technology transfer
design seminar
publication
HANDLING
AND
\
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. Joseph P. Farrell
National Environmental Research Center
Environmental Protection Agency
Cincinnati, Oliio
November 13-14,1972
Royal Inn of Anaheim
Anaheim, California
United States Environmental Protection Agency
Technology Transfer Program
Washington, D.C.
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TABLE OF CONTENTS
SECTION 1 Importance of Sludge Processing and Disposal
SECTION 2 Current and Previous Methodology
SECTION 3 Nature and Handling Characteristics
of Sludges
SECTION 4 Sludge Stabilization Processes
SECTION 5 Case Studies - Plant Results - Chemical
Conditioning - Conventional Activated Sludge
SECTION 6A Oxygen Activated Sludge Process
SECTION 6B Oxygen Activated Sludge
Case Study - Fairfax - Westgate
SECTION 6C Oxygen Activated Sludge
Case Study New Orleans, Louisiana
SECTION 7 Thermal Processing of Sludge
SECTION 8 Final Disposal Processes and Case Studies
Page Number
1-1 1-7
2-1
3-1
4-1
5-1
6A-1
6B-1
6C-1
7-1
8-1
2-5
3-10
4-7
5-8
6A-4
6B-4
6C-4
7-8
8-3
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SECTION 1 - IMPORTANCE OF SLUDGE PROCESSING AND DISPOSAL
1. Amounts and Types of Sludges Produced
Sludges: Liquid to semi-solid residues from wastewater processing. Solid
contents: 1 to 10 percent.
Masses of sludges produced in conventional wastewater processing (see Table
1-1, Reference 1).
The use of anaerobic digestion to reduce mass and volume (see Table 1-1 and
Figure 1-1, Reference 2).
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 1-2, from Reference 3).
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 1-3).
Measured quantities were about 20 percent higher than calculated values.
2. Costs of Sludge Processing and Disposal
Costs of slutlge processing are a function of:
Treatment sequence
The raw sewage
Location (the surrounding neighborhood)
Climate
i
Scale of operation
Regulations, etc.
1 - 1
-------
Costs are sensitive to all of the above and individual author's assumptions. If
possible, get all comparisons from the same unbiased source (see Figure 1-2,
calculated from Eilers and Smith, Reference 4).
1 -2
-------
TABLE 1-1
SLUDGES PRODUCED IN CONVENTIONAL TREATMENT*
Overall SS Removal (%)
Total raw sludge (Ib d.s.^ng)
% solids (from clarifier)
% solids (after 2 days thickening)
Digested sludge (Ib d.s./mg)
% solids
% reduction in sludge mass
% reduction in volatile solids
Drying bed loadings (Ib d.s./ft2 - yr)
Primary
Treatment
60
1020
6
8
555
8.8
45.5
65
35
Primary
+ TF
85
1310
5
6.5
710
6.9
45.5
65
30
Primary
+ AS
95
1615
4
5.3
1035
5.5
36
52
25
* From Fischer, A. J., Sewage Works Journal.
1 -3
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TABLE 1-2
CALCULATED SLUDGE MASS (Ib/mg)
Conventional
Feto
Primary
Feto
Aerator
Alto
Aerator
AltoTF
Clarifier
PRIMARY
SS Removal
Sludge Solids
Fe Solids
Al Solids
Total
ACTIVATED SLUDGE
Secondary Solids
Fe Solids
Al Solids
TRICKLING FILTER
Secondary Solids
Al Solids
TOTALS
50%
1250
0
0
1250
715
75%
1875
605
2480
536
50%
1250
1250
804
541
50%
1250
1250
804
425
50%
1250
1250
656
1965
3016
2595
2479
745
483
2478
BASIS FOR SLUDGE MASS CALCULATION
Cation/P Dose
(mol/mol)
Ib Chemical Sludge/lb Cation
Ib/lb Al Ib/lb Fe
1.5
1.75
Assumptions:
Cation/P Dose
Cation/P Dose
Influent Sewage
BOD
SS
P
3.9
3.8
1.5 mol/mol to aerator
1.75 mol/mol to primary or before trickling filter clarifier
230 mg/1
300 mg/1
10 mg/1
2.4
2.3
1 -4
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TABLE 1-3
CALCULATION OF SLUDGE QUANTITY:
LIME ADDED TO THE PRIMARY*
Data Available On influent and effluent: alkalinity, pH, calcium hardness, phosphorus.
Change in Ionic Content
(Influent - Effluent)
AHCO3, as CaCO3
ACO2,asCaCO3
AMg, as CaCO3
mg/1
223
14
66
Sludge Produced
hydroxyapatite
CaCO3
Mg(OH)2
27
460
38
Material Balance on Ca
Ca(OH)2 dose = 390 mg/1
Input-Output =-2.9 mg/1
Total Calcd. Sludge
Meas./Calcd.
525 mg/1
1.25
* Data from Run 6, Eimco's Salt Lake City Pilot Plant.
1 -5
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REFERENCES - SECTION 1
1. Fischer, A.J., Sewage Works Journal, 248 (1936).
2. Fair, G.M., Geyer, J.C., and Okum, D.A., "Water Purification and Wastewater Treatment
and Disposal." Water and Wastewater Engineering, 2, 36-6 - 36-8 (1968).
3. Adrian, D.D., and Smith, I.E., Jr., "Dewatering Physical-Chemical Sludges" Conference
on Application of New Concepts of Physical-Chemical Wastewater Treatment,
Vanderbilt University, September 18-22,1972 .
4. Eilers, R.G., and Smith, R., "Wastewater Treatment Plant Cost Estimating Program,"
AWTRL of EPA, April 1971, Internal Report (Computer Deck available).
1 -6
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Table 1-1
Table 1-2
Table 1-3
Figure 1-1
Figure 1-2
LIST OF FIGURES AND TABLES - SECTION 1
Sludges Produced in Conventional Treatment
Calculated Sludge Mass (Ib/mg)
Basis for Sludge Mass Calculation
Calculation of Sludge Quantity: Lime Added to the Primary
Sludge Quantities
Costs of Sludge Processing and Disposal Including Amortization
1-7
-------
FIGURE 1-1 SLUDGE QUANTITIES*
Basis: 1 million gallons of domestic vastevater
Quantities Before Digestion
Primary Settling
Activated Sludge
Clarifier
1 mg of
vastevater
Primary Sludge (72.2J& VS)
1190 Ib. solids.
If 5j> solids, 2830 gal.
(70.6J& VS)
Waste Activated Sludge
660 Ib. solids.
If 1.5£ solids, 5260 gal.
Quantities After Anaerobic Digestion
If primary only
is digested, (l&.ty VS)
DIGESTION
576 Ib.
If 1$ solids, 673 gal.
If primary and W.A.S. are combined,
1850 Ib. solids.
If k.5t solids, ^890 gal.
DIGESTION
890 ib. (^5.5^ vs)
If 1% solids, 1980 gal.
* These quantities vere taken from an example in Fair, G. M., Geyer, J. C.
and Okum, D. A., "Water and Wastevater Engineering, Vol. 2: Water Purifica-
tion and Wastevater Treatment and Disposal," pp. 36-6 to 36-8, J. Wiley
and Sons, N. Y. (1968).
