This chapter reviewed the background of activated sludge wastewater treatment plants. It presented the importance of wastewater treatment, its history and the structure of a conventional activated sludge wastewater treatment plant. The biochemistry and microbiology of the process are described. A review of the state of the art in modelling activated sludge wastewater treatment plants is also presented and discussed. The chapter concluded that the complexity of ASM1 and the detailed data required by microorganism's growth and decay means that it is not appealing to process operators. The ASM1 requires the determination of about 31 parameters, coefficients and variables, most of which are not routinely measured by large wastewater treatment plants. Furthermore, a certain number of simplifications and assumptions must be made in order to make a model of the WWT system practically useful. Some of these are associated with the physical system itself, while others concern the mathematical model.

M. Naveen Kumar (Research Scholar) is doing research in the area of environmental engineering, particularly application of microbial fuel cell for the treatment of industrial wastewater and energy production. He has published three papers in various refereed impact factor journals. He attended programs like seminars, conferences, workshops etc.