Water Quality Analysis and Pollution Prevention Options of Lake Ziway, Around Ziway City
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Date
2018-12
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Addis Ababa University
Abstract
Water is a key factor for ecological balance and to support biodiversity. But it is getting polluted
as a result of human interventions and natural phenomenon. Lake Ziway is one of the surface
waters getting devastating effects from floriculture farms, agricultural practices, and irrigation
schemes and usage of chemicals. The objective of this thesis is to analyze the pollution status of
the Lake. Water samples were collected and laboratory analysis was done for color, odor, pH, EC,
TDS, turbidity, ammonia, total hardness, sodium, potassium, total iron, manganese, calcium,
magnesium, alkalinity, bicarbonate, chloride, Sulphate, nitrate, nitrite, fluoride, phosphate, DO,
BOD and COD at seven sites from February to March in 21 runs. Sediment samples were also
taken from four sampling sites and analysis was done for pH, EC, CEC, total iron, manganese,
total nitrogen and total phosphorus in the same period with water quality analysis in12 runs. The
results were compared with WHO’s drinking water quality guide lines and also the datasets were
evaluated statistically. The mean values of turbidity, manganese, BOD and COD levels exceed the
WHO standards. All water quality parameters have a significance values of P≤ 0.05 for spatial
variation except BOD and COD that have P- values of 0.196 and 0.143 respectively. Whereas the
significant temporal variations are only observed for potassium (0.03), BOD (0.001) and COD
(0.002). The dendrogram diagram shows two significant clusters for both water and sediment
samples. Generally, the results revealed that the major causes of water quality deterioration are
inflow of effluents from the floriculture industries, domestics, agricultural practices, saline seeps
and other uncontrolled human interventions as observed in sites one, two, three, four and five. The
other cause results from people’s activities in boats and islands. Run off, silt, waste effluents and
etc. also are taken to be the causes of the lakes pollutions as shown in cluster one. Constructed
buffer zones, waste water treatment and recycling, integrated pest management practices, proper
disposal of liquid and solid wastes and other BMPs are recommended prevention and treatment
options to safeguard water quality.
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Keywords
Lake Ziway, Water quality, pollution, floriculture farms, statistical analysis, prevention, treatment options