United States         Off ice of Water        May 1980
Environmental Protection     Program Operations (WH-547)   430/9-80-005
Agency           Washington DC 20460
Wastewater Irrigation
of Rice

               Technical Report

        Wastewater Irrigation of Rice


               Jack L. Witherow

          Land Treatment Task Force

Robert S. Kerr Environment Research Laboratory

                Ada, Oklahoma
                   May 1980
     U.S. Environmental Protection Agency

      Office of Water Program Operations

       Municipal Construction Division

           Washington, D.C.   20460

                          Disclaimer Statement

     This report has been reviewed by the Environmental Protection Agency
 md 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 of commercial products constitute
endorsement or recommendation for use.

     This bulletin was prepared as one of a series of reports to finish
information on studies and current practices on use of municipal effluents
for crop production.  It was prepared in response to many requests for
technical guidance on this topic.

     The overall series provides indepth presentations of available
information on topics of major interest and concern related to municipal
wastewater treatment and sludge management.  It is a continuing effort to
provide current state-of-the-art information concerning sewage and sludge
processing and disposal/utilization alternatives, costs, transport,
environmental influences, and health factors.

     These reports are not a statement of Agency policy or regulatory
requirements.  They are published to provide planners, designers,
municipal engineers, environmentalists and others with detailed information
on specific municipal wastewater treatment and sludge management options.
                                         arold P.  Cahill,  Jr., Director
                                        Municipal  Construction Division
                                        Office of  Water Program Operations

                       WASTEWATER IRRIGATION OF RICE


                             Jack L. Witherow*


      The three areas evaluated in this report are:  the potential for
 and extent of wastewater reuse in rice production, the resulting food
 chain effects, and the cost effectiveness of this reuse.

      Rice irrigation occurs in Arkansas, Louisiana, Texas, Missouri,
 Mississippi and California and uses 2.8 million acres of land and over 8
 million acre feet/year of water.   In the counties with large acreage in
 rice production,  there are over 400 small or medium size communities
 having a combined wastewater discharge of about 100,000 acre feet/year.
 There are also three metropolitan areas with an estimated combined
 discharge of 400,000 acre feet/year.   The water requirement for rice
 irrigation far exceeds the local  wastewater discharges.   Many small or
 medium size municipalities have a high potential for a land treatment
 system,  which could reuse wastewater in rice irrigation.

      Six cases of municipal wastewater reuse for rice irrigation were
 found in the Central Valley of California.   These treated municipal
 wastewaters constitute up to 75 percent of the  waters used to irrigate
 rice.   Treatment  presently consists of primary  units and oxidation
 ponds.   However,  these cases of wastewater irrigation of rice have been
 ongoing  for 30 or more years,  and  some municipalities had only primary
 treatment  until recently.

      The published literature  documented wastewater irrigation of rice
 outside  of  the U.S.  and showed a worldwide practice of wastewater rice
 irrigation  with one  or more cases  in  the countries  of Italy,  Taiwan,
 Japan, China,  India  and USSR.   A case  where industrial wastewaters  were
 used  in  Japan  and another in Taiwan indicate  the  benefits of  organic
matter and  the detriment  of soluble solids  to rice  yields,  respectively.
A case in USSR, using  municipal wastewater  which  is mostly domestic,  had
preapplication treatment  similar to  that recommended in  EPA's  Construc-
 tion Grants Program Requirements Memorandum (PRM)  79-3.   The  treated
wastewater  applied to  the  rice  paddies  had  an average  BOD,,  of  39  mg/1.

 *Land Treatment Task Force,  Robert  S.  Kerr  Environmental Research
 Laboratory, Ada,  OK.

 After two days' retention in the paddles, the discharge had a BOD
 ranging from 1.5 to 2,0 mg/1 arid toral bacterial counts ranging from 10
 to 300/ml.

      The potential for introducing a health hazard into man's food chain
 is through metal contaminantss  biological contaminants, and biocidal
 contaminants (toxic chemicals).  Of the three, metal contaminants have
 resulted in the only known health hazard in wastewater irrigation of
 rice.   This was a case of untreated industrial wastewater, adding cadmium
 to the water used in nearby irrigation of rice.

      Many metal contaminants are not significant potential health hazards
 because they are generally present in low concentrations,  are not readily
 taken up by plants,  or are not  very toxic to man.   Several heavy metals
 (particularly Cd,  Zn,  Mo, Ni, Cu)  are labelled as  posing a potential
 health hazard.  A compilation of greenhouse and field experiments has
 indicated particular circumstance  and levels of  heavy metals which
 should be avoided.   For example,  to prevent health problems, zinc and
 cadmium should  be  maintained in tha soil at less than 500  mg/kg  and  40
 mg/kg,  respectively.   The "Process Design Manual for Land  Treatment  of
 Municipal Wastewaters," (EPA 625/1-77-008),  Table  5-4 lists maximum
 application of  these and other  metals "without need for further  investi-
 gation."  The inclusion of industrial wastewaters  into the municipal
 system is  the cause  of metal exceeding these maximum values.   Thus a
 review of  the industrial sources,  analyses of suspected metals from
 these  sources,  and use of Table 5-4 will prevent this potential  health

