INDUSTRIAL WATERS: WHERE THEY COME FROM, COMPOSITION, TYPES, TREATMENTS - ENVIRONMENT - 2024

The industrial waters are those used in industrial and commercial activities, and then discarded as waste or scrap. As waste they are called industrial wastewater or sewage.

Industrial waters are used for different purposes, such as raw material, solvent, energy source and hygiene of areas, implements and personnel. They come from natural sources or from the recycling of industrial wastewater. As industrial wastewater, its sources are very diverse, depending on each of the industries where they originate.

Water in the hydroelectric industry. Source: vadimpl

The composition of industrial wastewater varies depending on the type of industry in particular, even within the same industrial branch with a great variety of chemical substances.

Industrial wastewater can contain heavy metals, colorants, fats, oils, detergents, acids and drugs. They can also include animal and plant derivatives of different nature.

The types of industrial wastewater vary according to the industry origin, the use that is given to them and the raw materials used. They can also be classified according to the predominant type of substances dissolved in them. The treatments applied to purify industrial wastewater vary depending on the type of pollutants present.

Where do industrial waters come from?

The industry receives water from the public network, wells, rivers, sea water or recycled water from the industrial processes themselves. When used in various processes such as facility washing, use as a solvent, energy production, distillation, filtration and personal hygiene, wastewater is produced.

The paper and cardboard industry

It is one of the industries that consumes the most water in its processes and at the same time generates a large amount of industrial waste water. This industry consumes 27% of the industrial water of the entire industry.

Only 5 to 10% of the water used is consumed, being necessary to process the rest as industrial waste water.

Textile industry

Water in the textile industry. Source: Enric

It has a high consumption of water and a large generation of industrial wastewater and for each kilo of textile material, about 200 liters of water are required. On the other hand, industrial wastewater reaches high levels of contamination, due to the use of various chemical substances.

Chemical industry

It has a high water consumption and generates large amounts of industrial wastewater. The contamination of these waters is high and the dissolved contaminants are highly toxic in most cases.

Agribusiness

It consumes about 17% of industrial water, although in some areas such as the beverage industries most of it is incorporated into the final product. Within this branch, industrial wastewater varies enormously depending on the specific industry. Among others are the meat, dairy, beverage, canning and sugar industries.

Pharmaceutical industry

Industrial wastewater from the pharmaceutical industry is causing serious pollution problems. This is especially true in countries such as India and China, where there are few controls on industrial discharges.

In these industrial waters there are drugs, such as antibiotics, that once in the environment can generate resistance in strains of pathogenic bacteria.

Mining and metal processing

Large amounts of water are consumed, using it as a hydraulic impulse to disintegrate the rock in search of minerals. Subsequently, in the metal processing industry water is used primarily as a coolant.

Thermoelectric and nuclear plants

In these energy-generating industries, water is used as a refrigerant, producing large amounts of industrial wastewater. These waters are highly polluting, and can contain heavy metals and even radioactive elements.

Composition

Industrial wastewater. Source: Nigel Wylie

The composition of industrial wastewater is extremely variable, as it depends on the industrial processes that produce it. In general terms, they have a relatively low content of organic matter and heavy metals are the main pollutants in industrial wastewater.

Heavy metals

The main pollutants in this group are lead, mercury, cadmium and arsenic. Heavy metals are waste products in various industries, especially metal processing, oil, and chemicals.

In specific cases such as mercury, an important source is industrial wastewater from coal-based thermoelectric plants.

Hydrocarbons

They are incorporated into industrial wastewater by various industries, especially oil and petrochemicals.

Phenols

They are especially relevant in industrial wastewater from the leather tanning industry.

Surfactants

These are soaps and detergents and are found in many types of industrial wastewater. This is because they are widely used in cleaning areas and implements, as well as in the processing of raw materials. They are particularly polluting due to their negative effect on cell membranes.

Colorants

A wide variety of colorants are used in different industrial branches, for example in the paper, textile, food and chemical industries.

Fibers and cellulose

In industrial wastewater from the paper and textile industries, the presence of plant components such as fibers and cellulose is relevant.

Organic material

Industrial wastewater from the food processing industry is particularly rich in organic matter, of both plant and animal origin. In addition, they can incorporate a variety of microorganisms, some of them pathogens for animals, plants or humans.

Various chemicals

Industry uses a wide variety of chemicals in industrial processes, either as raw materials or as mediators of different reactions. Many of these elements and chemical compounds go as polluting waste in industrial waters.

Drugs

One of the large industrial branches is pharmaceuticals, which uses different organic and inorganic chemicals. With these medicinal compounds are made, traces of which in many cases end up in industrial wastewater.

Drugs have become emerging pollutants, of great relevance in public health. Relevant amounts of antibiotics, analgesics and other drugs have been detected in some bodies of water.

Types of industrial waters

Industrial waters can be classified from different points of view, either by the use made of them by industry or by industrial sector. In each case, the characteristics of the resulting industrial wastewater will vary.

- For its use

Sanitary

They are used in cleaning processes of raw materials, facilities, equipment and in the hygienic needs of personnel.

Heat transfer or cooling

In this case, industrial waters serve as thermal vehicles, either to extract heat from a process or to transmit it to it. For example, use as a refrigerant in the metal processing industry and for cooking in the food industry.

