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.
48-448: The Urban Waste Water Treatment Directive 1991 ( 91/271/EEC ) European Union directive concerning urban waste water "collection, treatment and discharge of urban waste water and the treatment and discharge of waste water from certain industrial sectors". It aims "to protect the environment from adverse effects of waste water discharges from cities and "certain industrial sectors". Council Directive 91/271/EEC on Urban Wastewater Treatment
96-554: A population equivalent of over 2000, and more advanced treatment in places with a population equivalent above 10,000 in sensitive areas. Member states in the European Union maintain and operate waste-water treatment plants to conform to the Urban Waste Water Treatment Directive which sets standards for both treatment and disposal of sewage for communities of more than 200 person equivalents. Each member state
144-738: 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
192-462: A 2004 Commission report on implementation by the member states, the Commission noted that some member states, in particular France and Spain, had been tardy in providing the required information, and infringement procedures had been initiated. The report mentioned Spain's non-provision of any advanced treatment in the catchment areas of rivers identified as sensitive in their downstream section, such as
240-508: A capacity of at least 10,000 person equivalents in the EU is estimated to be around €2.6 billion per year. The directive defines sensitive areas, as " freshwater bodies, estuaries and coastal waters which are eutrophic or which may become eutrophic if protective action is not taken", "surface freshwaters intended for the abstraction of drinking water which contain or are likely to contain more than 50 mg/L of nitrates", areas where further treatment
288-508: A directive in theory but has failed to abide by its provisions in practice. If a Member State fails to implement a Directive timely or correctly, the Directive itself becomes binding on the Member States, meaning that parties in proceedings against the state may rely on provisions of the untimely or incorrectly transposed Directive. An example of a case in which the applicant was able to invoke
336-593: A limited extent industry) generate wastewater. As the UWWTD will soon be revised in light of meeting the goals of the European Green Deal, this report carries out an evaluation of the directive. This was followed by an impact assessment in order to determine policy options for an update, fit for the future UWWTD. Over the last decade, the compliance rates have gone up, with 95% for collection, 88% for secondary (biological) treatment, and 86% for more stringent treatment. There
384-694: 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
432-400: A potential revision. Since its adoption in 1991, new technical advances on treatment techniques for waste and emerging pollutants have been identified that might require removal. In addition, the EU has since enlarged from 12 to 28 countries and new different experiences and challenges need to be taken into account. However, the biggest challenge of the revision will be to exploit the potential
480-471: 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
528-504: 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
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#1732851117336576-471: 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
624-572: Is Article 288 of the Treaty on the Functioning of the European Union (formerly Article 249 TEC ). Article 288 To exercise the Union's competences, the institutions shall adopt regulations, directives, decisions, recommendations and opinions. A regulation shall have general application. It shall be binding in its entirety and directly applicable in all Member States. A directive shall be binding, as to
672-454: Is a European Union directive regarding urban wastewater collection, wastewater treatment and its discharge, as well as the treatment and discharge of "waste water from certain industrial sectors". It was adopted on 21 May 1991. It aims "to protect the environment from the adverse effects of urban waste water discharges and discharges from certain industrial sectors" by mandating waste water collection and treatment in urban agglomerations with
720-528: Is an example of the detailed nature of European Union legislation and resulted in "significant costs in many member states". Nine years after the directive was adopted, considerable variations remained in the provision of sewage treatment in the different member states. On 13 July 2018, the European Commission published a Consultation on the Evaluation of the Urban Waste Water Treatment Directive ahead of
768-467: 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
816-461: Is necessary to comply with other directives, such as the directives on fish waters, on bathing waters, on shellfish waters, on the conservation of wild birds and natural habitats, etc. The directive contains a derogation for areas designated as "less sensitive"; such derogations were approved for areas in Portugal. Member states were required to make waste water treatment facilities available In
864-533: Is obliged to enact the requirements of the directive through appropriate local legislation. This directive also links to the Bathing Waters Directive and to the environmental standards set in the Water Framework Directive which are designed to protect all legitimate end uses of the receiving environment. Commission Decision 93/481/EEC defines the information that Member States should provide
912-413: Is positive trend in general, but full compliance with the directive is still not achieved. This is necessary, because this would show significant reductions in pollutant loads in the Member States. In the long term, more investments are needed to reach and maintain compliance with the directive. Several towns and cities are still building or renewing infrastructure for the collection of wastewater. To support
960-645: Is presented to the Parliament and the Council —composed of relevant ministers of member governments, initially for evaluation and comment and then subsequently for approval or rejection. There are justifications for using a directive rather than a regulation: (i) it complies with the EU's desire for "subsidiarity" ; (ii) it acknowledges that different member States have different legal systems, legal traditions and legal processes; and (iii) each Member State has leeway to choose its own statutory wording, rather than accepting
1008-1206: 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
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#17328511173361056-475: 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
1104-411: 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
1152-700: The Ebro and the Guadalquivir ; Italy's implementation in the catchment area of the Po River , the delta and adjacent coastal waters; and the United Kingdom's interpretation and implementation of the directive in regard to the catchment areas of sensitive areas. Most member states planned to achieve conformity with the Directive by 2005 or 2008 at the latest. In 2020 the Commission published its latest implementation report that covers over 23,600 agglomerations where people (and to
