slowing of the decomposition rate.
The temperature drops back to ambient, and the process is brought
to completion. The period takes about two more windrow weeks.
In finishing, some sort of screening or other removal procedure
is necessary if municipal solid waste fractions containing nondi-
gestible debris have been included, or if the bulking agent such
as wood chips is to be separated and recycled. The compost may
be pulverized with a shredder, if desired.
Equipment normally associated with windrow composting sludge in-
clude front-end loaders, tractor (drawn), harrow and rotary screen.
Equipment is currently being developed specifically for sludge
composting. A flow diagram of a windrow composting sludge system
is shown on the following page.
Date: 6/23/80 IV.7.6-6
-------
AIR
iLUUUt
BULKING AGENT
MI Yi Mr i«
COMPOSTING
I
CURING
SCREENING
COM POST _
(IF WOODCHIPS ARE RECYCLED)
NON-DIGESTIBLE
MATERIALS
Typical Design Criteria. Typical design criteria for
windrow composting of sludge are shown below. Sludge cannot be
composted by itself but must be combined with a bulking agent to
provide the biomass with the necessary porosity and moisture
content.
Design criteria
Value
Land required
Windrow size
Biomass specifications:
Moisture content
Carbon/nitrogen ratio
Carbon/phosphorus ratio
Air flow
Detention time
Approximately 1/3 acre/dry ton sludge
daily production
4- to 8-ft high, 12- to 25-ft wide at.
base; length variable
45 -
30 -
65%
35%
75/1 - 150/1
10 - 30 ft3/d/lb
6 wk - 1 yr
Costs. Purchased equipment and installation cost for esti-
mation of the total capital investment includes asphalt pads,
roads, sewer, drainage pond, electrical work, and engineering.
The following operating characteristics were assumed for cost
estimation.
Operating characteristic
Assumed value
Service life
Sludge production rate
Land requirement
17 yr
900 Ib/Mgal (dry solids!
0.35 acre/(ton/d)
digested
Costs are based on composting of digested or raw biological
sludge. Assumed land cost equals $10,500/acre.
To adjust costs for composting rates different from 900 Ib/Mgal
calculate the effective flow (QF) using the following equation:
QE = QDesign
new design :sludge mass
900 Ib/Mgal
Date: 6/23/80
IV.7.6-7
-------
References.
1. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency, Cincinnati, Ohio, 1978. 252 pp.
Date: 6/23/80 IV.7.6-8
-------
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(+
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MILLIONS OF DOLLARS/YEAR
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CO
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MILLIONS OF DOLLARS/YEAR
NJ
10
00
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IV.7.7 DEEP-WELL INJECTION [1]
IV.7.7.1 Description
Deep-well disposal of industrial wastes, which has been practiced
for over 25 years, is today a well-developed, carefully controlled,
method of liquid waste disposal. All types of waste from a wide
range of industries are being injected into deep wells. These
wastes vary from relatively innocuous to highly toxic, from
practically inert to highly reactive.
Basically, an industrial waste stream is deep-well injected only
after all reasonable alternative disposal methods have been eval-
uated and found less desirable in terms of environmental protec-
tion and dependability. Chemicals found in waste streams that
may have to be deep-well injected can be divided into organic and
inorganic types. They may be liquids, gases, or solids; the gases
and solids are either dissolved in the liquids or simply carried
along by them.
The organic chemicals include acids, such as maleic, formic,
adipic, cresylic, salicylic, and acetic; alcohols, such as methan-
ol, tertiary butanol, phenol, and isopropanol; solvents, such as
acetone, toluene, xylene, formaldehyde, ethylbenzene, benzaldehyde,
and methyl ethyl ketone; and other compounds, such as sodium
naphthenate, sodium cresylate, calcium and sodium acetate, and
large molecular structures such as styrene polymers and various
polymeric resins.
Inorganic chemicals include acids, such as sulfuric, hydrochloric,
and phosphoric; bases, such as sodium hydroxide; and salts, such
as sodium chloride, sodium sulfate, sodium sulfide, sodium car-
bonate, sodium sulfite, arsenic sulfide, ammonium bisulfate,
sodium bromide, and calcium carbonate.
A deep-well disposal system consists of a disposal zone, well, and
surface facility for pretreating the waste liquids. The disposal
zone must be located below potable-water aquifers, and isolated
from them by thick, relatively impermeable and fracture-resistant
strata such as shale, limestone, or dolomite. The zone must
totally contain the waste liquids and have no other utility value.
Deep-well disposal-zone depths vary from a few hundred to several
thousand feet.
