![What is Zero Liquid Discharge Diagram](https://upload.wikimedia.org/wikipedia/commons/f/f5/What_is_Zero_Liquid_Discharge_Diagram.png)
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 a
sanitary sewer
A sanitary sewer is an underground pipe or tunnel system for transporting sewage from houses and commercial buildings (but not stormwater) to a sewage treatment plant or disposal. Sanitary sewers are a type of gravity sewer and are part of an ...
or to a
surface water in the environment. Some industrial facilities generate wastewater that can be treated in
sewage treatment plants
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 for discharge to the surrounding en ...
. Most industrial processes, such as
petroleum refineries
An oil refinery or petroleum refinery is an industrial process plant where petroleum (crude oil) is transformed and refined into useful products such as gasoline (petrol), diesel fuel, asphalt base, fuel oils, heating oil, kerosene, liquefie ...
, chemical and
petrochemical
Petrochemicals (sometimes abbreviated as petchems) are the chemical products obtained from petroleum by refining. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewable so ...
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
ocean
The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...
s.
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
Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a t ...
) or nutrients such as
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...
. Some industries install a pre-treatment system to remove some pollutants (e.g., toxic compounds), and then discharge the partially treated wastewater to the municipal sewer system.
Most industries produce some
wastewater
Wastewater is water generated after the use of freshwater, raw water, drinking water or saline water in a variety of deliberate applications or processes. Another definition of wastewater is "Used water from any combination of domestic, industrial ...
. Recent trends have been to minimize such production or to recycle treated wastewater within the production process. Some industries have been successful at redesigning their manufacturing processes to reduce or eliminate pollutants. Sources of industrial wastewater include battery manufacturing, chemical manufacturing, electric power plants,
food industry, iron and steel industry, metal working, mines and quarries, nuclear industry,
oil and gas extraction
Petroleum is a fossil fuel that can be drawn from beneath the earth's surface. Reservoirs of petroleum was formed through the mixture of plants, algae, and sediments in shallow seas under high pressure. Petroleum is mostly recovered from oil dr ...
,
petroleum refining
An oil refinery or petroleum refinery is an industrial process plant where petroleum (crude oil) is transformed and refined into useful products such as gasoline (petrol), diesel fuel, asphalt base, fuel oils, heating oil, kerosene, liquefi ...
and
petrochemicals, pharmaceutical manufacturing,
pulp and paper industry, smelters,
textile mill
Textile Manufacturing or Textile Engineering is a major industry. It is largely based on the conversion of fibre into yarn, then yarn into fabric. These are then dyed or printed, fabricated into cloth which is then converted into useful goods ...
s, industrial
oil contamination, water treatment and
wood preserving. Treatment processes include brine treatment, solids removal (e.g. chemical precipitation, filtration), oils and grease removal, removal of biodegradable organics, removal of other organics, removal of acids and alkalis, and removal of toxic materials.
Types
Industrial facilities may generate the following industrial wastewater flows:
* Manufacturing process wastestreams, which can include
conventional pollutant A conventional pollutant is a term used in the USA to describe a water pollutant that is amenable to treatment by a municipal sewage treatment plant. A basic list of conventional pollutants is defined in the U.S. Clean Water Act. The list has been ...
s (i.e. controllable with
secondary treatment
Secondary treatment is the removal of biodegradable organic matter (in solution or suspension) from sewage or similar kinds of wastewater. The aim is to achieve a certain degree of effluent quality in a sewage treatment plant suitable for the inte ...
systems),
toxic
Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...
pollutants (e.g. solvents, heavy metals), and other harmful compounds such as
nutrients
A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excre ...
* Non-process wastestreams:
boiler blowdown Boiler blowdown is water intentionally wasted from a boiler to avoid concentration of impurities during continuing evaporation of steam. The water is blown out of the boiler with some force by steam pressure within the boiler. Bottom blowdown used ...
and
cooling water
Cooling tower and water discharge of a nuclear power plant
Water cooling is a method of heat removal from components and industrial equipment. Evaporative cooling using water is often more efficient than air cooling. Water is inexpensive and no ...
, which produce
thermal pollution
Thermal pollution, sometimes called "thermal enrichment", is the degradation of water quality by any process that changes ambient water temperature. Thermal pollution is the rise or fall in the temperature of a natural body of water caused by hum ...
and other pollutants
*
Industrial site drainage, generated both by manufacturing facilities, service industries and energy and mining sites
* Wastestreams from the energy and mining sectors:
acid mine drainage
Acid mine drainage, acid and metalliferous drainage (AMD), or acid rock drainage (ARD) is the outflow of acidic water from metal mines or coal mines.
Acid rock drainage occurs naturally within some environments as part of the rock weathering ...
,
produced water
Produced water is a term used in the oil industry or geothermal industry to describe water that is produced as a byproduct during the extraction of oil and natural gas, or used as a medium for heat extraction. Produced water is the kind of brackis ...
from oil and gas extraction,
radionuclides
* Wastestreams that are by-products of treatment or cooling processes:
backwashing (water treatment)
In terms of water treatment, including water purification and sewage treatment, backwashing refers to pumping water backwards through the filters media, sometimes including intermittent use of compressed air during the process. Backwashing is ...
,
brine.
Contaminants
Industrial sectors
The specific pollutants generated and the resultant effluent concentrations can vary widely among the industrial sectors.
