Wastewater treatment is a process which removes and eliminates contaminants from wastewater . It thus converts it into an effluent that can be returned to the water cycle . Once back in the water cycle, the effluent creates an acceptable impact on the environment. It is also possible to reuse it. This process is called water reclamation . 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 . Municipal wastewater or sewage are other names for domestic wastewater . For industrial wastewater, treatment takes place in a separate Industrial wastewater treatment , or in a sewage treatment plant. In the latter case it usually follows pre-treatment. Further types of wastewater treatment plants include Agricultural wastewater treatment and leachate treatment plants.
57-579: The Everett Water Pollution Control Facility is a wastewater treatment plant in Everett, Washington , United States. It serves the city of Everett and discharges treated water into the Snohomish River . The facility is located at the south end of Smith Island, adjacent to Interstate 5 and Spencer Island Regional Park, a noted birdwatching spot. The lagoon system was built in the 1960s and covers 200 acres (81 ha). A mechanical treatment plant
114-738: 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 (e.g. oil and grease), toxic pollutants (e.g. heavy metals, volatile organic compounds ) or nutrients such as ammonia . Some industries install
171-403: A conservation and replanting of timber that there can be a continuous, ongoing and sustainable use". The shift in use of "sustainability" from preservation of forests (for future wood production) to broader preservation of environmental resources (to sustain the world for future generations) traces to a 1972 book by Ernst Basler, based on a series of lectures at M.I.T. The idea itself goes back
228-694: A network of pipes and pump stations (called sewerage ) 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 (measured as biological oxygen demand ) from sewage, using aerobic or anaerobic biological processes. A so-called quarternary treatment step (sometimes referred to as advanced treatment) can also be added for
285-489: A new development path was required, one that sustained human progress not just in a few pieces for a few years, but for the entire planet into the distant future. Thus 'sustainable development' becomes a goal not just for the 'developing' nations, but for industrial ones as well. The Rio Declaration from 1992 is seen as "the foundational instrument in the move towards sustainability". It includes specific references to ecosystem integrity. The plan associated with carrying out
342-471: A pre-treatment system to remove some pollutants (e.g., toxic compounds), and then discharge the partially treated wastewater to the municipal sewer system. Agricultural wastewater treatment is a farm management agenda for controlling pollution from confined animal operations and from surface runoff that may be contaminated by chemicals in fertilizer , pesticides , animal slurry , crop residues or irrigation water. Agricultural wastewater treatment
399-426: A single specific definition of sustainability may never be possible. But the concept is still useful. There have been attempts to define it, for example: Some definitions focus on the environmental dimension. The Oxford Dictionary of English defines sustainability as: "the property of being environmentally sustainable; the degree to which a process or enterprise is able to be maintained or continued while avoiding
456-504: A treatment sequence to remove solids generated during oxidation or polishing. Grease and oil may be recovered for fuel or saponification . Solids often require dewatering of sludge in a wastewater treatment plant . Disposal options for dried solids vary with the type and concentration of impurities removed from water. Solids such as stones , grit, and sand may be removed from wastewater by gravity when density differences are sufficient to overcome dispersion by turbulence . This
513-402: A very long time: Communities have always worried about the capacity of their environment to sustain them in the long term. Many ancient cultures, traditional societies , and indigenous peoples have restricted the use of natural resources. The terms sustainability and sustainable development are closely related. In fact, they are often used to mean the same thing. Both terms are linked with
570-471: Is phase separation , such as sedimentation. Biological and chemical processes such as oxidation are another example. Polishing is also an example. The main by-product from wastewater treatment plants is a type of sludge that is usually treated in the same or another wastewater treatment plant. Biogas can be another by-product if the process uses anaerobic treatment. Treated wastewater can be reused as reclaimed water . The main purpose of wastewater treatment
627-450: Is bad for the environment. Others focus more on the trade-offs between environmental conservation and achieving welfare goals for basic needs (food, water, health, and shelter). Economic development can indeed reduce hunger or energy poverty . This is especially the case in the least developed countries . That is why Sustainable Development Goal 8 calls for economic growth to drive social progress and well-being. Its first target
