Treatment of a Metal-Cutting-Fluids Wastewater Using an Anaerobic GAC Fluidized-Bed Reactor

An anaerobic granular activated carbon (GAC) fluidized-bed process was studied to treat a simulated wastewater containing eight selected metal-cutting fluids at various loadings. With an influent chemical oxygen demand of 3300 mg/L, an empty bed contact time (EBCT) of 0.36 h, and after activated carbon adsorption capacity was exhausted, the effluent COD was reduced by approximately 60%. This COD residual did not change for several EBCTs, indicating that residual organics are nonbiodegradable in an anaerobic environment. Investigation indicates that more than one-half of the residual organics are biodegradable in an aerobic environment, suggesting that an anaerobic treatment followed by an aerobic polishing step can improve effluent quality. The initially low effluent COD concentration indicates that organics in the simulated wastewater are easily adsorbable and that periodic replacement of the GAC in the reactor is an option to improve effluent quality.