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45-490: The river's watershed drains approximately 67% of Costa Rica's untreated organic and industrial waste and is considered the most contaminated river basin in the country. The river's upper reaches form the northern border of the Carara National Park . It is a habitat for American crocodiles , while the marshes located at the river's mouth have many waterfowl and wading birds . Among the many herons and egrets are

90-474: A batch process, with the aluminium deposited at the bottom of the pots and periodically siphoned off. Particularly in Australia these smelters are used to control electrical network demand, and as a result power is supplied to the smelter at a very low price. However power must not be interrupted for more than 4–5 hours, since the pots have to be repaired at significant cost if the liquid metal solidifies. Aluminium

135-481: A ceramic matrix of nickel ferrite. Unfortunately, as the number of anode components increases , the structure of the anode becomes more unstable. As a result. cermet anodes also suffer from corrosion issues during reduction. Aluminium smelting is highly energy intensive, and in some countries is economical only if there are inexpensive sources of electricity. In some countries, smelters are given exemptions to energy policy like renewable energy targets . To reduce

180-496: A melting temperature of 1010 °C, and it forms a eutectic with 11% alumina at 960 °C. In industrial cells the cryolite ratio is kept between 2 and 3 to decrease its melting temperature to 940–980 °C. Cathode: Carbon cathodes are essentially made of anthracite, graphite and petroleum coke, which are calcined at around 1200 °C and crushed and sieved prior to being used in cathode manufacturing. Aggregates are mixed with coal-tar pitch, formed, and baked. Carbon purity

225-487: A mixture of CO and CO 2 is produced. Thus the idealised overall reactions may be written as By increasing the current density up to 1 A/cm , the proportion of CO 2 increases and carbon consumption decreases. As three electrons are needed to produce each atom of aluminium, the process consumes a large amount of electricity. For this reason aluminium smelters are sited close to sources of inexpensive electricity, such as hydroelectric . Electrolyte: The electrolyte

270-459: A paste with a doughy consistency. This material is most often vibro-compacted but in some plants pressed. The green anode is then sintered at 1100–1200 °C for 300–400 hours, without graphitization , to increase its strength through decomposition and carbonization of the binder. Higher baking temperatures increase the mechanical properties and thermal conductivity, and decrease the air and CO 2 reactivity. The specific electrical resistance of

315-405: A quantity of fluoride waste: perfluorocarbons and hydrogen fluoride as gases, and sodium and aluminium fluorides and unused cryolite as particulates. This can be as small as 0.5 kg per tonne of aluminium in the best plants in 2007, up to 4 kg per tonne of aluminium in older designs in 1974. Unless carefully controlled, hydrogen fluorides tend to be very toxic to vegetation around

360-423: A specific situation in aluminium smelting and depending on the type of anode, aluminium smelting is divided in two different technologies; “Soderberg” and “prebaked” anodes. Anodes are also made of petroleum coke, mixed with coal-tar-pitch, followed by forming and baking at elevated temperatures. The quality of anode affects technological, economical and environmental aspects of aluminium production. Energy efficiency

405-405: Is a molten bath of cryolite (Na 3 AlF 6 ) and dissolved alumina. Cryolite is a good solvent for alumina with low melting point, satisfactory viscosity, and low vapour pressure. Its density is also lower than that of liquid aluminium (2 vs 2.3 g/cm ), which allows natural separation of the product from the salt at the bottom of the cell. The cryolite ratio (NaF/AlF 3 ) in pure cryolite is 3, with

450-568: Is always an issue. Hazardous waste, chemical waste , industrial solid waste and municipal solid waste are classifications of wastes used by governments in different countries. Sewage treatment plants can treat some industrial wastes, i.e. those consisting of conventional pollutants such as biochemical oxygen demand (BOD). Industrial wastes containing toxic pollutants or high concentrations of other pollutants (such as ammonia ) require specialized treatment systems. ( See Industrial wastewater treatment ). Industrial wastes can be classified on

495-637: Is not as stringent as for anode, because metal contamination from cathode is not significant. Carbon cathode must have adequate strength, good electrical conductivity and high resistance to wear and sodium penetration. Anthracite cathodes have higher wear resistance and slower creep with lower amplitude [15] than graphitic and graphitized petroleum coke cathodes. Instead, dense cathodes with more graphitic order have higher electrical conductivity, lower energy consumption [14], and lower swelling due to sodium penetration. Swelling results in early and non-uniform deterioration of cathode blocks. Anode: Carbon anodes have

