Effluent is wastewater from sewers or industrial outfalls that flows directly into surface waters, either untreated or after being treated at a facility. [1] The term has slightly different meanings in certain contexts, and may contain various pollutants depending on the source. [2]
Effluent is defined by the United States Environmental Protection Agency (EPA) as "wastewater–treated or untreated–that flows out of a treatment plant, sewer, or industrial outfall. Generally refers to wastes discharged into surface waters". [1] The Compact Oxford English Dictionary defines effluent as "liquid waste or sewage discharged into a river or the sea". [3] Wastewater is not usually described as effluent while being recycled, re-used, or treated until it is released to surface water. Wastewater percolated or injected into groundwater may not be described as effluent if soil is assumed to perform treatment by filtration or ion exchange; [4] although concealed flow through fractured bedrock, lava tubes, limestone caves, [5] or gravel in ancient stream channels [6] may allow relatively untreated wastewater to emerge as springs. [7]
Effluent in the artificial sense is in general considered to be water pollution, such as the outflow from a sewage treatment facility or an industrial wastewater discharge. An effluent sump pump, for instance, pumps waste from toilets installed below a main sewage line. In the context of waste water treatment plants, effluent that has been treated is sometimes called secondary effluent, or treated effluent. This cleaner effluent is then used to feed the bacteria in biofilters. [8]
In the context of a thermal power station and other industrial facilities, the output of the cooling system may be referred to as the effluent cooling water, which is noticeably warmer than the environment and is called thermal pollution. [9] : 375 In chemical engineering practice, effluent is the stream exiting a chemical reactor. [10]
Effluent may carry pollutants such as fats, oils and greases; solvents, detergents and other chemicals; heavy metal; other solids; and food waste. [2] Possible sources include a wide range of manufacturing industries, mining industries, oil and gas extraction, and service industries. [11]
There are several kinds of wastewater which are treated at the appropriate type of treatment plant. Domestic wastewater (also called municipal wastewater or sewage) is processed at a sewage treatment plant. For industrial wastewater, treatment either takes place in a separate industrial wastewater treatment facility, or in a sewage treatment plant (usually after some form of pre-treatment). Other types of wastewater treatment plants include agricultural wastewater treatment and leachate treatment plants.
Treating wastewater efficiently is challenging, but improved technology allows for enhanced removal of specific materials, increased re-use of water, and energy production from waste. [2] [12] [13] [14]
In the United States, the Clean Water Act requires all direct effluent discharges to surface waters to be regulated with permits under the National Pollutant Discharge Elimination System (NPDES). [15] [16] Indirect dischargers–facilities which send their wastewater to municipal sewage treatment plants–may be subject to pretreatment requirements. [17] NPDES permits require discharging facilities to limit or treat effluent to the levels that result from using the most effective treatment technologies possible at a practical cost to mitigate the effects of discharges on the receiving waters. [16] EPA has published technology-based regulations, called "effluent guidelines", for 59 industrial categories. [11] The agency reviews the standards annually, conducts research on various categories, and makes revisions as appropriate. [16] Noncompliance with these standards and all other conditions in the permits is punishable by law. [18] Each year, effluent guidelines regulations prevent billions of pounds of contaminants from being released into bodies of water. [19]
EPA regulations require effluent limitations to be expressed as mass-based limits (rather than concentration-based limits) in the permits, so that discharging facilities will not use dilution as a substitute for treatment. In cases where setting mass-based limits are infeasible, the permit authority must set conditions in the permit that prohibit dilution. [20]
The U.S. "Secondary Treatment Regulation" is the national standard for municipal sewage treatment plants. [21]
Water pollution is the contamination of water bodies, usually as a result of human activities, so that it negatively affects its uses. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and groundwater. Water pollution results when contaminants mix with these water bodies. Contaminants can come from one of four main sources: sewage discharges, industrial activities, agricultural activities, and urban runoff including stormwater. Water pollution is either surface water pollution or groundwater pollution. This form of pollution can lead to many problems, such as the degradation of aquatic ecosystems or spreading water-borne diseases when people use polluted water for drinking or irrigation. Another problem is that water pollution reduces the ecosystem services that the water resource would otherwise provide.
A sanitary sewer is an underground pipe or tunnel system for transporting sewage from houses and commercial buildings to a sewage treatment plant or disposal. Sanitary sewers are a type of gravity sewer and are part of an overall system called a "sewage system" or sewerage. Sanitary sewers serving industrial areas may also carry industrial wastewater. In municipalities served by sanitary sewers, separate storm drains may convey surface runoff directly to surface waters. An advantage of sanitary sewer systems is that they avoid combined sewer overflows. Sanitary sewers are typically much smaller in diameter than combined sewers which also transport urban runoff. Backups of raw sewage can occur if excessive stormwater inflow or groundwater infiltration occurs due to leaking joints, defective pipes etc. in aging infrastructure.
