What are the methods of sewage disposal?

          Sewage is a watery mixture of all wastes that come from different sources which include residential as well as non-residential places. It includes human wastes, soapy and dirty water from sinks and bathrooms, food scrabs and other garbage washed down the drains. More than 90 percent of sewage is the water used to wash the wastes away. A household might produce hundreds of gallons of sewage every day. Do you know how it is disposed?

          There are two ways of disposing the sewage. It can be stored in underground septic tanks until it gets soaked into the soil, or it can be dumped into rivers and oceans. The big cities may produce millions of gallons of sewage every day. Since the ground doesn’t have enough space for all of it, the cities are forced to dump the wastes into rivers and oceans. Unfortunately, this causes serious pollution.

          The sewage may be carried from homes in underground pipes which lead to a sewage treatment plant. Once in the plant, the sewage undergoes primary treatment. It removes the solid wastes by allowing them to sink to the bottom of a large tank. The liquid sewage is drained off the top and the solid sewage is collected from the bottom and burnt. Some sewage plants provide for only primary treatment. The liquid sewage is then poured into rivers.

          Most modern sewage treatment plants have equipments for a secondary treatment which remove the harmful germs and the floating wastes. The sewage is mixed with those bacteria that breakdown the wastes into harmless products. This process of destroying the waste kills off many germs. Large amounts of chlorine are then mixed into the water to kill all the remaining germs and other micro-organisms.

          Today many modern treatment plants have introduced a third step also. It removes the nutrients and chemicals that make water undrinkable. So, when the water passes through a tertiary treatment plant, it gets clean enough and can be drunk.