Steam production

Water steam is used to drive steam turbines as well as in sterilization, heating, cleaning, hydration and humification processes.

Raw material

Industrial water is used directly as a raw material, especially in the food and beverage industry, and most of it leaves the system as part of the product.

Solvent

The character of water as a universal solvent makes this an important use of industrial water. In many processes in the chemical, food, paper, textile industries, among others, it is used for this purpose and generates large amounts of industrial wastewater.

Power source

Water is also used to generate hydraulic energy, in the hydroelectric industry. It has low levels of chemical contamination, but thermal contamination is important.

Treatment plants

Industrial water treatment plant. Source: Annabel

In the wastewater treatment process, a final residue is generated that can be recycled in the same process. However, a certain amount is not recoverable as in sedimentation treatments where up to 75% of the weight of the final sludge is water.

- By industrial branch

Industrial waters can also be classified as branches of different industries such as petrochemical, food, paper, textile, metalworking, mining, among others. In each case in turn, the classification of industrial waters can be subdivided according to the specialization of the specific industrial plant.

Treatments

Industrial water treatment plant. Source: Xavigivax

Depending on the type of industry, the processes and the raw materials used, the quantity and characteristics of industrial wastewater will depend. The selection of the treatment to purify them is associated with the type of wastewater and the degree of purification required.

- Parameters

Both prior to any treatment, and subsequently, it is necessary to evaluate certain quality parameters of industrial wastewater. These include chemical oxygen demand (COD), total suspended solids (TSS) and the presence of specific compounds.

Chemical oxygen demand

It is the most prominent parameter in the evaluation of water pollution, when measuring the amount of oxidizable substances present in the water. It is aimed especially at establishing the amount of organic matter present as a consumer factor for dissolved oxygen.

Total suspended solids

This parameter is very important in industrial wastewater that has been used as a solvent or cleaning. The quantity of solid non-sedimentable particles contained in industrial wastewater is measured.

Detection of specific compounds

Depending on the nature of the industrial wastewater, it is tested for specific elements or compounds. For example, the presence of heavy metals, organohalogen compounds, dioxins, among others.

- Treatment procedures

There are primary treatment procedures that include sedimentation and flotation phases that allow the separation of a portion of pollutants. In this case it is about those material particles that either settle due to their weight or float due to their density.

For non-sedimentable particles, coagulation-flocculation or chemical precipitation is used.

Coagulation-flocculation

To achieve sedimentation of the non-sedimentable suspended particles, a coagulant is added to the industrial wastewater. This is a compound that attracts said suspended particles forming flocs or clots that are extracted in a sedimentation tank.

Other primary processes

There are many specific processes, for example lime softening to remove calcium and magnesium salts from industrial waters.

Secondary treatments

Once the previous treatments have been applied, the industrial waters are subjected to different secondary treatments. Among these are activated sludge or sludge (aerobic biodegradation), anaerobic biodegradation, chemical oxidation, among others.

Tertiary treatments

Finally, third-order treatments such as filtering, ion exchange or extraction are applied to industrial wastewater. There is also reverse osmosis, incineration or electrochemical treatments.

Other disinfection treatments are ozonation, ultraviolet radiation, heat, or chlorination. Some are very specific such as degassing or stripping, to separate hydrogen sulfide, ammonia, alcohols, phenols and sulfides.

References

1. Changing Markets and Ecostorm (2016). Antibiotic resistance: How pollution from drug factories in India and China is triggering the emergence of superbugs. Spanish translation of Ecologists in Action.
2. COTEC Foundation for technological innovation (1999). 10. Industrial wastewater. COTEC documents on technological needs.
3. Gilpavas, E., Arbeláez-Castaño, PE, Medina-Arroyave, JD and Gómez-Atehortua, CM (2018). Treatment of wastewater from the textile industry by chemical coagulation coupled to Fenton processes intensified with low frequency ultrasound. International Journal of Environmental Pollution.
4. National Institute of Statistics (2012). Survey on the Environment in Industry. Results related to the Generation of Waste in the Industry Year 2010. Press releases.
5. López-Grimau, V. and Crespi-Rosell, M. (2015). Management of effluents from the textile industry. Project Improvement of regional economies and local development. Technological Notebook Nº 18.
6. Mänttäri, M., Viitikko, K. and Nyström, M. (2006). Nanofiltration of biologically treated effluents from the pulp and paper industry. Journal of Membrane Science.
7. Muñoz-Lucas, S. and Sánchez-García, R. (2018). Water in the food industry. Bulletin of the Spanish Society of Medical Hydrology.
8. Muzzarelli, RAA, Weckx, M., Filippini, O. and Sigon, F. (1989). Removal of trace metal ions from industrial waters, nuclear effluents and drinking water, with the aid of cross-linked N-carboxymethyl chitosan. Carbohydrate Polymers.
9. Rodríguez-Fernández-Alba, A., Pedro Letón-García, P., Rosal-García, R., Dorado-Valiño, M., Villar-Fernández, S. and Sanz-García, JM (2006). Advanced industrial wastewater treatment. Technology Watch Report 2.
10. Romero-López, T. de J., Rodríguez-Fiallo, H. and Masó-Mosqueda, A. (2016). Characterization of the wastewater generated in a Cuban textile industry. Hydraulic and Environmental Engineering.