FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
NORTHWEST REGION, PACIFIC NORTHWEST WATER LABORATORY
EVALUATION OF WASTE TREATMENT SYSTEM
CHEMAWA INDIAN SCHOOL
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EVALUATION OF WASTE TREATMENT SYSTEM:
Chemawa Indian School
Prepared by
B. David Clark
Kenneth A. Dostal
Technical Projects Branch
Report No. FR-6
United States Department of the Interior
Federal Water Pollution Control Administration, Northwest Region
Pacific Northwest Water Laboratory
200 South Thirty-fifth Street
Corvallis, Oregon 97330
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ABBREVIATIONS
BOD^ - Five Day Biochemical Oxygen Demand
COD - Chemical Oxygen Demand
TPO^ - Total Phosphate
OP04 - Ortho Phosphate
SS - Suspended Solids
TS - Total Solids
VSS - Volatile Suspended Solids
TKN - Total Kjeldahl Nitrogen; a measure of organically
bound nitrogen in the trinegative state. Does not
include nitrate and nitrite nitrogen.
Alk - Alkalinity
mg - Million Gallons
mgd - Million Gallons Per Day
gpd - Gallons Per Day
Hp - Horsepower
org/100 ml - Organisms per hundred milliliters volume
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CONTENTS
INTRODUCTION 1
Problem 1
Objectives and Scope 1
Authority 2
SUMMARY 3
Findings 3
Conclusions ^
Recommendations 5
DESCRIPTION OF PLANT 7
STUDY PROCEDURES 9
Sampling 9
Analysis 11
RESULTS 13
EVALUATION 25
REFERENCES 37
APPENDIX 39
Analytical Procedures 40
Analytical Data 42
Calculations 55
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LIST OF TABLES
Table Page
1 Summary of Survey Results 14
2 Raw Waste Characteristics 26
3 Aerated Lagoon Efficiency 26
4 Polishing Pond Performance 33
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LIST OF FIGURES
Figure Page
1 Treatment System 8
2 Sampling Stations 10
3 Waste Flows 15
4 Bacteriological Results 18
5 Aerated Lagoon Bottom Sludge Oxygen Uptake 21
6 Aerated Lagoon Bottom Sludge
Oxygen Uptake Rates versus Temperature 22
7 Aerated Lagoon Aerator Evaluation 29
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INTRODUCTION
Problem
The Bureau of Indian Affairs (BIA) operates a nine month
school for 900-1,000 Indians at Chemawa, approximately two miles
north of Salem, Oregon. The waste treatment plant for the school
is unique in this area, consisting of a facultative mechanically
aerated lagoon followed by a two-acre polishing pond and
chlorination.
Since this type of process appears to have considerable
application to waste treatment needs of other agencies, a detailed
investigation was conducted to evaluate the performance of each
unit in the system and costs involved.
Objectives and Scope
A sampling program was established to determine the
following:
1. Raw waste load and characteristics.
2. Solids and BOD removal in aerated lagoon.
3. Sludge accumulation in aerated lagoons.
4. MPN level in aerated lagoons.
5. Adequacy of aerator for mixing and oxygenation.
6. Effect of polishing pond on BOD, DO, MPN and S3.
7. Effect of chlorination on BOD, DO, MPN and SS.
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2
The sampling program consisted of a survey at the treatment
plant to cover a 48-hour period and supplemental grab samples on
one other day.
Authority
The Federal Activities Branch of the Northwest Regional
Office, FWPCA, requested the Technical Projects Branch, Pacific
Northwest Water Laboratory (PNWL), FWPCA, by memorandum dated
November 17, 1967, to conduct a monitoring program at the Chemawa
Indian School and to report on its findings. Authority for this
type of assistance is contained in the President's Executive
Order No. 11288.
Acknowledgments
The assistance and cooperation of the Bureau of Indian
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SUMMARY
Findings
1. The raw waste load at the Chemawa Indian School contains
a. BOD5 - 230 lb/day
b. SS - 167 lb/day
c. T?04 - 12.9 lb/day as P
d. TKN - 33.5 lb/day as N
e. Total Coliform - 6.6 x 10^ org/100 ml
2. The aerated lagoon removed 76 percent of the BOD5 and
62 percent of the SS at a detention time of 5.25 days and tem-
perature of 7.2 degrees C.
3. Approximately 6,600 cubic feet of sludge has accumulated
in the aerated lagoon since May 1965. This represents an average
depth of 4.5 inches over the lagoon bottom.
4. The total coliform level in the aerated lagoon was 1.4
6
x 10 org/100 ml as measured by the membtane filter method.
5. The 5 Hp aerator provides a horsepower-to-volume ratio
of 6.67 per million gallons and provides sufficient mixing to
maintain a uniform DO and suspended solids concentration through-
out the aerated lagoon.
6. The mechanical surface aerator was calculated to have an
oxygen transfer efficiency of 2.22 lb 02/Hp-hour at standard
conditions (zero DO, 20 degrees C and 1 atmosphere pressure).
7. The polishing pond was found to remove 51 percent of the
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4
coliform concentration by 95 percent; and decrease the SS by
13 percent.
8. Chlorination of the polishing pond effluent decreased
the BOD^ and SS by 10 mg/l; had no effect on DO; and decreased
the total coliforms to less than 10 org/100 ml.
9. The total annual cost of treatment at the Chemawa Indian
School including amortization of capital costs is $114/mg treated
or $0.0765 per lb BOD,, removed at 1965 price levels. Approximately
40 percent of the total cost is for operation and maintenance.
Conclusions
( U)
1. An equation proposed by Eckenfelderv 'can be used with
the survey data to exactly predict the aerated lagoon temperature.
