United States
Environmental Protection
Agency
Water Engineering Research
Laboratory
Cincinnati OH 45268
'/i
Research and Development
EPA/600/S2-85/052  June 1985
Project Summary
Slow Sand Filter and
Package Treatment Plant
Evaluation:  Operating
Costs  and  Removal  of
Bacteria,  Giardia,  and
Trihalomethanes
Gordon R. Pyper
  A study was conducted to evaluate
two simple methods of water filtration
for small water  systems: slow sand
filtration and pressure  diatomaceous
earth (DE) filtration. The study address-
es the concerns of small water systems
with regard to Giardia cysts, bacteria,
trihalomethanes (THM's) and operating
costs. Objectives are (1) to determine
effectiveness of the two filtration sys-
tems for removing bacteria, turbidity,
and Giardia cysts under various loading
conditions,  (2) to spike bacteria and
Giardia cysts into the raw water under
various loadings to determine the break-
through point, (3) to determine the level
of technical expertise needed to operate
the systems, (4) to obtain operating and
maintenance data and costs, and (5) to
evaluate the potential for the formation
of THM's with the two filtration sys-
tems.
  The study was conducted at Mclndoe
Falls, Vermont. Raw water was of high
quality with respect to most parameters,
but the  source was  a highly organic
impoundment site. Raw water values
were generally low for the principal
parameters studied (total  coliforms,
standard plate count, Giardia cysts,
particles, and water temperature).
  Slow sand filtration provided depend-
able water treatment with little attention
required, but capital cost  was high.
Bacteria and Giardia cysts were re-
moved very dependably at warm water
temperatures (above 5° to 10°C) but
less efficiently at lower temperatures.
Turbidity was below 1 IMTU 99.19% of
the time.
  Pressure DE filtration also reduced
Giardia cysts and bacteria dependably,
but the system required full-time, skilled
operation when  running and careful
attention to every detail.
  Both systems failed to reduce THM
precursors significantly, and both sys-
tems incurred comparable  costs for
producing small quantities of water.

  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
  This study compared two simple meth-
ods of water filtration that could be used
for small water systems. Many small
water utilities in traditionally cold, clear
water areas of the country have continu-
ously used such water without filtration
or other treatment, and some do not even
chlorinate. Chlorination might be consid-
ered a minimum requirementfor bacterial
control, but with the increasing occur-
rence of Giardia cysts in surface water
supplies, chlorination adequate to inactive

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coliform bacteria may not provide ade-
quate protection. Filtration is needed also.
  This study addresses the concerns of
the small water system with particular
emphasis on turbidity, bacteria, and
Giardia cysts. The principal objectives of
this study were:

  1.  To determine the effectiveness and
     efficiency of  slow sand  filtration
     and pressure diatomaceous earth
     (DE) filtration on removal of bacteria,
     turbidity, and Giardia cysts under
     various loading conditions.
  2.  To spike bacteria and Giardia artifi-
     cially into  the raw  water under
     various loading conditions to de-
     termine when the loadings might
     produce a breakthrough in the
     systems and contribute  bacteria
     and Giardia to the effluent.
  3.  To observe, record, and  evaluate
     the level of  technical expertise
     required to  operate the  systems
     (observations were  to be based
     primarily on ambient operating
     conditions).
  4.  To obtain operating data in terms of
     hours  and  costs associated with
     operating and maintaining the sys-
     tem (costs related to chemical addi-
     tions, cleaning and restoring the
     systems to operation, and similar
     well-defined  operational  require-
     ments).
  5.  To evaluate the potential  for  and
     formation of  trihalomethanes
     (THM's) in the untreated water and
     compare the results with those
     from the effluent of a slow  sand
     filter and a DE  package treatment
     plant treating the same source of
     supply.

