technology transfer
design seminar
publication
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TECHNOLOGY TRANSFER
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SLUDGE HANDLING AND DISPOSAL
This publication was prepared for use in the United States
Environmental Protection Agency Technology Transfer Design
Seminar Series. Emphasis is placed on technology which can be
incorporated into design and practice today.
Prepared by:
Mr. John R. Harrison
Black, Crow and Eidsness, Inc.
Wilmington, Delaware
Mr. Stanley J. Mogelnicki
The Dow Chemical Company
Midland, Michigan
Dr. James E. Smith, Jr.
National Environmental Research Center
Environmental Protection Agency
Cincinnati, Ohio
December 5-6,1972
The Copley Plaza
Boston, Massachusetts
United States Environmental Protection Agency
Technology Transfer Program
Washington, D.C.
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TABLE OF CONTENTS
Page Number
SECTION 1
SECTION 2
SECTION 3
SECTION 4
SECTION 5A
SECTION 5B
SECTION 5C
SECTION 6A
SECTION 6B
SECTION 6C
SECTION 7
SECTION 8
SECTION 9
SECTION 10
Importance of Sludge Processing and Disposal-
Current EPA Programs
Current and Previous Methodology
Nature and Handling Characteristics of Sludges
Sludge Stabilization Processes
Case Studies Plant Results Chemical Conditioning
Conventional Activated Sludge
Case Studies - Plant Results Chemical Conditioning
Primary Plants with Chemical Addition
Removal of Phosphorus from Wastewater by
Chemical Addition
Oxygen Activated Sludge Process
Oxygen Activated Sludge
Case Study Fairfax Westgate
Oxygen Activated Sludge
Case Study New Orleans, Louisiana
Thermal Processing of Sludge
Final Disposal Processes and Case Studies
Sludge Thickening and Blending
Sludge Dewatering
1-1 1-5
2-1 2-5
3-1 3-10
4-1 4-9
5A -1 5A - 8
5B -1 SB - 8
5C -1 5C - 7
6A -1 6A - 4
6B -1 6B - 4
6C -1 6C - 4
7-1 7-10
8-1 8-8
9-1 9-5
10-1 10-6
i
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SECTION 1 - IMPORTANCE OF SLUDGE PROCESSING AND DISPOSAL
CURRENT EPA PROGRAMS
1. Introduction
Solids removed in the processing of waters for human consumption, industrial
usage, or in the case of wastewaters, for discharge to a receiving stream, present
a disposal problem.
Disposal of sludges from wastewater treatment will today account for up to 50
percent of the total treatment cost.
Sludge is the settleable solids that are naturally present in water and wastewater
or that are formed during treatment.
Tighter effluent criteria, increasing land scarcity and population pressure
combine to make sludge disposal more difficult and expensive.
2. Quantities and Characteristics of Sludge to be Handled
Approximate amounts of sludge produced in the treatment of wastewater by
simple clarification, chemical treatment and biological processes are shown in
Table 1-1.
Activated sludge process contributes large quantities of sludge for disposal.
Sludge is a semi-liquid waste and the water content of all sludges is high, as
shown in Table 1-2.
Typical sludge masses to be handled are shown in Table 1-3.
The quantity of sludge can be calculated from wastewater analysis and
efficiency of the treatment units.
Physical-chemical treatment means new kinds of sludges, more mass and
sometimes more volume. A calculation of the increase in sludge mass when iron
and alum are used at various points in the wastewater treatment sequence is
presented (see Table 1-4, from Reference 7).
The sludge produced when lime is added to wastewater in the primary or as a
tertiary can be calculated from water and wastewater analysis (see Table 1-5).
Measured quantities were about 20 percent higher than calculated values.
1 -1
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3. Sludge Management Alternatives
Selection of treatment and disposal processes must consider pollution
potential, aesthetics and economics. Protection and Enhancement of
Environmental Quality are required by the National Environmental Policy Act
of 1969 and Executive Order 11514 (Reference 8).
Sludge can be ultimately disposed of in dry, dewatered filter cake, liquid or in
the form of ash and combustion gases.
Steps to be followed in solving a sludge handling and disposal problem are
indicated in Figure 1-1.
4. Costs of Sludge Processing and Disposal
Costs of sludge processing are a function of:
Treatment sequence
The raw sewage
Location (the surrounding neighborhood)
Climate
Scale of operation
Regulations, etc.
Costs are sensitive to all of the above and individual author's assumptions. If
possible, get all comparisons from the same unbiased source.
The cost of some sludge handling and disposal processes is given in Table
1-6.
The cost of some sludge handling and disposal process combinations is
given in Figure 1-2.
5. Current EPA Programs
Carried out primarily at the National Environmental Research Center in
Cincinnati by the Ultimate Disposal Research Program.
1-2
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Objective of EPA Programs
To develop new or improved sludge handling, disposal and utilization
technology so that the municipal sector will be able to achieve compliance
with present and future water quality standards. The development of
methods for nonpollutional disposition of sludges resulting from
treatment processes is critical to a successful water quality improvement
program.
Their implementation - by contracts, grants, and inhouse research.
Current projects are shown in Tables 1-7, 1-8, and 1-9.
1-3
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REFERENCES - SECTION 1
1. Keefer, C.E., "Sewage Treatment Works." McGraw-Hill Book Company, Inc., New York,
(1940).
2. Fair, G.M., and Imhoff, K., "Sewage Treatment." John Wiley and Sons, Inc., New York,
2nd Edition, (1965).
3. Babbitt, H.E., "Sewerage and Sewage Treatment." John Wiley and Sons, Inc., New York,
7th Edition, (1953).
4. McCabe, J., and Eckenfelder, W.W., "Advances in Biological Waste Treatment." Pergamon
Press (1963).
5. Burgess, J.V. Process Biochem.,3, 27-30 (1968).
6. Stanley, William E., Personal communication, Washington University, St. Louis, Mo.
(1967).
7. Adrian, D.D. and Smith, J.E., Jr., "Dewatering Physical-Chemical Sludges." Conference
on Application of New Concepts of Physical-Chemical Wastewater Treatment,
Vanderbilt University, September 18-22, 1972.
8. "Federal Guidelines, Design, Operation and Maintenance of Wastewater Treatment
Facilities." FWQA, Department of the Interior, September, 1970.
9. Patterson, W.L., and Banker, R.F., "Estimating Costs and Manpower Requirements for
Conventional Wastewater Treatment Facilities." Water Pollution Control Research
Series 17090 DAN 10/71, Government Printing Office, Washington, D.C., 1971.
10. Smith, R., and Eilers, R.G., Personal communication, May 31, 1972.
11. Eilers, R.G., and Smith, R., "Wastewater Treatment Plant Cost Estimating Program."
AWTRL of EPA, April, 1971, Internal Report (Computer Deck Available).
1-4
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LIST OF FIGURES AND TABLES - SECTION 1
Table 1-1
Table 1-2
Table 1-3
Figure 1-1
Table 1-4
Table 1-5
Table 1-6
Table 1-7
Table 1-8
Table 1-9
Figure 1-2
Typical Quantities of Sludge Produced in Wastewater Treatment Processes
Water Content of Sludges
Sludge Masses
Considerations in the Handling and Disposal of Sludge
Calculated Sludge Mass (lb/mg)
Calculations of Sludge Quantity. Lime Added to the Primary
Total Cost in Cents per 1,000 Gallons of Wastewater Processed for
Indicated Sludge Handling Processes
Recent Projects April, 1972 Ultimate Disposal
New Projects since April, 1972
In-House Activities - Ultimate Disposal
Costs of Sludge Processing and Disposal - Including Amortization
1-5
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TABLE 1-1
TYPICAL QUANTITIES OF SLUDGE PRODUCED
DM WASTEWATER TREATMENT PROCESSES
Treatment Keefer1 Imhoff & Fair2 Babbitt3 M&E4
Plain Sedimentation 2,950 3,530 2,440 3,000
Trickling Filter Humus 745 530 750 700
Chem. Precipitation 5,120 5,100 5,250 5,100
Activated Sludge 19,400 14,600 18,700 19,400
(Given as gallons/million gallons sewage treated)
1 See Reference 2
2 See Reference 3
3 See Reference 4
4 See Reference 5
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TABLE 1-2
WATER CONTENT OF SLUDGES
Treatment Percent Moisture Pounds of Water/Pound Sludge Solids
Primary Sedimentation
95
19
Chem. Precipitation
93
13.3
Trickling Filters
Humus-Low Rate
93
13.3
Humus-High Rate
97
32.4
Activated Sludge
98-99
-65.6
Well Digested Sludge
Primary Treatment
85-90
~ 7.0
Activated Sludge
90-94
11.5
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TABLE 1-3
SLUDGE MASSES1
Percent Percentage of
Suspended Solids lb/day/mg Volatile Materials Specific Gravity
Treatment Removal Removed Removed Suspended Solids
Plain Sedimentation 60
Trickling Filter Humus 30
Activated Sludge 92
(excess)
lmhoff Tank
Dig. 60
1,020 65 1.33
510 45 1.52
1,563 65 1.33
1,020 50 1.47
1 See Reference 6
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CONSIDERATIONS IN THE HANDLING
AND DISPOSAL OF SLUDGE
328107 0
328107
328107 2
328107 3
328107 4
328107 6
328107 5
328107 7
328107
328107 9
ULTIMATE
DISPOSAL PROGRAM
LAND DISPOSAL
a Land spreading
b Landfill
c Other
SUBSURFACE AND
OCEAN DISPOSAL
a Brine disposal
b Other
REUSE
a Animal feed supply
b By-product recovery
c Other
COLLECTION AND TRANSPORT
a Pumping
c Removal from clarifler
d Other
a Mechanical
b Drying beds
DEWATERING
c Chemical cond
d Other
ATMOSPHERIC DISPOSAL
a Drying
b Incineration
c Nitrogen removal
d Other
CHARACTERIZATION
a Source
b Type cone
c Toxic material
d Others
OTHER
a Cri tena dev
b Technology trans
c Other
PREPARATION FOR DEWATERING
ANO/OR DISPOSAL
a Thickening c Dig
b Stab111zation d Other
FIGURE 1 - 1
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TABLE 1-4
CALCULATED SLUDGE MASS (lb/rng)
Conventional
Fe to Fe to Al to A1 to TF
Primary Aerator Aerator Clarifier
PRIMARY
SS Removal
Sludge Solids
Fe Solids
Al Solids
Total
ACTIVATED SLUDGE
Secondary Solids
Fe Sobds
AJ Solids
TRICKLING FILTER
Secondary Solids
Al Solids
TOTALS
50%
1250
0
0
1250
715
656
1965
75%
1875
605
2480
536
50%
1250
1250
804
541
50%
1250
1250
804
425
50%
1250
1250
3016
2595
2479
745
483
2478
BASIS FOR SLUDGE MASS CALCULATION
Cafion/P Dose
(mol/niol)
lb Chemical Sludge/lb Cation
lb/lb Al
lb/lb Fc
1.5
1.75
Assumptions:
Cation/P Dose
Gitjon/P Dose
Influent Sewage
BOD
SS
P
3.9
3.8
1.5 mol/niol to aerator
1.75 mol/mol to primary or before trickling filter clanfier
230 mg/1
300 mg/1
10mg/l
2.4
2.3
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TABLE 1-5
CALCULATION OF SLUDGE QUANTITY:
LIME ADDED TO THE PRIMARY*
Data Available Qn an(j effluent: alkalinity, pH, calcium hardness, phosphorus.
Change in Ionic Content
(Influent Effluent)
AHC03> as CaC03
AC02, as CaC03
AMg, as CaC03
mg/1
223
14
66
Sludge Produced
hydroxyapatite
CaC03
Mg(OH)2
mg/1
27
460
38
Total Calcd. Sludge
525 mg/I
Material Balance on Ca
Ca(OH)2 dose = 390 mg/1
Input-Output = -2.9 mg/I
Meas./Calcd.
1.25
* Data from Run 6, Eurico's Salt Lake City Pilot Plant.
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TABLE 1-6
TOTAL COST IN CENTS PER 1,000 GALLONS OF WASTEWATER
PROCESSED FOR INDICATED SLUDGE HANDLING PROCESSES1
Plant Size
Process 1 mgd lOmgd 100 mgd
Gravity thickening of primary and
waste activated sludge
Gravity thickening of primary sludge
above
Air flotation thickening of waste
activated sludge above
Anaerobic digestion of combined
primary and waste activated sludge
Dewatering of digested sludge on
sandbeds
Dewatering thickened raw sludges
on rotary vacuum filters
Multiple hearth incineration of
filter cake
1.61 0.31 0.13
1.47 0.22 0.08
2.28 1.01 0.75
6.09 2.09 1.89
2.20 1.64 NA
8.39 5.15 3.70
13.53 5.02 1.16
1 See References 9, 10, and 11
Costs included are capital, debt, and operation and maintenance
NA - Not applicable
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TABLE 1-7
RECENT PROJECTS - APRIL, 1972
ULTIMATE DISPOSAL
Demonstration
1. Land Reclamation through the Use of Digested Sludge (Chicago MSD) Continuing
2. Park Development with Wet Digested Sludge (Metro Seattle)
Completed*
3. Microbiology of Sewage Sludge Disposal in Soil (Ohio ARS)
Completed*
4. Development of Treatment and Disposal Methods for Septic Tank
Sludges (University of Connecticut) Completed*
5. Utilization of Organic Matter in Waste Sludges
PB 194 784 (Foster D. Snell)
Continuing
in-house
6. Porteous Process for Heat Treatment of Sludge (Lake County,
Painesville, Ohio) plus in-house treatment of liquor
Continuing
7. Evaluation of a Top Feed Rotary Filter (Milwaukee, Wisconsin)
Continuation
pending Dec. '72
8. D.C. Sludge Pilot Plant (District of Columbia)
9. Aerobic Digestion of Sewage Sludge (Hollywood, Florida)
Continuing
Completed*
10. Evaluation of Conditioning and Dewatering Sewage Sludge by
Freezing Published GPO (Milwaukee, Wisconsin) (Not economical)
Completed
11. Sludge Slurry Pipeline and Strip Mine Reclamation
(Morgantown, West Virginia)
12. Application of Enzymes for Sludge Dewatering (Aerojet-General)
PB 207 480 (Not economical)
Completed*
Completed
13. Fly Ash Aid of Sewage Solids Dewatering and Disposal
(Cedar Rapids, Iowa)
Continuing
* Work completed, Final Report not yet published.
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TABLE 1-8
NEW PROJECTS SINCE APRIL, 1972
(No. 16 on)
14. Oil Flotation of Sludge (Esso)
15. Capillary Belt Filter (Westinghouse-Infilco)
16. Magnetically Assisted Dewatering of Waste Activated Sludge (R.P. Industries)
17. Lime Sludge Study (Central Contra Costa Sewage Treatment Plant, Walnut Creek,
California)
18. Centrate Dewatering Study (LACSD, California)
19. Survey of Land Spreading (Battelle, Columbus, Ohio)
20. Lime Stabilization of Sludge (Battelle-Northwest, Richland, Washington)
21. Phosphate Sludge Disposal in Forest Area (Ely, Minnesota)
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TABLE 1-9
IN-HOUSE ACTIVITIES
ULTIMATE DISPOSAL
1. Properties of Physical-Chemical Sludges
2. Testing Pilot-Scale Dewatering Equipment
3. Aluminum and Iron Sludges Recovery and Reuse
4. Evaluating Conditioning Sludge with Sludge Ash and Polymers
5. Determining Metals Buildup with Sludge Application
6. Determining Influence of Type of Sludge and Soil on the Growth of Several Plant Types
7. Analyzing for Metals, PCB's, etc., to Determine Quantities and Fate on Disposal
8. Treatment of Liquors from Porteous Process, etc.
9. Task Force on Mercury and Other Heavy Metals in Sludge
10. Task Force on Alternatives to Ocean Dumping
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THICKEN DIGEST. SAND BEDS
THICKEN, DIGEST, FILTER, LANDFILL
THICKEN, FILTER, INCINERATE
6
3
10
20
30
60
100
I II I I I L.
3 6 10 20 30 60 100
WASTEWATER FLOW (NGD)
THICKEN. DIGEST. SANO BEDS
THICKEN. DIGEST. FILTER. LANDFILL
THICKEN. FILTER. INCINERATE
3 6 10 20 30 60 100
WASTEWATER FLOW (MGO)
1-2
COSTS OF SLUDGE PROCESSING AND
DISPOSAL INCLUDING AMORTIZATION
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SECTION 2 - CURRENT AND PREVIOUS METHODOLOGY
1. Project Objectives Wastewater Treatment Plants
The way it used to be - The old climate surrounding design and startup of
wastewater treatment plants.
Partial funding for and somewhat limited role of the A/E firm.
Divided responsibility for design of sub-systems.
Emphasis on liquid handling R&D (Quote from agency document - Mea
Culpa).
Elastic enforcement policies (habit forming).
Problems with sludge handling systems.
The way it is now - The new climate (Figure 2-1). (Ostensibly, the objectives
have always been there but the new climate now makes them obtainable).
Plants must function properly, both initially and continually.
Both liquid and solids fractions must be processed satisfactorily.
Effluent standards are going to be enforced.
Capital, operating and maintenance costs must be essentially on forecast.
The consulting engineer is increasingly responsible for preceding needs.
2. Essential Ingredients (for a successful project)
(Figure 2-2)
Optimum Conceptual and Detailed Designs
New standards require new processes.
New processes mean text books are a questionable source.
The importance of being contemporary in process engineering disciplines.
2 - 1
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- Construction as Designed
Increased A/E involvement, new C.M. methods.
- Proper Operation and Maintenance
Following the Doctor's orders or he is not responsible for the results.
- Continuing Plant Service and Development
Nobody's perfect; even naval vessels still have a shakedown cruise.
A vital source of process improvement and future design information.
3. Sources Conceptual Design Information
(Figure 2-3)
- Textbooks and Literature
Must be reviewed but rarely give all the answers.
- Laboratory and Pilot Studies
Practically always necessary.
- Supplier's Recommendations
Equipment and product firms, their own R&D engineering work.
- Previous Experiences
All too seldom available.
- Visitation to Other Plants
Helpful but sometimes misleading.
- Client's Wishes (existing plant results)
Depends on the client's experience and capability.
2 - 2
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4. Special Considerations Design Rationale
(Figure 2-4)
- Adequacy of Available Literature
Self serving publications.
Strategic omissions.
Post-paper discussions (printed in U.K., not USA)
(Note L.A. article).
- Supplier's Recommendations
Essential but must be sifted carefully.
The importance of follow-up.
- Plant Data - Fact vs. Folklore
Reliability, a function of adequacy of O&M.
The "Shrinkage" example.
Defending an untenable position - mistakes die hard.
- Process Engineering
Unit operations technology.
Biological process technology.
Putting the whole thing together.
Experience in other industries and in plant operations.
5. The Total versus the Fractional Approach
(Figure 2-5)
- A careful choice of words
(System vs. Sub-System, actually, but, such terminology somewhat
disreputable).
- The Cardinal Sin: Optimization of a sub-system must be considered in light of
total system results.
2 - 3
-------
- Example = Dewatering Sludge
Analysis including only operating cost, production rate, cake moisture
content.
Should include complete material balance around process; effect of
recycle streams on rest of system; ratio of volatile solids to moisture
content (calorific value).
2 - 4
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LIST OF FIGURES AND TABLES - SECTION 2
Objectives Wastewater Treatment Plant Project
Essential Ingredients
Sources - Conceptual Design Information
Special Considerations Design Rationale
The Total versus the Fractional Approach
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OBJECTIVES
EFFECTIVE,RELIABLE PROCESSING OF WASTEWATER
(BOTH LIQUID AND SOLID FRACTIONS)
AT LOWEST PRACTICAL COST
CONCURRENT NON-POLLUTING EFFLUENT STREAMS
(LIQUID,SOLID AND GASEOUS)
FIGURE 2-1
ESSENTIAL INGREDIENTS
OPTIMUM CONCEPTUAL AND DETAILED DESIGN
CONSTRUCTION AS DESIGNED
PROPER OPERATION AND MAINTENANCE
CONTINUING PLANT PROCESS SERVICE AND
DEVELOPMENT
FGURE 2-2
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SOURCES-
CONCEPTUAL DESIGN INFORMATION
TEXT BOOKS AND LITERATURE
LABORATORY AND PILOT STUDIES
SUPPLIERS RECOMMENDATIONS
PREVIOUS EXPERIENCE
VISITATION TO OTHER PLANTS
CLIENTS WISHES (EXISTING PLANT RESULTS)
FIGURE 2-3
SPECIAL CONSIDERATIONS
-DESIGN RATIONALE
ADEQUACY OF AVAILABLE LITERATURE
SUPPLIERS RECOMMENDATIONS
PLANT DATA - FACT VS. FOLKLORE
PROCESS ENGINEERING
FIGURE 2-4
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THE TOTAL VERSUS
THE FRACTIONAL APPROACH
SOLIDS
SEPARATION
r
i
i
PROCESSING
LIQUID
EFFLUENT
SLUDGE
PROCESSING
SOLIDS
i EFFLUENT
FIGURE 2-5
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SECTION 3 - NATURE AND HANDLING CHARACTERISTICS OF SLUDGES
Fundamental Point
Need Knowledge/Insight
Nature of Sludges/Handling Characteristics
Potential Pitfall
(Figure 3-1)
"All generalities are inherently false, including this one."
But Methods of process study
Knowledge of process and equipment performance at various plants.
Supplement and guide work on a given sludge at a particular plant.
Raw Primary Sludge
Almost universally settles, thickens, dewaters and incinerates relatively easily.
Because (Figure 3-2) is usually coarse and relatively fibrous.
Vacuum filtration and centrifugation work well at low cost (Figure 3-3).
Note heavy thick cake and excellent release.
Costs are low and efficiencies good.
(Table 3-1)
Primary sludges give slightly compressible cakes but presence of sufficient gross
solids - (*ป 30% < 30 mesh) permits rapid formation of cake with sufficient
structural matrix = good capture and rapid dewatering.
Effect of Digestion (Primary Sludge)
(Table 3-2)
Anaerobic digestion, contrary to some information in the literature, makes
sludges somewhat more difficult to thicken and dewater.
But results are still good and costs low.
Shear effects on particle size and increased hydration of solids.
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4. Activated Sludges (Conventional)
Inherently more variable
Principal source of variation
Configuration and mode of operation of activated sludge system involved.
Also, Domestic/Industrial waste ratio and type, Nature of Collection System
can have real effect.
Structure
Generally finer in particle size.
6090 percent cellular organic matter.
Bioflocculated to some degree, by excretion of natural polymeric material
by the microorganisms.
Density close to density of water.
Water Content
(Figure 3-4)
Biomass from conventional air systems has much associated water.
Theoretically, if the loosely held and bound surface water disengaged, up
to 29 percent solids obtained.
Another way to overcome this problem
Endogenous respiration (Figure 3-5, Reference 3).
Greater degree of bioflocculation displaces extracellular water.
Improves settling and dewatering characteristics.
5. Summary Activated Sludges
Conventional Air Aeration Systems Excess Activated Sludge requires very
careful operation to give settleable sludge.
Activated sludge is sensitive to further processing. Hydration easily and tends
to float.
6. Handling Combined Primary and Activated Sludges
Existing plants, many cases designed one of two ways.
(Figure 3-6)
3 - 2
-------
- A. Recirculate E.A.S. to head of plant - Primaries
Results Primary Solids Capture goes to pot.
Greater BOD load on secondary system.
More E.A.S. created than necessary.
Combined Mixed Sludge
Settles poorly in digester, another recirculation load.
When elutriated (without flocculants) sludge fractionates - another low
efficiency process and recirculation load.
- B. E.A.S. mixed with Primary Sludge prior to gravity thickening
(Figure 3-7)
Results Better than recirculation to primaries but:
Dirty thickener overflow.
Activated portion will not settle in digesters or elutriation basins, so still
poor.
Remedy
Combine and thicken sludges just before dewatering.
Not early in process.
7. Oxygen Activated Sludges
- Biomass from oxygen process has better settling characteristics.
(Figure 3-8, Reference 4)
- Clarifier performance, based on overflow rate (Figure 3-9) is better with
oxygen process sludge (Watch bottom loading rates).
- Recycle sludge solids (Figure 3-10) are higher with oxygen activated sludge.
- Sludge volume indices are improved over air aeration sludge.
- Gravity thickening (Figure 3-11).
3 - 3
-------
Admittedly different plants involved but best data available, higher
underflow solids.
Chicago results from excellent article by Ettelt (Reference 13) and others.
Figure in parentheses for Chicago is for picket fence type thickener.
Summation - oxygen activated sludge appears to gravity thicken more
readily.
Flotation thickening (Figure 3-12)
(From Reference 6 by Stamberg, Bishop, Hais and Bennett of EPA).
These results are without floe aid use.
Figure 3-13 - additional results with polymer usage - lower costs and
greater efficiency for the O.A.S.
Vacuum Filtration
(Figure 3-14)
Batavia results are from a 3 ft2 pilot filter.
