Jump to content

Industrial wastewater treatment: Difference between revisions

From Wikipedia, the free encyclopedia
Browse history interactively
← Previous editNext edit →
Content deleted Content added
VisualWikitext
→‎Pollutants: I feel that a sub-heading is not needed at this place and have included those words in the sentence.
→‎Overview: moved from wastewater and re-arranged a bit but there might still be duplication
Line 9: Line 9:


{{TOC level|3}}
{{TOC level|3}}

== Sources of industrial wastewater ==
===Overview===
== Overview ==
Industrial processes may generate the following industrial wastewater flows:

* [[Backwashing (water treatment)]], flushing accumulated particles from filter beds
* [[Boiler blowdown]], impurities concentrated by steam generation
* [[Cooling water]], released with potential thermal pollution after use to condense steam or reduce machinery temperatures by conduction or evaporation
* [[Brine]], waste streams from water softening, ion exchange, reverse osmosis, or desalination
* [[Wet scrubber]] effluent, containing pollutants removed from smokestack combustion gases to meet air quality goals
* [[Acid mine drainage]], from dewatering coal and metal mines
⚫
* [[Produced water]], a byproduct from oil and natural gas production


Activities producing industrial wastewater include:{{citation needed|date=June 2021}}
Activities producing industrial wastewater include:{{citation needed|date=June 2021}}
Line 18: Line 27:
*Organic or [[Biodegradation|biodegradable]] waste including waste from [[hospital]]s, [[abattoir]]s, [[creamery|creameries]], and [[food]] factories.
*Organic or [[Biodegradation|biodegradable]] waste including waste from [[hospital]]s, [[abattoir]]s, [[creamery|creameries]], and [[food]] factories.
*Organic or non bio-degradable waste that is difficult-to-treat from [[pharmaceutical]]<ref>{{Cite journal|last1=Naddeo|first1=V.|last2=Meriç|first2=S.|last3=Kassinos|first3=D.|last4=Belgiorno|first4=V.|last5=Guida|first5=M.|date=September 2009|title=Fate of pharmaceuticals in contaminated urban wastewater effluent under ultrasonic irradiation|journal=Water Research|language=en|volume=43|issue=16|pages=4019–4027|doi=10.1016/j.watres.2009.05.027|pmid=19589554}}</ref> or [[pesticide]] manufacturing
*Organic or non bio-degradable waste that is difficult-to-treat from [[pharmaceutical]]<ref>{{Cite journal|last1=Naddeo|first1=V.|last2=Meriç|first2=S.|last3=Kassinos|first3=D.|last4=Belgiorno|first4=V.|last5=Guida|first5=M.|date=September 2009|title=Fate of pharmaceuticals in contaminated urban wastewater effluent under ultrasonic irradiation|journal=Water Research|language=en|volume=43|issue=16|pages=4019–4027|doi=10.1016/j.watres.2009.05.027|pmid=19589554}}</ref> or [[pesticide]] manufacturing
*Extreme [[pH]] waste from [[acid]] and [[alkali]] manufacturing
*Extreme [[pH]] waste from [[acid]] and [[alkali]] manufacturing
*[[Toxic waste]] from metal [[plating]], [[cyanide]] production, [[pesticide]] manufacturing, etc.
*[[Toxic waste]] from metal [[plating]], [[cyanide]] production, [[pesticide]] manufacturing, etc.
*[[Solids]] and [[emulsion]]s from [[paper]] mills, factories producing lubricants or hydraulic [[oil]]s, foodstuffs, etc.
*[[Solids]] and [[emulsion]]s from [[paper]] mills, factories producing lubricants or hydraulic [[oil]]s, foodstuffs, etc.
*Water produced [[dewatering]] mines may contain radionuclides or heavy metals either in suspension or dissolved in [[acid mine drainage]]
*Water produced [[dewatering]] mines may contain radionuclides or heavy metals either in suspension or dissolved in [[acid mine drainage]]
*Water used in [[hydraulic fracturing]]
*Water used in [[hydraulic fracturing]]
== Industrial processes ==
⚫
*[[Produced water]] from oil & natural gas production

