The modules are arranged vertically. Water enters them from one end, and is discharged from the other. The number of modules in one filter usually does not exceed two units. Due to this, fewer gaskets are required, which reduces the likelihood of leaks. Vertical modules are convenient to maintain and test. They are easy to install and remove.

Filter modes

When ultrafiltration of water is performed, filters can operate in dead-end and tangential modes. In the first case, all the water supplied is purified. The deposits from the membrane are periodically removed during the flushing process or with the drain stream. The membrane fouls quickly and the pressure drop across it must be kept low, which reduces the performance of the apparatus. The method is used for water treatment, with a small concentration of suspensions.

In the tangential mode, the medium to be filtered circulates along the surface of the membrane and little deposits form on it. The turbulence of the flow in the supply channel makes it possible to purify water with a high concentration of suspended matter. The disadvantages of this method are the increase in energy costs to create a high flow rate and the need to install additional pipelines.

Ultrafiltration parameters

The main parameters of ultrafiltration are:

1. Selectivity is the ratio of impurity concentrations in polluted water (C in) and in the filtrate (C out): R = (1 - C out / C in) ∙ 100%. For the ultrafiltration process, it is large, which allows you to retain the smallest particles, including bacteria and viruses.
2. Filtrate consumption - the amount of purified water per unit time.
3. The specific consumption of the filtrate is the amount of product passing through 1 m 2 of the membrane area. Depends on the characteristics of the filter element and the purity of the source water.
4. Diaphragm pressure drop - the difference between the pressure on the supply side and the filtrate side.
5. Permeability is the ratio between the specific flow rate of the filtrate and the pressure drop across the membrane.
6. Hydraulic efficiency - the ratio between the flow rates of the filtrate and the supplied source water.

Ultrafiltration for water disinfection

Traditional methods for removing microorganisms include technologies using reagents. Ultrafiltration of water consists in the physical separation of microorganisms and colloids from it due to the small size of the membrane pores. The advantage of the method is the removal of the corpses of microorganisms, algae, organic matter and mechanical particles. At the same time, there is no need for special water treatment, which is mandatory in other cases. It is only required to first pass it through a 30-micron mechanical filter.

When buying filters, it is required to determine the pore sizes of the membranes. To completely remove viruses, hole diameters should be at the level of 0.005 µm. If the pore size is large, the disinfection function will not be performed.

In addition, ultrafiltration technology provides water clarification. All suspensions are completely removed.

The water ultrafiltration plant contains devices connected in parallel, which provides the necessary performance of the process and the possibility of replacing them during operation.

Water purification before ion-exchange filters

The resin is effective at a retention size of 0.1-1.0 microns, but they quickly clog the granules. Flushing and regeneration are of little help here. It is especially difficult to remove SiO 2 particles, which are especially abundant in wells and river water. After clogging, the resin begins to overgrow with microorganisms in places that are not washed with cleaning solutions.

Ion exchangers are also actively clogged with emulsified oils that cannot be removed. The clogging is so severe that it is easier to change the filter than to separate the oil from it.

Resin filter granules are actively clogged with high molecular weight compounds. They are well removed by activated carbon, but it has a short service life.

Ion exchange resins are effective together with ultrafiltration removing more than 95% of colloids.

- ultrafiltration before reverse osmosis

Operating costs are reduced by staging filters with progressive reduction in particle size. If a coarser cleaning is installed before the ultrafiltration module, then it increases the efficiency of reverse osmosis systems. The latter are sensitive to anionic and non-ionic flocculants if coagulation of contaminants is performed at the preliminary stage.

Large molecular organic matter quickly clogs the pores of reverse osmosis membranes. They are quickly overgrown with microorganisms. Pre-filtering water solves all problems and is economically viable when used with reverse osmosis.

Effluent treatment

Wastewater treatment by ultrafiltration makes it possible to reuse it in industry. They are suitable for use in engineering, and the technogenic load on open water bodies for drinking purposes is reduced.

