Municipal solid waste
Municipal solid waste known as trash or garbage in the United States and rubbish in Britain, is a waste type consisting of everyday items that are discarded by the public. "Garbage" can refer to food waste, as in a garbage disposal. In the European Union, the semantic definition is'mixed municipal waste,' given waste code 20 03 01 in the European Waste Catalog. Although the waste may originate from a number of sources that has nothing to do with a municipality, the traditional role of municipalities in collecting and managing these kinds of waste have produced the particular etymology'municipal.' The composition of municipal solid waste varies from municipality to municipality, it changes with time. In municipalities which have a well developed waste recycling system, the waste stream consists of intractable wastes such as plastic film and non-recyclable packaging materials. At the start of the 20th century, the majority of domestic waste in the UK consisted of coal ash from open fires. In developed areas without significant recycling activity it predominantly includes food wastes, market wastes, yard wastes, plastic containers and product packaging materials, other miscellaneous solid wastes from residential, commercial and industrial sources.
Most definitions of municipal solid waste do not include industrial wastes, agricultural wastes, medical waste, radioactive waste or sewage sludge. Waste collection is performed by the municipality within a given area; the term residual waste relates to waste left from household sources containing materials that have not been separated out or sent for processing. Waste can be classified in several ways but the following list represents a typical classification: Biodegradable waste: food and kitchen waste, green waste, paper Recyclable materials: paper, glass, jars, tin cans, aluminum cans, aluminum foil, certain plastics, clothes, batteries, etc. Inert waste: construction and demolition waste, rocks, debris Electrical and electronic waste - electrical appliances, light bulbs, washing machines, TVs, screens, mobile phones, alarm clocks, etc. Composite wastes: waste clothing, Tetra Packs, waste plastics such as toys Hazardous waste including most paints, tires, light bulbs, electrical appliances, fluorescent lamps, aerosol spray cans, fertilizers Toxic waste including pesticides and fungicides Biomedical waste, expired pharmaceutical drugs, etc.
The municipal solid waste industry has four components: recycling, composting and waste-to-energy via incineration. There is no single approach that can be applied to the management of all waste streams, therefore the Environmental Protection Agency, a U. S. federal government agency, developed a hierarchy ranking strategy for municipal solid waste. The Waste Management Hierarchy is made up of four levels ordered from most preferred to least preferred methods based on their environmental soundness: Source reduction and reuse; the functional element of collection includes not only the gathering of solid waste and recyclable materials, but the transport of these materials, after collection, to the location where the collection vehicle is emptied. This location may be a materials processing facility, a transfer station or a landfill disposal site. Waste handling and separation involves activities associated with waste management until the waste is placed in storage containers for collection. Handling encompasses the movement of loaded containers to the point of collection.
Separating different types of waste components is an important step in the handling and storage of solid waste at the source of collection. The types of means and facilities that are now used for the recovery of waste materials that have been separated at the source include curbside collection, drop-off and buy-back centers; the separation and processing of wastes that have been separated at the source and the separation of commingled wastes occur at a materials recovery facility, transfer stations, combustion facilities and treatment plants. This element involves two main steps. First, the waste is transferred from a smaller collection vehicle to larger transport equipment; the waste is transported over long distances, to a processing or disposal site. Today, the disposal of wastes by land filling or land spreading is the ultimate fate of all solid wastes, whether they are residential wastes collected and transported directly to a landfill site, residual materials from materials recovery facilities, residue from the combustion of solid waste, compost, or other substances from various solid waste processing facilities.
