![]() ![]() Some types of sewage treatment produce sewage sludge which can be treated before safe disposal or reuse. With regards to biological treatment of sewage, the treatment objectives can include various degrees of the following: to transform or remove organic matter, nutrients (nitrogen and phosphorus), pathogenic organisms, and specific trace organic constituents (micropollutants). This is achieved by removing contaminants from the sewage. The overall aim of treating sewage is to produce an effluent that can be discharged to the environment while causing as little water pollution as possible, or to produce an effluent that can be reused in a useful manner. The terms water recycling center or water reclamation plants are also in use as synonyms. Strictly speaking, the latter is a broader term that can also refer to industrial wastewater treatment. The term sewage treatment plant (STP) (or sewage treatment works) is nowadays often replaced with the term wastewater treatment plant (WWTP). Terminology Activated sludge sewage treatment plant in Massachusetts, US The term sewage treatment plant is often used interchangeably with the term wastewater treatment plant. Sanitation also includes the management of human waste and solid waste as well as stormwater (drainage) management. The treatment of sewage is part of the field of sanitation. For example, while high-income countries treat approximately 74% of their sewage, developing countries treat an average of just 4.2%. However, sewage treatment rates are highly unequal for different countries around the world. On the other hand, advanced and relatively expensive sewage treatment plants in cities that can afford them may include tertiary treatment with disinfection and possibly even a fourth treatment stage to remove micropollutants.Īt the global level, an estimated 52% of sewage is treated. These systems include septic tanks connected to drain fields, on-site sewage systems (OSS), vermifilter systems and many more. In developing countries and in rural areas with low population densities, sewage is often treated by various on-site sanitation systems and not conveyed in sewers. ![]() : 215 Often, the main criteria for selection are: desired effluent quality, expected construction and operating costs, availability of land, energy requirements and sustainability aspects. Design engineers and decision makers need to take into account technical and economical criteria of each alternative when choosing a suitable technology. Secondary treatment can reduce organic matter (measured as biological oxygen demand) from sewage, using aerobic or anaerobic biological processes.Ī large number of sewage treatment technologies have been developed, mostly using biological treatment processes. Sewage treatment often involves two main stages, called primary and secondary treatment, while advanced treatment also incorporates a tertiary treatment stage with polishing processes and nutrient removal. For cities that have a combined sewer, the sewers will also carry urban runoff (stormwater) to the sewage treatment plant. These can range from decentralized systems (including on-site treatment systems) to large centralized systems involving a network of pipes and pump stations (called sewerage) which convey the sewage to a treatment plant. There are a high number of sewage treatment processes to choose from. ![]() Sewage contains wastewater from households and businesses and possibly pre-treated industrial wastewater. Sewage treatment (or domestic wastewater treatment, municipal wastewater treatment) is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable to discharge to the surrounding environment or an intended reuse application, thereby preventing water pollution from raw sewage discharges. Water pollution, Environmental health, Public health, sewage sludge disposal issues List of wastewater treatment technologies Sewage, could also be just blackwater (waste), greywater Įffluent, sewage sludge, possibly biogas (for some types) Wastewater treatment plant (WWTP), water reclamation plant Clockwise from top left: Aerial photo of Kuryanovo activated sludge STP in Moscow, Russia Constructed wetlands STP near Gdansk, Poland Waste stabilization ponds STP in the South of France Upflow anaerobic sludge blanket STP in Bucaramanga, Colombia. Sewage treatment plants (STPs) come in many different sizes and process configurations. ![]()
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