EPA/430/9-78/003
Agency
Office of Water June 19/8
Program Operation;-, iWH-b4fc. 4JO 9 78-003
Washington DC 20460
xvEPA
Environmental Changes from
Long-Term Land Application
of Municipal Effluents
MCD-26
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TECHNICAL REPORT
ENVIRONMENTAL CHANGES FROM LONG-TERM
LAND APPLICATIONS OF MUNICIPAL EFFLUENTS
by
T.D. Hinesly
R.E. Thomas
R.G. Stevens
Project Officers
Belford L. Seabrook
Lam K. Lim
MARCH 1978
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF WATER PROGRAM OPERATIONS
MUNICIPAL CONSTRUCTION DIVISION
WASHINGTON, D.C. 20460
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Disclaimer Statement
This report has been reviewed by the Environmental Protection Agency
and approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the Environmental
Protection Agency, nor does mention of trade names or commercial products
constitute endorsement or recommendation for use.
Project Officer's Note: The Bakersfield, CA, and the Lubbock, TX,
wastewater irrigation systems are both being expanded and modernized
to operate more effectively. Expansion of the Lubbock system is coupled
with a comprehensive research program to evaluate the performance of
the past operations to performance based on the present day basis for
design and operation of wastewater irrigation projects. Results from
this comprehensive effort will be an important part of the rapidly
expanding data base regarding today's design technology as well as
the soil-plant environment, surface waters, and groundwaters.
NOTES
To order this publication, "Environmental Changes from Long-Term
Land Application of Municipal Effluents" (MCD-26) from EPA, write
to:
General Services Administration (8FFS)
Centralized Mailing Lists Services
Building 41, Denver Federal Center
Denver, Colorado 80225
Please indicate the MCD number and title of publication.
Multiple copies may be purchased from:
National Technical Information Service
Springfield, Virginia 22151
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PREFACE
In Sec. 201(b)(2)(B) of the 1972 Federal Water Pollution Control Act Amend-
ments, PL 92-500, It is required that the Administrator of EPA will not make
grants for the construction of publicly owned sewage treatment works unless
the applicant has satisfactorily demonstrated that "the works proposed for
grant assistance will take into account and allow to the extent practicable
the application of technology at a later date which will provide for the
reclaiming or recycling of water or otherwise eliminate the discharge of
pollutants." Furthermore, the Administrator is required to encourage the
construction of revenue producing facilities that provide for (1) recycling
of potential sewage pollutants through the production of agriculture, silvi-
culture or aquaculture products; (2) reclamation of wastewater; (3) elimination
of the discharge of pollutants; and (4) treatment management that combines
open space and recreational considerations. All of these are conceptually
achievable by the use of soil-plant complexes to renovate effluents from con-
ventional primary or secondary wastewater treatment works. The concept for
utilizing soil-plant complexes has become identified as the land treatment
process. Land disposal of raw and treated sewage effluents is not new, but
was recognized only in recent times. There are many sites where relatively
large volumes of sewage effluent are used to irrigate agricultural lands.
The Muskegon, Michigan, system is an example of a large land treatment system
that has been recently established. Since operations were initiated in 1974,
this 40 mgd facility has produced a higher quality effluent at a lower cost
than is achievable with more conventional in-plant systems for providing
tertiary treatment and nutrient removal. However, questions about the
effective life of land treatment systems for removing various wastewater
contaminants, especially phosphorus, still persist. To obtain information
about changes in chemical properties of soils subjected to long-term irrigation
with sewage effluent, two sites were selected for study.
This report contains the results of various chemical analyses performed
on soil and plant samples collected from sewage effluent disposal sites during
March 1975 at Bakersfield, California, and at Lubbock, Texas, in June 1976.
At both sites approximately 16 mgd of effluent is applied daily throughout
the year on land used for the production of row and forage crops. Parts of
both farms have been annually irrigated with sewage effluent for more than
35 years. Except for changes in phosphorus concentrations, soil chemical
properties were not markedly affected by sewage effluent irrigations. Long-term
irrigations with sewage effluent have caused very little changes in the chemical
composition of plants grown on the disposal sites.
From the few data available, it appears that long-term disposal of sewage
effluent on farm land may have caused unacceptable concentrations of nitrates
in groundwaters. This problem could be easily corrected at both sites by
storing effluent during winter months. With adequate storage facilities,
effluent applications could be regulated so that nitrogen inputs were in balance
with nitrogen uptake by crop plants. If they were managed to remove nitrogen,
soils at both sites have potential capacities for removing contaminants from
wastewaters for many more years.
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TABLES
No. Page
1 Characteristics of effluents applied on land at Bakers-
field, California and Lubbock, Texas. 9
2 Average contents of selected chemical elements in the
profile of a Panoche clay loam soil irrigated with sewage
effluents for about 38 years as compared to chemical
characteristics of the same soil type treated with gypsum
and irrigated with well water at sites near Bakersfield,
California (all results are based on dry weight of soil). 16
3 Average total concentrations of selected chemical ele-
ments in whole barley plants collected at boot stage from
the sewage effluent irrigated farm at Bakersfield, Cali-
fornia and from a farm where only well water had been
used for irrigation (all results are based on dry weight
of tissue). 18
4 Average total contents of selected chemical elements in
the profiles of Acuff loam and Friona loam soils annually
irrigated with sewage effluents for various periods of
time at Lubbock, Texas (all results are based on dry
weight of soil). 19
5 Comparison of several characteristics of soils annually
irrigated with sewage effluent for different lengths of
time with those of soils irrigated with well water at
Lubbock, Texas. 22
6 Average total contents of selected chemical elements
in corn leaf tissues collected in June, 1976 from a field
that had been annually irrigated with sewage effluent
since 1957 at Lubbock, Texas (results are based on dry
weights of tissue samples). 24
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Preliminary Assessment of Environmental Changes Resulting
From Long-Term Applications of Sewage Effluent on Land
In recent years a rather voluminous literature has developed regarding
the benefits to be derived by society from various schemes to use soil-plant
complexes for renovating municipal sewage effluents. A sprinkler irrigation
network constructed at Muskegon, Michigan, and put into operation in 1974 is
an example of a large system designed specifically for renovating wastewater.