Battery manufacturing
Battery
Battery most often refers to:
* Electric battery, a device that provides electrical power
* Battery (crime), a crime involving unlawful physical contact
Battery may also refer to:
Energy source
*Automotive battery, a device to provide power t ...
manufacturers specialize in fabricating small devices for electronics and portable equipment (e.g., power tools), or larger, high-powered units for cars, trucks and other motorized vehicles. Pollutants generated at manufacturing plants includes cadmium, chromium, cobalt, copper, cyanide, iron, lead, manganese, mercury, nickel, silver, zinc, oil and grease.
Centralized waste treatment
A centralized waste treatment (CWT) facility processes liquid or solid industrial wastes generated by off-site manufacturing facilities. A manufacturer may send its wastes to a CWT plant, rather than perform treatment on site, due to constraints such as limited land availability, difficulty in designing and operating an on-site system, or limitations imposed by environmental regulations and permits. A manufacturer may determine that using a CWT is more cost-effective than treating the waste itself; this is often the case where the manufacturer is a small business.
CWT plants often receive wastes from a wide variety of manufacturers, including chemical plants, metal fabrication and finishing; and used oil and petroleum products from various manufacturing sectors. The wastes may be classified as
hazardous
A hazard is a potential source of harm. Substances, events, or circumstances can constitute hazards when their nature would allow them, even just theoretically, to cause damage to health, life, property, or any other interest of value. The probabi ...
, have high pollutant concentrations or otherwise be difficult to treat. In 2000 the
U.S. Environmental Protection Agency
The Environmental Protection Agency (EPA) is an Independent agencies of the United States government, independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon pro ...
published wastewater regulations for CWT facilities in the US.
Chemical manufacturing
Organic chemicals manufacturing
The specific pollutants discharged by
organic chemical manufacturers vary widely from plant to plant, depending on the types of products manufactured, such as bulk organic chemicals, resins, pesticides, plastics, or synthetic fibers. Some of the organic compounds that may be discharged are
benzene
Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms ...
,
chloroform,
naphthalene,
phenol
Phenol (also called carbolic acid) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile. The molecule consists of a phenyl group () bonded to a hydroxy group (). Mildly acidic, it ...
s,
toluene
Toluene (), also known as toluol (), is a substituted aromatic hydrocarbon. It is a colorless, water-insoluble liquid with the smell associated with paint thinners. It is a mono-substituted benzene derivative, consisting of a methyl group (CH3) a ...
and
vinyl chloride
Vinyl chloride is an organochloride with the formula H2C=CHCl. It is also called vinyl chloride monomer (VCM) or chloroethene. This colorless compound is an important industrial chemical chiefly used to produce the polymer polyvinyl chloride (PVC ...
.
Biochemical oxygen demand
Biochemical oxygen demand (BOD) is the amount of dissolved oxygen (DO) needed (i.e. demanded) by aerobic biological organisms to break down organic material present in a given water sample at a certain temperature over a specific time period. ...
(BOD), which is a gross measurement of a range of organic pollutants, may be used to gauge the effectiveness of a biological wastewater treatment system, and is used as a regulatory parameter in some discharge permits. Metal pollutant discharges may include
chromium,
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
,
lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
,
nickel
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...
and
zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
.
Inorganic chemicals manufacturing
The
inorganic chemicals sector covers a wide variety of products and processes, although an individual plant may produce a narrow range of products and pollutants. Products include aluminum compounds; calcium carbide and calcium chloride; hydrofluoric acid; potassium compounds; borax; chrome and fluorine-based compounds; cadmium and zinc-based compounds. The pollutants discharged vary by product sector and individual plant, and may include arsenic, chlorine, cyanide, fluoride; and heavy metals such as chromium, copper, iron, lead, mercury, nickel and zinc.
Electric power plants
Fossil-fuel power station
A fossil fuel power station is a thermal power station which burns a fossil fuel, such as coal or natural gas, to produce electricity. Fossil fuel power stations have machinery to convert the heat energy of combustion into mechanical energy, wh ...
s, particularly
coal
Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal is formed when ...
-fired plants, are a major source of industrial wastewater. Many of these plants discharge wastewater with significant levels of metals such as
lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
,
mercury,
cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...
and
chromium, as well as
arsenic
Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, ...
,
selenium
Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, ...
and
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
compounds (
nitrates and
nitrites). Wastewater streams include
flue-gas desulfurization,
fly ash,
bottom ash and
flue gas
Flue gas is the gas exiting to the atmosphere via a flue, which is a pipe or channel for conveying exhaust gases from a fireplace, oven, furnace, boiler or steam generator. Quite often, the flue gas refers to the combustion exhaust gas produc ...
mercury control. Plants with air pollution controls such as
wet scrubber
The term wet scrubber describes a variety of devices that remove pollutants from a furnace flue gas or from other gas streams. In a wet scrubber, the polluted gas stream is brought into contact with the scrubbing liquid, by spraying it with the ...
s typically transfer the captured pollutants to the wastewater stream.
Ash pond
An ash pond, also called a coal ash basin or surface impoundment,U.S. Environmental Protection Agency (EPA), Washington, D.C. "Hazardous and Solid Waste Management System; Identification and Listing of Special Wastes; Disposal of Coal Combustion ...
s, a type of surface impoundment, are a widely used treatment technology at coal-fired plants. These ponds use gravity to
settle out large particulates (measured as
total suspended solids
Total suspended solids (TSS) is the dry-weight of suspended particles, that are not dissolved, in a sample of water that can be trapped by a filter that is analyzed using a filtration apparatus known as sintered glass crucible. TSS is a water qu ...
) from power plant wastewater. This technology does not treat dissolved pollutants. Power stations use additional technologies to control pollutants, depending on the particular wastestream in the plant. These include dry ash handling, closed-loop ash recycling,
chemical precipitation
In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leadin ...
