SPATIAL ANALYSIS OF SITE SUITABILITY FOR WASTE WATER TREATMENT PLANT IN KANO METROPOLIS, NIGERIA
Discharge of wastewater especially from industries and residential areas of Kano metropolis is a real threat to the public health and the environment. The study focused on the spatial analysis of site suitability for wastewater treatment plant in the study area. Field survey, landsat satellites, administrative map, public responses through questionnaire administration and interview as well as the use of Descriptive statistics and GIS – based Multi-Criteria Decision Analysis (MCDA) were the materials and methods used for the study. The results of the study shows that Pit latrine (38%) and soak away (55%) are the major means of discharging black water in the study area, while canal serves as the major method of discharging grey water with 76.3%. The environmental impacts of wastewater disposal have been found to be breeding of disease-causing organisms and bad odour with 61.2% and 22.7% respectively. The result also shows that the health implications from the public response were malaria that accounted for 47.9% and typhoid with 35.8%. The study further showed that, residential, commercial, agricultural and industrial activities serve as the major sources of wastewater discharge in the study area. The results show 10 best sites for offsite wastewater treatment plants in the study area with the size of 41 acres, 28 acres, 16.9 acres, 17.8 acres, 77 acres, 61.6 acres, 20.3 acres, 31.2 acres, 51.8 acres, and 45.4 acres. In conclusion, farmers utilize wastewater for irrigation activities and the source of water to Challawa and Tamburawa conventional water treatment plants mixes with untreated wastewater, hence, public and ecosystem health were at risk. It is therefore recommended that, wastewater should be given a special treatment through construction of offsite wastewater treatment plant in a suitable location, so as to minimize the impact of wastewater to the public and ecosystem.
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).
1.2 Statement of the Research Problem
Untreated and partially treated wastewater in the study area and elsewhere in the world are being discharged into the environment and nearby water bodies which consequently result to various environmental and public health implications. Wastewater is highly responsible for the spread of various kinds of diseases. According to Young (1985), lack of adequate water and wastewater treatment plants resulted in catastrophic epidemics of waterborne diseases during 1840s and 50s. Consequently, this brought about the struggle to find a way of treating wastewater in United State and Europe towards the end of the 19th and early 20th century through the construction of wastewater treatment plant, but these developments were not successful in developing countries and hence the wastewater treatment coverage remained low. According to UNEP (2000), only 2% of the cities in Sub – Sahara Africa had wastewater treatment plant and only 30% of these were operating satisfactorily.
Site selection through analysis of variables, such as, distance from surface water and built-up areas becomes necessary, because, environmental and public health problems‟ resulting from the disposal of wastewater does not end with the construction of WWTP. IRC (2017) observes that, during super storm sandy in 2012, several WWTPs in New York and New Jersey were inundated with storm surge, causing hundred million gallons of untreated sewage to spill into neighboring water ways. This is because, many of these plants were constructed at the bottom of watersheds and riverine areas, but since the plants have developed resilience plans and increased infrastructure fortification against floods and storm surge, these problems were not destructive (IRC, 2017).
Negative implications of wastewater to public health and environment especially nearby water bodies in the study area has been studied by many researchers such as, Dawaki, Dikko, Noma and Aliyu (2013); Bernerd and Ogunle (2015); Koki and Jimoh (2015), others include, Mukhtar, Indabawa and Imam (2010), also evaluated the suitability of ponds within Kano metropolis for the discharge of sewage. Data were gathered, through visits to the existence sewage ponds. The result of the study showed high concentration of disease vectors, such as mosquito, offensive odour, toxic chemicals and pathogenic bacteria in the ponds, which are threat to public health.
