... of the River Swale will be in quite good condition as it is flowing from the mountains meaning that it will be quite fresh. River's, which aren't fresh and are polluted, is mainly because of organic pollution. Organic pollution includes sewage and silage effluent. Organic wastes are 'oxygen-requiring' because they are decomposed by bacteria and bacteria use up the oxygen in their process of respiration. Bacteria place a high oxygen demand upon the water. The quality of the water can be measured by taking its biochemical oxygen demand (BOD). This is what we are going to do as a class. The lower the oxygen biochemical oxygen demand, the fewer bacteria present. If fewer bacteria are present, this indicates that there is less organic material in the water. I, also, think that the Swale will be fairly oxygenated as there are lots of rocks and stones in it, obstructing the natural flow of ...

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