, biological treatment (such as an
activated sludge
The activated sludge process is a type of biological wastewater treatment process for treating sewage or industrial wastewaters using aeration and a biological floc composed of bacteria and protozoa. It uses air (or oxygen) and microorganism ...
process), membrane systems, and evaporation-crystallization systems.
Technological advancements in
ion-exchange membrane An ion-exchange membrane is a semi-permeable membrane that transports certain dissolved ions, while blocking other ions or neutral molecules.
Ion-exchange membranes are therefore electrically conductive. They are often used in desalination and c ...
s and
electrodialysis
Electrodialysis (ED) is used to transport salt ions from one solution through ion-exchange membranes to another solution under the influence of an applied electric potential difference. This is done in a configuration called an electrodialysis ...
systems has enabled high efficiency treatment of
flue-gas desulfurization wastewater to meet recent EPA discharge limits. The treatment approach is similar for other highly scaling industrial wastewaters.
Food industry
![Seafood waste Sitka AK 2003](https://upload.wikimedia.org/wikipedia/commons/d/d9/Seafood_waste_Sitka_AK_2003.jpg)
Wastewater generated from agricultural and
food processing operations has distinctive characteristics that set it apart from common municipal wastewater managed by public or private
sewage treatment
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 for discharge to the surrounding e ...
plants throughout the world: it is
biodegradable and non-toxic, but has high Biological Oxygen Demand (BOD) and
suspended solids (SS). The constituents of food and agriculture wastewater are often complex to predict, due to the differences in BOD and
pH in effluents from vegetable, fruit, and meat products and due to the seasonal nature of food processing and post-harvesting.
Processing of food from raw materials requires large volumes of high grade water. Vegetable washing generates waters with high loads of
particulate matter and some dissolved
organic matter. It may also contain surfactants and pesticides.
Aquaculture facilities (fish farms) often discharge large amounts of nitrogen and phosphorus, as well as suspended solids. Some facilities use drugs and pesticides, which may be present in the wastewater.
Dairy processing plants generate
conventional pollutant A conventional pollutant is a term used in the USA to describe a water pollutant that is amenable to treatment by a municipal sewage treatment plant. A basic list of conventional pollutants is defined in the U.S. Clean Water Act. The list has been ...
s (BOD, SS).
Animal slaughter
Animal slaughter is the killing of animals, usually referring to killing domestic livestock. It is estimated that each year 80 billion land animals are slaughtered for food. Most animals are slaughtered for food; however, they may also be slau ...
and processing produces organic waste from body fluids, such as
blood
Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...
, and
gut contents. Pollutants generated include BOD, SS,
coliform bacteria
Coliform bacteria are defined as either motile or non-motile Gram-negative non- spore forming Bacilli that possess β-galactosidase to produce acids and gases under their optimal growth temperature of 35-37°C. They can be aerobes or facultative ...
, oil and grease,
organic nitrogen and
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...
.
Processing food for sale produces wastes generated from cooking which are often rich in plant organic material and may also contain
salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...
,
flavouring
A flavoring (or flavouring), also known as flavor (or flavour) or flavorant, is a food additive used to improve the taste or smell of food. It changes the perceptual impression of food as determined primarily by the chemoreceptors of the gus ...
s,
colouring material and
acids or
alkali. Large quantities of fats, oil and grease ("FOG") may also be present, which in sufficient concentrations can clog sewer lines. Some municipalities require restaurants and food processing businesses to use
grease interceptor
A grease trap (also known as grease interceptor, grease recovery device, grease capsule and grease converter) is a plumbing device (a type of trap) designed to intercept most greases and solids before they enter a wastewater disposal system. Co ...
s and regulate the disposal of FOG in the sewer system.
Food processing activities such as plant cleaning, material conveying, bottling, and product washing create wastewater. Many food processing facilities require on-site treatment before operational wastewater can be land applied or discharged to a waterway or a sewer system. High suspended solids levels of organic particles increase BOD and can result in significant sewer surcharge fees. Sedimentation, wedgewire screening, or rotating belt filtration (microscreening) are commonly used methods to reduce suspended organic solids loading prior to discharge.
Iron and steel industry
The
production of iron from its ores involves powerful
reduction reactions in blast furnaces. Cooling waters are inevitably contaminated with products especially
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...
and
cyanide
Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms.
In chemistry, a cyanide () is a chemical compound that contains a functional group. This group, known as the cyano group, consists of ...
. Production of
coke from coal in coking plants also requires
water cooling
Cooling tower and water discharge of a nuclear power plant
Water cooling is a method of heat removal from components and industrial equipment. Evaporative cooling using water is often more efficient than air cooling. Water is inexpensive and non ...
and the use of water in by-products separation. Contamination of waste streams includes gasification products such as
benzene
Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms ...
,
naphthalene,
anthracene
Anthracene is a solid polycyclic aromatic hydrocarbon (PAH) of formula C14H10, consisting of three fused benzene rings. It is a component of coal tar. Anthracene is used in the production of the red dye alizarin and other dyes. Anthracene is col ...
, cyanide, ammonia,
phenol
Phenol (also called carbolic acid) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile. The molecule consists of a phenyl group () bonded to a hydroxy group (). Mildly acidic, it ...
s,
cresol
Cresols (also hydroxytoluene or cresylic acid) are a group of aromatic organic compounds. They are widely-occurring phenols (sometimes called ''phenolics'') which may be either natural or manufactured. They are also categorized as methylphenol ...
s together with a range of more complex
organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. T ...
s known collectively as
polycyclic aromatic hydrocarbon
A polycyclic aromatic hydrocarbon (PAH) is a class of organic compounds that is composed of multiple aromatic rings. The simplest representative is naphthalene, having two aromatic rings and the three-ring compounds anthracene and phenanthrene. ...
s (PAH).
