Aspects of Wastewater Collection, Treatment and Reuse: Review of Principles and Practices

Wastewater is defined as "spent" or "used" water of a community or industry which contains dissolved and suspended matter as pollutants. On the basis of sources, wastewater may be classified as domestic wastewater, industrial wastewater and stormwater, depending on whether its generated as a result of domestic and industrial activities or runoff due to rainfall in buildings and adjoining lands. The sources of wastewater also influence their composition and characteristics. Sewage is often used interchangeably with wastewater, although it often refers to liquid waste (mostly urine and faeces from residential, industrial, institutional and commercial establishments. The purpose of wastewater treatment is to improve its quality for various purposes including drinking, domestic, industrial and agricultural uses. Two common methods of wastewater treatment are: biological treatment method (where microorganisms are used to reduce the BOD level in the wastewater) and mechanical treatment method (where a combination of physical, biological and chemical processes are used to achieve a treatment objective, which are generally to reduce BOD, COD and TSS in the wastewater. Untreated wastewater in the environment before or after disposal maybe source of pollution of surface and groundwater in the area and contribute to spread of communicable diseases caused by pathogenic organisms present in the wastewater. In most rural areas and towns in Nigeria, there is no wastewater treatment system, collection and disposal are through pit latrines, water closet/septic tanks, soakaway pits and sometimes discharge into streams. Few wastewater collection and treatment plants, using biological and mechanical methods exist in urban areas/academic institutions including residential areas in Abuja, Lagos, Kaduna, Eungu and Port Harcourt; and academic institutions such as AfeBabaloa University Ado Ekiti, ObafemiAwolowo University He- Ife and IITA, Ibadan. Some industrial facilities including NNPC, SHELL Petroleum Office and Staff Quarters (Warri); CHEVRON and SHELL Petroleum Offices in Port Harcourt and Nigeria Brewery (Benin and Lagos). Some towns / Academic institutions such as Makurdi, Kano and UCH, University of Ibadan, have installed but non functional water treatment plants. In Nigeria and other countries of the world, treated wastewater may be used for groundwater recharge, as liquid in fire extinguishers and agricultural purposes (including irrigation).