WATER POLLUTION CONTROL RESEARCH SERIES • ORD-1
Joint Municipal
and
Semichemical Pulping
Waste Treatment
U.S. DEPARTMENT OF THE INTERIOR • FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
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WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Reports describe the
results and progress in the control and abatement of pollution in
our Nation's Waters. They provide a central source of information
on the research development and demonstration activities in the
Federal Water Pollution Control Administration, in the U. S. Dept.
of the Interior, both inhouse and through grants and contracts with
Federal, State and local agencies, research institutions, and indus-
trial organizations. The exchange of such data should contribute
toward the long-range development of economical, large-scale manage-
ment of our Nation's water resources.
\ Water Pollution Control Research Series will be distributed
to requesters as supplies permit. Requests should be sent to the
Industrial Pollution Control Branch, Office of Research and Develop-
ment, Federal Water Pollution Control Administration, Washington,
B.C. 202^*2.
ORD-1
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JOINT MUNICIPAL AND SEMICHEMICAL PULPING
WASTE TREATMENT
A PILOT PLANT STUDY EVALUATING COMBINED TREATMENT OF DOMESTIC
SEWAGE AND WEAK SEMICHEMICAL PULPING AND PAPERMAKING WASTES
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
DEPARTMENT OF THE INTERIOR
By
THE CITY OF ERIE, PENNSYLVANIA
AND
HAMMERMILL PAPER COMPANY
PROGRAM NO. 11060 EOC
GRANT NO. WPRD-223-01-68
JULY,1969
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FWPCA Review Notice
This report has been reviewed by the Federal
Water Pollution Control Administration and
approved for publication. Approval does not
signify that the contents necessarily reflect
the views and policies of the Federal Water
Pollution Control Administration.
ii
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ABSTRACT
A * ^e ?*? °f Eri6' Pennsylvania and Hammermill Paper Company
made a study of the joint treatment of domestic sewage and pulp anT
paper-making wastes A pilot plant was constructed and operated in a
in the £L^™rn ? d exp!riments' Supplemental studies were conducted
*"1" including the °perati°n °f
It was demonstrated that a joint treatment plant could
effectively treat a mixture of domestic sewage and pulp and paper
mill wastes from Hammermill's Erie Division. A full-scale loint
treatment plant should obtain a BOD removal of approximately 90% in
a^v m°np^ "J l°?-85* ln Wlnter m0nths« Pri™ry treatment should
SilT ? ? red»ction in BOD ™* * ^ reduction in suspended solids.
f l±sol°rf miXeVastes bv the activated sludge process will require
a long solids aeration period and a relatively low BOD to volatile
solids loading to avoid high sludge volume indicies. The activated
sludge process does not reduce the color of the mixed wastes and the
final Affluent will have about 1»0 mg/1 of suspended solids. Se
chlorine demand of the final effluent averaged over 60 mg/l. A
NH3-C12 mixture added at a level of 2.6l Ppm NH, and 15-17 ppm C1P
loOO100°S?e ^ S disinfectant with colifo™ Counts generSly below
This report was submitted in fulfillment of Research and
Development Grant Number WPRD-223-01-68 between the Federal Water
Pollution Control Administration and the City of Erie, Pennsylvania.
Key Words:
Pilot Plants - Pulp Wastes - Municipal Wastes - Sewage Treatment -
Activated Sludge - Sludge Disposal - Oxygenation - Disinfection -
Annual Costs.
iii
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CONTENTS
Section Page
Abstract iii
Contents iv
Tables v
Figures vi
I Conclusions and Recommendations 1
II Introduction 5
III Background 1
IV Description of Pilot Plant 13
V Objectives 19
VI Primary Treatment 21
VII Activated Sludge Treatment 27
VIII Sludge Disposal 67
IX Disinfection 87
X Supporting Studies 93
XI Significance for Design 99
XII Costs 111
XIII Acknowledgments 113
XIV References 115
XV Appendices 119
iv
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TABLES
Ho. Page
I Characteristics of Hammermill Wastes 11
II Primary Treatment 22
III Calculation of K2 Values ^5
IV Oxygen Uptake Determinations 53
V Calculation of Average Oxygen Needs 55
VI Calculation of Buildup of Excess Biological Cell
Material 58
VII Sludge Concentration with Flotation 69
VIII Vacuum Filtration Studies 71
IX Sludge Dewatering Centrifuge Tests 7^
X Performance of Pilot Digesters 79
XI Analysis of Sludge Cake 85
XII Chlorine Levels Required to Bring Total Coliform
Counts Below 1000 per 100 ml in Final Effluent 88
XIII Treatment of Joint Effluent with Premixed NH3-C12 90
XIV Effect of Time on Disinfection 92
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FIGURES
No. Page
1 Pilot Plant Waste Treatment Flow Dia.gram 1**
2 Pilot Plant - General View 15
3 Pilot Plant - At Operating Level l6
U Lbs. BOD Applied per 100 Lbs. TSS Under Air 28
5 Plot of BOD Removal vs. BOD Loading per 100 Lbs. VSS 29
6&6A Plot of Various Loading Parameters for Activated
Sludge Process 31 and 31*
7 Plot of BOD Remaining vs. MLVSS and Time in Aeration
Tanks for Conventional and Sludge Reaera,tion ^7
8 Plot of BOD Remaining vs. MLVSS and Time in Aeration
Tanks ^9
9 Plot of BOD Remaining vs. MLVSS and Time in Aeration
Tanks for Various Operating Temperatures 50
10 Plot of Volatile MLGS vs. BOD Loading Divided by
Aeration Time 6l
11 Plot of Final Effluent SS vs. SV1 63
12A,B&C Sludge Digestion Loading and Reduction Curves 75
13 Pilot Sludge Digesters 77
lU Plot of Percentage TS with Time for the Pilot Plant
Sludge Digesters 80
15 Plot of Volatile Solids with Time for the Pilot
Plant Sludge Digesters 8l
16 Plot of Alkalinity with Time for the Pilot Plant
Sludge Digesters 82
17 Plot of pH with Time for Pilot Plant Sludge
Digesters 83
VI
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I
CONCLUSIONS & RECOMMENDATIONS
The operation of the pilot plant, the Hammer-mill bench plant
and the associated studies demonstrated that a joint treatment plant
could effectively treat a mixture of domestic sewage from the City of
Erie and pulp and paper mill wastes from Hammermill's Erie division.
A BOD removal of approximately 9®% during summer months when mixed
liquor temperatures are 70° F. or higher and 80% to 85% reduction in
winter months when mixed liquor temperatures are around 50° F. should
be attained by a plant treating mixed wastes.
Combined neutralized Hammermill waste mixed with sewage in
1 to 1 proportions is effectively treated by primary sedimentation.
Treatment of Hammermill waste by itself was less effective. Pilot
plant primary treatment removed j6% of the suspended solids in mixed
wastes and reduced BOD and COD by 25^-30$. The high concentration of
soluble COD and BOD kept the percentage reduction low. The pilot plant
was operated at a constant flow. Flow fluctuations in a joint treat-
ment plant would make primary treatment less effective but reductions
of at least 25% of the BOD and 60% of suspended solids should be ob-
tained. Sludge from the primary treatment plant contained 1.5$ solids,
substantially less than expected in normal primary municipal solids.
The pilot plant primary sludge averaged 80% volatile, while municipal
primary sludge is normally less than 10% volatile. The suggested pri-
mary tank design is 1,000-1,150 gal./sq. ft./day.
No trouble was encountered in treating the mixed wastes by
the activated sludge process. The addition of supplemental nitrogen
or phosphorus was not required to obtain good BOD reductions. Nitrogen
content of the wastes ranged between 3%-5% of its 5-day BOD and phos-
phorus ranged from 2%-k%. High sludge volume indices were encountered
and microscopic examination showed the presence of heavy filamentous
growths. Methods to control these growths other than increasing aera-
tion time were not investigated. A joint treatment plant should be
designed for a sludge volume index of at least 200. To avoid even higher
indices the volatile content of the activated sludge must be prevented
from exceeding Q0% by the use of long solids aeration periods and rela-
tively low BOD to volatile suspended solids loadings. A ratio integrat-
ing these factors was established and used in the preliminary design
calculations.
BOD Loading/Day (ibs) x 100 1 t.
Total VSS (ibs) x Aeration Period (hrs)
Additional verification of the = 6 figure used as a limiting factor in
the preliminary design calculations might show that a higher figure
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could be used. Additional studies of methods for controlling the
volatile content of the suspended solids and the sludge volume index
are also advisable.
Pilot plant operations demonstrated that a 10° C. change in
mixed liquor temperature effected a fourfold change in reaction rates
when treating a 50-50 mixture of Hammermill waste and municipal sewage.
Experience indicates that the reaction rate change is two or threefold
per 10° C. for municipal sewage. 0)In treating mixed wastes a high oxygen
requirement and low floe build-up will be encountered at high tempera-
tures, the reverse will be true at low temperatures. Conventional
activated sludge operation without use of sludge reaeration is indicated
for low temperature operation of a joint treatment plant. Sludge re-
aeration is indicated during warm weather operation.
Conventional spiral flow aeration tanks such as those now in
use at the City of Erie experience serious short-circuiting. Aeration
periods in a joint plant should be increased by about 25% over those
established by pilot plant studies where completely mixed aeration tanks
were used. Use of turbine type dispersers and single pass tanks is
recommended to reduce short-circuiting. Preliminary design calculations
indicated that the total aeration tank volume should be equal to approxi-
mately one third the average daily flow with return sludge rates of 75$-
100$ in the summer. Twenty to thirty per cent of the total aeration
tank volume would be used for sludge reaeration in warm weather. In
cold weather sludge reaeration would be discontinued and all tanks would
be used for mixed liquor aeration. About one third of the tanks should
be constructed so they can be used for either mixed liquor aeration or
sludge reaeration.
The processing of the low phosphate pulping and paper-making
wastes with domestic sewage in a joint treatment plant reduced the in-
coming phosphates by 30%-h3% but left 3 to 7 mg/1 in the final discharge.
Some type of supplemental treatment would "be required to obtain higher
phosphate removal. The nitrate content of the effluent seldom exceeded
1 mg/1.
The overall removal of suspended solids by the pilot plant
activated sludge process was in the 70$ to 80$ range. A full-scale
plant treating mixed wastes could produce lower suspended solids than
the pilot plant but the final effluent would probably contain kO mg/1
of suspended solids.
The activated sludge process does not reduce the color of the
mixed wastes. The extensive investigation conducted by Hammermill did
not turn up a method which was economically feasible. Additional inves-
tigative work may be in order on other techniques.
Tests of gravity thickening and air flotation indicated that
either process could produce a sludge containing 3% solids when handling
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excess activated sludge, or a mixture of primary and excess activated
sludge. Thickening by air flotation released less phosphate. Gravity
thickening of primary sludge and air flotation thickening of waste ac-
tivated sludge may be desirable.
The final effluent had a high chlorine demand averaging
over 60 mg/1. The high cost of such a chlorine usage dictated a search
for a less expensive method of disinfection. The investigation showed
that a premixed NHo-Clg solution applied at the rate of 2.6l mg NHo and
15-17 mg Cl2 per liter resulted in colifonn counts generally below
1,000/100 ml in the final waste effluent. The use of the premixed NHg-
Clp solution was found to work equally well on City of Erie effluent.
The cost of the NH^-C^ treatment for the mixed waste effluent was 15%
less than the use of chlorine by itself. Additional investigation work
could well be done on the stability of the solution, the ratio of the
two chemicals, the amount required for disinfection and on methods of
application.
Variations in hourly uptake of oxygen needs further investi-
gation since aeration devices must be designed to meet maximum oxygen
needs. Additional corrosion studies and studies of coatings are indi-
cated. Detailed design work may indicate need for supplementary sludge
concentrating studies.
Tests conducted in the Hammermill laboratories indicated
that a HO-day retention period with a loading not over 0.1 Ib. volatile
solids per day per cubic foot would be required for effective anaerobic
digestion of the mixed sludge. Considerable lime would be required to
maintain suitable alkaline conditions. It was concluded that anaerobic
digestion would not be practical in a joint treatment plant. Incinera-
tion is the preferred ultimate disposal method. Studies of the use of
centrifuges and vacuum filters for sludge dewatering prior to incinera-
tion indicated that the lower cost and potentially higher per cent
solids in the cake obtained by filtration made it the preferred method.
No pilot studies of incineration were possible but sufficient informa-
tion is believed to be available to size the equipment.
The cost of constructing the addition to the present Erie
municipal plant to provide additional sewage capacity and for the treat-
ment of Hammermill Paper Company wastes was not estimated in detail.
Rough preliminary estimates indicate that Hammermill1s share, before
any subsidy, of the capital cost for the addition to the plant required
to handle the increased waste flow would be approximately $16,000,000.
If apportioned in relation to effluent flow, the Hammermill share would
be $37,000 per ton of daily pulp production and $H,600 per ton of daily
paper production. The operating costs were also roughly estimated and
it was indicated that the cost would be $i+.00 per ton of pulp produced
plus $.U5 per ton of paper produced. The treatment costs for the com-
bined wastes, using the disinfection procedures developed in the project,
were roughly estimated at $.05 per 1,000 gallons. Phosphate removal
would add an estimated $.01-$.015 per 1,000 gallons of mixed wastes.
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II
INTRODUCTION
The City of Erie through its Bureau of Sewers and Hammermill
Paper Company of Erie, Pennsylvania are studying the feasibility of
treating the sanitary vaste from the City jointly with the pulp and
paper mill effluent from the Erie Division of Hammermill. Both the
City and Hammermill are under orders from the Sanitary Board of the
Commonwealth of Pennsylvania to provide additional degrees of treat-
ment in order to improve the quality of Lake Erie. A joint treatment
venture appears desirable for a variety of reasons, including the
economy of scale.
The prime factor in the research program was the construction
and operation of a pilot plant to provide joint treatment under a vari-
ety of controlled conditions. The general purpose of the pilot plant
and the associated laboratory studies was to demonstrate the feasibility
of such a venture, to determine optimum parameters for full plant design,
and to establish the nutrient removal which could be obtained. The
treatment of a relatively high BOD waste from wood pulp bleaching and
paper-making operations in conjunction with sanitary sewage has industry-
wide application.
The City of Erie made application to the Federal Water Pollu-
tion Control Administration for a Research and Development Grant for
this work as provided in the "Clean Water Restoration Act of 1966".
The City of Erie on June 20, 1968 accepted an FWPCA Research
and Development Grant (WPRD-223-01-68) of $88,230 or 15% of eligible
project costs, whichever was less. Eligible costs for the grant were
limited to the preliminary studies and reports and postconstruction
studies and reports. These costs were 2.5% of the estimated total cost
of the project. This report was prepared to make the findings of the
pilot plant study available in a form requested by the Water Pollution
Control Administration.
Hammermill constructed the pilot plant immediately adjacent
to the municipal plant. The pilot plant started operation in July,
1967, and operated continuously until late in January, 1968. Hammermill
wastes were first admitted on August 1 and their proportion gradually
increased to the 1 to 1 proportion used throughout the experimental
program. Concurrently with the construction and operation of the pilot
plant, numerous laboratory and bench scale investigations were conducted
in the Hammermill laboratory. These included the construction and
operation of the bench scale, continuous flow, activated sludge facility
and four bench scale anaerobic digesters. The pilot plant did not con-
tain any facilities for studying anaerobic digestion, but did provide
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for studies of primary sedimentation, secondary treatment by the acti-
vated sludge process with and without separate sludge reaeration, sludge
concentration and sludge dewatering.
The bench scale continuous flow activated sludge facility was
first placed in operation during April, 1967, and remained in continuous
operation throughout the period covered by this report. Bench scale
anaerobic digesters were operated by Hammermill during the last half of
196T.
The Chester Engineers of Pittsburgh, Pennsylvania were engaged
as consultants and provided technical advice on the conduct of the
studies. Professional personnel in Chester Engineers did the majority
of the interpretive work on the data obtained in the studies and pre-
pared the design material. They presented a detailed report, the basis
for this report, to Hammermill Paper Company on combined treatment of
Hammermill and Municipal wastes.
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Ill
BACKGROUND
The pollution problems of Lake Erie have received wide study
and documentation. The most comprehensive work is that done by the
Federal Water Pollution Control Administration (FWPCA) under the Depart-
ment of Interior (formerly under the U. S. Public Health Service) and
documented in the report on Pollution of Lake Erie and Its Tributaries
released in July, 1965. This report formed the basis for the confer-
ence on Pollution of Lake Erie and Its Tributaries called by the Depart-
ment Secretary and resulting in the adoption of a series of recommen-
dations for improving Lake Erie.
The report stated that Pennsylvania's part in the Lake Erie
problems stemmed mainly from the Erie municipal treatment plant and from
the discharges from Hammermill Paper Company. It was recommended that
additional levels of treatment be provided by both of these to accom-
plish improvement in the Pennsylvania offshore waters of Lake Erie.
Special emphasis was placed on reduction of phosphate and nitrate as a
means of reducing algae growth.
The Division of Sanitary Engineering of the Pennsylvania
Department of Health (Mr. Walter Lyons, Chief) has suggested that the
best solution to these two problems might be expansion of the domestic
treatment plant to a capacity which would provide both for the needed
expansion for the growing domestic population and for the effluent from
Hammermill Paper Company. A joint treatment approach appears feasible
and has many important advantages such as lower capital cost, reduced
operating costs, simplified operation and control, easier regulatory
surveillance and qualification for major Federal aid. In addition,
phosphate and nitrate discharges should be reduced because of the nu-
trient requirement of Hammermill's waste which could be satisfied by
the excess in the domestic waste.
As a result of this suggestion, a preliminary study was made
by the Chester Engineers, Pittsburgh, Pennsylvania, Hammermill's con-
sultants. Their results, which were reviewed and concurred in by Consoer,
Townsend & Associates, consulting engineers for the Erie Sewer Authority,
indicated that joint treatment might be feasible. However, both engi-
neering firms strongly recommended that prior to design and construction
of a major plant, a pilot plant be built and operated. This pilot plant
would demonstrate the feasibility of the concept and provide the design
information necessary for a successful full-scale plant. The pilot
plant was constructed and the appropriate research studies were made.
Present City Plant
The sewage treatment plant serving the Erie community is owned
by the Erie Sewer Authority. It is operated by the City of Erie on a
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lease-back arrangement. This plant provides sewage treatment facilities
for a population of approximately 180,000 people and serves the sur-
rounding area including the political subdivisions of the City of Erie,
Wesleyville Borough, Lawrence Park Township, Millcreek Township and part
of Harborcreek Township.
The sewage from the City flows by gravity to the headworks of
the sewage treatment plant. The headworks consist of a coarse bar screen
to remove large particles, two aerated-type grit chambers and two bar-
minutors for comminuting the wastes.
The comminuted wastes then flow by aerated channel to the pri-
mary settling tanks. There are two sets of primary settling tanks at the
plant: the old primary settling tanks, capable of providing primary
treatment for a flow of 22.5 mgd; and the four settling tanks placed in
operation in 1956, also capable of treating 22.5 mgd. The settling tanks
are equipped with sludge collecting mechanisms to remove the settled
solids (sludge). The floating scum solids are collected in skimming
pipes and removed.
After primary treatment, the settled wastes flow to five aera-
tion tanks. The aeration tanks are of the two-pass type. Air is intro-
duced to the aeration tanks through swinging-type diffusers.
The aerated mixed liquor passes from the aeration tanks to six
final settling tanks. The final settling tanks are of octagonal shape
and the flow to each settling tank is proportioned by means of a Parshall
Flume at the inlet of each tank. In these tanks the majority of the
mixed liquor solids are settled and returned by four variable speed re-
turn sludge pumps to the influent of the aeration tanks. The clarified
liquor is then discharged from the final tanks to the chlorine contact
chamber where chlorine is added for disinfection purposes and the 10,500
feet of 72-inch outfall sewer provides the contact time for the chlorina-
tion prior to discharging the treated effluent to the lake.
The air necessary to support the activated sludge system is
supplied by three positive displacement blowers and the blowers are
driven by dual fuel, four cycle, eight cylinder super charged engines.
The mixed liquor solids that are periodically wasted are re-
turned to the primary settling tank. That sludge as well as the sludge
settled in the primary settling tanks are pumped to two primary high-
rate sludge digesters.
The primary digesters are equipped with facilities for gas
recirculation for the complete mixing of the sludge. Sludge heaters are
also provided to keep the digesters at an optimum operating temperature.
The digesters are of the so-called accelerated digestion process. The
digested sludge is periodically discharged to the secondary digesters
which are conventional digesters used primarily for storage of sludge
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and supernatant separation. The secondary digesters are not directly
heated but remain at a somewhat elevated temperature as a result of the
continual addition of heated sludge. Some additional digestion occurs
in the secondary system. Gas produced during the digestion process is
discharged to a gas storage sphere. The digester gas is used as aux-
iliary fuel to heat the digester.
The digested sludge solids are conveyed to two elutriation
tanks now used as sludge storage tanks. The solids, containing about
95$ moisture, are pumped to a tank where a polyelectrolyte compound is
added to enhance the filterability of the solids. The treated sludge
is then dewatered on two coil vacuum filters. The filtrate is returned
to the primary settling tanks and the dewatered solids, containing about
80$ moisture, are hauled away to disposal sites.
To serve the growing population of the area and to provide
complete treatment rather than a modified degree of treatment, a major
expansion is required in the city plant. The expansion will increase
the city treatment capacity 20 - 25 million gallons per day.
Complete treatment is defined by the Pennsylvania State Sani-
tary Water Board as "such treatment that will remove practically all the
suspended solids, at least 85$ of the organic pollution load as measured
by the biochemical oxygen demand (BOD) test, provide satisfactory disposal
of sludge and produce a final effluent that is suitable for discharge
to the receiving stream."
Hammermill Paper Company
The Erie Division of Hammermill Paper Company operates an
integrated pulp and paper mill producing 385 tons per day of Neutracel
pulp (a patented neutrasulfite semichemical pulping process) and 360
tons per day of fine printing and writing paper. The Neutracel process
is unique in that a fine paper pulp can be produced from typical hardwood
trees found in northwestern Pennsylvania. Congruent to the benefits of
this process is the absence of any sound technology for reclaiming the
pulping chemical and eliminating the pollution load caused by the organic
material found in the spent pulping and bleaching liquors.
Hammermill has spent over $^ million in research and installa-
tions to find a practical solution to this problem. These efforts have
resulted in the installation of two deep disposal wells which are cur-
rently disposing of the concentrated spent liquor from the pulping
operations. The deep well installations are described in the Journal
of Water Pollution Control Federation (2).
Deep well disposal has permitted Hammermill to eliminate 60%
of the BOD in the pulping waste. The remaining wastes are very dilute
and voluminous and consequently hard to treat. This residual waste
consists of the process water from pulp washing and bleaching and amounts
to 21 - 25 million gallons per day.
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In addition to the dilute wastes from pulping and bleaching,
there is also a waste discharge from the paper mill operation which
contains the normal materials such as papermaking fiber, starch and
paper additives associated with the production of fine writing paper.
For many years paper mill wastes have been treated by sedimentation
prior to discharge to the lake. The volume and BOD load from papermak-
ing is a small fraction of the total volume but would be included in
the total plant effluent. Table I characterizes these wastes.
Activated sludge treatment of pulp and paper mill wastes has
been reported in the literature and is in operation. However, there
are no known facilities treating wastes with as high a BOD load as is
discharged from Hammermill's Erie operation. The treatment of these
wastes in combination with domestic sewage is, thus, an unproven concept
which requires careful study.
The utilization of the deep wells is essential for an economi-
cally successful biological treatment. If the wells were not in opera-
tion, the BOD load would exceed the practical level for secondary treat-
ment. Thus, consideration of secondary treatment prior to the deep wells
was impossible.
Hammermill is under orders from the Commonwealth of Pennsylvania
to effect treatment of its remaining wastes. The City of Erie has sub-
mitted to the Commonwealth a schedule for increased treatment of its
sanitary wastes up to the point where the decision is made to go or not
to go with joint treatment. Beyond this the city's schedule calls for
either joint treatment or expansion without Hammermill depending on the
outcome of the pilot plant studies and the joint treatment agreement
negotiations. The date of compliance is December 31, 1970 in either case.
It is seen that the operation of the pilot plant is a necessary and criti-
cal part of both the city's and Hammermill's programs.
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TABLE I
Characteristics of Hammermill Wastes
Maximum
Minimum
Average
Present Discharge
Paper Mill*
Flow - mgd
BODc - mg/1
COD - mg/1
Suspended Solids - rag/1
pH
Pulping & Bleaching-**-
Flow - mgd
BODc - mg/1
COD - mg/1
Suspended Solids - mg/1
pH
3.1
280
700
360
7.4
25
700
3,080
292
3.6
2.2
190
500
64
4.4
21
500
2,300
169
2.8
2.8
250
570
180
6.3
23
600
2,680
232
3.1
Probable Discharge to Joint Plant#*&
Flow - mgd
BODr - mg/1
COD - mg/1
Suspended Solids - mg/1
pH
30
650
2,950
335
7.5
25
450
,200
220
6.5
27.5
570
,550
280
7-0
-"- After present primary treatment.
-* Excludes spent pulping liquor which is presently disposed
in deep wells.
Anticipated growth, abandoning paper mill primary treatment
and fiber filtering, waste neutralization and continued
pulping liquor disposal in deep wells.
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IV
DESCRIPTION OF PILOT PLANT
A flow diagram of the pilot plant as constructed and operated
is presented on the next page, following pages contain photographs of
the plant. As indicated on the flow diagram, Hammermill wastes after
pH adjustment with lime are delivered by tank truck to the pilot plant
where they are stored in a wooden tank equipped with agitator. They are
then pumped to the pilot plant treatment system. Municipal sewage,
after grit removal and comminution, is pumped to the pilot plant.
Separate V-notch weir boxes with adjustable heads are pro-
vided to measure the volume of both sewage and Hammermill wastes de-
livered to the pilot plant. After mixing, the two wastes enter a flash
mixer having an effective volume of approximately ^20 gallons from which
the mixed wastes enter a rectangular clarifier 2-1/2 feet wide by 10 feet
long and approximately 7 feet deep, which has an effective volume of
1,31*0 gallons. Incoming wastes enter the tank at one end, after passing
under an inlet baffle, flow longitudinally across the tank and out over
a single effluent weir 2-1/2 feet long at the opposite end of the tank.
Solids settling to the bottom of the tank are drawn to the hopper bottom
sludge outlet by means of a screw conveyor.
After primary treatment the mixed wastes discharge over adjust-
able weirs to either or both of two circular wood stave aeration tanks
equipped with sparger rings and turbine-type gas diffusers. Each of
these tanks has an effective volume of 6,600 gallons when operated singly.
When operated in series, i.e. for sludge reaeration ahead of mixed liquor
aeration, the first or sludge reaeration tank, has an effective volume
of 6,960 gallons while the volume of the second or mixed liquor tank
remains 6,600 gallons.
Two tanks originally intended for aeration were used for the
storage and thickening of both primary and excess activated sludge result-
ing from pilot plant operations.
After aeration, mixed liquor flows to a single, hopper bottom,
final clarifier having a 7 ft. diameter and 7-1/2 ft. side water depth.
Thus, its effective volume is approximately 2,180 gallons. The conical
bottom is an additional 7 ft. in depth; therefore, the total volume of
the tank is approximately 2,800 gallons. The tank is arranged for periph-
eral feed and center overflow, i.e. it utilizes the "rim flow" design
promoted by Chain Belt Company.
Two calibrated, positive displacement, Moyno Pumps are provided,
one for withdrawing sludge from the primary clarifier, and one for with-
drawing sludge from the final clarifier. Final clarifier sludge is pumped
to a headbox from which it is discharged over adjustable weirs to either
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AVAILABLE
DIGITALLY
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i
EXHIBIT II Pilot Plant - Aeration tanks in center, Surfpac Tower at right,
Hamnermill effluent unloading and storage at left.
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EXHIBIT III Pilot Plant Operating Level - Primary sedimentation
in center foreground, Surfpac Tower at left, Erie
Sewage Plant Flume in background.
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waste or process return. Both waste activated sludge and primary
sludge are discharged to one or both of the two wood stave sludge
storage tanks.
A "Surfpac" pilot trickling filter, rented from Dow Chemical
Company, was installed and piping was arranged so that it could be
operated as a roughing filter between the primary clarifier and the
activated sludge process.
