United States
Environmental Protection
Agency
Municipal Environmental Researc,
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81-173 Oct. 1981
Project Summary
Demonstration Physical
Chemical Sewage Treatment
Plant Utilizing Biological
Nitrification
James F. Kreissl and Ronald F. Lewis
This study involved the design, con-
struction and operation of a hybrid
physical-chemical (P-C) biological
treatment facility. Evaluation of this
system was based on two factors: its
utility as a transportable facility for
interim high quality treatment of
wastewaters at different locations and
its value as a treatment concept to
incorporate the best attributes of both
methods (P-C and biological) of treat-
ment.
Although the system produced a
consistent, high quality effluent, its
utility as a transportable system was
only partially demonstrated and its
viability as a treatment sequence
could not be confidently stated due to
several design and operational prob-
lems.
This summary presents an overview
of this joint USEPA-DHUD project.
This Project Summary was devel-
oped by EPA's Municipal Environmen-
tal Research Laboratory, Cincinnati,
OH, to announce key findings of the
research project that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
Experience has shown that a need
exists for flexible and efficient sewage
treatment units able to meet the ever
more stringent regulations imposed by
government. Urban fringe developments
are particular problem areas that
outstrip the service ability of urban
sewage authorities.
Small housing, commercial, and
public developments spring up beyond
the range of central sewage transport
systems and must have acceptable
sewage treatment on a permanent or
temporary basis. Often, the temporary
nature of the treatment facilities com-
pounds the problem, resulting in heavy
capital equipment outlays prorated over
relatively short time perfods. The small
size and nature of such development
areas frequently provide flow variations
that are not conducive to effective
biological treatment. Daily, as well as
seasonal, fluctuations may be extreme
in both hydraulic and organic loadings.
The need for treatment processes that
can be placed in service quickly and with
a minimum of delay to meet strict
effluent limitations has long been
recognized. Development areas on
urban fringes frequently discharge to
small streams with neither little dry
weather flow nor periodic high rainy
weather flow and effluent limitations
are generally based on the most
extreme low flow conditions.
This demonstration project was
conducted to show that wastewater
could be treated in a physical-chemical
wastewater treatment plant employing
a biological intermediate stage for
oxidation of nitrogenous material to
produce a high quality effluent and
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provide different treatment levels to
meet a variety of effluent requirements.
The physical-chemical plant chosen
was of a modular design employing
high-rate processes which normally
facilitate a relatively speedy installation,
a minimum amount of lag time to
produce the desired effluent quality,
and ease of transport for relocation to
other critical areas when needed.
The plant was located in the drainage
area of a planned residential develop-
ment known as Beechgrove Village in
the southern part of Kenton County,
Kentucky. The wastewater was domestic
in nature, with no commercial or
industrial sources.
Facility Description
The facility consisted of a modular
physical-chemical (P-C) wastewater
treatment plant which was skid-mounted
for ease of transport, an intermediate
biological nitrification tower, an equali-
zation tank and a sludge holding tank.
Any of these ancillary units to the P-C
plant could be constructed of materials
which would facilitate relatively fast
startup at a new location. Sizing of the
plant components was based on a flow
of 190 cu m/d (50,000 gallons per day).
The treatment process sequence con-
sisted of screening, flow equalization,
chemical flash mix, flocculation, clarifi-
cation, pH control, biological nitrifica-
tion, filtration, granular activated carbon
adsorbtion, and chlorination. Excess
sludge from the clarifier was periodically
transferred to the sludge holding tank
from which settled solids were occa-
sionally transported by truck to a
disposal site. A treatment process flow
schematic of the demonstration plant is
shown in Figure 1.
Influent Flow Control
Wastewater for the demonstration
plant was taken from an existing man-
hole above the lift station serving the
Beechgrove Village development. A
diversion dam within the manhole
provided a flooded section from which
the demonstration plant was fed. In the
outlet pipe (0.2 m in diameter) an air-
activated pinch valve was located in the
flooded pipe which, when activated by
liquid level controls in the equalization
tank, opened and allowed diversion of
the wastewater to the demonstration
facility through the 845-m gravity line.
