Dosing MPE50 polymer to increase MBR flux rates
Annual Conference
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Stormwater ingress and infiltration (I&I) into the wastewater reticulation in Te Aroha is high, with the hydraulic capacity of the membrane bioreactor (MBR) being inadequate to treat wet weather flows (WWF). Nalco have developed a polymer, MPE50, specifically for use as a flux-enhancer in MBR plants. The polymer is designed to bind extracellular polymeric substances (EPS) into the floc, reducing the membrane fouling potential.
Laboratory tests were initially undertaken to determine whether MPE50 would be suitable for Te Aroha WwTP, followed by a full-scale trial in winter 2008 after the bench trials proved effective. The laboratory tests indicated the optimal MPE50 dose to be 450mg/l for Te Aroha. An initial bulk dose of 200 litres was required to achieve the required polymer concentration, with a daily polymer dose applied to maintain the desired polymer residual. Particle size analysis confirmed that the polymer addition resulted in an increase in floc size and filterability.
The average flux rate was increased from 19.5 to 28.9 LMH during the period of polymer addition, representing an increase of 48%. This average increase was maintained over a period of 82 days, after which polymer addition ceased as flows reduced.