MAY 1974
                         Environmental Protection Technology Series
          A  Waste Treatment System  for
       Confined Hog Raising  Operations
                                   Office of Research and Development

                                   U.S. Environmental Protection Agency

                                   Washington, D.C. 20460

Research reports of the  Office  of  Research   and
Monitoring,   Environmental  Protection Agency,  have
been grouped into five series.   These  five  broad
categories  were established* to facilitate further
development   and  application   of   environmental
technology.    Elimination   of traditional grouping
was  consciously  planned   to  foster   technology
transfer  and  a  maximum   interface  in  related
fields.   The five series are:

   1.  Environmental Health Effects Research
   2.  Environmental Protection Technology
   3.  Ecological Research
   4.  Environmental Monitoring
   5.  Socioeconomic Environmental studies

This report  has been assigned to the ENVIRONMENTAL
PROTECTION   TECHNOLOGY   series.    This   series
describes   research   performed  to  develop   and
demonstrate    instrumentation,     equipment     and
methodology   to  repair  or  prevent environmental
degradation  from point and  .non-point  sources  of
pollution.  This work provides the new or improved
technology  required for the control and treatment
of pollution sources to meet environmental quality
                    EPA REVIEW NOTICE
 This report has been reviewed by the Office of Research and
 Development, EPA, and approved for publication. Approval does
 not signify that the contents necessarily reflect the views
 and policies of the Environmental Protection Agency, nor does
 mention of trade names or commercial products constitute
 endorsement or recommendation for use.
  Tor nh> by the Superintendent at Documents, U.S. Government Printing Office, Washington, P.O. 20402 - Price $1.20

                                             May 1974

         William R. Park,  P.E.
        Project No. 13040 EVM
       Program Element  1BB039
           Project Officer

          Ronald R. Ritter
    Chief, Grants Administration
U.S. Environmental Protection Agency
           1735 Baltimore
              Room 249
    Kansas City, Missouri  64108
            Prepared for
       WASHINGTON, D.C.  20460

A waste treatment system was installed in conjunction with an exist-
ing confined swine feeding operation at Schuster Farms, Gower, Missouri.
The system consisted of a concrete aeration tank equipped with mechani-
cal surface aerators, followed by a settling pond.  Wastes from the
1,000-hog feeding operation were flushed through a gutter in the con-
crete feeding floor into the aeration tank, where they were aerobically
digested.  All aeration tank discharges were retained in the settling
pond where the liquids evaporated.

The waste treatment facility operated continuously and dependably over
a 2-year period, with treatment efficiency averaging 90% to 95%.  The
system effectively controlled objectionable odors and insects, contained
all liquid runoff emanating from the feeding operation, and left only
a dry, inert residue suitable for land disposal.

Installation cost for the system was $12,000.  Net operating costs, in-
cluding amortization of capital costs, were $7.33 per day.  Thus, total
environmental control was achieved at a cost of approximately $1.00 per
hog, or 1/2 cent per pound (1.1 cent per kilogram) of weight gained
while on the feeding floor.

Abstract                                                     ii

List of Figures                                              iv

List of Tables                                                v

Acknowledgments                                              vi


I        Summary and Conclusions                              1

II       Introduction                                         2

III      The Waste Treatment Facility                         8

IV       Chronological History of the Demonstration Project  42

V        System Design                                       55

VI       System Operation and Economics                      60

VII      Appendix                                            68


No.                                                              FaRe

1         Swine Waste Management System at Schuster Farms          9

2         Plan View of Demonstration Site Showing Location and    14
             Direction of Photographs



1         General Design Parameters for Proposed Swine Waste       57
             Treatment Plant at Schuster Farms, Gower, Missouri

2         Raw Waste Characteristics                                61

3         Performance of Swine Waste Treatment Facility at         62
             Schuster Farms, Gower, Missouri

4         Minimum Recommended Tank Size and Equipment Requirements 66
             for Swine Waste Treatment

This demonstration swine waste treatment system was built and operated
at Schuster Farms, Gower, Missouri.  The farm is owned and operated by
Mr. Lee R. Schuster.  Funds for the demonstration were provided in part
by the U.S. Environmental Protection Agency, under Project 13040 EVM.
Mr. Ronald R. Ritter, Chief of Grants Administration, Region VI,
Environmental Protection Agency, served as Project Officer.

In addition to Mr. Schuster, Mr. Gary Ellington and Mr. Don Farr of
Schuster Farms assisted in operation and evaluation of the waste treat-
ment system.

Technical aspects of the operation, including specification of design
and operating characteristics, startup and testing of equipment, per-
formance monitoring, and evaluation of system performance were the
responsibility of Midwest Research Institute.  The Midwest Research
Institute program was directed by Mr. William R. Park, P.E.  Dr. Ross
McKinney, University of Kansas, and Dr. William Garner, formerly of
MRI and presently of the U.S. Environmental Protection Agency, assisted
in system design.

                           SECTION I

                    SUMMARY AND CONCLUSIONS
The project described in this report was undertaken to demonstrate the
feasibility and effectiveness of a swine waste treatment concept suit-
able for use with existing confined feeding operations.  The demonstra-
tion was conducted at Schuster Farms, Gower, Missouri.  The demonstration
site was Schuster's Feeding Floor No. 7, a 70 ft by 220 ft (21 m by 67 m)
partially enclosed concrete floor, having a capacity of 1,000 feeder
pigs ranging in size from 30 to 225 lb  (14 to 102 kg).

The heart of the treatment system consists of a 20 ft x 40 ft x 13 ft
(6.1 m x 12.2 m x 4.0 m) deep reinforced concrete aeration tank equipped
with two 7.5 hp bridge-mounted, gear-driven, mechanical surface aerators.

Wastes are scraped from the concrete  feeding floor into a gutter, where
they are flushed down into the aeration tank with water drawn from a
nearby pond.

Biological reactions in the aeration  tank convert  some 90% to 957. of
the organic wastes into water, bacterial cells  and harmless  gases.
Any overflow  from the tank is retained  in a  75  ft  x  125 ft  (23 m x 38 m)
settling basin where liquids evaporate, leaving only an inert,  odorless,
humus-like granular residue which  can harmlessly,  even beneficially, be
returned to the  environment via  land  spreading.

The total  cost of the  system was  $12,000.   Annual  costs,  including both
capital charges  (depreciation,  interest,  etc.)  and operating expenses
 (chiefly electric power), were  $11.62/day,  lowered to a net  cost  of
$7.33/day  by  the labor  savings made possible by reduced manure  handling.
This^amounts  to  roughly $1.00  per hog,  or 1/2  cent per  pound (1.1  cent
per kg) of weight gained  while  on the feeding floor, an amount  that
must  eventually  be  passed on  to  the pork consumer at the  retail level.

This  demonstration  waste  management system,  in summary, provides  for
 total environmental control—of  liquid runoff,  odors, and solid wastes—
at a  cost  that  should  be  acceptable to both pork producers and  pork

                          SECTION II



As every feedlot operator knows, the handling and disposal of pig
manure can be a real problem in a large-scale swine operation.  Tradi-
tional waste disposal practices have frequently led to lawsuits and/or
large expenditures for labor, equipment, and facilities; and even with
substantial investments, in many cases control practices have failed to
achieve the expected results in terms of solving air, water and solid
waste pollutional problems.

While the environment can assimilate small quantities of raw pig manure,
large amounts of this pollutant can have disastrous effects.  During
periods of intensive rainfall, great quantities may wash into receiving
waters.  This in itself is serious enough; but, unfortunately, the possi-
bility that these contaminants may reach an otherwise unimpaired water-
course has greatly increased as a consequence of recent changes in the
scale of hog raising operations.

In the past, hog growing operations have presented relatively few prob-
lems from a water pollution  standpoint.  Hog raising has traditionally
been carried out on a small  scale, and  since it has been a widely
scattered activity, the raw  manure could be  left on the land without
posing any serious environmental threat.   Hog raising is, in fact,
still a widely scattered activity, although a definite trend toward
confined feeding is becoming increasingly evident.

In the future, more and more hogs are certain to be raised in confine-
ment.  This trend will result in far greater quantities and concentra-
tions of wastes than have yet been encountered, with the accompanying
possibility of serious health hazards and costly stream pollution unless
the wastes are stabilized in an environmentally acceptable manner.

Large quantities of raw pig  manure are  extremely objectionable even
when large land areas are available for their disposal.  However, hog
wastes are readily biodegradable, and their  stabilization can be
accomplished effectively by  means of relatively simple and inexpensive
biological treatment systems.

The effectiveness of aerobic stabilization of hog wastes has been demon-
strated in confined hog raising operations that employ  slotted concrete

floors.  The defecated material passes through the slots into an oxi-
dation pit below, where aerobic digestion takes place.

The slotted-floor concept, while proven effective in newly constructed
facilities, cannot easily be adapted to existing operations.  Therefore,
a real need exists for an economical waste treatment system that can be
employed in conjunction with established hog raising operations.

As in cattle feeding, mush and wetness in the hog pens are an economic
liability.  Foot rot and other diseases are a direct result of damp-
ness , while the energy expended by the animal working through mush or
across slick concrete floors detracts from the weight-building body
processes.  For this reason, concrete-floored animal pens are scraped
clean rather than flushed clean.  Hydraulic cleaning and carriage of
manures may seem attractive from a sanitary engineering viewpoint, but
the attendant wetness in the pens would be most objectionable for the
hog raiser.

The problem, then, is to stabilize large quantities of a highly putres-
cible semisolid and thus eliminate the potential of stream deterioration
from this material.