The level controls were of the solid-rod
type located directly in the main
equalization basin. Signals from the
electrodes were transmitted via a
telephone circuit to a solid-state control
relay located near the pinch valve. The
relay in turn controlled a 3-way solenoid
valve which was installed in an air pipe
between the pinch valve and an air
compressor. The air pressure in turn
activated the pinch valve. Excess waste-
water flow was discharged to the
existing sewer from the manhole
overflow.
Flow Equalization Tank and
Screening
A bar screen with approximately 25
mm (1-in) openings was located in the
influent structure of the flow equaliza-
tion tank to remove larger objects that
might damage the system. The flow
equalization tank consisted of a rec-
tangular 75.7-cu m (20,000-gal) pre-
fabricated coated steel tank and in-
corporated a diffused-air system to
ensure solids suspension and mixing
and also to maintain aerobic conditions
during storage. The buffer capacity of
this tank allowed continuous operation
during normal low flow conditions
encountered at night. The tank also
received filter and adsorber spent back-
washes. In addition to the influent flow
control liquid-level sensors, electrodes
were also installed to provide emergency
shut down of the remaining treatment
processes in the event of low level
conditions in the flow equalization tank.
The wastewater was pumped from the
flow equalization tank to the treatment
unit by a constant-speed, progressive-
cavity pump.
Chemical Clarification
Chemical clarification was achieved
using hydrated line fed at a periodically
adjusted constant rate in a 10 percent
slurry form. Lime slurries were made up
on a daily basis using commercial
hydrated lime in 22.7 kg (50 Ib) bags. A
1.363-cu m (360 gal) plastic tank served
as the makeup and storage tank. Con-
stant mixing of the lime tank was
provided to maintain the slurry using a
0.37 kw (0.5 hp) constant-speed mixer.
Lime slurry was fed to the 0.25-cu m
j(65-gal) flash-mix tank using a variable-
speed, diaphragm-type slurry metering
pump. A constant-speed mixer provided
thorough mixing of the lime slurry with
the incoming wastewater from the
equalization tank. Theoretical detention
time within the flash mix unit was 1.87
minutes at the design flow rate of 190
cu m/d (50,000 gal/d).
Flocculation was provided in a square-
shaped 2.16-cu m (570-gal) tank. J
Agitation was carefully controlled using [
a variable-speed, vertical-shaft mixer.
Theoretical detention time was 16.2|
minutes at design flow rate.
Flow from the flocculation tank was!
introduced to the 17.83-cu m (4,710-
gal) circular clarifier through a distribu-
tion box which channeled the flow to a I
peripheral-feed inlet near the bottom of I
the clarifier. A theoretical detention!
time of 135 minutes was available in the I
clarifier at the design overflow rate of 261
cu m/sq m/d (640 gal/sq ft/d). The!
design, overflow weir rate was 21 cul
m/m/d (1,700 gal/ft/d). The clarifierj
was equipped with motor-driven sludge!
raking and skimming and an effluent!
"V-notch" weir around the circumfer-f
ence of the tank.
pH Control
A neutralization step was necessary!
following lime clarification in order tol
prevent deposition of calcium carbonate!
in subsequent processesand to facilitate!
the biological nitrification process. For!
large-scale systems this is often ac-l
complished by recarbonation of the high!
pH clarified wastewater with carbon!
dioxide (COz). For this facility, sulfuric|
acid was used because of the capita
cost and space savings inherent in this
approach.
Sulf uric acid was purchased in 49- orl
57-liter (13- or 15-gal) plastic carboys,!
and the required solution was made up!
daily. A 0.3-cu m (80-gal) plastic tank!
was used for mixing and storage of the!
20% sulfuric acid solution. A small!
mixer was installed in this tank tol
ensure the initial blending of the water!
and acid. A variable-speed chemical!
feed pump was used to transfer the!
solution to the 0.19-cu m (50-gal)|
neutralization tank for the lime-clarified!
effluent. Thorough mixing of the acid I
feed solution and high-pH effluent was!
provided. The tank was equipped with!
electrodes for pH measurement which!
provided signals to the pH control unit!
which, in turn, controlled the off-onj
operation of the acid feed pump. Experi-l
ence demonstrated that acid added!
directly into the clarifier effluent piping!
upstream of the baffled neutralization
tank (baffled to separate the mixing and I
sensing functions) were necessary tol
obtain satisfactory operation. The
neutralization tank effluent was then
pumped to the nitrification towers
during most of the operational period, I
even though flexibility was available to I
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Chemical Feed
Influent
Mix I *
^ Tank J
Activated
Carbon
Columns
Figure 1. Demonstration plant process flow schematic.
vary the sequence of all subsequent
processing steps.
