Sewage treatment is the process of removing contaminants from waste water, including household sewage and runoff effluents. It includes physical, biological and chemical processes to remove contaminants. The objective of the sewage treatment is to produce an environmentally safe fluid waste stream or treated sludge suitable for disposal or reuse. There are number of biological treatment processes and technologies in literature and practice, however, for the purpose of this report, sewage filtration technologies are described. Since trickling filters only receive liquid waste, they are not suitable where water is scarce or unreliable. Compared to other technologies, trickling filters are compact, although they are still best suited for peri-urban or large, rural settlements. Trickling filters can be built in almost all environments, but special adaptations for cold climates are required.