Waste is anything that is no longer useful and has to be thrown. Types of waste include;

1. Liquid waste (sewage): this is waste that is in the form of liquid. E.g. dirty water from industries.
2. Gaseous waste: this is waste that is in the form of gas e.g. CO2, CO and smoke etc
3. Solid waste (garbage): they are solid in nature e.g. plastics etc.
4. Hanadow (dangerous) waste: it is a kind of waste that is very harmful e.g. cylinder and all clinical waste.