United States
Environmental Protection
Agency
Water Engineering
Research Laboratory
Cincinnati OH 45268
I //
Research and Development
EPA-600/S2-84-191 Mar. 1985
SERA Project Summary
Feasibility Study of Alternative
Technology for Small Community
Water Supply
John S. MacNeill, Jr. and Arthur MacNeill
A cooperative demonstration project
was funded by the U.S. Environmental
Protection Agency (EPA) to enable the
Village of Cayuga, N.Y., to install and
demonstrate water filtration technology
that may be appropriate for small water
systems that use surface water sources.
The demonstration project was under-
taken because the existing facilities
were not able to meet the turbidity
requirements of the New York State
Health Department. A prefabricated
filtration system consisting of two
cyclone separators in parallel followed
by three parallel treatment trains, each
employing a contact clarifier, a mixed
media filter, and a granular activated
carbon filter, was installed at Cayuga's
existing water treatment plant. The new
equipment replaced facilities built in the
1930's, consisting of aeration, sedi-
mentation, and filtration. After installa-
tion, careful records of the first year's
operation were kept to document water
quality, operating labor needs, and
operating costs, including power and
chemicals.
Data collected showed that, with
respect to turbidity removal, the per-
formance of the treatment plant ex-
ceeded the goals set forth in the study.
As for costs, chemicals totaled 5
cents per 1000 gallons, and power,
including raw water pumping but
excluding treated water pumping, was
10 cents per 1000 gallons, at a rate of
6.20 per kilowatt-hour (KWH). Installa-
tion cost for the 150 gallons per minute
(gpm) system was $268,000.
This Project Summary was developed
by EPA's Water Engineering Research
Laboratory, Cincinnati, OH, to announce
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).
Introduction
The Village of Cayuga, New York,
obtains its drinking water from the
shallow northern end of Cayuga Lake. For
a number of years the water treatment
plant, which employed aeration, sedi-
mentation, and filtration, had from time to
time failed to provide water that met the 1
nephelometric turbidity unit (NTU) limit
setbytheEPA In 1981 Cayuga received a
demonstration grant to assist the village
in installing, operating, and monitoring a
prefabricated 150 gpm water filtration
system manufactured by Culhgan USA *
This report describes the installation and
start-up of the system and includes
construction cost, operating cost, and
water quality data developed during the
installation of the system and the
subsequent 12-month operating period.
Equipment
The new filtration equipment was
installed in the original water filtration
plant built in the 1930's. When the initial
portion of the filtration system was ready
for operation in the remodelled facility,
the shutdown for the switch-over was
less than 16 hours—well under the 24-
hour maximum shutdown stipulated by
the New York State Department of Health
(NYSDOH). The construction of this initial
portion was started about April 1, 1982,
and switchover occurred on June 21,
"Mention of trade names or commercial products
does not constitute endorsement or recommendation
for use
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1982. Carbon filters for effluent polishing
were completely installed on August 24,
1982, and the full system was operational
on August 26, 1982.
In the 150 gpm, prefabricated filtration
system (see Fig. 1), raw water first passes
through two cyclone separators operated
in parallel. The primary treatment train
consists of coagulation with alum and a
cationic polymer followed by three 36-
inch-diameter contact flocculators con-
taining 40 inches of coarse sand operating
in parallel at a rate of 7 gpm/ft2
Next in line are three multimedia filters
also operated at 7 gpm/ft2 in parallel. For
effluent polishing, three granular activated
carbon (GAC) filters operating in parallel
at 5 gpm/ft2 are used. Chemical feed for
coagulation is related to raw water
turbidity, which is measured contin-
uously. When raw water turbidity is 35
NTU or lower, a single set of feed pumps
is used. When turbidity of the lake water
exceeds 35 NTU, a second set of chemical
feed pumps is activated, resulting in a
doubling of the alum and polymer doses.
Backwashing for the contact clarifiers
and the multimedia filters is done
automatically, based upon differential
pressure through the filters The plant
operator initiates backwashing of the
GAC; this need is also based on head loss.