Disposal wells are constructed using oil- and gas-industry-proven
technology, incorporating special adaptions for problems unique
to waste injection. The key to a successful deep-well system is
compatibility of the waste liquids with the materials of construc-
tion, the formation fluid, and the formation itself.
A diagramatic sketch of a deep-well disposal system is shown on
the following page.
Date: 6/23/80 IV.7.7-1
-------
ANNULUS AREA FILLED WITH
BIOCIDES AND CORROSION
INHIBITORS
...i.*.*— i.^A-^^^'*- •
OTECTION CASING
CEMENT-..!.
INJECTION TUBING ?-
SEALING PACKOFF «-
LIMESTONE OR I.
LDOLOMITE DISPOSAL
: PROTECTION CASINGS
I—SETTING DEPTH —
SHALE
IV.7.7.2 Typical Design Criteria
The design of a given deep-well disposal system must be based
upon the type of disposal zone, its permeability and storage
capacity, the volume of waste to be injected, the rate at which
it is to be injected, and the type of waste.
IV.7.7.3 Costs
Several factors determine the economics of a deep-well disposal
system. The major factors are depth of disposal zone, proposed
rate of injection, preinjection treatment required, formation
injectivity, power costs, labor costs, and contract drilling
costs.
Costs vary with each operation, but, in general, installation of
a deep-well disposal system costs about $750,000 to $1,000,000
in 1979 dollars.
Date: 6/23/80
IV.7.7-2
-------
For a well that is one mile deep and has an injection rate of
6 Mgal/mo (140 gpm), maintenance costs in 1979 dollars are about
$60,000/yr/active well; energy costs run about 2C/gal °r less,
depending on utility rates. If neutralization of the waste is
required prior to injectuon, this could cost as much as $150,OOO/
yr/active well.
IV.7.7.4 References
1. Smith, M. E. Solid-Waste Disposal: Deepwell Injection.
Chemical Engineering, April 1979. pp. 107-112.
Date: 6/23/80 IV.7.7-3
-------
IV.8. BIBLIOGRAPHY
The sources listed below are those to which information included
in this volume was cited in the primary reference for this man-
ual, "Innovative and Alternative Technology Assessment Manual,"
(EPA-430/9-78-009 [draft], U.S. Environmental Protection Agency,
Cincinnati, Ohio, 1978; 252 pp.). They are presented in their
original form.
U.S. EPA, "Areawide Assessment Procedures Manual," Vol. I,
Report No. 600/9-76-014 (July 1976).
U.S. EPA, "Areawide Assessment Procedures Manual," Vol. II,
Report No. 600/9-76-014 (July 1976).
U.S. EPA, "Areawide Assessment Procedures Manual," Vol. Ill,
Report No. 600/9-96-014 (July 1976) .
U.S. EPA, "Energy Conservation in Municipal Wastewater Treatment,"
Report No. 430/9-77-011 (March 1977).
U.S. EPA, "Construction Costs for Municipal Wastewater Treatment
Plants: 1973-1977," Report No. 430/9-77-013 (January 1978).
U.S. EPA, "Costs of Wastewater Treatment by Land Application,"
Report No. 430/9-75-503 (June 1976).
Metcalf & Eddy, Inc., Wastewater Engineering: Collection,
Treatment, Disposal, McGraw-Hill, 1972, 1978.
U.S. EPA Technology Transfer, "Process Design Manual for Sludge
Treatment and Disposal," Report No. 625/1-74-006 (October 1974).
U.S. EPA Technology Transfer, "Process Design Manual for Land
Treatment of Municipal Wastewater," Report No. 625/1-77-008
(October 1977).
Piecuch, Peter J., "Journal Water Pollution Control Federation,"
Literature Review (June 1978).
U.S. EPA Technology Transfer, "Flow Equalization," (May 1974).
Date: 6/23/80 IV.8-1
-------
Culp/Wesner/Culp, "A Comparison of Oxidation Ditch Plants to
Competing Processes for Secondary and Advanced Treatment of
Municipal Wastewater," U.S. EPA Report No. 600/2-78-015
(March 1978).
U.S. EPA, "Cost Estimates for Construction of Publicly-Owned
Wastewater Treatment Facilities - Summaries of Technical Data
for Combined Sewer Overflows and Storm Water Discharge, 1976
Needs Survey," Report No. 430/9-76-012 MCD Report No. 48C
(Feb. 10, 1977).
U.S. EPA Technolohgy Transfer Seminar Publication, "Upgrading
Lagoons," Report No. 625/4-73-OOla (August 1973).
U.S. EPA, "Costs of Wastewater Treatment by Land Application,"
Report No. 430/9-75-003 (June 1975).
Water Pollution Control Federation, "Wastewater Treatment Plant
Design," Lancaster Press, Inc., 1977 Manual of Practice.
