&EPA
United States
Environmental Protection
Agency
Municipal Environmental Research EPA-600/2-78-171
Laboratory September 1978
Cincinnati OH 45268
Research and Development
Full Scale
Demonstration
of Lime
-------
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.
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EPA-600/2-78-171
September 1978
FULL SCALE DEMONSTRATION
OF
LIME STABILIZATION
By
Richard F. Noland
James D. Edwards
Mark Kipp
Burgess & Niple, Limited
Consulting Engineers & Planners
Columbus, Ohio 43220
Contract No. 68-03-2181
Project Officer
Steven W. Hathaway
Wastewater Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
s
Promotion Agency,
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 Environ-
mental 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 the mention
of trade names or commercial products constitute endorsement or
recommendation for use.
'U.sr-Environmchtai' Protection
-------
FOREWORD
The Environmental Protection Agency was created because of
increasing public and government concern about the dangers of
pollution to the health and welfare of the American people.
Noxious air, foul water, and spoiled land are tragic testimony
to the deterioration of our national environment. The complexity
of that environment and the interplay between its components
require a concentrated and integrated attack on the problem.
Research and development is that necessary first step in
problem 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.
Development of safe and economical methods for disposing of
the sludges produced from wastewater treatment operations is one
of the most pressing environmental needs. This publication pro-
vides information on the stabilization of municipal sludge which
will be a valuable tool for Engineers and Treatment Plant Mana-
gers who are responsible for the management and disposal of
sewage sludge.
Francis T. Mayo, Director
Municipal Environmental
Research Laboratory
111
-------
ABSTRACT
The objective of the full scale research project was to
demonstrate and evaluate the feasibility, economics, and bene-
fits of stabilizing primary, waste activated, septic, and an-
aerobically digested sludges by lime addition. The project
confirmed the findings of previous laboratory and pilot scale
tests and focused on the application of lime stabilization and
land disposal techniques to a wastewater treatment plant oper-
ating in the range of 3,785 to 5,675 cu m/day (1.0 to 1.5 MGD).
Emphasis was placed on the chemical, bacterial, and patho-
logical properties of raw, lime stabilized and anaerobically
digested sludges. The effects of long-term storage on the
chemical and bacterial characteristics of lime stabilized sludges
were also determined.
Ultimate disposal of all lime stabilized sludges was ac-
complished by spreading as a liquid on agricultural land and on
controlled test plots. Full scale land application was prac-
ticed over an eight month period, beginning in early March and
extending through October 1976. Lime stabilized sludge was
applied to wheat, hay, and soybeans. Test plots included corn,
soybeans, and swiss chard.
Lime stabilized sludges had negligible odor, minimum po-
tential for pathogen regrowth and were suitable for application
to farmland. Pathogen concentrations in lime stabilized sludges
were 10-1,000 times lower than for comparable anaerobically di-
gested sludges.
Actual construction costs were summarized for incorporating
the lime stabilization facilities into the existing treatment
plant. Estimates of capital and annual operation and mainte-
nance costs for comparable anaerobic digestion and lime stabili-
zation facilities were also developed, including costs for land
application of the stabilized sludges.
IV
-------
CONTENTS
Foreword iii
Abstract iv
Figures vi
Tables viii
Abbreviations and Symbols xi
Acknowledgement xiii
1. Conclusions 1
2. Background 2
3. Lime Stabilization Facilities 4
General 4
Revisions to the Existing Wastewater
Treatment Plant 6
Operation and Sampling 10
4. Raw Sludge Characteristics 11
General 11
Chemical Properties 13
Parasite Analyses 14
Pathogenic Properties 15
5. Results and Analysis 17
General 17
Lime Requirements 17
pH Versus Time 20
Odors 22
Chemical Properties 27
Pathogen Reduction 29
Parasites 31
6. Land Application 32
General 32
Land Application Results 35
7. Sludge Dewatering Characteristics 48
General 48
Results of Lebanon Studies 48
8. Economic Analysis 50
Lebanon Facilities 50
Capital Cost of New Facilities 51
9. Lime Stabilization Design Considerations 59
Overall Design Concepts 59
Lime Requirements 63
Types of Lime Available 63
Lime Storage and Feeding 65
Mixing 65
Raw and Treated Sludge Piping, Pumps,
and Grinder 67
References 68
v
-------
FIGURES
Number
1
2
3
4
5
6
8
9
10
11
12
13
14
15
Treatment plant flow schematic prior
to incorporating lime stabilization
Treatment plant flow schematic after
incorporating lime stabilization
Lime stabilization process flow diagram
Combined lime dosage vs pH for all
sludges
Lime dosage vs pH primary sludge
Lime dosage vs pH anaerobic digested
sludge
Lime dosage vs pH waste activated
sludge
Ld,me dosage vs pH septage sludge
Lime stabilized primary sludge pH
vs time
Site plan Glosser Road land disposal
area
Site plan Utica Road land disposal
area
Bacteria concentration vs time laboratory
regrowth studies
Layout of land disposal area Glosser
Road
Layout of Utica Road test plots
Layout of land disposal area Utica Road
(continued)
Page
5
7
8
18
Appendix
Appendix
Appendix
Appendix
23
24
25
26
36
40
45
VI
-------
Number Page
16 Dewatering characteristics of various
sludges on sand drying beds 49
17 Conceptual design for lime stabilization
facilities for a 3,785 cu m/day treatment
plant 60
18 Conceptual design for lime stabilization
facilities for a 18,925 cu m/day
treatment plant 61
19 Conceptual design for lime stabilization
facilities for a 37,850 cu m/day
treatment plant 62
VII
-------
TABLES
Number Page
1 Design Data for Lime Stabilization Facilities 6
2 Anaerobic Digester Rehabilitation Design Data 9
3 Chemical Composition of Sewage Sludges 12
4 Bacteria Data for Sludges 12
5 Chemical Composition of Raw Sludges at
Lebanon, Ohio 13
6 Heavy Metal Concentrations in Raw Sludges
at Lebanon, Ohio 14
7 Pathogen Data for Raw Sludges at Lebanon,
Ohio 15
8 Identified Parasites in Lebanon, Ohio Raw
Sludges 15
9 Lime Required for Stabilization to pH 12
for 30 Minutes 19
10 Comparison of Lime Dosages Required to
Treat Raw Primary Sludge 20
11 Comparison of Lime Dosages Predicted by the
Counts Equation to Actual Data at Lebanon,
Ohio 20
12 Chemical Composition of Lime Stabilized
Sludges at Lebanon, Ohio 27
13 Volatile Solids Concentration of Raw and
Lime Stabilized Sludges 28
14 Nitrogen and Phosphorus Concentrations in
Anaerobically Digested and Lime Stabilized
Sludge 28
(continued)
Vlll
-------
Number Page
15 Pathogen Data for Lime Stabilized Sludges
at Lebanon, Ohio 30
16 Comparison of Bacteria in Anaerobic Digested
Versus Lime Stabilized Sludges 30
17 Identified Parasites in Lebanon, Ohio Lime
Stabilized Sludges 31
18 Range of N, P and K Contents of Sewage
Sludge 32
19 Annual N, P and K Utilization by Selected
Crops 33
20 Influence of Previous Crop on N Fertilization
Rates for Corn 34
21 Application Rates for Nutrients in Sludge
Glosser Road Site 37
22 Glosser Road Wheat Field Yield Analysis 38
23 Utica Road Test Plot Sludge Application Data 39
24 N and P Application Rates to Utica Road Test
Plots 41
25 Corn Yield Analysis for Utica Road Test Plots 42
26 Soybean Yield Analysis for Utica Road Test
Plots 43
27 Application Rates for Nutrients in Sludge
for Full Scale Field Studies Utica Road
Site 46
28 Pods and Heights of Soybeans from Various Plots
Utica Road Full Scale Field Studies 44
29 Heavy Metals in Soybeans Utica Road Full Scale
Field Studies 47
30 Actual Cost of Digester Rehabilitation and
Lime Stabilization Facilities Construction 50
(continued)
ix
-------
Number
31 Total Annual Cost for Lime Stabilization
Excluding Land Disposal for a 3,785 cu m/day
Plant 53
32 Total Annual Cost for Single Stage Anaerobic
Sludge Digestion Excluding Land Disposal for
a 3,785 cu m/day Plant 55
33 Land Application Cost for Lime Stabilized and
Anaerobically Digested Sludges for a 3,785
cu m/day Plant 57
34 Comparison of Total Annual Capital and
Annual O&M Cost for Lime Stabilization
and Anaerobic Digestion Including Land
Disposal for a 3,785 Cu M/Day Plant 58
35 Mixer Specifications for Sludge Slurries 66
-------
LIST OF ABBREVIATIONS AND SYMBOLS
ABBREVIATIONS
average
five day biochemical oxygen demand
British thermal unit
cation exchange capacity
centimeter
chemical oxygen demand
cubic centimeter
cubic foot (feet)
cubic feet per minute
cubic yard
cubic meter
degree(s)
degree Celsius
degree Fahrenheit
diameter
feet (foot)
feet per second
gallon(s)
gallons per day
gallons per minute
hectare
horsepower
hour(s)
inch(es)
kilograms per hectare
kilogram(s)
liter
membrane filter
milligram(s) per liter
milligram(s) per kilogram
millimeter
million gallons per day
minute(s)
most probable number
number per 100 ml
oven dry weight
percent
pound(s)
pounds per acre
side water depth
square foot (feet)
avg
BOD
BTU
CEC
cm
COD
cc
cu ft
cfm
cu yd
cu m
deg
°C
OF
dia
ft
fps
gal
gpd
gpm
ha
HP
hr
in
kg/ha
kg
1
MF
mg/1
mg/kg
mm
MGD
min
MPN
#/100 ml
ODWT
%
Ib
Ib/ac
SWD
sq ft
XI
-------
square meter
suspended solids
standard cubic foot (feet)
standard cubic feet per minute
temperature
thousand kilograms
thousand kilograms per hectare
total dissolved solids
total dynamic head
total solids
volatile solids
waste activated sludge
weight
year(s)
SYMBOLS
aluminum
Ammonia/ammonium
boron
cadmium
calcium hydroxide (hydrated lime)
calcium oxide (quicklime)
carbon dioxide
chlorine
cobalt
ferric chloride
hydrogen sulfide
iron
lead
magnesium
manganese
mercury
nickel
nitrite
nitrate
oxygen
phosphorus
sulfur
sulfur dioxide
sulfuric acid
zinc
m2
SS
scf
scfm
temp
kkg
kkg/ha
TDS
TDH
TS
VS
WAS
wt
Al
NH /NH
B j
Cd
Ca(OH)
CaO
CO
C12
Co/
Fed-
H2S
Fe
Pb
Mg
Mn
Hg
Ni
NO:
S
S02
H2S04
Zn
XII
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ACKNOWLEDGEMENTS
The lime stabilization project officer was Steven W.
Hathaway, under the direction of Dr. J. B. Farrell of the U. S.
Environmental Protection Agency Municipal Environmental Research
Laboratory, Cincinnati, Ohio. Their direction and assistance
were greatly appreciated during the study.
Tim Oppelt, Jon Bender, the staff of the National Environ-
mental Research Center Pilot Plant, Lebanon, Ohio, and Jack
Whitaker and his staff at the Lebanon Wastewater Division were
of great assistance during the completion of the lime stabiliza-
tion project. Dr. James Ryan and his staff were responsible for
setting up the test plot studies. Ellis C. Thompson of Lebanon
was more than cooperative in donating the use of his property
and equipment for the sludge disposal and growth studies.
Parasite analyses were performed by Tulane University, School of
Medicine, New Orleans, Louisiana.
Mark Kipp of Burgess & Niple, Limited operated the lime
stabilization and land application phases of the research. Kay
Wilson was responsible for typing the final manuscript.
Xlll
-------
-------
SECTION 1
CONCLUSIONS
Lime stabilization was shown to be an effective sludge
disposal alternative when there is a need to:
provide alternate means of sludge treatment during the
period when existing sludge handling facilities (e.g.
anaerobic or aerobic digesters) are out of service for
cleaning or repair.
supplement existing sludge handling facilities (e.g.
anaerobic or aerobic digesters, incineration or heat
treatment) due to the loss of fuel supplies or because
of excess sludge quantities above design.
upgrade existing facilities or construct new facilities
to improve odor, bacterial, and pathogenic organism
control.
Lime stabilization effectively eliminates odors. Regrowth
of pathogens following lime stabilization is minimal. Of the
organisms studied, only fecal streptococci have a potential for
remaining viable.
Lime stabilized sludges are suitable for application to
agricultural land; however, lime stabilized sludges have lower
soluble phosphate, ammonia nitrogen, total Kjeldahl nitrogen,
and total solids concentrations than comparable anaerobically
digested primary/waste activated sludge mixtures.
Lime stabilization facilities can be constructed and oper-
ated at lower capital and annual operation and maintenance costs
than comparable anaerobic digestion facilities, and present an
attractive alternative either as a new process or to upgrade
existing sludge handling facilities.
-------
SECTION 2
BACKGROUND
Sludge constitutes the most significant by-product of
wastewater treatment; its treatment and disposal is perhaps the
most complex problem which faces both the designer and operator.
Raw sludge contains large quantities of microorganisms, mostly
fecal in origin, many of which are pathogenic and potentially
hazardous to humans. Slu'dge processing is further complicated
by its variable properties and relatively low solids concentra-
tion. Solutions have long been sought for better stabilization
and disposal methods which are reliable and economical and able
to render sludge either inert or stable.
Historically, lime has been used to treat nuisance condi-
tions resulting from open pit privies and from the graves of
domestic animals. Prior to 1970, there was only a small amount
of quantitative information available in the literature on the
reaction of lime with sludge to make a more stable material.
