Biochemical characterisation of water from River Ntabago and implication on water quality and safety

Abstract

This study analysed the biological and chemical components characterising water from River Ntabago. The composition of the water determines its quality and affects the lives of aquatic organisms and other water consumers. The study was carried out from January to July 2009. Human activities such as brewing, farming, and washing fabrics; and natural processes like erosion, affect the biochemical composition of the water, its quality and people’s health. The water has a bad smell, bitter taste and contains black particles that make it look unpleasant. There are complaints of skin irritations and/or ulcerations when the water is used for bathing and abdominal pains when drunk. The objectives of this study were: to determine the phytoplankton composition of the water; to quantify heavy metals in water: cadmium, chromium, cobalt, copper, iron, lead, manganese, nickel, zinc; and anions: chloride, fluoride, sulphate and sulphide. The study also determined water quality parameters: pH, temperature, specific conductance, dissolved oxygen, coliforms, alkalinity, turbidity, hardness, and nutrients; so as to assess the quality of the water and its safety as a source for domestic use. The biological parameters were determined using microcopy, heavy metals using atomic absorption spectrophotometry, while anions and water quality parameters were analysed using various titration and colorimetric methods. The study revealed the concentration of phytoplaktons to be very high and increasing downstream. These reduced water quality through production of: toxins, irritant lipo-polysaccharides, taste and odour substances; reduction of dissolved oxygen and increasing turbidity and colour of the water. Concentrations of coliform bacteria were fairly high. The study also revealed the existence of cadmium, iron, lead, manganese and nickel above their NEMA and WHO recommended values for potable and drinking water, raising concerns for the health of water consumers. The health effects of metals include: lowering energy levels; damaging the central nervous system and mental function; damaging blood composition, lungs, kidneys, liver and other vital organs. Turbidity and alkalinity were shown to be high, hardness fairly moderate, while dissolved oxygen and nutrients were very low in comparison to their recommended values. The biochemical composition and water quality of the river were functions of growing population pressure, changing settlement and development patterns, siltation due to loss of vegetation cover and land degradation, seasonal variations in rainfall, agricultural runoffs, water-flow fluctuation rates, heavy metal discharges from weathered rocks and wetland drainage. The water of River Ntabago is therefore considered unsuitable for human and livestock consumption because of high phytoplankton and heavy metal concentration, high turbidity, low dissolved oxygen and the presence of coliforms. Hence, there is need for: a watershed management program in the area, more research to be done, treatment of water in order to meet standards for potability, planning some alternative water, promotion public awareness and sustainability issues, proper land utilization and improved agricultural practices; frequent surveys and monitoring programs to ensure the quality of water.