"Membership Directory," Water and Wastewater Equipment Manu-
facturers Association, Inc., 7900 Westpark Drive, Suite 304,
McLean, Va (March 1978).
U.S. EPA, "Cost-Effective Comparison of Land Application and
Advanced Wastewater Treatment," Report No. 430/9-75-016.
U.S. EPA Technology Transfer, "Process Design Manual for Up-
grading Existing Wastewater Treatment Plants" (October 1974).
U.S. EPA Technology Transfer, "Process Design Manual for
Nitrogen Control" (October 1975).
U.S. EPA Technology Transfer, "Process Design Manual for Phos-
phorus Removal," Report No. 625/1-76-OOla (April 1976).
Great Lakes - Upper Mississippi River Board of State Sanitary
Engineers, "Recommended Standards for Sewage Works Ten States
Standards," Health Education Service, Albany, NY, 1974 Revised
Edition.
U.S. EPA Technical Report, "A Guide to the Selection of Cost-
Effective Wastewater Treatment Systems," Report No. 430/9-75-002
(July 1975).
Epstein, Eliot et al., "Land Disposal of Toxic Substances and
Water-Related Problems," JWPCF, Vol. 50, pp. 2039-2042
(August 1978).
U.S. EPA, "Alternatives for Small Wastewater Treatment Systems,
Cost/Effectiveness Analysis," Report No. 625/4-77-011 (October
1977).
Date: 6/23/80 IV.8-2
-------
U.S. EPA, Technology Transfer Seminar Publication, "Land Treat-
ment of Municipal Wastewater Effluents - Design Factors-I,"
Report No. 625/4-76-010 (January 1976).
U.S. EPA Technology Transfer Seminar Publication, "Land Treat-
ment of Municipal Wastewater Effluents - Design Factors-II,"
Report No. 625/4-76-010 (January 1976).
Walzer, James G., "Design Criteria for Dissolved Air Flotation,"
Pollution Engineering, Vol. 10, No. 2, February 1978, pp. 46-48.
Sieger, Ronald B, Patrick M. Maroney, U.S. EPA Technology Trans-
fer, "Incineration-Pyrolysis of Wastewater Treatment Plant
Sludges," Design Seminar for Sludge Treatment and Disposal, 1977.
U.S. EPA Technology Transfer, "Wastewater Filtration, Design
Considerations," Seminar Publication Report No. 625/4-74-007a.
U.S. EPA Technology Transfer, "Nitrification and Dentrification
Facilities, Wastewater Treatment," Seminar Publication (August
1973) .
U.S. EPA Technology Transfer, "Oxygen Activated Sludge Waste-
water Treatment Systems, Design Criteria and Operating Experi-
ence," Seminar Publication (August 1973).
U.S. EPA Technology Transfer, "Physical-Chemical Nitrogen Removal,
Wastewater Treatment," Seminar Publication (July 1974).
Water Pollution Control Federation, "Chlorination of Wastewater,"
Manual of Practice No. 4, 1976.
Water Pollution Control Federation, "Sludge Dewatering," Manual
of Practice No. 20, 1969.
U.S. EPA Technology Transfer, "Process Design for Carbon Ad-
sorption," (October 1973).
U.S. EPA, "Anaerobic Sludge Digestion," Operations Manual Report
No. 430/9-76-001 (February 1976).
U.S. EPA, "Cost Estimating Manual - Combined Sewer Overflow
Storage and Treatment," Report No. 600/2-76-286 (December 1976).
U.S. EPA, "Procedural Manual for Evaluating the Performance of
Wastewater Treatment Plants," under Contract No. 68-01-0107.
U.S. EPA, "Attached Growth Biological Wastewater Treatment
Estimating Performance and Construction Costs and Operating and
Maintenance Requirements," MERC, Cincinnati, OH. (January 1977).
Date: 6/23/80 IV.8-3
-------
U.S. EPA, "Analysis of Operations & Maintenance Cost for Munici-
pal Wastewater Treatment Systems," Report No. 430/9-77-015
(February 1978).
Burd, R. S., "A Study of Sludge Handling and Disposal," Federal
water Pollution Control Administration Publication WP-20-4
(May 1968).
Antonie, Ronald L., et al, "Evaluation of a Rotating Disk Waste-
water Treatment Plant", Journal Water Pollution Control Federa-
tion, Vol. 48, No. 1 (January 1976).
Lue-Hing, Cecil, et al, "Biological Nitrification of Sludge
Supernatant by Rotating Disks," Journal Water Pollution Control
Federation, Vol. 48, No. 1 (January 1976).
