ASSESSMENT OF EUTROPHICATION LEVEL OF MUNICIPAL SURFACE WATER IN ABUJA NIGERIA
The level of some nutrient elements in Abuja surface water were investigated for six months to determine the eutrophication profile and make logical inference on the fate of surface water system in the nearest future. Samplings were done monthly for a period of six months covering October to March and standard methods were used for the measurement of some nutrients constituting the indices of eutrophication. The results showed high levels of microbial activities. Biochemical oxygen demand (BOD) showed high levels of pollution which varied with time and velocity of water current. Other parameters investigated were chemical oxygen demand (COD), nitrate concentration, total dissolved solid (TDS), conductivity, algae count, temperature, pH, phosphate and potassium concentrations. Maximum and minimum values of some eutrophication parameters in the sites were recorded as follows: BOD ( Orozo 38mg/L- 7.37mg/L, Gidan Mangoro 31.2mg/L- 5.08mg/L, Nyanya 32.4mg/L- 10.05mg/L, Wuse 40.30mg/L- 7.007mg/L, Jabi 26.50mg/L- 3.10mg/L). Similarly total dissolved solid maximum and minimum values in the sites were given as Orozo 1222mg/L- 105.1mg/L, Gidan Mangoro 861.0mg/L-148.8mg/L, Nyanya 676.0mg/L- 127.6mg/L, Wuse 200.0mg/L- 86.2mg/L, Jabi 846.0mg/L-151.8mg/L. These results point to eutrophication indicators in Abuja surface water system. The results showed that the concentrations of nitrogen, phosphorus and potassium may be significantly increased beyond their compensation level by the growing human population in Abuja metropolis.
Eutrophication is the natural process whereby a confined water body (e.g. lake or dam) ages with time due to accumulation of silt or organic matter in the lake (Ademoroti, 1996). A young lake is characterized by low nutrient level and consequently low plant productivity and at this stage is described as oligotrophic (few food) lake. The water body gradually acquires inorganic and organic nutrient from catchment areas and these promote aquatic growth and increased biological productivity causing the lake to become murky with decaying organic matter and phytoplankton. The water body is said to be eutrophic (well fed) and consequently, the decaying organic matter depletes its available oxygen. Increase in the accumulation of silt and organic matter, makes the water body shallower and sunlight penetrate slowly to the bottom, making the water warmer. Plants take roots along the shallow edges and the lake slowly transforms into a marsh or swamp which may eventually lead to dry land (Ademoroti, 1996).