Anaerobic digestion of industrial and domestic wastewaters is an effective way of alleviating pollution problems. The treatment of vinasse, a residue of ethanol fermentation, and brewery/soft drink wastewaters was investigated by IPT for several years. This paper presents data and discusses the technical and economical feasibility of treating these wastewaters using UASB reactors. With vinasse, it is possible to operate industrial plants with organic loading rates exceeding 15 kg COD m−3 day−l, removing 95% of the initial BOD. The produced gas can be used as a substitute for diesel oil in vehicles and also to produce steam, replacing bagasse. The pay-back period of the capital investment is estimated at around 4 to 5 years. For brewery/soft drink wastewaters, it is possible to operate UASB reactors with a HRT of 6 hours, removing more than 90% of the initial BOD. The reactor showed a good capacity to handle temperature shocks. Capital investments for both cases are presented in terms of total investment per kg of COD and m3 of reactor installed.

This paper discusses the present state of municipal solid waste (MSW) disposal in Brazil , focusing on the particular situation in the City of Sao Paulo, and indicates the future trend of the anaerobic digestion approach for this residue. Also, some results, representative of several studies developed at IPT on anaerobic digestion of MSW mixed with primary sewage sludge, are presented. These studies were conducted using agitated reactors of 2 or 8 liters capacity, continuously operated at 35°C and in the pH range 6.8 to 7.2. The studies were on: start-up of reactors, MSW to sewage sludge ratio, organic loading rate and hydraulic retention time. The results presented in this paper indicate the great interest in achieving anaerobic digestion of MSW in presence of sewage sludge, utilizing reactors with high solids content, which is the approach already observed, and certainly will be developed in the future.