As indicated on the flow diagram, two chemical feeders were
provided, one arranged so that nutrients, either diammonium phosphate
or ammonium hydroxide, might be fed to the Hammermill wastes and mixed
with them in the Hammermill waste storage tank prior to pumping those
wastes through the pilot plant. The other feeder was provided to permit
pH adjustment of the mixed waste in the flash mixer immediately ahead
of the primary clarifier. Although the pH of the Hammermill wastes was
adjusted at the paper mill prior to trucking them to the pilot plant,
it was feared that further pH adjustment might be required at the pilot
plant. This fear was not realized and there was no need for additional
pH adjustment. The pH of the wastes ranged from 6.5 to 7.5, but was
generally about 6.8.
In October, the pilot plant facilities were expanded to per-
mit the installation of rented sludge flotation, vacuum filter and
centrifuge units so better studies on the dewatering characteristics
of the resulting sludges could be conducted than were found possible
with conventional laboratory equipment.
Normally the plant was manned two shifts per day, seven days
a week. The shifts were 7 a.m. to 3 p.m. and 7 p.m. to 3 a.m. each day.
Thus, there were two it-hour periods during which no one was in attendance.
Tests were run on 2U-hour composite samples. Those samples
were measured into a refrigerated jar at 2-hour intervals, missing two
a day (5 p.m. and 5 a.m.). The composites taken were:
1. Influent
2. Primary effluent
3. Final effluent
b. Mixed liquor (last tank in series if applicable)
5. Return sludge
6. Reaerated sludge or other special samples as required.
The pilot plant operators took DO's and settleabilities on the
mixed liquor (and reaerated sludge when applicable) every four hours.
The pH of the neutralized Hammermill waste was checked twice a shift,
as it had a tendency to drop gradually. Other duties included pumping
out primary sludge periodically, skimming off floating surfaced solids,
and a number of mechanical tasks necessary for the maintenance and opera-
tion of the plant.
17
-------
The operators kept a daily log of pilot plant operations.
Operating data sheets were completed daily and then compiled for each
month's operation.
During the construction phases of the pilot plant, a batch
aeration system and a bench-scale activated sludge plant were operated
to show the general treatability of a mixture of Hammermill and City
wastes. Each of these systems is briefly described below:
Batch System; Activated sludge from the City of Erie treatment
plant was gradually acclimated to a 50-50 mixture of Hammermill
and City wastes in a series of three-gallon aerated pails.
These were maintained by settling, drawing off the supernatant
and adding fresh waste once each day. This system showed that
the 50-50 mixture could be treated to 90% BOD removal levels.
The BOD removal curve with time showed no evidence of any toxicity.
Bench Plant: An activated sludge system has been in operation in
Hammermill's laboratory since April, 1967. It is designed to
handle a mixed liquor flow of 1.5 gallons per hour. This flow
can be proportioned between influent and sludge return at the
discretion of the operator. Influent for the system is subjected
to a screening operation designed to simulate primary treatment.
Hammermill waste is neutralized with lime in the laboratory be-
fore use.
The plant used City waste with sufficient glucose added to bring
the BOD level to 300 mg/1. This was treated successfully without
supplemental nutrient addition, showing the feasibility of handling
a BOD load equal to that of the 50-50 mixture of Hammermill and
City wastes. Subsequently, the glucose was gradually replaced
with Hammermill waste, making a smooth transition to joint treat-
ment of a 50-50 mixture of Hammermill and City waste. The system
was run at three different loadings using the 50-50 mixture to
show the effect of loading on BOD and COD removal.
18
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V
OBJECTIVES
The general objective of this project was to build and operate
a pilot plant to demonstrate the feasibility of joint treatment and
to obtain certain design parameters. The plant was designed to provide
answers to the following immediate objectives:
1. To demonstrate the success of activated sludge treatment
of domestic sewage from the City of Erie and industrial
pulp and paper mill wastes from Hammermill's Erie Division
in a joint treatment facility.
2. To determine the reduction in phosphate and nitrate dis-
charged to the lake in the treated combined effluent through
the utilization of the nutrients by biological treatment of
industrial waste.
3. To determine the proper design criteria and consequently the
cost of a joint treatment facility.
h. To determine the parameters necessary to estimate the costs
of facilities to treat Hammermill1s waste alone and of
facilities to take care of the City's needed expansion so
that these costs may be compared to those of joint treat-
ment.
5. To estimate the operating costs.
6. To determine the characteristics of the treated wastes to
assure they meet regulatory requirements.
It is anticipated that any joint treatment facility would be
capable of treating almost all of the pollution load attributable to
domestic sewage and industrial waste which is discharged to Lake Erie
from almost all of the Lake Erie drainage basin in Pennsylvania.
Hammermill retained the Chester Engineers to determine the
feasibility of joint treatment. Their preliminary study indicated that
such a plant was feasible from a process standpoint. They recommended
that prior to the design and construction of a joint plant, a pilot
plant be built and operated. This pilot plant was to demonstrate pro-
cess feasibility and provide the design information necessary for a
successful full-scale plant. The Chester Engineers prepared a detailed
report on the operation of the pilot plant and supporting studies, and
this report is largely drawn from it.
19
-------
To expedite the accomplishment of the objectives, Hammermill
built and operated a batch aeration and a bench-scale activated sludge
plant. The bench plant continued in operation during the operation of
the pilot plant to complement the pilot plant program and to determine
the feasibility of treating 100$ Hammermill waste by the activated
sludge process.
In addition, Hammermill conducted laboratory studies on
analytical methods, sludge digestion, primary settling, neutralization,
disinfection, corrosion, tertiary treatment, phosphate removal, foaming
and color.
20
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VI
PRIMARY TREATMENT
Pilot Plant Operation
The primary clarifier of the pilot plant was in continuous
operation from July 18, 1967 to January 21, 1968 to provide primary
treatment ahead of the activated sludge process.
Initially, the clarifier inflow consisted of 20 gpm of munici-
pal sewage. Hammermill wastes were first admitted to the clarifier
late on July 31, at a rate of 1 gpm, together with 19 gpm of City sewage.
The proportion of Hammermill waste was gradually increased, while that
of sewage was correspondingly reduced. With only a few exceptions,
the influent to the clarifier has generally consisted of a 50-50 mix-
ture of sewage and Hammermill waste from August 6 to the end of the run.
The principal exception was the holiday season from December 22 to Janu-
ary 2, when the inflow consisted of only 9 gpm of City sewage. Composites
of hourly samples of both influent and effluent were collected and ana-
lyzed almost daily throughout the run. The results of those analyses
are summarized in Table II.
The table also summarizes rates of inflow to the clarifier
during the periods when samples were collected. The rates varied from
15 to 2H gpm at various times. However, the inflow was always uniform
throughout a single day. At an inflow of 20 gpm, the theoretical deten-
tion period in the flash mixer was 21 minutes and that in the primary
clarifier was 1.1 hours. The surface settling rate in the clarifier was
1,150 gallons per square foot per day and the weir overflow rate was
11,500 gallons per foot per day.
To study the various factors bearing on the performance of the
clarifier, the data upon which Table II is based have been subdivided
into I1* chronological periods. The duration of the various periods ranged
from as little as four days to as much as 28 days; their length was de-
pendent upon the particular factors being considered.
Period 1 covers the last 11 days of July during which the pilot
plant was in full operation on municipal sewage, but had not received
any Hammermill waste. During that period the inflow to the clarifier
averaged 138 mg/1 of total suspended solids (TSS) and 107 mg/1 of 5-day
biochemical oxygen demand (BOD). The annual report of the Bureau of
Sewers of the Erie Department of Public Works for 1965-66 indicates that for
the year 1966, the sewage influent averaged 136 mg/1 of TSS and 105 mg/1
of BOD. Therefore, it is apparent that the inflow to the clarifier during
Period 1 may be considered typical of present sewage composition.
21
-------
TABLE II
NJ
Period
From
To
Flow, gpm
Sewage
Hammermill
Total
Total SUSP. Solids
Influent, mg/1
Effluent, mg/1
Percent Removed
Vol. Susp. Solids
Influent, mg/1
Effluent, mg/1
Percent Removed
5-Day BOD
Influent, mg/1
Effluent, mg/1
Percent Removed
COD
Influent, mg/1
Effluent, mg/1
Percent Removed
Phosphates as POy,
Influent, mg/1
Effluent, mg/1
Percent Removed
Organic & Ammonia
Nitrogen
Influent, mg/1
Effluent, mg/1
Percent Removed
1
7-20
7-31
20
0
20
138
30
78
96
26
71
107
56
48
273
U5
47
19
17
10
23
20
33
2
8-5
8-8
12.5
11.5
24
353
100
72
278
75
73
314
262
17
1336
1036
22
13
9
31
10
9
10
Primary
3
8-9
8-31
10
10
20
290
73
75
208
58
72
327
216
34
1199
830
31
10
9
10
10
7
30
4
9-1
9-8
10
10
20
295
82
72
218
63
71
301
239
21
1129
923
18
10
10
0
5
5
0
5
9-12
9-15
7.5
7.5
15
404
70
83
-
328
213
35
1167
858
26
10
9
10
6
6
0
6
9-16
9-25
10
10
20
467
65
86
296
65
78
452
340
25
1709
1091
36
12
10
17
13
8
38
Treatment
7
9-26
9-29
10
10
20
429
62
86
-
453
313
31
1715
1215
29
11
9
8
11
8
27
8
10-1
10-4
8.4
8.4
16.8
710
73
89
-
410
233
42
1391
995
29
:
-
• 9-
10-6
10-11
10
10
20
268
99
63
-
316
237
25
1223
997
19
-
-
10
10-12
10-24
7.5
7.5
15.0
350
62
82
-
370
280
24
1573
1244
21
7
6
1A
-
11
10-29
11-25
9
9
18
264
68
74
225
42
81
330
241
27
1245
947
24
5
5
0
10
9
10
12
11-27
11-30
12
12
24
201
59
71
370
295
20
1333
1125
16
6
5
17
11
9
18
13 V+
12-1 1-4
12-21 1-21
9
9
18
278
57
80
221
42
81
305
218
29
1316
899
25
6
5
17
9
9
18
223
60
73
172
49
72
274
213
22
966
847
12
6
5
17
11 12
10 11
9 9
-------
The weighted average of the various analyses of the inflow
to the clarifier for Periods 2 to ih inclusive, indicates that it had
the following average composition:
TSS 312 mg/1
BOD 337 mg/1
Chemical Oxygen Demand (COD) 1,285 mg/1
As this inflow consisted of a 50-50 mixture of Hammermill waste and
sewage and based upon the assumption that the sewage handled during
Period 1 was typical of the City sewage, it may be calculated that
during the entire period that Hammermill wastes were handled in the
clarifier, they had the following average composition:
TSS i486 mg/1
BOD 567 mg/1
COD 2,297 mg/1
Table I indicates that the probable future average discharge
of Hammermill wastes will contain 280 mg/1 of TSS, 570 mg/1 of BOD,
and 2,550 mg/1 of COD. From a comparison of the two analyses it is
apparent that the actual inflow of Hammermill waste during the period
of pilot plant operation was quite similar to the expected composition
of those wastes insofar as BOD or COD is concerned, but contained far
more suspended solids. This difference is attributed to the fact that
it was impossible to prevent a certain amount of sedimentation and con-
centration of suspended matter in the sampling and storage facilities
provided at the Hammermill plant and, therefore, the wastes tank-trucked
to the pilot plant were abnormally high in suspended solids. However,
it is apparent that the solids which become insoluble were of an inert
nature and so did not affect either the BOD or the COD of the wastes
delivered to the pilot plant.
It is believed that the removals of BOD and COD, as shown in
Table II, are typical of what can be expected. However, we were con-
cerned that the removal of total suspended solids may be somewhat high
because of the abnormally high concentration of suspended solids in those
wastes.
Studies were made on the settling characteristics of Hammermill
and City wastes in the Hammermill laboratory concurrently with the opera-
tion of the pilot plant. Those studies indicated that when considered
separately, the sewage settled better than did either the pulp mill or
the paper mill wastes, but that when the three wastes were combined in
the proportions of hO% pulp mill, 10% paper mill and 50% sewage and neu-
tralized to a pH of 7, a 60-minute settling of the mixed waste generally
effected substantially the same percentage removal of suspended solids
as did a 60-minute sedimentation of sewage alone.
23
-------
Laboratory testing of four different samples of mixed wastes
containing initial suspended solids concentrations of 196, 228, 276 and
536 mg/1 respectively, produced effluents after 60 minutes sedimentation
containing 96, 96, 7^ and 13^ mg/1 respectively, thus indicating corre-
sponding percentage reductions in suspended solids of 51, 58, 73 and
75 per cent. These data seem to indicate that the abnormal concentra-
tion of solids in the influent to the primary clarifier may have had far
less effect upon its performance than one would initially anticipate.
Pilot Plant Performance
The following tabulation summarizes the effect of variations
in flow of mixed waste on the performance of the clarifier.
Rate of inflow of mixed wastes, gpm 2^ 20 18 l6.8 15
Number of days in operation 8 51 67 U 17
Average reduction in TSS, % 71 76 76 89 82
Average reduction in BOD, % 19 29 26 h2 27
Average reduction in COD, % 19 28 21 29 22
It is probable that the four days of operation at l6.8 gpm was
too short a period to be of much significance, and might well have been
omitted from the above tabulation. The data give an indication that the
primary clarifier could effectively handle flows up to 20 gpm without
sacrificing treatment efficiencies, but that at flows in excess of that,
efficiencies dropped off, particularly BOD and COD removals.
Nothing in Table II indicates that changes in temperature
materially influence the effectiveness of primary sedimentation. Per-
centage reductions obtained during December (Period 13) were comparable
with those obtained during August and September. The removals of BOD
and COD obtained during January (Period ik) were somewhat lower than had
been obtained during previous periods, but both the BOD and COD of the
incoming waste were also lower during Period I1*.
Insofar as percentage removals of total and volatile suspended
solids are concerned, it seems apparent from Table II that the mixed
waste is as amenable to primary treatment as is the municipal sewage
alone, and this fact was substantiated by work in the Hammermill labora-
tory. However, primary treatment cannot effect as great a reduction
in BOD and COD of the mixed waste as it does in the municipal sewage.
This result was to be expected since the pulp mill wastes are far higher
in soluble BOD and COD than municipal sewage.
On or about September l6, a malfunction of the deep well dis-
posal system caused a considerable increase in the BOD and COD of the
industrial waste delivered to the pilot plant. Although that discharge
24
-------
was corrected within a day or two, considerable time elapsed before the
strong wastes stored in the neutralization and pilot plant storage tanks
was worked off. As a result, the BOD of the influent to the pilot plant
was abnormally high during Periods 6, 7 and 8. Apparently this dis-
charge had no deleterious effect insofar as percentage reductions in
either solids, BOD or COD by primary treatment are concerned. In fact,
the percentage reductions in suspended solids were higher during those
periods than during the periods preceding or following them.
During the initial period of pilot plant operation, the City
was feeding a polyelectrolyte to the sewage ahead of the pilot plant.
Such polyelectrolytes might affect the performance of the pilot plant
primary unit. On September 9, the City temporarily discontinued the use
of polymers. From a comparison of runs of Periods 6 and 7, during which
no polymer was used with Runs 3 and U during which the polymers were
used, it does not appear that the polymer had any appreciable effect on
the performance of the pilot plant primary clarifier.
The pH of the primary effluent was quite uniform throughout
the period covered by Table II. Normally it ranged from 6.8 to 7.2.
Primary treatment did not reduce the color and generally yielded
only very insignificant reductions in nitrogen or phosphate. (During
Periods 8 and 9 di-ammonium phosphate was being added to the Hammermill
waste and ammonium hydroxide was added during Period 10. Therefore, some
of the data on nutrient removal by primary treatment during those periods
has been omitted from Table II.)
Normally, good primary treatment of municipal sewage can be
expected to effect a 60 to 70 per cent reduction in suspended solids,
and at least a 35 per cent reduction in BOD. However, as indicated by
the result of Period 1 in Table II, primary treatment of municipal sewage
alone in the pilot plant yielded considerably higher reductions.
In contrast, the annual report of the Bureau of Sewers of the
Erie Department of Public Works for 1965-66 indicates the following for
the year 1966:
Raw Primary
Sewage Effluent
TSS, Ib/day 36,992 29,858
BOD, Ib/day 28,1*68 18,692
Based on these data alone, it would appear that the primary clarifiers
at the Erie Municipal Plant were effecting reductions of only 20$ of the
suspended solids, but 3^% of the BOD.
25
-------
Those reductions are misleading however, for the Erie clari-
fiers received not only raw sewage, but also waste activated sludge,
digester supernatant and filtrate from the sludge filters. The volume
of these three in-plant wastes is quite small, in fact, their combined
volume represents less than 1% of the average sewage flow. However, all
three wastes are extremely high in suspended solids and the supernatant
and filtrate are also high in BOD. Although the aforementioned annual
report contains no data on the BOD of these in-plant wastes, it does
contain some information from which their solids content may be estimated.
Calculations showed that the average annual removal of suspended solids
through the Erie clarifiers during 1966 was approximately $6% instead
of 20%,
26
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VII
ACTIVATED SLUDGE TREATMENT
Pilot Plant Operation
The number of microorganisms present and their health and
activity influence the results obtained by the activated sludge process.
Figure k is a plot of the weights of BOD removed per 100 pounds of total
suspended solids under aeration against the weights of BOD applied to
those solids for each day the necessary tests were run at the pilot
plant during the period of August 8 to October 27, inclusive. Figure 5
is similar to Figure U, except that the BOD loadings and removals are
calculated on the basis of volatile suspended solids, instead of total
suspended solids, under aeration. Note that in either chart the points
tend to fall along a straight line. The deviation from that tendency
is slight when consideration is given to all the possible errors that
might occur in a single day's sampling and analysis.
Both charts indicate that the mixture of Hammermill waste with
Erie sewage may be more difficult to treat by the activated sludge pro-
cess than is municipal sewage alone, i.e. the treatment of the mixed
waste yields a BOD reduction of nearer &h% than the 90^ reduction that
could be obtained by the treatment of municipal sewage. Figure 5 indi-
cates that an Sh% BOD reduction might be expected at BOD loadings as
high as 55 pounds per day per 100 pounds of volatile suspended solids
under aeration (MLVSS). At higher loadings the reduction drops off gradu-
ally.
The start-up of the pilot plant activated sludge process cov-
ered the period from July loth through 30th. Initially the two aeration
tanks and the final clarifier were filled with mixed liquor drawn from
the aeration tank of the municipal plant. City sewage alone was then
fed to the pilot plant at a rate of 20 gpm. The activated sludge process
followed the conventional flow diagram, i.e. the two aeration tanks were
operated in series for mixed liquor aeration. Sludge was withdrawn from
the final clarifier and returned to the aeration tanks at a rate of 8 gpm.
Dissolved oxygen levels in the aeration tank were maintained between 3
and 5 mg/1. The incoming sewage was relatively weak and primary treat-
ment was quite efficient, (see Period 1 of Table II) and the BOD to solids
loading was low. The average for the entire period was only 8.2 pounds
per 100 pounds of MLVSS. Although no activated sludge was wasted, the
concentration of mixed liquor solids decreased throughout the period,
indicating that "autodigestion" was taking place. On July 30 there were
only 77 pounds of suspended solids under aeration and the volatile con-
tent of those solids was only h2%.
Hammermill wastes were first admitted to the pilot plant on
July 31, and at the same time the pattern of flow was changed to sludge
27
-------
/
/
V
r? •
c
v
oo/
.X* *
) ' /
•/*•*.
* •
X.
0
X
LEGEND
• AUGUST
X SEPTEMBER
0 OCTOBER
FIGURE U - PLOT OF BOD REMOVED
vs BOD LOADING PER 100 LB TSS.
10 20 30 40 50 60
-------
/
/
/*
X
^
/ •
OCfc
.f
s.
0*
/*
i*^
Jjx^® %
, X
vX
o
•»
jT* •
o
X
o >^
X
X
./*•
X
LEGEND
• AUGUST
x SEPTEMBER
o OCTOBER
10 20 30 40 50 60 70 80 90 100 110 120 130
LB B.O.D. APPLIED PER 100 LBS. V.S.S. UNDER AIR
FIGURE 5 - PLOT OF BOD REMOVED vs BOD LOADING PER 100 LB VSS
-------
reaeration. During the next seven days the proportion of Hammermill
wastes was gradually increased. Starting August 8 the inflow to the
plant consisted of equal volumes of sewage and paper mill waste. The
admission of Hammermill waste increased the BOD or food supply and
hence the number of microorganisms and the amount of sludge under
aeration increased. On August 7, the plant had 315 pounds of suspended
solids under aeration, about 60% of which were volatile.
From August 9 to September 5, the plant operated at a constant
flow of 20 gpm and the sludge return rate was also 20 gpm. Appendix II
summarizes the performance of the activated sludge process during this
period. As indicated therein, BOD reductions by the activated sludge
process alone ranged from 79 to 89 percent and averaged 83%. However,
the reductions in phosphates and suspended solids were considerably
lower and varied from day to day over wide limits.
Total BOD input to the plant remained in the range of 1+5 to 55
pounds per day most of the time, see Figure 6. Some activated sludge
was wasted daily and the rate of wasting was purposely varied to study a
number of loading variations. The rate of wasting exceeded the rate of
buildup for on September 5, the plant contained only 117 pounds of
suspended solids under aeration, 11% of which were volatile, i.e. the
inventory of volatile suspended solids on September 5 was only half of
what it had been on August 7- Because of this change in sludge inventory,
there was a wider fluctuation in the BOD loading per 100 Ib. MLVSS than
there was in the total BOD input. It ranged from 27 to 6U pounds and
averaged 1*3.
From September 6 through the 20th, the plant continued to
operate on a 20 gpm inflow of a 50-50 mixture of sewage and Hammermill
wastes with a sludge return rate of 20 gpm. No excess sludge was wasted
during this 15-day period and as a result, the sludge inventory gradually
increased, reaching 280 pounds of total suspended solids, 16% of which
were volatile on September 20. Appendix III summarizes the performance
of the plant during this period. BOD loadings per 100 Ib. MLVSS were
highest at the start of this period. They exceeded 80 pounds per day
on September 6th, 7th and 8th. As the inventory of solids under aeration
increased, the loading per 100 pounds of those solids gradually diminished
through September 15, (total BOD entering plant was normal) and then
jumped up again because of the accidental pulp liquor discharge and
sharply increased total BOD load. For the entire 15-day period the BOD
loading averaged 56 pounds per 100 Ib. MLVSS, as compared with only 1(3
pounds per 100 Ib. MLVSS during the first period. The sludge volume
index remained relatively low and, was slightly less during this second
period than it was during the first period. BOD reductions were
essentially the same during the two periods. The removal of suspended
solids was particularly poor during the latter period. Phosphate removal
was considerably better during the second period than the first, but
still averaged only 39$.
30
-------
80
60
40
20
20
I
B.O.D. LOADING LB. PER DAY PER 100 LB. V.S.S. UNDER AIR
i
B.O.D. LOADING/HR. OF SOLIDS AERATION
10
n^
i
M.L.S.S.% VOLATILE
80
70
60 ^
200
IOO
SLUDGE VOLUME
PtF
L
r1
i I I I i I I I I
20 25
i i i i i i i i i i i i i i
5 10
NOV.
10 15
TT
I I I I I I I I I
20 25
1 1
AUG.
i i
i i i i i i i i i
5 10
i i i i i i i i i i i i i i i i
15 20 25
SEPT.
I I M I I I i i i
5 10
i i I i i
15
OCT.
FIGURE 6 - PLOT OF VARIOUS LOADING PARAMETERS FOR ACTIVATED SLUDGE PROCESS
-------
During both periods the rate of returning sludge was approx-
imately 100$ of the rate of waste inflow and as a result the return
sludge was quite dilute. Generally, it contained less than 0.2%
suspended solids. This high rate of return had been used in the hope
that it would improve the removal of phosphates and suspended solids
by the activated sludge process. It resulted in a much shorter sludge
reaeration period than would have obtained had a more concentrated
sludge been returned at a lower rate.
The periods of both mixed liquor and sludge reaeration were
cut in half on September 21 by the use of "float" pumps, which were so
operated as to reduce the depth in both the aeration tanks to about 60%
of what it had been previously. Obviously this not only shortened the
aeration periods, but also practically doubled the BOD loading per
100 Ib. MLVSS. The microscopic life in the sludge deteriorated sharply
after the charge was made. Due in part to these changes, and in part
to the physical effect of pumping the mixed liquor to the final clarifier,
the performance of that clarifier was extremely poor during the period
September 21st to 25th.
On September 26, the pumping was discontinued as was the
practice of sludge reaeration. From September 26 to October 27, the
conventional flow diagram was followed with all primary effluent and
return sludge delivered directly to a single mixed liquor aeration tank.
Normally it is assumed that for good operation, the amount of
ammonia plus organic nitrogen entering the plant should be not less than
5$ of the BOD entering the plant. However, as indicated by Appendix II
and III, it had been almost constantly less than that amount. From
August 8 to September 5, it averaged only 3.3% of the applied BOD, and
from September 6th to 20th, it averaged only 2.8$. It was decided to
investigate the effect of nutrient addition. From October 1 to the 5th
inclusive, diammonium phosphate was added to the paper mill waste before
it entered the primary settling tank, but this increased the phosphate
feed and masked the effect of the activated sludge process on phosphate
reduction. Therefore, from October 6 to November 2, ammonium hydroxide
was substituted for the ammonium phosphate.
Appendix IV covers the performance of the plant from October 1
to 27 inclusive, except that the data on phosphates for the first six
days of the period are omitted from the table. Throughout this entire
period the nitrogen content of the primary effluent remained very close
to 5% of its BOD. The BOD loading per 100 Ib. MLVSS during this period
ranged from 26 to 60 pounds, and averaged 1+2 pounds, i.e. about the
same as it had been during the period from August 8 to September 5.
However, without sludge reaeration, the solids aeration period was
drastically reduced, i.e. it ranged from 2.75 to U.9 hours and averaged
only 3.3 hours, whereas during the previous two periods, it had averaged
close to 8.6 hours. With this shorter aeration period the volatile
content of the solids under aeration increased as did their sludge
32
-------
volume index. In fact, the sludge was in a semi-bulked condition
throughout most of the period. It was during this period that the
presence of microscopic filamentous organisms were first observed in
the sludge and it is quite possible that the development of these
filamentous growths contributed to the sludge bulking.
Despite the bulking, BOD reductions were about as good during
this period as they had been during either of the previous periods.
The removal of suspended solids was intermediate between that prevailing
during the periods covered by Appendix II and III. Phosphate removals
ranged over wide limits, from 0 to 75 percent, but averaged only ^0/5,
i.e. about the same as had been obtained during the September 6th to
20th period.
During October the bottom half of one tank was filled in and
the turbine aerator modified so as to effect a 50$ reduction in the
effective volume of that tank. The two tanks were then operated in
series, with conventional flow from October 28 to November 10, and the
results obtained are summarized in Appendix V. As indicated therein,
the rate of waste feed to the aeration tank was maintained at 18 gpm
and the rate of sludge return was 6l%, i.e. 12 gpm. Thus, the mixed
liquor aeration period was slightly more than 5.5 hours.
Despite the fact that the BOD loading per 100 Ib. MLVSS
averaged 50 pounds per day as compared with only *+2 pounds per day during
the previous period, both the volatile content of the sludge and its
sludge volume index decreased as a result of the longer aeration period.
However, there was a sharp decrease in the reduction of both BOD and
suspended solids. In fact, the final effluent contained more suspended
solids than did the primary effluent throughout much of the time. It
is possible that temperature had much to do with the deteriorations of
the purification processes for, during this period, mixed liquor
temperatures ranged from 5^ to 65° F., whereas during the previous
period, i.e. the period covered by Appendix IV, they had ranged from
6l to 71° F.
On November 11, conventional operation was discontinued and
the use of sludge reaeration restored with the smaller half tank being
used for sludge reaeration and the full size tank being used for mixed
liquor aeration. This mode of operation was continued throughout the
remainder of November and the results obtained are summarized in
Appendix VI. Again the final effluent contained more suspended solids
than did the primary effluent and BOD reduction by the activated sludge
process was extremely poor, i.e. only $6% as compared with fh% during
the previous period and 8l to 8k percent during the periods covered by
Appendix II to IV inclusive. The BOD loading was just slightly less
than during the previous period and the solids aeration period, of
course, was much longer. However, there was little or no change in
the average volatile content of the sludge or its SVI.