A modern sanitary landfill is not a dump. In the recent years environmental organizations, such as Freegle or Freecycle Network, have been gaining popularity for their online reuse networks; these networks provide a worldwide online registry of unwanted items that would otherwise be thrown away, for individuals and nonprofits to reuse or recycle. Therefore, this free Internet-based service reduces landfill pollution and promotes the gift economy. Landfills are created by land dumping. Land dumping methods vary, most it involves the mass dumping of waste into a designated area a hole or sidehill. After the waste is dumped, it is then
Solid waste policy in the United States
Solid waste policy in the United States is aimed at developing and implementing proper mechanisms to manage solid waste. For solid waste policy to be effective, inputs should come from stakeholders, including citizens, community based-organizations, non governmental organizations, government agencies and other research organizations; these inputs form the basis of policy frameworks. In the United States, the Environmental Protection Agency regulates household, industrial and commercial solid and hazardous wastes under the 1976 Resource Conservation and Recovery Act. Effective solid waste management is a cooperative effort involving federal, state and local entities. Thus, the RCRA's Solid Waste program section D encourages the environmental departments of each state to develop comprehensive plans to manage nonhazardous industrial and municipal solid waste. Solid waste means any garbage or refuse, sludge from a wastewater treatment plant, water supply treatment plant, or an air pollution control facility and other discarded material, including solid, semi-solid, or contained gaseous material resulting from industrial, commercial and agricultural operations, from community activities.
Solid waste does not include solid or dissolved materials in domestic sewage, solid or dissolved materials in irrigation return flows, or industrial discharges. The large scope of the term "solid waste" means that it must be managed in a variety of different ways and that various levels of government employ different policy instruments in order to accomplish this task; the term "solid waste" refers to non-hazardous waste, though according to the Resource Conservation and Recovery Act and other state regulations, "hazardous waste" is a part of solid waste. Municipal Solid Waste known as trash or garbage, includes all everyday thrown away items from households and institutional entities and road sweeping; this includes items such as packaging, cardboard, food scraps, plastic bags & containers, glass bottles, grass clippings, tires, electrical & electronic items, metals. In 2009, United States residents generated 243 million tons of trash, down from 255 million tons in 2007. In the same period, the per capita generation of MSW lowered to 4.34 lbs/person/day from 4.63 lbs/person/day.
Agricultural wastes include primary crop residues that remain in fields after harvest and secondary processing residues generated from the harvested portions of crops during food and fiber production. This is generated during the production and distribution through decomposition of food, vegetables, or meat, removal of non-usable parts, removal of substandard products, spoiling due to substandard packaging, thus agricultural waste is generated at all stages of food system including farming, storage and wholesaling. The food scraps generated by retailers and consumers are not included in this category as these scraps enter the waste stream as municipal solid waste. Animal wastes are wastes generated from farms and feedlots known as Animal Feeding Operations or Concentrated Animal Feeding Operations, consisting of leftover feeds and urine, dead animals, production operation wastes, they produce large amounts of waste in small areas. For example, EPA reports that a single dairy cow produces 120 pounds of wet manure per day equaling to that of 20-40 people.
The main problems of animal waste mismanagement are environmental water pollution. Industrial waste consists of a significant amount of solid waste. EPA reported that each year United States industrial facilities generate and dispose of 7.6 billion tons of industrial solid waste based on 1980s figures. This figure includes waste generated from 17 industrial manufacturers of organic chemicals, inorganic chemicals and steel, plastics and resins, clay, concrete and paper, kindred products. Industrial waste does not go into the municipal solid waste stream and therefore is landfilled or processed separately; as per EPA guidelines industrial waste management units have to consider waste characterization and minimization methods, waste constituent information factsheets, risk assessment tools, institutional mechanism/stakeholder partnership principles and proper design guidelines and air monitoring procedures, facility pre- and post-closure recommendations. C&D waste includes debris generated during the construction and demolition of buildings and bridges.