2. Complete-mix kinetics can be used with the survey data
to closely predict the actual aerated lagoon BOD5 removal efficiency
using a BOD^ removal rate of 0.034/day and a value of 1.035
as the constant in the Van't Arrhenius temperature correction
equation.
3. The aerated lagoon mechanical aerator is sufficient
for oxygen dispersion, but inadequate to meet the oxygen demand
at all expected operating conditions. At the present BOD5
loading level, of 230 lb/day, the aerator will not provide suf-
ficient oxygen at temperatures above 17 degrees C. With an in-
crease in BOD5 load of 25 percent, the maximum operating temperature
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5
4. The supplemental spray aeration system provides a minimal
quantity of oxygen per day on the basis of theoretical calculations.
Rscomnendations
1. The aerator capacity in the aerated lagoon be increased
to prevent development of anaerobic conditions.
2. Further study of the aerated lagoon be carried out to
confirm temperature and BOD^ removal relationships in this
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DESCRIPTION OF PLANT
The waste treatment plant consists of three units which
operate in series: a facultative aerated lagoon, a polishing
pond and a chlormation unit. (See Figure 1.)
The aerated lagoon;, which receives the raw sewage near the
bottom and center of the lagoon5 provides a volume of 0.755 mg
at a water depth of five feet. Primary aeration and mixing is
provided by a 5-Hp fixed mechanical turbine aerator located at
the center of the lagoon., Supplemental aeration is also provided
by a spray system. This includes a pump that draws the lagoon
contents into a header pipe that sprays the contents over the
lagoon surface. The lagoon is constructed of diked earth with
a bentonite clay sealed bottom.
The flow from the lagoon passes through a three-inch parshall
flume into the polishing pond. The polishing pond has a total
surface area of 1.8 acres and a volume of 2.34 mg at a depth
of four feet. Construction of the polishing pond is of diked
earth.
The chlorination facilities Include a gas chlorinator
followed by a poured concrete baffled contact chamber. The
volume of the contact chamber is 3,700 gallons at a depth of
one foot.
Effluent from the treatment plant is discharged to a small
creek. Downstream from the plant discharge, water is withdrawn
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RAW SEWAGE
MANHOLE
SUPPLEMENTAL
AERATION
AERATED
LAGOON
PARSHALL FLUM
MANHOLE
180
CHLORINE CONTACT
—,—r-, CHAMBER
POLISHING
POND
435'-
MANHOLE
FINAL EFFLUENT
TO SMALL CREEK
6' FREEBOARD
5 DEPTH]"/^" 4'DEPTH _3|_FREEB0ARD
t ^ /SIDE SLOPE \ f ^
'3:i SIDE SLOPE
150 0
AERATED LAGOON POLISHING POND
UNIT
AREA. ACRES
DEPTH/T
VOLUME.GAL.
SIDE SLOPES
AERATED
LAGOON
0.43
5
755,000
2:1
POLISHING
POND
1.8
4
2,340,000
3.1
CHLORINE
CONTACT
1
3,700
—
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STUDY PROCEDURES
Sampling Program
A single survey from midnight January 8 to midnight Jan-
uary 10 was planned to accomplish the objectives. Ten sampling
stations were established as shown on Figure 2 with the follow-
ing frequency of collection:
1. Samples were collected every thirty minutes and
combined for a twelve hour composite with time at stations 1,
3, 5, and 6.
2. Grab samples were collected every twelve hours at stations
2 and 4.
3. Samples were collected every two hours at station 1 and
every four hours at stations 3, 5, and 6 for bacteriological
analyses.
4. A DO and temperature cross-section of the aerated
lagoon at stations 7 through 10 at one and four foot depths
was made on January 9 using a temperature DO probe.
5. Sludge depth in the aerated lagoon was measured at
stations 7 through 10. Bottom sludge samples were collected
for analyses at stations 7 through 10.
6. Samples were collected on January 29 at stations 7
through 10 at one and 3.5 foot depths using a Kemmerer sampler.
These samples were then analyzed for suspended solids.
All samples were stored and returned on ice to the Pacific
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RAW SEWAGE
AERATED
LAGOON
WALKWAY
PAR SHALL FLUME
CHLORINE
CONTACT
CHAMBER
POLISHING POND
NOTES:
STA. I-COMPOSITE W/FLOW
STA.2- GRAB '
FIGURE 2
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11
During this survey, the flow was determined by reading the
flume staff gauge every thirty minutes and converting to flows.
(See Appendix B.)
Analyses
All analyses with the exception of the oxygen uptake of
bottom sludge and total and orthophosphates were performed in
accordance with the 12th edition of Standard Methods for the
Examination of Water and Wastewater.^ Appendix A contains
procedures for the non-standard analyses mentioned above. Analysis
was made in the field for DO, pH and temperature using battery
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RESULTS
All data obtained during this survey are given in Tables
B-l through B-10 in Appendix B found at the end of this report.
Table 1 in the text summarizes these data.
Flows
During the two day sampling period, the flow through the
treatment plant averaged 144,000 gallons per day (gpd) or
0.223 cfs. The flow was 184,500 gpd the first day (January 9)
and 103,000 gpd the second day (January 10). Figure 3 illustrates
the flow pattern for the period of this survey. Table B-l
contains these data.
During the survey period, there was heavy precipitation
which may have affected the data through infiltration and the
quantities falling in the open ponds. According to the U. S.
Weather Bureau Station at the Salem Airport (See Table B-2),
1.4 inches of rain fell on January 9 and 10. This would have
amounted to over 16,000 gallons on the aerated lagoon and 69,000
gallons on the polishing pond during the two day period. Flows
measured by the Parshall Flume would include the 16,000 gallons
that fell in the aerated lagoon, but would not include the amount
that fell on the polishing pond.