33
-------
•
i
100
80
B.QD. LOADING LB. PER DAY PER 100 LBS:
VS.S. UNDER AIR
B.O.D. LOADING/HR. OF SOLIDS
AERATION
M.L.S.S. % VOLATILE
70
400
300
200
^U~-
SLUDGE VOLUME INDEX
100
1 I I I 1 I I I I I ' I I f ' I I I t I i I I I I
5 10 15 20 25
NOV.
i t i i i i i i
5 10
i i
15 20
DEC.
25 30
10 15 20
JAN.
FIGURE 6A - PLOT OF VARIOUS LOADING PARAMETERS FOR ACTIVATED SLUDGE PROCESS
-------
Inspection of Figure 6-A shows that during the early part
of the period, i.e. November llth to l6th, there was a slight decrease
in the volatile content of the sludge solids and also in the SVI, but
that from about November 22 to the end of the period, both parameters
increased markedly. BOD loadings per 100 Ib. MLVSS were lower and
temperatures were higher during the first few days of this period than
they were toward its end. The average mixed liquor temperature for
the entire period was 11.7° C.
Until this time the "Surfpac" trickling filter unit had not
been in operation. However, during the last four days of November,
the filter was acclimated with a 6 gpm side stream of primary effluent.
Then from December 1st to the l^+th, it was used as a roughing filter,
without recirculation, between the primary sedimentation basin and the
activated sludge process. Appendix IX summarizes its performance.
Effluent from the filter was treated by the conventional activated
sludge process, but only the small or half tank was used for mixed
liquor aeration. Appendix VII summarizes the performance of the
activated sludge process during this period.
On the whole, the performance of the "Surfpac" unit was
disappointing. It effected only an average of 22$ reduction in BOD,
a 9% reduction in COD and its effluent contained more suspended
solids than did its influent. No doubt the low temperatures prevail-
ing during the period of its operation contributed to the poor per-
formance. It is also quite possible that the acclimation of only
five days was too short to properly condition the filter. At any
event, it is obvious that the filter was totally incapable of effec-
tively treating a flow of 18 gpm which was applied to it during the
first few days of December.
The flow to the filter, and hence to the activated sludge
process, was reduced on December U, and thereafter was generally about
9 gpm. At this reduced flow, BOD loadings per 100 Ib. MLVSS ranged
from 30 to 50 pounds per day (see Figure 3-A) and after only one day
of operation at this reduced flow, there was a remarkable recovery in
the microscopic activity of the sludge which had been very low during
the high flow. However, its volatile content remained high and its
SVI increased steadily, being in excess of ^00 on the last day of the
period. The mixed liquor temperature during this period averaged only
10.2° C., but despite this fact, BOD reduction was slightly better,
i.e. an average of 60%, than the average of 56% that had been obtained
during the period covered by Appendix VI, and furthermore, the acti-
vated sludge process did effect a 33$ reduction in suspended solids.
In fact, the suspended solids of the effluent averaged hi mg/1 during
this period, which is less than the average obtained during any of the
periods covered by Appendix II to VI inclusive.
It is possible that the improved removal of suspended solids
by the activated sludge process during this period can be attributed
35
-------
to the pretreatment effected by the roughing filter. However, far
more data would be required to positively confirm the correctness of
such a presumption.
On December 15, the operation of the "Surfpac" unit was
discontinued and the mode of operation of the activated sludge pro-
cess was changed back to sludge reaeration, using the shallow half
tank for sludge reaeration and the full tank for mixed liquor aeration.
From December 15th to the 21st, the flow through the pilot plant
ranged from 10 to 18 gpm and consisted of 50$ City sewage and 50$
Hammermill wastes. Because of the brevity of this period, the re-
sults obtained have not been tabulated or presented herein. However,
in general, the performance as regards both BOD and suspended solids
were quite comparable to previous data.
From December 22 to January 3 inclusive, the pilot plant
received no Hammermill waste whatsoever and the flow of sewage through
it remained constant at only 9 gpm. The sludge return rate was 7.5 gpm,
or about 83$ of the sewage inflow. Analytical work in the laboratory
was curtailed and therefore samples of influent and effluent were not
collected or analyzed. However, it is obvious that BOD loadings per
100 Ib. MLVSS must have been very low throughout the period, while
both solids and mixed liquor aeration periods were considerably longer
than prevailed at any time since August 8. Nevertheless, there was
very little change in sludge inventory.
On December 21 the plant contained llj!4 Ibs. of total sus-
pended solids under aeration, while on January 3 it contained lU8 Ibs.
The corresponding inventories of volatile suspended solids under aera-
tion were 118 and 117, respectively. Thus, it is apparent that
"endogenous respiration" was progressing at a very slow rate and
hence there was no "autodigestion". This is in sharp contrast with
the high rate of autodigestion that was encountered late in July,
the only other period in which the pilot plant was operated on City
sewage alone. It clearly demonstrates the marked effect of tempera-
ture upon the rate of endogenous respiration. During the July period
the mixed liquor temperature was approximately 23° C, while during
the December period it was only 6° C.
• The SVI also remained high and practically constant through-
out the period of low loading and long aeration, being 272 on Decem-
ber 21, and 257 on January 3. However, the number of filamentous
organisms diminished greatly during this period.
Hammermill wastes were readmitted to the plant on January 3
and thereafter, until the plant was shut down on January 22; the flow
to the plant consisted of a 50-50 mixture of Hammermill wastes and
municipal sewage. From January 3 to January 7 inclusive, sludge
reaeration was practiced. However, this period was so short that a
tabulation of the results obtained during it does not appear to be
warranted.
36
-------
From January 8th to the 21st, conventional operation was
followed using both aeration tanks in series, i.e. primary effluent
and return sludge first entered the small aeration tank with the
mixed liquor overflow from that tank receiving further aeration in
the large tank. The results obtained during this period are summa-
rized in Appendix VIII.
Although mixed liquor temperatures remained extremely low
and averaged only 6.3° C, performance was relatively good. The
average BOD reduction was 12.% and the suspended solids in the final
effluent were practically the same as those in the primary effluent.
As indicated by Figure 6-A, the BOD loading per 100 Ib. MLVSS was
relatively low and very uniform throughout the period, as was also
the volatile content of the mixed liquor solids. The SVI decreased
gradually throughout the period.
Bench Scale Activated Sludge Plant
In addition to the afore-described pilot plant operations,
Hammermill constructed a small bench scale continuous flow activated
sludge system which was in continuous operation from April 1967. It
was designed to handle a mixed liquor flow of 1.5 gal per hr. Said
flow could be proportioned between influent and sludge return at the
discretion of the operator.
The plant consists of a 55-gal plastic storage drum, from
which the flow is pumped to a single plastic aeration tank. Flow is
then transferred by gravity to the settling tank, also plastic, from
which sludge is continuously returned to the aeration tank, or wasted.
Free flow plastic tees were used as aeration spargers. All pumps,
stirrers, and other equipment used is plastic, rubber, stainless
steel, or glass, thus avoiding color change or contamination. Com-
bined return and primary flow was 1-1/2 gph.
All pulp mill waste used was first passed through a 200 mesh
screen to remove approximately 50£ of suspended solids, similar to
that achieved in many municipal primary tanks. All City sewage used
was primary effluent. Prior to screening the pulp mill waste (about
pH 3), lime was added to bring it to a pH between 8.0 and 8.5. This
allowed for its characteristically rather rapid decrease in pH and
worked well in actual practice.
City samples were grab samples taken between 10:00 and 11:00
each morning, midway between minimum and peak flow. Suspended solids,
BOD, and phosphates are also known to be near the average daily values
at this time. Pulp mill samples vere 2U-hour composites. No nitrogen
or phosphorus was added.
Initially the plant was operated on settled sewage alone or
settled sewage to which glucose had been added in order to increase
37
-------
the BOD loading. After a good biologic sludge was accumulated,
Hammermill wastes were combined with City sewage in the influent to
the plant and the proportion of Hammermill waste to City sewage was
gradually increased until June 6, at which time the influent to the
plant consisted of a 50-50 mixture of Hammermill waste with City
sewage. Operation on this mixture continued until August 9, at
which time the operator began phasing out the City sewage for a
gradual changeover to 100$ Hammermill waste. From August IT to
December 20, the plant operated on 100% Hammermill waste. No
nutrients were used throughout the period between June 6 and August 9,
i.e. the period during which the plant was handling a 50-50 mixture
of City sewage and Hammermill waste, and at no time was there any
indication that nutrients were required.
The following tabulation will serve to summarize performance
of the plant when operating on a 50-50 mixture of the two wastes. It
covers the period July IT to August 8 inclusive, and indicates that
bench scale performance was quite comparable to pilot plant performance
under conventional operation and similar temperature conditions.
Median Maximum Minimum
Waste influent TSS (mg/l)
Final effluent TSS (mg/l)
TSS removed, %
Waste influent BOD (mg/l)
Final effluent BOD (ing/l)
BOD removed, %
Waste influent COD (mg/l)
Final effluent COD (mg/l)
COD removed, %
MLSS (mg/l)
MLSS, % volatile
Mixed liquor sludge volume index
Return sludge , % of waste inflow
132
50
65
252
38
8U
1,215
T55
36
3,986
82
108
38
232
TO
91*
356
TT
95
1.3U7
868
U8
M72
83
218
52
TT
8
1*3
126
11
TO
991
651
22
3.3U8
81
82
31
The changeover from a 50-50 mixture of sewage and Hammermill
wastes to 100/S Hammermill waste was accomplished over an 8-day period.
Nutrients were added during and after the changeover period. Appen-
dix X summarizes the performance of the plant on 100/5 Hammermill wastes
for the period September 21 to December 20, inclusive. From August 9
through November 8, the nutrient addition consisted of varying amounts
of a solution of diammonium phosphate. The amount of this solution
used was varied from time to time as indicated in Appendix X in order
to study various nitrogen levels.
It is significant to note that the use of diammonium phos-
phate resulted in the feeding of an over-abundance of phosphate.
38
-------
Starting on November 9, the use of diammonium phosphate was dis-
continued. From then until December 20, nitrogen vas supplied "by
feeding ammonia, vhile phosphorus vas supplied by feeding a solu-
tion of sodium phosphate. The data presented in Appendix X and the
effect of these various changes in nutrient feed is discussed under
the heading "Nutrient Requirements".
In addition to facilitating a study of nutrient require-
ments and demonstrating the feasibility of treating 100/5 Hammermill
waste, the "bench scale plant complemented the operation of the pilot
plant.
Sludge Bulking and Sludge Microscopy
Throughout this report wherever mention is made of a
"bulked" or "semi-bulked" activated sludge, it refers to a sludge
having a high SVI regardless of whether the final effluent is low
or high in suspended solids. Generally, a SVI of about 100 is
considered ideal and a bulked sludge might be considered as one
having an SVI of 200 or higher.
Generally, the sedimentation and compaction of sludge are
impaired by high BOD loadings and short aeration periods, whereas
an underloaded, over-aerated sludge, i.e. one undergoing autodiges-
tion, will be less flocculant and more granular than a normal sludge
and settle quite rapidly to a low SVI. However, because of its
granular character, such an over-aerated sludge might not have as
good a clarifying capacity as a normal or semi-bulked sludge.
However, other factors, in addition to BOD loading and
aeration, influence the SVI. One of these factors is the concentra-
tion of sludge floe itself. A mixed liquor of low suspended solids
concentration will have a lower SVI than will a liquor of high
solids concentration, even though the microscopic character and
specific oxygen uptake rates of the two sludges are identical.
Another factor greatly influencing the SVI is the presence
or absence of filamentous organisms in the sludge. A prolific
filamentous growth can produce a structurally bulked sludge even
though the BOD loading and the aeration period of such sludge are
well within acceptable limits. Periodic microscopic examinations
of the sludge are of value in determining the presence or absence
of filamentous organisms and they also reveal the presence or absence
of protozoa or higher organisms, some of which appear to be good
parameters of the oxidation adsorption balance of the sludge, i.e.
its reactivity.
Throughout the pilot plant operation microscopic examina-
tion of mixed liquor, reaerated sludge and return sludge was made
at frequent intervals.
39
-------
In the activated sludge process life forms may consist of
bacteria, flagellates, free-swimming ciliates, stalked ciliates and
rotifers. All have been seen in the pilot plant and it is interest-
ing to note that in the early stages of the test program, while using
two full aeration tanks and with temperatures between TO and 80 de-
grees Fahrenheit, life forms much larger than that of the rotifers
were seen. These forms included brightly orange-spotted worms which
were 20 times the size of the rotifer. There were also microbes
approximately one fourth larger than the rotifers which appeared to
be crustaceans. Their bodies were fixed or rigid as opposed to the
"soft" body of the rotifer and stalked ciliates. This appeared to
be a life form considerably higher than the rotifer. Over-all ac-
tivity at this time by all microorganisms was tremendously great
with free-swimming and stalked ciliates predominating in relative
numbers present.
Generally, as the BOD loading decreased, the stalked
ciliates predominated over the generally more active free-swimming
ciliates. This may be due to bacteria population shifts which they
probably feed on. The stalked ciliates served as the best indicators
of stress to the system—other than whole population shifts—simply
because they were present throughout the entire program almost with-
out exception.
The changes made on September 22nd and 26th reduced the
effective volume by 50%. This proved to be a shock to the system
and on September 27 there were none of the higher forms of life—
no worms, no rotifers, very few stalked ciliates. Free-swimming
ciliates predominated but were not in a healthy state. During the
next two weeks a recovery gradually took place and rotifers returned,
though few in number and slow in activity. During this time there
became evident a previously unseen animal which remained throughout
the month of October—it predominated most of the time. Its size
was slightly greater than that of the common free-swimming ciliate;
its body appeared firm with rather long legs on the underneath side.
(They did not at all appear to be cilia). Movement was always quick,
climbing over and around the biological floe. It had the ability to
stop and change directions rapidly.
On October 28 the use of 1-1/2 tanks of conventional sludge
was begun and a few days later the animal just described was gone.
Stalked ciliates grew fat and round and during the next week returned
to their normal shape. They remained large, however, with large
vacuoles. Rotifers did not increase in activity and remained very few
in number. Process temperatures were now approximately 55° F. and this
may well have been the reason rotifers remained generally inactive and
few in number. There were very few free-swimming ciliates.
Sludge reaeration using 1-1/2 tanks was begun on November 11
and continued for three weeks. There was no apparent change in the
40
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biological world other than slightly less over-all activity. It is
interesting to note that the relative microorganism populations did not
change even though the suspended solid's aeration vas increased from
5.6 hours in the conventional method to 8.5 hours in sludge reaeration.
After the introduction of the Dow Surfac at flows of l8 gpm
rotifers were no longer seen and nearly all stalked ciliates were
lifeless. For all practical purposes there was no visible life at
lOOx or U50x. Nearly half of all stalked ciliates were in an extremely
parched state. The bubble which appeared at the mouth was often as
large as the microbe itself and appeared to be protoplasm. It was very
clear and contained no vacuoles. Unparched ciliates also had very
small or no vacuoles at all.
After only one day of 9 gpm flow and a raw flow detention of
6.3 hours, the stalked ciliates had made a terrific recovery. Those
which were parched were nearly gone and those which were not parched but
totally inactive now showed at least some activity. At this time some
mastigophora were seen, probably introduced by the Surfpac. They later
increased in numbers and their activity was great. By December 10 the
free-swimming ciliates also increased in activity but remained generally
inactive. There were no rotifers and no free-swimming ciliates during
Surfpac use. Temperatures were approximately 50° F.
Samples of Surfpac effluent were centrifuged and examined
along with Surfpac influent (primary effluent). The influent revealed
no activity; the effluent was alive with very active mastigophora and
other life. The various microorganisms viewed had large vacuoles.
At a magnification of lOOOx much small life was seen, this small life
did not appear in the activated sludge. Only the mastigophora were
seen in the activated sludge and were less active, but considerably
larger than in the Surfpac effluent.
On December 15 sludge reaeration was again begun using 1-1/2
tanks. Activity remained as it was under Surfpac use, but with
decreasing numbers of mastigophora.
A 13-day run on City sewage only was begun December 22 by
abruptly stopping all Hammermill flow and continuing use of 1-1/2 tanks,
detention times increased from 9.^ hours to 18.8 hours. The third day
of this run revealed reasonably active stalked ciliates as the only
group of protozoa. No higher life forms were seen. Examination of the
City plant biological floe on this same day revealed identical activity
and there were no other life forms seen. By the end of the City sewage
run there were nearly no stalked ciliates and the bacteria were no
longer seen. (No change took place in City plant.) The biological
floe now appeared very lifeless but BOD removals remained good. The
work was obviously being done by bacteria not seen at l+50x.
41
-------
Full flow Hammer-mill waste was returned on January 3 using
contact-stabilization as the mode of aeration. Small animal activity
returned and as this activity became increasingly greater a number of
stalked ciliates appeared.
Plant operation was terminated on January 21. During this
last run no evident biological harm was done by abruptly introducing
Hammermill effluent. Temperatures were now approaching Uo° F. and were
sometimes lower. Stalked ciliates for all practical purposes remained,
as in previous weeks, the sole protozoa and source of observable
activity.
Filamentous fungi, usually identified with poor settling were
not specifically looked for prior to October when the SVI's were very
low, and it is not known if their numbers were less. The observations
since October revealed such a terrific network of these growths that it
was very difficult to see any difference between a SVI of 150 and 250.
There did appear to be some decrease at the lower SVI's. The biological
floe could be very clearly seen clinging to these long growths. Their
diameter is such that it is very difficult to see the inner structure.
Though this fungus was very difficult to see, it did not appear to be
branched.
In December when the plant was run on City sewage in the
absence of Hammermill effluent, these filamentous growths diminished
greatly. The fact that some did remain as long as 12 days later,
however, indicates that over-aeration and high return rates may be a
cause. As usual, City plant activated sludge revealed none at this
time. Their aeration times, return rates, and DO's were greatly less
than the pilot plant. These growths were also seen in the Surfpac
effluent but in vastly reduced numbers. None were present in the
influent (Primary effluent).
The last month of pilot plant operations (Jan. '68) revealed
microscopic bubbles which were best seen at lOOx. These bubbles were
seen in both aeration tanks and in the return sludge and are believed
to be entrapped air or oxygen. Because they were so numerous and large,
it was initially thought that these bubbles were the sole cause of
floating sludge. But it was later found that these bubbles grew to
full size within the 2 or 3 minutes it takes to prepare a slide. Exam-
ination outdoors, where the air temperature was nearly as cold as the
water (1*0° F.), revealed few such bubbles and of such size they were
barely visible at lOOx. They did, however, obviously contribute to
the generally poor settling at this time. City plant activated sludge
revealed some, but far fewer bubbles—temperatures were close to 55° F.
It was interesting to note that each bubble had one, and only one,
particle of floe attached to its surface.
Another interesting observation was that of life—believed to
be bacteria—within the Hammermill fibers. Very few of these fibers
42
-------
exist in the activated sludge, but those vieved at lOOOx were "alive".
It was at first thought that bacteria from the sludge entered these
cells. But further examination revealed that this action was present
in the Hammermill storage tank. Movement was vibratory in nature and
always within the cell. No bacteria Vere observed outside these cells.
It appears that the cell wall serves as a protective envelope. It is
not known if this activity exists in the pulp mill or paper effluent,
or both. That this activity was found helps explain the gradual
decrease in BOD's with time.
The presence of prolific growths of microscopic filamentous
organisms greatly impairs the sedimentation and compaction of the
sludge floe. This seems to be a purely physical phenomena and may be
true for any type of filamentous growth.
The filamentous growths observed in great numbers during
October were probably a species of sphaerotilus and such growths
probably remained predominant throughout November and early December.
However, it is doubtful that they could survive the 13 days of pro-
longed aeration at low BOD input that prevailed over the latter part
of December. The condition prevailing at that time would be more
suitable for the development of a growth of leptothrix and the fact
that the SVI decreased instead of increased when the load on the plant
was again increased during January, might further indicate that the
filaments observed during January were leptothrix instead of spaerotilus.
The joint treatment of Hammermill wastes with municipal
sewage will produce conditions favorable to the development of
spaerotilus growths and therefore, sludge volume indices of 200, or
even slightly higher, may be frequently encountered in any activated
sludge plant designed to treat such a mixture of waste.
Temperature Effects
Before oxygen can be utilized by the activated sludge process
it must be in solution. Both the rate of solution and the rate of
utilization are greatly influenced by the temperature of the liquor in
the aeration tanks. The rate at which oxygen may be put in solution in
raw or partially treated sewage or industrial waste steady state
aeration is given by the formula:
- SaR X1Q-3
" gCs - C (1)
= relative oxygen transfer coefficient - dimensionless
= overall oxygen transfer coefficient for clean water -
units per hour
= oxygen uptake rate - mg/l/hr
= relative oxygen saturation coefficient - dimensionless
= concentration of oxygen in clean water at saturation -
mg/1
43
-------
C = concentration of liquor under test - mg/1
Sa = average volatile suspended solids in liquor under
aeration - mg/1
R = Specific oxygen uptake rate - rag per gram of
volatile suspended solids per hour
Variations in temperature do not materially change the value
of either « or B, but exert a tremendous influence on biological
activity and hence upon oxygen uptake rates. In most activated sludge
plants the influence of temperature on biological activity far exceeds
its effect on oxygen solubility. Where the supply of food is high
(concentration of BOD) the following formula approximates.
b Lr
Kl = Sa K
Where the rate of biological growth is restricted by a limited
food supply the following formula approximates.
L - Lr /_x
—L = K2 Sat (3)
These roughly correspond to the inlet and outlet of long
spiral flow tanks such as those used at Erie. In a completely mixed
liquor aeration tank such as that used in the pilot plant.
Lr Kp Sat
L = 1 + (K2 Sat)
K]_ = logarithmic growth rate of organisms during the log
growth phase (natural logarithms)
K2 = logarithmic growth rate of organisms when growth rate
becomes BOD concentration dependent (natural logarithms)
b = fraction of Lr which is synthesized to sludge over any
time period
L = total amount of ultimate oxygen demand or BOD - mg/1
Lr = ultimate BOD removal - mg/1
Sa = average volatile suspended solids in liquor under
aeration - mg/1
t = time - hours
The rate of oxygen utilization will be uniform throughout a
completely mixed aeration tank. However, the total amount of oxygen
utilized in such a tank will still be the summation of that required
effect "L " and that needed for ultimate BOD removal and for endogenous
respiration.
Formulas (2), (3) and (M all involve a sludge growth or
reaction rate "K". This rate is highly dependent upon temperature.
Using formula (M KO values were calculated for a number of different
periods. It was assumed that Ig. was equal to the 5-day BOD. Table III
summarizes the results of the calculations.
44
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TABLE III
Ul
Appendix Numbers
Period Considered
From
To
Mode of Operation
Sludge Return, % of Waste Flow
5 Day BOD, mg/1
-"-Primary or "Surfpac" Effluent
Final Effluent
Aeration Tank Influent
Removed
Lr/L
Sa = MLVSS, mg/1
t = Mixed liquor aeration, hr
Sat x 10~3
K2 x 10"-^ at average mixed
liquor temperature
Average mixed liquor temp. °C
K2 x 10~3 at 20°C
IV
10-1
10-27
89
266
43
161
118
0.732
2209
3.3
7.29
0.374
18.8
0.442
Calculation
V
of K£ Values
VII*
10-28 12-1
11-10 12-14
PONVFWTTONAT —
67 75
248
65
175
110
0.629
1239
5.61
6.95
0.244
15.2
0.476
180
72
134
62
0.463
1958
2.50
4.90
0.099
10.2
0.390
VIII
1-8
1-21
87
201
57
134
77
0.574
1770
5.0
8.85
0.152
6.3
1.035
II
8-8
9-5
SLUDGE
100
220
38
129
91
0.706
707
2.75
1.94
1.215
23.5
0.745
in
9-6
9-20
REAERATION-
105
273
51
158
107
0.677
743
2.90
2.15
0.973
22.7
0.732
VI
n-n
11-30
67.5
241
105
186
81
0.435
935
3.70
3.46
0.223
11.7
0.7H
-"-Waste feed vias "Surfpac" effluent during period covered by Appendix VII, and primary effluent the remainder of the time.
-------
The general formula expressing the influence of temperature
on "biological oxidations is
Trial calculations indicated that 0 is probably about 1.15
for the pilot plant. Conversion of K2 values to 20° C is shown in
the bottom line of Table III.
From an inspection of the 20° C "K?" values shown in Table
III for the periods covered by Appendices II to VI inclusive, it appears
that for the particular plant and waste mixture under consideration,
the value of "K2" at 20° C is about 0.^6 x 10-3 when sludge reaeration
is not practiced, and 0.73 x 10-3 when sludge reaeration is being used.
Table III indicates a "K2" value at 20O C of only 0.39 x
10-3 for the period covered by Appendix VII, which is the period the
"Surfpac" filter was in operation ahead of the activated sludge process.
This is also the period during which the highest BOD loading per
100 Ib. MLVSS, the highest volatile contents, and the highest sludge
volume indices were experienced. It may be that the "Surfpac" unit
was removing the material most easily oxidized or synthesized by the
sludge organisms and hence their rate of attack on the remaining
material was slower than if the filter had not been in service.
The question of just what the true "K-j" value for conventional
operation at 20o C became even more confusing after the results of the
January operation became available, for as indicated in Table III, the
20° C "K2" value of 1.035 for the period January 8th to 21st was much
higher than any other period of operation, be it conventional or sludge
reaeration. A heavier organic load just prior to this period may have
created peak activity during this period. It is felt that the high
figure should be disregarded.
Therefore, it was assumed that the value of "K2" at 20° C
would be 0.1*6 x 10-3 for conventional operation, and 0.73 x 10-3 for
sludge reaeration in any plant design calculations.
It is of interest to see how much the individual daily re-
sults depart from those values. Figure 7 covers the period from
August 8 to October 27, i.e. the data summarized in Appendices II,
III and IV. Sludge reaeration was practiced from August 8 to Septem-
ber 20, inclusive (Appendices II and III). During that period mixed
liquor temperatures ranged from 21 to 26° C and averaged about 23° C.
A curve has been plotted by use of formula (3) and a "K" of 1.11 x 10~3
which is believed to represent the performance to be expected from
that mode of operation at 23° C. Of the 38 daily points, 7 are on
or very close to the curve, 1^ are below it, and 13 are above it.
46
-------
B.O.D. REMAINING -% OF BOD. IN AERATION TANK INFLUENT
_ — ro w .& y» en ->i jo
01 -fccno ooo tn O O OOOOO
K
\\
\
\
^
X
X
X
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\
V.
\
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x>
X
X
\
X
* x
*xxx
•^
s.
X
X
\
\
S.R. «
N
\
23° (
X IO"3
Sw
^
0
0
o
o
\
o
(2)
C
D("
5
O
O
O
^
CONV
"K = ox
^-^
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e 19
4 X 1C
^-^
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-3'
-
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3 23456789 10 1 12
M.L.V.S.S. X HR. OF MIXED LIQUOR AERATION X lO*3
LEGEND
X SLUDGE REAERATION TABLES E a 3T - MIXED LIQUOR
O CONVENTIONAL OPERATION TABLE 31
FIGURE T - PLOT OF BOD REMAINING vs MLVSS and
TIME IN AERATION TANKS FOR CONVENTIONAL and SLUDGE REAERATION
47
-------
Appendix IV covers conventional operation during the period
October 1st to 27th inclusive, when mixed liquor temperatures ranged
from 15 to 21.7° C and averaged 18.8° C. The upper curve on Figure 7
was plotted by the use of formula (12) and a "K" of O.HU x 10~3. It
is believed to represent the performance expected from conventional
operation at 19° C. Of the 26 daily points, k were near or on the
curve, 10 were below, and 12 above the curve. Points 1, 2 and 3 rep-
resent results when the mixed liquor volatiles were very high and the
return sludge was heavily loaded with adsorbed organic matter.
Figure 8 covers the period October 28 to November 30 inclusive,
i.e. that covered by Appendices V and VI. During the first period, when
conventional operation was being followed, temperatures averaged about
15° C. During the second period, when sludge reaeration was used, tem-
peratures of the mixed liquor were lower and averaged about 12° C.
