This chapter on industrial wastewater treatment is a companion to Chapter 12, which dealt with municipal wastewater treatment systems. Although municipal wastewater is similar from communities across the country, industrial wastewater, and consequently, the processes required to treat it can differ markedly both within and among industries. Three options, which are not mutually exclusive, are available in treating industrial wastewater, these being: (i) treatment at the point of generation (at the process level) within the plant, (ii) pretreatment of the industrial waste prior to discharge to a municipal wastewater treatment plant, or (iii) treatment of mixed industrial wastewater streams at an industrial wastewater treatment plant to the point that it can be discharged directly to a receiving stream or so that it can be reused within the plant. This chapter provides a general overview of industrial wastewater treatment through topics that include sources and characterization of industrial wastewater; a description of physical, chemical and biological industrial wastewater treatment processes; options for management of industrial wastewater effluent; sludge management; and future developments in industrial wastewater treatment. An application section provides six Illustrative Examples of industrial wastewater treatment concepts and treatment process trains.