Effects of anthropogenic activities on water quality of Streams: a case study of the Onyasia Stream in the Greater Accra Region

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June 2014
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Indiscriminate disposal of waste, use of pesticides and fertilizer on farms along the Onyasia has been of great concern. This study assessed the water quality of the Onyasia stream in the Greater Accra Region. Composite water samples drawn from sections of the Onyasia stream from fifteen sampling points, five each from Upstream, midstream and downstream were analyzed in the laboratory for heavy metals (Al, Mn, Fe, Cd and Cu), selected nutrients (PO3-4, SO42-, NO3-N and NH3-N) and Microbial counts (total and faecal coliforms). Physico-chemical parameters (pH, temperature, conductivity, turbidity, total dissolved solids and dissolved oxygen) were also analyzed in-situ using the Horiba water quality multi-checker. With the exception of turbidity (ranging from 68.86 to 129.24 NTU) which was far above the WHO limit of 5 NTU, all the other physical parameters (pH values ranging from 6.31 to 6.68, conductivity ranging from 1.31 to 1.71 μS/cm, TDS ranging from 0.76 to 0.97 mg/l and DO ranging 5.09 to 7.87mg/l) were below the WHO standards of 6.5-8.5, 1500μS/cm, 1000mg/l and 5mg/l respectively. With the exception of sulphate (47.00 to 76.40 mg/l), concentrations of phosphate (3.11 to 5.05 mg/l), nitrate-nitrogen (2.01 to 11.37 mg/l) and ammonia nitrogen (10.09 to 19.67 mg/l) the analyzed water samples were above the WHO limit of 250mg/l, 2.00mg/l, 3.00mg/l and 1.5mg/l respectively. There were high levels of Al (8.54-16.55mg/l) and Fe (0.81-2.5 mg/l) recorded compared to WHO limit of 0.05mg/l and 0.3 mg/l respectively; considerable concentrations of Mn, Cu and Cd (0.34-0.89, 1.36-2.80mg/l and 0.00-0.10mg/l) were recorded. The faecal coliform counts were significantly higher than the WHO standard for potable water of 0.00 cfu/100ml (P<0.05). Consequently, both total and faecal coliforms reached their maximum counts in the dry season when the stream turbulence is low and stream course choked with both organic and inorganic wastes. The study therefore concluded that the water from the Onyasia stream is not safe for human related activities.
A thesis submitted to the Department of Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfillment of the requirement for the degree of Master of Science in Environmental Science