What are industrial discharges in water and their treatment

The Waters They can be defined as the introduction of intentional pollutants or accidentally in the water masses. These direct or indirectly dumping They alter and harm water quality and, therefore, of the ecosystem assuming a threat to the communities of living beings that inhabit it.

Exist Three types of main spills:

• Agricultural or livestock.
• Urban.
• Industrialists

But they are in the latter on which we are going to focus our attention. The industrial spills They are those that come from the industry and are the most dangerous and polluting.

He Ministry for Ecological Transition of Spain It has established a general classification of discharges that, therefore, can also be applied to industrial discharges. According to this, spills can be classified as direct and indirect.

• Direct spills: They are those that are thrown directly into the continental waters (river courses, transition waters, coasts, lakes and lagoons, groundwater, etc.) or any other element belonging to the public hydraulic domain (surface waters, channels of the rivers and beds of lakes and reservoirs. Private waters or marine waters are not included). Those discharges that are injected directly into the ground and therefore contaminate groundwater are also included.
• Indirect spills: They are those that are carried out in the continental waters or in other elements of the public hydraulic domain through ditches, channels or wastewater or rainwater collection systems (storm tanks). In the case of groundwater these are those discharges that are filtered through the ground and the subsoil.

The law also contemplates some special cases, for example, the discharges to irrigation channels are considered direct, since they are poured into the water that belongs to the public hydraulic domain. Ramblas poured can be considered direct because they are poured into their waters or channel when it is dry and indirect to groundwater since they can infiltrate the ground. Finally, those discharges that are made to surface waters that can affect the quality of the receiving waters are considered indirect.

Once we know what industrial discharges are and what their classification is, we will talk about the Types of industrial discharges that exist. There is a great typology of industries and depending on the type these can generate more or less polluting waste than others. Next, we will explain the class of waste that can generate some of the main industries.

• Construction: The waste is rich in suspended solids, metals and can cause the variation of the pH of the receiving waters.
• Mining: It also produces suspended solids, heavy metals and can alter the pH. In addition, it generates organic matter and cyanides.
• Textile and skin: Waste from these industries can contain metals such as chromium, tannins, tenseactive substances, sulphides, dyes and dyes, fats, solvents, acids (acetic, formic, etc.) and suspended solids. Within these solids are synthetic textile fibers that are considered microplastics.
• Automotive: It is one of the most polluting industries. It produces oils, lubricants, paintings, metals, chips, fuels and wastewater.
• Naval: fundamentally oil, chemicals, solvents and pigments or dyes.
• Siderúrgica: Heavy metals, acids and bases, oils, chips and solids.
• Inorganic Chemistry: Above all chemical substances such as halogenates (fluorides), mercury waste (heavy metal), phosphorus, manganese, molybdenum, lead, silver, selenium, zinc and other compounds such as cyanides, ammonia, nitrogen compounds, acids and bases.
• Fertilizers: especially nutrients in the form of nitrates and phosphates
• Pasta and paper: Suspension solids, whitening (chlorine) and bases and other substances that can affect the amount of oxygen dissolved in receiving waters.
• Pesticides: They produce organic pollutants such as organohalogenate or organophosphate, carcinogenic, biocidal, etc.
• Chemical fibers: Oils, organic compounds and also substances that affect the amount of oxygen dissolved in the receiving waters.
• Paints, varnishes and dyes: Metal compounds such as some with zinc, chrome, selenium, molybdenum, titanium, tin, barium or cobalt among others.

Since industrial discharges can be of very different types and of different composition it is difficult to establish a general treatment that eliminates all waste. It is very important when defining the treatments to know the specific composition of each discharge, define the spills and establish the appropriate physical, chemical or biological purification methods.

Next, we are going to talk about the Treatments of industrial spills in water And what they consist of.

PRETRATATION

Although sometimes it is not present, the pretreatment is to eliminate some residual load to industrial waters before receiving treatments. Understand at least one of the following phases:

• Homogeneization: Since the flow of wastewater can vary throughout the days, the concentration resulting from pollutants will not be the same in wastewater at all times. The homogenization phase consists of that, in homogenize or match the concentration of contaminants of the waters of the industry in question. To do this, wastewater is stored in agitation tanks for days until the flows are equalized.
• Rough: necessary to protect the facilities of the entry of large objects that can obstruct and hinder the treatments. Implemented in industries such as agri -food, textile or paper.
• Degrees: It consists of cleaning oils and hydrocarbons. This process is especially important in those industries dedicated to the manufacture of these compounds or those that have grease circuits or which circulate oil substances.
• Disabled: This pretreatment is applied in industries or companies such as areneras, foundations or concrete.

Primary treatment

It is based mainly on the application of physical-chemical treatments to industrial wastewater. It may appear as the main treatment, an intermediate stage or as the final stage. Among the main treatments are:

• The precipitation of metals and toxic salts.
• The elimination of oils and suspended materials.
• The clarification, which consists in the reduction of organic matter.
• Other more generic treatments such as sedimentation, coagulation-floculation, flotation and neutralization.

Secondary treatment

It is based on the use of biological methods to purify wastewater. In order to apply this treatment, effluents or discharges must be biodegradable and their characteristics should be well known to avoid damage to biological reactors. Biological treatment is characterized by the following elements:

• Activated muds.
• Bacterial beds.
• Aerated or mixed gaps.

Tertiary treatment

When discharges contain non -biodegradable organic compounds or more complex substances such as solvents, aromatic hydrocarbons (benzene) or nitrogen and phosphorus compounds need more specialized techniques.

• Adsorption with active carbon of pollutants: By superficial attraction, the particles are adsorbed or retained in coal.
• Membrane separation: Some molecules can be separated according to their size, shape or molecular structure. They highlight reverse osmosis and microfiltration and ultrainfiltration.
• Ion exchange: It consists in the exchange of pollutants by other ions such as NA⁺h⁺ or oh^– They are present in a membrane. When the discharge passes through the membrane, the ions present in it are replaced by effluent pollutants.
• Chemical oxidation: It is achieved with the use of oxygen, ozone, chlorine … and consists in the elimination of both biodegradable and non -biodegradable organic compounds.

Learn more about this topic in this other Ecology post about the different types of wastewater treatment.

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