Temperature, pH» Alkalinity and DO
The average temperature decreased through each unit of the
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14
TABLE 1
SUMMARY OF SURVEY RESULTS
(a) ^
ANALYSIS WASTE
AERATED
LAGOON
EFFLUENT
POLISHING
POND
EFFLUENT
FINAL
EFFLUENT
Flow, gpd
BOD5
PH
SS
VSS
TPO4 as P
TKN as N
144,000
190
7.5
Alkalinity 111
138
118
10.70
27.9
45
7.6
176
52
52
7.61
29.8
22
8.0
175
45
45
7.30
25.2
12
8.0
166
35
35
7.20
24.1
TOTAL COLI
org/100 ml 6,600,000 1,400,000
Algae
1440/ml
71,000
18,400/ml
<10 Weighted
average
(a)
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0.5
04
Q3
AVERAGE FLOW 0.223 CFS
U 0.2
6
18
O
12
24
18
24
6
12
1-9-69 1-10-68
TIME, HRS
FIGURE 3
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16
aerated lagoon 7.2 degrees C, the polishing pond 4.5 degrees C
and the final effluent 4.2 degrees C for an overall reduction of
7.9 degrees or 65 percent. The average air temperature during
this period was approximately 7.2 degrees C as measured at the
Salem Airport. (Table 3-2.)
The average pH increased through the system from 7.5 in
the raw sewage to 8.0 in the final effluent. The greatest
increase occurred in the polishing pond from 7.5*ln to 8.0 out.
Alkalinity was also found to increase through the system from
111 mg/1 to 166 mg/1. Most of this increase occurred in the
aerated lagoon.
Dissolved oxygen (DO) also increased significantly through
the system from approximately 5 to 6 mg/1 in the raw sewage to
10.4 mg/1 in the final effluent. There was a drop in DO in the
aerated lagoon, but a considerable increase in the polishing pond.
Little change was noted through the chlorination unit.
These data for temperature, pH and DO are given in Table
B-3. Alkalinity data are given in Tables B-4, 5, 6, and 7.
The raw sewage BOD^ averaged 190 mg/1 for the two day
survey. It varied from a high of 280 mg/1 to a low of 78 mg/1
per 12-hour period. Peak concentrations for both days occurred
in the 1200-2400 period with lows in the 0-1200 period.
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17
the aerated lagoon, 51 percent in the polishing pond and 45 percent
in the chlorination unit. The overall reduction of the BOD^
by the treatment plant was 94 percent. Raw data are found in
Tables B-4, 5, 6, and 7 in Appendix B.
Solids
Suspended solids in the raw sewage averaged 138 mg/1 with
86 percent volatile and showed the same variation with time as
the BOD^
The aerated lagoon effluent, which is similar to the lagoon
contents, had an average suspended solids concentration of 52 mg/1
with 100 percent volatile during the January 9 and 10 survey.
On January 29, a cross-section of the lagoon contents was made
at depths of 1 and 3.5 feet from the surface for suspended solids
analyses. These samples indicated little variation in the lagoon
suspended solids contents. Microscopic analysis indicated the
lagoon contents to be primarily bacterial and protozoan with some
algae.
The effluent from the polishing pond had an average suspended
solids concentration of 45 mg/1. As indicated by Table 1, the algae
concentration was 18,400 mg/1 which was calculated to account for
approximately 6-10 mg/1 of the suspended solids.
The final effluent, after cfijlorination, had an average suspended
solids concentration of 35 mg/1.
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RAW SEWAGE
AERATED LAGOON EFF
f
/
\
*©— "
/ ^
A »
\ ^POLISHING POND EFF.
\
*
1200
1-9-68
2^00
iioo
1-10-68
2400
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19
system was 62 percent in the aerated lagoon, 5.5 percent in the
polishing pond and 7.5 percent in the chlorination contact tank
for a total reduction of 75 percent. Raw data are found in
Tables B-4, 5, 6, and 8.
Total Kjeldahl Nitrogen and Total Phosphate
Total kjeldahl nitrogen (TKN) was found to increase in the
aerated lagoon from 27.9 mg/1 in the raw sewage to 29.8 mg/1
in the lagoon effluent. This could be explained by a non-repre-
sentative raw sewage sample particularly regarding suspended
solids and settleable solids. A significant portion of the TKN
in raw domestic sewage is bound in the solids and, if the sample
were low in solids, then it would also be low in TKN. The low
SS concentration in the raw sewage tends to support this conclusion.
Total phosphate was decreased through the system from 10.7
mg/1 to 7.2 mg/1 for a reduction of 33 percent. Most of the total
reduction, approximately 86 percent, occurred in the aerated lagoon.
Raw data is found in Tables B-4, 5, 6, and 7 in Appendix B.
Total Coliform
Figure 4 illustrates the total coliform variation in the
raw sewage, aerated lagoon effluent and polishing pond effluent
during the survey period.. The weighted average of the coliform
data indicates a value of 6.6 x 10^ org/100 ml for the raw sewage,
1.4 x 10^ org/100 ml for the aerated lagoon effluent, 71,000
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20
the final effluent.
Table B-9 in Appendix B contains the raw data for the survey
periodo
Aerated Lagoon Sludge
The sludge depth in the aerated lagoon was measured at
four locations in the lagoon and found to increase with distance
from the aerator., Near the center of the lagoon, the depth was
three inches while at the outer edge, the depth increased to
five incheso The average depth on .the bottom was calculated to
be 4.5 inches.
