&EPA
United States
Environmental Protection
Agency
Research and Developmum
Municipal Envir
Laboratory
Cincinnati OH 45268
978
Beneficial Disposal
of Water
Purification Plant
Sludges in Waste-
Water Treatment
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
-------
EPA-600/2-78-089
May 1978
BENEFICIAL DISPOSAL OF WATER PURIFICATION
PLANT SLUDGES IN WASTEWATER TREATMENT
by
John 0. Nelson
North Marin County Water District
Charles A. Joseph
Novato Sanitary District
Hovato, California 94947
and
Russell L. Gulp
Culp/Wesner/Culp
Clean Water Consultants
El Dorado Hills, California 95630
EPA Grant No. S-803336-01-0
Project Officer
B. Vincent Salotto
Wastewater Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
-------
DISCLAIMER
This report has been reviewed by the Municipal Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. Approval does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
-------
FOREWORD
The Environmental Protection Agency was created because of increasing
public and government concern about the dangers of pollution to the health
and welfare of the American people. Noxious air, foul water, and spoiled
land are tragic testimony to the deterioration of our national environment.
The complexity of that environment and the interplay between its components
require a concentrated and integrated attack on the problem.
Research and development is that necessary first step in problem solu-
tion, and it involves defining the problem, measuring its impact, and
searching for solutions. The Municipal Environmental Research Laboratory
develops new and improved technology and systems for preventing, treating,
and managing wastewater and solid and hazardous waste pollutant discharges
from municipal and community sources, for preserving and treating public
drinking water supplies, and for minimizing the adverse economic, social,
health, and aesthetic effects of pollution. This publication is one of
the products of that research—a most vital communications link between
the researcher and the user community.
Development of safe and economical methods for disposing of the sludges
produced from wastewater treatment operations is one of the most pressing
environmental needs. This publication provides much needed information on
the feasibility of utilizing an integrated approach to municipal sewage
sludge and solid waste disposal. This report describes a unique method for
the disposal of sludge from a water treatment plant to a wastewater treatment
plant.
Francis T. Mayo, Director
Municipal Environmental
Research Laboratory
iii
-------
ABSTRACT
This report discusses the advantages and disadvantages of the disposal
of waste alum sludge from a water treatment plant to a municipal wastewater
treatment plant and is> submitted in fulfillment of Grant No. 803336-01 by
Novato Sanitary District and North Marin County Water District with techni-
cal help from Gulp,Wesner,Gulp. It covers the period from August, 1974 to
April, 1977.
The study indicated no adverse effects on the sewage treatment process;
however, solids loading to the digester was increased. BOD and COD removals
were not affected; phosphorus removal was slightly improved. Settling
characteristics of sludge in secondary clarification were improved.
IV
-------
CONTENTS
Foreword iii
Abstract iv
Figures vi
Tables vi
Acknowledgements vii
1. Introduction 1
2. Summary of Findings 2
3. Facilities Location and Ownership 4
4. Monitoring, Sampling, and Testing Program 10
5. Results 17
6. Comparison of Results With Those From Other Projects .... 21
Metric Conversion Factors 23
?echnical Report Data 25
-------
FIGURES
Number Page
1 Schematic diagram of water treatment process 5
2 Schematic diagram of wastewater treatment processes 7
TABLES
Number
1
2
3
Stafford WTP Sludge Data Summary Before WTP Expansion ....
Stafford WTP Sludge Data Summary After WTP Expansion
Stafford Water Treatment Plant Annual Production of Alum
Sludae and Potable Water
Page
11
12
13
Summary of Data Collected During Discharge of WTP Sludge
to Sewer 14
Comparison of Average Results of Wastewater Treatment
Plant Operation With and Without Addition of Water
Treatment Plant Sludge 15
Sludge Thickening and Digestion With and Without Alum Sludge . 16
VI
-------
ACKNOWLEDGEMENTS
This project was a cooperative venture which was sponsored by the
following participants:
1. Novato Sanitary District
2. North Marin County Water District
3. U. S. Environnental Protection Agency
Culp, Wesner, Gulp, Clean Water Consultants, El Dorado Hills, California,
furnished technical guidance during the course of the project.
The U. S. Environmental Protection Agency provided grant funds for the
work and technical assistance through its Project Officer, Mr. B. V. Salotto.
The cooperation and contributions of the management and staff of the
districts, especially Mr. William I. Wilson of the North Marin County Water
District, and Mr. Marvin J. Miller of the Novato Sanitary District, are
grate fu1ly acknowledge d.
vii
-------
SECTION 1
INTRODUCTION
The objectives of this study were to determine on a plant-scale basis
the beneficial and adverse effects and the costs of discharging water
treatment process waste .sludges into a sanitary sewer system, thence
through the processes of an activated sludge sewage treatment plant. The
work was carried out cooperatively by the Novato Sanitary District and
the North Marin County Water District, both of Novato, California.
-------
SECTION 2
SUMMARY OF FINDINGS
This study was conducted to determine the beneficial and adverse
effects of discharging alum sludge from a municipal water clarification
plant to a municipal wastewater treatment plant utilizing the activated
sludge process.
Background data was collected in August through December, 1974 and
in July and August, 1975. Data on the effects of alum sludge discharge
was collected from September 9 through November 21, 1975 and May 14
through October 29, 1976.
