A review on anaerobic–aerobic treatment of industrial and municipal wastewatersituation. When the opportunity cost of land is low, direct irrigation often proves most cost effective. Direct utilisation or by-product recovery offers the attraction of a return on capital and in some cases, particularly for grain distilleries, is essential to the profitable operation of the plant as a whole. Anaerobic treatment followed by aerobic polishing of the supernatant is attractive from the consideration of providing energy for the distillation stage. Depending on the wastewater characteristics, however, the reliability of the system is highly variable. From a technical viewpoint, the most reliable system appears to be evaporation and incineration with the ash being returned to the soil as a fertiliser. The increased interest in ethanol production should lead to a clarification of this position over the next few years. Cost data is not reported partly because the available information is scarce and, in some cases, no longer of relevance.