Louisville results are from filter leaf tests on location. Representative of a
workable - logical method. What could be expected in mixing primary and
O.A.S. sludges.
Centrifugation
(Figure 3-15)
Pilot solid bowl scroll type work by Sharpies.
Higher throughput, lower chemical cost and better capture for O.A.S.
Need results on typical mixed sludge.
8. Alum Use Primary Plant Mixed Chemical Organic Sludge
(Figure 3-16)
Work by OWRC and plant staffs (Reference 7).
With no chemical addition to primaries, ferric/lime conditioning, high yield and
low cost.
With alum, primary solids level drops, amount of sludge increases, yield
decreases and costs go up.
3 - 4
-------
Ferric and lime may not be best conditioning system for alum/organic sludge.
9. Lime Use - Conventional Activated Sludge Plant Mixed Lime/Organic Sludge (Raw)
(Figure 3-17)
2.0 mgd, lime added just ahead of primaries.
Sludge volume almost triples, but centrifugation looks easy and inexpensive
(centrate = 1030 MG/LP).
Low polymer dose to clean up centrate.
10. Alum and Lime Sludges Windsor Little River Conventional Activated Sludge Plant
(Figure 3-18)
First note that normal, untreated sludge conditioning costs are abnormally
high, particularly for a sludge feed to filters of 6.2 percent solids.
Lime usage gave a mixed sludge (with small amount of activated sludge
content?) which dewatered well at a lower cost.
Alum lowered sludge solids concentration, decreased yield and increased
conditioner costs. Cake solids were only 16 percent with alum use.
11. Ferric Chloride/Organic Sludge at North Toronto Conventional Activated Sludge Plant
(Figure 3-19, Reference 12)
Use of ferric chloride for phosphorus removal.
Tested for many months.
First applied at primary basins.
Current application point = at end of aeration basin.
Chemical conditioning costs about $8/ton.
Reasonable production rate and cake solids content realized.
12. Lake Tahoe Solids Handling
Process flow (Figure 3-20, Reference 9)
Two sludges handled separately in this tertiary plant.
3 - 5
-------
Organic sludges (from a system which recirculates activated sludge to head
of plant).
Lime sludges from tertiary type treatment.
- Organic Sludge'Processing
(Figure 3-21)
This section of plant has two design features which, in my opinion, result
in abnormal sludge handling costs.
First is the recirculation of the excess activated sludge to the primaries
which has been demonstrated to result in poor primary capture and poor
activated sludge quality.
Second is the attempt to gravity thicken a mixture of excess activated
sludge and primary sludge - net result is that no thickening occurs.
Hence feed to "Dewatering Centrifuge" is unthickened and high costs
result in dewatering. (Polymer dosage is actually higher than shown
because the basis is tons of dry solids to furnace which includes lime
wastage).
- Lime Sludge Processing
(Figure 3-22)
The centrifuge serves here as a classification device.
First centrifuge operated with high centrate loss to purge organics from
lime stream to be recalcined.
Second centrifuge, in series on centrate cleans up the more organic
portion.
Results shown are for 8 percent solids feed to lime - mud centrifuge. Cake
solids equal 37 percent. Looks like a good operation.
Cake solids from centrate centrifuge average 30 percent.
13. Aerobically Digested Activated Sludges
Aerobic digestion is an inherently "cleaner" means of reducing the volume of
activated sludge to be dewatcred and to stabilize same for land disposal.
Plant scale work current at several locations.
3 - 6
-------
Atlanta (Reference 10)
New 6 mgd Flint River Plant tests.
Digestion process works well.
Sludge compacts to 23 percent and can be dewatered via vacuum
filtration using ferric chloride.
Yield is on the lean side.
If aerobically digested sludge were mixed with thickened primary sludge,
dewatering and incineration would be more efficient.
3 - 7
-------
REFERENCES - SECTION 3
1. Reed, S.E., and Murph, R.S., ASCE Proceedings Paper 6747, August, 1969; and
Discussion by Dick, et al., ASCE Journal, 638-646 (1970).
2. Goodman, B.L., and Foster, J.W., "Notes on Activated Sludge," Smith and Loveless.
(1969).
3. Tenney, M.W., Echelberger, W.F., Coffey, J.J., and McAloon, T.J., "Chemical Condition-
ing of Biological Sludges for Vacuum Filtration."- Journal WPCF, 42, No. 2, Part 2,
R1-R20 (1971).
4. Private communications - Union Carbide Corporation.
5. Unox Design Information, EPA, TT Program, Metcalf and Eddy, Pittsburgh, Pennsylvania,
August 29, 1972.
6. Stamberg, J.B., et al., EPA, "System Alternatives in Oxygen Activated Sludge," WPCF
Meeting, Atlanta, Georgia, 1972.
7. Van Fleet, B.L., Barr, J.R., and Harris, A.J., "Treatment and Disposal of Chemical Phos-
phate Sludges in Ontario."
8. "Report on Phosphorous Removal," Water and Pollution Control, 16 (1972).
9. EPA W.P.C.R.S. 17010 ELQ08/71 "Advanced Wastewater Treatment as Practiced at
Lake Tahoe."
10. Cameron, J., "Aerobic Digestion of Activated Sludge to Reduce Sludge Handling Costs,"
WPCF Conference, Atlanta, Georgia, 1972.
11. Bolek, M., and Helekal, J., "Cake Removal from R.V. Filters by Air Blast, Filtration and
Separation," 146 (March, April, 1971).
12. Private communication, D.A. Clough, Director, Metro Toronto Water Pollution Control.
13. Ettelt, G.A., and Kennedy, T.J., "Research and Operational Experience in Sludge
Dewatering at Chicago." JWPCF, 38, No. 2, 248.
3 - 8
-------
LIST OF FIGURES AND TABLES - SECTION 3
Figure 3-1
Figure 3-2
Figure 3-3
Table 3-1
Table 3-2
Figure 3-4
Figure 3-5
Figure 3-6
Figure 3-7
Figure 3-8
Figure 3-9
Figure 3-10
Figure 3-11
Figure 3-12
Figure 3-13
Figure 3-14
Figure 3-15
Figure 3-16
Maxim - "All generalities are inherently false, including this one."
Closeup Raw Primary Sludge Filter Cake
Release Characteristics - Raw Primary Sludge Filters
Vacuum Filtration Raw Primary Sludge
Vacuum Filtration Digested Primary Sludge
Activated Sludge - Aqueous Fluid Distribution
Effect of Aeration Time on Biopolymer Production and Dewaterability
Secondary Plant with Surplus Activated Sludge to Head of Works
Secondary Plant with Surplus Activated Sludge Mixed with Primary Sludge
Prior to Thickening and Digestion
Settling Characteristics for Air and Oxygen Biomass (ISR vs. Concentration)
Typical Clarifier Performance for Air and Oxygen Sludges
(at 30 percent Recycle)
Typical Clarifier Performance for Air and Oxygen Sludges
(at 30 percent Recycle)
Gravity Thickening
Flotation Thickening
Flotation Thickening
Vacuum Filtration
Centrifugation, Oxygen andConventional Aeration Sludges
West Windsor Primary Plant Alum
3 - 9
-------
LIST OF FIGURES AND TABLES - SECTION 3
(Continued)
Figure 3-17 Newmarket Conventional Activated Sludge Plant Lime
Figure 3-18 Little River Conventional Activated Sludge Plant Phosphate Removal
Figure 3-19 North Toronto Conventional Activated Sludge Plant - Ferric Chloride
Figure 3-20 Lake Tahoe Solids Handling System
Figure 3-21 Lake Tahoe, Organic Sludge Handling
Figure 3-22 Lake Tahoe, Lime Sludge Processing
3 - 10
-------
MAXIM
" ALL GENERALITIES
ARE INHERENTLY FALSE
INCLUDING THIS ONE."
FIGURE 3-1
-------
FIGURE 3-2 CLOSE-UP RAW PRIMARY SLUDGE FILTER CAKE
-------
FIGURE 3-3
RELEASE CHARACTERISTICS - RAW PRIMARY SLUDGE FILTERS
-------
SOLIDS
% SLUDGE CONDITIONER COST YIELD CAKE CAPTURE
SOLIDS USED |$/TON| LB/FT2/HR SOLID |%) [%)
10 CATIONIC 1.67 10 32 90-95
POLYMER
TABLE 3-1
VACUUM FILTRATION - RAW PRIMARY SLUDGE
-------
CAKE SOLIDS
% SLUDGE CONDITIONER YIELD SOLIDS CAPTURE
SOLIDS COST |S/TON) #/HR/FT 1%) 1%)
12.7 2.64 7.4 28 90+
TABLE 3-2
VACUUM FILTRATION - DIGESTED PRIMARY SLUDGE
-------
ACTIVATED SLUDGE
AQUEOUS FLUID DISTRIBUTION
LOCATION
PARTS
CUMULATIVE
% SOLIDS
SOLIDS
1.0
100
WITHIN CELL
2.5
29
SURFACE BOUND
5.0
12
LOOSELY HELD
2.5
9
FIGURE 3-4
-------
600
500
400
300
800
600
400
200
0
E 3-5
0
POLYSACCHARIDE RELATIONSHIPS
POLYSACCHARIDE/BACTERIA
RATIO
ACCUMULATED
POLYSACCHARIDE
50
FILTRATION RATE
1.5
1.0
mg POLYSACCHARIDE
0.5 mg BACTERIA
0
j.
200
250
100 150
TIME - HOURS
EFFECT OF AERATION TIME ON BIOPOLYMER PRODUCTION AND DEWATERABILITY
-------
VACUUM
FILTERS
ANEROBIC
DIGESTION
ELUTRIATION
AERATION
BASINS
PRIMARY
CLARIFIERS
GRIT
REMOVAL
WASTE WATER
SLUDGE
PROCESS LIQUIDS
FIGURE 3-6 SECONDARY PLANT WITH SURPLUS ACTIVATED SLUDGE TO HEAD OF WORKS
-------
DIGESTION
SLUDGE
THICKENING
DEWATERING
PUMPING
GRIT
REMOVAL
HIGH RATE
ACTIVATED
SLUDGE
PRIMARY
CLARIFICATION
ELUTRIATION
WASTE WATER
SLUDGE
~ PROCESSING LIQUIDS
FIGURE 3-7 SECONDARY PLANT WITH SURPLUS ACTIVATED SLUDGE MIXED WITH PRIMARY SLUDGE PRIOR
TO THICKENING AND DIGESTION
-------
SETTLING
CHARACTERISTICS
FOR AIR AND
OXYGEN BIOMASS
(ISR VS. CONCENTRATION
OXYGEN
BIOMASS
INITIAL SETTLING
RATE, Fl/Hr.
BAIR|
BIOMASS
1000
10,000
CONCENTRATION mg/l
100,000
FIGURE 3-8
TYPICAL CLARIFIER PERFORMANCE FOR AIR AND OXYGEN SLUDGES
(AT 30 % RECYCLE)
10,000 r
8000
MLSS (mg/l ] 6000
4000
2000
OXYGEN SLUDGE
AIR SLUDGE
I L
I I
200 400 600 800
OVERFLOW RATE, GPD/FT
1000
2
1200 1400 1600
FIGURE 3-9
-------
TYPICAL CLARIFIER PERFORMANCE FOR AIR AND OXYGEN SLUDGES
(AT 30 % RECYCLE]
% RSS
5 r
FIGURE 3-10
GRAVITY THICKENING
FEED SLUDGE
TYPE
AIR W.A.S.
OXYGEN MIXED
SOLIDS
LOADING
2
UNDERFLOW
CONC.
% SOLIDS #/Ft. /DAY % SOLIDS LOCATION
OXYGEN W.A.S. 1.7 10 4.8 LOUISVILLE
0.9
2.3
20
1.4-2.8 CHICAGO
5.6
MIDDLESEX
AIR MIXED
1.1
20
3.3(4.4) CHICAGO
- OXYGEN SLUDGE
AIR SLUDGE
ฆ ' I 1 1 1 I
200 400 600 800 1000 1200 1400 1600
OVERFLOW RATE, GPD/FT2
FIGURE 3-11
-------
FLOTATION THICKENING
LOADING THICKENED
FEED SLUDGE #/Ft.2/DAY SOLIDS [%)
OXYGEN ACTIVATED 95 4
BLENDED OXYGEN 11
ACTIVATED (0.3) +
PRIMARY (1.0)
FIGURE 3-12
FLOTATION THICKENING
FEED SLUDGE POLYMER LOADING THICKENED
TYPE % SOLIDS #/TON #/Ft.2/HR. SOUPS (%)
OXYGEN
ACTIVATED (1.7)
AIR
ACTIVATED (0.9)
2.9 6.4-10.2 6.6
9.0 2.0-4.0 4.5
FIGURE 3-13
-------
VACUUM FILTRATION
FEED SLUDGE
CONDITIONER
#/T0N D.S. YIELD
CAKE
LOCATION TYPE % SOLIDS FeCI3 LIME #/Ft.2/HR. SOLIDS %
BATAVIA OXY.W.A.S. 4.4
200
5.1
14.5
LOUISVILLE
OXY.W.A.S.= 3
RAW PRIM +
DIG. = 6
5.3
50 142
7.2
26.4
FIGURE 3-14
CENTRIFUGATION
OXYGEN a CONVENTIONAL
AERATION SLUDGES
TYPE FEED POLYMER SOLIDS CAKE
SLUDGE % SOLIDS RATE [GPM| |#/T0N) CAP. |%] SOLIDS 1%)
OXYGEN
W.A.S. 2.5 95 3 92 9
AIR
W.A.S. 1.0 60 12.5 82 8.5
FIGURE 3-15
-------
WEST WINDSOR
PRIMARY PLANT-ALUM
CHEMICAL ADDITION PRIMARY SOLIDS $
METAL DOSE POLYMER SLUDGE JONS/ ? COND.
SALT MG/L MG/L % SOLIDS Ag. #/HR./Ft COST
NONE 11.5 0.5 11.3 3.10
ALUM 90 0.4 7.6 1.1 5.8 9.50
FIGURE 3-16
NEWMARKET
CONY ACT. SLUDGE PLANT-LIME
CHEMICAL ADDITION MIXED SOLIDS CENTRIFUGATION
METAL DOSE SLUDGE TONS/ POLYMER % CAKE SOLIDS
SALT MG/L % SOLIDS /M.G. |#/T0N| SOLIDS CAPTURE
NONE 3.5 0.85
LIME 200 10 2.45 <1 31 97
FIGURE 3-17
-------
LITTLE RIVER
CONV ACT. SLUDGE-PHOSP. REM.
CHEMICAL ADDITION MIXED SOLIDS FILTER S
METAL DOSE SLUDGE T0Nc, YIELD COND.
SALT MG/L % SOLIDS /M.G. #/HR/Ft.2 COST
NONE 6.2 0.8 5.2 16
LIME 125 11.6 1.2 7.2 11
ALUM 150 5.7 1.2 4.6 18
FIGURE 3-18
NORTH TORONTO
CONV ACT SLUDGE-FERRIC CHLORIDE
CHEMICAL ADDITION MIXED C0ND.|lb/T0N
METAL DOSE SLUDGE FERRIC % CAKE
SALT MG/L % SOLIDS CHLORIDE LIME Ib/HR/Ft.2 SOLIDS
FERRIC
CHLORIDE 25-35 8 104 200 3.3 21
FIGURE 3-19
-------
LAKE TAHOE SOLIDS HANDLING
POLYMER
RAW
INFLUENT
ACT IVATED
SLUDGE
FURTHER
PROCESSING
CENTRATE
CENTRATE
LIME TO
CHEM CLARIFIERS
ASH
RE-CALCINE
FURNACE
CENTRIFUGE
REACTION
BASIN
CENTRIFUGE
CENTRIFUGE
LIME
THICKENER
SLUDGE
THICKENER
CHEMICAL
CLARIFIERS
PRIMARY
CLARIFIER
SECONDARY
CLARIFIERS
AERATION
BASINS
FIGURE 3-20
LAKE TAHOE
-ORGANIC SLUDGE HANDLING
% FEED COND. FEED % SOLIDS % CAKE
SOLIDS #/T0N RATE CAPTURE SOLIDS
2.0 5.1 90 + 17
FIGURE 3-21
-------
LAKE TAHOE
-LIME SLUDGE PROCESSING
FEED RATE
16PM)
10
20
% SOLIDS
CAPTURE
93
79
FRACTION LOST TO CENTRATE
TOTAL ACTIVE
SOLIDS LIME PHOSPHATE MGO
0.10 0.04 0.19
0.17
0.20 0.08 0.39 0.35
FIGURE 3-22
-------
SECTION 4 - SLUDGE STABILIZATION PROCESSES
1. Anaerobic Digestion
Describes the biological conversion of organic matter in the absence of
molecular oxygen to simple compounds. Gas products are chiefly methane and
carbon dioxide.
Process advantages include:
Anaerobic digestion is the most frequently employed process for sludge
stabilization. When digestion operates properly, it converts raw sludge to a
stable material which is inoffensive to the senses, and which has a greatly
reduced pathogen content. A recent exposition of sludge digestion is
available (Reference 1).
Methane generated can be used for heating and to run generators.
Can usually obtain a 50 percent reduction in volatile solids.
Do not have to or want to maintain a high dissolved oxygen level.
Process disadvantages include:
Control is difficult because of sensitivity of micro-organisms to toxicity,
especially from industrial effluents.
Capital costs for facility construction and heating provision are high.
Supernatant is usually high in BOD, solids, and nutrients requiring further
treatment.
Anaerobic digestion produces changes in sludge which, on the average,
reduce the filter yield. If ferric chloride and lime are used, chemical
demand is increased (Reference 2). If sludge density is increased (e.g., by
two-stage high rate digestion), yield can by increased.
Design criteria for anaerobic digesters
Volume - allow 3 to 6 cubic feet per capita.
4-1
-------
Organic loading - allow from 0.02 to 0.15 pounds of applied solids per
day per cubic foot.
Reported costs
For anaerobic digestion followed by sand bed dewatering is approximately
$25/ton dry sludge solids (Reference 3).
For anaerobic digestion of activated sludge followed by reclamation of
farm land or a strip mine is approximately $15 to $16/ton dry solids
(Reference 4).
Design of digesters at Chicago's West-Southwest and Calumet Plants is shown in
Table 4-1.
The summary of a year's operating results for the Southwest Plant's
digesters is shown in Table 4-2. A similar summary for the Calumet Plant
is shown in Table 4-3.
Typical characteristics of digester supernatants are shown in Tables 4-4 and 4-5.
Note especially high solids, BOD and alkalinity.
Some recommended techniques for treating supernatants are given in Table 4-6.
2. Use of Aerobic Digestion
Describes the separate aeration of:
Waste primary sludge
Waste biological sludge, or
A combination of waste primary and biological sludges.
Aerobic stabilization is usually used to stabilize waste activated sludges or
the waste sludges from smaller plants which do not have separate primary
clarification. See Reference 1 for a recent presentation.
Usually designed for a 15-20 day retention.
4-2
-------
- Biological steps include:
Oxidation of biodegradable material.
Oxidation of microbial cellular material.
Process advantages include:
Relatively simple to operate.
Requires small capital expenditure compared to anaerobic digester.
Does not generate significant odors.
Reduces pathogenic organisms to low level.
Reduces grease or hexane solubles.
Produces a supernatant if clarified that is low in BOD, solids, and total P.
Reduces sludge volatile solids.
Reduces sludge respiration rate.
Production of a highly nitrified sludge which could be denitrified if sludge
is to be placed on land. (Note: nitrogen in any form can limit application
rates on the land, not just in the nitrate form).
Process disadvantages include:
High operating cost.
Unclear design parameters at present.
Aerobically stabilized sludge has poor dewatering characteristics on
vacuum filters although a recent publication claims otherwise (Reference
11). Ordinarily, this sludge is dewatered on sand beds or applied in liquid
form to cropland.
Important process parameters are:
Air requirements.
Time of aeration.
4-3
-------
Sludge age.
Proposed method of ultimate disposal.
Temperature and heat dissipation.
Some designs have been
To allow for a 5-day retention, a sludge concentration of 12,000 ppm and
to size at 1.4 cubic feet per capita, or
To load at a rate of 0.1 to 0.2 lb VSS/lb solids/day.
A 1970 Literature Survey led to the information in Table 4-7 and the following
conclusions (Reference 12).
Differences exist among investigators as to exactly what happens in the
process and how it should be operated.
Suggested loads range from 0.1 to 0.2 lb VSS/lb solids/day.
Suggested times of stabilization range from 10 to 20 days.
A low BOD supernatant should result from stabilization (a resultant BOD
= 10-30 ppm).
It should be possible to average a VSS reduction of 40 to 50 percent.
The resultant ammonia level in the supernatant should be about 10 ppm.
Resultant supernatant nitrate levels of 50 to 100 ppm or greater can be
expected.
Work by the Ultimate Disposal Research Program indicated findings in
accord with the above. In addition, we found a grease reduction in about
five days of 80 percent.
A recent survey (Reference 23) of seven facilities which employ the aerobic
stabilization process revealed the information given in the following tables:
Table 4-8 describes the seven facilities.
Table 4-9 describes the stabilizers' mode of action.
4-4
-------
Table 4-10 describes the feed to the units.
Table 4-11 describes the sludge in the digester.
Table 4-12 gives the supernatant characteristics.
Key factors related here are:
the feed sludge
aeration
detention
solidsliquid separation
loading
3. Chlorine Oxidation
The Purifax process oxidizes sludge with heavy doses of chlonne (circa 2,000
mg/1). Sludge dewaters well on sandbeds. Stability is excellent.
Purifaxed sludges present some difficulties when they must be dewatered on
vacuum filters. Chemical (or polymer) conditioning is needed, but the low pH
(circa 2) interferes with the action of conditioning agents. Pilot plant tests
indicate that pH must be increased to greater than 4 to get good conditioning
(Reference 24).
Supernatant and filtrate contain high concentrations of chloramines. They
should not be carelessly discharged.
Lime Treatment
Lime treatment of sludge stabilizes the sludge as long as the pH stays high (11.0
- 11.5). Kill of pathogenic bacteria is excellent (Reference 25). Sludge
dewaters well on sandbeds without odor.
Sludge filtrability is improved. Caution is advised on disposal of sludge cake to
landfills to avoid thick layers. The pH could fall to near 7 before the sludge
dries out, permitting regrowth and noxious conditions.
Actual data from a recent study is shown in Tables 4-13, 4-14, 4-15, and 4-16
(Reference 25).
Table 4-13 shows the magnitude of lime dose and the costs for treating
three different sludge types.
4-5
-------
Table 4-14 shows the bacterial response to lime addition.
Table 4-15 shows the lime requirement and cost for treating several
different sludges.
Table 4-16 shows the effect of lime addition on flltrability.
A key factor is the maintenance of a pH of 11.0 for a sufficiently long time (24
hours).
4-6
-------
REFERENCES - SECTION 4
1. Weston, Roy F., Inc., "Process Design Manual for Upgrading Existing Wastewater
Treatment Plants." EPA Report 17090 GNQ, October, 1971.
2. Teletzke, G.H., "Sludge Dewatering by Vacuum Filtration." presented at Annual Meeting
of Rocky Mountain Sewage and Industrial Wastes Association, Colorado Springs,
Colorado, October 24-26, 1960.
3. Burd, R.S., "A Study of Sludge Handling and Disposal." FWPCA Publication, No.
WP-20-4, May, 1968.
4. Dalton, F.E., Stein, J.E., and Lynam, B.T., "Land Reclamation A Complete Solution
of the Solid Disposal Problem." Journal Water Pollution Control Federation, 40, (5),
789 (May, 1968).
5. Lynam, B., McDonnell, G., and Krup, M., "Start-Up and Operation of Two New
High-Rate Digestion Systems." Journal Water Pollution Control Federation, 39, (4),
518 (April, 1967).
6. Ibid, No. 5.
7. Ibid, No. 5.
8. Maliva, J.F., Jr., and DiFilippo, J., "Treatment of Supernatants and Liquids associated
with Sludge Treatment." Water and Sewage Works, 1971 Reference Number, R-30.
9. Ibid, No. 8.
10. Ibid, No. 8.
11. Cameron, J.W., "Aerobic Digestion of Activated Sludge to Reduce Sludge Handling
Costs." 45th Annual Conference, Water Pollution Control Federation, Atlanta,
Georgia, October, 1972.
12. EPA Memo from J.E. Smith, Jr. to R.B. Dean, "Aerobic Stabilization of Activated
Sludge." January 4, 1970.
13. Barnhart, E.L., "Application of Aerobic Digestion to Industrial Waste Treatment."
Proceedings of the 16th Industrial Waste Conference at Purdue University.
4-7
-------
REFERENCES Continued
14. Private communication, Edward R. Grich, Consultant Chemist Edward R. Grich, Inc.,
Pequannock, New Jersey.
15. Lawton, G.W., and Norman, J.D., "Aerobic Sludge Digestion Studies." Journal Water
Pollution Control Federation, 36, No. 4,495-503 (April, 1964).
