ROBERT A. TAFT WATER RESEARCH CENTER
REPORT NO. TWRC-6
COST OF
WASTEWATER
TREATMENT PROCESSES
ADVANCED WASTE TREATMENT RESEARCH LABORATORY • VI
U.S. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
OHIO BASIN REG/ON
Cincinnati, Ohio
-------
COST OF WASTEWATER TREATMENT PROCESSES
by
DORR-OLIVER, INCORPORATED
David DiGregorio, Project Engineer
The Advanced Waste Treatment Research Laboratory
Robert A. Taft Water Research Center
This report is submitted in
fulfillment of Contract No.
14-12-60 between the Federal
Water Pollution Control
Administration and Dorr-
Oliver, Incorporated.
l':S- ^n(y'r;'nnr'-f-! prc^ction Agency
U. S. Department of the Interior
Federal Water Pollution Control Administration
Cincinnati, Ohio
December, 1968
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FOREWORD
In its assigned function as the Nation's principal natural resource
agency, the United States Department of the Interior bears a special obli-
gation to ensure that our expendable resources are conserved, that renew-
able resources are managed to produce optimum yields, and that all resources
contribute their full measure to the progress, prosperity, and security of
America -- now and in the future.
This series of reports has been established to present the results of
intramural and contract research studies carried out under the guidance of
the technical staff of the FWPCA Robert A. Taft Water Research Center for
the purpose of developing new or improved wastewater treatment methods.
Included is work conducted under cooperative and contractual agreements with
Federal, state, and local agencies, research institutions, and industrial
organizations. The reports are published essentially as submitted by the
investigators. The ideas and conclusions presented are, therefore, those of
the investigators and not necessarily those of the FWPCA.
Reports in this series will be distributed as supplies permit.
Requests should be sent to the Office of Information, Ohio Basin Region,
Federal Water Pollution Control Administration, 4676 Columbia Parkway,
Cincinnati, Ohio 45226.
ii
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CONTENTS
FOREWORD ii
ABSTRACT iv
INTRODUCTION 1
METHOD OF APPROACH 2
SEWAGE PRETREATMENT 3
Comminution 3
Grit Removal 3
Detritus Removal 3
PRIMARY TREATMENT 7
Primary Sedimentation 7
Sludge Digestion 7
SECONDARY TREATMENT 11
Activated Sludge 11
Trickling Filtration 16
Final Clarification 16
SLUDGE DEWATERING 19
Elutriation 19
Vacuum Filtration 19
Centrifugation 25
Sludge Drying Beds 30
SLUDGE COMBUSTION 31
NUTRIENT REMOVAL 37
TERTIARY TREATMENT 40
Sand Filtration 40
Carbon Adsorption 44
Membrane Ultrafiltration 44
PACKAGE SEWAGE TREATMENT 50
iii
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ABSTRACT
New capital cost information for conventional and some advanced
wastewater treating processes has been collected and correlated in terms
of capacity or physical size. Operating costs have been calculated for
some of the processes. Conventional processes considered include comminu-
tion, grit removal, primary settling, biological treatment by activated
sludge and trickling filter, final settling, and sludge treatment and
disposal,, Advanced processes include phosphate extraction, chemical
clarification and sand filtration, carbon adsorption, and membrane ultra-
filtration.
Most of the cost information was obtained from sales information of
Dorr-Oliver, Incorporated. Supplementary data from other sources were
utilized, however, when necessary.
IV
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INTRODUCTION
An important goal in the wastewater treatment field today is the
economic optimization of treatment systems. To optimize a treatment
system requires reasonably accurate estimates of the capital and operating
costs of the system components. Although some of the necessary cost
information is available in the literature, much of it remains in the hands
of equipment manufacturers. In this report an attempt has been made to
present cost correlations that include in most cases unpublished data from
Dorr-Oliver, Incorporated. Other data sources have been used when necessary
for completeness.
It must be pointed out that the costs presented here may differ
slightly from independent estimates published by FWPCA. The differences
probably result from the fact that assumptions must be made about certain
factors comprising capital and operating costs. These assumptions vary
among cost estimators. The assumptions made here are based upon the
experience of Dorr-Oliver and are considered realistic.
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METHOD OF APPROACH
An extensive survey of Dorr-Oliver sales information yielded a large
volume of data relating equipment costs to loading and equipment size.
Costs, including profit and installation, were updated by applying factors
derived from known equipment price increases. Construction costs, including
material, labor, profit, engineer's and contractor's fees, were estimated
from company experience and updated with Engineering News Record Construction
Cost Indexes. The information provided is concerned only with the unit pro-
cess under consideration. No effort was made to evaluate the costs of land,
excavation or inter-process requirements.
The method of least squares was used to correlate the generated data.
In many cases the data could be described by a straight line, Y = aX + b, on
an arithmetic or logarithmic plot. Where this description was not satis-
factory, an equation of the form Y = 1 was used. A computer program
aX + b
was written to facilitate the least square computations.
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SEWAGE PRETREATMENT
Comminution
Comminutors are sized on a volume flow basis, therefore, the plot of
cost versus average daily flow is a good cost performance representation for
most domestic sewage applications. Insofar as comminutors must be capable
of handling peak flows with a minimum head loss, design flow with respect to
comminutors may be estimated at 2.5 times the average daily flow for reason-
able size plants. Figure 1 shows a graphical representation of the cases
studied for the comminution process. The cost as shown is for equipment
only. No consideration was given to special housing or concrete structures.
