Aerobic and Anaerobic Biological Treatment and Characterization of Condensate Wastewaters from the Taciuk Oil Process

Abstract

Abstract Bench-scale investigations were conducted at Environment Canada's Wastewater Technology Centre to assess the feasibility of using biological activated sludge systems to treat fractionator sour water (PW5) and processor preheat steam vent water (Preheat) from the AOSTRA Taciuk Process when applied to bitumen recovery from oil sands. The PW5 wastewater sample was approximately 10 times more concentrated with regard to COD, TOC and ammonia concentrations than the Preheat sample. Phosphorus was lacking in each wastewater. High levels of cyanide were present in the Preheat sample and high levels of zinc in the PW5 sample. Aerobic treatment of the Preheat wastewater was shown to be feasible with regard to organic carbon removal. At a sludge retention time (SRT) of 20 days and hydraulic retention times (HRTs) ranging from 0.9 to 2.4 days, organic carbon removal of the Preheat wastewater in terms of BOD5 was greater than 95%. Nitrification was also achieved with ammonia removals of greater than 95%. The PW5 treatment system, operated at a 20-day SRT and HRTs ranging from 5 to 10 days, achieved BOD5 removals of approximately 90%. However, residual carbon levels of approximately 200-400 mg/L remained in the effluent. The addition of powdered activated carbon at the 5-day HRT level did not significantly improve system performance. Excessive foaming and effluent suspended solids losses contributed to operating problems. Nitrification was not established, possibly due to high influent ammonia values. Anaerobic toxicity testing showed that the Preheat wastewater was a relatively weak substrate which did not inhibit anaerobic microorganisms. The PW5 wastewater was toxic to these organisms and this was a substrate concentration-related phenomenon.