WATER POLLUTION CONTROL RESEARCH SERIES
16080—11/69
NUTRIENT REMOVAL FROM CANNERY WASTES
BY SPRAY IRRIGATION OF GRASSLAND
U.S. DEPARTMENT OF THE INTERIOR • FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
-------
WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Reports describe the
results and progress in the control and abatement of
pollution of our Nation's waters. They provide a central
source of information on the research, development*, and
demonstration activities of the Federal Water Pollution
Control Administration, Department of the Interior,
through inhouse research and grants and contracts with
Federal, State, and local agencies, research institutions,
and industrial organizations.
Water Pollution Control Research Reports will be distributed
to requesters as supplies permit. Requests should be sent
to the Planning and Resources Office, Office of Research
and Development, Federal Water Pollution Control Administration,
Department of the Interior, Washington, D.C. 20242.
-------
NUTRIENT REMOVAL FROM CANNERY WASTES
BY SPRAY IRRIGATION OF GRASSLAND
by
James P. Law, Jr., Research Soil Scientist, Project Leader
R. E. Thomas, 'Research Soil Scientist, In-Charge of Field Operations
Leon H. Myers, Research Chemist, In-Charge of Analytical Operations
Water Quality Control Research Program
Robert S. Kerr Water Research Center
South Central Region
Ada, Oklahoma
for the
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
U.S. DEPARTMENT OF THE INTERIOR
16080 11/69
November 1969
-------
FWPCA Review Notice
This report has been reviewed by the Federal
Water Pollution Control Administration and
approved for publication. Mention of trade
names or commercial products does not con-
stitute endorsement or recommendation for
use*
ii
-------
TABLE OF CONTENTS
Page
PREFACE ill
LIST OF TABLES vii
LIST OF FIGURES ix
SUMMARY xi
Chapter
I. INTRODUCTION 1
II. EXPERIMENTAL PLAN 5
III. WASTEWATER CHARACTERIZATION 9
IV. HYDROLOGY 17
V. WATERSHED TREATMENT EFFICIENCIES 25
VI. FARM EFFLUENT QUALITY 37
VII. SOIL AND SOIL WATER 47
VIII. SUPPLEMENTAL STUDIES 53
REFERENCES 63
APPENDIX I Description of Chemical Parameters . 67
APPENDIX II Chemical Data Form for Surface Water Samples . 71
APPENDIX III Chemical Data Form for Soil Water Samples. . . 73
-------
PREFACE
This study was part of a joint venture with the Campbell
Soup Company which sponsored investigations by C. W. Thornthwaite
•Associates of climatological and agricultural phases along with
sponsorship of North Texas State University's evaluations of
biological relationships.
A compendium of all the efforts of the various researchers
is available in Publications in Climatology, Volume 22, #2,
Laboratory of Climatology, Elmer, New Jersey. The major contrib-
utors to the research effort in other areas were D. M. Parmelee
and J. P. Ford of C. W. Thornthwaite Associates and A. S. Kester
and J. P. Vela, Biology Department, North Texas State University.
The authors wish to acknowledge the cooperation and
assistance of Mr. L. C. Gilde, Director-Environmental Engineering,
Campbell Soup Company, Camden, New Jersey, and Mr. Charles Neeley
and his associates at the Paris, Texas, plant. Their cooperation
made the conduct of this study possible and their detailed knowledge
of the system and its operation made the task much easier for
all participants.
J.P.L.
R.E.T.
L.H.M.
Ada, Oklahoma
November 1969
iii
-------
LIST OF TABLES
Table Page
1. Description of Experimental Watersheds 6
2. Spray Application Schedule for the Experimental Water-
sheds 7
3. Characteristics of Wastewater at the Four Experimental
Spray Lines from April 1968 Through October 1968 . . 10
4. Wastewater Composition Change During Collection and
Handling 11
5. .Daily Variation in Composition of Wastewater 14
6. Wastewater Characteristics, Means for All Sampling
Periods 15
7. Deviation of Rainfall and Evaporation from Normal. . . 19
8. Seasonal Water Balances 21
9. Percent Distribution of Water Accounted for on the
Four Experimental Watersheds '22
10. Mean Chemical Quality of Runoff and Concentration
Treatment Efficiency for Watershed G-4 27
11. Mean Chemical Quality of Runoff and Concentration
Treatment Efficiency for Watershed G-ll 28
12. Mean Chemical Quality of Runoff and Concentration
Treatment Efficiency for Watershed B-ll 29
13. Mean Chemical Quality of Runoff and Concentration
Treatment Efficiency for Watershed Y-l 30
14. Mean Mass Removal Percentages from April 1968 Through
October 1968 33
15. Mean Mass Removal Percentages from November 1968
Through April 1969 34
16. Farm Effluent Quality and Concentration Treatment
Efficiency, Mean Values 45
17. Soil Sample Analyses 4g
18. Summary of Soil Water Analyses 51
19. Treatment Efficiency Versus Distance Downslope from
Spray Line 54
20. Contaminants Removed by Filtration 55
21. Nitrate in Fixed and Unfixed Wastewater Samples. ... 57
vii
-------
LIST OF TABLES
Table Page
22. Recovery of Treatment Efficiency by Resting a Water-
shed 58
23. Mean Concentration of Rainfall Runoff and Subsequent
Wastewater-Spray Runoff from the Experimental
Watersheds 61
viii
-------
LIST OF FIGURES
Figure Page
1. Diurnal Variation in Composition of Wastewater. ... 13
2. Effect of Rainfall on the Fraction of Liquid Recov-
ered as Runoff 24
3. Daily Mean Electrical Conductivities 39
4. Effect of Rainfall on Electrical Conductivity of
Farm Effluent 41
5. Diurnal Variation of Electrical Conductivity of
Wastewater 43
6. Diurnal Variation of Electrical Conductivity of Farm
Effluent 44
7. Changes of Nitrate and Nitrite Concentrations with
Time in Unfixed Wastewater Samples 56
8. Effect of Extended Drying on Nitrogen Transformations
and Percent Removal 60
ix
-------
SUMMARY
A comprehensive 12-month study was conducted to deter-
mine treatment efficiencies of a spray-runoff system for cannery
wastes. A total of 133 inches of wastewater was applied to
four experimental watersheds during the study period. Hydro-
logical measurements, chemical removal efficiencies, and changes
in soil properties were evaluated in relation to years of waste-
water application, soil type, and spray schedule.
Hydrological measurements were made to account for all
liquid applied and lost from the experimental watersheds. The
measurement techniques employed accounted for 93 percent of the
applied liquid during the 12-month study. Water balances showed
that evaporative losses accounted for 18 percent of the total
liquid applied, runoff accounted for 61 percent, and deep-soil
percolation accounted for 21 percent. Runoff from the clay loam
soil was measurably greater than from the sandy loam soil. During
periods of heavy rainfall, runoff increased to a maximum of 80
percent of the total applied liquid.
The wastewater quality varied regularly according to
routine changes in the production schedule. The spray-runoff
system provided a buffering capacity, which eliminated most of
this variability from the quality of the stream leaving the system.
Rainfall provided dilution water and removed stored soluble salts
at low concentrations during periods of high flow.
The results of this study showed that a high degree
of treatment was achieved. Under its present operating schedule,
the system achieves mass removals of 92 to 99 percent of the
volatile solids and oxygen-demanding substances, 86 to 93 percent
removal of nitrogen, and 50 to 65 percent removal of phosphorus.
Mass removal efficiencies were consistently greater than con-
centration reduction efficiencies since the runoff ranged from
40 to 80 percent of the applied wastewater. Soil textural class
and system age had very little effect on treatment efficiencies.
xi
-------
Although the present system design and operating schedule provide
excellent treatment, the results of this study showed that treat-
ment efficiency was improved by spreading the wastewater load
over a greater fraction of the land area and by reducing the
frequency of application. The greatest change was in phosphorus
removal, which was increased from 40 percent to 88 percent by
changing from a one-per-day to three-per-week spray schedule.
Data from three farm effluent locations verified the ability of
the spray-runoff system to produce a highly treated effluent
throughout the year, although there appeared to be a slight
reduction in efficiency during the winter months.
Evaluation of surface and subsoil samples and soil
water samples collected monthly at the 3-foot depth indicated
an increase in salinity with age. Both total dissolved solids
and sodium showed increases on the older watersheds, but nitrogen
and phosphorus remained low. A substantial fraction of the phos-
phorus removed from the wastewater was accounted for in the
surface soil layer. The buildup of salinity and sodium on the
older watersheds indicates that these should be monitored again
in a few years to determine if a state of equilibrium were being
reached. If they should continue to increase, soil and plant
problems could develop at sometime in the future.
xii
-------
CHAPTER I
INTRODUCTION
The spray application of waste effluents to soil-plant
systems as a treatment method has received increased attention
in the past decade (1). It has been applied to such diverse
industrial wastes as those from paper mills and canneries as well
as municipal sewage treatment plant effluents (2,3,4,5,6). For
treatment efficiency, such a system relies not only on infiltration
and plant utilization but, in some cases, a rather large percentage
of the applied liquid receives treatment and returns as surface
runoff. Crop production is not usually the primary objective
of such waste treatment systems. However, a recent report (7)
showed that cash crop production over an 8-year period was excellent
with no apparent damage to crops or soil when irrigated regularly
with a paper mill waste effluent. Applications have been made
on areas ranging from forested to grassland, and the systems
have been referred to as grass filters and "living filters" (8).
A spray-runoff soil treatment system for cannery wastes
was designed for the Campbell Soup Company plant at Paris, Texas,
by C. W. Thornthwaite Associates of Elmer, New Jersey, and put
into operation late in 1964 (9). The initial system of about
250 acres was expanded to about 400 acres in 1965 to accommodate
an increase in wastewater flow. Through 1965, plant production
increased to a waste output level of 2.2 million gallons per day
(MGD). With the additional farm area, waste output reached about
3.2 MGD in 1968. This soil system receives the wastewater from
the production of the complete line of heat process soups.
Prior to levelling, terracing, and preparing for the
present system, the land was severely .eroded from cotton farming
during the 1930's and had been abandoned to native vegetation.
Extensive levelling obscured the remaining thin layer of topsoil
and exposed the gray to reddish clay subsoil in much of the area.
-------
2
Terraces and the intervening spray lines were located 200 to 300
feet apart on slopes ranging from 1 to 6 percent. There are
over 700 sprinklers on 77 individual spray lines that are semi-
automatically controlled by clock mechanisms. The spray lines
operate on a 24-hour basis—6 hours on, 18 hours off during cool
humid winter months; and 8 hours on, 16 hours off during late
spring, summer, and early fall. The slopes are covered with a
lush growth of Reed canarygrass, tall fescue, and red top. Reed
canarygrass predominates in the spray pattern and downslope in the
wettest areas. The other two varieties cover the remainder of
the slopes with some native hermuda persisting in limited areas.
During the first few years of operation, the grasses
were mowed and the litter left on the fields to decompose and
build up an organic layer. A partial harvest of hay was removed
in 1967 and in 1968 the entire area was harvested once.
Our interest in a research study of the system was
inspired by a visit to the plant in May 1967. At that time it
was learned that the 5-day biochemical oxygen demand (BOD) test
was the principal parameter used to judge the treatment efficiency
of the system. It was also learned that the untreated waste
had a BOD content of 500-800 mg/1, while the BOD of the runoff
was consistently less than 10 mg/1. The pH of the waste fluctuated
daily from a low of about 5 during raw material preparation and
product processing to a high of about 10 at night when kettle
washing and plant cleaning operations were in progress.