The statistical equation computed was:
Log (Cost) = 0.14 Log (MGD) + 1.76
Cost = Hundreds of dollars
Grit Removal
The capital costs for hydrocyclone degritting are shown on Figure 2.
This cost includes equipment and installation only since there are essen-
tially no concrete requirements. The operating costs for this type of
degritter are very low. Hydrocyclones, utilized for degritting purposes,
will make separations in the range of 150 mesh or 104 microns on sand
(hydrocyclones are available for separations as fine as 5 microns). This
is based on a 2.7 specific gravity and solids in the feed less than 2570
by weight. The equation computed was as follows:
Log (Cost) = 1.58 - 0.65 Log (MGD)
Cost = Hundreds of dollars/MGD
Detritus Removal
Figure 3 shows the capital costs for detritors. The cost includes
all concrete plus detritus collecting and separating equipment. The unit
will usually collect all grit coarser than 65 mesh. No more than 3% by
weight of putrescible organic matter will normally be contained in the grit.
The equation computed was:
Log (Cost) =
0.211 Log (Area) + 0.073
Cost = Dollars/square foot
Area = Square feet
-------
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I I I I I I I I J
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LOG (COST) =0.14 LOG (AVERAGE FLOW) + 1.76
FEB. 68 DOLLARS
1
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0.5 1 10
AVERAGE DAILY FLOW IN MILLIONS OF GALLONS PER DAY
Capital Cost of Comminution Equipment
Versus Average Daily Flow
50
Figure 1
-------
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AVERAGE PLOW IN MILLIONS OP GALLONS PER DAY
50
Capital Cost of Hydrocyclone Degritting
Equipment Versus Design Flow
Figure 2
-------
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LOG (COST) =
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0.211 LOG (AREA) + 0.073
FEB. 68 DOLLARS
I I
10
Cost includes concrete and detritus
collecting and separating equipment
_L
J_L
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J 1 » l l t I J
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10
100 1000
TANK FLOOR AREA IN SQUARE FEET
Capital Costs of Detritors Versus Tank Floor Area
5000
Figure 3
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PRIMARY TREATMENT
Primary Sedimentation
The capital cost of primary sedimentation is shown on Figure 4. Tank
floor surface area was plotted against total cost in dollars per square foot.
Performance of primary sedimentation is highly variable and subject to
local conditions and sewage composition. Figure 5 represents actual operating
data of primary clarifiers. While the curve does not permit absolute evalua-
tion of clarification performance, it does present a good performance approxi-
mation and follows design criteria recommended by Dorr-Oliver. For example,
primary clarifiers will normally provide 50-60% removal of total suspended
solids when the overflow rate (OR) equals 100 gal./ft /day per foot of side
water depth (SWD).
The equation computed for the capital cost of primary sedimentation
was :
Log (Cost) = o.233 Log (Area) + 0.758
Cost = Dollars/square foot
Area = Thousands of square feet
Digestion
Figure 6 shows the capital costs of sludge digestion. Total cost for
this process includes all heating, mixing and gas requirements, sludge pumps,
concrete tank requirements and a digester cover. The computed equation was:
Log (Cost) = o.31 Log (Volume) + 0.37
Cost = Tenths of dollars/cubic foot
Volume = Thousands of cubic feet
-------
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K
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50
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LOG (COST) =
0.233 LOG (AREA) + 0.758
FEB. 68 DOLLARS
EH
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PL,
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Cost includes concrete and collecting equipment
1
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J I t I I 1 I I
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TANK FLOOR AREA IN THOUSANDS OF SQUARE FEET
50
Capital Cost of Primary Sedimentation
Versus Tank Floor Area
8
Figure 4
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SECONDARY TREATMENT
Activated Sludge
The activated sludge cost analysis is summarized on Figures 7-10.
These curves were generated in a different manner from most work. A
design was performed for plant sizes ranging from 0.5 to 20 MGD using
Dorr-Oliver design criteria and available equipment information,, It was
assumed that the aeration step would follow primary sedimentation, the BOD
removal in the primary step would be 307, and that the activated sludge
system would remove 90% of the remaining BOD. Tank depth was about 15 feet.
The capital cost of activated sludge shown on Figure 7 includes con-
crete requirements and mechanical aerator costs. Figures 8-9 represent
blower capital (including prime movers) and power costs respectively.
Aerator power costs (aerating and mixing) are shown on Figure 10. Power
was assumed at 1.5 cents/kwh. The computed equations are given below.
Activated sludge capital cost:
Log (Cost) = 0.806 Log (Volume) + 0.306
Cost = Thousands of dollars
Volume = Thousands of cubic feet
Blower capital cost:
Cost
Cost
Capacity
Blower operating cost:
Cost
Cost
Capacity
Aerator operating cost:
Cost
3.58 Capacity + 2.53
Thousands of dollars
Thousands of SCFM
0.68 Capacity +0.14
Dollars/hr
Thousands of SCFM
= 1.42
(Volume )
Cost =
100,000
Dollars/hr
Volume = Cubic feet
11
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LOG (COST) = 0.806 LOG (VOLUME) + 0.306
FEB. 68 DOLLARS
10
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Cost includes concrete and mechanical aerators
» 1 I I > t M
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100 1000
TOTAL VOLUME IN THOUSANDS OF CUBIC FEET
Capital Cost of Activated Sludge
Versus Tank Volume
12
Figure 7
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Trickling Filtration
Figure 11 represents the capital cost of trickling filtration.
Included in this cost are concrete and equipment requirements underdrainage
and media. The media bed was assumed to be rock at a cost of 3 dollars /ton
(4.5 dollars/cubic yard). The cost of rock media is extremely variable.