-------
100
£ 80
o
CJ
=f 60
S 50
LU
Q_
° 40
"" 30
Ik.
Z
UJ
S 20
10
A THICKEN, DIGEST, SAND BEDS
B. THICKEN, DIGEST, FILTER, LANDFILL
C" THICKEN. FILTER, INCINERATE
10 20
WASTEWATER FLOW (MOD)
30
60
100
30
20
10
2I_L
FIGURE 1-2
A: THICKEN, DIGEST. SAND BEDS
B: THICKEN, DIGEST, FILTER, LANDFILL
C: THICKEN. FILTER. INCINERATE
10
20
30
60
100
WASTEWATER FLOW (MOD)
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
-------
Construction as Designed
Increased A/E involvement, new CM. 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
-------
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 = Dcwatcring 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
Figure 2-1 Objectives Wastewater Treatment Plant Project
Figure 2-2 Essential Ingredients
Figure 2-3 Sources - Conceptual Design Information
Figure 2-4 Special Considerations Design Rationale
Figure 2-5 The Total versus the Fractional Approach
2-5
-------
OBJECTIVES
EFFECTIVE,RELIABLE PROCESSING OF WASTEWATER
(BOTH LIQUID AND SOLID FRACTIONS)
AT LOWEST PRACTICAL COST
CONCURRENT NON-POLLUTING EFFLUENT STREAMS
CLIQUID.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
FIGURE 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
pip* dfectkMteiil - Wffcl-
ADEQUACY OF AVAILABLE LITERATURE
SUPPLIERS RECOMMENDATIONS
PLANT DATA - FACT VS. FOLKLORE
__» rn!«Hi6» a la
PROCESS ENGINEERING
FIGURE 2-4
-------
THE TOTAL VERSUS
THE FRACTIONAL APPROACH
INFLUENT
SOLIDS
SEPARATION
r
i
i
LIQUID
PROCESSING
LIQUID
EFFLUENT
SLUDGE
PROCESSING
SOLIDS
EFFLUENT
FIGURE 2-5
-------
SECTION 3 - NATURE AND HANDLING CHARACTERISTICS OF SLUDGES
1. 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.
2. 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 - (« 30% < 30 mesh) permits rapid formation of cake with sufficient
structural matrix = good capture and rapid dewatering.
3. 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 dewatcr.
But results arc still good and costs low.
- Shear effects on particle size and increased hydration of solids.
3- 1
-------
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.
60-90 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=10-30MG/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.
i
- 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 2-3 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 ah, 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 ah, 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
Dcwatering at Chicago." JWPCF, 38, No. 2, 248.
3-8
-------
LIST OF FIGURES AND TABLES - SECTION 3
Figure 3-1 Maxim - "All generalities are inherently false, including this one."
Figure 3-2 Closeup - Raw Primary Sludge Filter Cake
Figure 3-3 Release Characteristics - Raw Primary Sludge Filters
Table 3-1 Vacuum Filtration Raw Primary Sludge
Table 3-2 Vacuum Filtration - Digested Primary Sludge
Figure 3-4 Activated Sludge - Aqueous Fluid Distribution
Figure 3-5 Effect of Aeration Time on Biopolymer Production and Dewaterability
Figure 3-6 Secondary Plant with Surplus Activated Sludge to Head of Works
Figure 3-7 Secondary Plant with Surplus Activated Sludge Mixed with Primary Sludge
Prior to Thickening and Digestion
Figure 3-8 Settling Characteristics for Air and Oxygen Biomass (ISR vs. Concentration)
Figure 3-9 Typical Clarifier Performance for Air and Oxygen Sludges
(at 30 percent Recycle)
Figure 3-10 Typical Clarifier Performance for Air and Oxygen Sludges
(at 30 percent Recycle)
Figure 3-11 Gravity Thickening
Figure 3-12 Flotation Thickening
Figure 3-13 Flotation Thickening
Figure 3-14 Vacuum Filtration
Figure 3-15 Centrifugation, Oxygen andConventional Aeration Sludges
Figure 3-16 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.
11
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 [S/TONI 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 |$/TON| #/HR/FT2 1%) l%l
12.7 2.64 7.4 28 90+
TABLE 3-2 VACUUM FILTRATION - DIGESTED PRIMARY SLUDGE
-------
ACTIWTED SLUDGE
AQUEOUS FLUID DISTRIBUTION
CUMULATIVE
LOCATION PARTS % SOLIDS
SOLIDS 1.0 100
WITHIN CELL 2.5 29
SURFACE BOUND"*"* 5.0 12
LOOSELY HELD *«». 2.5 9 *»w*o
FIGURE 3-4
-------
ACCUMULATED
POLYSACCHARIDE
mg/l
600
500
400
300
800
600
400
200
POLYSACCHARIDE RELATIONSHIPS
POLYSACCHARIDE/BACTERIA
RATIO
ACCUMULATED
POLYSACCHARIDE
FILTRATION RATE
1.5
1.0
mg POLYSACCHARIDE
0.5 mg BACTERIA
50
200
250
FIGURE 3-5
100 150
TIME - HOURS
EFFECT OF AERATION TIME ON BIOPOLYMER PRODUCTION AND DEWATERABILITY
-------
GRIT
REMOVAL
PRIMARY
CLARIFIERS
AERATION
BASINS
FINAL
CLARIFIERS
........ i ..... in ........ i ...... mi ...... iniir^ .............. IIIIHIIIIII ........ iiiiiiiin
^IIIIIIH innim
ANEROBIC
DIGESTION
.........
ELUTRIATION
iiiiiiiiiniiiii
WASTE WATER
SLUDGE
~ PROCESS LIQUIDS
FILTERS
FIGURE 3-6
SECONDARY PLANT WITH SURPLUS ACTIVATED SLUDGE TO HEAD OF WORKS
-------
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REMOVAL rfY
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j j = i
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r___
SLUDGE
THICKENING
*
DIGESTION >
ELUTRIATION
*
j
DEWATERING
!
>
WASTE WATER
SLUDGE
- PROCESSING LIQUIDS
FIGURE 3-7 SECONDARY PLANT WITH SURPLUS ACTIVATED SLUDGE MIXED WITH PRIMARY SLUDGE PRIOR
TO THICKENING AND DIGESTION
-------
10.0
SETTLING
CHARACTERISTICS
FOR AIR AND
OXYGEN BIOMASS
(ISR VS. CONCENTRATION
i.o
INITIAL SETTLING
RATE, FI/Hr.
0.1
1000
AIR
BIOMASS
OXYGEN
BIOMASS
j iii
10,000
CONCENTRATION mg/l
FIGURE 3-8
100,000
TYPICAL CLARIFIER PERFORMANCE FOR AIR AND OXYGEN SLUDGES
(AT 30 % RECYCLE]
10,000r
8000
MLSS |mg/l ] 6000
4000
2000
OXYGEN SLUDGE
AIR SLUDGE
200 400 600 800 1000 1200
OVERFLOW RATE, GPD/FT2
1400 1600
FIGURE 3-9
-------
TYPICAL CLARIFIER PERFORMANCE FOR AIR AND OXYGEN SLUDGES
(AT 30 % RECYCLE)
5r
% RSS
OXYGEN SLUDGE
AIR SLUDGE
200 400 600 800 1000 1200 1400 1600
OVERFLOW RATE, GPD/FT2
FIGURE 3-10
GRAVITY THICKENING
FEED SLUDGE
TYPE
OXYGEN W.A.S.