Torpey, Wilbur N., et al, "Rotating Disks with Biological Growths
Prepare Wastewater for Disposal or Reuse", Journal Water Pol-
lution Control Federation, Vol. 43, No. 11, November 1971.
Azad, Hardam, "Industrial Wastewater Management Handbook," McGraw
Hill Book Company, 1976.
U.S. EPA, "Construction Costs for Municipal Wastewater Conveyance
System 1973-1977," Report No. 430/9-77-014.
U.S. EPA, Sludge Processing for Combined Physical-Chemical-
Biological Sludges," Report No. R2-73-250 (July 1973).
U.S. EPA, "Application of Plastic Media Trickling Filters for
Biological Nitrification Systems," Report No. R2-73-199 (June
1973) .
U.S. EPA, "Physical-Chemical Treatment of a Municipal Wastewater
Using Powdered Carbon," Report No. R2-73-264 (August 1973).
Epstein, E., et al, "A Forced Aeration System for Composting
Wastewater Sludge," Journal Water Pollution Control Federation,
Vol. 48, No. 4, pp. 688-694 (April 1976).
Colacicco, D., et al, "Costs of Sludge Composting," Agricultural
Research Service, ARS-ME-79, 18 pp. (February 1977).
Colacicco, D., et al, "Sludge Composting; Costs and Market Place
Development," Proceedings of the Third National Conference on
Sludge Management Disposal and Utilization, Miami Beach, FL
(December 14-16, 1976).
Parr, J. F., et al, "Composting Sewage Sludge for Landfill
Application," Agriculture and Environment, 4, (1978).
Date: 6/23/80 IV.8-4
-------
U.S. EPA, "Draft Development Document Including the Data Base
for the Review of Effluent Limitations Guidelines (BATEA), New
Source Performance Standards, and Pretreatment Standards for
the Petroleum Refining Point Source Category," (March 1978).
Davis, John C., "Activated Carbon: Prime Choice to Boost
Secondary Treatment," Chemical Engineering, April 11, 1977.
U.S. EPA, "Carbon Adsorption Isotherms for Toxic Organics,"
Municipal Environmental Research Laboratory, Cincinnati, OH
(May 1978).
Bernardin, F. E., "Results of Field Tests to Determine Effective-
ness of Granular Carbon for Removal of Polychlorinated Biphenyls
from industrial Effluent," Summary Report CAS-70-1, Calgon Ad-
sorption Systems, Calgon Corporation (undated).
Bernardin, F. E., and Froelich, E. M., "Practical Removal of
Toxicity by Adsorption", Proceedings of the 30th Annual Purdue
Industrial Waste Conference (May 8-9, 1975).
Hager, D. G. and J. L. Rizzo, "Removal of Toxic Organics from
Wastewater by Adsorption with Granular Activated Carbon,"
presented at the U.S. EPA Technology Transfer Session on Treat-
ment of Toxic Chemicals, Atlanta, GA (April 19, 1974).
Chemical Week, 1978 Buyers Guide Issue (October 26, 1977).
U.S. EPA, "A Review of Techniques for Incineration of Sewage
Sludge with Solid Wastes," Report No. 600/2-76-268 (December
1976) .
Gulp, Russell L. and Gordon L. Gulp, "Advanced Wastewater Treat-
ment," Van Nostrand Reinhold Co. (1971).
U.S. EPA, "Costs of Hauling and Land Spreading of Domestic
Sewage Treatment Plant Sludge," Report No. 670/2-74-010
(February 1974) .
"Chemical Engineering, Equipment Buyer's Guide Issue," Part Two,
Vol. 85, No. 16 (July 17, 1978).
Communication with Ken Decker, Big Wheels, Inc., P.O. Box 113,
Paxton, IL 60957.
U.S. EPA Technology Transfer, "Process Design Manual for Sus-
pended Solids Removal" (January 1975).
"Pollution Equipment News," 1975 Catalog and Buyers Guide
(November 1977).
Date: 6/23/80 IV.8-5
-------
"Lime, Handling, Application and Storage," Natural Lime Associ-
ation, Bulletin 213, 1949.
Kreissl, James F., Robert Smith, James A. Heidman, "The Cost of
Small Community Wastewater Alternatives," U.S. EPA, August 1978.
U.S. EPA, "Physical-Chemical Treatment of a Municipal Wastewater
Using Powdered Carbon, No. II," Report No. 600/2-76-235 (November
1976).
Ekenfelder, W. W., "Industrial Water Pollution.Control,"
Mcgraw-Hill, 1966.
"Water Treatment Handbook," Gulf Degremont, 1973.
U.S. EPA, "Supplement for Pretreatment to the Development Docu-
ment for the Petroleum Refinery Industry, "Existing Point Source
Category," Report No. 400/1-76-083 (December 1976).
