PLANA - Technologies of water treatment and purification of drinking water

The treatment technology is determined by the quality of the source water

Depending on the source of the source water — surface (river, pond), underground (artesian) — various contaminants and their combinations are subject to cleaning:

Mechanical impurities — sand, clay, silt, algae, rust, etc.
Chemical pollution — organic and inorganic substances.
Biological contaminants — bacteria and viruses.

Regulatory requirements for the quality of cleaning are given in SanPiN 2.1.4.1074-01 and SanPiN 2.1.3684-21.

Specialists of PLANА Engineering Group form a technological scheme for the purification of source water, selecting and combining the available methods and equipment: settling, aeration and oxidation, coagulation and flocculation, laminar separation and sedimentation, filtration, membrane methods, ion exchange, sorption, reagent and UV disinfection.

Thickening

The method is based on the principle of natural gravity. Suspended particles, conglomerates, dirt under the action of gravity sink to the bottom of the settling tank, the accumulated sediment is removed, dehydrated and disposed of. It is used at the preliminary or intermediate stage of water purification.

Macrofiltration

The first and necessary stage of preliminary purification of source water is the removal of large dispersed particles (sand, suspensions, algae, large organic and inorganic inclusions, etc.). Prevents damage to valves, clogging of pipelines and process equipment.

Protection filters — sump
Disk self-flushing filters
Automatic strainers

Reagent precipitation methods

Reagent treatment is necessary for water purification of various mechanical impurities, colloidal and suspended solids. The treatment of wastewater with a coagulant (based on aluminum or iron salts) ensures the unification of impurities suspended in water and their precipitation in the form of a flocculent sediment. The coagulant can be supplemented by treatment with a flocculant — a polymer-based reagent that «sticks together» coagulated suspensions into large flakes (flocculi). After chemical treatment, raw water is fed to a laminar sedimentation tank, to filters with a granular load, or to a micro/ultrafiltration unit to trap the precipitation products.

Settling / laminar separation

After treatment with reagents — a coagulant or a flocculant — the raw water enters the settling tank (separator), where it passes in an ascending laminar flow through thin-layer modules that ensure effective sedimentation and sedimentation of sand, suspensions and flakes. Floating inclusions and sediment are removed and sent for dehydration. The laminar separator allows you to economically clarify the water and reduce the load on the subsequent stages of filtration and water treatment.

Aeration / Oxidation

The method of aeration consists in saturating untreated water with air oxygen, as a result of which both water degassing occurs — removal of hydrogen sulfide and carbon dioxide, ammonia, methane — and the oxidation of various impurities — iron, manganese (iron removal and demanganation processes), etc. Aeration is used as an intermediate method and is supplemented by other cleaning methods — reagent treatment and filtration. It is also possible to use chemical oxidation of impurities with hypochlorite.

Filtering through grainy loads

Filters with granular loading are an intermediate stage of water purification and provide purification from suspended and organic impurities. Quartz sand, anthracite, etc. are used as a filtering load. Particles with a size of more than 10–20 microns are removed on these filters. Water purification occurs due to the retention of impurities on the surface and in the pores of the filter material, as well as due to the formation of a retaining film by impurities. Granular filters are subject to periodic water or water-air washing.

Sorption filtration

Sorption filtration allows you to remove impurities from water even with a small concentration and, as a rule, is carried out on filters with coal loading (activated carbon). This sorbent is able to retain harmful substances on its surface due to the porous structure. In addition to coal, silica gels, alumina gels, and zeolites can be used. This method is effective for purifying drinking water from organics, nitrates, herbicides and pesticides, phenols, surfactants, etc., as well as for improving organoleptic indicators — the taste and smell of water. The filter bed is periodically regenerated or replaced.

Ion exchange / desalination

Ion exchange filters (softening filters) use a special resin on which the ion exchange reaction takes place. The resin retains calcium and magnesium ions. The reaction product is harmless sodium salts that do not precipitate and do not cause scale. The ion exchange method can also capture other contaminants, such as harmful heavy metals. The resin requires periodic regeneration with saline.

Microfiltration / Ultrafiltration

Micro- and ultrafiltration is used, as a rule, as a preliminary purification stage before reverse osmosis systems, providing a high degree of mechanical purity and protecting reverse osmosis membranes. As an independent purification step, ultrafiltration allows you to preserve the salt composition of water, while simultaneously purifying it from elements such as iron and manganese, reducing turbidity and color of water, removing fine impurities, organic compounds and bacteria from it. The filtration degree can reach 0.01 micron. The membranes are subject to periodic backwashing and chemical cleaning.

Ultraviolet treatment / disinfection

Ultraviolet treatment — UV disinfection — consists in exposing water to ultraviolet radiation in the wavelength range of 200 — 400 nm, which ensures the death of most bacteria and microorganisms. Bactericidal UV installations are used instead of water treatment with chlorine-containing preparations that are potentially dangerous for human health. In addition to UV disinfection, methods such as water treatment with ultrasound, ozone, and reagent disinfection are used.

Reverse osmosis / nanofiltration

The efficiency of this universal method of drinking water purification is up to 99%. The principle of operation is the passage of water under pressure through a semi-permeable membrane, as a result of which impurities (mechanical, dissolved salts, metals, organics) remain in the initial solution and are subsequently discharged into the drain. At the outlet of the reverse osmosis unit, permeate is removed — purified water — and a heavily contaminated concentrate. Reverse osmosis is used in cases where other methods do not provide the necessary purification, or are not economically viable.

Conditioning / mineralization

As a result of deep purification (as a rule, after reverse osmosis), the quality of water becomes close to distilled. Demineralization of water, depriving it of many elements that are vital for a person, can adversely affect the health and quality of life of consumers. Therefore, the following measures are envisaged at the outlet of water treatment facilities: