United States
 Environmental Protection
 Agency	     	
Risk Reduction
Engineering Laboratory
Cincinnati OH 45268
 Research and Development
 EPA/600/S2-89/050 Mar. 1990
 Project Summary
 Point-of-Use  Treatment of
 Drinking  Water  in
 San  Ysidro,  NM
Karen Raborn Rogers
  This study was conducted to deter-
mine whether point-of-use  (POU)
reverse osmosis (RO)  units could
satisfactorily function  in lieu of  cen-
tral treatment to remove arsenic and
fluoride from  the  drinking  water
supply of San  Ysidro,  NM. POU treat-
ment was evaluated for  removal
efficiency, cost,  and management
effectiveness.
  Seventy-eight under-the-sink model
RO units  were Installed in private
homes,  and 72 were  monitored for
about 18 mo to evaluate operational
and  maintenance  data for POU treat-
ment
  This Project  Summary was  devel-
oped by EPA's Risk Reduction Engi-
neering 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 San  Ysidro is a small
rural  community of approximately 200
people located in the north central part of
the State of New Mexico approximately
45 mi (72  km)  north of Albuquerque.
Leedshill-Herkenhoff, Inc. (Engineers and
Architects),  was  initially  retained  by the
Village in June  1982 to evaluate  San
Ysidro's  water supply system. The Vil-
lage was having  problems meeting water
demands and was also out of compliance
with the National Interim Primary Drinking
Water Regulations for arsenic and  fluo-
ride.  Feasibility  studies were  to be per-
formed to determine whether economical
improvements  to the system  could be
recommended—improvements that would
solve  both San Ysidro's  water quantity
and quality inadequacies.
  The Village has had a  long  history of
water supply  problems  including  low
water pressure,  no water at  all, and
quality problems including taste,  color,
clarity, and odor in addition to arsenic
and fluoride contamination and sporadic
coliform violations.  The water supply
source is an infiltration gallery that pro-
duces an average of 27,000 gpd  in the
winter and 36,000  gpd in the summer
from the groundwater.  The Village uses
an average of 30,000 gpd, which equates
to about 150 gpd per person.  This con-
sumption rate pushed the production
limits of the gallery.
  The local groundwater contains  leach-
ate from geothermal activity in the  area's
abundant mineral deposits and  is  there-
fore high in mineral content. At the time
of the study, the groundwater  exceeded
the recommended  standards and/or
maximum contaminant levels (MCL's) for
arsenic, fluoride, iron, manganese, chlo-
ride, and total dissolved solids. The con-
taminants of concern in the Village water
supply were arsenic V and III and fluoride
which exceeded the MCL's by three to
four  times. Table  1 shows a typical
analysis of the water in  the infiltration
gallery. A  University of Houston  study
indicated that the arsenic present  in the
San Ysidro water supply  averaged 35%
as As III.
  A variance from  the Safe  Drinking
Water  Act  (SDWA) for  arsenic and
fluoride was granted  to the Village while
U.S.  Environmental  Protection  Agency

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(EPA) sponsored research was done (Dr.
Dennis  Clifford of  the  University of
Houston, Texas) to determine  an eco-
nomical  and effective solution to the
contaminant  problem.  The  treatment
technologies studied were activated
alumina and RO. Central  and  POU treat-
ment were considered.

Table 1.   Analysis  of Filtration Gallery
          Water in San Ysidro
  Analyte
Analytical Results
As
Cd
Cr
Pb
"9
Ca
Alkalinity
Cl
Hardness
Fe
Mg
Mn
pH
S04
N03 as N
F
Na
TDS
0.075
< 0,008
<0.02
<0.001
<0.01
86.4
447
88
272
0.06
13.6
0.05
778
30
0.1
1.6
135
914
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mgIL
mg/L
mg/L
mg/L
units
mg/L
mg/L
mg/L
mg/L
mg/L
  Central treatment of the entire water
supply was  not  considered  feasible for
many reasons. Firstly, a disposal problem
exists with both the arsenic-contaminated
wastes from  activated  alumina regen-
eration and the reject brine from an RO
system. Secondly, the capital costs and
the operation and maintenance costs of
central treatment were determined to be
higher than  POU treatment.  And, lastly,
central treatment  was  considered  too
complicated to be efficiently operated by
a community the size of San Ysidro. The
results of the study indicated  the  best
solution to  be POU treatment  with  RO
units.