AIR W.A.S.
OXYGEN MIXED
AIR MIXED
% SOLIDS
1.7
0.9
2.3
1.1
SOLIDS
LOADING
#/Ft.2/DAY
10
20
20
UNDERFLOW
CONC.
% SOLIDS LOCATION
4.8
5.6
LOUISVILLE
1.4-2.8 CHICAGO
MIDDLESEX
3.3(4.4) CHICAGO
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. SOLIDS |%|
OXYGEN
ACTIVATED (1.7) 2.9 6.4-10.2 6.6
AIR
ACTIVATED (0.9) 9.0 2.0-4.0 4.5
FIGURE 3-13
-------
VACUUM FILTRATIpN
LOCATION
CONDITIONER
#/TON D.S.
TYPE % SOLIDS FeCI3 LIME
FEED SLUDGE
BATAVIA OXY.W.A.S. 4.4
200
LOUISVILLE
OXY.W.A.S.= 3
RAW PRIM
DIG. = 6
TYPE
SLUDGE
5.3
50
142
YIELD
#/Ft.2/HR.
5.1
7.2
FIGURE 3-14
CAKE
SOLIDS %
14.5
26.4
CENTRIFUGATION
OXYGEN a CONVENTIONAL
AERATION SLUDGES
FEED POLYMER SOLIDS CAKE
% SOLIDS RATE (GPM) (#/TON) CAP. (%) SOLIDS (%)
OXYGEN
W.A.S.
2.5
95
92
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 TONS/ 9 COND.
SALT MG/L MG/L % SOLIDS >"lM.G. #/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
CONV ACT. SLUDGE PLANT-LIME
CHEMICAL ADDITION MIXED SOLIDS CENTRIFUGATION
METAL DOSE SLUDGE TONS/ POLYMER % CAKE SOLIDS
/M.G.
SALT MG/L % SOUPS /M.G. |#/TON| SOLIDS CAPTURE
NONE 3.5 0.85
LIME 200 10 2.45 <1 31 97
FIGURE 3-17
-------
tf LITTLE RIVER w ~
(CONV ACT. SLUDGE -PHOSP. REM.
CHEMICAL ADDITION MIXED SOLIDS FILTER S
METAL DOSE
SALT MG/L
NONE
- LIME 125
T*
ALUM 150
SLUDGE
% SOLIDS
6.2
11.6
5.7
TON^ YIELD
/M.G. #/HR/Ft.2
0.8 5.2
1.2 7.2
1.2 4.6
COND
COST
^BI^^BKBi
11
18
s,
FIGURE 3-18
NORTH TORONTO
CONV ACT. SLUDGE -FERRIC CHLORIDE
CHEMICAL ADDITION MIXED
COND.|lb/TON
METAL DOSE SLUDGE FERRIC % CAKE
SALT M6/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
RAV
INFLU
1
ENT
»
"* CENTM
ASH
P
c
kTE
RIMARY
-ARIFIER
1 '
SLU
THICK
1
CENT
,
FUR
1
DGE
tM
r
HFl
i
MAC
1
r
R
ICE
E
AERATION
BASINS
AC
S
riv
LU
ATED
5GE
LU
1
,
RE-C/
HE
ENER
i
i
ILCINE
SECON
CLARI
>
I
1
CENTRA!
DARY
FIERS
r
fE 1
LIME
CHEM. C
1
t ^. CHEMICAL
w CLARIFIERS
FURTHER
REACTION PROCESSING ^
TO
LARIFIERS
FIGURE 3-20
LAKE TAHOE
-ORGANIC SLUDGE HANDLING
% FEED
SOLIDS
COND.
#/TON
FEED
RATE
% SOLIDS
CAPTURE
% CAKE
SOLIDS
2.0
5.1
90
17
FIGURE 3-21
-------
LAKE TAHOE
-LIME SLUDGE PROCESSING
FRACTION LOST TO CENTRATE
FEED RATE
(GPM)
10
20
% SOLIDS
CAPTURE
93
79
TOTAL
SOLIDS
0.10
0.20
ACTIVE
LIME
0.04
0.08
PHOSPHATE
0.19
0.39
MGO
0.17
0.35
FIGURE 3-22
-------
SECTION 4 -SLUDGE STABILIZATION PROCESSES*'
1. Anaerobic Digestion
- Anaerobic digestion is the most frequently employed process for sludge
4r stabilization. When digestion operates properly, it converts raw sludge to a
\^r stable material which is inoffensive to the senses, and which has a greatly
v(r reduced pathogen content. A recent exposition of sludge digestion is available
* (Reference 1).
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 (Table 4-1 from Reference 2). If sludge density is increased (e.g., by
two-stage high rate digestion), yield can be increased.
Schepman and Cornell (Reference 3) conclude that raw sludges may vary from
very good to very poor yields, whereas digested sludges from different sources
are more uniform (Table 4-2).
Anaerobic digestion solubilizes much sludge, releases nutrients back to
treatment plant. High dissolved solids can interfere with chemical conditioning.
Table 4-3 shows some supernatant compositions reported recently (Reference
4).
2. Aerobic Stabilization
Aerobic stabilization is often 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.
Aerobically stabilized sludge has Bflfli_dewatering characteristics on vacuum
filters although a recent publication claims otherwise (Reference 6). Ordinarily,
this sludge is dewatered on sand beds or applied in liquid form to cropland.
3. Chlorine Oxidation
The Purifax process oxidizes sludge with heavy doses of chlorine (circa 2,000
mg/1). Sludge dewaters well on sand beds. 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 7).
4- 1
-------
Supernatant and filtrate contain high concentrations of chloramines. They
should not be carelessly discharged.
4. Lime Treatment
Lime treatment of sludge stabilizes the sludge as long as the pH stays high. Kill
of pathogenic bacteria is excellent (Reference 8). 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.
4-2
-------
TABLE 4-1
TYPICAL AVERAGE SEWAGE SLUDGE FILTRATION RATES
Average Chemicals
(percent)
Type of Sludge
Primary Sludge
Raw
Digested
Digested Elutriated
Primary - Trickling Filter
Raw
Digested
Digested - Elutriated
Primary - Activated Sludge
Raw
Digested
Digested Elutriated
Activated Sludge - Concentrated
Feed Solids2
(percent)
8
8
8
7
8
8
5
6
6
3
Filtration Rate
Drylb/hr-ft2
10.0
8.0
6.5
9.0
7.0
6.5
4.5
4.5
4.5
2.0
Average Cake
Moisture (percent)
66
70
71
68
71
72
79
76
78
84
FeClj
1.5
3.0
2.5
1.5
3.0
2.5
4.0
4.0
5.0
5.5
CaO
7.0
8.5
(4.0)1
8.0
8.5
(4.0)1
4.0
9.0
(5.0)1
0
1 Lime is frequently added to elutriated sludges to give higher filtration rates and lower cake moistures.
2 If feed sludge concentration differs from value listed, the expected filtration rate will differ directly in proportion to the change in
feed solids concentration. Example: If 9% solids raw primary sludge is filtered an average filtration rate of 9 x 10 = 11.25 lb/hr/ft2
O
may be expected. °
-------
TABLE 4-2
FILTRATION RATES AND CAKE MOISTURE
FOR DIFFERENT TYPES OF SLUDGES
Plant
Sludge
Cone. (%)
Chemicals (%)
CaO FeCl3
Filter
Rate1
Cake
Moisture (%)
Saginaw, Mich.