Membrane technologies are used for electroplating and textile production, in the food industry, iron removal systems, when removing urea, electrolytes, heavy metal compounds, oil products, etc. from solutions. This increases the cleaning efficiency and simplifies the technology.

At low molecular weight impurities, ultrafiltration can produce concentrates of pure products.

Particularly important is the problem of separating emulsified oils from water. The advantage of membrane technology is the simplicity of the process, low energy consumption and no need for chemicals.

Surface water treatment

Precipitation and filtration have previously been effective ways to purify water. Impurities of natural origin are effectively removed here, but now there are man-made pollutants that require other cleaning methods to remove them. Especially many problems are created by the primary chlorination of water, which forms organochlorine compounds. The use of additional purification stages with activated carbon and ozonation increases the cost of water.

Ultrafiltration allows you to get drinking water directly from surface sources: algae, microorganisms, suspended particles and other compounds are removed from it. The method is effective with preliminary coagulation. This does not require long-term settling, since the formation of large flakes is not necessary.

The water ultrafiltration plant (photo below) allows you to achieve consistently good quality of purified water without the use of complex equipment and reagents.

The use of coagulation methods becomes ineffective, since many organic compounds in water are not detected by the traditional method of oxidation with potassium permanganate. In addition, the content of organics varies widely, which makes it difficult to select the required concentration of reagents.

Conclusion

Ultrafiltration of water through membranes makes it possible to achieve its required purity with a minimum consumption of reagents. Wastewater after treatment can be used for industrial purposes.

Ultrafiltration is not always effective. The method does not allow removing some substances, for example, some humic acids. In such cases, multi-stage cleaning is used.

Ultrafiltration is a membrane process for the separation of solutions whose osmotic pressure is low. This method is used in the separation of relatively high-molecular substances, suspended particles, colloids, etc. Ultrafiltration, in comparison with reverse osmosis, is a more high-performance process, since high membrane permeability is achieved at a pressure of 0.2–1 MPa.

Depending on the goals of the ultrafiltration process, the membranes allow:

solvent and only low molecular weight compounds (separation of high and low molecular weight compounds and concentration of high molecular weight compounds);

only solvent (concentration of macromolecular compounds);

solvent and fractions of macromolecular compounds with a certain molecular weight or size of macromolecular coils (fractionation of polymeric compounds).

Ultrafiltration, unlike reverse osmosis, is used to separate systems in which the molecular weight of the dissolved components is much larger than the molecular weight of the solvent (water). In practice, ultrafiltration is used when at least one of the components of the solution has a molecular weight of more than 500 daltons.

The driving force behind the ultrafiltration process, like reverse osmosis, is the difference in pressures on both sides of the membrane, but since the osmotic pressures of solutions of macromolecular compounds are usually low compared to the operating pressure, they are not taken into account when determining the parameters of ultrafiltration. If the ultrafiltration membrane is not capable of retaining low molecular weight compounds (especially electrolytes), then in this case the osmotic pressures of solutions of low molecular weight compounds are also not taken into account when determining the driving force of the process. For high concentrations of polymer solutions, when the osmotic pressures reach values ​​commensurate with the operating pressure, the driving force is determined by the equation

P=P -1.

The efficiency of ultrafiltration separation of solvents of substances is determined by the specific ratio of the two main components of the process - equilibrium and non-equilibrium. If the contribution of the equilibrium component, which is expressed in terms of the distribution coefficient of the open substance between the membrane and the solution, is smaller, then for all other identical conditions, the membrane will better retain this solute. In the case of ultrafiltration, the main contribution in determining the value of the distribution coefficient belongs to steric limitation, usually taking into account the important role of the surface properties of membranes (hydrophilicity, charge, chemical nature of functional groups, etc.).

