Physical-Chemical Wastewater Treatment System

Disadvantages of  traditional chlorination led to a search for new methods of disinfection. As a result, and thanks to major achievements in the field of lighting and electrical engineering, the equipment for decontamination of water and sewage with ultraviolet (UV) radiation was created.

UV radiation kills most aquatic bacteria, viruses and spores. It destroys the pathogens of infectious diseases such as typhoid, cholera, dysentery, hepatitis, polio, and others. Applying UV radiation allows more effective disinfection than chlorination, especially against viruses.

UV disinfection initiates photochemical reactions inside the microorganisms, so the changing water characteristics have a much smaller effect on its efficiency than in chemical disinfecting.

Unlike oxidative processes, there are no negative effects in case of overdose.

This eliminates tests for determining residual concentration of disinfectant, which greatly simplifies the control of the disinfection process.

Time of disinfection with UV irradiation is 1-10 seconds in a continuous mode, so there is no need to establish contact reservoirs.

Current technologies allow a high degree of reliability of UV complexes. UV lamps and control equipment are commercially available and have a long service life.

Operating costs for UV irradiation are lower than chlorination and even more so ozone treatment. This is due to the relatively low cost of electric energy (3-5 times lower than in the ozone treatment) and no need for expensive reagents: liquid chlorine, sodium hypochlorite or calcium.

The UV equipment is compact, requiring minimal space. It is possible to introduce it into  acting operating processes without stopping flow and with minimum construction.

UV free-flow installation with submersible UV modules

Another innovative technology of tertiary treatment and disinfection of wastewater is the electrostatic field.

Under the influence of the electrostatic field in the aquatic environment, the structure of water changes, which increases the rate of physical and chemical processes. Thus, the efficiency partial disinfection is improved.

Wastewater treatment installation with electrostatic field EL 1-1.

Magnetic water treatment is the process of acting on water by a magnetic field. A number of powerful permanent magnets are arranged in a specific way.

Magnetic systems are installed at the inlet or outlet of the process area. Tertiary treatment of wastewater by a magnetic field improves the quality of wastewater treatment. This method accelerates the processes of coagulation, flocculation and sedimentation and increases the filtration efficiency. Also, magnetic treatment reduces corrosion.

The disadvantage of this method is that the water retains its magnetic properties after even a relatively short processing time.

During tertiary treatment and disinfection of wastewater, electrolysis may be applied to destroy organic substances and extract inorganic substances.

Electrolysis is a physico-chemical process in which electric current passes through the water, decomposing to a set of oxidants - ozone, oxygen, peroxide. In the electrolysis of water, the necessary reagents for cleaning and disinfection are extracted from the water to be treated and they do not require the addition of chemicals.

The electrolysis process is carried out in special devices called electrolyzers or electrolytic cells.

The result of electrolyzed treatment depends on the characteristics of the wastewater, the properties of the materials used for the electrodes and the distance between them, the current density, power consumption, presence of diaphragms and their material.

The disadvantage of wastewater treatment by electrolysis is the high power consumption.

Currently, much attention is paid to the use of pollution-free cleaning technologies for tertiary treatment of wastewater with ozone, atomic oxygen, and hydrogen peroxide.

The method of ozonation at tertiary wastewater treatment is very effective.

Ozone is produced by various methods, but the most economical method is based on airflow through a high voltage electrical discharge in the ozone generator - ozonizer.

Ozone is highly oxidizing, thus producing decontaminated effluent. It destroys organic matter. Ozone destroys all known bacteria, removes odors, operates for a few seconds, and can be produced on-site.

Its advantage is in the lack of chemicals. It meets the highest requirements for efficiency and environmental friendliness.

At the same time, this method has a number of negative aspects, which include: low solubility of ozone in water; increased toxicity and explosiveness; the relative complexity and high cost of equipment.

Disinfecting properties also include atomic oxygen, which is obtained by decomposing the ozone molecules consisting of three atoms of oxygen (O2 + O3 → O).

Using atomic oxygen on wastewater, all bacteria, viruses, protozoa, mold fungi and yeast are disintegrated.

Alternatively, hydrogen peroxide may be used.

Hydrogen peroxide is introduced in the form of aqueous solutions of various concentrations.

Hydrogen peroxide is eco-friendly, without the formation of toxic compounds.

The disadvantage of this method is the necessity of high concentrations of hydrogen peroxide, which lead to higher costs.