United States
Environmental Protection
Agency
Municipal Environmental Research EPA-600/2-80-020
Laboratory June 1980
Cincinnati OH 45268
Research and Development
Chemical and
Biological
Treatment of
Thermally
Conditioned Sludge
Recycle Liquors
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-,
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields;
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
-------
EPA-600/2-80-020
June 1980
CHEMICAL AND BIOLOGICAL TREATMENT OF
THERMALLY CONDITIONED SLUDGE RECYCLE LIQUORS
by
Mark B. Heyda
James D. Edwards
Richard F. Noland
BURGESS & NIPLE, LIMITED
Consulting Engineers and Planners
Columbus, Ohio 43220
Grant No. 11010 OKI
Project Officer
B. Vincent Salotto
Wastewater Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
-------
DISCLAIMER
This report has been reviewed by the Municipal Environmental
Research Laboratory, U.S. Environmental Protection Agency, and
approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the U.S.
Environmental Protection Agency, nor does mention of trade names
or commercial products, constitute endorsement or recommendation
for use.
11
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FOREWORD
The Environmental Protection Agency was created because of
increasing public and government concern about the dangers of
pollution to the health and welfare of the American people.
Noxious air, foul water, and spoiled land are tragic testimony
to the deterioration of our natural environment. The complexity
of that environment and the interplay between its components
require a concentrated and integrated attack on the problem.
Research and development is that necessary first step in
problem solution and it involves defining the.problem, measuring
its impact, and searching for solutions. The Municipal Environ-
mental Research Laboratory develops new and improved technology
and systems for the prevention, treatment, and management of
wastewater and solid and hazardous waste pollutant discharges
from municipal and community sources, for the preservation and
treatment of public drinking water supplies, and to minimize the
adverse economic, social, health, and aesthetic effects of
pollution. This publication is one of the products of that
research; a most vital communications link between the researcher
and the user community.
This research provides additional data to aid in the eval-
uation of chemical and biological treatment systems for thermally
conditioned sludge recycle liquor.
Francis T. Mayo, Director
Municipal Environmental Research
Laboratory
111
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ABSTRACT
The objective of the research project was to demonstrate
and evaluate the feasibility, effectiveness, and benefits of
treating undiluted thermally conditioned sludge recycle_liquors
with chemical and biological treatment processes. Chemical
treatment consisted of hydrated lime addition followed by
clarification both in bench scale facilities and in a 120 cu m
(32,000 gal) reaction clarifier. Biological treatment was
achieved in a 10.9 cu m/day (2,880 gpd) high rate activated
sludge plant. Recycle liquor for the project was generated from
a Zurn heat treatment process with 87 cu m/day (16 gpm) capacity.
The period of operation covered approximately a half a year for
the concurrent study of both the chemical and biological systems.
Pollutant removal efficiencies were measured for: 6005,
COD, ammonia and organic nitrogen, phosphorus, suspended solids,
turbidity, color, and heavy metals. BODs removal averaged 26%
for the chemical system and 93% for the biological system.
Color was reduced in both systems by at least 90%. In physical
terms, the recycle liquor was a pale straw yellow to amber after
chemical treatment and colorless to pale straw yellow after
biological treatment.
The economics of recycle liquor treatment (including
ultimate disposal of the resulting sludge) were evaluated for
both systems. Total annual costs for treatment of recycle
liquor generated from thermal conditioning of municipal sludges
were: Chemical - $0.012/kg ($13.67/ton) of sludge and Biologi-
cal -$0.027/kg ($29.78/ton) of sludge. However, on a pollutant
removal basis, biological treatment is cost effective—total
costs per tonne of BOD5 removed - $452 for chemical systems and
$370 for biological systems.
In addition to confirming previous laboratory and pilot
scale studies, the report also includes: a thermal conditioning
system process description, material and energy balances,
characterization of recycle liquors, K-rate and cell growth
coefficient studies, and design conditions for the chemical and
the biological treatment facilities.
This report was submitted in fulfillment of Grant No. 11010
OKI by Lake County, Ohio, under the sponsorship of the U.S. Environ-
mental Protection Agency. The report was prepared by Burgess and
Niple, Limited, for Lake County after the subgrantee had completed
the research study at the Mentor, Ohio, Sewage Treatment Plant.
This report covers the period May 1975 to December 1978, and work
was completed as of March 1979.
iv
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CONTENTS
FOREWORD
ABSTRACT
FIGURES
TABLES
LIST OF ABBREVIATIONS AND SYMBOLS
I
II
III
IV
V
VI
VII
INTRODUCTION
CONCLUSIONS
BACKGROUND
General
Willoughby-Mentor Wastewater Treatment
Facilities
Maintenance and Start-Up Difficulties
THERMAL CONDITIONING PROCESS DESCRIPTION
General
Material and Energy Balances
Characteristics of Recycle Liquor
Impact of Recycle Liquor
CHEMICAL TREATMENT OF RECYCLE LIQUOR
General
Operation and Sampling
Results
BIOLOGICAL TREATMENT OF RECYCLE LIQUOR
General
Operation and Sampling
Results
RECYCLE LIQUOR TREATMENT ECONOMICS
General
Chemical Treatment Costs
Biological Treatment Costs
Comparison of Treatment Costs
PAGE
iii
iv
vi
viii
x
REFERENCES
1
2
5
5
5
9
11
11
14
16
18
20
20
20
22
38
38
38
41
51
51
52
55
57
60
v
-------
FIGURES
Number
1
2
3
5
6
7
8
10
11
12
13
14
Willoughby-Mentor Wastewater Treatment
Plant Site Plan
Sludge Handling Flow Schematic
Zurn Sludge Heat Treatment Flow
Schematic
Zurn Thermal Conditioning System
Material Balance
Schematic of Chemical Treatment Facilities
Results of Lime Treatment on Recycle Liquor
BOD5
Results of Lime Treatment on Recycle Liquor
COD
Results of Lime Treatment on Recycle Liquor
Phosphorus
Results of Lime Treatment on Recycle Liquor
Nitrogen
Results of Lime Treatment on Recycle Liquor
Suspended Solids
Results of Lime Treatment on Recycle Liquor
Color & Turbidity
Results of Lime Treatment on Recycle Liquor
Heavy Metals
Biological Treatment Facilities
Influent and Effluent BOD5 Concentrations
and Organic Loading Rates for Biological
Treatment, of Recycle Liquor
Page
6
8
12
15
23
25
27
29
30
33
34
37
39
42
VI
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Number
15
16
17
FIGURES (continued)
The Effect of Loading on COD Removal from
Recycle Liquor
Recycle Liquor Influent and Effluent Suspended
Solids Concentrations for Biological Treat-
ment Study
Endogenous Decay Curves
Page
44
46
48
Vll
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TABLES
Number
1
2
. Page
5
6
10
11
12
13
Design Data - Wastewater, Willoughby-Mentor
Wastewater Treatment Plant
Design Data - Sludge Handling, Willoughby-
Mentor Wastewater Treatment Plant
Comparison of Various Thermal
Conditioning Systems
Recycle Liquors From Various Heat Treatment
Facilities
Recycle Liquor Characteristics - Mentor, Ohio
Additional Loading to Plant Aeration
Systems from Recycle Liquors at
Several Installations
Lime Dosage Requirement for Neutralization
of Recycle Liquors
BOD5 Concentrations in Recycle Liquor With
Lime Treatment at Various pH Levels
Phosphate Concentrations In Recycle
Liquor With Lime Treatment at
Various pH Levels
Nitrogen Concentrations in Recycle Liquor
With Lime Treatment at Various pH Levels
Color and Turbidity Levels in Recycle
Liquor With .Lime Treatment at Various pH
Levels
Heavy Metal Concentrations in Recycle Liquor
With Lime Treatment at Various pH Levels
Pilot Scale Biological Reactor Design
Parameters
13
17
18
19
21
24
28
31
35
36
40
Vlll
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TABLES (continued)
Number
14
15
16
17
18
19
20
21
22
Biological
several
C°effici-ts for various waste
Lime Treatment System Design Data
gage
43
45
49
50
52
54
55
57
58
IX
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LIST OF ABBREVIATIONS AND SYMBOLS
ABBREVIATIONS
biochemical oxygen demand
British thermal unit
chemical oxygen demand
cubic foot (feet)
cubic feet per minute
cubic meter
degree Celsius
eg
degree Fahrenheit
diameter
endogenous decay c
feet (foot)
Coefficient,
base 10
feet vlouu' 4-'^,
food to microorganism ratio .
gallon (s)
gallons per day
gallons per minute
gallons per hour
horsepower
hour(s)
o
Jackson turbidity units
joules
kilowatt hour
kilogram (s)
kilometer
liter
metric ton , • *. ,-
microgram(s) per liter
milligram(s) per
million gallons per day
minute(s) o^iids
SSd iiSSS ESST «•££-
nephelometric turbidity units
percent
platinum-cobalt color
pound(s) .
pounds per square inch
side water depth
square foot (feet)
square meter
suspended solids
avg
BOD,-
BTU
COD
cu ft
cfm
cu m
°C
op
dia
k
ft
F/M
gal
gpd
gpm
HP
hr
JTU
J
kwh
kg
km
1
tonne
ug/1
mg/1
MGD
min
MLSS
MLVSS
NTU
%
Pt-Co
Ib
psi
SWD
sq ft
sq m
SS
-------
LIST OF ABBREVIATIONS AND SYMBOLS (continued)
standard cubic foot (feet)
standard cubic feet per minute
temperature
total dissolved solids
total suspended solids
total dynamic head
total solids
volatile solids
waste activated sludge
weight
year(s)
SYMBOLS
cadmium
calcium hydroxide (hydrated lime)
calcium oxide (quicklime)
iron
lead
nickel
nitrogen
phosphorus
zinc
scf
scfm
temp
TDS
TSS
TDH
TS
VS
WAS
Wt
yr
Cd
Ca(OH)
CaO
Fe
Pb
Ni
N
P
Zn
XI
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ACKNOWLEDGEMENTS
Burgess & Niple, Limited, Consulting Engineers would like
to thank Mr. Robert Alban, Lake County Sanitary Engineer and Mr.
Gary Kron, Project Coordinator for their_assistance and coopera-
tion throughout the administration of this grant.
We would especially like to thank Mr. Lee Friedabaugh,
Superintendent of the Greater Mentor wastewater treatment plant
and his staff for their efforts and patience in the operation of
the heat treatment system and the associated research facili-
ties. Special thanks are also due to Ms. Robin Taylor and Mr.
Clarence Killer of.the Greater Mentor wastewater treatment plant
laboratory who collected and analyzed many of the samples which
form the basis of this research.
The project officer for the U.S. Environmental Protection
Agency Municipal Environmental Research Laboratory (Cincinnati,
Ohio) was Mr. B. Vincent Salotto, Chemist, Ultimate Disposal
Section, Wastewater Research Division. During the early phase
of the grant, the project officer was Dr. Joseph B. Farreii,
Chief, Ultimate Disposal Section, Wastewater Research Division,
MERL, USEPA. Their direction and assistance were much appre-
ciated during the study.