Procedures

System and Contractor
Selection
  A  notification letter  was sent to each
water customer, and a public hearing was
held on December 18, 1985,  in which the
cooperative  agreement  between  the
Village and the EPA was brought before
the villagers to explain the water quality
problem  and to  discuss the procedures
needed to  have  the  RO  POU devices
installed, maintained,  and tested  during
the study period. The Village passed an
ordinance requiring the installation  of an
RO system in  each  water customer's
home if the home had indoor  plumbing.
The  ordinance  was deemed necessary
because  POU treatment could  not be
considered a viable alternative  to central
treatment for a  public  water system
unless the utility furnished  safe drinking
water to  each water  customer.  Each
water customer also had to sign a per-
mission form to allow the Village to  install
the unit in their home and to allow access
to the unit for testing and  maintenance.
The permission form was necessary be-
cause an ordinance  could  not give the
Village the authority to enter a person's
house (only an individual can grant per-
mission to the Village to enter his home).
  A Request for Proposal was prepared
in which contractors were  asked to
prepare  competitive bid proposals for
furnishing approximately 80 RO  units,
including  installation  and 14 mo of unit
maintenance, to the Village of San Ysidro.
  The RO units  were  required  to be
under-the-sink models capable of pro-
ducing a  minimum of 5  gal of drinking
water per day with a storage capacity of
3 gal (Figure  1). The system  pressure
range was given  as 40  to  60  psi  maxi-
mum, with a minimum pressure of 20 psi.
The  units were  required to reduce the
contaminants to below the  established
MCL's as shown in Table 2.
  The contractor was required to perform
service checks and  preventive mainte-
nance on each unit every other month as
well  as  repairs to maintain  the  units
operational during an initial 14-mo period.
Maximum time allowed for service calls
was 3 working days. The contractor was
required  to cover the costs of any house-
hold damages resulting from malfunction
of the RO units during the service period.
  Based   on the above criteria,  each
bidder was required to submit  prices for
a per unit purchase  price, a  per unit
installation price, and  a per unit monthly
service charge. Each bidder was also re-
quired to  furnish manufacturer's  data
covering  typical installation  instructions,
construction details, and operating in-
structions.
  Four bid proposals  were  received and
evaluated by  Leedshill-Herkenhoff, the
EPA Project Officer, and a representative
of the State of New  Mexico  Environ-
mental Improvement  Division.  The pro-
posals were evaluated on  nine factors
(Table 3), and associated  weights, as
described in the Request  for Proposal,
were  given each factor.
  The selected proposal was  submitted
by  Southwest Water  Conditioning  (a
Culligan* representative in Albuque
The  price per  unit for  purchase,
lation, and monthly service was $2
$35.50, and  $8.60, respectively. Th
posal also included an  RO  test IT
on each  unit that consisted  of an
total dissolved solids (TDS) meter.
  Within  the first 4 mo of the proje
RO units were installed, and  5 more
added by the end of  the project p
Of the 78 units installed, however
72 were actually available for testin;
regular basis. At three homes, tot;
meters were also  installed  on the
line  to the  RO units to measur
amount of water used by the systen

Data Collection
  The  RO  units  were  operatec
monitored for an  18-mo  period.
samples  were scheduled to  be col
every  other month  for arsenic
fluoride  analyses.  In  addition,  the
were to  be sampled every 4 to 6 t
chloride,  iron, and manganese. Be
of various restrictions, only 40  unit;
analyzed for total coliforms.  Each r
an average of 31 units were sampl
arsenic and fluoride;  of  these, 15
also sampled  for chloride,  iron
manganese and 10 for total coliforrr

Results

Water Usage
  The average water use  by  th
systems  recorded at the three  f
with  totalizing meters varied from
17.0 gpd (Table  4).  Water use
because  of  the size of the  familie
their use of the  RO-treated water. P
water production  (recovery) by tt
system depends on inlet water pr
and  TDS but ranges from 20% to c
the total  flow into  the unit at 50 p
less  than 1,500  ppm TDS.

