Wastewater treatment methods using chemical, biological and mechanical means. Wastewater treatment methods - an analysis of the three main ways to process water.

Purification stages Wastewater industrial enterprises

Waste water treatment process production plant, as a rule, includes several stages, at each of which it is possible to use different methods of wastewater treatment and related process equipment. This situation is primarily due to the fact that many methods, especially fine wastewater treatment, cannot be used if they contain suspended solids and emulsions. In addition, most wastewater treatment methods have an upper limit on the concentrations of pollutants from which this method must clean the effluent. Therefore, there is a need for pre-treatment of wastewater before applying the main methods of their treatment. The use of staged wastewater treatment of industrial enterprises is also due to the fact that by combining several types of treatment processes it is possible to achieve the required degree of purification at minimal cost.

Different industrial productions use a different number of stages of water treatment. It depends on the organization of treatment facilities, the treatment methods used and the composition of the effluent. For the development of an information system, wastewater treatment processes should be considered on the basis of a more generalized approach.

The most rational, obviously, will be the division of the wastewater treatment process into four stages, in accordance with the division of pollutants on the basis of their state of aggregation according to the classification of Academician Kulsky.

At the first stage of wastewater treatment it is necessary to remove large particles of suspended solids and coarse impurities, neutralize toxins and remove oils from wastewater. If these pollutions are absent in wastewater, wastewater treatment should begin from the second stage, at which almost all mechanical impurities are extracted, and wastewater is also prepared for further treatment, namely, reducing the aggressiveness of wastewater, lowering unacceptable concentrations of individual pollutants. At the third stage of wastewater treatment, all pollutants are removed to a certain predetermined level. If the degree of purification is insufficient, a fourth stage of wastewater treatment is required, in which methods are used that allow the extraction of compounds that are in a soluble state.

The use of specific wastewater treatment methods or their combination at each stage of treatment is determined chemical composition And physical properties Wastewater. Depending on the presence or absence of certain classes of pollutants in the effluent, it is possible to exclude some stages of water treatment. It is not difficult to find that the second and third stages of treatment are an integral part of any technological scheme for wastewater treatment. These treatment stages - the first and second stages of wastewater treatment - are the basis of any technological treatment process. The first stage is pre-treatment, and the last stage is deep wastewater treatment. All stages of the wastewater treatment process of a manufacturing enterprise are shown in the Figure:

Preliminary stage of wastewater treatment. When industrial effluents contain large particles of suspended solids or fibers (as in the production of ceramic and silicate materials), as well as oil products, thorough pre-treatment of wastewater is required, including:

Sedimentation of wastewater with or without the use of chemical reagents, depending on the composition of the wastewater,

Filtration through grates or mesh filters,

Effluent supply to gravel filters (coarse cleaning),

Coagulation (dosing of solutions of iron or aluminum salts),

Extraction of harmful substances from wastewater by special methods,

The use of oil traps for wastewater treatment from oil and oil.

Under certain conditions, it is necessary to dose a flocculant into wastewater to enlarge suspended and colloidal particles and the process of flocculation.

The first stage of wastewater treatment. There are many various ways primary treatment of wastewater, with different efficiencies:

Mechanical primary wastewater treatment,

Enhanced reagent pre-treatment with low chemical dosing,

Primary processing of suspended solids,

Biological wastewater treatment

The purpose of primary wastewater treatment is primarily mechanical cleaning, as well as a significant reduction in the amount of pollution. This stage is ambiguous. The methods used in it can vary greatly according to the principle of wastewater treatment.

The second stage of wastewater treatment. The second stage is the main stage of wastewater treatment, which removes most of the pollutants. When processing at this stage, along with physicochemical methods, processes of biological degradation of waste are often used. The methods used in secondary treatment are generally sufficient to treat the effluent. Nevertheless, wastewater treatment to meet the stringent MPC requirements is sometimes achieved only after the stage of deep water treatment. At this stage, more effective physical and chemical methods of water purification and desalination are used, such as nanofiltration and.

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Every day a person solves several everyday tasks that are associated with the need to spend water. Morning washing, cooking, washing dishes, washing, taking a shower or bath - this is an incomplete list of these mandatory actions. In the process of solving such problems, water is seriously polluted and becomes unsuitable for further use. In addition, various elements and particles make such a liquid dangerous for environment.

Domestic wastewater undergoes special treatment

Referred to as domestic wastewater, this water is discharged into the sewer system. Through it, the liquid is delivered to special facilities designed to remove harmful and dangerous elements. In the process of disposal in treatment systems, various methods are used so that the water at the outlet, before descending into a reservoir or ground, does not pose a danger to humans and the environment. What cleaning methods are used and how do they work?