16. Dreier, D.E., "Aerobic Digestion of Solids." Proceedings of Purdue Conference, 1963.
17. Ibid, No. 15.
18. Loehr, R.C., "Aerobic Digestion Factors Affecting Design." Water and Sewage Works,
Reference Number 1965, 112, R169-R180.
19. Irgens, R.L., and Halvorson, H.O., "Removal of Plant Nutrients by Means of Aerobic
Stabilization of Sludge." Applied Microbiology, 13, 373-386 (1965).
20. Havan, V.T., "Digesting Sludge by Aeration - Study in India." Water Works and Waste
Engineering, (September, 1965).
21. Malina, J.R., and Burton, H.N., "Aerobic Stabilization of Primary Wastewater Sludge."
Proceedings of the 19th Industrial Waste Conference at Purdue University, 1964.
22. Jaworski, N., Lawton, G.W., and Rohlich, G.A., "Aerobic Sludge Digestion." Conference
of Biological Waste Treatment, April 20-22, 1960.
23. Ahlberg, N.R. and Boyko, B.I., "Evaluation and Design of Aerobic Digesters." Journal
Water Pollution Control Federation, 44, 634 (1972).
24. Personal communication with Mr. Pearson of BIF Purifax, Providence, Rhode Island.
25. Farrell, J.R., Smith, J.E., Jr., Hathaway, S.W., and Dean, R.B., "Lime Stabilization of
Chemical-Primary Sludges at 1.15 mgd." 45th Annual Conference, Water Pollution
Control Federation, Atlanta, Georgia, October, 1972.
4-8
-------
LIST OF FIGURES AND TABLES - SECTION 4
Table 4-1
Table 4-2
Table 4-3
Table 4-4
Table 4-5
Table 4-6
Table 4-7
Table 4-8
Table 4-9
Table 4-10
Table 4-11
Table 4-12
Table 4-13
Table 4-14
Table 4-15
Table 4-16
Design Data for Chicago Digesters
Summary of Operating Results - Southwest
Summary of Operating Results - Calumet
Properties of Digester Supernatant (Municipal Wastewater Sludge)
Analysis of Supernatant from Several Plants
Processes for the Removal of Constituents of Anaerobic Supernatant
Information Taken from References on the Aerobic Stabilization of Sludge
Physical Plant Data
Aerobic Digestion Process
Characteristics of Digester Feed Sludges (mg/1)
Characteristics of Digester Sludges (mg/1)
Characteristics of Digester Supernatants (mg/1)
Preliminary Comparison of Lime Costs for Raw, Alum and Iron Sludges
Bacteriological Studies of Sludge Produced in Plant-Scale Tests
Average Cost of Lime Addition: Plant-Scale Tests
Effect of Lime on Filtrabihty of Al+++ and Fe+++ Sludges
4-9
-------
TABLE 4-1
DESIGN DATA FOR CHICAGO DIGESTERS1
Solids to digesters, tons/day 100
Sludge to digesters, % solids 3.3
Sludge to digesters, % volatile 67
Digester displacement, days 14
Volatile solids digested, % 40 to 45
Gas per pound volatile solids digested, cu ft 16 to 18
Heat per cubic foot of gas, BTU 600 to 650
Temperature of digesters, ฐ F. 90 to 95
Sludge to digesters:
Activated sludge solids, % 80 to 100
Primary sludge solids, % 20 to 0
Note: Tons X 0.907 = metric tons
Cu ft/lb X 0.0617 = cu m/kg
BTU/cu ft X 9 = kg-cal/cu m
0 C. = 0.555 (ฐ F. - 32)
1 See Reference 5.
-------
TABLE 4-2
SUMMARY OF OPERATING RESULTS - SOUTHWEST1
Feed
Dry Solids Dry Solids
(percent) (tons/day)
Alkalinity gpd Volatile Solids Detention Temperature
Date Total Volatile pH (mg/1) x 1,000 Total Volatile (lb/day/cu ft) (days) (ฐ F.)
1964
Average
July2
3.1
60.1
6.5
493
354
47.1
28.3
0.042
23.0
95
Aug.2
2.7
63.3
6.5
591
591
65.8
41.5
0.062
21.8
95
Sept.2
2.5
64.2
6.5
575
649
69.0
44.3
0.066
15.5
95
Oct.2
2.7
63.5
6.6
493
714
80.4
51.1
0.076
14.0
94
Nov.2
2.5
65.3
6.5
458
762
79.2
51.9
0.077
13.2
94
Dec.2
2.6
68.2
6.4
549
671
72.8
49.6
0.074
14.9
90
Jan.3
3.0
70.0
6.4
791
742
92.7
64.8
0.096
13.5
87
Feb.3
3.1
70.8
6.4
898
755
98.7
69.5
0.103
13.2
89
Mar.3
3.0
67.5
6.5
800
735
93.0
62.9
0.093
13.6
90
Apr.3
4.0
65.2
6.5
790
631
104.1
68.0
0.101
15.8
92
May3
3.4
64.0
6.5
802
628
86.6
55.4
0.082
15.9
95
June3
4.2
61.4
6.5
815
605
105.9
65.0
0.097
16.5
95
3.1
65.3
6.5
671
653
82.9
54.4
0.081
15.95
93
1 See Reference 6
2 100 percent activated sludge used as feed
3 Mixture of activated and preliminary sludges
-------
TABLE 4-2 (Continued)
SUMMARY OF OPERATING RESULTS - SOUTHWEST1
Drawoff Volatile Solids Gas Produced
Dry Solids
(percent) Dry Solids Total Solids Total cu ft/lb
Alkalinity (total (reduced Reduction Reduction (1,000 Volatile
Date Total Volatile pH mg/1 tons/day) tons/day) (percent) tons/day cu ft/day) Destroyed
1964
1965
Average
July
3.8
49.8
7.0
1,245
44.7
2.4
32.2
9.1
340.9
18.7
Aug.
2.4
53.4
7.0
1,745
58.8
10.0
33.7
14.0
643.8
23.0
Sept.
2.1
54.8
7.0
1,933
56.0
13.0
32.4
14.3
620.5
21.8
Oct.
2.2
54.2
7.1
1,629
65.7
14.7
31.9
16.3
665.8
20.4
Nov.
2.1
57.3
7.1
1,612
66.1
13.1
28.3
14.7
642.6
21.8
Dec.
2.0
57.5
7.0
2,140
56.0
16.8
37.0
18.3
658.3
18.4
Jan.
2.1
59.6
7.0
2,437
65.6
27.1
36.9
23.9
943.8
19.7
Feb.
2.3
58.0
7.1
2,554
72.6
26.1
42.6
29.6
1,128.9
19.0
Mar.
2.1
55.4
7.1
2,520
64.8
28.2
40.2 1
25.2
1,089.7
21.5
Apr.
2.6
53.1
7.1
2,495
67.3
36.8
39.4
26.8
1,056.5
19.7
May
2.6
52.5
7.1
2,885
68.0
18.6
37.7
20.5
783.1
19.1
June
3.0
50.5
7.1
2,748
75.6
30.3
36.0
23.4
821.8
17.5
2.4
54.7
7.1
2,162
63.4
19.8
35.7
19.7
783.0
20.0
1 See Reference 6
Note: Gal x 3.785 = 1; tons x 0.907 = metric tons; lb/cu ft x 16.214 = kg/cu m; 0.5 (ฐ F. 32) = ฐ C.; cu ft x 0.028 = cu m; cu ft/lb
x 0.0617 = cu m/kg.
-------
TABLE 4-3
SUMMARY OF OPERATING RESULTS - CALUMET1
Feed Sludge
1965
(percent)
PH
Alkalinity
(mg/1)
gpd
x 1,000
(tons/day)
Volatile Solids
(lb/day/cu ft)
Detention
(days)
Tempei
(ฐ F.
Total
Volatile
Total
Volatile
Jan.
3.65
61.5
6.6
408
169.2
25.9
15.9
95
Feb.
3.79
61.4
6.6
464
358.5
55.7
34.2
0.082
18
95
Mar.
3.61
61.2
6.6
434
494.8
74.5
45.6
0.088
16
95
Apr.
4.23
58.8
6.6
636
418.7
73.8
43.5
0.084
19
95
May
4.00
58.8
6.6
863
552.3
91.7
53.9
0.105
15
95
June
3.14
60.1
6.6
632
637.2
82.5
49.6
0.075
13
95
July
3.63
57.9
6.6
855
443.4
66.3
38.4
0.058
25
95
Aug.
4.02
56.5
6.6
798
515.1
85.2
48.1
0.950
15
95
Average
3.76
59.5
6.6
636
448.7
69.4
41.2
0.084
17
95
1 See Reference 7
-------
TABLE 4-3 (Continued)
SUMMARY OF OPERATING RESULTS - CALUMET1
Drawoff Sludge Volatile Solids Gas Produced
Dry Solids
(percent) Dry Solids Total Solids cu ft/lb
Alkalinity Total Reduced Reduction Reduced Total Volatile
1965 Total Volatile pH (mg/1) (tons/day) (tons/day) (percent) (tons/day) (1,000 day) Destroyed
Jan.
2.95
45.8
6.9
1,472
11.9
14.0
-
238.6
Feb.
2.70
46.0
7.1
2,142
36.9
18.8
46.0
15.7
512.4
16.3
Mar.
2.57
46.8
7.2
2,711
48.5
26.0
44.2
20.2
678.6
16.8
Apr.
2.97
46.6
7.2
3,080
48.2
25.6
38.6
17.3
679.8
19.6
May
3.38
46.0
7.2
3,050
72.9
18.8
36.9
20.8
615.4
14.9
June
2.75
48.2
7.2
2,452
71.0
11.5
37.9
19,9
614.6
15.5
July
2.82
47.7
7.2
2,457
51.9
14.4
34.3
13.2
559.9
21.2
Aug.
3.11
48.2
7.2
2,405
65.2
20.0
29.5
14.5
567.0
19.5
Average
2.91
46.9
7.2
2,471
50.8
18.6
38.2
17.4
558.3
17.7
1 See Reference 7
Note- Gal x 3.785 = 1; tons x 0.907 = metric tons; lb/cu ft x 16.214 = kg/cu m; 0.555 (ฐ F.-32) = ฐ C.; cu ft x 0.028 = cu m;
cu ft/lb x 0.0617 = cu m/kg.
-------
TABLE 4-4
PROPERTIES OF DIGESTER SUPERNATANT
(MUNICIPAL WASTEWATER SLUDGE)1
Item Standard Rate High Rate
Temperature, ฐF.
85-90
110-125
Total susp. solids (mg/1)
4,000 - 5,000
10,000 - 14,000
Total solids (mg/1)
2,000 - 3,000
4,000 - 6,000
BOD (mg/1)
2,000 - 3,500
6,000 - 9,000
Volatile solids (mg/1)
650 - 3,000
2,400 - 3,800
Alkalinity (MO) (mg/1)
1,000- 2,400
1,900-2,700
Color (Co-Pt) (mg/1)
3,000 - 4,000
4,900 - 6,700
H2S (mg/1)
70-90
190-440
HN3 - Nitrogen (mg/1)
240 - 560
560 - 620
pH
7.0 - 7.6
6.4 - 7.2
Odor
Slightly offensive
Offensive
Digester Loading
0.15 lb/BOD/cu ft/day
0.4 lb/BOD/cu ft/day
1 See Reference 8
-------
TABLE 4-5
ANALYSIS OF SUPERNATANT FROM SEVERAL PLANTS1
Geneva Military Downers Aurora, Fort Worth, Hogsmill
III Installation Grove, 111. Colo. Tex. Valley, England
Item 1944 1944 1963 1963 1963 1966
BOD-Range 542-2,852 173-1,825 540-4,300
Average 1,328 398 2,460 2,300
COD-Range 2,300-20,000
Average 11,560
IODRange 80-250
Average 145
TotalRange
Solids 1,320-14,460 1,000-4,000
Average 3,108 14,673 12,100 3,300
Suspended
Solids-Range 1,228-15,484 404-4,032 2,700-28,980
Average 5,300 1,451 5,300 11,100
AlkalinityRange 5003,100
Average 2,630 1,900
Nitrogen
NH3-Range 510 320
organic 465 60
1 See Reference 9
-------
TABLE 4-6
PROCESSES FOR THE REMOVAL OF CONSTITUENTS
OF ANAEROBIC SUPERNATANT1
Constituent
Means of Removal
Suspended material
Phosphorus
Nitrogen
Coagulation, filtration, microstraining
Removal with suspended material,
chemical precipitation, ion exchange
Removal with suspended material,
stripping, ion exchange
C02
BOD
Lime addition, stripping, ion exchange
Removal with suspended material,
stripping of volatile acids, biological
treatment, adsorption on activated carbon
1 See Reference 10
-------
TABLE 4-7
INFORMATION TAKEN FROM REFERENCES ON
THE AEROBIC STABILIZATION OF SLUDGE
Reference
Information
Taken From
Type of
Sludge
Stabilized
Loading
(lb Volatile
Suspended Solids
per lb reactor
solids/day)
Days that
Sludge was
Stabilized
Volatile
Suspended
Solids
Reduction
(percent)
Nitrate
Level
Achieved
(mg/1)
Total
Kjeldahl
Nitrogen
(mg/1)
Supernatant
BOD level
(mg/1)
Other
Barnhart1
Mixed Primary
+ Activated
Total Poss.
= 60
Grich2
Waste
Activated
50-100
Greatly
Reduced
Lawton3 +
Norman
Mixed Primary
+ Activated
0.22
15
43
<900 w/
60 Days Air
Dreier4
Waste
Activated
0.145
10
43
50
<100
nh3-n
NearO
Lawton5 +
Norman
Waste
Activated
0.112
15
50
-
Loehr6
Waste
Activated
0.1 - 0.44
Limited to
40-60
-
Irgens7
Waste
Activated
0.1 - 0.4
High
Low
Low
<10
Havan8
Raw
Sludge
15
38
43
Low
Alkalinity
88
Malina9 +
Burton
Waste
Activated
0.14
15
43
COD Reduction
of 46%
-
Jaworski10
Waste
Activated
.
.
43
High
.
nh3-n
Low
In genera], a sludge age of IS to 20 days is recommended.
'^See References 1 through 10 respectively.
-------
TABLE 4-8
PHYSICAL PLANT DATA
Plant
Plant Type
Plant Flow
Design Present
(mgd)1 (tng/1)1
Digester
Digester Capacity Tank
Type (cu ft) Configuration
A Contact stabilization 0.33
B Conventional
D Conventional
E Conventional
0.50
C Contact stabilization 1.85
0.33
0.40
F Contact stabilization 0.54
G Extended aeration
0.05
0.40
0.25
1.40
0.37
0.03
0.90
0.03
Two-stage
Single-stage
Two-stage
Single-stage
Two-stage
Two-stage
Single-stage
#1-8,860
#2-4,430
#1-57,250
#2-10,800
#1-11,540
#2-6,060
#1-10,450
#2-13,500
Annular segment
Annular segment
15,700 Circular
Circular
Rectangular
9,720 Circular
Circular segment
Circular segment
Circular
Circular
1,370 Rectangular
1 Imperial gallons
Note: mgd x 4,545.9 = cu m/day; cu ft x 0.0283 = cu m
-------
TABLE 4-9
AEROBIC DIGESTION PROCESS
Loading Air Supply
Hydraulic
Retention Sludge Age Design Actual Design Actual
Plant and Digester (days) (days) (lb VS/cu ft/day) (cfm/1,000 cu ft)
A No. 1 Digester 14
No. 2 Digester
B Single-stage 30
C No. 1 Digester1 -
No. 2 Digester 20
D Single-stage 60
E No. 1 Digester 360
No. 2 Digester -
F No. 1 Digester 652
No. 2 Digester -
30
29
30
45
320
452
0.08
(overall)
0.0256
0.024
(overall)
0.05
0.0166
(overall)
0.0326
(overall)
0.024
0.025
0.025
0.027
0.0035
20
20
25
23
8.4
25
30
(both)
19
232
8.4
46
0.0122 19
(both)
G Single-stage
60
100
0.024
0.020
29
29
1 Occasionally used as a second-stage digester
2 Estimated
Note, lb/cu ft/day x 16.0 = kg/cu m/day, cfm/1,000 cu ft = cu m/min/1,000 cu m
-------
TABLE 4-10
CHARACTERISTICS OF DIGESTER
FEED SLUDGES (mg/1)
Parameter
Overall
Average
Range of
Plant Averages
Range of
Results
pH
COD
TS
TVS
Kjeldahl N
Total P
6.7
19,000
20,200
11,500
960
370
6.3-7.0
7,900-63,000
8,550-41,600
5,210-29,200
400-3,540
144-990
5.5-7.4
1,600-92,700
1,960-86,600
870-63,000
27-18,000
23-1,340
-------
TABLE 4-11
CHARACTERISTICS OF DIGESTER
SLUDGES (mg/1)
Overall
Range of
Range of
Parameter
Average
Plant Averages
Results
pH
6.8
6.2-6.7
5.4-8.4
COD
20,800
14,100-33,200
1,900-51,000
TS
27,600
13,600-39,400
4,040-59,800
TVS
14,400
9,500-21,500
1,940-36,000
Kjeldahl N
1,050
640-1,460
25-4,100
Total P
510
325-900
10-1,500
Soluble P
35
1.3-70
0.6-113
-------
TABLE 4-12
CHARACTERISTICS OF
DIGESTER SUPERNATANTS (mg/I)
Overall
Range of
Range of
Parameter
Average
Plant Averages
Results
pH
7.0
5.9-7.7
5.7-8.0
BOD
500
9-1,700
5-6,350
Filtered BOD
51
4-183
3-280
COD
2,600
228-8,140
24-25,500
SS
3,400
46-11,500
9-41,800
Kjeldahl N
170
10-400
2.9-1,350
Total P
98
19-241
2.1-930
Soluble P
26
2.5-64
0.4-120
-------
TABLE 4-13
PRELIMINARY COMPARISON OF LIME COSTS
FOR RAW, ALUM, AND IRON SLUDGES
Sludge Type Raw Alum FeCl3
Chemical Dose to Primary (mg/1) 0 27.3 A1 20.7 Fe
Sludge Suspended Solids (g/1) 89.1 32.1 20.1
Sludge Volatile Solids (% of SS) 64.0 55.9 45.7
pH before lime 5.2 6.2 6.2
pH after lime 11.0 11.0 11.0
Ca(OH)2 added, (g/1 sludge) 8.7 12.9 5.5
(g/g dry solids) 0.098 0.40 0.27
Cost of lime ($/ton dry solids)* 1.96 8.00 5.40
* Based on Ca(OH)2 cost of $20/ton. Multiply by 1.10 for $/metnc ton.
-------
TABLE 4-14
BACTERIOLOGICAL STUDIES OF SLUDGE
PRODUCED IN PLANT-SCALE TESTS
Bacterial Count (organisms/liter of sludge)
Salmonella Pseudomonas Total Aerobic
Sludge Species aeruginosa Count x 10"8
Alum-primary 110 1,300 41
Limed alum-primary None detected None detected 5.0
Ferric-primary > 24,000 610 190
Limed ferric-primary None detected None detected 0.29
-------
TABLE 4-15
AVERAGE COST OF LIME ADDITION: PLANT-SCALE TESTS
Sludge Ca(OH)2 Dose Cost1
Chemical Dose (ing/1) Solids (g/1) (g/1) (g/g) (dollars/ton)
Al^ 31.8 24.0 6.0 0.25 5.0
22.7 28.5 6.3 0.22 4.4
13.6 20.6 4.4 0.21 4.2
Fe^ 31.0 20.2 2.2 0.11 2.2
15.5 17.9 2.2 0.12 2.4
1 Ca(OH)2 at $20.00/ton.
-------
TABLE 4-16
EFFECT OF LIME ON FILTRABILITY OF Al44* AND Few SLUDGES
Lime
Sludge Property Addition
Al** Dose (mg/1)
31.8
22.7
13.6
Fe""* Dose (mg/1)
31.0
15.5
Buchner Funnel Tests
Specific Resistance at Before
20" Hg (cm/g x 10"11) After
19.0
3.8
28.0
4.5
29.0
3.8
14.9
7.0
21.6
5.5
Compressibility
Before
After
0.50
0.70
0.46
0.91
0.59
0.80
0.53
0.43
0.60
0.76
Filter Leaf Tests
Yield
(lb/hr/ft2)1
Before
After
0.98
1.97
0.94
2.10
0.95
2.58
1.06
1.57
1.57
2.40
Cake Moisture
(lb w/lb d.s.)
Before
After
4.31
3.87
4.35
3.92
4.37
3.83
4.10
4.28
3.75
3.75
1 Multiply by 4.86 to get kg/hr/m2
-------
SECTION 5A - CASE STUDIES - PLANT RESULTS - CHEMICAL CONDITIONING -
CONVENTIONAL ACTIVATED SLUDGE
CASE STUDY - WASHINGTON, D.C.
1. Extensive History, Plant Process Engineering Studies
Reference 2, Dahl, Zelinski and Taylor (WPCF award 1972).
Important regarding efficiency of various methods of handling organic sludges.
2. Plant Process
(Figure 5A-1)
Currently modified high rate activated sludge.
Expanded to activated sludge in 1959 - Original rationale - same solids handling
system as for primary sludge.
Gravity thickening of excess activated with raw primary.
Anaerobic high rate digestion, clutriation, vacuum filtration.
Problems
Dirty thickener overflow and very polluted elutriate.
Results - Fines build up in system, upset and high cost solid - liquid
separation steps.
Temporary solution
Vent elutriate (15-30 tons/day).
Accept poor primary capture.
Current solution
(Figure 5A-2)
Flocculation in clutriation basins.
Careful operation of basins to promote sludge compaction and thickening
and good solids capture.
5A-1
-------
3. Sludge Removal Practices and Costs
(Table 5A-1)
Initial results, even with venting of elutriate, costs were high and 3 lb/hr/ft2
filter yields experienced.
- During initial months of treating elutnation basins and providing good solids
removal rate, higher than normal rates were maintained to clean out plant
system. (Prior to this work, another long term attempt had been made to
recycle the elutriate - this loaded up the plant).
(Figure 5A-3 showing vacuum filters)
After prolonged efficient thickening, solids capture and removal rates being
attained, costs and required steady state rates became lower as a new plant
equilibrium established (4 lb/hr/ft2 yield).
4. Current Operations
New belt type filters installed.
(Figure 5A-4)
Interim use of alum/ferric m final clarifiers for increased BOD and solids
removals.
Some problems with release of cake from belt filters. Requires $3.80/ton more
ferric chloride than older drum filters.
Cloth use data comparison shows favorable results for drum type filters.
Drum cloth life = 2,000 hours: preliminary indications are belts go same time
before maintenance or changes required.
5A- 2
-------
CASE STUDY - METRO TORONTO MAIN PLANT
1. Definitive, Thorough Plant Process Studies By Plant Personnel
Plant expanded over 1967-71 period to provide full scale secondary treatment.
-Sludge processing problems encountered.
No separate activated sludge thickening, once again recirculation of same to
head of plant. Digestion of mixed sludges.
Plant personnel responded to the challenge.
2. Process Description
(Figure 5A-5)
Step aeration, two-stage anaerobic digestion, elutriation, vacuum filtration,
incineration.
Slide does not completely reflect all available options on recycle stream
directions.
Loadings and degree of treatment gradually increased 1967-71.
3. Effects of Increased Proportion of Activated Sludge
(Figure 5A-6)
Gradual decrease in solids content of elutriated sludge to filters.
By 1970, below 4 percent, that critical level as far as efficient dewatering is
concerned. By August, "to hell in a handbasket," below 3 percent regularly.
Concurrently (Figure 5A-7), the solids content of the raw sludge from the
primaries was decreasing. The effect of recirculation of activated sludge to the
head of the plant.
4. Sludge Removal Needs
(Table 5A-2)
Due to loadings increase and full secondary treatment, solids removal rates as
shown were essential.
But processing problems cited made attainment with normal mode of operation
questionable.
5A-3
-------
As recirculating solids occurred in plant, odor problems arose.
Work commenced to improve the elutriation/filtration process.
5. Elutriation/Filtration Studies
(Table 5A-3)
Over two month period, small polymer add in feed to elutnation, ferric
chloride in decreasing amounts, plus polymer at vacuum filters.
Elutriated sludge solids up to 4 percent with corresponding increase in filter
production rate.
After 2-3 months of operation (Table 5A-4), results improved even further as
some of the fines were cleaned out of the plant.
The elutriation/filtration (Figure 5A-8) process improved in uniformity and
ease of operation. Note excellent cake discharge and thickness of filter cake.
5A-4
-------
CASE STUDY - RICHMOND, CALIFORNIA
1. On-Going, Plant Process Studies on Solids Handling
During 1967-69 (Figure 5A-9) expanded plant to secondary treatment via
- -activated sludge process (surface aeration).
Design included provision for separate thickening of activated sludge via D.A.F.
Combined sludges then to two stage anaerobic digestion, elutriation and
vacuum filters. Filter cake to incinerator or landfill (40 mgd hydraulic
capacity, average flow = 9 mgd).
2. Process Considerations
While D.A.F. thickening of E.A.S., was a positive step, there was some
speculation about mixing the sludges early in the process.