It may be calculated that the value of "K2" would be 0.229 x
10~3 for conventional operation at 15° C and 0.238 x 10~3 for sludge
reaeration at 12° C. These two values are so nearly the same that a
single curve could be plotted on Figure 8 to represent the expected
performance of both modes of operation during the respective periods
covered by Appendices V and VI. Note that most of the points represent-
ing daily results with sludge reaeration fell very close to the curve.
The points representing daily results with conventional operation are
more widely scattered. The mixed liquor temperature for each of those
days is shown on the plot. The variation in daily temperatures may
account for most of the scattering.
From formula (5) it may be computed that at 10° C the values
of "K2" will be only 0.21*8 as great as they are at 20° C. At 30° C the
corresponding factor would be h.Oh. The reaction velocity changes four-
fold for each 10° C change in temperature. This is a greater change
than is frequently experienced. The literature (l) indicates that for
municipal sewage, a two to threefold change per 10° C of temperature
change is more normal. However, the literature also indicates that
wastes high in soluble BOD are more sensitive to temperature change
than is sewage or wastes high in colloidal BOD. Hammermill wastes are
high in soluble BOD.
Inspection of formula (U) shows that both the mixed liquor
aeration period and the concentration of volatile suspended solids in
that liquor also influence the reduction in BOD. Figure 9 has been
prepared to illustrate that influence. The curves shown thereon were
plotted by the use of formula (U) and the indicated values of "K". Among
other things, Figure 9 indicates that if mixed liquor aeration periods
and volatile solids concentrations are increased sufficiently, it should
be theoretically possible to reduce the BOD of the inflow to the aeration
tank at least 75$ even at mixed liquor temperatures as low as 10° C.
(With a sludge return of 100% of the waste flow, such a reduction would
increase to about 86% of the BOD of the waste inflow. If the rate of
sludge return was only 50$, the corresponding figure would be about
48
-------
BOD. REMAINING-% OF B.OD. IN AERATION TANK INFLUENT
ro tu .&. en en ->i o>
en o o> o o ooooo
\
\
^N
S^ x
X*
#
* X
xN
"V
r^>
16
0
X. «
^^^^
o
19
o"
n '*
°e£>
>c%
013 *
OI6
©18
©19
315
^-^
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VS.R.
CON
^-^
e 12
/ e u
^^^
^ c. a
>° c.
-— — .
D 3 4- 5 6 7 8 9 10 II 12
MLV.SS. X HR. OF MIXED LIQUOR AERATION X 10
LEGEND
X SLUDGE REAERATION TABLE 3m-MIXED LIQUOR
O CONVENTIONAL OPERATION TABLE 3EL
13 TEMPERATURES °C
FIGURE 8 - PLOT OF BOD REMAINING vs
MLVSS and TIME IN AERATION TANKS
49
-------
46 8 10 12 14 16 18 20
M.LVS.S. X HR. OF MIXED LIQUOR AERATION X IO'3
LEGEND
SLUDGE REAERATION
CONVENTIONAL OPERATION
22 24
FIGURE 9 - PLOT OF BOD REMAINING vs MLVSS and TIME
IN AERATION TANKS FOR VARIOUS OPERATING TEMPERATURES
50
-------
Oxygen Uptake
Appendices II through VII indicate that average air usage in
the pilot plant ranged from 63 to 208 cubic feet per pound of applied
BOD. The low air requirements of the pilot plant indicate that the
turbine-type gas dispersers used in the pilot plant have a higher oxy-
genation efficiency than the devices used in many plants.
On October 5, one of the aeration tanks was scrubbed and then
filled with clean water. The water was deoxygenated and the reoxygena-
tion capacity of the turbine was measured by the unsteady state aeration
procedure, as fully described in (3). Air was supplied at the rate of
9.5 cfm. The effect of sparger submergence was ignored. A test at
62° F. gave a Kla value of 5.6? and a test of 6i*° F. a value of 7.0^.
Adjusting to 20° C and averaging gave a "%a" of 6.72. By using that
value of "Kia" in the standard formula (ibs/hr oxygen into solution =
Kla (CS-C) 8.31* Vol. of liquor) it may be computed that at 20° C and
0.0 mg/1 of dissolved oxygen the turbine would put 3.31 lb. of oxygen
into solution per hour. Air temperature at the blower intake was 70° F
so, assuming a barometric pressure of 760 mm, each cubic foot of air
contained about 0.0171* lb. of oxygen. On this basis, the oxygenation
absorption efficiency of the turbine was 60 x'j?.!?** II.01 (ft or 33.3%.
This turbine efficiency is higher than normally encountered
in the waste treatment field. The high efficiency is primarily a result
of a high mixer horsepower in relation to gas (blower) horsepower. As
no other tests were run with clean water, there are no means of estimating
the numerical effect of variations in rate of air supply on oxygenation
efficiencies.
Late in October the depth of one of the aeration tanks was
halved. This materially reduced the submergence of the sparger ring.
Certainly such a change should decrease both the "Kla" value and the
oxygenation efficiency of the turbine, but it was not possible to numeri-
cally evaluate that effect.
Note that the calculated oxygen absorbed rate in lb. of oxygen
per turbine horsepower per hour for the pilot plant is extremely low
due to the abnormally high ratio of mixed horsepower to blower horse-
power (15:l).
The rate of oxygen utilization is frequently reported in milli-
grams per liter per hour and termed the "oxygen uptake rate" - "r". As
indicated in Table IV, this rate was measured on several different occa-
sions. The August 15 run was performed by turning off the air supply
and turbine to the aeration tanks and measuring the rate of depletion
of oxygen by means of a galvanic cell oxygen probe submerged in the
tanks. Problems with the submerged probe dictated a new procedure for
the remaining tests. In the balance of the tests the procedure was to
place a magnetic stirrer in a BOD bottle and then fill it with activated
51
-------
sludge, a galvanic cell oxygen probe was inserted and the dissolved
oxygen concentration vas read and recorded at 5 to 30 second intervals
while the content of the bottle was continually stirred. Ideally the
plot of oxygen concentrations against time should be linear from the
initial high concentration down to some low residual of 0.5 mg/1 or
less. The oxygen uptake, expressed in mg/1 per hour, is determined by
the slope of the plot. This ideal situation only prevailed in the case
of the three measurements made on August 15-
In three tests the oxygen decline from the initial high value
was uniform for a period of several minutes and then practically ceased
despite the fact that the residual DO was still relatively high. In
these cases only the first portion of the plot was used to compute the
uptake rate. In nine cases the indicated oxygen concentrations dropped
very rapidly during the first 10 to 90 seconds and then declined at a
slower and more uniform rate thereafter. In these cases the initial
decline was ignored in computing the oxygen uptake rates.
From line 10 of Table IV it may be noted that oxygen uptake
rates varied from 10.5 to 75.0 mg/1 per hour. Had the oxygenation
capacity of the aeration system been limited, such a wide variation
might have been extremely significant. However, such was not the case
in the pilot plant.
Line 11 shows the approximate concentration of volatile sus-
pended solids in the various samples. By dividing the values in line
10 by those in line 11 the "specific oxygen uptake rates", "R", ex-
pressed in mg. of oxygen per hour per gram of volatile suspended solids
were obtained. They are shown in line 12 of Table IV. At least in
this particular case, these specific uptake rates are believed to be
much more significant than those shown in line 10.
If retention in the final clarifier does not alter the char-
acter or activity of the return sludge then, on the average, its specific
uptake should be the same as that of the mixed liquor entering the final
clarifier. To evaluate this the data in Table IV may be summarized as
follows:
Specific Uptake Loading Sludge
Mixed Return BOD/100 Return
Liquor Sludge Ib
Aug. 15 (1 sample of each) 39.5 36.5 3^.6 100
Oct. 2U-25 (3 samples of
each) 10.1 Ik.6 1*7.8 95
Nov. 29-29 (2 samples of
each) lU.5 20.7 60.0 67
52
-------
TABLE IV
Oxygen Uptake Determinations
!. Date 8-15 8-15 8-15 10-24 10-24 10-25 10-25 10-25 10-25 11-28 11-28 11-28 11-29 11-29 11-29
2 Time ? ? ? 6;30 P.M. H;00 A.M. 6:00 P.M. 3:00 P.M. 9;00 A.M.
Sludge Sludge Sludge
Mixed Return Reaera- Mixed Return Mixed Return Mixed Return Mixed Return Reaera- Mixed Return Reaera-
3. Sample Source Liquor Sludge tion Liquor Sludge Liquor Sludge Liquor Sludge Liquor Sludge tipn, Liquor Sludge tion
4. Sample Temp °C 26 26 26 17 17 15 14 15 13 10 10 10 10 10 10
5. Time required
for meter
stabilization, . _
seconds 0 0 0 30 15 10 0 0 10 90 30 60 0 30 30
6. Length of period
m of uniform D.O. ,«,.„«,.
" decline min. 3.5 2.0 8.0 4.5 1.75 5.83 2.0 6.0 1.6 5.5 1.5 5.5 4.0 0.5 2.75
Dissolved Oxygen mg/1
7. Initial
8. Start of uniform
decline
9. End of uniform
decline
10. Oxygen uptake.
mg/l/hr 34.3 60.0 27.? 22.7 34.3 18.6 60.0 22.0 75.0 19.7 36.0 12.0 10.5 48.0 18.3
11. VSS, mg/1 867 1646 1290+ I960 3980 1950 3850+ 2400 3850+ 1060 2460 2080 1010 1780 2110
12. Specific 02
Uptake mg/hr/ . ,..
gram solids 39-5 36.5 21.5 11.6 8.6 9.5 15-6 9.2 19.5 18.6 14.6 5.75- 10.4 26.9 8.65
2.4 2.4
2.4 2.4
0.4 0.4
4.1
4.1
0.4
4.0
3.2
1.5
4.0
2.5
1.5
7.0 4.0
6.0 4.0
4.2 2.0
6.8
6.8
4.6
5.3
4.2
2.2
6.6
4.1
2.3
3.0
0.9
0.0
5.4
4.0
2.9
5.0
5.0
4.3
6.0 5.2
2.4 3.7
2.0 2.8
-------
These facts indicate that the higher the BOD to solids loading
the more important it may be to utilize a high rate of sludge return,
particularly if sludge reaeration is not being used. The wide variation
in the specific uptake rates shown in Table IV is also significant.
Although some of the variation may have been due to temperature differ-
ences or experimental errors, it is believed that much of it was due
to variation in BOD input. The BOD of municipal sewage varies from
hour to hour and, therefore, it is reasonable to expect variations in
oxygen uptake rates, even though the rate of sewage inflow remained
constant. Table IV is based entirely on the analysis of only 15 grab
samples. Hundreds of such analyses would be required to empirically
establish dependable data on oxygen requirements. A review of known
relationships might offer a better approach to the problem.
The oxygen requirement is that used by the amount of 5-day BOD
removed plus the oxidation of volatile suspended solids. For this par-
ticular plant the following empirical formula was developed.
Ib. of 02 required per day = (0.5 x Ib. of BOD removed per day)
+ (0.2 x Ib. of VSS under aeration) -f- 1.15 (2°-T) (6)
The value 0.5 is taken from the literature and 0.2 determined
by trial calculations.
To illustrate the validity of this formula, Table V has been
prepared. The data in lines 3, 12 and ih are taken directly from the
averages shown in the tables listed in line 1. The BOD reductions
shown in line H were computed from the average BOD concentrations of
primary and final effluents shown in the same tables and the tempera-
tures shown in line 2 are averages for the periods covered by those
tables.
The oxygen requirements shown in line 7 were computed by
formula (6) and are the sums of the quantities shown in lines 6 and 5,
i.e. the quantities computed by the two parts of that formula.
The requirements shown in line 7 are expressed in pounds per
day per 100 Ib. MLVSS. By dividing those quantities by 2.^, the oxygen
needs are expressed in mg. per hr. per gram of VSS and are shown in
line 8. These quantities are compared with the specific oxygen
uptakes shown in Table IV by averaging some of the data.
Although the comparisons are far too limited to prove the
dependability of formula (6), they certainly indicate the possibility
of its validity. As a further check of that formula, an attempt was
made to compare the calculated oxygen requirements shown in line 7 of
Table V with the actual average air usage shown in line Ik. It was
assumed that the barometric pressure averaged 1^.7 psia through each
period and that average atmospheric temperatures were as shown in
line 10.
54
-------
TABLE V
Calculation of Average Oxygen Needs, Etc.
I. Period Covered by Appendix II III IV V VI VII vill
2. Mixed Liquor Temp. °C 23.5 22.7 18.8 15.2 11.7 10.2 6.3
3. BOD Loading, lb/100 VSS/day 43 56 42 50 47 52 29
4. BOD Removed, % 83 81 80 74 56 60 72
5. Lb 02/100 Ib VSS for endogenous
respiration if rate 0.2 Ib/lb @ 20°C 32.6 26.6 17.0 10.2 6.2 5.0 3-1
6. Lb 02/100 Ib VSS for BOD removal
0 0.5 lb/lb BOD 9 20°C 17.9 22.6 17-7 18.5 13.2 15.6 10.4
7. Total 02 lb/day/100 Ib VSS @ 20°C 50.5 49.2 34.7 28.7 19.4 20.6 18.5
8. Total 02 mg/Wgram VSS 9 20°C 21.0 20.5 14-5 12.0 8.1 8.6 7-7
9. CFD of 60°F air/lb VSS 9 100# efficiency 28.5 27.8 19.6 16.3 11.0 11.6 10.4
10. Assumed atmospheric temp. °F 68 66 50 46 40 38 25
11. CFD atmospheric air/lb VSS @ 100#
efficiency 29.0 28.2 19.2 15.9 10.6 11.1 9.7
12. Activated sludge, % vol. 73 77 84 81 83 85 81
13. CFD atmospheric air/lb TSS @ 100#
efficiency 21.1 21.6 16.1 12.9 8.8 9.4 7-8
U. Actual CFD of air/lb TSS 57 56 62 63 24 43 21
15. Indicated Oxygenation Efficiency, % 37 39 26 21 37 22 37
16. Number of turbines in use 22122 12
17. Average air flow per turbine, scfm 3-40 4.32 6.15 2.92 1.68 1.80 1.96
-------
The calculated volumes of atmospheric air shown in line 11
were multiplied by the percentages of volatiles in the sludge (line 12)
to obtain the cubic feet of atmospheric air that would have been re-
quired per pound of TSS under air had the oxygenation efficiency been
100$, see line 13. These quantities were then compared with the actual
air usage shown in line ll* to obtain the indicated oxygenation effi-
ciencies shown in line 15.
The indicated efficiencies for the periods covered by Appen-
dices II, III, VI and VIII are substantially higher than those for the
other three periods. The differences in oxygenation efficiencies cannot
be attributed to the effect of temperature on "Cs" or "Kla". It so
happens that sludge reaeration was practiced during three of the four
periods of high efficiency while conventional operation prevailed
throughout the other periods. However, there is no biological based
reason why oxygen requirements should be any different for one mode of
operation than for the other. Differences in turbine submergence and
air flow rates are apparently responsible for the observed efficiency
variations.
It is concluded that for the mixture of sewage and Hammermill
wastes, formula (6) is completely valid for computing the daily oxygen
requirements of an activated sludge plant. If the variation in the rate
of BOD removal throughout the day is known, the formula can be easily
modified to calculate the oxygen requirements over shorter periods of
time. However, it can only give average oxygen needs for the period
under consideration. The formula yields no indication of how the up-
take rates differ from that average at various locations within the
aeration tanks. In completely mixed tanks, such as those used in the
pilot plant, the uptake rate, at any given instance, must be the same
throughout.
With a high suspended and colloidal BOD in the waste feed a
high proportion of total oxygen will be used in the reaeration tank.
On August 15 the pilot plant was utilizing half of its then available
aeration volume for sludge reaeration, and judging from the oxygen up-
take rates shown in line 10 of Table IV, reaeration required some ^5$
of the total oxygen needs. On November 28-29, only one-third of the
tankage was used for reaeration. From line 10 of Table IV, it may be
calculated the same average oxygen uptake, namely 15.1 mg/l/hr, prevailed
in each tank. Therefore, sludge reaeration required only 33% of the
total oxygen needs.
Much of the oxygen needed for sludge reaeration is utilized
for endogenous respiration which progresses faster at high temperatures
than at low temperatures. It is concluded that if sludge reaeration is
to be used in the joint plant, the reaeration tanks, during the summer
and early fall, may use as much as k5% to 50* of the total daily oxygen
requirements of the plant, as computed by formula (6). However, during
the winter and early spring, they may use as little as 30? to 35^ of the
formula (6) total. Unduly long or short reaeration periods would prob-
ably alter those percentages.
56
-------
Sludge Production
After numerous trial calculations based on general formulas,
it was concluded that for the particular mixture of sewage and paper
mill waste under consideration, the net build-up of excess biological
floe could be computed by the following variation of the standard formula.
The value .55 is from the literature and a temperature effect is included
in the formula:
excess biological floe Ib/day = (0.55 x Ib/day BOD removed) -
(0.1 x Ib VSS under aeration) (?)
During the operation of the pilot plant the BOD input and
removal, the inventory of volatile solids under aeration, and the amount
of excess sludge wasted, varied over wide limits. Because of these
variations it is impossible to make day to day calculations of floe
production. However, as indicated by lines H to 12 inclusive, of Table
VI, overall calculations for the seven periods covered by Appendices
II to VIII inclusive have been made. Lines 13 to 19 of the same table
show the application of formula (7) to those same periods. The last
line, line 20 of the table, indicates the percentage relationship that
the weights of cell material calculated by the formula, bear to those
indicated from pilot plant data (line 12). Although these percentages
varied from a minimum of 75% during the period covered by Appendix II
to a maximum of 13W for the period covered by Appendix V, the average
percentage for the seven periods was 101%, which demonstrates the va-
lidity of the formula. Therefore, formula (7) may be depended upon for
estimating the build-up of excess biological floe under widely varying
conditions of BOD loading and mode of operation.
The average BOD loadings, solids aeration periods, sludge
volume indices and volatile content of the mixed liquor solids during
the periods covered by Appendices II to VIII compare as follows:
Appendices
Mos.
II
III
IV
V
VI
VII
VIII
BOD Loading
lb/day/100 Ib
VSS under
Aeration
56
U3
50
1*7
52
29
Solids
Aeration
Period
Hours
7.55
8.9
3.3
5.61
8.8
2.5
5.0
MLSS
Percent
Volatile
72
76
8U
81
82
85
81
Sludge
Volume
Index
101
66
191
151
153
316
221+
57
-------
TABLE VI
Calculation of Buildup of Excess Biological Cell Material
1. Period Considered and Appendix No. II HI IV V VI VII VIII
2. From 6-8 9-6 10-1 10-28 11-11 12-1 1-9
3. To 9-5 9-20 10-2? 11-10 11-30 12-14 1-21
4. Susp. Solids under aeration at start, Ib 315 117 202 132 16? 27 173
5. Susp. Solids under aeratiop at end, Ib 117 280 132 16? 123 52 195
6. Increase in solids inventory, Ib -198 +163 -70 +35 -44 +25 +22
7. Solids wasted during period, Ib 499 0 464 75 244 130 162
8. Total solids accumulated during period,Ib 301 163 394 110 200 155 164
9. Length of period, days 29 15 2? 14 20 14 13
10. Gross solids buildup, Ib/day 10.4 10.9 14.6 7.9 10.0 11.1 14-2
11. Average difference between susp. solids
in primary and final effluents, Ib/day -6.0 +0.2 -1.4 +4.3 +4.2 -3.7 +0-2
12. Indicated buildup of excess biological
cell material, Ib/day 4-4 11.1 13.2 12.2 14.2 7.4 14-4
13. Average 5 day BOD removed, Ib/day 43.9 49.0 43.2 39.0 29.0 16.8 30.9
14. Average weight of VSS under air, Ib 128 318 121 102 114 54 16?
15. Average mixed liquor temp. °C 23.5 22.7 18.8 15.2 11.7 10.2 6.3
16. Value of "b" at above temp, if "b" is
0.1 at 20°C 0.163 0.132 0.085 0.051 0.031 0.025 0.016
17. Line 13 x 0.55 24.1 27.0 23.8 21.5 16.0 9-2 17.0
18. Line 14 x Line 16 20.8 15.6 10.3 5.2 3.5 1.4 2.7
19. Excess biological cell material by
Formula (19), i.e. Line 17-Line 18, Ib/day 3.3 11.4 13.5 16.3 12.5 7.8 14.3
20. Line 19 as a percentage of Line 12 75 103 102 134 88 105 99
-------
It will be noted that although the BOD loadings vere almost
identical during the periods covered by Appendices II and IV, the
volatile content of the mixed liquor and its sludge volume index were
much higher during the latter period. The solids aeration time during
the period covered by Appendix IV was less than half of that prevailing
through the first period. As the BOD loads were the same, the volatile
activated sludge solids were absorbing the same amount of BOD during
the two periods, but during the period covered by Appendix IV, those
solids were not aerated long enough to oxidize all of the adsorbed
material. Therefore, their volatile content increased as did the
sludge volume index.
On Figure 6, there is plotted chronologically the daily
variations in BOD loadings, volatile contents of mixed liquor sus-
pended solids, sludge volume indices and the quotient of the BOD load-
ing divided by the hours of solids aeration for the period August 8
to November 10. All four parameters varied considerably from day to
day. However, certain trends are apparent. For example, it appears
that generally the SVI did not exceed 100 so long as the volatile con-
tent of the mixed liquor suspended solids did not exceed 80$, but that
once the volatile content of those solids exceeded 80%, the SVI started
to rise. The longer the volatile content remained above 80$, the more
rapid the rate of increase in the SVI.
The maximum index that can be carried in any activated sludge
plant is a function of final clarifier design and the rates of flow
of both incoming waste and return sludge. However, invariably there
will be some index that cannot be exceeded without the loss of solids
in the final effluent. From Figures 6 and 6-A it would appear that with
mixed sewage and Hammermill waste, it would be desirable to prevent the
volatile content of the mixed liquor solids greatly exceeding 80$.
Figure 6 indicates that there may be one or more days lag
between changes in the above-mentioned quotient and the corresponding
changes in the volatile content of the mixed liquor. This is to be
expected since the entrainment or adsorption of suspended and of
colloidal organic material on the surface of the sludge is an extremely
rapid process, while biological cleansing of the sludge requires time.
Figures 6 and 6-A both indicate a tendency for the SVI to rise
with or soon after an increase in the volatile content of the mixed
liquor solids, and to decline following a decline in the volatile con-
tent. However, the rate of decline in the index was frequently very
slow and gradual. It appears that once the index is high, it tends to
remain high for protracted periods of time, despite the decline in the
volatile content of the mixed liquor solids. We believe that this ten-
dency can be attributed to the effect of the large number of filamentous
organisms known to be present in the sludge throughout October and
subsequent months.
59
-------
Figure 10 is a plot of the volatile content of the mixed
liquor solids against the quotient in BOD loading in Ib. per day per
100 lb. MLVSS divided by the hours of solids aeration for the period
August 8 to November 10, inclusive. (On the five days where there vas
a sharp drop or jump of one day duration, the average of the volatile
percentages for the days immediately before was used.) Although there
is some scattering of the points, it does appear that if the volatile
content of the mixed liquor solids is not to exceed 80$, then the value
of that quotient must be less than 6. This curve is similar to the
"Sat-BOD" removal curve. This conclusion is generally applicable so
long as the mixed liquor temperature remains above 15 to 18° C. How-
ever, the experience gained during late December indicates that when
temperatures are as low as 6° C, even extremely prolonged aeration has
little effect upon the volatile content of the mixed liquor solids.
Throughout the operation of the pilot plant, high rates of
sludge return were used. Rates as high as 175$ °f the inflow were used
on a few occasions and sludge return rates have averaged 100$ or more
for the periods covered by Appendices II and III. Rates of less than
50$ were seldom, if ever, used and the lowest average rate for any of
the periods was 67.5$ of the inflow.
Prom a purely theoretical viewpoint the higher the rate of
sludge return, the higher will be the BOD reduction. However, the law
of diminishing returns applies to this consideration, i.e. each suc-
ceeding increase and rate of sludge return yields a smaller theoretical
benefit. The higher the rate of sludge return, the larger will be the
aeration or sludge reaeration tanks required to provide the necessary
detention time. However, high rates of return are an absolute must when
high sludge volume indices in the mixed liquor are encountered.
It was previously stated that because of the likelihood of
experiencing infestation of filamentous organisms, any plant designed
to provide joint treatment for Hammermill wastes with municipal sewage
should be capable of operating with a mixed liquor SVT of 200, i.e. a
SDI of approximately 0.5. After careful consideration of various fac-
tors, it is felt that during the summer months, the concentration of
solids in the return sludge should not exceed 80$ of that density index,
i.e. U,000 mg/1, but that during winter time, when mixed liquor tempera-
tures are in the order of 10° C, return sludge concentrations of 1.3
times the SDI would not be particularly harmful.
Suspended Solids Removal
As indicated by Appendices II to VIII, suspended solids
reductions by the activated sludge process have been generally low and
highly variable. In contrast, when treating only municipal sewage,
the conventional activated sludge process generally effects about as
high reductions in suspended solids as it does in BOD.
60
-------
30
40-
50
60
-'
£70
.
80
90
24 6 8 10 12 14 16 18 20 22 24 26
LB. BO.D. PER 100 LBS. YS.S. UNDER AIR/HR. OF SOLIDS AERATION
FIGURE 10- PLOT OF VOLATILE MLSS vs BOD LOADING
DIVIDED BY AERATION TIME
61
-------
Although the loadings on the final clarifier expressed in
gallons per square foot per day of waste inflow did not exceed 750
gallons per day, the distance from the inlet to the outlet of the pilot
plant clarifier was extremely short when compared with conventional
clarifiers used in municipal plants. Therefore, we at first thought
it possible that the pilot plant final clarifier was overloaded. To
check on this, effluent solids concentrations when treating 20 gpm
were compared with those prevailing when treating only 15 gpm. The
following tabulation (based on August through October) summarizes that
comparison:
Rate of Waste Feed 20 gpn 15 gpm
Number of days included ^5 2k
Maximum suspended solids in final
effluent, mg/1 130 110
High Decil 92 98
High Quatril 60 80
Median 1(8 57
Low Quatril 32 1*5
Low Decil 2 it 28
Minimum 18 20
Average Uk 6l
Certainly the above tabulation does not indicate that a
reduction in inflow to the final clarifier improved its effectiveness.
Figure 11 was prepared to see if there was any relationship between
the SVI and the suspended solids content of the effluent. It clearly
shows that no correlation exists.
During the pilot plant operations the average suspended
solids concentration of the final effluent was as follows for the
periods covered by Appendices II to VIII inclusive.
Appendix No. mg/1
II 50
III 6h
IV 614
V 91
VI 79
VII U7
VIII 57
62
-------
UENT SUSPENDED SOLIDS mg/L
d-jooioo — roc
>oooooooc
_l iJW
u.
u_
UJ
-I 40
<
2
U.
30
20
Q
0 <
X
X
X
X
X '
K
X
X
x"
X
x
X
X
X
X
X
y
X
' y
X
,
X
X
X
X
X
X
X
X
>
©
Gx
X
C
0
O
O
D
O
G
O
0
o
n
O
i
(
U
O 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 25
SLUDGE VOLUME INDEX
LEGEND
O 15 G.PM. INFLOW
^ 20 G.RM. INFLOW
FIGURE 11- PLOT OF FINAL EFFLUENT S3 vs SVI
-------
A full scale clarifier can effect a better removal of solids
than did the pilot plant clarifier even though both were operated at
the same surface settling rates. However, there is no assurance that
the effluent discharged from an activated sludge plant treating the
mixed sewage and Hammermill waste will average less than hO mg/1 of
suspended solids. Chester Engineers in their work at two paper mills
treating wastes by the activated sludge process found that it was diffi-
cult to produce a final effluent of low suspended solids concentration.
Other paper mills have had difficulty in removing suspended solids by
the activated sludge process (^,5) and this may be an indication that
similar difficulties are to be expected whenever paper mill wastes are
treated by the activated sludge process.
It is possible that the use of polyelectrolytes, flocculation,
etc., prior to the final clarifier may improve suspended solids removal
if such removal becomes mandatory. Unfortunately, there was no oppor-
tunity to fully evaluate the various treatment schemes which can be
used to further clarify the effluent.
