LAND APPLICATION OF WASTEWATER
by
Belford L. Seabrook, Professional Engineer
Municipal Waste§Water Systems Division
Office of Water Program Operations
ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460, U.S.A.
Prepared for presentation at a
Workshop Conference sponsored by
The International Reference Group on
Great Lake Pollution from Land Use Activities
University of Guelph
Guelph, Ontario, Canada
September 11-12, 1973
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LAND APPLICATION OF WASTEWATER
INDEX
page
SUMMARY 1
HIGHLIGHTS 7
OVERVIEW 10
THE STUDY - SECTION II 12
SURVEY INVESTIGATIONS - SECTION III 13
OPINIONS AND REGULATIONS OF STATE HEALTH AND
WATER POLLUTION CONTROL AGENCIES - SECTION IV 17
SUMMARY OF FOREIGN EXPERIENCE - SECTION V 18
GUIDELINES FOR IMPLEMENTATION OF LAND APPLICATION
SYSTEMS - SECTION VI 20
PLACING LAND APPLICATION OF EFFLUENTS IN PERSPECTIVE:
AN INTERPRETATION - SECTION VIII 21
DEMOGRAPHIC EVALUATION OF LAND APPLICATION TECHNIQUES 23
CLIMATIC CONDITIONS ... 26
SIZE OF WASTEWATER FACILITY 30
CONTINUITY OF OPERATION 31
METHODS OF DISTRIBUTION 33
LAND AVAILABILITY, LAND USE AND LAND VALUE 34
FATE OF MATERIALS APPLIED TO THE LAND 36
CONCLUSIONS 42
RECOMMENDATIONS 51
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CLIMATIC ZONES
A-MEDITERRANEAN CLIMATE-
DRY SUMMER - MILD, WET
WINTER
B-ARID CLIMATE - HOT, DRY
C-HUMID SUBTROPICAL - MILD
WINTER, HOT, WET SUMMER
(WASH., ORE., AREA MILD,
MOIST SUMMER
D-HUMID CONTINENTAL - SHORT
WINTER, HOT SUMMER
E-HUMID CONTINENTAL - LONG
WINTER, WARM SUMMER
LAND APPLICATION OF WASTEHATER
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LAND APPLICATION OF WASTEWATER /^
by
Bel ford L. Seabrook, Professional Engineer /**
SUMMARY
The American Public Works Association Research Foundation, in
1972, conducted an on-site field survey of approximately 100 facilities
in all climatic zones where community or industrial wastewaters are
being applied to the land, as contrasted to the conventional method
of treating such wastes and discharging them into receiving waters.
Additional data were gathered from many existing land application
facilities across the country by means of a mail survey addressed to
responsible officials. Another survey was carried out to ascertain
the nature and extent of State health and water pollution control
regulations governing the use and control of land application systems.
To augment information on U.S. practices, a survey was made of exper-
iences gained in certain foreign countries. In addition, an extensive
bibliography was compiled of literature on all pertinent phases of
land application practices.
l^_ For presentation at a Workshop Conference sponsored by the
International Reference Group on Great Lakes Pollution from
Land Use Activities, at the University of Guelph, Guelph,
Ontario, Canada, September 11-12, 1973
** Sanitary Engineer, Municipal Waste Water Systems Division, Office
of Water Program Operations, Environmental Protection Agency,
Washington, D. C. 20460
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The facilities surveyed were relatively large long-established
operations. These were selected to obtain as much information as
possible on the operating experience of those using this technique.
The surveyed facilities whose municipal wastes were applied on land
were predominately located in western and southwestern portions of
the U.S., while industrial facilities were generally sited in the
northeastern section, because this is where the majority of such
installations are in service. This method of handling waste water has
been used to meet definable needs and 1s technically feasible in most
areas.
Land application of effluent has been employed for a variety of
reasons. Those most frequently mentioned were:
1. to provide supplemental irrigation water,
2. to give economical alternative solutions for treating
wastes and discharging them into receiving waters,
without causing degradation of rivers, lakes and
coastal waters,
3. to overcome the lack of suitable receiving waters and
eliminate excessive costs of long outfall lines to reach
suitable points of disposal into large surface bodies of water.
Among the major means of accomplishing land application of waste-
waters are:
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1. irrigation of land areas by spraying, with high-pressure
or low-pressure devices, using either stationary or moveable
types of distribution systems;
2. ridge and furrow irrigation systems;
3. use of overland flow or flooding methods; and
4. use of infiltration lagoon or evaporation ponds.
Although facilities of all types were surveyed, this report is
primarily concerned with irrigation-type facilities for supplying
supplemental water to crop areas, forest areas and unharvested soil
cover acreages. The other types are not as widely used, because the
climate or soil conditions in some locations have an adverse impact
on these alternative methods of applying wastewater to land.
Irrigation-type facilities were found to be used in many instances
under a wide variety of climate and soil conditions, with various degrees
of prior treatment of the applied wastewater and various types of ground
cover utilized.
Each method of application has inherent advantages and disadvantages
which must be evaluated for their feasibility and efficacy.
Land application of wastewaters has been practiced extensively
in various parts of the world for many years, long before the turn
of the century. The majority of earlier facilities applied untreated
domestic wastewaters with varying degrees of control and success.
As knowledge of wastewater treatment processes improved, and
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techniques were developed, confining, in a relatively small area,
the entire process needed to produce a "treated" effluent for disposal
into receiving waters, land application was relegated, in most states,
to being an undesirable and unacceptable process.
New concerns about preserving the quality and re-use of the
nation's water resources have resulted in a reawakening of interest in
land application as a viable alternative to conventional wastewater
treatment and disposal into receiving waters. Increasing volumes of
sewage and industrial wastes, growing complexity of such raw wastes,
and mounting needs for water to serve growing urban and industrial
processing needs, have created doubts about the ability of receiving
waters to assimilate effluents which do not meet high-quality standards
In addition, increasing evidence of eutrophtcation of non-flowing
receiving waters has focused attention on the need to eliminate the
presence of nutrients in wastewater effluents. Further, the presence
of toxic trace elements in effluents is sometimes considered a threat
to the safety of receiving waters. Thus, advanced treatment methods
have been developed and utilized to avoid discharge of such objection-
able components. Inasmuch as land application appears to offer
comparable or superior degrees of treatment by augmenting waste
treatment with the "natural" purification offered by soil contact,
land application is again being considered as one of the acceptable
means of achieving full treatment of wastewaters.
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However, a most important factor of the current land application
concept is that it be limited to the use of treated wastes. Generally,
effluents are being conventionally treated to meet secondary treatment
quality criteria. In at least three observed facilities, applied
effluents have received tertiary treatment, to the point where
the effluent would fully meet the generally prescribed, as well as
proposed, criteria for discharge to receiving waters. Thus, land
application 1s being used to give a degree of advanced waste treatment,
including high degrees of nutrient and bacterial removal. In this
context, land application can be viewed as an alternative to physical-
chemical processes and other methods of ultra-treatment which are
designed to achieve a high quality effluent.
Economics of construction cost, operating costs, energy require-
ments, and efficiencies of performance of land application systems
must be balanced with the ability to acquire the right to apply
wastewater upon the required land areas. The cost of advanced
waste treatment by conventional means must be weighed in the light
of the cost and complexities of land application systems.
Two informative reports were published on the subject of land
application in 1972. Green Lands - Clean Streams, a report by Temple
University Center for the Study of Federalism, is a frankly written
advocacy of the land application of wastewaters and sludges.
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Wastewater Management by Disposal on the Land by the U.S. Army Corps
of Engineers is a thorough review of the physical, chemical, and
biological interactions involved in the technique of land application.
