The Use of Phosphates in Water Treatment for Corrosion Control & Sequestration

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Presented by Carus Corporation at the Maine Water Utilities Association, April 13, 2017.

This presentation explores the use of phosphates in water treatment for corrosion control and sequestration. Topics include compliance with the US EPA’s Lead and Copper Rule, factors influencing corrosion, chemical inhibitors, dosage rates, and the benefits of using phosphates. Case studies demonstrate real-world applications, with results like improved water quality, reduced metal corrosion, and cost savings. The document also outlines methods for monitoring corrosion control success and emphasizes safety in handling treatment chemicals.

Agenda

  • US EPA Lead and Copper Rule
  • Corrosion Definition
  • Chemical Factors Influencing Corrosion and Corrosion Control
  • Factors to Reduce Corrosion
  • Phosphates in Water Treatment
  • Chemical Inhibitors
  • Dosage Rates
  • Selection of Phosphates/Benefits of Phosphates
  • Case Studies
  • Monitoring Corrosion Control Success

Lead and Copper Rule (LCR)

  • Introduced June 7, 1991, by the US EPA.
  • Action Levels:
    • Lead: 0.015 mg/L (Maximum Contaminant Level Goal – MCLG: 0 mg/L)
    • Copper: 1.30 mg/L (MCLG: 1.30 mg/L)
  • Health Effects:
    • Lead: Delays in child development, kidney issues, high blood pressure.
    • Copper: Gastrointestinal, liver, and kidney problems.

Sampling and Compliance

  • 90th percentile of water samples determines compliance.
  • Samples are based on size and high-risk sites, taken from cold water taps unused for at least 6 hours.
  • Frequency of sampling can reduce if consistent compliance is maintained.

Corrosion Overview

  • Defined as the destructive attack of a material by chemical/electrochemical reaction with its environment.
  • Influenced by factors like pH, alkalinity, dissolved oxygen (DO), chlorine, total dissolved solids (TDS), and hardness.

Phosphates in Water Treatment

  • Used since 1887 for corrosion control and sequestration.
  • Categories:
    • Orthophosphates
    • Condensed (poly) phosphates
    • Zinc phosphates
  • Benefits include:
    • Improved water clarity.
    • Reduced flushing times.
    • Decreased lead and copper corrosion.

Case Studies

  • Examples where phosphates improved water quality:
    1. Carus 4105: Reduced lead and copper levels, improved taste, and decreased costs.
    2. Carus 8500 Blended Phosphate: Reduced hydrant flushing times and lead levels.
    3. Aqua Mag Blended Phosphate: Addressed tuberculation, improved flow, and reduced copper levels.

Monitoring and Maintenance

  • Methods include phosphate residual tests, coupon-based monitoring, and assessment of sequestering effectiveness.
  • Use of personal protective equipment (PPE) when handling phosphates.

Summary

  • Phosphate use offers significant benefits in water treatment, including reduced corrosion, improved water quality, and cost efficiency.

Download The Use of Phosphates in Water Treatment for Corrosion Control & Sequestration (PDF)

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