Ultrafiltration or traditional water purification technology - a comparative analysis. Ultrafiltration of wastewater Composition of an ultrafiltration unit
Ultrafiltration is a membrane process for separating solutions whose osmotic pressure is low. This method is used to separate relatively high-molecular substances, suspended particles, colloids, etc. Ultrafiltration, compared to reverse osmosis, is a more highly productive process, since high membrane permeability is achieved at a pressure of 0.2-1 MPa.
Depending on the purposes of the ultrafiltration process, the membranes pass:
solvent and only low molecular weight compounds (separation of high and low molecular weight compounds and concentration of high molecular weight compounds);
solvent only (concentration of high molecular weight compounds);
solvent and fractions of high molecular weight compounds with a certain molecular weight or size of macromolecular coils (fractionation of polymer compounds).
Ultrafiltration, in contrast to reverse osmosis, is used to separate systems in which the molecular weight of dissolved components is much greater 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 over 500 daltons.
The driving force of the ultrafiltration process, like reverse osmosis, is the difference in pressure on both sides of the membrane, but since the osmotic pressures of solutions of high molecular weight compounds are usually low compared to the operating pressure, they are not taken into account when determining ultrafiltration parameters. 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 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 is determined by the specific ratio of the two main components of the process - equilibrium and nonequilibrium. If the contribution of the equilibrium component, which is expressed through the coefficient of distribution of the dissolved substance between the membrane and the solution, is smaller, then under all other identical conditions the membrane will better retain this dissolved substance. 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 nonequilibrium component of the process, when the membrane is located 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-porous (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 low-molecular compounds. The diffuse transfer of exposed high-molecular 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 result in a significant or catastrophic decrease in the volumetric flow of solvent through the membrane and an increase in the retention coefficient, that is, the helium layer is capable of self-retention and actually acts as a membrane.
So, solving a specific problem of ultrafiltration separation often consists of a compromise solution: using a less permeable membrane, but one that has a high degree of pore monodispersity, a certain surface charge or degree of hydrophilicity.
Unlike reverse osmosis, when membrane permeability decreases as membrane retention increases, during ultrafiltration, depending on 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 determines low hydrodynamic resistance to filtrate flow and, therefore, high permeability. By changing the colloidal chemical properties of this layer (porosity, hydrophilicity, surface charge, etc.), one can further regulate its retention and permeability.
Unlike reverse osmosis membranes, which must be hydrophilic (this is due to the mechanism of desalination of the membranes), ultrafiltration membranes, as a rule, have low hydrophilicity or even hydrophobic.
The advantages of hyper- and ultrafilter methods are: simplicity of equipment; the ability to separate solutions at normal temperatures, isolate chain products, and simultaneously purify water from organic, inorganic and bacterial contaminants; low dependence of cleaning efficiency on the concentration of contaminants in water. Along with this, there are also significant disadvantages. These include the phenomenon of concentration polarization, which consists in an increase in the concentration of a dissolved substance at the surface of the membrane due to the preferential transfer of solvent through it, as well as the need to carry out the process at increased pressure in the system.
Industrial reverse osmosis and ultrafiltration devices.
Currently, the following types of devices are used, differing in the way membranes are placed.
- 1. “Filter-press” feed devices with flat-chamber filter elements. Used for low productivity installations. The filter element package is clamped between two flanges and tightened with bolts. The main disadvantage of these devices is the low specific surface area of the membranes (60-300 m 2 per 1 m 3 of 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 turbolization of the solution. Disadvantage of the devices: low specific surface area of the membranes (100-200 m2/m3), difficulty in replacing failed membranes.
3. Devices with roll or spiral filter elements.
They have a large specific membrane surface area (300-800 m2/m3). The semi-permeable membrane with the substrate is rolled up in the form of a spiral 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 capacity of approximately 1.8 m 3 of water per day. The disadvantage of these devices is the difficulty of installing and changing membranes.