The Consulting Engineering firm of Metcalf and Eddy has also prepared
a companion report for the U.S. Environmental Protection Agency,
concerned with engineering considerations of land application systems,
entitled Wastewater Treatment and Reuse by Land Application. The
M&E report will be printed by the U.S. Government Prining Office in
1973. These three reports, together with this report on the study
conducted by the AWPA Research Foundation, should be considered in
evaluating land application systems, because they deal with somewhat
different aspects of the common problem.
The report on the AWPA studies has made no special effort to
examine the specific aspects covered in detail in the other reports.
Rather, it is concerned with reporting upon the policies, practices
and performances of a representative group of the relatively larger
land application systems within the U.S.; policies, or lack of policies,
of State regulatory agencies; and the experience with land application
in certain foreign installations.
Systems which were under construction, such as Muskegon County,
Michigan, and several major domestic and industrial systems which were
intimately known to Metcalf and Eddy project personnel were not
investigated for this report. However, the firm of Metcalf and Eddy
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has supplied copies of its field interviews at such sites to APWA
evaluators and data on many of these installations have been
incorporated in this report. Conversely, all field information
obtained during the APWA investigations was supplied directly to
the firm of Metcalf and Eddy for its use in analyzing its own study
results.
HIGHLIGHTS
The following highlights from the field survey are presented
to give a composite picture of the observations made during the land
application site visits:
1. Communities generally use their land application
system on a continuous basis. Food processing
plants, the predominant industrial users of the
system, generally use discharge-to-land
systems for three to eight months per year.
2. Ground cover utilized for municipal systems is divided
between grass and crops. Industries generally use
grass cover.
3. Land application systems are generally used on a daily
basis, seven days per week.
4. Application rates for crop irrigation are very low in
terms of inches of water per week. Two inches or less
was commonly used. (Two inches per week equals 48,000
gallons per acre per week.)
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5. Many types of soils were used, although sand, loam
and silt were the most common classification given.
Two systems using applications over many feet of sand
were applying up to 8 inches per day once a week, and
one system on clay was applying a daily rate of 0.1 inch.
6. Most operating agencies, municipal and industrial, are
planning to either expand or continue their land application
installations. The few examples of systems which had been
abandoned were due to either the desire to make a higher
use of the land, or because of reported overloading and
incompetent operation of the land application facilities.
7. Industries surveyed generally treat their total waste flow®
by land application. Practices of municipalities varied
from less than 25 percent, to all the wastewaters discharged.
8. Secondary treatment is generally, but not always, provided
by municipalities prior to land application, often times
accompanied by lagooning. Industries, using this technique
frequently treated their process wastes by screening only.
9. Spray irrigation is the most frequently used (57 facilities)
method of application, although most municipalities use
more than one method. Ridge-and-furrow irrigation is used
at 23 facilities and flooding irrigation by 34 systems.
Industry generally used spray irrigation.
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10. Land use zoning for land application sites is
predominantly classified as fanning, with some
residential zoning in contiguous areas.
11. Wastewater generally is transported to the application
site by pressure lines, although a number of
municipalities are able to utilize ditches or gravity
flow pipelines.
12. Many municipal land application facilities have been
in use for several years -- more than half for over
15 years. Industrial systems generally have been in use
for a lesser period of time.
13. Renovated wastewater is seldom collected by under-
drains; rather, evaporation, plant transpiration,
and groundwater recharge take up the flow.
14. Land application facilities generally do not make
appreciable efforts to preclude public access.
Residences are frequently located adjacent to land
application sites. No special effort is made to seclude
land application areas from recreational facilities and
from those who use these leisure sites.
15. Monitoring of groundwater quality, soil uptake of
contaminants, crop uptake of wastewater components,
and surface water impacts is not carried out with
any consistency.
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OVERVIEW
In order to present all of the details and data relating to the
conduct of the studies, and to explore the influence of possible
factors Influencing the handling of sewage from many sources, at many
sites, and with many and diverse methods of application, the APWA
report has resulted in a rather large document.
Among other things, the report has been compiled to answer the
inquiries of the U.S. Environmental Protection Agency from other U.S.
Government agencies, municipalities, industries and engineering
consultants. The total report is valuable, not because of its size
but due to Its contents. This is the first time some of this data
has ever been assembled, evaluated and reported. It will become
available from the U.S. Government Printing Office in the autumn of
1973 and from the National Technical Information Service (NTIS) of
the U.S. Department of Commerce.
This overview is for those who require a brief summary of the
contents of the American Public Works Association report, entitled,
Survey of Facilities Using Land Application of Wastewaters. and an
equally concise evaluation of the principles, practices and performances
of the land application systems now in service in the United States
and in certain foreign countries. Summaries of the basic intent and
information contained in each Section of the report are presented as
well as a demographic evaluation and a discussion of the fate of
materials applied to the land.
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The conclusions drawn from the study serve to verify the relative
success of present land application systems for supplementing ground-
water sources; providing economical means of effluent utilization where
discharge to surface waters would be excessively difficult and costly;
affording augmented effluent quality improvement by soil uptake of
constituents which would adversely affect receiving water quality; offering
opportunities to enhance crop growths and silviculture; and augmenting
indigenous water supplies for recreational and aesthetic purposes.
Successful application of effluent wastewaters to land areas
is not without its problems. This management technique is not a
universal panacea.
The need for public acceptance of land application methods is
strongly advocated, particularly for proposed installations covering
large volumes of flow to extensive acreage in relatively densely
populated regions. Over and above the problem of neutralizing the
aesthetic and psychological objections to any direct or indirect
contacts with wastewaters or wastes residues, unfounded fears of
virological or pathological infections must be overcome by carefully
planned and effectively executed public education programs.
This public relations problem emphasizes the recommendation that
irrefutable findings on the presence or absence of health hazards in
land application practices must be defined and reported before
guidelines for this method of wastewater effluent management are
promulgated. Guidelines are soon interpreted as "the law" rather
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than suggested criteria. This gives credence to the sound suggestion
that formalization of "guidelines" be deferred until "interim
evaluation procedures" are published and given the opportunity to
bridge the gap between today's rather limited use of land application
systems and any greatly expanded utilization of this treatment-
disposal procedure in the future.
THE STUDY - SECTION II
The studies conducted by the American Public Works Research
Foundation on behalf of the U.S. Environmental Protection Agency
were planned and consummated to produce the fundamental information
needed to give validity to the intent of Section 201of the 1972
Amendments to the Water Pollution Control Act such as:
oAffirmation of design and operational data for a large number
of U.S. installations in various climatic regions, handling waste-
waters of various types and volumes; by various methods of application;
for different purposes; on various types of soil, ground cover and
cropping; and demonstrating different local environmental conditions
and monitoring practices.
oCollection and interpretation of similar data on foreign
installations where land application has been in effect for longer
periods and under varying conditions.
0Collation of bibliographic records and references on every
conceivable facet of land application, including design, operation,
physical, chemical, pathological, virological, parasitic, aesthetic,
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hydrologic, agricultrual, herbicultural, silvicultural benefits
and detriments, and other related matters.
^Evaluation of all data in terms of practical interpretation of
their meaningful answers and guidelines to land application practices
The studies, in great measure, achieved these goals.
SURVEY INVESTIGATIONS - SECTION III
On-site, in-depth investigations of more than 67 community and
20 industrial land application systems were carried out by trained
engineering specialists. The 87 installations designated provided
data of significance. These sites were chosen to be representative
of national experiences with varying types of wastewaters, applied
to varying types of soils, ground cover and other indigenous
conditions under diverse climatic conditions.
To augment the findings of the on-site surveys, a mail
investigation of similar land application sites was carried out,
covering the same study subjects explored by the field study
team. Significant data were obtained for approximately the same
number of municipal and industrial installations covered by the
field studies. Five climatic zones, each with their own temperature,
precipitation, humidity and seasonal characteristics, were designated.
Evaluation of survey findings was interpreted on the basis of the
impact of climatic conditions on wastewater application to land
areas and other factors influenced by meteorological phenomenon.
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The demographic, geographic, geologic, hydrologic and other factors
and impacts of land application practices, procedures and performance
are discussed in this section.
The findings of the survey offer evidence of acceptable operating
experiences, which should be useful in guiding future land application
decisions. An important finding, among all of the diverse conclusions
that can be drawn from field and mail survey data, is the fact that
90 percent of communities and 95 percent of industries making use of
land application methods plan to continue their use; nearly 50 percent
of communities and one-fifth of the industries contemplate increasing
or expanding their systems. If the "proof of the pudding" is in
the performance, the approval of users is the final appraisal of the
land application technique.
The study indicated that existing land application systems are
serving, predominantly, in relatively small communities and industrial
sites, in terms of population and flow loadings. Future applications
may involve larger loadings, greater irrigation areas and greater land
values, but the expansion of facilities may represent an orderly
enlargement of scope and a manageable increase in costs. It is
significant that the costs involved in existing land application systems
apparently lie within the capabilities of smaller communities and
industry installations. Choice of this means of wastewater disposal
has been based on various factors: Need for supplemental irrigation
water; augmentation of ground water resources; simplicity and economy
of providing required degrees of treatment; problems of excessive
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cost of providing treatment and outfall lines to distant points of
effluent discharge into suitable receiving waters; and merely "to
get rid of the sewage" in a convenient, trouble-free manner that is
acceptable to the community.
The findings of the survey are so manifold and technological
that any attempt to capsulate them would hinder their value and endanger
their interpretation. The following points are borne out by the report:
Existing practice stresses land application of treated effluents, not
raw wastewaters; the percentage of land application acreage frequently
represents only a portion of the land reserved by the owners for their
systems; application periods may vary from one month to twelve months
a year, and from one to seven days a week, depending on climatic
conditions, need for land application for surplusage flows, seasonal
industrial processing, such as in the food industry, and other local
factors; land values are relatively low, zoned for either agriculture
or residential uses, often in undeveloped areas, and subject to minimal
degradation of value due to use for irrigation purposes; all types of
soil are utilized, with sand, clay and silt most favored; groundwater
interference problems influence choice of sites and, after choice of
unaffected sites, cause minimal difficulties with land application
methods; predominant wastewater distribution methods are spray irri-
gation, overland flooding irrigation and ridge-and-furrow irrigation.
Use of the irrigated land varies with the owner's needs and dictates,
from no ground cover to grass cover, cultivated crops and forested areas.
Grass is the most common ground cover in community systems. It is
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evident that the cropping value of supplemental irrigation with wastewaters
and their nutrient components is not universally utilized.
Rates of application of sewage effluents to the land, and duration
of uninterrupted application vary from 0.1 inch per day to over 1 inch
/•-"
per day, with varying periods of irrigation and resting. The most
commonly used application rate is two inches per week. Few systems
are over-stressed by such loadings; it is apparent that increased rates
of application could be practiced without jeopardy to the system or the
environment, and with more effective and economical utilization of
assigned acreages. The follow-the-leader trend in application rates
is apparent; proposed guidelines—either tentative or final—would do
much to establish more rational application rates, based on facts rather
than blind adherence to the accidental or arbitrary rates used by other
researchers.
Little concern and protective measures have been shown for the
deterioration of the environment in application areas, or to the impact
on contiguous lands and their occupants. Security provisions are not
universally used to protect against intrusion of trespassers or against
the dispersal of on-site conditions to surrounding land areas. Fencing
and patrolling is not universally practiced; buffer zones to isolate
land application areas and impede dispersal of aerosol sprays are used
but no common practice is in effect; monitoring of groundwater, surface
water sources, soils, crops, animals and insects is practiced in some
locations and minimally used in others, often dependent solely on the
requirements of public health authorities.
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It is hazardous to characterize the above thumbnail findings as
truly representative of the practices and experiences disclosed by the
survey. Similarly, these factors do not represent all of the disclo-
sures of the study. They do however, give indication for those who
will not study the full text and details of the comprehensive
investigations explored in the full report, that land application
methods have been found to be workable and relatively amenable to the
local environment, even under control and regulatory procedures which
must be improved in all future land application practices. The future
will require more complete supervision of land application sites,
supported by definitive proof of the capabilities of such systems to
serve as wastes handling facilities worthy of the term "alternative"
techniques.
OPINIONS AND REGULATIONS OF STATE HEALTH AND WATER POLLUTION CONTROL
AGENCIES - SECTION IV
The survey conducted by APWA with State health and water pollution
control agencies indicated that most State agencies have no set policies
on this phase of wastewater handling or attendant environmental impacts,
do not impose specific conditions on installations, seldom inspect
existing systems, and seldom require monitoring procedures and the
filing of official reports on operation.
Only four States reported rules governing the types of crops that
.can be grown on sewage-irrigated lands. The few agencies which invoke
restrictions of this nature specify the quality of effluents applied
to land areas. Of 27 State control agencies which participated in the
i
data-gathering program, a maximum of 25 percent involved themselves with
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any single item of the 11 guideline criteria covered by the opinion
survey.
In defense of this record of irrelevance with the land application
practice, it must be said that some States have few such installations
and even fewer have installations of any major significance. In
addition, States contend that they have been deeply involved with the
control and regulation of conventional sewage treatment facilities and
stream quality protection. Shortage of qualified personnel has been
offered as the reason for absence of attention to the installation,
operation and monitoring of land application installations.
In the absence of formal State regulations, some agencies have used
unofficial staff opinions as the basis for land application decisions.
Similarly, each-case-for-itself decisions on health hazards have been
invoked or expressed by State health agencies but a minimum of trans-
lation of such policies into specific regulatory actions was disclosed
by the survey.
SUMMARY OF FOREIGN EXPERIENCE - SECTION V
Data from such widely located countries as Argentina, Australia,
Belgium, India, Israel, Hungary, and Mexico confirm the use and value
of the land application technique for various purposes, for a variety
of growing crops, under diversified conditions, and with different results,
Enhancement of soil productivity, through the mechanics of supplemental
irrigation with waste water and the enrichment of soil with the organic
constituents of sewage and industrial processing waters are widely
acknowledged.
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Health hazards have been studied in various countries and
protective measures have been invoked. Some countries, such as
water-short Israel, utilize wastewaters for irrigation purposes
--where over 100 systems are in service, but they tend to avoid the
use of raw, untreated sewage and contact with crops that are eaten
raw by humans or domesticated animals.
On the North American continent, the most dramatic land appli-
cation system on record is in Tula Hidalgo, Mexico, where lands operated
by the Mexican Federal Department of Agriculture are assigned to
Ejidos, heads of families, in units of limited hectares. On 47,000
hectares, equivalent to 115,000 acres, some 1,476,000 metric tons
of food products were grown in 1971. Approximately the same tonnage
was produced in 1972. Additional arid land is available for cultivation
when additional wastewater from Mexico City becomes available. Currently
some 570 million gallons per day of raw untreated sewage flows by canal
to this area, 95 percent of which reach the cropland. During the rainy
season there is an additional storm water flow through the same canal,
most of which is impounded in a series of dams for use during the dry
season for cropland irrigation.
In England the Hertfordshire facility has had over 20 years
experience irrigating liquid digested sludge containing about 3 per cent
solids. Technically this land application system is more related to
sludge than to sewage effluents, but its long and successful experience
confirms the feasibility of that method of land application of wastewaters
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There is a non-technical 16 rrm color film, entitled, Wealth from Waste,
which shows the Herfordshi re operations.