     Biological contaminants in food have  been extensively studied..
 Bryan  has  compiled a lengthy list  of disease outbreaks through foods
 which were  irrigated with wastewater.   Examination  of the  list shows
 that the outbreaks occurred  with food  eaten  raw.  Rice,  like wheat,  is  a
 cereal  crop which is not  eaten  raw.   However,  unlike  wheat,  a  part of
 the rice harvested is  eaten  in  the  grain  form.   This  causes  special
 concern  because  of the  direct prolonged  contact  of  the rice  with  the
 irrigation wastewater.  There are  a number of  factors which  reduce this
 potential hazard to the  food chain  to  nonsignificant  levels,   Pretreatment
 and the  six to nine month  storage of  the wastewater greatly  reduce the
 parasites, bacteria and virus.  The  hot air drier used  to reduce moisture
 prior to storage of the grain further  reduces  any surviving  pathogens.
Milling  removes  the surface  of  the  grain which contacted the wastewater.
Most significant, however, is the necessity of cooking  at  a boiling
 temperature prior to human consumption.

     Biocidal contaminant investigations have been made on the common
 toxic organic chemicals used in rice production.   The  concentrations
required to increase the uptake  or  residual on the unhulled rice grain
are two to four orders of magnitude greater than the  concentration of
these types of compounds in domestic wastewater.   The placement of toxic
persistent organics in man's food chain will not occur via irrigation of

  rice  with domestic  wastewatet.  However,  an industrial  discharge with
  high  levels  of  biocidai  contaminants  would need  i.c,  be  evaluated prior  to
  reuse in  the irrigation  of  rice.

       A cost  comparison of three land  treatment schemes was made to
  determine if wastewater  irrigation  of rice, is cost  effective.   The  land
  and capital  costs for nine  months of  wastewater  storage  for  rice irriga-
  tion  was  compared with two  months of  storage plus forage  irrigation and
  with  one  month  of storage plus  an overland flow  process.  The  overland
  flow  system  is  expected  to  have less  land  and capital  costs  than nine
  months  of  storage.  The  forage  irrigation  system will  have capital  costs
  similar to nine months of storage.  The  costs of land  treatment  systems
  are very  site specific,  but these comparisons show  that an overland flow
  or a  forage  irrigation system may be  cost  effective and should be fully
  evaluated.   Controlling  factors which must be added to these cost
  comparisons  are:  site characteristics,  differences in transportation
  distances, crop revenues, operation and maintenance, and purchase of the
 water or storage by the  rice farmer.


      Wastewater irrigation of rice should be viewed as having the same
 health hazards as wastewatar irrigation of wheat or other controlled
 agricultural food crops which are not eaten raw.   (PKM 79-3 recommends
 prior to reuse:   "Biological treatment by lagoons or inplant processes
 plus control of fecal coliform counts to less than 1,000 MPN/100 ml.")

      The industrial  discharges to the municipal  systems should be inven-
 toried and analyses  made  of  heavy metals and persistent organics that
 are suspected of being present and of being a health hazard to man.   If
 concentrations of these materials are less than  those maximum values in
 the "Process  Design  Manual for Land  Treatment of  Municipal Wastewater"
 or less than  the toleranceresiduals  levels of the commonly-used registered
 biocides,  the treated  wastewater should be acceptable for reuse in rice
 irrigation.   If  the  concentrations are greater,  several courses of
 action should be considered.   Among  these are denying approval  for reuse
 on rice irrigation,  requiring  pretreatment to reduce the  concentrations
 to acceptable values,  or  approving reuse  on the condition that  annual
 monitoring of the  soil  and crop  for  heavy metal and  persistent  toxic
 organic  show  concentrations  below recommended values.

     Monitoring  and  reporting  requirements  should be established  to
 determine  new industrial  discharges  to the  municipal system that  contain
 heavy  metals  or  persistent toxic organics,  and to determine the  environ-
 mental quality of water discharged from the storage  lagoons and  the  rice
 paddies  to both  surface and  ground water  sources.

                      Potential  for  and Extent of Reuse

     The potential for reuse of  municipal wastewater for irrigation  of
 rice is dependent upon the acreage of  rice  grown  and the amount of local
wastewater. Annual rice production of  12  billion  pounds in the United

 States is derived from about 2.8 million acres.   The producing states
 are Louisiana,  Arkansas,  Texas,  California,  Mississippi and Missouri.
 The breakdown of the 1975 production by acres,  pounds,  and dollar value
 is shown in Table 1.

 	TABLE 1.   1975  RICE PRODUCTION (1)
25 , 064
(1) in thousands
     To establish  feasibility,  the extent of existing wastewater  irrigation
of rice was determined.  However, the United States has only  1 percent
of the acreage used  for rice  cultivation throughout the world, and  the
practice of irrigating rice with wastewater was found to be more  common
in foreign countries.

     Arkansas - Rice is produced in 35 counties in Arkansas, mostly  in
the eastern half of  the state.  Counties having the largest acreage
ranked in order are:  Arkansas, Prairie, Lonoke, Poinsett, and Cross.
In counties with substantial  rice production, there are several cities
and numerous small towns.  Each county has about a dozen small towns
with less than 1,000 population, and two communities with populations
between 1,000 and 5,000.  The cities of Pine Bluff, Stuttgard, Searcy,
Jonesboro, and Forest City are located in heavy rice-producing counties.
These cities with populations over 10,000 have sufficient wastewater to
irrigate several hundred acres of rice.  A consultant for Searcy has
made a preliminary investigation and proposed a scheme to use that
city's wastewater to irrigate part of 10,000 acres of nearby rice production.