Analyses of the sludge indicated an average total solids of
8.6 percent with 42 percent volatile and high concentrations
of TKN and TPO^. TKN was 22.5 percent of the dry solids and
the TPO4 was 8.4 percent of the dry solids both of which are
high when compared to a digested sludge with typical values of
1-3 percent and 0=3-1 percent of dry solids for total nitrogen
and TPO^ respectively. Apparently, nutrients contained in the cell
structure of the lagoon solids and the settleable solids of the
raw sewage are concentrated on the lagoon bottom when considered
in terms of percent dry solids because of the degradation of the
volatile portion of the solids.
Table B-10 in Appendix B presents data which were obtained
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g
1000
2400
JAN. 31
1200
2400
1200
FEB. I
FIGURES AERATED LAGOON BOTTOM SLUDGE
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T-20
Kt/*20- 113
TEMPERATURE C
FIGURE 6 AERATED LAGOON BOTTOM SLUDGE
OXYGEN UPTAKE RATES VS.
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23
Oxygen Uptake of Aerated Lagoon Sludge
The variation in rate of oxygen uptake of the lagoon sludge
is plotted on Figure 5 for varying temperatures. The curve at
20 degrees C starts out with a rate of approximately 1.0 mg/l/hr.
increased to a rate of approximately 3.6 mg/l/hr. and then decreases
exponentially to 0.7 mg/l/hr. The increased rate of uptake
shown in Figure 5 is attributed to bacterial removal of organic
matter that was suspended when the experiment was initiated rather
than endogenous respiration of the sludge. Rates at the lower
temperatures were decreased accordingly with the lowest rates
found for temperatures at 6.5 degrees C.
Figure 6 presents the log of the ratio of oxygen removal
rates at temperature T to the corresponding removal rate at 20
degrees C versus temperature T. This curve plots as a straight
line on semi-log paper which indicates that it would follow
the Van't Ar^entus^temperature conversion formula
*r ¦ KdT'20
For these data, the value of £ was calculated as 1.13.
Table B-10 in Appendix B contains all data which were obtained
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EVALUATION
Raw Waste Characteristics
While the actual strength of the raw waste, as determined
by this survey, may be misleading due to Infiltration In the
sewers, the total pounds of the various waste constituents should
be representative. Table 2 summarizes the raw waste characteristics
In pounds per day and on a per capita basis assuming 900 con-
tributing persons at the Indian School. With exception of BOD5,
which is high, the per capita contributions are typical of
domestic sewage. However, the average BOD5 is normal for a
system using grinders extensively such as at Chemawa, but the SS
is low. Watson reports an average per capita load increase in
wastewater from individual homes due to garbage grinders as 26
(3)
percent for SS and 17 percent for BOD,..
Aerated Lagoon
Efficiency
Approximately 40 percent of the heat load carried by the
raw waste is dissipated in the lagoon with a temperature re-
duction from 12.1 to 7.2 degrees C. This heat loss agrees
closely with a calculated value using the method of Eckenfelder.
(See Appendix B.) However, it should be noted that the calculated
value is based on an air temperature calculated using an average
temperature of eight days prior to the survey plus the two days
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26
TABLE 2
RAW WASTE CHARACTERISTICS
PARAMETER LOAD PER CAPITA LOAD
Flow 135,000 gpd
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may or may not be correct and would need additional data for
verification.
Heat loss in a biological system is an important consideration
because it decreases the overall efficiency of the system by
reducing the BOD removal rate and the endogenous rate of solids
reduction. For example, if the temperature of the aerated lagoon
were the same as the influent sewage, 12 degrees C, the overall
BOD removal efficiency would be approximately 82 percent rather
than 76.5 percent.
The BOD^ and SS reductions through the aerated lagoon were
measured at 76.5 percent and 62 percent, respectively, with a
total effluent BOD^ of 45 mg/l and SS of 52 mg/1. During this
study, the lagoon was operating at a detention time of 5.25
days, temperature of 7.2 degrees C and an organic loading of
0.7 lb BOD^/lb MLSS/day. The BOD5 removal compares quite favor-
ably with a calculated value of 77.5 percent assuming complete-
mix kinetics with a BOD5 removal rate of 0.034/day(5) and a
temperature coefficient of 1.035^. (See Appendix C for cal-
culations.) For comparison, if this system were operated as a
complete-mix system with a higher horsepower-to-volume ratio,
the overall efficiency of the lagoon would be reduced to a
BODj removal of 70 percent and SS would be Increased from 52
mg/1 to 150-160 mg/1.
Total phosphates were reduced 29 percent in the lagoon from
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28
new cells which settle out and to the sedimentation of insoluble
phosphates. The high concentration of TPO^ in the lagoon bottom
sludge supports this conclusion.
While data on the influent and effluent of the aerated
lagoon indicate no reduction of TKN, the percent of TKN in the
bottom sludge solids does indicate a reduction of over 8 mg/1.
This also indicates that the TKN value reported for the raw
sewage may be inaccurate. A limited amount of data (not re-
ported) together with the TKN data indicated that the lagoon is
not achieving nitrification. Since the Chemawa lagoon is loaded
at a rate of 0.7 lb BOD^/lb MLSS/day, this is in accordance
with work by Eckenfelder^ who states that little or no nitrifica-
tion occurs at loadings above 0.4 lb B0D5/day/lb MLSS.
Table 3 summarizes the efficiency of the aerated lagoon over
the period of this survey.