This can be bulky and heavy building materials consisting of concrete, building wood waste, asphalt from roads and roof shingles, drywall gypsum, bricks, glass, building components like doors and fixtures, trees, stumps and rock from construction and clearing sites. Since this consists of bulky and heavy materials, proper waste management can improve resources. EPA estimated that 136 million tons of building-related C&D waste was generated in the United States in 1996. Treatment waste consists of sludge, coproducts, or metal scraps resulting from a facility or plant. Sludge is any solid, semisolid, or liquid waste generated from a municipal, commercial, or industrial wastewater treatment plant, water supply treatment plant, or air pollution control facility exclusive of the treated effluent from a wastewater treatment plant; this includes electric arc furnace baghouse dusts. A byproduct is a material, not a primary product, not or separately produced in a production process whereas coproducts are intention
A factory or manufacturing plant is an industrial site consisting of buildings and machinery, or more a complex having several buildings, where workers manufacture goods or operate machines processing one product into another. Factories arose with the introduction of machinery during the Industrial Revolution when the capital and space requirements became too great for cottage industry or workshops. Early factories that contained small amounts of machinery, such as one or two spinning mules, fewer than a dozen workers have been called "glorified workshops". Most modern factories have large warehouses or warehouse-like facilities that contain heavy equipment used for assembly line production. Large factories tend to be located with access to multiple modes of transportation, with some having rail and water loading and unloading facilities. Factories may either make discrete products or some type of material continuously produced such as chemicals and paper, or refined oil products. Factories manufacturing chemicals are called plants and may have most of their equipment – tanks, pressure vessels, chemical reactors and piping – outdoors and operated from control rooms.
Oil refineries have most of their equipment outdoors. Discrete products may be final consumer goods, or parts and sub-assemblies which are made into final products elsewhere. Factories may make them from raw materials. Continuous production industries use heat or electricity to transform streams of raw materials into finished products; the term mill referred to the milling of grain, which used natural resources such as water or wind power until those were displaced by steam power in the 19th century. Because many processes like spinning and weaving, iron rolling, paper manufacturing were powered by water, the term survives as in steel mill, paper mill, etc. Max Weber considered production during ancient times as never warranting classification as factories, with methods of production and the contemporary economic situation incomparable to modern or pre-modern developments of industry. In ancient times, the earliest production limited to the household, developed into a separate endeavour independent to the place of inhabitation with production at that time only beginning to be characteristic of industry, termed as "unfree shop industry", a situation caused under the reign of the Egyptian pharaoh, with slave employment and no differentiation of skills within the slave group comparable to modern definitions as division of labour.
According to translations of Demosthenes and Herodotus, Naucratis was a, or the only, factory in the entirety of ancient Egypt. A source of 1983, states the largest factory production in ancient times was of 120 slaves within 4th century BC Athens. An article within the New York Times article dated 13 October 2011 states: "In African Cave, Signs of an Ancient Paint Factory" –... discovered at Blombos Cave, a cave on the south coast of South Africa where 100,000-year-old tools and ingredients were found with which early modern humans mixed an ochre-based paint. Although The Cambridge Online Dictionary definition of factory states: a building or set of buildings where large amounts of goods are made using machines elsewhere:... the utilization of machines presupposes social cooperation and the division of labour The first machine is stated by one source to have been traps used to assist with the capturing of animals, corresponding to the machine as a mechanism operating independently or with little force by interaction from a human, with a capacity for use with operation the same on every occasion of functioning.
The wheel was invented c. 3000 BC, the spoked wheel c. 2000 BC. The Iron Age began 1200–1000 BC. However, other sources define machinery as a means of production. Archaeology provides a date for the earliest city as 5000 BC as Tell Brak, therefore a date for cooperation and factors of demand, by an increased community size and population to make something like factory level production a conceivable necessity. According to one text the water-mill was first made in 555 A. D. by Belisarius, although according to another they were known to Pliny the Elder and Vitruvius in the first century B. C. By the time of the 4th century A. D. mills with a capacity to grind 3 tonnes of cereal an hour, a rate sufficient to meet the needs of 80,000 persons, were in use by the Roman Empire. The Venice Arsenal provides one of the first examples of a factory in the modern sense of the word. Founded in 1104 in Venice, Republic of Venice, several hundred years before the Industrial Revolution, it mass-produced ships on assembly lines using manufactured parts.
