- Types of impurities and contaminants in water
- Mechanical impurities
- Chemical pollution
- Biological contaminants
- Filters for sand and other mechanical impurities
- Coarse filters
- Fine filters
- Filters that purify water from ferrous iron
- Reagent-free filters
- Reagent filters
- Ion exchange filtration
- Reverse osmosis
- Complex schemes of purification and water treatment
Foreign inclusions in the water in solid and dissolved form harm both people and plumbing equipment. Especially a lot of contaminants are found in water from wells. We will talk about how to get rid of sand and iron in the water in summer cottages, houses and apartments, what filters should be used..
Is the water from the well natural, which means it is clean and healthy? Unfortunately, there is no single answer. How many wells, so many different test results for the presence of inclusions in it: useful, neutral and harmful. The situation with well water is no better. The good news is that by using various methods of disinfection and filtration, you can get water suitable for drinking and domestic needs..
Types of impurities and contaminants in water
Basically, water with foreign inclusions comes from alternative sources of water supply. However, people who are seriously concerned with their health or live in an area with questionable water treatment methods, it is also advisable to find out the composition of the supplied water and, possibly, take measures to purify it..
The main types of water pollution:
Each type has its own varieties and methods of purification, so that the water meets the hygienic requirements of GOST.
Table. Water performance standards (according to GOST 2874-82)
Index Standard Hydrogen exponent, pH 6-9 Iron (Fe), mg / l, no more 0.3 Total hardness, mg-eq / l, no more 7 Manganese (Mn), mg / l, no more 0.1 Copper (Cu), mg / l, no more 1 Residual polyphosphates (PO3–4), mg / l, no more 3.5 Sulfates (O2–4), mg / l, no more 500 Dry residue, mg / l, no more 1000 Chlorides (Cl–), mg / l, no more 350 Zinc (Zn), mg / l, no more five
Such impurities are in the form of sand and fine suspended matter and do not dissolve in water. The concentration of inclusions per cubic meter of water and the particle size determine the choice of one or a cascade of filters. In the presence of an intermediate settling tank, solid insoluble particles settle to the bottom and do not enter the water supply.
If the water is taken from shallow sources in which oxygen is present, compounds of tetravalent manganese and ferric iron may be present in the solid state. It is they who color the water in the color of rust and give it a “metallic” taste and smell..
Water is an excellent solvent, so its composition can tell a lot about the rocks and minerals through which an underground stream passes..
Water raised from a deep horizon located between two clay rocks is most often extremely poor in oxygen. In such an anaerobic environment, iron and manganese are found in a bivalent soluble form, and in the presence of oxygen they begin to oxidize, passing into an insoluble phase, after which they can precipitate. It is much more difficult to remove organic iron compounds from water, since it is in a colloidal state and does not pass into a precipitate.
Calcium, magnesium, sulfates, which make up water hardness, also refer to chemical pollution, eliminated by special equipment – softeners.
Fluorine, sodium ions, chlorides are also dangerous if their content is higher than the MPC
Pathogenic microflora of varying degrees of concentration and danger can also be present in the water. Some of its representatives can only be disposed of by boiling, while others die safely under the influence of UV emitters. Chlorination is most often used in centralized main water supply..
In order to prevent substances from entering the source from open sewer systems, the distances between structures must meet sanitary standards.
Filters for sand and other mechanical impurities
Mechanical filters are coarse and fine. This division is somewhat arbitrary, since it largely depends on the quality and characteristics of the equipment, as well as on the applied combination of sequentially installed filters.
To protect against inclusions of a coarse fraction of mechanical impurities, in particular, sand, even in the well, before rising to the surface, a coarse filter is installed, consisting of a perforated section with a filter layer, a sump, which must be regularly cleaned, and a supra-filter pipe.
Various types of such filters are produced: mesh, wire, slotted construction, combined – with gravel packing, possibly self-cleaning, preferably made of stainless steel or plastic (for shallow wells). You can buy a factory filter, or you can make it yourself. For how to do it yourself, see the video:
For water from a well or from a borehole with low turbidity, a coarse filter can be placed on the surface. This can be a disc, mesh or cartridge filter, with or without a self-cleaning function. They are often called mud collectors and are mounted not only at the water inlet into the house after an autonomous source, but also on main water pipelines. Sometimes several such filters are installed, with gradually decreasing cells in the grid..
Such filters retain only a relatively large fraction of sand and solid impurities. Smaller particles need to be captured by a fine filter, which can be:
- reverse osmosis.