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#1732787648265684-467: Is for the treated wastewater to be able to be disposed or reused safely. However, before it is treated, the options for disposal or reuse must be considered so the correct treatment process is used on the wastewater. The term "wastewater treatment" is often used to mean " sewage treatment ". Wastewater treatment plants may be distinguished by the type of wastewater to be treated. There are numerous processes that can be used to treat wastewater depending on
741-520: Is for: "at least 7 per cent GDP growth per annum in the least developed countries". However, the challenge is to expand economic activities while reducing their environmental impact. In other words, humanity will have to find ways how societal progress (potentially by economic development) can be reached without excess strain on the environment. The Brundtland report says poverty causes environmental problems. Poverty also results from them. So addressing environmental problems requires understanding
798-412: Is known through scientific study to applications in pursuit of what people want for the future." The 1983 UN Commission on Environment and Development ( Brundtland Commission ) had a big influence on the use of the term sustainability today. The commission's 1987 Brundtland Report provided a definition of sustainable development . The report, Our Common Future , defines it as development that "meets
855-462: Is necessary to address many barriers to sustainability to achieve a sustainability transition or sustainability transformation . Some barriers arise from nature and its complexity while others are extrinsic to the concept of sustainability. For example, they can result from the dominant institutional frameworks in countries. Global issues of sustainability are difficult to tackle as they need global solutions. Existing global organizations such as
912-411: Is not a new phenomenon. But it has been only a local or regional concern for most of human history. Awareness of global environmental issues increased in the 20th century. The harmful effects and global spread of pesticides like DDT came under scrutiny in the 1960s. In the 1970s it emerged that chlorofluorocarbons (CFCs) were depleting the ozone layer . This led to the de facto ban of CFCs with
969-569: Is often thought of as a long-term goal (i.e. a more sustainable world), while sustainable development refers to the many processes and pathways to achieve it." Details around the economic dimension of sustainability are controversial. Scholars have discussed this under the concept of weak and strong sustainability . For example, there will always be tension between the ideas of "welfare and prosperity for all" and environmental conservation , so trade-offs are necessary. It would be desirable to find ways that separate economic growth from harming
1026-1206: Is required for continuous confined animal operations like milk and egg production. It may be performed in plants using mechanized treatment units similar to those used for industrial wastewater . Where land is available for ponds, settling basins and facultative lagoons may have lower operational costs for seasonal use conditions from breeding or harvest cycles. Animal slurries are usually treated by containment in anaerobic lagoons before disposal by spray or trickle application to grassland. Constructed wetlands are sometimes used to facilitate treatment of animal wastes. Leachate treatment plants are used to treat leachate from landfills . Treatment options include: biological treatment, mechanical treatment by ultrafiltration , treatment with active carbon filters, electrochemical treatment including electrocoagulation by various proprietary technologies and reverse osmosis membrane filtration using disc tube module technology. The unit processes involved in wastewater treatment include physical processes such as settlement or flotation and biological processes such oxidation or anaerobic treatment. Some wastewaters require specialized treatment methods. At
1083-405: Is the most common method used in municipal wastewater treatment. Sustainability Sustainability is a social goal for people to co-exist on Earth over a long period of time. Definitions of this term are disputed and have varied with literature, context, and time. Sustainability usually has three dimensions (or pillars): environmental, economic, and social. Many definitions emphasize
1140-475: Is typically achieved using a grit channel designed to produce an optimum flow rate that allows grit to settle and other less-dense solids to be carried forward to the next treatment stage. Gravity separation of solids is the primary treatment of sewage , where the unit process is called "primary settling tanks" or "primary sedimentation tanks". It is also widely used for the treatment of other types of wastewater. Solids that are denser than water will accumulate at
1197-411: Is widely used for disinfection. Advanced oxidation processes are used to remove some persistent organic pollutants and concentrations remaining after biochemical oxidation. Disinfection by chemical oxidation kills bacteria and microbial pathogens by adding hydroxyl radicals such as ozone , chlorine or hypochlorite to wastewater. These hydroxyl radical then break down complex compounds in
