SU916434A1 - Method for purifying concentrated effluents containing surfactants - Google Patents

Description

The invention relates to the purification of pro- ^{* 1} 'thinking wastewater containing charge higher concentrations of organic contaminants, including surface-active agents (surfactants), such as a wool-washing.

The known method of biological treatment of concentrated wastewater containing synthetic surface-active substances (SAL), which consists in processing them with pre-adapted activated sludge in two stages at certain doses of activated sludge and loads on it with SAL and biological oxygen consumption (MIC) (1) ,

This method does not allow purification without _(| ; pre-dilution of highly concentrated wastewater with a concentration of contaminants on BOD more than 8000 mg / l, respectively, on chemical oxygen consumption (COD) more than 20 g / l, on surfactants more than 600 mg / l. It also It requires significant costs for treating and disinfecting a large amount of precipitation (excess sludge), which is dangerous for cleaning up wool-contaminated drains in relation to infectious diseases. Purified drains are also non-sterile.

The closest to the proposed technical essence and the achieved result is a method of purification of concentrated wastewater (COD 3050 g / l) containing surfactants, including the liquid-phase oxidation of organic pollution of wastewater at a pressure of 15 MPa and 300 ° C and their subsequent biological purification [2].

The disadvantage of this method is the high cost of the cleaning process, due to the need for dilution of wastewater during biological purification of not less than ten times the volume of domestic wastewater, the cost of processing excess activated sludge and high pressure of the liquid-phase oxidation process, also reducing the reliability of the equipment. Way tre3 916454

The use of defoaming in aerotanks to prevent the loss of activated sludge, which at a low sludge dose typical for the method (1.5 g / l or a little more), is unacceptable. _five

Biological cleaning in one stage of wastewater containing surfactants, as well as the possibility of their accumulation in activated sludge and its degradation, also worsen the reliability of the cleaning process.

The goal of izofeteliya - increase the efficiency of the process with a similar degree of wastewater treatment.

The goal is achieved by the fact 15 that the biological stage treatment is carried out in effluent 2-3 steps, the resulting foam was separated, mixed with excess activated sludge, and subjected to liquid phase oxidation in conjunction with the source _of waste water at a pressure of 6-10 MPa at a temperature of 220-270 ° C.

The lower limit of the parameters of the process of liquid-phase oxidation (pressure of 6 MPa,

220 ° C) is determined by the condition of the autothermality of the process; below the adopted parameters, additional heating of the effluents entering the reactor is required, which leads to an increase in the cost of their cleaning.

The implementation of the process of liquid-phase oxidation ₃₀ at a pressure of more than 100 MPa and a temperature of more than 270 ° C also leads to an increase in the cost of cleaning due to an increase in capital and operating costs.

Multistep biological recovery scheme ^{35 more} economical single-stage.

A sufficient number of stages of biological treatment of wastewater depends on the quality of wastewater after pretreatment, i.e. from the parameters of liquid-phase oxidation and ⁴⁰ is two steps in the case of liquid-phase oxidation at 10 MPa and 270 ° C and three steps in the case of liquid-phase oxidation at 6 MPa and 220 ° C.

The drawing shows tehnologiyaes- * ³ kai diagram of the proposed method.

The concentrated wastewater containing surfactants are supplied to averager 1 from which the high-pressure pump 2 vmes- those ⁵⁰ with air supplied from the compressor 3 through heat exchanger 4, and (if necessary) via the starting heater 5 to the reactor 6, wherein pressure 6–10 MPa and temperature 220–27 ° C ⁵⁵

liquid-phase oxidation of organic contamination of the treated liquid is carried out.

The gas-liquid mixture from the reactor enters the heat exchanger 4, where it heats the initial mixture of wastewater and air, then it is cooled in the refrigerator 7 and sent to the separator 8, where the liquid and gaseous phases are separated, the gas is discharged to the atmosphere through the corresponding valves 9 and 10 the liquid enters the sump 11 to separate the solid dispersed phase. The sediment from the settling tank is processed by known methods (centrifugation, drying), and the clarified liquid is sent to a multi-stage biological purification, where it successively passes aeration tanks 12 and secondary clarifiers 13.

Foam formed in aerotanks containing surfactants, as well as other impurities floated during aeration, is removed from the aerotank surface and, after compaction (destruction) in seal 14, is sent together with excess active sludge from secondary clarifiers 13 to averaging agent 1 for treatment with liquid-phase oxidation.

Example. The test of the proposed method is carried out on an experimental installation of liquid-phase oxidation with a capacity of 20-40 l / h and biological three-stage purification with a volume of aeration tanks of each stage of 30-36 l.

Purification by liquid-phase oxidation - (ZhFO) is subjected to wool-washed wastewater with a concentration of pollutants on COD 25-40 g / l and the content of surface-active substances (soap) 1.5—

3 g / l at a pressure of 7 MPa and 250 ° C. Decreasing the COD is an average of 70%.

Biological treatment is carried out with aeration time in each stage of 2428 hours and doses of sludge in the first stage of 68 g / l: in the second 4-6 g / l; in the third 1.5-2.5 g / l, the amount of foam removed from the aerotanks is 3-6% of the weight of the wastewater being cleaned. Foam and excess sludge is subjected to liquid-phase oxidation together with the initial effluents, while the quality of their purification does not deteriorate.

Indicators of the cleaning process in stages are presented in the table.

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Wastewater COD, g / l MIC mg / l Wool fat, mg / l Surfactant (soap), mg / l Before cleaning 25-40 12000-18000 4000-8000 1500-3000 After cleaning ZhFO 7-10 5000-8000 300-700 600-1200 In aeration tanks: 1st stage 1.6-2.7 400-600 80-200 100-300 2nd stage 1.2-1.9 80-200 30-60 20-80 3rd step 0.5-1.1 10-20 0.5-2 0.8-4 -

As a result of purification of wool-washing wastewater by the proposed method, the purification quality is the same as that of the treated effluent (20 mg / l) obtained during purification according to the well-known method 20.

Thus, the use of the proposed method of purification of concentrated wastewater containing surfactants, provides and compared with the known increase in technical and economic efficiency (reduction of capital investments and operating costs by 1.5 times) by reducing the parameters of liquid-phase oxidation, 39 applications more efficient stepwise biological treatment and its intensification by removing with the price of hardly oxidizable substances, the treatment of excess sludge together with foam liquid-phase oxidation m, _and more reliable cleaning process (due to reduction of zhidkofazno- oxidation parameters and application step of biological purification with removal of foam), the complete decontamination of waste water and precipitation and to reuse treated waste water in the process wash wool.

Claims (1)

Claim Οι is a method of purification of concentrated wastewater containing surface-active substances, including liquid-phase oxidation and biological purification of effluents, characterized in that, in order to increase the efficiency of the process at a similar degree of purification, biological purification is carried out in 2-3 steps, the resulting foam is depleted, mixed with excessive active sludge and is subjected to liquid-phase oxidation together with the source and wastewater at a pressure of 6-10 MPa and a temperature of 220-270 ° C.