MEMBRANE BIOREACTOR TREATMENT OF A SIMULATED METALWORKING FLUID WASTEWATER

A laboratory-scale membrane bioreactor (MBR) system was used to treat a simulated wastewater prepared from a semi-synthetic metalworking fluid (MWF) without mineral oil. The MBR system was operated with two solids retention times, and with and without ethylenediaminetetraacetic acid (EDTA) in the wastewater. The performance of the MBR was evaluated in terms of removal of chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), EDTA, and dicyclohexylamine (DCHA). Removal of COD was effective and stable and averaged 97% throughout the study. Removal of TKN was just as effective, averaging 96%–98%, but was more prone to disruption due to variations in operating conditions, particularly prolonged episodes of low dissolved oxygen. The operating conditions appeared to result in the simultaneous denitrification of as much as 34% of the influent nitrogen. EDTA removal averaged 96–97% during stable operating periods, but was more prone to disruption than TKN removal. Residual EDTA levels averaged