Types of wastewater and methods for removing contaminants

All wastewater is usually divided into three types. Atmospheric drains include storm sewers, irrigation, melt and rain water. Industrial (industrial) waste liquids are the result of the activities of factories and enterprises. Domestic sewage is the result of human activity, water that enters the centralized or autonomous sewer networks.

Domestic wastewater can have three types of pollution:

Mineral.
Organic.
Biological.

Mineral pollutants include: parts of the soil, salts, chemical elements and compounds of inorganic origin. Organic pollutants include: complex elements of animal and vegetable origin, various chemical and polymeric organic compounds.

Biological pollutants - various bacteria, fungi, viruses and other simple microorganisms that are in sewer networks, carrying out vital activity due to the contents of effluents.

Due to the favorable environment, there is a high concentration of biological contaminants in domestic wastewater. They can serve as a source serious illnesses Therefore, wastewater treatment is of great importance. Typically, sewage contains all three types of contaminants. Mineral and organic impurities are in a ratio of approximately 3 to 2.

There are several methods of wastewater treatment. Treatment facilities, depending on the tasks, may include a different number of systems in which a certain combination of methods is applied in stages.

In centralized systems for the treatment of domestic wastewater, mechanical, biological and disinfection methods are necessarily used. Industrial enterprises are characterized by the additional use of physicochemical and chemical methods.

Mechanical Methods

The task of mechanical treatment technologies is to remove insoluble particles and elements from the liquid. There are two main methods of such a procedure:

The use of coarse filtering devices in the watercourse (grids, sand traps, filters).
Settling in special tanks, when heavy particles settle to the bottom (primary settling tanks, septic tanks).

Mechanical cleaning technologies include:

Settling.
Straining.
Filtration.

Such methods are used as the primary stage in the treatment plant system and allow the removal of up to 75% of all pollutants. Mechanical devices include: gratings, sieves, sand traps, oil traps, settling tanks, septic tanks, filters. These methods are the simplest and cheapest.

Mechanical cleaning systems are mounted in networks storm sewer, since storm sewage contains a large amount of large insoluble debris - soil particles, leaves, branches. Sand traps are installed in the sewer pipes, which filter and remove large debris from the system.

biological methods

Biological wastewater treatment methods involve the removal of dissolved components due to the vital activity of aerobic or anaerobic microorganisms and bacteria.

Aerobic organisms require a constant supply of oxygen to function. Anaerobic organisms carry out the oxidation of dissolved organic matter in a liquid without the presence of oxygen.

Biological treatment facilities:

Septic tanks.
Biofilters.
Aerotanks.
Metatenki.
biological ponds.

A septic tank is a sealed container where, due to the presence of oxygen and the biological environment, oxidative processes occur, which allow the removal of organic matter from the liquid. Simple septic tanks can be classified as a means of simple mechanical cleaning.

A septic tank with biofilters is equipped with a special tank with a drainage system of crushed stone and sand. The drainage is covered with a special biofilm. Passing through such a filter layer, which contains bacteria and protozoa, the liquid is freed from the vast majority of contaminants.

Aerotanks are artificial reservoirs where cleaning takes place due to mixing of activated sludge with bacteria and protozoa in the wastewater when oxygen is supplied.

Methane tanks are sealed containers where the oxidation process takes place due to the vital activity of anaerobic bacteria with the release of methane.

Bioponds are artificial reservoirs of shallow depth (up to 1 meter), where natural conditions are created for aerobic wastewater treatment. Ponds are naturally oxygenated from the air, and the sun heats the liquid at a shallow depth, which helps to create a favorable environment for bacteria and protozoa.

Physical and chemical methods

For cleaning at home, these methods are rarely practiced. Their use is practiced for wastewater treatment at industrial enterprises. These methods include:

Coagulation. These elements bind the particles of pollution and form large compounds that settle as precipitation.
Sorption (absorption and adsorption) is the absorption by a solid or liquid of various substances.
Centrifugation is the separation of particles from a liquid by rotation in a special centrifuge.
Oxidation.
Heat treatment, evaporation and evaporation.
Flocculation is a type of coagulation. Purification occurs as a result of the formation of flakes as a result of the addition of flocculants and their settling in the form of precipitation. Use of starch and dextrin as flocculants.
ion exchange method.
Hyperfiltration.
Electrolysis. The method is very effective: it destroys organic matter, removes metals and acids.
Extraction is the extraction of certain substances from a liquid by means of a solvent.
Evaporation - wastewater treatment using water vapor.
Electrocoagulation.
Crystallization.