Shortly after the advent of activated sludge operation, the same problems arose
as in Toronto and Washington. Recirculation of loaded digester supernatant
elutriate caused solids build-up within plant.
3. Remedial Action
Plant personnel carried out process studies on elutriation/filtration process
(Table 5A-5).
Note that with primary sludge, before secondary treatment, things were rosy.
During the period when solids recirculation was occurring, note in column 2
the high costs - low yields and low cake solids obtained.
After realizing good compaction and solids capture in elutriation via fiocculant
use, note dramatic improvement in filtration performance.
4. Current Results
After protracted operation with effective elutriation (Table 5A-6)the results were as
shown.
Total conditioning costs in elutriation and on filters (ferric chloride/lime) were
about $11.00/ton.
5A-5
-------
Richmond has belt filters which do not have particularly good cake release
capabilities. This necessitates a higher than normal ferric/lime dosage. How
many times have you seen a filter cake with all those drying cracks?
More important, if the thickened activated sludge could be mixed with primary
sludge just before filtration, results would improve and costs would decrease.
5A-6
-------
REFERENCES - SECTION 5A
1. Goodman, B.L, and Whitcher, C.P., "Polymer Aided Sludge Elutriation and Filtration."
Journal WPCF,31,]2, 1643 (1965).
2. Dahl, B.W., Zelinski, J.W., and Taylor, O W., "Polymer Aids Dewatenng and Eliminates
Solids Loss in Elutriation," presented at the 43rd Annual WPCF Conference,
Boston, Massachusetts, October 6, 1970.
3. Ashman, P.S., "Operating Experiences of Vacuum Filtration at St. Helens." Water
Pollution Control, 20-39 (1969)
4. Ashman, P.S.,and Roberts, P.F., "Operating Experiences with Vacuum Filtration at St.
Helens. A Solution to the Problem." Water Pollution Control, 638-648 (1970).
5. Stanbridge, H.H., "Operation and Performance of the Hogsmill Valley Sewage Treatment
Works of the Greater London Council, 19581966." Water Pollution Control, 67,21
(1968).
6. Private communications with: David A. Clough, Director of Metro Water Pollution
Control; Earl Baldock, Assistant Director of Water Pollution Control, Wadid Salib,
Plant Engineer Main Plant.
7. Private communications with: E.L. MacDonald, Jr., Superintendent, and William
Kennedy, Plant Supervisor, City of Richmond, California.
5A-7
-------
LIST OF FIGURES AND TABLES - SECTION 5A
Figure 5A-1 Plant Flow Diagram - District of Columbia
Figure 5A-2 Elutriation/Filtration System District of Columbia
Table 5A-1 Sludge Removal Practices and Costs - District of Columbia
Figure 5A-3 Vacuum Filter Operation District of Columbia
Figure 5A-4 New Filter Installation with Individual Conditioning Boxes - District of
Columbia
Figure 5A-5 Plant Flow Diagram Metro Toronto
Figure 5A-6 Percent Solids in Elutriated Sludge - Metro Toronto
Figure 5A-7 Percent Solids in Raw Sludge Metro Toronto
Table 5A-2 Sludge Removal Needs - Metro Toronto
Table 5A-3 Elutriation/Filtration Results October-November Metro Toronto
Table 5A-4 Elutriation/Filtration Results 1971 Metro Toronto
Figure 5A-8 A View of Filters Metro Toronto
Figure 5A-9 Plant Flow Diagram Richmond, California
Table 5A-5 Filtration Results Richmond, California
Table 5A-6 Elutriation/Filtration Operations Richmond, California
5A-8
-------
INFLUENT
EFFLUENT
PRIMARY
BASINS
THICKENER
0 FLOW
THICKENER
ELUTRIATE
HIGH
RATE
DIGESTION
WASH
WATER
VACUUM
FILTER
15-25%
FILTER
CAKE
BOD REMOVAL 70-90%
SLUDGE
COND
ELUTRIATION
AERATION
BASINS
GRIT
REMOVAL
FINAL
CLARIFIERS
SS REMOVAL 70-90%
FIGURE 5A1 PLANT FLOW DIAGRAM - DISTRICT OF COLUMBIA
-------
ELUTRIATE
WASH RECYCLED OR TO RIVER
VACUUM
FILTERS
2 STAGE
ELUTRIATION
DIGESTED
SLUDGE
FILTER
CAKE
X = CATIONIC POLYELECTROLYTE APPLICATION POINT
FIGURE 5A-2 ELUTRIATION/FILTRATION SYSTEM - DISTRICT OF COLUMBIA
-------
TONS/DAY CHEMICAL COST (S/TON)
REMOVED ELUTRIATION FILTRATION
ELUTRIATE TO RIVER 45 13.50
POST ELUTRIATE
RECYCLE PERIOD
(POLYMER IN ELUTRIATION) 80 4.68 7.42
AFTER PROLONGED
POLYMER USE IN
ELUTRIATION 70 TOTAL = 9.75
TABLE 5A1 SLUDGE REMOVAL PRACTICES AND COSTS - DISTRICT OF COLUMBIA
-------
-> .
w **
FIGURE 5A-3 VACUUM FILTER OPERATION - DISTRICT OF COLUMBIA
-------
FIGURE 5A-4 NEW FILTER INSTALLATION WITH INDIVIDUAL CONDITIONING BOXES - DISTRICT OF COLUMBIA
-------
PLANT
INFLUENT
PLANT EFFLUENT
* FILTRATE
j ELUTRIATE
'f S.N.
TO INCINERATORS
iiiiii
VACUUM
FILTRATION
2 STAGE
ELUTRIATION
FINAL
CLARIFIERS
PRIMARY
DIGESTION
ACTIVATED
SLUDGE
GRIT
REMOVAL
SECONDARY
DIGESTION
PRIMARY
CLARIFICATION
WASTE WATER
SLUDGES
PROCESS LIQUIDS
FIGURE 5A-5 PLANT FLOW DIAGRAM - METRO TORONTO
-------
MONTHLY AVERAGES
9.0 r
8.0
1967
7.0
1968
6.0
1969
4.0
1970
3.0
JFMAMJJ ASOND
FIGURE 5A-6 PERCENT SOLIDS IN ELUTRIATED SLUDGE - METRO TORONTO
-------
7.0
6.0
5.0
4.0
3.0
2.0
1.0
III!
I I I
I I I
J-JL
I i ป
I i
7.0
6.0
5.0
4.0
3.0
2.0
1.0
JAN.
JUNE
1968
DEC.
JUNE
DEC.
1969
JUNE
1970
FIGURE 5A-7 PERCENT SOLIDS IN RAW SLUDGE
METRO TORONTO
-------
DRY TONS/MO.
#/HR./FT.2
OPERABLE
1970
2000
3.0
PREFERRED
1970
2500
3.7
REQUIRED
1971
3000
4.4
TABLE 5A-2 SLUDGE REMOVAL NEEDS - METRO TORONTO
-------
POLYMER USED
1970 l#/TON|
PERIOD ELUT. FILT.
OCTOBER 1.26 7.77
NOVEMBER 1.75 8.20
TABLE 5A-3 ELUTRIATION/FILTRATION
SLUDGE CAKE
SOLIDS . SOLIDS
1%) #/HR./FT |%1
3.6 4.7 16
4.1 4.3 16
RESULTS OCTOBER-NOVEMBER - METRO TORONTO
-------
ELUT. FLOW POLYMER ELUTRIATE
[MGPDI [#/TON| S.S. (PPM) SLUDGE
WASH DIGEST. S0LIDS
WATER SLUDGE ELUT. FILT. 1ST 2ND l%l
1.0 0.6 1.94 10.96 120 18 6.1
3.5 1.4 0.62 9.34 6250 208 3.5
TABLE 5A-4 ELUTRIATION/FILTRATION RESULTS 1971 - METRO TORONTO
-------
FIGURE 5A-8
A VIEW OF FILTERS - METRO TORONTO
-------
PLANT
GRIT
REMOVAL
PRIMARY
AERATION
FINAL
PLANT
INFLUENT "
r
>
*
<
CLARIFIERS
A p
BASINS
CLARIFIERS
EFFLUENT
j
k
*
*
^
D.A.F.
THICKENER
PRIMARY
DIGESTION
WASTE WATER
f
SECONDARY
DIGESTION
ELUTRIATION
SLUDGE
VACUUM
FILTERS
PROCESS LIQUIDS
FIGURE 5A-9
PLANT FLOW DIAGRAM - RICHMOND. CALIFORNIA
-------
MIXED SLUDGES
PRIMARY NO POLYMER IN
SLUDGE POLYMER ELUTRIATION
YIELD (LB./HR./FT.2) 7-9 1-2 5-7
CONDITIONER COST (S/TONJ $3.80/54.00 $25/530 $11/514
CAKE SOLIDS (%| 29-31 16-18 20-22
TABLE 5A-5 FILTRATION RESULTS - RICHMOND. CALIFORNIA
-------
DIGEST
SLUDGE
% SOLIDS
ELUTRIATE
SLUDGE
% SOLIDS
POLYMER
#/TON
ELUTRIATION
3.85
7.8
2.12
FILTER
FeC!3 LIME CAKE
S/TON S/TON % SOLIDS
FILTRATION 3.00 4.85 20.8
ELUTRIATE
SOLIDS
PPM
450
TABLE 5A-6 ELUTRIATION/FILTRATION OPERATIONS - RICHMOND, CALIFORNIA
-------
SECTION 5B - CASE STUDIES - PLANT RESULTS - CHEMICAL CONDITIONING -
PRIMARY PLANTS WITH CHEMICAL ADDITION
CASE STUDY - DETROIT
1. Primary plant since 1939 with sludge filtration and incineration
- One of the early users of polymer for sludge conditioning.
2. Under expansion for secondary treatment
- Replaced the 12 drum filters with belt filters and individual sludge conditioning
tanks for each filter prior to 1970.
- Started interim chemical treatment to remove 56 percent of the phosphorus
in February, 1972.
3. Table 5B-1 shows plant results without and with chemical treatment for P removal.
4. Table 5B-2 shows sludge filtration data without and with chemical treatment for P
removal
5B-1
-------
CASE STUDY - WAYNE COUNTY, MICHIGAN
1. Primary plant since 1939 with sludge filtration and incineration
2. Under expansion for secondary treatment
Plant overloaded.
Interim chemical treatment to upgrade treatment and remove phosphorus.
3. Table 5B-3 shows plant removals BODSSP.
4. Table 5B-4 shows sludge filtration data.
5B -2
-------
CASE STUDY - CLEVELAND WESTERLY
1. Primary plant for over 35 years
Primary tanks are Imhoff tanks.
- . .Separate sludge digestion.
Sludge filtration and incineration.
2. Full plant long-term trial to upgrade treatment and remove phosphorus
- In preparation for expansion to generate some data.
3. Presently using chemical treatment for interim upgrading of treatment and
phosphorus
4. Table 5B-5 shows plant removals BODSSP.
5. Table 5B-6 shows sludge filtration data.
5B-3
-------
CASE STUDY - EAST LANSING, MICHIGAN
1. Primary treatment with contact stabilization
- Plant overloaded.
-Must improve to meet phosphorus removal requirement.
2. Full plant trial to upgrade treatment and remove phosphorus
3. Presently using chemical treatment as proved in plant trial to meet effluent requirements-
4. Table 5B-7 shows plant removals BODSSP.
5. Table 5B-8 shows sludge filtration data.
5B-4
-------
CASE STUDY - GRAND RAPIDS, MICHIGAN
1. Primary treatment with high rate activated sludge
Some plant improvement needed.
Must increase phosphorus removal to meet effluent requirement.
2. Full-scale plant trial to upgrade treatment and remove phosphorus
Many interruptions due to floods, construction, digester failure, and lack of
sludge disposal capability.
3. Longer term study resumed at present.
4. Table 5B-9 shows plant removals BODSSP.
5. Table 5B-10 shows sludge filtration data.
5B-5
-------
CASE STUDY - TONAWANDA, NEW YORK
1. Primary plant with sludge filtration and incineration
- Overloaded.
- Need to upgrade to meet phosphorus removal requirement.
2. Full-scale plant trial to upgrade and remove phosphorus
3. Table 5B-11 shows sludge filtration data.
SB-6
-------
CASE STUDY - AMHERST, NEW YORK
1. Primary plant with sludge digestion and sludge filtration
Grossly overloaded.
- - - Operations improvement needed to handle overload.
2. Full-scale trial with chemical treatment
3. Interim chemical treatment implemented.
4. Table 5B-12 shows sludge filtration data.
5B-7
-------
LIST OF FIGURES AND TABLES - SECTION SB
Table 5B-1
Detroit, Michigan - Primary Treatment with Chemical Addition
Plant Results
Table 5B-2
Detroit, Michigan - Primary Treatment with Chemical Addition
Raw Sludge Filtration Data
Table 5B-3
Wayne County, Michigan Primary Treatment with Chemical Addition
Plant Results
Table 5B4
Table 5B-5
Wayne County, Michigan - Primary Treatment with Chemical Addition
Sludge Filtration Data
Cleveland Westerly Primary Treatment with Chemical Addition
Plant Results
Table 5B-6
Cleveland Westerly Primary Treatment with Chemical Addition
Sludge Filtration Data
Table 5B-7
East Lansing, Michigan Primary Treatment with Chemical Addition
and Contact Stabilization - Plant Results
Table 5B-8
Table 5B-9
East Lansing, Michigan Primary Treatment with Contact Stabilization
Grand Rapids, Michigan - Primary Treatment + High Rate Activated Sludge
Chemical Addition to Primary - Plant Results
Table 5B-10 Grand Rapids, Michigan Primary Treatment + High Rate Activated Sludge
Chemical Addition to Primary Treatment Sludge Filtration Data
Table 5B-11 Tonawanda, New York Primary Plant with Chemical Addition
Raw Sludge Filtration Data
Table 5B-12 Amherst, New York - Primary Plant with Chemical Addition
Digest Sludge Filtration Data
5B-8
-------
DETROIT, MICHIGAN
PRIMARY TREATMENT WITH CHEMICAL ADDITION
PLANT RESULTS
% REMOVAL
CHEMICAL TREATMENT BOH Sฃ E
NONE 35 55-60 19
10 PPM Fe^+
0.25 ppm Anion Polymer 55-60 70-75 56
TABLE 5B-1
-------
DETROIT/ MICHIGAN
PRIMARY TREATMENT WITH CHEMICAL ADDITION
RAW SLUDGE FILTRATION DATA
Chemical Treatment
None
5 ppm Fe^+
10 ppm Fe^+
0.25 ppm Anion Polymer
TABLE 5B-2
Filter Yield Sludge Conditioning
lb/ft2/hour Chemical $/Tqn
8-10 Cation Polymer 1,67
8-14 Anion Polymer 1.39
7-10 Anion Polymer 0.90
-------
WAYNE COUNTY/ MICHIGAN
PRIMARY TREATMENT WITH CHEMICAL ADDITION
PLANT RESULTS
% REMOVAL
CHEMICAL TREATMENT m SS. E
None ^3 60 19
10 ppm Fe^+
30 ppm NaOH 75 78 71
0.5 ppm Anion Polymer
TABLE 5B-3
-------
WAYNE COUNTY/ MICHIGAN
PRIMARY TREATMENT WITH CHEMICAL ADDITION
SLUDGE FILTRATION DATA
Treatment
None
20 ppm Fe^+
30 ppm NaOH
0.5 ppm Anion Polymer
17 ppm Fe^+
0.7 ppm Anion Polymer
Chemical
Cation Polymer
Cation Polymer
Anion Polymer
$/Tqn
< 1.0
3.0
1.35
TABLE 5B-4
-------
CLEVELAND WESTERLY
PRIMARY TREATMENT WITH CHEMICAL ADDITION
PLANT RESULTS
% REMOVAL
CHEMICAL TREATMENT BQfi SS E
None 34 33 21
20 PPM Fe3+ R8 7C
0.5 ppm Anion Polymer 00 ' 5
TABLE 5B-5
-------
CLEVELAND WESTERLY
PRIMARY TREATMENT WITH CHEMICAL ADDITION
SLUDGE FILTRATION DATA
Chemical Treatment
None
20 ppm Fe^+
0.5 ppm Anion Polymer
Raw Sludge Chemicals and Dose Filter Yield
% Solids lb/Ton lb/ft /hour
4,4 FECL3/CAO 1.0
1# Anion + 35# Cation
Polymer Polymer ^-10
TABLE 5B-6
-------
EAST LANSING/ MICHIGAN
PRIMARY TREATMENT WITH CHEMICAL ADDITION
AND CONTACT STABILIZATION
PLANT RESULTS
I REMOVAL
f.HFMICAL TREATMENT BOH Si E
None 59 45 18
20-25 ppm Fe3+ 78 87 34
0.3-0,4 ppm Anion Polymer
TABLE 5B-7
-------
EAST LANSING/ MICHIGAN
PRIMARY TREATMENT WITH CONTACT STABILIZATION
Chemical Treatment
None
25 ppm Fe^+
0,4 ppm Anion Polymer
25 ppm Fe^+
0,4 ppm Anion Polymer
Slude Conditioning
Chemical $/Tqn
Cation Polymer 2,5
Cation Polymer 7-11
Cation Polymer 4.0
TABLE 5B-8
-------
GRAND RAPIDS/ MICHIGAN
PRIMARY TREATMENT + HIGH RATE ACTIVATED SLUDGE
CHEMICAL ADDITION TO PRIMARY
PLANT RESULTS
Treatment
None
17-20 ppm Fe^+
0,3-0,4 ppm Anion Polymer
TABLE 5B-9
% REMOVAL
PRIMARY TOTAL PLANT
BOH ฃS R BOH Si I
20 26 13 m 71 39
m 55 61 79 75 72
-------
GRAND RAPIDS/ MICHIGAN
PRIMARY TREATMENT + HIGH RATE ACTIVATED SLUDGE
CHEMICAL ADDITION TO PRIMARY TREATMENT
SLUDGE FILTRATION DATA
Chemical Treatment
None
Raw Sludge
% Solids
9.0-5.9
Filter Yield
lb/ft /hour
.Sludge Conditioning
Chemicals
9.7-3.9 FeCl3/CaO
$/Ton
1.75 - 8.09
17-20 ppm Fe^+
0.3-0.1 ppm Anion Polymer
10.1-6.2
9.2-3.0 FeCl3/CaO
2.15 - 7.69
TABLE 5B-10
-------
TONAWANDA, NEW YORK
PRIMARY PLANT WITH CHEMICAL ADDITION
RAW SLUDGF FILTRATION DATA
Chemical Treatment
None
25 ppm Fe^+
0.5 ppm Anion Polymer
25 ppm Fe^+
0.5 ppm Anion Polymer
Filter Yield Sludge Conditioning
lb/ft^/hour Chemicals $/Ton
2,5 Nonionic Polymer 0-2
2.5 Anion + Cation Polymer 3-4
3.5 Cation Polymer 5-6
TABLE 5B-11
-------
AMHERST, NEW YORK
PRIMARY PLANT WITH CHEMICAL ADDITION
DIGEST SLUDGE FILTRATION DATA
Chemical Treatment
15 ppm Fe^+
0,5 ppm Anion Polymer
Filter Yield
lb/ft2/hour
~2.0
Sludge Conditioning
Chemicals
FeClt/CaO
$/Ton
10 - 15
15 ppm Fe^+
0,5 ppm Anion Polymer
4.0
Cation Polymer
TABLE 5B-12
-------
SECTION 5C -
REMOVAL OF PHOSPHORUS FROM WASTEWATER BY CHEMICAL ADDITION
1. Introduction
In wastewater treatment the principal new source of sludge solids to be handled
is from chemical precipitation processes.
Need information on the production rates, dewatering characteristics,
dewatering methodologies and the costs of treating sludges produced by the
addition of chemicals to primary, secondary, and tertiary systems for the
removal of phosphorus.
2. Expected Sludge Masses and Volumes with Phosphorus Removal
Available data is very limited. It is mostly from laboratory and pilot studies.
A recent review of 13 case histories provided sludge production information on
primary, secondary and tertiary phosphorus removal schemes (Reference 1).
Table 5C-1 shows the additional sludge to be handled when chemicals are
added to the primary to remove phosphorus.
Table 5C-2 shows the additional sludge to be handled when chemicals are
added to the secondary to remove phosphorus.
Table 5C-3 shows the additional sludge to be handled when chemicals are
added to the secondary effluent for removing phosphorus.
Table 5C-4 gives a way of interpreting this data and relating it back to the
chemical dose.
From Table 5C-4
The greatest increase in sludge mass occurred when aluminum was added
to secondary effluent.
The minimum increase occurred when lime was added at a level of from
800-1,600 mg/1 to raw sewage.
The maximum amount of additional sludge volume to be handled was
with iron addition to secondary effluent.
5C - 1
-------
The minimum additional volume was With lime addition to raw sewage.
3. Difficulty in Dewatering these Physical-Chemical Sludges
Recent work performed at Salt Lake City studied the removal of phosphorus
from raw wastewater by adding aluminum, iron or lime (Reference 2). Their
- data is given in Table 5C-5.
Dow Chemical Company reports (see References 3, 4, 5, and 6) indicate little
change in filtering primary and digested primary sludges containing iron salts,
although one case of vacuum filter blinding was reported (Reference 7).
Some investigators have found a filter yield of 1.0 lb/ft2/hr for an iron sludge
(Reference 8).
Work done recently at the Chapel Hill, North Carolina 4 mgd primary and high
rate trickling filter system (shown in Figure 5C-1) is reported on in Table 5C-6
(Reference 9).
Alum is added to the trickling filter stream just prior to the final clarifier
in the amount of 180 ppm based on liquid alum.
Thickening tests revealed that sludge with alum thickened at a rate less
than 2/3 that of the sludge with no alum.
Washington, D.C. (alum added to secondary) (Reference 10).
The Blue Plains Plant in Washington, D.C. will utilize the three-sludge
system for wastewater treatment. The plant will comprise primary
treatment, high rate activated sludge, nitrification, and denitnfication.
Aluminum will be added to the high rate activated sludge process for
phosphate removal. The Blue Plains Plant has recently started to add alum
to their activated sludge plant to start lowering phosphate levels in their
effluent. Results from the full-scale plant are not well established at this
point. Design information has been collected in experimental runs at the
Blue Plains Pilot Plant, operated by Fred Bishop for the District of
Columbia and EPA. The data reported below were obtained at the pilot
facility.*
Information below has been supplied by Steve Bennett, Blue Plains Pilot Plant.
5C-2
-------
Thickening
On 1 ft2 Komline-Sanderson air flotation thickener, alum-activated sludge
thickened without polymers to 4.06.1 percent solids (inlet solids =circa
1.3 percent solids, solids loading = circa 2 lb/ft2-hr). Underflow
concentration < 500 mg/1. Large scale units might need polymers.
Gravity thickening of alum-activated sludge produced 57 percent solids.
Prediction from thickening data indicate 4.5 percent underflow
concentration at a solids loading of 7 lb/ft2 /day.
Primary + alum-activated sludge settled to 16-18 percent solids over a
24-hour period. Thickening curves indicated that at a solids loading of 57
lb/ft2-day, underflow concentration of 10 percent would result.
Dewatering
Results were obtained on a pilot rotary vacuum filter (Eimco 3 ft diam. x
1 ft face, belt-type), a Sharpies 6-inch diameter solids bowl centrifuge
(Model P600), and a pressure filter with 1 ft x 1 ft plates (Nichols).
Solids concentrations and chemical costs are shown in Table 5C-7, and
production rates are shown in Table 5C-8. Alum-activated and primary +
alum-activated sludge show filter yields very similar to activated and
primary + activated sludges. The moisture content of the primary +
alum-activated seems lower than would be expected for a primary +
activated sludge. The ratio of alum secondary to primary sludge was 1.5 to
1 (dry weight basis) for these tests.
Full-Scale Plant
The full-scale plant has been introducing alum into the secondary by
steps. Level is now at 80 mg/1. Filter yields on mixed digested sludge have
not changed. However, solids content has dropped from circa 24 percent
to circa 19 percent. Costs of conditioning chemicals for elutriation have
increased.
4. Contra Costa* Case Study (Reference 11)
The Contra Costa County Sanitary District has an agreement to supply
renovated water to the CCC Water District for industrial uses. A 30 mgd plant
will be constructed.
* Information was supplied by Dr. Denny Parker of Brown and Caldwell.
5C-3
-------
The CCCSD will treat the wastewater by the ATTF system (Advanced
Treatment Test Facility). It comprises lime coagulation-sedimentation,
nitrification, and denitrification. The ATTF system is shown in Figure 5C-2. As
noted in the diagram, biological sludges are returned to the primary and are
removed with the primary sludge. The use of lime in the primary removes much
of the organic carbon load from the oxidation-nitrification stage, thus
allowing stable oxidation of ammonia to nitrate. In addition to removal of
organic matter, the lime enhances the removal of phosphates, heavy metals, and
pathogenic bacteria.
