WATER RECLAMATION FROM MUNICIPAL WASTE-WATER USING COMBINED MICROFILTRATION REVERSE-OSMOSIS (ME-RO) - PRELIMINARY PERFORMANCE DATA AND MICROBIOLOGICAL ASPECTS OF SYSTEM OPERATION

Hollow fibre microfiltration (MF) was used as a pretreatment to revers e osmosis (RO) for evaluation of the production of high-quality water from secondary effluent. Four different low operating pressure RO memb ranes (PVD, CTA, TFCL and NF45) produced a target flux of 20 L/m(2) h at the relatively low operating pressures of 230 kPa, 750 kPa, 550 kPa and 360 kPa, respectively. Conductivity measurements revealed rejecti ons of ionic species of 99.2% and 41% for TFCL and NF45, respectively. TFCL and NF45 totally removed orthophosphates from microfiltered seco ndary effluent, but nitrite/nitrate were only partially removed. PVD a nd NF 45 were exposed to microfiltered secondary effluent in stirred c ells for up to 4 d for detailed evaluation of bioadhesion. Bacteria ra pidly attached and grew on these membranes and produced significant am ounts of extracellular polymers. Adhesion of these organisms was rando m on some membranes, but aggregates were observed on others. The numbe rs of bacteria on the surfaces of the RO membranes began to diminish a fter 72 h incubation in microfiltered secondary effluent. Three differ ent primary colonizing microbes were isolated from membrane surfaces, two of which were tentatively assigned to the genus Pseudomonas.