Waste water treatment - methods and special equipment. Wastewater treatment methods using chemical, biological and mechanical means.
Human waste products and waste from industrial enterprises have a very aggressive component, so it is necessary to clean them from harmful substances and impurities.
In view of the fact that wastewater contains complex mixtures of solids and dissolved substances, their removal and neutralization occur in several stages. For this, treatment plants are used, where, depending on the specifics of pollution, various cleaning methods are used.
There is no other choice - no automation: floating container with chlorine tablets, test work to determine the excess concentration of chlorine and the reaction medium, washing the water wash filter for water, etc. those. constant care for this Building, and if you still have time - redeem it. Mercedes is a complex car, but it works reliably, because high-tech technological solutions and reliable components are used, and Lada is a simple mechanism, but its super-simplicity often breaks down.
However, any complexity must be justified and aimed at achieving the main goal, in this case - the necessary cleaning efficiency, reliability, with the exception of energy and operating systems without permanent staff. These devices must be able to: - maintain a certain level in the installation area in order to create accumulation volumes with a small influx of sewage; - ensuring the recirculation of the sludge mixture between the reactors in proportion to the amount of wastewater introduced; - to pump wastewater after decantation and break down in the flow of floating active substances and particles; - Ensure the consolidation of several biological processes within a single structure.
The main methods of wastewater treatment, with the help of which the removal of contaminants and harmful substances, are considered: mechanical, chemical, biochemical and biological.
Each of the listed cleaning activities includes many different stages, during which special equipment and chemicals are used.
Based on the above, can we summarize how essential requirements should be a bit of respect for a treatment plant to ensure proper wastewater treatment without permanent staff with rising energy prices? Saving and chopping out sewerage. The self-cleaning mesh system contaminates impurities with debris in the receiving space. Provides insignificant wastewater discharge without removing sediment from the wastewater treatment plant. The technology must be installed with a minimum two-wheel system.
Chemical methods of wastewater treatment
Chemical cleaning includes the processes of neutralization, oxidation and reduction.
To purify wastewater from various acids and alkalis, the neutralization method is used. This process can have several types of cleaning.
The most common methods are mixing acidic and alkaline wastewater, filtering acidic water using neutralizing materials, various reagents, etc.
Provide biological nitrogen removal by creating conditions for a two-stage nitrification-denitrification process. Automatically removes excess sludge. Automatically maintains the desired concentration of activated sludge in the system with the possibility of regulation. Availability automatic system aerobic excess sludge stabilization automatically switches to economy mode when you change wastewater treatment to save energy, electrical equipment life and bring the biological process in line with long periods without sewage.
In most cases, acid and alkaline wastewater from industrial enterprises is subjected to neutralization, which cannot be drained into the sewer line without pretreatment.
Important! In the process of neutralizing acids in wastewater, limestone, chalk, soda, caustic soda, and alkaline waste are used. For this, many enterprises install special mechanisms and filters.
Switch to post-combustion at the wastewater inlet, as estimated above. Use high reliability sensors with a self-cleaning system. Output to control the parameters of the main controller controller with the ability to adjust the reactors: aeration time, mixing, sedimentation, wastewater pumping - preferably via a modem connection. Having an alarm at the initial stage of the installation to take action before an accident. The ability to repair or replace any device without stopping at the treatment plant.
They understand that they are detailed on the site and its technologies, it will be clear that such a system will not work. Small treatment plants available on the market can be divided into three groups. Therefore, systems based on this principle are inefficient. It is unauthorized releases to the atmosphere that activate sewage sludge, such systems "solve the problem" of removing excess sludge. After that, of course, it can be argued, ignoring the known laws of nature, that excess sludge does not form in such installations, or that it is enough to eliminate it once a year.
Photo: the process of neutralizing acids in wastewater
The oxidation method is suitable when all other cleaning methods do not lead to the desired result. They use calcium chloride CaC1 (C1O), calcium hypochlorite (Ca (ClO) 2) and sodium (NaOCl), potassium permanganate (KMnO4), potassium bichromate (K2Cr2O7), oxygen, etc.