Physicochemical methods have a number of indisputable advantages:

Removes wide range contaminants of various kinds.
The degree of purification has stable performance, is distinguished by greater depth and quality.
The cleaning process can be fully automated.
Do not require large reservoirs and reservoirs.

Simultaneously use all of the above technologies in treatment facilities not necessary. For each specific system, several methods are selected that are most suitable for a particular case.

Chemical methods and disinfection

Chemical cleaning methods are called by adding certain chemical elements to the liquid, which neutralize organic and biological contaminants. Thanks to the use of chemical reagents, up to 95% of insoluble contaminants and up to 25% of soluble contaminants are removed from the water. In urban wastewater treatment systems, treatment by adding chlorine is often used. For the disinfection of wastewater, special ultraviolet irradiation installations are used.

Cleaning Requirements

Strict requirements for wastewater treatment exist only for the industrial sector. The regulations specify the permissible concentrations of all elements and substances. There are no strict standards for effluents from sources of non-industrial origin. But the discharge of such liquids into open water or soil is also prohibited. They must undergo the necessary procedures to remove the most dangerous components. For domestic wastewater that is discharged into water bodies, there are regulatory requirements for content and concentrations.

IN modern conditions anthropogenic pressure on water bodies has seriously increased. A large number of toxicants enter the drains not only from industrial enterprises, their quantitative indicators are also growing at the household level. Such unfavorable conditions require tougher measures to control the treatment of domestic wastewater. Today, the list of elements that are contained in limited quantities in wastewater entering treatment systems is more than 1300 items. Great importance attached to measures to remove nitrogen and phosphorus.

The condition of treated wastewater is regulated by special sanitary rules and regulations. These documents provide a general list of maximum allowable concentrations and tentatively safe exposure levels. Such lists include about 1 thousand names of elements.

The control system is focused on maintaining a viable environment of fishery reservoirs, which include the vast majority of natural rivers, lakes, ponds, etc. That is, the discharged effluents after treatment should not pose a threat to fish living in the reservoir. The key indicator here is the concentration of oxygen in the water.

Based on the requirements of regulatory documentation for the quality and composition of wastewater, all treatment facilities are designed. They allow you to plan the required number of methods for removing contaminants. On this basis, the size and number of treatment tanks are calculated, a list of the necessary equipment and instruments is made.

Wastewater treatment plant

The equipment of various types of treatment systems is made based on the tasks that they will solve. They can be equipped with a different number of blocks, each of which implements a certain technology for removing contaminants.

Types of cleaning blocks:

Filtering and screening.
Biopurification.
Installations for the regulation of oxygen saturation.
Disinfectants.
Implementation of chemical and physical reactions to remove contaminants.

Structures can use blocks of above-ground or underground placement. The elements of the systems include tanks for the storage and transportation of wastewater. Serious requirements are imposed on the devices of treatment systems in terms of reliability and strength of materials. All blocks must be durable, in terms of efficiency of use (at least 30 years of useful work).

Requirements for planning the installation of treatment facilities:

The depth of groundwater.
The nature of the supply structures.
Completion: the number of cleaning steps, expressed in block structure.
Availability of sources of electricity and other resources.
Transport accessibility for the export of solid elements.
The nature of the output structures.
The need to use additional means of chemical and physical cleaning (reagents, etc.).

Scheme of modular treatment facilities (BIOS):

Grids and sieves.
Sand traps.
Primary sump.
Aerotank.
Secondary sump.
Cleaning block.

In tanks with grates, sieves, sand traps, mechanical wastewater treatment takes place. The same problem is solved by the primary sump, which precedes the aerotank. Grids allow you to remove large contaminants of mineral and organic origin. Sieves remove smaller undissolved impurities.

The filtered out contaminants are removed for processing to special sectors at the treatment plant itself or to separate processing plants.

The effluent then passes through a reservoir with sand traps. This is where fine particles are deposited. The flotation method is also used here. It is used with a grease trap, which allows you to remove fatty elements from the surface of the liquid due to cooling and slowing down the movement of the liquid when passing through special containers. The filtered sand is used in road works.

Next, the effluent enters the primary sump. In this tank made of reinforced concrete, with a depth of three to five meters, sedimentation of organic suspensions occurs. Contaminants are removed from the liquid with special scrapers. IN last years, membrane devices are used for deeper mechanical cleaning. Consisting of flat sheets, tubes, capillaries and fibers, they remove as much dirt as possible.