     An ample supply of irrigation water is necessary for successful
rice production.  About 33 inches of water are required to produce a
rice crop in eastern Arkansas.  Twenty to 24 inches of this amount will
have to be supplied  by irrigation.   The amount of irrigation water
needed will vary depending upon the amount and distribution of rainfall,
humidity, temperature,  evaporation,  type of soil,  and water management.
This last item, water management,  can overshadow the others.   USDA
personnel in several states have stated common practice is to apply
between seven and ten feet of water,  consume about three feet, and
discharge the rest.

     Texas - The principal Texas rice-growing area is in 19 counties
making up the physiographic area of the gulf coast prairie.  The rice
production in Texas is presently between five and six hundred thousand
acre.  The Texas Water Development Board has predicted that by 2020, the
acreage in rice will have doubled in Texas.  The gulf coast rice belt is
highly industrialized and populated.  The area includes Houston, the
largest city in the state, and over 50 other smaller communities.  Water
usage in rice production exceeds the municipal wastewater discharged in
this area.

     Louisiana - There are two principal rice-growing areas in Louisiana.
These consist of seven parishes (counties) in the southwest and six
parishes in northeast parts of the state.  The southwest parishes with
the largest acreage in rice production are Jefferson Davis, Acadia and
Vermilion.  There are about 10 small communities in each of these three
parishes.  The only large municipalities, Lake Charles and Lafayette,
are in adjacent parishes, and transport distance  will likely prevent
wastewater irrigation of rice.  In the northeast area, Morehouse and
Richland are the parishes with the largest acreage in rice production.
In each parish, there are less than 10 small communities.  Monroe, the
only city in northeast Louisiana, is in Quachita parish, and rice is
grown in this parish.  The opportunity for irrigation of rice with
municipal wastewater in Louisiana will be mainly small communities and
Monroe.  Between 30 and 36 inches of water are consumed to produce rice
in Louisiana.  Thus, each acre of rice irrigated will require a sewered
population of 35 to 40 people.

     Mississippi - The rice growing area is in the west central portion
of the state.  Most of the rice acreage is in Bolivar, Washington,
Sunflower, LeFlore, Tunica, Coahoma, Humphrey and Sharkey counties.
This acreage is concentrated in the flood plains of the Mississippi,
Sunflower and Tallahatchie rivers.  These counties contain 80 small
communities and the larger municipalities of Greenville, Greenwood and

     Missouri - Of the six rice-producing states, Missouri has the
smallest acreage in rice cultivation.  Rice is grown in the southeast
part of Missouri.  The principal rice-growing counties are Butler,
Ripley, and Stoddard.  In these counties, Popular Bluff, with c< population
of about 17,000, is the only large community, but there are also 40
small communities.  The opportunities for irrigation of rice w'th municipal
wastewater will be limited to a few communities with nearby rice paddies.

     California - California has wastewater reclamation criteria for
irrigation of food crops.  The required levels of preapplication treatment
would in almost all cases produce an effluent suitable for discharge.
However, exceptions are made to the required quality of the reclaimed
water when it is to be used to irrigate a food crop which must undergo
extensive commercial, physical or chemical processing sufficient to
destroy pathogenic agents before it is suitable for human  consumption.

Wastewater irrigation of rice is being practiced in a limited manner in

     In California, water consumption is about 36 inches per year for
rice production.  Application of the seven to nine feet per year is
practiced with most going to the drainage system.  Irrigated agriculture
in the Central Valley is highly organized through irrigation districts
and water rights.  The rice-growing areas are loca.ted in 16 counties.
Most of the acreage is in Butte, Colusa, Fresno, Glen, Sacramento,
Sutler, Yolo and Yuba,  All of chese counties except Fresno are locaced
in the northern half of the Central Valley.  There are between 13 and 25
small communities in each of these northern counties.  In the rice-
growing areas, there are three communities with populations between
40,000 and 60,000, but Fresno and Sacramento are the only major cities.

     Extent of Reuse in tag._jjJLS_1 - Water reuse is common and highly
encouraged by"the state of California.  Irrigation water transport and
drainage canals are publicly owned,  Wastewater from several segments of
society are discharged to these public-funded canals.  The State is  not
aware of rice paddies wholly irrigated by municipal wastewater; however,
there are a number of sioall towns in the northern part of the Central
Valley that for 30 years or more ha\re been discharging their wastewater
into a drainage system.  All of these small towns now have primary
treatment followed by oxidation ponds.  This wastewater is used for  the
irrigation of rice.

     Examples of irrigation of rice with wastewater provided by California's
Central Valley 'water Quality Board follow:

     (1)  The town of Colusa discharges about 0.5 mgd into Powell  Slough.
          The flow in the slough is half treated sewage and half  irrigation
          return flow.  A farmer has been  using  this water for irrigation
          of rice  for a number  of years.   Until  just  recently, the
          sewage received only primary  treatment.  The farmer recently
          initiated a suit against the  City to  retain use of  their
          wastewater  for rice  irrigation.

     (2)  The town of Willows  also discharges 0.5 mgd into a  public  drain
          which  constitutes ha]f of the flow  in the  drain.  This
           is used  for irrigation of rice.

