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 least 1330 reactors constructed in the world, it is considered to have reached technological maturity. Until recently however, it was used quite exclusively for the treatment of food industry effluents. It is only during the last 10 years that anaerobic digestion has started to be applied massively to the treatment of sewage and effluents from other industrial activities. During the 1970s and 1980s, the chemical and petrochemical industries were almost refractory to the introduction of anaerobic digestion. The situation has reversed since 1990 and at least 80 full-scale anaerobic plants are nowadays treating this type of waste. Nevertheless, a great amount of promotion is still required before anaerobic digestion can be considered as an accepted technology by this industry. The paper presents the actual situation of anaerobic treatment at full-scale inthis industrial sector as well as recent developments at lab-scale and discusses some important concepts to consider 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 development of anaerobic treatment are also discussed and it is shown that anaerobic digestion has been the solution to treatment problems for which aerobic systems were inefficient.