After the primary settling tank, the liquid enters the aerotanks, where the stage of biological water treatment begins. After the aeration tanks, the treated effluents are transferred to secondary settling tanks. Here, with the help of special pumps, activated sludge is removed from the liquid, which is returned through special pipes to the aerotank. If necessary, tanks can be connected to the system, in which certain physical and chemical cleaning procedures are carried out.

Waste water is water contaminated as a result of human activities and is discharged through a sewer collector to a place of accumulation for further processing and treatment. Moreover, waste waters are considered to be waters formed (contaminated) both at industrial enterprises and formed as a result of human household activities. Such water contains a lot of pathogenic microorganisms, salts of heavy metals, pesticides, nitrates and nitrites, as well as many harmful chemical and biological compounds. Therefore, in order to preserve water resources On Earth, a special wastewater treatment scheme was developed, which is aimed at discharging already neutralized clarified water into reservoirs and soil. This attitude towards ecology allows us to save fresh water on the planet for future generations.

Methods of neutralization (purification) of effluents

Waste water, depending on the type and type of impurities in it, is today purified by several methods. Moreover, both a specific method and a combined treatment technology can be used, if necessary for the qualitative neutralization of wastewater. The most commonly used cleaning methods are:

Mechanical water treatment(settling and filtering). This is the easiest and cheapest way to purify water.
Chemical wastewater treatment(mixing wastewater with chemical neutralizing agents). As a result of adding reagents to water, reactions occur that completely or partially neutralize harmful impurities in effluents.
Physical and chemical treatment of contaminated water(UV treatment or ozonation of wastewater).
Biological wastewater treatment. In this case, in aquatic environment a certain amount of bacteria is loaded that feed on specific pathogens, reducing their number in the water to zero.

Wastewater treatment plants and special systems for wastewater treatment

The most effective and in demand in the process of neutralizing wastewater are such installations and devices:

UFS - self-cleaning filter unit.
Sand traps.
Grease traps.
Settling ponds.
Septic tanks and membrane structures.

Let us consider in more detail the principle of operation of each device.

Filtration plant

A device that passes waste water through its filters and thereby purifies it. Filters should be self-cleaning, but in practice, industrial enterprises use standard gratings and sieves instead of self-cleaning filters, which require manual raking or using special devices.

Such an installation works on the principle of separating debris and large impurities from the liquid. Moreover, gratings and filtering nets in such an installation can have a completely different structure (crushing, screw, stepped, in the form of plates or rods). The smallest fraction of the grate of such a device is 2 cm. All garbage collected on grates or nets is immediately sent for recycling or disposal. If screens with a crushing structure are used, then debris impurities are neutralized directly in the treated water.

In addition to meshes and gratings, drum sieves can take part in mechanical wastewater treatment. The fraction of cells in a sieve is up to several tenths of a millimeter. These devices have a finer fraction compared to gratings and are designed to remove impurities from the water in the form of gravel, sand, small glass fragments, etc. The drum, rotating in the water, absorbs all foreign impurities into its cavity.

sand traps

The next stage in water purification is mechanical. After the water passes through the drum screens and grates, the effluents are sent further to the sand traps. Here, the devices additionally screen out the smallest particles of impurities in the form of sand. In sand traps, water can move both horizontally and vertically. The cleaning effect of this is not reduced. Sand traps work thanks to the force of gravity, which settles all the small particles of sand to the bottom. At the same time, it is worth knowing that the higher the flow rate of water, the weaker the force of gravity. And this means that for the high-quality work of the sand trap, the speed of the movement of effluents must be reduced.

Important: sand separated from water in this way is most often used later in construction work.

Grease trap

This type of treatment plant is usually installed next to the sand trap. The grease trap has a closed shape and is designed for some cooling of wastewater. As a result of lowering the temperature of the water, all soluble fats take on a certain shape and float to the surface of the water. Further, the effluents flow into the settling tanks, and the fats are removed from the grease traps.

sump

Such shallow home-made modern ponds are designed for further settling of water. Here, effluents can settle for up to 3 hours. As a result of settling, all impurities and suspended particles of debris remaining in the water are additionally removed.

Important: the efficiency of settling with the use of such a wastewater treatment scheme is 50%. Efficiency can also be increased if the depth of the settling pond is reduced by an order of magnitude and at the same time its area is increased.

After settling, the water is clarified using special coagulants, which turn into flakes in the water, thereby filtering the effluents, further clarifying them.