Randall Wilson and Greg Knapp of Burgess & Niple, Limited
contributed an extra effort in conducting extensive laboratory
analyses for this project. Kay Wilson was responsible for
typing the final manuscript.
XII
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SECTION I
INTRODUCTION
A number of municipal wastewater treatment facilities in
the United States use thermal conditioning as a sludge process-
ing method. A by-product of this process is a highly concen-
trated recycle liquor which is often returned to the. main
treatment facilities. Substantial quantities of BOD5, nitrogen,
phosphorus, and solids are solubilized in the thermal condition-
ing process and remain in the recycle stream. Although the
volume of the recycle stream is small, its effect on the treat-
ment plant is significant. Additional treatment demands by
recycle liquors may result in overloading for those plants
without sufficient excess capacity to accommodate these supple-
mental loads. For other plants that have not yet reached their
design loadings, recycle liquor loads may force premature
expansions.
Although much research has been conducted concerning
optimum processing parameters for heat treatment systems,
additional study devoted to the evaluation of recycle liquor
treatment has been needed. To that end, this report addresses
the operation and expected performance of separate treatment
facilities for recycle liquor using both chemical and biological
processes.
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SECTION II
CONCLUSIONS
1. Chemical treatment of thermally conditioned sludge recycle
liquors with hydrated lime was explored as a method of
reducing their impact on wastewater treatment plants.
Laboratory jar tests were performed to evaluate pollutant
reductions at pH 8.5, 9.5, 10.5, and 11.5. The solutions
were flocculated for 30 min and then allowed to settle for
60 min. The resulting supernatant s were tested. The
results of these analyses were:
a. Lime dosages of about 1.6 kg CaO per 1,000 1 (13.4 Ib
CaO per 1,000 gal) were required to achieve a pH of
10.5.
b. BODs and COD levels were marginally reduced by lime
treatment. The greatest removals occurred at pH 11.5.
At that pH, maximum BOD5 reductions were 35% with
treated effluents in the range of 1,150-3,300 mg/1
BODs . Reductions of 11-38% were achieved with treated
effluents in the range of 1,900-11,800 mg/1 COD.
c. Lime treatment was effective in removing phosphorus
from recycle liquor. Initial phosphorus concentra-
tions were reduced from an average of 270 mg/1 P to
less than 3 mg/1 P at pH's exceeding 8.5 for an
average phosphorus removal of 99%. In one full scale
test, phosphorus removal of 96% was achieved.
d. Chemical treatment with lime achieved average ammonia
nitrogen reductions from 129 mg/1 to 95 mg/1 at pH 9.5
and greater. Average organic nitrogen reductions from
122 mg/1 to 38 mg/1 at pH 11.5 were achieved.
e. Average suspended solids removals from 475 mg/1 to 27
mg/1 were achieved with lime clarification at pH 9.5
and greater .
f . Turbidity and color removals from recycle liquor were
also successful using chemical treatment with lime.
Color was reduced from initial average concentrations
of 4,250 Pt-Co color units to an average of 380 Pt-Co
color units at pH 11.5. Visually, the treated liquor
-------
2.
retained a yellow to amber tint. Average turbidity
reductions were from 100 NTU to- 3 NTU at pH 11.5.
Heavy metals such as cadmium, trivalent chromium,
copper, lead, nickel, and zinc all form hydroxides
SS "?** arf relativelY insoluble at alkaline
s. The data show that removal of the metals
n fr°? fr^016 li(2uor is essentially constant at
any level of lime treatment above pH 8.5. Average
concentrations Before and after treatment were as
no/^°r:^C admtUm' 3°° Ug/1 to 15 U9/1? chromium, 800
?g;Lt0 2,6 ug/1; c°PPer, 500 ug/1 to 17 ug/1; lead
1,100 ug/1 to 160 ug/1; nickel, 500 ug/1 to 37
and zinc, 900 ug/1 to 34 ug/1. ^.J/.
the
An activated sludge process operated in the high rate mode
was used to evaluate biological treatment. OpSrating
parameters were: mean cell residence time 1.3 days,
^n^ 2ad/?g™n 1'6-2-4 k^ BOD5 Per day/cu m (100-150 Ib
0 ?5to I 2ay/1'000 CU ft)' 4,000-5,000 mg/1 MLSS and F/M of
a.
b.
c.
d.
BODc reductions averaged 93% with influent concen-
trations of 1,500-3,500 mg/1. Effluent BODC concen-
trations ranged from 10-560 mg/1. 5
COD reductions averaged 76% with influent concentra-
tions _ of 2,800-7,600 mg/1. Loadings to the system
were in the range of 2.5-4.5 kg COD/cu m/day. Ef-
fluent COD concentrations ranged from 340-1,930 mg/1.
Ammonia and organic nitrogen were approximately re-
moved as predicted by the nutrient requirements for
heterotrophic bacteria, i.e., 6 parts nitrogen per 100
parts_BOD5 removed.(24) The sum of ammonia aSd
organic nitrogen removed was 6.2 kg N per 100 kg BODC
^°Sia no?r°gen and. ^cmic nitrogen removals averaged
bb-s and 62%, respectively.
Total phosphorus reductions of 5 kg P per 100 kg BOD^
were achieved. This did not confirm earlier research
by Come (23) and Erickson(22) nor the nutrient
requirements for heterotrophic bacteria shown by
Helmers,U4) i>e>/ I part phosphorus per 100 parts
BOD_ removed
b
*• j* ~^ fr ~~»^**- **fc^ j<* \^j- ^ \j \j t~sCL.
Phosphorus removal averaged 89%.
-------
e. Suspended solids reductions averaged 88% with influent
concentrations from 600-2,000 mg/1.
f The average endogenous decay coefficient (k-rate) for
recycle liquor generated from the Zurn process was_
determined to'be 0.13 day'1. Therefore, the aeration
requirements for this waste would be approximately the
same as for ordinary domestic sewage.
q The cell growth coefficient for the recycle liquor
generated for this project was determined to be 0.49
kg volatile solids produced per kg BOD5 removed.
3 The total annual cost of chemical treatment of recycle
liquor generated from a 2.2 cu m/second (50 MGD) wastewater
treatment plant is $226,800 per year [$0.012/kg ($13.67/
ton)] of thermally conditioned sludge] including capital
and operation and maintenance cost. This cost is based on
lime treatment using hydrated lime, a reaction clarifier,
transportation, and land application of the resulting lime
sludge (without dewatering). Additional treatment costs
due to incomplete pollutant removal by chemical treatment
were not included.
4 The total annual cost of biological treatment of recycle
liquor generated from a 2.2 cu m/second (50 MGD) wastewater
treatment plant is $493,900 per year [$0.027/kg ($29. 78/
ton)] of thermally conditioned sludge] including capital
and operation and maintenance cost. This cost is based on
a high rate activated sludge process, anaerobic digestion
of the resulting sludge, transportation, and land disposal
of the liquid sludge. No additional treatment costs for
the recycle of treated recycle liquor were computed.
5 Comparison of total annual costs on a pollutant removal
basis shows that biological treatment is more cost effec-
tive than chemical treatment. Since the removals for
phosphorus and suspended solids were essentially the same
with either process, treatment costs were compared based on
annual removals of BOD5. Assuming 35% BODr reduction for
chemical treatment and 93% BOD5 reduction for biological
treatment, the costs for recycle liquor treatment were:
Chemical treatment $451.79/tonne BODs removed.
Biological treatment $370.09/tonne BOD5 removed
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SECTION III
BACKGROUND
GENERAL
The Willoughby-Mentor wastewater treatment plant, Mentor,
Ohio, was placed in operation in September 1965,, The plant
provided for influent pumping and primary treatment with the
addition of chemicals followed by discharge to Lake Erie.
Sludge disposal was by anaerobic digestion and vacuum filtra-
tion. Subsequent to the original treatment plant construction,
the state regulatory agency determined that all plants dis-
charging into Lake Erie should provide secondary treatment
including phosphorus removal. Accordingly, plans were begun to
upgrade the primary treatment facilities.
In 1968, the need to investigate alternate methods of
sewage sludge processing and disposal became apparent. The heat
treatment process was emerging as an attractive process alterna-
tive and was considered in detail for incorporation into the
Willoughby-Mentor treatment plant. On September 20, 1968, a
formal application was made to the Federal Water Pollution
Control Administration requesting funds for the construction and
demonstrative operation of the "Porteous Process" for heat
treatment of sludge. A grant was offered by the FWPCA dated
December 20, 1968, and was accepted by resolution of the Board
of County Commissioners on December 23, 1968.
Subsequent to the grant award, detailed construction draw-
ings and specifications were prepared and the project was bid.
The Erie Energy Division of Zurn Industries was ultimately
selected to construct and demonstrate an experimental innovative
modification to the Porteous process at the Willoughby-Mentor
wastewater treatment plant. The unit was planned to be incor-
porated into the expanded primary/secondary treatment plant as
described in the following section. Construction was begun in
April 1971, and was completed in April 1973.
WILLOUGHBY-MENTOR WASTEWATER TREATMENT FACILITIES
The expanded Willoughby-Mentor wastewater treatment plant
utilizes an activated sludge biological treatment system.
Figure 1 shows the plant site plan and general wastewater flow.
The biological treatment is preceded by comminution, grit
-------
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cu
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cu
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0)
+J
fO
QJ
4J
CO
fO
s-
o
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sz
01
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3
O
-------
removal, and primary sedimentation and is followed by disin-
fection. Phosphorus removal is accomplished by chemically
treating the wastewater within the biological treatment system.
Design data for the treatment plant are summarized in Table 1.
TABLE 1. DESIGN DATA - WASTEWATER
WILLOUGHBY-MENTOR WASTEWATER TREATMENT PLANT
Description
Capacity
Design Flow
Average Flow
Design BOD Loading
@ 200 mg/1
Design Solids Loading
@ 240 mg/1 SS
30,280 cu m/day
(8 MGD)
18,900 cu m/day
(5 MGD)
6,056 kg/day
(13,350 Ib/day)
7,267 kg/day
(16,020 Ib/day)
Sludges^produced during the treatment of the wastewater
include primary sludge and waste activated sludge. Facilities
are provided for anaerobic and aerobic digestion, chemical
conditioning, heat treatment, and dewatering the; sludges. A
reactor clarifier is provided for chemically tresating super-
natants from the sludge treatment processes with hydrated lime
before the liquid is discharged back into the waistewater treat-
ment system.
The principal flow patterns between the sludge treatment
processes are shown schematically on Figure 2. The principal
flow pattern for the primary sludge is thickening in the sludge
holding tank, heat treatment, thickening in the decant tanks,
and vacuum filtration.
Waste activated sludge is processed by aerobic digestion
prior to gravity sludge dewatering and/or land application.
Waste activated sludge also can be processed with primary
sludge by anaerobic digestion followed by vacuum filtration and
landfill.