  This study was conducted at Mclndoe
Falls, Vermont, at the site of the  slow
sand filtration plant.  The water source
was a small brook fed from a marsh. The
raw water was of high quality with respect
to most parameters, but the source was a
highly organic impoundment  site. The
water could be described as low in color,
turbidity, chloride, manganese,  calcium,
hardness, alkalinity, nitrate, and  sus-
pended solids; pH was neutral. The water
had moderate to heavy levels of iron (0.1
to 1.5 mg/L), total Kjeldahl nitrogen (17
to 56 mg/L), ammonia nitrogen (7 to 25
mg/L), and sodium (1 to 155 mg/L). No
primary standard chemicals were found
to be above MCL limits.
  The principal parameters considered
during  the study were turbidity,  total
coliforms, standard plate count, Giardia
cysts, particles (7- to 12-/um range), and
water temperature. Raw water values for
these parameters were generally low.
Raw water turbidity  averaged  1 .4 NTU
during the study (83% of the  samples
were 2.0 NTU or less), but some high
spikes occurred during storms or during
road work in the impoundment  area.
Concentrations  of total  coliform  and
standard plate count bacteria were  in-
fluenced by rain and snow storms. Levels
averaged 296/1 00 mL for total coliforms
and  185/mL for standard plate count
bacteria. Fifty percent of the total coliform
samples have values of 1 00/1 00 mL, and
the standard plate count  had values of
80/mL  or fewer. The average  particle
concentration (7- to  12-//m range) was
1 2,780 per mL, and 50% of the samples
contained 5300 per mL or fewer. Water
temperature tended to be cold most of the
time except in the middle of the summer.
The average temperature was 9.7°C, but
38% of the readings were 2°C or below
from about April 4 to December 1 5.

Slow Sand Filtration
  The slow sand filter was operated under
normal  ambient  conditions and under
special biological stress conditions. The
rate  of  filtration was maintained at a
constant value of 0.08  m/hr (2 million
gallons per acre per day [mgad]) through-
out the study because summer flows
from the source were  not  dependable
above this rate.

Total Coliforms and Standard
Plate Counts
  The total coliform and standard  plate
count results for ambient conditions are
summarized in Figures 1 and 2 and Table
                                        1.  Under ambient loading conditions,
                                        reductions averaged 80% for total coli-
                                        forms and 90% for standard plate count
                                        bacteria. However, 90% of the total
                                        coliform and standard plate count samples
                                        showed reductions of 80% or more. Also,
                                        60% of the effluent samples contained
                                        total coliform concentrations of 1/100
                                        mL or fewer, and standard plate count
                                        values were 2/mL or fewer. Eighty per-
                                        cent of the effluent samples showed total
                                        coliform values of 7/100 mL or fewer and
                                        standard  plate count values of 4/mL or
                                        fewer. These results showed  relatively
                                        dependable bacterial quality in the efflu-
                                        ent with rather variable raw water quality.
                                        The slow sand  filter did not  show  an
                                        immediate response to sudden improve-
                                        ments in raw water quality. When the
                                        bacterial  concentration  rapidly declined
                                        in  the raw  water, the concentration of
                                        bacteria in the filtered water may have
                                        been close to or greater than the concen-
                                        tration in the raw water for a day or so.
                                        This circumstance would cause very low
                                        removal percentages or negative removal
                                        percentages (increases).

                                        Recovery of Filter After Scraping
                                          Normal recovery after filter scraping
                                        was an important consideration for filter
                                        operation. Bacterial quality of the water
                                        did suffer immediately after filter clean-
                                        ing, particularly during cold water condi-
                                        tions. About 2  days after  cleaning,
                                        reductions decreased from approximately
                                        95% to 20% for total coliforms, and from
                                        about 90% to -300% for standard plate
                                        count bacteria. In warmer water situa-
                                        tions, the reduction  in  total  coliforms
                                        dropped to about 55% in about 7 days and
                                        to  approximately 93% for the standard
                                        plate count  in the same time period. This
                                        disruption of the treatment capability was
    700
 I
    80
 o?  40
  §  20
                                                o Total Coliforms - Influent

                                                • Total Coliforms - Effluent
                                                I   ill
                        JO                100

                             Total Coliform No./100 mL
                                                          WOO
Figure  1.
             Total  coliforms  in  influent  and effluent  of  slow  sand filter during
             normal operation, filtration rate of 0.08 m/hr.

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  I
  I
  CO
700


 80


 60


 40


 20
                                              o Standard Plate Count - Influent
                                              • Standard Plate Count - Effluent
               \   \  \
                                                      \  \  \
                                                                     \
                          10                100
                         Standard Plate Count Bacteria/mL
                                                       1000
Figure  2.     Standard plate  count  bacteria  in  influent  and effluent of slow sand
             filter during normal operation, filtration rate of 0.08 m/hr.
Table  1.    Percent Reduction of Bacteria by Slow Sand Filtration*
Parameter
Total Coliforms/ 100 mL
Standard plate count
bacteria
Number of
Samples
67
67
Mean
79%
89%
Maximum
99.99%
99.99%
Minimum
-60%
-200%
*Ambient operation for all periods from 6/18/82 to 5/4/84.
much less severe. These results demon-
strated that temperature must  be con-
sidered when evaluating any biological
impact on slow sand filtration.