Since that time, the literature contains numerous references
concerning the effectiveness of lime in reducing microbiological
hazards in water and wastewater.^)(2)(3) Information is also
available on the bactericidal value of adding lime to sludge. A
report of operations at the Allentown, Pennsylvania wastewater
treatment plant states that conditioning an anaerobically di-
gested sludge with lime to pH 10.2 to 11, vacuum filtering and
storing the cake destroyed all odors and pathogenic enteric
bacteria.(4) Kampelmacher and Jansen(5) reported similar ex-
periences. Evans(6) noted that lime addition to sludge released
ammonia and destroyed bacillus coli and that the sludge cake was
a good source of nitrogen and lime to the land.
Lime stabilization of raw sludges has been conducted in the
laboratory and in full scale plants. Farrell et al^7' reported,
among other results, that lime stabilization of primary sludges
reduced bacterial hazard to a negligible value, improved vacuum
filter performance, and provided a satisfactory means of stabi-
lizing sludge prior to ultimate disposal.
(8)
Paulsrud and Eikum reported on the effects of long-term
storage of lime stabilized sludge. Their research included
laboratory investigations of pH and microbial activity over
periods up to 28 days.
-------
Pilot scale work by C.A. Counts et al(9) on lime stabiliza-
tion showed significant reductions in pathogen populations and
obnoxious odors when the sludge pH was greater than 12. Counts
conducted growth studies on greenhouse and outdoor plots which
indicated that the disposal of lime stabilized sludge on crop-
land would have no detrimental effect.
A research and demonstration contract was awarded to
Burgess & Niple, Limited in March, 1975 to complete the design,
construction, and operation of full scale lime stabilization
facilities for a 3,785 cu m/day (1 MGD) wastewater treatment
plant, including land application of treated sludges. The
contract also included funds for cleaning, rehabilitating, and
operating an existing anaerobic sludge digester. Concurrent
with the research and demonstration project, a considerable
amount of full scale lime stabilization work was completed by
cities in Ohio and Connecticut. Wastewater treatment plant
capacities which were representative ranged from 3,785 to 113,550
cu m/day (1 to 30 MGD). A summary of these results has prev-
iously been reported.(10'
-------
SECTION 3
LIME STABILIZATION FACILITIES
GENERAL
Facilities for lime stabilization of sludge were incorpor-
ated into an existing 3,785 cu m/day (1.0 MGD) single stage
activated sludge wastewater treatment plant located at Lebanon,
Ohio. Lebanon has a population of about 8,000, and is located
in southwestern Ohio, 48.27 km (30 mi) northeast of Cincinnati.
The surrounding area is gently rolling farmland with a small
number of light industries, nurseries, orchards, and truck
farms.
Major unit processes at the wastewater treatment plant
include influent pumping, preaeration, primary clarification,
conventional activated sludge, and anaerobic sludge digestion.
Average influent BOD5 and suspended solids concentrations are
180 and 243 mg/1, respectively. The treatment plant flow sche-
matic is shown on Figure 1.
Prior to completing the sludge liming system, the existing
anaerobic sludge digester was inoperative and was being used as
a sludge holding tank. The digester pH was approximately 5.5 to
6.0. Grit and sand accumulations had reduced its effective
volume to 40-50% of the total. Waste activated sludge was being
returned to the primary clarifiers and resettled with the primary
sludge. Combined primary/waste activated sludge was being
pumped to the digester and ultimately recycled to the primary
clarifiers via the digester supernatant. Typical supernatant
suspended solids concentrations were in the range of 30,000 to
40,000 mg/1. When possible, sludge was withdrawn from the
digester and dewatered on sand drying beds.
USEPA made the decision to utilize lime stabilization at
Lebanon not only as a full scale research and demonstration
project, but also as a means of solids handling during the
period while the anaerobic digester was out of service for
cleaning and repair.
-------
Ul
INFLUENT
PUMP
STATION
CREEK
Rgure L Treatment Plant Flow Schematic Prior to Incorporating Lime Stabilization
-------
REVISIONS TO THE EXISTING WASTEWATER TREATMENT PLANT
Lime Stabilization
The lime stabilization process was designed to treat raw
primary, waste activated, septic tank, and anaerobically di-
gested sludges. The liming system was integrated with the
existing treatment plant facilities, as shown on Figure 2.
Hydrated lime was stored in a bulk storage bin and was augered
into a volumetric feeder. The feeder transferred dry lime at a
constant rate into a 94.6 1 (25 gal) slurry tank which dis-
charged an 8-10% lime slurry by gravity into an existing 25 cu
m (6,500 gal) tank. The lime slurry and sludge were mixed with
diffused air. A flow schematic for the lime stabilization
facilities is shown on Figure 3. Design data are shown in
Table 1.
TABLE 1. DESIGN DATA FOR LIME STABILIZATION FACILITIES
Mixing Tank
Total volume
Working volume
Dimensions
Hoppered bottom
Type of diffuser
Number of diffusers
Air supply
Bulk Lime Storage
Total volume
Diameter
Vibrators
Fill system
Discharge system
Material of construction
Type & manufacturer
Volumetric Feeder
Total volume
Diameter
Material of construction
Type & manufacturer
Feed range
Average feed rate
30 cu m (8,000 gal)
25 cu m (6,500 gal)
3.05 m x 3.66 m x 2.38 m
(101 x 12' x 7.8')
0.91 m (31) @ 27° slope
Coarse bubble
4
14-34 cu m/min (500-1,200 cf/min)
28 cu m (1,000 cu ft)
2.74 m (91)
2 ea Syntron V-41
Pneumatic
15 cm (6") dia. auger
Steel
Columbian Model C-95
0.28 cu m (10 cu ft)
71 cm (28")
Steel
Vibrascrew LBB 28-10
45-227 kg/hr (100-500 Ib/hr)
78 kg/hr (173 Ib/hr)
(continued)
6
-------
PRIMARY
CLARIRER
PRIMARY
CLARIFIES
RETURN SLUDGE
WASTE ACTIVATED SLUDGE
BULK
LIME
STORAGE
BIN
VOLUMETRIC FEEDER
LIME SLURRY TANK
WATER
FOR MIXING
PRIMARY
ANAEROBIC
DIGESTER
WASTE ACTIVATED SLUDGE
DIGESTED SLUDGE
SLUDGE WELL
a PUMP
ATED SLUDGE TO
K TRUCK FOR
LAND DISPOSAL
Figure 2. Treatment Plant Flow Schematic After incorporating Lime Stabiiization
-------
00
-VOLUMETRIC FEEDER
—LIME SLURRY TANK
DIFFUSED AIR
FOR MIXING
TREATED SLUDGE
ANAEROBIC DIGESTED SLUDGE
PRIMARY SLUDGE
WASTE ACTIVATED SLUDGE
TREATED SLUDGE
TANK TRUCK FOR LAND
DISPOSAL
SLUDGE
WELL 8
PUMP
00—00
Figure 3. Lime Stabilization Process Flow Diagram
-------
TABLE 1 (continued)
Lime Slurry Tank
Total volume 94.6 1 (25 gal)
Diameter 0.61 m (21)
Septic Tank Sludge Holding Tank (Septage Tank)
Total volume 18.4 cu m (650 cu ft)
Working volume 15 cu m (4,000 gal)
Dimensions 3.66 m x 1.92 m x 2.62 m
(12fx6.3'x8.6')
Mixing Coarse bubble
Number of diffusers 1
Air supply 2.8-8.4 cu m/min (100-300 cf/min)
Transfer Pumps
Raw and treated sludge 1,136 1/min (300 gpm)
Septage transfer pump 379 1/min (100 gpm)
Anaerobic Digester
As previously described, the existing single stage anaerobic
sludge digester was inoperative and was being used as a sludge
holding tank. The digester and auxiliary equipment were com-
pletely renovated and returned to good operating condition which
allowed a comparison of anaerobic digestion and lime stabiliza-
tion. The digester was cleaned, a new boiler and hot water cir-
culating system was installed, and all necessary repairs were
made to piping, valves, pumps, and electrical equipment.
The anaerobic digester design data are shown in Table 2.
TABLE 2. ANAEROBIC DIGESTER REHABILITATION DESIGN DATA
Tank dimensions 15 m (50') dia. x 6.1 m (20') SWD
Total volume 1,223 cu m (43,200 cu ft)
Actual volatile solids
loading 486 g VSS/cu m (0.03 Ib
VSS/ft3)
Hydraulic detention time 36 days
Sludge recirculation
rate 757 1/min (200 gpm)
Boiler capacity 240,000 BTU/hr
-------
Septage Holding Facilities
Because the Lebanon wastewater treatment plant routinely
accepted septic tank pumpings, an 18.4 cu m (5,000 gal) tank was
installed to hold septic tank sludges prior to lime treatment.
The tank was equipped with a transfer pump which could be used
to either feed the lime stabilization process or transfer
septage to the primary tank influent at a controlled rate.
Ultimate Sludge Disposal
Treated sludges were applied to sand drying beds, to test
plots, and to three productive agricultural sites. Land spread-
ing operations began in early March and continued through
October 1976. The sludge hauling vehicle was a four-wheel drive
truck with a 2.3 cu m (600 gal) tank.
OPERATION AND SAMPLING
Raw sludge, e.g., primary, waste activated, septage or
digested sludge, was pumped to the mixing tank where it was
mixed by diffused air. Four coarse bubble diffusers were mounted
approximately 30.5 cm (1 ft) above the top of the tank hopper
and 38 cm (1.25 ft) from the tank wall. This location permitted
mixing to roll sludge up and across the tank at which point lime
slurry was fed. Lime which was used for the stabilization of
all sludges was industrial grade hydrated lime with CaO and MgO
contents of 46.9% and 34%, respectively. All lime requirements
have been converted and are expressed as 100% Ca(OH)2 except as
noted. Samples were taken from the untreated, but thoroughly
mixed, sludge for chemical, pH, bacteria, and parasite analyses.
After the initial pH determination, the lime slurry addition
was started. Hydrated lime was augered from the lime storage
bin to the volumetric feeder which was located directly above
the sludge mixing tank. The lime was slurried by the tangential
injection of water into a 94.6 1 (25 gal) slurry tank. The lime
solution (8-10% by weight) then flowed by gravity into an open
channel with three feed points into the sludge mixing tank.
The sludge pH was checked every 15 min as the lime slurry
was added until the sludge reached a pH of 12, at which time it
was held for 30 min. During the 30 min period, lime slurry
continued to be added. After 30 min, samples were taken for
chemical, bacteria, and parasite analyses. Air mixing was then
discontinued, allowing the limed sludge to concentrate. The
sludge then flowed by gravity to a sludge well from which it was
pumped to the land disposal truck.
10
-------
SECTION 4
RAW SLUDGE CHARACTERISTICS
GENERAL
Samples of raw and treated sludges were taken during each
operating day of the lime stabilization operations. Anaerobically
digested sludge samples were taken at the same time and analyzed
for use in comparisons of chemical, bacterial, and pathogen
properties.
Sample preservation and chemical analysis techniques were
performed in accordance with procedures as stated in "Methods
for Chemical Analysis of Water and Wastes," USEPA, (H) and
"Standard Methods for the Examination of Water and Wastewater."( '
Salmonella species and Pseudomonas aeruginosa were deter-
mined by EPA staff using the method developed by Kenner and
Clark.(13) Fecal coliform, total coliform, and fecal streptoc-
cocus were determined according to methods specified in "Standard
Methods for Examination of Water and Wastewater." Parasite
analyses were performed by the Tulane University School of
Medicine.
Several authors have previously attempted to summarize the
chemical and bacterial compositions of sewage sludges.(14)(15)(16)
Recent data on the nutrient concentrations for various sludges
as prepared by Sommersd5) have been included for reference in
Table 3. Data on lime stabilized sludges have been included in
a following section.
Bacterial data on various sludges as presented by Stern '
have been summarized in Table 4 for reference.
11
-------
TABLE 3. CHEMICAL COMPOSITION OF SEWAGE SLUDGES
a(15)
Component
Total N
4
NO ™N
p
K
Ca
Mg
Fe
Number of
Samples
191
103
45
189
192
193
189
165
Range , *
mg/kg
0.1 -
0.1 -
0.1 -
0.1 -
0.1 -
0.1 -
0.1 -
0.1 -
17.6
6.8
0.5
14.3
2.6
25.0
2.0
15.3
Median
Percent
3.3
0.1
0.1
2.3
0.3
3.9
0.5
1.1
Mean
Percent
3.9
0.7
0.1
2.5
0.4
4.9
0.5
1.3
aData are from numerous types of sludges (anaerobic, aerobic,
activated, lagoon, etc.)
*Dry Solids
TABLE 4. BACTERIA DATA FOR LIQUID SLUDGES
(17)
Sludge Type
Salmonella
t/100 ml
Pseudomonas
aeruginosa
#/100 ml
Fecal
Coliform,
MF
Raw Primary 460 4.6 x 10
Raw Waste Activated-A 74 1.1 x 10"
Raw Waste Activated 3 -
Thickened-B 9.3 x 10 2.0 x 10"
Raw Waste Activated-C 2.3 x 103 2.4 x 10*
Anaerobic Digested
Primary 29 34
Anaerobic Digested
Waste Activated 7.3 1.0 x 10"
Aerobic Digested
Waste Activated N/A 0.66
i
Trickling Filter 93 1.1 x 10'
4
11.4 x 10
2.8 x 10(
2.0 x 10
2.0 x 10(
3.9 x 10'
3.2 x IO-
6
1.15 x 10
12
-------
CHEMICAL PROPERTIES
Analyses for heavy metals were conducted on grab samples of
Lebanon, Ohio, raw primary, waste activated, and anaerobically
digested sludges. These data have been reported in Table 5 as
mg/kg on a dry weight basis and include the average and range of
values.