GUIDELINES FOR IMPLEMENTATION OF LAND APPLICATION SYSTEMS - SECTION VI
The survey provided many guidelines that could be translated into
"do's" and "don'ts" in land application procedures. In addition the
literature searches brought added criteria to light, confirming the
basic facts evolved from the survey. From these information sources
and others, the report suggests guidelines for the implementation of
land application systems.
For the guidance of the regulatory administrator staffs, decision-
makers, designers and owners of future land application installations,
some tenative procedures have been presented as they may be affected
by climatic conditions and applicability of the process to specific
meterological phenomenon; availability and location of land areas
suitable for wastewater application; rates of application; types of
soils, crops and ground cover; methods of application and their
relationship with geological, topographical and hydro!ogical conditions;
types of wastewater pretreatment to assure proper and safe land
application; capital and operating costs; monitoring and health
protective measures; and other related aspects of system planning
and execution.
References have been drawn from all possible sources to support
the tenative parametric procedures outlined in the guidelines. The
listed criteria are not presented as "standards"; this would be
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improperly anticipatory of the next official step which must be taken
to distill from this study and the other parallel investigations sponsored
by the U.S. Environmental Protection Agency on land application techniques.
Rather the guidelines are offered as suggested criteria, a necessary
input into the overall fund of information upon which eventual official
guidelines must be based. As mentioned in the Overview this gives
credence to the suggestion that formalization of guidelines be deferred
until "interim evaluation procedures" are published.
PLACING LAND APPLICATION OF EFFLUENTS IN PERSPECTIVE: AN INTERPRETATION -
SECTION VII:
This section stresses the importance of placing land application
techniques in their proper perspective, and interpreting the alternative
"pluses" and "minuses" on the basis of local factors and local needs.
It is evident that an "alternative" must be compared with something
for which it is an alternative. Thus, the determination of the choice
of wastewater utilization process must be based on a full-dimensional
decision; and that decision must stem from placing the land application
process into the proper perspective with itself and with other means
of managing wastewaters.
When viewed in this light, land application technology is not a
panacea for all wastes, in all areas, under all circumstances. It is
not a "quick and easy" means of getting rid of unwanted wastewaters.
It involves adequate pretreatment, effective operational procedures,
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rigid monitoring controls and rational cost evaluations. As a substitute
for the return of waters into the drainage basins from whence it originally
came, it can affect the "cycle of water" and create an imbalance in the
water resources of a region. Land application can no longer be compared
with disposal of wastes by dilution; just as conventional wastewater
treatment now involves high degrees of treatment, so land application
must assure that the soil will receive highly treated influent water
or that the soil will provide the equivalent of tertiary treatment
and removal of deleterious components by biological-chemical-physical
phenomenon. The effectiveness of land application must be judged
by what it accomplishes—not merely as a means of eliminating the
direct discharge of comparably well treated effluents into receiving
waters.
To fulfill its full possibilities and benefits, land application
must be examined from the standpoint of what has become known as the
"4-R cycle" -- 'return of waste water to the local land rather than being
lost by stream flowage to downstream areas; renovation of the waste-
water by soil and vegetative actions; recharge of the groundwater
resources which then become the reservoir aquifer which feeds surface
water sources; and the reuse of wastewater either directly off the
land or via the tapping of the groundwater reservoir. Practical
examples of these land application benefits are available; they must
be placed in proper perspective with the needs and potentialities of
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the area in which a proposed land application project will be constructed
as an alternative to conventional wastewater treatment works.
DEMOGRAPHIC EVALUATION OF LAND APPLICATION TECHNIQUES
Demography is the science of social statistics. Wastewaters are
the product of people and of industrial production in an urban industrial
society. The nature of wastes produced by^community life and industrial
processing and the amounts of such wastewaters are affected by regional
conditions and their impact on life and living processes. Automatically
then, the manner in which wastewaters are handled and disposed of is
influenced by demography, or regional, environmental needs. For
example, the degree of sewage and industrial treatment in the past
was influenced by the water resources needs of regional areas and how
regulatory bodies interpreted these needs to protect the natural environ-
ment and preserve public health and safety. Over and above the natural
setting for any region, policies were and will continue to be, affected
by population densities, water needs, public desires and antipathies,
and other factors. This represents demography in action.
If it were possible to relate the applicability of wastewater
management on land areas to such factors as climatic conditions,
population and population densities, economic-social patterns, and
similar demographic parameters, these would serve as important guides
for the choice of this alternative method of wastewater treatment and
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utilization vis-a-vis today's conventional treatment standards and
the advanced degrees of effluent quality that will be required in the
future. If such relationships could be established, based on the
findings of the APWA Report, or by parallel investigations now sponsored
by EPA, the viability of the land application technique could be
verified or clinically questioned.
The factors involved in a full demographic evaluation of land
application practices appear to be too numerous, too complex and too
interwoven to be capable of clarification by the current APWA study.
Many of the factors are too intangible to be explained by basic
survey data; the type of study parameters used in the current study
could not include such incomprehensible implications. But the study
did involve the relationships between land application and climatic
conditions, and concurrent relationships involving urban populations
and densities, industrial operations, local ecological conditions
¥*"£
and other indigenous factors.
Climate is a major factor in the applicability of land application
procedures, on the purpose and continuity of operation, and on the
performance of this alternative technique. In recognition of the
importance of climatic conditions, the study was based on the choice
of site investigations in five climatic regions of the United States
and evaluations were aimed at determining the impact of the specific
zonal meteorological characteristics on every phase of the study.
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Broadly characterized, Zone A (mid and south Pacific coast) is an
area of dry summers and mild wet winters; Zone B (the southwest) is an
arid region, with hot, dry climate; Zone C (southeast-Gulf coast-Atlantic
coast and Pacific northwest) experiences hot wet summers and mild winters;
Zone D (east-continent and northeast Atlantic coast) is subject to humid
weather, with short winters and hot summers; Zone £ (mid-continent
and far northeast) is a humid area, with long winters and warm
summers.
While climatic conditions have the most significant impact on the
land application principle, other factors have potential bearing: size
of the community and the industry; the volume of wastes flow; the
population contributing sanitary wastes plus the population equivalent
of the industrial wastes contributed to the municipal sewer system; the
availability of open land for irrigation use; the land-use zoning of
the region; the cost of land; the type of crops to be grown with supple-
mental irrigation and the market needs and demands for such crops; the
groundwater depth and quantities, and their use for water supply purposes,
protection against salt water intrusion into aquifers and other functions;
the nature of the soil; the proximity of surface waters which can become
recipients of conventionally treated effluents; and other correlated
circumstances of local or indigenous nature.
It is not difficult to rationalize the effects of these climatic-
demographic conditions on land applicaiton practices, and conversely,
the impacts of land application on these environmental conditions. It is
difficult, however, to translate the findings of the subject into these
25
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relationships. Efforts have been made to draw every possible relation-
ship between these various factors but the findings are often too
indeterminate to warrant such translations.
The following highlights can provide valuable guidance for decision-
makers and designers of land application systems, even though they are
not always affirmed and confirmed by study findings.
CLIMATIC CONDITIONS: The 67 community systems and 20 industrial land
application sites covered by the on-site visits, and the comparable
numbers of such installations covered by the mail inquiry, were
representative of the actual total projects in each of the five climatic
zones. The major number of community systems surveyed was located
in Zones A and B, with California sites predominating. These two zones
represent dry and arid conditions which make supplemental water resources--
reused water in the form of effluents—a precious commodity. No
industrial sites in these zones were surveyed by on-site investigators
because minimal use of land application techniques is made by local
industrial installations. In lieu of such industrial irrigation
projects, communities in Zones A and B accept industrial wastes into
public sewers and onto publicly owned application sites in the form
of population equivalent loadings.