Sorption filter device: 1 – body; 2 – control unit; 3 – gravel substrate; 4 – lower distribution system; 5 – activated carbon; 6 – distribution riser; 7 – water direction
Sorption is a storage equipment containing a sorbent (coal, aluminosilicate, clean sand) as a filtering layer, the inlet and outlet of water from which are located at different levels. The sand should be periodically cleaned of accumulated dirt by flushing. The coal and aluminosilicate contained in the cartridge are replaced by a block. Some of these filters are even capable of retaining lead, iron, chloride compounds, microorganisms.
Reverse osmosis is a filter with a semi-permeable membrane, through the microscopic holes of which only water molecules can pass. Installed in high pressure water flow. Very high degree of purification: even useful substances that are required by the body are retained. To prevent the membrane from becoming dirty too quickly, such a filter is installed in the water treatment system after several coarse and fine filters. A complex of such devices is a household reverse osmosis unit..
Reverse osmosis system
Filters that purify water from ferrous iron
The human body needs iron, but not on the “industrial” scale that water from a well can give. Laundry, washed in such water, acquires a shade of rust, and plumbing equipment and pipes, an increased content of this element, can generally be damaged. Therefore, iron, if its concentration exceeds the MPC, it is necessary to get rid of.
Ferric iron is captured by coarse mechanical filters and sorbents. The water-soluble ferrous iron is removed in a slightly different way. There are several main ways.
If you contact a company that deironizes water in a non-reagent way, they will start with analyzes not only for the content of iron, but also for manganese, as well as some other elements that reduce the rate of oxidation of dissolved iron to a trivalent insoluble salt.
Reagent-free filters are a filter column with specially prepared filler:
- Birm – aluminosilicate with oxidation catalyst.
- МЖФ – modified granular dolomite.
- Quantum – catalyst sand.
- Shungite – crushed natural mineral, etc..
Filtration column with filter bed
As an iron oxidizer, reagent-free filters use oxygen from atmospheric air (non-pressure aeration). If necessary, air is supplied to the purified water under pressure. This process is called pressure aeration..
This equipment is used when the iron content in water is significantly exceeded over the MPC. Such filters are also made in the form of columns with filling, but various chemical compounds are used as an oxidizing agent, for example, ozone or chlorine, but most often – “potassium permanganate” (potassium permanganate). The installation consists of two tanks, one of which contains a strong oxidizer (solution tank), an oxidizer dosing pump and a column with filter media.
Reagent filtration unit
Ion exchange filtration
Ion exchange filters are designed for water purification and softening. In them, the ions of iron, manganese, magnesium, calcium and potassium in water are replaced in the process of exchange for sodium ions, and they themselves are deposited on the surface of the synthetic resin. Since iron is released in the form of trivalent insoluble salts, the surface becomes dirty and stops working. Therefore, such purification is used as a second or third purification stage to completely remove iron from water. The operation of the filter is not interfered with by the “enemy” of reagent and reagent-free filtration – manganese, which is an advantage of the method.
Ion-exchange filter operation diagram: 1 – filter housing; 2 – drainage; 3 – source water; 4 – water to the house; 5 – control unit; 6 – inflow of saline solution during regeneration; 7 – brine tank; 8 – salt level
After contamination, the ion exchange resin can be easily regenerated by hand using 10% saline solution, after which the cartridge is reinserted into the filter. In automatic systems, regeneration is carried out at night when there is no water intake.
Since reverse osmosis passes only water molecules through the membrane, it traps ferrous iron very effectively, even more efficiently than ion exchange resins. The only condition for the long-term operation of the filter when removing ferrous iron is the absence of oxygen in the water so that the iron does not pass into the trivalent salt, which complicates the operation of the equipment.
Complex schemes of purification and water treatment
It is advisable to use not just one filter, but a whole complex of sequentially installed filters, each of which performs its own task. Coarse filters are installed as the first bastion on the path of pollution, after which sorption filters, ultraviolet disinfectants, iron removers of various designs come into play. The set of these filters, as well as their characteristics, must be selected in accordance with the flow rate, acidity and composition of the water..
Below are some of the complex systems for water treatment, iron removal and water softening with autonomous water supply.
1 – oxidizing tank; 2 – booster station; 3 – iron remover; 4 – softener; 5 – salt tank; 6 – fine filter; 7 – ultraviolet lamp
1 – pumping station; 2 – mud filter; 3 – aeration column; 4 – non-reagent iron remover; 5 – sorption filter; 6 – softener; 7 – salt tank; 8 – fine filter
1 – water from the well; 2 – mechanical cleaning; 3 – displacement of gases dissolved in water; 4 – removal of iron and salts; 5 – fine coal cleaning; 6 – reverse osmosis filter; 7 – clean industrial water; 8 – drinking water