The implementation of a non-equilibrium composite process, when the membrane is in a system where there is a concentration and pressure gradient on both sides, also has features compared to reverse osmosis membranes. This is due to the high permeability of relatively large-pore (pore diameter 5-500 nm) ultrafiltration membranes and low diffusion coefficients of macromolecules and colloids in solution, which are several orders of magnitude lower than those of low-molecular compounds. Diffuse transfer of disclosed macromolecular compounds and colloids is extremely small, and this feature predetermines their almost inevitable accumulation on the surface of ultrafiltration membranes (gelation), which significantly changes the pore structure and properties of the membrane. These changes turn out to be a significant or catastrophic decrease in the volume flow of the solvent through the membrane and an increase in the retention coefficient, that is, the helium reservoir is capable of self-retaining and actually acts as a membrane.

So, the solution of a specific problem of ultrafiltration separation often consists in a compromise solution: the use of a less permeable membrane, but one that has a high degree of pore monodispersity, a certain surface charge, or a degree of hydrophilicity.

In contrast to reverse osmosis, when membrane permeability decreases in the case of increased retention, during ultrafiltration, depending on the process conditions, these characteristics can simultaneously increase and decrease.

The main separation parameters - retention and productivity are determined by the upper active (selective) layer of the membrane. Its small thickness predetermines low hydrodynamic resistance to filtrate flow and, hence, high permeability. By changing the colloid-chemical properties of this formation (porosity, hydrophilicity, surface charge, etc.), its retention and permeability can be additionally controlled.

Unlike reverse osmosis membranes, which must necessarily be hydrophilic (this is due to the mechanism of the desalination action of the membranes), ultrafiltration membranes, as a rule, have low hydrophilicity or even hydrophobicity.

The advantages of hyper- and ultrafilter methods are: simplicity of equipment; the possibility of separation of solutions at normal temperature, separation of chain products, simultaneous purification of water from organic, inorganic and bacterial contaminants; low dependence of the cleaning efficiency on the concentration of contaminants in the water. Along with this, there are significant drawbacks. These include the phenomenon of concentration polarization, which consists in an increase in the concentration of a solute near the membrane surface due to the predominant transfer of the solvent through it, as well as the need to carry out the process at elevated pressure in the system.

Industrial reverse osmosis and ultrafiltration devices.

Currently, the following types of devices are used, which differ in the way the membranes are placed.

• 1. Apparatus pita "filter press" with flat-chamber filter elements. Applied at low productivity of installations. The package of filter elements is clamped between two flanges and tightened with bolts. The main disadvantage of these devices is the low specific surface area of ​​the membranes (60--300m 2 per 1m 3 of the device volume) and high metal consumption.
• 2. Devices with tubular filter elements (Fig. 3.3). They have a number of advantages: simplicity of design, low metal consumption, ease of turbulization of the solution. The lack of devices: low specific surface area of ​​the membranes (100--200 m 2 / m 3), the difficulty of replacing failed membranes.

3. Devices with filter elements of roll or spiral type.

They have a large specific surface area of ​​membranes (300-800 m2/m3). A semi-permeable membrane with a substrate is coiled and forms a cylindrical module with a diameter of up to 100 mm and a length of up to one meter (Fig. 3.4). One module of the "Gulf-Ayako" system with a membrane surface area of ​​4.65 m 2 and a volume of about 0.007 m 3 has a throughput of about 1.8 m 3 of water per day. The disadvantage of these devices is the complexity of installation and change of membranes.

4. Devices with membranes: from hollow fibers of small diameter (45 - 200 microns). Fibers (from cellulose acetate, nylon, etc.) are collected in bundles 2 - 3 m long, which are attached to the walls of the apparatus using epoxy resin (Fig. 3.5).

The specific surface area of ​​the membranes in these devices reaches 20,000 m 2 /m 3. The arrangement of the fibers can be linear, which requires embedding in two tube sheets, or U - shaped with embedding in one tube sheet. The DuPont model has a diameter of 35.5 cm, a length of 1 m and contains 900,000 fibers with a total surface of about 1700 m 2.

Devices with hollow fiber membranes are compact and high-performance. The lack of devices is the difficulty of replacing damaged fibers. If the solution to be separated flows inside the fibers, then it must be carefully cleaned from mechanical impurities.

The characteristics of the Dupont plant with a capacity of 40 m 3 of purified water per day are given below:

Installations with a productivity of 5-1000 m 3 / day are produced.

