Microfiltration membrane plant start up: A case study with autopsy and permeability recovery analysis

A potable water treatment plant, supplied from a low NOM (natural organic matter), low turbidity source with precoagulation and two‐stage pressure sand filtration, had a MF (microfiltration) membrane process added to meet UK Water Regulations. An autopsy of the membrane modules showed that despite upstream coagulation/filtration with chlorination, a biofilm of EPS (extracellular polymeric substances) and inorganic particulates had developed. Backwashing under laboratory conditions yielded an almost full recovery. Laboratory‐scale modules of fouled fibres from pre‐commissioning and post‐commissioning were assembled and cleaned. The recovery was modelled and optimized with a response surface experiment using variables of concentration, soak period and temperature. The pre‐commissioning fibres were more recovered by longer chemical soak times at higher cleanant concentrations than the post‐commissioning fibres. Comparative tests on post‐commissioning fibres indicated that full recovery was possible with orga...