1200-403: The wastewater treatment sector can contribute to the circular economy agenda and the fight against climate change . Globally, the wastewater treatment sector consumes 1% of the global total energy consumption. Under a business as usual scenario, this figure is expected to increase by 60% by 2040 compared to 2014. With the introduction of energy efficiency requirements, the energy consumption of
1248-452: The Brussels' official " Eurospeak " terminology. For example, while EU Directive 2009/20/EC (which simply requires all vessels visiting EU ports to have P&I cover) could have been a regulation (without requiring member states to implement the directive), the desire for subsidiarity was paramount, so a directive was the chosen vehicle. The legal basis for the enactment of directives
1296-526: The European Council. European Union directive A directive is a legal act of the European Union that requires member states to achieve particular goals without dictating how the member states achieve those goals. A directive's goals have to be made the goals of one or more new or changed national laws by the member states before this legislation applies to individuals residing in
1344-639: The European Court of Justice developed the doctrine of direct effect where unimplemented or badly implemented directives can actually have direct legal force. In the important case of Francovich v. Italy , the ECJ extended the principle of Van Gend en Loos to provide that Member States who failed to implement a directive could incur liability to pay damages to individuals and companies who had been adversely affected by such non-implementation. Wastewater treatment One common process in wastewater treatment
1392-403: The Member States, the commission has set up funding and financial initiatives. The Urban Waste Water Directive marked a shift from legislation aimed at end-use standards to stricter legislation aimed at regulating water quality at the source. The directive applied both to domestic waste water and to waste water from industrial sectors, both of which account for much of the pollution. The Directive
1440-437: The appropriate legislative procedure, both institutions can seek to make laws. There are Council directives and Commission directives. Article 288 does not clearly distinguish between legislative acts and administrative acts, as is normally done in national legal systems. Directives are binding only on the member states to whom they are addressed, which can be just one member state or a group of them. In general, however, with
1488-626: 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
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1536-566: The commission on the state of implementation of the Directive. Conventional wastewater treatment plants currently service over 90% of the EU population. Continuing implementation of the Urban Wastewater Treatment Directives plans to lower the EU's contribution to global microplastics discharge into the oceans. According to a cost-benefit analysis prepared for the proposed Directive, the investment required to implement quaternary treatment in wastewater treatment plants with
1584-542: The directive to be implemented correctly. This is done in approximately 99% of the cases. If a member state fails to pass the required national legislation, or if the national legislation does not adequately comply with the requirements of the directive, the European Commission may initiate legal action against the member state in the European Court of Justice . This may also happen when a member state has transposed
1632-572: The exception of directives related to the Common Agricultural Policy , directives are addressed to all member states. When adopted, directives give member states a timetable for the implementation of the intended outcome. Occasionally, the laws of a member state may already comply with this outcome, and the state involved would be required only to keep its laws in place. More commonly, member states are required to make changes to their laws (commonly referred to as transposition ) in order for
1680-483: 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
1728-497: The member states. Directives normally leave member states with a certain amount of leeway as to the exact rules to be adopted. Directives can be adopted by means of a variety of legislative procedures depending on their subject matter. The text of a draft directive (if subject to the co-decision process, as contentious matters usually are) is prepared by the Commission after consultation with its own and national experts. The draft
1776-764: 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
1824-437: 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
1872-463: The planned revision included stricter goals and policies. These had time frames on either 2030, 2035, or 2040. The revision would have inclusion of areas with smaller populations, stricter limits on Nitrogen and Phosphorus , reduction of Micropollutants, a goal of Energy Neutrality for all purification plants with over 10,000 person equivalents by 2040, tracking of diseases, additional sanctions, and other goals. This proposal has currently been read by
1920-711: The provisions of an untimely transposed Directive is the Verkooijen case, in which the European Court of Justice rendered a judgement on 6 June 2000 (case no. C-35/98). The United Kingdom passed a statutory instrument , the Unfair Terms in Consumer Contracts Regulations 1994 , to implement the EU Unfair Terms in Consumer Contracts Directive 1993 . For reasons that are not clear, the 1994 SI
1968-456: 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,
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2016-400: The result to be achieved, upon each Member State to which it is addressed, but shall leave to the national authorities the choice of form and methods. A decision shall be binding in its entirety upon those to whom it is addressed. Recommendations and opinions shall have no binding force. The Council can delegate legislative authority to the Commission and, depending on the area and
2064-456: 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
2112-429: 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
2160-403: 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
2208-488: The wastewater treatment sector can be reduced by 50% only by using current technologies. On top of that, there are also opportunities to produce enough energy from wastewater to turn the whole water sector energy neutral. It uses the energy embedded in the sludge by producing biogas through anaerobic digestion . These features have been mainly overlooked due to the over-riding objective for utilities to meet existing and future needs for wastewater treatment. In October 2022,
2256-515: Was adopted on 21 May 1991, amended by the Commission Directive 98/15/EC. It prescribes the waste water collection and treatment in urban agglomerations with a population equivalent of over 2000, and more advanced treatment in places with a population equivalent greater than 10,000 in "sensitive areas". The Urban Waste Water Treatment Directive (full title "Council Directive 91/271/EEC of 21 May 1991 concerning urban waste-water treatment")
2304-437: Was deemed inadequate and was repealed and replaced by the Unfair Terms in Consumer Contracts Regulations 1999 . The Consumer Rights Act 2015 , a major United Kingdom statute consolidating consumer rights, then abolished the 1999 SI; so presumably the 2015 Act complies with the 1993 EU directive, which remains extant. Even though directives were not originally thought to be binding before they were implemented by member states,
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