      (3)  The town of Williams  dicharges about  0.5 mgd  into  Salt  Creek
          which represents up  to 75 percent of  its flow.  This water is
           used  to  irrigate rice and other  crops.

      (4)   The small  town  of  Biggs  discharges  their wastewater to  a
           drain.   The discharge is  about  10 percent  of  the  flow anc  the
           water is diverted  to irrigate rice  and other  crops.

      (5)   Some  of  the wastewater from the  town  of  Live Oak  is used in a
           similar  manner  for rice  irrigation.

     (6)  The town of Maxwell discharges its wastewater into Stone
          Corral Creek, which flows into the Glenn-Calusa irrigation
          district's irrigation canal.  The municipal wastewater, which
          is about 10 percent of the flow, is used to irrigate rice.
          This irrigation district included 121,170 acres of cropland
          in 1978, 3/4 of which were devoted to rice production.

     Both the Regional Water Quality Board and State Health Department
are aware of the uses of treated municipal wastewater for rice irrigation
and do not feel a change is necessary, as problems have not occurred
from these long standing practices.

     In Arkansas, Texas, and Louisiana, rice is a major cash crop, and
they all have experimental stations which specialize in research on rice
production. These experimental stations are located at Stuttgart, Arkansas;
Beaumont, Texas; and Crawley, Louisiana.  All three stations are part of
the agricultural research program directed from the states' land grant
colleges.  Contact was made with these stations, but information was not
available on wastewater irrigation of rice in these states.

     Foreign - A literature search was made in June, 1979 by EPA's
library services.  This computer-based search of articles on rice irrigation
with wastewater, sewage, or sludge located eight articles.

     This limited list shows rice irrigation with wastewater has been
practiced in Italy, Taiwan, Japan, India, and USSR since 1969.  The
small number of references is probably due to the fact that computer-
based bibliographies were begun in the last decade and seldom contain
literature published prior to 1960. Outside of establishing that rice
irrigation with wastewater is practiced around the world, several of
these articles are germane to conditions that can be expected in rice-
growing areas in this country.  Two of the articles relate the increase
or decrease in rice yields to various constituents in industrial wastewater.

     Minami showed that yields increased with increasing BOD of the
water up to 50 ppm (COD 200 ppm), but above this level yields decrease.
High-level BOD water produced reducing conditions in the soil and promoted
the leaching of inorganic elements (Fe, Ca, Mg) with an associated
increase in acidity.  The wastewater was pulp mill sulphite liquor that
had been neutralized by dilution with river water.  Huang found rice
yield loss as high as 89 percent when wastewaters from a paper *nill or
an acetyl chloride plant were used as a part of the irrigation water.
The results of analysis indicate that both industrial wastewaters and
the polluted irrigation waters were not acceptable for irrigation purposes
because of high soluble solids and salts.

     The most significant article is by Koltypin, who describee the pre-
application treatment and use of sewage in rice paddies in the USSR.
The wastewater was from Dushanbe and consisted of 60-65 percent domestic
sewage and 35-40 percent industrial effluent.  The wastewater was
treated in four ponds in series, used in eight to twelve rice paddies in

series, and discharged.  The first pond served as a settling tank with
an area of. 2 ha (4.4 acres), a depth of 1.5 m (5 ft) and a detention of
10 hours.  The subsequent biological ponds had areas of 4 to 4.5 ha (10
to 11 acres) and a depttj of 0.6 m (2 ft).   The quantity of wastewater
discharged was 58,200 m'/day (15MGD).  The detention time in the three
biological ponds was 33 hours, and the BOD,- loading was 672 kg/ha/day
(600 Ib/acre/day).   The rice paddies had a total area of 25 ha (62
acres) with a mean water depth of 25 cm (10 inches).  Their total water
capacity was-62,500 m ; the inflow was 52,200 m /day and the discharge
was 30,000 m /day.   Thus the detention was about two days.

     A part of the analytical results are reported in Table 2.


BOD5 (mg/1)
Dissolved oxygen (mg/1)
Helminth eggs (per liter)
Ammonia (mg/1)
Total bacterial (counts/ml)
Raw Waste

Pond Effluent Paddy


   *Mean value from 26 determinations.

     The aquatic organisms in the paddies included algae, diatoms,
dragonfly larvae, carp, and mosquito fish.  The system depends upon both
the ponds and rice paddies for treatment.  The effluent from the paddies
is highly treated.

     Koltypin concluded "Extensive utilization of paddy fields for the
decontamination of sewage is possible in the rice-cultivating regions of
the USSR. In the vicinity of cities, with industrial-type sewage treatment
installations already in operation or under construction, paddy fields
may be used for the additional purification of sewage after leaving the
aeration tanks and biofilters.  In many cases, with small volumes of
effluents from enterprises, rest homes, pioneer camps, and other similar
sources, paddy fields may be combined with biological ponds.  Finally,
paddy fields may become an essential component of sewage farms in the
zone of rice cultivation in the south of the USSR."

     These treatment ponds are more heavily loaded and have shorter
detention than those used in the U.S.  In the U.S. where the wastewater
is to be used in controlled agriculture fields and on human food crops
not eaten raw (ie. rice), PRM 79-3 recommends preapplication treatment
by either biological lagoons or inplant processes plus control of fecal
coliforms to less than 1000 MPN/100 ml.