The Venice Arsenal produced nearly one ship every day and, at its height, employed 16,000 people. One of the earliest factories was John Lombe's water-powered silk mill at Derby, operational by 1721. By 1746, an integrated brass mill was working at Warmley near Bristol. Raw material went in at one end, was smelted into brass and was turned into pans, pins and other goods. Housing was provided for workers on site. Josiah Wedgwood in Staffordshire and Matthew Boulton at his Soho Manufactory were other prominent early industrialists, who employed the factory system; the factory system began widespread use somewhat when cotton spinning was mechanized. Richard Arkwright is the person credited with inventing the prototype of the modern factory. After he patented his water frame in 1769, he established Cromford Mill, in Derbyshire, England expanding the village of Cromford to accommodate the migrant workers new to the area; the factory system was a new way of organizing labour made necessary by the developm
Demolition waste is waste debris from destruction of buildings, bridges, or other structures. Debris varies in composition, but the major components, by weight, in the US include concrete, wood products, asphalt shingles and clay tile and drywall. There is the potential to recycle many elements of demolition waste. In 2014, 505.1 million tons of demolition debris was generated in the US. Out of the 505.1 million tons, the debris was composed of 353.6 million tons of concrete, 76.6 million tons of asphalt concrete, 35.8 million tons of wood product, 12.7 million tons of asphalt shingles, 11.8 million tons of brick and clay tile, 10.3 million tons of drywall and plaster, 4.3 million tons of steel. Before demolition debris is extracted, contamination from lead, asbestos or different hazardous materials must be resolved. Hazardous materials must be disposed according to federal regulation. Demolition debris can be disposed of in either Construction and Demolition Debris landfills or municipal solid waste landfills.
Alternatively, debris may be sorted and recycled. Sorting may happen as deconstruction on the demolition site, off-site at a sorting location, or at a Construction and Demolition recycling center. Once sorted, materials are recycled accordingly. Concrete and Brick Concrete and brick can be recycled by crushing it into rubble. Once sorted and contaminants are removed, reclaimed concrete or brick can be used in concrete aggregate, road base, or riprap. Mobile concrete crushers allow for recycling of concrete on-site. Wood Wood can be reused, recycled, or burned as bioenergy. Reused wood to eliminate the need for full-size new lumber if used for smaller building components. Repurposed or recycled wood can be used in pathways, mulches, animal bedding, or particleboard. Using recycled wood as a bioenergy feedstock is advantageous because it has lower water content, about 20% water, compared to virgin lumber, about 60% water. Drywall Drywall is made of gypsum. Once the gypsum is depapered, it can be added in cement production, as a soil amendment, used in aerated composting, or recycled into new drywall.
Gypsum recycling can be beneficial because in landfill conditions gypsum will release hydrogen sulfide, a toxic gas. Asphalt Asphalt, from shingles or asphalt concrete, is recycled and used in pavement. Metal Scrap metal is an established industry focused on the collection, buying and recycling of salvaged materials. Construction waste List of solid waste treatment technologies List of waste management topics
Toxic waste is any unwanted material in all forms that can cause harm. Many of today's household products such as televisions and phones contain toxic chemicals that can pollute the air and contaminate soil and water. Disposing of such waste is a major public health issue. Toxic materials are poisonous byproducts as a result of industries such as manufacturing, construction, automotive and hospitals which may contain heavy metals, dangerous pathogens, or other toxins. Toxic waste has become more abundant since the industrial revolution, causing serious global health issues. Disposing of such waste has become more critical with the addition of numerous technological advances containing toxic chemical components. Products such as cellular telephones, computers and solar panels contain toxic chemicals that can harm the environment if not disposed of properly to prevent the pollution of the air and contamination of soils and water. A material is considered toxic when it causes death or harm by being inhaled, swallowed, or absorbed through the skin.