Because of the physical nature of the manure, it defies composting.
Anaerobic digestion is both difficult to  control and  aesthetically
objectionable.  Thus, the desired restraints on the system are:

     1.  Mechanical cleaning of the pens;

     2.  Mechanical or hydraulic movement of the manure to a treatment

     3.  Aerobic-liquid stabilization;

     4.  Separation of the  stabilized solids; and

     5.  Dispersal of the stabilized  solids on adjacent croplands.

As in any waste  disposal problem, the ideal solution would be to
achieve complete recycling  of  all materials--in effect, a "closed-loop"
system.  For example, cropland produces  grains used in feed  for hogs;
each 3 unit weights of feed results in roughly 1 unit weight gain and
2 unit weights of waste material.  The waste material  can then be
collected  and distributed on the cropland as fertilizer to grow more
grain  to  feed more hogs and produce more waste.  Thus, the cycle could
continue almost  indefinitely.

However, this situation, while possible, is not economically feasible.
The scale of hog raising operations, the economy and convenience of
chemical fertilizers, and the use of processed and concentrated feeds
have all combined to decrease the relative economic value of hog manure
as a soil nutrient.  However, while the potential for economic reuse of
hog manure is negligible, its potential for polluting nearby streams
is increasing rapidly as disposal goes on as cheaply as possible--
usually by  dumping  without regard to possible effects on water quality.

The overall problem of returning hog wastes to the environment in a
nonpollutional and environmentally acceptable manner can be divided
generally into three phases:  (1) collection; (2) stabilization; and
(3) disposal.

The collection phase is by far the simplest, although it offers a number
of interesting possibilities.  Except in new installations utilizing
the slotted-floor concept, mechanical cleaning of pens is generally
required, for the reasons previously cited.  Existing facilities,
where hogs are confined outdoors on concrete slabs, usually involve
scraping the manure from the floor, either mechanically or manually,
and dumping it downwind or downstream.  If a waste-stabilization faci-
lity were available, the manure could be dumped in it with perhaps
even greater convenience.  Or, a system of open collection sewers or
lined trenches could be installed inexpensively, so that material
scraped from pens could be directed into the trenches and carried
hydraulically to the central treatment facility; the water used for
transporting the wastes could be drawn from either a pond or from the
treatment facility itself.  Such is the waste collection system de-
veloped for the demonstration project.

For stabilization of swine wastes, aerobic biological waste treatment
systems have proven to be effective.  However, many of the systems
currently in use are suitable only for newly constructed facilities.
In some of these, the hog confinement area is, in effect, built around
or over the waste treatment plant.

The primary interest of the hog raiser, however, is in raising hogs
and not in treating hog wastes.  An acceptable treatment system must
recognize this  fact  and offer the operator a convenient and economi-
cal means of handling the substantial quantities of waste material
generated by the confined hogs.

Only when disposal by means of treatment becomes more advantageous to
the hog raiser than disposal of the raw wastes—that is, when there is
a proven, direct, measurable economic benefit accruing to the operator

from the waste treatment process—will such treatment become an
accepted part of the hog raising business.


Schuster Farms initiated the extensive pollution control program
described in this report.  This waste management system solves many
of the costly environmental problems commonly associated with con-
fined feeding operations.  The program, incorporating waste handling,
treatment and disposal operations, virtually eliminates all pollu-
tional threats to the surrounding land, air and water.

The project involved a three-way cooperative effort between Schuster
Farms, Midwest Research Institute (MRI), and the Environmental Pro-
tection Agency (EPA).  The system design, monitoring and evaluation
were MRl's responsibility; Schuster Farms built and operated it; and
the demonstration project was partially financed by EPA.

The demonstration project was carried out at Schuster Farms, located
in Gower, Missouri.  The hog feeding operations are located on Missouri
State Road DD, about 50 (80 km)  north of Kansas City.

Schuster Farms has one of the largest integrated (farrowing and finish-
ing) swine facilities in the United States, with yearly sales of 15,000
butcher hogs.  At full capacity, there are ample facilities for 1,600
sows, 1,500 pigs in weaning pens, and 7,000 hogs in finishing pens, with
300 farrowing beds'and parlors housing 1,600 pigs.

The demonstration system described herein has been designed, constructed
and operated to accommodate the wastes from hogs of known characteristics,
confined in an existing building housing from 700 to 1,000 feeder pigs.

The treatment facility consists of a separate, outside, aerobic biologi-
cal system, capable of producing a biologically stabilized effluent
from raw hog wastes.  This system is readily adaptable to both existing
and new hog raising operations.

Because of the restraints on system design and since the effectiveness
of aerobic biological treatment of hog wastes has already been proven,
this type of system was selected for the demonstration.  In order to
conserve space and, at the same time, to provide a relatively high
degree of treatment at minimal cost, a surface-aerated complete mixing
activated sludge system was employed.

This approach offers several distinct advantages over the more conven-
tional slotted-floor, oxidation ditch concept.

      I.  It can be used with existing confined hog feeding opera-
          tions, as well as with newly constructed facilities.

      2.  It avoids the additional cost of slotted concrete floors
          (approximately $1.10 per square foot  ($11.84/m2) more than
          smooth floors), thus reducing the total cost of confined
          feeding and waste treatment operations.

      3.  A single treatment facility can be sized to treat wastes
          from a number of different buildings, thus affording
          economies of scale and eliminating the necessity for having
          several small, separate treatment systems.

      4.  Maintenance problems are significantly reduced by having
          fewer, more readily accessible parts  requiring repair or

The demonstration project described  in this report was carried out in
several distinct phases:

      1.  The engineering phase, which included actual laying out
          of the demonstration site; detailed  system design in view of
          the effluent requirements; construction; and startup.

      2.  The operational phase, during which  time the system was
          operated and data collected.  Samples were taken periodi-
          cally at various points in the system, over a  1-year period.
          At the same time, pertinent economic data were compiled,
          including  the costs of operation and maintenance and all
          other expenses incurred in handling  and disposing of the

      3.  The analysis phase, wherein the collected data were
          analyzed,  guidelines for future use  were developed, and
          the results of the project were carefully documented—both
          from a technical and economic viewpoint.

The entire project has been result-oriented, with the primary aim of
demonstrating that waste treatment can be accomplished at reasonable
cost  and  with a minimum of inconvenience to  the producer.

The success of this demonstration project is evidenced by both the
results achieved at the demonstration site and by the application and
adoption of the resulting knowledge and techniques to major swine
operations in other areas.

In summary, it is believed that the many lessons learned in connection
with this demonstration project constitute a major contribution to
knowledge in the area of agricultural pollution control.  The techniques
developed at the Schuster Farms demonstration site will prove invaluable
to farmers throughout the United States, and, properly applied, will
aid in achieving the goal of improved environmental quality at minimum

                           SECTION  III


The concept  of  the demonstration waste  treatment system installed by
Schuster  Farms  is quite  simple.  Figure 1  shows  the general  layout of
the facilities  involved.

The waste treatment  facility  consists of a concrete tank equipped with
mechanical aerators.  When  the pens  are cleaned,  wastes are  flushed
through a gutter and  into an  aeration tank where biological  reactions
remove some  95% of the pollutants.   The treated  wastes  flow  from the
tank  to a small pond, where the remaining  solids settle out  and  the
liquid evaporates, leaving  only an inert humus-type material for
spreading on cropland as a  soil conditioner.

The basic unit  in the treatment system  is  a 20 ft x 40  ft x  13 ft  deep
(6.1  m x  12.2 m x 4.0 m  deep) aeration  tank, designed to handle  the
wastes from  a maximum of 1,000 hogs  weighing 220  Ib (100 kg) each.

This  aeration tank is connected to the  feeding floor by an 11 in.  wide
x 6 in. deep  (28 cm wide x  15 cm deep)  gutter system that runs the entire
length of  the building.  The building was  converted from a cattle  feed-
ing barn,  which shows the adaptability  of  this system to almost  any
existing  facility.   There are four individual pens  measuring 70  ft x
55 ft (21 m x 17 m),  each equipped with  self-feeders and automatic
waterers.   Below the aeration tank is a  75  ft x  125 ft  (23 m x 38  m)
settling basin that catches  any overflow  from the  tank.

The cleaning of these pens now consumes  the efforts  of  two men for
1.5 hr every other day.  The only major  piece of  equipment is a  four-
wheel-drive Melroe Bobcat front-end  loader.  The  loader is used  to
scrape the manure from the pens into the gutter.  The second man
scrapes around the feeders and waterers with a shovel and assists  the
Bobcat operator.  Water is pumped from a nearby pond into the gutter
at a rate of about 25 to 30 gal/min  (95  to  115 liters/min) in order to
flush the wastes down the gutter and into the tank.