Its cost, more than anything else, is a function of how far it has to be
shipped to the plant location. Underdrainage blocks were assumed to cost
1 dollar/square foot. This will also vary considerably with freight charges.
Media plus underdrainage, at the assumed prices, constitute about 30% of the
total trickling filter cost for a reasonable size unit. It is therefore
recommended that some consideration be given to possible price variations
of these items .
The degree of purification realized by trickling filtration is
affected by weather conditions, sewage composition and operating policy,
The effects of high rate operation or recirculation on performance are
great. Fair and Geyer state that these effects can be evaluated using the
following equation:
P
y x 2 9
VF =
13800
V = Acre-feet of filter
F = Recirculation factor
y0 = Daily BOD loading
P,., = Degree of purification
The equation computed for capital costs of trickling filters was:
Log (Cost) = o.l8 Log (Area) +0.78
Cost = Dollars/square foot
Area = Thousands of square feet
Final Clarification
The capital costs of final clarification are shown on Figure 12 and
include equipment and concrete construction costs. The computed equation was
Log (Cost) = o.20 Log (Area) + 0.57
Cost = Dollars/square foot
Area = Hundreds of square feet
16
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T I I I I I I J
LOG (COST) =
0.18 LOG (AREA) + 0.?8
FEB. 68 DOLLARS
!_ Cost includes concrete, distributor,
media and underdrainage
1 l I I t 1 I i I
1 1 I I I l l
.1
10
TANK FLOOR AREA IN THOUSANDS OF SQUARE FEET
Capital Cost of Trickling Filtration
Versus Tank Floor Area
17
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T I I T III! V
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SLUDGE DEWATERING
Elutriation
Sludge elutriation is a washing operation whereby substances that
interfere physically with chemical conditioning and filtration are washed
out of the sludge. There is a reduction in required chemical conditioning
of sewage sludge when filtration is preceded by elutriation,,
Since the introduction of polymers in place of dewatering aids such
as ferric chloride, sludge elutriation has been regarded highly impractical
and unnecessary. Chemical conditioners must initially satisfy the coagulant
demand of the liquid fraction of sludge which is exerted by the alkalinity
of bicarbonates. Polymers have the advantage of not reacting with the
alkalinity thus reducing chemical (polymer) requirements without the elutria-
tion process. With polymer flocculents continually improving sludge elutria-
tion will prove to be unnecessary and both physically and economically
unattractive.
An economic comparison of dewatering using ferric chloride and lime
yielded the following costs:
Primary, digested sludge 9 Dollars/Ton Dry Solids
Primary, digested, elutriated
(including amortized capital cost) 4.5 Dollars/Ton Dry Solids
Primary, digested (using polymers) 4.5 Dollars/Ton Dry Solids
The elutriation step was assumed to be the two stage countercurrent type
and chemical requirements were computed from Center's Equations^. The
sludge was assumed to have the following characteristics: pH = 7, solids =
57», volatile content = 457<>, alkalinity of digested sludge = 3000 ppm and
alkalinity of elutriated sludge = 300 ppm (9070 removal). Ferric chloride
was taken at 4 cents/lb0 and lime at 1 cent/lb.
What these results indicate is that there is a choice between
elutriating before dewatering or dewatering using polymers. Considering
the nature of the elutriation process, the space required, the additional
operating equipment and so on, the responsible engineering approach will
be to use polymer sludge conditioning.
Vacuum Filtration
Figure 13 shows the capital costs of vacuum filtration. Included
are all necessary piping and pumps associated with the operation of the
vacuum filter.
Operating costs were divided into power and chemical costs. Power
costs in cents per hour of operation are plotted on Figure 14. Chemical
19
-------
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T 1 i I I I I I J
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CL,
CO
K
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3
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EH
CO
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LOG (COST) = 0.65 - 0.66 LOG (AREA)
FEB. 68 DOLLARS
Cost includes filter, pumps and piping only
.1
1 1 1 t 1 I
.1
1 10
FILTER AREA IN HUNDREDS OF SQUARE FEET
Capital Cost of Vacuum Filtration
Versus Filter Area
20
Figure 13
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requirements for vacuum filtration are highly variable and subject to chemical
and physical characteristics of the sludge. Ferric chloride requirements
(percent of dry solids in feed) may be found from Center's Nomograph^ on
Figure 15 or by calculation:
Total FeCl3 (70) = Liquid Demand % + Solids Demand %
where Liquid Demand (%) = "2° (%) X PPm Alkalini^ * °'OOQ1 * *'*
Solids in Sludge (%)
j r. 1 • j ™ A t°i\ 1.6 x % Volatile Matter (Dry Basis)
and Solids Demand (/i) = „ —— r^rr* <-
% Ash (Dry Basis)
Lime (hydrated) dosage may be approximately determined by knowing the percent
solids, methyl orange alkalinity and pH:
,,. „ ,. . , - CO? (ppm) x 100 x 1.68
(1) Percent lime required for C09 = —L ^vv
z % Solids x 1,000,000
i r,n / nn \ Alkalinity (ppm as CaCOo)
where C00 (as G09) = _—_ ii
1 *- Ratio
(Ratio from Figure 16)
(2) Percent lime required for ammonium carbonate =
Ammonium Carbonate (ppm) x 100 x 0.74
% Solids in Sludge x 1,000,000
where Ammonium Carbonate Alkalinity = Methyl Alkalinity - C00 Alkalinity
•JtHt-
.„. _, . - . , _ _ „, Atomic Wt. Lime x 3 x FeClo Used
(3) Percent lime required for FeClo =
Atomic Wt. FeCl3 x 2
(4) Percent lime required for solids demand = °L solids in sludge. Total
percent lime as Ca(OH)2 required =(l)+(2)+(3)+(4). This method will only
yield approximate chemical requirements. Actual filter performance, more
than anything else, will determine quantities of chemicals used.