A new rational nature, and if possible, then it would be a man created by God, without much pleasantness - to the toilet. Such systems operate without automation, as they say "completely", whether sewage enters the plant or not, which leads to the problems highlighted above. Since the amount achieved by such wastewater installations is violated, as mentioned above, the estimated time of wastewater treatment in the individual zones of the installation. Worst of all, when the number arrives at the wastewater treatment plant, the wastewater treatment time does not increase as needed to provide the required and reduced treatment.
If easily recoverable substances are present in wastewater, recovery treatment is used: arsenic, mercury, and chromium compounds are removed from the wastewater.
For this, iron sulfate, hydrogen, sodium hydrosulfite, sulfur dioxide and other chemical elements are used.
Biochemical
Biochemical treatment (oxidation) is used for both industrial and domestic wastewater.
These are some of the many problems of "cheap, simple and reliable wastewater treatment systems". We can add more than such facilities - these are not much cheaper plants that are part of the first group, and if we add an excessively high price of electricity, in the absence of sewage intake and clogging, then this is a cheap "gold". For cleaning methods, it should not be used when the water structure is disturbed and the biological activity changes. The wastewater treated in their properties is suitable in a natural way.
Since the technology was created with almost "zero", it is not based on any part, and it does not have the shortcomings of other technologies, the truth was its own, but they appeared, the author of the technology tried to solve them through new approach to their permission. All of the above devices and tools are patented and pending in international patent applications. After the introduction of a system of self-cleaning sensors, their failures in last years have not happened yet. Not only are the level sensors duplicated, they are linked by doubling the secondary logic controller: the principle is if the top sensor in the reactor is closed and the bottom is open, the performance of the lower sensor system is "ignored".
This method is well suited for the removal of dissolved organic and inorganic compounds from wastewater. For this method of oxidation, special treatment facilities are being built.
Aerobic - include biological ponds, filtration and irrigation fields.
The truth is more necessary to connect the cabin installation to external networks via a modem, this is not because the system works reliably and the sensor compressors are duplicated, but if you had such a desire, this is enough. Just buy a cable to configure the control and connect it via modem. The result is an 8-speed 3 cm, fully automated system self-management - a biopneumatic system with a returnable four-circuit recirculating active sediment.
Thus, the bacteria in the activated sludge will leave contaminated pollution outside of these scales. A multi-loop recirculation and multi-stage system allows these "leftovers" to circulate in an activated sludge return "impact" with effluent capable of removal, where organic nitrogen and phosphorus are in the lower range, most of the report says. Thus, activated sludge microorganisms, "eat" said pollution in the usual way, will "recycle" the waste recycling cycle.
Anaerobic - such facilities include various septic tanks, settling tanks, devices for anaerobic fermentation - digesters.
Photo: anaerobic fermentation device
Biofilters are structures in which effluents pass through filter elements consisting of gravel, slag, expanded clay and other materials.
Apparatus Biotic conditions for the simultaneous removal of nitrogen and phosphorus by biological means. To do this, under alternative anoxic conditions and oxide during the period of activated sludge for more than 25 days. At the same time, the development of facultative microorganisms is actively involved in the purification process in oxygen and in free oxygen conditions. This increases the amount of aerobic sludge in the system and can be efficiently removed using nitrogen and phosphorus biologically. The operation of the system occurs in steps 6-8, the meaning of which depends on which of the six installation modes.
The film covering the entire feed material consists of colonies of microorganisms that oxidize organic substances.
Photo: biofilter
Air filters and aerotanks. Unlike a biological analogue, an air filter can have a filter layer up to 4 meters and has an air supply device in its design, which allows several times to increase the oxidation process.
Mixing takes place in a denitrification process with a double effect - denitrification with nitrogen storage and oxidation of organic pollutants that enter the nitrite wastewater in the denitrification process. This ensures that the detention effect of detention is 5 times higher than the classical defense. All parameters of the biotal installation can be viewed and, if necessary, changed the log of the program controller. You can also control and change installation options in emergency from the dispatch service via a modem connection.