Wastewater treatment is a process which removes and eliminates contaminants from wastewater and converts this into an effluent that can be returned to the water cycle. Once returned to the water cycle, the effluent creates an acceptable impact on the environment or is reused for various purposes. The treatment process takes place in a wastewater treatment plant. There are several kinds of wastewater which are treated at the appropriate type of wastewater treatment plant. For domestic wastewater, the treatment plant is called a Sewage Treatment. For industrial wastewater, treatment either takes place in a separate Industrial wastewater treatment, or in a sewage treatment plant. Further types of wastewater treatment plants include Agricultural wastewater treatment and leachate treatment plants.
The Clean Water Act (CWA) is the primary federal law in the United States governing water pollution. Its objective is to restore and maintain the chemical, physical, and biological integrity of the nation's waters; recognizing the responsibilities of the states in addressing pollution and providing assistance to states to do so, including funding for publicly owned treatment works for the improvement of wastewater treatment; and maintaining the integrity of wetlands.
Sewage disposal regulation and administration describes the governance of sewage treatment and disposal.
Industrial wastewater treatment describes the processes used for treating wastewater that is produced by industries as an undesirable by-product. After treatment, the treated industrial wastewater may be reused or released to a sanitary sewer or to a surface water in the environment. Some industrial facilities generate wastewater that can be treated in sewage treatment plants. Most industrial processes, such as petroleum refineries, chemical and petrochemical plants have their own specialized facilities to treat their wastewaters so that the pollutant concentrations in the treated wastewater comply with the regulations regarding disposal of wastewaters into sewers or into rivers, lakes or oceans. This applies to industries that generate wastewater with high concentrations of organic matter, toxic pollutants or nutrients such as ammonia. Some industries install a pre-treatment system to remove some pollutants, and then discharge the partially treated wastewater to the municipal sewer system.
New Source Performance Standards (NSPS) are pollution control standards issued by the United States Environmental Protection Agency (EPA). The term is used in the Clean Air Act Extension of 1970 (CAA) to refer to air pollution emission standards, and in the Clean Water Act (CWA) referring to standards for water pollution discharges of industrial wastewater to surface waters.
The Hyperion Water Reclamation Plant is a sewage treatment plant in southwest Los Angeles, California, next to Dockweiler State Beach on Santa Monica Bay. The plant is the largest sewage treatment facility in the Los Angeles Metropolitan Area and one of the largest plants in the world. Hyperion is operated by the City of Los Angeles, Department of Public Works, and the Bureau of Sanitation. Hyperion is the largest sewage plant by volume west of the Mississippi River.
Effluent Guidelines are U.S. national standards for wastewater discharges to surface waters and publicly owned treatment works (POTW). The United States Environmental Protection Agency (EPA) issues Effluent Guideline regulations for categories of industrial sources of water pollution under Title III of the Clean Water Act (CWA). The standards are technology-based, i.e. they are based on the performance of treatment and control technologies. Effluent Guidelines are not based on risk or impacts of pollutants upon receiving waters.
Wastewater quality indicators are laboratory test methodologies to assess suitability of wastewater for disposal, treatment or reuse. The main parameters in sewage that are measured to assess the sewage strength or quality as well as treatment options include: solids, indicators of organic matter, nitrogen, phosphorus, indicators of fecal contamination. Tests selected vary with the intended use or discharge location. Tests can measure physical, chemical, and biological characteristics of the wastewater. Physical characteristics include temperature and solids. Chemical characteristics include pH value, dissolved oxygen concentrations, biochemical oxygen demand (BOD) and chemical oxygen demand (COD), nitrogen, phosphorus, chlorine. Biological characteristics are determined with bioassays and aquatic toxicology tests.
Secondary treatment is the removal of biodegradable organic matter from sewage or similar kinds of wastewater. The aim is to achieve a certain degree of effluent quality in a sewage treatment plant suitable for the intended disposal or reuse option. A "primary treatment" step often precedes secondary treatment, whereby physical phase separation is used to remove settleable solids. During secondary treatment, biological processes are used to remove dissolved and suspended organic matter measured as biochemical oxygen demand (BOD). These processes are performed by microorganisms in a managed aerobic or anaerobic process depending on the treatment technology. Bacteria and protozoa consume biodegradable soluble organic contaminants while reproducing to form cells of biological solids. Secondary treatment is widely used in sewage treatment and is also applicable to many agricultural and industrial wastewaters.