Performance of vacuum filters is subject to many variables. The
physical and chemical characteristics of the sludge will greatly affect
the production rate of filtration. Table 1 provides rough figures of
production based on degree of treatment., These are very general rates
and can vary with chemical dosage, type of chemical conditioner, nature
of solid content and chemical content of sludge among others.
*Methyl Orange Alkalinity (ppm)
I'cif
FeClo solids demand only used when computing lime and is considered
minimum. Many operators use much more to increase the filter rate.
22
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TABLE 1
VACUUM FILTER PRODUCTION
Type of Pretreatment Production Ib Dry Solids/ft2/hr
Raw Primary 5
Raw Primary Plus
Trickling Filtration 4
Raw Primary Plus
Activated Sludge 205
The computed equations for vacuum filtration were:
Capital Cost
Log (Cost) = 0.65 - 0066 Log (Area)
Cost = Hundreds of doliars/square foot
Area = Hundreds of square feet
Power Coat
Cost =0.15 (Area)
Cost = cents/hr
Area = square feet
Centrifugation
The capital costs for dewatering by centrifugation are plotted on
Figure 17. Only the cost of the centrifuge was considered.
Polymer (polyelectrolytes) costs were based on three types of sludge -
that produced from: (1) primary treatment (raw), (2) primary plus trickling
filtration and (3) primary plus aeration. These costs are shown on Figures
18-20, respectively. The upper and lower limits indicate the probable range
while the solid line indicates the average chemical cost for the various
types of sludges.
Power costs for centrifuges normally used in sanitary applications
run about 90 cents per ton of dry solids (1.5 cents/kwh).
Table 2 gives a good indication of the performance of centrifugal
dewatering.
25
-------
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K
g
1000
CL,
Q
525
B
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PL,
§
O
Q
EH
OQ
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H
Pu
U
100
LOG (COST) = 2.50 - 0.193 LOG (INFLUENT FLOW)
FEB. 68 DOLLARS
Cost includes only the centrifuge
10 L
_L
J I I Mill
» 1 I l > l l J
J L
100
1000 10000
INFLUENT FLOW IN POUNDS DRY SOLIDS PER HOUR
Capital Cost of Centrifugation
Versus Influent Flow to Centrifuge
26
Figure 17
-------
1 i i i i i i i r
i r
10
8
w
W
05
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CO
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05
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COST - 0.0005 (INFLUENT FLOW)
I I l I t 1 I l I
lower limit = 0
1 l l i i i i i j
100
1000 10000
INFLUENT FLOW IN POUNDS OF DRY SOLIDS PER HOUR
Cost of Polymer For Treatment of Primary
Sludge For Dewatering by Centrifugation
27
Figure 18
-------
1 I I I 1 I I I I
I I I I I 1 J
COST = 0.006 (INFLUENT FLOW)
100
O
a
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ft
O
O
EH
VI
8 10
w
1
100
J
I I I [ 1 I L I
J I ! I I 1 I J
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1000 10000
INFLUENT FLOW IN POUNDS OF DRY SOLIDS PER HOUR
Cost of Polymer For Treatment of Primary Plus
Trickling Filter Sludge For Uewatering by
Centrifugation
28
Figure 19
-------
500
I I
1 I I I I \
t r
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100
K
W
ft
OT
Q
Sz;
M
H
02
O
w
Oi
ich
COST = 0.008 (INFLUENT FLOW)
» 1 1 t I t 1 M
J 1 I 1 1 » 1
100 1000 10000
INFLUENT FLOW IN POUNDS OF DRY SOLIDS PER HOUR
Cost of Polymer For Treatment of Primary
Plus Activated Sludge For Dewatering by
Centrifugation
29
50000
Figure 20
-------
TABLE 2
SOLIDS RECOVERY BY CENTRIFUGATION
Percent Recovery
(Total Solids - Dry Basis)
Type of Pretreatment W/0 Chemicals W/Chemicals
Raw Primary 85-95 90-100
Raw Primary Plus
Trickling Filtration 65-85 90-100
Raw Primary Plus
Activated Sludge 65-80 90-100
The computed equation for the capital cost of centrifugation was:
Log (Cost) = 2.50 - 0.193 Log (Influent flow)
Cost = Dollar/lb/hr
Influent flow = Ib Dry Solids/hr
The computed equations for the cost of chemicals for dewatering by
centrifugation were:
Primary sludge:
Cost = 0.0005 (Influent flow)
Primary plus trickling filtration sludge:
Cost = 0.006 (Influent flow)
Primary plus waste activated sludge:
Cost = 0.008 (Influent flow)
where:
Cost = Dollars
Influent flow = pounds of dry solids per hour
Sludge Drying Beds
Sewage sludge dewatering using sludge drying beds is becoming impractical.
Drying beds, either glass covered or open, are constructed with a system of
underdrains covered by a layer of graded rock from 12 to 18 inches deep followed
by a layer of sand 6 to 12 inches deep. The area of the bed varies to meet
individual conditions of sludge quantities and climatic conditions, but is
usually figured on 1 to 2 square feet per capita. Dried sludge is removed from
the bed by hand labor or mechanical lift devices. Land cost and availability
greatly affect the cost of drying beds.