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#17327876482651254-730: The Montreal Protocol in 1987. In the early 20th century, Arrhenius discussed the effect of greenhouse gases on the climate (see also: history of climate change science ). Climate change due to human activity became an academic and political topic several decades later. This led to the establishment of the IPCC in 1988 and the UNFCCC in 1992. In 1972, the UN Conference on the Human Environment took place. It
1311-569: The UN and WTO are seen as inefficient in enforcing current global regulations. One reason for this is the lack of suitable sanctioning mechanisms . Governments are not the only sources of action for sustainability. For example, business groups have tried to integrate ecological concerns with economic activity, seeking sustainable business . Religious leaders have stressed the need for caring for nature and environmental stability. Individuals can also live more sustainably . Some people have criticized
1368-531: The natural resources and ecosystem services needed for economies and society. The concept of sustainable development has come to focus on economic development , social development and environmental protection for future generations. Scholars usually distinguish three different areas of sustainability. These are the environmental, the social, and the economic. Several terms are in use for this concept. Authors may speak of three pillars, dimensions, components, aspects, perspectives, factors, or goals. All mean
1425-516: The "integrity of the earth's life-support systems" was essential for sustainability. The authors said that "the SDGs fail to recognize that planetary, people and prosperity concerns are all part of one earth system, and that the protection of planetary integrity should not be a means to an end, but an end in itself". The aspect of environmental protection is not an explicit priority for the SDGs. This causes problems as it could encourage countries to give
1482-441: The "three dimensions of sustainability" concept. One distinction is that sustainability is a general concept, while sustainable development can be a policy or organizing principle. Scholars say sustainability is a broader concept because sustainable development focuses mainly on human well-being. Sustainable development has two linked goals. It aims to meet human development goals. It also aims to enable natural systems to provide
1539-400: The 17 Sustainable Development Goals (SDGs) with their 169 targets as balancing "the three dimensions of sustainable development, the economic, social and environmental". Scholars have discussed how to rank the three dimensions of sustainability. Many publications state that the environmental dimension is the most important. ( Planetary integrity or ecological integrity are other terms for
1596-458: The 1960s and 1970s. This led to discussions on sustainability and sustainable development. This process began in the 1970s with concern for environmental issues. These included natural ecosystems or natural resources and the human environment. It later extended to all systems that support life on Earth, including human society. Reducing these negative impacts on the environment would improve environmental sustainability. Environmental pollution
1653-577: The Brundtland Report, the environment and development are inseparable and go together in the search for sustainability. It described sustainable development as a global concept linking environmental and social issues. It added sustainable development is important for both developing countries and industrialized countries : The 'environment' is where we all live; and 'development' is what we all do in attempting to improve our lot within that abode. The two are inseparable. [...] We came to see that
1710-499: The Rio Declaration also discusses sustainability in this way. The plan, Agenda 21 , talks about economic, social, and environmental dimensions: Countries could develop systems for monitoring and evaluation of progress towards achieving sustainable development by adopting indicators that measure changes across economic, social and environmental dimensions. Agenda 2030 from 2015 also viewed sustainability in this way. It sees
1767-439: The SDGs. It should also show how to address the trade-offs between ecological footprint and economic development. The social dimension of sustainability is not well defined. One definition states that a society is sustainable in social terms if people do not face structural obstacles in key areas. These key areas are health, influence, competence, impartiality and meaning-making . Some scholars place social issues at
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1824-761: The UN launched eight Millennium Development Goals . The aim was for the global community to achieve them by 2015. Goal 7 was to "ensure environmental sustainability". But this goal did not mention the concepts of social or economic sustainability. Specific problems often dominate public discussion of the environmental dimension of sustainability: In the 21st century these problems have included climate change , biodiversity and pollution. Other global problems are loss of ecosystem services , land degradation , environmental impacts of animal agriculture and air and water pollution , including marine plastic pollution and ocean acidification . Many people worry about human impacts on