Operational  Problems
  The initial 14-mo maintenance a
signed  with Southwest Water (
tioning was  extended to 20 mo
contractor could train a Village em
to perform  routine RO  system (
and  maintenance.
  Operational problems  were  re<
during the  study.  Within the first
six  RO  modules  were replaced <
installations  required  service bees
                                                              "Mention of trade names or commercial pn
                                                               does  not constitute endorsement or r
                                                               mendation for use

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             Legend

        Tap Connection to Existing Water Line

        Pre-filter

    @ Carbon Filter

    ^y Reverse Osmosis Unit

    ^) Storage Tank

    ^y Carbon Post-filter

    \7j Faucet with Built-in Air Gap for Drain Line

    ^y Existing Sink

    ^y Drain Connection to Existing Sink Drain


gure  1.  Typical under the sink reverse osmosis unit.
\tile 2.   RO  Requirements for  Contaminant
         Reduction
                         Contaminant-mg/L
     Contaminant
From
To
ron
Manganese
Chloride
:luoride
Ursemc V & III
'otal Dissolved Solids
2.0
0.2
325.0
5.2
0.2
1000.0
0.3
0.05
250.0
1.8
0.05
500.0
leaks, IDS monitor problems, or  water
flow  problems.  A summary  of service
calls  performed during the 20-mo
service period is shown in Table 5.
  Because  a  few  RO-treated  water
samples tested  positive for coliform and
the central water system did not test
positive during the sampling period, an
extensive investigation was conducted to
determine the cause. During  the investi-
gation, all RO units  were found to have
been  installed  with  the RO  drain con-
nected directly to the  kitchen sink drain
(without  an air gap). Because every
home in  San Ysidro has a septic tank,
the cross-connection  between the  RO
dram line and disposal line was strongly
suspected  to be  causing the positive
coliform tests. The installer modified  all
systems  to eliminate  the  cross-
connection  by  providing an air  gap
between  the discharge  line and  drain
line. After the  air-gap  problem  was
corrected,  no   more  positive coliform
tests were obtained. Only a few months
of samples were taken after the change,
however,  and  therefore the  air-gap
problem  could  not  be positively  iden-
tified as the source of the problem.

Chemical Contaminant Removal
  The  RO units effectively removed
arsenic and fluoride from the water. The
RO units also effectively removed chlo-
ride, iron, manganese, and TDS, but did
not quite meet the removal rates stated
in the manufacturer's  cause of  the
number and concentration of  literature.
This  was  probably  because of  the
contaminants in the water supply.  Table
6 shows average removal percentage for
each  of  the contaminants  during  the
project period.
  Because of the high costs of arsenic
and  fluoride  analyses,  conductivity
measurements  were evaluated  as  a
substitute for arsenic  and fluoride tests.
An analysis of the arsenic, fluoride and
conductivity data  showed  a  rule  of
thumb could be established whereby a
conductivity measurement of  less than
600 micromohs/cm  would maintain less
than 0.03 mg/L  of arsenic and less than
1.0 mg/L of fluoride.