Although all phases of the treatment system satisfied
the requirements of the State Health Department, there remained
many unanswered questions regarding the efficiency of the system
from a pollution control viewpoint. No doubt the organic content
was successfully removed. No data were available relating to the
total nitrogen and phosphorus content of the waste or the runoff.
The question was raised as to whether the BOD test alone was an
-------
adequate criterion for judging the success of the operation. No
measurements of the runoff volume had ever been made, but it was
estimated to be as low as 20 percent in the ^hot summer months
and 80 percent or higher during humid winter weather.
Further observations in the fields revealed a tough
organic layer on the soil surface within the sprinkler areas.
It appeared that such an organic layer would greatly reduce
infiltration in those areas, since it could be peeled from the
soil showing very little penetration of the surface. In areas
where it had dried, it tended to crack and curl, exposing the
soil underneath. Interesting questions were raised regarding
the role of this organic layer in the treatment process. Does
it act similarly to the slime coating of a trickling filter?
The following additional questions formed the basis for conducting
a detailed study of the treatment, system:
a. What is the treatment efficiency with regard to
the nutrient compounds of nitrogen and phosphorus?
b. How does the treatment efficiency vary with a range
of loading and runoff conditions?
c. How much runoff actually occurs and how does it
vary with the seasons? .
d. What is the character, quantity, and fate of the
percolating soil water?
e. How does the soil moisture profile vary with loading?
f. What range of salinity is encountered in the waste
and runoff?
g. What is the effect of a wide range, in pH on soil
plants?
h. What is the sodium content of the waste, and what
long-term effects oh the soil may be expected?
i. Should the grass be harvested and removed or left
on the fields to decompose?
j. Does the present spray schedule constitute the
optimum loading rate?
-------
4
Objectives of the Study
Subsequent discussions with company officials revealed
their interest and willingness to permit a 12-month detailed
study of the treatment system. Plans were formulated for this
proposed study with the following specific research objectives:
a. To determine the nutrient removal efficiency of
spray irrigation of grassland as it is presently
being practiced at the Campbell Soup Company plant,
Paris, Texas.
b. To determine infiltration, surface runoff, and
soil moisture fluctuations under different loading
conditions.
c. To correlate nutrient removal efficiency to pres-
ently observed reduction in BOD and suspended solids.
d. To more fully elucidate the mechanisms responsible
for treatment efficiencies observed in the spray
irrigation "grass filter" type of waste treatment
system.
Our research plan was approved and made a part of a
comprehensive study involving four organizations. Campbell Soup
Company coordinated the three-phase research study and financed
the microbiological, microclimatological, and crop management
research conducted by the Biology Department of North Texas State
University and C. W. Thornthwaite Associates. The Robert S. Kerr
Water Research Center conducted a concurrent and independent
study to evaluate the hydrology and treatment efficiency of the
system. This report presents the results of the treatment
efficiency data collected during the 12-month detailed study of
the spray-runoff treatment system.
-------
CHAPTER II
EXPERIMENTAL PLAN
A 12-month experimental period was selected to provide
an evaluation of the system under the climatic conditions for
all four seasons. Several existing watersheds which were rep-
resentative of the whole system were selected for experimental
study. These watersheds were instrumented to provide a continuous
record of the hydrology, the quality of the applied wastewater,
and the quality of the water leaving the treatment system.
The four watersheds were selected to represent the
known differences in date of establishment and soil textural class.
Descriptions of the four experimental watersheds are summarized
in Table 1. These watersheds were isolated so that the only liquid
reaching them was natural rainfall or wastewater spray
actually falling within the watershed. Isolation was accomplished
by modifying existing terraces, taking advantage of natural divides,
and forming boundaries with lawn edging. Composite soil samples,
obtained from 15 subsamples, were taken to determine the effects
of wastewater spraying on the soil. Samples at the 0- to 2-inch
and 11- to 13-inch depths were taken from the experimental area
receiving wastewater and from the border area not receiving waste-
water .
Spray applications to these four watersheds were continued
on the same schedule as the rest of the treatment system except
for two minor changes. One change insured that each experimental
area received continuous application throughout each scheduled
spray period, whereas the normal spray schedule permitted intermittent
spraying during some of the scheduled spray periods. The other
change was to program the experimental areas out of weekend operation
while the normal schedule called for weekend operation once every
three or four weeks. The spray application schedule for the
four experimental watersheds is presented in Table 2. The periods
when no spray was applied were times when the plant was shut down,
when crops were being harvested, or when a line needed a rest
5
-------
TABLE 1
DESCRIPTION OF EXPERIMENTAL WATERSHEDS
Identification
Code
G-,4
Y-l
G-ll
B-ll
Year Spray
Started
1964
1964
1966
1966
Area
(Acres)
3.9
2.6
1.5
3.4
Slope
Percent
2-3
2
4-6
2
Length (ft)
320
280
150-280
220
Soil Textural Class
0- to 2-inch depth
sandy loam
clay loam
sandy loam
loam
11- to 13-inch depth
sandy clay loam
clay
sandy clay loam
clay
-------
TABLE 2
SPRAY APPLICATION SCHEDULE FOR THE EXPERIMENTAL WATERSHEDS
G-4
Dates
4/22/68 - 6/1/68
6/2/68 - 7/29/68
7/30/68 - 8/24/68
8/25/68 - 9/25/68
9/26/68 - 10/7/68
10/8/68 - 10/31/68
11/1/68 - 4/25/69
Spray
(in. /week)
3.8
5.1
0.0
6.2
0.0
4.5
3.2
Y-l
Dates
4/22/68
6/2/68
7/22/68
8/19/68
9/26/68
10/8/68
11/1/68
2/25/69
3/8/69
- 6/1/68
- 7/22/68
- 8/18/68
- 9/25/68
- 10/7/68
- 10/31/68
- 2/24/69
- 3/7/69
- 4/25/69
Spray
(in. /week)
4.4
6.0
0.0
7.1
0.0
5.2
3.1
0.0
3.1
G-ll
B-ll
Dates
4/22/68 - 6/1/68
6/2/68 - 7/29/68
7/30/68 - 8/24/68
8/25/68 - 9/25/68
9/26/68 - 10/7/68
10/8/68 - 10/31/68
11/1/68 - 2/20/69
2/20/69 - 3/1/69
3/2/69 - 4/25/69
Spray
(in. /week)
3.8
5.1
0.0
6.2
0.0
4.5
3.8
0.0
3.8
Dates
4/22/68
5/7/68
6/23/68
8/25/68
9/26/68
10/8/68
11/1/68
4/16/69
- 5/6/68
- 6/22/68
- 8/24/68
- 9/25/68
- 10/7/68
- 10/31/68
- 4/16/69
- 4/25/69
Spray
(in. /week)
3.2
0.0
4.3
5.1
0.0
3.8
3.5
0.0
-------
8
to recover its ability to treat the wastewater. The variation
in the amount of spray scheduled for application was the result
of seasonal operating changes, watershed characteristics, and
changes in plant production requirements. During the 12-month
study period, the experimental areas averaged 43 weeks of spray
application and received an average of 133 inches of wastewater.
Volume measurements of the liquid applied and the water
losses from the experimental area were determined to make a
complete water balance. Rainfall and spray were the only sources
of applied liquid, and the loss of liquid was attributed to spray
evaporation, evapotranspiration, runoff, and soil percolation.
Rainfall was measured with rain gauges; wastewater spray volumes
were calculated from nozzle delivery rates and time information;
spray evaporation was determined empirically; evapotranspiration
was calculated from weather data collected at an on-site weather
station; runoff was determined with flow measuring flumes; and
soil percolation was estimated from changes in the soil moisture
content following spray applications.
Four sampling points were selected for monitoring the
changes in the quality of the wastewater as it was treated.
These points were the wastewater spray line, the runoff flume,
the stream leaving the treatment system, and the soil water at
the 3-foot depth. Abrupt changes in the quality of the wastewater
being applied and design characteristics of the wastewater treat-
ment system made it necessary to use special care in obtaining
representative liquid samples. Fifteen chemical parameters
were used to evaluate the quality of the liquid samples.
Detailed explanations of the experimental procedures
and special instrumentation employed are included in the appro-
priate sections which follow.
-------
CHAPTER III
WASTEWATER CHARACTERIZATION
Methods and Procedures
Determination of changes in concentration of all chemical
parameters studied was dependent on establishing the composition
of the wastewater for each sampling period. Wastewater samples
were collected in the spray pattern of each experimental line
by using three powder funnel-and-jug arrangements. The jugs
were supported on metal stands above the vegetation and were
spaced equidistant along the spray lines. At each spray line,
one jug was placed near a nozzle, one midway of the spray pattern,
and one near the outer edge of the pattern. At the completion
of a spray period, the wastewater sample was taken by compositing
a one-gallon sample from the three collecting jugs. Fifteen
chemical parameters were used to characterize the wastewater.
The analytical procedures used were the Official Interim Methods
of the Federal Water Pollution Control Administration (10). •
Descriptions of the chemical parameters, abbreviations used, and
sample analytical data-forms are included in Appendices I, II, and III,
Results and Discussion
During the first six months of the study, wastewater
samples were collected at each of the four experimental lines
to determine the variability in composition. The results of
this evaluation of five parameters are presented in Table 3.
Statistical analyses of these data indicated that there were no
significant differences in the composition of the wastewater
spray collected at the four experimental lines. Therefore, the
wastewater sampling procedure was modified to reduce the number
of individual samples. From November 1968 through April 1969,
composite wastewater samples were obtained from lines G-4 and G-ll.
9
-------
10
TABLE 3
CHARACTERISTICS OF WASTEWATER AT THE FOUR EXPERIMENTAL
SPRAY LINES FROM APRIL 1968 THROUGH OCTOBER 1968
Spray line
G-4
Y-l
G-ll
B-ll
Concentration, mg/1
BOD
467
486
516
451
COD
721
697
762
759
VSS
179
174
183
189
T-P
8.4
8.4
8.6
9.0
T-N
18.8
17.1
18.8
21.2
Note: Abbreviations of chemical parameters are
explained in Appendix I.
The method of collecting and handling wastewater samples
provided both time and conditions suitable for some loss of
biodegradable constituents before analysis. The extent of this
loss was evaluated during the latter six months of the study.
This was accomplished by simultaneously collecting two sets of
wastewater samples on each of the two experimental lines, G-4
and G-ll. One set-was collected in bottles containing concentrated
sulfuric acid to immediately fix the sample and stop all biological
activity. The other set was collected and handled in the normal
manner. The results of this comparison for four parameters are
presented in Table 4. The concentrations of the major organic
parameters in the acid-fixed samples were consistently greater
than those in the unfixed samples. The indicated losses ranged
from a low of 4 percent for phosphorus to a high of 12 percent
for total nitrogen. A statistical analysis of the data showed
that the differences in the concentration for COD and TOG were
significantly different at the 5 percent level of probability,
-------
11
TABLE 4
WASTEWATER COMPOSITION CHANGE DURING COLLECTION AND HANDLING
Method of Sample
Collection
Non-fixed
Fixed
Concentration, mg/1
COD
1010
1140
TOC
300
340
T-P
6.7
7.0
T-N
19.2
21.7
Note: Abbreviations of chemical parameters are explained
in Appendix I.
while the differences for total phosphorus and total nitrogen were
not. It is apparent that the composition of the wastewater changed
somewhat during the normal sampling and handling procedure.