The system performed satisfactorily at pH's of 10.2, 11.0 and 11.5. Most of the
effort was concentrated on pH 11.0. At this pH, a supplemental dose of ferric
chloride was needed to bring the P-level in the primary effluent to below 1.0
mg/1.
Interpretation of data is complicated somewhat by the seasonal impact of food
processing wastes from a cannery. Sludge solids concentrations from the
primary clarifier are summarized as follows:
2H
Solids Content
(Wt. %)
10.2
<4.5
With polymer
(ICI Atlasep 3A3),
6.0
11.0
5.0 (up to 9.0, but
handling problems at
7.0 in pilot plant)
Cannery opera ting,<4.5
CCCSD has received a State Water Resources Control Board and EPA R,D,&D
grant to document results of tests on their solids processing system. A report
will probably be available in a few months.
The solids processing system being designed and tested is shown in Figure 5C-3.
A two-stage centrifuge system is used to classify sludge into a fraction (cake)
containing most of the lime, and a fraction (centrate) containing most of the
organics, magnesium, and phosphate. The system is nearly the same as utilized
at Lake Tahoe, but the feed is a primary-lime sludge, whereas at Tahoe, the
sludge is a tertiary-lime sludge. The following summarizes conditions and
results:
First centrifuge:
Machine operates at low g (circa 1,600), high throughput, and no
polymer. Cake contains 80 percent of the CaC03, 30-40 percent of the
organics, 1020 percent of the phosphate, and 40 percent of the
magnesium. Cake solids 50 percent.
5C-4
-------
Second centrifuge:
Machine operates at high g (circa 2,000). Little wear because there is no
grit. Polymer is needed. Cake is wet, circa 1319 percent solids.
- Lime is regenerated by incineration and calcination of first centrifuge cake.
This lime, along with makeup, is used as the lime charge to the primary
clarifier. Of the solids appearing in the underflow from the primary clarifier,
approximately 22 percent is estimated to be recycled inerts.
For more information, refer to "Full-Scale Testing of a Water Reclamation
System," by G.A. Horstkotte (CCCSD), D.G. Niles (CCCSD), D.S. Parker
(Brown and Caldwell), and D.H. Caldwell (Brown and Caldwell), presented at
the 45th Annual Conference, WPCF, Atlanta, October, 1972.
5C-5
-------
REFERENCES - SECTION 5C
1. Adrian, D.D., and Smith, J.E., Jr., "Dewatering Physical-Chemical Sludges." Conference
on Application of New Concepts of Physical-Chemical Wastewater Treatment,
Vanderbiit University, September 18-22, 1972.
2. Burns, D.E., and Shell, G.L., "Physical Chemical Treatment of a Municipal Wastewater
Using Powdered Carbon." Water Pollution Control Research Series 17020 EFB,
Government Printing Office, Washington, D.C., 57 (1972).
3. Avon, "Application of Chemical Precipitation, Phosphorus Removal at the Cleveland
Westerly Wastewater Treatment Plant." Dow Chemical Company, Midland,
Michigan, April,1970.
4. Cherry, A.L., and Schuessler, R.G., "Private Company Improves Municipal Waste
Facility." Water and Wastes Engineering, 8, 32 (1971).
5. Avon, "Phosphorus Removal Trial, Ford du Lac, Wisconsin." Dow Chemical Company,
Michigan, July, 1971.
6. Hennessey, J., Jelinski, R., Beeghly, J.H., and Pawlak, T.J., "Phosphorus Removal at
Pontiac, Michigan." Presented at the Michigan State Water Pollution Control
Association Meeting, Bryne Mountain, Michigan, June, 1970.
7. Stonebrook, W.J., Dykhuzen, V., Beeghly, J.H., and Pawlak, T.J., "Phosphorus Removal
at a Trickling Filter Plant, Wyoming, Michigan." Dow Chemical Company, Midland,
Michigan, 1971.
8. Farrell, J.B., Smith, J.E., Jr., Hathaway, S.W., and Dean, R.B., "Lime Stabilization of
Chemical-Primary Sludges at 1.15 mgd." 45th Annual Conference, Water Pollution
Control Federation, Atlanta, Georgia, October, 1972.
9. Hathaway, S.W., Personal communication, October, 1972.
10. Bennett, S., Personal communication, Blue Plains Pilot Plant, Washington, D.C., October,
1972.
11. Horstkotte, G.A., Niles, D.G., Parker, D.S., and Caldwell, D.H., "Full-Scale Testing of a
Water Reclamation System." Presented at 45th Annual Conference, Water Pollution
Control Federation, Atlanta, Georgia, October, 1972.
5C-6
-------
LIST OF FIGURES AND TABLES - SECTION 5C
Table 5C-1 Additional Sludge to be Handled with Chemical Treatment Systems
Primary Treatment for Removal of Phosphorus
Table 5C-2 Additional Sludge to be Handled with Chemical Treatment Systems:
Phosphorus Removal by Mineral Addition to Aerator
Table 5C-3 Additional Sludge to be Handled with Chemical Treatment Systems:
Phosphorus Removal by Mineral Addition to Secondary Effluent
Table 5C-4 Additional Sludge to be Handled with Chemical Treatment Systems.
Primary Treatment for Removal of Phosphorus
Table 5C-5 Vacuum Filtration Leaf Tests for Salt Lake City Raw Wastewater
Figure 5C-1 Schematic Representation of Chapel Hill Plant
Table 5C-6 Field Test Results at Chapel Hill
Table 5C-7 Cake Solids and Chemical Cost
Table 5C-8 Loadings
Figure 5C-2 ATTF System
Figure 5C-3 ATTF Solids Processing System
5C - 7
-------
TABLE 5C-1
ADDITIONAL SLUDGE TO BE HANDLED WITH CHEMICAL TREATMENT SYSTEMS:
PRIMARY TREATMENT FOR REMOVAL OF PHOSPHORUS
Sludge Production Conventional Lime Addition to Lime Addition to Aluminum Addition Iron Addition to
Parameter Primary Primary Influent Primary Influent to Primary Influent Primary Influent
Level of Chemical
Addition (mg/1) 0 350-500 800-1,600 13-22.7 25.80
Percent Sludge Mean 5.25 11.1 4.4 1.2 2.25
Solids Range 5.05.5 3.019.5 2.1-5.5 0.42.0 1.0-4.5
lb/mg Mean 788 5,630 9,567 1,323 2,775
Range 600-950 2,500-8,000 4,700-15,000 1,200-1,545 1,400-4,500
gal/nig
Mean
Range
4,465 8,924 28,254 23,000 21,922
3,600-5,000 4,663-18,000 16,787-38,000 10,000-36,000 9,000-38,000
-------
TABLE 5C-2
ADDITIONAL SLUDGE TO BE HANDLED WITH CHEMICAL TREATMENT SYSTEMS:
PHOSPHORUS REMOVAL BY MINERAL ADDITION TO AERATOR
Alw Addition Co Aerator Fe ** Addition to Aerator
Sludge Production Conventional With At ** Conventional With Fe+H"
Parameter Secondary Addition Secondary Addition
Level of Chemical
Addition (mg/1)
Percent Sludge Mean
Solids Range
lb/mg Mean
Range
gal/mg Mean
Range
0
0.91
0.58-1.4
672
384-820
9,100
7,250-12,300
9.4-23
1.12
0.75-2.0
1,180
744-1,462
13,477
7,360-20,000
0
1.2
1.0-1.4
1,059
918-1,200
10,650
10,300-11,000
10-30
1.3
1.0-2.2
1,705
1,100-2,035
18,650
6,000-24.000
-------
TABLE 5C-3
ADDITIONAL SLUDGE TO BE HANDLED WITH CHEMICAL TREATMENT SYSTEMS:
PHOSPHORUS REMOVAL BY MINERAL ADDITION TO SECONDARY EFFLUENT
Sludge
Production
Parameters
Lime
Addition
Alum
Addition
Iron
Addition
Level of Chemical
Addition (mg/1)
Percent Sludge
Solids
lb/mg
gal/mg
268-450 16
Mean 1.1 2.0
Range 0.61.72
Mean 4,650 2,000
Range 3,100-6,800
Mean 53,400 12,000
Range 50,00063,000
10-30
0.29
507
175-781
22,066
6,000-36,000
-------
TABLE 5C-4
ADDITIONAL SLUDGE TO BE HANDLED WITH CHEMICAL TREATMENT SYSTEMS
Chemical Level of Addition Lb. Additional Sludge Gal. Additional
Added (mg/1) Solids/lb Chemical Sludge/lb Chemical
Primary Treatment for Removal of Phosphorus
Lime 350-500 1.4 1.3
Lime 800-1,600 0.9 2.4
Aluminum - Al**" 1322.7 3.6 125
Iron-Fe** 25-80 4.5 40
Phosphorus Removal by Mineral Addition to Aerator
A1 9.4-23 3.8 32
Fe 10-30 3.9 48
Phosphorus Removal by Mineral Addition to Secondary Effluent
Lime
A1
Fe
268-450
16
10-30
1.6
15
3.0
18
90
132
-------
TABLE 5C-5
VACUUM FILTRATION LEAF TESTS FOR
SALT LAKE CITY RAW WASTEWATER
Feed Cycle Filter Cake
Chemical Solids Time Yield SoUds
Treatment Test (percent) min. lb/hr-ft2 (percent)
FeCl3 + Polymer
A1
2.5
16
0.37
15
FeCl3 + Polymer
A2
3.3
20
0.32
17
FeCl3 + Polymer
A3
1.6
25
0.27
20
FeCl3 + Polymer + 24% Ca (OH)2
A4
1.6
5
1.0
18
FeCl3 + Polymer + 47% Ca (OH)2
A5
1.6
5.3
1.0
17
A1(S04)3 . 14HjO + .43%
Anionic polymer
B1
0.70
8
0.38
15
Al2 (S04)3 . 14H20 + 0.70%
Cationic polymer
B2
0.36
23
0.14
23
Ca (OH)2
CI
17.9
1.8
12.8
33
Ca (OH)2
C2
9.4
3.0
4.5
28
1 Series A tests were for ferric chloride doses of 95-145 mg/1 and 0-1.5 mg/1 polymer. Series B
tests were for alum doses of 143 mg/1. All filter yields were for 33 percent submergence, a
3/16 inch cake, a 20 in Hg vacuum and a 0.8 scale-up factor.
-------
SCHEMATIC REPRESENTATION OF CHAPEL HILL PLANT
SLUDGE
EFFLUENT RECYCLE
FINAL
RICKLIN
FILTER
PRIMARY
SLUDGE
RAW
DEGRITTED
SEWAGE
DIGESTER
SAME AS ABOVE
FINAL
EFFLUENT
FIGURE 5C - 1
-------
TABLE 5C-6
FIELD TEST RESULTS AT CHAPEL HILL1
Solids r'xlO" Filter Cycle Polymer
Type of Content (at 15 Hg) Yield Time Dose
Sludge (g/1) (cm/g) (lb/hr/ft2) Min. Type (lb/ton)
TF 20.6 1.58 2.1 2 WT-2660 19
TF-A 7.7 47.0 Not Filterable - 837A
P-TF 39.0 8.38 2.9 4 WT-2660 10
P-TF-A 30.0 2.55 3.6 2 WT-2660 10
1 Personal communication with S. Hathaway
-------
TABLE 5C-7
CAKE SOLIDS AND CHEMICAL COST
Vacuum Filter Leaf Test Centrifuge Filter Press
Cake Chemical Cake Chemical Cake Chemical Cake Chemical
Solids Cost Solids Cost Solids Cost Solids Cost
(percent) (dollars/ton d.s.) (percent) (dollars/ton d.s.) (percent) (dollars/ton d.s.) (percent) (dollars/ton d.s.)
Alum 14-15 10-11 11-14 9 9-12 0.50-1.25 30-31 8-10
Alum-Primary 20-23 7-14 20-22 9-13 16-18 3-6 33-34 8-9
IPC Low Lime 2829 none 2731 none 2329 1.04.5 4547 none
FerricPrimary 2123 511 2022 -
-------
Alum
Alum-Primary
FerricPrimary
IPC Low Lime
TABLE 5C-8
LOADINGS
Vacuum Filter Leaf Test
Yield, psf/day Yield
4-62 2.5-3.03
(3.64.7)4
4-6 3-4
2-6 3.6
1.8-3.0 1.6-2.5
Centrifuge Filter Press
tons/day 16 d.s./ft3 day1
.38-.57 150-175
20-30 150-170
85-115 210-310
1 Chemical weight included
2 Includes weight of chemicals
3 Four minute cycle time, 25 percent submergence
4 Estimate value after subtracting weight of flocculants
-------
ATTF SYSTEM
RAW SEWAGE
POLYMER OR
FERRIC CHLORI
SLUDGE TO
- SOLIDS
PROCESSING
CHEMICAL
PRIMARY
EFFLUENT
RETURN
SLUDGE
WASTE SLUDGE
RAW SEWAGE
METHANOL
XING
RETURN
SLUDGE
WASTE SLUDGE
RAW SEWAGE
CHLORINE CONTACT
PRIMARY
SEDIMENTATION TANK
OXIDATION-
NITRIFICATION TANK
AERATED
STABILIZATION TANK
FINAL
SEDIMENTATION TANK
DENITRIFICATI ON
TANK
LIME REACTOR
(PREAERATI ON)
SECONDARY
SEDIMENTATION TANK
ADDITIONAL TREATMENT
FOR INDUSTRY
FIGURE 5 C
-------
ATTF SOLIDS PROCESSING SYSTEM
MAKEUP
LIME
WASTE BIOLOGICAL SOLIDS
RECYCLED LIME
^ PRIMARY
EFFLUENT
WET
CLASSIFICATION
ATTF
PRIMARY CLARIFIER
SEWAGE
REACTOR
FIRST
STAGE
THICKENER
FIRST STAGE
CENTRIFUGE
SECOND
STAGE
THICKENER
CENTRATE
2nd STAGE
CENTRIFUGE
GAS
SCRUBBER
MULTIPLE
HEARTH
RECALCINE
FURNACE
CENTRATE TO
PR IMARY
RECALCINED
ASH
MULTIPLE
HEARTH
FURNACE
REJECTS
ASH TO DISPOSAL
HIGH LIME
ACCEPTS
MAKEUP
CENTRATE RETURN
RECYCLE
LIME
STORAGE
SLAKER
LIME
REACTOR
(PREAER-
ATION)
ATTF
PRIMARY CLARIFIER
RAW
SEWAGE
DRY
CLASSIFICATION
PRIMARY
EFFLUENT
FIGURE 5C - 3
-------
SECTION 6A - OXYGEN ACTIVATED SLUDGE PROCESS
1. Significant Process Development
Engineering innovations
Production and cost of oxygen,
Application of oxygen within system,
Two major suppliers
Union Carbide - Unox system.
Air Products and Chemicals - Oases system.
Many pilot plants and several full scale plants
Overriding Importance
Improvement in sludge handling and disposal processes and costs.
Through documentation, both suppliers and TTP. Note reference list - only
broad generalities here.
2. Basic Process Nature
(Figure 6A-1)
Utilization of pure oxygen in place of air in activated sludge basins
Higher oxygen transfer driving force (more totally aerobic conditions)
Higher mixed liquor solids inventory
Lower production of excess activated sludge
3. Oxygen Activated Sludge Aeration Basins
(Figure 6A-2) - Sparger type oxygen injection system (low pressure) Note gas
recirculation compressors 90 percent oxygen efficiency.
(Figure 6A-3) - Surface aerator type oxygen system - Power requirements for
dissolution =1/5 1/6 of that for air systems.
6A - 1
-------
4. Oxygen Availability
Generation = 2 systems
Cryogenic
Pressure Swing Adsorption
-Liquid (for small plants)
5. Oxygen Process Characteristics
(Figure 6A-4)
Concurrent gas flow
High D.O. levels - all stages
System pressure 2/4 inches
Resistance to shock loads
6. Reasons for Process Effectiveness
(Figure 6A-5)
Oxygen utilization efficiency - 90+%
Power requirements - low
Improved sludge characteristics
7. Comparison of Design Conditions
(Figure 6A-6)
Most important for purposes of this seminar.
Recycle sludge concentration - 2/4 percent vs. 0.5/1.5 percent Sludge
Volume Index.
8. Summary Design Data Oxygenation Tanks
(Figure 6A-7)
Comparison of design figures for Carbide and results of Metcalf and Eddy study
and design - Middlesex City.
(References 5 and 7)
Seem to be comparable - tank sizing a little low in Middlesex County.
6A - 2
-------
9. Middlesex County Costs Forecast
(Figure 6A-8)
Large municipal/industrial plant.
Most speculative portion = sludge processing and disposal costs. Wonder what
-detailed design shows.
In any event, impressive.
10. Detroit Costs Forecast
(Figure 6A-9)
Billion gallon/day plant with several modules.
Side by side oxygen and air aeration modules.
Impressive forecast.
11. Plants Constructed, Under Construction or Publicly Announced Design Phase
(Figure 6A-10)
An impressive total (35).
Many more in consideration or bidding phase.
12. Estimated New Plant Total Treatment Costs, Air Aeration and Oxygen Activated Sludge
(Figure 6A-11)
From Reference 17, an excellent summation by Stamberg of EPA.
Once again, how much is due to solids handling savings?
13. Typical Plant Installation
(Figure 6A-12)
Compact, relatively simple plant.
Full scale operations with regular plant personnel have been demonstrated.
6A - 3
-------
LIST OF FIGURES AND TABLES - SECTION 6A
Figure
6A-1
Figure
6A-2
Figure
6A-3
Figure
6A-4
Figure
6A-5
Figure
6A-6
Figure
6A-7
Figure
6A-8
Figure
6A-9
Figure
6 A-10
Figure
6A-11
Figure
6 A-12
Oxygen Process Flow Sheet
Schematic Diagram of Oxygen System with Rotating Sparger
Schematic Diagram of Oxygen System with Surface Aerator
Oxygen Process Characteristics
Reasons for "Cost Effectiveness" of the Oxygen System
Comparison of Process Design and Performance Parameters
Design Data - Oxygenation Tanks
Middlesex County Costs
Detroit Costs
Oxygen Activated Sludge
Estimated Costs Comparison Air Aeration and Oxygen Aeration
Typical Plant Photograph
6A - 4
-------
OXYGEN PROCESS FLOW
SHEET
OXYGEN GAS
RETURN
SLUDGE
WASTE GAS
PUMP
SOURCE &
STORAGE
OXYGEN
FINAL
SETTLING
TANKS
RAW OR SETTLED WASTE WATER
MIXED LIQUOR
COVERED
OXYGENATION
TANKS
WITH MIXERS,
OXYGEN
COMPRESSORS
AND SPARGERS
WASTE EFFLUENT
SLUDGE
FIGURE
6A-1
-------
AERATION GAS RECIRCULATION
TANK COVER
COMPRESSORS
CONTROL
VALVE ,
AGITATOR
OXYGEN
FEED GAS
EXHAUST
GAS
C3
WASTE
LIQUOR
FEED
MIXED LIQUOR
EFFLUENT TO
CLARIFIER
STAGE BAFFLE
M O
ฐ
RECYCLE
SLUDGE "
FIGURE 6A-2 SCHEMATIC DIAGRAM OF OXYGEN SYSTEM WITH
ROTATING SPARGER
-------
AERATION
TANK COVER
CONTROL
VALVE
OXYGEN
FEED GAS
WASTE
LIQUOR
FEED
AGITATOR
fl
H
RECYCLE
SLUDGE-
STAGE BAFFLE
N\
K-7 ^
r^\ //-.
FIGURE 6A-3 SCHEMATIC DIAGRAM OF OXYGEN SYSTEM WITH
SURFACE AERATOR
-------
OXYGEN PROCESS CHARACTERISTICS
COCURRENT GAS-LIQUID FLOW
HIGH DO. LEVELS IN ALL STAGES
LOW SYSTEM PRESSURE (2-4 INCH W.G.)
LOW WASTE GAS VOLUME
HIGHLY AEROBIC WASTE GAS
OXYGEN DISSOLUTION DRIVING FORCE AND
STAGE UPTAKE DEMAND ARE MATCHED
HIGH MLVSS- SHORT DETENTION
AUTOMATIC OXYGEN FEED CONTROL
RESISTANCE TO SHOCK LOADS
FIGURE 6A-4
-------
REASONS FOR "COST EFFECTIVENESS" OF
THE OXYGEN SYSTEM
HIGH PURITY OXYGEN IS GENERATED ON-SITE ECONOMICALLY
IN ALL PLANT SIZES
OXYGEN UTILIZATION GREATER THAN 90% IS TYPICAL
POWER REQUIREMENTS FOR OXYGEN DISSOLUTION ARE
EXTREMELY LOW
MIXING POWER INPUT CAN BE OPTIMIZED
REDUCED WASTE ACTIVATED SLUDGE PRODUCTION IS
EXPERIENCED
DEWATERING AND HANDLING CHARACTERISTICS OF WASTE
SLUDGE ARE UNIQUE
HIGH RATE TREATMENT IS EASILY ACHIEVED
FIGURE 6A-5
-------
COMPARISON OF PROCESS DESIGN
AND PERFORMANCE PARAMETERS
"UNOX" CONVENTIONAL
SYSTEM AIR SYSTEMS
1. DO. LEVEL (mg/l) 6-10 1-2
2. DETENTION TIME (hrs) 1-2 3-6
3. MLSS CONC. (mg/l) 6,000-10,000 1,500-4000
4. VOLUMETRIC ORGANIC LOADING 150-250 30-60
(lbs BOD/DAY/1,000 f )
5 F/m RATIO 0.4-0.8 0.3-0.6
(lbs BOD/DAY/lb MLVSS)
6. RECYCLE SLUDGE RATIO 0.2-0.5 0.3-1.0
7 RECYCLE SLUDGE C0NC.(ma/l) 20,000-40,000 5,000-15,000
8. SLUDGE PRODUCTION 0.3-0.45 0.5-0.75
(lbs VSS/lb BOD REMOVED)
9. SVI 30-50 100-150
FIGURE 6A-6
-------
DESIGN DATA- OXYGENATION TANKS
MIDDLESEX CTY. SUMMARY
MIXED LIQUOR D.O. 3-9 MG/L 8-10 MG/L
MIXED LIQUOR SUSP. SOLIDS 5500 MG/L 6-10,000 MG/L
MIXED LIQUOR V.S.S. 5000 MG/L 4-6500 MG/L
FOOD BIOMASS RATIO 0.51 0.4-0.8
TANK SIZING[ # BOD/K Cu. Ft.) 160 215 +
FIGURE 6A-7
MIDDLESEX COUNTY COSTS
OXYGEN AIR
PROCESS AERATION
CAPITAL 83,580,000 104,020,000
OPERATING/YEAR 7,390,000 8,290,000
FIGURE 6A-8
-------
DETROIT COSTS
OXYGEN PROCESS AIR AERATION
CAPITAL 39,500,000 51,700,000
OPERATING YEAR 1,599,000 1,911,000
FIGURE 6A-9
OXYGEN ACTIVATED SLUDGE
STATES NO. OF PLANTS FLOW TOTAL - MGD
FLORIDA 4 171
PENNSYLVANIA 3 370
N. YORK/N. JERSEY 3 144
MICHIGAN/OHIO 3 422
OTHERS 22 779
TOTAL 35 1886
FIGURE 6A-10
-------
ESTIMATED COSTS COMPARISON-
AERATION AND OXYGEN AERATION
TYPICAL RANGES
TOTAL TREATMENT COSTS
NEW PUNTS WITH PRIMARY SEDIMENTATION
40 60
PLANT SIZE M60
FIGURE 6A-11
-------
FIGURE 6A-12 TYPICAL PLANT PHOTOGRAPH
-------
SECTION 6B - OXYGEN ACTIVATED SLUDGE
CASE STUDY - FAIRFAX - WESTGATE
]. Detailed Study - (Reference 13)
Robson, Block, Nickerson, Klinger
A landmark paper
Conversion of an overloaded intermediate treatment level plant into a 90
percent BOD removal plant
Dispatch and efficiency (180 day conversion)
2, Most Important Facet
Sludge handling data generated
3. Original Plant
(Figure 6B-1) = Process Flow
Comminution - Sedimentation/Aeration/Clarification
Chlonnation (digesters not used)
Vacuum filtration (landfill)
(Figure 6B-2) = Longitudinal Section - Sedimentation Tank
Original use building moratorium problems
Westgate Plant Functions - (Figure 6B-3)
Original plant design
Overload by 1970
Interim chemical treatment 1971
Oxygen activated sludge October 1971
6B - 1
-------
4. Current Westgate Process Flow
(Figure 6B-4)
- Converted 3 phase tank to do two jobs
(Oxygen activated sludge use)
- "Installed 2 - 120' diameter x 11' S.W. depth clarifiers
- Installed 2 - 250 ft2 D.A.F. units
- Installed 2 - 5 hp mixers on sludge decant tanks
- LOX because of temporary nature
5. Results Liquid Treatment
(Figure 6B-5)
- Liquid treatment has been highly successful.