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540-487: Is not hazardous. This category includes trash, rubbish and refuse; and may include materials such as construction debris and yard waste. Hazardous waste typically has specific definitions, due to the more careful and complex handling required of such wastes. Under US law, waste may be classified as hazardous based on certain characteristics: ignitability , reactivity , corrosivity and toxicity . Some types of hazardous waste are specifically listed in regulations. One of

585-425: Is produced by electrolytic reduction of aluminium oxide dissolved in molten cryolite . At the same time the carbon electrode is oxidised, initially to carbon monoxide Although the formation of carbon monoxide (CO) is thermodynamically favoured at the reaction temperature, the presence of considerable overvoltage (difference between reversible and polarization potentials) changes the thermodynamic equilibrium and

630-430: Is related to the nature of anode materials, as well as the porosity of baked anodes. Around 10% of cell power is consumed to overcome the electrical resistance of prebaked anode (50–60 μΩm). Carbon is consumed more than theoretical value due to a low current efficiency and non-electrolytic consumption. Inhomogeneous anode quality due to the variation in raw materials and production parameters also affects its performance and

675-559: Is to: 1) collect necessary information (known as the Remedial Investigation (RI) phase); 2) assess alternatives to deal with any potential risks to the environmental and human health (known as the Feasibility Study (FS) stage); 3) determine the most suitable remedies that could lower the risks to more adequate levels. Some sites are so contaminated because of past waste disposals that it takes decades to clean them up, or bring

720-578: Is tracked. The EPA now manages 2.96 million tons of solid, hazardous and industrial waste. Since establishment, the RCRA program has undergone reforms as inefficiencies arise and as waste management processes evolve. The 1972 Clean Water Act is a broad legislative mandate to protect surface waters (rivers, lakes and coastal water bodies). A 1948 law had authorized research and development of voluntary water standards, and had provided limited financing for state and local government efforts. The 1972 law prohibited, for

765-901: The American crocodile , caiman , common basilisk and large iguanas , are also easily seen. This article related to a river in Costa Rica is a stub . You can help Misplaced Pages by expanding it . Industrial waste Industrial waste is the waste produced by industrial activity which includes any material that is rendered useless during a manufacturing process such as that of factories , mills, and mining operations. Types of industrial waste include dirt and gravel , masonry and concrete , scrap metal, oil, solvents , chemicals, scrap lumber, even vegetable matter from restaurants. Industrial waste may be solid, semi-solid or liquid in form. It may be hazardous waste (some types of which are toxic ) or non-hazardous waste. Industrial waste may pollute

810-613: The Solid Waste Disposal Act of 1965 , and in 1984, Congress passed the Hazardous and Solid Waste Amendments (HSWA) which strengthened RCRA by: Furthermore, the EPA uses Superfund to find sites of contamination, identify the parties responsible, and in the occurrences where said parties are not known or able to, the program funds cleanups. Superfund also works on figuring out and applying final remedies for cleanups. The Superfund process

855-667: The boatbill and bare-throated tiger heron , and other birds found here include double-striped thick-knee , mangrove warbler and American pygmy kingfisher . The total list known of birds well exceeds 320 species including the little known Guacalillo Canals. The avian biodiversity is substantial including rare birds such as Agami Heron, Rufous-necked Woodrail, Jabiru, Yellow-billed Cotinga and recently found an Orinoco Goose. It's also home of Howler and White-faced Capuchin Monkeys. Less commonly seen are Silky Anteater, Sloths, Grinson, Jaguarundi, River Otter and Northern Tamandua. Reptiles, such as

900-662: The RCRA regulations through approved waste management programs. State compliance is monitored by EPA inspections. In the case that waste management guideline standards are not met, action against the site will be taken. Compliance errors may be corrected by enforced cleanup directly by the site responsible for the waste or by a third party hired by that site. Prior to the enactment of the Clean Water Act (1972) and RCRA, open dumping or releasing wastewater into nearby bodies of water were common waste disposal methods. The negative effects on human health and environmental health led to

945-515: The Royal Thai Government, which is organized as central (national) government, regional government, and local government. Each government is responsible for different tasks. The central government is responsible for stimulating regulation, policies, and standards. The regional governments are responsible for coordinating the central and local governments. The local governments are responsible for waste management in their governed area. However,

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990-579: The basis of their characteristics: Many factories and most power plants are located near bodies of water to obtain large amounts of water for manufacturing processes or for equipment cooling . In the US, electric power plants are the largest water users. Other industries using large amounts of water are pulp and paper mills , chemical plants , iron and steel mills , petroleum refineries , food processing plants and aluminum smelters . Many less-developed countries that are becoming industrialized do not yet have

