United States
Environmental Protection
Agency
Robert S. Kerr Environmental Research^
Laboratory
Ada OK 74820
Research and Development
EPA-600/S2-83-023 July 1983
SERA Project Summary
Optimization of Wastes
Treatment with Reference to
Biogas and Protein Recovery
Jan A Oleszkiewicz and Szymon Koziarski
Detailed technological and economic
evaluations of the presently used treat-
ment processes for the dilute waste-
waters from hog farms, with capacity
exceeding ten thousand head, is pre-
sented. The present systems of treat-
ment for stream disposal encompass
sophisticated multi-stage chemical-
biological treatment with high unit
cost due to consumption of power, oil,
and chemicals.
The intent of the research part of the
project was the optimization of the
unit process and whole treatment trains
selection, rather than unit process
operational parameters. The unit pro-
cesses investigated in the laboratory
and pilot scale included: sedimenta-
tion, coagulation, activated sludge as a
roughing unit and as a polishing unit
algal-bacterial (oxidation) polishing
ponds, anaerobic digestion in flow-
through and contact reactors with
suspended microorganisms and in an-
aerobic biofliters, anaerobic ponds,
aerated lagoons, and yeast generation,
as a method of treatment and protein
recovery.
The results indicate the need for
diametrical shift in research emphasis
in animal wastes, towards high-rate,
short detention time anaerobic unit
process combined with high-rate aero-
bic secondary treatment and anaerobic-
aerobic polishing treatment Several
fu 11 technological treatment trains were
evaluated and compared from the stand-
point of treatment efficiency, level of
recovery, ease of maintenance and
economic efficiency indices. The sys-
tems recommended were comprised
of anaerobic biofiltration or contact
digestion followed by anaerobic biofil-
tration, anaerobic biofiltration and
reaeration, with anaerobic sludge di-
gestion as a separate sludge train or
incorporated in the wastewater treat-
ment train. Economic analysis has
shown that the application of these
new treatment trains can make in-
dustrial-scale farming more profitable
with the increase in the size of the
farm. This is contrary to the presently
observed trend toward limrtingthe con-
struction of large farms, due to the
environmental constraints. The pre-
vailing trend stems from the applica-
tion of either conventional wastewater
treatment technology to these concen-
trated effluents or application of agri-
cultural utilization practices as used
for concentrated manures from smaller
farms.
The technology proposed in the pro-
ject shows an increase of the economic
efficiency, when compared to conven-
tional systems. The new technology
incorporates biogas recovery and a
sludge treatment subsystem in the
overall treatment-recovery train. Al-
though the report is confined to swine
wastes, the results are applicable to
other concentrated effluents from the
agricultural industry.
This Project Summary was developed
by EPA's Robert S. Kerr Environmental
Research Laboratory, Ada. OK, to an-
nounce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
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Introduction
Project Aim
The shortage of litter and the growing
demand for animal protein have caused
several countries to turn to industrial-scale
animal production. Large hog production
plants in central Europe usually house
from 10 to 40 thousand animals. In
several instances, larger farms were built,
notably in Romania and the USSR, where
the size may approach 250 thousand
hogs. The magnitude of operational prob-
lems and the environmental requirements
associated with these enterprises can be
realized by taking into accountthe fact that
a 36.5 thousand hog farm will require
annually over 1.9 x 108 watthours of
power, up to 18 x 106 kg of fodder and
close to 3.2 x 105m3 of water.
Figure 1. (A) illustrates the hog pro-
duction trends in two countries, Holland
and Poland. Figure 1. (B) shows the
increase of industrial-scale hog and cattle
production in Poland. It should be noted
that industrial-scale farms are responsible
for a much larger segment of overall pig
production in such countries as the German
Democratic Republic (29 percent), Hungary
(47 percent), Romania (60 percent), and
Bulgaria (65 percent). Due to technical
constraints, new farms are frequently sited
in areas unfit for land disposal, and the
inevitable stream discharge of effluents
requires the highest practicable treatment
technology.
The overview of foreign practice in pig-
gery wastewater treatment obtained during
visits to plants in USA, Italy, Holland, and
Scotland, as well as through the literature
perusal, revealed the lack of data on treat-
ment of dilute wastewaters. The trends in
these countries is to keep the farms small
and manure as concentrated as possible
through recycle and decreased water con-
sumption. Thus, available information
concerns concentrated effluents for which
the process economics are different The
project report fully describes and character-
izes the full-scale treatment of dilute pig
wastes and evaluates the technological,
economic, and environmental applicability
of the novel alternative wastewater treat-
ment processes featuring biogas produc-
tion and single-cell protein recovery.