Many questions have been raised with regard to how long land treatment systems
will provide effective treatment of wastewaters. Several of the questions
center on long-term gradual changes in soil physical and chemical properties,
which may affect plant growth. To assess the long-term effectiveness of land
treatment systems, two sites where wastewaters have been annually applied on
land for more than 35 years were selected for study. These two sites handle
portions of the wastewater flows from Bakersfield, California and Lubbock,
Texas, respectively.
Background Information
1. Bakersfield, California. Bakersfield is located about 100 miles
northeast of Los Angeles in about the center of Kern County and is the most
populous city in the county. Census population for the City of Bakersfield
was 69,515 in 1970 and for the Greater Bakersfield Area it was 178,316.
Both are probably somewhat greater now, but growth in the last
few years has been slow (1 percent or less) because the economy is based
mainly on agriculture and the decreasing influence of oil associated
industries.
The Greater Bakersfield Area is served by five wastewater treatment
plants, three of which are operated by the City of Bakersfield. The other
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two treatment plants, known as the Mount Vernon County Sanitary District and
the North of the River Sanitary District plants, serve some of the suburban
areas around Bakersfield. The two treatment plants of interest from the
standpoint of collecting information relative to environmental changes asso-
ciated with long-term applications of sewage effluent and sludges are the
City of Bakersfield's Plant No. 1 and Plant No. 2, located in the southeast-
ern part of the city.
The City of Bakersfield has had a sewer system since 1911, but did not
have a treatment plant until Plant No. 1 was constructed in 1939 as a WPA
project. From 1911 through 1939, raw sewage was irrigated on the land owned
by the city which lies southeast from the present location of treatment
Plant No. 1. When Plant No. 1 was constructed to provide primary treatment,
it had a design capacity of 9.0 mgd but an earthquake in 1952 destroyed the
chemical coagulation equipment (Fed.,) . Subsequently, its practical capacity
was reduced to about 4.0 mgd. At the present time, Plant No. 1 receives aver-
age sewage flows of about 3.8 mgd, but it has pumping capacity to handle peak
flows of 6.6 mgd with one pump on standby. Effluent from primary clarifiers
is pumped without disinfection to a holding pond prior to its use in irrigat-
ing grain, fiber and forage crops.
The City of Bakersfield's Plant No. 2 is also a primary treatment plant
and is located approximately two miles south of Plant No. 1. The second
plant, constructed in 1952, has a design flow of 16 mgd and peak flow capacity
of 23 mgd. Inplant treatment consists of about six hours of aeration prior
to transferring the sewage to clarifiers where the solid material is allowed
to settle and is scraped to a sludge hopper by mechanical sludge rakes. The
solids are pumped to a primary anaerobic digester. Effluent flows from the
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clarifiers by gravity either to a small reservoir with a detention capacity
of 3 days or directly to a pumping station. From the reservoir effluent can
be transferred through ditches for irrigation of crops in fields lying south-
east of Plant No. 2. Effluent going directly to the pumping station is lift-
ed toward the northern part of the city owned farm (toward Plant No. 1). It
is pumped to the northern part of the farm where land surfaces have a grade
of about 0.1 percent from north to south, permitting the use of furrow or
border application methods. This results in some intermingling of effluents
from Plants No. 1 and No. 2 as applied on part of the 2,400 acre farm. City
owned farm lands include parts of sections 3, 9, 10, 15, 16, 21 and all of
22, T.30S, R.28E. Only the land south of treatment Plant No. 1 in section 3
has been irrigated exclusively with water from that plant. Land south of
treatment Plant No. 2, irrigated by gravity flow, has occasionally received
anaerobically digested sludge. A1.1 of these circumstances were considered
in selecting soil and crop sampling sites in order that the information col-
lected could be related to a particular sewage treatment plant effluent.
The city owned farm is leased to a local farmer. The lease contract is
for a 5-year period and requires the farmer to handle the entire quantity of
effluent from both city Plants No. 1 and No. 2. The contract results in rev-
enues of about 16 dollars per acre for the city. Apparently, it is also
rather rewarding for the farmer, because he does not use any supplementary
fertilizers to grow cotton, corn, barley, and alfalfa on the farm. Alfalfa,
irrigated twice and cut once a month from March to October has yielded 7 to
8 tons/acre during the growing season. Barley yields have varied from 1% to
2% tons/acre. Corn, harvested for silage and produced in a double-cropping
system with barley, has yielded between 18 and 30 tons per acre. Barley is
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usually irrigated at two week intervals from the middle of March to the mid-
dle of May. After corn is planted on the land in late May or early June, it
is irrigated at a rate to supply about 2% to 3 inches of effluent per week.
Cotton yields of 600 to 800 Ibs. of lint per acre have been about 20% below
county averages. Land planted to cotton is generally irrigated with 1 to 2
ft. of effluent prior to planting in April. These application rates provide
too much nitrogen, causing too much vegetative growth and low set of cotton
bolls. To overcome this problem, the farmer blends well water with the sew-
age effluent used for cotton irrigation from about the first of June to the
last of August. About 750 to 800 acres of the less productive soil areas are
used to produce grass for grazing beef animals. Pasturelands irrigated with
3 to 4 inches of blended tailwaters and effluents at a frequency of once dur-
ing each 2 week interval during the year, have supported 1.5 to 2 animal units
per acre. Except for cotton, crop yields and pasture carrying capacities have
been somewhat higher than those reported as county averages.