Additional wastewater treatment plants

In addition to the systems and devices listed above, so-called membrane devices are also used in wastewater treatment. In the design of such installations there are special membrane sheets, overflow pipes and capillaries. Thanks to this design, the wastewater is divided into two parts in the membrane installation. At the same time, their pressure and compositions differ. Membrane installations can be made of polymers or ceramics.

Hydrocyclones and centrifuges

These modern devices are also used for sedimentation of suspended particles in effluents. Thanks to centrifugal force, into which wastewater enters, all impurities are separated from the liquid and the water is considered to have passed the stage of mechanical treatment.

Hydrocyclones, unlike centrifuges, are open (work with light impurities) and pressure (designed to separate heavy debris from wastewater). This classification allows the use of installations depending on the type and degree of wastewater pollution.

In turn, the classification of the centrifuge looks like this:

Settling;
Filtering.

The design of filtering industrial centrifuges includes thin metal sheets with perforations for better particle settling. Also, the devices have main grids made of copper, aluminum or steel and dense fabric partitions. The type and type of filter completely depends on the intended task, that is, on the rate of separation of impurities, their size, type of effluents, liquid pressure and concentration of debris in the effluents.

Aerotank

Water treatment device for biological wastewater treatment. Here, the water is treated with special organic sludge under the influence of oxygen injected into the plant. As a result, bacteria eat harmful impurities contained in the water. Most often, this basic method of wastewater treatment is used in case of contamination with organic debris.

The principle and scheme of contaminated wastewater treatment today

Having studied all the existing devices for the neutralization of wastewater, you can consider how the neutralization of wastewater occurs. It consists of several stages:

First, all effluents from enterprises and residential areas of the city fall into a specially mounted water collector, from where they are then transported to a treatment plant.
The first main stage in the neutralization of industrial (industrial) effluents is mechanical treatment. That is, the passage of wastewater through special filters, nets and grates to separate large debris. Debris particles are sent to the sludge collector.
The next stage (stage) of water purification is its pumping into a special sump, where the remaining debris particles are further settled and removed from the water. A sand trap also takes part in settling, which passes through itself the water entering the settling pond.
Further, the settled water goes through the stage of clarification using coagulants and is sent to press filters. Here, under high pressure, water passes through special filters that trap all remaining particles. This stage is the final one in mechanical wastewater treatment.
Further, depending on the initial type of wastewater pollution, water is sent for further biological, chemical or physico-chemical treatment. That is, water will be affected either by bacteria, or chemicals, or ultraviolet or ozone.

Important: the efficiency of wastewater treatment using the initial mechanical method is 60%. Further manipulations with water allow you to clean the drains by 90-98%.

Further disinfection of wastewater

In addition to wastewater treatment, it is also necessary to carry out the stage of its disinfection. The most common method is chlorination. But according to the Canadian Environmental Protection Act, this method poses a threat to the environment, therefore, in Russia, a decision was made to additionally dechlorinate wastewater before discharging it into ponds, soil or water bodies.

In addition to chlorination, very effective way disinfection of wastewater is ozonation. But this method is quite expensive. Used only in European countries.

An alternative and high-quality method of wastewater treatment is water treatment with ultraviolet light. Special UV lamps act on the surface of the water, disinfecting it and destroying residual pathogenic microorganisms in the liquid.

It should be noted that when water is treated with UV lamps, water does not take part in the reaction. Only bacteria and ultraviolet interact with each other. The efficiency of such water treatment is 90%.

Important: ultraviolet wastewater disinfection units do not take up much space and are fully automated. In addition, they do not pose a threat to humans.

Wastewater treatment refers to their special treatment in order to remove harmful substances present in it. On the this moment A lot of cleaning methods have been developed and used. The choice in favor of one or another method of wastewater treatment directly depends on the characteristics of pollution and a whole list of conditions. Let's briefly review each of these methods.

The essence of the mechanical method of wastewater treatment is that all kinds of impurities are excluded from contaminated effluents through mechanical filtration. Various kinds of particles are retained by special fine gratings, sieves, gas separators and other cleaning elements. Through mechanical cleaning systems, up to 70% of contaminants are removed.

The essence of the chemical method lies in the fact that specific chemicals are supplied to the wastewater, which act on pollution, which leads to their precipitation in the form of precipitation. With the help of such wastewater treatment systems, the insoluble impurities are reduced by up to 95%. This method is considered one of the most effective among all existing ones.

The essence of the biological method is to use the biochemical and physiological principles of self-purification of natural reservoirs for cleaning. The main role in industrial biological treatment systems is played by bacteria that are added to the effluents and which clean them. The scheme of biological treatment is shown in the photo.