In Zones C, D, and E, industrial sites were surveyed because the
use of land application is practiced more generally in these parts of
the nation. The industries involved are primarily food canning-processing
26
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factories, dairy processing plants, pulp and paper mills, and organic
chemical manufacturing firms.
The differentiation between the zonal incidences of community
systems and industry sites is explained, at least in part, by the needs
for supplemental water and the uses for such water. Thus, climatic
water-short and water-rich areas dictate the retention of sanitary
wastewaters in the areas which produce them, or whether to permit
them to flow away downstream into other receiving watersheds and water
basins.
In regions A and B, water is in relatively short supply, due
to dry summers and year-round aridity, and wastewaters are often times
considered by communities as a valuable commodity for land irrigation,
for groundwater augmentation, and for use for such ancillary purposes
as golf course and highway median watering and the creation of recre-
ational water facilities. Industries in these areas however, as in other
areas, are less concerned with such beneficial uses of wastewater and may
not practice land application; they may use this management procedure
primarily for the purpose of "getting rid" of such effluents in the
cheapest and simplest manner without adversely affecting the environment.
This brings the matter of wastewater, or used water, economic and
ecologic value and utilization into focus as the determining factors
in the practice of land application. In arid regions, land application
offers strong incentives. In wet, humid regions water-husbanding is
not a vital motivating reason for land application installations; but
27
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such motivation can be found in the economies of producing high-quality
effluent by means of the "free" purification capabilities of soil.
Whether planned as a water resource conservation procedure or not, the
ultimate fate of wastewaters applied to land areas by spray irrigation
and surface application, such as, ridge-and-furrow methods is a means
of enhancement of the local groundwater reservoir. The fact that 85
percent of the water stored in the United States is contained in sub-
surface aquifers adds significance to this wastewater fate.
Climatic, geographic and geologic conditions have other influences
on the choice of wastewater disposal systems. Inland areas that have
no convenient receiving waters may find it cheaper to apply wastewaters
to the land rather than constructing long, expensive outfall lines
from their treatment plants to suitable discharge points. On the other
hand, the water-cycle imbalance which may occur in local waters by taking
water supplies from them and not returning wastewater back to the same
rivers and lakes may place a negative aspect on land application
procedures. This type of water resource imbalance does not apply to
coastal waters.
The relationship between hard winters and land application systems
is obvious. In areas where full-year irrigation can be practiced, land
application would have greater applicability than where adverse
winter conditions would make irrigation inappropriate or inefficient.
While land application is practiced in some ice, snow and sub-freezing
conditions, optimum conditions are represented by year-round mild
weather such as is experienced in Zones A, parts of B, and in C.
28
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Similarly, the relationship between climatic conditions and holding
pond capacities is equally understandable. Where seasonal cessation of
land application is necessary, the principle of "not one drop of
wastes into water resources" impells the construction and use of
adequate holding facilities. "Adequacy" is a relative term; 31 percent
of community and industrial systems use ponds with capacities of five
days or less. In Zones A, B and C, 75 percent of the sites have
holding capacities of less than 30 days, or less than needed for a full
winter season. One installation in a cold zone provides a 50 million
gallon pond for a daily flow loading of 0.5 mgd.
Of some significance, if not as perinent as other seasonal
conditions, is the amount of rainfall in humid areas which may impede
soil absorption of applied wastewaters and require the use of flow-
equalization or flow-holding of excess waters until required rates of
application can be reinstated. As stated, where rainfall is generally
adequate, if not always predictable, land application for enhancement
of crop growths, forest growths and groundwater augmentation is not the
dominant reason for the choice of this wastewater management technique.
While the survey studies brought these climatic relationships into
focus, they did not a1 sways provide postitive proof of these effects
and impacts. This does not detract from the validity of the above
observations. No attempt has been made to draw all possible climatic-
environmental relationships with land application principles and
practices; however, the rationale is adequate to demonstrate that
there is a direct correlation which must be considered before choice
of wastewater management is made for each individual project. No set
29
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standards can be established; each case will require.its own rela-
tionship evaluation.
SIZE OF WASTEWATER FACILITY: In the case of publicly owned systems,
the population served is translatable into volumetric and qualitative
loadings. For industries, the flow loading is a factor of volume
and population equivalency of the organic constituents, as measured
by BOD, COD, suspended solids and other significant parameters.
The survey indicated that some outstanding large community land
application installations have been in service in the United States
and foreign countries. However, the major percentage of current
operating installations are in the smaller-size range.
The on-site survey disclosed that 73 percent of communities
studied have land application capacities of under 5 mgd; the mail
survey covered no community systems with over 10-mgd capacity. Industry
installations covered by the on-site survey were all under 5-mgd
capacities; the mail-surveyed installations were all under 10-mgd
size. It is conjectured that the small cities and industries have
found land application within their economic range and that adequate
conventional treatment would have been more costly.
Size factors are numerous but few showed definitive relationships
with other land application site acreage parameters. The area used for
irrigation application varied without basic reason from the total acreage
owned by the community or industry. In some cases the major extent of
the area is used for distribution; in other instances only a portion is
so used, the rest of the acreage being devoted to holding ponds, buffer
30
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zone and general isolation of sites.
The size of the area varies, naturally, with the volume of flow
applied, the nature of the soil and its absorptive character. The
effect of climatic conditions, such as rainfall, humidity arid temper-
ature, on irrigation area acquired by communities and industries is
minimal, despite any impression that such a direct relationship should
exist. No specific trend was found in buffer zone regulations and
usage. The open land available for such buffering or isolation
facilities is undoubtedly influenced by State regulatory agency
requirements and the type of distribution systems used (Spray irriga-
tion tends to be associated with buffering acres and plantings to impede
the off-site dissemination of aerosol mists and particulates.)
CONTINUITY OF OPERATION: The relationship between continuity of waste-
water application, on a days-per-week or a months-per-year basis, and
land acreages used for land application was found to be indeterminate.
Continuity of operation appeared to be dictated by other factors than
availability of site acreage. It is obvious that rates of application
should have a bearing on the land areas required, particularly on sites
that are limited in size and not over-generous in dimensions. While
the analysis of study data does not disclose this relationship, it is
undebatable since the failure of irrigated land to handle distributed
wastewaters for planned periods will necessitate the resting of such
t
areas and the immediate utilization of other equivalent acreages to
replace the overloaded or ponded soil plots.
If wastewater production is in effect for longer weekly or monthly
periods and pond storage capacity is not available to retain excess
31
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f1ows> i.Vigation areas rr^ be a-fec-ed by the requirement that direct
appli.:i'ion of produced .r,ow< rrjS; be provided. Similarly, the land-
r.eed requirements for any site will be influenced by whether the system
••.'-'11 function on a twelve-month basis or shorter yearly periods.
Communities tend to maintain yearly continuity of land application
more completely than industries; Droadly interpreted, communities
operate full-year at 60 percent of installations, and industries at
40 percent of sites. The relationship between climate and continuity
of irrigation was partia.'iy clarified by the study, despite the fact
that positive patterns were not confirmed. The on-site survey-interview
procedures used in the study disclosed that twelve-month continuity of
community operation for Zones A, B, C, D and E was practiced in 76, 63,
56, 71 and 67 percent of sites, respectively, while industrial systems
showed similar year-round irrigation service in Zones C, D and E of 50,
06 and 30 percent of sites, respectively.
The mail survey showed that industries in Zones A and B (not
surveyed in the on-site program) operated on a 12-month basis at 100
percent of the sites of the sites involved, with 100 percent of the
Zone C community installations functioning on a full-year basis. Thus,
the zonal factors showed little effect of widely divergent climatic
conditions on whether systems functioned without cessation.
