The treatment of saline wastewater containing oil and organic matter of different biodegradability was examined for 35 days using a laboratory-scale membrane bioreactor (MBR) at a thermophilic condition (50°C). The performances were compared with those of a room-temperature reactor. The removal of COD was comparable for the two reactors. The half-life of mineral oil (C 15 − C 22 alkanes) was around 3 hours in the reactor. However, the operation at high temperature condition decreased the removal of dark brown (melanoidin) color from 58% to 44%. The fouling of the membrane was more severe for the thermophilic reactor. The room-temperature reactor maintained a volume flux of 0.22 m/day, while keeping the volume flux at the same level was difficult for the thermophilic reactor. It was suggested that lower flux operation of the membrane and worse effluent quality have to be considered, if high-temperature operation is required.

The advantage of acidic operation below pH of 3 in membrane bioreactors (MBRs) for the treatment of molasses wastewater was examined. Stable operation of both an acidic reactor and a neutral pH reactor was observed for 91 days. Percent COD removal was 48.5% for the acidic reactor and 63.6% for the neutral pH reactor when biologically pretreated molasses wastewater was fed to the reactors. Higher percentage removals of COD (89.0% for the neutral pH reactor and 84.0% for the acidic reactor) were observed, when molasses wastewater (COD 650 mg/L) was directly fed to the reactor because of higher concentration of biologically degradable organic matter in the feed solution. In spite of lower percentage of COD removal in the acidic reactor, higher percentage of color removal was observed spectrophotometrically with the low pH operation. Higher percentage of color removal in the acidic reactor was probably due to the enhanced adsorption of colored substances in the acidic environment followed by gradual biological degradation.