Total annual rainfall is only about 6 to 6.5 inches and potential evapo-
transpirational moisture losses are in the neighborhood of about 5 ft., thus,
in such an area, effluent has considerable value as an irrigation water supply.
Irrigation water costs about $15 per acre-ft. whether it is pumped from
wells or purchased from one of the water supply services or districts. Vol-
umes of effluent supplied to city-owned farm lands amount to about 9 acre-ft.
per year. However, the lack of winter effluent storage facilities forces the
farmer to apply effluent continuously throughout the year. Most of the rain-
fall occurs during the period from December through March when evaporational
losses are low and thus during this period of the year, effluent applications
cause a serious hydraulic overload. While there is some collection and storage
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of tailwater at the south end of the farm which is returned for blending with
effluent in the latter part of June, July, and August it is not enough to
meet requirements during this peak water demand period for growing crops.
During this period some supplemental well water is used for irrigation of cot-
ton on the city farm, as mentioned above.
2. Lubbock Texas. Lubbock is located on the southern High Plains of
West Texas that would be featureless except for ubiquitous shallow depres-
sions, called "playas". The playas range in size from a fraction of an acre
to about 200 acres and have a density of about one per square mile. They col-
lect water from surrounding uplands when amounts of precipitation are inter-
mittently sufficient to cause runoff. Minor amounts of playa stored water are
used for irrigation and some infiltrates to ground water, but most of it is
lost by evaporation.
Where Lubbock is located, average annual precipitation is about 18 inches
and potential evapotranspiration losses of soil moisture is about 65 inches
per year. Thus, water is the most limiting factor for crop production. Never-
theless, the increase in Lubbock's population from about 128,000 in 1960 to
165,000 in 1975 is attributed mainly to the existance of a thriving agricul-
tural economy made possible by the use of water from the Ogallala aquifer for
irrigation of crops. This aquifer underlies much of the high plain area.
However, the ground water is being mined because less than 5 percent of the 6
to 8 million acre-ft. of water pumped from the aquifer each year is replen-
e
ished by natural recharge. During the last 30 years the aquifer water table
has been dropping at the rate of 1 to 3 feet per year. Because fuel and elec-
trical power prices have drastically increased at a time when higher amounts
are required to pump water from ever increasingly greater depths, many farmers
are now reverting to dry land farming operations.
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Until about 1925 the City of Lubbock discharged primary effluents to a
tributary of the Brazos River, which is a small intermittently flowing stream
in the bottom of a 45 to 75 foot-deep canyon located in the north and east
part of the city. To remove the threat of contaminating privately owned rec-
reational lakes in Yellow House Canyon, several miles downstream from the sew-
age treatment plant, operations were changed to permit the discharge of efflu-
ent to a nearby upland area. In 1937, the city entered into a 20-year contract
with Frank Gray, a local farmer, to take the effluent from a city owned reser-
voir and spread it on land. At that time Mr. Gray was responsible for handling
about 1 to 1.5 mgd. In the beginning he was able to dispose of the effluent
on about 200 acres of land, where alfalfa and small grains were grown. But,
as the city grew, more land had to be purchased to handle steadily increasing
flows. The first trickling filter plant was constructed in 1941 with a design
capacity of 6 mgd. A second trickling filter plant with a design capacity
of 7 mgd was put into operation in 1950. After a newly constructed waste
activated sludge treatment plant, capable of treating 12 mgd, was put into
operation in 1972, the plan was to abandon the trickling filter plants. How-
ever, because of the rapid growth of the city, both trickling filter plants
are now being returned to service. Until about 4 mgd of effluent was diverted
for use as cooling water by a power plant constructed in 1971 near Lubbock,
Mr. Gray was required to take about 16 mgd of secondary effluent. Most of
this quantity of treated wastewater had to be applied each day because the ef-
fluent storage reservoir was only large enough to store 60 to 70 hours of flow.
No animal or human health problems were ever observed even though secondary
effluents were not chlorinated until the waste activated sludge treatment plant
was put into operation in 1972.
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Effluent is applied on 3,680 acres of land that is managed directly by
Mr. Gray and, before the 4 mgd was diverted to the power plant, some was sold
to neighboring farmers during the growing season. Until 1974, all effluent
was applied by the furrow and border irrigation methods. In 1974 Mr. Gray
installed 5 center-pivot sprinkler irrigation systems, each capable of irri-
gating almost 160 acres. However, he does not plan to change to sprinkler
application systems throughout the farm because he has to continue to apply
secondary effluents during winter periods. Ice formation on the sprinkler
equipment being used now would cause insurmountable problems.
Irrigation of various row crop, small grain and forage species with sec-
ondary-treated sewage effluent has been rather profitable for Mr. Gray. Al-
falfa yields of 7 to 8 tons/acre compare favorably with yields produced with
well water. Grain sorghums yields have been about 6,500 Ibs. per acre as com-
pared to 4,000 to 5,000 Ibs./acre under well water irrigation. Wheat yields
have averaged nearly 80 bu/acre as compared to 30-40 bu/acre on adjacent farm
land irrigated with well water. Lint cotton yields have generally been in
the range of 900 to 1200 Ibs. per acre as compared to 600 to 800 Ibs. per acre
on land irrigated with well water. Since very little supplementary fertilizer
is used on the farm, production costs for row crops are considerably less than
those for other farmers. However, to handle the effluent in a satisfactory
manner, over the years Mr. Gray has bench leveled about 1600 acres of land and
constructed about 40 miles of underground concrete and plastic pipelines plus
ponds at the lower ends of fields to collect tailwaters for later reuse.