30
-------
SLUDGE COMBUSTION
The capital costs of fluid bed combustion are shown on Figure 21.
As demonstrated on the figure, there is a decrease in the capital cost
as the solid content of the feed increases.
The following processes are included in this cost:
Solids preparation, including comminution and pumping
Solids dewatering, including centrifugation
Combustion air supply
Solids combustion, including conveying, feeding and
burning
Stack gas treatment, including ash removal, gas scrubbing
and ash handling
Also included are all electrical and piping requirements.
Operating costs for fluid bed combustion were based on three types
of sludges - those produced from (1) primary treatment (raw), (2) primary
treatment plus trickling filtration and (3) primary treatment plus aeration.
This was done since the dewatering characteristics of sludges are a function
of degree of treatment.
The operating costs shown on Figures 22 through 24 include fuel,
chemicals and power. Fuel, usually No. 2 oil at 11.5 cents/gal, is used
to maintain operating temperatures when the heat value of the burning
sludge is inadequate for autogenous burning. Chemicals (polyelectrolytes)
are used to control the performance of the dewatering equipment. Power
was assumed to be 1.5 cents/kwh. These costs were based on Ibs of dry
solids entering the reactor and consideration was given to heat recover-
able from the sludge. The upper and lower limits give some indication as
to the range which may be experienced. The solid line indicates the average
cost.
Labor costs will vary considerably depending upon operation, but 0.25
man-hours per hour of operation is generally used. Labor costs were not
included in Figure 22 - 24.
The equations computed for capital costs of fluid bed incineration
are given below:
With 22% solid feed:
Log (Cost) = ., T . , ,.., -—7^ r ., ,.
& 1.14 Log (Influent flow) -1.64
With 40% solid feed:
Log (Cost) =
2.18 (Log Influent flow) -4.38
Cost = Hundreds of dollars/lb/hr
Capacity = Lb Dry Solids/hr
31
-------
K
I
K
W
CU
O
CO
K
P
fe
0 100
P
O
ou
K
W
IX,
CO
8
W 10
K
P
55
CO
O
o
H
O
1 1 1 1 1 1 i 1 1
i i r i i i i 11
l I T
For 22$ solids feed: A - A
1
LOG COST =
1.14 LOG (INFLUENT FLOW) - 1.64
For 40^ solids feed: B - B
LOG COST =.
2.18 LOG (INFLUENT FLOW) - 4.38
FEB. 68 DOLLARS
Cost includes solids preparation (comminution)
and dewatering, combustion (conveying, feeding,
burning and air supply), stack gas treatment
(ash removal, gas scrubbing and ash handling)
and all electrical, piping and pumping require-
ments.
_L
j » i i i i n
J 1 l I I M I
_L
J L
100 1000 10000
INFLUENT FLOW TO REACTOR IN POUNDS OF DRY SOLIDS PER HOUR
Capital Cost of Fluid Bed Sludge Combustion
Versus Influent Flow to Reactor
32
Figure 21
-------
T 1—I I I I I I
1 1 1—I Mill
10
K
t>
O
PL,
K
O
S5
H
EH
.1
COST = 0.002 (INFLUENT PLOW)
Cost includes power, chemicals and oil
requirements
1
I i I I 1
i 1 i
t I i
100
1000 10000
INFLUENT FLOW IN POUNDS DRY SOLIDS PER HOUR
Operating Cost For Combustion of Primary Sludge
Versus Reactor Influent Flow
33
Figure 22
-------
T I I I | I I I \ I T I I II I I J I I I
ffi 1 OOf-
CD
K
W
Cu
CO
K
H
EH
CO
O
O
10
H
O
COST = 0.0087 (INFLUENT PLOW)
/ Cost includes power, chemicals and oil
/ requirements
1
100
i l i i l t l t l I I 1 I I I 1 I 1 I I L
1000 10000
INFLUENT FLOW IN POUNDS DRY SOLIDS PER HOUR
Operating Cost For Combustion of Primary
Plus Trickling Filter Sludge Versus
Reactor Influent Flow
34
Figure 23
-------
1 1—I—i I I I IJ
T 1 1—I I I I I I
COST = 0.0122 (INFLUENT FLOW)
100
g
Ol
CO
8
2
H
EH
CO
O
O
O
H
X
Cost includes power, chemicals and oil
requirements
1 I 1 I 1 1 i II
1000
» 1 1 I I i I ]
100
10000
INFLUENT FLOW IN POUNDS DRY SOLIDS PER HOUR
Operating Cost For Combustion of Primary
Plus Waste Activated Sludge Versus
Reactor Influent Flow
35
Figure 24
-------
The equations computed for the operating costs of fluid bed incineration
including power, chemicals and oil requirements are given below:
Primary sludge:
Cost = 0.002 (Influent flow)
Primary plus trickling filter sludge:
Cost = 0.0087 (Influent flow)
Primary plus waste activated sludge:
Cost = 0.0122 (Influent flow)
where:
Cost = Dollars/hr
Influent flow = Lb dry solids/hr
-------
NUTRIENT REMOVAL
3
The comparative costs for phosphorous removal are shown in Table 3.
In recent years, significant strides have been made in the basic approaches
to phosphate removal. New concepts and arrangements of treatment plant unit
processes have reduced the cost and have made it feasible for government
and state agencies to consider enforcement of phosphate removal standards.
