SU1130539A1 - Method for purifying effluents - Google Patents

Abstract

A METHOD FOR CLEANING WASTE WATERS, including treatment with lime, from, sediment division and ozonation, characterized in that, in order to reduce ozone consumption during wastewater treatment of an ini-paint production, lime treatment, sludge separation and ozonation are carried out in steps, and at each step the waste water after ot dividing the precipitate is acidified to a pH of 6.5-7.5, ozonation is carried out while maintaining a constant pH to achieve a constant concentration of ozone at the exit from the ozonizer at the first stage, followed by a decrease in Ozone ozone ha 40-60 at each subsequent stage.

Description

with

about

SP

with so

The invention relates to methods for the purification of industrial wastewater having a high concentration of hardly oxidizable organic compounds and mineral pollutants, in particular, waste waters of aniline dye industry.

A known wastewater treatment method of an enclosed industry includes pretreatment of effluent with excess activated sludge and lime milk in three-stage neutralizers, then biological treatment in a two-stage aeration tank, and also after-treatment with adsorption, activated carbon or ozone days) and biologically in a three-section biological pond and passing through the sand: filters D).

The disadvantage of this method is insufficient: the degree of pre-treatment of wastewater before biological oxidation in aeration tanks, which makes it necessary to apply multi-stage purification by adsorption, biological oxidation and filtration.

The closest to the invention of the technical essence of the invention is a sewage treatment method that combines ozonation with physico-chemical treatment. Wastewater is purified by a two-step, scheme by adding lime milk (so g / m), aluminum sulfate (50-250 g / m) and polyacrylamide (1.5 g / m) at the first stage. The resulting precipitate 35 is separated by flotation, and the clarified waste water is ozonized under pressure with a dose of 5000 mg / l. Purified water with a COD of 50–95 mg and a BOD of 10–25 mg Ol / L passes the degassing chamber and is discharged into the reservoir {YJ.

However, in the known method, there are no neutralization stages after liming and during ozonation, which leads to a reduction in the cleaning effect and to an increase in ozone consumption, first due to spontaneous decomposition of ozone in a strongly alkaline medium, and then during ozonation due to the formation of ozone-resistant acidic products oxidation.

The purpose of the invention is to reduce the consumption of ozone in wastewater treatment of aniline production.

. The goal is achieved 55 by the fact that according to the method of purification of water, including lime treatment, sludge separation and ozonation, lime treatment, sludge separation and ozonation are carried out stepwise, and at each step the wastewater is acidified to pH 6.5-7 after separation. , 5, ozonation is carried out while maintaining a constant pH value until a constant ozone concentration is reached at the outlet from the ozonizer at the first stage with a subsequent decrease in the ozone dose by 40-60% at each subsequent stage.

The inclusion of an acid neutralization stage after lime and the conduct of an ozonation stage while simultaneously neutralizing with alkali to maintain a pH in the range of 6.5-7.5 prevents excessive self-propelling. The voluntary decomposition of ozone in a highly alkaline medium after liming (pH 11-12) and accelerates the oxidation of the organic acids formed during the ozonation process. As a result, the degree of purification increases at a given ozone dose. Or equivalently, the specific ozone consumption for achieving the desired purification rate decreases. The pH values of 6.5-7.5 are optimal for carrying out the ozonization process and are selected on the basis of the dependence of COD reduction during ozonization of aniline production wastewater. The data obtained are presented in Table. one. . Carrying out the ozonation process in the optimal pH range makes it possible to reduce the required ozone dose by about 1.3 times as compared with the known method.

Treatment of wastewater from lime and ozone under optimal conditions, carried out in steps, allows one to reduce the consumption of ozone by a factor of three in comparison with the known method.

The method is carried out as follows.

The wastewater is treated with lime, the precipitate is separated, the clarified water is neutralized with acid and ozonized while simultaneously neutralizing with alkali while maintaining a constant pH value of 6.5-7.5 until a constant concentration of ozone in the gas from the ozonizer is reached at the first stage. Achieving a practically constant ozone concentration in the gas mixture leaving the ozonizer means achieving an equilibrium pe

bench press At this point, the oxidative destruction of the primary components in the wastewater is terminated, and a further increase in the ozone dose is uneconomical. Then the ozonized waste water is again treated with lime, the precipitate is separated, the clarified water is neutralized with acid and ozonized while maintaining a constant pH value of 6.5-7.5 with a dose of ozone of 40-60% of the dose of ozone in the first stage, etc. d. The ozone dose at each subsequent stage is reduced by 40-60%. When the dose of ozone is less than 40% of the previous one, the number of processing steps increases, and if to introduce ozone in an amount greater than 60%, the maximum reduction in the total ozone consumption will not be achieved. An example. The original waste water with COD 3600 mg Oj / l from the averager enters the mixer of the first stage. Then, a 15% solution of milk of Ca (OH) (in terms of CaO 3.6 g / l) is introduced with vigorous stirring (n / m 300 rpm) and at the same time air is blown at an air flow rate of 0.01- 0.06 mo / s to remove ammonia. The precipitate formed, the content of CaCOj.CaSO and organic matter with a moisture content of about 50% is separated in a sump. pH of clarified water with COD 3000 mg 02 / l with sulfuric acid to 6.5-7.5 and ozone05394

at a constant pH to achieve a constant concentration of ozone in the gas mixture leaving the ozonizer (cpc 2300 mg C) y / l,. dose of absorbed ozone 1000 mg / l). The ozonized solution enters the 2 stage mixer and introduces a new portion of milk of lime (in terms of CaO 3.6 g / l). The precipitate formed is separated in a sedimentation tank and, together with the sediment from the first sedimentation tank, is sent for recalcination to produce calcium oxide for reuse in the liming of waste water. The pH of clarified water with a COD of 1800 mg 02 / l is adjusted to 6.5-7.5 with sulfuric acid and ozonized a second time at a constant pH value with a dose of 500 mg / l. An ozonized solution with LC, 1500 mg 0- / L enters the 8-level mixer, where its COD drops to 1,300 mg Cu / L as a result of lime, and as a result of ozonization with a dose of ozone 250 mg / L reaches a predetermined COH conditional pure water 1200 mg. The corresponding experimental data and a comparison of the stepwise processing method with the known one are given in Table. 2

Technical and economic advantage of the proposed method concludes

c in reducing the consumption of ozone from the treatment of water and, in view of the increased consumption of lime, reducing the cost of cleaning, which is very important when introducing cleaning methods by ozonation.

Table 1

.Table 2

 mg Oj / n

3600

Ozone dose

COD reduction to

2300 mg, mg

Ozone dose to reduce

5ShK to 1500 mg mg

O. / l

7

Ozone dose to reduce COD to 1200 mg O. / L,

mg Oh ,, / l

3

optimum pH

3600

3600

1000

1000

2400

1500

3400

1750

Claims (1)

WASTE WATER TREATMENT METHOD, including lime treatment, sludge separation and ozonation, characterized in that, in order to reduce ozone consumption during wastewater treatment, aniline-paint production, lime treatment, sludge separation and ozonation are carried out stepwise, and at each stage the wastewater after RT divisions of the precipitate are acidified to pH 6.5-7.5, ozonation is carried out while maintaining a constant pH until a constant concentration of ozone is reached at the exit of the ozonizer in the first stage, followed by a decrease in the dose of ozone ya 40-60? at each subsequent step. 1 11