The conversion of iron or steel into sheet, wire or rods requires hot and cold mechanical transformation stages frequently employing water as a lubricant and coolant. Contaminants include
hydraulic oil
A hydraulic fluid or hydraulic liquid is the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water. Examples of equipment that might use hydraulic fluids are excavators and backhoes, ...
s,
tallow
Tallow is a rendered form of beef or mutton fat, primarily made up of triglycerides.
In industry, tallow is not strictly defined as beef or mutton fat. In this context, tallow is animal fat that conforms to certain technical criteria, includ ...
and particulate solids. Final treatment of iron and steel products before onward sale into manufacturing includes ''pickling'' in strong mineral acid to remove rust and prepare the surface for
tin
Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal.
Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...
or
chromium plating or for other surface treatments such as
galvanisation
Galvanization or galvanizing ( also spelled galvanisation or galvanising) is the process of applying a protective zinc coating to steel or iron, to prevent rusting. The most common method is hot-dip galvanizing, in which the parts are submerged ...
or
painting. The two acids commonly used are
hydrochloric acid
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid
Acid strength is the tendency of an acid, symbol ...
and
sulfuric acid. Wastewaters include acidic rinse waters together with waste acid. Although many plants operate acid recovery plants (particularly those using hydrochloric acid), where the mineral acid is boiled away from the iron salts, there remains a large volume of highly acid
ferrous sulfate
Iron(II) sulfate (British English: iron(II) sulphate) or ferrous sulfate denotes a range of salts with the formula Fe SO4·''x''H2O. These compounds exist most commonly as the hepta hydrate (''x'' = 7) but several values for x are kn ...
or
ferrous chloride
Iron(II) chloride, also known as ferrous chloride, is the chemical compound of formula FeCl2. It is a paramagnetic solid with a high melting point. The compound is white, but typical samples are often off-white. FeCl2 crystallizes from water as ...
to be disposed of. Many steel industry wastewaters are contaminated by hydraulic oil, also known as ''soluble oil.''
Metal working
Many industries perform work on metal feedstocks (e.g. sheet metal,
ingot
An ingot is a piece of relatively pure material, usually metal, that is cast into a shape suitable for further processing. In steelmaking, it is the first step among semi-finished casting products. Ingots usually require a second procedure of sha ...
s) as they fabricate their final products. The industries include automobile, truck and aircraft manufacturing; tools and hardware manufacturing; electronic equipment and office machines; ships and boats; appliances and other household products; and stationary industrial equipment (e.g. compressors, pumps, boilers). Typical processes conducted at these plants include
grinding
Grind is the cross-sectional shape of a blade.
Grind, grinds, or grinding may also refer to:
Grinding action
* Grinding (abrasive cutting), a method of crafting
* Grinding (dance), suggestive club dancing
* Grinding (video gaming), repetitive and ...
,
machining,
coating
A coating is a covering that is applied to the surface of an object, usually referred to as the substrate. The purpose of applying the coating may be decorative, functional, or both. Coatings may be applied as liquids, gases or solids e.g. Pow ...
and painting,
chemical etching and milling,
solvent degreasing Solvent degreasing is a process used to prepare a part for further operations such as electroplating or painting. Typically it uses petroleum, chlorine, dry ice or alcohol based solvents to dissolve the machining fluids and other contaminants t ...
,
electroplating and
anodizing
Anodizing is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal parts.
The process is called ''anodizing'' because the part to be treated forms the anode electrode of an electr ...
. Wastewater generated from these industries may contain heavy metals such as cadmium, chromium, copper, lead, nickel, silver and zinc; cyanide and various organic chemical solvents; and oil and grease.
Mines and quarries
![Wastewater effluent](https://upload.wikimedia.org/wikipedia/commons/0/0a/Wastewater_effluent.JPG)
The principal waste-waters associated with
mine
Mine, mines, miners or mining may refer to:
Extraction or digging
* Miner, a person engaged in mining or digging
*Mining, extraction of mineral resources from the ground through a mine
Grammar
*Mine, a first-person English possessive pronoun
...
s and
quarries
A quarry is a type of open-pit mine in which dimension stone, rock, construction aggregate, riprap, sand, gravel, or slate is excavated from the ground. The operation of quarries is regulated in some jurisdictions to reduce their envir ...
are slurries of rock particles in water. These arise from rainfall washing exposed surfaces and haul roads and also from rock washing and grading processes. Volumes of water can be very high, especially rainfall related arisings on large sites.
Some specialized separation operations, such as
coal
Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal is formed when ...
washing to separate coal from native rock using
density gradients, can produce wastewater contaminated by fine particulate
haematite and
surfactants
Surfactants are chemical compounds that decrease the surface tension between two liquids, between a gas and a liquid, or interfacial tension between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming ...
.
Oil
An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturated ...
s and hydraulic oils are also common contaminants.
Wastewater from metal mines and ore recovery plants are inevitably contaminated by the minerals present in the native rock formations. Following crushing and extraction of the desirable materials, undesirable materials may enter the wastewater stream. For metal mines, this can include unwanted metals such as
zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
and other materials such as
arsenic
Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, ...