TABLE 3
COMPARATIVE COSTS FOR PHOSPHOROUS REMOVAL
Added Cost for
Phosphorous Removal
(cents/1000
Method Capital Operating
Phosphate Extraction Process 0 1.0
Activated Sludge Chemicals 1.5 3oO
Tertiary System Chemicals 1.0 6<,5
Land Disposal 9.0 3.0
Ion Exchange 1,0 23.0
The tertiary system approach consists of utilizing metallic coagulants
in conjunction with polymers. Removal is based on fixed chemical stoichio-
metrics since the majority of the poly- and metaphosphates are hydrolized in
aeration basins and appear as soluble orthophosphate in the tertiary system.
The activated sludge method consists of the addition of alum to the
aeration basin. Removal is realized by chemical combination and incorporation
of phosphorous in the activated sludge cell.
The phosphate extraction process (PEP) is a Dorr-Oliver, proprietary
approach. The complete PEP system, as it is presently being marketed, is
shown on Figure 25. Except for the recirculation of chemical sewage floe
around the primary clarifier and the use of flocculating clarifier, there
is essentially no difference from conventional treatment flowsheets.
The PEP approach takes advantage of low ratios of soluble to total
phosphate in the primary clarifier. A coagulant, such as lime, is added
to the primary clarifier where gross removal of phosphorous is efficiently
completed by adsorption and settling. Residual phosphorous is then scavenged
by the activated sludge culture.
The PEP process operates at a much lower chemical dosage than other
tertiary systems. There are two reasons for this: (1) lime dosing in the
37
-------
m
bD
•H
d §
° '•£
+j fu
rt U
f—I -rH
H VH
51
W
U3
<
o
1
00
fi
•2 CuO
M
o ,^
u <->
CuO
c
0)
Q
ao
fi
(U
0)
CO
nJ
u
•r-(
g
rt
X!
ft
CO
o
a
O
00
-------
primary clarifier results in the extraction of that portion of the phosphate
(60-707o) which is easiest to remove and (2) recirculation of chemical sewage
sludge around the primary clarifier results in an increased chemical effici-
ency (100-150%). The flocculator-clarifier step removes 60-70% of the BOD
because of the increased chemical efficiency which results in a $10/MG (1
cent/1000 gal.) savings in secondary treatment and sludge handling facilities.
Consequently, while the PEP approach runs about 2 cents/1000 gal. for operating
and capital costs, the 1 cent/1000 gal. savings realized from high BOD removal
across the primary step results in a net added cost for phosphorous removal of
about 1 cent/1000 gal. which is essentially operating cost.
For plants incorporating the fluid bed sludge combustion system, there
is a capability for lime recovery for chemical reuse» However, this is not
economically rewarding for plants utilizing small quantities of chemicals.
For larger plants, lime recovery could drop the cost of phosphorous removal
to 0.5 cents/1000 gal.
The PEP approach removes about 80% of the phosphorous coming into the
plant. By adding a tertiary step, 99% removal can be realized without
affecting PEP's relative economic attractiveness.
39
-------
TERTIARY TREATMENT
Sand Filtration
Tertiary treatment by sand filtration is presented on the basis of
both small and large plants. The installed capital and operating costs
shown on Figures 26-27 are appropriate for plants as large as 100,000 GPD
and include rapid sand filtration plus chlorination. The equations computed
were:
Capital Cost
Log (Cost) = 0.631 Log (Influent flow) + 0,305
Cost = Thousands of dollars
Influent flow = Thousands of gallons per day
Operating Cost
Log (Cost) = 1>763 _ 0.575 Log (Infiuent flow)
Cost = Hundreds of dollars per year
Influent flow = Thousands of gallons per day
The total installed treatment cost on Figure 28^ which is pertinent
for plants between 1 and 100 MGD, was derived from a study of thirty water
treatment plants. Filtration is preceded by coagulation and settling.
This cost Includes capital investment for 30 years at 470 interest (fixed
annual cost of 7.78% of plant investment adjusted to 1964), labor, power,
chemicals, maintenance and repair, heating of buildings, and other miscel-
laneous costs. It assumes that the plant is operating at full capacity
(U = 1.0 in Koenig's paper) and that the cost of water filtration equals
that for filtration of secondary effluent. This latter assumption is
reasonable since the equipment involved is comparable. The 10 and 90
percentiles drawn on Figure 28 were based on factors of 0.76 and 1.32,
respectively.
The equation of the curve presented in Koenig's paper may be
computed as:
Log (Cost) = 1.176 - 0.336 Log (MGD)
Cost = cents/1000 gal.
40
-------
100
co
o
CO
g
<
g
o
55
H
CO
O
o
H
0-,
<
O
10
1 1—I—I I I 1 I I—
LOG (COST) = 0.631 LOG (INFLUENT PLOW) + 0.305
JULY 67 DOLLARS
_L
I I I I I I I I
J_
J I
1 I t 1 J
I l
10 100
INFLUENT PLOW IN THOUSANDS OP GALLONS PER DAY
Capital Cost For Tertiary Treatment by Rapid
Sand Filtration Plus Chlorination Versus
Influent Flow
41
Figure 26
-------
W
>*
K100
W
Cu
CO
ce
o
CO
5 10
EH
CO
O
o
CU
S5
H
EH
W
OH
O
I I I I I I 1 I I
LOG (COST) =.