However, this change in composition of the wastewater does not
detract from the validity of the treatment efficiencies reported,
since it represents a small negative effect on the calculated
values.
Variability in composition. The major source of
variability in wastewater composition was the diurnal changes
associated with the schedule of operations in the processing plant.
Raw vegetable processing began about 0500 each workday and continued
until mid-afternoon. Workers arriving at 0700 began preparing
the raw products for cooking and canning the assigned batches
of finished products for the day's production. The late evening-
to-midnight shift completed the cooking and canning operations.
Workers arriving at midnight carried out the major cleanup oper-
ations for the day, washing down cooking kettles, all processing
machinery, processing plant floors, etc., all in preparation
for the next day's operations. Thus, the operations being
performed in the processing plant at different periods of the
-------
12
day had an influence on the wastewater characteristics. The
diurnal variation in wastewater composition is summarized in
Figure 1.
BOD, COD, and VSS exhibited very similar patterns of
variation. Minimum concentrations occurred during the early
morning cleanup period and maximum concentrations occurred during
daytime and evening when the major operations were processing
and canning. Phosphorus concentrations were greatest during
the plant cleanup operation. Changes in the nitrogen concentration
were relatively minor and did not follow the pattern of any of
the other parameters. Phosphorus showed the greatest range of
variability, ranging froma high mean of 16.8 mg/1 during cleanup
to a low mean of 3.1 mg/1 during processing and canning.
Four times during the 12-month study, intensive study
periods of one week each were conducted. These were scheduled
at 3-month intervals so that all seasons were represented.
The daily variation in the composition for these intensive study
periods is shown in Table 5. There were large day-to-day changes
in the composition of the wastewater during each of the four seasonal
sampling periods. The.daily changes in composition occurred
randomly, and there was no consistent pattern to wastewater
composition changes during the week.
A complete summary of wastewater characteristics is
presented in Table 6. The four 6-hour sampling periods represent
the October through May spray schedule, and the three 8-hour
sampling periods represent the June through September spray
schedule. The 24-hour composite was obtained by taking a weighted
average of the data collected for the seven time intervals.
Summary and Conclusions
The sampling procedures used to characterize the waste-
water established many factors pertinent to evaluating the nutrient
removal efficiency of the treatment system. The hypothesis that
the wastewater quality would be variable was substantiated.
-------
1000
eoo-
600
o
LU
O
Z
O
o
400-
200
COD
VSS
4AM
10AM
20
18
16
14
10
4PM 10PM 4AM
MIDPOINT OF 6-HOUR SAMPLING PERIOD
10AM
4PM
10 PM
FIGURE I -DIURNAL VARIATION IN COMPOSITION OF WASTEWATER
-------
14
TABLE 5
DAILY VARIATION IN COMPOSITION OF WASTEWATER
Season
Monday
Tuesday
Wednesday
Thursday
BOD, mg/1
Summer
Fall
Winter
Spring
517
663
521
646
506
556
578
593
483
341
425
700
590
557
596
COD, mg/1
Summer
Fall
Winter
Spring
734
590
1040
1040
872
708
944
1012
802
718
664
871
1030
863
577
1055
VSS, mg/1
Summer
Fall
Winter
Spring
116
279
202
193
242
270
248
203
112
128
240
181
232
288
T-P, mg/1
Summer
Fall
Winter
Spring
3.4
1.5
4.5
4.7
4.0
4.8
4.2
4.6
3.5
4.6
2.5
3.6
3.1
3.6
4.0
3.2
T-N, mg/1
Summer
Fall
Winter .
Spring
16.5
6.5
36.1
22.5
20.8
9.5
26.8
30.5
23.6
9.9
12.1
16.8
25.6
10.9
21.5
21.8
Note: Abbreviations of chemical parameters are explained
in Appendix I.
-------
TABLE 6
WASTEWATER CHARACTERISTICS, MEANS FOR ALL SAMPLING PERIODS'
Parameter
b
pH, units
EC, ymhos/cm
Cl
M.O. Alk
TSS
VSS
TP
N03-N
N02-N
NH3-N
Kjeldl-N
Total-N
COD
TOC
BOD
Time interval for collecting composite samples
1 a.m.-
7 a.m.
8.2
490
58
106
230
201
16.7
0.4
<0.05
16.9
17.3
655
198
463
7 a.m.-
1 p.m.
6.6
420
40
60
246
219
5.2
0.2
<0.05
15.7
15.9
869
284
562
1 p.m.-
7 p.m.
6.9
400
38
80
267
245
3.0
0.2
<0.05
16.3
16.5
925
282
693
7 p.m.-
1 a.m.
6.6
430
39
42
305
277
4.1
0.2
<0.05
19.4
19.6
1005
300
737
7 a.m.-
3 p.m.
6.0
480
36
35
226
206
3.3
0.1
<0.05
14.7
14.8
697
211
494
3 p.m.-
11 p.m.
4.8
450
38
18
211
162
3.8
0.1
<0.05
16.8
16.9
667
234
476
11 p.m.-
7 a.m.
6.6
500
54
93
166
148
11.7
0.1
<0.05
_ __
•17.2
17.3
629
194
409
Q
^All concentrations in mg/1 except where noted
24-hour
Composite
6.6
450
44
68
245
218
7.4
0.2
<0.05
1.0
17.0
17.2
806
250
572
Median values instead of a mean
Note: Abbreviations of chemical parameters are explained in Appendix I.
-------
16
Much of the variability was shown to be related to changes in
the plant operation. It was shown that there was no measurable
difference in the quality of wastewater delivered to the four
- experimental watersheds, therefore, differences in the composition
of the wastewater would not bias the comparison of treatment
efficiencies between watersheds. The sample collection and handling
procedure allowed a measurable loss of oxygen demand of about 10
percent. This loss had little effect on the percent removal of
oxygen demand because the removals were in the 95 to 99 percent
range. There were no composition changes related to the day
of the week so the Wednesday samples used throughout the 12-month
study were taken to be indicative of operations on any day of
the week.
-------
CHAPTER IV
HYDROLOGY
The evaluation of the system's hydrology depended
on identifying and accurately measuring the effects of the
processes which contributed or withdrew liquid from the experimental
watersheds. Selection and isolation of the watersheds limited
the contributing processes to rainfall and wastewater spray.
Spray evaporation* evapotranspiration, runoff, and soil percolation
were selected as the withdrawal processes which would contribute
measurably to the total water loss. The method chosen for measuring
each of these six parameters is discussed briefly and an estimate
of the reliability of the method is given.
Methods and Procedures
A network of three rain gauges provided an accurate
record of rainfall data, and no difficulties were experienced
in determining this fraction of the liquid load with a high
degree of accuracy. The spray volume was calculated from nozzle
delivery rates and time data. Occasional mechanical malfunctions
such as nozzle plugging, valve failures, pressure variations,
and spray line leaks caused discrepancies in the determination
of spray volumes. A routine practice of reporting operational
procedures and problems was used to eliminate most of the data
influenced in this manner. Evaluation of the characteristics
of runoff peaks provided a final check on the volume of spray.
Persistent mechanical leaks of less than 5 percent of the daily
spray volume were detected with these cross-checking procedures.
The reliability of the determination for wastewater spray was about
±10 percent.
The initial liquid loss was direct evaporation of the
*spray before it reached the ground'. This loss has been reported to
range from 2 to 8 percent (11). An empirical method was chosen
to estimate this relatively small component of the total water
17
-------
18
loss. The empirical method was based on an arbitrarily derived
relationship between the 2- to 8-percent range, the time of day,
and evapotranspiration values.
Evapotranspiration was calculated from the weather
observations taken at the on-site weather station. Daily values
were calculated by the Thornthwaite and Mather method (12).
These values were subsequently recalculated to correct for seasonal
discrepancies which are inherent in this method.1 A reliability
range of ±22 percent is generally accepted as good for estimates
of potential evapotranspiration (13).
Runoff was measured with the H-flume developed by the
U. S. Department of Agriculture (14). This flume was selected
because of its high accuracy over a wide range of flow rates.
The flumes installed had a working range of 0.001 to 5.33 cfs.
This range provided very accurate measurement for the low runoff
rates following summer spray applications as well as the high
runoff rates from high intensity rain showers.
A neutron soil moisture logger was used to obtain data
for estimating soil percolation. The instrument used produced
very accurate soil moisture profiles at a logging speed of 2.5 feet
per minute. The method of Rose, Stern, and Drummond (15) was
used to calculate deep soil percolation from a series of soil
moisture profiles and soil-water suction data. Such estimates
of deep soil percolation have a reliability of about ±25 percent (16)
Results and Discussion
Liquid applied. The rainfall and evaporation data
presented in Table 7 show that climatic conditions during the
12-month study deviated considerably from normal. Rainfall at
the experimental site was 57.00 inches for the study period.
This exceeded the normal for the official weather station at
Paris, Texas, by 11.89 inches. The nearest weather station
Personal communication with J. R. Mather, C. W.
Thornthwaite Associates, Elmer, New Jersey, February 1969.
-------
19
TABLE 7
DEVIATION OF RAINFALL AND EVAPORATION FROM NORMAL
Month
1968 May
June
July
August
September
October
November
December
1969 January
February
March
April
Deviation, inches
Rainfalla
+0.21
+1.57
+0.66
-1.95
+4.47
+0.34
+2.50
-0.64
+3.15
+2.07
+1.77
-2.26
Evaporation
-1.50
-2.15
-2.09
-0.73
-1.24
-0.06
-0.43
+0.28
-0.18
-0.37
-1.04
-1.14
Rainfall deviation is from normals for
Weather Bureau Station at Paris, Texas.
Evaporation deviation is from normals
for Weather Bureau Class A Pan at Denison
Dam which is 65 miles west of Paris, Texas.
-------
20
measuring evaporation was at Denison Dam, which is 65 miles west
of the experimental area. The evaporation at this station was
10.65 inches below normal for the 12 months of the study. These
weather conditions increased rainfall as a fraction of the liquid
applied and increased runoff in comparison to results for normal
or droughty weather conditions. The applied liquid for the study
period was 24 percent rainfall and 76 percent wastewater spray.
In a year with the same amount of wastewater spray and rainfall
10 inches below normal, rainfall would account for only 16 percent
of the total applied liquid.
Water balance. The major objective of the hydrology
study was to obtain a complete water balance for each of the
experimental watersheds so that nutrient removal efficiences
could be evaluated on a mass basis. These water balances are
summarized in Table 8. These data showed that similar balances
were achieved for each of the watersheds under all operating
conditions. Each water balance was best in the spring and poorest
in winter with the fall and summer values intermediate. The
overall water balances ranged from 91 to 97 percent. The errors
inherent in the determination of spray volume, evapotranspiration,
and deep soil percolation could easily account for the apparent
losses of 3 to 9 percent of the applied liquid.
Distribution of water accounted for. The distribution
of the liquid accounted for is summarized in Table 9. Monthly
distributions between the evaporative losses, runoff, and deep
soil percolation for each of the watersheds showed similar patterns
due to the influence of climatic conditions and changes in the
operating schedule. The evaporative losses showed the characteristic
summer peak and the runoff losses showed a concurrent summer low.