Application examples of reverse osmosis and ultrafiltration

Reverse osmosis and ultrafiltration can be successfully used to treat wastewater from chemical, petrochemical, pulp and paper and other industries.

The results of studies on the purification and concentration of wastewater by reverse osmosis at a pressure of 4.1 MPa are presented in table 1

From the above data, it can be seen that the reverse osmosis method provides effective wastewater treatment from mineral impurities. The resulting concentrated solution can be sent for regeneration to extract and use valuable impurities. The method of hyperfiltration treatment is promising for the recovery of salts of heavy metals from wastewater.

With the help of cellulose acetate membranes, it will be possible to concentrate chromium-containing wastewater from galvanic industries by 50–100 times at an optimum pressure of 8–10 MPa. The reverse osmosis plant achieved 93% efficiency in wastewater treatment from chromium. The resulting concentrated solution is then sent to cationite filters for purification from Na+, Ca+, Fe2+ and Fe3+ ions and returned to production.

Experimental data show that at a pressure of 3 - 3.5 MPa and a selectivity of membranes for NaCl equal to 93.5%, salt retention is provided for solutions of K2Cr2O7, CuSO4 and ZnSO4 by 96.5 - 99.0%.

At an industrial plant with a capacity of 0.45 m 3 / h, operating at a pressure of 3 MPa, NiCl2 and NiSO4 are extracted from the wastewater of the galvanic production. The resulting nickel salts are reused in production. Cellulose acetate membranes were replaced once every 1.5 years.

With the help of semi-permeable membranes, it is possible to concentrate solutions of alkalis, ammonium, phosphate and nitrate salts in the production of fertilizers, glycerin, alcohol, etc.

The reverse osmosis method can be successfully used for "tertiary" wastewater treatment from phosphorus and nitrogen compounds. The results of long-term operation of a semi-industrial reverse osmosis plant for domestic wastewater treatment showed that the content of phosphorus was reduced by 94%, ammonia - by 90% and nitrate - by 64%.

Wastewater treatment by reverse osmosis without pre-treatment is carried out at a pilot plant in San Diego (USA). Dissolved salts are removed from the water by more than 95%, and alkaline earth elements, nitrate, phosphate and sulfate ions - by more than 98%. After purification, the water is not potable, but can be used in agriculture and industry, including recycling water supply systems. The use of untreated water led to mechanical damage to the membranes by solid particles of contaminants and a high degree of wear of the feed pumps. To avoid this, preliminary filtration of wastewater through the wall was introduced, as well as coating of the membranes with a durable composition.

As a result of the use of reverse osmosis for the treatment of wastewater contaminated with radioactive substances, the activity of water in most cases decreases by 2 - 3 orders of magnitude.

Ultrafiltration on an industrial scale is used to regenerate silver salts from solutions formed in the production of photographic emulsions.

The cost of water treatment depends on the capacity of the plant and the degree of extraction of valuable impurities. It should be noted that the cost of changing membranes is very high and ranges from 4 to 12 dollars per 1 m 2. Nevertheless, the cost of water purification by reverse osmosis and ultrafiltration, especially at large installations, does not exceed the cost of water purification by well-known methods.

Ultrafiltration— the process of removing suspended and colloidal particles in the size range from 0.03 to 0.1 µm on low-pressure polymer hollow fiber membranes.

The purpose of the ultrafiltration unit as part of a water purification system is to prepare water according to quality indicators before the desalination stage.

Natural waters are a complex multicomponent dynamic system, which includes salts (mainly in the form of ions, molecules and complexes), organic substances (in molecular compounds and in a colloidal state), gases (in the form of molecules and hydrated compounds), dispersed impurities, bacteria and viruses. Thus, the extremely complex molecular composition of surface waters, as well as seasonal changes in such parameters as turbidity, color and oxidizability, do not allow us to accurately calculate the operation of an ultrafiltration plant and predict its mode of operation. To determine the effective mode of operation of the ultrafiltration plant, the correct calculation of the ultrafiltration scheme and the implementation of design work, it is necessary to conduct pilot tests.