Sludge processing by thermal conditioning has been limited
to primary sludge although primary-waste activated sludge
mixtures could be processed.
-------
AEROBIC
DIGESTION
z
o
SLUDGE
NCENTRAT
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-------
Design data for the sludge handling facilities are sum-
marized in Table 2.
TABLE 2. DESIGN DATA - SLUDGE HANDLING
WILLOUGHBY-MENTOR WASTEWATER TREATMENT PLANT
Description
Aerobic Digester
Sludge Concentrators
for WAS
Anaerobic Digesters, (2) , total
Holding-Thickening Tank, volume
Vacuum Filter, area
Loading rate
@ 30% dry solids
Heat Treatment, design flow
Process Temperature, max
Process Pressure, max
Vacuum Filter
@ 30% dry solids
Phosphorus Removal Facilities
Reaction Clarifier
Design Flow
Lime Feed, range
Capacity
1,246 cu m
(44,000 cu ft)
7.6 cu m/hr (2,000
gph)
3,478 cu m (122,840
cu ft)
84 cu m (2,980 cu ft)
12.3 sq m (132 sq ft)
40 kg/sq m/hr
(8 Ib/sq ft/hr)
3.6 cu m/hr (16 gpm)
204°C (400° F)
1.9 x 106 newton/
sq m (275 psi)
5.9 sq m (63 sq ft)
52 kg/sq m/hr
(10»6 Ib/sq ft/hr)
22.8 cu m/hr (6,000
13.6-136 kg/hr
(30-300 Ib/hr)
MAINTENANCE AND START-UP DIFFICULTIES
Construction of the sludge heat treatment facilities was
completed in April 1973. Acceptance tests began in May 1973
and were completed on December 30, '1975. During this period,
numerous difficulties were encountered. Problems were accen-
tuated by the construction of the secondary treatment facili-
ties. Because the grit removal facilities were either under
construction or inoperable, severe difficulties were encountered
-------
with large stones and rags plugging both the sludge thickener
drawoff line and heat treatment feed lines. Secondly, the
stones caused mechanical problems with the sludge grinders and
high pressure pump rotors and stators. Numerous test runs were
required because of the failure of the heat treatment system to
operate within the allowed natural gas requirements and vacuum
filter cake production rates. Finally, a considerable period of
time was required to evaluate vacuum filter cloths and to
determine the proper operation of the vacuum filter system.
10
-------
SECTION IV
THERMAL CONDITIONING PROCESS DESCRIPTION
GENERAL
Seed
process ^
conditioning can also be
systems such as
ommon thermal treatment
The purpose of sludge
condition primary and waste
for additional chem^l treat
either reduced or eliminated.
used in place of °^**^1B
aerobic or anaerobic dl9es^s- ^ee process, and Neptune-
systems are: Zimpro proce ss, BSP ^teous P compared with the
Nichols or Parrer process. These syst^a ^ ^ s
Zurn process in Table 3. ™e Nept direct steam injection
are essentially th^*m|dan^g2 is heated indirectly with a
into the sludge. J^Jjd, siuage and zimpro processes use
heat exchanger. _ The BSP-Porteous and Zimp £^ ^
flfdge ^sUge^cnSs^nd direct air injection.
A schematic
This tank
with
it ls
Snsss-tsfussss s^b1fiSliSSt-
and high pressure sludge pumps. The thickens
rx^el^"3?- -" -L^rSS
process. The untreated sludge is then he&t transfer
the sludge heat exchanger (132^ m °| ^r_s ft-°F]) by hot
coefficient, U=469 J/sec-sq m- C [84 BT u/nr 4 Heated
water circulating G°unter^f^eWit is reSinld for approxi-
sludge flows into the reactor where it is r fiQwB through
mately 1 hr. From the reactor, the Create ^ ^^ j/sec-sq
the sludge heat exchanger 152 jq m o± t recovered by the hot
m-°C [110 BTU/hr-sq ft- Flji,w^es5^qe is cooled. Downstream
water circulating system and the sludge « valve which is
autSatlcflfy Tegufatel ^^2^^^ sludge level and maintains
11
-------
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03
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o
-a
co
s_
3
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CD
CD
iZ
12
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ro
tn
55
0
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of these tanks is eqiped with a
further concentrate the sludge
then is
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• 1Ck?ing device to
process (lime treatment,
MATERIAL AND ENERGY BALANCES
Material
r
Although the volume of the"i™Or
main plant flow, the recycle ha?
treatment facilities. In oJdSr
zurn thermal conditioning sySm
wastewater treatment n]ani-
The reactor was oSraS^
of 60 min for two 16 hr runs Th2
weighed on a truck soal» »?5' 5
from two point^n ?SS Srufa?"!
.
"hen COI"Pared to the
substf;tial impact on the
«T, the himpact of the
MlUoughby-Mentor
:larj ™S con"ructed.
™ sludge residence time
™cuum filter output was
°f ^ «•«
recirculating solids repsen
processed by the thermal
recircuiating solids
Energy Balance
17°
These
tOtal solids
this
. oosts
cost information f or S?L I vari°us sizes. They
and maintenance costf for many heJf t?eJtm 1?clud±nST operation
in the United States. Their av£??L ^ atmfnt systems operating
kg/day (5 ton/day) thermal "oSitioni dlrect+.costs for a 4,535
energy cost for pumping? healina and "3Syfte™ included an
are summarized on page 16 usSa ,',n^ dewatering. These costs
BTU for fuel and. sHJ/kwh former COStS °f $2'8° per
14
-------
^»*^l» " ^ » • ^* • *
(1
V
1
_._, Grinder Seal Water
J J 1.9 cum (500 gal)
«=^^^ 1
SLUDGE
THICKENING J
\. TAI
[ i THICKENED SLUDGE
«K .x^
59.6 cu in (15,750 gal)
@ 6.2% solids
TS = 3,676 kg (8,104 Ib
SS = 3,560 kg
DS = 161 kg
(7,848 Ib.
( 356 Ib)
•61.5 cu m (16,250 gal)
@ 5.8% solids
TS =1,541 kg (7,807 Ib)
SS = 3,193 kg (7,039 Ib)
DS = 349 kg ( 769 Ib)
20.0 cu m
TS = 151 kg
SS = 18 kg
DS = 134 kg
(5,289 gal)
(333 Ib)
( 39 Ib)
(295 Ib)
TREATED SLUDGE
DECANT
41.5 cum (10,96 ga1)
TS = 3,390 kg 7,474 Ib
SS = 3,175 kg 7,000 b
DECANT/
THICKENING
TANK
DS = 215 kg
( 474
THICKENED
SLUDGE
RECYCLE
LIQUOR
TS = 479 kg (1,057 Ib)
SS = 244 kg ( 539 Ib
OS = 235 kg ( 519 Ib)
50.8% Solids
CAKE Total weight = 4740 kg (10,450 Ib)
Dry solids = 2406 kg (5305 Ib)
REACTOR CONDITIONS
60 nrin. residence time @ 193° C.
Figure 4. Zurn thermal conditioning system material balance.
15
-------
Swets, Pratt, and Metcalf( * reported energy costs for a
larger 63,490 kg/da (70 ton/day) heat treatment system at
Kalamazoo, Michigan. Their cost for fuel reflected a credit
for incinerator waste heat recovery. These costs with the same
unit prices previously stated are summarized below.
The energy consumption of the Zurn heat treatment system at
Mentor, Ohio, including pumping, vacuum filtration, and heating,
was also measured. Energy costs were calculated based on the
same unit prices. These costs are essentially the same as those
reported by EwingU) ana are summarized below.
Facility Size
Fuel
Swing, et al
4,535 kg/day
(5 ton/day)
$0.008/kg
($7.18/ton)
Zurn
Power
Total Energy
$0.006/kg
($5.48/ton)
$0.014/kg
($12.66/ton)
*Includes credit for incinerator
3,628 kg/day
(4 ton/day)
$0.009/kg
($7.92/ton)
$0.006/kg
($5.39/ton)
$0.014/kg
($12.82/ton)
Swets, et al
63,490 kg/day
(70 ton/day)
$0.004/kg*
($3.56/ton)
$0.007/kg
($6.18/ton)
$0.Oil/kg
($9.74/ton)
waste heat recovery
Additional energy requirements for recycle liquor treatment
would also have associated fuel and power costs. These costs
are presented later in this report.
CHARACTERISTICS OF RECYCLE LIQUOR
A general range of characteristics for heat treatment
recycle liquor has been reported by Ewing(2) as:
Suspended Solids
BOD
Ammonia as N
Phosphorus as P
Color
100 - 20,000 mg/1
5,000 - 15,000 mg/1
10,000 - 30,000 mg/1
400 - 1,700 mg/1
150 - 200 mg/1
1,000 - 6,000 Pt-Co units
Variation in recycle liquor concentrations arises from several
factors: (a) concentration of sludge influent to the process;
(b) reactor temperature and residence time; (c) processing con-
ditions such as steam and air injection; (d) type of sludges
processed; (e) settling time in the decant tank; and (f) de-
watering conditions. These factors vary widely from one in-
stallation to another depending upon local processing needs.
To illustrate the variation in recycle liquors, data from
various thermal conditioning plants including Jackson Pike and
Southerly in Columbus, Ohio, are presented in Table 4 along with
data from Ewing(2) and Sherwood.^>
16
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17
-------
The average characteristics of the recycle liquor used in
this study are shown in Table 5. The reactor was operated at
150° C at about 3.6 cu m/hr (16 gpm) for a residence time of 60
min using primary sludge only.
TABLE 5. RECYCLE LIQUOR CHARACTERISTICS-Mentor, Ohio
Average
Range
BOD5/ total, rag/1
BOD,-, soluble mg/1
COD? mg/1
Solids
Total, mg/1
Suspended, mg/1
Ammonia nitrogen, mg/1
Organic nitrogen, mg/1
Phosphorus , mg/1
PH
Color, Pt-Co units
3,330
2,430
6,860
3,690
1,290
140
125
190
5.1
4,000
2,550-3,850
2,100-3,500
6,000-8,050
3,130-5,000
700-1,850
100-186
40-175
120-270
4.8-6.2
800-6,000
IMPACT OF RECYCLE LIQUOR
Substantial organic and solids loading to treatment
facilities by recycle liquors from sludge thermal conditioning
has been reported. At the Colorado Springs, Colorado wastewater
treatment plant, an analysis of the impact due to the recycle of
heat treated liquor has been made by Boyle and Gruenwald.(5)
Their material balance on the heat treatment system showed that
21% of the BOD5 and 30% of the suspended solids influent to the
30 MGD treatment plant were due to recycle liquor. They also
noted an increase in the plant effluent color and turbidity.
The final effluent averaged 60-100 Pt-Co color units and 10-20 JTU
after the heat treatment system was started up.
Haug, et al also reported that recycle liquor from the
Los Angeles Hyperion plant would have a considerable impact upon
the secondary treatment plant. Material balances showed a 30%
increase in the oxygen demand on the aeration system would
result from recycle liquor. This was considered unacceptable
and further recycle liquor treatment studies were begun.