Full-week service seemed to be dictated more by the actual purpose
of land application than by otr.er factors. Full-week irrigation was
founc co be more common than when crop irrigation was practiced than when
waste1* .?r disposal onto gras .-cover lands was utilized for groundwater
a ussier tat ion or for the s'.aiple purpose of effluent disposal. Application
32
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rates and continuity of irrigation were, surprisingly, unaffected by
soil types.
METHODS OF DISTRIBUTION: The relationship between the method of
application and climatic conditions was brought into focus by the
study. In general, spray irrigation is more commonly used in humid
areas than in arid sectors; and surface application techniques, such
as ridge-and-furrow irrigation and overland irrigation, are more
frequently utilized in arid regions. Zones A and B were characterized
by surface application sites.
The relationship between size of site and type of distribution used
showed a trend of more or less specificity. Smaller sites were served
by twice as many spray systems as surface application facilities.
Larger sites, over 1,000 acres in size, were usually equipped with
surface application systems; intermediate-sized sites, from about 100
acres to 1,000 acres, utilized spray and surface application systems
about equally. In surface application installations, so-called overland
flooding which depends on sheet-flow action has been used more frequently
than ridge-and-furrow distribution.
No specific correlation was found between distribution methods
and soil types, but some generalized patterns were evaluated: Spray
irrigation is more commonly used on loam, silt and clay lands; spray
an
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sites handling under 1-mgd flows were most commonly grass-covered,
while larger areas of over 1-mgd capacity generally stressed crop growth.
Forest irrigation was practiced more frequently in humid areas than arid
regions, probably because tree growth is more common in the humid
climatic regions. Cropping on arid region lands is relatively common,
indicating the value of wastewater for supplemental irrigation.
Groundwater depths are a dominant factor in choice of sites but,
once acquired, these application lands experience minimal impacts on
choice of application methods and on operation performance. Obviously
groundwater depths are greater in arid regions and are less of a factor
in choice of land application sites. Application rates, while not
consistently influenced by climatic conditions or soil character, and
while varying minimally from the almost traditional level of one-half
inch per day and two inches per week, are influenced by aridity and high
humidity-precipitation conditions.
LAND AVAILABILITY, LAND USE AND LAND VALUE; A direct relationship
between demographic criteria and land availability, zoning use and
acreage price is unavoidable. The first requirement of a land application
system is land. It must be available in reasonably close proximity to
the source of community or industrial wastes; the land must be useable
for wastewater application by zoning and other use regulations; the
price must not be prohibitive.
These conditions are most commonly met in areas of low population
density where open lands are available, and where undeveloped and
properly zoned properties can be acquired at relatively low cost. This
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is why the survey showed the predominance of land systems in use by
small communities and relatively small industries, and land prices
ranging basically in the under-$500 per acre price level. Areas of
the nation will become progressively more densely populated because
over a million acres of rural lands are absorbed annually in urbanization
and related facets of community growth. The availability of nearby
lands, zoned for agriculture or residential purposes, and priced at
low enough levels, will become a greater problem for users of land
application systems. The cost of long-distance wastewater transmission
will become an important factor in determining the economic feasibility
of land application for wastewaters.
The impact of land application installations on neighboring areas
and their residents can be in direct ratio to population density. While
existing systems have demonstrated their ability to be "good neighbors"
to residents living as close as 500 feet of application site, this close
f
proximity may not be good practice in all cases. Reported complaints
have been minimal against present installations despite the fact that,
for example, 20 percent of community systems in Zone A are located less
than 500 feet from the nearest neighbors and 22 percent are similarly
located in Zone B. Industrial sites are located in Zones C, D and E
within 500 feet of residences in 10, 10 and 21 percent of the cases
investigated, respectively.
The relationship between local demographic conditions and land
application system monitoring is obvious. The degree of monitoring
was found to be less related to zone climatological conditions than to
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State health and water pollution control regulations in the limited
cases where such governmental stipulations are imposed. It is
understandable that increasing population intrusions in an area, and
the density of the residential population, will dictate that
closer attention should be given to the impacts of land application on
land and water resources and on persons exposed to actual wastewater,
sludge residues, spray mists and animals and insects which come in
contact with irrigation liquids and vegetative growths. The frequency
and location of monitoring points, such as test wells and other sampling
facilities, and the extent of monitoring parameters will be intensified
in the future to satisfy actual hazards or the psychological impressions
of local residents.
Site security measures, such as fencing may be required and buffer
zones may be specified. Operation and maintenance costs will react to
all such monitoring and security requirements but the reasonable cost
levels for present systems could be increased without seriously affecting
the feasibility and economy of land application techniques. Future
wastewater treatment works, particularly those requiring full secondary
treatment and processing to remove such components as phosphorous,
nitrogen, trace metals and organic pesticides, will require similar
augmentation of present specific laboratory control and site safety
and security measures.
FATE OF MATERIALS APPLIED TO THE LAND
To complete this extended summary of the land application of
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wastewaters a review of the fate of applied materials is presented
to round out the information which has been presented. Reference is
made to two papers entitled, Experiences with Land Spreading of
Municipal Effluents, and Fate of Materials Applied, prepared by
Richard E. Thomas, Soil Scientist, Robert S. Kerr Water Research
Center, Environmental Protection Agency, Ada, Oklahoma. For the
future applicability of land utilization of wastewaters, it is
important to know with some measure of certainty what the fate of
wastewater components will be.
The materials contained in wastewaters are reminiscent of the
origin of these flows—either sanitary, sanitary and combined storm
water, industrial process water, or combinations of sanitary and
industrial wastes. Since the application of raw wastewaters onto
land areas is not contemplated under the definition of this alternative
waste management technique, all such wastes have been subject to some
degree of pretreatment before they are applied to land. The purpose
of monitoring of influent flows onto land areas is to ascertain the
composition of the wastewater after the stages of pretreatment provided.
A classification of wastewater materials could be: Suspended
materials; major plant nutrients; and other constituents. Another
delineation of the wastewater components, based on the actual
physical nature of the substances is: Suspended solids; colloidal
solids; dissolved organic materials; and dissolved inorganic substances.
The fate of these substances during the process of land application
will vary with the type of distribution system, the nature of the soil,
37
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the rate of application, the climate, the resting periods, and the
location and proximity of the groundwater aquifier and the surface
water source which receives runoff from the site. The phenomena
involved include: The physical condition of entrapment or mechanical
filtration; the biological, biochemical, electrochemical and other
manifestations in and in contact with the soil; evaporative factors;
atmospheric oxidation; bacteriological, germicidal, and bacteriophage
or anti-contamination reactions, and others which are not totally
understood even by highly trained and experienced scientists.
Suspended solids entrapped in the interstices of the soil or
adhering to soil particles by electrochemical entrainment can experience
biological oxidation and decomposition into stabilized substances. The
fate of this suspended material can vary; it can remain in the soil to
form humus soil conditioning or nutritive material or, in course media,
it may be sloughed off and percolated into lower soil depths or into
the groundwater.
Colloidal materials—solids of minute size which may be able to
filter through soil media—can be coalesced or coagulated by electro-
cnt:mica'i agglomeration and then adsorbed onto soil particles. The
fate of this material, normally considered to possess electrical
charge, may parallel that of true suspended solids, by oxidation-
digestion phenomena. Accumulations in the soil may affect the rate
of application of subsequent wastewater loadings.
38
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Organic dissolved solids may be utilized by plant crops, retained
in the body of the soil by chemical fixation or other bonding
phenomena or may be oxidized by atmospheric reactions, in the course of
air contact with sprays or sheets of wastewater flowing over the land.