4. Devices with membranes: made of hollow fibers of small diameter (45 - 200 microns). Fibers (from cellulose acetate, nylon, etc.) are collected into 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 m2.
Devices with hollow fiber membranes are compact and highly efficient. The disadvantage of the devices is the difficulty of replacing damaged fibers. If the solution to be separated flows inside the fibers, then it must be thoroughly cleaned from mechanical impurities.
The characteristics of a DuPont installation with a capacity of 40 m 3 of purified water per day are given below:
Installations with a capacity of 5-1000m3/day are produced.
Examples of application of reverse osmosis and ultrafiltration methods
Reverse osmosis and ultrafiltration can be successfully used for purification Wastewater chemical, petrochemical, pulp and paper and other industries.
The results of studies on the purification and concentration of wastewater using reverse osmosis at a pressure of 4.1 MPa are presented in Table 1
From the above data it is clear that the reverse osmosis method provides effective cleaning wastewater from mineral impurities. The resulting concentrated solution can be sent for regeneration to extract and use valuable impurities. The hyperfiltration purification method is promising for salt regeneration heavy metals from wastewater.
Using cellulose acetate membranes it will be possible to concentrate chromium-containing wastewater from electroplating industries by 50 - 100 times at an optimal pressure of 8 - 10 MPa. The reverse osmosis plant has achieved 93% efficiency in treating wastewater from chromium. The resulting concentrated solution is then sent to cation exchange filters to remove Na+, Ca+, Fe2+ and Fe3+ ions and returned to production.
Experimental data show that at a pressure of 3 - 3.5 MPa and a membrane selectivity for NaCl equal to 93.5%, salt retention for solutions of K2Cr2O7, CuSO4 and ZnSO4 is ensured by 96.5 - 99.0%.
On industrial installation with a productivity of 0.45 m 3/h, operating under a pressure of 3 MPa, NiCl2 and NiSO4 are extracted from wastewater from galvanic production. The resulting nickel salts are again used in production. Cellulose acetate membranes were replaced once every 1.5 years.
Using 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 the treatment of domestic wastewater showed that the phosphorus content was reduced by 94%, ammonia by 90% and nitrates by 64%.
Wastewater treatment by reverse osmosis without pre-treatment carried out at a pilot plant in San Diego (USA). Dissolved salts are removed from 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 in water recycling systems. The use of untreated water led to mechanical damage to the membranes due to 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 membrane coating with a durable composition.
As a result of the use of reverse osmosis for the purification of wastewater contaminated with radioactive substances, the activity of water in most cases is reduced by 2 - 3 orders of magnitude.
Ultrafiltration is used on an industrial scale for the regeneration of silver salts from solutions formed in the production of photographic emulsions.
The cost of water purification depends on the productivity of the installation and the degree of extraction of valuable impurities. It should be noted that the cost of replacing membranes is very high and ranges from 4 to 12 dollars per 1m2. However, the cost of water purification by reverse osmosis and ultrafiltration, especially in large installations, does not exceed the cost of water purification by widely known methods.
Equipment models
Purpose of water ultrafiltration
Ultrafiltration of water is used to purify liquids from proteins and high-molecular organic compounds. The installations are capable of partially retaining viruses and bacteria. Cleaning from finely dispersed mechanical impurities is carried out.
The fairly broad capabilities of the method determine its wide demand in various industries:
- preparation of feed water in softening and reverse osmosis installations (boiler rooms, boiler rooms, body exchange equipment);
- cleaning water flow from open sources from bacteria and viruses (preparation of drinking and process water);
- industrial wastewater treatment.
The final stage of post-treatment after biological treatment facilities.