The essence of the physicochemical method of wastewater treatment is to remove finely dispersed substances from them and to destroy poorly oxidized compounds. In most modern industrial physical and chemical treatment plants and equipment, wastewater treatment methods such as sorption, coagulation and extraction are used.

Consider each cleaning method and each cleaning system in more detail.

Biological wastewater treatment

As already mentioned, this purification method is based on the ability of certain microorganisms to mineralize organic matter. It is according to such a cleaning system that natural self-purification is carried out in reservoirs and rivers. To speed up cleaning by this method, special bacteria are used in biological installations and equipment, which both speed up the process of biological cleaning and increase its efficiency.

At biological method use aerobic and anaerobic microorganisms.

Aerobic bacteria exist only in an environment where oxygen is present. Under the influence of such bacteria, the complete destruction of organic substances to carbon dioxide and water is carried out. The aerobic method alone is rarely used in biological treatment: as a rule, it is used in conjunction with the anaerobic treatment method.
Anaerobic bacteria in biological treatment can exist in an environment in which there is no oxygen. Usually anaerobic treatment systems are used in conditions of high concentration of organic matter, which exceeds the allowable level for aerobic microorganisms. At the same time, in the case of a low level of organic matter, the anaerobic cleaning method is ineffective. That is why in most cleaning systems, after cleaning with anaerobic microorganisms, an additional cleaning with aerobic bacteria is performed.

The principle of biological treatment technology is discussed in detail in the video below.

Mechanical

The mechanical cleaning method is used to separate large enough contaminants from wastewater by straining or filtering. The main features of the mechanical cleaning method are as follows:

To remove coarse-grained substances, the method of filtering wastewater through grates and all kinds of sieves is used.
To exclude substances with a higher / lower particle density (compared to water) from the effluents, the settling method is used. With the method of settling, the lightest compounds float to the surface, and the heaviest precipitate.
To remove various mineral contaminants, the sedimentation method is used with the use of special systems of sedimentation tanks. A photo of the sedimentation tanks is shown below.
To remove substances that are light compared to water (oils, oil, fats), which float to its surface during cleaning, special treatment plants are used - oil traps, oil traps, etc. For the most part, such a method and such equipment are used to treat industrial wastewater.

Most often, mechanical treatment methods and equipment for mechanical treatment are used in the treatment of industrial wastewater. In all other cases, mechanical cleaning is used as an initial cleaning before biological treatment is carried out.

The technology of mechanical wastewater treatment is discussed in detail in the video:

Chemical

Chemical wastewater treatment systems involve the use of special chemicals to remove contaminants. In particular, chlorine, lime, hydrochloric acid are used.

Chemical wastewater treatment is carried out in several stages:

Neutralization of contaminants. This method involves mixing acid-containing effluents with alkaline and subsequent filtration with appropriate substances. At the same time, dolomite, cement, ammonia water are used in the acid water neutralization technology.

Oxidation. Oxidation is carried out to disinfect contaminants in the wastewater treatment process. Sodium chlorate, ozone, liquefied chlorine, etc. are used as oxidizers. It should be noted that the most effective oxidizing agent is fluorine. However, it is rarely used at stations and systems, since it is a rather aggressive chemical. Chlorine is the most common oxidizing agent used in industrial plants and chemical wastewater treatment systems.

Chemical wastewater treatment is discussed in detail in the video.

Physical and chemical cleaning methods

This cleaning method can be used both independently and in conjunction with other methods and technologies - chemical, mechanical and biological cleaning.

The most common methods of physical and chemical wastewater treatment include coagulation, ion exchange, and flotation. Let's look at each of these methods in more detail:

The coagulation method involves the preparation of special solutions containing flocculants and coagulants in their composition. Such solutions are added to the wastewater installation. As a result of the reaction, flakes are formed from the contaminants, which are subsequently removed by the mechanical processing system.
The ion cleaning method involves the selection of ions from a special electrolyte solution in exchange for the same amount of ion exchanger ions. This wastewater treatment method is reversible and can be used not only for wastewater treatment, but also in equipment and installations designed for water softening.
The flotation method involves the supply of air bubbles to the waste water. At the same time, contaminant particles adhere to these bubbles, which leads to the formation of foam on the surface. If, due to their properties, the polluting particles do not stick to the bubbles, then special reagents are added to the treatment system. Subsequently, the foam with contaminants is removed mechanically. A photo of the foam substance is shown below.

Flotation cleaning equipment is most often used in industrial and manufacturing enterprises involved in the processing of petroleum products. Photo of wastewater flotation system.

The technology of physical and chemical removal of contaminants is discussed in the video below.