Biological reactions  taking place in the aeration tank are the key to
the system's effectiveness in eliminating pollution.  In a properly
operating aerobic waste treatment system—one where plenty of oxygen


                                                                   Water for
         Bypass for Use When
         Disinfecting Pens
                                                       Raw Wastes to
                                                       Aeration Tank
                                                                                           11 "Wide by 6"
                                                                                           Deep (28cm x
                                                                                           15cm). Gutter,
                                                                                           Running  Entire
                                                                                           Length of Floor
Concrete Feeding Floor with
Four 70'x 55' (21 m x 17m)
Pens Equipped with Self
Feeders & Automatic Waterers
                                                      20'x40'xl3' Deep
                                                      (6.1m  x  12.2m x 4.0m)
                                                      Reinforced Concrete
                                                      Tank with Two 7.5Hp
                                                      Mechanical Surface
                                                      Aerators Mounted on
                                                      Steel Bridges
                              Treated Wastes Overflow
                              to Settling Basin
Figure 1  -  Swine waste management system at Schuster  Farms

 is available—the wastes are eaten  by  bacteria  and  converted  into  bac-
 terial cells, along with several  inoffensive  by-products:  water  (HoO)j
 carbon dioxide  (CC^), and ammonia (NH3).   The C02 and  NH3  enter the
 atmosphere  as harmless  gases,  leaving  only water behind.   Basically,
 the reaction that takes place  in  a  properly engineered waste  treatment
 process  like this is:
   Organic Wastes + Bacteria -f Oxygen * More  Bacteria + H20 + C02  + NH3

Within an hour,  these bacteria can eat  more than 907. of the waste  materials
dumped in the  tank.  Then, instead of the  tank  being full of  water and
manure,  it contains  primarily water and bacterial cells.  If  the bacteria's
food supply  (the manure in this case) stops,  the bacteria will slowly
starve to death, shrinking to only about a fifth of  their original mass.
These dead bacterial cells form the inert  humus residue from  the system
that ends up in  the  settling basin.

For these reactions  to take place, it is essential that sufficient
oxygen be available.  Otherwise,  the aerobic  bacteria cannot  function,
and the  system will  turn anaerobic, or  septic.   Should  this happen,
methane  and hydrogen sulfide will be generated  as by-products instead
of C02 and ammonia,  and the waste will  stink.   This  commonly  happens
when a rotor breaks  down in an oxidation ditch  beneath  the slotted
floor in totally confined indoor  swine  facilities, or when an aerated
lagoon is overloaded because of poor design or  inadequate aeration


A great deal of  care must be exercised  in  selecting  aeration  equipment
to be used in  treating swine wastes.  Most commercially available
aerators are not designed for this type of waste,  and are physically
incapable of supplying oxygen at  the rate  required,  regardless of  the
claims made for  "oxygen transfer" by sales engineers!  There  are few
manufacturers  of aeration equipment that can effectively and  economi-
cally do the job required in this type of  system.

In the Schuster system, two 7.5 hp bridge-mounted mechanical  surface
aerators (manufactured by Smith & Loveless in Lenexa, Kansas) were  in-
stalled.  They run continuously,  24 hr/day, 365 days/year, to  insure
that there is plenty of oxygen in the tank at all  times.  The  system
design is such that a single aerator, mounted in the center of a 20 ft
x 20 ft x 10 ft deep (6 m x 6 m x 3 m) module will handle the wastes


from 500 full-grown hogs.  Thus, a 1,000-hog operation uses two
aerators in a 20 ft x 40 ft (6 m x 12 m) tank, and a 1,500-hog opera-
tion could be easily handled just by adding another module (with an
aerator) to the tank, making it 20 ft x 60 ft (6 m x 18 m); to handle
the wastes from 2,000 hogs, a 20 ft x 80 ft (6 m x 24 m) or 40 ft x
40 ft (12 m x 12 m) layout could be used.  Any tank configuration is
acceptable, just so it is built in 20 ft x 20 ft (6 m x 6 m) modules
having a 10 ft (3 m) liquid depth and an appropriate aerator mounted
in the center of each module.


The total cost of this particular system ran $12,000, of which about
half was for the two aerators and bridges and the remainder was for
construction of the tank and settling basin, wiring, grading, pipe,

Operating costs, including electric power, maintenance, and depreciation
and interest on the tank and equipment are $4,200 annually.  However,
savings in manure handling over the old scrape, haul and dump method
previously used, amount to nearly $1,600 yearly because of the require-
ment for less labor and equipment, so the net additional cost of this
system  is actually less  than $2,700/year, or $7.40/day.  This is roughly
1/2 cent per pound  (1.1  cent per kg) of weight gain, or $1.00 in addi-
tional  costs on each hog,  spread over its time spent on this feeding

It must be realized, however,  that even  though this  system  is about
the cheapest way to provide  complete environmental  control  in swine
raising operations, the  extra  dollar added  to the cost  of each market-
ready hog represents a substantial portion  of the profit  in that hog.
Eventually, the dollar will have to be  passed on to the pork consumer
as his  cost of environmental protection.


As a direct result of implementing this  program at  Schuster Farms,  the
pen cleaning operation is  now  a faster,  more  efficient  operation than
before, and provides total pollution  control  at a cost  that can at
least be lived with.

The system has proven to have  a number  of advantages,  some  of which are:

1.  It requires little change of existing facilities.  If a
    gutter can be put somewhere in, or by, an existing building,
    this is the only structural change needed.

2.  It requires a small amount of land.  The tank uses a 20 ft x
    40 ft (6 m x 12 m) area.  A lagoon to handle the same amount
    of waste could require as much as 20 acres (8 hectares).  This
    is very important when land sells for $400 or more per acre
    ($989 per hectare).

3.  Cleaning can be done in any weather or season.  It is not
    necessary to wait until crops are out to spread, or to wait
    for a field to dry sufficiently so it can be driven on.

4.  It requires less time, men, and equipment than a conven-
    tional system.  In this case, cleaning requires an hour
    less  than before, one  less man than was used previously,
    and a truck, manure spreader, and tractor are no longer
    needed to dispose of the waste.

5.  There are no mechanical parts  in hard-to-service areas.
    With  an  oxidation  ditch or manure drag chain, there are many
    moving parts  in contact with manure  at all times.  The aeration
    tank  has only  two  rotors  that  revolve in the  top 6 ft  (2 m) of
    the tank.

6.  There is no  runoff to  area  streams  or adjoining farms.   Run-
    off is a problem that  has  closed  down many  large-scale opera-
    tions in the past.

7.  There is no  air pollution.   There is essentially no  odor
     from the tank;  this will  become  increasingly  important as
    cities expand  closer  to the livestock feeding areas.

8.  There is no  solid waste buildup.   Huge waste  piles  serve as
    breeding grounds for  flies and other disease  carriers.
    Disease  spreads quickly in high density  populations  and every
     control  measure can mean the difference  between profit and

 9,   The control measures  employed comply with every existing
     federal  and state law governing feedlot waste removal.  With
     zero runoff, no odor,  and no solid waste buildup,  this sys-
     tem can pass the most stringent laws now on the books or
     proposed for the next 15 years concerning feedlot waste.


At a cost of 1/2 cent per pound (1.1 cent per kg) gain this system has
proven to be an efficient and economical solution to Schuster Farms'
waste disposal problems.


The following 27 photographs describe the operation of the demonstra-
tion swine waste treatment facility, along with some of the problems
encountered and overcome during the evolution of the system as it now

Figure 2, a plan view of the general layout, shows the approximate
location and direction in which each photograph was taken.

 Figure 2 - Plan view of demonstration site showing location and direction of  photographs

Photo 1.  Herein lies the problem.  A feeder pig eats between 3 Ib
and 3-1/2 Ib (kg) of food for every pound  (kilogram) of weight it
gains.  This means, in simple terms, that  for every pound  (kilogram)
of pork, two or more pounds  (kilograms) of pig manure are  generated.

Photo 2.  At present, most pig manure is discharged into the environ-
ment in an uncontrolled manner, often causing serious environmental

Photo_3.   Schuster Farms, located at Gower, Missouri, recognized the
problem and felt a responsibility to do something about it.  This
site—Schuster's Feeding Floor No. 7--was chosen as the location for
a demonstration waste management system.  The pond in the foreground
supplies water to the feeding floor.

Photo 4.  Feeding Floor No. 7, the demonstration site, consists of
an old cattle barn converted to confined swine operations.

                                          *      p~ % "
                                          i      E-
Photo 5.  The facility consists of a concrete feeding floor of some
15,400 sq ft (1,430 m2), fenced into four 70 ft x 55 ft (21 m x 17 m)
pens, each equipped with self-feeders and automatic waterers.

Photo 6.  Each of the four pens has a capacity of some 250 feeder
pigs.  Pigs are placed on the floor at about 30 Ib  (14 kg) and
marketed when they reach around 200 Ib (91 kg), after some 14 weeks,

Photo 7.  An 11 in.  (28 cm) wide by 6 in.  (15 cm) deep gutter runs
the entire length of the floor, sloping down continuously from east
to west (right to left).

Photo 8.  The pens are normally scraped clean at least two or three
times weekly during the summer and once weekly during the winter.
The cleaning process  employs  one man operating a small front-end
loader and another man on foot with a shovel, pushing the wastes
into the gut ter.

Photo 9.  Water pumped from the pond  into  the  gutter  carries the
wastes through the gutter to  the west end  of the  feeding  floor,
where they flow into a small  concrete collecting  trough.

Photo 10.  At the end of the trough, there are two routes that the
wastes can follow.  The drain on the bottom bypasses the aeration
tank.  By putting the plug over the bottom drain, wastes are directed
into the aeration tank.

Photo 11.  Here, the plug is in place and the wastes flow into the
open end of the pipe.

Photo 12.  The wastes flow from the collecting trough through this
pipe .  . .

Photo 13.   . . . and into the aeration tank,

Photo 14.  The 20 ft x 40 ft x 13 ft deep (6.1 m x- 12.2 m x 4.0 m
deep) reinforced concrete aeration tank is equipped with two of
these 7.5 hp, bridge-mounted mechanical surface aerators.  Only the
aerator blades come in contact with the water.

                               , -^_ifm
Photo 15.  The rotating blades on the aerators throw the tank's
contents into the air, thoroughly mixing incoming wastes with the
mixed liquor already in the tank.


Photo 16.  The wastewater thus thrown in the air absorbs oxygen from
the air, necessary for the desired biological reactions to take place.