Exceeded removal goals
93 percent instead of 80 which was goal
Equivalent to conventional aeration with 3 times tank volume
T.S.S. removal efficiencies of 90 percent
Stable operation with routinely qualified personnel
Oxygen cost = lower than predicted
6. Solids Settling Results
- Excellent Settling Characteristics
Note good SVI
Reasonable zone settling velocity
- Significantly less excess activated sludge produced - due to
endogenous respiration.
7. Thickening and Dewatering Results
(Figure 6B-6)
- D.A.F. units worked but ingenuity and benefits of oxygen activated sludge
prevailed.
- Mixture of O.A.S. and primary sludge proved very amenable to gravity
thickening.
61} - 2
-------
Small dose of flocculant = clear supernatant and rapid thickening to 6-8
percent solids.
Key point = mixers provided on sludge decant or blend tanks
So many plants not provided.
-Efficient thickening and good drainability characteristics of Primary/O.A.S.
blend = efficient, economical dewatering
(Figure 6B-7 - Sludge Filters).
Production rate = 5 lb/hr/ft2
(Good for 90+% removal plant.
Cake solids = 2228 percent also good.
Filtrate = 0.05 percent T.S. (very low recycle rate).
Sludge conditioning = can and have used both polymers and FeCl3/lime
combinations.
Routinely use FeCl3hme because of odor control problem in haulage.
Normal optimized conditioning cost based on proper conditioning for
vacuum filtration = 5 to 6 dollars/ton.
For purposes of odor control and adding excess lime for landfill and
haulage purposes, use about $8.00/ton of feme and lime.
If plant were not going - phase out other odor control and lower costs.
(Figure 6B-8) - Photograph of plant.
Note proximity to residential areas.
6B - 3
-------
LIST OF FIGURES AND TABLES - SECTION 6B
Figure 6B-1 Westgate - Original Process Flow
Figure 6B-2 Westgate Sedimentation Tank Longitudinal Section
Figure 6B-3 Westgate Plant Functions
Figure 6B-4 Current Westgate Process Flow
Figure 6B-5 Results - Westgate Oxygen Process
Figure 6B-6 Thickening and Vacuum Filtration Westgate Oxygen Process Sludge
Figure 6B-7 Photograph of Sludge Off Filters
Figure 6B-8 Photograph of Plant
6B - 4
-------
WESTGATE- ORIGINAL PROCESS FLOW
PLANT
PLANT
INFLUENT
EFFLUENT
LAND FILL
COMMINUTION
CHLORINATION
DIGESTION
VACUUM
FILTRATION
PRIMARY SEDIMENTATION
CLARIFICATION
AERATION
FIGURE 6B-1
WESTGATE SEDIMENTATION TANK
LONGITUDINAL SECTION
r COMMINUTION
PRIMARY
CLARIFICATION
SECONDARY
CLARIFICATION
AERATION
BAFFLE
BAFFLE
SUMP
SCRAPERS
AIR DIFFUSERS
FIGURE 6B-2
-------
WESTGATE PLANT FUNCTIONS
PERIOD
1954
1970
1971
1971-72
DESIGN % REMOVAL
FLOW (MGD) BOD 5 PLANT PROCESS
8
12
12
12
75
+
50 + ORIGINAL
35-40 ORIGINAL
CHEMICAL Ppt.
80-90 OXYGEN
ACTIVATED SLUDGE
FIGURE 6B-3
CURRENT WESTGATE PROCESS FLOW
PLANT [
INFLUENT
COMMINUTION
PRIMARY SEDIMENTATION
DUAL OXYGEN
ACTIVATED SLUDGE
BASINS
FILTER
CAKE
t
1J
SECONDARY
CLARIFIERS
-~
12)
EFFLUENT
i
V
VACUUM
SLUDGE
D.A.F.
4
-
FILTERS
DECANT
UNITS
FIGURE 6B-4
-------
RESULTS
WESTGATE OXYGEN PROCESS
W.fl.S. ZONE
% REMOVAL lb V.S.S. SETT. VEL.
BOD 5 T.S.5. S.V.I. lb BOD REMOVED [Ft./HR|
93 + 90 + 35-56 0.33 6.0
FIGURE 6B-5
THICKENING AND VACUUM FILTRATION
WESTGATE OXYGEN PROCESS SLUDGE
THICKENING VACUUM FILTRATION
POLYMER % SOLIDS % CAKE
METHOD Ib./TON THICK. SLUDGE Ib/HR/Ft2 SOUPS
GRAVITY 3 6-8 4.0-5.0 22-28
FIGURE 6B-6
-------
FIGURE 6B-7
PHOTOGRAPH OF SLUDGE OFF FILTERS
-------
FIGURE 6B-8
PHOTOGRAPH OF PLANT
-------
SECTION 6C - OXYGEN ACTIVATED SLUDGE
CASE STUDY - NEW ORLEANS, LOUISIANA
1. Reference 8
Grader and Dedke of Union Carbide
Powell and Wiebelt of New Orleans
Sewerage and Water Board
"Pilot plant results using pure oxygen for treating New Orleans Wastewater" -
A.E.CH.E. Meeting.
Consultant - Waldemar S. Nelson and Co., Inc.
Design Criteria 141 mgd East Bank Plant
2. Characteristics of New Orleans Sewage
(Figure 6C-1)
Primarily domestic
Brewery, food processing (chicken/shrimp)
BOD = 200 mg/1
COD/BOD =1.5 (high fraction organic biodegradablcs)
Flow Variation -*ฆ Sunday - 160 mg/1 BOD
Wednesday - 266 mg/1 BOD
3. Proposed Plant Process Flow
(Figure 6C-2)
Screening - grit removal - oxygenation tanks - clanfiers - chlorination
Solids handling - to be determined
4. Unox Pilot Plant Used
Biological Reactor
Liquid Depth = 5' x 2"
Stage Volume = 400 gallons
Total Liquid Volume = 1,600 gallons
6C - 1
-------
Clarificr
Two different ones used
Details later
5. Process Results
(Figure 6C-3)
Phased Study
Steady state design flows
Diurnal flow feed pattern
Steady state with centrate recycle (all gave 93-95 percent BOD removal
and 88-90 percent S.S. removal)
6. Excess Sludge Production
(Figure 6C-4) (Biomass Loading vs. Excess Sludge Production)
Staged process = high degree of endogenous respiration
High D.O. levels = lower excess sludge production
Slide shows higher loading = more net excess activated sludge
Claimed ซ 30-50 percent less excess sludge than air system
7. Settling and Compacting of Excess Sludge in Clarifier
2.5 to 3.2 percent solids in clarifier
Underflow (at least double what could be expected in air systems)
Mass loadings = 50 lb/SS/ft2 /day at 699-900 gpd/ft2
8. Centrifugation Tests
(Figure 6C-5)
Evaluation carried out solid bowl scroll type centrifuge
Purpose
Dewatering performance of oxygen E.A.S.
6C - 2
-------
Provision
Recycle solids laden centrate
Evaluate
Effect on oxygenation system and centrifuge performance
- Results
(Figure 6C-6)
As expected - without polymers - centrifuge fractionates sludge.
Heavy solids captured
Light solids in centrate
Postulation made
Operation of centrifuges on excess oxygen A.S. without sludge
conditioning (solids capture of 35-60 percent) is feasible 111 that polluted
recycle stream can be handled in oxygen system (Figure 6C-7).
Observations
No data presented on feed rates. Centrate solids data skimpy. An
incomplete picture.
9. Intrenchnient Creek Work
(Figure 6C-8)
- Two stage trickling filter plant
90 percent removal - 20 mgd design
90 percent removal - 14 mgd design
- Interesting Ccntrifugation Works
(Figure 6C-9)
Relatively economical and efficient dewatcung
Question = production rate data
Optimized centrate recycle load
(Plant at 14 = 70 peiccnt design capacity
20
6C - 3
-------
LIST OF FIGURES AND TABLES - SECTION 6C
Figure 6C-1 New Orleans, Louisiana Feed Wastewater Characteristics
Figure 6C-2 New Orleans, Louisiana Process Flow
Figure 6C-3 Oxygen System - New Orleans, Louisiana
Figure 6C-4 "Unox" System New Orleans, Louisiana, Effect of Biomass Loading on
Solids Wasting Rate
Figure 6C-5 "Unox" System New Orleans, Louisiana, Flow Diagram with Centrate Recycle
Figure 6C-6 "Unox" System New Orleans, Louisiana, Centrifuge Performance
Figure 6C-7 Centrifugation - New Orleans, Louisiana Oxygen Activated Sludge
Figure 6C-8 Intrenchment Creek Flow
Figure 6C-9 Centrifugation Atlanta
Mixed Sludge - Primary and T.F.
6C - 4
-------
REFERENCES - SECTIONS 6A, 6B, AND 6C
1. Union Carbide Corporation Unox System Status of Unox Sludge Pretreatment and
Dewatering.
2. Robson, C.M., Nickerson, G.L., Clinger, R.C., and Burke, Donald, "Pure Oxygen
Activated Sludge Operation in Fairfax County, Virginia," WPCF Meeting, Roanoke,
Virginia, 1972.
3. EPA Technology Transfer Program, New York City, February, 29, 1972, "Operating
Experience and Design Criteria for Unox Wastewater Treatment Systems," by Union
Carbide Corporation, Linde Division, Tonawanda, New York.
4. EPA 17050 DNW 02/72, "Activated Sludge Processing," February, 1972, by Union
Carbide Corporation, Linde Division, Tonawanda, New York.
5. McWhirter, J.R., Union Carbide, "Oxygenation Challenges Air Aeration." Water and
Wastes Engineering, 53 (September, 1971).
6. McWhirter, J.R., Union Carbide, "New Era for an Old Idea." C. & E. News,31 (April 26,
1971).
7. EPA Technology Transfer Program, Pittsburgh, Pennsylvania, August 29, 1972, Unox
Design Information for Contract Documents, by Metcalf and Eddy, Inc., Engineers.
8. Grader, R.J., Dedeke, W.C., Union Carbide, and Powell, C.J., Wiebelt, A.H., of New
Orleans, Louisiana, "Pilot Plant Results Using Pure Oxygen for Treating New
Orleans Wastewater," 71st National Meeting of A.I.Ch.E., Dallas, Texas, February
21, 1972.
9. Stamberg, John B., Bishop, D.F., Hais, A.B., and Bennett, S.M., "System Alternatives in
Oxygen Activated Sludge," EPA, paper presented at WPCF Atlanta Meeting,
October, 1972.
10. Speece, R.E., and Humenick, M.J., University of Texas, "Solids Thickening Limitation
and Remedy in Commercial Oxygen Activated Sludge," presented at WPCF Atlanta
Meeting, October 9, 1972.
11. Dick, R.I., and Young, K.W., "Analysis of Thickening Performance of Final Settling
Tanks," Purdue Industrial Waste Conference, May 2-4, 1972.
-------
REFERENCES (Continued)
12. Eckenfelder, W.W., Jr., "Boost Plant Efficiency." W. & W. Engineering, E-l (September,
1972).
13. Robson, C.M., Block, C.S., Nickerson, G.L., and Khnger, R.C., "Operational Experience
of a Commercial Oxygen Activated Sludge Plant," presented at WPCF Atlanta
Meeting, October, 1972.
14. Wastewater Treatment, Unox System, Union Carbide, 82-0258.
15. Newtown Creek project, personal communication, William Pressman, Project Engineer,
New York City Department of Water Resources.
16. Vandiver, E.C., and Noble, James A., "Centrifuge Improves Intrenchment Creek Water
Pollution Control Plant." Water and Sewage Works, (September, 1972).
17. EPA Research and Development Activities with Oxygen Aeration, Technology Transfer
Design Seminar, Pittsburgh, Pennsylvania, August, 29, 1972.
-------
NEW ORLEANS, LA.
FEED WASTE WATER CHARACTERISTICS
PARAMETER DEGRITTED RAW WASTE
AVERAGE
CHEMICAL OXYGEN DEMAND, mg/l
TOTAL 316
SOLUBLE 183
BIOCHEMICAL OXYGEN DEMAND,mg/l
TOTAL 210
SOLUBLE 98
SUSPENDED SOLIDS,mg/l
TOTAL 183
VOLATILE 133
pH 7.4|6.6-8.8]
TEMPERATURE, ฐF 71|65-83|
FIGURE 6C-1
NEW ORLEANS PROCESS FLOW
PLANT
EFFLUENT
GRIT
REMOVAL
CLARIFIERS
CHLORINATE
SCREENING
OXYGENATION
TANKS
FIGURE 6C-2
-------
OXYGEN SYSTEM-NEW ORLEANS
STEADY
STATE
DESIGN
DIURNAL
FLOW
PATTERN
CENTRATE
RECYCLE
RETENTION (HRS.j
1.8
1.4
1.8
MLSS (mg/l)
5560
5770
7350
lb. B0D/KFt3-DAY
181
246
193
0VERFL0W|GAL/Ft2/DAY]
655
855
655
SLUDGE VOL. INDEX
79
64
48
FIGURE 6C-3
EXCESS SLUDGE
PRODUCTION
LB TSS
LB. BODa
0.8
07
0.6
0.5
0.4
0.3
0.5
"UNOX" SYSTEM
NEW ORLEANS, LA.
EFFECT OF BIOMASS LOADING ON
SOLIDS WASTING RATE
PHASE III
PHASE V (CENTRATE)
PHASE
0.6 0 7
BIOMASS LOADING
PHASE IV
0.8 0.9
LB. BODA
LB. MLVSS-DAY
1 0
FIGURE 6C-4
-------
"UNOX" SYSTEM
NEW ORLEANS, LA.
FLOW DIAGRAM WITH CENTRATE RECYCLE
CLARIFIER
EFFLUENT
SECONDARY
CLARIFIER
RAW 9
DEGRITTED
WASTEWATER
RECYCLE SLUDGE
CENTRATE
CENTRIFUGE
UNOX
REACTOR
SOLID CAKE
FOR DISPOSAL
FIGURE 6C-5
% DRY SLUDGE
SOLIDS IN CAKE
20
15
10
20
AVG
"UNOX" SYSTEM
NEW ORLEANS, LA.
CENTRIFUGE PERFORMANCE
3 RUNS V AVG 6 RUNS
AVG 4 RUNS
SOLID BOWL SCROLL TYPE
CENTRIFUGE
NO CHEMICAL CONDITIONING
ฑ
30
40
50 60
% RECOVERY
70
80
AVG 5 RUNS
90
DATA ST NEC ORLEANS
AND JMARH.BS
FIGURE 6C-6
-------
CENTRIFUGATION-NEW ORLEANS
OXYGEN ACTIVATED SLUDGE
FEED COND.
% SOLIDS GPM
% SOLIDS
CAPTURE
% CAKE
SOLIDS
CENTRATE
SOLIDS l%l
60
35
15
20
- 2.1
FIGURE 6C-7
INTRENCHMENT CREEK FLOW
PLANT
INFLUENT
SCREENS
GRIT
PRIMARY
REMOVAL
CLARIFIERS
CENTRATE
TWO STAGE
TRICKLING FILTERS
RECYCLE
J
SOLID
BOWL
CENTRIFUGE
SECONDARY
PRIMARY
FINAL
DIGESTERS
DIGESTERS
CLARIFIERS
PLANT
EFFLUENT
CAKE TO
TRUCK
FIGURE 6C-8
-------
CENTRIFUGAT ION-AT L ANTA
MIXED SLUDGE -PRIMARY a T. E
FEED COND. % SOLIDS % CAKE POLYMER
% SOLIDS GPM CAPTURE SOLIDS $/T0N
FIGURE 6C-9
4-6 - 90 21 5.74
4-6 - 80 24 4.05
-------
SECTION 7
- THERMAL PROCESSING OF SLUDGE
1. High Temperature and High Pressure Sludge Treatment
- Two basic types - European origin (wet air oxidation and thermal
conditioning).
Old processes - few installations - 1930's (not widely adopted in Europe).
- Thermal conditioning - August - 1970, ."Wastewater Treatment in Great
Britain" - "A few years ago much interest and promise were shown with heat
treatment and sludge pressing, but lately there is less enthusiasm for this type
of plant."
Wet air oxidation - relatively few U.S. plants in operation, some have closed
down. Still, a few more are being built.
WET AIR OXIDATION
2. Process Description
(Figure 7-1)
Flameless combustion, burning of sludge at 450ฐ- 550ฐ F. and high pressures
(1,200 psig) with air injection.
Equipment - sludge grinder, heating tank, heat exchangers, high pressure
reactors, separators, expansion engine and auxiliaries.
End products - ash and sludge liquor.
Insoluble organics converted to soluble organics C02, H20, ammonia, sulfates,
acetates.
At 250ฐ C. and 83.4 percent COD reduction of sludge the oxidized liquor
shows a COD of 10,000 mg/1 + BOD is only 54 percent of COD.
The pH of the oxidized liquor is 4.8.
Summation, W.A.O. docs reduce sludge volumes and produce a stable solid
residue, but the nature of the oxidized acidic liquor and the costs of the
process arc of some concern.
7- 1
-------
3. installations and Operating Experiences
Chicago - South West, Wheeling - West Virginia, Rye - New York, South
Milwaukee - Wisconsin, Wausau - Wisconsin (have been in operation for a
number of years).
Few additional installations underway.
4. Wheeling, West Virginia Installation
(Figure 7-2)
Plant = thickened raw primary sludge 25 mgd design/8 mgd flow 5.6 tons/day
dry solids.
W.A.O. process - 500ฐ and 1,200 psig.
Maintenance = alternate caustic and muriatic acid washing of exchangers.
Capital cost = $284,000 in 196365.
Design and Operating Conditions (Table 7-1)
90 percent removal of insoluble organic matter.
But7? Quantity and quality of oxidized liquor9
Sludge Disposal Costs (Table 7-2).
$20/ton for raw primary sludge operating and maintenance
(No amortization)
(Not particularly low contrasted to plants employing conventional
methods)
5. Chicago, South West, Wet Air Oxidation
Commenced operation 1962 (500ฐ F. - 1,500 psi)
$17,900,000 for 300 tons/day design capacity.
Modifications = $4,000,000
Total = $20/annual ton (design)
Capacity achieved = 125-188 tons/day
Actual = $32/annual ton performance - maximum
Safety improvmcnts - $ 1,000,000.
Two serious accidents - 4 fatalities.
7-2
-------
- Over years much intensive R&D to improve performance.
- W.A.O. costs = $50/ton (including high rate digestion).
- Ceased operation about September 1, 1972.
6. Summation
- Very few new installations.
- Cost Analysis (Kansas City - Reference 21) (Primary Sludge).
Annual
Plant Cost Operation Cost
Dewatering and Incineration 1.0 1.0
Wet Air Oxidation 1.97 1.54
THERMAL SLUDGE CONDITIONING
7. Two Similar Processes
- Porteous (Figure 7-3) steam injection, batch process.
- Sludge storage - grinding - pre/heater - high pressure and temperature (365ฐ F.
and 250 psi) - decanter/thickener - dewatering - auxiliary liquor treatment - off
gas deodorizer - steam boiler.
- Zimpro LPO (Figure 7-4) same as Porteous except adds air via compressors.
- Farrer (Figure 7-5) same as Zimpro but claims continuous operation mode.
8. Installations
- Porteous - U.S. 1 operating and 2/3 planned (10 in U.K.).
- Zimpro - 14 built and 12 under construction.
- Farrer - No U.S. installations, to my knowledge.
7-3
-------
9. Porteous Type Process
Coon/Golden (5.0 mgd plant)
- Activated sludge plant - 5.0 mgd.
- . Domestic and brewery wastes.
- 1970 - Porteous type plant installed.
- Vacuum filters - still required 3.8 percent ferric chloride (Table 7-3).
- Cooking liquor - sometimes as high as 20,000 ppm solids content.
- Discontinued after about one year's operation.
10. Colorado Springs
- Only domestic Porteous installation.
- Currently 66 percent BOD removal trickling filter plant - 25 mgd.
- Porteous unit - built 1968/69 - 2,000 lb/hr 370ฐ F. and 250 psi.
- Results reported (to some extent).
- Reference 4 - Good vacuum filtration results (12 lb/hr/ft2 - 37 percent).
(Cake Solids)
- No chemical conditioning required (used to be $18-20/ton).
- Stated filtrate and decant streams easily handled with no additional aeration
requirement.
- Does not provide even cursory material balance data on process.
- Periodic visits to plant reveal many problems encountered with the recycle load
from heat treatment and with odor.
- Recycle load is much greater than expected even though this is a primary and
trickling filter sludge (not activated sludge).
- Lengthy plant process woik trying to reduce recycle load. Including massive
lime chemical piccipitation of liquors.
7-4
-------
Stated cost of operation for Portcous process and dewatenng = $2/ton.
Reference 9 - State's chemical conditioning costs used to run $20-$40/ton.
State's operating costs for Porteous run $15/ton (fuel, power, labor and water).
Current plans - convert to activated sludge. Porteous = 400ฐ F. and 300 psi
.(this will surely increase recycle load).
11. United Kingdom Experiences
Very little published definitive data.
Most informative = Reference 13, 14 and 16.
(Brooks - Fisher/Swanwick)
Lab and subsequent plant scale analyses/cooking liquors (Table 7-4).
Brooks - Based on solids percent solids in sludge - this data assumes 4 percent
sludge (typical).
Fisher/Swanwick - Both W.A.O. and thermal conditioning at various
temperatures and pressures (Figure 7-6).
Up to 66 percent suspended solids dissolved and recycled - thermal
conditioning.
Up to 79 percent during W.A.O.
Effect most marked for activated sludge.
About 33 percent of cooking liquor not amenable to biological treatment.
12. Borough of Pudsey - United Kingdom Farrer
(Reference 23)
The only paper seen which attempts to present thorough definitive data on
plant performance.
Farrer process - 1969/70 - sludges about 82 percent content trickling filter and
18 percent activated sludge.
One and one half years operation.
Many qualifying statements reflect severe operation and maintenance problems
encountered.
7-5
-------
- "Teething troubles were perhaps to be expected - unfortunately these
expectations have been realized and substantial periods of nonoperation of the
plant have been due to the necessity of carrying out modifications."
- "The operator requires to be of a higher skill than the grade of labor normally
associated with natural sludge dewatcring "
- Cost Data - "Here again the authors found themselves in some difficulty since
the operation so far makes running costs appear disproportionate due to the
modifications, maintenance and supervision required during the first year.
Sufficient experience has, however, been gained to make it possible to estimate
costs, these excluding cake disposal and liquor treatment" (Figure 7-7).
- Total heat treating and dewatering costs are estimated to be $37.20/ton dry
solids, assuming problems mentioned are easily overcome.
- Cost of treating recycle liquors from heat treatment (50 percent BOD
reduction via plastic trickling filter) are estimated to be $5/ton.
- Thus exclusive of press cake disposal, total costs, on an optimistic basis are
$42.20/ton of dry solids.
13. Kalamazoo
- Reference papers 17 and 24 describe installation and operation of Zimpro LPO
unit at Kalamazoo.
- Activated sludge, 1965, 34 mgd.
Influent = domestic + paper mills + pharmaceutical wastes.
- Sludge volatile/inert =1:1 originally (supposed to settle in lagoons).
- Sludge 1.5:1 volatile/inert because of change in influent characteristics (77
percent waste activatcd/23 percent raw primary now).
- Quote - "Our sludge is unusual, what with large proportion of paper mill wastes
and pharmaceutical wastes loads, and requires very high chemical dosages in
order to dewater either by vacuum filtering or centnfuging."
- Installation Costs (Figure 7-8)
Zimpro - $1,908,557 (97.5 tons/day)
Incinerator - $658,511
7-6
-------
Electrical - $154,950
General Contract -51,212,534
Treating lagooned sludge initially
Operating temperatures = 358ฐ F.
(Figure 7-9) Pressure = 400+psi
Performance (Figure 7-10) thickening and dewatering
Good gravity thickening - no data on decantate
Cake solids good, but only 4.9 lb/hr/ft2" rate
Cost Data - Not clear = $20/ton processing costs, but docs not include
operating and maintenance labor, must be amortization (SlO/ton) plus fuel,
power, etc.
No significant data on
Recycle liquor loads
Effect of same on plant
Total cost of systems
7-7
-------
REFERENCES - SECTION 7
1. Lumb, C., "Heat Treatment as an Aid to Sludge Dcwatenng - Ten Years Full-scale
Operation." Water and Sanitary Engineer, (March, 1951).
2. Mulhall, K.G., and Nicks, B.D., "The Heat Treatment of Sewage Sludge," a paper
presented for discussion by the East Anglian Branch of the Institute of Water
Pollution Control.
3. Personal communication with R.J. Sherwood, Director of Marketing, Municipal
Equipment Division, Envirotech Corporation.
4. Sherwood, R., and Phillips, James, "Heat Treatment Process Improves Economics of
Sludge Handling and Disposal." Water and Wastes Engineering, 42 (November,
1970).
5. McKinley, J.B., "Wet Air Oxidation Process, Wheeling, West Virginia." Water Works and
Wastes Engineering, (September, 1965).
6. Bjorkman, A., "Heat Processing of Sewage Sludge," 4th International Congress of the
I.R.G.R., Basle, June 2-5, 1969.