Effluent Color
Although the activated sludge process is effective in reducing
the BOD of the mixed waste, it does not reduce its color. In fact,
oxidation seems to intensify the color slightly. This is indicated by
the following tabulation:
Average Color
Primary Final
Appendix No. No. of Samples Effluent Effluent
II 22 1121 1229
III 3 I2h3 1895
IV 11 12UO 1330
V 5 1381 1558
VI 6 1133 122?
VII U lOUl 1165
VIII 0
Chlorine Demand of Activated Sludge Effluent
Although the activated sludge process generally effected a
30$ to kO% reduction in the chemical oxygen demand of the primary effluent,
the final effluent from the activated sludge process still had a very
substantial chlorine demand. This is indicated by the following tabu-
lation :
64
-------
Average Chlorine
Appendix Ho. No. of Samples Demand, mg/1
II Ik 31
III 0
IV 6 52
v 3 57
VI 5 66
VII h 81
/III 2 38
65
-------
VIII
SLUDGE DISPOSAL
The primary sludge obtained from the pilot plant had the
appearance of municipal sludge, but it contained an average of 1.5$
solids, with 80$ of the sludge solids being volatile. Although the
pilot plant sludge appeared to be of the same consistency and contain
as high a concentration of solids as municipal primary sludge, the
weight of the solids was surprisingly less. This is attributed to
the hydrous condition and properties of the fibrous pulp waste solids.
Througnout our pilot plant work, it was noted that the pilot plant
primary sludge had the consistency and handleability of municipal
sludge containing two or more times the total solids concentration.
The excess sludge from the pilot plant was similar to that found in
a municipal plant except for the color which was deep (burnt) orange.
Thickening
Sludge thickening was studied in the pilot plant by both
settling and flotation. It is practically impossible to simulate a
continuous flow gravity thickener in pilot plant operations of the size
installed by Haramermill at the Erie Treatment Plant, because of the
impossibility of simulating area to depth ratios that prevail in con-
ventional gravity thickeners. Therefore, it was impossible to conduct
continuous flow tests of gravity thickening at the pilot plant. Numerous
batch settling tests were made and indicated that when the mixed
primary and excess activated sludge from the pilot plant was subjected
to 2 to 2-1/2 hr. sedimentation periods and solids retention on the
order of one day, the resulting sludge contained 2 to 2.5$ total solids.
By increasing the settling period to 3 hours or more and sludge holding
periods to over one day, concentrations in the order of 3% total solids
were obtained.
From these rather crude tests, it was concluded that if
gravity thickening is to be applied to the mixture of primary and
excess sludge resulting from the joint treatment of Erie sewage and
Hammermill wastes, such units should be designated for overflow rates
of only 600 gallons per sq. ft. per day. Our tests did reveal that
retention of the mixed sludge for two to three hours in the batch
settling tests resulted in the release of appreciable amounts of phos-
phates. If sludge were to be retained for a day or more in full-scale
gravity thickeners, the effluent from such thickeners might be expected
to contain between 100 and 150 mg/1 of suspended solids and possibly
30 mg/1 of phosphates.
To determine the suitability of flotation thickening of the
pilot plant sludge, a 1 sq. ft. pilot flotation unit was obtained from
Komline-Sanderson Engineering Corporation. The unit was operated with
65 psi air and internal recycle. The unit's operation was supervised
67
-------
by a representative of the manufacturer, and the results obtained were
reviewed and evaluated with Komline-Sanderson engineers.
Waste activated and a combination of waste activated and
primary sludges were tested and the results of these tests are set
forth on Table VII. The results show that flotation can thicken the
waste activated sludge or the combination of waste activated and primary
sludges from a joint plant to a concentration of 3% TS. The effluent
would contain from 150 to 200 mg-1 of SS and some 12 mg/1 of phosphates.
These results are similar to those expected by gravity thickening except
that as expected the phosphates did not have as much opportunity to
resolubilize as in the gravity thickener because of the prevailing
aerobic conditions and were, therefore, significantly lower.
Pilot plant results indicate that a flotation unit can con-
centrate waste activated sludge to 3% TS if the loading does not exceed
2k Ib. solids per sq. ft. per day, and the flow rate 1000 gpd per sq.
ft. A combination of primary and vaste activated sludge can also be
concentrated to 3% TS if the loading does not exceed U8 Ibs. solids per
sq. ft. per day or 600 gpd per sq. ft.
Polymeric flocculants were used in some of the flotation runs,
but they did not materially improve the results. However, it is
advisable to incorporate facilities for feeding aids in a plant for we
can envision conditions and situations where the flocculants could
assist in concentrating the sludge.
The studies indicate that the sludge from a joint plant can
be concentrated to 3% TS by using either gravity or flotation thickening
on the combined primary and waste activated sludges. There is every
reason to believe that a combination of gravity thickening of primary
and flotating thickening of waste activated sludge would yield compa-
rable results.
Sludge Dewatering
Vacuum filtration is the most widely accepted means of
dewatering sludge in large waste treatment plants. As the name implies,
this method consists of placing a filtering medium under vacuum to
separate the liquid from the sludge.
The proper pre-conditioning of the sludge is perhaps the most
critical and troublesome requirement for good filter performance. The
cationic polymers have been used with most success for sludge conditioning.
The Erie Plant uses Dow "Purifloc C-31" cationic polymer to condition
sludge prior to filtering.
Initial filtration studies were performed with a 0.1 sq. ft.
filter leaf test kit. Tests were initially conducted to determine if
filtration would work, to establish the proper type and dosage of
68
-------
TABLE VII
VD
Sludge Concentration with Flotation*
Date
11/16
11/16
11/16
11/30
11/30
11/30
11/31
11/31
Type
Sludge
WA
WA
WA
WA
WA
WA
P + WA
P + WA
Feed
Rate
(gpm)
1
0.75
0.50
0.95
0.71
0.47
0.47
0.24
Feed
SS
(mg/1)
3,000
3,270
2,370
1,590
1,590
1,620
11,860
10,880
Float
SS
(*)
2.10
2.76
2.93
1.55
2.46
2.72
2.98
3.12
Effluent
SS
(ms/1)
190
210
188
360
170
160
1,220
340
Aid (C-31)
Dosage
(50
0
0
0
3
3
3
1
1
lb/hr/sq
1.50
1.23
0.60
0.76
0.56
0.38
2.84
1.27
Loading
ft gpm/sq ft
1,0
0.75
0.50
0.95
0.71
0.47
0.47
0.24
*Komline-Sanderson Engineering Corporation Model HR/SR-1 used for all runs,
NOTE: WA = Waste Activated. P + WA = Primary + Waste Activated.
-------
flocculant, and the mesh and type of filter medium. Initial tests
indicated that undigested combined primary and waste activated sludge
produced by the pilot plant and thickened to 2 to 3% TS could be
successfully filtered by using 2 to 3% by weight of "C-31" flocculant
based on the solids content of the sludge and Eimco Corporation's
Filter Medium No. 527-F a 157 x 62 mesh Nylon cloth. Typical filter
leaf results were:
Feed "C-31" Cake
TS Dose TS Yield
2.2% 3% 18$ 3.2 Ib/sq ft/hr
2.1*6$ 2% 21% 2.85 Ib/sq ft/hr
These results compared favorably with the 1966 vacuum filtra-
tion data for the City Plant.
Because of the large quantity of sludge that must be handled
at a joint plant and the significant portion of the capital cost that
will be reflected in sludge treatment facilities, it was decided to
study this method of treatment in more detail and to refine the design
parameters.
A 9.5 sq. ft. cloth-belt vacuum filter complete with accessories
and a Nylon No. 527 filter medium was obtained from The Eimco Corporation.
That pilot unit was operated by Eimco engineers. Chester personnel
collected the data and analyzed the results. A series of l6 filter runs
were made on four different days. In all cases the combined primary
and waste activated sludge produced by the pilot plant and thickened in
the fill-and-draw gravity thickener was used as feed to the filter. The
results of the runs are presented on Table VIII.
A review of the results will clearly indicate that filter
performance is dependent upon the concentration of the solids in the
feed and dosage of flocculant aid. With the feed solids constant,
yield increases with aid dosage increase and similarly with aid dosage
constant the yield increases with increase in solids in the feed, as
one normally expects.
With a sludge fed with 3% TS a design filter yield of 3.5
Ib/sq ft/hr with 20% TS in the cake and a polymeric flocculant dosage
of 1$ could be expected. The consistency of the pilot plant filter
cake was greater and the filtrate was significantly clearer than that
of the municipal plant. The filter cake produced with sludge from the
pilot plant came off in sheets. Filter performance and cake quality
is likened to the results obtained in the filtration of raw primary
sludge, but without any of the associated odors.
The filtrate from all pilot plant runs was of very good quality
and was, in fact, without the characteristic rust color. The brief work
70
-------
TABLE VIII
Vacuum Filtration Studies*
Yield
Date (%) (%)" (mg/1) (%) Ib/sq ft/hr
10/25 2.5 2.45 35 24 5.70
5.20
2.80
5.00
1.25
2.30
Feed
TS
121
2.5
2.5
2.5
2.5
2.5
2.5
2.2
2.2
2.2
3.0
3.0
3.0
3.0
2.3
1.8
1.8
Aid (C-31)
Dosage
(%)
2.45
2.45
2.10
1.75
0.56
1.33
1.55
1.90
1.90
0.84
0.85
0.63
0.55
2.10
1.90
2.0
Filtrate
SS
(mg/1)
35
40
-
50
-
-
36
-
-
_
110
205
—
165
200
-
Cake
TS
(%)
24
22
20
17
17
18
22
23
23
17
18
17
18
20
18
18
10/26 2.2 1.55 36 22 2.55
3.00
3.30
11/16 3.0 0.84 - 17 2.65
3.92
2.43
2.05
11/17 2.3 2.10 165 20 3.40
1.67
2.86
*Studies conducted with The Eimco Corporation 9.5 sq ft cloth-belt
filter.
71
-------
to determine the cause for the loss of color indicated that the color
so prevalent in the waste was apparently adsorbed by the sludge with
the long detention time in the thickener. Filtrate suspended solids
ranged from 35 to 200 mg/1 and contained 22 mg/1 of phosphates.
To evaluate filter performance on digested activated sludge,
filter leaf tests were made using the standard 0.1 sq. ft. test kit on
sludge taken from the four pilot digesters. The filter medium was
Nylon No. 527-F and the pickup and drying time as well as the vacuum
and the dosage of Dow "C-31" were kept constant in all cases so that
the results are comparable. The following tabulation presents the
results of these tests as well as the City's average vacuum filtration
performance for 1966.
Feed "C-31" Dose Cake Filtrate Yield
& TS(» SS(mg/l) Ib/sq ft/hr
City 1966 Average
It. 6 1.2 20.U No data 3.1*
Municipal Sludge from Pilot Digesters:
High Rate I
7.0 1.5 21.6 1080 6.7
High Rate II
U.5 1.5 15.2 1380 3.7
Pilot Plant Sludge from Pilot Digesters:
High Rate I
2.8 1.5 13.0 UUO 1.2
High Rate II
2.0 1.5 16.8 870 0.8
The laboratory filtration rate for the municipal sludge from
High Rate I pilot digester compares favorably with the actual performance
of the City's filtering system. The filtration rates on the pilot plant
digested sludges are significantly less than those for the municipal
digested sludges. More significant is the fact that the filtration
rates for the digested pilot plant sludge are about one-third the rates
obtained for the undigested pilot plant sludge. This fact supports the
contention that undigested activated sludge can be dewatered more
readily and economically than can digested activated sludge.
72
-------
The possible advantages of centrifugalion over filtration
and the reasonably good results obtained by devatering the pilot plant
sludge with a clinical centrifuge led to experimentation with a
larger machine.
A Model No. P-660 Super-D-Canter was obtained from the
Sharpies Equipment Division of Pennsalt Chemicals Corporation and
operated on three different days on gravity thickened sludge obtained
from the pilot plant. Sharpies' engineers operated the centrifuge and
Chester personnel collected and analyzed the data. The data are
presented on Table IX.
The optimum rate for that centrifuge appears to be a 2 gpm
feed which contained some 3% TS and a "C-31" dosage of 2% by weight;
instead of 1% by weight. This produced a reasonably dry cake with 20%
TS and a centrate containing about 1000 mg/1 SS, with a solids capture
efficiency in the order of 95$.
A joint plant sludge containing 3% TS could be dewatered by
centrifuges for about the same capital cost as filters. However, it is
believed that the operating costs of the centrifuges would be signifi-
cantly greater than the vacuum filters and the dewatering results
somewhat poorer. Power requirements of centrifuges are three times
that of filters and more polymeric flocculants would be required to
obtain satisfactory results with the centrifuge. The quality of the
centrate would be much poorer than that of the filtrate. Accordingly,
it is concluded that vacuum filters would be the most satisfactory and
economic means of dewatering the sludge.
Sludge Digest ipri
Digestion is the most common treatment for readying sludge
solids for final disposal. Digestion reduces the quantity of sludge
solids, renders them ready for disposal and produces a gaseous end-
product which is normally used to sustain the temperatures required for
the process and may be used as fuel to drive mechanical equipment or to
generate electricity.
Digestion may reduce the quantity of sludge by as much as 50%
by the destruction of the volatile solids in the sludge. The reduction
of sludge volatile solids is the commonly used gauge of when a sludge
is properly digested. The percentage reduction of volatile solids by
digestion depends in part on the amount of volatile matter in the raw
sludge, see Figure 12B.
If the solids and volatile matter content in the feed are
known, the required detention to produce a given reduction in volatile
solids can be obtained from graphs, as per Figure 12A.
For a conventional digestion process where the capacity of the
digester is dependent upon the detention period, the volume of digester
73
-------
TABLE IX
Run
No.
PILOT
1
2
3
4
5
6
7
8
9
Rate
(gpm)
PLANT SLUDG
2.0
0.75
1.0
1.0
0.5
1.0
2.0
2.0
3.0
Feed
Suspended
Solids
(ms/1)
E
31,000
31,500
27,200
27,200
27.200
27,200
27,200
34,800
36,000
Sludge Dewatering Centrifuge Tests
Centrate Cake
Volume of
Solids
00
-
23.3
23.3
23.3
23.3
23.3
-
-
Aids
0
0
1.8
2.6
5.0
3.7
1.9
0
1.0
Suspended
Solids
(mg/1)
11,400
11,400
1,040
940
560
530
1,210
9,780
21,110
Volume of Total
Solids Solids
(*) (*)
18.0
19.0
14 20.0
12 19.5
2 19.5
3.8 20.0
13.4 20.0
11.5
14.0
Capture Efficiency
By By
Volume Weight (#)
(#) (Approx.)
-
40
48
92
84
43
-
—
64
64
96
96
98
98
95
72
49
-------
<:<
z-70
9
•
PERCENTAGE Or VOLATILE SOLIDS,
IN RAW SLUDGE
S_S__8_38_g
x"
^
^
^
OxJ
— '
^
o
^L
X"
*r
x"
20 30 40 SO 60 70 BO *
PERCENTAGE REDUCTION OF ORIGINAL VOLATILE MATTER
WHEN SLUDGE IS CONSIDERED TO BE DIGESTED
FIG. B - REDUCTION IN VOLATILE MATTER BY DIGESTION
Ref. (6)
40
|| |
20
SO
\Q
ro
DETENTION, IN DAYS BASED ON RAW SLUDGE
FEED
FIG. A -REDUCTION IN VOLATILE SOLIDS IN RAW SLUDGE FOR DETENTIONS
FROM 15 TO 70 DAYS T - B5° TO 95°F
Ref. (T)
FIGURES12A, B & C - SLUDGE DIGESTION LOADING
and REDUCTION CURVES
UNHEATED 6O°F
MESOPHILIC 80°F
MESOPHILIC IOO°F
THERMOPHILIC 120°
0
SOLIDS
468
SLUDGE ADDED,IN %
FIG. C -UNIT CAPACITIES OF DIGESTION TANKS (BASED ON
LABORATORY BATCH TESTS)
Ref. (8)
-------
capacity required per pound of total solids added per day would vary
with the percentage of dry solids in the feed. This is shown on
Figure 12C.
The following factors are measures of the effectiveness of
digestion action: gas production (both quantity and quality), solids
balance (total and volatile), acidity-alkalinity, pH, volatile acids
and sludge characteristics and cation concentration.
In order to determine the design loading and detention time
for possible sludge digesters, as well as the suitability of the
digestion process for a joint treatment plant, laboratory scale di-
gesters were designed, built and operated by Hammermill.
It was first thought that comparison of sludge from the pilot
plant with sludge from the Erie sewage system might be made in simulated
High-Rate digesters. On this basis the first digester (Municipal,
High-Rate I) was made and filled with municipal sludge about July 12, 196?.
By July 28 it was considered to be operational on a daily fill-and-draw
schedule to give a 15 to 16 day sludge retention period. After further
consideration it was thought advisable to also construct a digester that
more closely simulated the present digesters used by the City of Erie,
that is, a minimum of 30 days sludge retention. This unit, (Municipal,
High-Rate II) was started during the week of August 20, 19^7 and was
considered operational by September ?5, 196?. Meanwhile a similar type
digester (Pilot, High-Rate II) was started September ih on sludge from
the pilot plant. Sampling of digested sludge from this digester was
started October 6. A fourth digester having 15 to l6 day sludge reten-
tion, and treating pilot plant sludge (Pilot, High-Rate I) was started
October 12 and was considered operational by October 25, With only a
few exceptions, totaling some four days, once digesters were operational,
digested sludge was withdrawn and fresh sludge added to each digester
every day.
The construction of the digesters is shown in Figure 13. The
conventional digesters were inverted 5 gal. bottles filled to the l6
or IT liter level. Tubular openings near the top of the digester were
provided for the withdrawal of supernatant and the addition of fresh
sludge. Digested sludge was withdrawn from the bottom of the digester.
Through the stopper opening in the top, tubes were installed for the
collection of gas and for the recycling of gas to provide agitation for
mixing the upper two-thirds of the digester contents when fresh sludge
was added. A 1-inch wide by h foot long heating tape wrapped around
each digester and regulated by a variable voltage controller provided
uniform heating for all digesters that seldom varied more than one
degree from 32°C.
The operation of the High-Rate II digesters consisted of
daily withdrawal of ^00 ml of stabilized sludge from the bottom of the
digester. Based on a total volume of l6 to 17 liters this provided a
calculated retention time of Uo - U2 days for the sludge. At the same
76
-------
High Rate II
High Rate I
FIGURE 13 - PILOT SLUDGE DIGESTERS
-------
time all the supernatant that was available was withdrawn. The
digester was then agitated by recycled digester gas. Following this,
fresh sludge equal in volume to the sum of sludge and supernatant
withdrawn was added and the upper two-thirds of the digester was
thoroughly mixed by recirculated digester gas. Then the digester
was not disturbed until the following day when supernatant and sludge
were again withdrawn. These digesters were self-regulating in that
the amount of supernatant withdrawn controlled the amount of fresh
sludge that could be added. This in turn was determined by the total
solids content and the liquefaction rate of preceding sludge additions.
The High-Rate I digesters were also 5 gal bottles provided
with a tubular opening near the bottom for the withdrawal of sludge
and one near the top for the addition of fresh sludge. Mechanical
mixing was provided by a stirrer entering from the top of the bottle
through a mercury seal. Additional mixing was provided by recircu-
lation of digester gas as in the other digesters. Each day, after
a thorough mixing of the entire digester contents by a combination
of mechanical stirring and recycling of digester gas, a liter of
sludge was withdrawn from the bottom. A liter of fresh sludge was
then added through the top tube and the contents of the digesters
well mixed. Further mixing was carried out throughout the day ex-
cept when gas measurements were being made. The volume of the con-
tents of the digester was always maintained at l6 liters. The
average retention time of the sludge could then be considered to
be 16 days.
The digesters operating on municipal sludge were the
control digesters and each digester had a twin operating on the
sludge from the pilot plant.
Results:
Daily readings were taken of the TS,VS, of the sludge feed
and sludge withdrawn from each of the four digesters as well as the
pH and alkalinity of the digesters' contents. The average perfor-
mance of each of the digesters is presented on Table X and plots of
the total solids are shown on Figure ih, volatile solids on Figure 15,
alkalinity on Figure l6 and pH on Figure 17.
Although one set of digesters had a solids detention time
corresponding to conventional digestion, the solids loading of these
digesters were in the range normally associated with High-Rate diges-
tion, i.e. greater than 0.07 lb VS/cu ft. We have designated these
digesters as Municipal, High-Rate II and Pilot, High-Rate II. The
performance of each of these two digesters was quite good and the
digestion process progressed to reasonable limits. Some 55$ of the
volatile solids were destroyed, the concentration of total solids
increased after digestion and some 8 cu ft of digester gas per lb
VS added was produced in each digester. The municipal unit was loaded
at 0.13 lb VS/cu ft and the pilot unit at 0.10 lb VS/cu ft and the
78
-------
TABLE X
Digester
Municipal
Pilot Sludge
Municipal
Pilot Sludge
Digester
Municipal
Pilot Sludge
Municipal
Pilot Sludge
High Rate I
High Rate I
High-Rate II
High Rate II
High Rate I
High Rate I
High Rate 'II
High Rate II
Performance of Pilot
Operated
(Days)
128
60
76
70
Detention
(Days)
16
16
40
40
Digesters
Feed Sludge
TS (%}
5.17
2,31
5.65
2.15
VS (56) TS
56.9 3
80.1 1
62.0 6
80.1 3
Gas Production
TVS Destroyed
«)
37.5
63.5
53.7
56.5
Loading
Ib VS/cu ft
0.12
0.07
0.08
0.08
Feed Basis
cu ft/lb VS
4.1
6.9
5.7
6.7
Destroyed Basis
cu ft/lb VS
10.8
10.8
10.6
11.8
Digested Sludge
(30 VS (*)
.84 44.5
.75 59.5
.93 43.0
.56 62.0
Methane
Production
(SO
59.7
55.0
60.0
55.5
-------
•
»
!
LJ
"'•
- (
lij
UJ
Q
00
-
CITY SLUDGE HI-RATE I
CITY SLUDGE HI-RATE H
PILOT PLANT HI-RATE I
PILOT PLANT HI-RATE EL
DIGESTED SLUDGE
FEED SLUDGE
I I i I I
9/12 9/18
10/12 10/18
10/24 10/30
11/24 11/30 12/6
12/12 12/18
-------
100
I
KEY
CITY SLUDGE HI-RATE I
CITY SLUDGE HI-RATE
PILOT PLANT HI-RATE I
PILOT PLANT HI-RATE
DIGESTED SLUDGE
FEED SLUDGE
-. -n O •-<>-
9/6 9/12 9/18 9/24 9/30 10/G 10/12 10/18 10/24 10/30 11/6 11/12 11/18 11/24 11/30 12/6 12/12 12/18
DATE
FIGURE 15 - PLOT OF VOLATILE SOLIDS WITH TIME FOR THE PILOT PLANT SLUDGE DIGESTERS
-------
3400-
CITY SLUDGE HI-RATE I
CITY SLUDGE HI-RATE H
X PILOT PLANT HI-RATE I
D PILOT PLANT HI-RATE
() gm Co(OH)2 ADDED
1000
9/6 9/12 9/18 9/24 9/30 10/G 10/12 10/18 10/24 10/30 11/6 11/12 11/18 11/24 I 1/30 12/6 12/12 12/18
-------
i
9
•
E
.5
.2
.1
7-
6-
•
.
i
F
F
Xy
A
-
MTY SLUDGE HI-RATE I
MTV SLUDGE HI-RATE H
>ILOT PLANT HI-RATE I
MLOT PLANT HI-RATE n
^^-.
— N/^
A
\
N A
v1-
V
/
A
fi
•
/>*r
V'
"^
'\'~'
LI
Dl
^
ME AC
GESTE
v
-v
>DED 1
RS
/
/
ro PIL
>
OT PL
••i
ANT
1
t- 96 9/12 9/18 9/24 930 10/6 10/12 10/18 10/24 10/30 11/6 1/12 11/18 \/& VM \t/*>
DATE
FIGURE IT - PLOT OF pH WITH TIME FOR PILOT PLANT SLUDGE DIGESTERS
-------
sludge detention period was Ho days in each.
It is interesting to note that although the unit loaded
vith pilot plant sludge performed nearly as well as the municipal
unit, the pilot plant sludge required frequent additions of lime to
sustain reasonable pH and alkalinity levels. The volatile acid
content of the pilot plant sludge was consistently two times that
of the municipal unit. Also of interest is the phosphate content
of the supernatant from the pilot sludge digester which averaged
170 mg/1 as
The two digesters termed Municipal, High-Rate I and
Pilot, High-Rate I had a solids detention time of l6 days. The
performance of these units was not satisfactory. Although the
digester receiving pilot sludge was loaded somewhat lower than
High-Rate II (0.07 lb VSS/cu ft), and 6^ of the volatile solids
were destroyed, large and frequent additions of lime were required
to sustain the digestion process. The volatile acid concentration
was 1280 mg/1 on October 25 and it required daily lime additions
for some 10 days to bring that concentration to the 100 mg/1 level.
Lime dosage averaged 3 mg/1 during November.
The performance of the two digesters receiving municipal
sludge can reasonably be considered the base line for comparison
with the digesters treating pilot plant sludge. Pilot plant sludge
requires 70% to &0% destruction (Figure 12B) of volatile matter for
reasonably satisfactory digestion.
The results of this pilot study indicate that digesters
for a joint treatment plant should provide at least ^0 days sludge
retention and have a solids loading of no more than 0.10 Ib VSS/day/
cu ft and have facilities for continual addition of lime in order
to have reasonably successful digestion. The digestion volume re-
quired for a ItO-day loading and a low solids loading indicates that
sludge digestion would not be desirable or practical in a joint plant.
Combustion has been considered as the means of ultimate
sludge disposal. To evaluate this process, four samples of sludge
cake from the pilot vacuum filter were analyzed by "Commercial
Testing & Engineering Company" to determine the proximate and ulti-
mate analysis of the filter cake. The analytical results are sum-
marized on Table XI and they indicate that the cake could be readily
burned and would be, in fact, auto-combustible with a higher percent-
age of moisture than municipal sludge.
The proximate and ultimate analysis provide sufficient
information for sizing incineration equipment and that information
indicates that sludge disposal by this process is most feasible.
Multiple-hearth incinerators to properly incinerate the filter cake
which may contain PO? moisture are recommended. The filters and
84
-------
TABLE II
oo
Commercial Testing
& Engineering Co.
Number
CL-62026
CL-6202?
CL-62028
CL-62029
Totals
Average
CL-62026
CL-6202?
CL-62028
CL-62029
Carbon
43 .U.
42.37
42.34
41.98
169.83
42.44
Analysis of Sludge Cake
Ultimate
Hydrogen Nitrogen
5.88 1.96
5.93 2.16
5.89 2.29
5.86 2.26
23.56 8.67
5.89 2.17
Proximate
(Dry Basis)
% Ash % Volatile
34.26 70.78
14.04 71.53
15.22 70.17
14.02
Sulfur Oxygen Ash
0.75 34.01 14.26
0.74 34.76 L4.04
0.78 33.48 15.22
0.73 35.15 14.02
3.00 137.40 57.54
0.75 34.35 14.36
% Fixed Carbon % Sulfur
14.96 0.75
14.43 0.75
14.61 0.78
0.73
Btu
12,217
12,077
12,218
12.079
48,581
12, U5
-------
incinerator would have to process an estimated 8200 Ib/day/million
gallon raw waste.
86
-------
IX
DISINFECTION
The State standards require disinfection to 1,000 coli-
form per 100 ml, recently revised to 200 fecal coliform per 100 ml.
It is generally believed that disinfection to 1,000 coliform of
municipal final effluent will meet these new standards and that
this will be the case on the 50-50 effluent. Historically the
Pennsylvania Department of Health requires that the Erie municipal
treatment plant maintain a chlorine residual of 1.5 mg/1 after a
15-minute contact period. Preliminary work by Hammermill indicated
that to satisfy such a requirement may demand that the effluent
from a joint plant be dosed as high as 100 mg/1. Such a require-
ment gave impetus to the investigation into the actual dosages re-
quired to effect a satisfactory kill of microorganisms, as well
as possibly substituting other agents to accomplish that kill.
There were also some investigations into the possibility of varying
the point(s) of application in hope of reducing requirements.
The basic objective was to find an agent which would
disinfect without being chemically consumed in the Hammermill-
municipal waste solution.