A major concern is centered on the nitrogen and phosphorous in
wastewaters. The presence of these dissolved constituents can influence
the use of land application systems in lieu of advanced treatment and
discharge into surface receiving water, primarily because they can act
as "triggers" in the eutrophication of surface waters. Similarly, if
these materials can adversely "fertilize" lakes, why cannot they be used
to fertilize land?
The fate of nitrogen and phosphorous will be influenced by many
factors, including the type of wastewater distribution system utilized,
and the type of ground cover and crops grown. The factors involved in
the different land application methods are covered in excellent details
in the above-refereneed papers, and it is not the intent here to explore
these manifestations beyond brief reference to the fact that the fate of
these two basic elements can be regulated by proper practices to avoid
serious effects on groundwater or surface water sources. The ability of
soil to retain and fix phosphorous is more important than its capacity
to handle nitrogen because phosphorous delivery to the soil may be
greater than the crop uptake ability to utilize it. Fortunately, soil
retention is able to prevent phosphorous intrusion into groundwaters
that are adequately deep for any effective land application site.
Nitrogen could enter the groundwater in concentrations that might
39
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exceed the safe levels of this material in water for human consumption.
However,, the ability of land application techniques to complete a
nitrification-denitrification cycle can be utilized to prevent this
fate, as in the spray-runoff technique. A substantial proportion of
the phosphorous contained in applied wastewaters in the same spray
runoff process could reach surface water sources unless steps are
taken to improve phosphorous removal by land contact.
Other constituents of land-applied wastewaters have fates that
may influence the use of land methods, either in favor of this alternative
process or opposed to its utilization. These include heavy metals, even
in trace amounts, pesticides and other organo-compounds, and various.
salts. Evaporation and evapotranspiration of liquids from soil,
vegetative surfaces or water surfaces will not change the fate of these
dissolved materials; the evaporative process parallels the distillation
phenomenon, in that the water is converted to vapor or gaseous form and
the solids are thus concentrated in the soil or vegetation. Salts may
thus reach the groundwater by percolation and leaching action. Heavy
metals and pesticides can undergo physical, chemical and biochemical
interactions with the soil, making land application an auxiliary means of
providing so-called "tertiary" treatment for wastewaters, in lieu of more
complex and more costly artificial wastes treatment processes.
To repeat the statement made above, the intent of this dissertation
on the fate of materials applied to land areas is to point out that the
soil and vegetative forms do offer a "bonus" factor that must be given
consideration in determining the future of the land application process.
40
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Current concern about the impacts of nitrates, phosphorous, trace
metals, pesticides and ,other organic compounds on receiving waters is
sufficient reason for knowing more about the fate of these objectionable
materials in the land application process. More remains to be known
about them, and about the way various methods of wastewater distri-
bution, various types of soil and topographic and climatic conditions,
and other factors and combinations of factors, influence their fate.
The fate of wastewater contaminants during the land application
process, in short, offers opportunities for beneficial use for soil and
crop enhancement which must be considered as a "plus" for this
alternative technique. In addition, the capability of the land appli-
cation system to remove, modify and stabilize pollutants which would
require augmented processing in conventional sewage treatment systems
offers another advantage for this alternative management procedure.
But, these benefits must be evaluated in the light of whether the applied
materials will in any way adversely affect the water and soil environment
of the region where land application systems will be utilized. Only
through a weighing of the benefits and hazards can the feasibility and
applicability of land application processes be properly judged for each
specific installation and each specific wastes problem.
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CONCLUSIONS
1. Land application of wastewaters from community and industrial
processing sources is practiced successfully and extensively
in the United States and in many countries throughout the world.
Facilities investigated handled from less than 0.5 mgd, providing
service for sixty days per year, to over 570 mgd applied on a
year-around basis.
2. Land application of wastewaters is practiced for several specific
reasons. Among the major reasons were: to provide for supplemental
irrigation water; the desirability of augmenting groundwater sources;
excessive distances to suitable bodies of receiving waters or
extraordinary cost to construct facilities to reach suitable disposal
sites; economic feasibility, as contrasted with the cost of
construction and operation of advanced or tertiary treatment
facilities; and inability of conventional treatment facilities to
handle difficult-to-treat wastes.
3. Present land application facilities generally are not "stressing"
the system. Many facilities were found to be using effluent on
a crop-need basis. Even where efforts were being made to use land
as the only point of disposal, application rates were generally
conservative and the soil-plant components of the system were not
stressed to limits of assimilation or used to their optimum capacities,
thus providing a large factor of safety.
4. A variety of beneficial uses are being made of wastewater effluents.
Uses include irrigation of parks, golf courses, cemeteries, college
grounds, street trees, highway median strips, sports grounds,
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ornamental fountains and artificial lakes. Wastewater effluents are
also used to irrigate many types of crops, including grasses, alfalfa,
corn, sorghum, citrus trees, grapes, and cotton. Forest lands are also
being irrigated in many areas. Groundwater augmentation to prevent
salt water intrusion is being practiced. In Mexico, a wide variety of
truck garden crops has long been irrigated with effluent. Crops
appeared to benefit from both the nutrients and the increased amount
of water which is applied.
5. A large variety of potential opportunities for land application
of wastewater exist in many communities. Wastewaters that are given
a high degree of treatment could well be considered for irrigating large
public and private facilities to relieve the demand for irrigation with
potable water supplies. Golf courses, cemeteries, parkways, school
grounds, parks, airports, planned unit developments, green belts,
forest preserves, and marginal land all offer the useful application of
effluents to the land.
6. Sale of effluent for beneficial use has been generally unsuccessful.
Few examples were found where a public agency had been able to obtain
more than a token payment for supplying treated effluent. In several
cases it was reported that land for the treatment plant had been given
in consideration of a right to all or a portion of the effluent. Where
an agency received a tangible dollar return, it was generally based
upon use of both land and the effluent.
7. Successful operation of a land application system requires the
inputs^ from a variety of disciplines. For many systems, the services
of a geologist and environmental engineer are required. For system
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designed to augment the indiger;,us crop water requirements by
supple.nental irrigation, the advice and guidance of soils specialist
will be needed. For larger systems, social and behavioral scientists,
as well as medical-health personnel may be required to assist in
evaluating and securing acceptance of this alternative means of
disposal.
8. Operation of land application facilities can be accomplished
without creating a nuisance or downgrading the adjacent environment.
The survey indicated that a majority of the facilities were conducted
by well-trained personnel, aware of the need for careful operation of
the systems. Training, supervision, and adequate monitoring of
pertinent factors are necessary to ensure that systems will not be
over-stressed. If ponding on the land is not allowed, odors will not
be a problem. The hazard of creating other adverse effects on the
environment by discharging treated effluent on land is minimal.
9. Monitoring of land application facilities and effects has been
minimal and mostly inadequate. Few states appear to have taken an active
role in requiring use of monitoring facilities, apparently because there
was no direct discharge of effluents to receiving waters. Many of the
municipal systems surveyed had little or no monitoring, inasmuch as
the effluent was being used only for supplemental irrigation.
Industrial systems were generally better monitored, but control in most
cr.ies cannot be characterized as being adequate.
10. Environmental analysis of the effects of land application
facilities reflects a general improvement of the environment rather
44 and 45
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than impairment of the indigenous ecology. Many facilities were
observed where the effluent provided the only irrigation water
available. Land values for sites with a right to such waste waters
were greater than that of adjacent land because crop and forest growth
was enhanced, and use of potable water supplies reduced. No instances
of health hazards were reported from any existing facilities, although
the State of Delaware indicated concern over potential virus
transmission. Farming and recreation potentials exist, as well as
improved habitat for wild life.