Bacteria Samples
  Over a  13-mo  period,  131   water
samples  were collected from 40 RO  unit
special taps for  coliform analysis  by
membrane filter technique. Nine of these
tests were positive  for coliforms. In  ad-
dition, 10 tests  showed non-coliform
counts from 11 to too-numerous-to-count
(TNTC). Of the  microbiological tests, 15

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Table 3.    Factors and Weights for Proposal Evaluation
                                        Table 6.    Contaminant Removal by RO Systems
 Factor
                          Weight
 1.  Construction of Unit
 2.  History of Similar Installations
 3.  Proposal Completeness
 4.  Removal Efficiencies (including amount
    of water wasted by treatment)
 5.  Maintenance Record
 6.  Ease of Maintenance
 7.  Maintenance Service Contract
 8.  Price of Units and Installation Cost
 9.  Maintenance Service Contract Costs
                                    Total
Contaminant
Arsenic
Fluoride
Chloride
Iron
Manganese
TDS +
Average
Influent
(mg/L)
0.059
2.7
91
0.58
0.09
780
Average
Effluent
(mg/L)
0.008
0.339
14.59
0.019
0.012
93
%
Removal
86
87
84
97
87
88
% Remo\>
(Manufactui
Data)
68/96'
82
94
-
97
94
                                         * 68% removal of Arsenic III, 96% removal of Arsenic V.
                                         *As tested by contractor's service technicians on routine checks
Table 4.   Water Usage by RO Units
Family
r
2 +
3*
Family
Size
6
2
5
Average
Flow (god)
8.5
14.2
17.0
Maximum
Flow (gpd)
13.3
20.0
30.0
 " Water used for cooking only.
 * Water used for cooking and drinking.
* Water used for all purposes.
Table 5.    Service Calls by Types for 20-Month Period
 Type
Number
           Comments
 Leak
 TDS Monitor
 Flow Problem
 Routine Check
 Other
 Routine Check-
  No One home
   38
   11
  217
  150
  122
8% of leaks were not from the RO
unit.

All calls regarding red light of
monitor. 3 calls required a part
replacement, others required
adjustments only.

2 of reported flow problems were
due to low system pressure (25
psi).

25% of routine checks resulted in
repair or adjustment of unit not
identified by customer.

Other customer complaints
included taste or odor problems,
broken faucet handles, noisy air
gaps, and reinstallations.

This is 36% of the total routine
checks attempted. The actual
percentage is probably higher
since some "not at home" calls
were unrecorded.
             Total
   412'
"Average number of calls per month = 412/20 = 20.6.
 Number of calls required by contract = 33 to 35.
 Contract required checks on each installed unit every other month.
 Number installed varied over contract period.
of the 131  samples  from the  RO  ui
showed  some  evidence  of  bacte
contamination.
  Five water samples were collected fr
sink taps, and three of these tested I
high noncoliform counts. None  of thi
samples  tested  positive  for coliforms
did any  of  the  community's chlorina
water  supply  samples test  positive
coliform  during  the study.  The carl
prefilter in the RO unit removes chlorint
protect the polyamide RO membrane.
  An  extensive  investigation was m«
into the coliform  problem. A gene
description  of the  investigation  and
action  taken to  correct  the  problem
given in  the previous  section on Opt
tional Problems.

Regulations and Compliance
  When  the project started,  the VilU
passed an ordinance requiring each w<
customer to have an RO unit, if the ho
had indoor  plumbing. Also, each w<
customer had to sign a permission forn
allow the Village personnel access to tl
home to  install, test, and  maintain the
unit.  At  the  end  of  the  project,
ordinance  was  modified to  deal w
several  problems and  situations  t
developed  during  the project.  The  r
ordinance required  "commercial users'
provide  water  treatment to  meet
drinking  water standards  and allowed
Village to sample their water. The Villa
therefore,  maintained  complete con
over the residential systems and tra
ferred  all responsibility for providing  s
drinking  water to  the commercial  us
The ordinance also provided some latiti
to the commercial user  in  selecting
most economical treatment method.
  The new  ordinance  required that
residential RO units continue to be own
maintained,  and monitored by the Villa
but   made  certain  requirements of

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individual water customer. The ordinance
prohibits tampering  with the RO unit  in
any way and requires a weekly check for
leaks and  operation  of the IDS  test
switch. Also, the user  is required to  pro-
tect the unit from freezing and  standing
dry.
  The new ordinance also addressed two
liability issues. The  Village assumed lia-
bility for damages  to the users home
caused  by the  RO  unit, with limitations.
The user is held liable for damages if the
user did not perform the maintenance
check, tampered with the unit, or allowed
the membrane to be destroyed because
of temperature (freezing) or drying out.