TABLE 5. HEAVY METAL CONCENTRATIONS IN
RAW SLUDGES AT LEBANON, OHIO
Cadmium, average mg/kg
Cadmium, range mg/kg
Total Chromium, average mg/kg
Total Chromium, range mg/kg
Copper, average mg/kg
Copper, range mg/kg 2
Lead , average mg/kg
Lead, range mg/kg
Mercury, average mg/kg
Mercury, range mg/kg
Nickel, average mg/kg
Nickel, range mg/kg
Zinc, average mg/kg
Zinc, range mg/kg 4
Raw
Primary
Sludge
105
69-141
633
287-979
2,640
,590-2,690
1,379
987-1,770
6
0.4-11
549
371-727
4,690
,370-5,010
Waste
Activated
Sludge
388
119-657
592
133-1,050
1,340
670-2,010
1,624
398-2,850
46
0.1-91
2,109
537-3,680
2,221
,250-3,191
Anaerobic
Digested
Sludge
137
73-200
882
184-1,580
4,690
4,330-5,050
1,597
994-2,200
0.5
0.1-0.9
388
263-540
7,125
6,910-7,340
Chemical data for Lebanon, Ohio, raw primary, waste acti-
vated, anaerobically digested, and septage sludges have been
summarized in Table 6. Data for each parameter include the
average and range of the values observed.
13
-------
TABLE 6. CHEMICAL COMPOSITION OF RAW SLUDGES AT LEBANON, OHIO
Parameter
Alkalinity, mg/1
Alkalinity Range, mg/1
Total COD, mg/1
Total COD Range, mg/1
Soluble COD, mg/1
Soluble COD Range, mg/1
Total Phosphate, mg/1 as P
Total Phosphate Range, mg/1
as P
Soluble Phosphate, mg/1 as
P
Soluble Phosphate Range,
mg/1 as P
Total Kjeldahl Nitrogen, mg/1
Total Kjeldahl Nitrogen Range
mg/1
Ammonia Nitrogen, mg/1
Ammonia Nitrogen Range, mg/1
Total Suspended Solids, mg/1
Total Suspended Solids Range,
mg/1
Volatile Suspended Solids,
mg/1
Volatile Suspended Solids
Range, mg/1
Volatile Acids, mg/1
Volatile Acids Range, mg/1
Raw
Primary
Sludge
1,885
1,264-2,820
54,146
36,930-75,210
3,046
2,410-4,090
350
264-496
69
20-150
1,656
1,250-2,470
223
19-592
48,700
37,520-65,140
36,100
28,780-43,810
1,997
1,368-2,856
Waste
Activated
Sludge
1,265
1,220-1,310
12,810
7,120-19,270
1,043
272-2,430
218
178-259
85
40-119
711
624-860
51
27-85
12,350
9,800-13,860
10,000
7,550-12,040
N/A
N/A
Anaerobically
Digested
Sludge
3,593
1,330-5,000
66,372
39,280-190,980
1,011
215-4,460
580
379-862
15
6.9-34.8
2,731
1,530-4,510
709
368-1,250
61,140
48,200-68,720
33,316
27,000-41,000
137
24-248
Septage
Sludge
1,897
1,200-2,690
24,940
10,770-32,480
1,223
1,090-1,400
172
123-217
25
21.6-27.9
820
610-1,060
92
68-116
21,120
6,850-44,000
12,600
3,050-30,350
652
560-888
PARASITE ANALYSES
Parasite data for Lebanon, Ohio raw primary, waste acti-
vated, anaerobically digested and septage sludges have been
summarized in Table 7. Species which were identified were in
general agreement with other investigations. In addition to
these parasites, mites (adult, larva and eggs) and nematodes
(adult, larva and eggs) were found in all sludges.
14
-------
TABLE 7. IDENTIFIED PARASITES IN LEBANON, OHIO RAW SLUDGES
Primary
Waste
Activated
Sludge
Septage
Anaerobic
Digested
Toxacara
Toxacara
Toxacara
Toxacara canis
Toxacara cati
Trichuris
vulpis
Trichuris
trichiura
Enterobius
vermicularis
larva
Ascaris
lumbricoides
Trichuris
trichiura
Trichuris
vulpis
Ascaris
Trichuris
vulpis
PATHOGENIC PROPERTIES
Pathogen data for Lebanon, Ohio raw primary, waste acti-
vated, anaerobically digested, and septage sludges have been
summarized in Table 8. In general, the data are in agreement
with the values reported by Stern, with the exception of
Salmonella and Pseudomonas aeruginosa, which are lower than the
reported values.
TABLE 8. PATHOGEN DATA FOR RAW SLUDGES AT LEBANON, OHIO
Parameter
Salmonella avg. #/100 ml
Salmonella range, #/100 ml
Ps. aeruginosa avg.,
#/100 ml
Ps. aeruginosa range.
#/100 ml
Fecal coliform avg. Mf ,
#/100 ml
Fecal coliform range MF,
1/100 ml
Fecal coliform avg. MPN,
#/100 ml
Fecal coliform range MPN,
1/100 ml
Raw
Primary
Sludge
62
11-240
195
75-440
N/A
N/A
Q
8.3 x 10
1.3xl08-3.3xl09
Waste
Activated
Sludge
6
3-9
5.5 x 103
91-1.1 x 104
2.65 x 107
2.0xl07-3.3xl07
N/A
N/A
Anaerobically
Digested
Sludge
6
3-30
42
3-240
2.6 x 105
3.4xl04-6.6xl05
1.45 x 106
1.9xl05-4.9xl06
Septage
Sludge
6
3-9
754
14-2.1 x 103
1.5 x 107
1.0xl07-1.8xl07
N/A
N/A
(continued)
15
-------
TABLE 8 (continued)
Parameter
Total coliform avg. MF,
#/100 ml
Total coliform range MF,
1/100 ml
Total coliform avg. MPN,
#/100 ml
Total coliform range MPN,
#/100 ml
Fecal streptococci avg.,
t/100 ml
Fecal streptococci range,
#/100 ml
Raw Waste Anaerobically
Primary Activated Digested Septage
Sludge Sludge Sludge Sludge
N/A 8.33 x 108
N/A 1.66xl08-1.5xl09 :
2.9 x 109 N/A
1.3xl09-3.5xl09 N/A
3.9 x 107 1.03 x 107
2.6xl07-5.2xl07 5xl05-2xl07
2.42 x 107 2.89 x 108
L.3xl05-1.8xl08 1.8xl07-7xl08
2.78 x 107 N/A
N/A
2.7 x 105 6.7 x 105
3.3xl05-1.2xl
16
-------
SECTION 5
RESULTS AND ANALYSIS
GENERAL
During the period March-October 1976, approximately 868,700 1
(229,500 gal) of primary, waste activated, septage, and anaero-
bically digested sludges from the Lebanon, Ohio wastewater
treatment plant were lime stabilized. Ultimate disposal of all
lime stabilized sludges was accomplished by spreading as a
liquid on agricultural land and on controlled test plots. The
results of these studies are summarized as follows.
LIME REQUIREMENTS
The lime dosage required to exceed pH 12 for at least 30
min was found to be affected by the type of sludge, its chemical
composition, and percent solids. As an operational procedure, a
target of pH 12.5 was selected to insure that the final pH would
be greater than 12. A summary of the lime dosage required for
various sludges is shown in Table 9. Of the total amount of
lime which was required, an excess of 0 to 50% was added after
pH 12 was reached in order to maintain the pH. Figure 4 shows
the combined lime dosage vs. pH for primary, anaerobically
digested, waste activated, and septage sludges. Figures 5-8
have been included in the Appendix and describe the actual lime
dosages which were required for each sludge type.
Table 10 compares the Lebanon results with the data prev-
iously presented by Farrell, et. al, Counts, et. al, and Paulsrud
and Eikum for raw primary sludges. In general, excellent
correlation was achieved.
(9)
Counts has proposed the following equation for predicting
the lime dosage required for primary and secondary sludges from
the Richland, Washington trickling filter plant:
Lime Dose =4.2+1.6 (TS)
When: Lime dose is expressed in grams
Ca(OH)2 per liter of sludge and
TS is the total solids fraction
in the sludge.
17
-------
13.0
12.0-
10.0--
I
Q.
9.0-
80
7.0- -
6.0
/
I
/
---- AVERAGE
RANGE OBSERVED
-I
h
1,000 2POO 3,000 4,000 5,000
DOSAGE Co (OH)2 MG/L
Rgure 4. Combined Lime Dosage vs. pH For All Sludges
18
-------
Sludge Type
Primary sludge
Waste activated
sludge
Septage
Anaerobic
Percent
Solids
3-6
1-1.5
1-4.5
6-7
2
Average Lbs
Ca (OH) 2/Lbs
Dry Solids
0.12
0.30
0.20
0.19
2
Range Lbs
Ca (OH) 2/Lbs
Dry Solids
0.06-0.17
0.21-0.43
0.09-0.51
0.14-0.25
Total3
Volume
Treated
(gal)
136,500
42,000
27,500
23,500
Average
Total
Solids,
mg/1
43,276
13,143
27,494
55,345
Average
Initial
PH
6.7
7.1
7.3
7.2
Average
Final
PH
12.7
12.6
12.7
12.4
Includes some portion of waste activated sludge
Numerically equivalent to Kg Ca(OH) per kg dry solids
Multiply gallons x 3.785 to calculate liters
-------
TABLE 10. COMPARISON OF LIME DOSAGES
REQUIRED TO TREAT RAW PRIMARY SLUDGE
Investigator
Lime Dose,*
kg lime/kg sludge dry solids
Present Investigators
Farrell, et al
Counts, et al
Paulsrud, et al
0.120
0.098
0.086
0.125
(b)
(c)
(a)
(b)
(a) Based on 4.78% solids
(b) Based on pH 12.5 for sludges reported
(c) Based on pH 11.5 for sludges reported
*As 100% Ca(OH)0
Table 11 compares the values predicted by the Counts equa-
tion to the Lebanon data for raw primary, waste activated,
anaerobically digested, and septage sludges:
TABLE 11. COMPARISON OF LIME DOSAGES PREDICTED
BY THE COUNTS EQUATION TO ACTUAL DATA AT LEBANON, OHIO
Sludge Type
Percent Actual Lime Dose,
Solids kg lime/kg D.S.
Counts'
Lime Dose,
kg lime/kg D.S,
Raw primary
Waste activated
4.78
1.37
0.120
0.300
0.086
0.305
Anaerobically
digested
Septage
6.40
2.35
0.190
0.200
0.065
0.180
With increasing solids concentrations, the Counts equation
results in lower than actual lime dosages.
pH VERSUS TIME
Previous research has attempted to determine the magnitude
of pH decay versus time and to quantify the variables which
affect pH decay. Paulsrud(8) reported that negligible pH decay
occurred when the sludge mixture was raised to pH 12 or greater
or when the lime dose was approximately five times the dose to
20
-------
reach pH 11. In either case, for raw primary sludge, Paulsrud's
dose was in the range of 0.100 to 0.150 kg lime/kg dry solids,
which was approximately the dosage used at Lebanon.
(9)
Counts hypothesized that pH decay was caused by the
sludge chemical demand which was exerted on the hydroxide ions
supplied in the lime slurry. He further concluded that the
degree of decay probably decreased as the treated sludge pH
increased because of the extremely large quantities of lime
required to elevate the pH to 12 or above. However, this pH
phenomenon is probably_because pH is an exponential function,
e.g., the amount of OH at pH 12 is ten times more than the
amount of OH~ at pH 11.
In the full scale work at Lebanon, all sludges were lime
stabilized to pH 12 or above and held for at least 30 min with
the addition of excess lime. All treated sludges had less than
a 2.0 pH unit drop after six hours. Limed primary sludge was
the most stable with septage being the least stable. During the
full scale program, only the pH of limed primary sludge was
measured for a period greater than 24 hours, which showed a
gradual drop to approximately 11.6 after 18 hours beyond which
no further decrease was observed.
The total mixing times from start through the 30 min
contact time at Lebanon were as follows:
Primary sludge 2.4 hours
Waste activated sludge 1.7 hours
Septic tank sludge 1.5 hours
Anaerobic digested
sludge 4.1 hours
Mixing time was a function of lime slurry feed rate and was
not limited by the agitating capacity of the diffused air system.
Mixing time may have been reduced by increasing the capacity of
the lime slurry tank.
To further examine the effects of excess lime addition
above the levels necessary to reach pH 12, a series of labora-
tory tests were set up using a standard jar test apparatus. The
tests were made on six one-liter portions of primary sludge with
2.7% total solids. The pH of each of the samples was increased
to 12 by the addition of 10% hydrated lime slurry. One sample
was used as a control. The remaining samples had 30%, 60%, 90%,
120%, and 150% by weight of the lime dose added to the control.
The samples were mixed continuously for six hours and then again
ten minutes prior to each additional pH measurement. There was
a negligible drop in pH over a ten day period for those tests
where excess lime was added.
21
-------
A second laboratory scale test was completed using_a 19 1
(5 gal) raw primary sludge sample which was lime stabilized to
pH 12.5 and allowed to stand at 18° C. Samples were withdrawn
weekly and analyzed for pH and bacteria concentration. The
results of the pH and bacteria studies are shown on Figures 9 and
12, respectively. After 36 days, the pH had dropped to 12.0.
In conclusion, significant pH decay should not occur once
sufficient lime has been added to raise the sludge pH to 12.5
and maintain that value for at least 30 min.
ODORS
Previous work(9^ stated that the threshold odor number of
raw primary and trickling filter sludges was approximately
8,000, while that of lime stabilized sludges usually ranged from
800 to 1,300. By retarding bacterial regrowth, the deodorizing
effect can be prolonged. Further, it was concluded that by
incorporating the stabilized sludge into the soil, odor poten-
tial should not be significant.
