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Water and Sewage Treatment

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Introduction

Plan: Water and Sewage Treatment The following describe how water from a reservoir is purified in treatment plant and how wastewater is treated and cleaned. Purifying Water in Treatment Plants As water leaves the reservoir, it passes through a screen to remove objects such as rubbish and twigs. Filters made from chemicals, sand and gravel remove smaller particles that could scour (wear away) the inside of water pipes, damage industrial equipment, or make drinking water cloudy. Bacteria or viruses, which may cause disease and death, are dealt with bubbling toxic gases, such as chlorine or ozone, through the water. Wastewater Treatment Raw sewage includes waterborne waste from sinks, toilets, and industrial processes. Treatment of the sewage is required before it can be safely buried, used, or released back into local water systems. In a treatment plant, the waste is passed through a series of screens, chambers, and chemical processes to reduce its bulk and toxicity. The three general phases of treatment are primary, secondary, and tertiary. During primary treatment, a large percentage of the suspended solids and inorganic material is removed from the sewage. The focus of secondary treatment is reducing organic material by accelerating natural biological processes. Tertiary treatment is necessary when the water will be reused; 99 percent of solids are removed and various chemical processes are used to ensure the water is as free from impurity as possible. ...read more.

Middle

Anaerobic 'digestion' of the sludge by bacteria such as Mathanobacterium converts the organic material into methane, carbon dioxide and hydrogen gases along with water and minerals. * In our experiment, after sedimentation, the effluent is passed through a column of different sized stones and sand. The largest stones should be at the bottom and the smallest at the top. Sand can also be used at the top of the column. Some important points to follow when making a rock column are to make sure the stones are clean and there are no gaps. This will remove any large insoluble particles that weren't removed during sedimentation. * The effluent that is collected after the rock column will be filtered at least twice through a filter funnel and filter paper. In industrial plants a process called Trickling Filter is used. In this process, a waste stream is distributed intermittently over a bed or column of some type of porous medium. A gelatinous film of microorganisms coats the medium and functions as the removal agent. The organic matter in the waste stream is absorbed by the microbial film and converted to carbon dioxide and water. The trickling-filter process, when preceded by sedimentation, can remove about 85 per cent of the BOD5 entering the plant. The following processes in our experiment are all forms of treatment following the filtering processes: * You may treat the filtered water with liquid chlorine or laundry bleach. ...read more.

Conclusion

* After at least two days the agar plate should be checked. If the agar plate is clear and there are no signs of bacteria present, then the water should be safe to drink. But if there are signs of colonies of bacteria forming then the water will be unsafe to drink. Variables * Instead of the sedimentation process the dirty water in our experiment can be passed through a series of sieves. The first filter would be the one with the largest pores and last one would be the sieve with the smallest pores. The sieves would mainly remove large pieces of material such as stones, sand dirt etc. * An alternative treatment replacing the use of bleach is to use Iodine tablets. * The purity of the water can be tested using agar plates after each of the individual processes in the experiment in order to see which one was the most effective. Prediction I think that the most effective form of treatment will be the distillation process and after a few days the agar plate will show no signs of bacteria present. If only the distillation process was carried out I would still predict that the distilled water would be pure. Distillation will separate the pure water from insoluble particles and anything else that was dissolved in the water. Any bacteria present will be eliminated due to the high temperature (over 100�C) reached. 1 1 ...read more.

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