Several similarities exist between the sewage effluent irrigation systems
at Bakersfield and Lubbock. Both were established at about the same time for
the same purpose of avoiding the discharge of partially treated effluent to
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streams which flowed only intermittently. Both systems have been expanded
during the last 40 years until they are presently handling about the same quan-
tities of effluent on about the same land acreage where about the same kinds
of crops are grown. Both systems employed surface irrigation systems, until
Mr. Gray recently installed center-pivot sprinklers. Winter storage of efflu-
ent is not practiced at either of the operations at Bakersfield and Lubbock.
At both locations, the farmer is required to take the effluent throughout the
year compelling him to apply large quantities (15 to 16 mgd) during the winter
time when row crops are absent and forage crops are not growing. A disease
incident involving man or livestock has never been linked to the effluent ir-
rigation operation at either location. This is in spite of the absence of
chlorination at Bakersfield since 1952 and at Lubbock until 1972. Beef ani-
mals are used to harvest grass and other forage crops from areas where surplus
effluent is applied during the part of the year when it is not needed for
small grain and row crop production on both farms. The lack of facilities for
storing effluent for about 3 months is probably the major deficiency at both
locations. The main difference between the two operations is that at Bakers-
field, practically all the effluent is applied on city owned lands, while at
Lubbock, practically all of the effluent is applied on privately owned lands.
Wastewater Characteristics - Bakersfield and Lubbock
Very little data for characterizing the effluents applied on land was
available from treatment plants at either Bakersfield or Lubbock. What infor-
mation was available has been summarized by Crites (1974) for Bakersfield and
by Sweazy and Whetstone (1975) for Lubbock. These data, as previously report-
ed, were summarized here in Table 1 for the readers' convenience. Crites
stated that the concentrations for several constituents in effluents at
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Table 1. Characteristics of Effluents Applied on Land at
Bakersfield, California and Lubbock, Texas.
Analyte
COD
BOD
Total organic carbon
Suspended Solids
Total Dissolved Solids
Dissolved oxygen
Total N
[\
NO ^N
Org.-N
Total P
Chloride
Sulfate
Boron
Calcium
Magnesium
Sodium
Potassium
Alkalinity
Sodium Adsorption ratio
Soluble Sodium Percentage
pH, units
Bakersfield^/
mg/1 except
150
48
380
28
25
0
3
6
60
90
0.5
15
18
112
12
220
4.4
65%
7.2
Lubbockk/
J
32-129
8-22
20
8-19
1194-1235
2-6
12-15
2-4
5-8
3-4
11-12
318
39*
24*
344*
16*
236-262
6
7.4-7.5
* Crites, R. W. 1974 - Primary effluent.
' Freese, Nichols and Endress Consulting Engineers Report,
1971. Sweazy and Whetstone, 1975. Wells, Sweazy, Gray,
Jaynes, and Bennett, 1976 - Secondary effluent.
Estimated from Northwest Lubbock treatment plant data
reported by Sweazy and Whetstone, 1975.
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Bakersfield were those to be expected in a blend of effluents from the two
treatment plants as used for irrigation. All of the values reported in Table
1 for Lubbock effluents are characteristic of wastewaters from the Southeast
treatment plant that are applied on the Gray farm, except Ca, Mg Na, and K
concentrations which were estimated from contents of these elements in efflu-
ents from the small (0.75 mgd) Northwest treatment plant in Lubbock. Total
dissolved solids and chloride contents in effluents from the small treatment
plant in Northwest Lubbock are about 2 times higher than levels in the South-
east Plant. The differences are evidently the result of the use of large
quantities of demineralized water in campus laboratories and the heating and
cooling plant of Texas Tech University. Residual waters, with increased levels
of soluble substances, are discharged to the Northwest Wastewater Treatment
Plant sewers. Concentrations of Ca, Mg, K, and Na in effluents from the
Southeast treatment plant were assumed to be about one-half those reported
by Wells et al. (1976) as concentrations in effluents from the Northwest
Treatment Plant.
Comparing wastewater characteristics at Bakersfield with those produced
at the Lubbock Southeastern treatment plant, the former has considerably
higher BOD and total N levels while the latter has higher concentrations of
total dissolved solids, Cl, and Na. Differences in BOD may not be as great
as indicated in Table 1, because Wells, et al. (1976) stated that researchers
at Texas Tech University had found that the BOD of effluents from the Lubbock
Southeastern plant had averaged about 75 mg/1 over the past ten years. Both
BOD and total N concentrations in effluents at Bakersfield and Lubbock are
about what would be expected on the basis of differences in levels of waste-
water treatment practiced at the two locations prior to application on land.
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Total dissolved solids concentrations are relatively high in Lubbock waste-
waters because they are high in city water supplies. Prior to the construc-
tion of Lake Meredith on the Canadian River, north of Amarillo, Texas, water
supplies for the city of Lubbock were obtained from wells penetrating the
Ogallala aquifer. Water samples collected from 42 wells in the Southern
High Plains area of Texas had conductivities that ranged from 476 to 1750
micromhos/cm (Cronin, 1964). Beginning in 1968, Lubbock has received a por-
tion of its water supply from Lake Meredith. Total dissolved solids concen-
trations in lake water varies, but averages about 1,200 mg/1. Currently,
about 75% of the water used in Lubbock comes from the lake.