Providence, R.I.
Wyandotte, Mich.2
Rockford, 111.
Schenectady, N.Y.
Long Beach, N.Y.3
Greenwich, Conn.
Dallas, Texas
PRIMARY SLUDGES
16 9.9 0
5.5 6 2.2
8.0 15 5
DIGESTED - PRIMARY SLUDGES
9.5
8.5
3.8
5.6
7.5
7.1
6.0
17.0
6.0
5.5
5.4
4.0
3.5
3.0
2.5
8.5
13.0
8.0
11.5
11.5
14.0
11.0
14.5
ELUTRIATED - DIGESTED - PRIMARY SLUDGES
Cincinnati, Ohio
Toronto, Ont.
East Providence, R.I.
Dallas, Texas
8.5
7.7
9.0
8.0
0
0
0
0
4.5
4.0
1.5
0.8
3.1
8.0
20.0
15.5
54.0
73.0
70.0
71.5
77.0
73.0
74.0
72.5
64.0
70.0
72.5
70.5
DIGESTED - PRIMARY - ACTIVATED SLUDGE
Nassau County, N.Y. 4.5 12.0 8.0 3.0
79.0
ELUTRIATED - DIGESTED - PRIMARY - ACTIVATED SLUDGES
Cranston, R.I.
Houston, Texas
Ann Arbor, Mich.
Cleveland, Ohio
Hyperion, (L.A.) Calif.4
2.4
2.7
5.0
5.5
5.1
0
0
15.0
9.0
0
7.0
5.5
3.0
2.5
1.9
3.4
5.5
5.0
6.3
5.8
85.0
84.2
72.5
71.5
76.5
1 Filter rate or yield, lb/(hr)(ft2)
2 Sludge hauled to plant from other collecting points in county; therefore, it is somewhat
septic, depending on temperature and elapsed time.
3 Testing conditions prevented optimum operation.
4 Separan also added at approximately 0.02 percent.
4-4
-------
TABLE 4-3
AVERAGED RESULTS OF ANALYSES
OF DIGESTER SUPERNATANTS (MG/L)
PH
Suspended Solids
Total Solids
Total Volatile Solids
Total PO4 (as P)
Soluble-Ortho-PO4 (as P)
NH3-N
Organic-N
Alkalinity
COD
Hardness
Irvington
7.3
2,200
4,540
2,930
143
66
850
290
3,780
4,560
264
Milpitas
7.0
383
1,470
814
63
45
253
53
1,350
1,380
322
Massolli*
7.3
3,260
1,540
56
402
1,675
890
* Reference 5
4-5
-------
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. Schepman, B.A., and Cornell, C.F., "Fundamental Operating Variables in Sewage Sludge
Filtration." Sew. and Industrial Wastes, 28, No. 12, 1443-1460 (1956).
4. Bennett, G.E., "Development of a Pilot Plant to Demonstrate Removal of Carbonaceous,
Nitrogenous, and Phosphorus Materials from Anaerobic Digester Supernatant and
Related Process Streams," U.S. EPA, Report ORD-17010 FKA 05/70, May, 1970.
5. Masselli, Joseph W., et al., "The Effect of Industrial Wastes on Sewage Treatment," New
England Water Pollution Control Commission, Boston, Massachusetts, 1965 .
6. Cameron, J.W., "Aerobic Digestion of Activated Sludge to Reduce Sludge Handling
Costs," 45th Annual Conference, Water Pollution Control Federation, Atlanta,
Georgia, October, 1972.
7. Personal communication with Mr. Pearson of BIF Purifax, Providence, Rhode Island.
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.
4-6
-------
LIST OF FIGURES AND TABLES - SECTION 4
Table 4-1 Typical Average Sewage Sludge Filtration Rates
Table 4-2 Filtration Rates and Cake Moisture for Different Types of Sludges
Table 4-3 Averaged Results of Analyses of Digester Supernatant (mg/1)
4-7
-------
SECTION 5 - 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 5-1)
- 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, elutriation, 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 5-2)
Flocculation in elutriation basins.
Careful operation of basins to promote sludge compaction and thickening
and good solids capture.
5- 1
-------
3. Sludge Removal Practices and Costs
(Table 5-1)
- Initial results, even with venting of elutriate, costs were high and 3 lb/hr/ft2
filter yields experienced.
- During initial months of treating elutriation 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 5-3 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 5-4)
Interim use of alum/ferric in 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.
5-2
-------
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 5-5)
- 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 5-6)
- 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 5-7), 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 5-2)
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.
5-3
-------
As recirculating solids occurred in plant, odor problems arose.
Work commenced to improve the elutriation/filtration process.
5. Elutriation/Filtration Studies
(Table 5-3)
- Over two month period, small polymer add in feed to elutriation; 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 5-4), results improved even further as
some of the fines were cleaned out of the plant.
- The elutriation/filtration (Figure 5-8) process improved in uniformity and ease
of operation. Note excellent cake discharge and thickness of filter cake.
5-4
-------
CASE STUDY - RICHMOND, CALIFORNIA
1. On-Going, Plant Process Studies on Solids Handling
During 1967-69 (Figure 5-9) 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 5-5).
Note that with primary sludge, before secondary treatment, things were rosy.
During the period when solids recirculation was occurring, note in column 2
the nigh costs - low yields and low cake solids obtained.
After realizing good compaction and solids capture in elutriation via flocculant
use, note dramatic improvement in filtration performance.
4. Current Results
After protracted operation with effective elutriation (Table 5-6) the results were as
shown.
Total conditioning costs in elutriation and on filters (ferric chloride/lime) were
about $11.00/ton.
5-5
-------
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.
5-6
-------
LIST OF FIGURES AND TABLES - SECTION 5
Figure 5-1
Figure 5-2
Table 5-1
Figure 5-3
Figure 5-4
Figure 5-5
Figure 5-6
Figure 5-7
Table 5-2
Table 5-3
Table 5^
Figure 5-8
Figure 5-9
Table 5-5
Table 5-6
Plant Flow Diagram - District of Columbia
Elutriation/Filtration System - District of Columbia
Sludge Removal Practices and Costs - District of Columbia
Vacuum Filter Operation District of Columbia
New Filter Installation with Individual Conditioning Boxes - District of
Columbia
Plant Flow Diagram - Metro Toronto
Percent Solids in Elutriated Sludge - Metro Toronto
Percent Solids in Raw Sludge - Metro Toronto
Sludge Removal Needs Metro Toronto
Elutriation/Filtration Results October-November - Metro Toronto
Elutriation/Filtration Results 1971 - Metro Toronto
A View of Filters - Metro Toronto
Plant Flow Diagram Richmond, California
Filtration Results Richmond, California
Elutriation/Filtration Operations - Richmond, California
5-7
-------
REFERENCES - SECTION 5
1. Goodman, B.L, and Whitcher, C.P., "Polymer Aided Sludge Elutriation and Filtration."
Journal WPCF.37, 12, 1643 (1965).