Composition of ultrafiltration units of the PVO-UF series
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Basic equipment: |
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Mechanical pre-filter mechanical cleaning, 300 µm; |
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Coagulant dosing |
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Static mixer; |
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Contact capacity; |
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Ultrafiltration modules; |
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Automatic membrane washing system; |
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CEB-washing reagent dosing stations |
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Backwash pump; |
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Protection of the pump from operation in dry running mode; |
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Hydraulic-filled inlet and working pressure gauges; |
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Visual flow meters of purified and rinsing water; |
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System for adjusting operating parameters; |
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System of delay and smooth start of the pump; |
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Working pipelines made of PVC-U / polypropylene; |
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Powder-coated steel frame; |
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Stainless steel frame; |
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Diaphragm valves for flow control; |
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Electric valves with manual override for flow control; |
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Hypochlorite dosing station; |
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Panel for water sampling; |
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System automatic control controller-based installation; |
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Control cabinet with control panel; |
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Frequency control of pumping equipment; |
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Permeate production counter; |
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Set of sensors (dry running, permeate pressure, differential pressure in the module, float for the tank) |
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Options (on request): |
Equipment |
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Advanced control system based on an industrial controller; |
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System for preliminary preparation of source water before ultrafiltration installation; |
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Dispatching the equipment control process with output to the computer of a process engineer or operator; |
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Containers of clean and/or water for rinsing; |
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Feed pump made of stainless steel; |
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Reservation of main equipment; |
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CIP flushing system; |
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Dosing station for pH level adjustment; |
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Adsorption unit; |
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Extended warranty - 5 years. |
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Design of water ultrafiltration modules:
How ultrafiltration works
Ultrafiltration as a class refers to baromembrane separation processes. The acting force is the pressure difference on different sides of the filter partition (membrane).
To prevent rapid equipment failure, incoming water must be pre-treated to remove small mechanical impurities. This function is performed by a mechanical “dirt filter”.
If necessary, auxiliary reagents - coagulants and flocculants - are added to the input line. With their help, it is possible to retain particles whose sizes are smaller than the diameter of the membrane pores. Addition of reagents to the stream causes the formation of small flocs. Colloidal and organic impurities that need to be removed are fixed on the surface of the resulting flakes.
Periodically, to restore the operation of the installation, the filter module must be washed. It is carried out by the reverse flow of water from the permeate collector.
When strong chemical precipitates form, additional reagents (acid, alkali or sodium hypochlorite) are used. The washing solution passes from the outside of the fibers, washing out all accumulated contaminants into the drainage line.
Ultrafiltration unit design
The main element of an ultrafiltration installation is the filter module. An ultrafiltration installation implemented by the company, the modules are made using Multibore® technology.
A stream of water is passed through a bundle of multichannel fibers. The fibers are made from polyestersulfone. A special feature of this material is the presence of small structural pores with a diameter of up to 0.02 microns. In fact, the walls of the fibers are a filter made of a semi-permeable membrane.
The module layout ensures that the incoming water flow is directed into the fiber bundle. The filtration process takes place from the inside out. Trapped contaminants remain inside the channels. Clean water (permeate) comes out through the walls and is removed from the housing.
Composition of an ultrafiltration unit
Depending on operating conditions, requirements for the quality of purified water and the required level of automation, the composition of the main structural elements may vary slightly. The basic, standard version has the following composition:
- block of filter modules;
- reagent block (dosing of coagulant and flocculant solutions);
- pre-filter;
- automatic washing unit;
- automatic control unit;
- piping and pipeline fittings.
Additionally, at the request of the customer, or if necessary, the equipment of the installation can be expanded. Additionally, the composition includes:
- storage tank for collecting filtrate;
- injection pump on the inlet line;
- control and measuring equipment (the number and functional purpose of devices determines the degree of automation of the system).
The advantage of ultrafiltration
Production in the Russian Federation.
. Installment payment.
. Possibility of use in complex water purification systems.
. Free shipping.
. Wide range of models.
. Long period of operation.
. 5 year warranty.
. Compactness.
. Possibility of full automation.
. Modular design, possibility of increasing productivity.
. Low power consumption.