ii i i r
I I T
1.763 - 0.575 (INFLUENT FLOW)
I i i t t I l 1
J
i i » l l
10 100
INFLUENT FLOW IN THOUSANDS OF GALLONS PER DAY
Operating Cost For Tertiary Treatment
by Rapid Sand Filtration Plus
Chlorination Versus Influent Flow
42
Figure 27
-------
fi
w
EH
W
CO
CO
p
o
w
O-i
co
w
o
EH
CO
O
O
EH
O
EH
10
1—I—1 I I 11 I
T T
.1
LOG (COST) = 1.176 - 0.336 LOG (INFLUENT FLOW)
Cost includes capital investment for 30 years
at 4%, labor, power, chemicals, maintenance
and repair and heating of buildings
1 10
INFLUENT FLOW IN MILLION GALLONS PER DAY
J L
50
Total Cost of Tertiary Treatment by
Coagulation and Settling Followed by
Rapid Sand Filtration Versus
Influent Flow
43
Figure 28
-------
Performance of sand filters depends largely on the processes which
precede filtration. A properly operated sand filter preceded by processes
such as coagulation and sedimentation, can remove most of the suspended
solids, color, turbidity and bacteria. Rapid sand filters are capable of
bacterial removals of 90-99% when the bacterial loading is reasonably low,
but adequate chlorination should follow filtration under all conditions of
operation.
Carbon Adsorption
Figure 29 summarizes the total treatment.cost in cents/1000 gal. for
tertiary treatment by powdered activated carbon" . These estimates were based
on a two-stage countercurrent adsorption process with a carbon dosage of 300
mg/1, carbon cost of 7 cents/lb, power 1 cent/kwh, steam 1 doliar/mi11ion Btu,
amortization for 20 years at 4% interest, maintenance at 3% fixed capital
investment, polyelectrolytes at 1 dollar/lb, carbon loss at 5% per cycle and
an average secondary effluent COD of 40 mg/1. The COD of the tertiary efflu-
ent averaged 5 mg/1. The flowsheet assumed is shown on Figure 30.
The equations representing treatment costs for tertiary treatment by
activated carbon were computed as given below:
Capital Cost:
Log (Cost) = 0.839 - 0.495 Log (Influent flow)
Operating Cost:
Log (Cost) = o.45 Log (Influent flow) + 1.06
Total Cost:
i
Log (Cost) =
0.396 Log (Influent flow) + 0.83
where:
Cost = Cents per thousand gallons
Influent flow = Million gallons per day
Membrane Ultrafiltration
Figures 31-32 show the total installed capital and operating costs
for complete treatment by membrane systems which would replace conventional
primary and secondary processes. The operating costs shown include power,
operating and maintenance labor and equipment replacement. System component
production has not been optimized as yet therefore the information given
will change substantially as the art is developed and large scale production
is realized. The equations representing present economic data were computed
as follows:
44
-------
50
1 r
i I i i i \
i i i i r n i
Q
W
EH
a
K
E-i
CO
10
o
Q
EH
«
W
CO
EH
2
W
O
H
EH
CO
O
w
K
EH
.1
CAPITAL: LOG (COST) = 0.839 - 0.495 LOG (INFLUENT FLOW) -
OPERATING: LOG (COST) =
TOTAL: LOG (COST)
_
0.45 LOG (INFLUENT FLOW) + 1.06
_ 1_ _ __
0.396 LOG (INFLUENT FLOW) +0.83
Cost includes amortization for 20 years at 4%,
carbon @ 7^/lb, power @ Ijjf/KWH, STEAM @ $1.00/
million Btu, chemicals @ $1.00/lb and mainte-
nance at 3% fixed investments
t t 1 I 1 I
1 I I i I i I J
i i
10
INFLUENT FLOW IN MILLION GALLS PER DAY
100
Tertiary Treatment Costs by Activated Carbon
Versus Influent Flow
45
Figure 29
-------
N.
4h-8
L
n
T3 ^ h fl
c; c 0 ?H o
CO CO -P 0 -H
CO -P rH >j-P
•H JH CO
•H C 0
o,iH a c a
CO -P O O 0
CD £-1 £H >£>
rH rH
CO O £-4
CQ («H ^
o -p -p
co 0 -H
•H H In
T3
rHrHrH
CO
CO 0 0 X! 0
cO X I bD M 1><
-P -H CO CH -H
0 0 0 -P 0 4^
SGOC04JS0OCO-P
cO-HCrH-HOCfirH-H
cO O
a
§T3
0
co 0
m
rd-H0r-HO>iH0rHO
0
-------
CO
0>
o
*
o
H
+
9"
O
EH P
3
in
EH
CO
O
O
CO
W
h>
o
OJ
rH
O
O
O
CO
o
cu
o
o
o
a\
o
CO
o
O
o
o
on
o
CM
O
O
P
w
cu
a
§
w
EH
3
fl
rt
OJ
3
a M
O
ffl
3
W
?n
(D
a c
S O
O -H
O -P
M -P -H
>, M
-------
(N
CO
3
&JD
•H
cr\
ro
+
I
I
H
O
II
GO
O
O
0
O
a
•H
ns
bfi fi
S3 a;
•H s
•P 0
d o
SH at
0 rH
a a
O 0
S
a
•H
3
O1
O fl
a e«
•H
!H
-P O
W X2
O oJ
O 1-1
O
O
O
o
co
o
o
o
o
on
o
cu
0-,
O
PC,
O
8
55
> >n
ax: Q
S
55
W
PC,
H
rH S3
a 0
3 B
S3 -P
fl BJ
-------
Capital Cost:
Cost = 1.65 (Influent flow) + 10.5
Cost = Thousands of dollars
Influent flow = Thousands of gallons per day
Operating Cost:
Cost = 0«51 (Influent flow) + 1.39
Cost = Thousands of dollars per year
Influent flow = Thousands of gallons per day
"Complete treatment" provided by membrane systems produces an effluent
which is equivalent or better than that from conventional primary plus second-
ary treatment. Membrane "diffusate" is a high quality water containing no
suspended solids and a BOD of 0-20 mg/1. Coliform content is very low, but
dependent upon "membrane integrity," a term used to describe the physical
condition of the membrane itself.
