19.1 Types and sources of liquid waste
In Study Session 18 you learned that liquid waste includes human waste, sullage, industrial waste and runoff (also referred as storm water or flood water).
What is the difference between sewage and sullage?
Sewage includes human wastes (i.e. faeces and urine), as well as wastewater from various sources. Sullage is the wastewater that arises from domestic activities such as washing in bathrooms and kitchens, including water from food preparation and dishwashing; it does not contain human excreta.
Human waste and sullage can arise from public institutions such as schools, as well as from individual households. Industrial waste arises from different industries as a result of processes to produce goods and services. The content of industrial waste may vary depending on the type of industry, the raw materials (inputs) used and the processes undertaken. Industrial waste may be toxic and thus hazardous in nature, or it could contain non-hazardous substances. Therefore, unlike the other types of liquid waste, some industrial wastes may require special treatment before discharge from the industry.
Runoff is simply flood water that arises from rain or the release of collected water from a pond or dam. It can carry many types of wastes along with it, including human waste. Therefore, it is potentially harmful to the health of the community. Liquid waste is also produced in healthcare facilities but this will be dealt with in detail in Study Session 23.