Spiking the Filter After Cleaning—
  During the summer months when  the
water was warm (22°C), the filter was
spiked with bacteria immediately after it
was cleaned. The filter showed very little
disruption of bacterial treatment capabil-
ity after being cleaned, even with heavy
spikes of total coliform and standard plate
count organisms. The filter effluent aver-
aged 7/100 mL for total coliform 8 to 10
days after cleaning and 2 to 3/100 mL 15
to 20 days after cleaning. The standard
plate  count  results  were similar.  The
effluent averaged 2/mL for standard plate
count bacteria 8 to 10 days after cleaning,
and it decreased to 1/mL 20 days after
cleaning.

Turbidity After Filter Cleaning—
  Turbidity reductions after filter cleaning
were similar  to bacterial results. Under
warmer ambient water conditions, turbid-
ity reductions tended to remain at 92% to
95% removal throughout the recovery
period. I n cold water conditions, removals
dropped from 92% to 95% to about 50% in
                                  1 to 5 days. Recovery during cold weather
                                  tended to take  10 to 20 days and was
                                  much more erratic than warm weather
                                  results. However, under the worst of the
                                  cleaning  conditions,  the filtered water
                                  never exceeded 0.9 NTU except for the
                                  start-up condition when the filter had just
                                  been cleaned. The erratic response would
                                  be expected because the filter had not
                                  been  used for  several years and  thus
                                  represented a biologically immature sand
                                  bed. The  results for all values, including
                                  turbidity,  were very erratic and irregular
                                  for  about 100 days  after this  initial
                                  cleaning,  a result completely different
                                  from subsequent cleaning  and normal
                                  operating results.

                                  Particle Count After
                                  Filter Cleaning—
                                    Information on reductions of particles
                                  (7-  to 12-//m range) proved to be very
                                  erratic for this water. Reductions were at
                                  times in  the 90% to 95% range; but  at
                                  other times they were -100% to -200%,
                                  with no particular pattern to their changes.
                                  For normal ambient operation, the aver-
                                  age particle reduction was about 45%,
                                  and during recovery from cleaning, aver-
                                  ages were about the same. Recovery from
                                  cleaning  with bacterial spiking demon-
strated severe impacts, with an average
reduction of -8%. Little correlation was
apparent with  bacteria,  turbidity,  or
Giardia  removal. Slime  growths in the
water were believed to contribute to this
erratic  behavior,  as such  organisms
occasionally clogged the particle counter
and did  continuously clog the automatic
turbidimeters, often  within a day  after
cleaning.

Bacterial Spiking
  Bacterial spiking was also evaluated
under normal operating conditions. The
temperature influence was again demon-
strated during cold water conditions (1 °C).
Effluent bacterial reductions deteriorated
steadily during spiking and showed signs
of breakdown in treatment about 10 days
after the spike started. During  warmer
water conditions(9°C), the effluent hardly
showed any  disruption for either  total
coliforms  or  standrd  plate count,  with
bacterial loads of 1000 to 10,000/100
mL for total coliforms and 100 to 1000/mL
for standard plate count organisms.

Cyst Reduction
  The removal of Giardia  lamblia cysts
was an  important consideration in this
research. Eight  spikes of fluorescent-
tagged cysts were applied to the  slow
sand filter during this study, including a
series of  5  spikes applied at 1-month
intervals. After each  spiking, 8% of the
filter effluent was sampled each day on a
continuous basis. The sampling periods
ranged in length from 6 days to 5 months;
the 5-month sampling period was done
during the series of  5 cyst spikes.  Cyst
removal was excellent, even though some
cysts did  appear in  the  effluent.  Cyst
reduction through the  filter is summarized
in Figure 3 and Table 2. Removals tended
to be best (99.9%) during warm water
conditions and  less  effective (99.5%)
during cold water conditions, except for
one result in cold water that yielded only a
93.7% reduction. This somewhat lower
reduction occurred during sewage spiking
(water temperature 0.5°C), and it appear-
ed that the biological capabilities of the
filter were stressed almost to the  limit
since removals of both bacteria  and
Giardia cysts showed degradation in their
removal patterns. This hypothesis should
be investigated further because it has
important ramifications when considering
cold water situations that might involve
sewer breaks or other contamination with
Giardia  cysts. During the study, water
temperatures were 2°C or below for 3.5
months or more per year.

