WRRCSR No. 3.12:84 Rotating Biological Contactor for Brackish Wastewater Effluent Treatment

Abstract

The rotating biological contactor CRBC) is an attached (fixed) growth, biological treatment unit which consists of closely spaced, rotating shaft-mounted discs that generally have approximately 40% of their surface submerged in wastewater. The RBC unit, which generally serves as a secondary treatment process, has only been used in the United States since 1969 and, as yet, has not been widely used in this country. On Oahu, Hawaii, RBCs have apparently not been used except for experimental purposes. Of the RBC studies that have been reported nationally and internationally, the efficiency of the RBC process has not been reported for tropical and subtropical climatic conditions for brackish wastewater. A bench scale RBC unit, utilizing settled, brackish wastewater effluent from the Sand Island Wastewater Treatment Plant on Oahu, showed that 5-day biochemical oxygen demand and suspended solids removals of approximately 90% and slightly less than 80% were achievable at typical (full-scale) hydraulic disc loading rates. Thus, salinity (at least chlorides up to 2000 mg/ ℓ) apparently does not seriously interfere with the RBC’s treatment efficiency.