During the full scale operations at Lebanon, there was an
intense odor when raw sludge was first pumped to the lime sta-
bilization mixing tank which increased when diffused air was
applied for mixing. As the sludge pH increased, the sludge odor
was masked by the odor of ammonia which was being air _ stripped
from the sludge. The ammonia odor was most intense with an-
aerobically digested sludge and was strong enough to cause nasal
irritation. As mixing proceeded, the treated sludge acquired a
musty humus like odor, with the exception of septage which did
not have a significant odor reduction as a result of treatment.
As described later, all treated sludges were applied to
farmland. At the Glosser Road site, shown on Figure 10f
-------
13.0
12.0
11.0 • •
10.0' •
x
Q.
9.0 •-
8.0 •-
7.0- •
6.0
10
LEBANON, OHIO DATA
DATA BY PAULSRUDC8)
20
30
40
50
DAYS
Figure 9. Lime Stabilized Primary Sludge pH vs Time
23
-------
fj
WIND DIRECTION
WHEN ODOR COMPLAINT
WAS RECEIVED
LOCATION OF RESIDENT WHO
REGISTERED ODOR COMPLAINT
'SCALE: |"= |,250
Figure 10. Site Plan. Glosser Road Land Disposal Area
24
-------
Woods
•^ri
TEST PLOTS
SCALE: I =1,250
Figure II. Site Plan. Utica Road Land Disposal Area
25
-------
E
O
O
t-
z
8
<
0
03
100,000,000
lopoopoo
ipoopoo
100,000
10,000
ipoo
100
0
100,000,000
10,000,000
ipoo.ooo
100,000
10,000
1,000-
100
0
loopoopoo
10,000,000
1,000,000
100,000
10,000-
ipoo
100
0
20
10
0
50
40
30
20
10
0
(
1 1 1 1
•
.x\
.s
jf
\S^_____^/XX/X^//^
FECAL STREP
\
^-FECAL COLIFORM
^- TOTAL COLIFORM
L/PS. AERUGINOSA
/^SALMONELLA
L_ , 1 1 1 1 '
} 10 20 30 40 5
TIME , DAYS
Figure 12. Bacteria Concentration vs Time Laboratory Regrowth Studies
26
-------
CHEMICAL PROPERTIES
The addition of lime and mixing by diffused air altered the
chemical characteristics of each sludge. In all sludges, lime
stabilization resulted in an increase in alkalinity and soluble
COD and a decrease in soluble phosphate. Total COD and total
phosphate decreased for all sludges except waste activated.
Ammonia nitrogen and total Kjeldahl nitrogen decreased for all
sludges except waste activated. The results of the chemical
analyses are summarized in Table 12.
TABLE 12. CHEMICAL COMPOSITION OF LIME STABILIZED SLDDGES AT LEBANON, OHIO
Parameter
Alkalinity, mg/1
Alkalinity range, mg/1
Total COD, mg/1
Total COD range, mg/1
Soluble COD, mg/1
Soluble COD range, mg/1
Total Phosphate, mg/1
Total Phosphate range, mg/1
Soluble Phosphate, mg/1
Soluble Phosphate range,
mg/1
Total Kjeldahl nitrogen,
mg/1
Total Kjeldahl nitrogen
range, mg/1
Ammonia nitrogen, mg/1
Ammonia nitrogen range,
mg/1
Total suspended solids,
mg/1
Total suspended solids
range, mg/1
Volatile suspended
solids, mg/1
Volatile suspended
solids range, mg/1
Raw
Primary
Sludge
4,313
3,830-5,470
41,180
26,480-60,250
3,556
876-6,080
283
164-644
36
17-119
1,374
470-2,510
145
81-548
38,370
29,460-44,750
23,480
19,420-26,450
Waste
Activated
Sludge
5,000
4,400-5,600
14,700
10,880-20,800
' 1,618
485-3,010
263
238-289
25
17-31
1,034
832-1,430
64
36-107
10,700
10,745-15,550
7,136
6,364-8,300
Anaerobically
Digested
Sludge
8,467
2,600-13,200
58,690
27,190-107,060
1,809
807-2,660
381
280-460
2.9
1.4-5.0
1,980
1,480-2,360
494
412-570
66,350
46,570-77,900
26,375
21,500-29,300
Septage
Sludge
3,475
1,910-6,700
17,520
5,660-23,900
1,537
1,000-1,970
134
80-177
2.4
1.4-4.0
597
370-760
110
53-162
23,190
14,250-29,600
11,390
5,780-19,500
27
-------
The volatile solids concentrations of raw and lime sta-
bilized sludges are shown in Table 13. The actual volatile
solids concentrations following lime stabilization are lower
than those which would result only from the addition of lime.
Neutralization, saponification, and hydrolysis reactions, which
convert solids into soluble forms with the lime probably result
in the lower volatile solids concentrations.
TABLE 13. VOLATILE SOLIDS CONCENTRATION OF
RAW AND LIME STABILIZED SLUDGES
Raw Sludge Lime Stabilized Sludge
Volatile Solids Volatile Solids
Solids Concentration, Solids Concentration,
Sludge Type mg/1 mg/1
Primary
Waste activated
Septage
Anaerobically
digested
73.2
80.6
69.5
49.6
54.4
54.2
50.6
37.5
Heavy metal analyses were not performed on lime stabilized
sludges.
In terms of the agricultural value, lime stabilized sludges
had lower soluble phosphate, ammonia nitrogen, total Kjeldahl
nitrogen, and total solids concentrations than anaerobically
digested primary/waste activated mixtures at the same plant, as
shown in Table 14. The significance of these changes are dis-
cussed in the section on land disposal.
TABLE 14. NITROGEN AND PHOSPHORUS CONCENTRATIONS IN
ANAEROBICALLY DIGESTED AND LIME STABILIZED SLUDGE
Total
Total Kjeldahl Ammonia
Phosphate Nitrogen Nitrogen
Sludge Type as P, mg/1 as N, mg/1 as N, mg/1
Lime Stabilized Primary
Lime Stab. Waste Activated
Lime Stabilized Septage
Anaerobic Digested
283
263
134
580
1,374
1,034
597
2,731
145
53
84
709
28
-------
PATHOGEN REDUCTION
Considerable research has been conducted on the degree of
bacterial reduction which can be achieved by high lime doses.
In general, the degree of pathogen reduction increased as
sludge pH increased with consistently high pathogen reductions
occurring only after the pH reached 12.0. Fecal streptococci
appeared to resist inactivation by lime treatment particularly
well in the lower pH values; however, at pH 12, these organisms
were also inactivated after one hour of contact time.(9)
The indicator organisms which were used during the full
scale project at Lebanon were the Salmonella species, Pseudomonas
aeruginosa, fecal coliforms, total coliforms, and fecal strep-
tococci.In all sludges, Salmonella and Pseudomonas aeruginosa
concentrations were reduced to near zero. Fecal and total
coliform concentrations were reduced greater than 99.99% in the
primary and septic sludges. In waste activated sludge, the
total and fecal coliform concentrations decreased 99.97% and
99.94%, respectively. The fecal streptococci kills were as
follows: primary sludge, 99.93%; waste activated sludge, 99.41%;
septic sludge, 99.90%; and anaerobic digested, 96.81%. (Based
on raw sludge data as shown in Table 7 and lime stabilized
sludge values as shown in Table 15).
Pathogen concentrations for the lime stabilized sludges are
summarized in Table 15.
Anaerobic digestion is currently an acceptable method of
sludge stabilization.(19) For reference, lime stabilized sludge
pathogen concentrations at Lebanon have been compared in Table 16
to those observed for well digested sludge from the same plant.
Pathogen concentrations in lime stabilized sludge range
from 10 to 1,000 times less than for anaerobically digested
sludge.
A pilot scale experiment was completed in the laboratory to
determine the viability and regrowth potential of bacteria in
lime stabilized primary sludge over an extended period of time.
The test was intended to simulate storing stabilized sludge
in a holding tank or lagoon when weather conditions prohibit
spreading. In the laboratory test, 19 1 (5 gal) of 7% raw
sludge from the Mill Creek sewage treatment plant in Cincinnati
was lime stabilized to pH 12.0. Lime was added until equivalent
to 30% of the weight of the dry solids which resulted in a final
pH of 12.5. The sample was then covered with foil and kept at
room temperature 18.3 C. (65° F.) for the remainder of the test.
The contents were stirred before samples were taken for bacterial
analysis.
29
-------
TABLE 15. PATHOGEN DATA FOR LIME STABILIZED SLUDGES AT LEBANON, OHIO
Parameter
Salmonella avg., 1/100 ml
Salmonella range, #/100 ml
Ps. aeruginosa avg., #/100
Ps. aeruginosa range,
#/100 ml
Fecal coliform avg. MF
#/100 ml
Fecal coliform range MF,
#/100 ml
Fecal coliform avg. MPN,
#/100 ml
Fecal coliform range MPN,
#/100 ml
Total coliform avg. MF,
t/100 ml
Total coliform range MF,
f/100 ml
Total coliform avg. MPN,
1/100 ml
Total coliform range MPN,
#/100 ml
Fecal streptococci avg. ,
#/100 ml
Fecal streptococci range,
t/100 ml
Raw
Primary
Sludge
<3*
-------
The results are shown on Figure 12, and indicate that a
holding period actually increases the bacteria kill. Salmonella
in the_raw sludge totaling 44 per 100 ml were reduced to the
detection limit by lime stabilization. Pseudomonas aeruginosa
totaling 11 per 100 ml in the raw sludge were reduced to the
detection limit by lime stabilization. The initial fecal coli-
form count of 3.0 x 107 was reduced to 5 x 103 after lime sta-
bilization, and after 24 hours was reduced to less than 300.
The raw sludge contained 3.8 x 108 total coliform, but 24 hours
after lime stabilization the total coliform were less than 300.
The fecal strep count4in the raw sludge was 1.8 x 108 which
decreased to 9.6 x 10 after lime stabilization. After 24
hours, the count was down to 7.0 x 103 and after six days
reduced to less than 300. The count increased to 8 x 105 after
40 days.
PARASITES
The high pH of the sludge seemed to have little or no
effect on the viability of the parasites in the limed sludges.
Viable parasites were found in both limed and unlimed samples
with reduced numbers in the limed samples. All the sludges had
similar parasites as shown in Table 17 with Toxacara, mites, and
nematodes common to each of the sludges. Viable parasites were
found in both anaerobic digested and limed sludges.
TABLE 17. IDENTIFIED PARASITES IN LEBANON,
OHIO LIME STABILIZED SLUDGES
Primary
Waste
Activated
Sludge
Septage
Anaerobic
Digested
Toxacara
Trichuris
vulpis
Trichuris
trichura
Enterobius
vermicularis
larva
Toxacara
Toxacara
Ascaris
lumbricoides
Trichuris
trichiura
Trichuris
vulpis
Toxacara Canis
Toxacara cati
Ascaris
Trichuris
vulpis
31
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SECTION 6
LAND APPLICATION
GENERAL
. (14) (15) (19) (20) available
Numerous references are avaiiaoj-e
the application of anaerobically digested sludges to agricultural
land. The application of sewage sludge on land has generally
been viewed from two standpoints, either as a rate of applica-
tion consistent with the utilization of nutrients in sludge by
growing plants (i.e., agricultural utilization), or as the
maximum amount of sludge applied in a minimum amount of time
(i.e., disposal only). USEPA guidelines generally favor the
former approach. The successful operation of a program utilizing
the application of sewage sludge on land is dependent upon a_ _
knowledge of the particular sludge, soil, and crop characteristics,
Organic matter content, fertilizer nutrients, and trace
element concentrations are generally regarded as being vital to
the evaluation of the applicability of land application of
sewage sludge. The range of nitrogen, phosphorus, and potassium
concentrations for sewage sludges have been reported by Brown et
al(14) as shown in Table 18.
TABLE 18. RANGE OF N,
Component
P AND K CONTENTS OF
Range of
Percent
by Weight
SEWAGE SLUDGE'
Range of
Kg/1,000 Kg
Total Nitrogen
Organic Nitrogen
P as phosphorus
Potassium
K20 (potash)
3.5-6.4
2.0-4.5
0.8-3.9
1.8-8.7
0.2-0.7
0.24-0.84
70-128
40- 90
16- 78
36-174
4-14
5-17
32
-------
Sommers^ has also summarized fertilizer recommendations
for crops based primarily on the amount of major nutrients
(nitrogen, phosphorus, and potassium) required by a crop and on
the yield desired. The amounts of nitrogen, phosphorus, and
potassium required by the major agronomic crops are shown in
Table 19.
TABLE 19. ANNUAL N, P AND K UTILIZATION BY SELECTED CROPS
a
Crop Yield N P K
kg/hectare kg/hectare
Corn
Corn silage
Soybeans
Grain sorghum
Wheat
Oats
Barley
Alfalfa
Orchard grass
Brome grass
Tall fescue
Bluegrass
9,413
11,296
71,717
3,362
4,034
8,964
4,034
5,379
3,586
5,600
17,929
13,447
11,206
7,844
6,723
208
269
225
289b
377b
281
140
209
168
168
505b
337
186
152
225
39
49
39
24
33
45
25
27
27
27
39
49
33
33
27
200
223
228
112
135
186
102
150
140
140
447
349
237
173
167
Values reported are from reports by the Potash Institute of
America and are for the total above-ground portion of the
plants. For the purpose of estimating nutrient requirements
for any particular crop year, complete crop removal can be
assumed.