Biological Nitrification
Three separate biological nitrification
towers were constructed from 1.85-m
(72-in) diameter concrete pipe sections.
Overall height of each unit was 5.18-m
(17-ft), and they were packed to a depth
of 4.57-m (15-ft) with a high specific
surface plastic media which was light-
weight and provided 187 sq m/cu m
(57-sq ft/cu ft) of surface area with 93
percent void space and a bulk density of
64 kg/cu m (4 Ib/cu ft) by virtue of
random packing in the towers.
The three nitrification units were
designed for parallel operation, with
adjustable flow rates to each unit. The
system design allowed for total recycle
of "seed" sludge in order to obtain a
biological population capable of effecting
nitrification within a reasonable period
(4 to 6 weeks) after startup. Rotary
distributor arms were used in each
tower to provide uniform surface
distribution. The underdrains from each
tower discharged to a commom sump
for pumping to the subsequent process.
Based on the 7.88 sq m (84.8 sq ft) of
surface area contained in the three
towers, the design surface loading rate
was 9.8 cu m/sq m/m (0.4 gal/sq
ft/m).
As with all processes following
clarification/neutralization steps, ef-
fluent from the nitrification towers
could be directed to the dual-media
filters or to the granular activated
carbon adsorption towers; the former
scheme was used throughout this
study. System design was based on the
presumption from earlier pilot studies
that there would be a low net solids
production associated with the nitrifica-
tion towers so that intermediate clarifi-
cation prior to filtration would not be
required.
Dual-Media Filtration
The filter used was a downflow
pressure system employing the dual-
media concept, i.e., a 0.3-m (1-ft) layer
of AWWA B 100 medium (0.45 to 0.55
mm effective size) sand overlain by a 0.3
m (1 ft) layer of anthracite, AWWA B100
No. 1 (0.6 to 0.8 mm A 1.6-cu m) (424-
gal) surge tank preceded the pressure
filter and provided flow storage during
the filter backwash cycle. In addition,
the surge tank was equipped with liquid
level sensors that served as controls for
the pressure filter feed pump. Flow rate
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through the 0.66-sq m (7.1-sq ft)
surface area filter was controlled by a
variable orifice, pressure-compensated
flow regulator at 12.2 cu m/sq m/h (5
gal/sq ft/m). Backwash operation was
automatic with intervals between back-
wash cycles being operator selectable
on a 24-hour time clock. The manu-
facturer suggested backwash initiation
at 28 to 35 k Pa (4 to 5 psig) pressure
differential across the pressure filter.
This corresponds to a head loss of
between 2.8 and 3.5 m (9.2 and 11.5ft).
Flexibility also existed for controlling the
length of each backwash sequence. The
chlorine contact tank served as the
backwash source, and backwashing
flow was regulated through a constant-
flow control valve at a rate of 43 cu
m/sq m/h (17.7 gal/sq ft/m). To
facilitate backwash efficiency, a pre-
backwash air source was provided.
Spent backwash was returned to the
flow equalization tank.
Granular Activated Carbon
Columns
Two granular activated carbon columns
were used to provide removal of
dissolved organic matter. The two
columns were operated in series with
the first column being an upflow type
and the second being of downflow
design. Empty-bed contact time for each
column was approximately 21.6 minutes.
Each 1.22-m (4-ft) diameter by 2.44-m
(8-ft) tall column contained approxi-
mately 1.22 m(4-ft)of granular activated
carbon (Calgon Filtrasorb 300) underlain
by a 0.3-m (1 -ft) layer of selected gravel.