Photo: air filter
In aerotanks, the process of oxidation of substances of organic origin occurs in an activated sludge medium, which is formed by colonies of microorganisms.
Biological
The method consists in the destruction of hazardous compounds in drains with the help of microorganisms that process contaminants into harmless substances.
biological standard work program, designed for wastewater treatment, so there is no need to change them, it may be necessary to regulate the operation of the municipal and industrial plant for wastewater treatment and with a slight waterlogging of wastewater design. This is a 7-stage 2-sludge system with 3 active loop waste circuits in one of the 6 programs automatically switches depending on the amount of wastewater entering it.
This plant option includes an aerobic active sludge stabilizer, a sludge dewatering unit and a biological lamellar filter colony. Ideal for complex sites with a high content of organic pollutants. In this option, there is no need for an efficient and non-liquid drive, the technology is all in one package and installed in the well. Type 2 and 4 systems require a larger sludge removal hatch or a 50 cm deep installation for increased sludge removal - in this case a standard hatch can be used.
In this case, activated sludge is formed, in which there are all conditions for maintaining the vital activity of bacteria. It should be noted that this method achieves the most efficient and high level cleaning.
Aerobic and anaerobic processes are used, the principle of which is based on the combination of various microorganisms.
Waste water tank; And two zones for processing excess sludge: an aerobic active sludge stabilizer; Dehydration. As organic nitrification oxidation begins to dominate. Finally, stooped sewers flowing from the appliance. This was made possible thanks to mass production, modernization and technology. For this, it should be added that the high groundwater level, especially when pumping sewage from a repair facility, can be removed due to the floating ability of Archimedes.
The weight of the weight must be greater than this buoyancy. Installation - the tank is the same, only lighter and weaker. However, the company producing such plants was able to "reject" the law and then provide them with "calculations". The round body as well as the high-quality plastic rigidity, even the thinner ones, are about the same and statically remain the same task as the cellular plastic used for other settings. We installed the unit in concrete pits because they are used to doing everything well and consistently.
In cases where wastewater has an organic component, the biological oxidation method is often used. For this process, special aerotanks are built.
Important! These buildings use a large number of activated sludge, and in some modifications - oxygen. Due to the fact that aerotanks are able to purify wastewater up to 98%, there is no need for additional measures.
If we talk about raising the price, it will be up to $ 100, it is easy to calculate: the distance from the building to the installation is usually 5-15 meters. Such a low cost will pay you more than once. The compressors installed in the basement are first pumped and supplied to the basement warm air installation, which has a beneficial effect on the biological processes in winter, because the temperature drops below the mixed process of the rapid deterioration of the biological process of 12 degrees, while almost 5 degrees cease.
Second, when installing air compressors, vent under the floor or into another room where they are forced to. With regard to automation located inside the device, there is a high probability of condensation inside the automation, followed by contact oxidation. If the machine is in the basement, it is enough to control the plant to go down to the basement. This can result in loss of life and lead to poor automation and compressors. When the drainage moves, flooding can occur.
Purified water can be supplied directly from this facility for irrigation and other household needs.
The principle of operation of the aeration tank is to mix activated sludge and waste liquid in special tanks. For a more active process of mixing (aeration) of the components, various devices or compressed air are used.
Photo: filtration fields
For biological wastewater treatment, there are specially created ponds and filtration fields, where, under the influence of all the same microorganisms, the purification process takes place.
But the disadvantage of such structures is the seasonal principle of operation, the danger of contamination entering the groundwater and, of course, the need for large land areas.
Physical and chemical cleaning methods
Physical and chemical methods play an important role in the process of wastewater treatment of industrial enterprises. Every year the scope of these methods is expanding.
All processes can be carried out both independently and in combination with other cleaning methods - chemical, biological and mechanical.
The most common methods of physical and chemical purification are coagulation, ion exchange, flotation, extraction, evaporation, reverse osmosis, etc.
1 - capacity; 2 - dispenser; 3 - mixer; 4 - CWC; 5 - sump
For the cleaning process, coagulation methods prepare special solutions containing coagulants and flocculants.
