Water Treatment Technology Assistance CenterUniversity of New HampshireUniversity of Tennessee-KnoxvilleMembrane SystemsLimestone Contractors ModuleUV Disinfection Module

  • List of Contents

  • Introduction
  • Process Description
    • Process Description
    • Membranes
    • Challenge Testing
    • Theory
    • Typical Pressure & Vacuum Systems
    • Integrity Testing
    • Indirect Integrity Monitoring
    • Post Treatment
    • Residuals Treatment & Disposal
  • Typical Membrane Unit
    • Typical Membrane Unit
    • Screening
    • Pretreatment
    • Membranes
    • Typical Pressure & Vacuum
    • Post-Treatment
    • Backpulsing
    • Chemical Cleaning
    • Residuals Treatment & Disposal
    • Integrity Testing
    • Indirect Integrity Monitoring
  • Design Criteria
    • Design Criteria
    • Theory
  • Example Plans & Specifications
  • Treatment Performance
  • Operation
    • Operation
    • Indirect Integrity Monitoring
    • Direct Integrity Testing
      • Testing Requirements
      • Determining UCL
  • Automation Potential
    • Automation Potential
    • Example SCADA Screens
  • Advantages
  • Limitations & Concerns
  • Pilot Plant Objectives
  • Costs
  • References
  • Contacts

INTEGRITY TESTING

For membrane systems that are used to comply with the LT2ESWTRLT2ESWTR:
  The Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) is an EPA regulation targeting control of Cryptosporidium and other microbial contaminants.  It mandates treatment efficiency, i.e., log removal values, and gives credit to various treatment technologies to achieve the needed treatment efficiency., integrity testing is required and is good practice in all cases. The goal of integrity testing is to determine whether the membrane system has suffered any breaks or leaks that are allowing unfiltered water to bypass the membrane barrier. The "breachesBreach or integrity breach:
A breach refers to leakage in the membrane module to due a broken fiber, leaking seal or other leak that can allow microbes and particulates to bypass the membrane and pass directly into the finished water." may have been caused by improper installation that did correctly seat and seal the interconnections and by membrane fiber damage from punctures, high pressures, abrasion or long term fatigue or from chemicals. There are two types of integrity tests:

1. Direct test methods: Direct test methods are tests on the membrane units themselves to determine whether a breach has occurred and potentially determine its general location. Direct methods are non-destructive and cannot be conducted while the unit is in service. Consequently, the test is done on each membrane unit or subunit separately in order to avoid having many units out of service simultaneously. Daily testing is required by the LT2ESWTR for systems using MFMicrofiltration (MF) membranes:
 Microfiltration membranes are typically hollow-fibers with a pore size range of approximately 0.1 – 0.2 μm (nominally 0.1 μm). and UFUltrafiltration (UF) membranes:
 Ultrafiltration membranes are typically hollow-fibers with a pore size range of approximately 0.01 – 0.05 μm (nominally 0.01 μm). membranes to meet its requirements. Regardless, daily testing is good practice and individual states have their own requirements. The most common type of direct test is the pressure decay test which measures the rate of decline of pressure across a membrane and compares this to acceptable values. Nearly all currently available systems from manufacturers have this test capability built in. Other direct test methods are to measure the flow of air or water from breaches or the concentration of particles spiked into the water. The exact location of a leak may be able to be located by submerging the membrane in water and forcing air through it and observing the air bubbles. Compromised membrane fibers are typically removed and the connection points sealed.

2. Indirect test methods: Indirect methods typically rely on measuring water quality parameters such as turbidityTurbidity:
  Turbidity is a measure of  the cloudiness of a water as well as a gross measure of the amount of suspended solids in a water.. Any unusual rise in turbidity is potentially a sign of a compromised membrane in which case a direct integrity testDirect integrity test:
A direct integrity test refers to the process usually performed daily to detect breaches in the membrane system.  Integrity tests are pressure-based or marker-based. would be conducted. Such indirect methods can be conducted continuously.

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