. Low water consumption.
. 100% removal of suspended solids.
. Removing bacteria and viruses from water.
. Purification of water with high turbidity and color.
. Removal of high molecular weight organic compounds.
. Integration with existing systems management.
. The highest level of purification among all clarification technologies.
. Individual preliminary tests (pilot tests).
The effectiveness of the equipment offered by SPC Promvodochistka is confirmed by the results of a large number of implemented and successfully operating facilities throughout Russia.
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Technological layout options
Ultrafiltration installations of SPC PromVodOchistka can be used in technological processes of varying complexity. Depending on the quality of the incoming water, the layout of the stages of the purification process can be performed in several options:
- option 1:
- rough mechanical cleaning;
- ultrafiltration.
It is used to purify water coming from a well. The incoming flow is characterized by a high content of suspended solids while other parameters are within normal limits.
- option 2:
- rough mechanical cleaning;
- mechanical filtration through a layer of inert material;
- ultrafiltration;
- filtration through a layer of sorption material.
A similar scheme is used when treating water with a high content of iron compounds, suspended solids and high turbidity. It is used to purify water taken from open water intake sources.
- option 3
- rough mechanical cleaning;
- ultrafiltration;
- water softening.
The main area of application is water from surface sources with a high content of magnesium and calcium salts.
- option 4
- rough mechanical cleaning;
- ultrafiltration;
- filtration through a layer of sorption material;
- treatment in reverse osmosis units.
The main purpose is the treatment of water with a high content of heavy metal ions and exceeding the regulated organoleptic indicators. At the same time, removal of suspended solids, iron, calcium and magnesium salts can be carried out.
The possibilities for using ultrafiltration installations are not limited to the above options. When contacting SPC PromVodOchistka, specialists from the design department will help you select the entire technological cycle of treatment using membrane equipment for any conditions.
Ultrafiltration is a membrane process that occupies an intermediate position between microfiltration and nanofiltration. Membranes for ultrafiltration have pore sizes from 0.05 microns (the minimum pore size of microfiltration membranes) to 10 nm (the maximum pore size of nanofiltration membranes).
The main area of application of ultrafiltration is the separation of macromolecular substances from solutions, while the minimum limit of released solutes corresponds to molecular masses of several thousand Daltons. For the separation of dissolved organic compounds with a molecular weight of several hundred to several thousand Daltons ( Yes) uses a membrane process - nanofiltration. Ultrafiltration membranes are porous, therefore particle retention is determined mainly by the shape and size of the pores. Solvent transport in this case is directly proportional to the applied pressure. With micro- and ultrafiltration, the same membrane phenomena occur and the same separation principle is produced.
However, ultrafiltration membranes, unlike microfiltration membranes, have an asymmetric structure. In this case, the hydrodynamic resistance is determined by a small fraction of the total thickness of the membrane for ultrafiltration of water, while in microfiltration, apparently, the full thickness of the membrane contributes to the hydrodynamic resistance. The thickness of the top layer of the ultrafiltration membrane is, as a rule, no more than 1 micron.
Cross section of ultrafiltration polysulfone membrane under an electron microscope (x 10000)
An industrial application of ultrafiltration technology is the fractionation of macromolecules: large molecules are retained by the membrane, while small molecules, together with solvent molecules, pass freely through the membrane. To select ultrafiltration membranes, manufacturers use the concept of molecular weight "cutoff". However, in addition to molecular weight, the selectivity of ultrafiltration membranes is significantly influenced by the phenomenon of concentration polarization. For example, an ultrafiltration membrane with a cutoff of 40 KYes completely permeable to cytochrome with a molecular weight of 14.4 KYes. Moreover, in a mixture of cytochrome and albumin (67 KYes) both albumin and a significant portion of cytochrome will be retained. The reason for this phenomenon is concentration polarization. The membrane is impermeable to albumin, which forms an additional layer on the membrane surface that acts as a dynamic membrane that retains cytochrome. Various solutes, such as linear macromolecules (polyethylene glycol, dextran, etc.) or globular proteins, significantly affect the membrane cutoff characteristics during ultrafiltration. Therefore, when supporting ultrafiltration membranes for various technological processes it is necessary to take into account the influence of concentration polarization and the molecular weight distribution characteristic of most polymers.