     Metal Contaminants - The food chain involves acquisition of the
metal by rice plant roots, transport into the rice grain, and then

consumption by man.  Many metals are not a significant potential hazard
either because they are generally present in low concentrations, are not
readily taken up by plants under normal conditions, or are not very
toxic to plants and/or animals.  Several metals (particularly Cd, Zn,
Mo, Ni, Cu) are labeled as posing a potential serious hazard under
certain circumstances.

     Except for certain accumulation species, plants are excellent
biological barriers.  This is notably true for nickel, copper, and lead.
Molybdenum is an exception to the plant barrier rule, but only ruminants
that consume forages can be affected.  Zinc can be transferred to foliar
tissue such as spinach and to the edible tissues of other plants such as
tomato, peas, and potato.  Soil levels of zinc in excess of 500 mg/kg
may cause, at least, a decline in forage quality through lower palatability
and at worst some overt toxicity symptoms.  Humans are probably protected
from food-chain transfer toxicity because their diet also includes
fruits, grains, and animal meats.  In all cases, zinc transferred from
substrates high in zinc is much lower in these tissues than in foliar
tissues of plants.

     Cadmium is currently the element of greatest concern as a food
chain hazard to humans.  The widely publicized Itai-Itai disease in
Japan is attributed to cadmium introduced into the Jintsu River from
mining activities which was transferred to man through several sources,
including irrigated rice.  The World Health Organization has recomriended
a  safe value of 400 to 500 ug/week of cadmium.  The base level average
dietary intake of  cadmium has been reported to range from 175 to 525
>ig/week for an adult  consuming 1.5 kg/day of food. Cadmium intake of  the
people affected by Itai-Itai disease may have been 4200 to 7000 ug/week.
The limit recommended by the Japanese investigations as the maximum
permissible concentration was  1.0 ug Cd/g of rice  grain.  Their results
associated a concentration of  15.5 ;ag Cd/g extracted from the soil with
0.1 N HC1 with excessive levels of Cd in rice grain.

     Two important foodstuffs, rice and wheat, are able to take up
considerable quantities of Cadmium from soils.  Kobayashi et al. added
cadmium oxide to  soil in pots where rice and wheat were growing.  The
results are in Table  3.  The wheat grain accumulated more cadmium than
did rice.  Concentrations above  10 ug/g  (.001 percent) in soil  reduced
the yield of both rice and wheat.  However, concentration of  100 pg/g in
the soil did not  result in the rice grain's reaching  the maximum level
of 1.0 ^ig Cd/g recommended by  the Japanese.

of Cd
to Soil
(% of CdO)


Cd (ug/g)

Cd (ug/g)


Whole grain
Cd (tig/g)
 From Kobayashi et al.,  1970.

     Bingham et al., in  a greenhouse investigation conducted in California
in  1975, showed the uptake of cadmium by rice grain increased with
increased amount in the  soil, but was much less under flooded than non-
flooded cultures.  Under flood and non-flood conditions, rice grain with
concentrations in excess of 1.0 ^ig Cd/g was produced when DTPA-TEA soil
extractable Cd was 40 and 15 pg/g, respectively.  Thus, with flood
culture rice, design calculations should be required showing an accumulation
of  cadmium in the soil of less than 40 ug/g.  Naturally-occurring levels
of  Cd in soil average 0.06 ug/g and range from 0.01 to 5. ug/g (extracted
with 0.1N HC1).

     Biological Contaminants - Enteric pathogens survive some stages and
sometimes the entire process of wastewater treatment.  Viable pathogens
are therefore applied to the land and the crop in the process of irrigation
with wastewater.  After  application, the pathogens must survive long
enough to be present when the crops are harvested.

     The greatest health concern is with low-growing crops such as
vegetables which have a greater chance of contamination and are often
eaten raw.  Outbreaks of disease have occurred from foods contaminated
by wastewater.   Bryan has compiled a lengthy list which shows outbreaks
occurred with food eaten raw.

     Prior to and during reuse of wastewater for rice irrigation,  biological
pathogens will die due to long exposure to unfavorable environmental
conditions in the preapplication treatment facilities, storage ponds and
rice paddies.   The most common treatment facilities will be lagoons with
about a month detention.  Storage ponds will have 7 to 9 months detention,
and the paddies will  remain flooded for 3 to 5 months.  Reduced water
levels in the storage ponds and discharges from the paddies during the
growing season will reduce these detention times.

      The  removal  of both virus  and  bacteria  in  ponds have been  shown  to
 be  time and  temperature dependent.   Sagik, et al., have  shown the
 reduction of virus is  quite  rapid at 20  C as is illustrated  in  Figure
 1., which is results from  research  in Texas.  Similar  results for  fecal
 coliforms have been found  in wastewater  ponds,  and Bowles has developed
 the following equation describing the die-away  function.
                    In  Ci/Cf  . K 8(T  20)
     where:  t = Actual  detention  time  in days
           Ci = Entering  counts/100 ml
           Cf = Final counts/100  ml
             K = 0.5  in  warm months
              = 0.03 in cold months
             9 = 1.072
             T = liquid  temperature  (C)

     Short circuiting occurs in almost every pond.  The actual detention
time was found to range from 25 to 89% of the design time with a geometric
mean of 46%.  Using  Bowies' equation,  about 18 days is required to reach
the recommended fecal coliform count of 1000/100 ml at 20 C.  This is
similar to the time  required for  virus removal shown in Figure 1.