These results were modified somewhat by the operating schedule
changes on June 1, 1968, and October 1, 1968. On June 1 the
wastewater spray period was increased from 6 hours per day to 8
hours per day. This 33 percent increase in wastewater loading
-------
TABLE 8
SEASONAL WATER BALANCES
21
Season
Spring
Summer
Fall
Winter
Year
mean
range
mean
range
mean
range
mean
range
mean
range
Recovery as Percent
of Water Applied
G-4
103
85-127
90
79-106
91
83-99
88
79-112
92
79-127
G-ll
97
72-111
91
77-113
89
75-104
89
72-116
91
72-116
B-ll
96
74-126
94
85-109
92
78-104
89
70-108
92
70-126
Y-l
103
92-125
93
96-102
98
90-113
90
74-106
Seasonal
Mean
100
92
92
89
97
74-125
repressed the increase in evaporative losses as a percentage
of the total liquid accounted for and maintained runoff as a
substantial fraction of the total throughout the summer months.
In October the wastewater spray period was returned to 6 hours
per day. This decrease in the daily wastewater load caused a
relative increase in the percent evaporative loss. The result
was similar evaporative losses for September and October followed
by a resumption of the normal seasonal decline in evaporative
losses during November. The combined influence of climatic
conditions and the changes in the operating schedule caused
deep soil percolation to vary in a more random pattern than
evaporative losses or runoff. In general, soil percolation losses
were relatively greater when evaporative losses were lower.
-------
TABLE 9
to
PERCENT DISTRIBUTION OF WATER ACCOUNTED FOR ON THE FOUR EXPERIMENTAL WATERSHEDS
1968
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
1969
Jan.
Feb.
Mar.
Apr.
12 -month
mean
Watershed G-4
Evaporative losses
Runoff
Soil percolation
20
62
18
24
58
18
35
40
25
30
44
26
18
63
19
18
58
24
12
56
32
9
61
30
10
68
22
12
61
27
19
44
37
27
42
31
20
54
26
Watershed G-ll
Evaporative losses
Runoff
Soil percolation
21
56
23
23
57
20
37
33
30
— —
_-
16
65
19
18
54
28
— —
--
8
65
27
10
70
20
3
78
19
9
61
30
24
44
32
17
58
25
Watershed Y-l
Evaporative losses
Runoff
Soil percolation
22
64
14
20
68
12
28
59
13
21
65
14
15
74
11
14
71
15
9
73
18
9
69
22
11
73
16
4
80
16
5
81
14
24
55
21
15
69
16
Watershed B-ll
Evaporative losses
Runoff
Soil percolation
26
53
21
23
61
16
36
43
21
26
61
13
19
66
15
19
61
20
10
68
22
9
70
21
10
72
18
10
70
20
12
64
24
28
48
24
19
61
20
-------
23
The difference between the sandy loam soil and the heavier
loam and clay loam soils was readily distinguishable by comparing
the 12-month data for the four watersheds. The percent runoff
•was lowest on watersheds G-4 and G-ll which have the sandy loam
soil. Runoff from B-ll with the loam soil was intermediate, and
the runoff was greatest from Y-l with the clay loam surface soil.
The percent runoff was also directly related to rainfall
events of varying intensity and quantity. The effect of rainfall
quantity on percent runoff is shown in Figure 2. The large
variability in the data was due to the effects of soil textural
class, rainfall intensity, seasonal effects, and errors in meas-
urements. The average runoff for the four watersheds ranged from
about 50 percent when there was no rainfall to about 80 percent
when rainfall accounted for about 0.6 of the total applied liquid.
Summary and Conclusions
The objective of achieving a water balance of ±10 percent
was attained as 93 percent of the calculated volume of applied
liquid was accounted for with the water loss measurements used in
this study. Evaporative losses accounted for 18 percent of the
total liquid applied, runoff accounted for 61 percent, and deep
soil percolation accounted for 21 percent. Runoff from the clay
loam soil was measurably greater than runoff from the sandy loam
soil. Increasing the wastewater load in the summer months main-
tained the runoff at more than 40 percent. Runoff increased to a
maximum of about 80 percent during periods of heavy rainfall.
-------
24
a:
£
o
UJ
"^
o
u
o
o
3
o
_l
t_
r~
o
1-
ti.
u.
o
z
3
a:
.90
.80
.70
.60
.50
.40
.30
.20
.10
0
—
o *o o
- ° °° ^ *
00 ° •
^k
0 ^ o
- o °oo o ••* • • •
0 ° 0*0 A •
°0000 ° d» * •
•Sp°0** *• *
%0 0 0 ^ •
^D«fi Q\ •
-W^ _ • o
u *v • •
-*^o* ••* °
O o
^^
--*•••
^^B
•-SANDY LOAM SOIL
- o—LOAM AND CLAY LOAM SOIL
1 1 1 1 1 . ...
0 .10 .20 .30 .40 .50 .60 .TO .80
RAINFALL/TOTAL LIQUID APPLIED
FIGURE 2 - EFFECT OF RAINFALL ON THE FRACTION
OF LIQUID RECOVERED AS RUNOFF
-------
CHAPTER V
WATERSHED TREATMENT EFFICIENCIES
Liquid sampling stations to evaluate the treatment
efficiencies of the four experimental watersheds were located
at the wastewater spray lines and the runoff flumes. Weekly
quality data collected at these stations were combined with the
hydrological data to obtain the treatment efficiencies on a
mass basis.
Methods and Procedures
The runoff was sampled with a flow proportional device
to obtain a representative composite sample after each spray
period. The sampling device was a modification of one developed
by the Tennessee Valley Authority.2 This sampler consisted of
a series of orifices and weirs that took a sample equal to
1/10,000 of the volume passing through the flume. The quality
of the liquid samples was determined with the same procedures
which were used to characterize the wastewater. Sample analytical
forms for the runoff samples are included in Appendix II.
All four watersheds were operated identically from
April through October 1968. This period of operation was used
to evaluate the effects of system age and soil textural class
on treatment efficiency. Watersheds Y-l and B-ll were operated
on different schedules while G-4 and G-ll were kept on the original
schedule from November 1968 through April 1969. A second parallel
spray line was installed on Y-l and B-ll. This additional line
increased the spray-covered area from 40 percent to 75 percent
of the watershed area. Smaller nozzles were installed on both
of the B-ll lines so that the same weekly load could be maintained
without changing the daily spray schedule. Spray nozzles were
kept at the same size on Y-l and the same weekly load was maintained
rt
^Personal communication with James W. Beverage, Chief,
Hydraulic Data Branch, Tennessee Valley Authority, Knoxville,
Tennessee, February 1968.
25
-------
26
by changing to a three-times-a-week spray schedule. The net
effect of the changes on B-ll was to maintain the same operating
schedule and total load while spreading the load over approximately
twice as much soil area. The net effect of the changes on Y-l
was to maintain the same weekly load and unit area load while
changing the frequency of application.
Results and Discussion
The characteristics of the wastewater were summarized
in Table 6 (Chap. 3). The mean concentrations for the 24-hour
composite in Table 6 were the values used to determine all percent
concentration changes between the quality of the wastewater and
the quality of the watershed runoff.
Runoff quality. The chemical quality of the runoff
and the concentration treatment efficiencies for each of the
watersheds are summarized in Tables 10, 11, 12, and 13. All
watersheds produced a highly treated runoff from April 1968 through
October 1968 when the watersheds were all being operated on the
same schedule. The data showed that this spray-runoff system
was very efficient for the removal of oxygen-demanding substances
and suspended solids. It is of particular interest to note
that the electrical conductivity and the chloride concentration
of the runoff showed a consistent increase of 10 to 15 percent.
This was probably the result of evaporation losses which increased
the concentration of dissolved salts.
Comparisons of the data for individual watersheds from
April 1968 through October 1968 showed that soil textural class
and years of service had little, if any, effect on the quality
of the runoff or the treatment efficiency as measured by concen-
tration changes. The effect of soil textural class was obtained
by comparing the data for G-4, Table 10, to the data for Y-l,
Table 13, and the data for G-ll, Table 11, to the data for B-ll,
Table 12. These direct comparisons showed that soil textural
-------
27
TABLE 10
MEAN CHEMICAL QUALITY OF RUNOFF AND CONCENTRATION
TREATMENT EFFICIENCY FOR WATERSHED G-4
Chemical
Parameter
PH
EC
Cl
M.O. Alk.
TSS
VSS
TP
N03-N
N02-N
NH3-N
Kjeldl. N
Total-N
COD
TOC
BOD
Apr. T68 thru Oct. '68
Runoff
Quality
7.0
520
50
132
10
6
4.1
0.10
<0.05
0.2
2.9
3.0
65
27
9
Concentration
Change %
+16
+11
+95
-96
-97
-45
-50
-80
-83
-83
-92
-89
-98
Nov. '68 thru Apr. '69
Runoff
Quality3
7.7
460
44
142
19
12
4.2
<0.05
<0.05
3.3
3.4
70
22
11
Concentration
Change %
+ 2
0
+110
- 92
- 94
- 43
- 81
- 80
- 91
- 91
- 98
aAll concentrations in mg/1 except: pH - units;
EC - umhos/cm
Note: Abbreviations of chemical parameters are explained in
Appendix I.
-------
28
TABLE 11
MEAN CHEMICAL QUALITY OF RUNOFF AND CONCENTRATION
TREATMENT EFFICIENCY FOR WATERSHED G-ll
Chemical
Parameter
PH
EC
Cl
M.O. Alk.
TSS
VSS
TP
N03-N
N02-N
NH3-N
Kjeldl. N
Total-N
COD
TOC
BOD
Apr. '68 thru Oct. T68
Runoff
Quality3
7.0
520
50
131
20
13
5.0
0.5
<0.05
0.2
3.6
4.1
92
31
11
Concentration
Change %
+ 16
+ 11
+ 94
- 92
- 94
- 32
+150
- 80
- 79
- 76
- 89
- 88
- 98
Nov. '68 thru Apr. '69
Runoff
Quality3
7.4
490
45
139
31
24
4.4
<0.05
<0.05
4.2
4.2
160
51
62
Cone entration
Change %
+ 9
+ 2
+106
- 87
- 89
- 41
- 75
- 75
- 80
- 80
- 89
a
All concentrations in mg/1 except: pH - units;
EC - ymhos/cm
Note: Abbreviations of chemical parameters are explained in
Appendix I.
-------
29
TABLE 12
MEAN CHEMICAL QUALITY OF RUNOFF AND CONCENTRATION
TREATMENT EFFICIENCY FOR WATERSHED B-ll
Chemical
Parameter
pH
EC
Cl
M.O. Alk.
TSS
VSS
TP
N03-N
N02-N
NH3-N
Kjeldl. N
Total-N
COD
TOG
BOD
Apr. '68 thru Oct. '68
Runoff
a
Quality
7.0
500
49
107
23
18
5.9
0.10
<0.05
0.1
5.9
6.0
119
49
13
Concentration
Change %
+11
+11
+58
-91
-92
-30
-50
-90
-65
-65
i-
-85
-80
-98
Nov. '68 thru Apr. '69
Runoff
Quality3
7.5
470
42
138
33
25
4.7
<0.05
<0.05
4.8
4.8
120
37
34
Concentration
Change %
+ 5
- 5
+104
- 87
- 89
- 37
- 72
- 72
- 85
- 85
- 94
r*
All concentrations in mg/1 except: -pH - units;
EC - ymhos/cm
Note: Abbreviations of chemical parameters are explained in
Appendix I.