2. Dahl, B.W., Zelinski, J.W., and Taylor, O.W., "Polymer Aids Dewatering 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.P., "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, 1958-1966." 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.
5-8
-------
INFLUENT
GRIT
REMOVAL
N PRIMARY
BASINS
AERATION
BASINS
THICKENER
0-FLOW
4
ELUTRIATE
HIGH
RATE
DIGESTION
WASH
WATER
B.O.D. REMOVAL 70-90%
SS REMOVAL 70-90%
ELUTRIATION
FINAL
CLARIFIERS
EFFLUENT
15-25%
FILTER
CAKE
FIGURE 5-1
PLANT FLOW DIAGRAM - DISTRICT OF COLUMBIA
-------
WASH
WATER
DIGESTED
SLUDGE
ELUTRIATE
RECYCLED OR TO RIVER
2 STAGE
ELUTRIATION
VACUUM
FILTERS
FILTER
CAKE
X = CATIONIC POLYELECTROLYTE APPLICATION POINT
FIGURE 5-2
ELUTRIATION/FILTRATION SYSTEM - DISTRICT OF COLUMBIA
-------
TONS/DAY CHEMICAL COST (S/TON)
REMOVED ELUTRIATION FILTRATION
ELUTRIATE TO RIVER
POST ELUTRIATE
RECYCLE PERIOD
(POLYMER IN ELUTRIATION]
AFTER PROLONGED
POLYMER USE IN
ELUTRIATION
45
80
70
13.50
4.68
7.42
TOTAL = 9.75
TABLE 5-1
SLUDGE REMOVAL PRACTICES AND COSTS - DISTRICT OF COLUMBIA
-------
FIGURE 5-3
VACUUM FILTER OPERATION - DISTRICT OF COLUMBIA
-------
FIGURE5-4
NEW FILTER INSTALLATION WITH INDIVIDUAL CONDITIONING BOXES - DISTRICT OF COLUMBIA
-------
PLANT
INFLUENT ^
f
GRIT
REMOVAL
T
PRIMARY
CLARIFICATION
=
ACTIVATED
SLUDGE
FINAL
CLARIFIERS
PLANT EFFLUENT
»
11111111111111111
PRIMARY
DIGESTION
^
w~~~\ S.N.
SECONDARY
DIGESTION
{ELUTRIATE
*
2 STAGE
ELUTRIATION
* FILTRATE
VACUUM
FILTRATION
TO INCINERATORS
WASTE WATER
. PROCESS LIQUIDS
FIGURE 5-5
PLANT FLOW DIAGRAM - METRO TORONTO
-------
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
MONTHLY AVERAGES
FIGURE 5-6
M A M J J A S 0
PERCENT SOLIDS IN ELUTRIATED SLUDGE - METRO TORONTO
N
-------
7.0
6.0
5.0
4.0
3.0
2.0
1.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
JAN.
JUNE
1968
DEC.
JUNE
DEC.
1969
FIGURE5-7 PERCENT SOLIDS IN RAW SLUDGE
METRO TORONTO
JUNE
1970
-------
OPERABLE PREFERRED REQUIRED
1970 1970 1971
DRY TONS/MO. 2000 2500 3000
#/HR./FT.2 3.0 3.7 4.4
TABLE 5-2 SLUDGE REMOVAL NEEDS - METRO TORONTO
-------
POLYMER USED SLUDGE CAKE
1970 I#/TO.N| SOLIDS 2 SOLIDS
PERIOD ELUT. FILT. |%] #/HR./FT.
OCTOBER 1.26 7.77 3.6 4.7 16
NOVEMBER 1.75 8.20 4.1 4.3 16
TABLE 5-3 ELUTRIATION/FILTRATION RESULTS OCTOBER-NOVEMBER - METRO TORONTO
-------
ELUT. FLOW POLYMER ELUTRIATE
IMGPDI I#/TONI s.s. IPPMI SLUDGE CAKE
WASH DIGEST SOLIDS %&/ SOLIDS
WATER SLUDGE ELUT. FILT. 1ST 2ND l%l /TT.2 1%)
1.0 0.6 1.94 10.96 120 18 6.1 4.7 16.0
3.5 1.4 0.62 9.34 6250 208 3.5 5.8 15.4
TABLE 5-4 ELUTRIATION/FILTRATION RESULTS 1971 - METRO TORONTO
-------
FIGURE 5-8
A VIEW OF FILTERS - METRO TORONTO
-------
PLANT
INFLUENT '
GRIT
REMOVAL
r
PRIMARY
CLARIFIERS
AERATION
BASINS
FINAL
CLARIFIERS
PLANT
EFFLUENT
SIIIIIIIIIIIIIIIIIJIIIIIIIIIIIII Hill Illll Mil Hill""""!
IIUI
Illllllllllllllll Illlllllllllllllllll
(lllllllllllllllllllllllllllllllllllllllllll
L
D.A.F.
THICKENER
4,,;
PRIMARY
DIGESTION
r
SECONDARY
DIGESTION
iimi
1
ELUTRIATION
VACUUM
FILTERS
WASTE WATER
FIGURE 5-9
i mi
SLUDGE - PROCESS LIQUIDS
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 |$/TON) $3.80/$4.00 S25/S30 $11/$14
CAKE SOLIDS (%) 29-31 16-18 20-22
TABLE 5-5 FILTRATION RESULTS - RICHMOND, CALIFORNIA
-------
ELUTRIATION
DIGEST
SLUDGE
% SOLIDS
3.85
ELUTRIATE
SLUDGE
% SOLIDS
7.8
POLYMER
#/TON
2.12
ELUTRIATE
SOLIDS
PPM
450
FILTRATION
FeCI3
S/TON
3.00
LIME
$/TON
4.85
FILTER
CAKE
% SOLIDS
20.8
TABLE 5-6
ELUTRIATION/FILTRATION OPERATIONS - RICHMOND, CALIFORNIA
-------
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 Oxygen Process Flow Sheet
Figure 6A-2 Schematic Diagram of Oxygen System with Rotating Sparger
Figure 6A-3 Schematic Diagram of Oxygen System with Surface Aerator
Figure 6A-4 Oxygen Process Characteristics
Figure 6A-5 Reasons for "Cost Effectiveness" of the Oxygen System
Figure 6A-6 Comparison of Process Design and Performance Parameters
Figure 6A-7 Design Data Oxygenation Tanks
Figure 6A-8 Middlesex County Costs
Figure 6A-9 Detroit Costs
Figure 6A-10 Oxygen Activated Sludge
Figure 6A-11 Estimated Costs Comparison Air Aeration and Oxygen Aeration
Figure 6A-12 Typical Plant Photograph
6A -4
-------
OXYGEN PROCESS FLOW SHEET
RETURN
SLUDGE
PUMP
WASTE
SLUDGE
RAW OR SETTLED WASTE WATER
MIXED LIQUOR
IN
COVERED
OXYGENATION
TANKS
WITH MIXERS,
OXYGEN
COMPRESSORS
AND SPARGERS
OXYGEN GAS
WASTE GAS
FINAL
SETTLING
TANKS
EFFLUENT
OXYGEN
SOURCE &
STORAGE
FIGURE 6A-1
-------
AERATION
TANK COVER
GAS RECIRCULATION
COMPRESSORS
CONTROL
VALVE
OXYGEN
FEED GAS
WASTE
LIQUOR
FEED
RECYCLE_
SLUDGE
EXHAUST
GAS
MIXED LIQUOR
EFFLUENT TO
CLARIFIER
FIGURE 6A-2
SCHEMATIC DIAGRAM OF OXYGEN SYSTEM WITH
ROTATING SPARGER
-------
AERATION
TANK COVER
CONTROL
VALVE
OXYGEN
FEED GAS
WASTE
LIQUOR
FEED
RECYCLE
SLUDGE"
AGITATOR.