Legumes obtain nitrogen from symbiotic N fixation so fertilizer
nitrogen is not added. ^
33
-------
As shown for corn, the yield desired will determine the
amount of nitrogen, phosphorus, and potassium required. Since
cropping systems alter the level of plant available nutrients to
different extents, the previous crop exerts an influence on the
nitrogen recommendations for corn at different yield levels
(Table 20). These differences arise because crops such as
legumes actually increase the nitrogen availability in soils
through symbiotic nitrogen fixation. Primary emphasis in de-
veloping sludge guidelines is placed on the ability of sludges
to satisfy the nitrogen needs of a crop.
TABLE 20. INFLUENCE OF PREVIOUS CROP ON
N FERTILIZATION RATES FOR CORNa
Previous Crop
Yield Level, kkg/ha
6.28- 6.97- 7.91- 9.48-
6.90 7.84 9.41 11.0
Kg N/hectare
11.0-
12.0
Good legume
(alfalfa, red
clover, etc.) 45
Average legume
(legume-grass
mixture or
poor stand) 67
Corn, soybeans,
small grains,
grass sod 112
Continuous corn 135
79
112
135
168
112
135
157
157
180
191
180
213
224
202
247
258
Purdue University Plant and Soil Testing Laboratory Mimeo, 1974.
/ g\
Counts conducted greenhouse and test plot studies for
lime stabilized sludges which were designed to provide informa-
tion on the response of plants grown in sludge-soil mixtures
ranging in application rate from 11 to 220 metric tons per
hectare (5 to 100 tons/acre). Counts concluded that sludge
addition to poor, e.g., sandy, soils would increase productivity,
and therefore would be beneficial. The total nitrogen and
phosphorus levels in plants grown in greenhouse pots, which
contained sludge-soil mixtures, were consistently lower than
plants which were grown in control pots. The control set, which
contained only soil with no sludge additions received optimum
34
-------
additions of chemical fertilizer during the actual plant growth
phase of the studies. Calcium concentration in plant tissues
from the sludge-soil pots were higher than those for the controls
The pH values of the various sludge-soil mixtures were lower
after plant growth than before. Counts attributed the decrease
to carbon dioxide buildup in the soil which resulted from bio-
logical activity.
LAND APPLICATION RESULTS
Land application studies at Lebanon, Ohio were conducted by
spreading liquid sludge on agricultural land and on controlled
test plots. Winter wheat, soybeans, and hay were grown on
fields which were in normal agricultural production. Corn,
swiss chard, and soybeans were grown on 22 test plots, each with
an area of 0.0085 ha (0.021 acre).
Sludge application was accomplished by spreading as a
liquid using a four-wheel drive vehicle which was equipped with
a 2.3 cu m (600 gal) tank. The width of sludge spread per pass
was approximately 60 cm (24 in).
Two agricultural areas were used for disposal of lime
stabilized sludges. The Glosser Road site, as previously shown
on Figure 10, comprised a total area of 16 ha (40 acres). The
predominant soils were of the Russell and Miami-Xenia-Wynn
associations which are light colored silt loams and are moder-
ately well drained.
The entire field had been planted in winter wheat the
previous fall. At that time, a fertilizer application of 281
kg/ha (250 Ibs/acre) of 16-16-16 was made. Approximately two
weeks prior to starting land application, an additional 55
pounds/acre of urea were applied to all areas except those which
were to receive sludge.
Two 0.73 ha (1.8 acre) test areas ("A" and "B"), as shown
on Figure 13, were used for land application studies. The wheat
was approximately 2.54 cm (1 in) high when lime stabilized
primary sludge was first applied on March 1, 1976. Weather
permitting, lime stabilized sludge was applied twice weekly
through April 19, 1976. The narrow sludge application swath, as
previously described, required numerous trips across the field
which resulted in some damage to the wheat. Secondly, the lime
stabilized sludge formed a filamentous mat 0.32 to 0.64 cm (1/8-
1/4 in) thick which, when dry, partly choked out the wheat
plants. The mat partly deteriorated over time, but significant
portions remained at the time of harvest. Application rates for
nutrients have been summarized in Table 21.
35
-------
U)
cn
O
CO
ff
O
Q.
o
m
O
m
CO
XI
I
m
>
yj
O
o»*
•o
o
CO
Q
II
GRAVEL LANE TO RESIDENCE
unMVCL. L.MIMC. iu nc^jmuii^E. -\
— — — ~~* ~~~ —-— —— ^—— ^^^ ~~ ___ ^~ ... __ ___^__ __ ^_
APPROXIMATELY 800' EAST FROM GLOSSER ROAD
TO RESIDENCE
-------
TABLE 21. APPLICATION RATES FOR NUTRIENTS IN SLUDGE
GLOSSER ROAD SITE
Parameters
Area "A" Area "A" Area "B" Area "B"
Kg/hectare Lb/acre Kg/hectare Ib/acre
Lime as Ca (OH) ,,
Total phosphorus as
P2°5
Soluble phosphorus
as P205
Total Kjeldahl
nitrogen as N
Ammonia nitrogen
as N
979
110
14.4
238
27
872
98
12.8
212
24
545
52
8.6
135
15.7
485
46
7.7
120
14
The sludge application rates were 8.19 metric tons per
hectare (3.65 tons/acre) and 4.53 metric tons per hectare (2.02
tons/acre) to areas "A" and "B", respectively. (Values based on
tons dry solids.)
Nitrogen application rates to the test areas were less than
the fertilized control as shown below:
Test Area "A"
Test Area "B"
Control Field
Fertilizer
Nitrogen
kg/ha
40
40
107
Sludge*
Nitrogen
kg/ha
13
8
0
Total
Available
Nitrogen
kg/ha
53
48
107
volatilization
Random wheat samples were taken as shown on Figure 13.
Areas C-l, C-2, C-3, and C-4 were used as controls. Areas A-l,
A-2, A-3, and A-4 had approximately twice the sludge application
rate as Areas B-l, B-2, B-3, and B-4. Yield data are shown in
Table 22.
37
-------
TABLE 22. GLOSSER ROAD WHEAT FIELD YIELD ANALYSIS
Area
Control
01
C-2
C-3
C-4
Average
Area "B"
B-l
B-2
B-3
B-4
Average
Area "A"
A-l
A- 2
A- 3
A- 4
Average
No.
Shafts
Per 7
1.47 m
(4!x4')
Area
657
747
N/A
672
692
386
441
487
495
452
522
288
620
662
523
Grain
ODWT*
kg/ha
3,426
3,500
N/A
3,210
3,379
1,602
1,817
2,302
1,945
1,916
1,709
1,306
2,053
2,672
1,935
Chaff
kg/ha
397
323
N/A
478
399
195
202
209
202
202
350
316
424
565
414
Shaft
ODWT*
kg/ha
2,571
2,645
N/A
2,248
2,488
1,184
1,238
1,629
1,359
1,353
1,777
1,036
1,629
2,207
1,662
Biomass
kg/ha
6,394
6,468
N/A
5,936
6,266
2,981
3,257
4,139
3,506
3,471
3,836
2,658
4,247
5,445
4,046
Yield,
gm/head
0.775
0.696
N/A
0.710
0.727
0.617
0.612
0.702
0.584
0.630
0.487
0.674
0.477
0.600
0.556
*ODWT = oven dry weight
Area "A" which had a greater level of mechanical abuse due to
the extra sludge applications had higher biomass and shaft
weights indicating slightly larger plants. Area "A" had a
higher number of shafts per acre but had smaller grain sizes,
thereby resulting in approximately the same yield as Area "B".
38
-------
Both Areas "A" and "B" had significantly lower yields than
the control area, resulting in part from the nitrogen deficiency,
A second land application area (Utica Road site), as shown
on Figure 11, was utilized. Soils in this area were of the
Fincastle-Brookston association. The predominant soil was Fin-
castle silt loam, which is a light colored, somewhat poorly
drained soil. The Utica Road site had been previously tiled to
compensate for the poor drainage. A total area of 263 ha (650
acres) were under production for corn, soybeans, and hay at this
site.
Three major study areas were used at this site. Twenty-two
0.0085 ha (0.021 acre) test plots were used for corn, soybean,
and swiss chard growth studies. An area of approximately 3.86
acres was divided into seven plots ranging in size from 0.11 to
0.78 ha (0.28 to 1.93 acres) and were managed as a part of
normal farming operations. A third area of approximately 2 ha
(5 acres) was in hay production and received lime stabilized
sludges during the period July 19-October 5, 1976. Sludge was
incorporated into the soil approximately two weeks after appli-
cation on all areas except to the hay field.
A layout of the 22 test plots is shown on Figure 14.
Table 23 summarizes the sludge types and application rates which
were used.
TABLE 23. UTICA ROAD TEST PLOT SLUDGE APPLICATION DATA
Sludge Type
Dry Solids
Application,
kkg/ha
Dry Solids
Application,
tons/acre
Plot No,
Raw Primary
Anaerobically Digested
Lime Stabilized Anaer.
Digested
Lime Stabilized Primary
Lime Stabilized Primary
Lime Stabilized Primary
11
11
11
11
22
44
5
5
5
5
10
20
4,21,22
1,9,18
14,19 20
5,12,17
7,15,16
3,11,13
Nitrogen, phosphorus, and potassium application rates for
each of the test plots have been summarized in Table 24.
39
-------
45 5' 45 5 45
O
CO
in
"o
CM
m
"a
m
"o
-------
TABLE 24. N AND P APPLICATION RATES TO UTICA ROAD TEST PLOTS
N Applied P Applied*
Sludge Type Plot No. kg/ha kg/ha
Raw Primary
Anaerobically Digested
Lime Stabilized Anaer.
Digested
Lime Stabilized Primary
Lime Stabilized Primary
Lime Stabilized Primary
4,21,22
1,9,18
14,19,20
5,12,17
7,15,16
3,11,13
46
160
110
28
56
112
65
131
86
52
103
207
*Based on total P in sludge, reported as P
The test plots received no fertilizer or herbicide appli-
cations prior to sludge application. Yields for corn and soy-
beans are summarized in Tables 25 and 26, respectively.
Actual application rates for nitrogen, phosphorus, and
potassium have been compared to the targets previously shown in
Table 19 as follows:
Target Actual Range
Crop N p*** K N p*** K
kg/ha kg/ha kg/ha kg/ha kg/ha kg/ha
Corn*
Soybeans**
208 39
24
200
112
46-160
46-160
52-207
52-207
N/A
N/A
*9,413 kg/ha (150 bu/acre) yield
**3,362 kg/ha (50 bu/acre) yield
***reported as P
With the exception of 44 kkg/ha raw limed sludge, all
sludge applications increased the corn yield above the control.
Increasing lime stabilized raw primary sludge resulted in de-
creasing corn yields, even though the nitrogen requirements were
approached at the higher sludge application rates. Soybean
yields were similarly influenced.
Swiss chard was utilized as an indicator for heavy metal
uptake; however, at the time of this writing, the data are not
available.
41
-------
TABLE 25. CORN YIELD ANALYSIS FOR UTICA ROAD TEST PLOTS
10
Treatment
Rep 1 - Rep 2
Grain Grain
kg/ha kg/ha
Rep 3 Grain
Grain kg/ha
kg/ha avg
Average
bu/acre
Number of Plants
Rep 1 Rep 2 Rep 3
Control 6,253 3,726 4,840 4,940 73 42 30 41
Raw (11 kkg/ha) 6,896 5,397 6,125 6,139 91 47 37 40
Raw Limed (11 kkg/ha) 5,996 7,282 5,397 6,225 92 46 48 47
Raw Limed (22 kkg/ha) 7,068 5,612 4,883 5,854 87 43 44 42
Raw Limed (44 kkg/ha) 5,654 4,112 3,384 4,383 65 38 32 29
Anaerobic (11 kkg/ha) 6,468 6,039 5,012 5,840 86 45 45 41
Anaerobic Limed (11 kkg/ha) 7,239 5,569 5,654 6,154 91 48 36 47
Average
Number
of
Plants
38
41
47
43
33
44
44
-------
U)
Rep 1 Rep 2 Rep 3 Soybean
Grain Grain Grain kg/ha
Treatment kg/ha kg/ha kg/ha avg
Control 2,104 2,300 2,057 2,154
Raw (11 kkg/ha) 2,193 2,343 2,453 2,330
Raw Limed (11 kkg/ha) 2,229 2,009 2,109 2,116
Raw Limed (22 kkg/ha) 1,731 2,035 1,952 1,906
Raw Limed (44 kkg/ha) 1,799 1,552 1,362 1,571
Anaerobic (11 kkg/ha) 2,099 1,810 2,251 2,053
Anaerobic Limed (11 kkg/ha) 2,067 1,95S 2,459 2,162
Average
Number
Average Number of Plants of
bu/acre Rep 1 Rep 2 Rep 3 Plants.
38 179 177 178 178
42 153 174 204 177
38 182 186 205 191
34 158 186 203 182
28 172 154 165 164
37 155 156 183 165
39 167 158 209 178
-------
Seven plots were used, as shown on Figure 15, for the full
scale field studies. Plot Nos. 2 and 5 were 0.22 ha (.55 acre)
and Plot Nos. 3, 4, and 6 were 0.11 ha (.275 acre). Plot Nos. 1
and 7 were used as control. The limed primary sludge was ap-
plied after the field had been plowed and roughly disked. The
sludge formed a thick filamentous mat which was easily disked
under before planting. All sites were planted with soybeans;
site 1 the first week in May; sites 2, 3, and 4 the first week
of June; and sites 5, 6, and 7 the first week of July. The test
areas had been fertilized in previous years but did not receive
fertilizer prior to sludge spreading. Sludge and nutrient
application rates are shown in Table 27.
Table 28 summarizes a random selection of three soybean
plants which were designated A, B, and C from individual plots.