1881-629: The bottom of quiescent settling basins . More complex clarifiers also have skimmers to simultaneously remove floating grease such as soap scum and solids such as feathers, wood chips, or condoms . Containers like the API oil-water separator are specifically designed to separate non-polar liquids. Oxidation reduces the biochemical oxygen demand of wastewater, and may reduce the toxicity of some impurities. Secondary treatment converts organic compounds into carbon dioxide , water , and biosolids through oxidation and reduction reactions. Chemical oxidation
1938-460: The environment . This means using fewer resources per unit of output even while growing the economy. This decoupling reduces the environmental impact of economic growth, such as pollution . Doing this is difficult. Some experts say there is no evidence that such a decoupling is happening at the required scale. It is challenging to measure sustainability as the concept is complex, contextual, and dynamic. Indicators have been developed to cover
1995-590: The environment . These include impacts on the atmosphere, land, and water resources . Human activities now have an impact on Earth's geology and ecosystems . This led Paul Crutzen to call the current geological epoch the Anthropocene . The economic dimension of sustainability is controversial. This is because the term development within sustainable development can be interpreted in different ways. Some may take it to mean only economic development and growth . This can promote an economic system that
2052-540: The environment includes society, and society includes economic conditions. Thus it stresses a hierarchy. Another model shows the three dimensions in a similar way: In this SDG wedding cake model , the economy is a smaller subset of the societal system. And the societal system in turn is a smaller subset of the biosphere system. In 2022 an assessment examined the political impacts of the Sustainable Development Goals. The assessment found that
2109-495: The environment less weight in their developmental plans. The authors state that "sustainability on a planetary scale is only achievable under an overarching Planetary Integrity Goal that recognizes the biophysical limits of the planet". Other frameworks bypass the compartmentalization of sustainability into separate dimensions completely. The environmental dimension is central to the overall concept of sustainability. People became more and more aware of environmental pollution in
2166-415: The environment, society, or the economy but there is no fixed definition of sustainability indicators . The metrics are evolving and include indicators , benchmarks and audits. They include sustainability standards and certification systems like Fairtrade and Organic . They also involve indices and accounting systems such as corporate sustainability reporting and Triple Bottom Line accounting . It
2223-421: The environmental dimension. This can include addressing key environmental problems , including climate change and biodiversity loss . The idea of sustainability can guide decisions at the global, national, organizational, and individual levels. A related concept is that of sustainable development , and the terms are often used to mean the same thing. UNESCO distinguishes the two like this: " Sustainability
2280-426: The environmental dimension.) Protecting ecological integrity is the core of sustainability according to many experts. If this is the case then its environmental dimension sets limits to economic and social development. The diagram with three nested ellipses is one way of showing the three dimensions of sustainability together with a hierarchy: It gives the environmental dimension a special status. In this diagram,
2337-539: The factors behind world poverty and inequality. The report demands a new development path for sustained human progress. It highlights that this is a goal for both developing and industrialized nations. UNEP and UNDP launched the Poverty-Environment Initiative in 2005 which has three goals. These are reducing extreme poverty, greenhouse gas emissions, and net natural asset loss. This guide to structural reform will enable countries to achieve
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2394-492: The idea of sustainability. One point of criticism is that the concept is vague and only a buzzword . Another is that sustainability might be an impossible goal. Some experts have pointed out that "no country is delivering what its citizens need without transgressing the biophysical planetary boundaries". Sustainability is regarded as a " normative concept ". This means it is based on what people value or find desirable: "The quest for sustainability involves connecting what
2451-561: The intersection of economics, the environment, and the social. There are many broad strategies for more sustainable social systems. They include improved education and the political empowerment of women . This is especially the case in developing countries. They include greater regard for social justice . This involves equity between rich and poor both within and between countries. And it includes intergenerational equity . Providing more social safety nets to vulnerable populations would contribute to social sustainability. A society with
2508-481: The long term. The concept of sustainability, or Nachhaltigkeit in German, goes back to Hans Carl von Carlowitz (1645–1714), and applied to forestry . The term for this now would be sustainable forest management . He used this term to mean the long-term responsible use of a natural resource. In his 1713 work Silvicultura oeconomica, he wrote that "the highest art/science/industriousness [...] will consist in such