===Battery manufacturing===
===Battery manufacturing===
[[Electric battery|Battery]] 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, oil & grease, silver and zinc.<ref>{{cite web |url=https://www.epa.gov/eg/battery-manufacturing-effluent-guidelines |title=Battery Manufacturing Effluent Guidelines |author=<!--Not stated--> |date=2017-06-12 |publisher=U.S. Environmental Protection Agency (EPA) |location=Washington, D.C.}}</ref>
[[Electric battery|Battery]] 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, oil & grease, silver and zinc.<ref>{{cite web |url=https://www.epa.gov/eg/battery-manufacturing-effluent-guidelines |title=Battery Manufacturing Effluent Guidelines |author=<!--Not stated--> |date=2017-06-12 |publisher=U.S. Environmental Protection Agency (EPA) |location=Washington, D.C.}}</ref>

Revision as of 12:43, 24 August 2021

Wastewater from an industrial process can be converted at a treatment plant to solids and treated water for reuse.
Part of a series on
Pollution
Air pollution from a factory
Air
Biological
Digital
Electromagnetic
Natural
Noise
Radiation
Soil
Solid waste
Space
Thermal
Visual
War
Water
Topics
Misc
Lists
Categories

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 or to a surface water in the environment. Some industrial facilities generate wastewater that can be treated in sewage treatment plants. Most industrial processes, such as petroleum refineries, chemical and petrochemical plants have their own specialized facilities to treat their wastewaters so that the pollutant concentrations in the treated wastewater comply with the regulations regarding disposal of wastewaters into sewers or into rivers, lakes or oceans.[1]: 1412  This applies to industries that generate wastewater with high concentrations of organic matter (e.g. oil and grease), toxic pollutants (e.g. heavy metals, volatile organic compounds) or nutrients such as ammonia.[2]: 180  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.[3]: 60 

Most industries produce some wastewater. 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, through a process called pollution prevention.[4] Sources of industrial wastewater include battery manufacturing, electric power plants, food industry, iron and steel industry, mines and quarries, nuclear industry, oil and gas extraction, organic chemicals manufacturing, petroleum refining and petrochemicals, pulp and paper industry, smelters, textile mills, industrial oil contamination, water treatment, 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, removal of toxic materials.

Overview

Industrial processes may generate the following industrial wastewater flows:

  • Backwashing (water treatment), flushing accumulated particles from filter beds
  • Boiler blowdown, impurities concentrated by steam generation
  • Cooling water, released with potential thermal pollution after use to condense steam or reduce machinery temperatures by conduction or evaporation
  • Brine, waste streams from water softening, ion exchange, reverse osmosis, or desalination
  • Wet scrubber effluent, containing pollutants removed from smokestack combustion gases to meet air quality goals
  • Acid mine drainage, from dewatering coal and metal mines
  • Produced water, a byproduct from oil and natural gas production

Activities producing industrial wastewater include:[citation needed]

Industrial processes

Battery manufacturing

Battery 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, oil & grease, silver and zinc.[6]

Electric power plants

Illustration of wastewater streams discharged by typical coal-fired electric power plants in the United States.

Fossil-fuel power stations, particularly coal-fired plants, are a major source of industrial wastewater. Many of these plants discharge wastewater with significant levels of metals such as lead, mercury, cadmium and chromium, as well as arsenic, selenium and nitrogen compounds (nitrates and nitrites). Wastewater streams include flue-gas desulfurization, fly ash, bottom ash and flue gas mercury control. Plants with air pollution controls such as wet scrubbers typically transfer the captured pollutants to the wastewater stream.[7]

Ash ponds, 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) 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, biological treatment (such as an activated sludge process), membrane systems, and evaporation-crystallization systems.[7] Technological advancements in ion-exchange membranes and electrodialysis systems has enabled high efficiency treatment of flue-gas desulfurization wastewater to meet recent EPA discharge limits.[8] The treatment approach is similar for other highly scaling industrial wastewaters.

Food industry

Seafood processing waste discharged to the town harbor in Sitka, Alaska

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 plants throughout the world: it is biodegradable and non-toxic, but has high Biological Oxygen Demand (BOD) and suspended solids (SS).[9] 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.[10]

Dairy processing plants generate conventional pollutants (BOD, SS).[11]

Animal slaughter and processing produces organic waste from body fluids, such as blood, and gut contents. Pollutants generated include BOD, SS, coliform bacteria, oil and grease, organic nitrogen and ammonia.[12]

Processing food for sale produces wastes generated from cooking which are often rich in plant organic material and may also contain salt, flavourings, colouring material and acids or alkali. Very significant quantities of oil or fats may also be present.

