Types of Sewage Treatment: Activated Sludge Process Plant - Activated Sludge Process Plant is a process for treating sewage and industrial waste-water using air and a biological flock composed of bacterial and protozoa. In activated sludge process waste water containing organic matter to aerate in an aeration basin in which Micro – Organism metabolize the suspended and soluble organic matter. Part of organic matter is synthesized into new cells and part is oxidized to CO2 and water to drive energy. In activated sludge system the new cells formed in the reaction are removed from the liquid system in the form of a flocculent sludge in settling tanks. A part of this settled biomass described as activated sludge in returned to the aeration tank and the remaining forms waste to excess sludge Extended Aeration System - The Extended Aeration Process, a modification of the Activated Sludge Process, effectively treats the contaminants in wastewater. The standard basis of design includes an aeration system, providing a 24-hour detention time and a final settling tank, with an effective 4-hour detention time. Diffused air is introduced into the aeration tank, this provides the proper environment for the development of aerobic bacteria. These bacteria thrive on the materials contained in the wastewater. The prolonged period of aeration, in addition, oxidizes a portion of the solids in the system. Oxygenation by diffused aeration provides operating flexibility and standby reserve to meet the demanding requirements of varied package plant applications. Submerged Aerobic Fixed Film (SAFF) Technology Plant - Submerged Aerobic Fixed Film Technology Plant is based on aerobic growth process and used in the waste water treatment plant. The aeration tank contains polymer based bio-media fixed into the tank. The aerobic environment in the SAFF is achieved by the use of fine bubbles diffused aeration equipments, which also serves to maintain the mixed liquor in a completely mixed regime. The mixer of new cells and old cells overflows in a secondary sedimentation tank, where the cells are separated from the treated waste water. A portion of the settled cells in recycled to maintain organisms in SAFF Reactor and the remaining portion is wasted to aerobic sludge digester cum thickener tank for further treatment. MBBR System - The MBBR System is the latest advance in attached growth aerobic biological treatment technology. MBBR employs (RING PAC MEDIA) neutrally buoyant bio-film carrier elements to achieve outstanding BOD/COD removal productivity from a compact bioreactor. In MBBR the liquid to be treated is pumped through a bed of small media at a sufficient velocity to cause fluidization. In the fluidized state the media provide a large specific surface for attached biological growth and allow biomass concentration to develop. SBR System - The Sequencing Batch Reactor process (abbreviated SBR procedure) is a variation of the conventional activated sludge process. The SBR consists of a reaction chamber which first operates as a biological reactor and then as sedimentation chamber. Unlike reactors where the wastewater flows through continuously, the SBR is filled and emptied discontinuously. The conventional physical separation of the biological processes and the sedimentation is replaced by a chronological one. The cycle starts with the filling phase where the first decomposition processes start under anaerobic or anoxic conditions. In the actual decomposition or reaction phase, the reactor is ventilated. Depending on the cleaning target, unventilated phases can be projected as well. Afterwards, in the sedimentation phase, the activated sludge sediments and the Clear water layer develop. The supernatant Clear water is removed in the sedimentation phase. Then, the cycle starts from the beginning. A separate secondary sedimentation is not required in the SBR process. MBR System - Membrane bioreactor (MBR) is the combination of a membrane process like microfiltration or ultra filtration with a biological wastewater treatment process, the activated sludge process. It is now widely used for municipal and industrial wastewater treatment. When used with domestic wastewater, MBR processes can produce effluent of high quality enough to be discharged to coastal, surface or brackish waterways or to be reclaimed for urban irrigation. Other advantages of MBRs over conventional processes include small footprint, easy retrofit and upgrade of old wastewater treatment plants. Constructed Wetland System- A constructed wetland (CW)-is an artificial wetland to treat municipal or industrial wastewater, grey-water or storm-water runoff. It may also be designed for land reclamation after mining, or as a mitigation step for natural areas lost to land development. Constructed wetlands are engineered systems that use natural functions vegetation, soil, and organisms to treat wastewater. Depending on the type of wastewater the design of the constructed wetland has to be adjusted accordingly. Constructed wetlands have been used to treat both centralized and on-site wastewater. Primary treatment is recommended when there is a large amount of suspended solids or soluble organic matter (measured as BOD and COD). Similarly to natural wetlands, constructed wetlands also act as a biofilter and/or can remove a range of pollutants (such as organic matter, nutrients, pathogens, heavy metals) from the water. Constructed wetlands are designed to remove water pollutants such as suspended solids, organic matter and nutrients (nitrogen and phosphorus). All types of pathogens (i.e., bacteria, viruses, protozoan and helminths) are expected to be removed to some extent in a constructed wetland. Subsurface wetland provide greater pathogen removal than surface wetlands. There are two main types of constructed wetlands: subsurface flow and surface flow constructed wetlands. The planted vegetation plays an important role in contaminant removal. The filter bed, consisting usually of sand and gravel, has an equally important role to play.[2] Some constructed wetlands may also serve as a habitat for native and migratory wildlife, although that is not their main purpose.