"Carter Water and Waste Treatment Equipment," Catalog 0662,
Ralph B. Carter Company.
American Society of Civil Engineers, U.S. EPA, Municipal Sludge
Management, Proceedings of the National Conference of Municipal
Sludge Management, Pittsburg, PA (June 11-13, 1974).
U.S. EPA, "Flow Equalization Evaluation of Applications in Muni-
cipal Sewage Treatment," Second Review Draft, Contract No. 68-03-
2512 (January 1978).
Communication with (via telephone) Dale Bentley, Ralph B. Carter
Company, Hackensack, New Jersey, Subject: Costs for Belt Filter
Press, September 14, 1977.
U.S. EPA, "Laboratory Ozonation of Municipal Wastewaters,"
Report No. 670/2-73-075, September 1973.
"Ozone Gives Wastewater the Treatment," Chemical Week, June 21,
1978, p. 49.
"Ozone Use Grows as Effluent Disinfectant," ENR, May 11, 1978,
p. 18.
Stopka, Karel, "Ozone-Activated Carbon Can Remove Organics,"
Water and Sewage Works, May 1978, p. 88.
Fair, G. M., J. C. Geyer, and D. A. Okun, "Water and Wastewater
Engineering, John Wiley and Sons, 1968.
Communication (via telephone) with Dick Sobel, Sharpies-Stokes,
New York, September 26, 1978, Subject: Cost Data for Thickening;
Solid Bowl and Disc Centrifugal.
Date: 6/23/80 IV.8-6
-------
Communication (via telephone) with Bob Honeychurch, Dorr-Oliver,
Stanford, CT, September 26, 1978, Subject: Lost Data for Thicken-
ing; Solid Bowl and Disc Centrifugal.
Walsh, James J., Coppel, Wayne, "Seminar Sludge Treatment and
Disposal, Part II, Sludge Disposal," U.S. EPA, March 1978.
Otis, Richard J., W. C. Boyle, "U.S. EPA Training Seminar for
Wastewater Alternatives for Small Communities, On-Site Alterna-
tives," August 14-18, 1978; August 28- September 1, 1978.
U.S. EPA "Appraisal of Powdered Activated Carbon Processes for
Municipal Wastewater Treatment," Report No. 600/2-77-156
(September 1977).
Communication (via telephone) with G. Burde, Burde Associates,
Paramus, N. J. Subject: Package Plant Treatment Costs, Extended
Aeration and Contact Stabilization.
Bauer, David H. et al., "Identification, Evaluation and Compari-
son of On-Site Wastewater Alternatives," Draft Final Report, U.S.
EPA, August 1978.
U.S. EPA, "Cost Estimating Manual-Combined Sewer Overflow Stor-
age and Treatment," Report No. 600/2-76-286 (December 1976).
Kalinske, A. A., "Comparison of Air and Oxygen Activated Sludge
Systems," Journal Water Pollution Control Federation. Vol. 48,
No. 11, November 1976, pp. 2472-2485.
Parker, D. S., M. S. Merrill, "Oxygen and Air Activated Sludge:
Another View," Journal Water Pollution Control Federation, Vol.
48, No. 11, November 1976, pp. 2511-2528.
U.S. EPA, "Process Design Manual—Municipal Sludge Landfills,"
Technology Transfer, Report No. 625/1-78-010 SW-705 (October
1978).
Pickett, Edward M., "Evapotranspiration and Individual Lagoons,"
Proceedings of the Northwest On-Site Waste Water Disposal Short
Course," University of Washington, December 8-9, 1976.
Communication (via telephone) with Walter Kuntz, Foley Machinery,
Piscataway, New Jersey, Subject: Sludge Trenching.
U.S. EPA, "Pilot Plant for Tertiary Treatment of Wastewater with
Ozone," Report No. EPA-R2-73-146, Janury 1973.
Stetzer, R. H., "FMC Pure Oxygen, An Effective Solution to Waste-
water Treatment and Process Applications," paper presented at
70th Annual AICHE Meeting, November 15, 1977, New York, NY.
Date: 6/23/80 IV.8-7
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Pearlman, S. R. , and D. G. Fullerton, "Full Scale Demonstration
of Open Tank Oxygen Activated Sludge Treatment," U.S. EPA Grant
No. S803910, draft report to Municipal Environmental Research
Laboratory, Office of Research and Development, U.S. EPA,
Cincinnati, OH.
Gulp, Wessler and Gulp, Suspended Growth Biological Wastewater
Treatment - Construction, Operating and Maintenance Cost Esti-
mates, Vol. 2, unpublished EPA Document, El Dorea Hills, CA.