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 and cyanide. Production of coke from coal in coking plants also requires water cooling and the use of water in by-products separation. Contamination of waste streams includes gasification products such as benzene, naphthalene, anthracene, cyanide, ammonia, phenols, cresols together with a range of more complex organic compounds known collectively as polycyclic aromatic hydrocarbons (PAH).[13]

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 oils, tallow 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 or chromium plating or for other surface treatments such as galvanisation or painting. The two acids commonly used are hydrochloric acid 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 or ferrous chloride 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, ingots) 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). Wastewater generated from these plants may contain heavy metals such as cadmium, chromium, copper, lead, nickel, silver and zinc; cyanide and various organic chemical solvents; and oil and grease.[14][15]

Mines and quarries

Mine wastewater effluent in Peru, with neutralized pH from tailing runoff.

The principal waste-waters associated with mines and quarries 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.[16] Some specialized separation operations, such as coal washing to separate coal from native rock using density gradients, can produce wastewater contaminated by fine particulate haematite and surfactants. Oils and hydraulic oils are also common contaminants.[17]

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 and other materials such as arsenic. Extraction of high value metals such as gold and silver may generate slimes containing very fine particles in where physical removal of contaminants becomes particularly difficult.[18]

Additionally, the geologic formations that harbour economically valuable metals such as copper 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, which is often rich in heavy metals (because acids dissolve metals), is one of the many environmental impacts of mining.[18]

Nuclear industry

The waste production from the nuclear and radio-chemicals industry is dealt with as Radioactive waste.

Researchers have looked at the bioaccumulation of strontium by Scenedesmus spinosus (algae) in simulated wastewater. The study claims a highly selective biosorption capacity for strontium of S. spinosus, suggesting that it may be appropriate for use of nuclear wastewater.[19]

Oil and gas extraction

Oil and gas well operations generate produced water, which may contain oils, toxic metals (e.g. arsenic, cadmium, chromium, mercury, lead), salts, organic chemicals and solids. Some produced water contains traces of naturally occurring radioactive material. Offshore oil and gas platforms also generate deck drainage, domestic waste and sanitary waste. During the drilling process, well sites typically discharge drill cuttings and drilling mud (drilling fluid).[20]

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, chloroform, naphthalene, phenols, toluene and vinyl chloride. Biochemical oxygen demand (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, lead, nickel and zinc.[21]

Petroleum refining and petrochemicals

Pollutants discharged at petroleum refineries and petrochemical plants include conventional pollutants (BOD, oil and grease, suspended solids), ammonia, chromium, phenols and sulfides.[22]

Pulp and paper industry

Wastewater discharge from a paper mill in the United States

Effluent from the pulp and paper industry is generally high in suspended solids and BOD. Plants that bleach wood pulp for paper making may generate chloroform, dioxins (including 2,3,7,8-TCDD), furans, phenols and chemical oxygen demand (COD).[23] Stand-alone paper mills using imported pulp may only require simple primary treatment, such as sedimentation or dissolved air flotation. Increased BOD or COD loadings, as well as organic pollutants, may require biological treatment such as activated sludge or 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.

See also: Environmental impact of paper

Smelters

The pollutants discharged by nonferrous smelters vary with the base metal ore. Bauxite smelters generate phenols[24]: 131  but typically use settling basins and evaporation to manage these wastes, with no need to routinely discharge wastewater.[24]: 395  Aluminum smelters typically discharge fluoride, benzo(a)pyrene, antimony and nickel, as well as aluminum. Copper smelters typically generate cadmium, 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.[25]

Typical treatment processes used in the industry are chemical precipitation, sedimentation and filtration.[24]: 145 

Textile mills

Textile mills, including carpet manufacturers, generate wastewater from a wide variety of processes, including cleaning and finishing, yarn manufacturing and fabric finishing (such as bleaching, dyeing, resin treatment, waterproofing and retardant flameproofing). Pollutants generated by textile mills include BOD, SS, oil and grease, sulfide, phenols and chromium.[26] 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)[27] 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, TSS and heavy metals (chromium, zinc, 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 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 preserving plants generate conventional and toxic pollutants, including arsenic, COD, copper, chromium, abnormally high or low pH, phenols, oil & grease, and suspended solids.[28]

Pollutants

The composition of industrial wastewater varies widely. This is a partial list of chemical or physical pollutants that may be contained in industrial wastewater:

Treatment methods

Dissolved air flotation systems are widely used at oil refineries, chemical plants and paper mills

Overview

The various types of contamination of wastewater require a variety of strategies to remove the contamination.[1] Most industrial processes, such as petroleum refineries, chemical and petrochemical 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.[1]: 1412  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.[33]

An industrial wastewater treatment plant may include one or more of the following rather than the conventional treatment sequence of sewage treatment plants:

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 from steam assisted gravity drainage (SAGD), produced water from natural gas extraction such as coal seam gas, frac flowback water, acid mine or acid rock drainage, reverse osmosis reject, 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 or weak acid cation exchange; or evaporation processes, such as brine concentrators and crystallizers employing mechanical vapour recompression and steam.