Flow was introduced into the upflow
column via a perforated distributor
buried in the supporting gravel layer. In
order to maintain a fluidized condition in
the carbon bed at the liquid upflow rate
of 6.8 cu m/sq m/h (2.8 gal/sq ft/m), a
stream of air was also introduced at a
manually controlled rate through a
second perforated distributor within the
gravel layer. Overflow from the upflow
carbon column was screened prior to
overflow to the surface of the downflow
column. Backwash facilities similar to
those for mixed media filtration were
incorporated in the design of the down-
flow carbon column. The backwash flow
rate was 19.5 cu m/sq m/h (8.0 gal/sq
ft/m), and a surface wash was provided
during the backwash cycle. The chlorine
contact tank also served as the backwash
water source for this operation, and
spent backwash was returned to the
equalization tank.
Effluent Subsystem
The effluent subsystem included a
water meter for recording plant effluent
flow and the chlorination facilities for
disinfection of the final effluent. A 4.46-
cu m (1,178-gal) chlorine contact tank
provided a theoretical contact time of
33.6 minutes at the design flow.
Chlorine was fed from a 45.4 kg (100 Ib)
liquid chlorine cylinder using a solution-
feed, vacuum-operated gas chlorinator,
mounted directly on the cylinder. The
operating vacuum was provided by a
hydraulic injector unit, with a close-
coupled diffuser attached to a sub-
mersible pump mounted on the contact
tank floor.
Sludge Handling Facilities
A 30.28-cu m (8,000 gal) rectangular
sludge storage tank was provided to
handle the excess lime sludge from the
chemical clarification unit. As lime
sludges generally show good settling
properties, provisions were made in the
storage tank to gravity thicken the
sludge. Supernatant drawoff ports were
placed at selected elevations along the
upper section of the sludge storage tank
to allow decanting of the supernatant
during settling. The decent was returned
to the flow equalization tank.
A diffused-air system was installed to
prevent anaerobic conditions and ex-
cessive compacting and to facilitate
removal of the thickened sludge. Cou-
plings were installed at the bottom
sludge draw-off valve toallow tank truck
disposal of excess accumulated solids.
The design and intent of the sludge
storage-thickening unit was to aerate
the sludge to prevent anaerobic condi-
tions and to periodically stop aeration to
permit thickening and subsequent
supernatant drawoff. Withdrawal of
thickened solids for disposal was
permitted only during the aeration cycle
to assist in fluidizing the tank contents
for easier withdrawal.
Evaluation Factors
Sampling
Automatic composite samplers were
used for collecting samples from the
equalization tank (influent) and the
effluent from the carbon adsorbers prior
to chlorination (effluent). Also, periodic
grab samples were taken of the clarifier
effluent, neutralization tank effluent,
nitrification tower effluent and filter
effluent. All samples were refrigerated
including samples for biochemica
oxygen demand (BOD5) and suspended
solids (SS). Besides refrigeration
samples for chemical oxygen demand
(COD), total organic carbon (TOC), tola
Kjeldahl nitrogen (TKN), ammonia
nitrogen (NH3-N) nitrite nitrogen (N02
N), nitrate nitrogen (NO3-N), acid
hydrolyzable phosphate (AHP), and
orthophosphate were further preserved
by the addition of 2 ml of H2S04 per lite
of sample following collection. Al
testing was done in conformance with
"Standard Methods for Examination o
Water and Wastewater," Fourteenth
Edition, 1975.
Construction and Start Up
Project planning and plant design an
specifications were completed in Feb
ruary 1975. Due to the nature of th
project and the equipment required, tw
separate contracts were awarded. On
contract encompassed the skid-mountec
physical-chemical treatment system,
while the other covered site work
nitrification towers, the flowequalizatio
tank, the sludge storage/thickene
tank, and other miscellaneous items. A
bids for both contracts were considerabl
in excess of the budget limits of th
project. Negotiations with the lo\
bidders coupled with numerous desig
changes resulted in the eventual
signing of both contracts within th
original budget estimates. The physical
chemical (P-C) plant was delivered i
January 1976. The work scheduled i
the second contract was to be complete
in late November 1975, but due t
financial difficulties on the part of th
contractor and subsequent unantici
pated requirements resulting from thi
problem, the construction phase an
initial testing were not completed unt
late 1977.
