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 organic acids. It was concluded that start-up of new membrane plants may involve fouling conditions not necessarily representative of those under routine operating conditions, such that modification to prescribed cleaning operations may be required.
Porcelli
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N
Cranfield University, Cranfield, Bedfordshire, MK43 OAL, UK.
Hillis
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P
Judd
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S
D018441:Biofilms / Q000254:growth & development*; D005374:Filtration / Q000295:instrumentation* / Q000379:methods; D008567:Membranes, Artificial; D010539:Permeability; D018508:Water Purification / Q000295:instrumentation / Q000379:methods*
D008567:Membranes, Artificial