Utilisation, treatment and disposal of distillery wastewater

Abstract

A comprehensive review of the methods for handling distillery wastewater is presented. Wastestreams from such plants are generally high in both dissolved organic and inorganic materials, posing particular treatment difficulties; the volume to be treated per volume of ethanol produced is also high. With the increasing interest in ethanol from biomass as a liquid fuel alternative, appropriate treatment of this wastestream will become essential. Although a number of treatment schemes are being used or have been proposed, there is no widespread agreement on the most suitable methods. These discrepancies reflect in part the wide variations in the characteristics of distillery wastewater—in turn these are the result of different raw materials, agricultural practices, and distillery operating techniques. In many studies to date detailed analyses of the wastewater are not provided and this imposes limits on the relevance of the results to a particular situation. 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.