WATER POLLUTION LEVELS IN THE SUWUNG ESTUARYBALI BASED ON BIOLOGICAL OXYGEN DEMAND

Biological Oxygen Demand (BOD) is generally used for determining the water pollution level in water bodies. Estuary is a semi-enclosed water, that can be influenced by pollution from land areas or rivers. This research was aimed to determine the spatial distribution of water pollution levels based on BOD analysis. This research was conducted in January and February 2016 in Suwung estuary, Bali. Samples were taken in 20 points (19 points were located in Suwung Estuary and one point was located outside the Suwung estuary as a control point) and the BOD samples were analyzed in the laboratory. The method for BOD analysis was using amperometric method in National Field Manual for the Collection of Data Water-Quality, Chapter A7. The BOD Samples were taken at all tide cycles, during ebb to high tide and high tide to ebb. The range of BOD values were: 0.84 mg/L – 9.47 mg/L during ebb to high tide and 0.96 mg/L – 8.75 mg/L during high tide to ebb. The result of BOD analysis showed that the water pollution level in the Suwung estuary was slightly contaminated in both tide conditions. The spatial distribution of BOD value tended to be higher around the cage aquaculture area, near the river, landfill area and around Benoa harbour.