The data indicate that plots 2 and 5 with a higher sludge appli-
cation rate would have a higher yield per acre than plots 1
or 4. Plant growth shows plots 2 and 5 yielded plants 5.1 cm
taller than plots 1 and 4.
TABLE 28. PODS AND HEIGHTS OF SOYBEANS FROM VARIOUS PLOTS
UTICA ROAD FULL SCALE FIELD STUDIES
Pods per Plant Plant Height in Centimeters
Plot No. A B C Average ABC Average
1
4
2
5
49
48
39
29
32
33
44
34
33
33
37
58
38
38
40
40
95
90
99
94
84
88
74
104
81
99
97
94
81
92
90
97
A random sample of soybeans was selected for heavy metal
analysis. The results are shown in Table 29. No consistent
increase in metal concentration as a result of increasing sludge
application was observed. Only zinc concentration increased
with increasing sludge application rate. The lack of increases
in other metals probably resulted from the relatively low con-
centrations of these elements in the sludge.
44
-------
0 QQ
3+60
3+90
4+20
4+50
4+80
5+10
5+40
5+70
o o o
400
n
, 75'
o
ro
-o
o
AREA FOR LAND APPLICATION
OF LIMED SLUDGES 3.86 ACRES
o
o
PLOT 7
PLOT 6
/
PLOT 5
)>
PLOT 3
PLOT 2
PLOT |
X^
LIMIT OF WOODS
8
*0
10
8
Figure 15. Layout of Utica Road Land Disposal Area
45
-------
hfe.
TABLE 27. APPLICATION RATES FOR NUTRIENTS IN SLUDGE FOR FULL SCALE FIELD STUDIES
UTICA ROAD SITE
Parameter
Lime as Ca{OH) 2
Total Phosphorus as P20j
Soluble Phosphorus as ?205
Total Kjeldahl Nitrogen as N
Ammonia Nitrogen as N
Sludge Application Rate*
Kg/ha
1,226
236
40
438
56
14,147
Plot 2
Lbs . /Acre
1,092
211
.4 36
391
50
12,600
Kg/ha
849
120
20.
220
28
6,961
Plot 3
Lbs./Adre
756
107
2 18
196
25
6,200
Kg/ha
989
161
28
297
38
9,566
Plot 5
Lbs. /Acre
881
144
25
265
34
8,520
Plot 6
Kg/ha Lbs. /Acre
520 463
102 91
18 16
188 168
24 21
5,951 5,300
*Dry solids/acre
Note: Plots 1, 4 & 7 were used as control and received no sludge application.
-------
TABLE 29. HEAVY METALS IN SOYBEANS
UTICA ROAD FULL SCALE FIELD STUDIES
Lime Stabilized
No Sludge Primary Sludge
Plot 1 Plot 4 Plot 7 Plot 3 Plot 6 Plot 2 Plot 5
Metals ppm* ppm* ppm* ppm* ppm* ppm* ppm*
Cadium
Copper
Cobalt
Lead
Potassium as K
Potassium as
K20
Mercury
Nickel
Zinc
0.35
6.3
1.9
0.5
3,110
3,750
1.5
3.6
5.5
0.20
6.2
1.7
0.5
5,380
6,480
4.0
3.7
5.4
0.1
13.6
0.4
0.3
6,530
7,860
4.0
3.1
5.1
0.3
6.9
1.6
0.5
4,750
5,720
5.5
3.6
9.3
0.2
11.0
1.0
0.5
4,400
5,300
0.3
3.0
9.3
0.45
8.6
1.4
0.3
5,290
6,370
6.5
3.1
5.6
0.3
12.6
1.0
0.5
7,350
8,860
0.3
2.8
11.6
*Results are recorded as ppm dry weight
Plot 2 = 14.1 kkg/ha Plot 5 = 9.57 kkg/ha
Plot 3 = 6.96 kkg/ha Plot 6 = 5.95 kkg/ha
Lime stabilized anaerobically digested, waste activated,
and septage sludges were applied to a two hectare (5 acre)
hayfield during the period July 19-October 5, 1976, after a
second cutting of hay had been made.
Spontaneous growth of tomatoes was significant in both the
test plots and full scale soybean field areas. Seeds were
contained in the sludge and were not sterilized by the lime.
These plants were absent at Glosser Road, even though no herbi-
cide was applied, probably because of frequent frosts and the
lack of sludge incorporation into the soil. During the next
year's growing season, an increase in insect concentration was
noticed on the fields which had received lime stabilized sludge,
47
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SECTION 7
SLUDGE DEWATERING CHARACTERISTICS
GENERAL
Farrell et al have previously reported on the dewatering
characteristics of ferric chloride and alum treated sludges
which were subsequently treated with lime. Trubnick and
Mueller(21) presented, in detail, the procedures to be followed
in conditioning sludge for filtration, using lime with and
without ferric chloride. Sontheimer(22) presented information
on the improvements in sludge filterability produced by lime
addition.
RESULTS OF LEBANON STUDIES
Laboratory scale dewatering studies were not conducted at
Lebanon. Standard sand drying beds which were located at the
wastewater treatment plant were used for sludge dewatering
comparisons. Each bed was 9.2 m x 21.5 m (301 x 70'). For the
study, one bed was partitioned to form two, each 4.6 m x 21.5 m
(15' x 70'). Limed primary sludge was applied to one bed with
limed anaerobically digested sludge being applied to the other
side. A second full sized bed was used to dewater unlimed
anaerobically digested sludge. The results of the study are
summarized on Figure 16.
Lime stabilized sludges generally dewatered at a lower rate
than well digested sludges. After ten days, lime stabilized
primary sludge had dewatered to approximately 6.5% solids as
opposed to 9% for lime stabilized anaerobically digested sludge,
and 10% for untreated anaerobically digested sludge.
The anaerobically digested sludge cracked first and dried
more rapidly than either of the lime stabilized sludges. Ini-
tially, both of the lime stabilized sludges matted, with the
digested sludge cracking after approximately two weeks. The
lime stabilized primary sludge did not crack which hindered
drying and resulted in the lower percent solids values.
48
-------
20i l i l i I i l I i I i i i i I i i i i i i i i
V)
Q
_i
o
CO
I-
z
UJ
o
or
LJ
a.
15- -
O1i i i i [ i i i i I i
10 15 20 25
TIME-DAYS
i | i i i l | l l I I
30 35 40
Figure 16. Dewatering Characteristics of Various Sludges on Sand
Drying Beds
49
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SECTION 8
ECONOMIC ANALYSIS
LEBANON FACILITIES
As previously described, the anaerobic sludge digestion
facilities at Lebanon were essentially inoperable at the start
of the lime stabilization project. Funds were allocated to
construct lime stabilization facilities, as well as to rehabil-
itate the anaerobic digester. In both cases, the existing
structures, equipment, etc., were utilized to the maximum extent
possible. Table 30 includes the actual amounts paid to con-
tractors, following competitive bidding, and does not include
engineering fees, administrative costs, etc.
TABLE 30. ACTUAL COST OF DIGESTER REHABILITATION AND
LIME STABILIZATION FACILITIES CONSTRUCTION
Anaerobic Digester Cleaning
Cleaning contractor $5,512.12
Temporary sludge lagoon 2,315.20
Lime for stabilizing digester contents 514.65
Temporary pump rental 300.30
Subtotal Digester Cleaning $8,642.27
Anaerobic Digester Rehabilitation
Electrical equipment, conduit, etc. $1,055.56
Natural gas piping 968.76
Hot water boiler, piping, pump, heat
exchanger repair 7,472.26
Control room rehabilitation 1,465.00
Sludge recirculating pump repair 771.00
Piping and valve rehabilitation 8,587.30
Floating cover roof repair 1,014.04
Repair utilities, drains 211.52
Miscellaneous 1,946.88
Subtotal Digester Rehabilitation $23/492.32
(continued)
50
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TABLE 30 (continued)
Lime Stabilization Process
Electrical equipment, conduit, etc. $1,692.00
3" & 4" sludge lines, supports, valves,
and fittings 6,140.19
4" sludge crossover, pipe, valves, and
fittings 1,101.48
1 1/2" air line and diffusers 1,310.00
3/4" water lines and hose bibbs 865.00
Lime bin, auger, vibrators 7,229.44
Volumetric feeder, trough and gate 3,46o!00
Existing pump repairs 3,399.00
Miscellaneous metal l,20o!oO
Relocate sanitary service line 200.00
Repair utilities 134!00
Miscellaneous 934^34
Contractor's overhead 1,842^00
Subtotal Lime Stabilization $29,507.45
Septage Holding Tank
Septage holding tank and pump $6,174.70
Subtotal Septage Holding Tank $6,174^0
Total Cost for Digester Cleaning &
Rehabilitation, Lime Stabilization,
and Septage Facilities $67,816.74
The cost of the lime stabilization facilities was $29,507.45
compared to $32,134.59 for cleaning and repair of the anaerobic
sludge digester.
CAPITAL COST OF NEW FACILITIES
Capital and annual operation and maintenance costs for lime
stabilization and anaerobic sludge digestion facilities were
estimated assuming new construction as a part of a 3,785 cu m
(1.0 MGD) wastewater treatment plant with primary clarification
and single stage conventional activated sludge treatment processes
The capital costs for lime stabilization facilities in-
cluded a bulk lime storage bin for hydrated lime, auger, volu-
metric feeder and lime slurry tank, sludge mixing and thickening
tank with a mechanical mixer, sludge grinder, all weather treat-
ment building, electrical and instrumentation, interconnecting
piping and transfer pumps, and 60 day detention treated sludge
holding lagoon. The basis for design is as follows:
51
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Daily primary sludge dry solids
production
Average primary sludge volume
@ 5% solids
Daily waste activated dry solids
production
Average waste activated sludge
volume @ 1.5% solids
Average lime dosage required per
Daily lime requirement as Ca(OH)2
Treatment period
Bulk lime storage bin volume
minimum
Bulk lime storage bin detention time
Lime feeder and slurry tank
capacity (spared)
Influent sludge grinder capacity
Sludge mixing tank volume
Sludge mixing tank dimensions
Sludge mixer horsepower
Sludge mixer turbine diameter
Turbine speed
Sludge transfer pump capacity
(spared)
Treated sludge percent solids
Sludge holding lagoon volume
Sludge holding lagoon maximum
detention time
Treatment building floor area
Treatment building construction
Instrumentation:
568 kg/day (1,250
Ibs/day)
11,015 I/day (2,910
gal/day)
493 kg/day (1,084
Ibs/day)
32,470 I/day (8,580
gal/day)
0.20 kg/kg (0.20
Ib/lB)
216 kg/day (475
Ib/day)
3 hrs/day
28 cu m (1,000
cu ft)
39 days
0.14-0.42 cu m/hr
(5-15 cu ft/hr)
757 1/min (200 gpm)
57 cu m (15,000 gal)
4.3mx4.3mx3m
(14'xl4'xlOl SWD)
15 HP
135 cm (53")
68
106 1/min (400 gpm)
4%
2,860 cu m (100,000
cu ft)
60 days
13.9 m2 (150 ft2)
Brick and block
pH record
Treated sludge
volume
52
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Capital costs for the lime stabilization facilities were
based on July 1, 1977 bid date, and were as follows:
Site work, earthwork & yard piping $ 6,000
Lime storage bin and feeders 30,000
Treatment tank, pumps, sludge
grinders, and building structure 52,000
Electrical and instrumentation 10,000
Sludge holding lagoon 20,000
Subtotal Construction Cost $118,000
Engineering 12,000
Total Capital Cost $130,000
Amortized cost @ 30 yrs., 7% int.
(CRF = 0.081) $ 10,500
Annual Capital Cost per unit feed
dry solids $ 24.65
Lime stabilization operation assumed one man, two hours per
day, 365 days per year, at $6.50 per hour, including overhead.
Maintenance labor and materials assumed 52 hours per year labor
at $6.50 per hour and $800 per year for maintenance materials.
The total quantity of 46.8% CaO hydrated lime required was 83
tons per year at $44.50 per ton.
The total annual cost for lime stabilization, excluding
land application of treated sludge, has been summarized in
Table 31.
TABLE 31. TOTAL ANNUAL COST FOR LIME STABILIZATION
EXCLUDING LAND DISPOSAL FOR A 3,785 CU M/DAY PLANT
Item
Operating labor
Maintenance labor
and materials
Lime
Laboratory
Capital
Total Annual Cost
Total
Annual
Cost
$ 4,700
1,100
6,200
500
10,500
$23,000
Annual
Cost
Per kkg
Dry Solids
$12.14
2.84
16.02
1.29
27.11
$59.40
Annual
Cost
Per Ton
Dry Solids
$11.03
2.58
14.55
1.17
24.65
$53.98
The basis for design of a single stage anaerobic sludge
digester for the same treatment plant was as follows:
53
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Daily primary sludge dry solids
production
Average primary sludge volume
@ 5% solids
Daily waste activated dry solids
production
Average waste activated sludge
volume @ 1.5% solids
Daily volatile solids production
Volatile solids loading
Digester hydraulic detention time
Digester gas production
Average volatile solids reduction
Digested sludge dry solids
production
Digested sludge percent solids
Digester net heat requirement
Mechanical mixer horsepower
Sludge recirculation pumps (spared)
568 kg/day (1,250
Ib/day)
11,015 I/day
(2,910 gal/day)
493 kg/day (1,084
Ib/day)
32,470 I/day (8,580
gal/day)
743 kg/day (1,634
Ib/day)
0.81 kg/cu m/day .,
(0.05 Ib VSS/ft /
day)
21 days
0.37 cu m/lb VSS feed
(13 cu ft/lb VSS
feed)
50%
689 kg/day (1,515
Ib/day)
6%
186,000 BTU/hr
15 HP
1,234 1/min ea. (350
gpm ea.)