Q
Q
^
r^
*~
5
-------
OXYGEN PROCESS CHARACTERISTICS
COCURRENT GAS-LIQUID FLOW
HIGH D.O. 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
I. D.O. 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
(lbsBOD/DAY/l,OOOft3)
5 F/m RATIO 0.4-0.8 0.3-0.6
(IbsBOD/DAY/lbMLVSS)
6. RECYCLE SLUDGE RATIO 0.2-0.5 0.3-1.0
7 RECYCLE SLUDGE CONC.(m8/l) 20,000-40,000 5,000-15,000
8. SLUDGE PRODUCTION 0.3-0.45 0.5-0.75
(Ibs 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
PENNSYLVANIA
N. YORK/N. JERSEY
MICHIGAN/OHIO
OTHERS
TOTAL
4
3
3
3
22
35
171
370
144
422
779
1886
FIGURE 6A-10
-------
ESTIMATED COSTS COMPARISON-
AIR AERATION AND OXYGEN AERATION
TYPICAL RANGES
TOTAL TREATMENT COSTS
NEW PLANTS WITH PRIMARY SEDIMENTATION
40 60
PLANT SIZE-M6D
FIGURE 6A-11
-------
FIGURE 6A-12 TYPICAL PLANT PHOTOGRAPH
-------
SECTION 6B - OXYGEN ACTIVATED SLUDGE
CASE STUDY - FAIRFAX - WESTGATE
1. 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
Chlorination (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 1P 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.
6B -2
-------
Small dose of flocculant = clear supernatant and rapid thickening to 68
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 = 22-28 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 FeCl3 lime 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 S8.00/ton of ferric 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
INFLUENT
COMMINUTION
PRIMARY SEDIMENTATION
AERATION
CLARIFICATION
CHLORINATION
LAND FILL
DIGESTION
PLANT
EFFLUENT
FIGURE 6B-1
WESTGATE SEDIMENTATION TANK
LONGITUDINAL SECTION
COMMINUTION
PRIMARY
CLARIFICATION AERATION
SECONDARY
CLARIFICATION
SUMP
SCRAPERS
AIR DIFFUSERS
FIGURE 6B-2
-------
WESTGATE PLANT FUNCTIONS
PERIOD
DESIGN % REMOVAL
FLOW IMGDI BOD 5 PLANT PROCESS
1954
1970
1971
1971-72
8
12
12
12
50 +
35-40
75 +
80-90
ORIGINAL
ORIGINAL
CHEMICAL Ppt.
OXYGEN
ACTIVATED SLUDGE
FIGURE 6B-3
CURRENT WESTGATE PROCESS FLOW
PLANT
INFLUENT
COMMINUTION
PRIMARY SEDIMENTATION
DUAL OXYGEN
ACTIVATED SLUDGE
BASINS
SECONDARY
CLARIFIERS
12)
CHLORINATION
PLANT
>
EFFLUENT
1
FILTER
CAKE
VACUUM
FILTERS
SLUDGE
DECANT
D.A.F.
UNITS
FIGURE 6B-4
-------
RESULTS
WESTGATE OXYGEN PROCESS
W.A.S. ZONE
% REMOVAL Ib V.S.S. SETT. VEL.
BODS T.S.S. S.V.I. Ib 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 SOLIDS
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
r
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 biodegradables)
Flow Variation -» Sunday -160 mg/1 BOD
Wednesday - 266 mg/1 BOD
3. Proposed Plant Process Flow
(Figure 6C-2)
Screening - grit removal - oxygenation tanks - clarifiers - 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 * 3050 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 in 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. Intrenchment Creek Work
(Figure 6C-8)
Two stage trickling filter plant
90 percent removal - 20 mgd design
90 percent removal - 14 mgd design
Interesting Centrifugation Works
(Figure 6C-9)
Relatively economical and efficient dewatering
Question = production rate data
Optimized centrate recycle load
(Plant at 14 = 70 percent design capacity
?0
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
-------
NEW ORLEANS, LA.
FEED WASTE WATER CHARACTERISTICS
PARAMETER
CHEMICAL OXYGEN DEMAND, mg/l
TOTAL
SOLUBLE
BIOCHEMICAL OXYGEN DEMAND.mg/l
TOTAL
SOLUBLE
SUSPENDED SOLIDS,mg/l
TOTAL
VOLATILE
PH
TEMPERATURE, °F
DEGRITTED RAW WASTE
AVERAGE
FIGURE 6C-1
316
183
210
98
183
133
7.4(6.6-8.8]
71(65-831
NEW ORLEANS PROCESS FLOW
SCREENING
GRIT
REMOVAL
k.
OXYGENATION
TANKS
PLANT
EFFLUENT
CHLORINATE
^
CLARIFIERS
FIGURE 6C-2
-------
OXYGEN SYSTEM-NEW ORLEANS
RETENTION [HRS.j
MLSS (mg/l)
Ib. BOD/KFt3-DAY
OVERFLOW(GAL/Ft2/DAY|
SLUDGE VOL. INDEX
STEADY
STATE
DESIGN
1.8
5560
181
655
79
DIURNAL
FLOW
PATTERN
1.4
5770
246
855
64
CENTRATE
RECYCLE
1.8
7350
193
655
48
FIGURE 6C-3
EXCESS SLUDGE
PRODUCTION
LB. TSS
LB. BODA
0.8
0.7
0.6
0.5
0.4
0.3
0.5
"UNOX" SYSTEM
NEW ORLEANS, LA.
EFFECT OF BIOMASS LOADING ON
SOLIDS WASTING RATE
PHASE II
PHASE III
PHASE V ICENTRATEj
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
RAW
DEGRITTED
WASTEWATER
*
UNOX
REACTOR
RECYCLE SLUDGE
CENTRATE
SECONDARY
CLARIFIER
CLARIFIER
EFFLUENT
CENTRIFUGE
SOLID CAKE
FOR DISPOSAL
% DRY SLUDGE
SOLIDS IN CAKE
20
15
10
FIGURE 6C-5
AVG.
3 RUNS V
^>
"UNOX" SYSTEM
NEW ORLEANS, LA.