Surveys by Harrison( ' and Ewing^ of various heat treat-
ment systems indicated that substantial BOD5 and suspended
solids loads were due to recycle liquors. These loads expressed
as a percentage of the total wastewater treatment plant loadings
are summarized in Table 6. Recycle loads for the Mentor plant
are also included. The Mentor loads are based on an average
18
-------
BODc and TSS wastewater concentrations of 200 mg/1 each, a plant
flow of 0.22 cu m/second (5 MOD), a heat, treatment flow of 87 cu
in/day (16 gpm), and average recycle liquor concentrations.
TABLE 6. ADDITIONAL LOADING FROM
RECYCLE LIQUORS AT SEVERAL INSTALLATIONS
Recycle Loads* (%)
BODC Suspended Solids
Gresham, Oregon
Vancouver, Washington
Kalamazoo, Michigan
Colorado Springs, Colorado
Portland, Oregon
Mentor , Ohio
41
35
35-40
21
16-28
7.2
59
11
w
30
16-28
2.8
* Based on total plant design loads
The imposition of additional organic and solids loads from
heat treatment facilities to plant secondary systems may be even
more significant than suggested in Table 6 due to the high
soluble fraction of BOD and the colloidal nature of a large
portion of the suspended solids. It follows that the major
impact of recycle liquors has been the premature commitment of
reserve capacities and treatment problems. ^-1' '
19
-------
SECTION V
CHEMICAL TREATMENT OF RECYCLE LIQUOR
GENERAL
Chemical treatment of thermally conditioned sludge recycle
liquors with lime was explored as one method of reducing the
impact on wastewater treatment plant. The primary interest was
to reduce the high BOD5 levels in the recycle liquor. Other
goals of chemical treatment were to reduce the levels of ammonia
nitrogen, phosphorus, suspended solids, turbidity, color, and
heavy metals.
Lime has been used extensively in wastewater treatment
processes primarily because of its low cost.(?) The results of
several previous studies on the application of lime treatment
for the removal of phosphate, color, suspended solids, BOD5, and
nitrogen have been reported in the literature. Pilot plant work
by EldridgeW on tannery wastes treatment with lime determined
BOD5 and suspended solids removals. Buzzell and Sawyer(g)
investigated pollutant removals from raw municipal wastewater
using chemical treatment with lime. Lime treatment of raw
wastewater was also reported by Horstkotte, et al.(10) Wilson,
et aH-1-1-' and HaynesUZ) reported lime studies by the kraft
paper industry on the treatment of highly colored processing
wastes. G. E. Bennett(13) investigated the effects of lime
treatment on anaerobic digester supernatants using pilot plant
facilities.
Recycle liquor treatment by the lime -clarification process
was selected for study in light of the results of studies
reported in the literature cited above. A reaction clarifier at
the Willoughby-Mentor treatment plant was employed to evaluate
the feasibility, effectiveness, and benefits of chemical treat-
ment of recycle liquors with lime.
OPERATION AND SAMPLING
All of the recycle liquor treatment studies were conducted
with supernatant from the treated sludge decant tanks. Problems
with the vacuum filtration equipment prevented the production of
filtrate from the dewatering of heat treated sludge. Decant
liquor was produced from heat treating primary sludge at 150°C.
20
-------
Bench scale studies on lime treatment were carried out
concurrently with the full scale work. Only two runs were
completed with the full scale lime clarifier because of the
limited quantity of recycle liquor. The data presented, there-
fore, is primarily based on the bench scale lime treatment
facilities.
Commercial grade hydrated lime with 73% calcium oxide was
used for all lime treatment studies.
Bench Scale Tests
A standard jar testing apparatus was used for the bench
scale tests. One percent hydrated lime slurries were slowly
added with rapid mixing for five min. The treated liquor was
flocculated for 30 min, followed by settling for 60 min.
Clarified supernatant was siphoned off from the settled lime
sludge to prevent agitation of the light floe. .
Target pH values of 8.5, 9.5, 10.5 and 11.5 were used in
the pilot scale studies. Initial liquor pH was approximately 5-
6 as previously described. Lime requirements for neutralization
of the heat treatment liquor have been summarized in Table 7.
TABLE 7. LIME DOSAGE REQUIREMENTS FOR
NEUTRALIZATION OF RECYCLE LIQUORS
Lime Dosage*
kg CaO per lb CaO per
cu m 1,000 gal
8.5
9.5
10.5
11.5
1.1
1.5
1.6
1.8
9.1
12.2
13.4
15.3
* Expressed as 100% CaO.
The amount of lime required to raise the liquor to pH 9.5 is
approximately ten times that required for normal sewage. Ben-
nett'14' has reported lime dosage requirements of 6,000 mg/1
commercial grade calcium hydroxide (3.4 kg CaO/cu m) to reach pH'
10.7 with anaerobic digester supernatant which is approximately
twice that observed for recycle liquor.
21
-------
Full Scale
The 120 cu m (32,000 gal) reaction clarifier located at the
wastewater treatment plant was designed to be used with anaero-
bically digested filtrates and supernatants as well as heat
treatment recycle liquors. Lime was stored in a bin and dis-
charged by gravity into two volumetric lime feeders (recipro-
cating plate type). A dissolving tank was located directly
beneath each feeder and adjacent to the clarifier.
Hydrated lime was slurried in each of two 0.2 cu m (50 gal)
dissolving tanks and fed by gravity through an open trough into
the stirred reaction well of the clarifier. The process was
designed to operate continuously. The rate of lime application
could be controlled by changing the volumetric feed rates on
each feeder. Recycle liquor was pumped into the reaction well
Of the clarifier near the point of slurry application. Figure 5
shows a schematic of the facilities.
Two factors prevented the proper use of the chemical
treatment facility:
1. Hydrated lime was subject to frequent arching or
bridging inside the storage bin. Upon collapse of the
lime bridges, the volumetric feeders became inundated
with lime.
2. The system was unable to function well on a batch
basis. Heat treatment recycle liquor was not avail-
able in sufficient quantity to operate on a continuous
basis.
The following lime transfer system modification should be
incorporated into the facilities to circumvent the first problem
outlined above. In addition to the existing vibrators mounted
on the sloping section of the storage bin (designed to break up
any bridging which may occur), the system should include hori-
zontal augers to transfer the hydrated lime to the feeders.
This will prevent "flooding" of the dissolving tanks.
The second problem arose because the vacuum filter system
for dewatering thickened heat treated sludge was not used.
Operational problems with the filter system existed that were
beyond the scope of simple plant maintenance solutions.
RESULTS
The effectiveness of chemical treatment with hydrated lime
in reducing pollutant levels for heat treatment recycle liquors
was variable. Phosphorus, for example, was almost totally
removed with relatively small lime dosages. On the other hand,
22
-------
UME
STORAGE
BIN
VIBRATOI
REACTION
CLARIFIER
pH METER O
TURBINE
DRIVE-^
•—LIME FEEDER
'LIME DISSOLVER
TREATED EFFLUET
RECYCLE LIQUOR INFLUENT
RECIRCULATION
DRUM
TO SUJDGE TRUCK
UME
SLUDGE
PUMPS
TO VACUUM FILTER
Figure 5. Schematic of chemical treatment facilities,
23
-------
was resistant to the chemical treatment. Removal efficien-
cies for each parameter are discussed separately and compared,
if possible/ with plant and pilot scale industrial or municipal
applications of wastewater lime treatment.
Biochemical Oxygen Demand
Buzzell^ and Horstkotte( ' have previously reported up
to 74% -BODs removals in municipal sewage with lime treatment.
Eldridge(8T has reported BOD5 reductions of 55% in tannery waste
with lime treatment. BOD5 removals are generally linked to
improved flocculation and sedimentation of suspended solids
which contribute to the total BOD5 load. Unlike domestic
sewage, the BODs in recycle liquor primarily results from
dissolved solids. About 95% of the BODs in decant liquor is
soluble BODs and therefore, simple flocculation, precipitation
mechanisms were not expected to be as effective when applied to
recycle liquor. The results are shown on Figure 6 and listed in
Table 8.
TABLE 8. BOD5 CONCENTRATIONS IN RECYCLE LIQUOR WITH
LIME TREATMENT AT VARIOUS pH LEVELS
Biochemical Oxygen Demand, mg/1
Run:
*pH 5.5
pH 8.5
pH 9.5
pH 10.5
pH 11.5
Total
Soluble
Total
Soluble
Total
Soluble
Total
Soluble
Total
Soluble
A
1,580
N/A
N/A
N/A
1,250
N/A
1,275
N/A
1,150
N/A
B
1,950
1,860
1,900
1,750
1,750
1,700
1,550
1,540
1,340
1,200
C
3,675
N/A
3,100
N/A
3,200
N/A
3,300
N/A
3,300
N/A
D
3,700
3,050
2,800
2,500
2,580
2,250
2,400
2,600
2,390
2,450
* Untreated
The maximum BOD5 reductions occurred at the highest pH.
BOD5 removals varied from 10-35% at pH 11.5. In addition to the
precipitation of suspended BODs' minor entrainment and/or absorp-
tion of BOD5 contributed to the BODs which was extracted from
the solution.
24
-------
4000
3000 -
C*
10
o
o
m
(E
o
§ 2000 -h
o
o
UI
(T
JOOO - -
TOTAL
— SOLUBLE
Note: Letters A, B, C, D refer
to run designations.
—« 1 i—
5.5 6.5 7.5
8.5
pH
9.5
10.5
11.5
Figure 6. Results of lime treatment on recycle liquor BODg concentration.
25
-------
Chemical Oxygen Demand
(14)
Bennett" reported COD removals from anaerobic digester
supernatants with lime treatment to pH 11.3 to be about 48%
(initial COD about 5,400 mg/1).
At the Mentor plant, COD removals were similar to results
obtained for BOD5 removals. Figure 7 shows results of lime
treatment of recycle liquor for COD removal.
COD reductions averaged 33% at pH 11.5 with influent con-
centrations of 2,840-14,400 mg/1. Reductions of 11-38% were
achieved with treated effluents in the range of 1,900-11,800 mg/1
COD.
Phosphorus
The chemistry of the reaction of phosphate and heavy metals
such as iron and calcium has been reported by Stumm and Mor-
gan. I14) They explained that the equilibrium between the
soluble complexes of calcium and phosphate and the insoluble
complexes are pH dependent. Given an excess of calcium in
solution, complexes such as calcium orthophosphate (CaHPO4)
react to form the more stable insoluble species (hydroxyapatite,
Ca5OH[PO4]3) as the pH increases.
Buzzell^ and Horstkotte '1:L' reported phosphate reductions
from 11.5 mg/1 P to 2.p mg/1 P (Marlbough, Mass.) and 9.4 mg/1
P to 0.96 mg/1 P (Contra Costa County Sanitary District, CCCSD,
San Francisco Bay area), respectively, using lime treatment of
raw sewage at pH 11.5.