Photo 17.  Each aerator is located at the center of a 20 ft x 20 ft
(6.1 m x 6.1 m) section of the 20 ft x 40 ft  (6.1 m x 12.2 m) tank,
assuring good, continuous mixing characteristics thoughout the tank,

Photo 18.   The aerators operate continuously, 24 hr/day, 365 days/year,
Overall treatment efficiency falls generally in the 90% to 95% range.
However, since no wastes whatsoever are discharged to the environment,
treatment efficiency has only minor significance.

Photo 19.  The waste treatment facility is relatively inconspicuous.
It is free of odor and insects, and  its electric motors operate

Photo 20.  The liquid in the tank must be maintained at a constant
level to achieve maximum aerator efficiency.  The overflow pipe on
the west side of the tank is set to maintain the optimum liquid
level.  As additional raw wastes are flushed into the tank, an equal
quantity of treated wastes will flow out through the overflow to
be retained in a settling pond for additional stabilization and
ultimate disposal.

Photo 21.  The system has now operated dependably for more than 2 years.
It requires practically no maintenance, causes no nuisances, and need
only be checked occasionally by farm personnel to make sure the liquid
level in the tank is adequate.  Here, the system designer Bill Park (left),
and Schuster Farms' waste management specialist Gary Ellington (right),
discuss the project, obviously unmolested by noise, odors or insects.
The clean, quiet, odor-free operation is one of the system's most
important features.

Photo 22.  The first aeration tank was constructed of concrete  block
by farm personnel.

Photo 23.  The concrete block tank was completed,  the bridges were
mounted on the tank, and the aerators were attached to the  bridges.
Then the process of filling the tank with water began.

Photo 24.  The tank filling process ended shortly after it began.
With the water depth at about 4 ft (1.2 m), a lack of structural
integrity was noted in the west wall of the tank.

Photo 25.  Fortunately, the large cracks that developed in the block
wall permitted rapid evacuation of the  tank's contents and thereby
averted further disaster.  Had the wall collapsed, the mechanical
equipment would have crashed onto the concrete floor below, per-
haps causing irreparable damage.  As it was, however, the equip-
ment was unaffected, remaining in place atop the  fractured wall.

Photo 26.  It was decided that, rather than attempt repairs on the
concrete block walls, a new reinforced concrete tank would offer a
better long-range solution.  Consequently, the equipment was removed,
the block walls were demolished, and the new tank was built by a
contractor on the original foundation and floor slab.

Photo 27.  At first, a major area of concern was the possibility of
freezing during winter operation.  Freezing often adversely affects
mechanical surface aeration systems.  Here, however, the problems
were minimal even during the coldest weather, with the equipment
functioning normally throughout extended periods of extreme cold.
Floating foam sometimes froze, blocking the overflow pipe, but the
problem was quickly corrected.

                             SECTION  IV



Development of design criteria and parameters for the proposed waste
treatment plant, to provide a basis for evaluation of aeration equip-
ment, constituted the first major task in the demonstration project.

Available aeration equipment was carefully evaluated from manufacturers'
literature and from discussions with manufacturers' technical representa-
tives.  Equipment that appeared to be capable of satisfying the specified
design criteria received further evaluation from three standpoints:

      1.  Technical. The oxygen transfer capacity and fluid pump-
          ing characteristics of the equipment were of primary
          importance  in evaluating the expected performance of the
          various types of equipment under operating conditions.

      2.  Economic.   Since a major objective of this project was
          to demonstrate an economically feasible approach to waste
          treatment for the farmer,  the expected cost of aeration
          equipment to farmers who might wish to use it in their
          own future  operations was  an important consideration.

      3.  Convenience.  The ease of  installation and maintenance,
          and the adaptability of the aeration equipment to a wide
          range of operating conditions, made up the third important

Based on these considerations, bids were obtained from manufacturers
of  the aeration equipment believed most suitable for the purposes of
the demonstration project.  After receiving the bids, recommendations
were made regarding the specific  equipment to be purchased.

The equipment ultimately selected for the project consisted of  two  7.5 hp
bridge-mounted, mechanical surface aerators, manufactured in Lenexa,
Kansas,  by  the Smith  & Loveless Division of Ecodyne Corporation.

The necessary reagents and equipment for performing the  chemical and
biochemical laboratory analyses to be used in monitoring the plant
operation were also  prepared  at this time.

It was decided that established laboratory analysis routines would be
adequate for making initial studies of the startup operations.  Then
laboratory studies of the analytical techniques that were made would
permit modification of the routines to meet specific requirements of
the sampling and analytical program best suited to the conditions of
actual operation of the treatment unit.

At first the aeration tank was to be built of reinforced concrete, and
located at the west end of the finishing floor.  These original plans
were, however, altered as follows:

      1.  The aeration tank would be located 50 ft (15 m) west of
          the end of the finishing floor, instead of adjacent to it.
          The purpose of this move was to allow additional flexibility
          in handling slug loads when the pens were cleaned.  Should
          a sudden influx of organic material cause foaming or other
          problems, there would be sufficient room available to build
          a surge basin at the floor drain outflow.  In this way, the
          waste flow to the aeration tank could be leveled out.

      2.  Instead of using reinforced concrete for the aeration tank
          walls, concrete blocks would be employed.  This substitution
          was believed to be desirable for several reasons.

               a.  Most farmers are accustomed to working with
                   concrete block, which can be handled without
                   special equipment and with a minimum of out-
                   side help.

               b.  Concrete block is substantially cheaper than
                   reinforced concrete for this size structure in
                   a remote location.

               c.  By eliminating the need for form work and
                   reinforcing steel, construction could be
                   greatly simplified and could proceed at the
                   farmer's conven ience.

      3.  In the original concept for this system, it was proposed  that
          mixed liquor would be drawn from the aeration tank and pumped
          to the top  (east) end of the finishing  floor drain to provide
          for hydraulic carriage of manure down the drain and back  into
          the tank.  At Floor No. 7, the mixed liquor would have to be
          pumped some 200 ft  (61 m) against a 25-ft (7.6-m) head, re-
          quiring  considerable pumping capacity.  To minimize pumping
          requirements and reduce costs, it was decided instead to  draw
          flush water from a pond above and northeast of the pens.


Meanwhile, with construction under way, all necessary laboratory prepara-
tions were completed.

Tentative procedures for analyzing samples taken from the several pro-
cessing stages in the operation of the waste treatment unit were developed.
The procedures were adaptations of the "Standard Methods of Water and
Wastewater11 techniques which incorporate appropriate modifications for
handling  the types of samples to be available from the process units.
These modifications included sampling techniques, methods for sample
preservation and minor details of analytical procedures.

The nature of  the operation and the distance to the Midwest Research
Institute laboratory where analyses were to be made required that samples
be preserved and transported in a manner that would retain sample integrity,
A tentative sampling schedule was devised  for securing, preserving, and
transporting samples, and reagents and equipment  for  sampling the opera-
tions and conducting the analyses were stocked.


During  the  first  part of this  period, weather problems  hampered  con-
 struction of  the  aeration  tank at  Finishing Floor No.  7, while delivery
 problems  delayed  fabrication of the  aeration equipment.

According to Dr.  Ross  E. McKinney, project consultant,  the  delays were
 probably  beneficial.   Dr.  McKinney felt that biological treatment  systems
 such as this  should not start  up during cold weather, since the  necessary
bacterial activity could not evolve.

 By starting the system during March,  the biological loading in the
 aeration tank should be built up to its normal  operating level in late
 April.   This should provide ideal conditions from an operating standpoint.

 Smith & Loveless reported  that the delay in equipment fabrication was
 caused by their gearbox supplier.   Consequently, they changed gearboxes
 and obtained all necessary components.  The bridges were completely
 fabricated, painted,  and ready for delivery, and the aeration units
 were to be assembled and ready for shipment on March 8, 1971.

 The waste treatment facility was actually completed in May.  The aeration
 equipment was delivered, the steel bridges were mounted on the aeration
 tank, and the aerators were installed on  the bridges.  All electrical
 wiring was completed, the switchgear connected, and the mechanical
 equipment tested.  A drainage system was  devised to permit discharge of
 wastes directly from the finishing floor  into the tank, with provision
  for bypass of wastes should problems arise.  Oxygen transfer tests on


the completed system were scheduled for June 2, 1971.  These initial
tests were to be conducted by the Research Division of Clow Corporation.

The west wall of the aeration tank gave way on June 1.  Fortunately,
the large cracks which developed in the concrete block wall permitted
rapid evacuation of the tank contents, thereby avoiding any more serious
damage.  The mechanical equipment was not damaged and remained mounted
atop the tank, though with less than optimum structural stability.

This temporary setback will provide a valuable lesson to others who, in
their own pollution abatement programs, might otherwise be tempted to
merely duplicate the facility installed here.  The mishap which occurred
clearly demonstrated the importance of sound structural design, accom-
panied by good construction practices.  While economy in construction
is desirable, it should not be achieved by sacrificing structural in-
tegrity.  This small-scale structural failure may well have averted
some future large-scale structural disaster.

Consequently, in order to minimize the possibility of similar problems
occurring in the future, specific tank design and construction details
were developed, clearly delineating all dimensions, construction mate-
rials and reinforcing details.

To restore the damaged treatment facility to an operable condition would
have entailed the following steps:

      1.  Remove bridges, mechanical and electrical equipment and

      2.  Remove the damaged portions of the tank walls.

      3.  Thoroughly flush the tank, and divert the waste stream
          around the tank.

      4.  Drill holes in the floor slab so that a new wall could
          be firmly anchored.

      5.  Pour additional concrete footings for supporting pilasters.

      6.  Replace walls and construct pilasters with reinforced
          block, providing for firm bonds between floor slab,
          pilaster footings, pilasters, and walls.