Project Scope
Based on mail surveys, literature data,
field trips, and on-site long-term round-
the-clock surveys, a summary of the hog
production and wastewater treatment
trends is presented. Treatment effects are
described and the economic efficiency of
various practiced unit processes is critically
.8,
21
20
19
18
17
16
15
14
13
12
22
18
14
10
6
2
• - Poland
o - Holland
1960
1970 1977,
Years
•I
Q.
12
10
8
6
4
2
1970 1980 1990 2000
Years
Figure 1. (A) Overall hog production in
two countries; (B) Planned pro-
duction increase of the industri-
al farms in Poland.
evaluated. Both practiced and promising
future polishing treatment processes are
discussed. In-depth feasibility studies are
presented, leading to the optimization of
the operation of current systems treating
effluents for stream disposal and novel
systems proposed forfuture use. Finally, a
set of proposals is given setting forth the
required treatment for stream disposal, for
agricultural utilization, or for combined
treatment with other effluents. The pro-
posals are based on a comparison of costs,
treatment effects, and non-economic factors
which are beginning to play an important
role in the agricultural industry (e.g. the
shortage of qualified manpower, sight and
odor nuisance, lack of adequate land for
agricultural disposal).
Technical Conclusions
The project is aimed at optimizing exist-
ing treatment systems for dilute effluents
from large piggeries, at optimization of
loadings and sequence of unit processes
and operations for piggery wastes. The
project also places new waste treatment -
recovery systems in the proper economic
and technological perspective. The project
topics could be grouped as follows: a)
detailed technological and economic anal-
yses of presently used waste treatment
systems (WTS) for dilute wastewaters for
several large industrial pig farms; b) an in-
depth analysis of results of laboratory- and
pilot-scale studies of 14 individual unit
processes for treatment of pig wastes; and
c) application of results to the design and
economic assessment of 12 new complete
WTS for two types of large pig farms with
partial effluent recycle (i.e. water use 20
dm3/ hog/day and without recycle, i.e.
28 dm3/ hog/day).
Operation of today's sophisticated chemi-
cal-biological waste treatment system re-
quires close cooperation between farm
managers and WTS personnel to keep
hydraulic loads within the design limits.
Generally, these systems are vulnerable to
influent variability, are highly inefficient,
and, as costs rise for power, imported
chemicals, and oil, are increasingly expen-
sive to operate.
Research in this project shows that
piggery waste treatment systems should
include a sequence of high-rate processes
followed by low-rate low loading processes.
Chemical treatment should be replaced by
plain sedimentation and/or anaerobic pre-
treatment The use of activated sludge
should be limited in the high-rate pro-
cesses class and excluded from the low-
rate processes class. Oxidation ponds as a
polishing WTS should be used in combina-
tion with fish cultivation as a method of
biomass harvesting.
The comparison of the various modes of
anaerobic digestion shows that dilute pig-
gery waste should be treated in systems
having high solids retention time (SRT),
low hydraulic retention time (HRT). Gas
production and sludge build-up decrease
with increasing solids retention time, while
the removal ratio and process stability
increase. The recovery of gas is econom-
ically efficient even at today's power costs,
because the anaerobic processes pro-
posed provide large removals of organics.
The recovery of single cell protein (SCP)
through aerobic fermentation is found
feasible; however, the present costs of
protein and nutrients (N and P) make it
uneconomical from the standpoint of both
the SCP production and waste treatment.
Large carbon supplementation is required
in order to fully utilize the nutrients con-
tained in piggery wastes.
In all cases, the alternative of combined
treatment with other, nutrient lacking, ef-
fluents should be investigated because
the benefits are usually much higher than
the cost of long-distance pressure trans-
port systems.
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Long detention time lagoons (anerobic-
aerated - oxidation) are a viable WTS, easy
to implement and operate in rural condi-
tions. The most efficient WTS, however,
includes mesophilic anaerobic biofiltration
(ANBIOF) followed by aerobic biofiltration
and polishing anaerobic biofiltration. The
system utilizes most of the methanogenic
potential of wastes by means of a separate
anaerobic sludge digestion in an anaerobic
flow-through reactor without recycle
(ANFLOW) or anaerobic contact reactor
with sludge recycle (ANCONT).
The ANBIOF type reactor should always
be incorporated in any treatment system
as a first or second stage anaerobic diges-
tion, since it significantly improves pro-
cess stability and allows (as a second
stage after an ANCONT reactor) for an
increase in organic loading without im-
pairing the gas production or organics
removal efficiency.
