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SPWSTAC 2006
From POU to Centralized Arsenic Treatment: A Small Water System Case Study
2006 NGWA Naturally Occurring Contaminants Conference
J. Mitchell Spear, Charles A. Cole, Yuefeng Xie and Alison Shuler
Penn State Harrisburg
Objective
Conduct an evaluation of a POU device for removal of arsenic in a small public water system to determine the feasibility and cost effectiveness with respect to a similar centralized treatment technology.
SPWSTAC 2006
POU vs. Centralized Treatment
The advantages of decentralized (POU) treatment in small public water systems.
1) Lower capital cost
2) Treating only water for consumption
(approx. 10- 40 percent total water)
3) No highly skilled operators needed
4) Waste disposal not a problem
5) Cost saving in smaller systems
SPWSTAC 2006
POU vs. Centralized Treatment
The advantages of centralized treatment in small public water systems
1) Treats all water
2) Lower annual costs
3) Little customer involvement
4) Cost saving in larger systems
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POU vs. Centralized Treatment Cost Comparison
Most studies estimated this number is between 100 to 200 connections
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Number of Service Connections
Co
st (
$/ye
ar)
Overview
Community Selection
Treatment Technology Selection
POU Installations
Arsenic Removal Results
POU Costs
Centralized Treatment Installation and Costs
Summary
SPWSTAC 2006
BackgroundSystem selection
Within US EPA Region III
CWS – primarily residential
Arsenic Concentration (10 µg/L<[As]<50 µg/L )
Population less than 500
Service connections (between 30 - 200)
No plan to meet upcoming MCL
SPWSTAC 2006
BackgroundSystem selection
Mohrsville, PA
Population size 375
Service Connections 125
Production (GPD) 17000
Storage Capacity (Gallons) 125000
Wells 1
Disinfectant 12.5% sodium hypochlorite
SPWSTAC 2006
Water Quality Characteristics
Parameter UnitspH 7.3
Arsenic, total 28.6 µg/L
Chlorine residual 0.2-0.3 mg/L
Alkalinity 86.0 mg/L
Total solids 220 mg/L
Total dissolved solids 216 mg/L
Calcium 37.5 mg/L
Magnesium 8.05 mg/L
Iron 80.0 µg/L
Manganese 40.0 µg/L
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Treatment SelectionGeneral Factors to Consider
Water Chemistry
S.S., Iron, pH, organics, bacteria
Infrastructure Constraints
Available space, electricity, sewer
Permitting Constraints
Labor
Availability and skill
SPWSTAC 2006
Treatment Technology Selection
Ability to treat both As+3 and As+5
NSF 61 approval
NSF 53 approval
Residuals (TCLP and WET)
Ability to scale up (POU to Central treatment)
--- Isolux™ - Magnesium Elektron, Inc. (Zirconium hydroxide adsorptive media)
SPWSTAC 2006
Installations
POU Treatment Design
Sed
imen
t filt
er
GA
C C
artr
idge
Isol
ux M
edia
RawTreated
FlowMeter
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Installations
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POU Pilot Test Result
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0
5
10
15
20
25
0 500 1000 1500 2000 2500 3000 3500
Gallons Treated
Ars
enic
Co
nce
ntr
atio
n (
ug
/L)
Monitoring Results on all POUsby GFAA
SPWSTAC 2006
0
5
10
15
20
25
30
35
0 1 2 3 4 5 6 7 8 9 10 11 12 13
Months after installation
Ars
en
ic (
ug
/L)
Raw
Treated
Monitoring Results by Flowmeter
Flow (gal/min) Gallons Treated
Mean 0.7 376
Median 0.8 330
Minimum 0.3 90
Maximum 0.9 781
SPWSTAC 2006
POU Piloting Costs (1st year)Item Dollar amountInstallation 90.00POU system 267.50
T-valve 6.50Housing 95.00
Pre filter (2X/year) 18.00 Carbon Filter (2X/year) 36.00
Isolux™ 70.00 Flow Meter 42.00
Field testing (2X) 6.00Compliance testing 15.00Operation & Maintenance* 0 - 200.00
Total 378.50 - 578.50
POU Annual Cost
Capital Costs $ 2004
Installation 90.00
T-Valve 6.50
Housing 95.00
Flow meter 42.00
Total 233.50
6% for 10 years 317.30
Total (yearly) 31.73
Total (monthly) 2.64
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Operating Costs $ 2004
Pre-filter 18.00
Carbon filter 36.00
Isolux™ 70.00
Field testing 6.00
Compliance 15.00
O & M 200.00
Total (yearly) 345.00
Total (monthly) 28.75
Total - $31 / unit / month
POU Acceptance?
25 Pa. Code § 109.602 Acceptable design.
(e) Point-of-use devises which are treatment devices applied to a single tap are not an acceptable treatment methods for complying with an MCL or treatment technique requirement.
SPWSTAC 2006
Centralized Treatment
75 gpm Treatment System w / 100% redundancy
Two 48 x 6 inch towers – 2 inch inlet and outlet
1 Flow meter / totalizer
Particulate prefilter housing
36 – 42 inch Isolux removal cartridges
3 hp booster pump
SPWSTAC 2006
Centralized Treatment Annual Cost
Capital Costs $ 2006 Treatment Modules
47000
Transportation 200
Cartridges (36) 6480
Start up and Training
2880
Total 56560
6% for 10 years 76848
Total (yearly) 7684
SPWSTAC 2006
Total - $9 / connection / month
Operating Costs $ 2006 Cartridges 5913
Particulate Filter 139
Transportation 150
Media Management 175
Total (yearly) 6377
Total Capital + Operating (yearly)
14061
Estimated Monthly Cost Comparison
Type of System Cost/Connection
POU $15 - $31
Centralized $9* Treatment
* Based on proposal for Isolux media, does not include additional time for operations
SPWSTAC 2006
POU vs. Centralized Treatment Cost Comparison
SPWSTAC 2006
Number of Service Connections
Co
st (
$/ye
ar)
User Survey Results
Amount willing to pay for POU (monthly)
Average $5
Minimum $0
Maximum $8
Amount willing to pay for centralized treatment (monthly)
Average $10
Minimum $0
Maximum $32
SPWSTAC 2006
Initial “hurdles”
Financial
Water association vs. public water utility
Water association awarded special allowance grant
Permitting
Contracted with licensed engineer for state permitting and overall site plan design
Site Location
No Available space near well house
SPWTAC 2006
Current Status
Proposal submitting to Pa DEP
Site plan accepted by Association Board
Contractors designated for site work
Targeted start up – March 2006
SPWSTAC 2006
Summary
POU effective for removing arsenic
Might be more economical solution in very small water systems
Record keeping, communication, increased sampling
Centralized Treatment chosen for Mohrsville site
SPWSTAC 2006
Acknowledgements
US EPA Small Public Water Systems Technology Assistance Center Grant for funding the study
Magnesium Elektron, Inc. and Jim Knoll for their technical guidance
Alice Renshaw (President of Mohrsville Water Association) for her cooperation
All participating homeowners
SPWSTAC 2006
Contact Information
US EPA Small Public Water System Technology Assistance Center
J. Mitchell Spear
Laboratory Supervisor, ETC
(717) 948-6357
SPWSTAC 2006