      7.  Install vertical reinforcing in block holes.

      8.  Pour a 4-in. (10-cm) reinforced concrete cap, tied to the
          block wall and allowing for a strong structural connection
          between the tank and the steel bridges.

      9.  Reinstall the bridges, electrical and mechanical equipment.

Because, at best, the above procedure would have resulted in a patched-
up tank certain to cause considerable mental anxiety among designers,
builders, operators and observers, it was decided to completely scrap
the block walls and arrange with a contractor for construction of a
reinforced concrete tank, as originally envisioned.


The first half of this period could best be regarded as a period for
reconstruction, consolidation and reflection on the valuable insights
gained during the preceding period.

Probably the most important points demonstrated thus far in connection
with the project concerned the many and diverse problems that a typical
livestock producer might be expected to encounter in constructing a
waste treatment facility.  To briefly review just a few of the delay-
causing highlights:

      1.  Rock was encountered during excavation for the aeration
          tank, which necessitated some revision in the original
          plans.  This could pose a serious problem for many farmers
          in constructing below-grade facilities of this type.

      2.  Concrete block was substituted for the originally planned
          reinforced concrete walls, to reduce costs and to permit
          the work to be performed by farm personnel.  While a
          reinforced concrete tank may be somewhat "overdesigned"
          in terms of the anticipated structural loadings, an
          ordinary basement foundation-type concrete block structure
          might be considered equally "underdesigned"  in terms of
          its structural stability.

      3.  Delays in the fabrication and delivery of aeration equip-
          ment were experienced.  This, of course, could be expected
          in almost any type of project.

      4.  The tank broke as it was being filled, strikingly empha-
          sizing the importance of sound structural design and good
          construction techniques.  Thus, between the  original design


          and the actual construction, the problem was "bracketed,"
          with both overdesigned and underdesigned structures identi-
          fied.  The reconstructed tank represents a near optimum
          point between these two extremes.

In summary, a number of important points were clearly demonstrated that
must be considered  in the planning and construction of a livestock waste
treatment facility.  While there was  admittedly some disappointment felt
in having encountered so many problems, it was far better to have ex-
perienced them in connection with a pioneering demonstration project
where the results can greatly benefit those who follow.

Finally, the reconstructed waste treatment facility became fully operable
and evaluation of the system's  operating  characteristics and equipment
performance commenced.

Preliminary oxygen  transfer tests were conducted  on November 17 with
Smith & Loveless research personnel familiar with the equipment.  Some
minor problems were encountered in the tests and  the results were incon-
clusive, though  impressive.

Some dilute swine wastes were present in  the aeration tank, washed in by
rain during the  preceding week. The  oxygen uptake rate  in the tank, as
determined by  Smith & Loveless  in their  laboratory, was  102  nag/liter/hr.

The aerators raised the dissolved oxygen  (DO)  level in  the mixed  liquor
from 0.5 part  per million  (ppm) to 5.5 ppm in  8  min,  an  average net gain
of 0.6 ppm/min or 37.5  ppm/hr.   During this time, the motors were  each
drawing 6.5 actual  horsepower.

Simply adding  the oxygen uptake rate  in the waste (102 mg/liter/hr) to
the net oxygen transfer rate  (37.5 ppm/hr) gave  a gross  transfer rate
of 139.5 mg/liter/hr  in the dilute waste.  For the 50,000-gal.
 (189,250-liter)  tank, this represented a  total oxygen transfer of
approximately  59 Ib/hr  (27 kg/hr), or 4.5 Ib  (2  kg)/hp-hr.   Since
the equipment  was rated by its  manufacturer  at only 4.0 Ib (1.8 kg)/hp-hr
in tap water,  these results were not  at all disappointing, however crude
crude the methods by  which they were  obtained.

Flushing  of  swine wastes  into the  tank was scheduled to  begin  in  mid-
December.  Although cold weather is  admittedly a poor time  to begin
operation  of  a biological  treatment  system,  this schedule would  facili-
tate  a  gradual buildup  of  organic  material in  the tank  and  allow  observa-
 tion  of  the  mechanical  performance  of the system throughout  the winter



Cold weather set in before the treatment system's operating characteris-
tics could be fully evaluated.  Clow Corporation research personnel
attempted some oxygen transfer tests on December 1 and 2, but below-
freezing temperatures prevented their obtaining any useful results.

While biological activity in the waste treatment system was essentially
nil during cold weather, the mechanical performance of the system was
outstanding.  It is difficult to visualize any worse weather conditions
than those that were encountered during the winter of 1971-1972.  Tem-
peratures at the demonstration site reached 17 degrees below zero, and
below-zero temperatures prevailed over an entire week.  Nevertheless,
the equipment continued to operate and the tank contents did not freeze.

Only a few minor problems were encountered during the first 3 months of
operation, most of them related to the weather and none of them serious.

Considerable foaming occurred as the tank was filling with wastes.  This
is to be expected during the startup of any mechanically aerated bio-
logical waste  treatment  system and corrects itself as warmer weather
permits the bacterial action necessary to metabolize the organic mate-
rials in the waste.

A second problem was brought about by the sudden cold weather, which
quickly froze the foam that was floating on top of the water in the tank.
The frozen foam then plugged the overflow drain.  Then, as additional
liquids flowed into the tank, the aerator motors became overloaded and
were shut off by the circuit breakers.  The situation was temporarily
rectified by pumping some liquid out of the tank, dropping the level to
where the aerators could function normally.  A variable-level discharge
device could provide a permanent solution to this problem.

Everything considered, the system operated quite successfully over an
extremely difficult period.  Sampling and laboratory analysis began as
soon as the weather permitted.

Initial oxygen transfer tests on the aeration equipment indicated an
oxygen transfer rate of approximately 3 Ib (1.36 kg)/hp-hr in the waste.
The addition of a 2-day accumulation of wastes to the tank over a 1-hr
period lowered the dissolved oxygen level in the mixed liquor from
9.4 mg/liter to 6.3 mg/liter.  Thus, it appeared that the system would
accommodate considerably heavier loadings than it was currently experi-

The sampling and laboratory analysis program was initiated on April 27.
Samples were taken prior to, during, and after pen cleaning, as follows;

      1.  Raw waste samples were scraped from the feeding floor at
          10 random locations.  The sample included whatever was on
          the floor and could be expected to end up in the aeration
          tank—manure, spilled food, straw, dirt, etc.

      2.  A sample of the mixed liquor in the aeration tank was drawn
          from near the center of the tank at about a 5-ft  (1.5-m)

      3.  While the pen was being cleaned, samples were drawn  from the
          wastes flowing into the tank.  These  samples were taken at
          1-min intervals during the time that  cleaning was under way.
          When cleaning was completed, a sample was taken from the
          composite mixture.

      4.  After the waste inflow to the tank stopped, another  sample
          of the mixed liquor in the aeration tank was taken at the
          same location as  before  (in Sample 2).

All  samples were then placed  in an  ice  chest and  brought  directly  to
MRI  for laboratory analysis.

The  laboratory tests  encompassed both  the manure  characteristics  and
the  treatment  system's operating characteristics.  The  following  tests
were performed:

           1.  Manure  Characteristics (Sample 1)

               a.   Moisture  content

               b.   Ash

               c.   Manure strength

                  (1)   BOD

                  (2)   COD

                  (3)   Organic nitrogen

                  (4)   Ammonia nitrogen

           2.  Treatment Efficiency  (Samples 2, 3 and 4)

               a.  BOD

               b.  COD

               c.  Suspended solids

               d.  Volatile suspended solids

               e.  Soluble solids

               f.  Volatile soluble solids

               g.  Organic nitrogen

               h.  Ammonia nitrogen

               i.  Nitrite nitrogen

               j.  Nitrate nitrogen

The early tests, while inconclusive, did indicate that the system was
functioning satisfactorily, with some 967. of the BOD removed in the
aeration tank.


Sampling and  laboratory analysis continued on a weekly basis throughout
the first 3 months of this period, with interesting results.

The 14-week sampling period was divided into three parts, covering the
first four, middle six, and last four weeks.  This allowed comparison
of waste characteristics and treatment plant performance between the
different periods as the hogs increased in size from a 50 Ib (23 kg)
average during the first period, to 100 Ib (45 kg) during the second,
and 175 Ib  (79 kg) during the final period.  Average hog weight over
the 14-week period was approximately 110 Ib  (50 kg).

Waste samples, scraped from random locations on the feeding floor,
ranged from fresh to 3 days  old  and included manure, spilled feed,
dirt, straw,  and whatever else might be on the floor.  The average
5-day BOD of  these raw wastes was 152,500 rag/liter, substantially
higher than values reported in the literature.

These raw wastes, diluted with pond water used for flushing, made up
the influent  to the aeration tank.  From 1,500 to 2,700 gal. (5,700
liters to 10,200 liters) of water were used for flushing the wastes
through the gutter, the amount depending on how long the floor-scraping
process took.

The raw waste's 152,500 mg/liter average BOD was diluted to 46,440 mg/
liter by the time it entered the treatment tank.  The average effluent—
actually an average of the mixed liquor in the tank before and after
the floor cleaning operation--was 1,680 mg/liter, representing a re-
duction of 96.47=.

Similarly, over the 14-week period, COD was reduced by 91.7%; suspended
solids by 89.3%; and total nitrogen by 89.67..

