Characterization and Treatment of Eastern Oil Shale Retorting Wastewater: Low Pressure Membrane Separation

摘要

Oil shale retorting produced wastewater with moderate to high concentrations of organics (such as phenols, short-chain acids, and free and emulsified oils) and inorganics (such as ammonia, Cl(-1), S(-2), etc.). The use of reverse osmosis (RO) membranes coupled with pretreatment by activated carbon resulted in 25 - 40% flux declines, as compared to 60% for untreated water. Pretreatment with CC14 extraction resulted in a 50% flux decline. Membrane rejections of conductivity, ammonia, TOC, chloride, alkalinity, and sulfide were usually 80 - 90%. Color rejection was greater than 99% in all cases. Extensive membrane studies revealed that the principal foulant is the oils, both free and emulsified. Partial removal of the oils resulted in up to 28% higher rejections. The rejection of ammonia was poor (33%) at pH = 10.1, while at pH = 8.3 ammonia (present as NH4(+1) rejection was 94%. HPLC characterization revealed high concentrations of phenolics (200 - 280 mg/l) in the raw retort waters. Phenolics rejection was 75 - 94%. Rejection of other peaks (as area) was generally 80 - 95%. Membrane rejection based on HPLC peak area (at 280 nm) was found to increase with elution (HPLC) time.