Many systems were given consideration, including gamma
radiation, formaldehyde, iodine, colloidal silver, sulfamic acid
and bactericides. In addition, the leading manufacturers of bac-
tericides were contacted in hopes of finding a suitable agent. In
fact, two companies, namely, Metasol Products, Division cf Merck &
Company, Inc., and Buckman Laboratories, Inc., conducted extensive
investigations into economic means of disinfecting the effluent from
the pilot plant.
Bacteriological studies performed by Hammermill and
independent laboratories have shown that the chlorine requirements
for adequate kill are for all practical purposes equal to those
given by the chlorine demand of the effluent. To reach 1.5 mg/1
chlorine after 15 minutes requires a 60-100 mg/1 dose rate. The
information presented in Table XII shows that an average chlorine
dosage of at least 60 mg/1 would also be required to properly dis-
infect the joint plant effluent.
The high cost of adequate disinfection by chlorine of the
joint plant effluent dictated additional research to find the
optimum agent(s) and/or application of such an agent. The final
effluent from the bench activated sludge plant was used in the tests
made in the research study. As was to be expected, it was found
that the chlorine required for disinfection increased with increased
COD of the effluent. Stepwise addition of chlorine was tried in an
attempt to increase and prolong the chlorine residual. No improvement
87
-------
TABLE XII
Chlorine Levels Required to Bring Total
Coliform Counts to a Level Below 1000 per
100 ml in Final Effluent
Chlorine Requirement, mg/1
Test
No.
1
2
3
U
5
6
7
8
9
10
11
12
EMB Agar Plate
Method
> 80
< TO
< 50
< 1+0
< 30
> 50
70
60
90
60
Average 60
MPN
Method
> 50
1*0
80
60
70
50
52
88
-------
in the residual or better kill was found. Tests showed no disin-
fection improvement after one hour even though residuals may be found
up to two hours. The addition of chlorine water to the final efflu-
ent changes the pH but pH adjustment is unlikely to improve the kill
qualities.
Start C12 Added Final
7.1* 60 ppm 5.8
7.1* 90 ppm 5.2
Iodine showed no promise. Sulfamic acid used alone and
in combination with chlorine was tried. The kill was very poor
with sulfamic acid alone, improved some with the addition of an
equal quantity of chlorine and showed further improvement with
greater amounts of chlorine. Disinfection with this combination
was poor at best. The commercial biocides showed little promise.
Colloidal silver gave poor results and had a cost approximately
hO times the cost of chlorine to obtain the same disinfection. After
many tests it was concluded that none of these materials were suitable
as an economical replacement for chlorine.
Tests on the bench plant mixed effluent for ammonia had
shown amounts ranging from 0 to .5 ppm. City final effluent was
found to have approximately 8 ppm. It was decided to test to see
if the use of ammonia with chlorine would improve the disinfection
action. Ammonia at the rate of 2.6l ppm was added to the effluent
followed by chlorine. It was found that 30 ppm chlorine was required
to obtain disinfection. When the chlorine was premixed with the
ammonia it was found that the same disinfection could be obtained
with only 15-17 ppm of chlorine. In all the tests the NH^ solution
was prepared by diluting concentrated NHj(OK with distilled water
before mixing it with the chlorine solution. The chlorine solution
was prepared by diffusing Clg through water until a 5-5 gram per
liter concentration was reached.
The timing of the premixing of the ammonium hydroxide and
chlorine was found to be critical. Maximum disinfection was obtained
when the premixed solution was added to the effluent within sixty
seconds of mixing. When the mixture was exposed to the air for even
a few minutes the disinfection was poor. It was found that when
properly mixed and applied, 2.6l ppm NH^ premixed with 15-17 ppm Cl2
resulted in coliform counts generally below 1,000/100 ml. The dis-
infection action with varying proportions of KHo and Cl2 are shown
in Table XIII. The use of the premixed NHo-Clp solution was found
to work equally well on City of Erie effluent at the same dose rates,
thus making it too costly for use on effluents with a low chemical
chlorine demand.
89
-------
TABLE XIII
Treatment of Joint Effluent with Premixed
NH3-C12
1 Hour after
ppm NH3
1.31
1.31
1.96
1.96
2.61
2.61
2.61
2.61
2.61
2.61
2.61
2.61
2.61
2.61
2.61
3.26
3.26
3.26
ppm C12
6.8
8.1
9.9
11.8
13.4
13.4
13.4
13.4
14.3
15.1
15.1
15.3
17.3
17.3
20.2
19.5
20.8
23.1
Control Count
710,000
710,000
710,000
710,000
1,100,000
800,000
360,000
640,000
710,000
3,500,000
570,000
770,000
3,500,000
570,000
3,500,000
3,500,000
3,500,000
3,500,000
Treatment Count
232,000
250,000
18,000
14,000
1,000
1,000
0
3,000
3,000
300
3,200
2,500
1,000
100
100
0
10
10
90
-------
Counts are of the coliform group, tested by the membrane
Filter Technique, incubated l8-2li hours at 35(H.5° C and expressed
per 100 ml. Pore size of the membrane was 0.1*5 micron. 1 ml samples
were used except where noted. Controls generally required .01-.001 ml.
Samples were sent to an outside laboratory for testing by
the Multiple Tube Fermentation technique as in Standard Methods.
Correlation of results was reasonable.
Data accumulated to date indicates that a minimum of 2.6l
ppm NH^ is required to obtain effective disinfection action - there
does not appear to be a limiting upper value. At IT ppm C12 and
2.6l ppm NH3 the cost is $.00508 per 1,000 gal effluent (C12 @
$60/ton, NH3 § $T5/ton) nearly 75% lower than the use of chlorine
by itself.
A Wallace & Tiernan amperometric titrator revealed a
continuous reduction of chlorine residual when the fresh NH-^-C^
mixture was added to the final effluent, or to distilled water.
Meter deflection ceased after approximately ten minutes, at which
time chlorine residuals are nearly zero. The disinfection tests
shown in Table XIV indicate that disinfection is accomplished within
the first 15 minutes.
The action of the NH3-C12 mixture is not completely under-
stood but is by far the most effective and economical. Premixing
of the solution and immediate use was found to be critical to the
success of the solution. A minimum of 2.6l ppm of NHg was found to
be necessary in the premixed solution. C12 in the solution at IT
ppm gave good disinfection action, use of more C12 improved the
disinfection action but increased the cost. Additional studies of
the pH of premixed C12 and NHg may indicate a pH where improved kill
can be obtained. Additional studies would be required before a
disinfection system based on the findings could be installed.
91
-------
Table XIV
EFFECT OF TIME ON DISINFECTION
ppm C3-2
13.2
13.5
15.3
15.5
13.2
13.2 *
15.0
15.0 *
17.0
17.0 *
Count
2
Control Count 15 min.
2,000,000 100
1,020,000 200
1,020,000 100
2,000,000 0
1,300
1,150
0
500
0
470
after
. 63, ppm
30 min
100
0
100
200
—
--
—
—
--
—
Treatment
NH-*
60 min.
300
0
0
100
1,400
3,060
1,800
870
1,100
810
*10 ml. sample
-------
X
SUPPORTING STUDIES
To complement the pilot plant studies and to provide a
complete characterization of the possible process requirements and
considerations for the successful treatment of the combined wastes,
a number of related studies were performed, as described below.
Analytical Methods
Because of the unusual nature of the Hammermill waste,
many standard test methods were found unsatisfactory and required
modification. Unless noted otherwise, standard methods were used
throughout (Standard Methods for the Experimenting of Water and
Vastewater, 12th Edition, 1965). Studies made and planned on the
various testing procedures are given below:
1. Suspended Solids - It was found that the
drying time in the usual procedure for
suspended solids was often insufficient.
This was solved by resorting to the more
rigorous laboratory practice of reweighing
everything to constant weight. This
greatly improved the reliability of results.
2. Phosphates - Because of color interference
in the waste stream, a modification was de-
vised involving bleaching out the color with
chlorine and removing the available chlorine
with heat. In addition to the normal total
phosphate determination run on filtered ef-
fluent a determination is also made on the
unfiltered effluent. This was known as
"Nutrient" phosphate and is based on the
idea that undissolved phosphates are also
available to the microbiological life.
3. Nitrate - A simple modification has not been
found to enable routine nitrate testing, mainly
because of high color and chloride contents. A
rather complicated scheme has been developed
which allowed some limited nitrate testing. The
chemical methods were found to be too lengthy;
therefore, a nitrate sensitive electrode was
purchased and used, thus providing a simpler
method.
h. Sulfates - A su3fate procedure has been studied
but has not been perfected.
93
-------
5. BOD - A BOD procedure was used which eliminated
interference from the spent sulflte liquor in the
waste. Dissolved oxygen was determined by the
Winkler method on the original saturated sample
before incubation as well as on the test sample
after the usual 5-day incubation. This assumes
that the same interference is present before and
after incubation, thus canceling the error. BOD's
of various durations other than five days were run
to show that oxygen uptake was quite constant and
free from any toxicity effects.
6. COD - Chloride interference was removed by the
mercury complexing method. This has been shown
to give results equal to those corrected by the
Mohr titration for chloride.
T. Foam - A lengthy study of foaming characteristics
has provided a test method which relates foaming
tendency to concentration of a standard foaming agent.
Neutralization
The Hammermill wastes, as presently discharged, have a pH
of about 3. Therefore, they must be neutralized to be amenable to
biological treatment. Laboratory and pilot scale tests were performed
to determine alkali requirements, as well as neutralization techniques.
These studies revealed that the pH of the waste must be initially
adjusted to about 8.5 to compensate for a backsliding effect of the
waste; two to four hours after neutralization to 8.5, the pH adjusts
to 6.5 to 7.0 and remains at that level. No acid conditions were
experienced at the pilot plant once Hammermill wastes were adjusted
to a pH of 8.5 by lime.
Color
The characteristic color of the Hammermill wastes will not
appreciably change after treatment by the activated sludge process,
except for the effect of dilution with the municipal waste.
The removal of color has been studied by Hammermill for some
two years. Laboratory studies have included the use of lime precipi-
tation, alum precipitation, activated carbon adsorption, chlorine
bleaching and in-plant bleaching process modification. Each scheme
was tried singly and in combination with others. These methods of
color removal proved to be most uneconomical. The costs associated
with removal of color are exorbitant and could well be as great as
the cost of providing secondary treatment.
Color Removal
In the cooking operation, lignins and extractives are
solubilized, appearing in the waste liquor and subsequent washes.
Nearly two-thirds of the color generated comes from cooking. Most
94
-------
of the rest of the color load results from the chlorine and extrac-
tion stages of the "bleaching sequence, in which additional lignin
is solubilized. The small amount of color generated in vood handling
and paper-dyeing operations makes up the remainder of the color load
(less than 1% of the total).
It should be noted that the dissolved materials which
create color are almost completely non-biodegradable. Thus, the
color problem is entirely one of appearance of the receiving water
and has no relationship to oxygen demand or marine life in any way.
The deep well disposal system removes over half of the
color produced by cooking, or about one-third of all generated color.
The remainder is carried by the sewer system.
It has been of interest to Hammermill to remove some of
the color from the pulp mill sewer stream. Research work was under-
taken in the spring of 1965 and has been pursued almost continuously
up to the present. Following is a brief description of the major
studies made and their conclusions:
METHOD
Lime Precipitation
Alum Precipitation
Other Precipitation
Processes
Activated Carbon
Lime & Carbon in
Series
Hypochlorite Oxidation
Lime & Chlorine in
Series
Membrane Processes
Other Bleaching
Processes
COLOR REMOVAL
Maximum
COST
Equivalent to combined
primary & secondary treat-
ment costs
Same as lime precipitation
No success (ferric salts, silica gel,
polyelectrolytes)
All plus BOD
All plus BOD
50£ +
5055 +
Most + BOD
Triple combined primary and
secondary treatment costs
No advantage over activated
carbon
Same as lime precipitation
No advantage over lime
precipitation
Greater than activated carbon
(Many studied, nitric acid extensively -
technical and by-product marketing problems
too great)
95
-------
METHOD
Deep Well Disposal
In-plant Modifica-
tions
Corrosion
COLOR REMOVAL
All
COST
Volume too great for deep
wells
More favorable than lime
precipitation but color
reduction inadequate.
Samples of cast iron, low carbon steel and stainless steel
Types 30l+, 3l6, 3l6L and 1+1+0 were placed in the aeration tanks at the
pilot plant to determine the degree of corrosion. At the end of 38
days the samples were removed, inspected, weighed and then returned to
the tank.
After 58 days, the samples were removed, inspected, weighed
and measurements taken to determine the volume and surface area. From
these data, the average surface erosion in mils per year was calculated,
as shown in the following tabulation:
Cast Iron
Low Carbon
Steel
Stainless
#3Ql+
Stainless
#316
Stainless
#3l6L
Stainless
#1+1+0
Initial
Weight
31.50l6g
128.5196
89.2888
86.5863
86.8768
81+ . 3191
Final
Weight
31.3*+51g
128.1900
89.2865
86.5711
86.8609*
81+.2921
Weight
Lost
0.1565g
0.3296
0.0023
0.0152
0.0159*
0.0270
Thickness
Weight Loss
Lost mil/year
0.1+9
0.27
0.0026
0.017
0.018*
0.032
1.6
1.6
0.018
0.12
0.18
0.1+0
Refer-
ence
(1)
(2)
(3)
(M
(5)
(6)
•After 38 days. Other samples 58 days.
(l) Surface pitted and oxide particles on surface
(2) Surface pitted; oxide particles easily removed
(3) No visible surface or weld change
(1+) Some surface corrosion visible; no weld damage obvious
96
-------
(5) No visible surface or veld change
(6) Large areas of surface corroded; no visual weld damage.
Additional samples, using brass, bronze, and copper were run
for the first 38 days; however, these samples were lost prior to the
termination of the test because of their light weight and strong agita-
tion in No. 3 tank.
On the basis of the results shown in the tabulation, all
samples tested should be satisfactory for the application, with certain
qualifications. Their suitability for use is based on the fact that,
in each cs.se, the loss due to erosion and chemical attack was less than
2 mils per year.
The fact that the cast iron and low carbon steel surfaces
were pitted, would indicate the possibility of greater attack than
calculated because of the -formation of cathodic and anodic areas in the
vicinity of and within the pits. To obtain more meaningful data, it
will be" necessary to plot P weight loss curve vs. time based on a test
of longer duration than Sp days. It is recommended that such long-
duration tests be conducted prior to the design of the combined treat-
ment plant.
Foaming Tendencies
There has been some tendency of the combined wastes to foam
with aeration, and defoamer was periodically added to control this
condition. It should be noted that pilot plant aeration tanks were not
equipped with water sprays. Water sprays could have alleviated most of
the foam problems experienced at the pilot plant.
Hammer-mill effluent presently contains large quantities of
defoamer: this, plus lime neutralization, and flowing in an inter-_
cepting sewer to*a joint treatment plant, should suppress the foaming
tendencies of the pulp wastes.
It is believed that a well-designed foam spray system could
suppress most, if not all, the foam which may occur on the aeration
tanks for the joint plant.
97
-------
XI
SIGNIFICANCE FOR DESIGN
Primary Treatment
When handled separately, any or all of the Hammermill wastes
appear less amenable to treatment by primary sedimentation than does
municipal sewage alone. However, when the combined Hatnmermill waste
is neutralized and mixed with sewage in the proportions of 1 to 1, the
resulting mixture is effectively treated by primary sedimentation. The
percentage reductions in suspended solids of the mixed wastes are quite
similar to those obtained by primary sedimentation of municipal sewage
alone. In pilot plant operations such reductions were generally in the
order of "{6%.
Primary treatment also effected ?5 to 30 per cent reductions
in the BOD and COD of the mixture of the Hammermill wastes and
municipal sewage. While these reductions are not as high as those
obtained by primary sedimentation of municipal sewage alone, the
difference is attributed to the fact that the Hammermill wastes con-
tained higher concentrations of soluble COD or BOD than municipal
sewage.
The pilot plant was operated at a constant flow. The rate
of inflow to municipal plants varies widely from hour-to-hour, day-to-
day and season-to-season. This variation in flow, even though smoothed
some in a joint plant by a relatively constant flow from Hammermill,
will fluctuate widely and joint primary treatment will not be as
effective as the pilot plant primary unit.
Provision for retention in the primary unit of a joint plant
for 1.5 hours and a surface overflow rate of 1,000-1,100 gal/sq ft/day
should result in the removal of 25% of the incoming BOD and 60% of the
suspended solids.
The consistency of the sludge resulting from the primary
treatment of the mixed wastes appeared to be quite similar to that of
normal municipal primary sludge. However, repeated analyses proved
this appearance to be misleading. The sludge withdrawn from the pilot
plant primary settling tank generally contained only about 1.5/» solids,
whereas normal municipal primary sludge may be expected to contain at
least h to 6 percent solids. The pilot plant sludge was also materially
higher in volatile matter. On a dry basis, it averaged approximately
80% volatile, whereas municipal primary sludge normally contains less
than 70^ volatile matter.
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Activated Sludge Treatment
After primary treatment the mixture from Hammer-mill wastes
and municipal sewage proved to be quite amenable to treatment by the
activated sludge process, and the addition of supplemental nutrients,
i.e. nitrogen or phosphorun, appeared unnecessary to effect good BOD
reduction. Throughout pilot plant operations the organic plus ammonia
nitrogen content of the feed generally ranged between 3 and 5 percent
of its 5-day BOD, while the phosphate (P0lt) content generally ranged
from 2 to U percent.
High sludge volume indices were encountered in both the
bench scale plant and the pilot plant throughout much of the time they
were in operation. Microscopic examination of the pilot plant sludge
revealed the presence of heavy filamentous growths, which no doubt
contributed to the sludge bulking. It is possible that had the ratio
of nitrogen to BOD in the feed been higher, and the BOD to volatile
solids loading been lower, the development of filamentous growths might
have been retarded or prevented. However, further protracted pilot
plant operations under varying temperature conditions would be required
to prove the truth of this statement. Even if the use of supplemental
nitrogen were to curtail such growths, its use as a method of control
is questionable, not only because of the cost involved, but because
the nitrogen content of the final effluent would be increased if the
nitrogen feed to the process was greater. An effluent high in nitrogen
would contribute to the eutrophication of the Lake and defeat one of
the purposes and inherent benefits of joint treatment of Kammermill
wastes with municipal sewage.
If a joint treatment plant is to be considered, it should be
designed to operate successfully at a sludge volume index of at least
200. It appears that if still higher indices are to be avoided, the
volatile content of the activated sludge must be prevented from materi-
ally exceeding 80$ and that this may best be done by the use of long
solids aeration periods and relatively low BOD to volatile suspended
solids loadings. The means of controlling sludge volume indices has
not been completely explored in the operation of the bench scale
continuous flow plant. Based on pilot plant operations only, it
appears that if the volatile content of the activated sludge is to be
kept from exceeding 80$, the quotient of the BOD loading expressed in
pounds per day per 100 pounds of volatile suspended solids under
aeration divided by the solids aeration period should not exceed 6.
Early operation of the pilot plant indicated that effective
BOD removals could be obtained over short periods of time at BOD
loadings as high as 50 to 55 Ib. per day per 100 Ib. of volatile
suspended solids under aeration, but did not demonstrate that such
loadings could be continually maintained without encountering
excessively high volatile contents and high sludge volume indices in
the activated sludge. Those early studies were all made during August
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to October, inclusive, when mixed liquor temperatures ranged between
l3° and 2h'J C. The pronounced effect of temperature variations upon
the process did not become apparent until much later.
Pilot plant operations definitely established the fact that
a 10° C. change in mixed liquor temperature effected a fourfold change
in reaction rates when treating the 50-50 mixture of Hammermill waste
and municipal sewage. This fact is firmly established and is perhaps
the most significant conclusion thus far drawn from pilot plant opera-
tion. It has a tremendous bearing on the oxygen requirements of the
process, upon the build-up of excess biological floe and upon the
degree of BOD reduction that can be reasonably expected from the
process .
The rate of endogenous respiration varies directly with the
"K" value and thus , high oxygen requirements and only a minimum of
floe build-up will be encountered at high temperatures, while the
reverse is true at low temperatures .
BOD removal by the activated sludge process is a function of
the reaction rate ("K"). the length of the mixed liquor aeration
period, and the concentration of volatile solids in the mixed liquor.
Therefore, low temperatures and resulting low "K" values can, within
limits, be compensated for by increasing mixed liquor solids and
aeration times. This means that conventional operation, i.e. straight
mixed liquor aeration without the use of sludge reaeration, is the
process best suited to cold weather operation and judging from pilot
plant performance, the only one that can effect reasonable BOD reduc-
tions. Even then. BOD loadings per 100 Ib . of volatile suspended
solids must be Quite low. However, drastic reductions in both the
mixed liquor solids concentrations and aeration periods are an abso-
lute necessity at higher temperatures if extremely high oxygen re-
quirements are to be avoided.
Therefore, much shorter mixed liquor aeration periods and
much lower mixed liquor solids concentrations are essential curing
warm weather to keep oxygen requirements within bounds, hence, BOD
loadings per pound of volatile suspended solids must increase. At _
first it might a^ear that this could be accomplished by simply taking
mixed liquor aeration tanks out of service, but if this were all that
was done the BOD to volatile solids loading would soon become so high,
and the solids aeration period so short that their ratio would
materially exceed the limiting value of 6, causing the volatile
content of the sludge and its sludge volume index to ^ease so
rapidly that the process would become uncontrollable. For ^is
reason, sludge reaeration must be an essential feature of the plant
during warm weather operation. In cold weather when higher concen-
tration of solids in the return sludge are permiss ible
ra
longer mixed liauor aeration periods are required, it is ^commende
tha? the practice of sludge reaeration be discontinued and that all
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aeration tanks be used for mixed liquor aeration.
The fact that short-circuiting occurred in some spiral flov
tanks has been known for decades, but the recent work of the FrfPCA
group working out of the Robert S. Kerr Water Research Center, has
shed a new light on the seriousness of that problem. By the use of
radioactive tracers, they measured the actual times of flow through
the aeration tanks at several different plants and found that actual
detention time ranged from 16% to S$% of the theoretical detention
time, with a higher length to width ratio apparently improving the
actual detention time.
At present Erie has five aeration tanks, each of which is
a two-pass tank with a length to width ratio of 12. It seems proba-
ble that their actual detention period is less than 80« of their
theoretical displacement period. If so, it would appear that unless
the present tanks are modified, aeration periods contemplated in the
design of the joint plant should be increased over those recommended
from pilot plant studies by about 25%.
It is not practical to convert the existing Erie aeration
tanks to completely mixed tanks. However, an approach to such a
conversion and the elimination of short-circuiting, might be accom-
plished by: (l) converting the five two-pass tanks to ten single-
pass tanks, and (2) replacing the existing method of aeration with
turbine type dispersers, equally spaced along the length of the
tanks. Turbine type gas dispersers have a much higher oxidation
efficiency than do porous diffuser tubes. An arrangement such as
suggested above would make it possible to supply more oxygen to a
given tank and hence increase the BOD loading on that tank over what
it could be if porous diffuser tubes were used for aeration. It
would also reduce air requirements and the number or size of the
blowers required. In calculating aeration tank capacity for the
joint treatment of Hammermill wastes and Erie sewage, it was assumed
that any additional aeration tanks required would be of similar
design and capacity.
Preliminary aeration tank design calculations were made for
the 20° C. temperatures expected in summer months and for the cold
weather operation at a 10° C. temperature. In the calculations,
return sludge flows of 50, 75, 100 and 150 per cent of the average
daily waste flow were used. The calculations for a 100$ return sludge
flow will be used to illustrate the calculations made for 20° C.
temperatures.
The five-day BOD of the mixture of Hammermill wastes and
sewage at 1985 volumes will be 280 mg/1. With a 25% BOD reduction
in primary treatment the primary effluent would have a 210 mg/1 five-
day BOD. The BOD of the final effluent would be 28 mg/1 for a plant
removing 90% of the incoming five-day BOD. The influent to the
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aeration tanks will be a mixture of primary effluent and returned
sludge. With a sludge return of 100£ the BOD of the mixture vould
be 210 + 28 = 119 mg/1. The BOD remaining in the final effluent
2
as a per cent of incoming BOD would be 28 x 100 = 23. 5f with a 100?
119
sludge return.
Work reported earlier showed that a K of 0.73 x 10~3 is ex-
pected for sludge reaeration at 20° C. Going to figure 9 a Sat x 10-3
of h.k x 10"3 is the value for 23.5% remaining EOD. Using trial cal-
culations, a mixed liquor tank volume can be selected which will fit
into a logical plant design. For the proposed Erie joint plant, a
total mixed liquor aeration volume equal to 23. 6£ of the daily waste
flow was selected for 100$ sludpe return. This volume would give a
mixed liquor aeration time of 0.236 x 2h = 2.83 hrs . and the mixed
1+1
liquor volatile solids (Sa) would be k.h x IP"3 = 1,560 mg/1. The
2.83
volatile suspended solids content of the return sludge would be
3,120 mg/1. With a volatile content of Bd% the total solids would
be 3;12Q = 3,900 mg/1 - approximating the ^,000 mg/1 maximum solids
.8
concentration deemed permissible in return sludge during warm weather.
Solids reaeration should be used in summer months. Through
trial calculations a total sludge reaeration volume was selected
which gave a ratio of less than 6 when the total BOD loading per
100 pounds of solids was developed by the total solids aeration time.
A sludge reaeration volume amounting to 10.3$ of the total daily
waste flow was selected. This gave a sludge reaeration time of
1 x .103 x 2U = 2.1*9 hrs. making a total solids aeration time of
5 32 hrs. The total volatile solids in the activated sludge system
would be (1.560 x .236) + (3.120 x .103) = 690 mg. for each liter/day
of primary effluent with a five-day BOD of 210 mg/1. The BOD loading
per 100 units of volatile solids divided by the solids aeration time
gives 210 x 100 =5.72 which is below the 6 set as an upper limit.
690 x 5.32
Similar calculations for 50, 75, 100 and. 150 per cent sludge
return showed that the total aeration volume was approximately the
same for sludge returns of 75 and 100 T,er cent. Lower or higher sludge
returns would require a larger aeration tank volume and it was recom-
mended that a total aeration tank volume equal to 3^ of the expectea
average daily mixed waste flow be used. With this volume the BOD_
loading per 1,000 cubic feet of aeration capacity would be *pproxi-
39 Dounds -e- day. The Dipins should be arranged so all tanks
' *
s -e- .
for' mixed liquor aeration and at least 1/3 could be used
for sludge reaeration.
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Calculations were made for cold weather operation (10° C.)
using all aeration tanks for mixed liquor aeration. It was assumed
that the return sludge would contain the maximum permissible concen-
tration of suspended solids of 6,500 mg/1 or 1.3 times the sludge
density of a mixed liquor having a sludge volume index of 200. This
time using a 75$ sludge return to illustrate the calculations, the
mixed liquor total solids would be 0.75 x 6,500 = 2,790 mg/1 and if
1 + .75
80$ volatile the volatile solids would be 2,230 mg/1. With a mixed
liquor aeration volume available of 3*+$ of waste flow, (established
by summer calculations) the mixed liquor aeration time would be
0.3U x 2k = k.66 hours. The Sat x 10-3 = 2.23 x k.66 x 10~3 = 10.k
1<75
and then using a K of O.llt x 10-3 (conventional operation) and read-
ing from the curve in figure 6 the BOD remaining in the effluent would
be k6%. Then to establish the final effluent BOD the equation
1.75 EFFBOD = .1+6 or 68 mg/1. The per cent BOD overall reduc-
210 + .75 EFFBOD
tion is 280 - 68 x 100 = 76$. The reduction with the same volume and
280
100$ sludge return is 78$. The volatile solids under aeration would
be 2.230 x 3k = 760 mg. per liter for 75$ sludge return. The BOD
loading per 100 units of volatile solids divided by the aeration time
is 210 x 100 =5.93 which is just under 6. It is also under 6 for
760 x k.66
100$ sludge return indicating that sludge reaeration is not needed
during the winter months. Average daily oxygen requirements can be
calculated by formula (6) and the probable build-up of excess biologi-
cal floe by use of formula (7)
Average oxygen requirements -
pounds/million gallons mixed waste
Sludge Return
75$ 100$
20° C. 1,750 1,910
10° C. 920 1,020
Excess biological floe-pounds/
million gallons mixed waste
20° C. 370 300
10° C. 510
The most economical design for 20° C. operation is an aeration
tank volume equal to 3k% of the daily mixed waste flow and with re-
turn sludge rates of 75$ to 100$. It is felt that sludge return
facilities should be designed to permit peak rates of return of 125$
and preferably 150$ of daily waste flow. At least 1/3 of the tanks
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should be piped so they can be used for mixed liquor aeration or
sludge reaeration.