All sampling techniques and laboratory analyses were conducted in
accordance with Standard Methods, and the week-to-week results were
remarkably consistent throughout the test period.

Additional experimentation was planned for the following period, employ-
ing a new type of aerator.  A single, 7.5 hp, floating aerator (manu-
factured by Roycraft Industries, Kansas City, Missouri), was supplied
and installed totally at the manufacturer's expense for evaluation.  It
was believed that 7.5 hp would provide sufficient mixing and oxygen
transfer for these wastes; the system would thus benefit in several ways:

      1.  Energy costs would be cut in half.

      2.  The capital tied up in equipment would be approximately half.

      3.  The floating unit would maintain optimum performance regard-
          less of the level of liquids in the aeration tank.

In terms of system economics, then, it was hoped that this new approach
would constitute a major breakthrough.   Instead of the $1.00/hog,  1/2 cent/
Ib (1.1 cent/kg) of pork cost estimated  for  the original system, costs
could drop perhaps to the  $0.60  to  $0.70/hog,  1/3 cent/lb  ($0.73/kg)  level.
This, of course, would make it far  more  desirable from the farmer's stand-

The  original  system was  nevertheless  considered an outstanding  success
as a demonstration project, both technically and  in  terms  of the amount
of favorable  publicity  it  received  in newspapers  and  farm  magazines.

The  two bridge-mounted  aerators  were  moved  to the ends of  the aeration
tank and  disconnected,  and the  single floating  unit  moored in place at
the  center  of the  tank.

The  new  installation functioned  smoothly for some time without major
incident,  proving  generally satisfactory in performance  and  dependable
in operation.  Several shutdowns occurred,  all  of which were handled


promptly by the manufacturer, Roycraft Industries, Inc., of Kansas City,
Missouri.  Most of the mechanical difficulties experienced could be
considered normal "startup" type malfunctions, for which the necessary
modifications were made.

Sampling was discontinued with the advent of cold weather when little
biological activity was taking place, pen scraping was irregular, and
fewer pigs were on the feeding floor.

Several observations were worth noting on the overall system performance.
Mechanically, both the bridge-mounted and the floating aerators performed
dependably and continuously even during the coldest weather, with ambient
air temperatures remaining well below freezing for prolonged periods,
and frequently droping below 0* F (-18° C).  The tank contents did not

The floating unit was far less sensitive to variations in the liquid
level in the aeration tank than the fixed, bridge-mounted equipment.
However, the floating aerator was anchored to the tank sides with cables,
and when the liquid level dropped more than about 2 ft (0.6 m), the
aerator was suspended in the air by its cables, hanging above the water.
This could cause considerable damage to the motor.

In contrast, however, the bridge-mounted aerator allows a maximum vari-
ation in liquid  level of only a few inches; even a 1 in.  (2.5 cm) fluctua-
tion affects treatment efficiency by as much as 17%.

It appeared, therefore, that in an operation where equipment care and
maintenance must be kept to an absolute minimum, the floating aerator
might be preferable to the fixed unit,.especially when there is no
continuous inflow to the aeration tank.  The remaining question dealt
with the relative treatment efficiency of  the  two types of  aerators.


 Che treatment system continued to function well during  late 1972 and
early  1973, with several short shutdowns occurring; .these,  however, were
handled by the equipment manufacturer without  incident.   They  switched
to a different and  reportedly  more dependable  motor and experimented
with different  components in order to  find the combination  best  suited
to this  operation.

During late  fall and winter when  pen  cleaning operations  were  conducted
 less  frequently  than  in the  summer,  the  liquid level  in the aeration
 tank  tended  to  drop substantially, necessitating  the  addition  of water
 to keep  it at  a  satisfactory level.   Thus, the treatment  facility was


found to be not only zero-discharge, but negative-discharge; fresh-
water had to be added just to keep the mixed Liquor at a constant
volume.  There was, of course, no discharge of any kind reaching any
rivers or streams at any time.  Tank overflows, when they occurred,
were retained in the settling pond.

There were no complaints of objectionable odors from the treatment

In all, the treatment facility continued to demonstrate that environ-
mental protection could be compatible with existing confined livestock
feeding operations.

The floating "Aerolator" was in service throughout this 6-month period.

Sampling of waste influents and effluents during the time that the equip-
ment was functioning properly indicated highly satisfactory performance
and treatment efficiency, with from 90%-95%of the pollutants removed
in the aeration process.

However, some serious mechanical problems developed in early spring
which eventually led to abandonment of the floating aeration unit.

Blocks of wood  (2 in. x 4  in.  (5  cm x  10  cm))  frequently  found  their
way  into the aeration tank and were drawn into  the  aerator, causing
severe damage on several occasions.  The  source  of  these  boards was
never  found, nor was the means by which they gained entry to the  tank.
Possibly, the boards were  dislodged from  the fence  by the pigs  and
subsequently washed down the  gutter and into the tank.  Or, they  could
have been thrown or dropped  in the  tank.

Nevertheless, the problem  recurred  frequently enough  to be quite  trouble-
some,  both  for  the  operator  and  the manufacturer.   While  the equipment
was  shut down,  solids would  build up  in the  tank and  objectionable odors
would  develop.  Consequently,  it  was decided to  return the two  Smith  &
Loveless bridge-mounted aerators  to service.

Still  there was no  doubt that the floating aerators could do an adequate,
dependable  job, especially if they were  incorporated during the  design
phase  of a  project. The  tank configuration at  the  demonstration site
was  specifically designed  for the bridge-mounted units, and the  problems
associated  with the floating aerator  should  in  no way be  considered a
reflection  on  the equipment.


With the original Smith & Loveless aerators back in service, the waste
treatment system has operated continuously, dependably and efficiently.
The results can be considered nothing less than 100% effective.

The small quantity of wastewater flowing from the aeration tank to the
settling pond dries into a granular substance that has absolutely no
odor.  Surprisingly, there are no flies around the entire tank area.
The system has effectively eliminated all air, water and solid waste
problems commonly associated with confined hog raising.

In summary, the demonstration project has proven remarkably successful
from a technical standpoint.  And economically, the system appears to
offer at least a reasonable solution to what could otherwise become an
expensive problem.

                            SECTION V

                          SYSTEM DESIGN

The waste treatment plant design was based on a hog population of 1,000,
ranging in size from 30 Ib to 225  Ib (14 kg to 102 kg) and averaging 100 Ib
(45 kg) each.  Waste flow, consisting  of urine, manure, spilled food and
water, was estimated at 1,500 gal.  (5,700  liters) daily.  The 5-day bio-
logical oxygen demand  (BOD) of  the raw waste was expected to be around
33,000 mg/liter.

By way of comparison,  the hydraulic waste  loading would be comparable to
that generated by only 15 people,  while the organic loads on the treat-
ment facility would exceed those produced  by more than 2,400 people.  The
raw wastes going into  this treatment plant are more than 100 times as
concentrated as the inflow to most municipal  treatment plants.

In terms of treatment  efficiency,  the  equivalent of conventional second-
ary treatment was desired.  For a  completely mixed aerated lagoon, treat-
ment efficiency is related to detention time, and to  achieve the desired
95% BOD removal attainable in a well designed municipal treatment plant
requires that wastes be held in the aeration  tank for some 30 days.

The detention time and daily waste flow,  then,  set the minimum  tank size
at 1,500 gal. (5,700 liters)/day x 30  days -  45,000 gal.  (171,000 liters).
It was decided to use  a 50,000-gal. tank.

To obtain good mixing  and fluid flow in this  type of  system, the tank
should be set up in square or round modules,  each with a depth  of about
half  its length or diameter.  Square,  rectangular and circular  configura-
tions were examined.

The dimensions required  in these various  shapes were  found to be approxi-
mately as follows:

      Square: 24  ft x 24  ft x  12 ft deep   (7.3 m x 7.3 m x 3.7 m deep)

      Round:  26  ft  diameter x  13  ft deep  (8 m diameter x 4 m deep)

      Rectangular  (two  square modules):  19 ft x 38  ft x  9.5  ft  deep
                                        (5.8 m x 11.6  m x 2.9 m  deep)

These three designs should perform equally well.  However, it was felt
that the depth should not exceed 10 ft (3 m) for several reasons, the
most important one being that a thick layer of rock was encountered at
about that depth.  Also, the smaller module offers better adaptability
to a wide range of operating conditions, and permits the use of smaller
aeration equipment.  Each 19 ft x 19 ft x 9.5 ft (5.7 m x 5.7 m x 2.9 m)
module can accommodate the wastes from 500 hogs, and any size hog raising
operation can be handled by adding modules.

In this case, the aeration tank dimensions were finally set at 18 ft x
38 ft x 13 ft deep (5.5 m x 11.6 m x 4 m) (allowing for a 10 ft (3 m)
liquid depth plus 3 ft (1 m) of freeboard); outside, the tank measures
a convenient 20 ft x 40 f t x 13 ft (6.1 m x 12.2 m x 4 m).

For reasons noted earlier in this report, reinforced concrete construc-
tion is strongly recommended for the aeration tank.  Dimensions and rein-
forcing details are included in the Appendix.


In order for the desired biological reactions to take place in the aeration
tank, the system design must provide for the transfer of adequate quanti-
ties of oxygen  from the atmosphere to the wa'stewater.

This oxygen transfer requirement, in turn,  imposes certain mechanical
requirements on the pumping capacity of the aeration equipment.