Soil and Site Characteristics
1. Bakersfield, California. The predominant soil on the City of Ba-
kersfield's effluent irrigation farm is classified as belonging to Panoche
series. The Panoche series consists of well drained, calcareous, light brown-
ish gray and very pale brown loam and clay loam soils, found on alluvial fans
derived from granitic rock sources. Slopes are less than 2 percent and in
several places on the farm, are practically level. Soils belonging to the
Panoche series have profiles which are moderately alkaline and water perme-
abilities classed as moderate to moderately slow. Available water holding
capacities range from 0.20 to 0.25 inches per inch depth. In the surface
horizon, Panoche soils have pH values of 8.0 to 8.2 and sodium occupies 6 to
18 percent of the total cation exchange capacity. Productivity has been much
improved by effluent irrigation on several sandy loam basin and alkali flat
areas on the farm. At the beginning of effluent irrigation of alkali flat
areas sodium occupied more than 70 percent of the cation exchange capacity.
At a depth of 10 to 15 feet, nearly all of the farm is underlain by densely
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compacted subsoil materials which are only very slowly permeable to water
infiltrating the soil surface. Until lost by slow percolation and evapo-
transpirational processes during the summer months, excess water accumulates
to produce perched groundwater tables under the low-lying southern part of
the farm.
2. Lubbock, Texas. The soils on the Gray farm at Lubbock, Texas, are
mapped as Acuff loam and Friona loam, with some Amarillo fine sandy loam
along the north side of the farm. Most of the cultivated areas have slopes
varying from practically level to about 3 percent, with runoff drainage to
playas in the northern and to constructed ponds on the edge of Yellow House
Canyon (mentioned earlier) in the southern part of the farm. All soil types
have a horizon at 20 to 36 inches below the surface where CaCO~ masses make
up 30 to 40 percent of the soil volume. These soils are moderately permeable
and have available water holding capacities that range from 0.15 to 0.20
inches per inch depth. Evidently, no water impermeable layers exist between
the soil surface and the Ogallala aquifer since surface applications of ef-
fluent have, over the years, resulted in higher water table levels in the
formation where it underlies the farm.
Sample Collection and Preparation
2. Bakersfield, California. In March, 1975, soil and vegetation (bar-
ley) samples were collected from one field immediately south of Plant No. 1,
on the effluent irrigated farm at Bakersfield. This field had been irrigated
with primary effluent for at least 35 years and was irrigated with raw sew-
age for about 10 years prior to the construction of Wastewater Treatment
Plant No. 1.
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13
Six soil samples were collected to a depth of 36 inches, using 1-inch
diameter stainless steel tubes, at each of three sites about 150 feet south
of an effluent distribution ditch lying in an east to west direction adjacent
to the small holding reservoir associated with treatment Plant No. 1. At
each of the sampling sites, the 6 soil core samples were segmented into depth
samples of 0-7, 7-13, 13-24, 24-33 and 33-36 inches, conforming to differ-
ences in soil horizons. Soil samples were composited by incremental depths
and placed in labeled polyethylene-lined paper bags. At each of the 3 loca-
tions where soil samples were collected, 25 to 30 whole barley plant samples
were collected, washed in distilled water, placed in paper bags and dried
overnight in an oven at 60 C. Both soil and vegetation samples were collect-
ed in a similar manner from a field in the southwest 160 acres of section 11
of T.30S, R.28E (one mile east of the Bakersfield City farm) which had been
irrigated with well water only. All soil and plant samples were shipped to
the U.S.E.P.A. Water Research Laboratory, Ada, Oklahoma where they were ana-
lyzed for selected chemical elements.
2. Lubbock, Texas. In much the same way as described for the sampling
operations at Bakersfield, soil samples were collected from 3 fields on the
Gray Farm at Lubbock, Texas, which had been annually irrigated with effluent
for a period of at least 38, 19, and 6 years. Soil samples were collected
in each field from sites located about 50 feet from the effluent distribution
ditch, midway through the length of the field and about 150 feet inside the
tailwater end of the field. For each of the two soil types sampled on the
sewage effluent irrigated farm, representative sites were sampled in adjacent
fields which had been irrigated with well water only. Corn was growing on
the field that had been irrigated with sewage effluent for 19 years and was
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14
at tassel stage of growth. Samples of corn leaves, located nearest the pri-
mary ear formation, were collected from plants growing in the vicinity of
each of the soil sampling sites. All soil samples, collected in polyethylene-
lined bags, were dried, crushed, split, and pulverized to pass a 60-mesh
screen and leaf tissue samples, which had previously been rinsed in distilled
water, were dried at 60 C in a forced air oven and ground in a Wiley mill.
After these operations had been performed on the samples in the Department of
Plant and Soil Science laboratories at Texas Tech University, the samples
were subdivided and portions were shipped to the Department of Agronomy, Uni-
versity of Illinois. Responsibilities for analyses and measurements to char-.
acterize the soils on sewage effluent and well water irrigated farms were di-
vided between laboratories at the two Universities.
Analytical Procedures
Methods used to analyze soil samples were the same as those described
in American Society of Agronomy Monograph No. 9 with few exceptions. One
important exception was that soil samples from Bakersfield were analyzed
for surface adsorbed or precipitated heavy metals using the HNO» and HC1
digestion procedure outlined by Oliver (1973), whereas total heavy metals
were determined in soil samples from the Lubbock sites. Soil samples from
Lubbock sites were ashed at 500 C, digested in concentrated HC1-HF and sub-
sequently dissolved in 1 N_ HC1 prior to analysis by atomic absorption spec-
troscopy techniques. Another difference between analytical methods was
that plant tissue samples from Bakersfield were dry ashed in a furnace at
450°C, whereas corn leaf samples from Lubbock were wet ashed by digesting in
HN03 at 90°C. At both laboratories, metal contents were determined on atomic
absorption spectrometry instruments equipped to make simultaneous deuterium
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15
arc background corrections to the data. All determinations were made from
triplicate subsamples of each soil and plant sample. After no appreciable
differences were observed in results from soil samples collected at differ-
ent locations within a particular field at the Lubbock site, they were pre-
sented for discussion as average values.