CENTRIFUGE PERFORMANCE
AVG. 6 RUNS
AVG. 4 RUNS
SOLID BOWL SCROLL TYPE
CENTRIFUGE
NO CHEMICAL CONDITIONING
AVG. 5 RUNS
5
2
0 30 40 50 60 70 80 90
% RECOVERY »..."
AND SHARPLES
FIGURE 6C-6
-------
CENTRIFUGATION-NEW ORLEANS
OXYGEN ACTIWTED SLUDGE
FEED COND.
% SOLIDS GPM
% SOLIDS
CAPTURE
% CAKE
SOLIDS
CENTRATE
SOLIDS [%|
60
35
15
20
- 2.1
FIGURE 6C-7
INTRENCHMENT CREEK FLOW
PLANT
CENTRATE
TWO STAGE
TRICKLING FILTERS
FINAL
CLARIFIERS
PLANT
EFFLUENT
CAKE TO
TRUCK
FIGURE 6C-8
-------
CENTRIFUGATION-ATLANTA
MIXED SLUDGE -PRIMARY a T. E
FEED COND. % SOLIDS % CAKE POLYMER
% SOLIDS GPM CAPTURE SOLIDS $/TON
FIGURE 6C-9
4-6 - 90 21 5.74
4-6 - 80 24 4.05
-------
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,3l (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. Eckenfclder, W.W., Jr., "Boost Plant Efficiency." W. & W. Engineering, E-l (September,
1972).
13. Robson, C.M., Block, C.S., Nickerson, G.L., and Klinger, 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.G., 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.
-------
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 450°- 550° 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 CO2, H2 O, ammonia, sulfatcs,
acetates.
- At 250° 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 - 500° and 1,200 psig.
- Maintenance = alternate caustic and muriatic acid washing of exchangers.
- Capital cost = $284,000 in 1963-65.
Design and Operating Conditions (Table 7-1)
90 percent removal of insoluble organic matter.
But?? Quantity and quality of oxidized liquor?
- 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 (500° 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 = S50/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 - liigh pressure and temperature (365° 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.
- Fairer (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.).
Ziinpro - 14 built and 12 under construction.
Farrer - No U.S. installations, to my knowledge.
7-3
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9. Porteous Type Process
Coors/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 Ib/hr 370° 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 SI820/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 work trying to reduce recycle load. Including massive
lime chemical precipitation of liquors.
7-4
-------
- Stated cost of operation for J'ortcous process and dcwatering = $2/ton.
- Reference 9 - State's chemical conditioning costs used to run $20-S40/ton.
States operating costs for Portcous run $15/lon (fuel, power, labor and water).
- Current plans - convert to activated sludge. Porteous = 400° 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 nonopcration 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 $51.40/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
$56.40/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 activated/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 dewatcr either by vacuum filtering or centrifuging."
- Installation Costs (Figure 7-8)
Zimpro - $1,908,557 (97.5 tons/day)
Incinerator - $658,511
7-6
-------
Electrical-SI 54,950
General Contract - $1,212,534
Treating lagooncd sludge initially
- Operating temperatures = 358° 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 does 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 Dewatering - 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, P.P., and Cardinal, P.J., "Solid Waste Disposal." Chemical Engineering,
(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 Control, 92 (1970).
7-8
-------
REFERENCES (Continued)
14. Everett, J.G., and Brooks, R.B., "Dewatering of Sewage Sludges by Heat 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. Swels, D.H., Pratt, L, and Mctcalf, C., "Combined Industrial - Municipal Thermal Sludge
Conditioning and Multiple Hearth 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 Works, (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 Fairer 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 - Thickening and Dewatering
Figure 7-10 Cooking Liquor Treatment
7-10
-------
RAW SEWAGE
GRIT TANKS
y
GRIT
PRIMARY
XSETTLING
CHLORINE
CONTACT
DILUTE RAW
SLUDGE AND SCUM
SLUDGE
THICKNER
THICKNED RAW
i SLUDGE
AND SCUM
SLUDGE
STORAGE
OHIO
RIVER
OXIDIZED
SLUDGE
ZIMPRO
SLUDGE OXIDATION UNIT
FIGURE 7-1
WHEELING, WEST VIRGINIA FLOW DIAGRAM
-------
REACTOR
HEATING
VWVW-Ii
COILS
HELIFLOW
HEAT EXCHANGER
HIGH PRESSURE PUMP
AIR
WATER AND
CONDENSATE
FIGURE 7-2
WET AIR OXIDATION SYSTEM - WHEELING, WEST VIRGINIA
-------
TABLE 7-1 DESIGN AND OPERATING CONDITIONS -
WHEELING, WEST VIRGINIA
Conditions
Max. & Min.
Processing
Rates
Processing Rate tons
per day dry solids
Flow gpm
Total Solids %
Chemical Oxygen De-
mand g/l
Insoluble Organic
matter removed %
Design
5.6
15.5
6
90
90
Ave. Max.
7.35 12.2
17.35 21.0
7.14 9.7
70 95
90 82.6
Maximum Insoluble Organic Removal = 93.
Min.
4.1
16.7
4.0
43.0
90.2
2%
-------
TABLE 7-2 SLUDGE DISPOSAL - OPERATING COSTS
WHEELING, WEST VIRGINIA
Cost/Ton Solids
Processed
To January 1,
1965
Electricity $ 6.11
Chemicals 4.13
Start-up Fuel 1.65
Maintenance 1.17
$13.06
Labor1 man during Zimpro
Unit Operation 6.91
Total Operating Cost$/ton $19.97
-------
BOILER FDR PROCESS STEAM
STEAM
RAW SLUDGE
STORAGE DISINTEGRATOR
PUMP
I HEAT EXCHANGER REACTION VESSEL
AUTOMATIC DISCHARGE VALVE
THICKENED
SLUDGE
RESIDUAL LIQUORS
I ED SLUDGE
VACUUM FILTER
FIGURE 7-3
FLOW DIAGRAM OF THE PORTEOUS PROCESS
-------
SLUDGE
GRINDER
AIR
AIR COMPRESSOR
TO INCINERATOR
GROUND
SLUDGE
HOLDING
TANK
i ir
PUMP
POSITIVE
DISPLACEMENT
SLUDGE PUMP
OXIDIZED
SLUDGE
TANK
HEAT
EXCHANGER
REACTOR
EXHAUST GAS
PRESSURE
CONTROL
VALVE
VAPOR
COMBUSTION
UNIT
TREATED
BOILER
WATER
FILTER
PUMP
BOILER
FIGURE 7-4 THERMAL SLUDGE CONDITIONING AND DEWATERING
-------
REACTOR
SECOND HSAT
EXCHANGER
PRE- HEATER
THICKENER
CONTROL
PANEL
BOILER
CIRCULATING
PUMP
1H P
4%5V COMPRESSOR / '
₯
\
"AUTOMATIC
VALVES
(ONE BACK-UP)
LEVELING
VESSEL
DECANTING
AND STORAGE
TANK
CENTRIFUGE
ih-»
TO FS SOIL LAND FILL
CONDITIONING
GRINDER PUMP
FIGURE 7-5
FLOWSHEET FOR THE DORR-OLIVER FARRER SYSTEM
-------
LABORATORY PLANT SCALE
WOKINGHAM 35,880 35,940
FARNSBOROUGH 29,800 29,800
TABLE 7-3 TOTAL SOLIDS PPM - HEAT TREATMENT LIQUORS
-------
TEMPERATURES % SUSPENDED SOLIDS
(°C.| SOLUBILIZED
(HEAT TREATMENT) "0:200:230 66
W 0
|WET AIR OXIDATION) 170:200:230 79
TABLE 7-4 PERCENT SOLIDS SOLUBILIZED - HEAT TREATMENT AND WET AIR OXIDATION AT VARIOUS TEMPERATURES
-------
COST DATA-PUDSEY
|$/TON OF SLUDGE-EX CAKE DISPOSAL]
0/M
19.20
CAPITAL
32.20
TOTAL
51.40
LIQUOR TREAT.