To improve the operation of the ultrafiltration plant (increasing the specific filtration capacity), it is necessary to provide for the preliminary heating of the source water to 20-25°C.

Structure of the ultrafiltration plant

The ultrafiltration unit consists of the following blocks:

• pre-cleaning,
• filter modules,
• coagulant dosing systems,
• installation flushing.

Schematic diagram of the ultrafiltration plant

Precleaner An ultrafiltration unit (UF) consists of a feed water pump, usually a Grundfos, and a pre-filter with a 200µm cut-off to prevent coarse suspended matter from fouling the membranes.

Blocks of filter modules designed for the filtration process.

Coagulant dosing unit designed to coarsen impurities and facilitate their removal. The coagulant dosing unit consists of dosing pumps and a coagulant preparation tank. Aluminum polyoxychloride, for example, Aqua-Aurat 18, is usually used as a coagulant in ultrafiltration.

In order to store an hourly supply of source water and ensure the independence of the operation of the treatment plant in terms of hydraulic parameters, a raw water tank.

To ensure the required hydraulic parameters of the plant operation, the ultrafiltration plant includes source water pumping station.

Based on the described purpose of the elements below is given algorithm of operation of the ultrafiltration unit.

Water from the source water tanks is taken by pumps for treatment. Before the source water pumps, a coagulant is supplied to the treated water by a dosing pump at a flow rate proportional to the flow rate of the source water. The flow rate of the coagulant is determined during pilot tests of the ultrafiltration unit.

Dosing of the coagulant contributes to the effective reduction of organic and iron-containing compounds, allows you to enlarge the contained particles of colloidal substances, thereby increasing the efficiency of the water purification process.

The source water after treatment with a coagulant is fed to the pre-filter, and then to the ultrafiltration filter modules.

Water after ultrafiltration modules is directed into the clarified water tank.

Backwashing and chemically enhanced filtering modules is carried out using flushing unit ultrafiltration unit, consisting of washing pumps, coarse filters with a cut-off of 200 microns to prevent large inclusions from entering the tank, sulfuric acid dosing pumps, dosing pumps and a biocide dosing tank. Backwashing is carried out 3-5 times per hour to remove suspended solids accumulated during filtration, with a reverse flow of clarified water. Chemically enhanced washing is carried out 1-3 times a day and allows cleaning of ultrafiltration membranes from organic (alkaline washing) and inorganic (acid washing) contaminants.

All flow switching in the installation is performed automatically by the automated process control system (APCS). The parameters of the clarification process (pressure, flow rate, pH) are controlled according to the readings of the installed instruments.

The main parameters of the use of ultrafiltration plants

Purified water quality: Suspended solids in source water up to 1,000 mg/l

Decrease in the main indicators in % of the original:

• Suspended solids: up to 100%
• Oxidability: up to 70%
• Iron: up to 97%
• Color: up to 96%
• TMF: up to 99.9%

Comparison of ultrafiltration and conventional treatment

By traditional cleaning we mean clarifiers and mechanical filters.

Ultrafiltration:

• access to drinking water
• compactness
• full automation and autonomy of work
• in most cases primary chlorination is not required
• low operating costs

Traditional cleaning:

• water quality does not always meet drinking standards
• bulkiness
• complexity of automation (clarifiers)
• primary chlorination required
• high operating costs

Brief description of the units of the ultrafiltration plant

a) Coagulation block It is designed for coarsening impurities and their better removal to ultrafiltration units. The coagulation unit is completed with coagulant dosing tanks, dosing pumps (redundancy), instrumentation, pipelines and necessary fittings. It is supposed to use a liquid coagulant - aluminum polyoxychloride (the type and dose of the reagent is specified in pilot tests).