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 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 management and more general waste management.

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 or (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.

Analyzing the oily water to determine droplet size can be performed with a video particle analyser. 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 DAFs, centrifuges, media filters and hydrocyclones.

API separators
Main article: API oil-water separator
A typical API oil-water separator used in many industries

Many oils can be recovered from open water surfaces by skimming devices. Considered a dependable and cheap way to remove oil, grease and other hydrocarbons from water, oil skimmers can sometimes achieve the desired level of water purity. At other times, skimming is also a cost-efficient method to remove most of the oil before using membrane filters and chemical processes. Skimmers will prevent filters from blinding prematurely and keep chemical costs down because there is less oil to process.

Because grease skimming involves higher viscosity hydrocarbons, skimmers must be equipped with heaters powerful enough to keep grease fluid for discharge. If floating grease forms into solid clumps or mats, a spray bar, aerator or mechanical apparatus can be used to facilitate removal.[36]

However, hydraulic oils and the majority of oils that have degraded to any extent will also have a soluble or emulsified component that will require further treatment to eliminate. Dissolving or emulsifying oil using surfactants or solvents usually exacerbates the problem rather than solving it, producing wastewater that is more difficult to treat.

The wastewaters from large-scale industries such as oil refineries, petrochemical plants, chemical plants, and natural gas processing plants commonly contain gross amounts of oil and suspended solids. Those industries use a device known as an API oil-water separator which is designed to separate the oil and suspended solids from their wastewater effluents. The name is derived from the fact that such separators are designed according to standards published by the American Petroleum Institute (API).[37][38]

The API separator is a gravity separation device designed by using Stokes Law to define the rise velocity of oil droplets based on their density and size. The design is based on the specific gravity difference between the oil and the wastewater because that difference is much smaller than the specific gravity difference between the suspended solids and water. The suspended solids settles to the bottom of the separator as a sediment layer, the oil rises to top of the separator and the cleansed wastewater is the middle layer between the oil layer and the solids.[37]

Typically, the oil layer is skimmed off and subsequently re-processed or disposed of, and the bottom sediment layer is removed by a chain and flight scraper (or similar device) and a sludge pump. The water layer is sent to further treatment for additional removal of any residual oil and then to some type of biological treatment unit for removal of undesirable dissolved chemical compounds.

A typical parallel plate separator[39]

Parallel plate separators are similar to API separators but they include tilted parallel plate assemblies (also known as parallel packs). The parallel plates provide more surface for suspended oil droplets to coalesce into larger globules. Such separators still depend upon the specific gravity between the suspended oil and the water. However, the parallel plates enhance the degree of oil-water separation. The result is that a parallel plate separator requires significantly less space than a conventional API separator to achieve the same degree of separation.[39]

Hydrocyclone oil separators

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 processes such as activated sludge or trickling filter.[1][37] 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.[citation needed]

Activated sludge process

Main article: Activated sludge
A generalized diagram of an activated sludge process.

Activated sludge is a biochemical process for treating sewage and industrial wastewater that uses air (or oxygen) and microorganisms to biologically oxidize organic pollutants, producing a waste sludge (or floc) containing the oxidized material. In general, an activated sludge process includes:

  • An aeration tank where air (or oxygen) is injected and thoroughly mixed into the wastewater.
  • A settling tank (usually referred to as a clarifier or "settler") to allow the waste sludge to settle. Part of the waste sludge is recycled to the aeration tank and the remaining waste sludge is removed for further treatment and ultimate disposal.[citation needed]

Trickling filter process

Main article: Trickling filter
Image 1: A schematic cross-section of the contact face of the bed media in a trickling filter
A typical complete trickling filter system

A trickling filter consists of a bed of 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. 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.[citation needed]

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, 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 neutralised under controlled conditions. Neutralisation frequently produces a 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 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, thallium, etc.) acids, alkalis, non-metallic elements (such as arsenic or selenium) 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.[40]

Removal of thermal pollution

To remove heat from wastewater generated by power plants or manufacturing plants, and thus to reduce thermal pollution, the following technologies are used:

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.[35]: 40-4–40-11 

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.[42]: 300–302 

See also

References

  1. ^ a b c d Tchobanoglous, G., Burton, F.L., and Stensel, H.D. (2003). Wastewater Engineering (Treatment Disposal Reuse) / Metcalf & Eddy, Inc (4th ed.). McGraw-Hill Book Company. ISBN 0-07-041878-0.{{cite book}}: CS1 maint: multiple names: authors list (link)
  2. ^ "Chapter 3: Analysis and Selection of Wastewater Flowrates and Constituent Loadings". Wastewater engineering : treatment and reuse. George Tchobanoglous, Franklin L. Burton, H. David Stensel, Metcalf & Eddy (4th ed.). Boston: McGraw-Hill. 2003. ISBN 0-07-041878-0. OCLC 48053912.{{cite book}}: CS1 maint: others (link)
  3. ^ Von Sperling, M. (2015). "Wastewater Characteristics, Treatment and Disposal". Water Intelligence Online. 6 (0): 9781780402086–9781780402086. doi:10.2166/9781780402086. ISSN 1476-1777.
  4. ^ "Pollution Prevention Case Studies". EPA. 3 March 2021.
  5. ^ Naddeo, V.; Meriç, S.; Kassinos, D.; Belgiorno, V.; Guida, M. (September 2009). "Fate of pharmaceuticals in contaminated urban wastewater effluent under ultrasonic irradiation". Water Research. 43 (16): 4019–4027. doi:10.1016/j.watres.2009.05.027. PMID 19589554.
  6. ^ "Battery Manufacturing Effluent Guidelines". Washington, D.C.: U.S. Environmental Protection Agency (EPA). 12 June 2017.
  7. ^ a b "Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category". EPA. 30 September 2015.
  8. ^ "Lowering Cost and Waste in Flue Gas Desulfurization Wastewater Treatment". Power Mag. Electric Power. March 2017. Retrieved 6 April 2017.
  9. ^ European Environment Agency. Copenhagen, Denmark. "Indicator: Biochemical oxygen demand in rivers (2001)." Archived 2006-09-18 at the Wayback Machine
  10. ^ EPA (2002-09-12). "Effluent Limitations Guidelines and New Source Performance Standards for the Concentrated Aquatic Animal Production Point Source Category." Proposed rule. Federal Register, 67 FR 57876
  11. ^ "Dairy Products Processing Effluent Guidelines". EPA. 30 November 2018.
  12. ^ Technical Development Document for the Final Effluent Limitations Guidelines and Standards for the Meat and Poultry Products Point Source Category (Report). EPA. 2004. EPA 821-R-04-011.
  13. ^ "7. Wastewater Characterization". Development Document for Final Effluent Limitations Guidelines and Standards for the Iron and Steel Manufacturing Point Source Category (Report). EPA. 2002. pp. 7–1ff. EPA 821-R-02-004.
  14. ^ "Metal Finishing Effluent Guidelines". EPA. 5 July 2019.
  15. ^ "Products and Machinery Effluent Guidelines". EPA. 16 July 2018.
  16. ^ Development Document for Effluent Limitations Guidelines and Standards for the Mineral Mining and Processing Category (Report). EPA. July 1979. EPA 440/1-76/059b.
  17. ^ Development Document for the Coal Mining Category (Report). EPA. September 1982. EPA 440/1-82/057.
  18. ^ a b Development Document for Final Effluent Limitations Guidelines and New Source Performance Standards for the Ore Mining and Dressing Point Source Category (Report). EPA. November 1982. EPA 440/1-82/061.
  19. ^ "Biosorption of Strontium from Simulated Nuclear Wastewater by Scenedesmus spinosus under Culture Conditions: Adsorption and Bioaccumulation Processes and Models". Int J Environ Res Public Health. 2014. doi:10.3390/ijerph110606099.
  20. ^ Development Document for Interim Final Effuent Limitations Guidelines and Proposed New Source Performance Standards for the Oil and Gas Extraction Point Source Category (Report). EPA. September 1976. pp. 41–45. EPA 440/1-76/055a.
  21. ^ Development Document for Effluent Limitations Guidelines, New Source Performance Standards and Pretreatment Standards for the Organic Chemicals, Plastics And Synthetic Fibers Point Source Category; Volume I (Report). EPA. October 1987. EPA 440/1-87/009.
