In waste disposal, the term refers to the collection, processing, & recycling or depositing of waste materials generated by human activity. Waste is categorised according to its origin and composition. Waste materials can be classified as either liquid depending on their physical state, and their constituents can be classified as either harmful or inert depending on their effects on human health and environment. Waste disposal, sewage (wastewater), toxic materials, & electronic waste are all examples of waste that are commonly referred to as waste.
Water waste from municipal sources is channelled through sewage systems in industrialised countries, where it is subjected to wastewater treatment, also known as sewage treatment. Before wastewater, or sewage, can enter groundwater supplies or surface waterways such as rivers, lake, estuaries, and seas, this procedure eliminates the majority of the contaminants from the wastewater or sewage before they can reach them.