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Printer Friendly VersionSelected Information - Completed Research

CP334  Optimisation of Filter Backwashing Water Treatment
Project Appreciation and Objectives

Regulatory changes have led to much tighter monitoring and control of water treatment, and in particular improvement in the efficiency of particle removal by rapid filtration processes. Overall operation of filtration is less well optimised however, and there is scope to both reduce costs and increase security by suitable monitoring. Filter backwashing, in particular, is critical to the filtration process. A system to monitor backwashing directly and automatically would provide added security by detecting any deterioration in efficiency while reducing energy and water usage. The system could be based on one or more approaches including: monitoring of headloss across the bed during either water wash or air scour or direct monitoring of suspended solids in the backwash stream.

This work examined current approaches to monitor solids capture (filtration) and solids release (backwashing). Alternatives were identified, developed and tested in order to provide a monitoring system which will allow energy and water usage to be optimised while ensuring that deterioration is detected.

Benefits to Clients

  • Reduced cost of filter operation through optimised use of water and energy for backwash.
  • Greater security and improved operational management by earlier identification of faults with filter operation.

Work Programme

  1. Review current approaches to setting backwash regimes, and monitoring of the backwash cycle.
  2. Utilise existing information (e.g. headloss across bed during backwash, pressure in air blower delivery line) to provide information on the nature of the dirty filter bed and the air nozzles. This will include simulation of the effect of broken filter nozzles.
  3. Explore the benefits and feasibility of alternative approaches to monitoring of backwash, including on-line monitoring of backwash solids.
  4. Monitor filter backwashing at a trial site using either existing or new techniques, or both, in order to evaluate the benefits of the approach(es).

Project Outputs

  • A detailed report providing options for using existing information to optimise process efficiency. Alternative monitoring approaches were reviewed both theoretically and from field evaluations. Opportunities for implementing technology to optimise filtration were highlighted.
  • A workshop to disseminate project results to all contributors. Additional, tailored, presentations were given to contributors to facilitate implementation of findings.

Related WRc Work

  • Media testing for commercial clients including: sand (2006); ferric hydroxide absorbent (2004), pumice and anthracite (2001).
  • WRc regularly undertakes media testing in support of process audits.
WRc's Portfolio Programme
Summary of the £1.5 million per annum research programme

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