Results
Results are presented for both costs
and water quality. To evaluate the water
quality data, results obtained from
treatment are compared both to the EPA
Maximum Contaminant Levels (MCL) for
turbidity (1 NTU) in the Primary Drinking
Water Reg u lations a nd to the performa nee
criteria set by the NYSDOH, which are set
forth m Table A as provided by the
NYSDOH (Table 1). The performance
criteria are used to evaluate those water
filtration processes not designed on the
basis of the 1982 Recommended Stan-
dards for Water Works (commonly referred
to as the "Ten State Standards") Note
that performance criteria for turbidity,
microscopies, and aluminum vary accord-
ing to the frequency of occurrence. For
example, 95 percent or more of the
turbidity values are to be < 0.50 NTU; 75
percent or more, < 0 30 NTU; and 50
percent or more, < 0.20 NTU. These
criteria are for process evaluation only.
For public drinking water, the NYSDOH
uses the 1 NTU MCL
The contaminant of greatest concern at
Cayuga was turbidity. The 1 NTU MCL
had been exceeded on numerous occa-
sions by the old treatment plant. During
the first year's operation, the prefabricated
filtration system was able to meet the
MCL. In addition, the system proved
capable of meeting the much more
stringent NYSDOH process evaluation
criteria.
An important concern was the system's
ability to react to rapid changes in raw
water quality. Cayuga Lake, with abun-
To Clear
/\ Denotes Sampling Points
Figure 1. Pilot study pressure filtration system schematic pilot study. Village of Cayuga, NY.
2
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Table 1. Water Quality Criteria to be Met at New Facilities not Designed in Accordance with Recommended Standards for Water Works, from New
York State Sanitary Code. Chapter 1, Part 5
Performance Criteria' Pretreatment and Filtration
Table A
Process
% of values
95 or more
75 or more
50 or more
4/24/75
Pretreatment Effluent
Turbidity Microscopies Aluminum Color
area! std
units units/ml rng/l units
<:so <1 4.000 <:o7o <:/o
52.3 <3.000 ^045 5/0
5?0 56,000 ^030 ?70
AWWA Goals
(tor comparison) w
Filter Effluent
Turbidity
units
<050
5030
5020
5o w
Microscopies
areal std
units/ml
<:woo
<400
<300
no live
organisms
Aluminum
mg/l
<:o 15
<009
~005
^005
Color
units
<5
Z5
?5
^3
Water Supply Design & Construction Section
Bureau of Public Water Supply
New York State Department of Health
dant summer weed growth, is generally
less than 10 feet deep near Cayuga.
Winds from the south can cause big
waves at the northern end of the lake. The
new filtration equipment was able to cope
with turbidity increases from about 10
NTUto60-100NTU in times as short as 2
or 3 hours and meet the 1 NTU MCL
One aspect of the filtration equipment
seemed to be related to slightly elevated
filtered water turbidities. When the raw
water turbidity rose or fell to and
remained at the point (35 NTU) at which a
second set of chemical feed pumps
turned on to double the alum and polymer
doses, filtered water turbidity rose
somewhat but did not exceed 1 NTU. A
series of changes (increases and de-
creases) in chemical dose caused by the
system's response to raw water having a
turbidity close to 35 NTU may have
caused the rise in turbidity Use of propor-
tional feed pumps might have eliminated
this problem
Another aspect related to raw water
quality and process equipment was that
aluminum passed through the treatment
plant when the raw water pH exceeded
7 5. Often the NYSDOH criteria for
aluminum in filtered water were not met
because the treatment plant had no
provision for lowering the raw water pH
to the bestpH range for alum coagulation
When the raw water pH was above 7.5,
monthly average aluminum concentra-
tions in the filtered water ranged from 0.1
to 0.5 mg/L. During winter and spring,
when pH was generally below 7.5,
concentrations generally averaged well
under 0.1 mg/L.