-------
30
TABLE 13
MEAN CHEMICAL QUALITY OF RUNOFF AND CONCENTRATION
TREATMENT EFFICIENCY FOR WATERSHED Y-l
Chemical
Parameter
PH
EC
Cl
M.O. Alk.
TSS
VSS
TP
N03-N
N02-N
NH3-N
Kjeldl. N
Total-N
COD
TOC
BOD
Apr. '68 thru Oct. ?68
Runoff
Quality3
7.2
500
49
135
22
12
4.5
0.06
<0.05
0.3
3.6
3.7
76
29
8
Concen tr a t ion
Change %
+ 11
+ 11
+100
- 91
- 94
- 39
- 70
- 70
- 79
- 79
- 91
- 88
- 99
Nov. '68 thru Apr. '69
Runoff
Quality3
7.6
470
43
124
24
16
2.3
0.12
<0.05
2.9
3.0
91
28
24
Concentration
Change %
+ 5
- 2
+84
-90
-93
-69
-40
-83
-83
-89
-88
-96
All concentrations in mg/1 except: pH - units;
EC - vonhos/cm
Note: Abbreviations of chemical parameters are explained in
Appendix I.
-------
31
class had no appreciable effect on the quality of the runoff or
the treatment efficiency as measured by concentration changes.
The effect of system age was obtained by comparing the data for
G-4 to that of G-ll and the data for Y-l to that of B-ll. In
this comparison the older watersheds G-4 and Y-l showed a minor
but definite advantage over their younger counterparts G-ll and B-ll.
During the period from November 1968 through April 1969,
watersheds G-4 and G-ll were continued on the same operating
schedule while watersheds Y-l and B-ll were used to evaluate
the effects of different operating schedules on the quality of
the runoff and the treatment efficiency. A comparison of data
for watershed G-4, Table 10, showed that the quality of the runoff
and the treatment efficiency remained essentially unchanged. The
data showed this soil system was capable of achieving excellent
treatment throughout the calendar year. The other control
watershed, G-ll, failed to maintain the same runoff quality as
it had during the warmer months, although the treatment efficiency
was equal to or better than that of conventional treatment plants (17).
The spray line for this watershed was plagued with mechanical
malfunctions throughout this six-month period. These malfunctions
caused the watershed to receive excessive quantities of wastewater
through leaks and unscheduled wastewater sprays. The results
for the other three watersheds substantiate the authors' opinion
that the relatively lower treatment efficiency for this watershed
was caused by the overloading due to the mechanical malfunctions
of the spray line.
Watershed Y-l was operated on a three-times-per-week
spray schedule instead of the regular once-per-day schedule.
This change in schedule produced a substantial improvement in
the phosphorus removal while maintaining the excellent treatment
efficiency achieved during the first six months for most of the
other parameters. A notable exception was the loss in BOD
removal as indicated by the increase in the BOD concentration
from 8 mg/1 for April 1968 through October 1968 to 24 mg/1 for
-------
32
November 1968 through April 1969. This increase may be partially
due to seasonal effects, but the results for the control water-
shed G-4 indicate that most of the BOD change was due to the change
in the operational schedule. The instantaneous loading rate for
Y-l was increased from 0.13 inches per hour to 0.17 inches per
hour concurrent with the change to the three-times-per-week spray
schedule. It is possible that this change contributed to the
loss of BOD removal since it reduced the liquid detention time
on the watershed slope.
Watershed B-ll was operated on the same once-per-day
spray schedule, but the wastewater was spread over about 75 percent
of the watershed area instead of the original 40 percent of the
area. The data for the two 6-month periods, Table 12, do not
show a consistent change in treatment efficiency. Phosphorus,
total nitrogen, and total organic carbon removals were increased
while BOD removal was decreased after the operational change.
Spreading the wastewater load over more of the available area
did not improve runoff quality for this watershed.
Mass removal efficiencies. The concentration reductions
do not give a complete picture of the treatment efficiency because
there is a substantial volume reduction as well as concentration
changes. Five key parameters were selected for this evaluation
and monthly data are presented in Tables 14 and 15.
The data for April 1968 through October 1968 which are
presented in Table 14 showed results which differ considerably from
the concentration reductions. Mass removal percentages were
greater for all five parameters. Phosphorus showed the greatest
improvement with an increase of about 20 percent. Although the
concentration data showed no effect due to soil textural class,
the mass removal data showed that the sandy loam soil on watersheds
G-4 and G-ll gave small but consistently better removals than
the loam and clay loam soils on B-ll and Y-l. This difference
was the result of smaller runoff percentages for the sandy loam
-------
TABLE 14
MEAN MASS REMOVAL PERCENTAGES FROM APRIL 1968 THROUGH OCTOBER 1968
Experimental
Line
G-4
Y-l
G-ll
B-ll
Apr.
98.5
98.0
98.5
85.1
May
99.2
98.6
99.3
June
98.4
98.7
98.8
97.2
July
BOD
99.5
99.4
99.4
98,2
Aug.
99.2
97.7
Sept.
99.0
99.5
99.1
Oct.
Weighted
Average
99.3
98.6
99.2
99.1
99.1
98.7
99.1
96.5
COD
G-4
Y-l
G-ll
B-ll
95.7
94.8
93.9
79.6
93.8
90.7
89.0
94.0
91.5
93.2
89.0
96.8
95.5
96.6
94.0
92.4
84.7
95.3
95.9
93.5
96,4
97.6
97.5
94.9
97.0
95.1
95.7
93.3
94.3
91.3
VSS
G-4
Y-l
G-ll
B-ll
99.7
94.9
96.1
80.3
99.2
92.6
95.1
97.0
94.3
95.6
98,5
98.1
97.1
96.2
97.7
96.0
97.2
99.4
98.3
99.2
96.9
97.8
95.0
94.4
96.1
98.3
95.5
96.0
93.4
T-N
G-4
Y-l
G-ll
B-ll
90.6
85.6
90.0
76.5
89.1
80.0
82.1
90.3
82.0
88.5
70.3
91.9
90.6
92.5
90.2
73.2
61.2
82.4
82.8
90,9
89.5
91.5
95.3
93.6
96.0
92.3
90.7
86.2
90.1
86.6
T-P
G-4
Y-l
G-ll
B-ll
85.6
86.7
86.6
74.4
57.1
52.8
65.6
67.9
53.9
44.7
40.2
62.8
50.7
54.4
29.9
83.2
82.4
88.3
52.0
-31.8
55.8
-0.1
53.8
16.3
60.9
58.9
64.6
48.6
61.5
50.4
Note: Abbreviations of chemical parameters are explained in Appendix I.
-------
TABLE 15
MEAN MASS REMOVAL PERCENTAGES FROM NOVEMBER 1968 THROUGH APRIL 1969
Experimental
Line No
G-4 99
Y-l 99
G-ll
B-ll 99
v. Dec.
.4 • 99.4
.9 97.7
94.2
.2 93.9
Jan.
BOD
99.1
97.3
92.6
97.8
Feb.
99.3
98.0
97.5
Mar.
99.5
99.4
95.8
98.5
Apr.
98.5
98.3
94.5
94.0
Weighted
Average
99.1
98.0
94.0
96.8
COD
G-4 97
Y-l 95
G-ll
B-ll 94
.3 97.2
.6 95.4
84.8
.2 91.3
96.5
96.3
92.2
94.3
98.1
97.6
96.7
97.9
98.3
93.8
96,5
95,0
95.5
90.7
81,6
96,6
96.2
90,9
92.8
VSS
G-4 98
Y-l 98
G-ll
B-ll 97
.5 99.2
.4 98.6
93.5
.9 88.0
98.8
98.2
97,3
98.4
99.6
98.6
98.4
98.9
98.4
96,4
98.3
96.3
95.8
91,8
83.6
98.2
97.6
94.9
94.6
T-N
G-4 94
Y-l 95
G-ll
B-ll 92
.9 96.1
.5 95.3
90.3
.4 93.2
92,4
93.8
92,6
92.5
94.3
91.9
94.4
96,7
97.5
93.8
95.0
86.3
92,9
83.1
63.2
92.2
93.9
89.3
88,9
T-P
G-4 75
Y-l 66
G-ll
B-ll 56
.9 69.4
.9 75.6
37.0
.9 43.6
38,2
76.8
55.6
44.8
72.1
87.7
67.1
55.4
88.9
71.5
62.1
59.6
88.6
69.3
59,0
58.5
81.2
61.4
55.5
Note: Abbreviations of chemical parameters are explained in Appendix I.
-------
35
soil. The slight advantage which was shown for the older water-
sheds by the concentration data was less evident for the mass
removal data. These minor effects due to soil textural class
and system age indicate that any soil textural class is suitable
for use in a soil treatment system and that this system has had
no loss in treatment efficiency after more than four years of use.
The data for November 1968 through April 1969 are presented
in Table 15. The data for watershed G-4 corroborated the results
of the concentration data and showed that consistently high removals
were maintained throughout the calendar year. The data for G-ll
showed the loss in treatment efficiency which was attributed to
mechanical malfunctions in the discussion of the concentration
data. The mass removal for B-ll showed a slight but consistent
improvement over the results for the first six months of the study.
This result was different from the result observed for concentration
reductions and suggested that overall system efficiency might be
improved by spreading the wastewater load over 75 percent instead
of 40 percent of the soil area. The change in the removal of
total phosphorus on watershed Y-l is shown clearly by the monthly
data in Table 15. An apparent transition period from November
1968 through January 1969 was followed by consistent mass removals
of about 88 percent for the last three months of the study. This
is an increase of 40 percent over the average removal of 48
percent achieved during the first six months and shown in Table 14.
This watershed also showed slight improvements in the removal
of total nitrogen, VSS, and COD, but there was a slight decline
in BOD removal. These results showed that the overall treatment
efficiency of this soil treatment system could be improved by
changing the present once-per-day application schedule to a
three-times-per-week schedule.
-------
36
Summary and Conclusions
The results of this 12-month study showed that the
individual watersheds in this soil system achieved a very high
degree of treatment. Mass removal efficiencies were substantially
better than concentration reduction efficiencies because the
runoff ranged from 40 to 80 percent of the applied wastewater.
Soil textural class and system age had very little effect on
treatment efficiencies. Treatment was excellent throughout the
calendar year but there may have been a slight decline in the
winter months.
Although the present system design and operating schedule
do provide excellent treatment, the results of this study showed
that mass removal was improved by spreading the wastewater load
over a greater fraction of the land area and by reducing the
frequency of application. The greatest change was in phosphorus
removal which was increased from 48 percent to 88 percent on
watershed Y-l by changing from a once-per-day to a three-times-
per-week application schedule.
-------
CHAPTER VI
FARM EFFLUENT QUALITY
Farm effluent quality was monitored at three locations
for varying periods during the 12-month study. Two 55-acre
watersheds representative of the older part of the treatment system
and one 20-acre watershed on the younger part of the system were
sampled. All three watersheds were completely contained within
the treatment system and received no runoff from outside sources.