The source of the alum sludge was the Stafford Water Treatment Plant
operated by the North Marin County (California) Water District. The
clarification-filter plant has a capacity of 6.2 mgd (million gallons per
day)*. Alum sludge from settling basins and filter backwash was discharged
to sanitary sewers which were a part of the collection system of the
Novato Sanitary District. The Novato activated sludge plant had a capacity
of 3 mgd.
Based on information collected during the study, the addition of alum
sludge produced the following loadings on the wastewater treatment plant:
1. 0.25% more flow,
2. 23% more solids (dry basis) to the digesters,
3. 30% more solids to sludge dewatering and disposal facilities.
The study indicates the following changes due to addition of alum
sludge:
1. The efficiency of primary settling decreased about 10%.
2. The efficiencies of COD (chemical oxygen demand) and BOD
(biochemical oxygen demand) removals were not changed.
3. Phosphorus removal was improved about 12%.
4. Scum removal and sludge settling were improved in secondary
clarification.
*For metric units see Conversion Factors at end of report.
-------
5. The capacity of centrifuges for sludge dewatering was increased
by a range of 12 to 50%.
6. Digester gas production increased beyond that attributable to
the greater load of volatile solids applied, presumably due to
improved mixing of digester contents.
7. Drying characteristics of dewatered sludge containing alum were
not determined.
8. A slight improvement in final effluent turbidities was noted.
9. No adverse effects on overall wastewater treatment plant perfor-
mance were observed.
-------
SECTION 3
FACILITIES LOCATION AND OWNERSHIP
The facilities utilized in this study are the Stafford Water Treatment
Plant owned and operated by the North Marin County Water District and the
sewers and Novato Sewage Treatment Plant owned and operated by the Novato
Sanitary District. Both organizations are public agencies but operate in-
dependently from other local agencies and each other. The facilities pro-
vide almost entirely domestic service to areas in and adjacent to the City
of Novato, California.
STAFFORD WATER TREATMENT PLANT
Stafford Water Treatment Plant utilizes the water from Stafford Lake
which derives its supply entirely from runoff from the adjacent 8.4 sq mi
Novato Creek watershed. This supply currently provides approximately one-
third of the domestic water requirement of the City of Novato service area.
The remaining supply for Novato is obtained via pipeline from the Russian
River, about 30 miles to the north of Novato.
The average annual runoff at Stafford Lake is about 4,900 acre-feet;
however, output of the treatment plant has historically been restricted to
the "safe yield" of the source of 2,000 acre-feet/yr. The historical mode
of operation has been to utilize Stafford water throughout the year in
proportion to demand. In the past few years, due to restricted Russian
River pipeline capacity, the mode of operation has become increasingly a
summer peaking operation using Stafford water at higher rates and for
shorter periods during the high-demand summer season.
From the time the Stafford system was constructed until about the time
application for this grant study was submitted, the treatment plant capacity
was 4 mgd, and normal operating rates varied from 2.0 to 3.5 mgd. In order
to accomodate the need for additional summer peaking capacity, an expansion
project was completed in the spring of 1974 which increased plant capacity
to 6.3 mgd. Since that time, the plant has been operated at rates from
2.0 to 6.3 mgd.
In addition to increasing capacity, the expansion project encompassed
process modifications that materially altered the nature of the sludge pro-
duced, the most significant being that lime is no longer fed in the sedi-
mentation basin. The current water treatment process is as follows (refer
to Figure 1): raw water enters the plant and is chlorinated to excess of
breakpoint. Alum is added at the inlet to the sedimentation basin and
recirculated sludge flow downward in the center mixing chamber, then the
-------
LEGEND
Sample point
BACKWASH
WATER
SUPPLY
TANK
T
~1
Raw
water
inlet
line
from
Stafford
lake -v
/ Chlorine -j
Recycled \
backwash water-.
1
Waste sludge
to sanitary sewer
Pump
Filtered w<
Liquid Recycled Powdered
alum-^ sludge—) activated
f~—Lm r—mm^Lm COrbon
1 1 (optional)-}
Polymer f _
FLOC SETTLING 1 "* FILTERS
| £'.-.;::.'J"y£
J 1 1
r 4 II
(U;V;.IU,.M J -^ 9 1 1
1 4
' * Filtered water -
. — Waste sludge . i ...
/^ If Sulfur
(i -* 1 Dioxide
^ >H & NoOHo
1 ^«. Backwash water ~^ . S ^—
# j
I BACKWASH • CLEAR
-*-O-> WATER ^ 1 "WELL
^ p RECOVERY
Pump 1 TANK
1 t Booster ' '
* ^ ,.
I
.J
Pump
distribution system
Figure 1. Schematic diagram of water treatment process
North Marin County Water District
-------
clarified water flows upward in the outer clarifier chamber to overflow
weirs. In the expansion project, plastic tube settlers were installed in
the upper area of the clarifier to increase the allowable flow-through
rate. Polymer is added as a filtration aid in the inlet channel to the
four mixed media filters. Occasionally, granulated activated carbon is
added at the filters to combat taste and odor problems. Filtered water
enters a storage well, .where sodium hydroxide is added to adjust pH and
sulphur dioxide is added to neutralize excess chlorine. The finished
water then flows by gravity, or is pumped, to the distribution system.
The waste materials produced in the treatment process include the
sludge accumulated in the sdeimentation basin and the waste backwash water
from cleaning of the filters. The material of greatest significance to this
study is the WTP sedimentation basin sludge.