Wastewater Treatment Equipment

For maximum clarity, we will consider modern systems, equipment and installations used for the treatment of industrial and domestic sewage.

Sewer pumping station

Such a station is designed and used for pumping wastewater in cases where it is not possible to transport it by gravity. Depending on the requirements and operating conditions, industrial pumping stations for pumping sewage can be self-priming or submersible. A photo pumping station presented below.

Station for mechanical wastewater treatment

The system is designed for the initial treatment of wastewater from pollution by sedimentation. The main structural element of most industrial mechanical cleaning stations is the desander. It is with the help of this system that wastewater is purified from coarse pollutants. A photo of an industrial wastewater treatment plant by mechanical means is shown below.

Grease system

The grease trapping system is designed to isolate fats of various origins from wastewater. The grease trap is an essential equipment of the sewer system, since the accumulation of fats significantly reduces throughput the entire system. Grease trapping systems are used in the treatment of industrial polluted waters. The grease trapping system is shown in the photo below.

Biological wastewater treatment plant

Such a station is a kind of square-shaped container made of stainless steel alloy or fiberglass. The principle of operation of such a system is based on the use of certain microorganisms and the alternation of aerated zones with sludge recirculation. This method and such systems are widely used in the organization of domestic, non-industrial sewer systems. A photo of an industrial biological wastewater treatment plant is displayed below.

Equipment for biological treatment can be buried or above ground. In industry, as a rule, underground biological treatment plants are used. Ground biological treatment plants are used if underground installation is not possible or a mobile wastewater treatment plant is required. A photo of the mobile cleaning station is shown below.

It should be noted that very often a biological treatment plant is called an aerotank. This name was given to the biological treatment plant due to the use of aerobic bacteria treatment technology in it. A photo of the aeration tank is shown below.

Chemical wastewater treatment plant

Stations that use the chemical technology of wastewater treatment are intended primarily for the construction of treatment systems in large industries. It should be noted, however, that universal industrial installations for such wastewater treatment, as well as universal treatment technologies, do not exist. In each specific case, a specific station is required, which is designed to carry out chemical cleaning of certain contaminants and uses the appropriate cleaning method in its work. If it is impossible to confine ourselves to the chemical treatment system alone, this technology is used in combination with mechanical or physico-chemical wastewater treatment.

A photo of the chemical treatment plant is shown below.

Membrane cleaner

This system can be called one of the most advanced among all existing ones. The main advantage of such a station is wastewater treatment at the molecular level. After passing through such a system, purified water can subsequently be used for certain technological and production processes. Photo of industrial membrane equipment:

Wastewater treatment plant

Let us consider in detail the most common options for wastewater treatment plants that are used in domestic treatment systems. Most often, when creating sewer systems in private homes, biological wastewater treatment plants are used. The principle of operation of such a system is as follows:

The initial treatment of wastewater is carried out in the so-called septic tank. A septic tank is a special chamber in which organic pollutants are decomposed by anaerobic bacteria. Of course, to ensure the fermentation process in the septic tank, oxygen is excluded. A photo of the septic tank is displayed below.

Anaerobic purification technology is carried out by hydrolysis of organic compounds into less complex particles. In order to increase the efficiency of anaerobic treatment, special equipment is used - a bioreactor, which is a special filler that has honeycombs with anaerobic bacteria. Thanks to these honeycombs, the efficiency of the treatment plant is significantly increased. A photo of the bioreactor is shown below.

Wastewater treatment technology: video

For maximum clarity, we suggest you watch a video in which the technology of wastewater treatment is considered in detail.

The state of ecology today, unfortunately, leaves much to be desired. This is the result of careless use. natural resources. Human consumption of water is constantly growing, and reserves pure water in nature are decreasing every year. The use of detergents and various household chemicals greatly pollutes the wastewater of modern cities, which greatly complicates wastewater treatment. Wastewater contains a lot of different pollutants, from mechanical components to complex chemical compounds, so wastewater treatment is a complex and multilevel process.

All methods of wastewater treatment can be conditionally divided into destructive and recuperative. The result of destructive cleaning methods will be the decomposition of complex polluting compounds into simple ones, they will be removed from the water in the form of gases, or precipitate, or remain dissolved in water, but neutralized. The result of recuperative treatment methods will be the extraction of all valuable substances from wastewater for further processing.