U.S. EPA, "Estimating Costs and Manpower Requirements for Con-
ventional Wastewater Treatment Facilities," Report 17090 DAN,
October 1971.
Finstein, M. S. and M. Morris, "Composting," New Jersey Effluents.
Vol. 11, No. 1, April 1978.
Gray, K. R., et al., "Review of Composting, Part 2 - The Practical
Process," Process Biochemistry, p. 22, October 1971.
Via telephone, Frank Carlson, Royer Foundry & Machine Co., 158
Pringle Street, Kingston, PA 18704.
Villiers and Farrell, "A Look at Newer Methods for Dewatering
Sewage Sludges," Civil Engineering ASCE, p. 66, December 1977.
Gulp, Wessler and Gulp, Attached Growth Biological Wastewater
Treatment - Construction, Operating and Maintenance Cost Esti-
mates , Vol. 1, unpublished EPA Document, El Dorea Hills, CA.
U.S. EPA, "Lime Use in Wastewater Treatment Design and Cost Data,"
U.S. EPA-600/2-75-036, October 1975.
U.S. EPA, "Evaluation of Dewatering Devices for Producing High
Sludge Solids Cake," Draft Report, Contract No. 68-03-2455, MERL
1978.
Burant, W., and T. J. Vollstandt, "Full-scale Wastewater Treatment
with Powdered Activated Carbon," Water and Sewage Works, November
1973.
Adams, A. D., "Powdered Carbon: Is It Really That Good?," Water
and Waste Eng., March 1974.
Stern, G. , "Processing, Economics and Sale of Heat Dried Sludge,"
Proceedings of the 1975 National Conference on Municipal Sludge
Management and Disposal, Anaheim, California, August 18-20, 1975.
Date: 6/23/80 IV.8-8
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Letter, Nichols Engineering to Mr. Leo Pinczuk, Burns and Roe
Industrial Services Corp., August 15, 1978.
"The Co-Disposal of Sewage Sludge and Refuse in the Purox System"
EPA 600/2-78-198, December 1978.
Date: 6/23/80 IV.8-9
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APPENDIX A
ECONOMIC ASSUMPTIONS
COST COMPONENTS
Total capital investment and annual operating cost curves were
generated for wastewater treatment technologies grouped into the
following classifications: wastewater conditioning, primary
wastewater treatment, secondary wastewater treatment, tertiary
wastewater treatment, sludge treatment, and disposal. The fol-
lowing sections discuss general factors contributing to these
costs and assumptions used in this manual to generate total cap-
ital investment and annual operating cost curves, respectively.
Total Capital Investment
Total capital investment, the total amount of money to supply the
necessary treatment facilities plus that required for initial
operation of the facilities, is herein the sum of the fixed cap-
ital investment and a small amount of working capital. Fixed
capital investment was divided into direct cost components and
indirect cost components as shown in Table A-l, which lists the
major components of the total capital investment and the assump-
tions used in estimating the total capital investment from pur-
chased and installed equipment values presented in the literature.
Assumed values are similar to those presented in Reference 1 with
adjustments resulting in a lower percentage for working capital.
Total Annual Operating Cost
The total annual operating cost curve is presented on the same
graph as cost curves for labor, materials, chemicals, power, and
fuel, when applicable, and a curve for total direct operating
cost (calculated as the sum of the costs for labor, materials,
chemicals, power, and fuel). Table A-2 lists the major components
of the annual operating cost and the assumptions used in estima-
ting the annual operating cost from labor, materials, chemical,
power, and fuel values presented in the literature. Cost com-
ponents marked with an asterisk are those which have been plotted,
where appropriate.
Date: 6/23/80 IV.A-l
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TABLE A-l. COST ASSUMPTIONS AND BREAKDOWN
OF TOTAL CAPITAL INVESTMENT
Cost component Assumed value
Fixed capital investment:
Direct costs
• Purchased equipment and installation PE&I
• Instrumentation and controls 10% PE&I
• Piping 21% PE&I
• Electrical equipment and materials 13% PE&I
• Buildings 26% PE&I
• Yard improvements 7% PE&I
• Service facilities 41% PE&I
Indirect costs
• Engineering and supervision 29% PE&I
• Construction expenses 32% PE&I
• Contractor's fees 7% PE&I
• Contingency 27% PE&I
Total fixed capital investment 3.13 PE&I
Working capital 0.47 PE&I
Total capital investment 3.6 PE&I
TABLE A-2. COST ASSUMPTIONS AND BREAKDOWN
OF TOTAL ANNUAL OPERATING COST
• Labor (L)
• Materials (M)
• Chemicals (C)
• Power (P)
• Fuel (F)
• Total Direct Operating cost (TDC) = (L+M+C+P+F)
Plant overhead - (60% L)
Taxes and insurance - ( 2% FCI)
General and administrative expenses - (40% L)
Depreciation - (10% FCI)
Interest on working capital - (12% WC)
Annual operating cost - (TDC + L + 12% FCI + 12% WC)
Date: 6/23/80 IV.A-2
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The following paragraphs briefly describe the individual cost com-
ponents [2] .