Ultrafiltration is widely used in industry and laboratories to solve problems associated with the separation of high and low molecular weight compounds. This includes wastewater treatment from industrial enterprises, separation and concentration of products in food and dairy production, extraction of high molecular weight compounds (HMCs) in chemical and textile industry, metallurgy, in the leather industry, as well as in paper production.
To solve existing problems in wastewater treatment from heavy metals to low concentrations of maximum permissible concentrations, a number of modern treatment facilities have been created that allow industrial water purification from suspended solids, heavy metals, petroleum products, synthetic surfactants (surfactants), and other harmful substances. The operation of treatment facilities is based on new water purification technologies: electroflotation and ultrafiltration.
Technological scheme for wastewater treatment using ultrafiltration
Above is technology system purification of wastewater from galvanic production with subsequent discharge of purified water into the sewerage system, or supply to a reverse osmosis installation for desalination when creating a recycling water supply for the enterprise. This system industrial water treatment is recommended for use in the design of new treatment facilities, or reconstruction of existing wastewater treatment systems to improve their environmental safety and economic efficiency.
A similar water purification technology has been successfully implemented at several treatment facilities of electroplating industries in the Russian Federation. The technology provides for the treatment of acid-base and chromium-containing wastewater in independent technological chains. The technology provides deep purification of wastewater from heavy metals to a level of 0.005 mg/l, suspended solids and oil products to a level of 0.01-0.05 mg/l. Recommended for newly constructed treatment facilities in regions with strict MPC standards.
Ultrafiltration installation based on ceramic with a productivity of 2.5 m 3 / hour
The presented technologies have found application in modular, block-modular and prefabricated installations. Various modifications of modular plants have been developed depending on the composition of wastewater and climatic conditions.
Modular water purification plants with a capacity of 0.1 to 50 m 3 /h meet modern hygienic standards and are designed for industrial water purification to the requirements of maximum permissible concentrations for fishery reservoirs.
Ultrafiltration is a membrane process located between microfiltration and nanofiltration. Ultrafiltration membranes have a pore diameter of 0.005-0.2 microns and allow the retention of highly dispersed and colloidal particles, macromolecules with a lower molecular weight limit of up to several thousand, microorganisms and algae. A comparative table of the filtering abilities of various membrane processes is presented (the table was prepared by specialists from the D.I. Mendeleev Russian Chemical Technical University).
Ultrafiltration is the forcing of liquid through a semi-permeable membrane, which is permeable to ions and small molecules and, at the same time, impermeable to colloidal particles and macromolecules. Ultrafiltration of solutions containing BMS molecules (highly dispersed systems), in contrast to ultrafiltration of sols, is called molecular filtration. Ultrafiltration can be thought of as hyperfiltration, where the membrane allows only solvent molecules to pass through, or as pressure dialysis. In the first case, the membrane process is usually called reverse osmosis.
Characteristics of some ultrafiltration membranes
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Detained substances |
Selectivity |
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"Amicon" |
Polyelectrolyte |
Raffinose |
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Myoglobin |
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Dextran T10 |
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Albumen |
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Chymotrypsinogen |
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Aldolaza |
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Apoferritin |
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19S globulin |
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"Millipore" |
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"Deitsel" |
Copolymers |
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Membranes for ultrafiltration are usually made in the form of cylindrical cartridges or plates from microporous inorganic materials, but most often from synthetic polymers (polyamides, polysulfones, polyethersulfones, PVDF etc.). The maximum size of molecular particles (particles) passing through the membrane ranges from several microns to hundredths of microns. The selectivity (separation ability) of membranes depends on their physicochemical properties and structure, the composition of the filtered medium, pressure, temperature and other factors.