Methods and Procedures
The electrical conductivity of the wastewater and farm
effluent was monitored continuously. Grab samples of the farm
effluent for chemical analyses were obtained weekly. These
grab samples were compared to 24-hour composite samples on several
occasions to verify that the grab samples were representative
samples. The composite samples of the stream were obtained with
a constant-speed pump sampler. The farm effluent samples were
analyzed in the same manner as the wastewater and watershed runoff.
Results and Discussion
Continuous conductivity monitoring. Mean daily values
of the electrical conductivity of the wastewater and farm effluent
are shown in Figure 3. The much greater fluctuation in the
electrical conductivity of the farm effluent resulted from the
influence of rainfall events. There was a general increase in
the electrical conductivity of the farm effluent from May 1968
through July 1968 followed by a sharp decrease in early September
1968. This increase closely paralleled the increase in evaporative
losses described in the hydrology chapter and the increase was
probably the result of concentrating effects due to evaporation
losses.
The effect of rainfall on the electrical conductivity
of the farm effluent is shown in Figure 4. The data summarized
in this figure showed that rainfall events of 0.1 inch or less had
37
-------
PAGE NOT
AVAILABLE
DIGITALLY
-------
-100 —
-90
(U
-80
3 -70
5.22
u. -6O
O
Ul
o
1C
111
0.
-50
-40
>-
> -30
O
O
-20
-10
0
+ 10
420
* • ••
.5
1.0
I
I
1.5 270
RAINFALL, Inches
2.5
3.0
FIGURE 4- EFFECT OF RAINFALL ON ELECTRICAL CONDUCTIVITY OF FARM EFFLUENT
-------
42
little, if any, effect on the conductivity of the runoff water.
Such rainfall events did not contribute enough volume to alter
the composition of the runoff contributed by the applied wastewater.
Rainfall events of 0.1 inch to about 2.0 inches had a marked
effect on the conductivity of the runoff. The volumes contributed
by rainfalls in this range diluted the runoff to a steadily in-
creasing degree. Rainfall events greater than 2.0 inches had
little additional effect on the conductivity.
Another interesting relationship was the diurnal var-
iation in the conductivity. This relationship is shown in
Figures 5 and 6. The plant operational schedule included a
daily cleanup starting at about midnight. The effect of this
cleanup on the conductivity of the wastewater is clearly demon-
strated in Figure 5. The data plotted in this figure also
emphasized that there was no relationship between seasons and
the conductivity of the wastewater during the processing period
of the day. The diurnal changes in the farm effluent conductivity
are shown in Figure 6. There was no peak associated with the daily
cleanup period. The spray-runoff system acted as a buffer and
virtually eliminated the effect of the cleanup period on the field
effluent conductivity. Arranging the data by seasons clearly
demonstrated the seasonal changes in the farm effluent conductivity
which have already been discussed.
Chemical quality of farm effluent. The chemical quality
of the farm effluent from the three monitoring locations is
summarized in Table 16. The quality of the effluent varied
considerably from one location to another, but each sampling
site produced an effluent of very high quality. The pH, electrical
conductivity, and chloride differences are similar to seasonal
differences which were observed for individual watersheds. These
differences did not represent a" difference in treatment capacity.
-------
800 -
700 -
Spring
Summer
Fall
Winter
600 -
•i 500 -
h-
o
z>
o
o
400
M
3
300
o1
I
I I I I 1 1 1
N
TIME OF DAY
6
M
FIGURE 5 - DIURNAL VARIATION OF ELECTRICAL CONDUCTIVITY OF WASTE WATER
U)
-------
e
eoo
CO
o
.C
o
_o
E 500
O
O
O
u
400
o •
X-
Summer
Fall
Spring
Winter
1
I
1
9 N
TIME OF DAY
M
FIGURE 6 - DIURNAL VARIATION OF ELECTRICAL CONDUCTIVITY OF FARM EFFLUENT
-------
TABLE 16
FARM EFFLUENT QUALITY AND CONCENTRATION
TREATMENT EFFICIENCY, MEAN VALUESa
Chemical
Parameter
pH, units1*
EC, ymhos/cm
Cl
M.O. Alk
TSS
VSS
T-P
N03-N
N02-N
NH3-N
Kjeldl. N
Total-N
COD
TOG
BOD
Three watersheds separately
WY (old)
6.8
430
40
124
23
11
3.9
0.2
<0.05
0.2
2.6
2.8
63
25
6
GWY (old)
7.2 .
520
48
128
14
6
4.1
0.3
<0.05
2.5
2.8
50
24
7
B (new)
7.6
500
50
136
13
8
4.9
<0.5
<0.05
2.8
2.8
75
21
16
All data combined
Concentration
7.2
490
47
130
16
8
4.3
0.2
<0.05
0.5
2.6
2.8
67
23
9
Concentration change,
percent
+ 9.6
+ 6.6
+92.6
-93.5
-96.3
-42.5
-84.7
-83.9
-91.7
-90.8
-98.4
n
, All concentrations in mg/1 except where noted
Median values instead of a mean
Note: Abbreviations of chemical parameters are explained in Appendix I.
-------
46
The higher concentration of oxygen-demanding -substances in the
B-area effluent substantiated the results observed for individual
watersheds where it was shown that the younger areas were somewhat
less efficient than the older areas.
The mean concentrations, based on all data combined,
showed that the farm effluent is similar in quality to the runoff
from the individual watersheds when they are performing satis-
factorily as all four of the experimental watersheds were from
April 1968 through October 1968 (Tables 10, 11, 12, and 13).
One consistent difference of significance was the total nitrogen
concentration. The total nitrogen content of the runoff from the
four experimental watersheds ranged from 3.0 to 6.0 mg/1 from
April through October 1968, while the concentration in the farm
effluent was 2.8 mg/1. This difference indicated that additional
reduction in the concentration of total nitrogen was achieved
as the liquid flowed through the collection channels to the
locations where the farm effluent samples were collected.
Summary and Conclusions
The results of analyses conducted on samples collected
from three different sites during the 12-month study showed that
the farm effluent was similar in composition to the runoff from
the four experimental watersheds when the experimental watersheds
were achieving their best treatment efficiency. The spray-runoff
treatment system acted as a buffer to prevent wide diurnal var-
iations in the wastewater quality to show up in the quality of
the farm effluent. Seasonal variations in the electrical conductivity
of the farm effluent could be related to evaporative losses of
water with the resultant increase in dissolved solids concentration.
The electrical conductivity of the farm effluent was decreased pro-
portionately by rainfall events from 0.1 inch to 2.0 inches.
Rainfall events above this range had little additional effect
on the electrical conductivity.
-------
CHAPTER VII
SOIL AND SOIL WATER
Soil samples were obtained from each experimental
watershed and from the border areas in the watershed vicinity.
The border, area samples were used as controls to evaluate the
effects of wastewater spraying on soil properties. Soil water
samples were obtained at the 3-foot depth to determine the
quality of the liquid percolating through the soil.
Methods and Procedures
Soil samples were taken at the 0- to 2-inch and 11- to
13-inch depths. Each sample was obtained by compositing 15
subsamples selected systematically to represent the average soil
composition. Routine procedures for crushing, mixing, and
subdividing the samples were used to prepare the soil samples
for analysis or extraction. The analytical procedures and
extraction procedures were selected from those presently recommended
for routine soil analyses (18).
The soil water samples were obtained with soil water
samplers which consist of a porous ceramic tip bonded to plastic
pipe. When necessary,-vacuum was applied to the sampler to with-
draw liquid from unsaturated soil. Six of these samplers were
installed on each watershed to obtain a composite sample repre-
sentative of the whole watershed. Samples were taken once a month
and subjected to chemical analysis to determine the soil water
quality. Analytical procedures for the soil water samples were
obtained from the same source as the procedures for surface
water samples. A sample of the chemical data form for soil water
samples is included in Appendix III.
Results and Discussion
Soil analyses. The results of the analyses on the
soil samples are summarized in Table 17. With the exception of
experimental line B-ll soil, pH was similar for the sprayed and
non-sprayed samples at both sampling depths. Conductivity at
47
-------
TABLE 17
SOIL SAMPLE ANALYSES
oo
Experimental
Area pi
Conductivity
H millimhos/cm
Cation Exchange Capacity (CEC)
and Exchangeable Cations,me/100 g
, CEC Ca
Mg K Na
Exchangeable
Na
Percentage
gm/100 gm
Total-P
Organic
Carbon
0- to 2-inch plot samples
G-4 6.5 0.16
Y-l 6.2 0.14
G-ll 6.5 0.16
B-ll 6.2 0.10
G-4 6.2 0.08
Y-l 6.7 0.10
G-ll 6.4 0.06
B-ll 5.1 0.05
16,2 6.4
30.3 11.6
15.2 6.4
13.1 5.8
0- to 2-inch
23.8 9.8
32.1 14.6
21.2 9.6
22.8 6.1
0.7 0.5 0.5
1.5 0.8 0.7
0.7 0.3 0.9
0.7 0.4 0.4
border samples
2.0 0.5 0.3
1.8 0.6 0.2
1.0 0.6 0.6
1.6 0,3 0.2
5.8
4.6
10.3
5.9
2.6
1.0
5.0
2,7
0.042
0.043
0.046
0.023
0.027
0.036
0.026
0.015
0.94
1.42
0.71
1.46
1.92
1.91
0.94
0.75
11- to 13-inch plot samples
G-4 5.0 0.12
Y-l 4.8 0.12
G-ll 5.0 0.11
B-ll 4.7 0.10
G-4 5.3 0.11
Y-l 5.2 0.09
G-ll 5.2 0.05
B-ll 4.7 0.07
27.6 7.2
40.0 9.7
38.4 13.8
43.6 9.4
11- to 13-inch
25.8 9.3
45.2 15.0
24.5 3.8
36.0 10.2
2.9 0.2 1.0
2.4 0.2 0.9
2.5 0.3 0.5
2.1 0.2 0.9
border samples
3.1 0.2 1.2
3.0 0.3 0.6
0.5 0.1 0.3
2.5 0.2 0.7
9.1
7.0
3.1
7.6
8.6
3.0
5.8
5.3
0.018
0.010
0.090
0.013
0.017
0.015
0.017
0.017
0.41
0.56
0.34
0.45
0.68
0.60
0.34
0.38
Note: Abbreviations of chemical parameters are explained in Appendix I,
-------
49
the 0- to 2-inch depth under spray was approximately double that
of the non-sprayed area. This effect was much less noticeable
at the 11- to 13-inch depth. The conductivity of all samples
was representative of a strongly leached soil. The data for ex-
changeable cations showed a definite change at the 0- to 2-inch
depth, but the effect was not noticeable at the 11- to 13-inch
depth. At the 0- to 2-inch depth, there was a decrease in exchange
capacity and the exchangeable cations, calcium and magnesium.
There was an increase in exchangeable sodium and the exchangeable
sodium percentage. Although these changes indicated a trend toward
detrimental sodium effects on the soil, they did not indicate
conditions to be concerned about at this time. The fact that the
younger spray lines, G-ll and B-ll, exhibited changes similar to
the older lines, G-4 and Y-l, suggested that changes may approach
an equilibrium condition after three to five years of operation.