The aqueous solution obtained during this mixing is added to the treated waste water in certain doses. During the chemical reaction, flakes are formed, which are removed mechanically.
The essence of the ion-exchange method is the selection of ions from an electrolyte solution in exchange for a similar amount of ion exchanger ions.
Ion-exchange materials act as the “receiving” side. The exchange process itself is reversible and is mainly used to soften water.
Photo: ion exchange method
The flotation method is used to purify effluents, which contain impurities of oil products.
The essence of the method is based on the ability of particles to stick to air bubbles, which are fed directly into wastewater.
Photo: flotation method
The result is the formation of a surface layer of foam. If the particles do not have the properties of sticking to air bubbles or if this ability is too small, reagents are included in the flotation process that increase their hydrophobicity - non-wetting by water.
Subsequently, the foam layer is removed by raising the water level: the foam is discharged through special trays, or mechanically - scrapers (foamers) remove the foam to the same trays.
The flotation method has several types: mechanical, pneumatic, foam, pressure, biological, etc.
Mechanical and physical methods
Mechanical cleaning methods are used to remove undissolved impurities and large floating contaminants from wastewater.
In most cases, this method is a preliminary measure, during which the largest and most suspended substances are removed. For the mechanical type of wastewater treatment, straining, filtering and settling are used.
The straining method is used to remove coarse and partially suspended impurities from wastewater. For this procedure, there are special grates and sieves that are built into the channel or tank with recyclable effluents.
Filtration is used to capture the smallest particles in wastewater. Filters can be fabric materials (grids), porous and fine-grained materials.
Also for filtration, drums are used, called micro-strainers, in which contaminants are retained by the filter mesh. Particles that have not been filtered are washed into the hopper using specially equipped nozzles.
To remove mineral and organic contaminants from wastewater, there is a settling method. For this, sand traps and settling tanks of various modifications are created - dynamic, tubular, static, etc.
Photo: sand trap
The principle of operation of sand traps is based on the action of gravity and flow velocity. The use of settling tanks is typical for large industrial enterprises and serves to capture both settling and floating pollution.
AT modern world When environmental safety is one of the priorities, properly and competently organized wastewater treatment activities are of great importance.
Application the latest technologies and methods for the removal of pollution allows you to achieve the maximum effect in the field of processing and disposal of waste.
Video: Methods and facilities
Wastewater classification.
Waste water is water used for domestic, industrial or other needs, and contaminated with various impurities that have changed their original chemical composition and physical properties, as well as water flowing from the territories settlements and industrial enterprises as a result of precipitation or street irrigation. Depending on the origin, type and composition, wastewater is divided into:
domestic wastewater (from toilets, showers, baths, laundries, canteens, hospitals) coming from residential and public buildings, from amenity premises of industrial buildings;
· industrial wastewater used in technological processes and no longer meeting the requirements for their quality. This category includes water pumped to the surface of the earth during mining;
· surface sewage generated by atmospheric precipitation, snowmelt, watering and street washing.
In practice, the concept is also used city wastewater, which are a mixture of domestic and industrial wastewater in a variety of quantitative ratios. Discharge of domestic, industrial and surface waters can be both joint and separate.
Waste water composition
Wastewater is a complex heterogeneous mixture containing impurities of organic and mineral origin, which are in an undissolved, colloidal and dissolved state. The degree of wastewater pollution is estimated by concentration, i.e. mass of impurities per unit volume, mg/l or g/m 2 . In domestic wastewater, organic pollution is about 58%, and mineral - about 42%. Wastewater from industrial enterprises is the most complex in composition; it is distinguished by its diversity and multiple superiority in terms of the number of pollutants and the degree of toxicity. Industrial wastewater is divided into polluted and non-polluted (conditionally clean) water. Contaminated industrial wastewater is divided into three groups:
1. Contaminated mainly with mineral impurities (enterprises of the metallurgical, machine-building, ore and coal mining industries; factories for the production of acids, construction products and materials, mineral fertilizers, etc.).
2. Contaminated mainly with organic impurities (enterprises of meat, fish, dairy, food pulp and paper, microbiological, chemical industries).