Ultrafiltration as a method of water purification, wastewater concentration, and/or fractionation of BMCs and multicomponent systems is widely used in industrial production. Ultrafilters are used to purify water from ionic and non-ionic pollutants, organic solvents, diesel fuel and oils, separation of protein mixtures (extraction of phospholipids from phosphatide concentrate), production of vitamins and enzymes. Ultrafiltration is used for microbiological and dispersion analysis, as well as analysis of air and water pollution from household and industrial waste.
Tips for the beekeeper: drinking bowls.
Every living thing on Earth needs water. Bees also need it in excess for excellent metabolism, to regulate body temperature, and so on. It’s a pity that beekeepers simply forget about this: beginners - due to ignorance; some are just lazy; and some simply believe that the bees, if necessary, will find water themselves. It’s good if there really is water nearby, for example, a river. But, if the water is far away, then the beekeeper must take care of it.
Bees look for water based on temperature, not taste. Although the taste of water is also important for them. They prefer to replenish water supplies where it is warmer, for example, this could be a swimming pool or well, or drinking bowls for pets. But they don’t like tap water, and it’s understandable why, because it doesn’t bring any benefit to humans either. Yes, and it is cold for bees, and if they drink cold water, then their body temperature decreases, and water makes up half of their body weight. If bees are accustomed to flying to a specific place for water, then it will be extremely difficult to wean them off, especially if they have been flying there for more than one month, and even more so, for more than one year.
And yet, where to start for a beekeeper who has decided to lure bees away from their usual watering place? It is necessary to build a drinking bowl for the bees in early spring; this drinking bowl should always be filled with fresh water. Then the bees will save both strength and energy that were previously spent searching for water. The requirements for the drinking bowl are simple:
Ease of disinfection;
Quick assembly and disassembly,
Facilities for bees and beekeepers,
Easy to fill with water,
And it should also be easy and quick to put into action.
Sanitary requirements:
The drinking bowl should be in a dry place,
Sunny place;
Windy place;
And where the bees’ flight direction is not the main direction.
Types of drinking bowls.
As a rule, beekeepers use two types of drinkers:
Individual.
Are common.
Various vessels and utensils, glass, wood, metal or plastic, are also used as drinking bowls. Use specially manufactured utensils, utensils specially made by beekeepers, or simply utensils adapted in the form of a drinking bowl.
And there is nothing wrong with the fact that the beekeeper did not buy a drinking bowl for the bees, but invented it himself. The main thing is that the vessel meets all functional and sanitary requirements. The water in it should be:
Fresh.
Clean.
Warm.
Most often in the apiary you can see drinkers general type. This is a container with a small tap. Under the crane there is a board at an angle. The board has grooves and various pebbles for beauty. Beekeepers also add shells to such drinkers to attract bees.
You should not give examples of homemade drinking bowls, supplement the examples with drawings - this is useless. Anyone can quickly design a drinking bowl. And in the store they are sold at an affordable price.
A method that is gaining increasing popularity in the field of combating microorganisms. An effective and comprehensive method of water disinfection.
Ultrafiltration for water disinfection is a relatively new method, since it has been known for a long time. Just other methods - reagent water disinfection and some physical methods of water disinfection are older. But also less perfect - from some points of view. Let's start with the definition.
Ultrafiltration is a method of water purification, simultaneous reagent-free disinfection and water clarification. Ultrafiltration removes insoluble impurities from water.
The principle of ultrafiltration in general
The principle of ultrafiltration technology is that water is forced through a semi-permeable barrier under a certain pressure. The holes in the barrier are smaller in size than viruses and other insoluble contaminants. Accordingly, everything that is larger than viruses is eliminated.
In addition, we should not forget that treating water with ultraviolet radiation requires special water preparation - which may not be carried out when disinfecting using ultrafiltration.
