Mechanical water filtration in Ukraine

This technique can be divided into several types:

  1. Filtration on mesh and disc filters.
  2. Filtration on granular loading.
  3. Filtration on cartridges and filter bags.

Mechanical filtration on mesh and disc filters

The essence of the technology lies in passing the medium to be filtered through a grid or block of disks with a certain cell size. In the process of mechanical water filtration in Ukraine, in such large cities as Kyiv, Dnipro, Zaporozhye, Kharkov, Lvov, Odessa, etc., with the accumulation of contaminants on the filter surface, a pressure difference arises at the inlet and outlet of the filter. Upon reaching a certain value in the differential pressure, the filter must be washed. Washing of the filter mesh or discs is carried out in manual or automatic modes, depending on the type and design of the filter. There are mesh and disc filters with a filtration rating from several tens of microns to several millimeters.

Mechanical filtration on granular loading

The method is based on passing water through a granular material inert to the medium being processed, loaded from the filter housing. This technique is widely used due to its simplicity and efficiency.

Filters with granular loading can be classified according to a number of main features:

  • By filtration speed – slow, fast and over-speed;
  • According to the pressure under which they work – open (non-pressure) and pressure;
  • According to the size of the filter material – fine, medium and coarse-grained;
  • By the number of filter layers – single, double and multi-layer.

The filtration process consists in the fact that when water containing suspended particles moves through the granular loading of filtering devices, the latter are delayed by the loading and the water is clarified. At the same time, impurities accumulate in the thickness of the load, as a result of which the free volume of pores decreases and the hydraulic resistance of the load increases. The time during which the load is able to clarify the water to the required degree is called the time of the protective action of the load. After this time, the quality of the filtrate begins to deteriorate rapidly. The time of the protective action of the load increases with an increase in the thickness of its layer and decreases with an increase in the filtration rate and grain size of the load. The time of the protective action of the load increases with an increase in the thickness of its layer and decreases with an increase in the filtration rate and grain size of the load. The filter cycle is determined by the volume of water passed through the granular load during the filtration process of which there is no decrease in the quality of the filtrate.

As a granular load, the following are most often used:

– quartz sand of various fractions;

– crushed anthracite;

– crushed pomegranate (garnet);

– special loads with certain properties.

The moment of filter operation, when the pressure loss in the filtering bed reaches the maximum allowable value or the quality of the filtrate begins to deteriorate, serves as a signal to turn off the filter for washing in order to restore the delay capacity of the load. Washing of the filter media is usually carried out with a reverse flow of water or air and water, for which, as a rule, filtered water is used. In the suspended state of the load, its individual grains are continuously in contact with each other, as a result of which the contaminants adhering to them are wiped off and, together with the flow of wash water, are removed from the filter housing. After washing, the filter is put into operation.

Mechanical filtration on cartridges and filter bags

This type of filtration consists in passing water through cartridges made of foam or wound material or through bags made of special filter cloth with a certain filtration rating. Typically, cartridges or filter bags are used with a filtration rating from 1 to 100 microns. Given the relatively short time of the protective action, it is advisable to use this technological method on relatively clean water as a barrier filtration. During the filtration process, due to contamination of the filter material, a pressure difference occurs at the inlet and outlet of the filter. When a certain value is reached, the cartridges or bags must be replaced.