2006 NGWA Naturally Occurring Contaminants Conference
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2006 NGWA Naturally Occurring Contaminants Conference. From POU to Centralized Arsenic Treatment: A Small Water System Case Study. J. Mitchell Spear, Charles A. Cole, Yuefeng Xie and Alison Shuler Penn State Harrisburg. SPWSTAC 2006. Objective.

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2006 NGWA Naturally Occurring Contaminants Conference

From POU to Centralized Arsenic Treatment: A Small Water System Case Study

J. Mitchell Spear, Charles A. Cole, Yuefeng Xie and Alison Shuler

Penn State Harrisburg

SPWSTAC 2006


Objective
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.

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Pou vs centralized treatment
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 treatment1
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
POU vs. Centralized Treatment Cost Comparison

Most studies estimated this number is between 100 to 200 connections

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Overview

Overview

  • Community Selection

  • Treatment Technology Selection

  • POU Installations

  • Arsenic Removal Results

  • POU Costs

  • Centralized Treatment Installation and Costs

  • Summary

SPWSTAC 2006


Background system selection

Background System 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

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Background system selection1

Background System selection

  • Mohrsville, PA

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Treatment selection general factors to consider

Treatment Selection General Factors to Consider

  • Water Chemistry

    • S.S., Iron, pH, organics, bacteria

  • Infrastructure Constraints

    • Available space, electricity, sewer

  • Permitting Constraints

  • Labor

    • Availability and skill

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Treatment technology selection

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)

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Installations

Installations

POU Treatment Design

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Installations1

Installations

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Pou pilot test result

POU Pilot Test Result

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Monitoring results on all pous by gfaa

Monitoring Results on all POUsby GFAA

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Monitoring results by flowmeter
Monitoring Resultsby Flowmeter

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Pou annual cost
POU Annual Cost

Total - $31 / unit / month

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Pou acceptance

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.

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Centralized treatment

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

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Centralized treatment annual cost
Centralized Treatment Annual Cost

Total - $9 / connection / month

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Estimated monthly cost comparison
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

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User survey results

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

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Initial hurdles

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

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Current status

Current Status

  • Proposal submitting to Pa DEP

  • Site plan accepted by Association Board

  • Contractors designated for site work

  • Targeted start up – March 2006

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Summary

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

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Acknowledgements

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

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Contact information

Contact Information

US EPA Small Public Water System Technology Assistance Center

J. Mitchell Spear

Laboratory Supervisor, ETC

[email protected]

(717) 948-6357

SPWSTAC 2006


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