RU2174103C1 - Method of water treatment - Google Patents

Abstract

FIELD: environment control; methods of cleaning natural water and sewage from toxic organic admixtures; reduction of organic compounds in water. SUBSTANCE: water is treated with plasma of electric discharge formed in gaseous phase above layer of fluid. Plasma is excited above surface of hydrophilic inert material continuously impregnated by treated liquid at density of current discharge of 1-10 mkA/sq.cm and voltage of 5-15 kV. EFFECT: enhanced efficiency. 1 tbl

Description

 The invention relates to environmental protection, in particular to methods for purifying natural and waste waters from toxic organic impurities, and may find application as a method for reducing the concentration of organic compounds in water.

BACKGROUND
A known method of wastewater treatment by treatment with a smoldering electric discharge created above a liquid layer using electrodes, one of which is placed in a liquid with a layer thickness of 0.4 - 1.6 mm, and the other in the gas phase. The process is carried out at a current strength of 50-100 mA, voltage 500-2000 V [Pat. Russian Federation N 2043969, cl. 6 C 02 F 1/46, from 09.20.95].

The disadvantages of this method are:
- the need to use technical means of the day creating a vacuum;
- the complexity of the device and maintenance of the main and auxiliary equipment for wastewater treatment;
- high specific energy consumption;
- low process efficiency with a layer thickness of less than 0.3 mm or more than 1.6 mm, as well as the physical unreliability of the resulting film.

 Closest to the invention in technical essence and the achieved result, i.e. the prototype is a method of wastewater treatment, including the treatment of water with a high-voltage pulse discharge created above its surface, using as a surface electrode a liquid layer [Auth. testimonial. USSR N 1011545, class C 02 F 1/46, 04/15/1983]. The method is as follows.

 After pre-filtration, industrial effluents and other liquids that are processed are fed into a system of chambers consisting of separate cells through which the liquid moves in a layer 1-5 mm thick. An oxygen-containing gas is supplied to the reaction chamber above the liquid layer. In the upper part of the chamber, made of a dielectric, electrodes are placed isolated from the chamber walls and connected to a pulse voltage generator, the process being carried out at a voltage of a high voltage pulse discharge of 100-500 kV. In the gap between the electrodes made of conductive material and the surface layer of the liquid to be disinfected and being the second electrode, a high voltage pulse discharge is initiated. Since the surface electrode of the liquid to be disinfected serves directly as the second electrode, it is in contact with the region of intense ionization, as a result of which the oxidation processes are intensified, leading to a reduction in the duration of the disinfection process.

The disadvantage of this method is the insufficiently high efficiency of the oxidation of organic impurities due to:
- low development of the interface, causing large reactor sizes and high specific energy consumption;
- the impossibility of the process in film mode;
- high temperature in the zone of a pulsed discharge, increasing the degree of entrainment of the cleaned liquid into the atmosphere;
- the need to use expensive equipment to create a discharge.

SUMMARY OF THE INVENTION
The objective of the invention was to create a method of water purification, which allows to increase the efficiency of the processes.

The problem is solved by the proposed method of water purification, including processing it with an electric discharge plasma generated in the gas phase above the liquid layer, the plasma being excited over the surface of a porous hydrophilic inert material continuously impregnated with the liquid being purified. The method is carried out at a discharge current density of 1-10 μA / cm ² and a voltage of 5-15 kV.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION
Example 1

Water with a phenol concentration of 5 mg / L (MPC _p.x. = 0.001 mg / L) is supplied through a nozzle located in the upper part of the discharge device, so that at such a rate that the liquid is evenly distributed and flows down into the fiberglass layer with a thickness of δ = 1.5 mm, located on the surface of the electrode (fiberglass is pre-modified for 1 min in a barrier discharge excited in an oxygen medium to increase their hydrophilic properties or wetting angle to 80 ^o ). Oxygen (99.9 vol.%) Is passed through the nozzle into the reaction chamber, passing over the layer of wetted material and discharged through the gas outlet nozzle. Between a grounded insulated electrode (covered with S-49 glass) and an electrode coated with wet material to which a high voltage source is connected, a barrier discharge plasma is excited in a gas gap of 2 mm thick using a high voltage transformer. The discharge has the following parameters: discharge current density 1 μA / cm ² , U = 5 kV, current frequency 50 Hz. Plasma-treated water is diverted through a fitting located at the bottom of the arrester.

 The number of such discharge devices is selected depending on the volumetric flow rate of water, and the length of each of them is limited by the required degree of purification. In order to reduce the amount of oxygen consumed, the device can operate in gas recycle mode (up to 50%).

 Example 2

Water containing 50 mg / l of anionic surfactant (sodium lauryl sulfonate) (MPC _r.h. = 0.1 mg / l) was treated under conditions similar to those described in example 1.

 Example 3

Water containing 2 mg / l of petroleum products (model mixture containing (by volume) decane - 51%, octane - 5%, benzene - 44%, which is similar to petroleum products containing easily volatile fractions) (MPC _r.h. = 0.05 mg / l), was processed under conditions identical to example 1.

 The above examples, as well as the cleaning efficiency for other declared values of the plasma parameters are given in the table.

As follows from the experimental data presented in the table, the proposed method improves the efficiency of the cleaning process compared to the prototype in the following indicators:
the process is implemented at a lower discharge burning voltage (5-15 kV) and an industrial frequency current (50 Hz);
the consumption of plasma-forming gas (oxygen) is 35 times less;
cleaning time is 11 times less.

Claims (1)

A method of purifying water by treating it with an electric discharge plasma generated in the gas phase above a liquid layer, characterized in that the plasma is excited over the surface of a porous hydrophilic inert material, which is continuously impregnated with the liquid to be cleaned, the treatment being carried out at a discharge current density of 1-10 μA / cm ² and a voltage of 5 - 15 kV.

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