. Extraction of high value metals such as
gold
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile me ...
and
silver
Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...
may generate
slime
Slime may refer to:
Biology
* Slime mold, a broad term often referring to roughly six groups of Eukaryotes
* Biofilm, an aggregate of microorganisms in which cells adhere to each other and/or to a surface
* Slimy (fish), also known as the pony ...
s containing very fine particles in where physical removal of contaminants becomes particularly difficult.
Additionally, the geologic formations that harbour economically valuable metals such as
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
and gold very often consist of sulphide-type ores. The processing entails grinding the rock into fine particles and then extracting the desired metal(s), with the leftover rock being known as tailings. These tailings contain a combination of not only undesirable leftover metals, but also sulphide components which eventually form sulphuric acid upon the exposure to air and water that inevitably occurs when the tailings are disposed of in large impoundments. The resulting
acid mine drainage
Acid mine drainage, acid and metalliferous drainage (AMD), or acid rock drainage (ARD) is the outflow of acidic water from metal mines or coal mines.
Acid rock drainage occurs naturally within some environments as part of the rock weathering ...
, which is often rich in heavy metals (because acids dissolve metals), is one of the many
environmental impacts of mining.
Nuclear industry
The waste production from the nuclear and radio-chemicals industry is dealt with as ''
Radioactive waste
Radioactive waste is a type of hazardous waste that contains radioactive material. Radioactive waste is a result of many activities, including nuclear medicine, nuclear research, nuclear power generation, rare-earth mining, and nuclear weapons r ...
.''
Researchers have looked at the bioaccumulation of
strontium by ''
Scenedesmus spinosus'' (
algae) in simulated wastewater. The study claims a highly selective
biosorption Biosorption is a physiochemical process that occurs naturally in certain biomass which allows it to passively concentrate and bind contaminants onto its cellular structure. Biosorption can be defined as the ability of biological materials to accumu ...
capacity for strontium of S. spinosus, suggesting that it may be appropriate for use of nuclear wastewater.
Oil and gas extraction
Oil and gas well operations generate
produced water
Produced water is a term used in the oil industry or geothermal industry to describe water that is produced as a byproduct during the extraction of oil and natural gas, or used as a medium for heat extraction. Produced water is the kind of brackis ...
, which may contain oils, toxic metals (e.g.
arsenic
Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, ...
,
cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...
,
chromium, mercury, lead), salts, organic chemicals and solids. Some produced water contains traces of
naturally occurring radioactive material
Naturally occurring radioactive materials (NORM) and technologically enhanced naturally occurring radioactive materials (TENORM) consist of materials, usually industrial wastes or by-products enriched with radioactive elements found in the envir ...
.
Offshore oil
Offshore drilling is a mechanical process where a wellbore is drilled below the seabed. It is typically carried out in order to explore for and subsequently extract petroleum that lies in rock formations beneath the seabed. Most commonly, the te ...
and gas platforms also generate deck drainage, domestic waste and sanitary waste. During the drilling process, well sites typically discharge
drill cuttings
Drill cuttings are broken bits of solid material removed from a borehole drilled by rotary, percussion, or auger methods and brought to the surface in the drilling mud. Boreholes drilled in this way include oil or gas wells, water wells, a ...
and
drilling mud (drilling fluid).
Petroleum refining and petrochemicals
Pollutants discharged at
petroleum refineries
An oil refinery or petroleum refinery is an industrial process plant where petroleum (crude oil) is transformed and refined into useful products such as gasoline (petrol), diesel fuel, asphalt base, fuel oils, heating oil, kerosene, liquefie ...
and
petrochemical
Petrochemicals (sometimes abbreviated as petchems) are the chemical products obtained from petroleum by refining. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewable so ...
plants include
conventional pollutant A conventional pollutant is a term used in the USA to describe a water pollutant that is amenable to treatment by a municipal sewage treatment plant. A basic list of conventional pollutants is defined in the U.S. Clean Water Act. The list has been ...
s (BOD, oil and grease,
suspended solids), ammonia, chromium, phenols and sulfides.
Pharmaceutical manufacturing
Pharmaceutical plants typically generate a variety of process wastewaters, including solvents, spent acid and caustic solutions, water from chemical reactions, product wash water, condensed steam, blowdown from air pollution control scrubbers, and equipment washwater. Non-process wastewaters typically include cooling water and site runoff. Pollutants generated by the industry include
acetone
Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour.
Acetone is miscib ...
, ammonia, benzene, BOD, chloroform, cyanide,
ethanol
Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...
, ethyl acetate, isopropanol, methylene chloride, methanol, phenol and toluene. Treatment technologies used include advanced biological treatment (e.g. activated sludge with nitrification), media filter, multimedia filtration, cyanide destruction (e.g. hydrolysis), steam stripping and wastewater recycling.
Pulp and paper industry
![EFFLUENT FROM THE INTERNATIONAL PAPER COMPANY MILL AT JAY GUSHES INTO ALLEN BROOK NEAR CONFLUENCE OF THE BROOK AND](https://upload.wikimedia.org/wikipedia/commons/0/07/EFFLUENT_FROM_THE_INTERNATIONAL_PAPER_COMPANY_MILL_AT_JAY_GUSHES_INTO_ALLEN_BROOK_NEAR_CONFLUENCE_OF_THE_BROOK_AND..._-_NARA_-_550713_color_adj1.jpg)
Effluent from the
pulp and paper industry is generally high in
suspended solids and BOD. Plants that bleaching of wood pulp, bleach wood pulp for paper making may generate
chloroform, dioxins (including 2,3,7,8-TCDD), furans, phenols and chemical oxygen demand (COD).