The phosphorus content of the soil in the sprayed area
increased at the 0- to 2-inch depth, but there was no consistent
effect shown at the 11- to 13-inch depth. These increases in the
0- to 2-inch depth for the sandy loam areas, G-4 and G-ll, were
equal to about 1300 Ibs/acre, and the increases for the heavier
soils, Y-l and B-ll, were equal to about 600 Ibs/acre. Since
phosphorus removal from the wastewater is about 300 Ibs/acre/year,
the phosphorus accumulating in the soil accounts for a significant
fraction of phosphorus removal.
The organic carbon content of the 0- to 2-inch samples
was lower under the spray lines for three of the four test areas.
It would appear that biological degradation of the plant residue
prevented a buildup in the organic matter content of the surface
soil. Organic carbon content at the 11- to 13-inch depth was
not affected by the wastewater spraying. Maintaining the organic
matter content of the surface soil should be considered in the
-------
50
selection of crop harvesting schedules. Some organic residue
must be returned to the soil to prevent biological depletion of
the native organic matter to the point where it becomes detrimental
to the operation of the treatment system.
Soil water quality. The results of the soil water
analyses are summarized in Table 18. The quality of the soil
water under the four experimental areas varied substantially.
The most obvious and greatest differences were related to system
age. All of the parameters except total phosphorus exhibited
differences related to system age. The older areas, G-4 and Y-l,
had soil water with a higher pH and generally greater concentrations
for all of the other parameters. The total dissolved salts were
estimated by conductivity to be 2 to 4 times greater for these
areas than for the younger areas, G-ll and B-ll. The concentrations
of nitrogen and phosphorus were of particular interest since
the treatment efficiency evaluation showed that they were removed
from the runoff by the treatment system. The data for the soil
water samples showed that these constituents were not being
released to groundwater by deep percolation. Less than one
percent of the applied phosphorus and about 2 percent of the
applied nitrogen were contained in the soil water percolating
past the 3-foot depth. The soil water should be monitored
again after a few years to determine if the present conditions
under G-4 and Y-l are approaching a stable state. If salinity
continues to increase, it could become a problem and impose
limitations on the usefulness of the system at sometime in the
future.
Summary and Conclusions
Soil samples and soil water samples were collected
to evaluate the effects of the wastewater applications on soil
properties. There was a salinity increase with age in the soil
and in the soil water. Present salinity levels are not detrimental
and a comparison of the 3- and 5-year-old areas of the treatment
-------
TABLE 18
SUMMARY OF SOIL WATER ANALYSES
Experi-
mental
Area
G-4
Y-l
G-ll
B-ll
median
range
median
range ,
median
range
median
range
pH
6.7
5. 0-7. A
6.6
6.0-6.8
6.0
5.3-7.2
5.9
5.5-6.9
Conductivity
y mhos /cm
1300
830-2000
13'00
750-2900
240
160-350
600
440-750
Concentration, rag/liter
Total
Phosphorus
0.3
<.05-1.4
0.4
<.05-1.6
0.6
<.05-1.5
0.1
<. 05-1.1
Total
Nitrogen
3.1
1.5-5.0
2.2
1.8-4.0
0.2
<0. 1-2.1
1,4
0.3-5.5
Na
240
204-264
198
130-314
25
20-30
109
100-114
Ca
66
38-109
66
20-137
16
6-24
17
14-22
Mg
15
8-21
12
4-40
2.6
1.0-13
2.4
0.5-14
K
0.9
0.3-5.7
0.4
0.2-2.8
0.2
0.1-0.6
0.2
<0. 1-1.0
Cl
190
164-720
236
180-508
65
40-240
138
63-160
SOJ+
413
300-570
212
120-290
10
6-25
74
55-94
-------
52
system suggests that the level of salinity is approaching an
equilibrium level. The salinity increase was primarily due to
sodium and the exchangeable sodium percentage also increased
considerably. A substantial fraction of the phosphorus removed
from the wastewater was retained in the soil at the 0- to 2-inch
depth. Only a negligible fraction of the total phosphorus and
nitrogen removed from the wastewater was retained in the soil
water percolating past the 3-foot depth.
-------
CHAPTER VIII
SUPPLEMENTAL STUDIES
Several short-term studies were conducted during the
12-month experimental period. These studies were conducted to
clarify questions arising from routine experimental procedures.
In addition, opportunities to obtain information of a special
nature were often provided by unscheduled changes in operation
of the treatment system. The results of these studies are
presented as indications rather than conclusions since they are
based on a limited quantity of data.
Slope Study
A one-day study compared the runoff quality at the
midpoint on the slope to the runoff quality at the toe of the
slope on watershed Y-l. The midpoint of the slope was 80 feet
from the spray line (40 feet from the perimeter of the spray
pattern), and the toe of the slope was 160 feet from the spray
line (120 feet from the perimeter of the spray pattern). Spray
samples from a single nozzle were collected as 2-hour composites
during a 6-hour spray period. Similar composite samples were
taken at the midpoint and toe of the watershed slope.
The effect of the distance downslope on the quality
of the applied wastewater is summarized in Table 19. On this
one-day study the distance downslope had little effect on pH
or electrical conductivity. The reduction in COD and TOC con-
centrations at 40 feet were equal to the reductions at 120 feet
downslope from the spray pattern. Additional reduction in the
phosphorus concentration was achieved between 40 feet and 120
feet downslope. There was an indication that a minimum nitrogen
concentration occurred at 40 feet downslope, and there was an
increase in nitrogen between 40 feet and 120 feet. The results
of this study suggested that optimum overall treatment for this
soil treatment system would be achieved with a dbwnslope run
somewhere between 40 and 120 feet.
53
-------
54
TABLE 19
TREATMENT EFFICIENCY VERSUS DISTANCE
DOWNSLOPE FROM SPRAY LINE
Distance downs lope
from spray perimeter, feet
0
40
120
pH
8.8
8.1
7.9
cond.
ymhos/cm
570
600
600
Concentration mg/1
TSS
430
8
TP
5.6
3.0
2.5
TN
15.0
0.7
1.0
COD
1060
43
43
TOC
355
18
19
Note: Abbreviations of chemical parameters are explained in
Appendix I.
Filter Study
The physical removal of contaminants by filtration was evaluated
by filtering a wastewater sample through a coarse filter paper (S&S No. 588).
Portions of the whole wastewater sample and the filtrate were analyzed to
determine the amount of contaminant removed by filtration. The-analytical
results are summarized in Table 20.
The analytical results for this single sample showed that 60
to 70 percent of the contaminants were not removed by this coarse filter
paper. These results suggested that physical and chemical adsorption
play an important role in retaining contaminants on the slopes of the water-
sheds long enough for the microbial population to degrade the organic
contaminants.
Nitrate Study
Deviations in nitrate concentration between wastewater grab
samples and spray composite samples had been noticed. To determine the
cause, grab samples were obtained from the wastewater sump. An initial
analysis was performed on each sample and hourly thereafter. As shown in
-------
55
TABLE 20
CONTAMINANTS REMOVED BY FILTRATION
Sample
Whole wastewater
Filtrate
Percent removal
Concentration, mg/1
Total-P
4.0
2.8
30
COD
577
352
40
TOC
312
188
40
BOD
577
391
32
Note: Abbreviations of chemical parameters are
explained in Appendix I.
Figure 7, the nitrate decline rate and the nitrite incline rate
are similar in appearance. The nitrate had depleted between the
third and fourth hour. The nitrite values had increased to the
maximum point by the third hour and declined to near depletion
by the sixth hour.
This change of values was due to bacterial action ,in
the collection bottle, depleting the dissolved oxygen of the
sample. Under anaerobic conditions, nitrate nitrogen is subject
to denitrification and loss to the atmosphere as nitrogen gas.
To substantiate the bacterial action hypothesis, four
samples were obtained at the one-half point and tail of the
wastewater sump. A fixed composite sample was prepared for each
location from each sample. Immediate analysis of the grab samples
was determined for nitrate. Four hours after obtaining the first
sample, nitrate determinations were made on each fixed composite
sample and an unfixed spray composite sample. Table 21 give the
result of these determinations.
-------
56
O.7 -
23456
ELAPSED TIME, hours
FIGURE 7- CHANGES OF NITRATE AND NITRITE
CONCENTRATIONS WITH TIME IN
UNFIXED WASTEWATER SAMPLES
-------
57
TABLE 21
NITRATE IN FIXED AND UNFIXED WASTEWATER SAMPLES
Sample
1/2 Point Grab, unfixed (avg)
1/2 Point Composite, fixed
Tail Grab, unfixed (avg)
Tail Composite, fixed
Field Spray Composite, unfixed
Nitrate, mg/1 N
1.29
1.36
1.18
1.28
<.05
The results of this investigation prompted the decision
to obtain two samples at the field spray sampling locations.
One was fixed with concentrated sulfuric acid and the other was
unfixed. Those results are shown in Table 4 (Chap. 3) of this
report.
Recovery of Treatment Efficiency by Resting
Previous experience with the treatment system had shown
that a rest of several weeks would allow a watershed to recover
its ability to treat the wastewater. The results of laboratory
studies have indicated that a rest of two to three weeks should
allow recovery.^ Experimental watersheds were shut down four
times during the one-year study because their treatment efficiencies
had declined markedly. The effect of the rest period on the
treatment efficiency of the watersheds is summarized in Table 22.
3Warren A. Schwartz, Thomas W. Bendixen, Richard E.
Thomas, "Project Report of Pilot Studies on the Use of Soils as
Waste Treatment Media," USDI, FWPCA-, Cincinnati, Ohio, 1967.
Unpublished data.
-------
58
TABLE 22
RECOVERY OF TREATMENT EFFICIENCY BY RESTING A WATERSHED
Watershed
B-ll
B-ll
G-ll
B-ll
Rest period
days
56
11
11
12
Percent concentration reduction
for total nitrogen and COD
before rest
N
50
3
65
0
COD
54
61
86
54
first week
after rest
N
64
10
87
39
COD
86
77
88
88
fourth week
after rest
N
83
92
87
87
COD
88
93
88
90
Note: Abbreviations of chemical parameters are explained in
Appendix I.
These data showed that a rest of 11 or 12 days was as effective as a rest
of 56 days in restoring the treatment efficiency of a watershed. The
data also showed that it takes several weeks after wastewater applications
are restarted to fully regain the treatment efficiency. The treatment
efficiencies for the fourth week after restarting wastewater applications
were as good as the average concentration reductions for the system
which were 84 percent for total nitrogen and 92 percent for COD. These
results substantiated the previous laboratory work on the effect of rest
periods and indicated that a rest period of two weeks is usually sufficient
to restore full treatment capacity to this system.
Nitrogen Transformations Due to Extended Drying of a Watershed
It was shown in Chapter V that the nitrogen concentration in
the field effluent- averaged 16 percent of that in the wastewater and
that the nitrogen in the field effluent is in the form of organic nitrogen
-------
59
under normal operating conditions. The 56-acre watershed draining
to the farm effluent sampling station was shut down for 4 weeks in
July and August. The percent nitrogen removal and the chemical
form of the nitrogen in the field effluent following the resumption
of wastewater applications are presented in Figure 8. These results
provide qualitative support of the hypothesis that microbial metabolism
plays an important role in the nitrogen removal process. The lag
time for the treatment system to regain full nitrogen removal capacity
is characteristic of processes depending on microbial activities.