7. Koenig, L., for U.S.P.H., AWTR - 3, "Ultimate Disposal of Advanced Treatment Waste,"
(October, 1963).
8. Martin, Louis V., "Wet Air Oxidation for Sludge Treatment." WPCF Deeds and Data,
(March, 1972).
9. Kochera, B., "Operation of a Thermal Treatment System for Sludge," WPCF Meeting,
Atlanta, Georgia, 1972.
10. Harrison, J. and Bungay, H.R., "Heat Syneresis of Sewage Sludges." Water and Sewage
Works," (May, 1968).
11. Sebastian, F.P., and Cardinal, P.J., "Solid Waste Disposal." Chemical Engineenng,
(October, 1968).
12. Bennett, E.R., and Rein, D.A., "Vacuum Filtration - Media and Conditioning Effects."
13. Brooks, R B., "Heat Treatment of Sewage Sludge." Water Pollution Contiol, 92 (1970)
7 - 8
-------
REFERENCES (Continued)
14. Everett, J.G., and Brooks, R.B., "Dewatering of Sewage Sludges by Meat Treatment."
Water Pollution Control, 458 (1970).
15. Bouthilet, R.J., and Dean, R.B., "Hydrolysis of Activated Sludge," 5th International
W.P.R. Conference, July - August, 1970.
16. Fisher, W.J., and Swanwick, J.D., "High Temperature Treatment of Sewage Sludges."
Water Pollution Control, London, 70, 355-373 (1971).
17. Swets, D.H., Pratt, L, and Metcalf, C., "Combined Industrial - Municipal Thermal Sludge
Conditioning and Multiple Health Incineration," WPCF Annual Meeting, Atlanta,
Georgia, 1972.
18. Bacon, V.W., and Dalton, F.E., "Professionalism and Water Pollution Control in Greater
Chicago." Journal WPCF, 40, No 9, 1586.
19. "Stickney Sludge Site Closed Temporarily," Chicago Tribune, October 1, 1972.
20. Hurwitz, E., Teletzke, G.H., and Gitchel, W.B., "Wet Air Oxidation of Sewage Sludge."
Water and Sewage Works, 298 (1965).
21. Weller, L., and Condon, W., "Problems in Designing Systems for Sludge Incineration,"
16th University of Kansas Sanitary Engineering Conference, 1966.
22. Grant, R.J., "Wastewater Treatment in Great Britain." Water and Sewage Works,"
266-270 (August, 1970).
23. Hirst, G., Mulhall, K.G., and Hemming, M.L., "The Sludge Heat Treatment Plant at
Pudsey," Northeastern Branch of the Institute of Water Pollution Control, March
25, 1971.
24. Swets, D.H., "Trials, Tribulations, and Now Triumph." Public Worlcs, (August, 1971)
7-9
-------
LIST OF FIGURES AND TABLES -
SECTION 7
Figure 7-1 Wheeling, West Virginia Flow Diagram
Figure 7-2 Wet Air Oxidation System Wheeling, West Virginia
Table 7-1 Design and Operating Conditions Wheeling, West Virginia
Table 7-2 Sludge Disposal Operating Costs Wheeling, West Virginia
Figure 7-3 Flow Diagram of the Porteous Process
Figure 7-4 Thermal Sludge Conditioning and Dewatering
Figure 7-5 Flow Sheet for the Dorr-Oliver Farrer System
Table 7-3 Total Solids PPM - Heat Treatment Liquors
Table 7-4 Percent Solids Solubilized - Heat Treatment and Wet Air Oxidation at
Various Temperatures
Figure 7-6 Cost Data - Pudsey Plant
Figure 7-7 Sludge Disposal Facilities
Figure 7-8 Operating Temperature Balance
Figure 7-9 Kalamazoo Tliickening and Dewatering
Figure 7-10 Cooking Liquor Treatment
7 - 10
-------
RAW SEWAGE
GRIT TANKS
PRIMARY
SETTLING
GRIT
CHLORINE iZ
CONTACT ฃ
DILUTE RAW
SLUDGE AND SCUM
SLUDGE
THICKNER
OHIO
RIVER
THICKNED RAW
SLUDGE
AND SCUM
SLUDGE
STORAGE
OXIDIZED
SLUDGE
ZIMPRO
SLUDGE OXIDATION UNIT
FIGURE 7-1
WHEELING, WEST VIRGINIA FLOW DIAGRAM
-------
REACTOR
SLUDGE
GRINDER
120"
STEAM
HEAT EXCHANGER GROUP
ACCUMULATION
TANK
SLUDGE
STORAGE
TANK
I TRANSFER |
PUMP
HEATING
120"
CONDENSATE
-CX-
COILS
STEAM
CONDENSATE
EFFLUENT
WATER
77 tX}
/ HELIFLOW
HEAT EXCHANGER
SEPARATOR
FEED PUMP
AIR
RECEIVER
VAPORS
0D
COMPRESSOR Pd
'TMOTOR
AIR
CONDENSER
HIGH PRESSURE PUMP
WATER AND
CONDENSATE
FIGURE 7-2
WET AIR OXIDATION SYSTEM - WHEELING, WEST VIRGINIA
-------
TABLE 7-1
DESIGN AND OPERATING CONDITIONS -
WHEELING, WEST VIRGINIA
Conditions 1
Max. & Min.
Processing
Rates
Processing Rate tons
per day dry solids
Flowgpm
Total Solids%
Chemical Oxygen De-
mandg/l
Insoluble Organic
matter removed%
Maximum Insoluble Organic Removal = 93.2%
Design
Ave.
Max.
Min.
5.6
15.5
6
7.35
17.35
7.14
12.2
21.0
9.7
4.1
16.7
4.0
90
70
95
43.0
90
90
82.6
90.2
-------
TABLE 7-2 SLUDGE DISPOSAL - OPERATING COSTS
WHEELING, WEST VIRGINIA
Cost/Ton Solids
Processed
To January 1,
1965
Electricity
Chemicals
Start-up Fuel
Maintenance
$ 6.11
4.13
1.65
1.17
Labor1 man during Zimpro
Unit Operation
$13.06
6.91
Total Operating Cost$/ton
$19.97
-------
BOILER FOR PROCESS STEAM
STEAM
RAW SLUDGE
RAM PUMP
HEAT EXCHANGER
REACTION VESSEL
RAW SLUDGE bECttJGE RAM PUMP
STORAGE DISINTEGRATOR
HEAT EXCHANGER REACTION VESSEL
$
I
i
AUTOMATIC DISCHARGE VALVE
RESIDUAL LIQUORS
DECANTER
PUMP
I ED SLUDGE
THICKENED
SLUDGE
VACUUM FILTER
FIGURE 7-3
FLOW DIAGRAM OF THE PORTEOUS PROCESS
-------
GROUND
SLUDGE
HOLDING
TANK
GRINDER
SLUDGE
AIR
PUMP
POSITIVE
DISPLACEMENT
SLUDGE PUMP
REACTOR
HEAT
EXCHANGER
AIR COMPRESSOR
EXHAUST GAS
VAPOR
COMBUSTION
UNIT
OXIDIZED
SLUDGE
TANK
PRESSURE
CONTROL
VALVE
TO INCINERATOR
TREATED
BOILER
WATER
PUMP
FILTER
BOILER
FIGURE 7-4
THERMAL SLUDGE CONDITIONING AND DEWATERING
-------
REACTOR
CONTROL
PANEL
BOILER
SECOND HEAT
EXCHANGER
VESSEL
PRE-HEATER
DECANTING
AND STORAGE
TANK
AIR
COMPRESSOR
AUTOMATIC
VALVES
(ONE BACK-UP)
CENTRIFUGE
THICKENER
TO FS
SOIL
CONDITIONING
LAND FILL
GRINDER
PUMP
FIGURE 7-5
FLOW SHEET FOR THE DORR-OLIVER FARRER SYSTEM
-------
LABORATORY PLANT SCALE
WOKINGHAM 35,880 35,940
FARNSBOROUGH 29,800 29,800
TABLE 7-3 TOTAL SOLIDS PPM - HEAT TREATMENT LIQUORS
-------
H.T.
(HEAT TREATMENT]
W.O.
|WET AIR OXIDATION]
TEMPERATURES
[ฐC.|
170:200:230
170:200:230
TABLE 7-4
PERCENT SOLIDS SOLUBILIZED - HEAT TREATMENT
% SUSPENDED SOLIDS
SOLUBILIZED
66
79
AIR OXIDATION AT VARIOUS TEMPERATURES
-------
COST DATA-PUDSEY
IS/TON OF SLUDGE-EX CAKE DISPOSAL]
0/M CAPITAL TOTAL LIOUOR TREAT
22.32 14.88 37.20 5.00
FIGURE 7-6
SLUDGE DISPOSAL FACILITIES
Exhaust
FAN
1 STEAM
GENERATOR
SCRUBBER
Sludge
Air
WASTE
HEAT
BOILER
Exhaust
HEAT
EXCHANGER
REACTOR
VAPOR
COMBUSTION
UNIT
Vapor
OXIDIZED
SLUDGE
THICKENER
PCV
ฆFILTER
*J"sKposal
ASH
STORAGE
BIN
&
VACUUM
MULTIPLE
FILTER HEARTH
INCINERATOR
FIGURE 7-7
-------
OPERATING TEMPERATURE BALANCE
HEAT
EXHANGERS
REACTOR
HIGH
PRESSURE PUMP
Feed Water
365 F
Sludge
INCINERATOR
WASTE HEAT
RECOVERY
STEAM BOILER
Air
108ฐF
Gases
DECANT
TANK
PCV
AIR COMPRESSOR
Feed Water-
Gat-
Thickened Oxidized Sludge
PROCESS STEAM
to Vacuum Filters BOILER
FIGURE 7-8
KALAMAZOO
-THICKENING AND DEWATERING
% SOLIDS
THICKENER THICKENED % CAKE COST
FEED SLUDGE Ib/HR/Ft.2 SOLIDS S/TON
5.0 9.7 4.9 45 20
FIGURE 7-9
-------
COOKING LIQUOR TREATMENT
JL
GAS
BURNER
CM
O
CO
O
PORTEOUS
EFFLUENT
ANAEROBIC
FILTERS
FEED/RECYCLE
PUMPS
(75 TO 90 PERCENT
BOD REDUCTION)
CM
O
CHLORINE
REACTION
VESSEL
RECYCLE
PUMPS
EFFLUENT TO SECONDARY
~
TREATMENT SYSTEM
(OXIDATION OF
SULFUR COMPOUNDS]
FIGURE 7-10
-------
SECTION 8 - FINAL DISPOSAL PROCESSES AND CASE STUDIES
1. Ultimate Disposal
Criteria to follow in selection of method.
Should be in accordance with interstate, state, and Federal Quality Office
requirements.
Should not result in any significant degradation of surface or
groundwater, air, or land surfaces.
No sludge residues, grit, ash, or other solids should be discharged into the
receiving waters or plant effluent.
Sludge disposal to ocean waters is not recommended if toxic materials
may be transmitted to the aquatic food chain. Present indications are that
ocean disposal will be banned.
Stabilization of sludge should be considered prior to spreading on land.
Ultimate disposal is the final treatment process. This transforms the sludge in
some instances and places it at its final site.
Incineration
Sludge is burned and reduced to combustion gases or ash.
Multiple hearth furnaces range in capacity from 200 to 8,000 lb/hr of
dried sludge and operate at 1,700ฐ F.
a. Furnace consists of refractory lined circular steel shell with refractory
hearths, wliich he one above the other.
b. Sludge enters through flopgatc and proceeds with the help of rabble
arms to move down from hearth to hearth until ash dischaiges at bottom.
c. Reported total annual cost for incineration vanes between $10 and
about $30/ton dry solids depending on the need for supplemental fuel,
pollution control, etc. (Reference 1).
8- 1
-------
d. Typical section of multiple hearth incinerator is shown in Figure 8-1.
e. Examples - continuous operation at Minneapolis, St. Paul intermittent
operation, town X.
In a fluiclizcd bed furnace, the dewatered sludge is fed into a fluidizcd sand-
bed that is supported by air at 3.5 to 5.0 psi.
a. The sludge solids are normally first degntted.
b. Fluid bed reactor is a single chamber unit where moisture evaporates
and combustion of organics occurs at 1,400 to 1,500ฐ F.
c. Reported total operating costs vary between about $26 to $35/ton dry
solids depending on the supplemental fuel requirement (Reference 1).
d. Typical section of a fluid bed reactor is shown in Figure 8-2.
e. Special cases - Air pollution measurements, Waldnch, New Jersey
Intermittent operation, East Cliff - Capitola, California
Use of Sludge in Agriculture
Stabilized, either biologically or by some other mode, sludge may be used
as a fertilizer or soil supplement. Raw sludge presents health and nuisance
problems.
Transportation costs must be considered.
Fertilizer value is normally measured by the nitrogen, phosphorus, and
potash content.
Fertilizer Value of Undigested Biological Sludge
Nitrogen 1 5%
Phosphate 1 3%
Potash 0.1 0.3%
The nitrogen and phosphorus contents arc generally reduced 40-50
percent by digestion.
Transportation costs can make this mode of disposal uneconomical.
8-2
-------
Advantages of land spreading are-
a. economy.
b. it is the final treatment process.
c. it utilizes the water, nutrients, and organic material.
d. it is nuisance-frce if done right.
Disadvantages are.
a. creation of health hazards and nuisance conditions when done wrong.
b. possible accumulation of toxic metals.
c. possible nitrate contamination of groundwater.
Quantity of sludge to be spread is determined by
a. soil characteristics.
b. climate.
c. land use or intended crop.
d. type and solids content of the sludge.
Typical application rates
a. for a corn field 10-30 tons of solids/acrc/yr.
b. for a strip mine 1,000 tons of solids/acre/yr.
Composting
Received attention because of its applicability to organic, industiial,
agricultural as well as domestic sludges.
Degree of interest in this country as well as abroad is dwindling for
economic reasons.
Difficulty exists in finding a market for the product.
8-3
-------
- Lagooning and Landfill
Lagoons may be used for
a. anaerobic digesters but aesthetics may rule this out.
b. as evaporation ponds.
c. as permanent lagoons or landfills if dewatenng is incomplete a full
permanent lagoon remains as a permanent Lability.
Area requirement and management are important.
- Drying of Sludge Filter Cake
Sell as soil conditioner.
Sell for manufacture of commercial fertilizer.
Reported to be safe hygienically.
Process is used in Houston, Milwaukee, and Chicago.
Reported cost is approximately $45/ton dry solids, net for Chicago
(Reference 2).
Figure 8-3 shows equipment used in flash drying.
2. Case Histories of Land Reclamation with Sludge
- Objectives
To improve soil quality.
To grow crops.
To provide an economically attractive solution for the disposal of
wastewater treatment plant sludges.
To encourage good public relations by not causing unsiglUliness,
obnoxious odors and health hazards.
8-4
-------
Site No. 1, Saint Marys, Pennsylvania (Reference 3)
Has 1.30 mgd activated sludge plant treating domestic and industrial
waste. Sludge is digested and the product contains about 5 percent solids.
Chose to dispose of their 900,000 gal/yr of wet digested sludge on fields
and have done so for last six years.
Requires about 10 minutes to load 1,500 gallon tank truck and about 5
minutes to empty in a 5 foot wide path. The average round trip is 5 to 8
miles.
Sludge is spread on hay, pasture, oats stubble, corn stubble, poor lawn,
brush, orchard and athletic fields.
The average application rates for two fields is shown below.
Field % Solids gal/acre/yr tons dry solids/acre/yr
Hay 4.25 19,600 3.54
Pasture 3.7 17,450 2.60
No complaints have been heard from liquid sludge spreading, rather there
has been a tremendous demand from farmers.
The cost of disposal has averaged SI9.92 per ton of dry solids.
Site No. 2, Hanover Park, Chicago, Illinois (Reference 4)
Has a 1.5 mgd treatment plant with primary, activated sludge, effluent
filtration, anaerobic digestion and sludge lagoon processes.
Chose to dispose of their liquid digested sludge after a short lagoon
retention on land. The soils of the area arc classed as medium tcxtuicd.
The land area is approximately 1-1/8 acre in area and is divided into six
plots. Furrow irrigation is used.
Corn is planted on ridges and all the fields drain into a central sand drain
bed.
8-5
-------
The sludge contains about 4 percent soljds and for study purposes has
been applied at levels of 0, 1/4, and 1/2 inch. The respective application
rates are shown below.
inchcs/acre
gallons/acre
tons dry solids/acre/yr
0
1/2
1/4
0
13,578
6,789
0
2.28
1.14
Response to land spreading
a. Very favorable response of corn.
b. Good public acceptance, area is situated right in housing development
and there have been no complaints.
Sole purpose is disposal of oily sludges.
Land areas are capable of assimilating petroleum wastes and oily sludges
efficiently under proper spreading and treatment procedures, although
vegetation will not survive if subjected to repeated applications of oily and
concentrated sludges. However, it will be able to again survive if
applications are suspended for a period of time.
Shell Oil Refinery in Houston has applied all of the petroleum sludges and
stable emulsion from tank bottoms, oil water separators, sewer boxes, and
ship ballast water to land since 1961.
Land area consists of 7 acres divided into 4 sections.
Sludge is spread to a depth of 6 inches over an entire section. This is then
mixed with about 6 inches of soil.
Consumption requires 3 to 9 months and is a function of temperature, soil
moisture and the type of hydrocaibon. This means that from 0.217 to
0.65 million gallons of sludge can be applied per acre per yeai.
Early work showed that decomposition of the oily wastes varied from 5 to
60 pounds of oil per cubic foot of soil per month.
Site No. 3, Houston, Texas (Reference 5)
8-6
-------
REFERENCES - SECTION 8
1. Balaknshnan, S., Williamson, D.E., and Okcy, R.W., "State of the Art Review on Sludge
Incineration Piacticc," Water Pollution Control Research Series, 17070DIV, FWQA,
USDI, April, 1970.
2. Dalton, F.E., Stein, J.E., and Lynam, B.T., "Land Reclamation A Complete Solution
of the Solid Disposal Problem." Journal Water Pollution Control Federation, 40, (5),
789 (May, 1968).
3. Wolfcl, R.M., "Liquid Digested Sludge to Land Surfaces - Experiences at St. Marys and
Other Municipalities in Pennsylvania." Presented at the 39th Annual Conference,
Water Pollution Control Association of Pennsylvania, August 11, 1967.
4. Rose, B.A., "Sanitary District puts Sludge to Work in Land Reclamation." Water and
Sewage Works, (September, 1968).
5. Dotson, C.K., Dean, R.B., Kenner, B.A., and Cooke, W.B., "Land Spreading a Conserving
and Non-Polluting Method of Disposing of Oily Wastes." Presented at the Fifth
International Water Pollution Rcseaich Conference and Exhibition, San Francisco,
California, July 26-August 1, 1970.
8-7
-------
LIST OF FIGURES AND TABLES - SECTION 8
Typical Section of Multiple Hearth Incinerator
Typical Section of a Fluid Bed Reactor (Dorr-Oliver, Inc.)
Flash Drying
8-8
-------
0h
WASTE COOLING AIR
TO ATMD SPHERE pi
CLEAN GASES TO
AT MD SPHERE
INDUCED DRAFT FAN
BYPASS ON POWER OR
. (WATER STOPPAGE
I NERCO-ARCO
JFVNs/"CYCLONIC JET
SCRUBBER
GREASE
SKIMMINGS
ฆฆSNA
w
PLY ASH
SLURRY
MAKEUP WATER
TO DISPOSAL
OATING DAMPER
A
FILTER CAKE
SCREEN-
INGS &
GRIT
COMBUSTION AIR
/"RETURN
0
t
0
^
-------
SIGHT GLASS
EXHAUST
SAND PEED
FLUIDIZED
SAND
PRESSURE TAP
ACCESS DOORS
-------
FLASH DRYING
FAN
PREHEATER
FAN
CYCLONE
DEODORIZER
PRODUCT
SLUDGE CAKE
FUEL
HOT GAS
CAGE
XER
FURNACE
FIGURE 8 - 3
-------
SECTION 9 - SLUDGE THICKENING AND BLENDING
1. Sludge Particles
Heterogeneous mixture of various materials ranging Aom the size of colloids to
the size of flocculated particles as shown in Table 9-1.
Type of matter can be animal, vegetable or mineral and can be fibrous, granular
or amorphous in shape.
Particles can be hydrophobic (non-water loving) or hydrophilic (water loving).
Hydropltilic particles, due to presence of polar groups such as hydroxy],
carboxyl, or amino, have a strong affinity for the water solvent and retain a
sheath of water around the particles which tend to resist compaction.
Surface charge of most particles such as paper fibers, bacterial cells, clays,
sands, hydrated metal oxides, and the usual material found in wastewater is
negative as shown in Figure 9-1.
Behavior of the particles is dependent on their size, surface charge, solvation,
and the temperature, pH, and ionic type and concentration of the water. But
particles can have capability of adsorbing positive or negative charge as is also
shown in Figure 9-1.
2. Sludge Blending
Varieties of sludges arc numerous pnmary, conventional activated, high rate
activated, oxygen activated, trickling filter humus, with or without chemical
addition m any of the above, then any of the foregoing may be raw,
anaerobically digested, aerobically digested, chlorinated oi heat ticated. Just
from the kinds above mentioned results in so many possible combinations as to
boggle even a sanitary engineer's mind.
Purpose of blending is to mix any two or three sludges that result from the
various kinds of wastewater treatment to eliminate or minimize variation,
eliminate duplication of facilities, and produce a decreased volume of sludge
with a higher solids concentration.
Important considerations
All of the factors previously discussed under sludge paitides arc obviously
important in sludge blending and thickening.
9- 1
-------
It is possible that blending will result in compaction as a result of particles
interacting with each other just like particles and chemicals as shown in Figure
9-2.
On the other hand, it is possible that blending will result in only a minimum of
compaction such as the case of the plant that blended primary sludge, waste
activated final effluent, and centrate from the heat treated sludge. The
resultant sludge thickened to a concentration of only 1 percent.
The question appears to be whether sludges should be blended to result in
thickening, or thickened and then blended for further processing. The latter is
called for in the design of the expansion at Washington, D.C., where activated
sludge will be thickened separately by flotation and primary sludge will be
thickened in gravity thickeners, and the two sludges will be blended enroute to
vacuum filtration.
3. Gravity Thickening (Sedimentation)
Gravity thickening has produced results that range from good to fair to
mediocre. Table 9-2 shows sludge concentrations obtained in primary settling
tanks with and without polymer used for raw sewage flocculation. Although
polymer improved the efficiency of suspended solids removal in all five plants,
the polymer increased sludge concentration in only four of the five plants.
Table 9-3 shows gravity thickening data for three types of sludges. Note the
effect of "picket-type" thickener and the difference in the thickened sludge
solids for the two primary + activated sludges.
Table 9-4 shows gravity thickening data for waste activated sludges. Note again
the effect of "picket-type" thickener and the effect of SVI on the thickened
sludge concentration. The oxygen sludge indicates better thickening, but also
shows a wide range in the solids loading parametei indicating the variability of
the sludges even from an oxygen activated sludge process.
Gravity thickening was formerly accomplished in anaerobic digesters which
produced thickened solids from the bottom and lelativcly low suspended solids
in the straw-colored supernatant. However, the present mode of operation
blends sludges in the digester not only physically but mechanically. This
produces sludge that docs not settle completely in the secondary digester and
thus produces a supernatant that is usually a sludge of only slightly lower solids
concentration than the digester underflow.
9-2
-------
An alternate or additional problem resulting from the digested sludges is the
decreased efficiency of solids capture in elutnation. But with the advent of new
polymer chemicals, solids capture and thickening arc again being accomplished
with these sludges in elutnation as shown in Tabic 9-5.
Satisfactory supernatant production was accomplished in at least two cases by
dosing the sludge being transferred to the secondary stage digester with catiomc
polymer.
4. Flotation Thickening
Flotation is the opposite of gravity thickening the solids arc caused to float
due to attachment and entrapment of fine air bubbles. Usually one volume of
water saturated with air at 40 psig will provide sufficient air bubbles to float
the solids in an equal volume of sludge containing suspended solids at a
concentration of 5,000 mg/1.
Table 9-6 shows one compilation of data on flotation thickening of activated
sludge without chemical conditioning.
Tabic 9-7 shows a compilation of data on flotation thickening of a combination
of primary and activated sludge without chemical conditioning.
Table 9-8 depicts data on flotation thickening of activated and contact
stabilization sludges with chemical conditioning. Note that solids capture with
chemical is usually 99 percent in contrast to 8399 percent range without
chemicals. The chemical costs appear to be a fair representation, although one
plant has a chemical cost as low as $2.50/ton while another plant has a cost as
high as $12/ton.
It should be noted that flotation with chemicals effects only marginal increase
in thickened sludge concentration, but use of chemicals does permit a 100
pei ' to 300 percent increase in solids loading and about a 10 percent
in* ntal increase in solids capture. The latter may be or may not be an
imp ..int consideration in a given plant regarding recycle of solids.