3. Contaminated with mineral and organic impurities (oil producing, oil refining, textile, light, pharmaceutical industries, factories for the production of sugar, canned food, organic synthesis products, etc.).
In addition to the above three groups of contaminated industrial wastewater, heated water is discharged into water bodies, which is the cause of the so-called thermal pollution.
Currently, there are a large number of wastewater treatment methods. In accordance with the process implemented during cleaning, it is customary to divide all methods into three groups: mechanical, physico-chemical and biological.
Mechanical wastewater treatment.
To clean wastewater from suspended solids, straining, settling, processing in the field of action of centrifugal forces, and filtration are used.
Straining, as the primary stage of processing, it is implemented in gratings and fiber traps, in which undissolved impurities with a size of 25 mm or more are separated.
settling is based on the free settling (floating) of undissolved impurities with a density greater (lower) than that of water. For this, sand traps, settling tanks, grease traps are used. Sand traps used for heavy mineral impurities are installed in front of other settling tanks.
Department of mechanical impurities in the field of action of centrifugal forces is carried out in open or pressure hydrocyclones, centrifuges. Hydrocyclones are much more productive than settling tanks, they separate particles of the solid phase, glass, building materials, scale, ceramics, etc. are removed in a rotating fluid flow.
Filtration wastewater is designed to purify them from finely dispersed solid impurities with a small concentration. The filtration process is also used after physicochemical and biological cleaning methods, since these methods are accompanied by the release of mechanical impurities into the cleaned liquid. Quartz sand, crushed slag, gravel, anthracite, etc. are used as filter materials.
Physico-chemical wastewater treatment.
Physico-chemical methods are used to treat wastewater, mainly from dissolved impurities, and in some cases from suspended solids. The use of circulating water supply systems increases the role of physical and chemical methods. This category of methods includes: flotation, extraction, neutralization, ion-exchange purification, hyperfiltration, evaporation, evaporation, crystallization.
Flotation is used to clean polluted waters from oil products. The supply of air under pressure into the flotation chamber contributes to the intensification of the process of oil products floating and the formation of foam on the water surface. The foam is raked from above by a special mechanism into the foam collector, and the purified (clarified) water is discharged from the bottom of the chamber. Process time 15-20 min.
Extraction is based on the process of redistribution of sewage impurities in a mixture of two mutually undissolved liquids (waste water and extractant).
Neutralization is designed to remove acids, alkalis, as well as metal salts based on acids and alkalis from wastewater. Neutralization of acids and their salts is carried out with alkalis or salts of strong alkalis: caustic soda, caustic potash, lime, limestone, dolomite, marble, chalk, magnesite, soda, alkali waste, etc. Widely used cheap and affordable reagent - calcium hydroxide (slaked lime). Sulfuric, hydrochloric, nitric and other acids are used to neutralize alkaline waters (wastewater from the pulp and paper, textile industries). As a result of the neutralization process, a neutral environment is created with a pH value of 6-7.
Sorption is used to treat wastewater from soluble impurities. As a sorbent, ash, peat, sawdust, slag, clay, activated carbon are used. Valuable dissolved substances suitable for subsequent use are recovered from wastewater, and purified water is often used for circulating water supply.
Ion-exchange stonecrop is used to provide and purify wastewater from metal ions and their impurities. Cleaning is carried out by ion exchangers - synthetic ion-exchange resins, used in the form of granules ranging in size from 0.2 to 2.0 mm. Ionites are practically water-insoluble polymeric substances that have an ion (cation or anion), which, under certain conditions, enters into an exchange reaction with ions of the same sign contained in wastewater.
Electrical treatment, in particular electrochemical oxidation, is carried out by electrolysis and is used to treat wastewater from galvanic processes containing simple ionides (KCl, NaCl) or complex cyanides of zinc, copper, iron and other metals. During electrolysis at the anode, cyanides are oxidized with their transformation into low-toxic and non-toxic products (cyanates, carbonates, carbon dioxide, nitrogen), and at the cathode - the discharge of hydrogen ions with the formation of gaseous hydrogen and the discharge of copper, zinc, cadmium ions.