The degree of filtration in ultrafiltration units varies. This ranges from 0.01 micron (ten-thousandth of a millimeter) to 0.001 micron. This indicator must be clarified when purchasing. So, if the manufacturer says that the ultrafiltration it offers removes all viruses from the water, and the pore size is 0.01 microns, then this is not true. There are viruses and smaller size. Diameters of approximately 0.005 microns are required to completely remove viruses.
That is, ultrafiltration is an exclusively physical method of water purification, without the constant use of chemical reagents.
Further, if the manufacturer says that it has a microfiltration membrane (for example, a track membrane), and it removes viruses and bacterial spores, then this is not true. Because the holes in the microfiltration membrane are BIGGER than bacterial spores and viruses. Bacterial spores are removed on an ultrafiltration membrane. And completely.
Thus, ultrafiltration technology disinfects water more effectively than ultraviolet radiation. In addition, to treat water using ultrafiltration, there is no need to seriously precondition the water. A 30 micron pre-filter for mechanical water purification is sufficient.
The big advantage of ultrafiltration technology is that it is a comprehensive technology. And if chemical disinfection and ultraviolet light are responsible for disinfection and, to some extent, adhesion of particles, then ultrafiltration technology, in addition to disinfection, performs the function of water clarification. That is, before cleaning the water was cloudy and with bacteria, and after it it was clear and disinfected.
There are two large groups of ultrafiltration devices.
First group - drinking systems, which are installed under the kitchen sink. The speed of water purification using a household ultrafiltration system is most often 2-3 liters per minute, but it can be more. That is, water is prepared in the quantity needed for drinking and cooking. Most often, drinking systems based on ultrafiltration are designed like multi-stage reverse osmosis systems. The same flasks, only instead of an osmosis membrane there is an ultrafiltration membrane. And there is no storage tank.
That is, the device does not consist of a bare ultrafiltration membrane, but also of several stages of water pre-purification (most often,). That is, a household ultrafiltration system removes not only bacteria and viruses, but also mechanical impurities, chlorine, and organic chlorine compounds.
Ultrafiltration membranes for drinking systems can be ceramic and organic. Most often, they are organized as hollow fibers, inside which dirty water flows, and filtration occurs from the inside out. Ceramic membranes are more durable. However, both of them have their own resource, after which they need to be replaced. It is also necessary to pay attention to the resource indicator when choosing a device.
Second group - high capacity ultrafiltration systems- from 500 liters per hour. These systems are designed for water purification for the whole, cottage, apartment, restaurant, production. Industrial ultrafiltration installations can be organized either as hollow fibers or as spiral coils.
Ultrafiltration for a house or apartment can be used not only for a house or apartment. Clean, disinfected water is necessary for many industries - for production, for medical institutions, for swimming pools and so on. In any of these cases, almost identical membrane modules are used.
It is important that the main working element of the ultrafiltration apparatus - the ultrafiltration membrane - requires periodic disinfection. If it's not ceramic. Bacteria love the material the membrane is made of and begin to eat it. Well, first the membrane turns into a microfiltration one, and then into a regular mechanical filter.
To prevent this from happening, regular disinfection of the membrane is necessary. The frequency of membrane disinfection is calculated by specialists based on bacterial analysis of water. The ceramic membrane can last almost forever, since it cannot be damaged by bacteria, and it can easily be washed with aggressive detergents. detergents. So, if possible, it is better to use ceramic ultrafiltration membranes.
If not, then you need to compare the available organic membranes with each other. And choose the most productive and most durable membrane. Even if it is more expensive, it is more profitable to purchase one that lasts longer. This way the economic costs are much lower.
So, ultrafiltration is an economical and reliable way to disinfect water.
Based on materials Selection of water filters: http://voda.blox.ua/2008/06/Kak-vybrat-filtr-dlya-vody-20.html