The solids content of the WTP backwash water also is of significance,
since occasionally it must be disposed of to waste. Supernatant backwash
water is normally pumped back to the sedimentation basin, but sludge (esti-
mated to be about 2,000 gal/month) collects on the bottom of the recovery
pond and must be disposed of at monthly intervals. In addition, under
relatively rare conditions of extremely difficult to treat lake water
quality, it is desirable to discontinue backwash water recycle and recovery
within the water plant and to waste all backwash water and sludge for a
period of time to straighten out the treatment process. This tactic has
been employed possibly three times in the 23 year operating history of the
WTP, including during the problem period of 1975. No backwash water or
sludge was discharged to the sewers prior to this study.
Until 1972, plant wastes were disposed of by discharging to Novato
Creek below the WTP. Since that time, WTP sludge has been disposed of by
spray irrigation on the hillside above the plant. Some problems have been
experienced with the spraying operation but in general it has been a satis-
factory method. The spray facilities are kept operable so that discharge
to the sewer system can be interrupted as may be required by the Sanitary
District.
SANITARY DISTRICT FACILITIES
The water treatment sludge discharges to the sanitary sewer system
approximately 4.5 sewer miles from the Novato sewer treatment plant.
(Travel time of the sludge in the sewer system as determined by test is
about two hours.) The Novato sewage treatment plant serves approximately
65% of the Novato service area. It has a current design capacity of 3 mgd
and an average dry weather flow of 2.5 mgd.
The current sewage treatment process is as follows (refer to Figure 2):
raw sewage and septic tank dumpings are pumped through the influent pump
station to the primary clarifier. From the primary clarifier, part of the
flow circulates through the biofilter, then back through the primary clari-
fier. The remaining flow and that recirculated after cycling through the
biofilter passes to the hydraulic jump aerators (not currently in use),
-------
LEGEND
Raw sewage flow
containing
WTP alum sludge
O
•*•» Solids flow
—^ Liquid flow
Sample point
SLUDGE
MIXING /re
TANKS
SECONDARY
CLARIFIER
LAND
SPREADING
OUTFALL
Figure 2. Schematic diagram of wastewater treatment processes
Novato Sanitary District
-------
then on to the activated sludge aeration tanks. Either aeration tank may
be used alone, or they can be operated in series or in parallel. Effluent
from the activated sludge tanks goes to the secondary clarifier, then to
the chlorine contact pond, then to the effluent pond, then on out the
outfall.
Primary clarifier sludge goes first to the sludge thickener. Part of
the secondary clarifier sludge is recirculated to the aeration tanks, and
the remaining excess goes to the sludge thickener. From the sludge
thickener, sludge is pumped to the digester and dewatered by centrifuging
or by drying in drying beds. Dewatered sludge is either spread directly
on adjacent fields or is sorted on the premises for subsequent spreading.
Supernatant from the sludge lagoon is recirculated back to the raw
sewage. Scum skimmed from the primary and secondary clarifiers goes
directly to the digester.
MODE OF COOPERATION BETWEEN THE TWO PLANTS
The original approach to accomplish study objectives was to construct
the facilities required to deliver the water treatment sludge to the sewer
system, to conduct a comprehensive sampling and testing program at pertin-
ent process locations (a) for three months prior to discharge of water
treatment sludge to the sewage system, and (b) for two months subsequently
during discharge of water treatment sludge to the sewer system. Then, to
analyze and evaluate the sample and other pertinent data and write a report
on the study and findings relative to the above stated objectives. The
entire study was to be completed within one year. The initial grant
authorization was for the period August 12, 1974 to August 11, 1975.
The initial pre-testing program was conducted during the period August
through December, 1974. An additional sludge dewatering background testing
program was conducted in July and August, 1975. Discharge of WTP (water
treatment plant) sludge was delayed by major process modifications in prog-
ress at both the WTP and the STP (sewage treatment plant), delays in con-
struction of the system for WTP sludge discharge to the sewer, and the
need to do additional background testing. Discharge to the sewer system
and additional sampling and testing were conducted from September 9 through
November 21, 1975, and from May 14, 1976 through October 29, 1976.
Previously, the manager of the Novato Sanitary District had requested
a change in plan to extend the study to encompass two periods of WTP sludge
discharge during the summer of 1975 and again through the summer of 1976.
(It was not believed that winter testing would provide meaningful data,
due to high infiltration in the sewage system. Also, the WTP is shut down
most of the winter.) Preliminary evaluation and report would be made at
the end of the first full cycle of testing, then any needed adjustments
would be made in the second cycle and a final report written upon comple-
tion of the second cycle. This plan was agreed to by the other parties
concerned and EPA subsequently issued a Grant Amendment changing the project
period to August 11, 1974 through April 11, 1977.
8
-------
For purposes of the Grant, the study is now complete, and the results
are reported herein. The Water District and the Sanitary District will
continue work on their own on certain aspects of the study, principally
on those items which bear on proper charges for acceptance and processing
of the alum sludge from the water treatment plant at the wastewater treat-
ment plant.
-------
SECTION 4
MONITORING, SAMPLING, AND TESTING PROGRAM
DATA ON PRODUCTION OF POTABLE WATER AND ALUM SLUDGE
Tables 1, 2, and 3 contain information on WTP production of potable
water and alum sludges. Table 1 summarizes data prior to WTP expansion.