The major error in disposal of dilute
piggery wastes in Europe, up to recent
times, was the application of either con-
ventional wastewater treatment technology
or the use of manure utilization systems
applicable to concentrated wastes. Based
on numerous examples of difficulties in
disposal of piggery effluents, large indus-
trial farm complexes are nowthoughtto be
economically and technologically inefficient
This project has shown that this is not
necessarily so, at least from the standpoint
of WTS. The accumulation of large organic
loadings and relatively tow volumes of wastes
may be regarded as an advantage in novel,
energy efficient, highly reliable gas and
nutrient recovery WTS, such as demon-
strated in this report
From the standpoint of the economics
of waste treatment piggeries with capacity
smaller than 5,000 head should rely on
land disposal. If stream disposal is the
final goal the size of the farm should not
have to be limited, since the proposed
technology of anaerobic wastewater treat-
ment and sludge disposal improves its
efficiency with the increase of farm size.
Another factor improving the efficiency of
the proposed systems is the decrease of
fresh water use through recycle of treated
wastewaters.
Outline of the Economic
Analysis
Economic optimization of waste treat-
ment/recovery systems is a complex pro-
cess, which, if done correctly, requires
sophisticated mathematical modeling and
computer simulation of unit processes
performance within the treatment train.
However, the effects of the sophisticated
approaches (which include presumably all
of the foreseeable variables) frequently
may not be representative due to an in-
adequate data base assumption. In the
case of animal wastes, most available data
are not consistent as to the actual price of
biogas, recovered protein, and the costs of
comparable unit processes. Due to varia-
tions in the technological and construction-
al know-how of treatment facilities, it is not
possible to apply literature data to pro-
cesses derived in this work.
To summarize the literature search, it is
impossible to gain any knowledge of the
true economic efficiency of the anaerobic
digestion as a waste treatment method,
with an additional gas recovery, based on
literature data Similar situations exist in
literature on economics of SCP recovery.
The authors decided that a special eco-
nomic analysis would have to be made in
this case of dilute piggery wastes from
typical industrial piggery -farms. The
method of analysis used assumes a ten-
year period of amortization of the capital
investments. The costs and economic
efficiencies of COD removal and of volume
of flow removal are based on current
1980 data.
In order to make economic comparisons,
several different treatment systems were
synthesized for two different sized farms
(10,500 and 15,000 head) using actual
field data. System I is consistent with the
now prevailing concept of rural treatment
plants consisting of earthen basins (an-
aerobic lagoons, oxidation ponds, and agri-
cultural utilization), which can be built by
local agricultural enterprises and that are
easy to operate. It should be noted that
costs are high for this system because of
low treatment system efficiencies System
II is the most complicated from an opera-
tional standpoint System II features an
ANFLOW reactor with a ten-day hydraulic
retention time followed by a thickener and
two-stage activated sludge tanks.
System III is similar to System II in the
primary, anaerobic, part of the treatment
train. The secondary part of System III is
much simpler to operate, has a larger
specific biogas production, a high-rate low
volume secondary treatment in an aerobic
biofilterand an anaerobic polishing biofilter.
System IV features a shorter detention
time anaerobic digestion in the ANCONT
reactors. Based on our experimental
evidence, System IV will have only a
slightly lower biogas production rate when
compared to System III. System IV offers
a much smaller volume of anaerobjc diges-
tion and a high removal efficiency making
for a more stable operation than the other
units.
System V features a setting/thickening
tank which feeds clarified wastes through
a heat exchange to the anaerobic biofilter,
where over 80 percent of the COD is
removed The secondary part of System V
consists of two-stage activated sludge
system, aerobic biofilter, followed by an-
aerobic biofilter and a polishing unit This
management allows for sludge treatment
in a separate ANFLOW reactor while the
low concentration wastewater is treated
by the anaerobic biofilter, thereby allowing
both systems to operate at optimum con-
ditions.
System VI features anaerobic pretreat-
ment of clarified wastewater for pathogen
destruction and odor stabilization followed
by three months storage prior to land
disposal and agricultural utilization.
In all systems, sludges and/or separated
solids are air dried and/or composted and
applied to land in some manner. Some is
used on land controlled by the pig farms
and some is sold or given to private
gardeners and farmers. Since larger pig-
geries are frequently sited close to large
municipalities and/or with industrial com-
plexes or areas otherwise unfit for land
disposal, the study investigated combining
pig wastes with other waste streams for
treatment Three possible treatment
combinations are discussed:
1. Production of yeast for feeding to
animals using piggery wastes and
combining these wastes with in-
dustrial yeast plant wastes;
2. Combined anaerobic digestion with
municipal sludge for biogas recovery;
and
3. Combined treatment with nutrient
deficient industrial wastes.
