DESIGN OF PRE-ACIDIFICATION REACTORS FOR THE ANAEROBIC TREATMENT OF INDUSTRIAL WASTEWATERS

Two-phase anaerobic digestion has often been considered beneficial for the treatment of high strength industrial wastewaters, especially whe n the first phase is used as a pre-treatment system known as pre-acidi fication. Several applications in the field of industrial wastewater t reatment have been reviewed in order to evaluate the advantages of the pre-acidification process and its effects on the methanogenic reactor . Although pre-acidification has obvious advantages, complete acidific ation may be detrimental to the efficiency of the overall process. The use of balancing tanks at full-scale has been common practice for the pre-acidification of a wide range of wastewaters yet no accepted desi gn criteria for acidogenic reactors have been formulated and two-phase applications are generally based upon previous experience. The paper summarizes the results of a two year investigation into pre-acidificat ion at both bench- and pilot-scale, presents the results of instant co ffee production wastewaters and discusses a wide range of parameters w hich have been evaluated. Operating criteria will be discussed and gui delines for the design of pre-acidification reactors will be presented . Finally alternatives to using the total VFA (volatile fatty acids) c oncentrations for expressing the efficiency of acidogenesis will be in troduced.