Table 2 shows the data after WTP expansion. The volume data for early
1975 are not representative of normal conditions, due to problems that
were being experienced with the polymer being used'as a filter aid, and
unusually difficult raw water quality conditions. Table 3 presents data
on annual production of alum sludge and potable water under 1976 normal,
and maximum operating conditions at the Stafford Water Treatment Plant.
PRE-DISCHARGE TESTING
In order to determine the effects of the discharge of alum sludge from
the water treatment plant upon wastewater treatment plant operations, it
was necessary to collect background data at the wastewater treatment plant
prior to discharge of alum sludge. This was done for a total of nine months
in 1974, 1975, and 1976. Sampling points for liquid processing are shown
on Figures 1 and 2.
Pre-discharge testing of solids thickening, digestion, and dewatering
at the wastewater treatment plant was also conducted over a nine-month
period in 1974, 1975, and 1976.
TESTING DURING DISCHARGE OF ALUM SLUDGE
Alum sludge was discharged to the wastewater treatment plant for a
period of about six months in 1975 and 1976. Additional liquids and
solids testing was done at this time.
The testing program is detailed in Table 4.
In January, 1976, testing of the effects of the WTP sludge on the cen-
trifuge dewatering process was undertaken. Removal of STP sludge from the
sludge lagoon is a batch process: it typically takes approximately six
months with STP sludge only to fill the lagoon with digested sludge. The
lagoon had been emptied prior to commencement of discharge of WTP sludge
on September 9 and was not full when discharge ceased. When it filled in
January, it had taken just four months to fill and the lagoon contained
about 32% sludge containing WTP sludge. Ordinarily, this batch would have
been disposed of by dumping it directly on the drying beds which is much
10
-------
Table 1. STAFFORD WTP SLUDGE DATA SUMMARY BEFORE WTP EXPANSION
1972
Sludge volume,
gal/day
Range
Mean
October
5,300-13,400
9,700
November
11,000-14,400
12,600
March
7,600-17,800
11,000
1973
April
9,200-18,500
13,700
May
0-15,000
11,300
Sludge solids, %
Daily plant
mg
Range
Mean
output ,
Range
Mean
1.03-2.16
1.45
1.58-2.27
1.97
-
0.36
1.74-2.20
2.06
0.4-1.49
1.16
1.7-2.01
1.83
0.59-1.49
0.85
1.53-2.07
1.86
0.54-1.20
0.91
1.71-3.79
2.64
No of days of plant
operation 25.4 12.3 30.2 28.3 30.3
-------
Table 2.
STAFFORD WTP SLUDGE DATA SUMMARY AFTER WTP EXPANSION
Daily sludge volume,
Month
JUNE,
JULY,
AUG. ,
SEPT.
OCT. ,
NOV. ,
APR. ,
MAY,
JUNE,
JULY,
AUG. ,
1974
1974
1974
, 1974
1974
1974
1975
1975
1975
1975
1975
DISCHARGE
SEPT.
OCT. ,
NOV. ,
MAY,
JUNE,
JULY,
AUG. ,
SEPT.
OCT. ,
, 1975
1975
1975
1976
1976
1976
1976
, 1976
1976
Range
1,700-22,700
1,400-37,500
2,200-16,100
2,000-20,200
1,800- 8,200
3,800- 8,600
6,600-37,000
6,100-62,500
10,900-69,600
6,200-98,200
4,700-28,900
TO SEWER 9/5/75
4,100-16,900
8,100-11,700
4,300-14,000
7,600-20,800
1,300-73,000
3,300-12,100
600-46,400
1,600-16,700
3,400-15,000
gal
Mean
10
8
5
3
3
2
12
24
34
17
11
,600
,900
,500
,400
,000
,300
,400
,800
,200
,100
,800
TO 11/26/75
7
6
9
13
22
7
5
8
9
,900
,700
,700
,100
,200
,100
,900
,600
,200
% %
Solids Volatile
in in
sludge solids
AND 7/17/76 TO 10/29/76
1.62 23.5
1.58 17.6
0.99 22.2
0.63 27.9
2.31 19.9
5.52 17.6
2.41 20.5
2.66 17.1
Daily plant
M.G.
Range
2
2
1
2
2
1
0
1
2
2
2
0
0
.96-4.
.40-5.
.44-4.
.37-3.
.13-2.
.25-2.
.67-1.
.08-6.
.69-6.
.13-5.
.97-5.
.39-3.
.39-3.
21
06
23
27
74
42
51
27
40
97
99
41
01
output,
Mean
3.
4.
3.
2.
2.
2.
1.
3.
4.
3.
3.
2.
2.
2.
2.
3.
3.
2.
2.
2.
71
19
02
69
36
18
32
36
67
54
61
79
37
29
24
59
59
33
48
95
No.
days
plant
op.