Results
1. Bakersfield, California. In comparison with concentrations in the
same soil irrigated with well water, results in Table 2 show that sewage ef-
fluent applications on the Bakersfield farm caused increased soil organic
matter and total N concentrations to depths of 2 feet. Concentrations of Ca
and Mg were higher and Fe and Al were lower in soil from all depths on the
sewage effluent irrigated farm as compared to concentrations of these ele-
ments in soil from the control site. Total P concentrations were higher in
the surface of the sewage effluent irrigated soil (0-7 inches), but concen-
trations were not different than those in control soil at deeper depths. Iron
and Al concentrations appeared to have been decreased throughout the soil pro-
file by sewage effluent applications. Concentrations of surface adsorbed
and/or precipitated Zn and Cu were apparently increased in the 0 to 24 inch
depth of soil by sewage effluent applications. Concentrations of surface
adsorbed and/or precipitated Ni, Pb and Cd were higher throughout the profile
of the effluent irrigated soil than where effluent had never been used for
irrigation. Extractable levels of Cd in the soil irrigated with only well
water were 0.2 to 0.5 ppm higher in subsurface layers than generally reported
as typical total levels in soils. If sewage effluent irrigations have caused
any changes in exchangeable Ca, Mg, and Na contents in the soil, it may be
that exchangeable Ca levels were increased at the expense of exchangeable Na
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17
levels, especially in the lower subsoil horizons. No doubt, long-term annual
sewage effluent applications caused appreciable increased extractable P levels
in soil as determined by the method discussed by Taylor and Gurney (1965).
Resin-extractable P levels were uniformally increased 4- to 5-fold in all soil
horizons by sewage effluent irrigations as compared to levels in respective
soil horizons where well water was used for irrigation. Except for extract-
able P, concentrations of all elements in all soil samples were within ranges
of concentrations found in normal agricultural soils.
Levels of selected chemical elements in whole barley plant tissues, as
presented in Table 3, suggest that sewage effluent applications have not ma-
terially affected the chemical composition of plants. However, low Fe con-
tents in plant tissue from the sewage effluent irrigated farm as compared to
tissue from plants growing on soil irrigated with well water, may be a re-
flection of differences in contents of the element in soils, as previously
noted.
2. Lubbock, Texas. Total concentrations of 15 elements and organic
matter, as shown in Table 4, indicate very few changes in the chemical status
of soils associated with long-term sewage effluent applications at Lubbock.
Other than increased concentrations of total P throughout the soil profile
irrigated with sewage effluent for 38 years, no other differences in chemi-
cal composition of soils can be attributed to the use of wastewater. Re-
gardless of treatment, all of these soils contained heavy metals at levels
somewhat below those considered as typical contents of normal agricultural
soils. Concentrations of B in all of the soils were in the upper range
generally reported for agricultural soils, but apparently were not affected
by applications of sewage effluent.
-------
18
Table 3. Average total concentrations of selected chemical elements in whole
barley plants collected at boot stage from the sewage effluent irri-
gated farm at Bakersfield, California, and from a farm where only
well water had been used for irrigation (all results are based on
dry weight of tissue) in comparison to typical range for forage
grasses and legumes.
Total Concentrations
Irrigation
with
Effluent
Well Water
2
3
N
.42
.16
P
0.43
0.37
K
°/
°
3.20
2.99
Ca
0.36
0.45
Mg
0.11
0.21
Na
253
269
Fe
87
159
Zn
- -ppn
59
43
Cu (
7
9
M Pb
:1 <6
a <6
Comparative
range
(2-4)
(.2-
.4)
(1.2-
2.8)
(.6-
.9)
(.2-
.4)
(250-
600)
(8-
60)
(2-
15)
(
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.8)
(1-10)
( ) Range for common range grasses and legumes from R.D. Johnson, et. al.,
Selected Chemical Characteristics of Soils, Forages, and Drainage Water
from the Sewage Farm Serving Melbourne, Australia. Department of the
Army, Corps of Engineers, page 23, January 1974.
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Toward a more complete characterization of the Lubbock soils, several
other measurements were made for which the results are exhibited in Table 5.
First, it may be observed that where the Acuff loam soil has been irrigated
for 38 years with sewage effluent, soil pH has been decreased by about one
unit in the 0-18 inch surface layer. Soil pH has been decreased only slight-
ly in Friona loam irrigated for 19 years with sewage effluents. Results
from electrical conductivity measurements of water saturated soil extracts
show that 38 years of irrigating Acuff loam soil with sewage effluent has
caused an increase in its salinity levels at all sampled depths of the pro-
file. In this soil, salinity levels are approaching the lower end of the
range where yields of many crop plants may be reduced (Wadleigh et al., 1951).
Where effluent has been applied for 19 and 6 years on Friona loam, soil sa-
linity levels were increased at all depths. The most notable differences
in salinity levels occurred at the lower depths of the profile. Concentra-
tions of K and P extracted with NH/OAC from soils have been markedly affect-
ed by sewage effluent irrigations. Except in the surface 0-12 inch zone,
the Acuff loam soil had nearly 2-fold contents of extractable K as compared
to the well water irrigated control soil. Friona loam soil irrigated with
effluent for 19 years had higher concentrations of extractable K at all
depths than were found in control soil. Concentrations of P significantly
increased at all soil depths where effluent was applied for 38 and 19 years.