At the request of the customer, it is possible to use the existing coagulant and the system for preparing the working solution of the reagent. Estimated annual consumption of 100% coagulant can be about 135 tons.

b) Source water pump block designed to supply water to the membrane blocks of the installation. It is completed with Sulzer pumps with a frequency drive, instrumentation, pipelines and necessary fittings. Each membrane unit is equipped with its own source water pump.

c) Coarse filter unit to protect ultrafiltration membranes from coarse suspensions, a self-washing protective barrier filter with a filtration fineness of 200 µm is provided. Washing of filters is carried out automatically by time or by pressure difference. The washing unit is equipped with source water pumps that supply water to the membranes. All pumps are equipped with frequency drives.

d) Block of filtering modules. The ultrafiltration unit is completed with blocks of membrane elements, including 1 reserve block for every 10 workers (the approximate capacity of one block, depending on the task, is 50-150 m 3 / h).

During normal operation of the plant, all units operate. The specific filtration flow on the water of a surface water source is usually 50-70 l/m 2 h and is specified during pilot tests and commissioning.

e) Membrane flushing unit operates in two modes:

• backwash;
• chemically enhanced washing.

During chemically enhanced washing, solutions of sodium hydroxide and an oxidizing agent (sodium hypochlorite), sulfuric acid are supplied to the membrane block in the reverse flow of the filtrate.

A chemically enhanced alkaline wash is made with 30% NaOH, and 14% NaOCl in a 3:1 ratio. Chemically enhanced acid washing is carried out with concentrated sulfuric acid. All stream switching is done automatically.

The approximate frequency of backwashing is once every 20-60 minutes (duration 1 minute); chemical washing - once a day. The hydraulic operating modes of the installation are specified during pilot tests.

The flushing unit is equipped with strainers and flushing pumps (working and standby) with frequency drives.

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For Russia and the CIS countries, the problem of a national scale has become the supply of the population with high-quality tap water. Traditional water treatment methods do a poor job of removing a significant amount of new man-made pollutants.

The deterioration of most water mains leads to secondary water pollution and an increase in accidental emissions. Traditional household main filters do not cope with the task of high-quality water purification. The solution to this problem is the use of the latest and promising method of ultrafiltration - the membrane method of water purification.

Company Waterman offers you ultrafiltration installations that successfully solve a whole range of water purification tasks. Our specialists will develop an optimal technological scheme for water treatment using ultrafiltration technologies, design, install and put the system into operation.

On an industrial scale, the ultrafiltration method for water purification has been used since the end of the 20th century. In a year, the total increase in the volume of water purified by ultrafiltration is about 25%.

The severity of the problem with clean tap water in Asian countries (such as Malaysia, Singapore, Taiwan, China) contributed to the establishment in 1985 of a research center in Singapore.

The center has developed reliable and inexpensive ultrafiltration technology for these countries. Now the household ultrafiltration module in Asian families (for example, in Malaysia) is the same household attribute as a TV or a refrigerator.

Ultrafiltration technology, improved and time-tested, did not go unnoticed by Europe and America.

Applications of ultrafiltration technology

Since the end of the twentieth century. the ultrafiltration method began to be used on an industrial scale. To date, hundreds of plants with a capacity of up to 4105 m 3 /day are operating in the world. About 25% is the annual total increase in the volume of water treated by ultrafiltration. Ultrafiltration provides high-quality purification of water from surface sources, drinking, recycled and process water at a minimum of operating costs. Below is a list of the main areas of application of ultrafiltration technology.

Using ultrafiltration method for water disinfection

Using standard ultrafiltration modules, viruses and bacteria are removed at a level of at least 99.99%. Unlike traditional methods of water disinfection (chlorination, ultraviolet disinfection, ozonation, etc.), ultrafiltration physically removes microorganisms from the water. This is achieved due to the fact that in the ultrafiltration membrane the pore diameter is much smaller than the size of viruses or bacteria (pore - 0.01 microns, bacteria - 0.4 ... 1.0 microns, virus - 0.02 ... 0.4 microns). Thus, microorganisms present in the water cannot penetrate such a barrier. As a result, the need for primary chlorination of water is eliminated, and disinfection is carried out immediately before water is supplied to the consumer.