The raw waste, with a 5-day BOD of 33,000 mg/liter and an average oxygen
uptake rate of  43 mg/liter/hr, required the transfer of 21.5 Ib  (9.8 kg)
of oxygen per hour at 20° C.  Alpha, the  ratio of oxygen transfer efficiency
in the waste to that in pure water, was estimated at 0.8; beta,  the ratio
of the oxygen concentration in the waste when  fully  saturated  to that
in tap water, was  estimated at 0.7.  The ambient oxygen  concentration  in
the mixed  liquor was  set  at 2.0 mg/liter.   The  general design  parameters
for the proposed swine waste  treatment  plant are summarized  in Table  1.

Given these parameters,  the oxygen concentration of  the wastewater at
saturation  is found  to  be 6.23 mg/liter.
 The oxygen transfer rate in wastewater (1^,  in pounds of oxygen per
 horse power -hour) could then be calculated from the following equation:

Average population

Average hog weight
Average waste  flow
Raw waste BOD5
Aeration  tank  size
              1,000 hogs

                  100  Ib
                  (45  kg)

               1,500 gpd
      (5,700 liters/day)

         33,000 mg/liter

   20 ft x 40 ft  x 10  ft
(6.1 m x 12.2 m x 3.1  m)
Average  oxygen transfer requirement

Average  oxygen uptake rate

Design temperature



Oxygen concentration at saturation (tap water)

Ambient  oxygen concentration in mixed liquor

Tank turnover time (KLa)

 Required pumping rate
              21.5 Ib/hr
             (9.8  kg/hr)

         43 mg/liter/hr

                  20°  C



           8.9 mg/liter

           2.0 mg/liter


         762,000 gal/hr
  (2,880,000 liters/hr)

       R   « the oxygen transfer rate in tap water
       Cgw = the oxygen concentration of the wastewater at saturation
       Ce  « the ambient oxygen concentration in the mixed liquor
       Cgt • the oxygen concentration of saturated tap water
       t   = the ambient temperature

This equation yields the following results;

       R__ = (0.8) (4.0) (6.23 - 2.0^ x (1 Q) „ 1>52 ib/hp-hr
                        \    8.9   )

          - (0.8) (1.816) (6-23 " 2'°| x (1.0) = 0.69 kg/hp-hr
                          \    8.9   /

and the required horsepower is found to be:
so two 7.5 hp mechanical aerators were recommended.

Based on these design parameters, it was determined that the aeration
equipment, in addition to transferring 21.5  Ib  (9.8 kg) of oxygen per
hour, should be capable of pumping at least  635,000 gal/hr (2,400 m3/hr)
of the liquid, thus "turning  over11 the aeration tank's contents at a
rate of 12.7 times per hour,  or  once every 4.7  min.


For mechanical surface aerators  rated at 4.0 Ib (1.82 kg) of oxygen
transfer per horsepower-hour  in  tap water (as most are), actual oxygen
transfer in the mixed wastes  under design conditions will be far less.
Here, only about  1.5 Ib (0.68 kg) of oxygen  transfer per horsepower-
hour is expected, thereby requiring some 15  hp  of installed aeration
capacity.  Since  the system is set up in two modules, two 7.5 hp units
were specified.

Only two mechanical surface aerators were available at the time that
appeared capable  of satisfying both the oxygen  transfer and fluid pump-
ing requirements  of the proposed system.  One was made by Clow Corpora-
tion, the other by Smith & Loveless.  Both claimed oxygen transfer of
4 Ib (1.82 kg)/hp-hr in tap water at 20° C;  both were rated at well over
the required pumping rate—the 7.5 hp Clow unit at 5,600 gal/min (21,100
liters/min) and the comparable S&L aerator at 20,000 gal/min (75,000

After carefully reviewing the performance characteristics of both manu-
facturers1 equipment, the Smith  & Loveless aerator was selected largely

on the basis of its higher pumping capacity; its lower price (approxi-
mately $1,000 per unit); and the proximity of the manufacturer to the
demonstration site.  This last point was considered especially import-
ant for a demonstration project employing a relatively new and unique
concept, although it should not normally preclude consideration of
other potentially acceptable units.

                          SECTION VI


The most significant result of the operation of the demonstration waste
treatment plant over a 2-year period was its clean, dependable, odor-
free operation, conducted without interfering with the normal farm
procedures.  It has provided complete environmental control at nominal
cost and with no inconvenience to the farmer-operator.

Treatment efficiency, important when wastes are discharged into receiving
waters, has little significance in this case.  Nothing is discharged to
the environment except the harmless gases (chiefly ammonia and carbon
dioxide) generated by the biological reactions in the aeration tank.
Solids are retained in the settling basin, drying to an inert, odorless
granular consistency having no particularly objectionable characteristics
and suitable for land disposal.  Liquids simply evaporate.  Should the
settling basin fill because of unusual amounts of rainfall, another pond
will be built and used until the first one dries out.  In terms of over-
all environmental effects, therefore, the treatment efficiency is

Table 2 shows the characteristics of the raw swine wastes being accommo-
dated by the treatment system.  Over the 14-week life span of a hog on
the feeding floor, the 5-day BOD averages just over 150,000 mg/liter;
the COD is 264,000 mg/liter; and the total nitrogen content averages
18,000 mg/liter.

The next table (Table 3) summarizes the effectiveness of the treatment
process over the hogs' life cycle, as they grow from about 30 Ib to
over 200 Ib (14 kg to 91 kg), with corresponding increases in their
production of manure.  As shown in Table 3, 8005 reduction averaged
96.4%; 91.7% of the COD was removed; suspended solids were reduced
by 89.37.; and 89.6% of the total nitrogen was dissipated.

In terms of conventionally measured treatment efficiency, then, this
system operates at a level comparable to the best, most expensive,
modern, sophisticated treatment plants.

                    First 4 weeks  Middle 6 weeks  Last 4 weeks  14-week
                      (4/27-5/18)   (5/25-6/29)      (7/6-7/27)   average

BOD (5-day) (rag/liter)     109,500     175,700        160,500    152,500

COD (mg/liter)             263,100     233,600        309,500    263,800

Moisture content (%)            67.5        66.1           66.9       66.7

Ash (%, wet basis)               5.0         5.6            5.7        5.5

Organic nitrogen (mg/liter) 13,900      13,320         11,680     13,020

Anmonia nitrogen (mg/liter)  6,930       5,430          4,350      5,550

Total nitrogen (mg/liter)   20,830      18,750         16,030     18,570

Average hog weight  (lb(kg))     50  (23)    100  (45)       175  (80)   110 (50)

                   First 4 weeks  Middle 6 weeks  Last 4 weeks  14-week
                    (4/27-5/18)    (5/25-6/29)     (7/6-7/27)   average
Average hog
  weight (lb (kg))

BOD (5-day)
  influent (ing/liter)
  effluent (mg/liter)
  percent reduction

  influent (ing/liter)
  effluent (mg/liter)
  percent reduction

Suspended solids
  Influent (mg/liter)
  effluent (mg/liter)
  percent reduction

Total nitrogen
  Influent (mg/liter)
  effluent (mg/liter)
  percent reduction
    50 (23)
   100 (45)     175 (80)   110 (50)
50,538       64,125     46,400
 2,112        1,967      1,680
    95.8         96.9       96.4
94,400      164,750     99,100
 7,358       12,453      8,210
    92.2         92.4       91.7
80,542      102,520     75,800
 8,002       12,886      8,130
    90.1         87.4       89.3
 6,618        8,616      6,760
   605          920        703
    90.9         89.3       89.6

But, to once more emphasize the most important operational characteris-
tics of the demonstration plant:

           1.  There  is no  objectionable odor; and

          2.  There is no pollutional discharge to the environment.

Construction of the aeration tank and purchase of the mechanical equip-
ment account for the bulk of the capital outlay in a system of this
type.  The total plant investment for a comparable system should run
about $12,000.

Electric power for the two 7.5 hp motors constitutes the major operating
expense, totaling $2,445 annually at a rate of 2.5 cents per kilowatt
hour.  Electric rates will, of course, vary widely among different
utilities and geographic areas.

Here is an approximation of the overall system economics:
      Capital  Costs;
          Construction of Tank
             Aerators  (2 at  7.5 hp)
             Wiring, tubing, etc.

      Operating Costs:

           Power--264 kwhr/day at 2.5 cents
                  = $6.60/day or

           Maintenance and miscellaneous
           Amortization (12 years at 8%)
                       Total Annual Cost

           Savings in Manure Handling

             6 hr/week (one man plus one truck)
               at $5.00/hr - $30.00/week
 $4,245/year or $11.62/day
             or $4.29/day

          Net  Cost:

          $11.62  -  $4.29 =  $7.33/day

          Time on feeding floor:   140 days
          Weight  gain:             195  lb/hog (88.5 kg/hog)

          Net  Waste Treatment Cost Based Upon  Full Capacity
             of 1,000 Hogs:

                ! 000— "  $1.026/hog,  or roughly  $1.00/hog
            Si 026
            f      - $0.0053/lb, ($0.00116/kg), or roughly 1/2 cent/lb
These costs are believed to be within the  limits of economic feasibility
for most large swine producers, and the demonstration project can be
generally considered a success from an economic as well as  technical
standpoint .

Profit margins in pork production hold the. key to the acceptability to
the producer of these costs and of the complete waste management concept.
The $1.00/hog incremental cost of waste treatment may constitute a sub-
stantial percentage of the farmer's net profit.  This additional cost
must eventually be passed on to the consumer.

There is little doubt that society will pay for pollution control
through higher costs at retail, but this is small comfort to the man
currently confronted with making a capital investment.  In other words,
currently, as he markets his livestock, he will not find in the competi-
tive market place that his pigs are worth one cent more for having been
produced in a facility with zero runoff.