Hyperfiltration involves the transfer of water and solute through a membrane made of a polymer (cellulose acetate, polyamide, etc.) with a service life of 1-2 years. This method has low energy consumption, is quite simple, can be easily automated, and is effective in circulating water supply systems.
Evaporation is realized by steam treatment of wastewater with volatile organic substances, which pass into the vapor phase and are removed from the wastewater together with the steam. The evaporation process removes ammonia, ethylamine, diethylamine, phenol, etc.
Evaporation, evaporation, crystallization are used to treat small volumes of wastewater with a high content of volatile substances.
Biological method of wastewater treatment.
Biological wastewater treatment is used to isolate finely dispersed and dissolved organic matter and is based on the ability of microorganisms to use organic substances (acids, alcohols, carbohydrates, etc.) contained in wastewater for their nutrition. The cleaning process is implemented in two stages, occurring simultaneously, but at different speeds. During the first stage, fine and dissolved organic substances are adsorbed from wastewater. During the second stage, the adsorbed substances are destroyed inside the cells of microorganisms during the biochemical processes occurring in them (oxidation or reduction). Both stages are realized under both aerobic and anaerobic conditions, depending on the type and properties of microorganisms.
Biological treatment is carried out both in natural and artificial conditions. Under natural conditions, cleaning occurs in filtration fields, in irrigation fields, in biological ponds. For artificial biological treatment, special facilities are used - aerotanks (reinforced concrete tanks), in which activated sludge (biocenosis) serves as a cleansing agent. Activated sludge is a collection of microscopic plants and animals created artificially. Such a component does not exist in nature. The aerotank is blown from below by a powerful stream of tiny air bubbles, which creates an excess of oxygen. In the environment of organic substances (wastewater), with an excess of oxygen in activated sludge, bacteria and microfauna rapidly grow and develop. Bacteria stick together into flakes with a large working surface, while enzymes are released that break down organic contaminants into simple ones. minerals. Bacteria actively divide, their mass increases, sticks together into flakes and, together with silt, settles to the bottom, separating from clean water. Thus, the mineralization of wastewater pollution is carried out. Purified water after biological treatment undergoes a chlorination process, and sludge is included in a new purification cycle. Process time - 6-12 hours.
The total cost of wastewater treatment averages 10-15% of the total cost of industrial enterprises. Sometimes these costs reach 30%. In addition, with the help treatment facilities it is not always possible to solve the problem of protecting the biosphere from harmful industrial discharges. The urgent task is to save water use, the solution of which is possible by creating resource-saving technological processes, as well as the use of recycled and recycled water supply (closed water circulation systems).
Wastewater quality control methods
Wastewater composition is controlled by the system the following indicators:
organoleptic indicators of water;
pH value of the medium;
the value of biological oxygen consumption (BOD value);
· the value of chemical oxygen demand (COD value);
The amount of oxygen dissolved in water
· concentrations of harmful substances for which MPC values exist.
Of the organoleptic indicators of water (color, smell, temperature, transparency), only color and smell are used in real practical situations. The color of water is determined by measuring its optical density on a spectrophotometer at various wavelengths of transmitted light.
The pH value is determined electrometrically.
When determining coarse impurities, measure mass concentration mechanical impurities and fractional composition of particles. To this end, water samples are filtered, evaporated and the amount of "dry" residue is measured.
BOD refers to the amount of oxygen dissolved in water (mg) required to oxidize organic matter contained in 1 liter of waste water over a certain period of time. In practice, a 5-day biological oxygen demand (BOD 5) is usually used. However, such an indicator does not say anything about contamination with biologically indegradable or difficult to decompose substances. Therefore, the COD indicator is additionally used, which determines the oxygen consumption for chemical oxidation. For an accurate determination of this indicator, chemical oxidizing agents are used (for example, a solution of potassium dichromate in sulfuric acid).
Measurements of the concentrations of harmful substances, for which MPC values are established, are carried out at various stages of treatment, including before discharge into water bodies.
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