Assessment of Some Physico-Chemical Parameters of River Ogun (Abeokuta, Ogun State, Southwestern Nigeria) in Comparison with National and International Standards

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Assessment of some Physico-chemical Parameters of River Ogun (Abeokuta, Ogun State, Southwestern Nigeria) in Comparison with National and International Standards DIMOWO, BENJAMIN ONOZEYI and ODULATE, DOMINIC OLANIYI

Department of Aquaculture and Fisheries Management, College of Environmental Resources Management, Federal University of Agriculture, Abeokuta, Ogun state, Nigeria benjamindimowo@yahoo.com
Abstract
This study assessed the physico-chemical quality of River Ogun, Abeokuta, Ogun state, Southwestern Nigeria. Four locations were chosen spatially along the water course to reflect a consideration of all possible human activities that are capable of changing the quality of river water. The water samples were collected monthly for seven consecutive months (December 2011 – June 2012) at the four sampling stations. pH, air temperature (0C), water temperature (0C), conductivity (µs/cm) and total dissolved solids (mg/l) were conducted in-situ with the use of HANNA Combo pH and EC multi meter Hi 98129 and Mercury-in-glass thermometer while dissolved oxygen (mg/l), nitrate (mg/l), phosphate (mg/l), alkalinity (mg/l) and hardness (mg/l) were determined ex-situ using standard methods. Results showed that dissolved oxygen, hydrogen ion concentration, total hardness and nitrate were above the maximum permissible limit of National Administration for Food, Drugs and Control (NAFDAC), Standard Organization of Nigeria (SON), Federal Environmental Protection Agency (FEPA), United States Environmental Protection Agency (USEPA), European Union (EU) and World Health Organization (WHO) for drinking water during certain months of the study period. Results also showed that water temperature and conductivity were within the permissible limits of all the standards excluding FEPA. However, total dissolved solids and alkalinity were within the permissible limits of all the standards. Adejuwon and Adelakun, (2012) also reported similar findings on Rivers Lala, Yobo and Agodo in Ewekoro local government area of Ogun state, Nigeria. Since most of the parameters measured were above the maximum permissible limits of the national and international standards, it can be concluded that the water is unfit for domestic uses, drinking and aquacultural purposes and therefore needs to be treated if it is to be used at all. The low dissolved oxygen values for the first four months was too low i.e. < 5 mg/l. This is most likely as a result of the amount of effluents discharged into the river. To prevent mass extinction of aquatic organisms due to anoxic conditions, proper regulations should be implemented to reduce the organic load the river receives. Key Words:Physico-chemical, quality assessment, River Ogun, water standards

INTRODUCTION
Water is a vital commodity (NBS, 2012) and its sources include rivers, streams, lakes, wells, boreholes, spring etc. Rivers are among the oldest water bodies in the world (Higler, 2012). In most urban-rural communities in the developing countries especially the Sub-Saharan Africa, surface waters (rivers, streams, and lakes among others) have been the most available sources of water used for domestic purposes. The water from these sources is contaminated with domestic, agricultural, and industrial wastes and likely to cause water related diseases (Ojekunle, 2000; Ayeni et al 2009). The four main sources of aquatic pollution include industrial wastes, municipal wastes, agricultural run-off, and accidental spillage (Walsh, 1980). Nigeria has a surface area of 94,185,000 hectares which extends from latitude 40 16’N to 130 52’N of the equator and longitude 20 49’E and 140 37’E (Ita, 1993). The freshwater resources of Nigeria are within the extensive river systems, lakes, flood plains and reservoirs and constitute about 12.4% of its surface area which is 11,678,940ha (Olaosebikan and Aminu, 1998). River Ogun is one of them with a total area of 22.4 km2 (2240ha) and a fairly large flow of about 393 m3secG1 during the wet...
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