Results from a pilot plant operation utilizing lime treat-
ment of anaerobic digester supernatant were reported by Ben-
nett. <13) The phosphorus concentrations of the supernatant
liquors studied were similar to those of recycle liquor as
studied in this report. From an initial phosphorus level of 141
mg/1, removals were studied at pH 9.6, 10.7, and 11.5. The
liquor concentrations after treatment were 27.3 mg/1, 26.0 mg/1,
and 18.7 mg/1, respectively. Approximately half of the remaining
phosphorus was present as polyphosphates.
The chemistry of lime in recycle liquor, however, is com-
plicated by competing reactions such as calcium carbonate for-
mation and humic acid neutralization. In addition, some of the
phosphorus is not available in a form that will react with lime
(organically bound phosphorus).(15) At pH 8 and greater, most
of the phosphorus remaining in solution is of the latter type
since the solubility of the hydroxyapatite is less than 1
mg/1. (--L^}
26
-------
8000
7OOO ••
o
o
u
o:
o
a
o
UJ
oc
o
<
tc
UJ
6000 •
5OOO '
4000 •—I •- 7—
5-5 6.5 7.5
8.5
pH
9.5
10.5 11.5
Figure 7. Results of lime treatment on recycle liquor COD concentration.
27
-------
The results of the previous studies are presented with the
results of lime treatment of recycle liquor in Table 9. Figure
8 shows the removal of phosphorus in recycle liquors at various
pH levels.
TABLE 9. PHOSPHORUS REMOVAL FROM RECYCLE LIQUOR,
RAW .SEWAGE, AND DIGESTER SUPERNATANT WITH
Location:
Wastewater :
Untreated
pH 8.5
pH 9.5
pH 10.5
pH 11.5
Mentor
Recycle
Liquor
195
11.7
2.4
0.8
0.0
Irvington
Anaerobic
Digester
Supernatant
141
N/A
27.3
26.0
18.7
CCCSD
Raw
Sewage
9.4
N/A
N/A
N/A
0.96
Marlbough
Raw
Sewage
11.5
N/A
N/A
N/A
2.0
All concentrations as mg/1 total phosphorus
N/A, not available
Average phosphorus removals of 99% were achieved with
influent phosphorus levels ranging from 70-270 mg/1. in one
full scale test, 7.0 mg phosphorus remained after lime treatment
to pH 11.5 with an initial concentration of 190 mg/1.
Ammonia and Organic Nitrogen
A 24% nitrogen reduction in raw sewage by lime treatment
was reported by Buzzell.O) Total nitrogen was reduced from 71
mg/1 to 54 mg/1 at pH 11.0.
Bennett(14) reported a 37% organic nitrogen removal from
digester supernatant using lime treatment. The initial concen-
tration of the supernatant was 282 mg/1 organic nitrogen.
Removals were based on lime treatment to pH 10.7.
The results of chemical treatment of recycle liquor with
lime is shown on Figure 9. Average removals of ammonia nitrogen
and organic nitrogen at pH 11.5 are 30% and 69%, respectively
and are listed in Table 10. y
28
-------
300
2 200-
to
ce
o
a.
w
o
a.
UJ
1.0
Figure 8.
Results of lime treatment on recycle liquor average total
phosphorus concentration.
29
-------
o«
E
bJ
0
§
I
O
I
CC
O
ft
111
Q
O
§
Z
O
LU
CE
UI
200
ISO
100 •
50 •
Org - N
5.5
6.5
7.5
8.5
PH
9.5
IO.5
11.5
Figure 9. Results of lime treatment on recycle liquor average
ammonia-nitrogen and organic-nitrogen concentrations.
30
-------
TABLE 10. NITROGEN REMOVALS FROM RECYCLE LIQUOR WITH
LIME TREATMENT AT'VARIOUS pH LEVELS
Ammonia Nitrogen, mg/1
Average Range
Organic Nitrogen, mg/1
Average: Range
Untreated
pH 8.5
pH 9.5
pH 10.5 .
pH 11.5
129
117
95
91
91
(104-160)
(117-118)
( 43-115)
( 45-129)
( 59-123)
122
78
40
52
38
(42-176)
(34-123)
( 0-146)
( 0-156)
( 0-126)
The removal of ammonia nitrogen from recycle is about the
same as the reduction achieved with raw sewage. Organic nitrogen
reductions from recycle liquor is about the same as for anaerobic
digester supernatant (84 mg/1 and 104 mg/1 removed, respectively).
The chemical composition of recycle liquor has been re-
ported by Teletzke, et al.(15) The organic nitrogen sources in
recycle liquor are largely proteins, free amino.acids, free fatty
acids, glycerides, sterol esters, choline and other minor com-
ponents. Ammonia nitrogen in the liquor is a product of the
decomposition of urea into ammonia and ammonium salts./
Chemical treatment of recycle liquor with lime converts all of
the ammonium salts to free dissolved ammonia which remains in
the liquor. Some ammonia vapor leaves the solution aided by
mixing. Since mechanical mixing was used, a relatively low
ammonia nitrogen removal was achieved. Greater ammonia nitrogen
removal could be achieved if diffused air mixing was used.
Lime treatment of the recycle liquor was more effective in
organic nitrogen removal. The mechanism for nitrogen reduction
differs from the preceding case. One explanation is that pro-
teins responsible for a large percentage of the organic nitrogen
were coagulated by the action of the lime in a process called
denaturation.(1V) The residual free amino acids and low nitro-
gen bearing compounds such as choline and polyglycerides, etc.,
are not attacked by the action of lime. These compounds which.
are not entrained or adsorbed by the floe would account for the
residual organic nitrogen.
Suspended Solids
As with other chemically assisted sedimentation processes,
the lime clarification process is generally effective in reduc-
ing the concentration of suspended solids from wastewater. In
31
-------
lime treatment studies on raw municipal sewage (TSS=199 mg/1)
reported by Horstkotte,(10) suspended solids removal of 79% to
41 mg/1 was achieved at a lime dose of 500 mg/1 calcium hy-
droxide, pH 11.5. Flow through the test facilities was about
4,920 cu m/day (1.3 MGD).during the studies. At a lower dose of
lime to pH 11.0, the average effluent suspended solids were 50
mg/1 (influent 206 mg/1 TSS).
Lime treatment pilot studies with digester supernatant
reported by Bennettt13) showed•. an average suspended solids
removal of 64%, from 2,251 mg/1 to 796 mg/1 at pH 11.3. Re-
movals were fairly constant at treatment levels pH 10.7-12.3.
This suggests that the suspended solids capture was not pH
dependent.
Lime treatment jar tests with recycle liquor at Mentor also
showed the removal of suspended solids to be pH insensitive.
Recycle liquor suspended solids were reduced to an average of 27
mg/1 after lime treatment at pH 9.5 to 11.5 with an average
initial TSS concentration of 475 mg/1.
Figure 10 shows the removal of suspended solids from re-
cycle liquor at various pH levels after lime treatment.
Turbidity and Color
The increase of color in wastewater plant effluents has
been attributed to the recycle of thermally conditioned sludge
cooking liquors. (5>-
Lime treatment for color reduction of paper mill bleach
effluents has been successful in the kraft paper industry. At
one kraft mill, consistent removal efficiencies of greater than
80% have been reported at lime dosages of 1,000 mg/1.<12)
Haynes^1^ reported kraft wastewater color reductions from 852
Pt-Co color units to 253 Pt-Co color units at pH 11.3, with a
lime treatment dosage of 523 mg/1 CaO. Wilson*11' also showed a
color reduction in kraft wastewater in pilot plant studies.
Lime treatment to pH 11.5 resulted in color reductions from
4,800 color units to 140 color units.
Boyle( reported that the Colorado Springs wastewater
treatment plant final effluent had typical color readings of 60
to 100 color units and turbidities of approximately 10-20 JTU
after the start-up of the heat treatment plant.
t _ For recycle liquor, the removal of color and turbidity was
similarly successful using chemical treatment with lime. Typ-
ical removals of color and turbidity are listed in Table 11.
The results are comparable to those reported for the kraft paper
industry and shown on Figure 11.
32
-------
500
400
en
o
O
V)
o
UJ
o
UJ
a.
(ft
I
UJ
-------
KRAFT PROCESS
LIQUOR (It)
«0.5 11.5
Figure 11.
°n
color and
34
-------
TABLE 11. COLOR AND TURBIDITY CONCENTRATIONS IN RECYCLE
LIQUOR WITH LIME TREATMENT AT VARIOUS pH LEVELS
Average
Range
Initial pH
Color, Pt-Co units
Turbidity, NTU
pH 8.5
Color, Pt-Co units
Turbidity, NTU
pH 9.5
Color, Pt-Co units
Turbidity, NTU
pH 10.5
Color, Pt-Co units
Turbidity, NTU
pH 11.5
Color, Pt-Co units
Turbidity, NTU
4,250
100
1,100
55
500
15
410
10
380
3
(3,000-6,000)
(100-110)
(1,000-1,250)
(18-91)
(200-800)
(6-24)
(200-700)
(4-20)
(150-650)
(2-4)
Average color removals at maximum lime dosage levels were
97% with color levels after treatment (pH 11.5) that ranged from
150-650 Pt-Co units. Average turbidity reductions of 97% were
similarly experienced with turbidity levels after treatment that
ranged from 2-4 NTU.
As illustrated on Figure 11, most of the color and turbid-
ity abatement occurred after partial treatment to pH 9.5 with
reductions of color and turbidity at 88% and 85%, respectively.
The incremental removals achieved by additional lime treatment
to pH 11.5 were smaller at 24% and 33%, respectively, indicating
diminishing returns on further treatment.
As the data shown in Table 11 indicate, the treated liquor
retained a yellow to amber tint even after high lime treatment.
Similar residual color was reported by Haug, et al(6) in. a study
of anaerobic filtration of recycle liquor. Refractory organic
compounds solubilized during the heat treatment process were
imputed to be responsible for the residual color after treat-
ment. Everett(18' stated that residual COD resistant to bio-
logical treatment was the cause of the liquor's color.
Filtering the lime treated recycle liquor was carried out
to determine the nature of the residual color. Since the color
passed through the filter, the coloring can be attributed to
fine colloidal particles and dissolved materials. Color and
35
-------
turbidity removals of this fraction would then be limited to
adsorption and entrainment in the lime floe.
Heavy Metals
Lime is widely used for removal of metals from wastewaters.
Cadmium, trivalent chromium, copper, lead, nickel, and zinc all
form hydroxides with lime. The solubility of these amphoteric
metal hydroxides, although pH dependent, is generally low at all
alkaline conditions.(19) Figure 12 shows typical metal con-
centration reductions achieved with lime treatment at various pH
levels. The application of lime at any dose over pH 8.5 was
sufficient to remove most metals. Table 12 summarizes the
average heavy metal concentrations following lime treatment.