The rise in the fraction of the nitrogen recovered as nitrate was
indicative that the environment was predominantly aerobic through
the tenth day after restarting wastewater applications. The subsequent
fall in the nitrate concentration and the continued drop in the total
nitrogen concentration suggested that denitrification processes became
dominant between 10 and 17 days. It would appear that the conditions
under which this soil treatment system was operated provided an
environment which supported denitrification as the final metabolic
process acting upon the nitrogeneous compounds in the wastewater.
The gaseous end products of this process could account for the apparent
loss of about 80 percent of the total nitrogen applied to the soil
treatment system.
Analysis of Rainfall Runoff
A set of runoff samples from rainfall only was obtained
on one occasion during the 12-month study. The analyses of these
samples and the subsequent wastewater-spray runoff for selected
parameters are presented in Table 23. The averages for July 10,
1968, are included as an indication of the quality for a comparative
period with no rainfall. This single comparison was for a rainfall
of 0.5 inches followed by a wastewater spray of 0.9 inches. The
results showed that a rainfall incident of this amount produced
runoff which is similar in composition to the runoff from the
subsequent wastewater spray. There was an indication that both the
rainfall runoff and subsequent wastewater-spray runoff were diluted
relative to the runoff for the comparable no-rainfall period.
-------
60
0.8 -
25
ELAPSED TIME AFTER RESTARTING WASTEWATER
APPLICATIONS, days
FIGURE 8-EFFECT OF EXTENDED DRYING ON NITROGEN
TRANSFORMATIONS AND PERCENT REMOVAL
-------
61
TABLE 23
MEAN CONCENTRATION OF RAINFALL RUNOFF AND SUBSEQUENT WASTEWATER-
SPRAY RUNOFF FROM THE EXPERIMENTAL WATERSHEDS
Runoff
Source
Rainfall
Wastewater spray
Four watersheds
7/10/68
Concentration in mg/liter
BOD
9
7
8
COD
47
32
100
TSS
14
14
18
T-N
3.4
3.5
4.6
T-P
5.4
6.9
4.6
Cl
69
46
81
Note: Abbreviations of chemical parameters are explained in
Appendix I.
-------
REFERENCES
1. Law, James P., Jr., "Agricultural utilization of sewage ef-
fluent and sludge, an annotated bibliography." U. S. Dept.
of the Interior, Federal Water Pollution Control Admin.,
Pub. CWR-2. Washington, U. S. Government Printing Office.
(Jan. 1968).
2. Bloodgood, D. E., Vogel, J. K., and Lugar, J. J., "Spray
irrigation'of paper mill waste." Proceedings, 15th Oklahoma
Industrial Waste Conference, Oklahoma State University,
Stillwater. (Nov. 17-18, 1964).
3. Luley, H. G. "Spray irrigation of vegetable and fruit processing
wastes," Journal Water Pollution Control Federation, Vol. 35,
No. 10. (October 1963). pp. 1252-1261.
4. Larson, W. C., "Spray irrigation for the removal of nutrients
in sewage treatment plant effluent as practiced at Detroit
Lakes, Michigan." Algae and Metropolitan Wastes, Transactions
1960 Seminar, Robert A. Taft Water Research Center, Cincinnati,
Ohio, Tech. Rep. W61-3. (1960).
5. Foster, H. B., Ward, P. C., and Prucha, A. A., "Nutrient removal
by effluent spraying." Proceedings American Society Civil
Engineers, Sanitary Engineering Division, Vol. 91, No. SA6.
(December 1965). pp. 1-12.
6. Wilson, C. W., and Beckett, F. E. (eds.), Municipal Sewage
Effluent for Irrigation. Proceedings of Symposium at Louisiana
Polytechnic Institute. Ruston. (July 1968).
7. Vercher, B. D., Sturgis, M. B., Curtis, 0. D., Nugent, A. L.,
and McCormick, L. L., "Paper mill waste for crop production
and its effects on the soil." Louisiana State University,
Agricultural Experiment Station, Bulletin No. 604. (Dec. 1965).
8. Kardos, Louis T., "Waste water renovation by the land—,
a living filter." ^Agriculture and the Quality of Our
Environment, AAAS Pub. No. 85, Washington, D. C. (1967).
pp. 241-250.
63
-------
64
9. Parmelee, D. M., and Glide, L. C., "Natural land filtration
treatment system, Campbell Soup Company, Paris, Texas."
Mimeographed. Presented at Texas ASM University, Water for
Texas Conference. (1966).
10. FWPCA Official Interim Methods for Chemical Analysis of
Surface Waters, Federal Water Pollution Control Administration,
Division of Research, Analytical Quality Control Branch,
Washington, D. C. (September 1968). Mimeo.
11. Hagan, R. M., Haise, H. R., and Edminster, T. W., (eds.),
"Irrigation of agricultural lands." Agronomy Monograph No. 11,
American Society of Agronomy, Madison, Wisconsin. (1967),
894 pp.
12. Thornthwaite, C. W., and Mather, J. R., "Instructions and
Tables for computing potential evapotranspiration and the
water balance." Climatology. Vol. 10, No. 3. (1957).
13. Gruff, R. W. and Thompson, T. H., "A comparison of methods
of estimating potential evapotranspiration from climatological
data in arid and subhumid environments." Geological Survey
Water Supply Paper 1839-M, U. S. Department of the Interior,
Washington, U. S. Government Printing Office. (1967).
14. Field Manual for Research in Agricultural Hydrology. Agri-
cultural Handbook No. 224, U. S. Department of Agriculture,
Washington, U. S. Government Printing Office. (1962).
15. Rose, C. W., Stern, W. R., and Drummond, J. E., "Determination
of hydraulic conductivity as a function of depth and water
content for soil in situ." Australian Journal of Soil Research,
Vol. 3. (1965). pp. 1-9.
16. Rose, C. W., and Stern, W. R., "Determination of withdrawal
of water from soil by crop roots as a function of depth and
time." Australian Journal of Soil Research, Vol. 5. (1967),
pp. 11-19.
-------
65
17. Imhoff, Karl, and Fair, G. M., Sewage Treatment. Second Edition,
Parts 1 & 2, New York: John Wiley & Sons. (1956), 338 pp.
18. Black, C. A., et al. (eds), Methods of Soil Analysis.
Agronomy Monograph No. 9, American Society of Agronomy,
Madison, Wisconsin, (1965), 1572 pp.
-------
APPENDIX
-------
APPENDIX I
Description of Chemical Parameters
pH—The pH value denotes the degree of alkalinity or acidity of a
sample. The neutral position on a pH scale is 7.0. Any value less
than 7.0 is of an acid nature, while that above 7.0 is alkaline. The
pH of most natural waters ranges from 6.0 to 8.0.
DISSOLVED OXYGEN—Dissolved oxygen is the quantity of free or uncombined
oxygen in water. The self-purification of streams is dependent on
the quantity of oxygen incorporated within the water.
CONDUCTIVITY (Cond.)—Electrical conductivity is a quick and reliable
measurement of electrolyte concentration in a water sample. The con-
ductivity measurement can be related to dissolved solids concentration
and is almost directly proportional to the ionic concentration of the
total electrolytes.
SUSPENDED SOLIDS
Total Suspended Solids (TSS)—Total suspended solids is a deter-
mination by weight/volume of the suspended material in water too large
to pass through a fine-porosity, glass fibre filter.
Volatile Suspended Solids (VSS)—The volatile suspended solids is
the loss of weight when the total suspended solids has been ignited
at 600°C. This is considered to be principally organic matter. The
difference between total suspended and volatile suspended solids is
the fixed suspended solids which are primarily the mineral constituents
of the water sample.
TOTAL PHOSPHORUS (T-P)—Phosphorus is a potential nutrient for plant
growth. A beneficial compound in water except when found in abundant
excess. The total phosphorus determination is performed by the per-
sulfate digestion procedure which breaks down all forms of phosphorus
to the ortho form.
CHLORIDE (Cl)—Chloride is found in all natural waters in a wide range
of concentrations. The effect of chlorides on soils and plants and
the concentration which various plants can withstand are replete in
literature. The USPHS suggests the maximum concentrations of chlorides
for drinking water not to exceed 250 mg/1 Cl .
67
-------
68
ALKALINITY—Alkalinity concentrations in water are primarily due to
the bicarbonate* carbonate, and hydroxide ions. The alkalinity repre-
sents the buffering capacity of the water. Increased concentrations
of alkalinity over the carriage water are due to Industrial wastes.
The relationships between total (T-Alk) and phenolpthalein (P-Alk)
alkalinity are located below:
Condition Type of Alkalinity
P=T Hydroxide
P=l/2 T Carbonate
Bicarbonate
P>l/2 T Hydroxide, Carbonate
P
-------
69
TOTAL ORGANIC CARBON (TOG)—This parameter is still in the developmental
stage, but the results obtained appear promising as a means to determine
the organic quantity in wastewater. Relationship values between the
COD and TOC are very encouraging. The value of this procedure is that
a sample can be analyzed in 15 minutes.
BIOCHEMICAL OXYGEN DEMAND (BOD)—This determination is a measure of
the oxygen required to oxidize the organic material in a sample of waste-
water by natural biological processes under standard conditions. This
test is presently universally accepted as the yardstick of pollution
and is utilized as a means for the degree of treatment in a waste
treatment process.
-------
APPENDIX II
CHEMICAL DATA FORM FOR SURFACE WATER SAMPLES
Date September 10, 1968
Spray Period
0700-1500
Sample
Spray
G-4
Runoff
G-ll
Runoff
B-ll
Runoff
Y-l
Runoff
GWY
Field Eff.
pH
5.5
7.6
7.8
7.6
7.8
7.2
Cond.
ymhos
/cm
400
440
400
375
450
390
Concentration, mg/liter
TSS
192
4
5
13
8
6
vss
176
2
4
9
4
3
T-P
4.1
4.0
3.7
6.0
4.1
3.7
Cl
45
36
37
32
36
31
P-Alk
0
0
0
0
0
0
T-Alk
20
144
96
106
151
105
NO 3
N
.09
.11
.07
.10
<.05
.08
N02
N
<.05
<.05
<.05
<.05
<.05
<.05
Kjel.
N
15.7
1.8
2.3
2.6
1.9
1.9
T-N
15.8
1.9
2.4
2.7
1.9
2.0
COD
751
62
77
33
62
62
TOC
228
25
29
25
23
27
BOD
485
8.9
11
10
3.5
2.5
Note: Abbreviations of chemical parameters are explained in Appendix I,
-------
APPENDIX III
CHEMICAL DATA FORM FOR SOIL WATER SAMPLES
Date
April 24. 1968
Spray Period 0100-0700
Sample
Area
G-4
G-ll
B-ll
Y-l
pH
6.7
6.0
6.0
6.6
Cond.
ymhos/cm
1300
240
440
1350
Concentration, mg/liter
P-Alk
0.0
0.0
0.0
0.0
MO
T-Alk
60.0
30.0
26.0
50.0
N03N
.07
<.02
.12
.12
N02N
<.05
<.05
<.05
<.05
OrgN
2.9
<.l
0.4
0.7
NH3N
0.2
<0.1
0.1
1.1
T-N
3.2
.6
1.9
T-P
0.3
1.5
0.4
0.4
S04
570
25
60
275
Ca
88
24
19
94
Mg
20
2
3
14
Na
257
30
110
225
K
1.4
0.6
1.0
1.7
Cl
190
69
63
322
Note: Abbreviations of chemical parameters are explained in Appendix I.
LO
------- |