What is wastewater treatment ?

What is wastewater treatment ?

 

What is wastewater treatment ? Waste water needs to be treated before it can be reused or released into a river. Waste water treatment is a process which removes impurities from waste water. What is the need for waste water treatment? Waste water from households is treated at a treatment plant to remove the physical, biological and chemical matter. Treatment of waste water reduces the toxicity of poisonous substances and pollutants in water resources Steps involved in Waste Water Treatment Plants (WWTP) The three steps of the wastewater treatment process include: primary treatment (mechanical process), secondary treatment (chemical process), tertiary treatment (biological process). So waste water treatment involves mechanical, chemical and biological treatment of water. Waste water is allowed to pass through different steps in a sequence. Step 1 - Bar Screens: Screening is first stage of the wastewater treatment process. Screening removes large objects like, sanitary items, bottles, plastics and rags that may block or damage treatment plant pump. Step 2 - Grit chamber: Waste water from the bar screens is allowed to pass through grit chambers in a slow manner. The slow movement of water makes grit, sand and dust particles to settle down. Step 3 - Clarifier: A clarifier is a tank with its central part inclined downwards so as to allow faeces to settle down. The waste settled at the bottom is termed as sludge. • Sludge is transferred to a separate tank where it is decomposed using bacteria. Finally, a skimmer is used to remove oils and grease. Clarified water is obtained after the separation of all physical contaminants from the sewage. Step 4 - Aerator: The clarified water is passed into an aerator. An aerator pumps air into the water to settle the bacteria to the bottom of the tank as activated sludge. Bacteria under aerated conditions consume impurities left in the water. The water present in the top is 95% clean and is let out into a water source while the activated sludge is dried in a sand bed and is used as manure. Using bacteria in decomposing waste is the biological treatment. Chemical treatment of waste water: • Chlorine tablets or chlorine gas is used to treat waste water chemically. • Water will be clean on the dissolution of a chlorine tablet. Hence, chlorine tablets are used to disinfect water in treatment plants. • Chlorine gas is introduced through many pipes into a tank with water stored after physical and biological treatment. • Ozone is also used in chemical purification of water.