In industry and at home, it is required purification of water from organic impurities, because after using water, its properties change in some way, and sometimes it even becomes unsuitable for further use. Such water is considered waste water and should be cleaned of organic (viruses, fungi, bacteria) and mineral (carbonates, sulfates, phosphates, chlorides, ammonium salts). Water treatment from mechanical impurities, as a rule, does not present great difficulties - for this, processes of filtration, centrifugation, and sedimentation are used. To carry out these processes, special devices are used and structures are being built - filters, hydrocyclones, centrifuges, septic tanks, sedimentation tanks, grids.
Modern devices for wastewater treatment and for the removal of organic impurities actively use coalescence, sorption and biological filter elements. But the most popular and common device is aeration tank. But for its functioning it is necessary to build additional secondary sedimentation tanks, where organic impurities - activated sludge - are removed from the water. Further processing of the resulting precipitate is possible on aerobic stabilizers or digesters.
There are many methods for removing organic impurities, but the sorption method is most popular. It is very effective for purifying water from phenol and other aromatic substances. Rectification purification is carried out on distillation columns - this method is widely used in chemical, pharmaceutical and food industries, it can be used to remove fats, alcohols, acids, aldehydes.
Based on its state of aggregation, organic impurities can be divided into insoluble substances (suspensions, films, foams), suspensions, colloids and soluble. At purification of water from organic impurities it is best to use the method of extraction, adsorption, dalysis, electroflotation, flocculation, coagulation and others. The removal of fine impurities is possible using filtering systems with granular or fabric cartridges. Reagents and further sedimentation can also be used for cleaning. Although flocculation and coagulation are most often used to purify water from highly dispersed organic impurities.
The composition of this type of water is extremely diverse, it mainly depends on the type of activity of the enterprise. And this already requires the use of more efficient and productive cleaning methods. For example, the installation for water purification from arsenic impurities is made not only in the form of a conventional electrocoagulator, but is also equipped with additional containers for preliminary water purification from various impurities. Cleaning is carried out using iron and ammonium sulfate, calcium salts and other elements.
At industrial enterprises, water purification from organic and mineral impurities in dissolved form in water is carried out by ion exchange, reverse osmosis of water, nanofiltration of ultrafiltration, adsorption and using chemical reagents. Evaporators, hydrocyclones, grease traps, oil separators, separators are used to remove insoluble impurities.
Organic impurities in water are often ions of organic acids, namely, lingogumic and humic substances. Iron is also present, but only in bound organic form. Such substances stain water in an unpleasant color - from yellowish brown to brown. Moreover, even after prolonged settling, the water does not clarify. But after using special treatment filters, the color and transparency of the water improve. Therefore, such water purification filters are often called traps for organic impurities.
It is considered very effective purification of water from organic impurities considered a method using anion exchange resin, which allows you to remove almost all of the organics, improve the transparency of water and eliminate color. In essence, such filters are themselves weak organic acids. Before such installations, to increase efficiency, it is recommended to install mechanical filters.
Organic water purification methods
Organic substances or impurities can be removed from water in the following ways:
- Oxidized to carbon dioxide and water,
- Activated Carbon (AC) Extraction,
- Selective extraction on anion exchangers (Purolite A500P ion exchange resin),
- Reverse osmosis method.
Oxidation is carried out by strong chemical oxidizing agents such as chlorine, potassium permanganate, ozone and oxygen. Oxygen, as a rule, is weakly effective against organic complexes. In rare and complex cases, our company uses the method of dosing sodium hypochlorite for installation filter for water purification from organics and organic iron. As a rule, this method is used when it is necessary to purify water not only from organics, but also from iron, ammonium and hydrogen sulfide, pressure and pressureless aeration are used, or dosing of the reagent directly into the deferrizing filter. In this case, the destruction of residual active chlorine occurs on cartridge filters of type BigBlue 20. Oxidation using potassium permanganate by our company is not used due to the obsolescence of the technology and the presence of many undesirable side effects. The most advanced method is ozone oxidation. We have a sufficient technical and information base for building ozonation systems. So far, the installation of ozonation systems has not become widespread in view of the high cost relative to standard balloon filters for water treatment. The following method of extracting organics from water using activated carbon has several disadvantages: firstly, filters with coal require annual refilling, and secondly, coal is a breeding ground for the development of bacteria and, as a result, contributes to the appearance of an unpleasant odor of water. The advantage of carbon filters is their low cost. To produce organic water purification and organic iron with a modern and effective method, special ion-exchange resins, for example, Purolite A500P, must be used. Recovery of the absorption capacity is carried out with 10% NaCl saline solution, as well as with water softening. The reverse osmosis method is not used to clean water from organics from private wells.