Microbiology

Microbiology Study Guide

©2018 of 132 Water Purification A number of methods are available to purify water by reducing the microbes so that it becomes and remains safe for the purpose of consumption. One popular method is to use a sedimentation task through which the solid waste matter settles at the bottom of the tank. Microorganisms are at the bottom of the tank with the help of flocculating materials like alum. The next step is to filter the water using slow sand or a rapid sand filter. By now, about 99 percent of the microorganisms are removed from the water. The difference between filters is the size of the grains of sand used for the filtration process. The slow sand filter uses finer grains, while the rapid sand filter uses larger sand grain particles. The time taken to filter in a slow sand filter is much higher than that in the rapid sand filter. The next step in the purification process is chlorination, whereby chlorine gas or hypochlorite is added to the water. The purpose of chlorination is to maintain purity of the water for a longer duration, which ensures that the water is safe for drinking. Sewage Treatment The treatment of sewage water involves a much more complex process since the quantum of organic matter and microorganisms are much higher than in used water. The treatment of sewage water involves three major stages: primary treatment, secondary treatment, and tertiary treatment. The first stage is primary treatment, which involves removal of the plant and other particulate matter using settling tanks. The solid sediments settle at the bottom, which is strained using filters. The sludge collected is either burnt or put in landfills. However, one of the eco-friendliest techniques to mitigate the sludge is to treat it using an anaerobic sludge tank. The second stage is secondary treatment through which the microbes and sludge are reduced using an anaerobic sludge-digester tank. During this process, different organisms are used to breakdown the proteins, lipids, and cellulose of the complex organic matter into smaller substances, like organic acids and alcohols, so that metabolism becomes possible. The outcome of secondary treatment is the release of methane gas, which is the source of energy for the operation of the wastewater treatment plant. The next part of secondary treatment is aerobic treatment in which the fluid waste is extracted and filtered using a trickling filter. A bed of crushed rocks and bark from trees is used, and the liquid is spread across them. The crushed rocks and bark act as successful filters of the microorganisms, bacteria, fungi, and protozoa, removing the organic matter and pollutants from the spread liquid waste. These microorganisms convert the organic matter into elements like carbon dioxide, sulfate, phosphates, and nitrates. This process helps to clean and purify the sewage and wastewater up to 99 percent. Many times, the activated digester is used to clean and purify liquid waste. In this process, slime- forming bacteria is used for many hours so that the microorganisms are trapped and then removed from the liquid. The sludge left at the end is either treated or dumped in landfills. Achieve Page 93

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