SU1717549A1 - Method of biological treatment of sewage - Google Patents

Abstract

The invention relates to the treatment of water, can be used in the biological treatment of wastewater containing hardly oxidizable organic compounds, and allows an increase in the degree of purification. Wastewater is treated in an aerosol in the presence of activated sludge while ozonating, which is carried out repeatedly and dispersed in the aerotank flow in a period corresponding to 0.2-0.8 aeration time, with increasing intervals between ozone injection points from 0.1 up to 0.3 aeration time and at the same time reducing the dose of ozone from 3.0 to 0.1 mg / l. When cleaning wastewater containing, mg / l: petroleum 45, phenol 0.6, resinous substances 5.0, COD 320, with aeration time of 6 hours and specific air flow rate of 20 m / m of water, the residual concentrations of the components in the purified water are , mg / l: petroleum products 3.2; phenol 0.03; resinous substances 1,1; COD 24.6 mg 02 / L.4 tab.

Description

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The invention relates to the field of water treatment and can be used in the biological treatment of wastewater containing hardly oxidizable organic compounds.

The aim of the invention is to increase the degree of purification.

In order to implement the method, the waste water is supplied to the aero tank, where it is mixed with active sludge, recirculating in the system, the azro tank — a secondary settling tank (or active or aeration tank regenerator), resulting in the process of biochemical oxidation of organic compounds, the duration of which is determined mixture in the volume of the aeration tank - aeration time. After 0.2 times the aeration time, the sludge mixture is treated with ozone as an ozone-air mixture. Then continue to process repeatedly and dispersed in

the flow of the aerotank in the period of 0.2-0.8 from the time of aeration. At the same time, the intervals between the ozone injection points increase from 0.1 to 0.3 times of aeration, and the dose of ozone is reduced from 3.0 to 0.1 mg / l.

Repeated and dispersed treatment of the sludge mixture with ozone within the specified limits allows increasing the ozonation intensity without creating toxic ozone concentration in the sludge mixture. Treatment of the sludge mixture with ozone before 0.2 aeration time does not lead to significant changes in the quality of purified water, since during this period of time the process of adsorbing organic compounds with cotton of active sludge and a bacterial cell and a decrease in the concentration of easily oxidizable organic compounds occurs due to intensive biological oxidation. .

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In this connection, the introduction of ozone earlier than 0.2 times of aeration can retard the process of biological oxidation due to the toxic effect on the cell, since the dehydrogenase activity of the cell during this period is the highest.

The introduction of ozone after 0.8 times of aeration leads to temporary changes in the biocenosis of the activated sludge and the bacterial cell (in particular, causes an increase in the sludge index), which for the remaining period less than 0.2 times of aeration cannot be eliminated. it is sufficient for the biological oxidation of the products of chemical oxidation of bacterial cell metabolites with ozone and hardly oxidizable organic compounds. The presence of such products leads to an increase in MIC and a decrease in the quality of purified water. Treatment of the sludge mixture with ozone can result in a dependence on the dose of ozone to swell the sludge, increase the sludge index and disrupt the separation process of the sludge mixture in the secondary sedimentation tank. Subsequent to the ozonization, the aeration sludge mixture reduces the sludge index and promotes the formation of durable and dense cotton sludge. However, the restoration of the original properties of sludge and giving it new properties that contribute to a better separation of the sludge mixture in the secondary settling tank is possible only with subsequent aeration within 0.2 of the total time of aeration of the sludge mixture.

The increase in the intervals between the ozone input points is due to the following reasons.

Treatment with ozone of the sludge mixture intensifies the activity of the bacterial cell and increases the specific oxidation rate of organic compounds with activated sludge. At the same time, at the beginning of the treatment period of the sludge mixture, high values of the specific oxidation rate are maintained for a short time, but at the end they increase. In order to maintain high values of the specific oxidation rate of organic compounds, the intervals between the ozone input points are increased. This ensures the creation of favorable conditions for the development and activity of the bacterial cell throughout the treatment period of the sludge mixture with ozone.

The introduction of ozone repeatedly and dispersed into the flow of the aerotank allows one to eliminate its constant impact on the bacterial cell. For a short period of time, ozone is not capable of causing a deep cell change. Its effect extends only to the shell, without affecting the nucleus, cytoplasm, and ribosomes. However, this effect is sufficient to intensify the activity of the bacterial cell.

Prolonged exposure to constant ozonation of the sludge mixture can lead to the penetration of ozone into the cells, inhibition of oxidative processes and

0 low quality purified water.

Thus, repeated and dispersed in the flow ozonization of the sludge mixture, along with the intensification of biological oxidation, allows increasing the degree of water purification from difficult-to-acid organic compounds due to the chemical oxidation reaction.

The dose of ozone required for treating the sludge mixture depends on the state of the thermal cell tank, the availability of metabolic products and the available food sources.

The maximum dose (3 mg / l) allows for the partial destruction of cotton.

5 of activated sludge, make it looser and more swollen, with the largest surface for adsorption and oxidation of organic compounds, but low sedimentation properties.

Treatment of high intensity sludge at the beginning of the process, and further reducing the dose to a minimum (0.1 mg / l), can provide a high rate and depth of oxidation of hardly oxidized organic compounds first, and then restore the sedimentation properties of the sludge and ensure the high quality of the purified water.

Example. Wastewater is cleaned

0 water, characterized by the following indicators, mg / l: petroleum 45, phenol 0.6, resinous substances of chemical plants 5.0. COD 320 mg Pa / l. - The silt mixture in the aeration tank is treated with ozone in the form

5 ozone-air mixtures with an ozone concentration of 10–25 mg / l with different ozonation periods, intervals between ozone injection points and its dose. The aeration time of the sludge mixture is 6 hours, the specific air flow rate

0 20m / m of water .. Data on the effectiveness of water purification are presented in Table. 1-3.

Comparative data on the effectiveness of wastewater treatment by known and proposed methods are presented in Table.

5 4.

The proposed method of biological wastewater treatment allows to increase the degree of purification from petroleum products by 37%, phenol by 63%, resinous substances by 47%, reduce the COC by 36%, increase the ability

to the separation of the sludge mixture by 18% and to ensure the maximum possible degree of purification for aerosols by the MIC. °

Claims (1)

The invention The method of biological wastewater treatment, including their aeration and ozonation in the aeration tank in the presence of activated sludge, followed by the separation of activated sludge from purified water and its recirculation Maintain constant 0.1 Keep constant 0.2 Reduced from 0.1 d 0.05 Increase from 0.1 to 0.3 Increase from 0.1 to 0.35 Increase from 0.2 to 0.4 0 characterized in that, in order to increase the degree of purification, ozonation is carried out repeatedly and dispersed in the aerotank stream during the period corresponding to 0.2-0.8 aeration time, with increasing intervals between ozone injection points from 0.1 to 0.3 time aeration and simultaneously reducing the ozone dose from 3.0 to 0.1 mg / l. Table 1 table 2 Table 3