Capital cost for the anaerobic sludge digestion facilities,
including the control building, structure, floating cover, heat
exchanger, gas safety equipment, pumps, and interconnecting
piping, assuming July 1, 1977 bid date, and engineering, legal,
and administrative costs is as follows:
Site work, earthwork, yard piping
Digester
Control building
Electrical and instrumentation
Subtotal Construction Cost
Engineering
Total Capital Cost
Amortized cost @ 30 yrs, 7% int.
(CRF = 0.081)
Annual Capital Cost per unit
feed dry solids
$ 44,000
233,000
133,000
47,000
$457,000
46,000
$503,000"
$ 40,700
$ 95.54
54
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Digester operation assumed one man, one hour per day, 365
days per year at $6.50 per hour, including overhead. Maintenance
labor and material assumed 52 hours per year at $6.50 per hour
and $1,500 per year for maintenance materials.
The cost of anaerobic digester operation was offset by
assuming a value of $2.10 per million BTU for all digester gas
produced above the net digester heat requirement.
The total annual cost for anaerobic sludge digestion,
excluding land application has been summarized in Table 32.
TABLE 32. TOTAL ANNUAL COST FOR SINGLE STAGE
ANAEROBIC SLUDGE DIGESTION EXCLUDING LAND
DISPOSAL FOR A 3,785 CU M/DAY PLANT
Annual Annual
Total Cost Cost
Annual Per kkg Per Ton
item Cost Dry Solids Dry Solids
Operating labor
Maintenance labor
and materials
Laboratory
Capital
Fuel credit
Total Annual Cost
$ 2,400
1,800
500
40,700
(2,900)
$42,500
$ 6.20
4.65
1.29
105.09
(7.49)
$109.74
$ 5.63
4.23
1.17
95.54
(6.81)
$99.76
Both the lime stabilization and anaerobic digestion alter-
natives were assumed to utilize land application of treated
sludge as a liquid hauled by truck. The capital cost for a
sludge hauling vehicle was assumed to be $35,000, which was
depreciated on a straight line basis over a ten year period.
Alternatively, a small treatment plant could utilize an existing
vehicle which could be converted for land application at a
somewhat lower capital cost.
The assumed hauling distance was three to five miles, round
trip. Hauling time assumed 10 minutes to fill, 15 minutes to
empty, and 10 minutes driving, or a total of 35 minutes per
round trip. The truck volume was assumed to be 5,680 liters
(1,500 gal) per load. The cost of truck operations, excluding
the driver and depreciation, were assumed to be $8.50 per oper-
ating hour. The truck driver labor rate was assumed to be $6.50
per hour, including overhead.
55
-------
Truck operation time was based on hauling an average of
1,812 1 (6,860 gal) of lime stabilized sludge, i.e., five loads
and 777 1 (2,940 gal) of anaerobically digested sludge, i.e.,
two loads per day. The reduced volume of anaerobically digested
sludge resulted from the volatile solids reduction during di-
gestion and the higher solids concentration compared to lime
stabilized sludge.
Although it may be possible to obtain the use of farmland
at no cost, e.g., on a voluntary basis, the land application
economic analysis assumed that land would be purchased at a cost
of $750 per acre. Sludge application rates were assumed to be
ten dry tons per acre per year. Land costs were amortized at 7%
interest over a 30 year period.
To offset the land cost, a fertilizer credit of $7.30 per
ton of dry sludge solids was assumed. This rate was arbitrarily
assumed to be 50% of the value published by Brown(14> based on
medium fertilizer market value and low fertilizer content. The
reduction was made to reflect resistance to accepting sludge as
fertilizer. The land cost was further offset by assuming a
return of $50 per acre, either as profit after farming expenses,
or as the rental value of the land.
Capital and annual operation and maintenance costs for land
application of lime stabilized and anaerobically digested sludges
have been summarized in Table 33.
For each item in Table 33, the total annual cost was cal-
culated and divided by the total raw primary plus waste activated
sludge quantity, i.e., 387 kkg/year (426 tons/year). Anaero-
bically digested sludge land requirements were less than for
lime stabilized sludge because of the volatile solids reduction
during digestion. Truck driving and operation costs were simi-
larly less for digested sludge because of the volatile solids
reduction and more concentrated sludge (6% vs. 4%) which would
be hauled. Fertilizer credit was less for digested sludge
because of the lower amount of dry solids applied to the land.
Land credit was based on the amount of sludge applied and was,
therefore, less for digested sludge.
The total annual capital and annual operation and mainte-
nance costs for lime stabilization and single stage anaerobic
sludge digestion, including land application for a 3,785 cu
m/day wastewater treatment plant, are summarized in Table 34.
56
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TABLE 33. ANNUAL COST FOR LAND APPLICATION OF LIME STABILIZED AND
ANAERQBICALLY DIGESTED SLUDGES FOR A 3,785 CU M/DAY PLANT
Cn
Item
Amortized cost
of land
Truck depreciation
Truck driver
Truck operation
Laboratory
Fertilizer credit
Land credit
Total Annual Cost
Lime
Total
Annual
Cost
$ 2,600
3,500
7,100
9,300
500
(3,100)
(2,200)
$17,700
Stabilization
Annual Annual
Cost
Per
Kkg
Solids
$ 6.75
9.04
18.35
24.03
1.29
(8.05)
(5.68)
$45.73
Cost
Per
Ton
Solids
$ 6.14
8.22
16.67
21.83
1.17
(7.30)
(5.16)
$41.57
Anaerobic Digestion
Annual Annual
Total
Annual
Cost
$1,700
3,500
2,800
3,600
500
(2,000)
(1,400)
$8,700
Cost
Per
Kkg
Solids
$ 4.39
9.04
7.24
9.30
1.29
(8.05)
(3.62)
$19.59
Cost
Per
Ton
Solids
$ 3.99
8.22
6.57
8.45
1.17
(7.30)
(3.29)
$17.81
-------
TABLE 34. COMPARISON OF TOTAL ANNUAL CAPITAL AND
ANNUAL O&M COST FOR LIME STABILIZATION AND ANAEROBIC
DIGESTION INCLUDING LAND DISPOSAL FOR A 3,785 CU M/DAY PLANT
Lime Stabilization
Annual
Facilities
Land application
Total Annual Cost
Total
Annual
O&M
Cost
$23,000
17,700
$40,700
Cost
Per
Kkg Dry
Solids
$59.40
45.70
$105.10
Anaerobic Digestion
Annual
Total
Annual
O&M
Cost
$42,500
8,700
$51,200
Cost
Per
Kkg Dry
Solids
$109.74
19.59
$129.33
58
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SECTION 9
LIME STABILIZATION DESIGN CONSIDERATIONS
OVERALL DESIGN CONCEPTS
Lime and sludge are two of the most difficult materials to
transfer, meter, and treat in any wastewater treatment plant
For these reasons, design of stabilization facilities should
emphasize simplicity, straightforward piping layout, ample space
for operation and maintenance of equipment, and gravity flow
wherever possible. Lime transport should be by auger with the
slurry or slaking operations occurring at the point of use
Lime slurry pumping should be avoided with transport being by
gravity in open channels. Sludge flow to the tank truck and/or
temporary holding lagoon should also be by gravity if possible.
Figures^17, 18, and 19 show conceptual designs for lime
facilities at wastewater treatment facilities with
m. „ „„ • and 37'850 cu m/day (1, 5 and 10 MGD) throughputs.
The 3,785 cu m/day (1 MGD) plant, as shown on Figure 17, utilizes
hydrated lime and a simple batch mixing tank, with capability to
treat all sludges in less than one shift per day. Treated
sludge could be allowed to settle for several hours before
hauling in order to thicken, and thereby reduce the volume
hauled. Alternately, the sludge holding lagoon could be used
for thickening.
Figure 18 shows the conceptual design for lime stabiliza-
tion facilities of an 18,925 cu m/day (5 MGD) wastewater treat-
ment facility. Pebble lime is utilized in this installation.
Two sludge mixing tanks are provided, each with the capacity to
treat the total sludge production from two shifts. During the
remaining shift, sludge could be thickened and hauled to the
land disposal site. Alternately, the temporary sludge lagoon
could be used for sludge thickening.
Figure 19 shows the conceptual design for lime stabiliza-
tion facilities of a 37,850 cu m/day (10 MGD) wastewater treat-
ment plant. A continuous lime treatment tank with two hours
detention time is used to raise the sludge PH to 12. A separate
sludge thickening tank is provided to increase the treated
sludge solids content before land application. Sludge transport
is assumed to be by pipeline to the land disposal site A
59
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DUST COLLECTOR
FILL
PIPE
INFLUENT SLUDGE
HYDRATED
LIME
STORAGE I
BIN ,
MECHANICAL TURBINE AGITATOR
TREATED SLUDGE TO LAGOON
-TANK TRUCK
SLUDGE
GRINDER
SLUDGE FROM LAGOON
LAGOON
Figure 17. Conceptual Design For Lime Stabilization Facilities For A
3,785 cu. meter/day Treatment Plant
-------
CTi
Figure 18. Conceptual Design For Lime Stabilization Facilities For An
18,925 cu. meter/day Treatment Plant
-------
OUST COLLECTOR
BUILDING
AUGERS
LIME SLAKERSV FEEDERS
•MECHANICAL TURBINE AGITATOR
MIX TANK W/2hr.
DETENTION TIME
SLUDGE
THICKENER
DEC4NT TO
PRIMARY^ INFLUENT
-CrN'4-
Or
00—00
•TANK TRUCK
TRttTED SLUDGE *-v
ITO LAGOON X
LAGOON
SLUDGE FROM LAGOON
Figure 19. Conceptua! Design For Lime Stabilization Facilities For A
37,850 cu. meter/day Treatment Plant
-------
temporary sludge holding lagoon was assumed to be necessary, and
would also be located at the land disposal site.
LIME REQUIREMENTS
The quantity of lime which will be required to raise the pH
of municipal wastewater sludges to pH greater than 12 can be
estimated from the data presented in Table 11 and from Figures
4-8. Generally, the lime requirements for primary and/or waste
activated sludge will be in the range of 0.1 to 0.3 Kg per Kg
(Ib per Ib) of dry sludge solids. Laboratory jar testing can
confirm the dosage required for existing sludges.
TYPES OF LIME AVAILABLE
Lime in its various forms, as quicklime and hydrated lime,
is the principal, lowest cost alkali. Lime is a general term,
and is unfortunately often used indiscriminately. Lime, by
strict definition, only embraces burned forms of lime - quicklime,
hydrated lime, and hydraulic lime. The two forms of particular
interest to lime stabilization, however, are quicklime and
hydrated lime. Not included are carbonates (limestone or
precipitated calcium carbonate) that are occasionally but er-
roneously referred to as "lime."^24)
Quicklime
Quicklime is the product resulting from the calcination of
limestone and to a lesser extent shell. It consists primarily
of the oxides of calcium and magnesium. On the basis of their
chemical analyses, quicklimes may be divided into three classes:
1. High calcium quicklime - containing less than 5%
magnesium oxide, 85-90% CaO
2. Magnesium quicklime - containing 5 to 35% magnesium
oxide, 60-90% CaO
3. Dolomitic quicklime - containing 35 to 40% magnesium
oxide, 55-60% CaO
The magnesium quicklime is relatively rare in the United
States and, while available in a few localities, is not generally
obtainable.
Quicklime is available in a number of more or less standard
sizes, as follows:
1. Lump lime - the product with a maximum size of 20.3 cm
(8") in diameter down to 5.1 cm (2") to 7.6 cm (3")
produced in vertical kilns.
63
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2. Crushed or pebble lime - the most common form, which
ranges in size from about 5.1 to 0.6 cm (2" to 1/4"),
produced in most kiln types.
3. Granular lime - the product obtained from Fluo-Solids
kilns that has a particulate size range of 100% passing
a #8 sieve and 100% retained on a #80 sieve (a dust-
less product).
4. Ground lime - the product resulting from grinding the
larger sized material and/or passing off the fine
size. A typical size is substantially all passing a
#8 sieve and 40 to 60% passing a #100 sieve.
5. Pulverized lime - the product resulting from a more
intense grinding that is used to produce ground lime.
A typical size is substantially all passing a #20
sieve and 85 to 95% passing a #100 sieve.
6. Pelletized lime - the product made by compressing
quicklime fines into about one inch size pellets or
briquettes.
Hydrated Lime
As defined by the American Society for Testing and Materials,
hydrated lime is: "A dry powder obtained by treating quicklime
with water enough to satisfy its chemical affinity for water
under the conditions of its hydration."
The chemical composition of hydrated lime generally reflects
the composition of the quicklime from which it is derived. A_
high calcium quicklime will produce a high calcium hydrated lime
obtaining 72% to 74% calcium oxide and 23% to 24% water in
chemical combination with the calcium oxide. A dolomitic quick-
lime will produce a dolomitic hydrate. Under normal hydrating
conditions, the calcium oxide fraction of the dolomitic quick-
lime completely hydrates, but generally only a small portion_of
the magnesium oxide hydrates (about 5 to 20%). The composition
of a normal dolomitic hydrate will be 46% to 48% calcium oxide,
33% to 34% magnesium oxide, and 15% to 17% water in chemical
combination with the calcium oxide. (With some soft-burned
dolomitic quicklimes, 20% to 50% of the MgO will hydrate.)
A "special" or pressure hydrated dolomitic lime is also
available. This lime has almost all (more than 92%) of the
magnesium oxide hydrated; hence, its water content is higher and
its oxide content lower than the normal dolomitic hydrate.
Hydrated lime is packed in paper bags weighing 23 kg (50
Ib) net; however, it is also shipped in bulk.