30
31
30
29
30
15
24
31
30
31
31
29
12
21
19
30
15/16
31
30
29
-------
Table 3. STAFFORD WATER TREATMENT PLANT ANNUAL PRODUCTION OF ALUM SLUDGE
AND POTABLE WATER
Month
JAN
FEE
MAR
APR
MAY
JUNE
JULY
AUG
SEPT
OCT
NOV
DEC
Water
output ,
acre- ft
0
0
0
0
129
326
326
212
225
259
0
0
1976
Sludge ,
gal
-
-
-
-
250,000
665,000
299,000
126,000
257,000
266,000
-
-
Solids,
Ib
-
-
-
-
21,000
34,100
61,500
63,500
62,600
60,300
-
_
Water
output ,
acre- ft
0
0
120
180
250
300
300
300
250
180
120
0
Normal
Sludge ,
gal
-
-
240,000
432,000
800,000
600,000
270,000
180,000
225,000
162,000
108,000
_
Solids,
Ib
-
-
30,000
36,300
67,200
50,400
56,700
75,600
47,300
20,400
13,600
_
Water
output
acre- ft
400
400
400
400
400
400
400
400
400
200
200
_
Maximum
Sludge ,
gal
800,000
800,000
800,000
960,000
1,280,000
800,000
360,000
240,000
360,000
180,000
180,000
_
Solids ,
Ib
168,000
134,400
100,800
80,600
107,500
67,200
75,600
100,800
75,600
22,700
22,700
_
Total
1,477
1,863,000 303,000
2,000
3,017,000 397,500
4,000
6,760,000 955,900
-------
TABLE 4. SUMMARY OF DATA COLLECTED DURING DISCHARGE OF WTP SLUDGE TO SEWER
*Loc
Ref
1
2
3
4
5
7
8
9
10
11
12
13
Test description
WTP sed. basin sludge
discharge record -
volume flow.
discharge periods
Solids data - total.
volatile, fixed.
settleable; settle-
able supernatant-
suspended solids.
volatile solids, COD
WTP washwater recovery
pond residue
Discharge record.
as above
Solids data, as above
Sewer inspection for
deposition
STP influent
Suspended solids,
settleable solids.
pH, BOD
Flow record
COD and PO4
SPT primary clarifier
effl. suspended solids.
pH, BOD
STP final effluent
COD and PO4
STP primary sludge
Total solids, pH,
volatile solids
Flow record
STP thickener effluent
Total solids, pH,
volatile solids
Flow record
STP primary digester effl.
Total solids, pH, alka-
linity, volatile acids,
volatile solids
Flow record
Gas production
STP sludge lagoon effluent
appearance, consistency.
pumpability
STP sludge centrifuge
effl. gen. character-
istics
STP sludge drying bed effl.
appearance, consistency,
removability
Background
Type and No. of
frequency samples
Continuous
Composite
twice
weekly
—
—
Visual 1
check
Composite
twice 17
monthly
Continuous
mo. comp. 4
Composite 36
twice
weekly
Composite 12
monthly
Grab, 49
twice
weekly
Continuous
Grab, 49
twice
weekly
Continuous
Grab, 49
twice
weekly
Continuous
Visual
Grab,
various
testing
Test
period
June 1974
on
Jan Feb
1976
Fall 1974
Fall 1974
Nov Dec 1975
Jan Feb 1976
12/74, 1/76
2/76
Fall 1974
Jan Feb 1976
Dec 1974
Nov Dec 1975
Jan Feb 1976
Fall 1974
11/75, 2/76
Fall 1974
Fall 1974
12/75, 2/76
Plant record
Plant record
July Aug 1975
Summer 1976
July Aug 1975
Summer 1976
None
Discharge
Test
period #1
Fall 1975
Fall 1975
None
None
None
Fall 1975
f
Fall 1975
Fall 1975
Fall 1975
Fall 1975
Fall 1975
Continuous
Fall 1975
Continuous
Fall 1975
Continuous
Continuous
Winter 1975
Winter 1975
None
testing
Test
period 82
Summer 1976
Summer 1976
Summer 1976
Summer 1976
Summer 1976
Summer 1976
Summer 1976
Summer 1976
Summer 1976
Summer 1976
Summer 1976
Summer 1976
Summer 1976
Fall 1976
Fall 1976
None
* For location of sampling points, see Figure 2.
14
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cheaper than centrifuging. However, to see what effects the partial load
of WTP sludge had, centrifuging was conducted for a short while.
TEST PROGRAM OBSERVATIONS
Factors under evaluation in the test program include the effects of
receiving alum sludge from the water treatment plant at the wastewater
treatment plant on:
1. Efficiency of primary settling
2. Efficiency of COD removal
3. Efficiency of phosphorus removal
4. Increased sludge production
5. Handling and dewatering characteristics of waste sludge
6. Overall wastewater treatment plant performance
7. Charges for processing alum sludge
Table 5 presents a summarized comparison of the results of wastewater
treatment plant operation with and without the addition of alum sludge dis-
charged from the water treatment plant. Table 5 gives the average values
for all background data and average values for all data during alum sludge
di s charge.
Table 6 provides two comparisons of sludge data with and without alum
sludge.
TABLE 5. COMPARISON OF AVERAGE RESULTS OF
WASTEWATER TREATMENT PLANT OPERATION
WITH AND WITHOUT ADDITION OF WATER TREATMENT PLANT SLUDGE
Flow, mgd
BOD, mg/1
COD, mg/1
PO4, mg/1
SS, mg/1
pH
BOD, mg/1
SS, mg/1
PH
Background data
INFLUENT
2.46
199
560
5.6
257
7.06
PRIMARY EFFLUENT
113
101
7.4
Discharge data
2.21
297
858
9.0
369
7.2
114
112
7.3
FINAL EFFLUENT
COD, mg/1 99 98
P04, mg/1 4.5 4.0
15
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TABLE 6. SLUDGE THICKENING AND DIGESTION
WITH AND WITHOUT ALUM SLUDGE
Background data
1974 1975
Discharge data
1975-76 1976
T.S.,
V.S. ,
PH
G.P.D.