1035-507: The cell stability. Prebaked consumable carbon anodes are divided into graphitized and coke types. For manufacturing of the graphitized anodes, anthracite and petroleum coke are calcined and classified. They are then mixed with coal-tar pitch and pressed. The pressed green anode is then baked at 1200 °C and graphitized. Coke anodes are made of calcined petroleum coke, recycled anode butts, and coal-tar pitch (binder). The anodes are manufactured by mixing aggregates with coal tar pitch to form

1080-571: The coke-type anodes is higher than that of the graphitized ones, but they have higher compressive strength and lower porosity. Soderberg electrodes (in-situ baking), used for the first time in 1923 in Norway, are composed of a steel shell and a carbonaceous mass which is baked by the heat being escaped from the electrolysis cell. Soderberg Carbon-based materials such as coke and anthracite are crushed, heat-treated, and classified. These aggregates are mixed with pitch or oil as binder, briquetted and loaded into

1125-896: The contaminant. Metals and chemicals released into bodies of water affect the marine ecosystems . Wastewater containing nutrients (nitrates and phosphates) often causes eutrophication which can kill off existing life in water bodies. A Thailand study focusing on water pollution origins found that the highest concentrations of water contamination in the U-tapao river had a direct correlation to industrial wastewater discharges. Thermal pollution —discharges of water at elevated temperature after being used for cooling—can also lead to polluted water. Elevated water temperatures decrease oxygen levels, which can kill fish and alter food chain composition, reduce species biodiversity , and foster invasion by new thermophilic species. Solid waste, often called municipal solid waste , typically refers to material that

1170-468: The contamination down to acceptable levels, thus requiring long-term management over those sites. Hence, sometimes figuring out a final remedy is not possible, and so, the EPA has developed the Adaptive Management plan. The EPA has issued national regulations regarding the handling, treatment and disposal of wastes. EPA has authorized individual state environmental agencies to implement and enforce

1215-422: The desirable properties of both; the electrical conductivity and toughness of the metal and stability of the ceramic. These anodes often consist of a combination of the above metal and ceramic materials. In industry, Alcoa and Rio Tinto have formed a joint venture, Elysis, to commercialize inert anode technology developed by Alcoa. The inert anode is a cermet material, a metallic dispersion of copper alloy in

1260-474: The electrolyte, and are therefore not consumed during the reduction process. Because the anode does not contain carbon, carbon dioxide is not produced. Through a review of literature, Haradlsson et al. found that inert anodes reduced the green house gas emissions of the aluminum smelting process by approximately 2 tonnes CO2eq/ tonne Al. Ceramic anode materials include Ni-Fe, Sn, and Ni-Li based oxides. These anodes show promise as they are extremely stable during

1305-540: The energy cost of the smelting process, alternative electrolytes such as Na3AlF6 are being investigated that can operate at a lower temperature. However, changing the electrolyte changes the kinetics of the liberated oxygen from the Al 2 O 3 ore. This change in bubble formation can alter the rate the anode reacts with Oxygen or the electrolyte and effectively change the efficiency of the reduction process. Inert anodes, used in tandem with vertical electrode cells, can also reduce

1350-436: The environment. Drinking water sources and irrigation water used for farming may be affected. The pollutants may degrade or destroy habitat for animals and plants. In coastal areas, fish and other aquatic life can be contaminated by untreated waste; beaches and other recreational areas can be damaged or closed. In Thailand the roles in municipal solid waste (MSW) management and industrial waste management are organized by

1395-465: The first time, uncontrolled discharges of industrial waste, as well as municipal sewage, into waters of the United States. EPA was required to develop national standards for industrial facilities and standards for municipal sewage treatment plants. States were required to develop water quality standards for individual water bodies. Enforcement is mainly delegated to state agencies. Major amendments to

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1440-628: The law were passed in 1977 and 1987. Aluminium smelting Aluminium smelting is the process of extracting aluminium from its oxide, alumina , generally by the Hall-Héroult process . Alumina is extracted from the ore bauxite by means of the Bayer process at an alumina refinery . This is an electrolytic process, so an aluminium smelter uses huge amounts of electric power; smelters tend to be located close to large power stations, often hydro-electric ones, in order to hold down costs and reduce

1485-586: The local governments do not dispose of the waste by themselves but instead hire private companies that have been granted the right from the Pollution Control Department (PCD) in Thailand. The main companies are Bangpoo Industrial Waste Management Center, General Environmental Conservation Public Company Limited (GENCO), SGS Thailand, Waste Management Siam LTD (WMS), and Better World Green Public Company Limited (BWG). These companies are responsible for