TABLE 3
Aerated Lagoon Efficiency
Parameter
Raw Waste
Aerated Lagoon
Effluent
Percent Reduction
Temp, degrees C 12.1
7.2
40.5
BOD 5 mg/1
SS mg/1
190
138
45
52
62
76.5
TPO4 mg/1 as P 10.7
TKN mg/1 as N 27.9
29.8
7.6
29
Total Coliform
org/100 ml 6.6 x 106 1.4 x 106
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20
18
16
14
12
10
8
6
4
2
0
T
T
OXYGEN DEMAND
0
OXYGEN AVAILABLE
FROM AERATOR
200
LB. OXYGEN PER DAY
300
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31
Sludge Accumulation
Since May 1965, when the aerated lagoon was placed in
service* approximately 6*600 cubic feet of sludge has accumulated
on the bottom of the lagoon to a depth of approximately 4.5
inches. This represents a rate of 79 pounds of solids accumulation
per day in the lagoon. The sludge accumulation rate has been
calculated to be 0.45 lb dry solids/lb BOD^ removed on the baBis
of the sludge analyses data in Appendix B and the computed
volume. (See Appendix C for the calculation.) This value is
similar to that reported for aerobic lagoons by Eckenfelder^
of 0.5 lb dry solids/lb BOD5 removed.
Aerator Evaluation
As indicated by data in Table B-8, Appendix B, the 5 Hp
aerator, which provides a horsepower-to-volume ratio of 6.67/mg,
was found to be sufficient to maintain a uniform DO and suspended
solids. Little difference in either DO or SS with depth or
distance from the aerators was noted. It is also pertinent to
note that, with the 6.67 Hp/mg ratio, a mixed liquor suspended
solids concentration of 52 mg/1 was maintained in the lagoon.
This value has been reported at a similar power-to-volume ratio.
Regarding oxygen transfer capability, the aerator was
calculated to have an efficiency of 2,22 lb 0^/Hp-hour which is
inadequate to meet the oxygen requirements at all operating
conditions. This ie Illustrated by Figure 7. At a BOD5 load
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32
temperatures below 17 degrees C. However, if the BOD5 load is
increased by 10 percent to 253 lb/day, the aerator is inadequate
above 15 degrees C, and at a 25 percent increase to 288 lb/day,
the operating temperature is reduced to approximately 11 degrees
C and below.
Reference is made to the calculations in Appendix B for
additional details regarding this analysis.
The supplemental spray aeration system was analyzed
theoretically assuming a water droplet 1/16" diameter, 50 gpm
pumping rate, a droplet exposure time of 5 seconds and a DO
of 0 mg/1 in the lagoon. At these conditions, the supplemental
spray aeration would provide approximately 1.6 lb 02/day. While
this quantity of oxygen relative to the amount provided by the
mechanical aerator is insignificant, it should be noted that the
effective droplet size could be much smaller than the assumed
1/16" diameter which could increase the oxygen transfer
significantly.
Polishing Pond Evaluation
The polishing pond, which is actually a facultative
stabilization pond, was loaded at a value of 31 lb BODj/acre/day
and had a hydraulic detention period of approximately 16 days.
The organic loading is well within the range of 20-50 lb BOD/
acre/day generally recommended and performance of the pond is
typical of stablization ponds. BOD^ reduction through the pond
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33
concentration in the lagoon and lagoon effluent is responsible
for most of the solids and BOD^.
As indicated by Table 12, the effluent from the polishing
/
pond had a BOD^ of 22 mg/1, for a reduction of 51 percent.
Solids were decreased by only 13.5 percent but converted from
bacterial solids to algae solids. This is indicated by the
increased concentrations of algae in the polishing pond from
1,440/ml in the aerated lagoon to 18,400/ml in the polishing
pond.
The DO increase through the polishing pond from 3.5 to 9.2
mg/1 is due primarily to algae photosynthesis, but is also in-
creased by the lower temperature which increases the saturation
level by approximately 0.8 mg/1.
The total kjeldahl nitrogen reduction of 15.5 percent is
attributed primarily to sedimentation of the bacterial solids
but would also include bacterial conversion or organic nitrogen
to nitrites and nitrates.
Table 4 summarizes the performance of the polishing
pond.
TABLE 4
Polishing Pond Performance
Parameter
Influent
Effluent
Percent Reduction
Temp, degree C 7.2
BOD^ mg/1 45
4.5
22
38
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34
TABLE 4 (CONT.)
Polishing Pond Performance
Parameter
Influent
Effluent
Percent Reduction
SS, mg/1
52
45
13.5
TKN, mg/1 as N
29.8
25.2
15.5
Algae/ml
1440
18,400
Total Coliform
org/100 ml
1,400,000
713000
95
DO, mg/1
3.5
9.2
Chlorination Evaluation
The chlorine contact chamber has a capacity of 3,700 gallons,
which provides a detention time of 37 minutes. At the time of
this study, the chlorine application rate was reported at 6 lb/day,
or approximately 5 mg/1. Data obtained on-site and in the labora-
tory for residual chlorine indicated a much higher application
rate than 5 mg/1, however. The 10 mg/1 reduction in SS and BOD^
through the chlorination unit indicates a chlorine dosage at
least greater than 10 mg/1. Perhaps the scales used to determine
the amount of chlorine used daily are reading inaccurately.
The chlorination unit was effective in reducing total
coliform as indicated by an average of less than 10 org/100 ml
in the final effluent.
Cost of Treatment
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35
three stages as the school grew in size. The first stage con-
sisted of a septic tank and drain field. The second stage
was the construction of a two-celled lagoon and conversion
of the spetic tank to a chlorine contact chamber. This con-
struction took place in 1961 at a cost of $30,000. The third
stage included construction of the aerated lagoon and conversion
of the two-celled lagoon to a single cell polishing pond. This
stage took place in May 1965, at an estimated cost of $32,500.
