SPWSTAC 2006 From POU to Centralized Arsenic Treatment: A Small Water System Case Study 2006 NGWA Naturally Occurring Contaminants Conference J. Mitchell.

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

SPWSTAC 2006

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

SPWSTAC 2006

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

SPWSTAC 2006

Installations

SPWSTAC 2006

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

SPWSTAC 2006

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

[email protected]

(717) 948-6357

SPWSTAC 2006