Ultrafiltration treatment of domestic and industrial wastewater

All over the world, they are trying to reuse treated wastewater, which is much more profitable not to be discharged into an open reservoir, but after ultrafiltration treatment, to be sent for industrial use. Thus, the technogenic load on water bodies for household and drinking purposes is significantly reduced.

Using ultrafiltration as a pre-stage to reverse osmosis systems

Typically, bag or cartridge filters (filter rating 5 µm) are used for pre-cleaning. Replacing them with ultrafiltration modules, which have a longer service life, will reduce operating costs.

The use of ultrafiltration modules makes it possible to stabilize the SDI colloidal index at the level of 1-2, as a result, the frequency of washing and replacing reverse osmosis membranes is significantly reduced.

The use of clarifier + flocculant technology as a pre-filter before reverse osmosis requires careful selection of flocculants. Cationic flocculants cannot be used as reverse osmosis membranes are negatively charged. Anionic and nonionic flocculants are used at minimum doses. It is difficult to restore the functionality of membranes after blocking the pores with a flocculant. This problem is completely absent in ultrafiltration treatment.

Reverse osmosis membranes are subject to biofouling under certain conditions. The occurrence of this problem is facilitated by the high temperature of the source water, the high content of "organics" (permanganate oxidizability is more than 3.0 mgO 2 /l), long interwash cycles, and significant contamination of the source water.

A significant amount of macromolecular “organics” contained in water with traditional clarification technology can block the pores of reverse osmosis membranes. The ultrafiltration process makes it possible for reverse osmosis systems to effectively treat water with a very high biofouling potential (eg treated domestic wastewater).

Ultrafiltration of washing waters of iron removal, clarification and sorption filters

The degree of water utilization rises to 99.8% if the wash water is subjected to ultrafiltration. These purposes are served by ultrafiltration filter presses, which provide mechanical dehydration of sediments.

Using Ultrafiltration to Clarify Water

When evaluating a new technology, attention is paid to the cost and quality of the resulting product. The lower cost of high quality clarified water is ensured due to the compactness of ultrafiltration units, ease of maintenance and low consumption of chemicals. Ultimately, the cost of clarified water obtained by ultrafiltration is determined by the quality of the source water and the capacity of the plant. The cost of purified water for small commercial installations (capacity less than 100 m 3 /hour) is in the range of 1.5-3.5 rubles / m 3, for installations with a capacity of more than 100 m 3 /hour, the cost of purified water is lower: 0.5-2 .0 rub/m 3 .

Water clarification when bottling (clarification of drinking and mineral water)

The purity of the natural source of water does not eliminate the need to pass it through a fine filter before bottling drinking water into bottles.

Water purification using the most commonly used cartridge type mechanical filters (for example, Big Blue 20) or bag type 1-5 microns does not provide the required degree of filtration. The most promising method for improving the quality of water (natural waters) is water clarification by ultrafiltration (improvement of water quality by sterilizing ultrafiltration).

Ultrafiltration as a preliminary purification step before ion-exchange filters

Great difficulties arise when using (especially in industry and energy). The particle size distribution of water is rarely taken into account when designing water filtration systems. Microfiltration and clarification pre-filters effectively remove suspended particles larger than 1.0 microns. Ion-exchange resins do not let through colloids with a size of 0.1…1.0 µm, but at the same time they are “plugged”. The result of "plugging" is a decrease in the intensity of ion exchange and resin resource. To avoid this, it is necessary to reduce the turbidity of the source water below 3 NTU (nephelometric turbidity units). This allows ultrafiltration (provides turbidity up to 0.1 NTU).