The waste can contain chemicals, heavy metals, dangerous pathogens, or other toxins. Households generate hazardous waste from items such as batteries, used computer equipment, leftover paints or pesticides. Toxic material can be either human-made and others are occurring in the environment. Not all hazardous substances are considered toxic; the United Nations Environment Programme has identified 11 key substances that pose a risk to human health: Arsenic: used in making electrical circuits, as an ingredient in pesticides, as a wood preservative. It is classified as a carcinogen. Asbestos: is a material, once used for the insulation of buildings, some businesses are still using this material to manufacture roofing materials and brakes. Inhalation of asbestos fibers can lead to lung cancer and asbestosis. Cadmium: is found in plastics, it can be digested when included as a pigment in food. Exposure leads to lung damage, irritation of the digestive track, kidney disease. Chromium: is used as brick lining for high-temperature industrial furnaces, as a solid metal used for making steel, in chrome plating, manufacturing dyes and pigments, wood preserving, leather tanning.
It is known to cause cancer, prolonged exposure can cause chronic bronchitis and damage lung tissue. Clinical wastes: such as syringes and medication bottles can spread pathogens and harmful microorganisms, leading to a variety of illnesses. Cyanide: a poison found in some pesticides and rodenticides. In large doses it can lead to paralysis and respiratory distress. Lead: is found in batteries and ammunition; when ingested or inhaled can cause harm to the nervous and reproductive systems, kidneys. Mercury: used for dental fillings and batteries, it is used in the production of chlorine gas. Exposure can lead to birth defects and kidney and brain damage PCBs, or polychlorinated biphenyls, are used in many manufacturing processes, by the utility industry, in paints and sealants. Damage can occur through exposure, affecting the nervous and immune systems, as well as the liver. POPs, persistent organic pollutants, they are found in chemicals and pesticides, may lead to nervous and reproductive system defects.
They can bio-accumulate in the food chain or persist in the environment and be moved great distances through the atmosphere. Strong acids and alkalis used in industrial production, they can cause internal damage to the body. The most overlooked toxic and hazardous wastes are the household products in everyday homes that are improperly disposed of such as old batteries, pesticides and car oil. Toxic waste can be reactive and corrosive. In the United States, these wastes are regulated under the Resource Recovery Act. Reactive wastes are those that can cause explosions mixed with water or compressed, they can release toxic gases into the air. They are unstable in normal conditions. An example is lithium–sulfur batteries. Ignitable wastes have flash points of less than 60 degrees Celsius, they are combustible and can cause fires. Examples are solvents and waste oils. Corrosive wastes are liquids capable of corroding metal containers; these are acids or bases that have pH levels of less than or equal to 2, or greater than or equal to 12.5.
An example is battery acid. With the increase of worldwide technology, there are more substances that are being considered toxic and harmful to human health; some of this technology includes cell computers. Such items have been given the name e-waste or EEE, which stands for Electrical and Electronic Equipment; this term is used for goods such as refrigerators and washing machines. These items can contain toxic components; the reduction in the cost of these goods has allowed for these items to be distributed globally without thought or consideration to managing the goods once they become ineffective or broken. In the US, the Environmental Protection Agency and state environmental agencies develop and enforce regulations on the storage and disposal of hazardous waste; the EPA requires that toxic waste be handled with special precautions and be disposed of in designated facilities around the country. Many US cities have collection days where household toxic waste is gathered; some materials that may not be accepted at regular landfills are ammunition, commercially generated waste, explosives/shock sensitive items, hypodermic needles/syringes, medical waste, ra
Global warming is a long-term rise in the average temperature of the Earth's climate system, an aspect of climate change shown by temperature measurements and by multiple effects of the warming. Though earlier geological periods experienced episodes of warming, the term refers to the observed and continuing increase in average air and ocean temperatures since 1900 caused by emissions of greenhouse gasses in the modern industrial economy. In the modern context the terms global warming and climate change are used interchangeably, but climate change includes both global warming and its effects, such as changes to precipitation and impacts that differ by region. Many of the observed warming changes since the 1950s are unprecedented in the instrumental temperature record, in historical and paleoclimate proxy records of climate change over thousands to millions of years. In 2013, the Intergovernmental Panel on Climate Change Fifth Assessment Report concluded, "It is likely that human influence has been the dominant cause of the observed warming since the mid-20th century."
