The characterization and treatment management of industrial wastewater are rarely studied in the scientific and technical literature, due to the diversity of industries and the industrial secret regarding waste production. In this chapter the characteristics of wastewaters of different industrial activities such as petrochemistry, refinery, textile, pulp and paper, or food industry are studied from their UV–visible spectra. The influence of industry nature, the variability of effluents quality and the estimation of some aggregate or specific parameters are considered. A large part is dedicated to the monitoring of treatment processes and to waste management, including treatability tests, spill detection, and shock load management. Finally, the monitoring of the environmental impact (discharge or leaks to groundwater) is briefly considered through some examples.