CHAPTER ONE INTRODUCTION
1.1 Background to the Study
Locally available fresh water which is colourless, tasteless and odourless liquid, that is a compound of hydrogen and oxygen (WHO, 2006) can easily be contaminated when mixed with wastewater, this call for proper management of wastewater before discharge. Wastewater management system is one of the most important means of protecting public health and environment, due to the fact that, unmanaged wastewater can widely impact negatively on the environment and public health. A wastewater is water which carries waste in suspension or solution usually originates from industrial, municipal, agricultural and commercial areas and drains mainly through drainage system.
Effluents entering water bodies carries pathogenic organisms that transmit diseases such as typhoid, cholera and skin infections to human beings and other animals which consequently lead to untold suffering and loss of life. Side effects of wastewater does not end at causing diseases to human and animals, but it affects the phenology and vigour of farm products and other plants. The use of wastewater for irrigation purpose is a common practice in many developing countries such as India, Pakistan, Egypt, Sudan as well as Nigeria. Chen, Wang, and Huang (2004) observed that crops produced with wastewater especially from coal industry are highly affected by aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs). They further argued that, the levels of persisted organic pollutants (POPs) in the water and a soil of irrigated land in India for example, is influenced by sewage sludge. In Kano metropolis, the practice of using wastewater has been on the increase especially in irrigation activities.
The term „treatment‟ of wastewater implies the use of chemical, physical or biological agents to remove pollutants and organic matter from wastewater; while wastewater treatment plant comprises the site, physical infrastructure and the process involved (FSC, 2003).
There are various techniques used to treat wastewater depending on the nature and extent of contamination; either the wastewater is grey water, black water, industrial or agricultural wastewater. These techniques may be categorized into decentralized and centralized techniques of treating wastewater. The decentralized or primary techniques are the on – site wastewater treatment system whereby the wastewater is partially treated close to where it was produced, such methods include the use of green plants, septic tanks, chemical toilet, compositing toilet, cesspool and so forth. According to USEPA (2015), the use of non – toxic and low sodium soap and personal care products is recommended to protect vegetation when reusing grey water for irrigation purposes. But of all various kinds of on – site treatment systems, septic tank is highly applicable in both developed and developing countries. USEPA (2008) observed that, about 20% of homes in United States use septic tanks and other on-site sewage facilities. Yet, septic tank is not applicable when the wastewater came from industrial centre or densely populated areas, because, the system is often suitable option for small – scale residential areas with sufficient land for an adequate drainage field (Environmental Alliance, 2006).
The centralized techniques of treating wastewater is otherwise known as off–site wastewater treatment system whereby package or passive wastewater treatment plants (WWTP) are used, wastewater that does not undergo any treatment or passes through primary treatment such as septic tank is sent to the centralized treatment plant through a watercourse or drainage field for further treatment. In package treatment plant for
instance, wastewater undergoes more than one process before discharge. When selecting best site for centralized treatment system factors such as slope, geology, and distance from settlement, road and water bodies should be put into consideration. Of the two treatment techniques, the decentralized system is more practicable in both developed and developing countries due to the influence of factors such as financial and site suitability.
The need for identifying a suitable site for construction of centralized (offsite) wastewater treatment plant has become necessary considering the population and the amount of wastewater being generated daily in the study area. Proper method of collection and nuisance free disposal of the liquid waste of a community are legally recognized as a necessity in an urbanized, industrialized society (Mc Graw-Hill, 2011).
Previous studies particularly on site selection have been hampered due to paucity nature of data. However, with the introduction of modern technology such as remote sensing and Geographical Information System (GIS), data on site selection and or suitability assessment is now available for effective study. Remote sensing is an extensive tool and technique that is used to capture the characteristics of the physical environment without onsite observation, while Geographical Information System (GIS) is a computer based information system that enables one to capture, store, retrieve, analyse and display geographically referenced data (ESRI, 1990).
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