     Studies have been  made on the viability of various pathogenic
organism on  crops irrigated with  wastewater.  The values in Table 4 show
the viability of such organisms varies from less than a day to 49 days.


Organism                           Media               Survival Times  (days)

Tubercle bacilli
Entamoeba histolytica cysts
Ascaris Ova

grass or clover




            20     40      60      80
                       Time (days)
   Figure 1.  Virus Survival in Ponds
100     120

increased 65 percent between 1950 and 1970.  Much of this increase in
consumption is in breakfast cereals or specialty prepared food.  These
uses require high temperature process t  t'> Tvhich will destroy biological
pathogens.  Direct use of rice v.raia. requires cooking which is universally
done with water at boiling temperature. The sequential and additive
effects of die off in storage, neat drying, and finally cooking of the
product provide a very effective barrier for biological contaminants.

     Biocida1 _CjHitamio?nLs_ -- Biocidal contaminants can be generally
described as chlorinated hydrocarbons, rrsenated hydrocarbons, urgano-
nitrogen pesticides, organophosphorus pesticides, herbicides and soil
sterilants.  Some of the most recognized compounds are DDT, Dieldrin,
2,4-D, Parathion and PCS.  The concentration of all of chese in wastewater
is negligible compared to other sources and are far below levels that
will cause scute health effects.

     The major concern in placing th^se compounds in man's food chain
has been in waste discharges to drinking water sources and surface
contact on foods.  Bej.-.use of Ch^ir persistence the possibility of
increased uptake by rir-i with increased concentrations in the  irrigation
water has been studied.  An unpublished paper by Yin-hsiao indicates the
degree of uptake in rice of a heavy metal, arsenic, end a persistent
organic compound, phenol.  (The major biocides used in rice culture in
the U.S. are phenolic compounds, ie. Propanil, Carbofuron and  Carbaryl.)
In experimental plots, each with an area of 0.66 m  and 80 cm  deep, rice
was irrigated with wastex^ater containing 0, 0.5, 50, 100, 250, and 500
ppm of phenol and in separate plots rice was irrigated with wastewater
containing 0, 5, 10, 20, and 50 ppm of Arsenic.  The uptake by the rice
is shown in Figures 2 and 3.  These figures show the uptake in the root
and in the stem and leaf is much greater than in the unhulled  rice.
Concentration of phenol and arsenic in the unhulled rice is the same
with concentrations of 0 and 50 ppm of phenol and 0 and 10 ppm of arsenic
in the irrigation water.  Yiu-hsiao concludes "The effect of the phenolic
compounds on the crops and their accumulation in the plant is  influenced
by various factors (temperature, humusv etc.), especially the  concentration
of phenolic in the. irrigated sewage.  Under the field condition^, wheat,
rice, and corn irrigated with a low concentration (under 1 ppm) of
sewage containing phenolic compounds show a good growth and development.
Their phenolic content do^rm't show a distinct difference in comparison
with those irrigated with clean water.  But under the experimental
conditions, if the phenolic concentration increases, the level of the
phenolic content and its accumulation are somewhat different.   lien the
concentration is 50 ppm, both In soil and water culture, the phenol
promotes the growth.  When the concentration increases further, however,
the result turns to the opposite.  Vhen concentrations are over 50 ppm
in soil culture, the phenolic content in the crops may be increased; as
the concentration raises up to 500 ppm, the crops growth is inhibited....

     "The effect of arsenic on the crops and its accumulation  is obviously
influenced by the arsenic concentration of the irrigated sewage....  At
low concentration (1 ppm~> arsenic promotes the growth of wheat and


      700 -
      600  .

                                    Stem and Leaf
                                    Unhulled Rice
rice.  However, as the concentration rises up to 5 and 10 ppm, the
growth of the wheat and rice are inhibited respectively, and the arsenic
accumulation in the crops became more evident.  As the concentration
rose to 50 ppm, the growth of wheat and rice are heavily injured, and
the arsenic content in plants increases."

     In the U.S. The four common biocides used in rice culture are
listed in Table 5 along with the recommended applications and the tolerances
for residue on the rice grain.  Brown has investigated these biocides
and developed management guidelines for their use.


                      Recommended Application       Tolerance on grain
     Herbicides               (Ib/acre)
     The tolerance limits on rice are  those found as residues when  the
recommended applications are followed.  The residue is measured on  a
ground  sample of  the unhulled rice  and includes  the residue  on the  hull,
bran, and grain.  The grain that is eaten will contain a  small part of
the  total residue that  is measured.

     Sokklov, et  al., studied the behavior of several biocides in rice
irrigation systems.  He measured the amount translocated  to  the soil,
rice plants and irrigation waters.   Using an application  of  14 kg/ha
(12.5 Ib/acre) of propanil, he  found different amounts of the biocide in
different years.  Sixteen days  after the applications, the rice plants
contained 3% in 1972 and nearly 15% in 1973 of the initial amount of
propanil applied.  The  concentration of propanil and its  metabolite
(3,4-DCA) was 25  ug/plant or less on the sixteenth day and decreased to
zero in two to three months.  This  study shows the small  amount of
translocation to  the whole plant with  an application rate of four times
that recommended  in the U.S.