Cost
  Cost data and information were  col-
ected on the replacement parts, mainte-
nance, bookkeeping, analytical tests,  and
nsurance. These data indicated that  a
nonthly service  charge  of $7  would be
necessary to cover the costs. If the  cost
Df the unit was included in the monthly
;harge,  the surcharge would be $12  to
 15, which is about half of the $30 to $40
jstimated cost  of central treatment for
he Village.  The actual  cost of treated
water based on  an  average  RO  produc-
ion of 7 gpd is, however, $0.06 per gal
 is compared to less than $0.01  per gal
or central treatment.

yublic  Acceptance
  A survey of the users (80 forms)  was
:onducted  at the end  of the   project.
Twenty-five  responses representing  73
residents were returned. Approximately
85%  of the  responses indicated they
were  pleased with the RO units, which
was  about  the same  as results from a
house-to-house survey.
  The majority of the negative comments
dealt  with the quantity of water produced
and  the water  pressure from  the unit's
faucet.  Thirty-eight  percent  were  not
pleased with the quantity, and all of these
comments were from  families  of four or
more persons.  Of the responses,  64%
indicated a willingness to pay  $5 to $10
per mo for continued use of the RO units,
20%  were willing to pay more than $10
per mo, and  16% were unwilling to pay
anything at all.


Conclusions and
Recommendations
  The following conclusions  were drawn
as a result of the San Ysidro study:
  POU treatment of drinking water is an
effective, economical,  reliable, and viable
alternative to  central treatment  in a small
community like  San  Ysidro to remove
arsenic as well as other contaminants.
  Adopting a POU treatment system in a
small community requires more care than
does  a central treatment system relative
to time-keeping to monitor the individual
systems.
  POU  systems require special regula-
tions  regarding customer responsibilities,
water utility  responsibilities, and the  re-
quirement of installation of the devices in
each  home obtaining water from the
utility.
  POU systems require special consider-
ations from regulatory agencies to deter-
mine  appropriate  methods for  record
keeping, monitoring, and  testing  fre-
quencies that  may differ from  existing
regulations.
  The  RO  units with polyamide  mem-
branes installed in San Ysidro resulted in
the following removal percentages, bring-
ing all of the contaminant  levels  well
below the MCL's: arsenic (total)  -  86%;
fluoride - 87%;  TDS  - 88%; chloride  -
84%; iron - 97%; and manganese - 87%.
  The  cost  to the  customer of  POU
treatment per month ($7) in San Ysidro is
less than half  of the estimated  cost  of
central treatment ($30 to $40 per mo).
The cost per gal of treated  water, how-
ever, is over three time? that of central
treatment, since  central  treatment treats
the entire water supply  and the  POU
device treats  a small  fraction  of the
supply.
  Total usage  of water through the RO
units,  including consumption, averaged
from 8.5 to 17.0 gpd. The units  were
designed to produce 5 to 8 gal of treated
water.
  The  full report was submitted in ful-
fillment of Cooperative Agreement  CR-
812499 by  Leedshill-Herkenhoff,  Inc.,
under the sponsorship of the U.S.  Envi-
ronmental Protection Agency.

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  Karen Raborn Rogers is with Leedshill-Herkenhoff, Inc., Albuquerque, NM 87103.
  Kim R Fox is the EPA Project Officer (see below).
  The complete report, entitled "Point-of-Use Treatment of Drinking Water in San
    Ysidro, NM," (Order No. PB 90-108 838/AS; Cost: $17.00. 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:
         Risk Reduction Engineering Laboratory
         U.S. Environmental Protection Agency
         Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300

EPA/600/S2-89/050
US.OFFICIAL MAIL*
         {J.S.POSTAR '

         s 0 .3 5 H

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