Organic P levels were increased in the surface (0-12 inches) of Acuff loam
subjected to long-term sewage effluent applications.
Average total contents of selected chemical elements in corn leaf tis-
sues, collected from the Friona loam site at the same time as were soil sam-
ples, are shown in Table 6. Irrigating this soil for 19 years did not affect
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25
plant composition since concentrations of selected chemical elements were
within the range to be expected in corn leaf tissues. However, leaf con-
centrations of Na and Fe were in the low and B in the high range of expected
levels in leaves from healthy corn plants. Eaton (1944) found that corn
plants suffered from B toxicity when leaves contained as much as 179 ppm
of the element.
Groundwater
1. Bakersfield, California. Very little is known with regard to ground-
water changes underlying the sewage effluent irrigated farm at Bakersfield.
What is known was summarized in a report prepared for the City of Bakersfield
by Metcalf and Eddy, Inc. (1973). Samples of water from a confined aquifer
below the effluent irrigated farm (300 ft.) had concentrations of nitrate
ranging from 50 to 60 ppm. However, it was pointed out that several miles
east of the effluent irrigated farm, water samples from wells in 40 percent
of the sections in Township 30S/Range 29E had maximum nitrate concentrations
of 90 ppm or greater. Water from 2 shallow wells (13 to 14 ft, deep) near
the eastern edge and middle of the sewage effluent irrigated farm, where
perched water tables were found at 11 to 12 ft. below the surface, had con-
centrations of nitrates that ranged from 4 to 39 ppm. Water from a deep well
(170 ft. deep) near one of the shallow wells in the center of the effluent
irrigated farm contained 4 ppm of nitrates. With only this limited informa-
tion it is not possible to assess groundwater quality changes attributable
to the practice of using sewage effluent for irrigation.
2. Lubbock, Texas. Only slightly more information about groundwater
quality at the Lubbock effluent irrigation farm is available than was found
for the Bakersfield operation. Sweazy and Whetstone (1975) reported that
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26
water from a well on the effluent irrigated farm at Lubbock had a total dis-
solved solids concentration of 1692 ppm. For comparison, Wells et al. (1976)
reported that water from a well near the Texas Tech University Campus had a
total dissolved solids concentration of 1140 ppm. Well water from the efflu-
ent irrigated farm contained 50 ppm of NO~-N, whereas water from the Univer-
sity well contained only 8.5 ppm of NO -N. The former well water had a pH
of 7.9 and the latter a pH of 7.7. Water from the University well contained
228 ppm of Cl while water from a spring fed by accumulated subsurface water
from the effluent irrigated farm had a mean concentration of 252 ppm of Cl.
No comparative information was found, but well water samples from the sewage
effluent irrigated farm had no measurable amounts of total coliform and fecal
coliform organisms, nor BOD . The same water samples did contain 10 ppm COD
and had a total phosphorus concentration of 0.08 ppm. From the few data
available, it appears likely that the long-term effluent irrigation operation
at Lubbock has caused increased dissolved solids and NO -N concentrations in
the groundwater immediately underlying the farm.
In an area where groundwater levels have been receding at an alarming
rate, the water table under nearly all of the effluent irrigated farm at
Lubbock is within 10 to 15 feet of the land surface. The water table under
the farm is high enough to supply water to playa lakes, used as a water source
by cattle, during periods of the year in which they would be dry under normal
conditions. If the farm had not been located adjacent to Yellow House Canyon,
to which natural subsurface drainage of the farm occurs, it probably would
have been necessary to have either curtailed amounts of effluent applied or
to have installed subsurface drains. However, because of the abundant avail-
ability of good quality water underlying the effluent irrigated farm, plans
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27
are presently being implemented by the City of Lubbock to recover it for use
as makeup water in a series of 4 recreational lakes that have been constructed
in Yellow House Canyon. The first stage construction of the 4 lakes provides
a continuous 8 mile chain of impounded water for recreational use within the
City. Make-up water will be pumped from 27 wells, being drilled on the efflu-
ent irrigated farm, through 14 miles of pipeline varying in diameter from 24
to 18 inches, to the upper lake. Some of the recovered water will be used
for irrigating parks and cemeteries and cooling water at a small city owned
power plant.
Before initiating the water reuse project, it was determined that the
percolated effluent from the farm would provide for a more dependable, higher,
water quality and at a lower cost than could be obtained from two alterna-
tive tertiary treatment processes evaluated (Freese, Nichols and Endress,
1971). From the results obtained from a model of the canyon lakes, Head-
stream et al. (1974) concluded that following percolation through soils, the
sewage effluent was suitable as a source of make-up water in lakes to be used
for primary contact recreation. However, because of the relatively high
level of NO,.-N in recovered effluent waters, some uncertainty exists with re-
gard to eutrophication problems that may arise in the first and second lakes.
Since the levels of P are rather low in recovered effluent water, eutrophica-
tion may not be as serious as would be anticipated from considerations based
on nitrate levels alone. From both public health and eutrophication consid-
erations, several questions exist with regard to the collection of storm
runoff water in the series of constructed lakes.
Discussion and Conclusions
In general, crop production has been increased by the use of municipal
sewage effluent for irrigation over that obtained with other sources of
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28
water and commercial fertilizer on neighboring farms, Increased production
has been realized in spite of frequent periods of hydraulic overloading with
effluent.
Measurements were not made, but visual observations did not indicate
that soil physical properties had been adversely affected by long-term efflu-
ent irrigations. Only a few changes in soil chemical properties were found.