The largest human influence has been the emission of greenhouse gases such as carbon dioxide and nitrous oxide. Climate model projections summarized in the report indicated that during the 21st century, the global surface temperature is to rise a further 0.3 to 1.7 °C to 2.6 to 4.8 °C depending on the rate of greenhouse gas emissions and on climate feedback effects. These findings have been recognized by the national science academies of the major industrialized nations and are not disputed by any scientific body of national or international standing. Future climate change effects are expected to include rising sea levels, ocean acidification, regional changes in precipitation, expansion of deserts in the subtropics. Surface temperature increases are greatest in the Arctic, with the continuing retreat of glaciers and sea ice. Predicted regional precipitation effects include more frequent extreme weather events such as heat waves, wildfires, heavy rainfall with floods, heavy snowfall. Effects directly significant to humans are predicted to include the threat to food security from decreasing crop yields, the abandonment of populated areas due to rising sea levels.
Environmental impacts appear to include the extinction or relocation of ecosystems as they adapt to climate change, with coral reefs, mountain ecosystems, Arctic ecosystems most threatened. Because the climate system has a large "inertia" and greenhouse gases will remain in the atmosphere for a long time, climatic changes and their effects will continue to become more pronounced for many centuries if further increases to greenhouse gases stop. Possible societal responses to global warming include mitigation by emissions reduction, adaptation to its effects, possible future climate engineering. Most countries are parties to the United Nations Framework Convention on Climate Change, whose ultimate objective is to prevent dangerous anthropogenic climate change. Parties to the UNFCCC have agreed that deep cuts in emissions are required and that global warming should be limited to well below 2.0 °C compared to pre-industrial levels, with efforts made to limit warming to 1.5 °C. Some scientists call into question climate adaptation feasibility, with higher emissions scenarios, or the two degree temperature target.
Public reactions to global warming and concern about its effects are increasing. A 2015 global survey showed that a median of 54% of respondents consider it "a serious problem", with significant regional differences: Americans and Chinese are among the least concerned. Multiple independently produced datasets confirm that between 1880 and 2012, the global average surface temperature increased by 0.85 °C. Since 1979 the rate of warming has doubled. Climate proxies show the temperature to have been stable over the one or two thousand years before 1850, with regionally varying fluctuations such as the Medieval Warm Period and the Little Ice Age. Although the increase of the average near-surface atmospheric temperature is used to track global warming, over 90% of the additional energy stored in the climate system over the last 50 years has accumulated in the oceans; the rest warmed the continents and the atmosphere. The warming evident in the instrumental temperature record is consistent with a wide range of observations, as documented by many independent scientific groups.
Examples include sea level rise, widespread melting of snow and land ice, increased heat content of the oceans, increased humidity, the earlier timing of spring events, e.g. the flowering of plants. Global warming refers with the amount of warming varying by region. Since 1979, global average land temperatures have increased about twice as fast as global average ocean temperatures; this is due to the larger heat capacity of the oceans and because oceans lose more heat by evaporation. Where greenhouse gas emissions occur does not impact the location of warming because the major greenhouse gases persist long enough to diffuse across the planet, although localized black carbon deposits on snow and ice do contribute to Arctic warming; the Northern Hemisphere and North Pole have heated much faster than the South Pole and Southern Hemisphere. The Northern Hemisphere not only has much more land, its arrangement around the Arctic Ocean has resulted in the maximum surface area flipping from reflective snow and ice cover to ocean and land surfaces that absorb more sunlight.