Adedokun and Agunwamba (2014) analyzed the influence of industrial effluents on the pollution of River Challawa in Kano metropolis. The study discovered high levels of pH values, Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), Total Suspended Sediment (TSS), Total Dissolved Solids (TDS) and Total Solids (TS) in the River beyond National Environmental Standards and Regulations Enforcement Agency (NESREA) standard. Plate 1 shows how wastewater from industrial area drains into River Challawa due to the absence of offsite wastewater treatment plant which consequently resulted in the contamination of the water body that serves as a major source of water supply to the conventional domestic water treatment plants situated at Tamburawa and Challawa.
In an attempt to reduce these problems, two WWTPs were constructed by the Kano state government at Nomansland and Tukuntawa in Kano metropolis around 1980s, but none of them is still functioning due to the fact that, the sewers that convey wastewater from source to the plants were blocked up, likewise, buildings and other structures have presently reached the plants, which render it dangerous to public health and environment. These problems were attributed to the fact that, traditional methods were used during the design path. Since then, no further attempt has been made for WWTP site selection in the study area, even though, UNIDO (2003) and Mukhtar, Indabawa and Imam (2010) called for the construction of offsite WWTPs at suitable locations in the study area. This study therefore, tried to find answers to the following issues of site suitability for wastewater treatment plants in Kano metropolis.
- what are the major sources of wastewater generation in the study area?
- what are the environmental and health implications of wastewater in the study area?
- where are the best sites for wastewater treatment Plant in the study area?
Plate I: Challawa Industrial Wastewater Drains into River Challawa
Source: Preliminary Survey, 2016
1.3 AIM AND OBJECTIVES
The aim of this study is to analyse suitable sites for wastewater treatment plants in the study area. The aim was achieved through the following objectives, to: –
- identify the major sources of wastewater generation in the study area.
- examine the environmental and health implications of wastewater in the study area.
- identify and map out best sites for wastewater treatment Plants in the study area.
1.4 JUSTIFICATION FOR THE STUDY
It is quite significant to reason out how best to tackle the problem of wastewater in our environment, for if no significant effort is done, there will be continues spread of diseases and consequent loss of lives. The lag of matter which is centered to this research is to evaluate the possibility of having a site that is suitable for the location of offsite wastewater treatment plant in Kano metropolis due to the high concentration of harmful substances, such as, pathogens, metals, organic compounds, metalloids and endocrine descriptor compound contained in wastewater. Any of these compounds especially in excess can cause harm to man and his environment (UNEP, 2010).
The growing amount of wastewater is an issue of great concern worldwide particularly in Kano metropolis as a result of the rate at which the population is fast expanding. Despite the efforts being made by government and other agencies to safe guard the life and properties of the public through various environmental programs, still wastewater poses a serious threat to the health of not only people in the study area but the crops they produce as well as the animals. Therefore, the provision of treatment plants at suitable locations in the study area will go a long way to reducing the potential risk of wastewater as well as enables the Kano state government to meet all laws and regulations governing water pollution and wastewater disposal.
1.5 SCOPE OF THE STUDY
The study covers eight Local Government Areas which form Kano metropolis, namely: Kano Municipal, Gwale, Nassarawa, Dala, Tarauni, Fagge, Kumbotso and Ungogo. Geographically, the area is located between Latitude 11o 52‟2 “N and 12o 7‟41” North of Equator and between longitude 8o 25‟3” E and 8o 39‟57” East of Prime meridian. The study examines major sources of wastewater generation in the study area and their environmental and public health implications. It also identifies and map out best sites for the siting of offsite wastewater treatment plant using land sat of 6 March, 2015 and Digital Elevation Models (DEMs) of 2006.
1.6 ORGANIZATION OF THE WORK
The entire study is organized and presented in five chapters; the first chapter focuses on the introduction which comprises the background to the study, statement of the research problem, research question, aim and objectives, justification and scope. Chapter two of the study covers review of related literature. Chapter three looks into the study area, materials and methods of the study. Chapter four deals with results and discussion while chapter five deals with summary, recommendation and conclusion as per the findings of the study.
SPATIAL ANALYSIS OF SITE SUITABILITY FOR WASTEWATER TREATMENT PLANT IN KANO METROPOLIS, NIGERIA