T.S., %
V.S., %
PH
T.S., %
V.S., %
PH
Alkalinity, mg/1
Volatile Acids, mg/1
PRIMARY SLUDGE
0.07 0.26 0.84 0.54
60.0 62.2 59.4 50.6
7.6 7.3 7.3 7.1
THICKENER SLUDGE
14,448 14,175 22,670 27,509
3.26 3.89 2.81 2.89
81.5 81.5 66.1 61.9
6.13 6.0 6.18 6.0
PRIMARY DIGESTER
1.20 1.61 1.54 1.75
79.2 61.0 59.0 50.7
7.23 7.22 7.23 7.06
3,310 3,681 2,118 2,761
244 265 196 210
16
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SECTION 5
RESULTS
Test results and observations during the course of the project indicate
the following:
EFFICIENCY OF PRIMARY SETTLING
For all of the background (no alum sludge discharge) data collected,
the average SS (suspended solids) concentration in primary effluent was
101 mg/1. When alum sludge was entering the wastewater treatment plant,
the average SS content (excluding atypical readings) in primary effluent
was 112 mg/1. Thus, the clarity of primary effluent was slightly better
without addition of alum sludge as measured by the SS test.
EFFICIENCY OF COD REMOVAL
Plant effluent COD values with and without alum sludge addition
averaged 99 and 98 mg/1 respectively. Thus, the COD value during alum
sludge addition was unchanged.
EFFICIENCY OF PHOSPHORUS REMOVAL
Average phosphate concentrations in plant effluent during background
testing was 4.5 mg/1 and during the test period with alum sludge addition
was 4.0 mg/1. There appeared to be a slight benefit in phosphorus removal
from alum sludge addition.
INCREASED SLUDGE PRODUCTION
The data from water treatment plant operations which are most appli-
cable to estimating quantities of alum sludge to be discharged to the
wastewater treatment plant are the figures collected since the revised
and expanded water treatment plant was placed into operation in June, 1974,
which are (see Table 2) :
WATER TREATMENT PLANT
Mean daily sludge volume, gallons 11,770.
Sludge, percent solids 2.35
Sludge, percent volatile solids 17.6
Dry solids, mean pounds per day 2,304.
Operation of WTP, days per year 194.
Sludge volume, million gallons/year 2.28
Dry solids, tons/year 223.
17
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Background information collected at the wastewater treatment plant
between 7-30-74 and 2-18-76 follows:
WASTEWATER TREATMENT PLANT
Plant flow, average, mgd 2.46
Plant flow, million gallons per year 909.
Average SS, mg/1 257
Average SS, Ibs/mg 2,141.
Average SS, tons/year (dry basis) 977.
Based on the above figures, on an annual basis the discharge of alum
sludge to the wastewater treatment plant will increase the solids (dry
basis) to the digester by 223 T 977 = 23%, and will increase the flow re-
quiring secondary treatment by 2.28 T- 909 = 0.25%.
Following digestion, the relative contribution of solids to dewater-
ing and disposal by the WTP and WWTP differ from the figures given above
for digester influent because of the higher content of non-volatile solids
in the WTP alum sludge. From the data, the volatile solids in the WTP and
WWTP sludges are 21% and about 61 respectively. If a 50% average reduction
in volatile solids in each case occurs during anaerobic .digestion, then the
discharge of alum sludge to the WWTP will increase the dry solids to de-
watering and disposal by: 223 (1.00-.5x.21) ^ 977 (1.00-.5x.61) = 223 x
.895 v 977 x .695 = 200 v 679 = 29.4%.
In summary, based on this preliminary information, it appears that
alum sludge discharge to the WWTP increases:
1. Hydraulic flow through the primary and secondary liquid
treatment processes by 0.25%,
2. Solids to the anaerobic digesters by 23% (dry basis), and
3. Solids to the lagoon sludge dewatering, and disposal facili-
ties by 29.5% (dry basis).
As percentages of the total increased load, the figures are 0.25%,
18.5%, and 22.8% respectively. 2.28 T 2.28 + 909 = 0.25%: 223 + 223 +
977 = 18.6%: and 200 T 200 + 679 = 22.8%.
HANDLING AND DEWATERING CHARACTERISTICS OF WASTE SLUDGE
Three important measures of these characteristics are: (1) the
amount of mixing of lagoon contents required to secure a homogenous mix-
ture of sludge solids and liquor in the centrifuge feed, (2) the percent
solids in the centrifuge sludge cake, (3) the clarity of the centrate as
measured by percent solids in the centrate, and (4) the capacity of the
centrifuge to process the different sludges in terms of pounds per hour.
These characteristics with and without alum sludge are evaluated on
the basis of two batches of sludge in the lagoons. One batch contained
about 30% alum sludge and the other about 60% alum sludge.
18
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The preliminary results are: (1) no serious adverse effects have been
observed; (2) it appears that less stirring and recirculation of the lagoon
contents are required to obtain a homogenous sludge feed to the centrifuge,
which is an advantage; (3) the average total solids content in the centri-
fuge cake was 14.80% without alum sludge and was 14.93% with a partial
load of alum sludge in the lagoon (this difference is not considered sig-
nificant) ; and (4) the average total solids in the centrate decreased from
0.56% to 0.51% when a partial load of alum sludge was present. Again, the
difference probably is not significant.