Sewage treatment is the process of removing contaminants from municipal wastewater, containing household sewage plus some industrial wastewater. Physical and biological processes are used to remove contaminants and produce treated wastewater, safe enough for release into the environment. A by-product of sewage treatment is a semi-solid slurry, called sewage sludge; the sludge has to undergo further treatment before being suitable for disposal or application to land. Sewage treatment may be referred to as wastewater treatment. However, the latter is a broader term which can refer to industrial wastewater. For most cities, the sewer system will carry a proportion of industrial effluent to the sewage treatment plant which has received pre-treatment at the factories themselves to reduce the pollutant load. If the sewer system is a combined sewer it will carry urban runoff to the sewage treatment plant. Sewage water can travel towards treatment plants via piping and in a flow aided by gravity and pumps.
The first part of filtration of sewage includes a bar screen to filter solids and large objects which are collected in dumpsters and disposed of in landfills. Fat and grease is removed before the primary treatment of sewage; the term "sewage treatment plant" is nowadays replaced with the term wastewater treatment plant or wastewater treatment station. Sewage can be treated close to where the sewage is created, which may be called a "decentralized" system or an "on-site" system. Alternatively, sewage can be collected and transported by a network of pipes and pump stations to a municipal treatment plant; this is called a "centralized" system. Sewage is generated by residential, institutional and industrial establishments, it includes household waste liquid from toilets, showers and sinks draining into sewers. In many areas, sewage includes liquid waste from industry and commerce; the separation and draining of household waste into greywater and blackwater is becoming more common in the developed world, with treated greywater being permitted to be used for watering plants or recycled for flushing toilets.
Sewage may include urban runoff. Sewerage systems capable of handling storm water are known as combined sewer systems; this design was common when urban sewerage systems were first developed, in the late 19th and early 20th centuries. Combined sewers require more expensive treatment facilities than sanitary sewers. Heavy volumes of storm runoff may overwhelm the sewage treatment system, causing a spill or overflow. Sanitary sewers are much smaller than combined sewers, they are not designed to transport stormwater. Backups of raw sewage can occur if excessive infiltration/inflow is allowed into a sanitary sewer system. Communities that have urbanized in the mid-20th century or generally have built separate systems for sewage and stormwater, because precipitation causes varying flows, reducing sewage treatment plant efficiency; as rainfall travels over roofs and the ground, it may pick up various contaminants including soil particles and other sediment, heavy metals, organic compounds, animal waste, oil and grease.
Some jurisdictions require stormwater to receive some level of treatment before being discharged directly into waterways. Examples of treatment processes used for stormwater include retention basins, buried vaults with various kinds of media filters, vortex separators. In regulated developed countries, industrial effluent receives at least pretreatment if not full treatment at the factories themselves to reduce the pollutant load, before discharge to the sewer; this process is called pretreatment. The same does not apply to many developing countries where industrial effluent is more to enter the sewer if it exists, or the receiving water body, without pretreatment. Industrial wastewater may contain pollutants which cannot be removed by conventional sewage treatment. Variable flow of industrial waste associated with production cycles may upset the population dynamics of biological treatment units, such as the activated sludge process. Sewage collection and treatment in the United States is subject to local and federal regulations and standards.
Treating wastewater has the aim to produce an effluent that will do as little harm as possible when discharged to the surrounding environment, thereby preventing pollution compared to releasing untreated wastewater into the environment. Sewage treatment involves three stages, called primary and tertiary treatment. Primary treatment consists of temporarily holding the sewage in a quiescent basin where heavy solids can settle to the bottom while oil and lighter solids float to the surface; the settled and floating materials are removed and the remaining liquid may be discharged or subjected to secondary treatment. Some sewage treatment plants that are connected to a combined sewer system have a bypass arrangement after the primary treatment unit; this means that during heavy rainfall events, the secondary and tertiary treatment systems can be bypassed to protect them from hydraulic overloading, the mixture of sewage and stormwater only receives primary treatment. Secondary treatment removes suspended biological matter.
Secondary treatment is performed by indigenous, water-borne micro-organisms in a managed habitat. Seconda