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Turbidity
Turbidity reductions under normal am-
bient conditions were uniformly good.
The results are summarized in Table 3.
The average slow sand filter effluent
turbidity value wasO.22 NTU, and 90% of
the effluent samples showed 0.5 NTU or
less.
Trihalomethane Precursors

THM precursor reduction was studied
for both warm and cold water conditions.
Precursor reduction was evaluated by
generating THM's under conditions of
excess free chlorine residuals. No appre-
ciable reduction in precursors occurred
when passing through the slow sand
filter.
Diatomaceous Earth Filtration
Diatomaceous earth filtration was
evaluated using pressure (0.74 and 0.93
m2, or 8 and 1 0 ft2 septum area filters).
Filtration ratesaveraged2.4and4.3 m/hr
using Celite 503®.* At low ambient
bacterial loads (5/100 mL of total coli-
forms and 30/mL or fewer standard plate
count bacteria), the reduction in bacteria
appeared to be low.

Total Coliforms and Standard
Plate Counts

The average reduction was 87% for
total coliform and 89% for standard plate
count bacteria. Of these runs, 50%
showed 92% reduction in total coliforms
and 90% or more reduction in standard
plate count bacteria. Filtration at 4. 3 m/hr
demonstrated slightly lower reductions in
bacteria compared with the 2.4 m/hr
rate: the average reduction was 77% for
total coliforms and 87% for standard plate
count bacteria at the high rate of filtration
compared with the 92% and 88%, respec-
tively, at the low rate; but this difference
did not constitute a significant variation.
Bacterial Spiking
Under bacterial spiking conditions, the
average reduction was 98% for total
coliforms and 93% for standard plate
count bacteria. Of these runs, 50% re-
duced total coliforms 98% or more and
standard plate count, 94% or more.



• jf

99.80 - /
/
/
| 99.60 -J
^
03
*
I 99.40 -
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1



















1
0 5 10 15 20



Temperature ° C

Figure 3. Slow sand filter reduction of
f filtration rate of 0.08 m/hr).


Giardia cysts at


various temperatures

Table 2. G iardia Cyst Removal with the Slow Sand Filter*
Days Since Number of
Most Recent 24-Hour
Filter Samples Cysts
Scraping Collected Recovered

34 6 4032
88 26 3214
117 26 3503

50 38 4090
144 28 485
174 32 51
82 7 8
35 5 42


Spike Date Sample Dates
2/28/83 3/ 1 / 83-3/6/83
1/16/84 1/17/84-2/14/84
2/14/84 2/15/84-3/12/84
12/8/83 12/9/83-1/16/84
3/12/84 3/13/84-4/9/84
4/9/84 4/10/84-5/11/84
5/ 1 6/83 5/ 1 7/83-5/23/83
8/8/83 8/9/83-8/12/83
'Filtration rate is 0.08 m/hr.

Number of
Samples With
No Cysts

3
9
10

19
2
19
6
2

Temperature
f°C)
0.5°
0.5°
0.5°
0.75°
0.75°
7.5°
11°
21°



Cyst
Removal t%)
_ _ —
93.7
99.62
99.46

99.36
99.91
99.99
99.98
99.98


Cysts Applied
2.1 x10e
2.55 x 107
2.31 x 107
2.3 x 107
2.55 x 107
2.31 x 10r
2.1 xW6
a
8 x 10e

Turbidity
  Turbidity reduction was fairly consis-
tent during  the  DE runs. The average
reduction was 71'
effluent of 0.5 NTU.
with an  average
'Mention of trade names or commercial products
 does not constitute endorsement or recommenda-
 tion for use.
Giardia Cyst Spiking
  One Giardia spike  of 8  x 106 cysts
produced 99.97% removal—a result con-
sistent with the DE results previously
reported by other researchers. No other
Giardia spike applications were conducted
because cyst supplies needed  to be
conserved and because other work had
shown similar results. The results of this
study are shown in Table 4. The reduction

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 Table 3.    Turbidity Removal with the Slow Sand Filter
                                                Turbidity (NTU)
Sample
Point
Influent
Effluent
Number of
Observations
674
701
Average
1.4
0.22
Maximum
59
8.0
Minimum
0.2
0.05
 Table 4.    G iardia Cyst Removal by the Diatomaceous Earth Filter with Celite 503®
Filtration
Rate m/hr
Temperature
°C
Cysts
Applied
Actual
Cysts
Recovered
Portion of
Effluent
Sampled
Cyst
Removal
      3.8
23°
8x10"
48
5.3%
99.97%
of 99.97% was excellent at the 4.3 m/hr
filtration rate.