One important difference noted in the centrifuging operations was the
fact that the yield increased from 600 to 800 pounds per hour for sewage
sludge to about 900 pounds jper hour for the alum sludge-sewage sludge mix-
ture. The drying characteristics of the sludge containing WTP alum sludge
are important, and have yet to be determined.
OVERALL WASTEWATER TREATMENT PLANT PERFORMANCE
As reported under Items 1, 2, and 3 above, the addition of alum sludge
to the WWTP flow had a slight detrimental effect on primary settling; a
slight beneficial effect on phosphorus removal; and had no apparent effect
on COD removal.
However, the WWTP operators report that visual observations to date
indicate that there may be some improvement in the settling characteristics
of activated sludge during alum sludge discharge to the plant. There was
an apparent reduction .of scum problems in the secondary clarifier which
allowed a higher mixed liquor suspended solids concentration to be carried
in the activated sludge aerators. This could provide better BOD removal,
greater ease of operation, and improved process control.* in primary
effluent, the background BOD averaged 113 mg/1, and during alum sludge dis-
charge averaged 114 mg/1 which indicates no effect on BOD removal.
With addition of alum sludge to the WWTP, an increase in digester gas
production beyond that generated by the increased load of volatile solids
applied. The speculation is that this was due to easier mixing of digester
contents.
No adverse effects on overall wastewater treatment plant performance
were observed during the study. The greater solids load reduces time of
solids in the digester, but no adverse effects have been detected to date.
CHARGES FOR PROCESSING ALUM SLUDGE
If alum sludge is accepted on a permanent basis at the WWTP, then
there will be a need to arrive at a fair and equitable annual charge for
receiving and processing the wastes.
*However, these effects could have been caused by something other than
the addition of alum sludge and further observations are required.
19
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It would seem that a minimum charge might be the incremental costs
involved, and the maximum charge might be the pro-rata costs involved.
As previously discussed, the three principal effects of the alum
sludge on wastewater treatment plant processing and costs are 0.25% in-
creased plant flow; 23% more solids to digestion; and 29.5% more sludge
solids to the lagoon, centrifuge, and disposal. It is assumed that the
annual charge would include portions of the annual amortization of capital
(construction) costs and interest in addition to a share of the annual
O&M (operation and maintenance) costs.
On the basis of incremental cost (minimum charge), the annual charge
would consist of the difference in cost between operation of the WWTP with
and without the alum sludge load, plus the difference between the annual
amortization costs for appropriate plant unit process capacities with and
without the greater load.
On a pro-rata basis (maximum charge), the annual charge would be based
on the construction and use of 0.25% of the primary and secondary liquid
processing capacity; plus 18.6% of digester costs; plus 22.8% of the
sludge lagooning, centrifuging, and disposal costs. The percent figures
are preliminary and would be appropriately adjusted after additional
test data are collected.
The actual capital expenditures and interest rates for plant construc-
tion should be used. If the records of actual construction cost are not
broken down into unit costs for the various plant processes involved, then
they can be accurately estimated as a percent of the actual total plant
construction cost in accordance with current costs for constructing simi-
lar unit processes in other plants of the same capacity. Likewise, if
WWTP cost accounting for annual O&M does not break costs down into figures
for individual processes affected by the alum sludge load, then the per-
cent of the total actual O&M costs assignable to the unit processes can be
estimated rather accurately from published EPA cost curves derived from
other plants of the same size. In sharing capital costs, Federal and
State grants must be considered.
20
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SECTION 6
COMPARISON OF RESULTS WITH THOSE FROM OTHER PROJECTS
OVERALL WASTEWATER TREATMENT PLANT PERFORMANCE
During this study no adverse effects on overall wastewater treatment
plant performance were identified. In this regard the findings agree
with those of Hsu and Pipes^', and Salotto, Farrell, and Dean^ '.
Zakrewski(3) reported a slight improvement in secondary settling of
activated sludge.
EFFICIENCY OF PRIMARY SETTLING
The data from this project show a slight (but insignificant) decrease
in the overall efficiency of primary settling during the addition of water
treatment plant sludge, but operator observations indicate that the sett-
ling of waste activated sludge solids discharged to the primary basin may
have improved with elimination of some scum problems in the secondary
clarifier. The work of Zakrewski^3' confirms the negligible effect at
low (less than 5%) water works sludge proportions, but at 8% WTP sludge
shows increases in removals in primary sedimentation as follows:
SS = 12.4%
BOD5 = 19.9%
COD = 26.2%
Salotto, Farrell, and Dean^2) reported improved settling of waste
activated sludge in the primary tank with addition of alum sludge. At
Tampe, Wilson, et al^ report a 33% increase in suspended solids removal
(1) Hsu, D.Y. & Pipes, W.O. The Effects of Aluminum Hydroxide on Primary
Wastewater Treatment Process. Presented at the 27th Purdue Industrial
Waste Conf., Purdue University, Lafayette, Ind. (May, 1972).
(2) Salotto, B.V., J.B. Farrell, and R.B. Dean. The Effect of Water-
Utility Sludge on the Activated Sludge Process. JAWWA 65(6), p.