Stand-alone paper mills using imported pulp may only require simple primary treatment, such as sedimentation (water treatment), sedimentation or dissolved air flotation. Increased BOD or COD loadings, as well as organic pollutants, may require biological treatment such as
activated sludge
The activated sludge process is a type of biological wastewater treatment process for treating sewage or industrial wastewaters using aeration and a biological floc composed of bacteria and protozoa. It uses air (or oxygen) and microorganism ...
or Upflow anaerobic sludge blanket digestion, upflow anaerobic sludge blanket reactors. For mills with high inorganic loadings like salt, tertiary treatments may be required, either general membrane treatments like ultrafiltration or reverse osmosis or treatments to remove specific contaminants, such as nutrients.
Smelters
The pollutants discharged by nonferrous Smelting, smelters vary with the base metal ore. Bauxite smelters generate phenols
but typically use settling basins and evaporation to manage these wastes, with no need to routinely discharge wastewater.
Aluminum smelters typically discharge fluoride, benzo(a)pyrene, antimony and
nickel
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...
, as well as aluminum. Copper smelters typically generate
cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...
, lead, zinc, arsenic and nickel, in addition to copper, in their wastewater. Lead smelters discharge lead and zinc. Nickel and cobalt smelters discharge ammonia and copper in addition to the base metals. Zinc smelters discharge arsenic, cadmium, copper, lead, selenium and zinc.
Typical treatment processes used in the industry are chemical precipitation, sedimentation and filtration.
Textile mills
Textile manufacturing, Textile mills, including carpet manufacturers, generate wastewater from a wide variety of processes, including Scouring (textiles), cleaning and finishing, yarn manufacturing and fabric finishing (such as bleaching, dyeing, resin treatment, Waterproof fabric, waterproofing and Flame retardant, retardant flameproofing). Pollutants generated by textile mills include BOD, SS, oil and grease, sulfide, phenols and chromium. Insecticide residues in fleeces are a particular problem in treating waters generated in wool processing. Animal fats may be present in the wastewater, which if not contaminated, can be recovered for the production of tallow or further rendering.
Textile dyeing plants generate wastewater that contain synthetic (e.g., reactive dyes, acid dyes, basic dyes, disperse dyes, vat dyes, sulphur dyes, mordant dyes, direct dyes, ingrain dyes, solvent dyes, pigment dyes) and natural dyestuff, gum thickener (guar) and various wetting agents, pH buffers and dye retardants or accelerators. Following treatment with polymer-based flocculants and settling agents, typical monitoring parameters include BOD, COD, color (ADMI), sulfide, oil and grease, phenol, Total suspended solids, TSS and heavy metals (chromium,
zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
, lead, copper).
Industrial oil contamination
Industrial applications where oil enters the wastewater stream may include vehicle wash bays, workshops, fuel storage depots, transport hubs and power generation. Often the wastewater is discharged into local sewer or trade waste systems and must meet local environmental specifications. Typical contaminants can include solvents, detergents, grit, lubricants and hydrocarbons.
Water treatment
Many industries have a need to treat water to obtain very high quality water for their processes. This might include pure chemical synthesis or boiler feed water. Also, some water treatment processes produce organic and mineral sludges from filtration and Sedimentation (water treatment), sedimentation which require treatment. Ion exchange using natural or synthetic resins removes calcium, magnesium and carbonate ions from water, typically replacing them with sodium, chloride, hydroxyl and/or other ions. Regeneration of ion-exchange columns with strong acids and alkalis produces a wastewater rich in hardness ions which are readily precipitated out, especially when in admixture with other wastewater constituents.
Wood preserving
Wood preservation, Wood preserving plants generate conventional and toxic pollutants, including arsenic, COD, copper, chromium, abnormally high or low pH, phenols, suspended solids, oil and grease.
Treatment methods
![REDOX DAF unit 225 m3-h-1000 GPM](https://upload.wikimedia.org/wikipedia/commons/6/6c/REDOX_DAF_unit_225_m3-h-1000_GPM.jpg)
The various types of contamination of wastewater require a variety of strategies to remove the contamination.
Most industrial processes, such as
petroleum refineries
An oil refinery or petroleum refinery is an industrial process plant where petroleum (crude oil) is transformed and refined into useful products such as gasoline (petrol), diesel fuel, asphalt base, fuel oils, heating oil, kerosene, liquefie ...
, chemical and
petrochemical
Petrochemicals (sometimes abbreviated as petchems) are the chemical products obtained from petroleum by refining. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewable so ...
plants have onsite 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.
Constructed wetlands are being used in an increasing number of cases as they provided high quality and productive on-site treatment. Other industrial processes that produce a lot of waste-waters such as paper and pulp production have created environmental concern, leading to development of processes to recycle water use within plants before they have to be cleaned and disposed.
An industrial wastewater treatment plant may include one or more of the following rather than the conventional treatment sequence of sewage treatment plants:
* An API oil-water separator, for removing separate phase oil from wastewater.
* A clarifier, for removing solids from wastewater.
[Kemmer, Frank N. (1979). ''The Nalco Water Handbook''. New York: McGraw-Hill Book Company. .]
* A trickling filter, roughing filter, to reduce the biochemical oxygen demand of wastewater.
* A carbon filtration plant, to remove toxic dissolved organic compounds from wastewater.
* An advanced electrodialysis reversal (EDR) system with
ion-exchange membrane An ion-exchange membrane is a semi-permeable membrane that transports certain dissolved ions, while blocking other ions or neutral molecules.
Ion-exchange membranes are therefore electrically conductive. They are often used in desalination and c ...
s.
