Many governments impose strict regulations regarding the maximum chemical oxygen demand allowed in waste water before they can be returned to the environment. For example, in Switzerland, a maximum oxygen demand between 200 and 1000 mg/L must be reached before waste water or industrial water can be returned to the environment [https://web.archive.org/web/20040310122559/http://www.csem.ch/corporate/Report2002/pdf/p56.pdf].