. 428. June, 1973.
(3) Zakrzewski, Dr. J. Effect of Water Work's Sludge on Wastewater
Treatment. University of Warsaw.
(4) Wilson, T.E., R.E. Bizzarri, T. Burke, P.E. Langdon, Jr., and C.M.
Lawson. Upgrading Primary Treatment With Chemicals and Water Treat-
ment Sludge. JWPCF 47 (12) , p. 2820. December, 1975.
21
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at comparable flow conditions with addition of 30 to 60 mg/1 of alum
sludge and 0.7 mg/1 of anionic polymer.
EFFICIENCY OF COD REMDVAL
During this study, the COD removals were unaffected by alum sludge
addition. On the other hand, Zakrzewski^' and Hsu and Pipes reported
increased COD removals from addition of alum sludge.
EFFICIENCY OF PHOSPHORUS REMOVAL
The results of this study show a slight increase in phosphorus re-
moval during addition of water treatment plant sludge. Salotto, et al^
reported no effect on phosphorus removal which they regarded as an un-
expected result as they thought phosphorus removal might be improved.
INCREASED SLUDGE PRODUCTION
In this study the production of sludge was increased during addition
of alum sludge. The reports of Salotto, et al^) f 3^3 jjsu an^ pipes
are in agreement with this.
EFFECTS ON SLUDGE CHARACTERISTICS
The percent volatile solids in mixed sludge is reduced by the addi-
tion of alum sludge to the wastewater treatment plant. This is uniformly
shown by the results of this study and by Salotto, et al'^) and Hsu and
Pipes' *•'.
During this study it appeared that the handling and dewatering
characteristics of waste sludge were not greatly changed except that:
(1) the combined sludge was easier to mix, (2) the centrifuge yield in-
creased from a range of 600 to 800 pounds per hour without alum sludge
to 900 pounds per hour with alum sludge present, and (3) the drying time
of mixed sludge was not determined.
22
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METRIC CONVERSION FACTORS
Length
1 inch =
I foot
1 statute mi =
1 centimeter =
1 meter =
1 kilometer =
2.540 centimeters
0.3049 meters
1.60935 kilometers
0.39370 inches
3.28 feet
3280.83 feet = 0.62137 mile
Area
1 square centimeter
1 square meter
1 hectate
1 square kilometer
1 square inch
1 square foot
1 square yard
1 acre
1 square mile
Volume
1 cu in
1 cu ft
1 cu yd
cu cm
cu m
1
1
1 liter
1 milliliter
1 U.S. liquid ounce
1 U.S. liquid quart
1 U.S. liquid gallon
Weight
1 gram
1 kilogram
0.155 square inch
10:76 square feet
1.196 square yards
2.47 acres
0.386 square mile
6.45 square centimeters
0.0939 square meter
0.836 square meter
0.405 hectare
2.59 square kilometers
16.387 cu cm
0.0283 cu m
0.765 cu m
0.0610 cu in
35.3 cu ft
1.308 cu yds
61.023378 cu in
0.035314 cu ft
0.264170 U.S. liquid gallon
0.2201 imperial gallon
0.0338 liquid ounce
29.57 milliliters
0.946 liter
3.785 liters
15.43 grains
0.0353 avoirdupois ounce
2.205 avoirdupois pounds
23
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METRIC CONVERSION FACTORS
(continued)
Weight (continued)
1 metric ton = 0.984 gross or long ton
= 1.102 net or short tons
1 avoirdupois ounce = 28.35 grams
1 avoirdupois pound = 0.4536 kilogram
Flow
= 1.547 cfs = 43.8 liters per second
= 28.32 Lps
24
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-78-089
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
BENEFICIAL DISPOSAL OF WATER PURIFICATION PLANT
SLUDGES IN WASTEWATER TREATMENT
5. REPORT DATE
May 1978 [Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
John 0. Nelson, Charles A. Joseph, and
Russell L. Gulp
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
North Marin County Water District
P. 0. Box 146
Novato, California 94947
10. PROGRAM ELEMENT NO.
1BC611B
11. CONTRACT/GRANT NO.
803336-01-4
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
Municipal Environmental Research Laboratory—Gin. ,OH
Office of Research and Development
U. S. Environmental Protection Agency
Cincinnati, Ohio 45268
Final 8/74 - 4/77
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES Report written by Culp/Wesner/Culp under agreement with North
Marin County Water District and Novato Sanitary District
Project Officer: B. Vincent Salotto 513/684-7667
16. ABSTRACT
This report discusses the advantages and disadvantages of the disposal of
waste alum sludge from a water treatment plant to a municipal wastewater treatment
plant and is submitted in fulfillment of Grant No. 803336-01 by Novato Sanitary
District and North Marin County Water District with technical help from Gulp,
Wesner, and Gulp. It covers the period from August 1974 to April 1977.
The study indicated no adverse effects on the sewage treatment process;
however, solids loading to the digester was increased. BOD and COD removals were
not affected; phosphorus removal was slightly improved. Settling characteristics
of sludge in secondary clarification were improved.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Sludge, Sludge Disposal
Alum Sludge,
Sludge Treatment
Wastewater Sludge
Waterworks Sludge
13B
18. DISTRIBUTION STATEMENT
Release to public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
33
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
25
U S. GOVERNMENT PRINTING OFFICE: 1978—757-140/1332
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