Based on ten months operating records from April 1967,
through January 1968, the total annual cost of operating this
system including amortization of capital costs adjusted to
1965 price level is $115 per mg treated or $0.0765 per lb
BOD,. removed. These costs are broken down as follows:
Cost/mg Cost/lb BOD^ removed
Capital $81.60 $0.05
0 & M $32.40 $0.0265
Operation and maintenance costs include 46.5 percent for
power, 14.4 percent for chlorine, 29 percent for operating labor
-------
REFERENCES
1. Standard Methods for the Examination of Water and Waste-
water, 12th Edition, APHA, AWWA, WPGF.
2. Beutra, J. K. , George, Mo G. and Sharma, M., "Contribution
of Algae to Physical and Chemical Characteristics of Water,"
Water and Sewage Works, March 1968.
3. Watson, K. S., et als "The Contribution from the Individual
Home to the Sewer System," JWPCF, Vol. 39, No. 12, December
1967.
4. Eckenfelder, W. W., Design and Performance of Aerated Lagoons
for Pulp and Paper Waste Treatment. 16th Purdue Industrial
Waste Conference.
5. Eckenfelder, W. W., Journal Sanitary Engineering Division,
ASCE, Volume 93, No. SA6, December 1967.
6. Eckenfelder, W. W., New Design Advances in Biological
Treatment of Industrial Wastes, 17th Annual Meeting,
Oklahoma Industrial Wastes and Pollution Control
Conference, November 15-16, 1966,
7. Fair, G. M„ and Geyer, J. C., 'VJater Supply and Waste-
-------
-------
-------
41
Oxygen Uptake of Bottom Sludge
The oxygen uptake of the bottom sludge was measured in
a sealed container using a DO probe with a continuous recording
chart. The sludge depth to water depth ratio was maintained
similar to actual field conditions. The unit was aerated,
completely sealed, agitated sufficiently to insure complete
liquid movement, yet not suspend the bottom solids, and the
oxygen uptake rate measured. The rate was measured at tem-
peratures from 5 to 27 degrees C.
Total Phosphate and Ortho-phosphate
Sample is digested with sulfuric acid and potassium
persulfate to convert phosphates to ortho-phosphate — modification
of Pacific Northwest Water Laboratory. References: J. Murphy,
and J. P. Riley, Analytical Chim. Acta. 27, 31 (1962); J. D. H.
Strickland and T. R. Parsons, "A Manual of Sea Water Analysis,"
p. 47, Bulletin No. 125, 2nd Edition revised, Fisheries Research
-------
-------
TABLE B-2
(a)
Climatological Data
43
Date Precipitation - Inches Ave. Air Temperature °C
January 1
5.6
January 2
2.2
January 3
2.8
January 4
0
January 5
3.3
January 6
-0.6
January 7
0.14
2.8
January 8
0.25
8.3
January 9
1.24
10.0
January 10
0.16
4.5
January 11
Trace
8.3
C d)
Data from State Climatologist, U. S. Weather Bureau, Salem
-------
TABLE B-3
Onsite Measurements on Grab Samples
Time of sample
Analysis Location
1-9-
>68
1^1(5-68
Ave
00:15
06:00
12:00
18:00
00:15
06:00
*'.12 £00
18:00
Temp.
°C Raw
9.4
10.0
8.0
15.0
12.3
17.5
916
15.0
12.1
A.L. Eff^
8.3
3.1
7.5
¦10.5-
8.5
8.2
» 7:Q
4.5
7.2
P.P. Eff^
3.1
3.1
6.5
6.5
5.0
4 .V
5:0
3.0
4.5
EJinal Eff.
3.1
2.9
5.7
5.5
4.5
3-5
s.o
3.0
4.2
pH Kaw
6.9
7.5
7.2
7.1
7.1
7.6
7:1
7.8
A.L. Eff.
7.4
7.6
7.1
7.1
7.2
7.5
7.1
8.1
P.P. Eff.
7.9
8.1
7.6
7.7
7.9
8.1
8;o
9.1
"^inal Eff.
! .1
7.9
7.6
J1,h
7.7
7.9
7 ^
8.3
D.O., mg/1 Raw
-
6.1
5.2
-
-
A.L. Eff.
4.3
5.4
3.2
3.3
3.9
P.P. Eff.
8.9
9.1
9.0
7.1
10.8
Final Eff.
10.1
9.7
8.8
7.6
10.4
-------
45
TABLE B-4
DATA ON RAW SEWAGE
Time of Composited Sample
Parameter*
1-9-68
1-
10-68
Average
0-12:00 1 12:00-24:00
0-12:00
112:00-24:00
Flow, gpd
144,000
225,000
80,000
126,000
144,000
pH
7.5
7.4
7.8
7.9
—
Alk
90
106
117
139
Ill
SS
80
210
60
126
138
vss
56
182
44
1??
118
t?04
5.4
13.6
6.8
14
10.7
TKN
15.2
34.2
18.3
36.9
27.9
COD
381
302
—
BOD,
86
280
78
218
190
-------
46
TABLE B-5
DATA ON EFFLUENT FROM AERATED LAGOON
Time of Composited Sample
Parameter* 1-9-68 1-10-68 Average
0-12:00
12:00-24:00
0-12:00
12:00-24:00
PH
7.6
7.5
7.6
7.5
Alk
189
177
165
165
176
SS
30
66
54
44
51
VSS
30
66
54
52
52
TPO as P
4
6.9
7.8
8.0
7.7
7.6
TKN
29.3
30.7
28.6
29.3
29.8
COD
154
116
—
bod5
48
43
42
47
45
-------
TABLE B-6
DATA ON POLISHING POND EFFLUENT
Time of Composited Sample
Parameter* 1-9-68 1-10-68 Average
0-12:00 12:00-24:00 0-12:00 12:00-24:00
pH 8.2 7.9 7.9 8.0
Alk 181 172 174 176 175
SS 42 46 40 48 45
VSS 41 46 40 48 45
TP0. 7.3 7.4 6.8 7.2 7.3
4
TKN 22.9 26.2 26.2 26.1 25.5
COD 68 72
BOD_ 23 21 23 23 22
-------
48
TABLE B-7
DATA ON FINAL EFFLUENT
Time of Composited Sample
Parameter* 1-9-68 1-10-68 Average
0-12:00 12:00-24:00 0-12:00 12;00-24:00
PH
8.1
8.0
7.9
8.0
Alk
166
167
167
165
166
SS
28
36
32
42
35
VSS
28
36
32
42
35
tpo4
7.2
7.1
7.3
7.3
7.2
TKN
22.9
25.0
25.0
23.2
24.1
COD
80
95
—
bod5
10
15
14
9
12
-------
TABLE B-8
DATA ON AERATED LAGOON
Parameter
Sample Depth
ft.