THM Precursors
  The DE filter did not affect the THM
precursor reduction, and the results were
similar to the  values for the slow sand
filter.
  For this water body, feed rates of 3 to 4
mg/L appeared to produce the best results
when  related  to pressure buildup. The
higher filtration rate (4.4 m/hr) appeared
to have a slight advantage over the lower
rate (2.4 m/hr) filtration.

Grade of Diatomaceous Earth
  DE grade effects were  not studied
extensively. From very limited studies, it
did appear that a finer grade might have
been advantageous for this water in that
body feed rates on the order of 28 mg/L
produced  much  longer  operation time
than the  3 mg/L  at the same rate of
filtration.  The  longest  operation times
were provided by the coarse grade at body
feed values of  about 3 to 4 mg/L and by
the fine grade at about 28 mg/L or
possibly more.

Water Plant Operation
  Operation and cost information was
accumulated during the course of this
study and analyzed to evaluate slow sand
filter needs and compare them with DE
operation.
  Cleaning requirements for  the  slow
sand  filter can  be expressed by the
relationship:
          Y = 1.6 +  3.5x±1.0
where Y = person hours to clean, and x =
removed sand volume (m3). A considerable
amount of variation existed in a  single
determination. The type of installation
                      and operating conditions affect the clean-
                      ing results.
                        The length of the slow sand filter runs
                      could not be extrapolated from head loss
                      information. For this full-scale filter and
                      the particular water source,  filter runs
                      could be expected to range from 100 to
                      250 days, but plots of head loss versus
                      time  tended to be very flat for many
                      months and then suddenly increase ex-
                      ponentially  to limiting head loss values.
                      Many more studies over 5 to 10 years
                      would be required to provide sufficient
                      data for predicting a pattern, if a pattern is
                      possible.
                        Operation time data were recorded
                      during the study to determine the time
                      required to  obtain and record turbidity,
                      temperature, and chlorine residuals and
                      also  to sample  for bacteria  and make
                      chlorine  solutions. The mean time re-
                      quirements  are  as follows:  1.46 hr for
                      reading, testing, and recording turbidity
                      and temperature;  1.54 hr for bacteria,
                      turbidity,  and temperature; 0.38 hr for
                      chlorine residual; and 0.20 hr for chlorine
                      preparation. Results will vary consider-
                      ably depending on facilities and person-
                      nel.
                        Production costs for water were eval-
                      uated. If the slow sand filter used in the
                      study were constructed new in 1984 and
                      operated  at full capacity (0.08  m/hr),
                      water would  cost  $4.60/1000  gal.  A
                      similar-capacity DE pressure filter might
                      produce water at a comparable cost. The
                      DE studies  did  not provide sufficient
                      operating data to permit extrapolating DE
                      costs in a meaningful  manner.  The re-
                      search included too many operational
                      variables to permit development of infor-
                      mation that would  be comparable to that
                      from  a functioning treatment plant. The
                      DE filtration research operating data were
                                                              not comparable to the slow sand filter
                                                              operating data.
                                                                The stated cost values are produced
                                                              costs, not delivered costs. These costs are
                                                              high. For small systems, however, they
                                                              are comparable to costs that could be
                                                              incurred when individuals drill wells and
                                                              install private water systems that can
                                                              produce high quality water equalling or
                                                              exceeding the Safe Drinking Water Act's
                                                              quality requirements.
Conclusions

Slow Sand Filtration
  1.  Slow sand filtration  provided de-
     pendable water treatment with a
     minimum of attention, but capital
     cost was high.
  2.  Turbidity was below 1 NTU 99.19%
     of the time. After the first 100 days
     of operation, the effluent turbidity
     values were below 1  NTU 99.68%
     of the time. Turbidity values were
     0.2 NTU, or less, 72% of the time.
  3.  Slow sand  filtration reduced total
     coliforms to 10/100 mL, or fewer,
     86% of the time under ambient load
     conditions.
  4.  The standard plate count bacteria
     were  reduced to 10/mL, or fewer,
     94% of thetime under ambient load
     conditions.
  5.  Massive spikes of total coliform and
     standard plate count bacteria were
     removed from raw water at tem-
     perature conditions  above 5° to
     10°C.
  6.  Slow  sand filtration  was  not  as
     efficient in removing bacteria at
     temperatures below 5°C, particu-
     larly around 0° to 1°C.
  7.  Giardia cysts were removed very
     dependably; 99.98%  removals or
     better were achieved under warm
     temperature conditions.
  8.  Giardia cysts were not as complete-
     ly removed at low temperatures; at
     temperatures below 7°C, removals
     were 99.36 to 99.91%.
  9.  Heavy applications of bacteria and
     Giardia cysts to the  filter at the
     same  time  under  cold conditions
     produced signs of competition for
     the biological treatment capability.
     Giardia cyst removal was reduced
     to  93.7%,  and reduction of  total
     coliforms and standard plate count
     bacteria dropped to 43% and to 79%
     to 82%, respectively.