2565-478: The long-term depletion of natural resources". The term sustainability is derived from the Latin word sustinere . "To sustain" can mean to maintain, support, uphold, or endure. So sustainability is the ability to continue over a long period of time. In the past, sustainability referred to environmental sustainability. It meant using natural resources so that people in the future could continue to rely on them in
2622-483: The main criteria for selection are: desired effluent quality, expected construction and operating costs, availability of land, energy requirements and sustainability aspects. 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. These systems include septic tanks connected to drain fields , on-site sewage systems (OSS), vermifilter systems and many more. On
2679-442: The needs of the present without compromising the ability of future generations to meet their own needs". The report helped bring sustainability into the mainstream of policy discussions. It also popularized the concept of sustainable development . Some other key concepts to illustrate the meaning of sustainability include: In everyday usage, sustainability often focuses on the environmental dimension. Scholars say that
2736-764: The organic pollutants into simple compounds such as water, carbon dioxide, and salts . Anaerobic wastewater treatment processes (for example UASB , EGSB ) are also widely applied in the treatment of industrial wastewaters and biological sludge. Polishing refers to treatments made in further advanced treatment steps after the above methods (also called "fourth stage" treatment). These treatments may also be used independently for some industrial wastewater. Chemical reduction or pH adjustment minimizes chemical reactivity of wastewater following chemical oxidation. Carbon filtering removes remaining contaminants and impurities by chemical absorption onto activated carbon . Filtration through sand (calcium carbonate) or fabric filters
2793-437: The other hand, advanced and relatively expensive sewage treatment plants may include tertiary treatment with disinfection and possibly even a fourth treatment stage to remove micropollutants. 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 (or effluent) may be reused or released to
2850-460: The removal of organic micropollutants, such as pharmaceuticals. This has been implemented in full-scale for example in Sweden. A large number of sewage treatment technologies have been developed, mostly using biological treatment processes. Design engineers and decision makers need to take into account technical and economical criteria of each alternative when choosing a suitable technology. Often,
2907-411: The same thing in this context. The three dimensions paradigm has few theoretical foundations. The popular three intersecting circles, or Venn diagram , representing sustainability first appeared in a 1987 article by the economist Edward Barbier . Scholars rarely question the distinction itself. The idea of sustainability with three dimensions is a dominant interpretation in the literature. In
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#17327876482652964-456: The simplest level, treatment of most wastewaters is carried out through separation of solids from liquids , usually by sedimentation . By progressively converting dissolved material into solids, usually a biological floc or biofilm , which is then settled out or separated, an effluent stream of increasing purity is produced. Phase separation transfers impurities into a non-aqueous phase . Phase separation may occur at intermediate points in
3021-429: 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 (including on-site treatment systems) to large centralized systems involving
3078-403: The type and extent of contamination. The treatment steps include physical, chemical and biological treatment processes. Types of wastewater treatment plants include: 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
3135-425: The very center of discussions. They suggest that all the domains of sustainability are social. These include ecological , economic, political, and cultural sustainability. These domains all depend on the relationship between the social and the natural. The ecological domain is defined as human embeddedness in the environment. From this perspective, social sustainability encompasses all human activities. It goes beyond
3192-488: Was opened in 1991 to accelerate water cleaning. Both systems were expanded in 2005–2007 to treat a combined 36 million US gallons (140,000 kl) of wastewater per day. The expansion also included measures to reduce foul odors from the plant, including lids on processing tanks and bio filters. 47°59′35″N 122°10′26″W / 47.993°N 122.174°W / 47.993; -122.174 Wastewater treatment One common process in wastewater treatment
3249-446: Was the first UN conference on environmental issues. It stated it was important to protect and improve the human environment. It emphasized the need to protect wildlife and natural habitats: The natural resources of the earth, including the air, water, land, flora and fauna and [...] natural ecosystems must be safeguarded for the benefit of present and future generations through careful planning or management, as appropriate. In 2000,
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