It should also be noted that the usual chemical used in flotation was a catiomc
polymer. However, anionic polymer is also sometimes effective and should not
be overlooked. This was recently dcmonstiatcd at one plant when a metal salt
addition to the activated sludge was implemented for operation improvement
pin poses. This changed the sludge characteristics which required use of an
anionic polymer to condition the sludge for flotation, but it appeals that thcie
was also a decrease from 8 pcicent to 6 percent m Ihc floated sludge
concentration. In another plant the sludge icspondcd cqiully to either uitiomc
or anionic polymer conditioning, so that choice could depend m such cases on
the iclative costs of the two chemicals.
9-3
-------
5. Centrifugal Thickening
- Centrifugal thickening is accomplished by utilizing centrifugal force which can
be developed in a centrifuge to exert the equivalent of 2,000 times the force of
gravity that was utilized in gravity thickening previously discussed.
- Table 9-9 shows operational data of two types of centrifuges on activated
sludge.
- Although the data in previous Table 9-8 indicate 50 percent operating
efficiency for the disc-nozzle type centrifuge, it is still being used and there is
at least one industrial application of the same type machine where activated
sludge is thickened to 4.0 percent solids concentration.
6. Considerations in Design for Thickening
- Provide variable speed sludge pumps so that blending and thickening can be
continuous.
- Provide for possible use of chemicals. Install chemical injection taps into
pipelines at points where sludges meet, or water and sludge meet, and also into
dilution water line upstream of where water meets the sludge. Install tap for
chemical injection immediately downstream of the pressure leducing valve or
the water line in the case of dissolved air flotation. Piping design should provide
for good mixing of water, sludge and polymer, and then minimum of
turbulence and shear to prevent deflocculation.
9-4
-------
LIST OF FIGURES AND TABLES -
SECTION 9
Table 9-1
Figure 9-1
Figure 9-2
Table 9-2
Table 9-3
Table 9-4
Table 9-5
Table 9-6
Table 9-7
Table 9-8
Table 9-9
Relative Sizes of Suspended Particles
Charged Particle
Polymer and Particle Interactions
Polymer Effect on Primary Sludge Solids Concentration
Gravity Thickening Data
Gravity Thickening Data
Elutriation
Flotation Thickening - Activated Sludge (No Chemical)
Flotation Thickening Primary and Activated Sludge (No Chemical)
Flotation Thickening Activated Sludge
Centrifugal Thickening - Activated Sludge
9-5
-------
RELATIVE SIZES OF SUSPENDED PARTICLES
Class
Colloidal
Dispersed
Coagulated
Flocculated
Diameter, mm
0.000001 - 0.001
.001 - .1
.1 - 1.
1. - 10.
TABLE 9-1
-------
CHARGED PARTICLE
l
HC
I
ANION POLYMER
H
H-N-C
I H
H
CATION POLYMER
FIGURE 9-1
-------
POLYMER AND PARTICLE
POLYMER
FIGURE 9-2
INTERACTIONS
VAN dor WAAL
FLOCCULATION
y\AAAAA/V\AAAAA>
INTERPARTICLE
BRIDGING
riAAA/WWWWXr
BRIDGING & INTRAPARTICLE
NEUTRALIZATION
OVTVA^/VVWWW
W/WVWWWV/^
INTRAPARTICULAR
NEUTRALIZATION
-------
POLYMER EFFECT ON PRIMARY SLUDGE
SOLIDS CONCENTRATION
% Total Solids in Primary Sludge
Plant No. Without RSF With R$F % Increase
1 3.4 4.7 38
2 4.6 7.5 63
3 6.6 6.6
4 7.9 9.0 14
5 6.0 8.2 36
TABLE 9-2
-------
GRAVITY THICKENING DATA
Thickened Sludge
% Sqlids
4 - 5
4 - 8
3.3 (4.4)*
7 - 9
"Results in 0 obtained with "picket-type" thickener
TABLE 9-3
FEED SLUDGE Solids Loading
Type % Solids LB/ft2/day
Primary 0.2 - 0.6 13 - 31
Primary + Activated 0.2-1.2 3-38
Primary + Activated 1.1 20
Trickling Filter - 8-10
-------
GRAVITY THICKENING DATA
FEED SLUDGE Solids Loading Thickened Sludge
Type % Solids lb/ft Vday I Solids
Waste Activated 0.8 - 3.5
Waste Activated 1.05 21 1.8 (3.0)*
(SVI = 74)
Waste Activated 0.87 20 1.4 (2,8)*
(SVI = 97)
Waste Activated 0.5 - 0.8 - 1.2 - 1.7
Oxygen Activated 1.5 - 3.5 7 - 34 4.0 - 8.0
"Results in 0 obtained with "picket-type" thickener
TABLE 9-4
-------
ELUTRIATION
Chemical % Elutriated Sludge Elutriate (ppm) % Solids
Treatment Suspended Solids Suspended Solids Capture
None 3,5 3,835 65.1
Anion Polymer 4 3 365 g5i3
1,6 lb/ton
TABLE 9-5
-------
FLOTATION THICKENING
ACTIVATED SLUDGE (NO CHEMICAL)
Feed Sludge
% Solids
Thickened Sludge
% Solids
Solids Capture
1
0.81
3.3
85.0
0.77
3.7
99.0
0.45
4.6
83.0
0.77
4.1
90.0
0.80
6.5
93.0
0.46
4.0
88.0
TABLE 9-6
-------
FLOTATION THICKENING
PRIMARY AND ACTIVATED SLUDGE (NO CHEMICAL)
Feed Sludge Thickened Sludge Solids Capture
% Solids % Solids I
2.30 7.1 91.0
1.77 5.3 88.0
0.64 8.6 91.0
TABLE 9-7
-------
FLOTATION THICKENING
ACTIVATED SLUDGE
Sludge Feed
Solids Loading
lr/ft^/day
Thickened Sludge
1 Solids
Solids
Capture
1
Chemical
Type % Solids
Type
$/T
Activated 1.19
3.9
5.0
99.7
Cat.
Pol.
4.50
Activated 0.8 - 0.9
2.5
3.5
- 6.5
99.0
Cat.
Pol.
4 - 5
Activated 0.5 - 0.7
2.8 - 4.2
4.1
- 5.5
99.0
Cat.
Pol.
6 - 8
Cont, Stab. 1.2
3.3
6.6
97.8
Cat.
Pol.
6.00
Cont. Stab. 1.3
3.2
6.4
99.6
Cat.
Pol.
4.50
TABLE 9-8
-------
CENTRIFUGAL THICKENING
ACTIVATED SLUDGE
Feed Cake Centrate Capture Cost
Type GฃM Solids % Solids % Solids % Chemical $/Ton
Solid 50 0.7 5-7 0.1 - 0.2 79 - 81 5 Cation Polymers 10 - 18
Bowl
DISC 50 0.7 5 0.1 - 0.2 85 None
'Daily disassembly required to unplug nozzles
TABLE 9-9
-------
SECTION 10 - SLUDGE DEWATERING
Definition
- Sludge dewatenng in this discussion means further dewatenng of slurries to
change the physical form of the sludge fiom a slurry or liquid to a cake which
should be a solid. However, some sludge filter cakes are not quite solid enough
to keep from splashing when the cakes drop from the filter media onto a
conveyor belt.
Purpose
- Reduce volume occupied by the solids in case of disposal of sludge cake.
- Reduce water associated with the solids in case of disposal by incineration.
- Change the physical form from liquid to solid for handling purposes.
Chemical Sludge Conditioning
- Very few wastewater sludges will dewater without any treatment.
- Inorganic chemicals have been used for many years. The most notabK have
been iron chloride, calcium oxide, iron sulfate, alum, aluminum chlondc. These
chemicals arc effective in most cases, but history tells us that there have been
many failures in the past and we even see them perfoiming poorly in certain
plants today.
- The need for something bettei than the inoiganic chemicals led to the
development of water soluble polymers for sludge conditioning. Polymers arc
water soluble, lugli molecular weight organic chemicals that arc available m
nonionic (110 formal electrical charge), anionic (negatively chaiged), or cationic
(positively charged). These polymers can be made in a variety of chaigc
densities and a variety of molecular weights.
- Other additives that are sometimes used 111 sludge filiation are fly ash, furnace
ash, and diatomaccous earth. Even rice hulls have been used as a sludge
filiation aid as well as paper pulp.
- Considerations for design of sludge conditioning process and equipment should
include laboratory and pilot plant studies, provide flexibility in the equipment
so that a variety of conditioning materials could be used, provide vanable speed
10- 1
-------
agitators and conditioning tanks where plug flow can be observed and
conditioning agents can be added easily in a variety of points along with the
conditioning tank for observation, piovide for gentle open trough handling of
conditioned sludges rather than through pipelines; avoid high shear of
conditioned sludge, provide ratio control of conditioning chemical to sludge
and also ratio contiol of watei to sludge where polymers may be used.
4. Dewatering Equipment and Results
- Vacuum Filters.
Coil filter, drum filter, and belt filter are three basic types. Coil filter and belt
filter have continuous washing of the media, but usually not found on a drum
filter. Drum and belt filters offer opportunity to change type of media but this
is not easily done with a coil filter. Drum filters have air blow-back feature to
aid in cake release and coil filter has tines to aid in cake release and cake
discharge. Drum filter also has "doctor" blade for cake discharge. Belt filters
have had successful and also some troublesome cake discharge problems even
with "doctor" blades and "flippers" or beaters. The coil filtei may produce a
dirtier filtrate than a drum or belt filter since the media cannot be changed.
All three types have been used with sludges conditioned with polymers as well
as inorganic chemicals.
Tables 10-1 through 10-7 show sludge filtration data obtained with various
types of filters on various types of sludges with comparative performance on
polymer conditioned sludge and sludge conditioned with FeCl3 and CaO.
Consideiations in design for vacuum filtration should take into account the
following the conditioned sludge to the filter pan should be distnbuted in
more than one or two points tins is especially important with icgard to low
solids concentration sludges, the under-filter agitator should have a vanablc
speed drive - How can a designer possibly know in advance the optimum
speed? make it vanablc and give the operator some leeway for adjustments
and compensations, the eccentric which determines the length of the swing of
the under-filter agitator should have provision for variability. Some filters
provide no variability, others provide limited variability, proper level control of
sludge in the filter pan should be provided so as to maintain continuous sludge
conditioning and filtration, filtrate pumps should be of adequate capacity to
accommodate as much as a 40 percent dilution factor when watci is used with
polymeis, vacuum puinp capacity should be adequate enough to maintain good
vacuum even with more porous cakes which can result with some sludges with
polymer or inorganic chemical conditioning, filter valve bridge blocks should be
piovidcd for adjustment as necessaiy in the field.
10-2
-------
Ccntufugcs There arc three basic types - horizontal solid bowl with scroll,
disc type with nozzles, and basket lype.
The horizontal solid bowl is the most widely used in wastewater sludge
dcwatering. This type of centrifuge can be put on the line and left to operate
with only occasional attention. The elficiency of this type of centrifuge can be
greatly increased by use of polyincis. Internal feed of polymer has been found
to reduce polymer dose and appears to be very beneficial.
Figures 10-1 thiough 10-7 show perfoimance data with horizontal solid bowl
centrifuge on several sludges and the effect of various polymers.
The disc type centrifuge is like the old farm cream separator. It is used for
thickening of activated sludge but has the disadvantage of nozzles which seem
to get plugged easily. Screening of the sludge has been tried with some success
and at lease one installation uses a disc type for thickening to 4 percent solids
in series with a horizontal bowl type which dewaters to about 20 percent
solids. No polymers arc used with the disc type. Table 10-7 shows comparative
data of a disc centrifuge and solid bowl type.
The basket type has recently been evaluated and reported to be in contention.
Polymers may or may not be used with this type machine which can be
automated even though it operates on a batch cycle.
Sandbeds have been used for sludge dewateung for many years. The more
sophisticated type sludges of today, no doubt, have not been dcwatering as well
as the digested sludges of yesteryeais. But that is because present day digested
sludges arc not very dewaterablc without conditioning.
Figures 10-4 through 10-6 show effects of polymer conditioning on digested
sludge and digester supernatant.
Press filters, moving bed filters, rotating cylindrical scieens and capillary type
dewatenng devices are marketed in this country, but no large installations arc
in operation as yet.
5. Polymer Preparation Equipment
Since polymers are useful and sometimes necessary foi sludge conditioning,
perhaps a discussion of polymei preparation equipment is in order.
Polymers arc available as dry flakes or powdcis and also as liquids.
Preparation of liquid polymers picscnts no pioblem because they mix with
watci very readily.
10-3
-------
Preparation of dry polymers is not difficult but care must be taken when
contacting the dry polymers with water. Unless each polymer particle is
quickly and thoroughly wetted, the particles stick together to form aggregates
of particles from the size and appearance of fish eyes to slubs as large as golf
balls or even larger.
To provide means for preparing solutions of dry polymers, polymer
manufacturers have developed manual devices and automatic equipment. Also
chemical feed equipment manufacturers have developed their own lines of
automatic equipment to meet the needs of the field.
Figures 10-7 through 10-11 depict schematics of manual and automatic dry
polymer dispersing systems and a liquid polymer preparation and feed system.
Several manufacturers of automatic equipment for handling and preparing
solutions of djy polymers aie listed below.
Acrison, Inc., Carlstadt, New Jersey
B1F Corporation, Providence, Rhode Island
Cliemix Corporation, Troy, Michigan
Wallace & Tiernan, Belleville, New Jersey
Several polymer manufacturers also market automatic equipment for preparing
solutions of dry polymers and these are listed below
Calgon Corporation, Pittsburgh, Pennsylvania
The Dow Chemical Company, Midland, Michigan
Hercules Inc., Wilmington, Delaware
6. Physical Sludge Conditioning
Freezing is an effective technique for conditioning sludge for dewatering but no
practical economical method has yet been woiked out, although the literature
cites a new method that is being investigated.
Heat treatment is another effective method of conditioning sludge for
dewatering. Midland, Michigan has a new heat treatment unit and heat treated
sludge is filtered at the same yield as polymer conditioned sludge, but filter
cake is drier.
This subject will be covered m more detail by other spcakeis.
10-4
-------
LIST OF FIGURES AND TABLES - SECTION 10
Tabic 10-1 Vacuum Filtration Raw Primary Sludge
Ennco Drum Filter, Open Synthetic Fiber Media
Tabic 10-2 Vacuum Filtration Elutriated Digested Pumary Sludge
Eimco Drum Filter, Napped Dacron Media
Table 10-3 Vacuum Filtiation Elutriated Digested Primary and Secondary Sludge
Dorr-Oliver Drum Filter, Napped Dacron Media
Table 10-4 Vacuum Filtration Raw Primary Sludge
Komline-Sanderson Coilfiltcr
Table 10-5 Vacuum Filtration Elutriated Digested Primary Sludge
Dorr-Oliver Drum Filter, Napped Dacron Media
Table 10-6 Vacuum Filtration Digested Primary Sludge Drum Filter
44 X 44 Saran Media
Table 10-7 Centrifuge Dewatenng Digested Primary and Secondary Sludge
Figure 10-1 Centnfugation of Primary Sludge
Figure 10-2 Centnfugation of Activated Sludge
Figure 10-3 Centnfugation of Primary-Activated Sludge Mixtuie
Figure 10-4 Digested Sludge Dewatered on Sand Drying Beds at Various Chemical Dosages
Figure 10-5 Sand Bed Dewatcring Digested Sludge (4%) + Cationic Polymer
Figure 10-6 Supernatant Dewatenng on Sand Bed with Cationic Polymer
Table 10-8 Toionto Digested Sludge Centnfugation
Figuie 10-7 Flocculant Feed System Utilizing Manual Dispeismg Equipment and
Separate Feed Tank
10-5
-------
LIST OF FIGURES AND TABLES - SECTION 10
(Continued)
Figure 10-8 Dispcrscr for Punfloc Flocculants (Cioss-scclion)
Figure 10-9 Flocculant Feed System Utilizing Automatic Dispersing Equipment
Figure 10-10 Automatic Flocculant Disperser
Figure 10-11 Liquid Flocculant Feed System
JO-6
-------
VACUUM FILTRATION RAW PRIMARY SLUDGE
EIMCO DRUM FILTER, OPEN SYNTHETIC FIBER MEDIA
%
SLUDGE
SOLIDS
%
CHEMICAL
USED
%
CAKE
SOLIDS
FILTER
YIELD
(Lb./sq.ft./hr.)
CHEMICAL
COST
(Dollars/fon)
15
4.0 FeCl3
14.0 LIME
40
5.0
12.50
12
0.9
CATION
POLYMER
30
7.0
8.00
TABLE 10-1
-------
VACUUM FILTRATION ELUTRIATED DIGESTED
PRIMARY SLUDGE EIMCO
DRUM FILTER, NAPPED DACRON MEDIA
%
SLUDGE
SOLIDS
%
CHEMICAL
USED
%
CAKE
SOLIDS
FILTER
YIELD
Lbs/Ft2/Hr
CHEMICAL
COST
$/TON
10.9
5.4 Fe2(S04)3
34
2.8
4.00
II.1
0.45
CATION
POLYMER
35
5.5
3.70
TABLE 10-2
-------
VACUUM FILTRATION ELUTRIATED DIGESTED
PRIMARY & SECONDARY*SLUDGE DORR-OLIVER
DRUM FILTER, NAPPED DACRON MEDIA
%
SLUDGE
SOLIDS
%
CHEMICAL
USED
%
CAKE
SOLIDS
FILTER
YIELD
Lbs/Ft 2/Hr
CHEMICAL
COST
$/TON
8.0
18 Fe2(S04)3
6 LIME
28.0
5. 1
9.00
9.0
I.I
CATION
POLYMER
25.0
7.25
8.00
* ACTIVATED 8 TRICKLING FILTER
TABLE 10-3
-------
VACUUM FILTRATION RAW PRIMARY SLUDGE
KOMLINE- SANDERSON COILFILTER
%
SLUDGE
SOLIDS
%
CHEMICAL
USED
%
CAKE
SOLIDS
FILTER
YIELD
(Lb./sq.ft./hr.)
CHEMICAL
COST
(Dollars / ton)
7.57
8.12 FeCl3
8.34 LIME
20.1
6.91
9.89
7.00
0.7
CATION
POLYMER
20.0
7.53
6.50
TABLE 10-1
-------
VACUUM FILTRATION ELUTRIATED DIGESTED
PRIMARY SLUDGE DORR-OLIVER
DRUM FILTER, NAPPED DACRON MEDIA
<
SLUDG
'/o
E SOLIDS
%
CHEMICAL
USED
%
CAKE SOLIDS
FILTER
YIELD
Lbs/Ft2/Hr
CHEMICAL
COST
$/TON
TOTAL
VOLATILE
TOTAL
VOLATILE
10.4
39.8
5.0 FeCl3
32.7
32.3
3.88
4.50
10.1
39.3
0.4
CATION
POLYMER
38.6
38.2
5.94
3.20
TABLE 10-5
-------
VACUUM FILTRATION DIGESTED PRIMARY SLUDGE
DRUM FILTER, 44 x 44 SARAN MEDIA
%
%
%
FILTER
CHEMICAL
SLUDGE
CHEMICAL
CAKE
YIELD
COST
SOLIDS
USED
SOLIDS
LBS/FT2/HR.
$/T0N
3.3 Fe CI 3
15
10.3 LIME
43
9.2
9.66
.85
15
CATIONIC
32
25.0
7.60
POLYMER
TABLE 10-6
-------
CENTRIFUGE DEWATERING
DIGESTED PRIMARY S SECONDARY SLUDGE
FEED
SOLIDS
%
MACHINE
CENTRATE
SOLIDS
%
CAKE
SOLIDS
%
REMOVAL
EFFICIENCY
%
CATION
POLYMER
lbs/ton
RPM
LOADING
GPM
7.1
1500
10
3.8
14.6
46.5
7.3
1500
25
4.3
21.8
41.1
7.8
1500
10
0.2
15.8
97.5
10
7.7
1500
25
0.1
17.2
98.8
11.5
TABLE 10-7
-------
CENTRIFUGATION OF PRIMARY SLUDGE
100
90
NONIONIC POLYMER
80
NONIONIC POLYMER
70
60
50
CATIONIC OR ANIONIC
POLYMER
40
30
0 2 4 6 8 10 12
DOSE, LBS./TON
FIGURE 10-1
-------
CENTRIFUGATION OF ACTIVATED SLUDGE
100
SOLIDS RECOVERY, %
90
80
CAT I ONIC POLYMER/
ANIONIC POLYMER -
70
60
50
40
30
NONIONIC POLYMER
20
FIGURE 10-2
60
30
40
20
50
10
0
DOSE, LBS/TON
-------
CENTRIFUGATION OF
PRIMARY-ACTIVATED SLUDGE MIXTURE
100
SOLIDS RECOVERY, %
90
NONIONIC POLYMER
80
NONIONIC POLYMER
70
60
50
CATIONIC POLYMER
ANIONIC POLYMER
40
30
0
10
2
4
6
6
12
DOSE, LBS /TON
FIGURE 10-3
-------
DIGESTED SLUDGE DEWATERED ON SAND
DRYING BEDS AT VARIOUS CHEMICAL DOSAGES
36
32
CATIONIC POLYMER
30 LBS./TON
28
24
CATIONIC POLYMER
20 LBS./TON
ฃ 20
CATIONIC POLYMER
10 LBS./TON
^CONTROL (NO TREATMENT
56
48
24
32
40
64
HOURS
FIGURE 10-/1
-------
SAND BED DEWATERING
DIGESTED SLUDGE (4%) + CATIONIC POLYMER
10-
co
LU
U
z
CONTROL
h-
7% SOLIDS
Q_
UJ
a
LU "4~
O
Q
9% SOLIDS
10#/TON
3
co
56% SOLIDS
20#/TON
TIME-DAYS
FIGURE 10-5
-------
SUPERNATANT DEWATERING ON SAND BED
WITH CATIONIC POLYMER
i 1 1
SOLIDS LOADING: 18% INCHES OF 1% SUPERNATANT
1.3% SOLIDS
X -X
CONTROL
2.8 LBS./1000 GAL
18% SOLIDS
4.5 LBS./1000 GAL.
51% SOLIDS
8 10
TIME-DAYS
FIGURE 10-6
-------
TORONTO
DIGESTED SLUDGE CENTRIFUGATION
SLUDGE FEED
GPM % SOLIDS
CHEMICAL
CONDITIONER
40
4.0
CATIONIC
POLYMER
CAKE CENTRATE COST
% SOLIDS % SOLIDS $/TON
15-17
0.2-0.8
18.00
TABLE 10-8
-------
FLOCCULANT FEED SYSTEM UTILIZING MANUAL DISPERSING
EQUIPMENT & SEPARATE FEED TANK
WATER
SUPPLY^
7?
A
B
C
D
E
F
6
FIGURE 10-7
DRY FLOCCULANT
TO ADDITION
POINT
VALVE
WATER METER
STORAGE TANK
DISPERSER
MIX TANK
FLOAT LEVEL CONTROL
MIXER
H
FEEDTANK
1
PUMP
J
TRANSMISSION
K
MOTOR DRIVE
L
DILUTION SYSTEM
M
PIPING
-------
FEED HOPPER
WATER INLET
DISPERSER FOR PURIFLOCฎ
FLOCCULANTS
(Cross-section)
/^FLOCCULANT
AIR VENT
" N.p.Ty
VARIABLE ORFICE
FITTING
AIR VENT
3/8"HEX
l"N.P.T.
FLOCCULANT SOLUTION
FIGURE 10-8
-------
FLOCCULANT FEED SYSTEM UTILIZING
DRY FLOCCULANT AUT0MAT|C DISPERSING EQUIPMENT
WATER
SUPPLY
A
B
C
D
E
F
G
VALVE
WATER METER
STORAGE TANK
DISPERSER
MIX TANK
FLOAT LEVEL CONTROL
MIXER
E,H
H
I
J
K
L
M
dmiId T0 addition
PUMP POINT
TRANSMISSION
MOTOR DRIVE
DILUTION SYSTEM
PIPING
FIGURE 10-9
-------
AUTOMATIC FLOCCULANT DISPERSER
Valve (Adjustable)
Valve
(Float Controlled)'
Valve (Solenoid)
Water Meter-
Water
Supply
100 Gal/Min)
I
{ Float Level
Control
Dry Flocculant
(<10 Lb/Min)
Screw Feeder
Mixing Funnel
_ Water Level
Overflow
Switch
Drain
Valve
Water Supply
( <100 Gal/Min)
Valve (Solenoid)
Feed
~ Tank
Float Chamber
Pump
FIGURE 10 - 10
-------
LIQUID FLOCCULANT FEED SYSTEM
A
B
C
D
E
F
G
SUPPLY
VALVE
WATER METER B
STORAGE TANK
DISPERSER
MIX TANK
FLOAT LEVEL CONTROL
MIXER
LIQUID FLOCCULANT
FEEDTANK
PUMP
TRANSMISSION
MOTOR DRIVE
DILUTION SYSTEM
PIPING
TO ADDITION
POINT
FIGURE 10-11
------- |