5.00
FIGURE 7-6
SLUDGE DISPOSAL FACILITIES
SCRUBBER
VACUUM
FILTER
MULTIPLE
HEARTH
INCINERATOR
FIGURE 7-7
-------
OPERATING TEMPERATURE BALANCE
HIGH
PRESSURE PUMP
Sludge-
HEAT
EXHANGERS
REACTOR
Feed Water,
35«fF
I08°F
uu
PCV
AIR COMPRESSOR
DECANT
TANK
JlOd0
Thickened Oxidized Sludge
to Vacuum Filters
Feed Water-
Gai-»
INCINERATOR
WASTE HEAT
RECOVERY
STEAM BOILER
PROCESS STEAM
FIGURE 7-8
KALAMAZOO
-THICKENING AND DEWATERING
% SOLIDS
THICKENER THICKENED
FEED SLUDGE
Ib/HR/Ft.'
% CAKE
SOLIDS
COST
S/TON
5.0
9.7
4.9
45
20
FIGURE 7-9
-------
COOKING LIQUOR TREATMENT
t
GAS
BURNER
PORTEOUS
EFFLUENT
ANAEROBIC
FILTERS
FEED/RECYCLE
PUMPS
CM
O
CHLORINE
REACTION
VESSEL
EFFLUENT TO SECONDARY
TREATMENT SYSTEM
(75 TO 90 PERCENT
BOD REDUCTION]
RECYCLE
PUMPS
(OXIDATION OF
SULFUR COMPOUNDS)
FIGURE 7-10
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SECTION 8 - FINAL DISPOSAL PROCESSES AND CASE STUDIES
1. Incineration
- Introduction
Incinerator types
Heat recovery by countercurrent action by heat recovery boilers
- Air pollution requirements, devices for controlling air pollution
Multiple hearth incinerator
Continuous operation, Minneapolis, St. Paul
Intermittent operation, town X
Fluidized bed incinerator
Air pollution measurements, Waldwich, New Jersey
Intermittent operation, East Cliff- Capitola, California
Flash drying/incineration
2. Landfill
Bad practice
Good practice
3. Land Spreading
a. Background
- Landsprcading is popular with wastewater plants treating less than 10 mgd, and
in a few largo cities. Its use is widespread in Europe. U.S. practice is being
critically assessed in an EPA study.
8-1
-------
- Potential problems are contamination of the soil with metals, and
contamination of the groundwatcr with nutrients. Both can be handled by
proper design. Chance of bacterial contamination can be reduced to a negligible
degree by proper procedures or, if indicated, by pasteurization.
- Sludge has been transported by truck, barge, or pipeline. The choice depends
on scale of operation and the circumstances.
Deep, well drained, permeable, level soils arc usually preferred. A careful survey
of the soils, geology, and hydrology is important for proper design of a land
disposal system. Lands that are used for tilled crops, pastures, forests, and
recreation have been used for sludge spreading.
b. Procedures
Methods for discharging sludge to the land
- Rates of application
Means for controlling pathogens
- Assessment of the hazard of metal contamination
c. Land Spreading at Chicago
Chicago is transporting sludge 200 miles by barge, and disposing it to the land
for a total cost, including digestion, of 572/dry ton. Barging costs are inflated
because dock and 20-mile pipeline had to be amortized over 3 years. When a
pipeline is built, costs will fall to $3S/dry ton.
8-2
-------
REFERENCES - SECTION 8
1. Dalton, F.E., and Murphy, R.R., "Land Reclamation," presented at the 45th Annual
Conference of the Water Pollution Control Federation, Atlanta, Georgia, 1972.
2. Lynam, B.T., Sosewitz, B., and Hinesly, T.D., "Liquid Fertilizer to Reclaim Land and
Produce Crops." Water Research, 6, 545-549 (1972).
3. Dotson, G.K., Dean, R.B., and Stern, G., "The Cost of Dewatering Digested Sludge on
Land," to be presented at the 65th Annual Meeting A.I.CH.E., New York, New
York, November, 1972.
4. White, R.K., and Hamdy, M.Y., "Sludge Disposal on Agricultural Soils," presented at the
27th Annual Purdue Industrial V/aste Conference, 1972.
5. Graham, R.E., and Dodson, R.E., "Digestion Sludge Disposal at San Diego's Aquatic
Park," presented at the 41st Annual Conference of the Water Pollution Control
Federation, Chicago, Illinois, September 22-27, 1968.
8-3
-------
LIST OF FIGURES AND TABLES - SECTION 8
Figure 8-1 Flash-Drying System with Mixed-Refuse Incinerator
Figure 8-2 Flow Diagram of Waste-Disposal System
Figure 8-3 Typical Section of Multiple Hearth Incinerator
Figure 8-4 Typical Section of a Fluid Bed Reactor (Dorr-Oliver, Inc.)
8-4
-------
_ _
'. r'f/.r.r.'f; i
Cyc I one
Coo Iing-Conveying
Ash
FIGURE 8-1 FLASH-DRYING SYSTEM WITH MIXED-REFUSE INCINERATOR
Refuse
Asn Quench
FIGURE 8-2 FLOW DIAGRAM OF WASTE-DISPOSAL SYSTEM
-------
WASTE COOLING AIR
TO ATMDSPHERB
CLEAN GASES TO
ATMS SPHERE
^INDUCED DRAFT FAN
BYPASS ON POWER OR
STOPPAGE
NERCO-ARCO
CYCLONIC JET
SCRUBBER
TING DAMPER
GREASE
/ SKIMMINGS
MAKEUP WATER
TO DISPOSAL
FILTER CAKE
SCREEN-
INGS &
GRIT
COMBUSTION AIR
/"RETURN
RABBLE ARM DRIVE
ASH PUMP
'ASH HOPPER
COOLING AIR
FIGURE 8-3
TYPICAL SECTION OF MULTIPLE HEARTH INCINERATOR
-------
SIGHT GLASS
EXHAUST
SAND FEED
FLUIDIZBD
SAND
PRESSURE TAP.
ACCESS DOOR
PREHEAT BURNER
THERMDCOUPLE
JLSLUDGB INLET
FLUIDIZING AIR
' INLET
FIGURE 8-4
TYPICAL SECTION OF A FLUID BED REACTOR (DORR-OLIVER, INC.)
------- |