Due to high toxicity, nonbiodegradeability, nutrient limitations, and excessive pollutant concentrations and concentration fluctuations, oil shale retort waters have not yet been shown to be economically treatable by conventional secondary treatment processes or process series. These characteristics are also associated with treatment problems encountered generally with synthetic fuels wastewaters, as well as most refinery and petrochemical industrial wastewaters. Environmental, public health, legal, and economic considerations necessitate that these wastewaters be successfully and cost effectively treated.