Numerous problems were encoun
tered during the initial attempts to chec
out the individual units in the system
and to verify their proper operation. Th
treatment system was designed fo
above ground operation to allow for
short installation time and to facilitat
movement of the system to anothe
location, should the need arise. The P-C
system was delivered to the site ir
January 1976. Because of the seriou
delays in completion of the othe
contract, this equipment was left at th
site, unused, for two years including
two winter seasons of unusually cold
weather. Proper precautions were not
taken to protect the units during this
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long period. Numerous pipes, valves,
fittings, and pumps suffered substantial
damage, requiring replacement or
repair. Breakdowns encountered with
pumps and motors continued to be a
major problem during the entire opera-
tional phase of the project, probably
caused by the long exposure.
Results
Overall Removals
Prior to system design 10 twenty-four
hour composite samples of the raw
wastewater gave the results presented
in Table 1.
During the operational phase, the
average BOD5 of the equalization tank
samples average characteristics were
159 mg/l of BOD5,368 mg/l of SS, and
435 mg/1 of COD, as shown in Table 1 in
parentheses. The significance of the
differences between these values is not
clear, since some are lower and some
higher. Certainly, some changes could
be due to the aerated flow equalization
tank prior to the pumping to the
clarification unit. Since the theoretical
retention time in the equalization tank
was between 5 and 10 hours, some
biological oxidation could have occurred,
and the recycle of certain streams from
the treatment system to this tank would
also account for some variance.
A summary of the treatment efficien-
cies achieved with each of the units
(clarifier, nitrification tower, dual-media
filtration, and carbon columns) is
presented in Table 2. The percent of
removal of BOD5, COD, TOC, SS, acid-
hydrolyzable phosphorous, and total
nitrogen, is presented. The data represent
paired samples where influent and
effluent samples were taken from each
unit and analyses performed. Thus, the
percentage of removal within one unit is
calculated from the difference of the
influent and effluent of that unit. The
percentage of cumulative removal is
calculated from the difference between
the clarifier influent and the effluent of
that unit. As can be seen, the removals
of BODs, COD, TOC and SS were
excellent, with cumulative removals
ranging from 88 percent for COD to 97
percent for suspended solids. The
greatest amount of organic material and
suspended solids was removed during
the lime clarification.
Phosphorus removal from an influent
concentration average of 12.3 mg/l was
also excellent but the nitrogen removal
was rather low. The major portion of the
phosphorus was removed during the
lime clarification. High lime feed with a
higher pH (11.4 as compared to 10.7 for
the low lime feed) significantly increased
the removal of phosphorus, i.e., from 63
to 87 percent. Recycle or non-recycle of
clarifier sludge had little influence on
the removal of phosphorus.
Nitrification never properly developed
during the course of the study, even
though nitrogen removals averaged 40
percent from the average influent con-
centration of 38 mg/l during the last
eight weeks of operation. The overall
removal of nitrogen averaged 32 per-
cent, with losses nearly equally split
between the clarification, filtration, and
carbon adsorption processes. In the first
two processes these removals can be
attributed to the organic nitrogen
content of the solids removed. In the last
process nitrogen removal appears to
have been due to denitrification in the
carbon beds.
Individual Process Performance
As noted in Table 2, the lime clarifica-
tion step accounted for the major
Table 1. Wastewater Characteristics*
portion of removal of all pollutants
measured. From the standpoint of
defined secondary effluent quality, the
clarifier effluent nearly met the BOD5:SS
requirement of 30:30, with actual
values of 46:21. Organics, as measured
by BODs, COD and TOC were removed
by average rates of 66 to 77 percent,
while 82 percent of the acid-hydrolyzable
phosphorus was removed.
The nitrification tower, though seem-
ingly ineffective in its intended role as
measured by nitrogen series analysis,
did provide significant additional re-
movals of BOD5, TOC and COD. The
reasons for the apparent lack of nitrifi-
cation remain somewhat mystifying
based on earlier published data which
indicated that the designed system
should be able to oxidize 3.2 to 8.2 kg of
NH4-N/day (7 to 18 Ib/d). Since the
approximate loading was 5.0kg of Nt-U-
N/day (11.0 Ib/day), the resulting
oxidation, as measured by NO2-N and
N03-N increase, of 0.27 kg/day (0.6
Ib/day) was disappointing. This is
especially true in light of favorable
wastewater temperatures and BOD5/
BOD5 COD TS VTS SS VSS DS VDS pH Alkalinity
as CaCO3
239 370 974 467 411 219 562 248 7.0 278
(159f (435f (368)*
* all analyses in mg/l, except pH
* operational phase averages
Table 2. Project Data Summary
Parameter Measured*
Subsystem
Clarifier
% Removal
% Cumulative
Nitrification
% Removal
% Cumulative
Dual-Media Filter
% Removal
% Cumulative
Carbon Columns
% Removal
% Cumulative
BODs
77
77
44
84
—
91
33
93
COD
73
73
13
76
4O
86
15
88
TOC
66
66
42
80
5
82
20
86
SS
86
86
Neg.
