Waste treatment refers to the activities required to ensure that waste has the least practicable impact on the environment. In many countries various forms of waste treatment are required by law.
Sewage treatment is the treatment and disposal of human waste. Sewage is produced by all human communities. Treatment in urbanized areas is typically handled by centralized treatment systems. Alternative systems may use composting processes or processes that separate solid materials by settlement and then convert soluble contaminants into biological sludge and into gases such as carbon dioxide or methane.[3]