     Jolley investigated the effects of chlorination on organic constituents
in effluents from domestic sanitary sewage treatment plants. He  found
32 stable organic constituents  in effluents from domestic sanitary
primary sewage treatment plants.  Twenty-three were quantified at 2 to
190  ug/1 levels.  Phenol, at 6  ug/1, was  the only  compound found  that  is
on the  priority pollutants list.   (This list contains  those  organic
compounds suspected of  being serious health hazards.)  Nine  stable
organic constituents were identified in the effluents  from domestic
sanitary secondary  sewage treatment plants.  Eight  of  these  were  quantified
at 5 to 90 fig/1 levels, but none are on the priority pollutant  list.
After  chlorinating  to a 1 mg/1  chlorine residual,  seventeen chlorine-


 containing stable organic compounds were present in the effluent from a
 secondary plant treating domestic sanitary sewage,   These seventeen
 compounds were quantified at the 0.5 to 4.3 yug/1 levels.  Two of the 17
 compounds are on the priority pollutant list.   These were 2-chlorophenol
 at 1.7 jag/1 and 4-chloro-3-methyl phenol at 1.5 ug/1.

      Jolley's work indicates the extremely low level of stable organic
 chemicals that can be expected in domestic wastewaters use in irrigation.
 Phenol and two chlorinated byproducts were the only compounds found
 which are considered to be a potential health  hazard.  The concentrations
 of these phenolic compounds were four orders of magnitude less than the
 level Yin-hsiao found causing an increase in the phenol content of
 unhulled rice grain and two orders of magnitude less than the tolerance
 limits for residual of several phenolic-base pesticides used in rice
 production.   An increase of persistent toxic organic in man's food chain
 will not occur via irrigation of rice with domestic wastewater; however,
 the inclusion of industrial wastewater with biocidal contaminants above
 the tolerance level would need to be evaluated prior to reuse in the
 irrigation of rice.

                             Economic Feasibility

 Storage - Wastewater irrigation of rice will require storage of the
 wastewater during non-irrigation periods.   The amount of storage is a
 controlling  economic factor.

      The length of time to grow rice is dependent upon the variety
 planted.   Very short season varieties require  120 days,  while short
 season or midseason  require 140 and 155 days,  respectively.   Rice may be
 flooded when rice seedlings are 4  to 6 inches  tall,  which will be 3 to 4
 weeks after  planting.   Water is added through  the growing season to
 maintain the depth of water between 4 and  6  inches.   The paddy is usually
 drained about  two weeks  prior  to harvest  to  allow the field  to dry and
 accommodate  mechanical  harvesting  equipment.   This  sequence  of events
 requires  use of  large quantities of irrigation water over a  three to
 four  month period.   In Arkansas, Mississippi,  Tennessee,  and  Missouri,
 storage of 8 to  9  months would  be  necessary  for growth of this single
 crop.   In  the  southern parts of  Louisiana  and  Texas,  a second crop  of
 rice  can be  produced from  the stubble  remaining after  the first  cutting.
 This  "stubble"  crop will consume another  12  inches  of water  and  extend
 the water use  period from  3 months  to  about  5% months.   Consequently,  in
 these  areas  with  longer growing  seasons, less  storage is  needed.

     The decline  in  the supply  of underground water  in the Grand  Prairie
 area in Arkansas has stimulated  interest in  reservoirs as a means of
 utilizing surface water for rice irrigation.  A survey made in 1958 by
 the Arkansas Agricultural Experimental  Station shows  106  reservoirs had
been constructed by farmers to  store water for rice  irrigation.   The
economic evaluation part of the  survey  showed  that the larger  reservoirs
 (80 to  160 acre) had less per acre cost than irrigation from wells, but
that smaller reservoirs (20 to 40 acre)had costs of  10 to 35 percent
higher than  the costs of irrigation from wells.  The major cost factor


 in reservoir storage was land.  When waste  land was  available,  cost
 savings  were obtained with 20 to 40 acre reservoirs.

      When using water from reservoirs,  farmers usually drained their
 fields only once,  compared with one to  three times  when well water  was
 used.  This drainage of the field fewer times and more rapid flooding
 when water was  applied resulted in farmers with reservoirs  using  less
 labor, about 2.5 hours per acre, in irrigating rice.

      Comparison of Alternative  Land Treatment Systems  - In  order  to
 determine the opportunity of wastewater irrigation  of  rice  being  cost
 effective,  a series of calculations were made to compare the relative
 costs  of rice irrigation,  forage crop irrigation, and  overland flow.
 Generalized design conditions were necessarily assumed to enable  such
 comparisons.  Since land treatment costs are very site-specific,  the
 results  can only suggest what alternatives should be fully  evaluated in
 a  facility plan.

      The three  comparison incorporated:  (1)  identical primary treatment,
 (2)  different amount of storage, (3) identical transport (pipeline  and
 pumping)  cost,  (4)  different periods and rates of wastewater application,
 and  (5)  municipally owned storage,  overland flow and forage irrigation
 sites  but privately owned  rice  paddies.