TABLE 12. AVERAGE HEAVY METAL CONCENTRATIONS IN RECYCLE
, LIQUOR WITH LIME TREATMENT AT VARIOUS pH LEVELS
Metal
Untreated pH 8.5
pH 9.5
pH 10.5 pH 11.5
Cadmium, ug/1
Chromium, ug/1
Copper , ug/1
Lead , ug/1
Nickel, ug/1
Zinc, ug/1
300
800
500
1,100
500
900
15
26
17
160
37
34
13
21
9
140
31
17
13
16
13
130
36
20
13
16
13
160
39
13
The data show that the -removal of metals from recycle
liquor is essentially constant at any level of lime treatment
for the pH range studied. Average removals of heavy metals after
lime treatment (pH 8.5 or greater) were: 95% for cadmium, 97%
for chromium and copper, 85% for lead, 93%. for nickel, and 98%
for zinc. Residual concentrations of cadmium, chromium, copper,
nickel, and zinc after treatment were uniformly below 40 ug/1.
Average lead concentrations after lime treatment ranged from
130-160 ug/1.
36
-------
Ul
2
s
ui
X
O o»
O 3
o .
-2
ui o
§8
K"
111
_J
2
Ul
o w'
§1
Ul
o
o
ui
o
o
ui
tr
ui
800
600 ••
400 ••
CADMIUM
CHROMIUM
COPPER
1100
90O • •
1O.5 11.5
Figure 12. Results of lime treatment on recycle liquor heavy
metal concentrations.
37
-------
SECTION VI
BIOLOGICAL TREATMENT OF RECYCLE LIQUOR
GENERAL
Previous research on biological treatment of recycle li-
quors has been conducted using anaerobic digestion, anaerobic
filtration, and activated sludge systems. Cooper(20) reported
that 85% BOD5 removals could be achieved by anaerobic digestion
with a ten day detention time. Salotto, et al(21) also con-
cluded that anaerobic digestion was a viable method of recycle
liquor treatment.
concluded that anaerobic filters were well suited
to the treatment of liquors produced from thermal conditioning
of waste activated sludge.
Laboratory activated sludge processes were investigated by
Everett(18) to determine the biodegradability of heat treatment
recycle liquor.
Larger pilot studies were conducted by Erickson and Knopp(22)
and Corrie(23) using the activated sludge process to treat
recycle liquors.
Biological treatment of thermally conditioned sludge re-
cycle liquors with a 10.9 cu m/day (2,880 gpd) high rate acti-
vated sludge process was evaluated at the Willoughby-Mentor
wastewater treatment plant as a method of reducing the liquor's
impact on the plant. BOD5, COD, nitrogen, phosphorus, and
suspended solids removals were determined to evaluate the effec-
tiveness and benefits of the biological treatment of recycle
liquors.
OPERATION AND SAMPLING
Facilities
A high rate activated sludge plant was used to evaluate the
treatment of recycle liquors. A schematic of the facility is
shown on Figure 13. Recycle liquor influent to the plant was
drawn from a storage tank assuring a constant supply of recycle
liquor. A positive displacement pump transferred the recycle
38
-------
Ut»
2
to
OJ
o
(O
M-
-P
c
CD
OJ
fO
O
CD
O
o
•I—
CO
O)
39
-------
liquor to the aeration tank. The design specifications for the
system are outlined in Table 13.
TABLE 13. BIOLOGICAL REACTOR DESIGN PARAMETERS
Storage tank
Recycle liquor transfer pump
Aeration volume
Clarifier volume
Clarifier surface area
Aeration diffusers
Blower capacity
Blower motor
Clarifier skimmer (air lift)
Return sludge pump (air lift)
120 cu m (32,000 gal)
5.5-27.3 cu m/day (1-5 gpm)
11.9 cu m (3,150 gal)
4.5 cu m (1,200 gal)
3.3 sq m (35.5 sq ft)
Coarse bubble
4.68 cu m/min (165 scfm)
3,728 watt (5 HP)
max. 0.08 cu m/min (20 gpm)
max. 0.23 cu m/min (60 gpm)
Sampling
Samples were collected five days a week by Lake County
treatment plant personnel. Samples were analyzed by the plant's
laboratory staff. Duplicate samples were analyzed by Burgess &
Niple, Limited laboratory to insure analytical accuracy.
Three samples were collected daily at the following points:
1. Influent pump suction - untreated recycle liquor
2. Aeration tank - mixed liquor
3. Effluent weir overflow - treated recycle liquor
Target Conditions
Since the waste treated by this process had approximately
ten times the BOD5 of normal domestic sewage, the plant was
operated at high rate loadings. The following operational
criteria were used:
1.
2.
3.
4.
5.
Organic loading to aeration, 1.6-2.4 kg BOD5 per
day/cu m (100-150 Ib BOD5 per day/1,000 cu ft)
F/M, 0.4-1.0 (kg BOD5 per kg MLSS under aeration)
Mixed liquor suspended solids, 4,000-5,000 mg/1
Dissolved oxygen level in mixed liquor, 2-4 mg/1
Minimize SVI (obtain good settleability)
Start-Up and Operation
Initially, the package plant was filled with settled sew-
age. Return activated sludge from the main plant was used to
seed the aeration tank. A dissolved oxygen level in the mixed
40
-------
liquor was maintained at 6-10 mg/1. The return sludge ratio was
initially set at 30:1. Hydraulic detention time through the
aeration tank was set at about 26 hr by controlling the intro-
duction of settled sewage to 10.9 cu m/day (2,880 gpd).
After a two week acclimation period, recycle liquor was
substituted as a feed stock to the reactor. Since the package
plant influent was not gradually changed to the stronger recycle
liquor, an additional two1 weeks were spent to acclimate the
microorganisms to the new waste. After target conditions were
established, the process performed satisfactorily. Sludge
volume indices were consistently below 90.
RESULTS
General
Biological treatment was conducted in two phases to deter-
mine if treatment would be affected by changing the character-
istics of the recycle liquor influent to the process. Recycle
liquor for the first phase was produced from heat treatment of
primary sludge at 150° C for 60 min. The second phase of the
study utilized recycle liquor produced from heat treatment of
primary sludge at 190° C. The activated sludge process was
operated close to target conditions for three weeks and two
weeks, respectively. The average mean cell residence time was
1.3 days for each phase.
Biochemical Oxygen Demand
Erickson^22' reported achieving BOD5 reductions of 96% with
Zimpro recycle liquor on a pilot scale. Treatment of recycle
liquor diluted with domestic sewage was studied by Corrie. <• ;
He reported 98% BODr reductions at 1.1 kg BOD5 per day/cu m (68
Ib BOD5 per day/1,000 cu ft) loadings.
The high rate activated sludge process at Mentor achieved
BODc reductions exceeding 93% for both phases of the research.
Figure 14 shows the influent and effluent BOD5 in relation to
the plant organic loadings and SVI during the total project
period. Effluent BOD5 averaged 86 mg/1 in the first phase and
265 mg/1 in the second phase. For the same periods, the average
loadings were 1.9 kg BOD5/cu m/day (120 Ib BOD5/day/l,000 cu ft)
and 2.1 kg BOD5/cu m/day (133 Ib BOD5/day/l,000 cu ft), respec-
tively.
Chemical Oxygen Demand
Previous studies have shown that recycle liquor COD is
substantially reduced by biological treatment with removals as
high as 80-90%.(9) The study-by Everett^18) shows a correlation
between COD loading and removals. Research at Lake County tends
41
-------
If
5 £
< 3
3 < 2-56
H- 0W2.24
f g 1-92
- 1.6
CO
IOO
60
60
40
3000
2000
o«
E
to
o 1000
500 •
INFLUENT
— Total BODK
3
Soluble BOD
EFFLUENT
12-7
12-17
Phase One
12-27 1-6
Time,Calendar Days
-H _ , .
3-2 3-12
Phase Two
Figure 14. Influent and effluent BOD concentrations and organic
loading rates for biological treatment of recycle liquors.
42
-------
to reinforce that conclusion. Figure 15 shows the agreement
with data from the biological treatment s.tudy at Lake County and
findings by Everett. Table 14 summarizes the Lake County data
for biological treatment phases. The data show that neither
suspended nor soluble COD is preferentially removed and that a
substantial portion of the total COD was resistant to biological
attack. An average of 24% of the influent COD was not removed.
This fraction of nonbiodegradable COD was more than three times
larger than previously reported by Erickson.(22)
TABLE 14. COD REMOVALS ACHIEVED WITH BIOLOGICAL TREATMENT
Total COD, mg/1 Soluble COD, mg/1 Removals
Date Influent Effluent Influent Effluent Total Soluble
150° C Liquor
12-27-77 3,480 1,120 N/A N/A 68% N/A
1-4-78 2,834 467 N/A N/A 84% N/A
190° C Liquor
3-2-78
3-7-78
3-8-78
3-16-78
5,960
6,720
6,506
7,618
1,930
1,260
1,200
1,883
3,950
4,536
4,451
5,050
1,260
1,008
770
1,198
68%
81%
82%
75%
68%
78%
83%
76%
Nitrogen and Phosphorus
Nitrogen and phosphorus are nutrients necessary for growth
of the microorganisms in activated sludge. Research by Helmers,
et al(24) established that these nutrients are utilized by the
activated sludge process in specific ratios. The average ratio
of nutrient utilization by heterotrophic bacteria was reported as
100:6:1 for BOD:N:P removed. The utilization of nitrogen by
nitrifying bacteria would be in addition to the carbonaceous
nutrient utilization.
Studies by Corrie^23^ and Erickson^22' on recycle liquor
treatment by the activated sludge process confirmed the BOD:N:P
relationship. Corrie reported a nutrient utilization of 100:6:
1.4 and Erickson reported a BOD:N:P ratio of 100:4:1.4. Data
from Lake County research on nitrogen and phosphorus removals
correlated to BOD,- removed is listed in Table 15.
43
-------
90%
85%
o
o
o
u.
o
I
UJ
DC
80%
75%-
• MENTOR PILOT STUDY
• EVERETT, REF. 18
A CORRIE, REF. 23
O ERICKSON,REF. 22
RANGE OF VALUES, ±
2345
COD LOADING, kg/curn-d
Figure 15. The effect of loading on COD removal from recycle liquor.
44
-------
TABLE 15. NITROGEN, PHOSPHORUS AND BODC
REMOVALS WITH BIOLOGICAL TREATMENT'
Run
12-15 12-27
1-4
3-2
3-8
3-16
BOD 5 removed, mg/1
Phosphorus, mg/1
Influent
Effluent
Soluble Phosphorus, mg/1
Influent
Effluent
Ammonia Nitrogen, mg/1
Influent
Effluent
Organic Nitrogen, mg/1
Influent
Effluent '
Total Nitrogen
Removed, mg/1
2,464 1,700 1,584 2,240 2,648 2,775
140
10
32
0
140
0.6
56
9.5
70
4
37
3
118
8.7
45
7.6
185.9 146.7
195
110
152
115
13
42
18
126
172
41
12
9
101
39
137
106
93
150
14
124
12
162
112
95
28
117
142
15
106
5
165
120
199
104
140
Removal per 100 parts BOD5
Total Nitrogen 7.5
Total Phosphorus
Soluble Phosphorus
5.3
1.3
8.6
3.8
2.0
8.0
5.3 ;
^~
4.2
5.8
0.1
4.4
5.1
4.2
5.0
4.6
3.6
The average BOD^tNiP ratio was 100:6:2.2 for the above data
considering only soluble phosphorus. The same ratio would be
100:6:2.5 for total phosphorus. Except for the higher phosphorus
removals, the relationship is almost identical to earlier find-
ings .
