SEWAGE TREATMENT PLANT (STP) STP plant handles sewage to make it suitable for safe disposal, agricultural or domestic use in toilets, etc. Sewage typically contains a high volume of organic and inorganic waste. It is necessary to treat the waste before it reaches any body of water. Generally, they can be grouped into the following system types: active sludge plant (ASP) Rotating disc system. Aerated beverage submerged (SAF). Sewage treatment is conducted in three stages: primary, secondary and tertiary. The main goal of wastewater treatment is to eliminate as many dissolved solids as possible until the remaining water, known as effluent, is released back to the atmosphere. It uses oxygen, which is required by plants and animals living in the water, as solid material decays.
The sewage treatment plant uses internal processes to break down solid waste to create safer, more environmentally friendly effluent. Wastewater and sewage are supplied to the primary tank where the solids and liquids are distributed. If the drainage system is a mixed sewer, the municipal runoff (stormwater) may also be transported to the sewage treatment facility.
Waste is waste created by private, institutional, commercial and industrial establishments. The STP plant handles sewage to make it suitable for safe disposal, agricultural or domestic use in toilets, etc. Sewage typically contains a high volume of organic and inorganic waste. It is necessary to treat the waste before it reaches any body of water. If the sewage is permitted to enter the water bodies without treatment, it can contaminate them; hence it is necessary to treat the sewage properly before it is allowed to enter the rivers or any other source of water.
In primary treatment, wastewater is fed to a screen to remove all large objects which are suspended in the water. After that the water goes into the Grit chamber, where the grit is extracted. Grit includes sand, dirt, egg shells, bone chips, seeds, and other material. Grit removal is important to reduce heavy deposits in aeration tanks, digesters, canals and ducts. The next phase consists of the primary settlement tanks. These tanks are typically wide in size and the solids settle down due to gravity and are collected from the bottom as sludge. In the meantime the oil is floating on the surface and skimmed off. 50-60 per cent of the suspended solids have been eliminated and a 30-40 per cent drop in the 5-day biological oxygen demand can be expected.
Secondary treatment is the second level of the treatment of wastewater. In primary therapy, suspended solids, colloidal particles, oil and fat are extracted. The second biological procedure is then performed on the wastewater to remove the organic matter.
This treatment is performed by indigenous and aquatic micro-organisms such as bacteria and protozoa that consume biodegradable soluble pollutants such as sugar, fat, detergent and food waste. These processes are temperature sensitive and with a rise in the temperature of biological reactions.
Secondary therapy is split into two separate treatment processes: 1. Aerobic Treatment – Aerobic wastewater treatment is a biological treatment that uses oxygen to break down organic matter and eliminate other contaminants such as nitrogen and phosphorus. Generally, aerobic therapy is done in sewage treatment.
Anaerobic treatment is a method in which wastewater or substance is broken down by micro-organisms without the assistance of dissolved oxygen. However, anaerobic bacteria can and will use oxygen present in the oxides added into the environment, or they can obtain it from organic wastewater content.