Flat sheet membrane bioreactor operationsl experiences - A New Zealand perspective

Membrane bio-reactor (MBR) technology is a relatively recent and maturing wastewater treatment technology. As such literature on actual operational experiences with full scale MBR plants and how these experiences may be translated into design and operational improvements is somewhat limited.

This paper discusses the operational experiences and the lessons learnt regarding operating full-scale flat sheet MBR municipal wastewater treatment plants. In particular the discoveries made when the first three of these types of treatment plants installed in New Zealand (at Tirau, Turangi and Te Aroha) were drained down for routine inspection and maintenance.

All three of the subject MBR plants experienced varying degrees of sludge caking between the individual membrane panels and lint build-up around the membrane module housings and associated appurtenances. The contributing factors and mechanisms for membrane caking, associated membrane performance parameters and operational issues are discussed along with observable operational warning signs of the onset of sludge build-up between the membrane panels.

How the membrane inspection and cleaning process was planned and executed is discussed along with lessons learned both operationally and from a treatment plant design perspective as to how this process can be done most efficiently to minimise both cost and treatment plant down-time.