Suspended Ion Exchange for organics removal

SIX® is a suspended ion exchange process, developed by PWNT as an alternative to coagulation for organics removal. It is suitable for treating surface waters to remove dissolved organics. The system uses an efficient resin contacting, separation and regeneration system, with brine used up to five times which helps reduce waste streams.

NOM-removal at SWTP Andijk (Netherlands) with a New Anion Exchange Process, called SIX®

Abstract: The new developed ion exchange process SIX presents an advanced solution for a world-wide challenge: How to remove NOM/DOC as a first step in surface water treatment to improve efficiency of downstream processes and to improve water quality. Besides the possibility to treat water containing suspended matter another advantage is the fact that the process has advanced to an economical and technical feasible process, guaranteeing a stable water quality, resulting in a large tolerance for flow fluctuations and relatively low contact times and small resin inventory. Most important advancement however is that almost every commercially available resin can be used creating the desired flexibility in suppliers for water supply companies. This paper describes the process and generates advantages and disadvantages compared to conventional technologies leading to the world first full-scale application with a capacity of 5500 m3/h.

The advantages of SIX® are:

  • Efficient removal of organics (60-90%)
  • High UV transmission achieved (>90%)
  • No iron or aluminium based sludge
  • Compatibility with a variety of commercially-available resins to achieve a wide range of required water quality
    targets, allowing flexibility to meet different conditions
  • Very minimal chemical requirement – the only major chemical requirement is salt (sodium chloride) for regeneration
  • Resin is recycled with low resin attrition and loss, thus low additional resin is needed over time
  • Short resin contact times, implying no risk of resin blinding and biofouling
  • Full-scale resin service life > five years
  • Other anions, such as sulfate and nitrate, are also removed
  • Possible regeneration with sodium bicarbonate

An Introduction to SIX®