85
71
95
39
97
AHP**
82
82
Neg.
80
17
85
Neg.
80
77V***
13
13
Neg.
11
11
24
10
32
Data represents paired samples where influent and effluent analyses were
performed.
Acid-Hydrolyzable phosphorus
1 Total Nitrogen
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TKN ratios. Initial attempts to provide
seeding to the nitrification towers were
unsuccessful due to hydraulic deficien-
cies in the plant, but sufficient operating
time was available for natural develop-
ment of nitrifiers. The fact that no such
development took place wou Id appea r to
be due to either the unreliability of the
neutralization step and/or the lack of
recirculation.
The dual-media performed well in
terms of solids removal and concomitant
removals of organics, TKN and AHP
associated with those solids. Suspended
solids removals of 70 percent were
achieved, along with COD, TOC, TKN
and AHP removals of 40, 5, 11 and 17
percent, respectively. However, the
media sizes were not well-suited to
handling the 44 mg/l of SS (average)
found in the filter influent. Therefore,
filter runs were frequently as short as
four hours, which represented a con-
siderable 0/M problem, because of the
fine coal size provided with the filter.
The activated carbon columns were
loaded very lightly during this study. The
COO removed by the adsorbtion process
had reached 0.18 Ib. of COD per Ib. of
activated carbon by the end of the
project, no apparent reduction in the
rate of COD removal verified that the
carbon had not been exhausted. The
system was designed with the capability
of removing spent carbon and adding
fresh carbon. Denitrification of the
nitrate produced by the nitrification
towers did occur in the carbon columns,
and no hydrogen sulfide problem was
encountered.
Performance Reliability
In spite of the equipment and opera-
tional problems encountered, the hybrid
(physical-chemical/biological) treat-
ment plant, as designed, was able to
produce a consistent, high-quality
effluent, when compared to typical
biological systems used to treat waste-
waters from small communities. Figure
2 compares the reliability of this hybrid
system for the removal of BOD5 and SS
versus extended aeration plants in the
Cincinnati area. Since this hybrid plant
also removes phosphorous, other bio-
logical systems would require ancillary
treatment steps to provide comparable
performance characteristics.
Operation and Maintenance
The normal operation and mainte-
nance of this plant was more time
consuming and complex than that
associated with most biological treat-
;oo
;oo
o
JO 20 30 40 50 60 70 80 90 95 98 99
Percent of Time Value was Less Than
figure 2. Comparison of BODs and SS reliability.
ment plants. Some of the work involved
the sampling and laboratory testing
required at the site for the experiments
of this project and included sample
preparation and delivery and prepara-
tion of logs and records. However, there
were a number of pumps, tanks, mixing
chambers, and backwash systems
which had to be cleaned, adjusted, and
occasionally repaired. The mixing of
chemicals (lime slurry and acid neutral-
izer) required knowledge of the opera-
tions and caution to avoid chemical
burns. One full time operator was
required with additional manpower
required for any unusual problem.
Weekend coverage of the plant was also
provided.
In order to properly conceive of the
0/M requirements, it should be noted
that an extended aeration package plant
capable of handling the same design
flow normally requires approximately
0.5 person-years/year. Therefore, the
manpower required for the hybrid
system was approximately three times
that required for an extended aeration
system. Likewise, increased chemical
costs are inherent to the hybrid system
design. The value of relatively instan-
taneous, high-quality effluent would
have to be weighed against these
increased O/M costs on a case-by-case
basis. The question of initial cost
comparison is far more difficult because
of the transport-ability of the physical-
chemical portion of the hybrid plant.
