Virtually every chemical or environmental engineer recognizes the historical role and importance of pilot plant studies in the development and application of new process concepts. In the area of wastewater treatment, the early 1970’s witnessed many such pilot studies, which were undertaken to provide the basis for designing systems which would satisfy USEPA-mandated BPT effluent limitations. In the years that followed, the objective of pilot testing found a new emphasis – in the optimization of existing treatment systems and in the evaluation of new, m ore cost-effective process concepts. Anaerobic treatment technologies represent a wellknown example of a promising treatment concept that continues to be refined in pilot plant studies. Moreover, as the new BAT/BCT effluent limitations are promulgated by EPA, we can expect even more interest in pilot plant projects.