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10.  Slow sand filtration did not produce
     any significant  reduction of THM
     precursors.
11.  Erratic particle reduction in the 7-to
     12-/ym range did not compare with
     the Giardia cyst removal results.
12.  Particle reduction did not provide a
     dependable method  of predicting
     Giardia cyst removal  in this full-
     scale  operating filter experiment
     with this particular water.
13.  The mature  filter recovered from
     cleaning within 2 weeks to provide
     dependable bacteria  and turbidity
     removal. Limited data showed that
     at times under warm weather con-
     ditions the effluent water contained
     satisfactory bacteria  and turbidity
     concentrations before 2 weeks had
     elapsed.
14.  A minimum of 1.5 hr of operation
     were  required each day to run the
     system properly and meet monitor-
     ing requirements.


Pressure Diatomaceous Earth
Filtration
  1.  Pressure  DE  filtration  removed
     Giardia cysts  dependably  using
     Celite 503® with 99.97% reduction.

  2.  Total  coliforms  were  reduced 86%
     or more in 70% of the samples, and
     standard plate count bacteria were
     reduced 80% or more in 70% of the
     samples.
  3.  Eighty-six percent of the average
     run values for total coliforms did not
     exceed 8/100 ml, and 82% of the
     average run  values  for  standard
     plate counts did not exceed 12/mL.
  4.  The average bacterial content in the
     effluent under ambient conditions
     was 38/100 mL for total coliforms
     and 6/mL for standard plate count
     bacteria.
  5.  Under spiking conditions, the aver-
     age reduction was 97.6% for total
     coliforms and 92.7% for standard
     plate count bacteria. Eighty percent
     of the average run values showed
     total coliform reductions of 95.8%
     or more and standard plate count
     reductions of 87.5% or more.

  6.  Under spiking conditions,  effluent
     total  coliforms  averaged 122/100
     mL (107/100 mL or fewer for 77%
     of the runs),  and standard plate
     counts averaged 47/mL (7/mL or
     fewer for 77% of the  runs).
 7.   Pressure DE filtration provided rapid
     cycle time and flexible filter water
     production capability.
 8.   The system required full-time oper-
     ation when  running  and  careful
     attention  to every detail of opera-
     tion.
 9.   Highly skilled operators are needed
     for dependable  production of the
     most satisfactory water the treat-
     ment process can produce.
10.   The costs for producing small quan-
     tities of water are comparable with
     those for the slow sand filter.
 11.  The process is labor-, energy- and
     materials-intensive,  as  compared
     with that of slow sand filtration.

 12.  Particle reductions in the 7- to 12-
     pim range were  erratic for this
     water. Slime organisms may have
     contributed to the erratic results.
  The full report was submitted in fulfill-
ment of Cooperative Agreement No. CR-
809284010 with  Mclndoe Falls  Fire
District #3, under the sponsorship of the
U.S. Environmental Protection Agency.
  Gordon R. Pyper is with Dufresne-Henry, Inc., North Springfield, VT 05150.
  Gary S. Logsdon is the EPA Project Officer (see below).
  The complete report, entitled  Slow Sand Filter and Package Treatment Plant
    Evaluation: Operating Costs and Removal of Bacteria, Giardia. and Trihalo-
    methanes,"(Order No. PB 85-197 051 /AS; Cost: $17.50. 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:
          Water Engineering Research Laboratory
          U.S. Environmental Protection Agency
          Cincinnati, OH 45268
                                                                                       t U.S. GOVERNMENT PRINTING OFFICE 1«W - 559-111/10862

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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
          OCOC329   PS

          U  3  ENVIR  PROTECTION AGENCY
          REGION  5 LIBRARY
          230  S DEAPBCRN STREET
          CHICAGO              It-   6Q<$0<

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