Average removals for phosphorus were 89%. Average ammonia
nitrogen and organic nitrogen removals were 66% and 62%, re-
spectively.
Suspended Solids
Overall suspended solids removal of 85-90% was achieved for
the biological treatment of recycle liquor. Figure 16 shows
the suspended so'lids data for both phases of the biological
study. The concentration of suspended solids was reduced to an
average of 100 mg/1 for the first phase and 180 mg/1 for the
second phase. Suspended solids removals averaged 94% at a MLSS
of 4,300 mg/1. Clarifier surface loading rates were 3.3 cu
m/day/sq m (80 gpd/sq ft).
45
-------
200O
O»
E
O
H
I-
Z
IU
O
z
O
O
CO
O
O
CO
O
III
O
z
Ul
ou
CO
3
CO
I50O •
INFLUENT
EFFLUENT
1000 ••
500 •
12-7
12-17
Phase One
12-27 1-6
Time, Calendar Days
3-2 3-12
Phase Two
Figure 16. Recycle liquor influent and effluent suspended solids
concentrations for biological treatment study.
46
-------
-• and TurPigJ-T-Y,
.BBS
The endogenous decay .coefficient, or k rate,
predict the aeration re quirement sgr waste wa^ carb
and to predict the rat e °| ^°°|o^eS . The value of k is the
er-reaction Kinetics: (25)
"
ultimate carbonaceous BOD remaining
o
BOO
processing Plant has been
as
^
lecyde liquor at
0.40 day 1.
The ic rates were measured for the
this study. Two other ^^sSred^r comparison. The studies
Columbus, Ohio were also .mea^BOn Ixerted by a recycle liquor
were conducted by m^s^^e^dB°DTS Surves^ere extrapolated
sample daily for a 12 ^ay period^ 1 BQD> This was s_
to obtain values for .ult"*^i^bji;i cause interference after
sary because ^ify^<3°x^^ Although not used in this
12 days unless inhibited. (Note. AX y sodium salt of
study, this can be ^oided by th J ^J ° from Hach chemical
BOD versus time Plo1r|^k"rate
a method by Thomas . ^
47
-------
3OO
200
Q
g
100
20
Figure 17. Endogenous decay curves.
48
-------
determined to be 0.13 day 1
Origin
k, day
Ultimate Carbonaceous BOD, mg/1
Mentor
Decant
Decant
Decant
Decant
Jackson Pike
Decant
Centrate
Southerly
Decant
0.12
0.14
0.11
0.14
0.1-7
0.17
0.11
2,600
2,874
1,800
1,800
4,000
5,000
7,000
Sludge Production
Biologlcal treatment of organic
quantify ^at relationship. The coeic unlt
SSbi°oL^caf SPoUdsCfXidLed? Torln activated Sludge process
the coefficient is calculated:
V
TVSS avg.
BOD
= aeration tank mixed liquor
volatile suspended solids
= volume under aeration
ff = average total volatile
.suspended solids in the
effluent
= influent BOD5
= effluent BOD5
= total daily flow
49
-------
and
in the literature <*'«>
recycle liquor at Mento? (SSSulatod SS S?X°al treatme*t of
summarized in Table 17. The valSS % y Cation above) are
slightly lower than those for municin?? recycle liquors are only
treatment of recycle liauoJ fn?? f sewage. Biological
to or less than Kulgi proSuSd bfS^' 8JUd?e in am°^ts equal
typical domestic sewage The Sin £ biological treatment of
treatment of recycle iJguor LauirS 5f°S"??d ^ the biolog
la-ke other was te^activated sludges ^ ^^°n and di^osa
handling must be included as an ?^ • iS addlti°nal sludge
treatment systems. an lndlr^ct cost inherent in heat
TABLE 17.
Description
Kg Volatile Solids
Produced Per
Kg BOD5 Removed
Glucose ligiior, (22)
Sewage, (22)
0.49
0.6
0.42
0.73
50
-------
SECTION VII
RECYCLE LIQUOR TREATMENT ECONOMICS
GENERAL
to capital and °P,on and maxntenanc^cos ^ ^ ^
cos .
on , .continuous
o
4 000 mg/1 and 500 mg/1, respectively
concentrations of
and
i a e
economics.
1978, and amortizations are for
'
30 ye av
leave vacations, .nsurance, etc J are
51
-------
...TABLE 18.
LIME TREATM^NT_SYSTEM DESIGN DATA
Recycle liquor processed
Lime storage
""SS: t2imjafeeders'
Daily_lime required as 73% CaO
Reaction clarifier (400 gpd/sq ft)
Sludge pumps, 2 ea '
pH metering and control
Lime sludge produced, dry solids
981 cu -in/day (0.26 MGD)
91 kg (100 ton)
2,356 kg/day (5,184 Ib/day)
60 sq m (648 sq ft) ' .
20 cu m/min (150 gpm)
4,200 kg/day (9,240 Ib/day)
Lime feeders and storage
Reaction clarifier
Control and pump building
Sitework, earthwork, and yard
Electrical and metering
t Subtotal Construction Cost
Engineering
Legal and Administration
Contingency
Total Project Cost
Amortized Project Cost, pwf = 12.
409
$ 45,000
96,000
190,000
40,000
43,000
$414,000
44,000
22,900
24,100
$505,000
$ 40,700
grade hydrated lime at 73% clo
and power consumed at 45 kw *60 S
Labor
Maintenance
Chemicals
Power
Total O&M
at $60.50/tonne ($55/ton)
Annual O&M Cost
$ 27,900
4,100
- 52,000
12,000
$ 96,000
52
-------
The disposal of liage
treatment was assumed fc°
a
Sasis over a five year period.
sludge hauling vehicle was
on a straight-l.ne
ng our.
PL hour, including overhead
(28)
The assumed hauling distance was. |-8 ^ (3-^milesK
trip. Hauling time assumed J0 ^^° ^ ^a trip. The truck
17 min driving, or a total of 42 min pe per load. The
volume was assumed to be 5,68 cu m (L£ | ^ depreciatlon,
cost of truck °Perati°ns' f operating hour. The truck driver
Tabofratfwas Ss^tS^^
Truck operation time washed on
week basis, approximately 12 »°ntha per y average volume hauled
the assumed 260 ha^n?Qf ^SJ? "TWO trucks were assumed to
S re^uired^wfth i^JJS'SSi of 26 loads per day.
Although it may be possible , to
no cost, e.g., on a vf^f ^^ftould be purchased at a cost of
nomic analysis assum^,^ri) g?udge application rates were
$1,875 per hectare j$750/a^e;;r £a per yr (10 tons/acre/yr .
assumed to be 22.4 dry tonne P^^J^J^ a 3() year period.
Land costs were am°riz * ^"sSming a return of $123 per
2 P - "-er farming expenses or as
the rental value of the land.
application or j-uue . ^ r mav,i*. 19
and have been summarized in lacie
Lime Sludge Application Costs:
Land: 4.2 dry tonne/day x 365 days/yr =
(1,533 tonne/yr)/(22.4 tonne/ha/yr)= 68.
68 hectare x $1,875/hectare/
12.409 pwf
Truck depreciation:
= $12,239/hr
= $70,000 capital
= $14,000/yr
53
-------
Truck driver: (130 cu m/day)/(8.l cu m/
truck/hr)
$8 50/hr x 2 shifts/da x
8 hr/shift
$136/day x 260
days/yr
Truck operation: 2 trucks x 8
hr/day x $8.50/
hr x 260 day/yr
Laboratory:
Land credit: 68.4 hectare x $123/
hectare
=16 hr/day
= $136/day
0 $35,400/yr
= $35,400/yr
= $l,500/hr
lump sum
= $8,400
""""™"""™~™™'*~™—^——i^__^______ '
Item
Amortized cost of land
Truck depreciation
Truck driver
Truck operation
Laboratory
Land credit
Total Annual Land Application Cost
Total Annual Cost
$12,200
14,000
35,400
35,400
1,500
(8,400)
$90,100*
*Ho credit taken for lime in sludge applled_
Chemical Treatment <-nst Summar
Project Cost (excluding land
disposal costs), from page 52
Amortized Project Cost,
Lime Treatment O&M, from pgs
Land Application, from Table if
Total Annual Cost for Chemical
Treatment System
52
$505,000
Annual Costs
$ 40,700
96,000
90,100
$226,800
54
-------
BIOLOGICAL TREATMENT COSTS
Biological Treatment System
Recycle liquor biological treatment system design data used
to estimate capital costs are listed in Table 20.
TREATMENT SYSTEM
Recycle liquor processed
Aeration tank (100 Ib BOD/1,000 cu ft-day)
Final settling (600 gpd/sq ft)
BlSwers, 3 @ 1,500 acf/lb BOD§ ea
Sludge pumps (return, waste, standby),ea
Biological sludge produced, dry solids
981 cu m/day (0.26
MGD)
2,450)Ou . (647,000
40 sq m (432 sq ft)
67,140 watt (90 HP)
1.36 cu m/min (360
gpm)
2,830 kg/day (6,220
Ib/day)
Capital costs for the biological treatment.system
on a Sly 1, ??78 bid date, and were as follows:
Aeration tank
Final settling tank
Control and pump building _ .
Sitework, earthwork, and yard piping
Electrical and metering_
Subtotal Construction Cost
Engineering
Legal and Administration
Contingency
Total Project Cost
Amortized Project Cost, pwf = 12.409
were based
$293,000
54,000
146,000
60,000
64,000
$617,000
61,000
34,000
36,000
$748,000
$ 60,300
application, were as follows
Labor
Maintenance
Power, 328 kw (440 HP)
Laboratory
Total Annual Cost
, for the activated sludge
digester operation and land
Annual Costs
$ 27,900
6,200
88,000
1,500
$123,600
55
-------
Description
Aerobic digester, 2,832 cu m (0 75
SSol^iSLi™^ *££
Engineering3" C°nStruCtion Coat
Legal and administration
Contingency
Total Project Cost
Amortized Project Cost, pwf
= 12. 409
Capital Cost
$384,000
154,000
65,000
70,000
$673,000
65,300
36,900
38,800
$814,000
$ 65,600
C°Sts *°r
Description
Labor
Maintenance
Power
Laboratory
Total Annual Cost
aerobic digestion
Annual Cost
$ 9,300
8,500
26,000
1,500
__
$ 45,300
^^^^^
utilinappl was assumed to
described for lime sludge Lnd anS?f sjmilar to that previously
tions have been used as Previously" e'xSlJ?'1^ 5he Same COSt ass™
application. Previously explained for chemical sludge
to b.1ro^f;«-ta were assumed
the digester. Sludge cSncentr?tinn T « S°lldS reducti°n .through
for lime sludge. concentration was assumed at 1% versus 4.5%
of $l23/ha ($50/
?8-03/to*ne (§7.30/
wa?oafbitrarily
ton) dry sludge
assumed to be 50% of the value
fertilizer mar.et
56
-------
.eduction was made to reflect resistance to accepting the sludge
as fertilizer.