Labor costs. Labor costs include the manpower required to
operate and maintain the facility, plus such support tasks as
supervision and administration, clerical work, laboratory work,
and yard work.
Material costs. Material costs include the various materials
required for routine maintenance of the facility. Examples are
paint, grease, and replacement parts. Such costs for mechanical
equipment, such as pumps and aerators, are generally higher than
those for structural equipment.
Chemical costs. Various unit processes require chemicals.
The quantities of chemicals required are based on the assumed
loading rates. The chemical costs are generated from the unit
price for each chemical and the assumed loading rate.
Power costs. Each mechanical operation at a treatment
facility, such as pumping, mixing, and aeration, consumes energy.
Horsepower requirements are converted into electrical units (kWh)
and a corresponding cost is developed using a unit price per kWh.
Fuel costs. Energy other than electricity is required for
some processes (such as incineration of sludge). In these cases,
the amount of energy (fuel) required is computed and the cost
determined on the basis of an assumed cost per unit.
DEVELOPMENT OF COST CURVES
A large number of both construction and operating and maintenance
cost curves were used as a basis for development of total capital
cost curves and annual operating cost curves for this manual.
These construction (purchased equipment and installation) cost
curves and operating and maintenance cost curves were derived
from the Innovative and Alternative Technology Assessment Manual
[3] and the Areawide Assessment Procedures Manual [2], and were
originally developed primarily from 1976 cost data and municipal
wastewater treatment technology. Cost data indexed to years other
than 1976 were also used as a basis for development of cost curves
in this manual. The costs from various years were indexed to
September 1979 using both Engineering News Record (ENR) cost in-
dices (ENR index equals 3119) and direct ratios. The ENR construc-
tion cost index was used to index purchased and installed
equipment to 1979 and thus to determine total capital investment
cost. Additionally, ENR common labor and material cost indices
were used to scale up labor and material costs; direct ratios were
used to scale up power and fuel costs; and chemical costs were
assumed to be unchanged.
Date: 6/3/80 IV.A-3
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As previously mentioned, the base for costs presented in this
manual is generally 1976 and these costs were subsequently indexed
to 1979. From Reference 3, the original base is primarily an ENR
index of 2475 and those assumptions listed in Table A-3.
TABLE A-3. COST AND DESIGN BASES FOR
REFERENCE 3 1976 COST DATA
Cost basis
Assumed value
ENR index & 2475, September 1976
Labor rate $7.50/hr including fringe benefits
Energy costs
Electric power $0.02/kWh
Fuel oil $0.37/gal
Gasoline $0.60/gal
Land $l,000/acre
Chemical costs
Liquid oxygen $65/ton
Methanol $0.50/gal
Chlorine, 150-Ib cylinders S360/ton
1-ton cylinder $260/ton
tank car $160/ton
Quicklime $25/ton
Hydrated lime $30/ton (as CaO)
Polymer (dry) $1.50/lb
Ferric chloride SlOO/ton
Alum $72/ton
Activated carbon
(granulated) $0.50/lb
Sulfuric acid (66° Be) $50/ton
Sodium hexametaphosphate $0.25/lb
SOa, 150-lb cylinders $450/ton
1-ton cylinder $215/ton
tank car $155/ton
Design basis
Construction costs and operation and maintenance costs are based
on design average flow unless otherwise noted.
Operation and maintenance costs include:
Labor costs for operation, preventative maintenance, and minor
repairs.
Materials costs to include replacement parts and major repair
work (normally performed by outside contractors).
Chemical costs.
Fuel costs.
Electrical power costs.
Construction costs do not include external piping, electrical,
instrumentation, site work, contingency, or engineering and
fiscal fees.
*Based on 1,500 hr/man-year and represents: a 5-day work week;
an average of 29 days for holidays, vacation, and sick leave;
and 6.5 hours of productive work time per day.
Date: 6/23/80 IV.A-4
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As an illustration of the procedure used in indexing and scaling
up the 1976 cost curves, the following example is presented.
Reference 3 gave this information for primary circular clarifica-
tion (with pump).
COSTS - Service Life = 50 years; ENR = 2475.
Design Basis;
nClarifier designed for surface overflow rate of 800 gal/d/ft2
(based on average Q).