Brine treatment
Brine treatment involves removing dissolved salt ions from the waste stream. Although similarities to seawater or brackish water desalination exist, industrial brine treatment may contain unique combinations of dissolved ions, such as hardness ions or other metals, necessitating specific processes and equipment.
Brine treatment systems are typically optimized to either reduce the volume of the final discharge for more economic disposal (as disposal costs are often based on volume) or maximize the recovery of fresh water or salts. Brine treatment systems may also be optimized to reduce electricity consumption, chemical usage, or physical footprint.
Brine treatment is commonly encountered when treating cooling tower blowdown,
produced water
Produced water is a term used in the oil industry or geothermal industry to describe water that is produced as a byproduct during the extraction of oil and natural gas, or used as a medium for heat extraction. Produced water is the kind of brackis ...
from steam-assisted gravity drainage (SAGD), produced water from natural gas extraction such as Coalbed methane, coal seam gas, frac flowback water, Acid mine drainage, acid mine or acid rock drainage, reverse osmosis reject, Chloralkali process, chlor-alkali wastewater, pulp and paper mill effluent, and waste streams from food and beverage processing.
Brine treatment technologies may include: membrane filtration processes, such as reverse osmosis; ion-exchange processes such as
electrodialysis
Electrodialysis (ED) is used to transport salt ions from one solution through ion-exchange membranes to another solution under the influence of an applied electric potential difference. This is done in a configuration called an electrodialysis ...
or Ion-exchange resin, weak acid cation exchange; or evaporation processes, such as brine concentrators and Crystallization#Evaporative crystallizers, crystallizers employing mechanical vapour recompression and steam. Due to the ever increasing discharge standards, there has been an emergence of the use of Advanced oxidation process, advance oxidation processes for the treatment of brine. Some notable examples such as Fenton's reagent, Fenton's oxidation and Ozone, ozonation have been employed for degradation of recalcitrant compounds in brine from industrial plants.
Reverse osmosis may not be viable for brine treatment, due to the potential for fouling caused by hardness salts or organic contaminants, or damage to the reverse osmosis membranes from hydrocarbons.
Evaporation processes are the most widespread for brine treatment as they enable the highest degree of concentration, as high as solid salt. They also produce the highest purity effluent, even distillate-quality. Evaporation processes are also more tolerant of organics, hydrocarbons, or hardness salts. However, energy consumption is high and corrosion may be an issue as the prime mover is concentrated salt water. As a result, evaporation systems typically employ titanium or Stainless steel#Types of stainless steel, duplex stainless steel materials.
Brine management
Brine management examines the broader context of brine treatment and may include consideration of government policy and regulations, corporate sustainability, environmental impact, recycling, handling and transport, containment, centralized compared to on-site treatment, avoidance and reduction, technologies, and economics. Brine management shares some issues with Leachate#Leachate management, leachate management and more general waste management. In the recent years, there has been greater prevalence in brine management due to global push for zero liquid discharge (ZLD)/minimal liquid discharge (MLD). In ZLD/MLD techniques, a closed water cycle is used to minimize water discharges from a system for water reuse. This concept has been gaining traction in recent years, due to increased water discharges and recent advancement in membrane technology.
Solids removal
Most solids can be removed using simple sedimentation techniques with the solids recovered as slurry or sludge. Very fine solids and solids with densities close to the density of water pose special problems. In such case filtration or ultrafiltration may be required. Although flocculation may be used, using alum salts or the addition of polyelectrolytes. Wastewater from industrial food processing often requires on-site treatment before it can be discharged to prevent or reduce sewer surcharge fees. The type of industry and specific operational practices determine what types of wastewater is generated and what type of treatment is required. Reducing solids such as waste product, organic materials, and sand is often a goal of industrial wastewater treatment. Some common ways to reduce solids include primary sedimentation (clarification), dissolved air flotation (DAF), belt filtration (microscreening), and drum screening.
Oils and grease removal
The effective removal of oils and grease is dependent on the characteristics of the oil in terms of its suspension state and droplet size, which will in turn affect the choice of separator technology. Oil in industrial waste water may be free light oil, heavy oil, which tends to sink, and emulsified oil, often referred to as soluble oil. Emulsified or soluble oils will typically required "cracking" to free the oil from its emulsion. In most cases this is achieved by lowering the pH of the water matrix.
Most separator technologies will have an optimum range of oil droplet sizes that can be effectively treated. Each separator technology will have its own performance curve outlining optimum performance based on oil droplet size. the most common separators are gravity tanks or pits, API oil-water separators or plate packs, chemical treatment via dissolved air flotations, centrifuges, media filters and hydrocyclones.
Analyzing the oily water to determine droplet size can be performed with a video particle analyser.
API oil-water separators
Hydrocyclone oil separators
Hydrocyclone, Hydrocyclone oil separators operate on the process where wastewater enters the cyclone chamber and is spun under extreme centrifugal forces more than 1000 times the force of gravity. This force causes the water and oil droplets to separate. The separated oil is discharged from one end of the cyclone where treated water is discharged through the opposite end for further treatment, filtration or discharge.
Removal of biodegradable organics
Biodegradable organic material of plant or animal origin is usually possible to treat using extended conventional
sewage treatment
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 for discharge to the surrounding e ...
processes such as
activated sludge
The activated sludge process is a type of biological wastewater treatment process for treating sewage or industrial wastewaters using aeration and a biological floc composed of bacteria and protozoa. It uses air (or oxygen) and microorganism ...
or trickling filter.
Problems can arise if the wastewater is excessively diluted with washing water or is highly concentrated such as undiluted blood or milk. The presence of cleaning agents, disinfectants, pesticides, or antibiotics can have detrimental impacts on treatment processes.
