Waste disposal in Harare. Image credit thezimbabwedaily.com

Waste disposal in Harare. Image credit thezimbabwedaily.com

ZIMSEC O Level Combined Science Notes: Waste disposal

  • Several terms are used when dealing with waste
  • Sewage-is the name given to human excrement (faeces and urine) when collected together.
  • Sewage also includes kitchen waste and industrial waste
  • Waste is also known as effluent
  • Sewage waste is collected in a watery form the waste is carried either in solution or in suspension
  • Refuse and garbage-refer to solid waste that accumulates as a result of domestic and industrial activity
  • Examples include paper, tins, plastic bags, bottles etc
  • Biodegradable waste-is waste that can be decomposed by bacteria and fungi.
  • Examples are food leftovers, vegetables and cereals
  • It is usually made up of organic substances
  • Non biodegradable refuse-is refuse that cannot be acted on by bacteria/fungi.
  • It includes plastics, polystyrene (e.g restaurant kaylite)
  • This type of refuse is usually made up inorganic materials
  • Recycling-this involves the use of waste and saves on raw materials in manufacturing
  • It minimises waste and pollution
  • It controls vectors such as rodents, flies and mosquitos thus helping to prevent spread of results

Methods of sewage disposal

  • Sewage is an ever present form of waste
  • Several methods have been devised to deal with it
  • Methods include-
  • Pit latrine
  • Blair ventilated pit toilet
  • Water closet(WC)

To access more topics go to the Combined Science Notes page