49
-------
PACKAGE SEWAGE TREATMENT
The information provided was based on a Dorr-Oliver market study
carried on during 1967.
In the independent market study conducted during the first part of
1967 by Dorr-Oliver, it is interesting to note the growth of the package
type sewage treatment plant. Ohio is generally considered to be the pioneer
state for the package type unit. In 1953, there were only seven plants in
operation in that state. It was estimated that in 1955, there were only
twenty plants in operation nationwide,, By 1967, there were between 6000-
7000 plants in operation. Of the total, Ohio alone accounted for over 3000
installations. Florida had over 1000 plants and New Jersey over 300. It
was estimated that the growth rate was 12-147o per year in the package sewage
treatment field. With the amount of package type plants growing in number
each year, this type of installation must be given serious consideration in
any study involving cost of waste water treatment systems.
The Dorr-Oliver market study, based on a survey of states nationwide
as well as equipment manufacturers data, indicated that the average selling
price of the package plant was about $13,000. The majority of plants were
of the extended aeration or contact stabilization type. Of the 30 states
responding to the market study questionnaire, 637» indicated that chlorination
of the effluent was a full-time requirement while the remaining 37% author-
ized part-time use of chlorine.
Table 4 presents data "now thought to be realistic" with respect to
performance of package units.
TABLE 4
PERFORMANCE OF PACKAGE UNITS
Extended Contact
Aeration Stabilization
Effluent SS 17-47 mg/1 10-60 mg/1
SS Reduction 65-91% 67-87%
Effluent BOD 6-60 mg/1 10-100 mg/1
BOD Reduction 75-95% 67-93%
The costs of conventional package sewage treatment by extended aeration
shown on Figure 33 were based on the following criteria: (1) capital cost
amortized at 7.5% total installed cost, (2) labor at 3 dollars/day, (3) power
at 1.5 cents/kwh and (4) maintenance at 3057o mechanical equipment cost.
50
-------
I I I I I 1
I I I I I I J
CO
o
a
CJ
p
55
co 1000
o
X
EH
CX.
CO
EH
2
W
O
2
H
EH
CO
O
O
Total: LOG (COST) = 2.61 -0.62 LOG (AVERAGE FLOW)
Capital: LOG (COST) = 2.22 - 0.57 LOG(AVERAGE FLOW)
Operating: LOG (COST) = 2.40 - 0.67 LOG(AVERAGE FLOW)
Cost includes aeration plant plus operation
w
s
EH
K
EH
100
10
I 1 1 I t 1 L I
1 1 I 1 I 1 1 J
I
J 1
10 100
AVERAGE FLOW IN THOUSANDS OF GALLONS PER DAY
Treatment Cost of Package Sewage Treatment
by Extended Aeration
51
Figure 33
-------
Treatment costs for conventional plus tertiary treatment are shown
on Figure 34. Included are the costs of the aeration plant from Figure 33,
sand filters, chlorinator and housing, erection and the building. Operating
costs include power, labor, chlorine and maintenance. The additional terti-
ary step produces an effluent with a total suspended solids of less than 5 mg/1
and a BOD removal of 95-9870.
The computed equations for the cost of package treatment are given
below:
Conventional Treatment:
Capital: Log (Cost) = 2.22 - 0.57 Log (Average flow)
Operating: Log (Cost) = 2.40 - 0067 Log (Average flow)
Total: Log (Cost) = 2.61 - 0.62 Log (Average flow)
Conventional Plus Tertiary Treatment:
Capital: Log (Cost) = 2.26 - 0.473 Log (Average flow)
Operating: Log (Cost) = 2.33 - 0.625 Log (Average flow)
Total: Log (Cost) = 2.58 - 0.53 Log (Average flow)
where:
Cost = Cents per thousand gallons
Average flow = Thousands of gallons per day
52
-------
CO
o
J
1-1
<-
O
o
l-i-4
Pn
H
CO
O
EH
I I I I I I 1 I I I 1 I I I I I I J
Totil: LOG(COnT) = 2 . 50- ">. oSLOfi ( AVERAGE FLOW )
Capital: LOG (COST) = 2. 20-0. 55LOG( AVERAGE I?LOW)
Oneratinj: LCr,(COST) = 2. 27-">. S2LCG ( AVERAGE FLO1',1)
Cost includes aeration plant plus operation cost
I T
I l l I 1 I l I
» i I i i i t ]
j i
AVERAGE FLO!' IN THOUSANDS OF GALLONS PER DAY
Treatment Cost of Package Sewage Treatment
by Extended Aeration
53
Figure 34
-------
REFERENCES
1. Fair, G. M. and Geyer, J. C0, "Water Supply and Waste Water
Disposal," John Wiley and Sons, p. 733.
2. Center, A. L., "Computing Coagulant Requirements in Sludge
Conditioning," Transactions of American Society of Civil
Engineers, 111, 641 (1964).
3. Nesbitt, J. B., "Removal of Phosphorous from Municipal Sewage
Plant Effluents," Engineering Research Bulletin B-93, 1966,
Pennsylvania State University,
4. Koenig, Louis, "The Cost of Water Treatment," Journal of
American Water Works Association, pp. 290-336 (March, 1967).
5. Davies, D. S. and Kaplan, R. A., "Activated Carbon Eliminates
Organics," Chemical Engineering Progress, pp. 46-50 (December,
1964).
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