Process Integration. Concepts of Integration and Coupling of Photocatalysis with Other Processes
Industrial wastewaters are more diverse and have more complex composition than municipal wastewaters, which usually have similar composition. Adequate treatment of industrial wastewaters, which contain a wide variety of compounds and at varying concentrations, needs a correct viability study on a case by case basis. Studies with model effluents could provide useful information but their findings cannot be applied directly to treat real wastewater. Therefore, this chapter will be mainly focused on showing different applications of integrated processes for treating complicated wastewaters such as wastewater containing biorecalcitrant compounds, highly biodegradable wastewater containing small concentrations of recalcitrant compounds, wastewater containing inhibiting compounds, or wastewater containing specific compounds that would accumulate in the medium. This chapter provides examples of the use of photocatalysis as a pretreatment followed by biotreatment, as well as cases in which the combination strategy is to first eliminate the biodegradable part and later the recalcitrant contaminants are removed by a photocatalytic post-treatment. Another example is the use of combined processes for the treatment of wastewaters containing “contaminants of emerging concern”. These substances are used in pharmaceuticals, personal care and other consumer products, and their adverse effects have only recently become apparent. Relevant to such application, a case study is discussed on how integration of membrane (filtration) technologies and photocatalysis for the treatment of micro-contaminants at low concentration could improve the overall efficiency.