Economic Conclusions
The so-called "natural" treatment sys-
tems featuring lagoons, oxidation ponds,
earthen structures, and agricultural utiliza-
tion (land disposal). Systems I and VI, have
been proved less economical for the
modern, large scale industrial pig farm,
which uses water in excess of 20 dm3/
hog/d, than the new systems proposed in
this project These new systems utilize full
biogas recovery and anaerobic treatment
System V.
Systems I and VI are, however, still more
economical than the presently used chemi-
cal-biological systems and some of the
anaerobic treatment systems now pro-
posed by various sources.
The high concentration of nutrients in
piggery wastes makes these effluents an
ideal substrate for combined treatment
with high-volume, low-concentration,
nutrient-deficient industrial wastes.
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Location of pig farms close to municipal-
ities creates an opportunity of combining
the separated solids from municipal sew-
age with pig wastes for a more efficient
biogas recovery operation.
The location of pig farms within agricul-
tural complexes creates an opportunity to
combine other concentrated effluents for
gas recovery, waste heat utilization opera-
tions m AN FLOW or ANCONT type di-
gesters.
The report concludes that pig farms
should have a capacity much lower than
10,000 head if agricultural utilization is to
be practiced. If larger farms are erected or
where land disposal is not feasible, the
piggery wastes should be treated in com-
bination with other industrial effluents or
municipal sewage. Due to the increased
size of such combined waste treatment
facilities and the concurrent generation of
marketable products (biogas and digested
sludge or compost), a better quality of
operation can be maintained than in local
plants. The decrease in capital costs is
usually significant (e.g. 20 to 25 percent)
despite the frequent need for transporting
the wastes to the central treatment plant
(CTP) site. The decrease in running costs,
even without accounting for the recovered
biogas, for the joint treatment facilities
may be as large as 20 to 50 percent of the
sum of these costs at individual plants.
In all cases, advanced biogas recovery
high-rate, treatment systems are more
technologically and economically efficient
than the present treatment systems and
will become the only alternative with the
increasing energy shortage.
Recommendations
Existing piggeries should initiate a pro-
gram of changes in water distribution and
sewerage systems to cut down the water
use, increase the temperature and concen-
tration of raw wastes, and apply recycle
with purified wastewaters for flushing
purposes.
Full-scale implementation of the pro-
posed anaerobic treatment systems is
needed; the design work is presently being
completed. Full-scale polishing oxidation
ponds are being constructed. A three-year
period of studies should encompass various
techniques of biomass growth enhance-
ment in cold conditions such as greenhouses,
mixed populations, and recycle. Fish culti-
vation should be researched as a method
of biomass harvesting and biological sludge
disposal.
New anaerobic treatment processes
such as phase separation and selective
organics removal systems might further
reduce the volume of anaerobic fermenters.
The majortrend in animal waste treatment
technology should be the further optimiza-
tion of gas recovery and utilization of
waste heat, as the rising power costs will
rapidly increase the applicability of anaerobic
digestion to concentrated organic effluents.
The work on yeast production should be
continued with other types of yeasts such
as those that require less of the readily
available carbon. Studies on continuous
cultures, mixed yeasts populations need
to be continued, since further rises in
protein prices should yield the process
more economical.
Methods of direct refeeding should not
be pursued as much as the methods of I
conversion into high protein feedstuffs^
Further studies should be conducted irW
open rather than in close cycles, i.e. feeding
other kinds of animals.
Wide technology transfer and agricultural
extension programs are needed in order to
show the growers, animal husbandry
specialists and the agricultural industry as
a whole that animal wastewaters can be
treated efficiently at any level of dilution, at
any volume and in any location. The new,
more sophisticated technology required
can be achieved with proper liaison be-
tween the producer and the sanitary
engineer.
This project has been conducted within
the frame of a bilateral financial arrange-
ment the Maria Sklodowska-Curie Fund
for cooperative programs between Poland
and the United States. The work has been
accomplished between October 1, 1976
and November 30,1980, by the Research
Institute on Environmental Development-
Wroclaw Division and U. S. Environmental
Protection Agency- Roberts. Kerr Environ-
mental Research Laboratory in Ada, Okla-
homa.
Jan A. Oleszkiewicz in with Duncan, Lagnese and Assoc.. Inc., Pittsburgh, PA
15237 and Szymon Koziarski is with the Research Institute on Environmental
Development, Wroclaw, Poland.
Lynn R. Shuyler is the EPA Project Officer (see below).
The complete report, entitled "Optimization of Wastes Treatment with Reference
to Biogas and Protein Recovery," (Order No. PB 83-183 020; Cost: $20.50,
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Robert S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
P.P. Box 1198
Ada. OK 74820
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
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