Distance
10
from Lagoon Center-fi
30 50 ' 70
o (a)
Temp., C
1
8.7
8.7
8.9
9.1
4
8.7
8.7
8.8
9.1
(a)
DO, mg/1
1
3.8
3.7
3.6
3.4
4
4.2
3.7
3.6
3.2
SS, mg/1^
1
30
44
40
40
3.5
44
40
44
76
^Samples taken 1-9-68
-------
50
TABLE B-9
TOTAL COLTFORM ANALYSES, org/100 ml
Station
6 6 4
Date Time 01 x 10 03 x 10 05 x 10 06
January 9 0 1.6 1.3 4.8
2 1.1 <10
4 1.6 1.0 4.3
6 7.4 <10
8 11.0 1.5 5.6
10 6.0 <10
12 3.3 1.2 6.5
14 18.0 <10
16 11.0 1.3 6.7
18 6.2 <10
20 3.3 1.3 18.0
22 4.1 100
24 2.7 1.5 6.4
January 10 2 3.1 <10
4 1.8 1.3 4.8
6 5.0
8 5.0 1.4 6.2
10 5.5 <10
12 1.3 1.4 5.3
14 4.5 <10
16 6.5 1.6 6.1
18 8.7 <10
20 6.6 1.9 5.4
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TABLE B- 10
Aerated Lagoon Sludge
Station
PH
TKN^b>
TPO^h)
T.S.
%
T.V.S.
%
% PO^ content
of dry solids
% TKN of
dry solids
Depth
in.
7
5.3
2110
832.
6.6
3.8
12.6
32
3
8
6.7
1085
544
8.4
2.2
6.4
12.9
3.5
9
6.1
2500
569
8.6
3.8
6.6
29.0
5
10
6.4
1810
939
9.4
4.2
10
19.3
5
Weighted
Average
1930
717
8.6
3.6
8.4
22.5
4.5
(a) Collected 1/9/68
-------
TABLE B-11
Date Time Temp. D.O. Sat. D.O. Sat. at
% Temp mg/1
1/31/68 1040 20 55 9.2
1330 20 26 9.2
1545 20 81 9.2
1815 20 52 9.2
1935 20 98 9.2
2300 20 34 9.2
2/1/68 0835 20 91 9.2
0940 20 53 9.2
1130 9 95 11.6
1210 9 90.5 11.6
1330 12 93 10.8
1400 12 89 10.8
1440 20 100 9.2
1510 20 90 9.2
Oxygen Uptake
% hr mg/l/hr
10.2
0.94
11.6
1.07
18.7
1.72
35.1
3.23
6.7
0.78
8.0
0.86
20.0
-------
Time
1555
1625
1840
2040
2240
0040
0240
0440
0640
0920
1035
1125
1225
1330
1405
TABLE B-11
(Cont.)
Temp. D.O. Sat. D.O. Sat. at Oxygen Uptake
% Temp mg/1 % hr mg/l/hr
15 74 10.1
15 70 10.1 8.0
6.5 77 12.3
6.5 73 2.0 0.25
6.5 70.5 1.3 0.16
6.5 68.5 1.0 0.12
6.5 66.0 1.2 0.15
6.5 63.0 1.5 0.18
6.5 62.0 0.5 0.06
12.5 74.0 10.7
12.5 70 3.2 0.34
19.5 77 9.25
19.5 70 7.0 0.65
27.5 77 8.0
27.5 64 13.7 1.10
VJl
-------
54
TABLE B-1,2
Operation-Maintenance Costs/Month
Date
Power
Chlorine
Operation
Maintenance
1/68
29.50
22.50
41.50
-
12/67
29.30
22.50
ii
35.00
11/67
-
II
it
-
10
-
II
II
13.30
9
60.00
II
II
15.00
8
-
15.00
II
15.00
7
-
15.00
II
10.00
6
-
15.00
II
10.00
5
105.00
22.50
II
28.00
4
104.50
22.50
II
15.00
Total
328.30
202.50
416 :oo
141.30
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56
Aerated Lagoon Temperature
Eckenfelder^) gives the following relation for predicting
aerated lagoon operating temperatures:
Tw = QTj + 12ATa
Q + 12A
where Tw = lagoon temperature
Q = waste flow, mgd
= Waste temperature
A = lagoon surface area, million square feet
Ta = air temperature
For the survey period, it is assumed the mean effective
air temperature can be computed by taking the average air tem-
perature for the survey dates and the preceding eight days.
This value is computed as 3.8 degrees C from data in Table B-2.