64
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Quicklime is obtainable in either bulk carloads or tanker
trucks or in 36.3 kg (80 Ib) multiwall paper bags. Lump,
crushed, pebble, or pelletized lime, because of the large par-
ticle sizes, are rarely handled in bags and are almost univer-
sally shipped in bulk. The finer sizes of quicklime, ground,
granular, and pulverized, are readily handled in either bulk or
bags.
LIME STORAGE AND FEEDING
Depending on the type of lime, storage and feeding can be
either in bag or bulk. For small or intermittent applications,
bagged lime will probably be more economical. In new facilities,
bulk storage will probably be cost effective. Storage facilities
should be constructed such that dry lime is conveyed to the
point of use and then mixed or slaked. Generally, augers are
best for transporting either hydrated or pebble lime. Auger
runs should be horizontal or not exceeding an incline of 30°.
The feeder facilities, i.e., dry feeder and slaking or
slurry tank, should be located adjacent to the stabilization
mixing tank such that lime slurry can flow by gravity in open
channel troughs to the point of mixing. Pumping lime slurry
should be avoided. Slurry transfer distances should be kept to
a minimum. Access to feeder, slaker and/or slurry equipment
should be adequate for easy disassembly and maintenance.
MIXING
Lime/sludge mixtures can be mixed either with mechanical
mixers or with diffused air. The level of agitation should be
great enough to keep sludge solids suspended and dispense the
lime slurry evenly and rapidly. The principal difference be-
tween the resultant lime stabilized sludges in both cases is
that ammonia will be stripped from the sludge with diffused air
mixing. Mechanical mixing has been used by previous researchers
for lime stabilization but only on the pilot scale.
With diffused air mixing, adequate ventilation should be
provided to dissipate odors generated during mixing and stabili-
zation. Coarse bubble diffusers should be used with air supplies
in the range of 150-250 cu m/min per 1,000 cu m (150-250 cfm per
1,000 cu ft) of mixing tank volume. Diffusers should be mounted
such that a spiral roll is established in the mixing tank away
from the point of lime slurry application. Diffusers should be
accessible and piping should be kept against the tank wall to
minimize the collection of rags, etc. Adequate piping support
should be provided.
With the design of mechanical mixers, the bulk velocity
(defined as the turbine agitator pumping capacity divided by the
cross sectional area of the mixing vessel) should be in the
65
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range of 4.6 to 7.9 m/min (15 to 26 fpm). Impeller Reynolds
Numbers should exceed 1,000 in order to achieve a constant power
number.(25) The mixer should be specified according to the
standard motor horsepower and AGMA gear ratios in order to be
commercially available.
For convenience, Table 35 was completed which shows a
series of tank and mixer combinations which should be adequate
for mixing sludges up to 10% dry solids, a range of viscosity,
and Reynolds number combinations which were as follows:
Max. Reynolds number 10,000 @ 100 cp sludge viscosity
Max. Reynolds number 1,000 @ 1,000 cp sludge viscosity
TABLE 35. MIXER SPECIFICATIONS FOR SLUDGE SLURRIES
Tank Tank
Size, Diameter,
liters meters
18,925 2.9
56,775 4.2
113,550 5.3
283,875 7.2
378,599 8.0
Prime Mover, HP/
Shaft Speed, rpm
7.5/125
5/84
3/56
20/100
15/68
10/45
7.5/37
40/84
30/68
25/56
20/37
100/100
75/68
60/56
50/45
125/84
100/68
75/45
Turbine
Diameter ,
centimeters
81
97
109
114
135
160
170
145
155
168
206
157
188
201
221
183
198
239
Table 35 can be used to select a mixer horsepower and
standard AGMA gear combination depending on the volume of sludge
to be stabilized. For example, for a 18,925 1 (5,000 gal) tank,
any of the mixer-turbine combinations should provide adequate
66
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mixing. Increasing turbine diameter and decreasing shaft speed
results in a decrease in horsepower as shown.
Additional assumptions were that the bulk fluid velocity
must exceed 7.9 m/min (26 ft/min), impeller Reynolds number must
exceed 1,000, and that power requirements range from 0.5 to 1.5
HP per 3,785 1 (0.5-1.5 HP/1,000 gal) is necessary. The mixing
tank configuration assumed that the liquid depth equals tank
diameter and that baffles with a width of 1/12 the tank diameter
were placed at 90° spacing. Mixing theory and equations which
were used were after Badger^25), Hicks^26' and Fair.(27)
RAW AND TREATED SLUDGE PIPING, PUMPS, AND GRINDER
Sludge piping design should include allowances for in-
creased friction losses due to the non-Newtonian properties of
sludge. Friction loss calculations should be based on treated
sludge solids concentrations and should allow for thickening in
the mixing tank after stabilization. Pipelines should not be
less than 5.08 cm (2 in) in diameter and should have tees in
major runs at each change in direction to permit rodding,
cleaning, and flushing the lines. Adequate drains should be
provided. If a source of high pressure water is available
(either nonpotable or noncross-connected potable), it can be
used to flush and clean lines.
Spare pumps should be provided and mounted such that they
can be disassembled easily. Pump impeller type and materials of
construction should be adequate for the sludge solids concentra-
tion and pH.
Sludge grinding equipment should be used to make the raw
sludge homogenous. Sticks, rags, plastic, etc., will be broken
up prior to lime stabilization to improve the sludge mixing and
flow characteristics and to eliminate unsightly conditions at
the land disposal site.
67
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REFERENCES
1. Riehl, M. L. et al, "Effect of Lime Treated Water on
Survival of Bacteria," Journal American Water Works Assn.,
44,466 (1952).
2. Grabow, W.O.K. et al, "The Bactericidal Effect of_Lime
Flocculation Flotation as a Primary Unit Process in a
Multiple System for the Advanced Purification of Sewage
Works Effluent," Water Resources 3, 943 (1969).
3. Buzzell, J. C., Jr., and Sawyer, C. N., "Removal of Algal
Nutrients from Raw Wastewater with Lime," Journal WPCF, 39,
R16, 1967.
4. "How Safe is Sludge?" Compost Science 10 March-April 1970.
5. Kempelmacher, E. H. and Van Noorle Jansen, L. M., "Reduction
of Bacteria in Sludge Treatment," Journal WPCF 44, 309
(1972) .
6. Evans, S. C., "Sludge Treatment at Luton," Journal Indust.
Sewage Purification 5, 381, 1961.
7. Farrell, J. B., Smith, J. E., Hathaway, S. W., "Lime Stab-
ilization of Primary Sludges," Journal Water Pollution
Control Federation, Vol. 46, No. 1, January 1974, pp 113-
122.
8. Paulsrud, B. and Eikum, A. S., "Lime Stabilization of
Sewage Sludges," Norwegian Institute for Water Research
Volume 9, pp 297-305, 1975.
9. Counts, C. A., Shuckrow, A. J., "Lime Stabilized Sludge:
Its Stability and Effect on Agricultural Land," EPA-670/
2-75-012, April 1975.
10. Noland, R. F., Edwards, J. D., "Stabilization and Disinfection
of Wastewater Treatment Plant Sludges," USEPA Technology
Transfer Design Seminar Handout, May 1977.
11. USEPA, "Methods for Chemical Analysis of Wastes," USEPA,
Cincinnati, Ohio, 1974.
68
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12. Standard Methods for Examination of Water and Wastewater,
13th & 14th Editions, AWWA, APHA, WPCF, American Public
Health Association, Washington, D.C.
13. "Enumeration of Salmonella and Pseudomonas aeruginosa,"
Journal WPCF, Vol #46, No. 9, Sept. 1974, pp 2163-2171.
14. Brown, R. E. et al, "Ohio Guide for Land Application of
Sewage Sludge," Ohio Agricultural Research and Development
Center, Wooster, Ohio, 1976.
15. Sommers, L. E., "Principles of Land Application of Sewage
Sludge," USEPA Technology Transfer Design Seminar Handout,
May 1977.
16. Sommers, L. E., et al, "Variable Nature of Chemical
Composition of Sewage Sludges," Journal of Environmental
Quality 5:303-306.
17. Stern, Gerald, "Reducing the Infection Potential of
Sludge Disposal."
18. U. S. Environmental Protection Agency, "Process Design
Manual for Sludge Treatment and Disposal," USEPA Technology
Transfer, Oct., 1974.
19. U. S. Environmental Protection Agency, "Municipal Sludge
Management: Environmental Factors," Federal Register,
Vol. No. 41, No. 108, p. 22533.
20. Zenz, D. R., Lynam, B. T., et al, "USEPA Guidelines on
Sludge Utilization and Disposal - A Review of Its Impact
Upon Municipal Wastewater Treatment Agencies," presented
at the 48th Annual WPCF Conference, Miami Beach, Fla., 1975.
21. Trubnick, E. H., Mueller, P. K., "Sludge Dewatering
Practice," Sewage and Industrial Wastes 30, 1364 (1958).
22. Sontheimer, H., "Effects of Sludge Conditioning with Lime
on Dewatering," Proc. 3rd Int'l Conference, Water Pollution
Research, Munich, 1966, in Advances in Water Pollution
Research.
23. "Application of Sewage Sludge to Cropland: Appraisal of
Potential Hazards of the Heavy Metals to Plants and
Animals," Council for Agricultural Science and Technology
Report No. 64, Iowa State University.
24. National Lime Association, "Lime Handling Application and
Storage in Treatment Processes Bulletin 213," National Lime
Assoc., Washington, B.C., pp 1-3.
69
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25. Badger and Banchero, "Introduction to Chemical Engineering,"
page 614, McGraw-Hill, 1955.
26. Hicks, R. W. et al, "How to Design Agitators for Desired
Process Response," Chemical Engineering, April 26, 1976, pp
103-106 ff.
27. Fair, G. M. and Geyer, J. C., "Water Supply and Wastewater
Disposal," John Wiley & Sons, New York, 1956.
70
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APPENDIX
13.0
\2.Q
11.0-
10.0- •
I
Q.
6% PRIMARY SLUDGE
3.5% PRIMARY SLUDGE
3% PRIMARY SLUDGE
4.5% PRIMARY SLUDGE
PRIMARY SLUDGE
PRIMARY SLUDGE
3% PRIMARY SLUDGE
3.5% PRIMARY SLUDGE
4% PRIMARY SLUDGE
4.5% PRIMARY SLUDGE
5% PRIMARY SLUDGE
6% PRIMARY SLUDGE
1,000 2pOO 3,000 4,000
DOSAGE Co (OH)2 MG/L
5,000
Figure 5. Lime Dosage vs pH Primary Sludge
71
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13.0
12.0 •
X
ex
6.0
2,000
4pOO 6,000 8,000
DOSAGE Ca(OH)2 MG/L
10,000
Rgure 6. Lime Dosage ys pH Anaerobic Digested Sludge
72
-------
13.0
12.0
11.0
10.0
i
a
9.0
8.0
7.0-
6.0
1%
1.5%
1,000 2,000 3,000 4,000
DOSAGE Ca (OH)2 MG/L
5,000
Rgure 7. Lime Dosage vs pH Waste Activated Sludge
73
-------
13.0
12.0
1,000
2,000 3,000
DOSAGE Ca (OH)2 MG/L
4,000
5,000
Figure 8. Lime Dosage vs pH Septage
74
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TECHNICAL REPORT DATA
ft'lease read Instructions on the reverse before completing)
EPA-600/2-78-171
AND SUBTITLE
Full Scale Demonstration of Lime Stabilization
3. RECIPIENT'S ACCESSIOI^NO.
5. REPORT DATE
, September 1978 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
Richard F. Nbland
James D. Edwards
8. PERFORMING ORGANIZATION REPORT NO.
PNAME AND ADDRESS
Burgess & Niple, Limited
Consulting Engineers & Planners
5085 Reed Road
Columbus, Ohio 43220
10. PROGRAM ELEMENT NO
1BC611
11. CONTRACT/GRANT NO.
68-03-2181
12. SPONSORING AGENCY NAME AND ADDRESS ~ '
Municipal Environmental Research Laboratory—-Cin.,OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
15. SUPPLEMENTARY NOTES ~~~ ~
13. TYPE OF REPORT AND PERIOD COVERED
4. SPONSORING AGENCY CODE
EPA/600/14
Project Officer: Steven W. Hathaway (513) 684-7615
16. ABSTRACT
The project objective was to demonstrate and evaluate the feasibility economics
and benefits of stabilizing primary, waste activated, septic, and^erobicaS SS'
sludges by lure addition. The project confirmed the findings of pre^SuS Jaborat
iSh^ f tS ** fOCUSed °n ** aPPlic^ion of lin£ stabilization and ?a5?dis
*•*"-* Plant OPerat^ * *" *»* * 3,785 to '
of
chemica1' bacterial, and pathological
oem dT Sted.slud^es- ^ effects^of log-
on the cdiemical and bacterial characteristics of lime stabilized sludges were
mined Ultimate disposal of all lime stabilized sludges was aoocapliSn?
as a liquid on agricultural land and on controlled test plots.
Lime stabilized sludges had negligible odor, minimum potential for pathoaen re-
17.
DESCRIPTORS
KEY WORDS AND DOCUMENT ANALYSIS
Sludge
Treatment
Sludge Disposal
3. DISTRIBUTION STATEMENT
Release Unlimited
EPA Form 2220-1 (9-73)
b.lDENTIFIERS/OPEN ENDED TERMS
Lime Stabilization
Sludge Stabilization
Sludge Treatment
Land Application
19- SECUHI I Y CLASS (ThisReport)
Unclassified
SECURITY CLASS (Thispage)
Unclassified
COSATl Field/Gr
13B
21. NO. OF PAGES
89
22. PRICE
* U.S. GOVERHUHIT PRINTING OFFICE; 1978— 757-140/1439
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