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

LIMITATIONS AND CONCERNS

• Pilot Plant TestingPilot testing:
  Pilot testing is the use of treatment units significantly smaller than the full scale plant but which would mimic the treatment of the full scale plant in order to determine design and operational factors. may be required due to less experience with 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)./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). membrane systems than with conventionalConventional treatment:
Conventional treatment refers to older established water treatment process such as coagulation, flocculation, and rapid sand filters. treatment systems.

• Membrane foulingMembrane fouling:
  Membrane fouling in microfiltration and ultrafiltration is the accumulation of particulates on the membrane surface or within the membrane that inhibits the flow of water through the membrane and leads to a higher transmembrane pressure or reduction in flux. and the need for periodic membrane cleaning are concerns.

• Consultants and equipment suppliers may overstate the advantages, benefits and life-cycleLife-cycle costs:
  Life-cycle costs include all the costs associated with an asset, i.e., cradle to grave costs including initial purchase/construction costs, operation and maintenance costs and final disposal/demolition costs. costs of membranes versus conventional treatment. Conventional treatment can be a cost effective option and deeper bed rapid sand filters (6-7 ft) can achieve log removalsLog removal value (LRV) or log reduction credit:
  The log removal value or log removal credit is the filtration removal efficiency for a target organism, particulate, or surrogate expressed as log10(feed concentration) – log10(filtrate concentration). of CryptosporidiumCryptosporidium:
 According to the U.S. Center for Disease Control, Cryptosporidium is a microscopic parasite that causes the diarrheal disease cryptosporidiosis. Both the parasite and the disease are commonly known as "Crypto." There are many species of Cryptosporidium that infect humans and animals. The parasite is protected by an outer shell that allows it to survive outside the body for long periods of time and makes it very tolerant to chlorine disinfection. While this parasite can be spread in several different ways, water (drinking water and recreational water) is the most common method of transmission. Cryptosporidium is one of the most frequent causes of waterborne disease among humans in the United States. comparable to membranes. (McEwen 2006)

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