Sewage 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. Sewage contains wastewater from households and businesses and possibly pre-treated industrial wastewater. There are a high number of sewage treatment processes to choose from. These can range from decentralized systems to large centralized systems involving a network of pipes and pump stations which convey the sewage to a treatment plant. For cities that have a combined sewer, the sewers will also carry urban runoff (stormwater) to the sewage treatment plant. 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. Secondary treatment can reduce organic matter from sewage, using aerobic or anaerobic biological processes.
In the United States, several federal agencies and laws have some jurisdiction over pollution from ships in U.S. waters. States and local government agencies also have responsibilities for ship-related pollution in some situations.
Sewage is a type of wastewater that is produced by a community of people. It is typically transported through a sewer system. Sewage consists of wastewater discharged from residences and from commercial, institutional and public facilities that exist in the locality. Sub-types of sewage are greywater and blackwater. Sewage also contains soaps and detergents. Food waste may be present from dishwashing, and food quantities may be increased where garbage disposal units are used. In regions where toilet paper is used rather than bidets, that paper is also added to the sewage. Sewage contains macro-pollutants and micro-pollutants, and may also incorporate some municipal solid waste and pollutants from industrial wastewater.
A Discharge Monitoring Report (DMR) is a United States regulatory term for a periodic water pollution report prepared by industries, municipalities and other facilities discharging to surface waters. The facilities collect wastewater samples, conduct chemical and/or biological tests of the samples, and submit reports to a state agency or the United States Environmental Protection Agency (EPA). All point source dischargers to ”Waters of the U.S.” must obtain a National Pollution Discharge Elimination System (NPDES) permit from the appropriate agency, and many permittees are required to file DMRs.
An effluent limitation is a United States Clean Water Act standard of performance reflecting a specified level of discharge reduction achievable by the best available technology or related standards for various sources of water pollution. These sources include all industries, businesses, municipal sewage treatment plants and storm sewer systems, and other facilities that discharge to surface waters. Effluent limitations are implemented in discharge permits issued by the Environmental Protection Agency (EPA) and state agencies, through the National Pollutant Discharge Elimination System (NPDES).
Water quality laws govern the protection of water resources for human health and the environment. Water quality laws are legal standards or requirements governing water quality, that is, the concentrations of water pollutants in some regulated volume of water. Such standards are generally expressed as levels of a specific water pollutants that are deemed acceptable in the water volume, and are generally designed relative to the water's intended use - whether for human consumption, industrial or domestic use, recreation, or as aquatic habitat. Additionally, these laws provide regulations on the alteration of the chemical, physical, radiological, and biological characteristics of water resources. Regulatory efforts may include identifying and categorizing water pollutants, dictating acceptable pollutant concentrations in water resources, and limiting pollutant discharges from effluent sources. Regulatory areas include sewage treatment and disposal, industrial and agricultural waste water management, and control of surface runoff from construction sites and urban environments. Water quality laws provides the foundation for regulations in water standards, monitoring, required inspections and permits, and enforcement. These laws may be modified to meet current needs and priorities.
Water pollution in the United States is a growing problem that became critical in the 19th century with the development of mechanized agriculture, mining, and industry, although laws and regulations introduced in the late 20th century have improved water quality in many water bodies. Extensive industrialization and rapid urban growth exacerbated water pollution as a lack of regulation allowed for discharges of sewage, toxic chemicals, nutrients and other pollutants into surface water.
Point source water pollution comes from discrete conveyances and alters the chemical, biological, and physical characteristics of water. In the United States, it is largely regulated by the Clean Water Act (CWA). Among other things, the Act requires dischargers to obtain a National Pollutant Discharge Elimination System (NPDES) permit to legally discharge pollutants into a water body. However, point source pollution remains an issue in some water bodies, due to some limitations of the Act. Consequently, other regulatory approaches have emerged, such as water quality trading and voluntary community-level efforts.
County of Maui v. Hawaii Wildlife Fund, No. 18-260, 590 U.S. ___ (2020), was a United States Supreme Court case involving pollution discharges under the Clean Water Act (CWA). The case asked whether the Clean Water Act requires a permit when pollutants that originate from a non-point source can be traced to reach navigable waters through mechanisms such as groundwater transport. In a 6–3 decision, the Court ruled that such non-point discharges require a permit when they are the "functional equivalent of a direct discharge", a new test defined by the ruling. The decision vacated the ruling of the United States Court of Appeals for the Ninth Circuit, and remanded the case with instructions to apply the new standard to the lower courts with cooperation of the Environmental Protection Agency (EPA).