During extreme cold weather, the overall BOD reduction may
be only lQ% even when the rate of sludge return is 100? of the waste
flow. Even during extreme cold weather it may be possible to main-
tain a "K" value considerably higher than the O.llU x 10~3 used in
the calculations. It may be entirely possible to maintain a "K"
value of 0.183 x 10~3, or even higher. With such a value, overall
BOD reductions in the order of 85$ could be obtained.
Mixed liquor temperatures may at times be as high as 23° to
25° C. and under such conditions, oxygen requirements will materially
exceed those prevailing at 20° C.
By the use of formulae (6) and (7), it was calculated that
under such conditions the oxygen needs of the process would average
2,8lO Ib/million gallons .of mixed waste and the build-up of excess
biological floe would be only 1^9 lb/day/million gallons of mixed
waste.
Bulking may become serious if the inventory of volatile solids
is reduced unless the hot spell were of short duration and filamentous
growths were completely absent. Therefore, the sizing of turbines and
blowers should be based on an oxygen need of 2,8lO Ib. per day per
million gallons of waste flow.
During the period the pilot plant was in operation, the reduc-
tion in phosphate by the activated sludge and the phosphate content
of the final effluent varied from day to day over wide limits. Average
percentage reductions in phosphate for various periods of operation
ranged from 30 to ^3 per cent. During the same periods the phosphate
concentration in the final effluent ranged from 3 to 7 rng/1. There
seems to be some correlation between the concentration of phosphates
in the final effluent and the amount of phosphate in the applied waste
when that amount is expressed as a percentage of the applied BOD. If
such is the case, then it is obvious that the addition of supplementary
phosphates should be avoided except under emergency conditions.
Although occasional phosphate removals in the general order
of 80? were observed, it is questionable if the activated sludge pro-
cess can be depended upon to consistently effect such removals and
still maintain satisfactory performance as regards BOD reduction,
sludge volume indices and suspended solids removal. Our recommendation
would be that the activated sludge process be designed and operated in
such a manner as to effect good overall BOD and solids performance and
that supplemental treatment be provided, if additional phosphate re-
moval is required.
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Final Settling Tanks
In general the removal of suspended solids by the pilot plant
activated sludge process has been somewhat disappointing and much
inferior to its removal of BOD. This phenomenon is not peculiar to
the pilot plant or the mixture of Erie sewage and Hammermill waste.
Other plants utilizing the activated sludge process to treat various
types of paper mill wastes have experienced similar difficulties in
the removal of suspended solids. A careful review of pilot plant
performance has indicated no correlation between the sludge volume
index of the mixed liquor and the suspended solids content of the
final effluent.
Full-scale sedimentation is one of the most difficult pro-
cesses to simulate in pilot plant operation, since of necessity, the
ratio of area to depth of pilot plant sedimentation units must be very
materially less than that of conventional full-scale settling tanks.
If a joint treatment plant were constructed and properly operated it
should produce a final effluent of lower suspended solids content than
was produced in the pilot plant. It is probable that even a full-
scale plant could not consistently produce a final effluent averaging
less than hd mg/1 of suspended solids. The detention period in the
final settling tanks should be approximately 1.9 hours based on mixed
liquor flow, or 3.8 hours based on waste flow. The settling rate,
based on the flow of mixed liquor, would be l,ll»0 gallons per square
foot per day. Overflow rates based on raw waste flow, would be only
about 7,300 gallons per day per linear foot of effluent weir.
The aforestated design criteria are ultraconservative. How-
ever, they are warranted in view of the apparent difficulty of obtain-
ing effective suspended solids reduction and the likelihood that mixed
liquor sludge volume indices in the order of 200 may be encountered
much of the time.
Suction type sludge collection equipment should be used in all
of the final settling tanks and it must be of special design in order
to permit operation at the high rates of sludge return recommended.
In addition, studies should be conducted to determine if the clari-
fiers should contain a flocculator type center well to enhance solids
settling.
Sludge Thickening
Thickening is generally accomplished in continuous flow units
which operate at low surface and high solids loadings. In municipal
practice it has been found that the thickening of mixtures of primary
and excess activated sludge can best be accomplished when the mixed
sludges are fed to the thickener at a low solids concentration and a
nominal liquid retention time of some 2.5 hours. Solids are generally
stored in the bottom of such thickeners for at least one and prefera-
106
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bly two days and when this is done , the underflow generally contains
from U to 8 per cent solids .
It was not possible to simulate a continuous flow gravity
thickener in pilot plant operations of the size installed by Hammermill
at the Erie Treatment Plant, because of the impossibility of simulating
area to depth ratios that prevail in conventional gravity thickeners.
Therefore, continuous flow tests of gravity thickening were not con-
ducted at the pilot plant. Numerous batch settling tests indicated
that when the mixed primary and excess activated sludge from the pilot
plant was subjected to 2 to 2.5 hour sedimentation periods and solids
retention on the order of one day, the resulting sludge contained
2 to 2.5 per cent total solids. By increasing the settling period to
3 hours or more and sludge holding periods to over one day, concentra-
tions in the order of 3^ total solids were obtained. Overflow rates
of 600 gallons per square foot per day and sludge holding periods in
excess of a day are indicated for gravity thickeners.
Unlike gravity thickening, air flotation may be conveniently
and reliably studied on a pilot plant scale. Such studies were con-
ducted on a 1 square foot pilot flotation unit. The results indicated
that air flotation could be depended upon to produce a sludge contain-
ing approximately 3% solids when handling either excess activated
sludge alone, or a mixture of primary and excess activated sludge
together. To accomplish such results with activated sludge alone, the
loading on the unit should not exceed 2U Ib . of solids, or 1,000
gallons per day per square foot. If a combination of primary and
waste activated sludge was to be concentrated, the corresponding load-
ings could be U8 Ib. of solids, or 600 gallons per square foot per day.
At many plants where air flotation has been used, the use of
polymeric flocculants has proved beneficial. However, such was not
the case with the pilot plant sludges. Nevertheless, if air flotation
is to be used, it would be prudent to incorporate facilities for feed-
ing such aids as a part of the installation.
The cost of operating and maintaining air flotation units is
considerably higher than that of operating and maintaining gravity
thickeners. In this instance, air flotation has specific advantages
over gravity thickening which stems from the fact that the solids are
retained in the air flotation unit for a much shorter time than they
of objectionable odors being released, and the returned
highly aerated.
ments.
These advantages may be offset by the higher power require-
It Erie "rigorous analysis might indicate that a combination
1C7
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of flotation and gravity thickening would be the preferable process.
Sludge Digestion
After concentration, the sludge in municipal plants is fre-
quently subjected to anaerobic digestion and then dewatered for ulti-
mate disposal. However, at several of the larger plants, anaerobic
digestion is omitted. The concentrated sludge is dewatered and then
disposed of by incineration.
Our studies indicate that even after concentration, the sludge
from the joint treatment of sewage and Hammermill waste will contain
only 2-1/2 to 3 per cent solids, which means that even if there were
no increase in the total amount of solids to be disposed of, the volume
of sludge to be digested would be twice that now handled.
The sludge digestion studies conducted in the Hammermill
Laboratory indicate that the mixed sludge from the joint treatment of
Hammermill wastes with municipal sewage is amenable to anaerobic diges-
tion, but that to be effective, the digester should provide about a
1+0-day retention period and should not be loaded in excess of 0.1 Ib.
of volatile solids per day per cubic foot. From this it was calcu-
lated that approximately one million cubic feet of digestion capacity
would be required as a minimum, i.e. some four times the volume of
the existing sludge digestion tanks. Furthermore, those studies re-
vealed that even at such loadings, considerable lime would be required
to maintain suitable alkaline conditions in the digestion tanks and
the resulting gas would be somewhat lower in methane and B.t.u. content
than the gas resulting from the digestion of typical municipal sewage.
For these reasons, we conclude that anaerobic digestion will not be
practical or desirable at a joint treatment plant.
Sludge Dewatering Prior to Thermal Decomposition
It is recommended that after concentration by air flotation,
the mixed primary and excess activated sludge solids be dewatered and
then disposed of by incineration.
Pilot studies were conducted by using both a centrifuge and a
vacuum filter as a means of sludge dewatering. Those studies indicated
that with either type of equipment, a cake containing approximately
205? solids could be produced. The pilot studies showed that vacuum
fillers should have a yield of 3.5 Ib/sq ft/hr with 20/J TS in the cake
when operating on a mixed sludge with 3% TS and using a 1% polymeric
flocculant dosage. The optimum rate for the Sharpies p-660 centrifuge
used in the studies appeared to be 2 gpm feed containing 3% TS and a
polymeric flocculant dosage of 2% to obtain a cake with 20% TS. The
capture of solids by vacuum filtration was far superior to that ob-
tained with the centrifuges and the dosage of polyelectrolyte required
by vacuum filtration appeared to be less than that required for
108
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reasonably successful operation of the centrifuges.
The studies seemed to indicate that with careful control of
solids feed and poly electrolyte usage, it should be possible to ob-
tain a vacuum filter cake containing as much as 25% instead of 20%
solids, but there appeared little likelihood that a cake containing
more than 20% solids could be obtained from the centrifuges. The
cost of incinerating a 25% solid cake would be materially less than
the cost of incinerating a 20% solid cake. For these reasons, we
recommend that a vacuum filtration be adopted as the means of dewater-
ing sludge ahead of incineration.
Thermal Decomposition of Sludge
No pilot studies of incineration were possible. However,
approximate and ultimate analyses of the sludge are contained in the
main body of the report and are believed to provide sufficient in-
formation for sizing incineration equipment. The foregoing recom-
mendation that sludge be concentrated by vacuum filtration prior to
incineration is predicated on the assumption that incineration would
be accomplished in multiple hearth furnaces, or fluidized bed furnaces.
Annual cost of operating the incinerator would be dependent
upon the demands of regulatory agencies. For example, if a gas out-
let temperature of 900° F. is acceptable for the control of odors
(our experience and that of others indicate that it is reasonable),
then the sludge would be auto-combustible and no auxiliary fuel will
be required during burning. At Erie an allowance of say $10,000 per
year for the gas required for warm-up, etc., should be more than
adequate. If, for example, the incinerators must operate with a gas
outlet temperature of 1UOO° F. , then the annual cost of auxiliary fuel
would approach $300,000. If the high temperature is required, then
there would be an incentive to investigating means of removing addi-
tional moisture from the cake by the use of some type of screw press,
or similar equipment. Very limited studies indicate that additional
dewatering by this method may be feasible. The benefits to be de-
rived by an increase in total solids of the filter cake from 20% to
25% are quite great in view of the fact that a hO% reduction in fuel
cost would result.
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Preliminary order of magnitude construction cost estimates
were prepared by two consulting firms for the additions to the Erie
City Waste Treatment Plant to obtain capacity to handle 53 mgd of
municipal sewage and 27.5 mgd of pulping and papermaking wastes. One
estimate was made of the construction costs of facilities to handle
53 mgd of sewage and no Hammer-mill wastes. The estimates were based
on an Engineering News Record construction cost index of 1300 and are
before any possible federal participation. As was to be expected with
this type of rough estimate, there was a substantial spread, $18,000,000-
$2*4,000,000, for total project cost. The allocation of the cost attrib-
utable to Hammermill introduces additional complications since there is
no one correct method. The use of incremental costs is one method. The
costs could also be allocated in relation to flow, BOD and suspended
solids of the respective wastes. Using $21,000,000 for a total project
cost the allocation of $16,000,000 to Hammermill is a reasonable figure
for illustrative purposes, although not necessarily the figure which
would be arrived at through negotiations.
Distributing the $16,000,000 used as the Hammermill allocation
on a flow basis - considerations of BOD and suspended solids eliminated
for simplicity - indicates that construction costs would be approxi-
mately $37,000 per ton of daily pulp production and $U,600 per ton of
daily packed paper productions.
The total annual operating costs were estimated, incorporating
the use of the NHo-Cl2 mixture for disinfection, at $1,200,000 at a
flow of 67.5 mgd in 1971. This gives a cost of $.0^9 per thousand gal-
lons for the mixed wastes, Allocation of operating .costs is as difficult
as the allocation of construction costs. There is no one right answer
and the problem would have to be solved by negotiations. Using $600,000
a year for -processing 27.5 mgd of Hammermill wastes, the cost would be
about $.06 per thousand gallons. The $600,000 a year cost would give
a cost of $U.OO per ton of pulp produced plus $0.1+5 per ton of packed
paper.
Before embarking on the construction of a joint treatment
plant a more definitive total construction cost estimate would have to
be prepared. A method of allocating construction costs and operating
costs would have to be established.
Ill
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ACKNOWLEDGMENTS
The support of the Mayor of the City of Erie, Pennsylvania,
Honorable Louis J. Tullio, is acknowledged vith sincere thanks. Mr.
Robert J. Waytenick, Director of Public Works of Erie, was Project
Director. Mr. Paul Cygan, Chief, Bureau of Sewers of Erie, provided
valuable assistance.
The construction and operation of the pilot plant, the
bench scale studies, analytical work and report preparation was per-
formed by a team from Hammermill Paper Company consisting of Dr. R. W.
Brown, Dr. C. W. Spalding, Messrs: R. M. Ludwig, C. C. Hassell, D. G.
Kirk, A. Brosig, C. H. Steinford, R. W. Arentson, C. G. Rapp, W. B.
Orellana, and H. S. Carpenter.
Mr. Walter Lyon, Chief of the Division of Sanitary Engineer-
ing of the Pennsylvania Department of Health, suggested an investigation
of joint treatment of Erie City Municipal and Hammermill Erie Division
wastes.
Mr. W. Zabban, Mr. A. F. Lisanti and Mr. T. R. Haseltine of
The Chester Engineers, Pittsburgh, Pennsylvania, who with their asso-
ciates, directed the design of the pilot plant and guided the operation
of the plant. Mr. Haseltine (now retired) did many of the calculations,
evaluated the collected data, and wrote a major share of an initial
report which was the basis for this report.
The support of the project by the Federal Water Pollution
Control Administration and the help provided by Dr. Leon W. Weinberger,
Mr. William J. Lacy and Mr. George R. Webster, the Grant Project Officer,
is acknowledged with sincere thanks.
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REFERENCES
1. Eckenfelder, W. W. and Weston, R. P., "Kinetics of
Biological Oxidation," Chapter 1-2, Biological Treatment
of Sewage and Industrial Wastes, Reinhold Publishing
Company, 1956.
2. Brown, R. W. and Spalding, C. W., "Deep Well Disposal of
Spent Hardwood Pulping Liquors," Journal of Water Pollu-
tion Control Federation, Volume 38, No. 12, 1916-1924.
(December 1966).
3. Cohway, R. A. and Kumke, G. W., "Field Techniques for
Evaluating Aerators," Journal of the Sanitary Engineering
Division of the American Society of Civil Engineers, 92
(SA2 No 4257), 21-42 (April 1966). ~~
4. Laws, R. L. and Burns, D. B., "Recent Developments in the
Application of the Activated Sludge Process for the Treat-
ment of Pulp and Paper Mill Wastes," Technical Bulletin
No. 138; National Council for Stream Improvement (March 20,
1961).
5. Weston, R. F. and Rice, W. D., "Contact-Stabilization
Activated Sludge Treatment for Pulp and Paper Mill Waste,"
TAPPI, Volume 45, No. 3, 223-237 (March 1962).
6. Schlenz, H. E., "Standard Practice in Separate Sludge
Digestion," Proceedings ASCE, 63, 114 (1937).
7. "Sewage Treatment Plant Design," FSIWA, Manual of Practice
No. 8, 214 (1959).
8. Sawyer, C. N. and Schmidt, H. E., "High Rate Digestion,,"
Journal ASCE, 42 (1955).
115
-------
OTHER REFERENCES
McKinney, R. E., "Complete Mixing Activated Sludge," Mater
and Sewage Works, 107, 70-71 (February 1960).
Haseltine, T. R., "A Rational Approach to the Design of
Activated Sludge Plants," Chapters 3-1, Biological Treatment
of Sewage and Industrial Wastes, Reinhold Publishing Company,
1956.
Haseltine, T. R., "Sludge Reaeration in the Activated Sludge
Process - A Survey," Journal WPCF, 33, 946 (September 1961).
Haseltine, T. R., "The Activated Sludge Process at Salinas,
California with Particular Reference to Causes and Control of
Bulking," Sewage Works Journal, 4_, 46l (May 1932).
Keefer, C. E., "Relationship of Sludge Density Index to the
Activated Sludge Process," Journal WPCF, 35, 1166 (September
1963).
Haseltine, T. R., "Some Recent Advances in the Design of
Activated Sludge Systems," presented at meeting of California
Water Pollution Control Association (April 1962).
Heukelekian, H., Orford, H. E., and Manganelli, R. M., "Fac-
tors Affecting the Quantity of Sludge Production in the
Activated Sludge Process," Sewage and Industrial Wastes, 23,
9^5 (1951).
Eckenfelder, W. W., "Activated Sludge," Advances in Sewage
Treatment Design, Sanitary Engineering Division, Metropolitan
Section ASCE, Manhattan College, New York (May 1961).
Haseltine, T. R., "Activated Sludge Plant Operation," Sewage
and Industrial Wastes, 24, 1533 (December 1952).
Haseltine, T. R., "Suggested Design Criteria for the
Activated Sludge Process, " Advances in Sewage Treatment Design,
Sanitary Engineering Division, Metropolitan Section ASCE,
Manhattan College, New York (May 1961).
Thomas, H. A. Jr. and McKee, J. E., "Longitudinal Mixing in
Aeration Tanks," Sewage Works Journal, l6, 42 (January 1944).
Helmers, E. N., et al, "Nutritional Requirements in the
Biological Stabilization of Industrial Wastes, I Experimental
Method," Sewage and Industrial Wastes, 22, 1200 (September
1950).
116
-------
Helmers, E. N., et al, "Nutritional Requirements in Biological
Stabilization of Industrial Wastes, II Treatment with Domes-
tic Sewage," Sewage and Industrial Wastes, 23, 884 (July 1951).
Helmers, E. N., et al, "Nutritional Requirements in Biological
Stabilization of Industrial Wastes, III Treatment with
Supplementary Nutrients," Sewage and Industrial Wastes, 24,
496 (April 1952).
Helmers, E. N., et al, "Nutritional Requirements in Biological
Stabilization of Industrial Wastes, IV Treatment on High Rate
Filters," Sewage and Industrial Wastes, 23, 596 (May 1953).
Torpey, Wilbur N., "Concentration of Combined Primary and
Activated Sludges in Separate Thickening Tanks," Proc. ASCE,
80, 443 (May 1954).
Katz, W. J. and Geinopolis, A., "Sludge Thickening by Dis-
solved Air Flotation," Journal WPCF, 39, 946-957 (June 196?).
Baker, H. A., "Archives of Microbiology," 7, 404-420 (1936).
Langford, L. L., "Digester Volume Requirements," Water and
Sewage Works (December 1960).
Nash, Norman and Chasick, A. H., "High Rate Digester Perform-
ance at Jamaica," Journal WPCF, 526-537 (May 1960).
117
-------
XV APPENDICES
Page
I Chronology of Operations 120
II Activated Sludge Performance Aug. 8 - Sept. 5 121*
III " " " Sept. 6 - Sept. 20 125
IV " " " Oct. 1 - Oct. 21 126
V " " " Oct. 28 - Nov. 10 127
VI " " " Nov. 11 - Nov. 30 128
VII " " " Dec. 1 - Dec. lU 129
VIII " " " Jan. 8 - Jan. 21 130
IX Surfpac Data !31
X Bench Scale Plant Performance on 100$ Kami. Waste 132
XI Grant Offer and Acceptance 133
119
-------
Appendix I
Page 1 of h
Chronology of Operations
A brief chronological summary is given below to show
the major phases of operation in the pilot plant schedule.
June 30
July 5
July 18
July 26
July 31
August 1
August 7
August 15
September 6
September 22
Construction was completed.
An initial start-up was attempted. Some
mechanical features were found to need
correction, necessitating a shutdown.
A successful start-up was accomplished,
running an influent of 20 gpm of City
sewage. Initial seeding was obtained with
activated sludge from the City treatment
plant. The mode was conventional activated
sludge. Return sludge was 40%.
The operation was changed to sludge reaeration
with equal volumes of reaerated sludge and
mixed liquor. Flow rates and total
detention were unchanged.
Hammermill waste addition was begun at 1 gpm
and gradually increased daily to replace
sufficient City flow to achieve a 50-50 blend.
Sludge return was increased to 100%.
A 50-50 mixture of Hammermill and City waste
was attained.
The second in a series of loadings to be
studied was attained.
The highest loading of the series was
reached. It required some time and some
special measures to resume a reasonable rate
of solids buildup.
The aeration solids were built up to a high
level so that the operation could be maintained
at one-half the former aeration volume. Both
aeration tank levels were lowered by inserting
float pumps. These float pumps destroyed the
flocculation ability of the sludge, producing
a severe solids carryover which forced the
temporary abandonment of this phase of the
experiment.
120
-------
Appendix I
Page 2 of U
September 25
September 30
October 2
October 4
October 5
October 6
October 12
October 15
October 20
October 28
November 3
Operation was changed to conventional
activated sludge at 3-6 hours aeration
time (mixed liquor basis). A sludge
bulking and flotation condition still
persisted.
Addition of nitrogen nutrient was begun to
compensate for the unusually high influent
BOD's experienced. Some changes in aeration time
and sludge return rate improved sludge
settleability.
The raw flow was cut to 15 gpm to aid final
clarifier performance.
Beginning of occasional addition of defoamer
to combat foam on aeration tanks.
The raw flow returned to 20 gpm and heavy
sludge wasting in an effort to improve high
sludge volume index (SVI) problem.
Nutrient changed to aqueous ammonia to keep
phosphate concentrations at level to permit
removal studies.
The raw flow and return rate cut to 15 gpm
to study effect detention time has on SVT.
Return sludge rate cut to 7.5 gpm.
Return sludge rate varied daily in relation
to sludge density index (SDI), to keep rate
of return at the minimum necessary to prevent
sludge buildup in final clarifier.
Conventional activated sludge was established
using 1-1/2 aeration tanks. Flow was 18 gpm
with 67% sludge return. Detention time 5.6 hr.
Ammonia nutrient addition stopped.
121
-------
Appendix I
Page 3 of 1
November 10
November 19
November 26
December 1
December 4
December 15
December 22
January 3
January 7
January 8
Sludge reaeration started at same influent
and sludge return rates.
Changes in influent lowered the loadings
well below desired 50 Ib of Biochemical
Oxygen Demand (BOD) per 100 Ib of volatile
suspended solids (VSS); therefore, heavy
wasting of solids to rectify this condition.
The primary flow was increased to 24 gpm,
of which 6 gpm was bled off to acclimate
"Surfpac" unit for future inclusion into
the total treatment scheme.
"Surfpac" included in the system between
primary and aeration tanks as a roughing
filter. Aeration changed to conventional
using only 1/2 tank. Influent 18 gpm with
61% return. Aeration time 1.9 hr; "Surfpac"
loading some 200 Ib BOD/1000 cu ft/day.
Flow to "Surfpac" and aeration lowered to 9
sludge return 100$. Excess flow after primary
wasted out of system. Aeration period 3.2
hr., filter loading some 130 Ib BOD/1000 cu
ft/day.
"Surfpac" removed from system, returned to
sludge reaeration at 18 gpm flow, 61% return
using 1-1/2 tanks; 3-8 hr mixed liquor, 4.7
hr reaeration detention times.
Hammermill flow discontinued for a period
of 12 days to simulate a long term plant
shutdown. Plant received 9 gpm sewage with
&3% sludge return (minimum pump setting).
No sludge wasted. Detention times were 7-5
hr reaeration and 6.9 hr mixed liquor;
loading 10 - 15 Ib BOD/100 Ib VSS.
Hammermill wastes returned and conditions
returned to those of December 15.
Hammermill waste was discontinued for a one
day period due to freezing problem at
collection facilities.
System switched to conventional with 18 gpm
influent and 100$ return. Detention time
became 4-7 hr.
122
-------
Appendix I
Page U of
January 13 Return rate reduced to 83%, changing detention
time to 5,1 hr.
January 22 The pilot plant was shut down.
123
-------
Appendix II
Activated Sludge Performance
August 8 to September 5, inclusive
Flow, gpm
Primary Effluent
Return Sludge
Total Suspended Solids
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
5 Day BOD
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
COD
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
Phosphate as PO^
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
Organic & Ammonia Nitrogen
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
% BOD in Primary Effluent
Mixed Liquor
Aeration Period, hr
Dissolved Oxygen, mg/1
TSS, mg/1
TSS, % Vol.
S.V.I.
Sludge Reaeration
Aeration Period, hr
Dissolved Oxygen, mg/1
TSS, mg/1
TSS, % Vol.
Return Sludge
% of Waste Flow
TSS, mg/1
TSS, % of MLSDI
Air Used
1,000 cfd
cu ft/'lb BOD applied
cu ft/lb TSS under air
BOD Loadings
lb/1000 cu ft aeration vol
lb/100 Ib TSS under air
lb/100 Ib VSS under air
Final Clarifier Loading,
G/3F/D
Waste inflow only
Mixed Liquor
No. of
Days
Observed
29
29
27
27
27
23
23
23
22
22
22
23
21
21
24
24
24
13
29
29
27
27
27
29
29
28
28
29
26
26
29
23
27
1. 23
22
21
Average
of Daily
Observa-
tion
20.1
20.0
75
50
18*
220
38
83*
867
549
35*
9
6
22*
7
3
56*
3.3*
2.75
3.4
962
72
101
5.8
3.3
2100
73
100
2008
20
9.8
198
57
29
29
43
Median
Value
20
20
66
49
34
219
36
83
800
540
35
8
6
20
7
4
57
3.3
2.75
3.4
941
73
101
5.8
3.6
1923
73
100
1967
19
9.2
185
54
28
31
43
High
Quatril
20
20
86
60
48
262
46
86
930
657
41
10
9
50
8
4
75
3.9
2.75
3.6
1196
76
111
5.8
4.2
2214
77
100
2160
24
10.6
239
61
32
36
48
Low
Quatril
20
20
54
30
20
189
27
81
735
430
28
5
4
0
5
2
50
2.7
2.75
2.9
818
68
87
5.8
3.1
1729
71
100
1783
16
8.6
160
49
24
23
32
High
Decil
20
20
118
82
55
324
55
89
1272
785
49
18
10
60
9
5
83
4.5
2.75
3.9
1690
78
174
5-8
4.5
3737
83
100
3610
31
12.7
286
84
43
43
64
Low
Decil
20
20
42
29
-81
163
21
79
623
414
22
5
2
-13
5
1
20
2.5
2.75
2.6
740
60
73
5.8
2.6
1571
61
100
1437
14
7.9
133
43
21
17
27
29
29
750
1500
750
1500
750
1500
750
1500
750
1500
750
1500
---percent removal in Tables IV through X are the average of all the daily averages.
124
-------
Appendix III
Activated Sludge Performance
September 6 to September 20, inclusive
Flow, gpm
Primary Effluent
Return Sludge
Total Suspended Solids
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
5 Day BOD
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
CCD
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
Phosphates as PO^
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
Organic & Ammonia Nitrogen
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
% BOD in Primary Effluent
Mixed Liquor
Aeration Period, hr
Dissolved Oxygen, mg/1
TSS, mg/1
TSS, % Vol.
S.V.I.
Sludge Reaeration
Aeration Period, hr
Dissolved Oxygen, mg/1
TSS, mg/1
TSS, % Vol.