Direct filtration processes (such as the
one at Cayuga) that do not employ settling
basins have sometimes been found to be
sensitive to water temperature, filtered
water quality declines when the water
temperature approaches the 0° to 5°C
range. On the other hand, cold tempera-
tures sometimes have no detrimental ef-
fect on treated water quality. One factor
for this may be the time available for the
alum coagulant to be m contact with the
water before it is filtered. Some evidence
for this was seen at Cayuga' in the first re-
moval process (the contact clarifier) when
raw water temperature was >10°C, tur-
bidity removal ranged from about 65 to 90
percent; when raw water was 0° to 5°C,
removal ranged from about 45 to 60 per-
cent. Theoretical detention time from the
point of alum addition to the discharge
from this unit was just under 4 minutes,
and total time through both the contact
clarifier and the multimedia filter, just
under 7 minutes. When the monthly
average raw water temperature was
<5°C, the multimedia filter was re moving
20 to 30 percent of the raw water tur-
bidity Perhaps of more significance, the
GAC filter (the third filtration process in
the treatment tram) was removing from
10 to 30 percent of the raw water tur-
bidity during the low temperature (<5°)
condition. Consideration should be given
to providing additional contact time when
water temperatures are expected to be
below 10°C to prevent formation of alum
floe after the water has been filtered and
to attain the most effective turbidity re-
moval.
The study showed that the filtration
equipment installed at Cayuga is well
suited to small water systems The
prefabricated filtration equipment could
be installed in an existing structure
without extensive structural retrofitting—
an important consideration in some
communities
The capital cost for this project was
$268,000: about $200,000 was spent for
filtration equipment, pumps, piping,
instruments, controls, etc , and about
$68,000 for structural changes, electrical
work, painting, and raw water intake
repairs
The system needs about 2 7 hours
operating time per day for inspection,
adjustments to inflow and feed rates,
sample analysis, and maintenance This
amounted to 0.022 hour of labor per
1,000 gallons of water pumped to the
distribution system.
The costs for treated water were
• power (including raw water pumping
but excluding pumping to the distri-
bution system) $0 102/1,000 gal
• distribution system pumping
$0 11/1,000 gal
• chemicals (alum, polymer, chlorine,
and sodium hydroxide)
90.049/lvOOO gal
• sludge disposal to approved landfill
$0.014/t,000 gal
• electric power rate SOQ62/KWH
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Results obtained at Cayuga suggest
that pilot studies should be conducted
before filtration plants are designed and
built, especially when direct filtration is
proposed Because turbidity m raw water
has various causes, the suitability of
treatment processes should be determined
at the pilot scale. Determining process and
equipment suitability in this way can help
provide the maximum return on the
investment in a treatment plant
Conclusions
The prefabricated water filtration
system installed at the Village of Cayuga
perfomed well under a number of raw
water conditions.
The system could be operated success-
fully by a conscientious small system
operator
The amount of detention time available
in direct filtration systems can influence
process performance when the raw
water temperature is <10°C.
When alum is used as a coagulant, raw
water quality may be such that only
adding alum to the raw water does not
give the best pH for coagulation. Equip-
ment for raising or lowering the pH may
be needed to attain the most effective
coagulation.
When direct filtration plants are under
consideration, questions about factors
such as the effect of very low raw water
temperatures or the pH range for effective
coagulation can best be answered by
performing pilot plant studies.
The full report was submitted in
fulfillment of Cooperative Demonstration
Agreement CS809411 by the Village of
Cayuga, NY, under the sponsorship of the
U S. Environmental Protection Agency.
JohnS. MacNeill and Arthur MacNeill are withJohnS. MacNeill, Jr, P C, Homer.
NY 13077.
Gary S. Logsdon is the EPA Project Officer (see below).
The complete report, entitled "Feasibility Study of Alternative Technology for
Small Community Water Supply," /Order No PB 85-143 287, Cost. $1450,
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:
Water Engineering Research L aboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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