  22. ^ Guide for the Application of Effluent Limitations Guidelines for the Petroleum Refining Industry (Report). EPA. June 1985. p. 5.
  23. ^ Permit Guidance Document: Pulp, Paper and Paperboard Manufacturing Point Source Category (Report). EPA. 2000. pp. 4–1ff. EPA-821-B-00-003.
  24. ^ a b c Development Document for Effluent Limitations Guidelines and Standards for the Nonferrous Metals Manufacturing Point Source Category; Volume 1 (Report). EPA. May 1989. EPA 440/1-89/019.1.
  25. ^ EPA (1984). "Nonferrous Metals Manufacturing Point Source Category." Code of Federal Regulations, 40 CFR Part 421.
  26. ^ "Textile Mills Effluent Guidelines". EPA. 30 June 2017.
  27. ^ M. Clark, ed. (2011). Handbook of Textile and Industrial Dyeing: Principles, Processes and Types of Dyes. Woodhead Publishing Series in Textiles. Cambridge, UK: Woodhead Publishing Ltd. ISBN 978-1-84569-695-5.
  28. ^ "Timber Products Processing Effluent Guidelines". EPA. 13 March 2018.
  29. ^ Arvaniti and Stasinakis, 2015. Review on the occurrence, fate and removal of perfluorinated compounds during wastewater treatment. Science of the Total Environment vol. 524-525, August 2015, p. 81-92. Arvaniti and Stasinakis, 2015
  30. ^ Bletsou et al., 2013. Mass loading and fate of linear and cyclic siloxanes in a wastewater treatment plant in Greece. Environmental Science and Technology vol. 47, January 2015, p. 1824-1832. Bletsou et al., 2013
  31. ^ Gatidou et al., 2016. Drugs of abuse and alcohol consumption among different groups of population on the Greek island of Lesvos through sewage-based epidemiology. Science of the Total Environment vol. 563-564, September 2016, p. 633-640. Gatidou et al., 2016
  32. ^ Gatidou et al. 2019. Review on the occurrence and fate of microplastics in Sewage Treatment Plants. Journal of Hazardous Materials, vol. 367, April 2019, p. 504-512. Gatidou et al., 2019
  33. ^ Byrd, J.F.; Ehrke, M.D.; Whitfield, J.I. (April 1984). "New Bleached Kraft Pulp Plant in Georgia: State of the Art Environmental Control". Journal (Water Pollution Control Federation). 56 (4): 378–385. JSTOR 25042250..
  34. ^ a b Patterson, James William (1975). Wastewater treatment technology. Ann Arbor, Mich.: Ann Arbor Science. ISBN 0-250-40086-3. OCLC 1988397.
  35. ^ a b c Kemmer, Frank N. (1979). The Nalco Water Handbook. New York: McGraw-Hill Book Company·        
  36. ^ Hobson, Tom (May 2004). "The Scoop on Oil Skimmers". Environmental Protection. Dallas, TX: 1105 Media, Inc.
  37. ^ a b c Beychok, Milton R. (1967). Aqueous Wastes from Petroleum and Petrochemical Plants (1st ed.). John Wiley & Sons. LCCN 67019834.
  38. ^ American Petroleum Institute (API) (February 1990). Management of Water Discharges: Design and Operations of Oil-Water Separators (1st ed.). American Petroleum Institute.
  39. ^ a b Beychok, Milton R. (December 1971). "Wastewater treatment". Hydrocarbon Processing: 109–112. ISSN 0887-0284.
  40. ^ Tylkowski, Bartosz; Jastrząb, Renata (2017). "Smart Capsules for Lead Removal from Industrial Wastewater". In Sigel, Astrid; Sigel, Helmut; Sigel, Roland K.O (eds.). Lead: Its Effects on Environment and Health. Vol. 17. pp. 61–78. doi:10.1515/9783110434330-004. ISBN 978-3-11-043433-0. PMID 28731297. {{cite book}}: |journal= ignored (help)
  41. ^ Profile of the Fossil Fuel Electric Power Generation Industry (Report). EPA. September 1997. p. 24. EPA/310-R-97-007.
  42. ^ Hammer, Mark J. (1975). Water and waste-water technology. New York: Wiley. ISBN 0-471-34726-4. OCLC 1176821.

Further reading

  • Water Environment Federation (2020). Industrial Wastewater Management, Treatment & Disposal; Manual of Practice FD-3 (3rd ed.). Alexandria, VA: Water Environment Federation. ISBN 978-1-57278-369-0.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Industrial_wastewater_treatment&oldid=1040417434"