Overview of the application of anaerobic treatment to chemical and petrochemical wastewaters

During the last 20 years, as a result of its low cost, anaerobic digestion has turned into a popular wastewater treatment technology, Today, with at l east 1330 reactors constructed in the world, ii is considered to have reach ed technological maturity. Until recently however, it was used quite exclus ively for the treatment of food industry effluents. It is only during the l ast 10 years that anaerobic digestion has started to be applied massively t o the treatment of sewage and effluents from other industrial activities. D uring the 1970s and 1980s, the chemical and petrochemical industries were a lmost refractory to the introduction of anaerobic digestion. The situation has reversed since 1990 and at least 80 full-scale anaerobic plants are now adays treating this type of waste. Nevertheless, a great amount of promotio n is still required before anaerobic digestion can be considered as an acce pted technology by this industry. The paper presents the actual situation o f anaerobic treatment at full-scale in this industrial sector as well as re cent developments at lab-scale and discusses some important concepts to con sider before the implementation of an anaerobic treatment. In particular a table is presented with the main characteristics of 65 of the 80 full-scale plants identified to date. The probable reasons for the slow initial devel opment of anaerobic treatment are also discussed and it is shown that anaer obic digestion has been the solution to treatment problems for which aerobi c systems were inefficient.