2. Costs include primary sludge pumps; sludge concentration of
4 percent solids; pump head assumed as 10 ft TDK.
3. Power Cost = $0.02/kWh
4. To adjust costs for alternative surface overflow rate, enter
flow at effective flow (Q^)
= 0
^
800 gal/d/ft2
Design New Design Surface Overflow Rate
1.0
10
Oi
001
0
1 . ..' ;i i COMSTRUCTIOH Cft?T-4-4 1
1 ' 1
;
1
• 'I
, i
;ii ;
—
1—
]
T|i ' 1 ' : : '
,
i' •
i i 1 in i
1
1
! LX1
i i ^^
' ' 1 ' i • : ^r^ i ' i .
^^"1
•
' i;^^i 1 ^
^
j
1
i
! 1 i
1
n
p**
i
1 !
;| i
JJX— -
-4
1
y
j/*
1
i
>
;
j j.
— . i . .,. , , , ..
'l! ' '
! ' i ' 1
i
ii , ; : ':.: i i • . ',
10
10
1 1
10
Rant Flow, Mg«l/d
1
a
!
- oi
7
I
S 0.01
0.001
00
01
3OPCRATION B MAINTENANCE COST
TTT
, :
^
000)
./• X i-r*4-
4rHuimai . \ '•
(O 10
PUnt Flow. Mgtl/d
ooooa
oo
-The total capital investment a;.J purchased and installed equipment
costs in 1979 dollars were estimated from the information above.
Using the ratio of 1979 to 1976 ENR indices (3119/2475 = 1.26),
the purchased and installed equipment cost was plotted in 1979
dollars. From the purchased and installed equipment cost, total
capital investment was then estimated by applying the factor of
3.6 shown in Table A-l.
Development of total direct operating and annual operating cost
curves required the use of individual indices for power, labor,
and material shown below. The following example shows that costs
were read from the graph for each of these components at flowrates
corresponding to 0.1, 1.0, 10, and 100 Mgal/d. Each cost component
was indexed to 1979 by either an ENR index or direct ratio.
Date: 6/23/80
IV.A-5
-------
These components were summed to give the total direct operating
cost in 1979 dollars, the factors presented in Table A-2 were
used to derive total annual operating cost, and the data were
used to plot curves for power, labor, materials, total direct
operating cost, and total annual operating cost in estimated 1979
dollars.
EXAMPLE TOTAL ANNUAL OPERATING COST CALCULATION
FOR PRIMARY CIRCULAR CLARIFICATION WITH PUMP
Flowrate , Mgal/d
Cost component
Labor
Materials
Chemicals
Power
Fuel
Total direct operating cost
Total annual operating cost
Factor
(L, from graph)
(L x 1.21)a
(M, from graph)
(M x 1.39)b
(C, from graph)
(P, from graph)
(P x 1.75)c
(F, from graph)
(F x 2.16)d
(L+M+C+P+F)
(TDCe+L+0.12 TCIf)
0.1
-
0.0013
0.0018
0.0007
0.00012
0.002
0.026
1.0
0.003
0.0036
0.0028
0.0039
0.00026
0.00046
0.008
0.066
10
0.02
0.024
0.01
0.014
0.0015
0.0026
0.041
0.281
100
0.18
0.22
0.068
0.095
0.01
0.0175
0.33
1.97
Note: Blanks indicate not applicable.
aBased on ENR common labor index. The ratio of September 1979 to 1976 indices is
5844
4~8T5~
or 1.21.
Based on ENR materials index. The ratio of September 1979 to September 1976
1449
indices is or I-39-
"Based on a direct ratio of 1979 costs to 1976 costs equal to approximately
?0.035/kWh
50.02/kWh
or 1.75.
Based on a direct ratio of 1979 to 1976 costs equal to approximately
$0.80/gal fuel oil
$0.37/gal fuel oil
or 2.16.
"TDC (total direct operating cost).
Total capital investment.
Date: 6/23/80
IV.A-6
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References
1. Peters, M. S., and K. D. Timmerhaus. Plant Design and Econ-
omics for Chemical Engineers, McGraw-Hill Book Company,
New York, New York, 1968. 850 pp.
2. Areawide Assessment Procedures Manual - Volume III, EPA-600/
9-76-014-3 (PB 271 866), U.S. Environmental Protection Agency,
Cincinnati, Ohio.
3. Innovative and Alternative Technology Assessment Manual,
EPA-430/9-78-009 (draft), U.S. Environmental Protection
Agency,- Washington, D.C., 1978. 252 pp.
•9U.S. GOVERNMENT PRINTING OFFICE: 1 98 0-3 2 5" I 57 / 6 3 92
Date: 6/23/80 IV.A-7
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