Multiple use of such a system by a
public or private entity at different sites
would determine whether such a
system would be economical.
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Discussion
Two factors were intended for testing
in this study, the technical feasibility of
the treatment sequence and the concept
of transportability. Although certain
shortcomings arose in the testing of
these factors, certain implications of the
study are relevant to each.
The transportability concept is impor-
tant to agencies such as DHUD in that
the potential health and ecological
dangers which often result from natural
or man-made disasters might be mini-
mized through prompt response with
nearly instantaneous high quality treat-
ment capability to meet most water
quality limitations. To a lesser degree,
an adjunct treatment capability for
"boom towns" or other sudden popula-
tion increases, which in recent times
have been associated with energy
development, could obviate the potential
impacts on a fragile ecology due to
sudden overload of existing sanitary
facilities and infrastructure.
As noted earlier, the physical-chemi-
cal (P-C) portion of the hybrid treatment
plant was skid-mounted and trans-
portable from site-to-site by tractor
traitor. The associated process needs,
i.e., equalization and sludge handling,
could quickly be provided at almost any
site by excavation and lining or other-
wise sealing of the soil to prevent
seepage and/or introduction of debris
to the wastewater, if such tankage is not
already available. Therefore, a complete
(P-C) unit could be quickly operable at
such locations, assuming necessary
power provisions at the plant site. The
nitrification tower is an unlikely addition
in the event that a nitrogen standard
must be met, not because of its marginal
performance during this study, but
because its inherent lag time to reach
proper nitrification is inconsistent with
the otherwise quick startup potential of
the unit. Therefore, the P-C system
alone would serve the transportability
function quite well if no nitrogen
standard were in effect and offer the
added benefits of phosphorus removal
and consistently high quality perform-
ance. Introduction of a nitrogen standard
would probably require the use of break-
point chlorination or stripping towers in
order to provide relatively instantaneous
nitrogen removal consistent with the
overall plant characteristics.
The technical feasibility of the hybrid
facility's processing sequence is a
separate issue. The concept of utilizing
biological nitrification with physical-
chemical processing was designed to
overcome two basic weaknesses in the
P-C treatment concept, i.e., high NI-U-N
concentrations in the effluent and odors
associated with the carbon adsorbers.
the perceptible nitrification was minimal,
the total system did remove about 30
percent of the nitrogen in the waste-
water, as opposed to the original
estimate of 36 percent. The major
The latter problem had been overcome
by the addition of NOa-N to the influent
of carbon adsorbers in sufficient quantity
to prevent H2S formation. The hybrid
facility was designed to utilize the
nitrogen already in the wastewater by
converting, all or part of, it to the N03-
form prior to carbon adsorption. Although
difference in the actual vs. estimated
effluent quality was the form of the
nitrogen, i.e., NH4-N rather than N03-N,
which could result in a significant
oxygen demand in the receiving stream.
The overall acceptability of a waste-
water treatment system is based on a
variety of factors including capital and
O/M costs, labor requirements and
performance characteristics. If one
assumes that the reasons for poor
nitrification tower performance can be
easily overcome through improved
neutralization and nitrification tower
design, the hybrid design studied (with
proper filter media) is capable of
producing a high-quality effluent un-
matched by either pure biological or
pure physical-chemical systems, incor-
porating the positive features of both
systems, e.g., compact size, reliability,
resistance to toxic upset, improved
toxics removal, phosphorus removal,
non-odorous operation, and nitrogen
reduction with ammonia removal.
The EPA authors James F. Kreissl fa/so the EPA Project Officer, see below) and
Ronald F. Lewis are with the Municipal Environmental Research Laboratory.
Cincinnati, OH 45268.
The complete report, entitled "Demonstration Physical Chemical Sewage Treat-
ment Plant Utilizing Biological Nitrification," was authored by E. Brenton
Henson of the Sanitation District No. 1 of Campbell and Kenton Counties,
Covington, KY 41 Oil fOrder No. PB 82-101 643; Cost: $9.50, 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:
Municipal Environmental Research Laboratory
U. S. Environmental Protection Agency
Cincinnati, OH 45268
•fr U. S. GOVERNMENT PRINTING OFFICE: I98I/559-092/332I
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