1530-461: The most devastating effects of industrial waste is water pollution. For many industrial processes, water is used which comes in contact with harmful chemicals. These chemicals may include organic compounds (such as solvents), metals, nutrients or radioactive material. If the wastewater is discharged without treatment, groundwater and surface water bodies—lakes, streams, rivers and coastal waters—can become polluted, with serious impacts on human health and

1575-463: The nearby soil or adjacent water bodies, and can contaminate groundwater, lakes, streams, rivers or coastal waters. Industrial waste is often mixed into municipal waste , making accurate assessments difficult. An estimate for the US goes as high as 7.6 billion tons of industrial waste produced annually, as of 2017. Most countries have enacted legislation to deal with the problem of industrial waste, but strictness and compliance regimes vary. Enforcement

1620-415: The need for such regulations. The RCRA framework provides specified subsections defining nonhazardous and hazardous waste materials and how each should be properly managed and disposed of. Guidelines for the disposal of nonhazardous solid waste includes the banning of open dumping. Hazardous waste is monitored in a " cradle to grave " fashion; each step in the process of waste generation, transport and disposal

1665-400: The overall carbon footprint . Smelters are often located near ports, since many smelters use imported alumina. The Hall-Héroult electrolysis process is the major production route for primary aluminium. An electrolytic cell is made of a steel shell with a series of insulating linings of refractory materials. The cell consists of a brick-lined outer steel shell as a container and support. Inside

1710-642: The plants. The Soderberg process which bakes the Anthracite/pitch mix as the anode is consumed, produces significant emissions of polycyclic aromatic hydrocarbons as the pitch is consumed in the smelter. The linings of the pots end up contaminated with cyanide-forming materials; Alcoa has a process for converting spent linings into aluminium fluoride for reuse and synthetic sand usable for building purposes and inert waste. Inert anodes are non-carbon based alternatives to traditional anodes used during aluminum reduction. These anodes do not chemically react with

1755-406: The principal formulation and the fundamental reactions occurring on their surface are the same. An aluminium smelter consists of a large number of cells (pots) in which the electrolysis takes place. A typical smelter contains anywhere from 300 to 720 pots, each of which produces about a ton of aluminium a day, though the largest proposed smelters are up to five times that capacity. Smelting is run as

1800-407: The reduction process at normal operating temperatures (~1000 °C), ensuring that the Al is not contaminated. The stability of these anodes also allows them to be used with a range of electrolytes. However, ceramic anodes suffer from poor electrical conductivity and low mechanical strength. Alternatively metal anodes boast high mechanical strength and conductivity but tend to corrode easily during

1845-430: The reduction process. Some material systems that are used in inert metal anodes include Al-Cu, Ni-Cu, and Fe-Ni-Cu systems. Additional additives such as Sn, Ag, V, Nb, Ir, Ru can be included in these systems to form non reactive oxides on the anode surface, but this significantly increases the cost and embodied energy of the anode. Cermet anodes are the combination of a metal and ceramic anode, and aim to take advantage of

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1890-517: The resources or technology to dispose their wastes with minimal impacts on the environment. Both untreated and partially treated wastewater are commonly fed back into a near lying body of water. Metals, chemicals and sewage released into bodies of water directly affect marine ecosystems and the health of those who depend on the waters as food or drinking water sources. Toxins from the wastewater can kill off marine life or cause varying degrees of illness to those who consume these marine animals, depending on

1935-418: The shell, cathode blocks are cemented together by ramming paste. The top lining is in contact with the molten metal and acts as the cathode. The molten electrolyte is maintained at high temperature inside the cell. The prebaked anode is also made of carbon in the form of large sintered blocks suspended in the electrolyte. A single Soderberg electrode or a number of prebaked carbon blocks are used as anode, while

1980-437: The shell. Temperature increases bottom to the top of the column and in-situ baking takes place as the anode is lowered into the bath. Significant amount of hydrocarbons are emitted during baking which is a disadvantage of this type of electrodes. Most of the modern smelters use prebaked anodes since the process control is easier and a slightly better energy efficiency is achieved, compared to Soderberg anodes. The process produces

2025-460: The waste they have received from their customers before releasing it to the environment, burying it. The 1976 Resource Conservation and Recovery Act (RCRA) provides for federal regulation of industrial, household, and manufacturing solid and hazardous wastes in the United States. RCRA aims to conserve natural resources and energy, protect human health, eliminate or reduce waste, and to clean up waste when needed. RCRA first began as an amendment to

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