The initial impetus for construction of similar facilities, then, is
likely to come from fear of urbanization, from fear of the neighbor's
lawsuit, or from fear of a governmental agency.

Thus, the results of this demonstration offer a ready solution to the
livestock man in trouble.  Here is a system which can be adapted
readily to variable terrain or livestock population.  Waste material
can be guttered or hauled to the tank, and dedication of land is minimal.
Modification to existing facilities likewise is minimal.  The demonstra-
tion and design, then, become practical, workable, and flexible — and
perhaps most important, salable to the livestock man in trouble.


While the swine waste treatment plant described herein was specifically
intended for the operation at Schuster Farms' Feeding Floor No. 7, it
can easily be adapted to virtually any confined swine feeding operation.

The treatment plant itself—consisting of  the aeration tank and the
settling basin—will accommodate  the wastes  from  approximately 1,000
feeder pigs, ranging in size from 30  lb  (14kg) to 225 Ib  (102 kg) and
averaging 110 lb  (50 kg).

Collection of the wastes is a separate function and must  be adapted
to a  particular feeding operation.  Gutters,  sewers, conveyors, or
trucks may constitute an appropriate means of transporting raw wastes
to the treatment  facility, depending on  the  local situation.

The aeration system demonstrated  at Schuster Farms has proven itself
more  than adequate.  Two 5-hp units would, in fact, probably  provide
sufficient aeration capacity  for  most  1,000-hog  operations.

Table 4  shows the minimum aeration  tank  dimensions and aeration equip-
ment  specifications recommended for various  hog  populations.  These
are  intended only as rules-of-thumb,  based on a  tank retention  period
of 30 days and  a  total  waste  flow of  1.5 gal/day/hog (5.7 liters/day/hog).
Either  fixed or floating  aerators can be used equally well, but the
manufacturer  should be  consulted regarding the test shape and type of
aeration tank.

The settling  pond into  which the aeration tank discharge flows  should
be sized according to local rainfall/evaporation relationships.  Properly
 sized,  the pond will evaporate as much water as  it receives.   The pond
 should,  in general, be from 3-5  ft (1-1.5 m) deep, allowing about 1 acre
 (0.4 hectare)  of surface area per thousand hogs—less in dry areas,  more
 in wet regions.

Aeration tank


ft m
18 5.5
23 7.0
26 7.9
29 8.8
50 15.2
52 15.9
56 17.1
58 17.7
60 18.3

of units
Aeration eauipment


Pumping capacity
m /min
a Allow additional depth for freeboard, depending on equipment manufacturer's recommendations.


Aeration Tank

The estimated cost of constructing a reinforced concrete tank having
the general specifications and features of the design given in the
Appendix is

     C » 500 -»• 0.4 d3 + 24 d2
    ( C - 500 + 14.1 d3 + 258 d2)

for a square tank, and

     C - 500 + 0.8 d3 + 40 d2
    ( C - 500 + 28.3 d3 + 431 d2 )

for a rectangular tank, where C = the cost in current (1973) dollars,
and d = the liquid depth in feet (meters).

A 20 ft x 20 ft x 10 ft (6.1 m x 6.1 m x 3.1 m) tank, then, would cost
$3,300 and a 20 ft x 40 ft x 10 ft (6.1 m x 12.2 m x 3.1 m) tank $5,300.

The depth (d) will be half the width; for rectangular tanks, the length
will be twice the width.

Aeration Equipment

Surface mechanical aerators capable of doing the necessary job both
in oxygen transfer and fluid pumping currently cost about $1,700 plus
$170/hp, including controls.  A 5-hp unit, then, would be expected to
cost about $2,550; a 10-hp aerator, $3,400; and a 20-hp unit, about
$5,100.  Costs are essentially the same for bridge-mounted and floating
aerators, the cost of a steel bridge being roughly comparable to a
good flotation collar.

Operating Costs

The total annual cost of a waste treatment system of this type amounts
roughly to the electric power cost plus 20% of the capital outlay (to
allow for depreciation, interest, maintenance, etc.).

The power cost will be approximately $0.50/day/hp, with the electric
rate at 2 cents per kilowatt-hour.  For other rates, the cost would be
directly proportional.

                           SECTION VII

The Appendix covers the construction details of the reinforced concrete
aeration tank installed at Schuster Farms' demonstration site.  As al-
ready described, it will accommodate the wastes from 1,000 feeder pigs,
ranging in size from 30 to 225 Ib (14 to 102 kg).

It must be emphasized, however, that the aeration tank described here
was designed specifically for the Smith & Loveless aerators; different
tank configurations may be required for other units, and manufacturers
should be consulted regarding the optimum tank shapes and dimensions
for their equipment.

Figure A-l is an elevation view of the tank installation at Schuster
Farms' Feeding Floor No. 7.  The tank is located 50 ft (15 m) west of
the west end of the feeding floor, connected by tile drain pipe.  The
slope of the drain is about 5 ft in 50 ft, or 1 in 10.  This slope pro-
vides adequate velocity for hydraulic transport of the manure and other

Figure A-2 is a perspective and sectional view of the tank.  The tank
installed at the demonstration site also has a concrete beam across its
width at the center, connecting the two long walls for additional
support; this is not really necessary, but after the mishap with the
concrete block walls, no chances were taken.

Figure A-3 is a sectional view of the tank, locating the inlet and out-
let.  The outlet height must be determined experimentally, since the
aerators push large volumes of water toward the sides.  An adjustable
outlet structure is therefore recommended, so that the liquid level
can be kept at the top of the rotor blades when the equipment is operat-

Figure A-4 is a plan view of the tank and a logitudinal section.
Figure A-5 covers the reinforcing details and shows how the tank walls
should be keyed into the floor slab.

                 Liquid Level
                                                  •50'± (15m)
                                   Tank Inlet
                                                        5*  (1.5m)
                                                     10'-9" (3.3m)

                                               ELEVATION VIEW
                                                                                    Existing Floor
Existing  Drain Outlet
               Figure A-l - Location of aeration tank with  respect to existing facilities

18'x38'xl3'Deep Inside
20lx40'xl3'Deep Outside
(5.5m x  11.6m x  4.0m Deep Inside)
(6.1m x  12.2m x  4.0m Deep Outside)
       Figure A-2 - General  configuration of aeration tank



-3« 10'-
cm) (328


  INLET & OUTLET: 6" (15.2cm) Set at Center of Long
                   (40'; 12.2m) Sides at  Heights Shown
Figure A-3 - Location  of  aeration tank inlet and outlet

                                                                        SEE DETAIL
                                         PLAN VIEW
                                        SECTION A-A
                     Figure A-4  -  Plan view and  section of aeration tank

                                                       2" (5cm)
                                                      8" (20.3cm)
                                                     _ 4 _
                                                        4  2"
                                             '4 BARS
                                        DETAIL B
                                                    '5 BARS-
*4BARS (2'-0" O.C.)


                                                      6"x6" -10/10 MESH
                                                   .,— (15.2cm x  15.2cm)
                       3"(7.6cm)      4" (10cm)  /
                          A   /	t	L
             (50.8cm)      (15.2)
                          REINFORCING DETAILS
           Figure A-5 - Aeration tank reinforcing  details

                    11. Report No.
• 3.  Accession No.
   4,  Title

                                         5,  KepvrtDat*


                                         8.  t rforating Or gar. i zatiott
   7.  Aathor(s)

 Park, William E.
   9,  Organization
 Midwest Research Institute
 425 Volker Boulevard
 Kansas City, Missouri 64110
                                         10.  Project No.
                                            13040 EVM
                                            Contract I Gtatst No.
                                            13040 EVM
   12.  Sr -nsorin ~ Organ1' it/on
                                         13  Type ^-i Repot <. and
                                            Period Covered
                         U. S. Rmrirnnmgntal  protection Agency
   15.  Supplementary Notes

     Environmental Protection Agency report  number, EPA-660/2-7U-OU7,  May
   16.  Abstract
 A waste treatment system was installed  in conjunction with an existing  confined swine
 feeding operation at Schuster Farms, Gower, Missouri.  The system consisted of a
 concrete aeration tank equipped with mechanical surface aerators, followed by a settling
 pond.  Wastes  from the 1,000-hog feeding  operation were flushed through a gutter in the
 concrete feeding floor into the aeration  tank,  where they were aerobically digested.
 All aeration tank discharges were retained in the settling pond where the liquids

 The waste treatment facility operated continuously and dependably over  a 2-year period,
 with treatment efficiency averaging 90% to 95%.   The system effectively controlled
 objectionable  odors and insects, contained all  liquid runoff emanating  from the feeding
 operation, and left only a dry, inert residue suitable for land disposal.

 Installation cost for the system was $12,000.   Net operating costs, including
 amortization of capital costs, were $7.33 per day.  Thus, total environmental control
 was achieved at a cost of approximately $1.00 per hog, or 1/2 cent per  pound (1.1 cent
 per kilogram)  of weight gained while on the feeding floor.
  17a. Descriptors

 Hogs, Waste treatment, Aeration, Settling pond

  17b. Identifiers

 Odor control, Economics,  Surface aerators, Flushing gutters, Aerobic digestion
  l~c. COWRR Field & Group
  18.  Availability
19. Security Class.

">!}. SecirityCJ 5s.
                 21.  ffo.of

                 J3.  Pr/cs
                                                        Send To:
                                                        WATER RESOURCES SCIENTIFIC INFORMATION CENTER
                                                        US DEPARTMENT OF THE INTERIOR
                                                        WASHINGTON. D. C. 2O24O
WRSIC 1O2 i«£V JUNF 197 !'•
            | Institution