     Primary treatment was included to  reduce solids for odor  and
 operational reasons and to reduce pathogens for health reasons.   Even
 though EPA will accept a minimum of comminution and screening  for overland
 flow systems, more  extensive primary systems,  such  as  the aerated lagoon,
 are  considered  necessary by Louisiana and  some other states.   However,
 assuming  the  primary treatment  costs to  be the same is a disadvantage to
 the  economics of the overland flow system.

     The  storage costs were calculated  for nine months of detention for
 rice irrigation, two months for  forage  irrigation,  and one  month  for
 overland  flow.  These  storage periods for  forage irrigation and overland
 flow are  one  month  longer  than minimum  recommended  by  EPA for  the rice
 producing areas.  This month was added  as  a safeguard  against  infrequent
 operation for small  treatment plants but is an economic  disadvantage  to
 both forage irrigation and  overland  flow systems.   Because  rice is  grown
 in relatively impermeable  soils  on  flat  terrain, unlined  storage lagoons
 and flood irrigation techniques  were assumed  for the three  systems.

     Outside  of California,  the  rice growing  areas  in  the U.S.  have more
annual precipitation than potential evapotransporation,  and  in these
areas hydraulic loading based on soil permeability  rather than nitrogen
loadings is the limiting constraint in design  of an irrigation system.
The acreage calculations for  forage irrigation  are based on  one inch/week
over ten months of the year.  The acreages  for  overland  flow are based
on an application of eight  inches/week over 11 months  of the year.  The
land values in Table 6  include 25% extra for  fences, roads,   and buffer

     An inventory showed three predominant sizes of communities in
counties with large acreage in rice production.  In accord with the
inventory, calculations were made for populations of 1000, 4000, and

     Storage costs were determined using EPA's report, 430/9-75-003,
"Costs of Wastewater Treatment by Land Application."  The cost curves
used are based on EPA Sewer Construction Cost Index of 194.2 for February,
1973.  The costs were updated to the April, 1979 Sewer Construction Cost
Index of 344.9.  The storage costs include reservoir construction and
embankment protection but not lining or land.  The land areas for storage
are calculated on:  (1) 5 ft water depth in reservoir less than 10
million gallons, (2) 12 ft water depth in reservoirs above 10 million
gallons, and (3) dike configuration as specified in the above report.

     The design factors which highly influence the economics of these
land treatment systems are storage volume and land areas for the application
site and the storage lagoons,  A tabulation of these items are shown in
Table 6-

                      .                            Populations
 Items                                      1000           4000        12000

 Million gallons/year                         25            100          300
 Capital Cost of Storage ($1,000)
   9 months                                   71            248          604
   2 months                                   51             87          195
   1 month                                    37             73          124

 Land for Storage (Acres)
   9 months                                  7.2           23.8         65.5
   2 months                                  3.8            6.5         16.5
   1 month                                   2.5            6.9          9.1

 Land for Application (Acres)
   Forage Irrigation @ l"/wk                25            100          300
   Overland Flow @ 8"/wk                     3             12           37
Differential Acres
(Forage Irrigation area & storage -
9 month storage)
Differential storage costs (9-2 months)
Differential storage cost per
differential acres ($l,000/acre)










     The capital costs for storage are shown for three population levels
and three storage periods.  The land required for these nine storage
ponds is tabulated as is the land for forage irrigation and overland
flow application sites.

     These economic evaluations of storage and land requirements for
rice irrigation, forage irrigation, and overland flow indicate the
overland flow system will have the least capital costs.  The economic
comparison shows similar capital costs between a municipally-owned
storage and forage irrigation system and a system with privately-owr5d
rice irrigation and municipal storage facilities.

     The overland flow system is likely to have considerable econond c
advantage over rice irrigation with wastewater.  The land requirements
for one month of storage plus the application area is less than the land
needed for nine months of storage for rice irrigation.  Nine-month
storage is two to five times more costly than one month.  This differential
in capital cost for storage is equal to about $12,000/acre to shape and
plant the land and provide an overland flow distribution system.  Use of
an overland system will also depend upon permit limitations, soil
characteristics, slope of the land, and transport distances.  These are
all site specific and cannot be evaluated in these calculations.

     Where an overland flow system is not feasible, forage irrigation
will be economically competitive to rice irrigation.  In the rice-
growing areas, it is likely that forage irrigation will be done on
municipal purchased land.  Forage irrigation can be managed to minimize
disposal cost without damage to the environment, but the crop selection
may not maximize the cash returns from the land.

     The differential in land requirements needed for forage irrigation
(areas for application plus 2 months of storage) minus the land needed
for nine months of storage with rice irrigation are shown in Table 6.
The differential in cost for 9 months over 2 months of storage are also
shown.  These differentials show the cost for additional storage needed
for rice irrigation is equal to between $900 and $1,900 per acre of
additional land needed for forage irrigation.  These amounts are sufficient
to purchase land in most ricegrowing counties. There are several site-
specific factors which must be included in this comparison prior to
concluding that forage irrigation will be the cost-effective system.
The major ones are purchase of the water or storage by the rice farmer,
forage crop revenues, operating, and maintenance costs and differences
in transportation distances.

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     Prairie Area.  Bulletin 606.  University of Arkansas, Fayetteville.

Bowles, D. S. et al.  Coliform Decay Rates in Waste Stabilization Ponds.
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Bingham, F. T., et al.   Cadmium Availability to Rice in Sludge-amended
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