The anaerobic process is in many ways ideal for waste treatment. It has several significant advantages over other available methods and is almost certainly assured of increased usage in the future. Anaerobic treatment is currently employed at most municipal treatment and also in some industrial sectors. However, inspite of the present significance and large future potential of this process, it has not yet enjoyed the favourable reputation it truly deserves. The primary obstacle has been a lack of fundamental understanding of the process, required both to explain and control the occasional upsets which may occur, and to extend successfully this process to the treatment of wide variety of industrial wastewaters.