Biological treatment of wastewaters: State-of-the-art and research needs

Biological operations play an important role in the treatment of wastewaters. Traditionally, biological wastewater treatment systems removed biodegradable organic matter. Then they also began to remove nutrients (nitrogen and phosphorus). More recently, biological treatment systems have begun to remove synthetic organic (xenobiotic) chemicals from liquid streams, ranging from highly specialized industrial wastewater to contaminated groundwater. This paper describes the innovative biological processes needed to fulfil these new aims. Innovation essentially means finding better ways to identify and accumulate desired microorganism to accomplish a treatment goal. In this regard, advantages from the use of sequential environments for enhanced biotransformation, are shown. Integration of chemical and biological processes may offer in several cases an attractive alternative for the detoxification of organic compounds. Recommendations for future studies are also presented.