Stabilized biological sludge land application costs are
summarized in Table 21.
Description
Amortized cost of land
Truck depreciation, 3 trucks
Truck drivers, 5/da
Truck .operation, 268 day/yr
Laboratory
Land credit
Fertilizer credit
Total Annual Cost
follows:
Annual_Co_s_t
$ 8,400
21,000
91,100
91,100
1,500
(5,700)
(8,300)
?199,100
Total Project Cost (excluding land
disposal costs)
Amortized Project Cost
Activated Sludge Process O&M
Aerobic Digester O&M
Land To?ai"nnual Cost for Biological
Treatment System
*lncludes sludge stabilization
COMPARISON OF TREATMENT COSTS
$1,562,000
Annual Costs
$ 125,900
123,600
45,300
_. 199,100
$ 493,900
system are summarized in Table 22.
57
-------
Facilities
Amortized project
costs
Operating labor
Maintenance labor
& materials
Chemicals
Power
Laboratory
Subtotal
Facilities
Land Application
Amortized cost of
land
Truck depreciation
Truck drivers
Truck operation
Laboratory
Land credit
Fertilizer credit
Subtotal Land
Application
Total Annual
Cost
Chemical Treatmen-h
AnnualAnnual Cost
Cost per Tonne*
$ 40,700
27,900
4,100
52,000
12,000
N/A
$ 2.23
1.53
0.22
2.85
0.66
$136,700 $ 7.49
$ 12,200
14,000
35,400
35,400
1,500-
(8,400)
N/A
$ 0.67
0.77
1.94
1.94
0.08
( 0.46)
N/A
Biological Treatment
AnnualAnnual Cost"
Cost per Tonne*
$ 90,100 $ 4.94
$226,800
$12.43
($13.67/ton)
$125,900
37,200
14,700
N/A
114,000
3,000
$ 6.90
2.04
0.81
N/A
6.25
0.16
$294,800 $16.16
$ 8,400
21,000
91,100
91,100
1,500
(5,700)
(8,300)
$ 0.46
1.15
4.99
4.99
0.08
( 0.31)
0.45)
$199,100 $10.91
$493,900
$27.07
($29.78/ton)
*ciry solids sludge feed to thermal conditioning systems
chemical treatment. Since the ?emS?ali%m°r\C°St effective than
pended solids were essential!? Se JSmJ for ?^horus ™* sus-
treatment costs were comnaT-li x-T * either process,
(recycle liquor SnuaJ^d = 1 !?? ?n annual f««>vals of BOD5
BOD, reduction for cSmicat treatment^ f??5ion Assrin? 3sl
biological treatment, the costs S? r^i ? • 5 reducti°n for
were: cosrs tor recycle liquor treatment
58
-------
Chemical treatment - $451.79/tonne BOD5 removed
Biological treatment - $370.09/tonne BOD5 removed
Other biological treatment processes should be considered
for recycle liquor treatment in order to make a more thorough
analysis. In addition, many different sludge handling and dis-
posal methods could be considered depending upon the initial
treatment process and local conditions.
These alternate treatment process trains were not addressed
in this report.
59
-------
REFERENCES
1. Harrison, J.R., "Review of Conditioning Thickening and
Dewatering of Sludge," USEPA Technology Transfer Design
Seminar Handout, February 1977.
2. Ewing, Jr., L.E., Almgren, H.H. and Gulp, R.L., "Effects
of Thermal Treatment of Sludge on Municipal Wastewater
Treatment Costs, USEPA, Cincinnati, Ohio (draft copy).
3. Swets, et al, "Thermal Sludge Conditioning in Kalamazoo,
Michigan," WPCF, 46-3, 1973, p 575.
4. Sherwood, R. and Phillips, Jr., "Heat Treatment Process
Improves Economics of Sludge Handling and Disposal,"
Water and Wastes Engineering, November 1970, p 42.
5. Boyle, J.D. and Gruenwald, D.D., "Colorado Springs Acti-
vated Sludge Plant Provides Treatment for Heat Treatment
Recycle Liquor," 47th WPCF Conference, October 1974.
6. Haug, R.T., et al, "Anaerobic Filter Treats Waste Acti-
vated Sludge," Water and Sewage Works, February 1977, p 40.
7. National Lime Association, "Lime Handling Application and
Storage in Treatment Processes - Bulletin 213," National
Lime Association, Washington, D.C., pp 1-3.
8. Rudolfs, W., ed. Industrial Wastes-Their Disposal and
Treatment, Reinhold, 1953, p 161.
9. Buzzell, J.C. and Sawyer, C.N., "Removal of Algal Nutrients
from Raw Wastewater with Lime," WPCF, 39, 1967, p R16.
10. Horstkotte, et al, "Full Scale Testing of a Water Reclama-
tion System," WPCF, 46-1, 1974, p 181.
11. U.S. Environmental Protection Agency, "Development Document
for Proposed Effl. Lim. Gds. and NSPS for the Unbleached
Kraft and Semichemical Pulp Point Source Category," EPA
440/1-74/025, USEPA, Washington, D.C., 1974, pp 110-120.
12. Ibid., pp 124-5.
60
-------
13. Bennett, G.E., "Development of a Pilot Plant to Demonstrate
Removal of Carbonaceous Nitrogenous and Phosphorus Materials
from Anaerobic Digester Supernatant and Related Process
Streams," U.S. Department of the Interior, Federal Water
Quality Administration, WPC Research Series, ORD-17010FKA05/70,
Washington, D.C., May 1970.
14. Stumm, W. and Morgan, J.J., Aquatic Chemistry, Wiley, 1970,
pp 520-3.
15. Teletzke, G.H., et al, "Components of Sludge and Its Wet
Air Oxidation Products," WPCF, 39, 1967, p 994.
16. Morrison, R.T. and Boyd, R.N., Organic Chemistry, Allyn
and Bacon, 2nd ed., 1966, p 924.
17. Ibid., p 1114.
18. Everett, J.G., "Biodegradability of Sewage Sludge Heat -
Treatment Liquor," Effluent and Water Treatment Journal
(G.B.) 12, 347, 1972.
19. West, C.M., et al, "Heavy Metal Removal from Wastewater
Treatment Plants by Chemical Treatment," 28th Purdue
Univ. Industrial Wastes Conf., 1973, p 117.
20. Cooper, O.K., "Anaerobic Digestion of Zimpro Heat Treatment
Liquors," unpublished work, Jackson Pike WWTP, Columbus,
Ohio, July 1976.
21. Salotto, B.V., et al, "Current Research to Heat Conditioning
of Wastewater Sludge," 4th US/Japan Conf. on Sewage Treat-
ment Tech., Cincinnati, Ohio, October 1975.
22. Erickson, A.H. and Knopp, P.V., "Biological Treatment of
Thermally Conditioned Sludge Liquors," Advances in Water
Pollution Research, Pergamon Press, Oxford arid New York,
1972, p II-33/1. ;
23. Corrie, K.D., "Use of Activated Carbon in the Treatment of
Heat - Treatment Plant.Liquor," WPCF (G.B.), 1972, p 629.
24. Helmers, E.N., et al, "Nutritional Requirements in the
Biological Stabilization of Industrial Wastes," Sewage
and Industrial Wastes, 23-7, 1951, p 884.
I
25. Metcalf and Eddy, Wastewater Engineering Collection Treat-
ment and Disposal, McGraw-Hill, 1972, pp 243-5.
61
-------
26. Andersen, D.R., et al, "Soybean Processing-Oil Refining
Wastewater: Characteristics and Treatment," 28th Purdue
Univ. Industrial Wastes Conf., 1973, p 38.
27. Young, J.C., "Chemical Methods for Nitrification Control,"
WPCF, 45-4, 1973, p 637.
28. Noland, R.F. and Edwards, J.D., "Lime Stabilization of
Wastewater treatment Plant Sludges," USEPA Technology
Transfer Sludge Treatment and Disposal, Part I, March,
1978.
29. Brown, R.E., et al, "Ohio Guide for Land Application of
Sewage Sludge," Ohio Agricultural Research and Development
Center, Wooster, Ohio, 1976.
62
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-80-020
2.
3. RECIPIENT'S ACCESSlON>NO.
4. TITLE AND SUBTITLE
CHEMICAL AND BIOLOGICAL TREATMENT OF THERMALLY
CONDITIONED SLUDGE RECYCLE LIQUORS
5. REPORT DATE
June 1980 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Mark B. Heyda, James D. Edwards, and Richard F. Noland
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Burgess § Niple, Limited
Consulting Engineers and Planners
Columbus, Ohio 43220
10. PROGRAM ELEMENT NO.
1BC821
11. CONTRACT/GRANT NO.
11010 DKI, SOS #1, Task A/17
12. SPONSORING AGENCY NAME AND ADDRESS
13, TYPE OF REPORT AND PERIOD COVERED
Municipal Environmental Research Laboratory--Cin.,OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
Final 1/69-5/78
14. SPONSORING AGENCY CODE
EPA/6DO/14
15. SUPPLEMENTARY NOTES
Project Office: B. Vincent Salotto (513) 684-7667
16. ABSTRACT
The objective of this research--project was to demonstrate and evaluate the
feasibility of treating undiluted heat treatment liquor prior to its rerouting back
to the head of the sewage, treatment plant. Chemical and biological treatment pro-
cesses were studied. Chemical treatment was effected by the addition of hydrated
lime followed by clarification both in bench-scale facilities and at full-scale in
a 3200 gallon reactor. Biological treatment was achieved in a 2800 gpd high rate
activated sludge pilot plant. Heat treatment liquor was generated by a Zurn heat
treatment system, 16 gpm, at the Mentor, Ohio, wastewater treatment plant.
Results of the study indicate phosphorus and heavy metals were almost completel
removed from the heat treatment liquor by the chemical lime addition, but 6005 and
COD were only marginally removed. Biological system removed BOD5 and COD much more
efficiently. A comparison of total annual costs on a pollutant removal basis showed
that biological treatment was more cost effective than chemical treatment.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. cos AT l Field/Group
Heat treatment liquor
Sludge heat treatment
Sludge thermal conditioning
Sludge treatment
Sludge disposal
Chemical conditioning
Chemical treatment
Biological treatment
Heat treatment liquor
recycle
13B
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
75
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
63
ft U.S. GOVERNMENT PRINTING OFFICE: 1980-657-146/5697
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