Wastewater treatment methods

Mechanical
Biological
Physico-chemical
Waste water disinfection
Thermal disposal

1. The mechanical method is the simplest. Mechanical treatment removes insoluble components polluting the water, both solid and surface fatty contaminants, from wastewater. Wastewater first passes through grates, then through sieves and sedimentation tanks. Smaller components are deposited by sand traps. Wastewater treatment from oil products is carried out with the help of grease traps and gasoline oil traps. An improved method of mechanical cleaning - membrane - is used in conjunction with traditional methods and allows for a more thorough cleaning. Mechanical wastewater treatment is a preparation for biological treatment and allows you to remove up to 70% of impurities from domestic wastewater, and up to 95% from industrial wastewater.

2. Biological wastewater treatment occurs due to the vital activity of microorganisms capable of oxidizing organic substances. The basis for the development of this method is the natural cleaning of rivers and reservoirs by the microflora inhabiting them. Thus, effluents are freed from organic nitrogen and phosphorus. Biological treatment is aerobic and anaerobic.

Construction for aerobic wastewater treatment due to the vital activity of bacteria

Aerobic wastewater treatment is carried out with the help of aerobic bacteria that require oxygen to live. Biofilters and aerotanks with activated sludge are used for such cleaning. Aerotanks have a high degree of purification and are more efficient than biofilters for wastewater treatment. In aerotanks, water is aerated and its deep biological treatment is carried out. In addition, the result is activated sludge, which is a good fertilizer.
Anaerobic wastewater treatment is carried out without access to oxygen. Under the influence of anaerobic bacteria, the process of fermentation and the conversion of organic matter into methane and carbon dioxide occurs. For this method, meta tanks are used. Anaerobic treatment requires less expense than aerobic treatment, since it does not require aeration.

3. The physico-chemical method includes electrolysis, coagulation and precipitation of phosphorus with iron and aluminum salts.
4. Disinfection of wastewater occurs by ultraviolet irradiation, chlorine treatment or ozonation. It is used for disinfection before discharge into water bodies.

Disinfection by ultraviolet irradiation is a more effective and safe method compared to chlorination, since it does not produce harmful toxic substances. Ultraviolet radiation It has a detrimental effect on almost all microorganisms and effectively destroys the pathogens of cholera, dysentery, typhoid, viral hepatitis, poliomyelitis and other diseases.
Chlorination is based on the ability of active chlorine to have a detrimental effect on microorganisms. A significant disadvantage of this method is the formation of chlorine-containing toxins and carcinogens.
Ozonation is the disinfection of waste water with ozone. Ozone is a gas consisting of triatomic oxygen molecules, a strong oxidizing agent that kills bacteria. This is a rather expensive method of disinfection, in which harmful substances are released: aldehydes and ketones.

5. Thermal disposal is used for process wastewater when other methods are ineffective. Its essence is that sprayed effluents are disinfected in a torch of burned fuel.

At modern wastewater treatment plants, wastewater is treated in stages, while the methods described above are consistently applied.

Thermal disposal of wastewater consists in the disinfection of wastewater in the flame of burning fuel

Stages of wastewater treatment at wastewater treatment plants

preliminary mechanical cleaning;
biological treatment;
post-treatment;
disinfection.

Mechanical cleaning equipment

gratings - rectangular rods with gaps up to 16mm;
sand traps (installed when cleaning more than 100m3 per day);
averaging agents (installed if composition averaging is necessary);
settling tanks (there are horizontal, vertical, radial, bunk);
septic tanks (used to treat wastewater going to filter trenches, wells and underground filtration fields);
hydrocyclones (needed to clean wastewater from suspended solids);
centrifuges (excrete finely dispersed substances when reagents cannot be used);
flotation plants (used to separate oils, fats, oil products);
degassers (remove gases dissolved in water).

Ilosos - a facility for wastewater treatment with activated sludge

Biological treatment facilities

preaerators and biocoagulators (reduce the concentration of heavy metal ions and other pollutants);
biological filters;
aeration tanks, sludge pumps, metatanks (aerobic and anaerobic cleaning facilities);
secondary clarifiers, desilters and filtration fields (designed for complete biological wastewater treatment);
biological ponds (designed for deep treatment of wastewater containing many organic substances).

In the post-treatment of wastewater, their neutralization and filtration are used. Disinfection or disinfection is carried out with chlorine (chlorine facilities are required) or electrolysis (the construction of electrolysis plants is necessary).

Those who wish to get acquainted in detail with the device and the principle of operation of the biological treatment station will be helped by watching the video.

As you can see, wastewater treatment is a multi-stage process that requires a scientific approach and compliance with all rules and sanitary standards. The considered methods of wastewater treatment are used in combination. The choice of method depends on the nature of the effluents, their quantity, type, as well as the concentration of pollutants.