Treatment of wastewater prior to land application has generally
been dictated by the desire to use the best practical means consistent
with available technology and to minimize any adverse effects upon the
environment. Land application of wastewater, by eliminating direct
discharges of effluent into receiving waters, could be regarded as
satisfying the ultimate national policy goal of "zero discharge" of
pollutants.
11. Energy requirements for land application systems may be an
important consideration. Reported energy requirements for most
advanced tertiary treatment proposals are very high, as compared to
conventional treatment. Depending upon the location and availability
of land, energy requirements associated with land application tech-
niques may be substantially less than other means of treatment and
effluent management. This factor deserves further evaluation.
12. The nature and quantity of receiving waters must be carefully
evaluated prior to diverting effluent to land application. Few existing
systems were found that used underdrains to collect the renovated
effluent. Rather, the groundwater aquifers received the flow. If a
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land application area is adjacent to the receiving water, much of
the groundwater may serve to augment the flow into the receiving
waters by a gradual seepage into the drainage basin. Elimination of
direct wastewater discharges to a stream could unbalance the flow
regimen associated with downstream beneficial uses, inhibit desirable
dilution of waste discharge, interfere with the tempering of thermal
water discharges. Land application can prevent the intrusion of saline
waters into normally fresh water zones. The impact of effluent
diversion onto land areas with respect to the basic principle of
riparian water rights must be considered where irrigation is planned
as an alternate to discharge into surface waters.
13. When w_astewater is discharged to land and this method is used as
a means of advanced treatment by natural means, the land must receive
priority for this use over other optional land uses. The needs of crop
production, recreation and other benefits can be in conflict with the
utilization of a land application system for the treatment of wastewater.
For instance, the planting, cultivation and harvesting of crops and the
use of recreation facilities may interfere with continuous application
of wastewater onto land areas. The need for the system to either
utilize all of the flow or provide sufficient retention storage for
needed periods of non-operation must be provided. The objective of
providing adequate treatment of the effluent can not be sacrificed for
other needs and uses of the land; proper handling of the wastewater
must be the first priority.
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14. Choice of ground cover can play an important role in the success
of a land application system. On other than sandy soil, it appears
that forested or minimally wooded or cultivated areas will accept
greater rates of application of effluent without ponding than will
cultivated agricultural areas. Many existing facilities utilize
forest areas and grassed areas for application. Forested areas appear
particularly useful for winter applications when fixed spray systems
are used. Reed Canary grass appears to be particularly well suited
for producing mulched ground cover which can enhance soil assimilation
and absorption characteristics.
15. Land application facilities that have been used for many years
are available for the study of long-term effects of such use. They
offer the opportunity to study effects on soils and groundwaters.
Thus, it appears unnecessary to support separate demonstration
facilities in each of several states and regions. During the course
of the study project, several small-scale research and demonstration
projects involving land application were disclosed. Some of these
projects appeared to have been instituted simply for the purpose of
convincing local and state officials of the safety of this alternative
method of treatment and disposal. Specific evaluation at established
systems in the various climatic zones would appear to be more fruitful
than new research installations for determining long-term effects upon
soil, vegetation, groundwater, and the indigenous ecology, or on the
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health of site workers and adjacent residents.
16. Observations in the field and the survey of land application systems
which handle municipal wastewater flows and industry-owned systems
which handle process waters did not reveal the existence of specific
health hazards and disclosed very little concern over threats to the
health of on-site workers, residents of neighboring areas, domestic
animals or wildlife, or of those who consume or come in contact with
land-applied wastewaters. The mail survey of other representative
municipal and industrial land application systems similarly provided
no evidence of any health problems associated with this method of
utilization.
Some concern over potential health hazards was, however, expressed
or inferred by officials of some state agencies, who supplied information
about their policies on land application of effluents as an alternative
means of wastewater management. Whether this concern was based on
specific information or mere suspicions, founded or unfounded, could
not be determined from their response.
Inquiries have been made with inconclusive results about the
health implications of land application systems by several Federal,
state and local agencies, and by other quasi-governmental and public
service organizations. Concern over "the unknown" was expressed for
such factors as potential viral and pathogenic hazards resulting from
dissemination of aerosol sprays or mists and contacts with sanitary
and industrial sludge residues.
While the study did not disclose the cause for such concerns, the
bibliographic abstracts*** prepared as an integral part of this
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investigative project to include references describing possible health
hazards which warrant further study and these potential problem areas
should certainly not be ignored. A balanced consideration of the concerns,
and of the absence of any study evidence to support these questions, would
be of great value at this time.
(***The bibliogaphy for the APWA report is being published separately,
entitled, Land Application of Sewage Effluents and Sludges: Selected Abstracts.)
The APWA report and the foregoing conclusions lead to additional con-
clusions:
17. Emphasis in the future should be on wastewater utilization, reuse, and
renovation, the 4-R cycle, and not on disposal.
18. Public acceptability is the primary factor limiting land treatment of
effluents and land utilization of sludges.
19. Land application of wastewater is not an alternative to secondary
treatment if secondary treatment is required as a pretreatment.
20. Land application of sewage effluents is_ an alternative to tertiary
treatment for the removal of nutrients, suspended solids and certain pollu-
tants. It is not effective for the removal of soluble salts.
21. In water-short areas land treatment of effluents may be considered
as part of the reuse cycle.
22. Small communities will probably continue to be the principal users of
land treatment of effluents for the near future, but stringent discharge
restrictions will make land treatment more attractive to large communities.
23. Admirable as it may be to obtain drinking water quality from the
land treatment of sewage effluents, since the goal of Public Health Service
Drinking Water Standards is not required for secondary treatment, and it doq|
not appear to be practical at present for land treatment either, it there-
fore should not be used to unduly limit the benefits to be derived from
the land application technique.
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RECOMMENDATIONS
1. Guidelines for land application of wastewaters should be prepared
by the U.S. Environmental Protection Agency to provide full consideration
o
of the wide choices of available methods and procedures. GUI deli nes
should be prepared in a manner which will not restrict unduly the ability
of local officials to make full use of this alternative method of
treating and managing wastewater.
2. Land application must not be considered as a panacea or universal
method of treatment. Suitability of each land application system can
only be determined as a result of an interdisciplinary study for the
particular site. Soils, climate, degree of pretreatment, ground water
conditions and availability of suitable land acreages are important
considerations.
3. Preparation of a suitable publication to inform the public about
the practice of sewage effluent on land should be sponsored by the U.S.
Environmental Protection Agency. Public relations problems are usually
encountered by agencies attempting to implement any large public wastewater
project. Recent efforts to consider land application as an alternative in
planning for regional approaches to wastewater management have highlighted
the need for such publication.
4. Training opportunities should be provided to bring to the attention
of all disciplines involved in the consideration and evaluation of a
land application facility the technical information which is available.
Widespread consideration and utilization of land application can not be /
made until such time as adequate information concerning the technique
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involved is made available. The experience gained by those who have
successfully utilized this wastewater management method should be
publicized.
5. Guidelines for the increased use of land application methods, which
could result from the implementation of Section 201 of the 1972 Amendments
to the Federal Water Pollution Control Law and its emphasis on alternate
wastes management techniques and systems, should clarify the question of
whether health hazards are a factor in the use of this system of treatment
and disposal. Definitive findings are essential to the acceptance of
land application systems, or to their adoption for municipal or industrial
effluent management. Such findings should be provided with promptness and
clarity, either through evaluation of existing data or any additional
necessary research. Without such positive information, published
guidelines might either be inadequate or tend to be too restrictive.
If they are too stringent, this could endanger the proper utilization
of land application systems as effective and economical solutions to
water pollution control problems and the rational use of wastewater /or
crop and groundwater enhancement and other environmental-ecological
benefi ts.
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