Activated sludge process
Trickling filter process
A trickling filter consists of a bed of Rock (geology), rocks, gravel, slag, peat moss, or plastic media over which wastewater flows downward and contacts a layer (or film) of microbial slime covering the bed media. wikt:aerobic, Aerobic conditions are maintained by forced air flowing through the bed or by natural convection of air. The process involves adsorption of organic compounds in the wastewater by the microbial slime layer, diffusion of air into the slime layer to provide the oxygen required for the biochemical oxidation of the organic compounds. The end products include carbon dioxide gas, water and other products of the oxidation. As the slime layer thickens, it becomes difficult for the air to penetrate the layer and an inner anaerobic layer is formed.
Removal of other organics
Synthetic organic materials including solvents, paints, pharmaceuticals, pesticides, products from coke production and so forth can be very difficult to treat. Treatment methods are often specific to the material being treated. Methods include advanced oxidation processing, distillation, adsorption, Glass transition, ozonation, vitrification, incineration, chemical immobilisation or landfill disposal. Some materials such as some detergents may be capable of biological degradation and in such cases, a modified form of wastewater treatment can be used.
Removal of acids and alkalis
Acids and alkalis can usually be Neutralization (chemistry), neutralised under controlled conditions. Neutralisation frequently produces a Precipitation (chemistry), precipitate that will require treatment as a solid residue that may also be toxic. In some cases, gases may be evolved requiring treatment for the gas stream. Some other forms of treatment are usually required following neutralisation.
Waste streams rich in hard water, hardness ions as from de-ionisation processes can readily lose the hardness ions in a buildup of precipitated calcium and magnesium salts. This precipitation process can cause severe ''furring'' of pipes and can, in extreme cases, cause the blockage of disposal pipes. A 1-metre diameter industrial marine discharge pipe serving a major chemicals complex was blocked by such salts in the 1970s. Treatment is by concentration of de-ionisation waste waters and disposal to landfill or by careful pH management of the released wastewater.
Removal of toxic materials
Toxic materials including many organic materials, metals (such as zinc, silver, cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...
, thallium, etc.) acids, alkalis, non-metallic elements (such as arsenic or selenium
Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, ...
) are generally resistant to biological processes unless very dilute. Metals can often be precipitated out by changing the pH or by treatment with other chemicals. Many, however, are resistant to treatment or mitigation and may require concentration followed by landfilling or recycling. Dissolved organics can be ''incinerated'' within the wastewater by the advanced oxidation process.
Smart capsules
Molecular encapsulation is a technology that has the potential to provide a system for the recyclable removal of lead and other ions from polluted sources. Nano-, micro- and milli- capsules, with sizes in the ranges 10 nm–1μm,1μm–1mm and >1mm, respectively, are particles that have an active reagent (core) surrounded by a carrier (shell).There are three types of capsule under investigation: alginate-based capsules, carbon nanotubes, polymer swelling capsules. These capsules provide a possible means for the remediation of contaminated water.
Removal of thermal pollution
To remove heat from wastewater generated by Power station, power plants or Factory, manufacturing plants, and thus to reduce thermal pollution
Thermal pollution, sometimes called "thermal enrichment", is the degradation of water quality by any process that changes ambient water temperature. Thermal pollution is the rise or fall in the temperature of a natural body of water caused by hum ...
, the following technologies are used:
*cooling ponds, engineered bodies of water designed for cooling by evaporation, convection, and radiation
*cooling towers, which transfer waste heat to the atmosphere through evaporation or heat transfer
*cogeneration, a process where waste heat is recycled for domestic or industrial heating purposes.
Other disposal methods
Some facilities such as oil and gas wells may be permitted to pump their wastewater underground through injection wells. However, wastewater injection has been linked to induced seismicity.
Costs and trade waste charges
Disposal of wastewaters from an industrial plant is a difficult and costly problem. Although economies of scale may favor use of a large municipal sewage treatment plant for disposal of small volumes of industrial wastewater, industrial wastewater treatment and disposal may be less expensive than correctly apportioned costs for larger volumes of industrial wastewater not requiring the conventional sewage treatment sequence of a small municipal sewage treatment plant.
Industrial wastewater plants may reduce raw water costs by converting selected wastewaters to reclaimed water used for different purposes. Industrial wastewater treatment plants may reduce wastewater treatment charges collected by municipal sewage treatment plants by pre-treating wastewaters to reduce concentrations of pollutants measured to determine user fees.
Society and culture
Global goals
The international community has defined the treatment of industrial wastewater as an important part of sustainable development by including it in Sustainable Development Goal 6. Target 6.3 of this goal is to "By 2030, improve water quality by reducing Water pollution, pollution, eliminating dumping and minimizing release of Dangerous goods, hazardous chemicals and materials, halving the proportion of Wastewater treatment, untreated wastewater and substantially increasing recycling and Reclaimed water, safe reuse globally". One of the indicators for this target is the "proportion of domestic and industrial wastewater flows safely treated".[Ritchie, Roser, Mispy, Ortiz-Ospina.]
Measuring progress towards the Sustainable Development Goals, Goal 6
''SDG-Tracker.org, website'' (2018).
See also
* Best management practice for water pollution (BMP)
* List of waste water treatment technologies
* Purified water (for industrial use)
* Water purification (for drinking water)
References
Further reading
*
External links
Water Environment Federation
- Professional society
Industrial Wastewater Treatment Technology Database
- EPA
{{waste
Waste treatment technology
Sewerage
Industrial processes
Water pollution
Sanitation
cs:Čištění odpadních vod