Return Sludge
% of Waste Flow
TSS, mg/1
TSS, % of MLSDI
Air Used
1,000 cfd
cu ft/lb BOD applied
cu ft/lb TSS under air
BOD Loadings
lb/1000 cu ft aeration vol
lb/100 Ib TSS under air
lb/100 Ib VSS under air
Final Clarifier Loadings
Q/SF/D
Waste Inflow only
Mixed Liquor
No. of
Days
Observed
15
15
12
14
12
15
15
15
11
11
11
7
7
7
8
7
i
7
8
15
15
14
13
14
15
15
15
14
15
15
14
15
15
15
xL. 15
15
15
Average
of Daily
Observa-
tion
18.6
19.3
63
64
-38
271
51
86
1046
663
36
10
7
39
rj
3
40
2.8
2.90
3.4
978
76
66
6.0
3.6
1760
78
105
1826
12
12.4
208
68
34
35
56
Median
Value
20
20
66
63
5
273
54
82
955
687
37
9
7
40
6
3
50
2.2
2.75
3.5
880
80
63
5.8
3.5
1447
79
100
1651
9
10.8
216
67
33
34
52
High
Quatril
20
20
79
86
45
300
64
87
1210
765
44
9
9
44
8
2
78
2.6
3.13
3.8
1387
81
75
5.8
4.1
2352
81
100
2442
18
16.2
231
&0
39
47
71
Low
Quatril
15
20
45
35
-31
220
39
71
874
544
30
10
5
29
5
3
25
1.7
2.75
3.1
725
71
57
5-8
3.0
1266
77
100
1256
8
9.4
181
58
24
24
40
High
Decil
20
20
84
126
53
397
68
90
1260
768
46
14
9
44
9
4
85
3.0
3.43
4.0
1617
82
93
6.8
4.4
2921
85
133
2937
27
19.4
265
82
50
52
88
Low
Decil
15
17
30
27
-107
195
21
71
869
525
22
8
5
29
4
2
-21
1.4
2.7!
3.0
706
71
55
5.8
2.8
1200
73
100
1217
7
8.8
156
53
21
21
32
15
15
700
1430
750
1500
750
1500
750
1320
750
1500
560
830
125
-------
Appendix IV
Activated Sludge Performance
October 1 to October 27, inclusive
Flow, gpm
Primary Effluent
Return Sludge
Total Suspended Solids
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
5 Day BOD
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
COD
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
Phosphates as PO^
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
Organic & Ammonia Nitrogen
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
% BOD in Primary Effluent
Mixed Liquor
Aeration Period, hr
Dissolved Oxygen, mg/1
TS3, mg/1
TSS, % Vol.
S.V.I.
Return Sludge
% of Waste Flow
TSS, mg/1
TSS, % of MLSDI
Air Used
1,000 cfd
cu ft/ib BOD applied
cu ft/lb TSS under air
BOD Loadings
No. of
Days
Observed
27
27
26
26
26
25
25
25
19
19
19
18*
18*
18*
24
24
24
23
27
26
26
24
26
27
26
26
27
25
25
lb/1000 cu ft aeration vol. 25
lb/100 Ib TSS under air
lb/100 Ib VSS under air
Final Clarifier Loadings
B/SF/D
Waste Inflow only
?frxed Liquor
25
25
27
27
Average
of Daily
Observa-
tion
16.2
14.6
71
64
9
266
k3
80
1122
689
39
7
4
40
13
6
57
5.2
3.3
3.5
2630
84
191
89
5046
96
8.85
181
62
58
36
42
608
1250
Median
Value
15
15
67
54
13
260
32
86
1040
660
42
7
4
41
13
6
58
5.4
3.7
3.5
2345
64
190
100
5121
95
9-15
176
63
57
36
44
560
1110
High
Quatril
20
20
86
84
42
310
50
91
1280
820
45
8
5
57
15
6
64
6.3
4.9
4.1
2980
85
216
100
5380
114
10.2
194
73
63
41
51
750
1500
Low
Quatril
15
8.5
58
43
-13
230
22
81
1020
550
30
5
3
28
12
5
50
4.1
2.75
3.1
2250
83
158
175
4517
74
7.0
147
53
48
30
35
560
840
High
Decil
20
20
92
98
50
330
93
92
1320
990
49
10
7
75
16
10
71
6.8
4.9
4.2
3653
86
248
118
6215
129
10.8
250
76
70
57
60
750
1500
Low
Decil
15
7.5
46
32
-48
210
17
66
890
500
16
3
3
0
11
4
38
3.5
2.75
3.0
2055
80
129
50
4149
69
6.5
120
49
42
22
26
560
840
-"-October 1 to 6 omitted because of phosphate additions on October 1 to 5 inclusive.
126
-------
Appendix V
Activated Sludge Performance
October 28 to November 10, inclusive
No, of
Days
Observed
low, gpm
Primary Effluent
Return Sludge
total Suspended Solids
Primary Effluent, mg/1
Final Effluent, mg/1
$ Removed
i Day BOD
Primary Effluent, mg/1
Final Effluent, mg/1
£ Removed
OD
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
hbsphates as PO^
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
rganic & Ammonia Nitrogen
Primary Effluent, mg/1
Final Effluent, mg/1
if Removed
if BOD in Primary Effluent
ixed Liquor ,
deration Period, hr
Dissolved Oxygen, mg/1
TSS, mg/1
J ^O*
TSS, % Vol.
S.V.I.
eturn Sludge
I of Waste Flow
TSS, mg/1
TSS, % of MLSDI
ir Used
1,000 cfd
cu ft/lb BOD applied
cu ft/lb TSS under air
OD Loadings
lb/1000 cu ft aeration vol.
lb/100 Ib TSS under air
lb/100 Ib VSS under air
inal Clarifier Loading
/SF/D
feste Flow Only
.fixed Liquor
14
14
13
12
13
12
12
12
10
10
10
12
12
12
13
13
13
12
14
14
13
13
13
14
13
13
14
12
12
12
12
12
14
14
Average
of Daily
Observa-
tion
17.8
11.9
71
7&
— O
248
57
77
988
703
28
7
4
31
10
4
51
4-1
5.61
4.2
1530
SI
151
67
3400
51
8.4
151
63
40
42
50
666
1110
Median
Value
18
12
72
83
-18
245
58
75
975
665
31
6
4
32
11
5
55
4.1
5.55
4.0
1571
82
144
67
3430
50
8.7
151
66
40
40
50
675
1125
High
Quatril
18
12
92
91
9
270
71
81
1065
900
42
7
5
40
12
6
68
4.6
5-55
4.2
1634
82
162
67
3558
54
10.4
175
77
43
45
55
675
1115
Low
Quatril
18
12
47
72
-35
230
49
72
895
645
21
4
3
0
7
4
33
3.2
5.55
3.6
1403
81
140
67
3256
48
6.3
119
49
37
37
45
675
1110
High
Decil
18
12
103
200
36
278
131
83
1128
760
36
8
6
83
13
6
71
6.1
5.55
4.8
1723
83
175
67
3974
58
10.3
195
79
44
53
64
675
1125
Low
Decil
16.7
11.2
41
71
-375
210
46
45
852
630
7
5
2
0
6
3
7
2.5
5.98
3.3
1232
80
135
67
2782
48
5.1
111
40
34
34
42
623
1045
127
-------
Appendix VI
Activated Sludge Performance
November 11 to November 30, inclusive
Flow, gpm
Primary Effluent
Return Sludge
Total Suspended Solids
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
5 Day BOD
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
COD
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
Phosphates as PO,
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
Organic & Ammonia Nitrogen
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
% BOD in Primary Effluent
Mixed Liquor
Aeration Period, hr
Dissolved Oxygen, mg/1
TSS, mg/1
TSS, % Vol.
f '
S.V.I.
Sludge Reaeration
Aeration Period, hr
Dissolved Oxygen, mg/1
TSS, mg/1
TSS, % Vol.
Return Sludge
% cf Waste Flow
TSS, mg/1
TSS, % of MLSDI
Air Used
1,000 cfd
cu ft/lb 3CD applied
cu ft/lb TSS under air
BOD Loadings
Ib/lOOOcu ft aeration vol
lb/100 Ib TSS under air
lb/100 Ib VSS under air
Final Clarifier Loading
G/SF/D
Waste Flow Only
Itixed Liquor
No. of
Days
Observed
20
20
20
19
19
20
19
19
14
14
14
20
20
20
20
18
18
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
. 20
20
20
20
20
Average
of Daily
Observa-
tion
17.4
12.0
59
79
-33
241
105
56
989
718
20
5
3
36
8
5
34
3.3
3.75
4.0
1125
83
153
5.1
4.4
2483
82
67.5
2398
32
3.4
67
24
43
39
47
654
1118
Median
Value
18
12
60
77
-28
240
122
56
1025
800
22
5
3
40
8
4
43
3.2
3.66
4.1
1098
82
141
5.1
4.4
2531
82
67
2435
36
3.1
59
22
44
43
51
675
1125
High
Quatril
18
12
70
94
-4
275
129
64
1155
895
26
5
4
53
9
5
50
3.7
3.66
4.5
1283
84
170
5.1
5.3
2688
84
67
2562
41
3.8
73
29
50
48
57
675
1125
Low
Quatril
18
12
52
63
-62
210
80
51
810
600
18
5
2
22
7
4
20
2.8
3.66
3.5
968
81
138
5.1
3.4
2163
81
67
2125
31
2.2
47
19
37
28
31
675
1125
High
Decil
18
12
86
100
+20
295
127
66
1195
995
28
7
5
71
11
&
56
4.5
3.76
5.0
1350
88
177
5.1
6.3
2957
85
69.5
2345
45
5.1
116
36
53
53
63
675
1125
Low
Decil
17.3
12.0
42
54
-90
175
169
48
735
590
5
3
1
0
5
4
0
2.3
3.61
3.1
916
80
134
5.1
3oO
2095
81
67
1931
29
2.2
39
15
31
24
29
650
1100
128
-------
Appendix VII
Activated Sludge Performance
December 1 to December 14, inclusive
Flow, gpm
Surf pa c Effluent
Return Sludge
Total Suspended Solids
Surf pa c Effluent, mg/1
Final Effluent, mg/1
% Removed
5 Day BOD
Surf pa c Effluent, mg/1
Final Effluent, mg/1
% Removed
COD
Surfpac Effluent, mg/1
Final Effluent, mg/1
% Removed
Phosphates as PO^
Surfpac Effluent, mg/1
Final Effluent, mg/1
% Removed
Organic & Ammonia Nitrogen
Surfpac Effluent, mg/1
Final Effluent, mg/1
% Removed
Mixed Li.quor
Aeration Period, hr
Dissolved Oxygen, mg/1
TSS, mg/1
TSS, % Vol.
S.V.I.
Return Sludge
% of Waste Flow
TSS, mg/1
TSS, % of MLSDI
Air Used
1,000 cfd
cu ft/lb BOD applied
cu ft/lb TSS under air
BOD Loadings
lb/1000 cu ft aeration vol
lb/100 Ib TSS under air
lb/100 Ib VSS under air
Final Clarifier Loading
G/SF/D
Waste Flow Only
Mixed Liquor
No. of
Days
Observed
14
14
14
14
14
13
14
13
10
10
10
1
14
1
1
1
14
14
14
14
14
14
14
14
14
13
14
. 13
13
13
14
14
Average
of Daily
Observa-
tion
13.0
9.8
71
47
35
180
72
58
949
649
21
3
3
67
7
4
57
2.50
4.0
2298
85
316
75
4583
143
2.6
102
43
65
45
52
487
830
Median
Value
9
9
78
47
36
190
70
61
940
710
20
3
3
67
7
4
57
3.07
3.9
2208
85
308
100
4635
155
2.4
104
40
54
37
44
386
675
High
Quatril
18
11
84
54
54
200
80
66
1070
825
28
-
4
-
-
4
-
3.07
4.4
2679
86
379
100
5450
171
3.3
114
45
78
58
69
675
1065
Low
Quatril
9
9
62
34
19
155
61
50
770
430
16
—
2
-
-
3
-
1.94
3.6
2097
84
261
67
3887
120
2.1
75
34
52
33
37
386
675
High
Decil
18
12
95
79
57
245
99
73
1290
1020
29
_
6
-
-
4
-
3.07
5.3
3220
89
412
100
6030
182
3.9
182
77
97
81
96
675
1125
Low
Decil
9
9
54
20
2
110
49
38
610
545
11
_
1
-
-
2
-
1.84
2.9
1430
83
218
61
2884
73
1.5
54
27
45
25
29
386
675
129
-------
Appendix VIII
Activated Sludge Performance
January 8 to January 21, inclusive
Flow, gpm
Primary Effluent
Return Sludge
Total Suspended Solids
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
5 Day BOD
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
COD
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
Phosphates as PO^
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
Organic & Ammonia Nitrogen
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
% BOD in Primary Effluent
Mixed Liquor
Aeration Period, hr
Dissolved Oxygen, mg/1
TSS, ng/1
TS3, % Vol.
S.V.I.
Return Sludge
% of Waste Flow
TSS, mg/1
TSS, % of ML5DI
Air Used
1,000 cfd
cu ft/lb BOD applied
cu ft/lb TSS under air
BOD Loadings
lb/1000 cu ft aeration vol
lb/100 lb TSS under air
lb/100 11 753 under air
Final Clarifier Loading
G/SF/D
Waste Flow Only
Mixed Licucr
No. of
Days
Observed
14
14
13
13
13
13
13
13
13
13
13
12
12
12
13
13
13
13
14
14
12
12
12
14
13
12
13
12
11
. 13
12
12
14
14
Average
of Daily
Observa-
tion
17.9
15.7
56
57
-5
201
57
71
795
542
31
6
5
18
10.5
5
55
5.3
5.0
4.1
2206
81
224
67
4130
94
3.9
96
21
32
23
29
668
1265
Median
Value
18
15
54
32
42
190
49
76
770
550
33
5
4
0
11
3
67
5.3
5.1
3.6
2198
81
214
83
4097
94
3.6
72
19
30
22
27
675
12/4.0
High
Quatril
18
17.5
62
76
47
230
63
78
860
590
36
7
7
40
11
6
71
5.8
5.1
4.4
2292
81
241
97
4269
109
4.0
100
22
37
26
32
675
1335
Low
Quatril
18
15
48
26
-11
180
40
68
735
480
26
5
3
0
10
3
46
4.7
4.7
3.2
2146
80
201
83
3831
82
2.4
62
15
29
21
26
675
1240
High
Decil
18
18
72
104
63
245
95
81
945
660
46
7
7
60
12
10
73
6.5
5.3
5.6
2425
82
280
100
5015
113
8.5
217
41
39
30
41
675
1355
Low
Decil
18
13.9
42
22
-231
165
40
47
625
440
16
4
2
0
10
3
-1
4.1
4,7
2 = 7
2040
77
191
62
3579
72
1.7
49
10
26
16
22
675
1205
130
-------
" Surfpac" Data
COD
Reduc-
Date
12/1
12/2
12/3
12/4
12/5
12/6
12/7
12/8
12/9
12/10
12/11
12/12
12/13
12/14
Average
Flow
GPM
18
18
18
15
9
9
9
9
14
9
0
9
9
18
13
pH
Inf.
7.5
7.4
8.7
7.5
7.3
7.3
7.5
-
7.6
7.3
6.9
7.1
7.2*
7.4
7.3*
7.3
7.4*
Eff.
7.9
7.7
8.3
7.7
7.4
7.5
7.6
-
7.5
7.4
7.3
7.3u
7.5
7.3*
7.3
7.5*
COD
Inf.
-
-
940
920
980
1590
1090
-
-
1100
1210
1150
1150*
810
850*
610
590*
1056
Eff.
-
-
880
850
890
1510
990
-
-
1010
1070
1070
1030*
690
770*
530
540*
949
tion
%
-
-
6
8
9
5
9
-
-
8
11
7
10
15
9
13
8
9
BOD
Reduc-
BOD
Inf.
180
200
220
210
240
310
270
-
230
250
260
260
280*
190
200
140
140
269
Eff.
120
170
190
170
190
290
200
-
180
200
190
200
200*
140
150
100
97
182
tion
%
33
15
14
19
21
7
26
-
22
20
27
23
29
26
23
28
31
22
S.S.
Inf.
72
38
18
86
44
50
68
68
68
74
72
88
82*
62
44*
64
36*
67
Eff.
84
54
28
80
54
66
80
92
78
84
60
98
76*
78
54*
62
42*
77
Total
V.S.S. Temp. PO^ Nitrogen
Inf. Eff. Inf.
44 53 -
24 42
52
51
53
54
55
50 72 54
50 74 54
- 52
- 52
- 52
- 52
- 51
52.7
Eff. Inf. Eff. Inf. Eff.
_____
_____
50
49
T=total PO/^
^ N=nutrient
P04
54 T-4 jj| 8 7
54
53
52
49
49
en
J\J —
48 - - -£•
3
a.
47 - - - - x
50.7 - - - - *
*After 2 hour settling time.
-------
Bench Scale Plant Performance on 100$ Hammermill Waste
From
To
Flow
Mixed Liquor, gal/hr
Primary Effluent, gal/hr
Return Sludge, gal/hr
Return Sludge, %
Suspended Solids
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
COD
Primary Effluent, mg/1
Final Effluent, mg/1
% Removed
HBOD
w Primary Effluent, mg/1
w Final Effluent, mg/1
% Removed
Ib applied per 100 Ib MLVSS
Ammonia Nitrogen added as N
mg per liter
% of applied BOD
Phosphate added as PO;
mg per liter
% of applied BOD
Mixed Liquor
Dissolved oxygen, mg/1
Total Susp. Solids, mg/1
Total Susp. Solids, % Vol.
SVI
Return Sludge
Total Susp. Solids, mg/1
Total Susp. Solids, % Vol.
BOD Loadings per 100 Ib VSS
Hr of solids aeration
Sludge Age, Days
Length of Period, Days
9-21
10-12
1.50
0.85
0.65
76
10-13
10-20
1.50
0.86
0.64
75
10-23
10-29
1.50
0.86
0.64
75
10-30
11-4
1.50
0.89
0.61
69
11-5
11-8
1.50
0.93
0.57
61
11-13
11-21
1.50
0.93
0.57
61
11-22
11-26
1.50
0.92
0.58
63
11-27
12-5
1.50
0.90
0.60
67
12-6
12-11
1.50
0.84
0.66
79
12-12
12-16
1.50
0.87
0.63
72
12-17
12-20
1.50
0.89
0.61
69
256
64
75
2700
1750
35
325
57
85
2570
1640
36
338
138
60
2600
1770
32
276
109
64
2495
1770
29
458
65
81
2330
1565
33
221
42
81
1860
1200
35
356
47
86
2160
1300
40
370
55
84
2320
1435
38
344
51
85
2260
1395
38
256
30
88
2135
1390
35
277
24
91
1550
870
44
550
76
89
42
26
4.7
177
32
4.1
5000
84
115
9800
86
8.4
7.4
22
460
59
89
36
21
4.6
143
31
3.9
4617
83
111
9415
85
7.2
5.6
8
515
81
85
41
19
3.7
129
25
4.4
4170
85
L49
6318
86
8.2
5.1
7
494
118
76
42
15
3.0
102
4.1
4322
84
164
9918
84
8.4
5.1
420
83
80
32
13
3.1
88
21
343
40
89
29
19
5.5
20
5.8
4.3 4.8
4760 4235
85 85
166 136
6.4
5.2
4
5.8
5.1
482
33
93
43
21
4.4
16
3.3
4.6
3990
79
L44
8300
80
8.6
5.0
5
464
42
91
41
22
4.7
12
2.6
4.5
3910
83
221
7353
82
8.2
4.8
425
34
94
37
22
5.2
9
2.1
4.5
4010
82
240
394
31
92
34
21
5.3
5
1.3
4.4
3600
85
269
318
15
95
36
20
6.3
3.5
1.1
4.2
2980
80
324
I
o>
7.4
4.1
6.8
4.2
X
X
7.2
4.4
4
-------
Appendix XI
Page 1 of 5
CITY OF ERIE
Municipal Building PENNSYLVANIA
J (-T////;n <7 L Q (D L- r> n •
'• -*"«•«> floseph (}. ~l\obie, executive
-------
Appendix XI
Page 2 of 5
UNITED STATES
DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
WASHINGTON. D.C. 20242
2 2 1968
Re: WPRD 223-01-68
Dear Mr. Tullio:
We are pleased to offer you a Research and Development Grant for the
project titled, "Joint Treatment of Domestic Sewage and Pulp and Paper
Mill Waste," as described in your application of January 19, 1968.
The Grant Offer is $88,230 or 15% of eligible project costs, whichever
is less, subject to the conditions and assurances set forth in the
enclosed Section I of the Offer and Acceptance document and attachments.
Acceptance of this offer must be made by completing the enclosed material,
including the Section II of the Offer and Acceptance document, and return-
ing the original copies of the material within the next thirty (30) days.
We are hopeful that this project will contribute significantly to advance-
ment of the Administration's Water Pollution Control Program by assisting
in the development of research and demonstration projects for prevention
of pollution by industry. The importance of this and other projects in
serving as useful demonstrations, having wide application, cannot be over-
emphasized.
Should you have questions concerning this Grant Offer, please contact our
Office of Research and Development.
Sincerely yours,
x / Joe G. Moore, Jr.
is Commissioner
Mr. Louis J. Tullio
Mayor - City of Erie, Pa.
Municipal Building
Erie, Pennsylvania 16501
Enclosure
134
-------
Appendix XI
3 of 5
Department of the Interior
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
Office of Research and Development
WPRD-223-01-68
Project Number
OFFER AND ACCEPTANCE OF FEDERAL GRANT FOR RESEARCH AND DEVELOPMENT
UNDER 33 U. S. C. 466 et. seq.
SECTION I
A. Location of Project (State, County, City)
Pennsylvania, Erie, Erie
B. Legal Name and Address of Applying Authority (herein called the "Applicant")
The City of Erie
Municipal Building
Erie, Pennsylvania 16501
C. Project Financing Under Terms of this Offer
Total estimated project cost $?3$.674. _
Estimated project cost eligible for Federal participation . $117^641 ..
FEDERAL GRANT OFFERED ................... $
or
15% of eligible project costs whichever is less.
D. Description of Project
Title of Project: "Joint Treatment of Domestic Sewage and Pulp and Paper
Mill Waste."
Project Objectives: Determine the technical success of Joint secondary
J J treatment, the economic factors involved and the
nutrient removal vhich may be obtained.
Grant Periods Six
135
-------
Appendix XI
Page k of 5
"The Commissioner of the Federal Water Pollution Control Administration
acting in behalf of the United States of America, pursuant to Section 6
of The Federal Water Pollution Control Act, as amended, hereby offers to
the Applicant named herein a grant to assist in the accomplishment of the
project described herein, provided the Commissioner receives from the
Applicant the assurances in the attached Rules and Regulations, a completed
Section II of this form, and provided that Acceptance is made within thirty
(30) days of the Offer, and subject to the following special conditions:
i Eligible costs for this grant are limted to those of preliminary
^rsrs^sss.-ffs
(30)
For the United States of America
Federal Water Pollution Control Administration
Joe G. Moore. Jr
_
(Bate) " I/ (Commissioner)
(Page 2)
-------
Arpendix XI
Fare 5 cf 5
ACCEPTANCE
SECTION II
On behalf of City of Erie
(Legal Name of Applicant)
I, the undersigned, being duly authorized to take such action, as
evidenced by the attached CERTIFIED COPY OF AUTHORIZATION BY THE
APPLICANT'S GOVERNING BODY, do hereby accept this Offer and make
the assurances contained in the Rules and Regulations attached
thereto.
Tunp 20. 1968
(Date) ^ignature of Representative)
T.onis T. Tullio. Mayor __ . .
(Name and Title of Representative - Type or Print)
(Page 3)
137
-------
BIBLIOGRAPHIC:
The City of Erie, Pennsylvania and Hammermill
I Paper Company, Joint Municipal and Semichemical
Pulping Waste Treatment, FWPCA Publication ORD-1
ABSTRACT:
I
The City of Erie, Pennsylvania and Hammermill
| Paper Company made a study of the joint treatment of
domestic sewage and pulp and papermaking wastes. A
| pilot plant was constructed and operated in a series of
controlled experiments. Supplemental studies were con-
. ducted in the Hammermill laboratories including the
I operation of a bench-scale activated sludge plant.
• It was demonstrated that a joint treatment plant
could effectively treat a mixture of domestic sewage and
pulp and paper mill wastes from Hammermill's Erie
I Division. A full-scale joint treatment plant should
obtain a BOD removal of approximately 90% in summer
| months and 80%-85% in winter months. Primary treatment
I BIBLIOGRAPHIC:
I The City of Erie, Pennsylvania and Hammermill
Paper Company, Joint Municipal and Semichemical
Pulping Waste Treatment, FWPCA Publication ORD-1
' ABSTRACT:
I The City of Erie, Pennsylvania and Hammermill
Paper Company made a study of the joint treatment of
domestic sewage and pulp and papermaking wastes. A
I pilot plant was constructed and operated in a series of
controlled experiments. Supplemental studies were con-
. ducted in the Hammermill laboratories including the
I operation of a bench-scale activated sludge plant.
I It was demonstrated that a joint treatment plant
could effectively treat a mixture of domestic sewage and
1 pulp and paper.mill wastes from Hammermill's Erie
Division. A full-scale joint treatment plant should
j obtain a BOD removal of approximately 90% in summer
months and 80%-85% in winter months. Primary treatment
BIBLIOGRAPHIC:
The City of Erie, Pennsylvania and Hammermill
Paper Company, Joint Municipal and Semichemical
Pulping Waste Treatment, FWPCA Publication ORD-1
' ABSTRACT:
I The City of Erie, Pennsylvania and Hammermill
Paper Company made a study of the joint treatment of
j domestic sewage and pulp and papermaking wastes. A
pilot plant was constructed and operated in a series of
j controlled experiments. Supplemental studies were con-
ducted in the Hammermill laboratories including the
operation of a bench-scale activated sludge plant.
It was demonstrated that a joint treatment plant
could effectively treat a mixture of domestic sewage and
| pulp and paper mill wastes from Hammermill's Erie
Division. A full-scale joint treatment plant should
j obtain a BOD removal of approximately 90% in summer
months and 80%-85% in winter months. Primary treatment
ACCESSION NO.
KEY WORDS:
P i lot P lants
Pulp Wastes
Municipal Wastes
Sewage T reatment
Activated Sludge
Sludge Disposal
Oxygenation
Disinfection
Annual Costs
ACCESSION NO.
KEY WORDS:
Pilot Plants
Pulp Wastes
Municipal Wastes
Sewage Treatment
Activated Sludge
Sludge Disposal
Oxygenation
Disinfection
Annual Costs
ACCESSION NO.
KEY WORDS:
Pilot Plants
Pulp Wastes
Municipal Wastes
Sewage Treatment
Activated Sludge
Sludge Disposal
Oxygenation
Disinfection
Annual Costs
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I
should achieve a 25% reduction in BOD and a 60% I
reduction in suspended solids. Treatment of mixed '
wastes by the activated sludge process will require a i
long solids aeration period and a relatively low BOD to I
volatile solids loading to avoid high sludge volume
indicies. The activated sludge process does not reduce |
trie color of the mixed wastes and the final effluent will
have about 40 mg/1 of suspended solids. The chlorine I
demand of the final effluent averaged over 60 mg/1. A '
NH3-C12 mixture added at a level of 2.61 ppm NH3 and
15-17 ppm C12 showed promise as a disinfectant with I
coliform counts generally below 1,000/100 ml.
should achieve a 25% reduction in BOD and a 60%
reduction in suspended solids. Treatment of mixed I
wastes by the activated sludge process will require a |
long solids aeration period and a relatively low BOD to
volatile solids loading to avoid high sludge volume
indicies. The activated sludge process does not reduce I
the color of the mixed wastes and the final effluent will '
have about 40 mg/1 of suspended solids. The chlorine
demand of the final effluent, averaged over 60 mg/1. A i
NH3-C12 mixture added at a level of 2.61 ppm NHa and |
15-17 ppm C12 showed promise as a disinfectant with
coliform counts generally below 1.000/100 ml.
should achieve a 25% reduction in BOD and a 60%
reduction in suspended solids. Treatment of mixed
wastes by the activated sludge process will require a
long solids aeration period and a relatively low BOD to
volatile solids loading to avoid high sludge volume
indicies. The activated sludge process does not reduce
the color of the mixed wastes and the final effluent will
have about 40 mg/1 of suspended solids. The chlorine
demand of the final effluent averaged over 60 mg/1. A
NHs-CIa mixture added at a level of 2.61 ppm NHs and
15-17 ppm C12 showed promise as a disinfectant with
coliform counts generally below 1,000/100 ml.
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