Ta = 3„8 degrees C
Q = 0.144 mgd
T^ = 12.1 degrees C
A = 0.01875 million square feet
Tw = (0.144K12) + (12) (0.01875") (3.8)
0.144 + 12 x 0.01875
T = 1.74 + 0.86
w 0.144 + 0.225
X = 7o2 degrees C
w
% Heat Loss = 12.1 - 7.2
-------
57
Solids Accumulation
Total sludge accumulated = 6600 cubic feet
Total elapsed time s 23 months or 690 days
Percent moisture in sludge, P » 91.4%
Percent volatile matter in sludge = 42%
Specific gravity of sludge, Sfl is given by the relation/7^
Sg 250/(100 + 1.5 P^
where Pv = percent volatile matter in
sludge
Wt of sludge, W8 is given by the relation, ^
Ws - 62.4 (100-P) S8V - P (S8-l)
100
Ss « 250/100 + 1.5 x 42 - 1.54
W = 62.4(100-91.4)(1.54)(6600)-(91.4)(1.54-1)
100
W8 c 5.450.000 - negligible
100
W " 54,500 lb
s
Sludge accum/day = 54.500 = 79 lb/day
690
lb of BODj removed/day 13 230 x .765 = 176 lb/day
Sludge accum/lb BOD removed = 79 = 0.45 lb solids/lb BOD5 removed
-------
58
Aerated Lagoon Efficiency
BOD^ removal efficiency can be calculated from the relation:
L/Lq = 1/1 + KSat
where LQ = influent BOD5 mg/1
L = effluent soluble BOD5 mg/1
K = BOD 5 removal rate/day
t = detention time, days
Sa = aeration volatile suspended solids
For the survey period
Assuming
where
then
L0
= 190 mg/1
Sa
= 52 mg/1
t
= 5.25 days
K20
= 0.034/day^ and Rj. =
(0.034)(1.035)
T
= 7.2 degrees C
Krji
= 0.022/day
L
190
= 27 mg/1
1 + 0.022 x 5.25 x 52
The total effluent BOD5 is computed from the relation:
BOD5 = L + BOD5 of solids
Assuming mg BCH^/mg SS = 0.3^
then BOD 5 = 27 +0.3 x 52 =43 mg/1
Calculated efficiency = 190 - 43 - 77 ^
-------
59
Aerator Evaluation
Assume steady state conditions and that the supplemental aeration
does not supply significant oxygen.
The following relation can be used to determine the rated
efficiency of the aerator:
N0 = N/ C.„ - Ct. x 1.02T"20 x oC
C20
where N0 = rated aerator output at 20°C, 1
atmosphere pressure, and 0 mg/1
DO, in lb 02/Hp-hr
N = aerator output at operating conditions,
lb 02/Hp-hr
C8W = DO saturation, mg/1 at temperature T
T = temperature, °C
CL = lagoon DO, mg/1
C20 = DO saturation at 20°C, mg/1
06 = transfer coeffient of waste/pure water
The aerator output at operating conditions N, can be computed
from the relation:
N = lb O2 = a' Lr + b1 Sa + BA
where a1 = lb O2 required per lb BOD5 removed
b' = lb O2 required per lb MLSS
Lr - lb BOD5 removed
B = bottom sludge oxygen demand, lb 02/day-ft
-------
60
a' = 0.6 and bj. = 0.28 x 1.0351"20, b7 2 = 0.18
Sa = 52 x 8.34 x 0.755 = 327 lb
Lr = (190-27) x 8.34 x 0.144 = 196 lb/day
B =1 mg/l/hr @ 20°C which = 0.00185 lb 02/day/ft2
Bt = B20 1.13t"20
B7<2 = (0.00185)(1.13)7*2"2°
= 0.00039 lb 02/day - ft2 at 7.2°C
A =TT * 1502/4 = 17,650 ft2
N = 0.6 x 196 + 0.18 x 327 + (0.00039)(17,650)
N =118+59+7
N = 184 lb 02/day per 5 Hp aerator
N = 1.53 lb 02/Hp-hr
Therefore, with
C8W = 12.14 mg/1
C2o = 9.17 mg/1
CL =3.5 mg/1
^ = assumed at 0.95
N0 = 1.54 12.14 - 3.50 x 1.027*2 " 20 x 0.95
9.17
N0 = 1.54/0.942 x 0.776 x 0.95
N0 = 1.54/0.695
-------
Assuming temperature rises to 20°C, the oxygen demand
would be calculated as,
L =190 = 18.5
1 + 0.034 x 52 x 5.25
Lr = (190 - 18.5)8.34 x 0.144 = 206 lb/day
b1 = 0.28
B = 0.00185
lb 02 required = 0.6 x 206 x 0.28 x 327 + 0.00185 x 17,650
= 123 +92+33
= 248 lb 02/day
Assuming a minimum oxygen level of 1.0 mg/1 should be
maintained in the lagoon,
N = 2.22 x 9.17 - 1.00 x 1.0 x 0.95
9.17
-------
62
Annual Cost Calculations
Annual Cost (Excluding Cost of Septic Tank)
Assuming an interest rate of 4%, and a structure life of
twenty-five years, costs adjusted with the ENR cost index.
Capital Costs
Stage 1
Stage 2
Total Cost
Annual Cost
1961 Cost = $30,000
ENR Cost in 1961 = $825
ENR Cost in 1965 = $950
Cost Adjustment factor = $1.15
Cost = $34,500
1965 Cost = $32,500
$67,000
$67,000 (erf. 4.25)
$67,000 x 0.06401 $4290
Operation-Maintenance Costs (Data from Table B-ll)
Power = 66 x 12 = $791/yr
Chlorine = 20.25 x 12 = $245/yr
Operation = 41.50 x 12 = $498/yr
Maintenance = 14.13 x 12=$170/yr $1704
Total Annual Costs
Cost/mg treated
Cost/lb BOD5 removed
$5994
$ 114
------- |