SiO2 colloids often found in river water and artesian well water cause problems in the ion exchange process. At a pH value less than 7 (after H-cationization), polymerization of SiO 2 can occur (molecules are combined into long chains). It is extremely difficult to remove such formations from the resin surface: long, weakly effective washings and restoration of the ion-exchange material are required. To prevent irreversible "plugging" of ion exchangers, it is enough to install an ultrafiltration system in front of ion-exchange filters that removes more than 95 (and sometimes more than 98)% of SiO 2 colloids. Under certain conditions, for example, in the presence of spaces in the system that are not washed with chemical solutions, an increase in the number of microorganisms occurs, which also cause “clogging” of ion exchange resins. In addition, it happens that seals, valves and untreated surfaces that come into contact with water do not meet sanitary requirements and technical standards. In such areas, at favorable temperatures and pH levels, the biofouling process is activated. The use of ultrafiltration can significantly slow down the course of this process on the surface of the resins.

In the petrochemical, chemical and wastewater industries, ion exchange resins become contaminated with oils in the water. Some of the oils are easily removed during settling, flotation or coalescence. But chemically or mechanically emulsified oils are difficult to remove. It is often cheaper to replace resins than it is to try to de-oil them. This problem is solved by preliminary ultrafiltration, which ensures the removal of up to 99% of emulsified oils before subsequent water treatment with resins.

Often the surface of the filter granules and the space between them are contaminated with high-molecular organic compounds. They try to solve the problem by using activated carbon or a certain mixture of ion exchange resins. However, activated carbon has a short service life and is overgrown with microorganisms, and resins often have to be regenerated (sometimes inefficiently). Given the increased operating costs and equipment downtime, we see that ultrafiltration is a more economically viable method of water purification from organic impurities.

Ultrafiltration treatment of surface waters and river, lake water

The methods of sedimentation and filtration with preliminary coagulation, widely used in public utilities and industry in Russia, have not undergone radical changes since the middle of the 20th century. Coagulation effectively removes impurities of natural origin. But there has been a significant increase in the number of man-made water pollutants, for the removal of which sedimentation and filtration methods may not always be effective. About 1,000 controlled chemicals are listed under the new sanitary standards. During the primary chlorination of water, hundreds of organochlorine compounds are formed, which causes great problems.

The content of organic substances is judged, as a rule, by the permanganate oxidizability of water. Due to the difficulty of oxidizing technogenic organic compounds with potassium permanganate, the true quality of water in terms of the content of "organic matter" is not reflected by this indicator. In the process of observations during the week, the composition of the water in the river. Kama noticed that the permanganate oxidizability varied in the range from 3.36 to 4.16 mgO 2 /l, while the bichromate oxidizability ranged from 15 to 43 mgO 2 /l. Fluctuations in the indicator are due to a constant change in the composition of organic compounds. Under such conditions, it is difficult to choose the optimal dose of the coagulant, which contributes to the unstable operation of clarifiers and additional load on subsequent purification stages. The introduction of such additional purification stages as ozonation, activated carbon sorption, etc. increases the operating costs and, accordingly, the cost of purified water.

Difficulties in providing the population of Russia with high-quality drinking water have led to the fact that this has become a real state problem. The traditionally used methods for obtaining clean drinking water using chlorination, coagulation, flotation, sedimentation and filtration have the following significant disadvantages:

• instability of treated water quality;
• large resource intensity and equipment dimensions;
• the danger of the formation of carcinogens when using chlorine-containing reagents for water disinfection;
• high costs of expensive chemical reagents, as well as solving the problems of organizing their preparation and storage.

Ultrafiltration is devoid of the above disadvantages. With its help, water is purified from suspended particles, bacteria, viruses, algae, colloids and high-molecular organic compounds. Significantly increases the effect of clarification and the degree of extraction of organic compounds during pre-coagulation. The efficiency of the ultrafiltration method depends little on changes in the dose of the coagulant, since the filtration of the formed flakes is carried out regardless of their size. It also does not take a long time to form large flakes and there is no need for a flocculation chamber. Water purified using the ultrafiltration method is microbiologically safe and has a consistently high quality, which does not depend on the composition of the source water.

Thus, the advantages of the ultrafiltration method - high purification efficiency, low operating costs and equipment reliability - make its application a profitable undertaking. Company specialists Waterman help you make it happen!

Our company provides its services for the sale, design and installation of water treatment systems for both industrial production of any scale and individuals. We work efficiently and efficiently!