At Bakersfield, long-term annual effluent irrigations have probably caused
increased soil organic matter and total N and P levels in the soil surface,
while Ca concentrations may have been increased and Fe concentrations de-
creased throughout the whole of the soil profile. Apparently long-term efflu-
ent irrigations have caused increased concentrations of surface adsorbed and/or
precipitated heavy metals in the soil surface at Bakersfield, although only
Zn and Pb levels were markedly different from those in soils irrigated with
well water. Long-term irrigations with effluents have apparently caused a
reduction in concentrations of exchangeable Na at depths below 24 inches and
concentrations of extractable P have been increased markedly throughout the
soil profile. Only concentrations of total and extractable P and total dis-
solved solids in soils have been appreciably increased by long-term sewage
effluent irrigations at Lubbock, Texas. Effluents applied for 38 years,
appeared to have caused increased concentrations of NH OAc extractable K
throughout the soil profile, although total K concentrations were not increased.
Increased conductivity of water saturated extracts of soil irrigated
with effluent at Lubbock, but not at Bakersfield, is evidently the result of
relatively high levels of total dissolved salts in the water source used by
the city. Considering the length of time that effluent has been irrigated on
land at Lubbock, it seems unlikely that salinity will be a serious problem as
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29
long as adequate over-irrigation is practiced to keep soluble salt levels
below those presently existing in the soil profile. Also, when subsurface
water tables have been lowered by the recycling program, the border-line
salinity problem may be dissipated.
The accumulations of P and heavy metals to higher levels in soils at
Bakersfield as compared to levels in soils at Lubbock may have been due to
the higher level of wastewater treatment practiced at the latter location.
No information about concentrations of metals in effluents was available
at either location. Nevertheless, levels of the elements in soil at Bakers-
field do not yet represent a potential problem. Zinc, Cu and other trace
elements supplied as constituents of effluent at Lubbock may significantly
benefit both plants and animals. Except for B, soils in the high plains area
have relatively low total concentrations of essential trace elements for plants.
On both the Bakersfield and Lubbock effluent irrigation farms, the ground-
water quality could be much improved with respect to NOs-N concentrations if
effluent-nitrogen loading rates were matched with crop uptake of the element.
At both sites it appears likely that the relatively high N03-M concentrations
in groundwater are due to applying too much effluent containing N on lands
during periods when growing crops are either absent or making little growth.
Effluent storage facilities would provide a means for making more efficient
use of both water and the plant nutrients contained in it.
Recommendat ions
The few data summarized in this report were inadequate for confidently
predicting the wastewater renovation capacities of soil-plant complexes. Both
of these sites are suitable for an in-depth characterization of long-term
effects with a well designed sampling and analytical program.
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30
At Lubbock, special attention should be given to amounts of B supplied
on agricultural land as a constituent of effluent. Because natural total B
levels are already relatively high in soils, additional accumulations in
soils may lead to reduced crop growth. Priority should also be given to
determining B levels in effluents and soils at Bakersfield.
Studies should be initiated to determine changes in soluble salt levels
in soils on the Lubbock farm as groundwater tables are lowered by the pumping
of make-up water for recreational lakes. Much work is needed to establish
minimum annual effluent applications required to keep soluble salts in soils
at a level sufficiently low for good plant growth. This information will be
especially valuable if the farm is expanded and emphasis is placed on effi-
cient use of wastewater for crop production rather than on effluent disposal.
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31
ACKNOWLEDGEMENTS
Comments about the manuscript from Dr. John M. Walker, which were help-
ful in the preparation of the final report, are gratefully acknowledged, but
the conclusions remain the responsibility of the authors. The authors ap-
preciate Dr. I. K. Iskandar's and Mr. E. L. Ziegler's assistance during the
collection of samples. The authors thank Mr. G. L. Barrett and B. E. Bledsoe
for a major portion of the analyses performed on the soil and plant samples.
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REFERENCES
Black, C. A. et al. 1965. Methods of soil analysis. Monograph No. 9,
American Society of Agronomy, Inc., Madison, Wisconsin.
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Cronin, J. G. 1964. A summary of the occurrence and development of
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Eaton, F. M. 1944. Deficiency, toxicity, and accumulation of boron in
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Freese, Nichols, and Endress Consulting Engineers. 1971. Report on make-
up water for the upper canyon lakes. City Manager's Office, Lubbock,
Texas. 26 pp.
Headstream, M., D. M. Wells, R. M. Sweazy, and E. D. Smith. 1974. Recrea-
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Metcalf and Eddy, Inc. 1974. Project report for the Bakersfield sub-
regional wastewater management plan. Prepared for the City of Bakersfield
and Mount Vernon County Sanitation District, California. 229 pp.
Oliver, B. G. 1973. Heavy metal levels in Ottawa and Redeau River sedi-
ments. Environ. Sci. and Tech., 7:135-137.
Sweazy, R. M. and G. A. Whetstone. 1975. Case history of effluent reuse
at Lubbock, Texas. Presented at the Spray Irrigation Seminar, Harrison
Hot Springs, British Columbia.
Taylor, A. W. and E. L. Gurney. 1965. The effect of lime on the phos-
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Sci. Soc. Amer. Proc., 29:482-483.
Wadleigh, C. H., H. G. Gauch, and M. Kolisch. 1951. Mineral composition
of orchard grass grown on Pachappa loam salinized with various salts. Soil
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Wells, D. M., R. M. Sweazy, F. Gray, C. C. Janes, and W. F. Bennett. 1976.
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U.S. Government Printing Office: 1979-678-681/324 Regions
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