Integration of photocatalytic and biological processes for treatment of complex effluent: Recent developments, trends, and advances

The presence of persistent organic pollutants (POPs) in wastewater remains a major challenge in worldwide. Conventional biological treatments that are most versatile and economical are not efficient in the complete removal of these pollutants due to their biorecalcitrant nature. Simultaneously, the application of advanced oxidation processes such as photocatalysis that are highly efficient in removing POPs is also limited due to their economic unviability, lack of scalability, operational difficulties etc. In this regard, the integration of photocatalysis with biological processes can completely eliminate POPs from wastewater. Consequently, recent studies emphasize the combined photocatalytic and biological process for the treatment of complex wastewaters and their process modifications. In this chapter, a comprehensive review of the integrated photocatalysis and biological processes are discussed. Enhancement in the treatment efficiency on combining photocatalysis as a pre-, post-, and multistep treatment to various biological methods such as activated sludge and attached growth processes are elaborated. Further, the chapter also reviews the various aspects of combined treatments such as toxicity reduction, mineralization potential along with the detailing of a few pilot-scale studies.