SU966036A1 - Method for two-stage biological purification of effluents - Google Patents

Description

(54) METHOD OF TWO-STEPS BIOLOGICAL TREATMENT OF WASTEWATER

The invention relates to the biological treatment of municipal and industrial wastewater. A known method of two-step biological treatment of wastewater in aerosols with settling tanks to separate recycled activated sludge from the treated wastewater after each step of purification. Excess activated sludge can be removed from the system in both the first and second purification stages 11 3. The main disadvantage of the known two-stage biological treatment of sewage in aeration tanks with separation of sludge mixture by settling is the low oxidative capacity of aerotanks due to relatively small concentrations of active sludge in them, which cannot be more than 1.5-3g / l due to the unsatisfactory performance of the secondary clarifiers. The closest to the invention in its technical essence and the achieved result is a two-step biological treatment method of wastewater, in which wastewater after mechanical treatment is supplied to the aeration tank of the first stage, where, together with returnable active sludge, high concentration is subjected to aeration, after which sludge The mixture is removed from the aero tank and mixed with second stage recirculating sludge saturated with air under excessive pressure. The resulting sludge mixture is floated. The return part of the floated sludge is directed to the first stage aeration tank, and the excess part is further processed by known methods. The wastewater that has been preliminarily clarified in the floater is sent to the second stage aeration tank, etc. The method allows to increase the concentration of ima in the aero-trough of the first stage to 12-16 g / l and to ensure the compaction of the sludge to 25-35 g / l t2. The disadvantages of this wastewater treatment method are: the relatively low specific oxidation rate of contaminants in the first stage aeration tank, associated with the deterioration of the conditions for the influx of nutrients and oxygen to the activated sludge microorganisms, as well as the deterioration of the metabopysis products from bacterial cells; a large total volume of the first stage aerotank and flotation cell, which is associated both with insufficiently high oxidation rates: contamination and the need to separately conduct wastewater treatment and flotation separation sludge. The purpose of the invention is to accelerate the rate of biochemical oxidation of contamination and reduce the volume of structures. This goal is achieved in that according to the method of two-step biological treatment of wastewater in aeration tanks, including the separation of activated sludge after the second stage of purification, air saturation and recirculation to the first stage of purification, flotation separation of the sludge mixture, recirculated activated sludge is mixed with the sludge after flotation separation sludge mixture in the first stage, inflate the mixture with air and served on the first stage in the aeration tank-t. In addition, after the flotation separation, sludge is aerated and mixed with oxygen before mixing with recirculated active sludge. With the proposed method, the processes of removing and oxidizing organic compounds in the first stool of wastewater treatment are intensified, due to effective dispersion of flotation sludge during pumping it with centrifugal pumps together with the recovery unit of the active second stage stage, as well as at the time of release of the sludge mixture into the flotation cell through a throttling device, is necessary o d for carried out pressure flotation. This achieves a significant improvement in the supply of nutrients and oxygen to microorganisms flotation actively from the conditions of removal of the product of metabolism. Saturation of the floated sludge with air under excessive pressure creates favorable conditions for the oxidation of previously absorbed organic pollutants due to elevated concentrations of dissolved oxygen in water. The developed method makes it possible to carry out sewage treatment and separation of the sludge mixture at the first stage of treatment in one facility - the flotation clarifier. In necessary cases, the floated UI at the first stage is subjected to regeneration in a separate structure by aeration with its known methods, which ensures the oxidation of sorbed scrap organic pollutants and the restoration of its active properties. The mixture of recycled active sludge of the second stage and the floated sludge of the first stage is saturated under the pressure of technical oxygen, which increases the concentration of dissolved oxygen in the flotation aeration clarifier. In addition, the implementation of the flotation process with oxygen bubbles allows one to obtain flotation sludge saturated with oxygen, which increases the oxidation rate of the sorbed pollutants. The drawing shows the implementation of the proposed method. The scheme includes pipeline 1 for supplying untreated sewage liquid, flotation aerator clarifier 2, functions for the first function of the aerotank mixer of the first stage, intermediate tank 3, aerator tank of the second stage, secondary settling tank 5 with pipeline 6 DPS for disposal of treated wastewater and pipeline 7 to feed recovered activated sludge into tank 8, recirculation pump 9 with ejector 10 mounted on a bridge between the pressure lines of the pump suction lines, pressure tank 11 for saturating the pumped sludge with air under pressure, a pressure pipe line 12 with a pressure reducing valve 13, a pipeline 14 for supplying sludge to the regenerator 15, a pipeline 16 for supplying regenerated flooded KPA, a pipeline 17 for removing excess sludge and sediment for processing. Wastewater treatment is carried out as follows. The wastewater through pipeline 1 is fed to the flotation aeration tank-mixer 2, where the first stage of biological wastewater treatment and flotation separation of the sludge mixture take place. The wastewater after the first stage of biological treatment is directed through an intermediate tank 3 to the aeration tank propellant 4, in which the process of biological treatment of wastewater is completed, and from there to the secondary sludge 5 to remove the activated sludge from the sludge mixture. Bleached wastewater is discharged through line 6. Active sludge deposited in the secondary clarifier 5 is sent to tank 8, where it is mixed with floated sludge fed via line 16 from the regenerator 15 of flotation sludge.

The mixture of recirculation and immobilized sludges is saturated with air through a water-jet ejector 10 installed on the bridge between the pressure and suction lines of the recirculation pump 9, pumped into the pressure tank 11 intended for complete saturation of the sludge mixture with air under pressure, and from there by pipeline 12, equipped with a pressure reducing valve 13, to the flotation aerotech-clarifier 2 of the first stage.

The floated activated sludge from the floatation light tank is diverted through pipe 14 and, if necessary, is regenerated by aerapies by known methods.

Example. Wastewater is treated with the following technological parameters:

Productivity1.8 m / h

Suspended substances, mg / l

442

Chemical need

in oxygen (COD),

mg

Biochemical need

in oxygen (EnKj-J,

mg. The results of the completed studies show high efficiency of biological treatment in the flotation clarifier aeration tank with a very short treatment time of 1.1 hours. The oxidizing capacity of the flotation clarification aerotank averages 4.12 kg of APC g per 1 m construction volume per day, and the entire system of two Duration of processing stock:

in the flotation aerotank clarifier1, 1 h

in the aeration tank second stage1,8 h

in the secondary settling tank 1.2 hours Recirculation sludge consumption from the secondary settling tank 1D m / h Recirculating flotation sludge flow rate Hydraulic load of the flotation aeration tank — sG4.1 (m) h) Air saturation pressure of the active sludge mixture and flotation sludge 0.28 mPa Duration stay of the mixture in the pressure tank 3 min. The concentration of flotation sludge in the regenerator is 18–32 kg / m. The concentration of active sludge in the aeration tank is 0.8–1.2 kg / m. The average performance of the pilot plant is two-stage th wastewater treatment bored in the table.

99318.0

96

75,686, 6

77,542,6

88,496,3

ZO, 212.2 speed purification - 1.43 kg BOD per 1 m per day, which is more than 2.5 times higher than the oxidizing power of ordinary aeration tanks. The use of the proposed method. Provides in comparison with the known: a decrease in the volumes of aeration tanks by more than 2 times; exclusion from the technological scheme of sewage treatment

Claims (3)

Claim 1. The method of two-stage biological treatment of wastewater in aeration tanks, 25 including the separation of activated sludge after the second stage of purification, air saturation and recycling to the first stage of purification, flotation separation of the sludge mixture, characterized in that, in order to increase the rate of biochemical oxidation of pollution and reduce volume of structures, recirculated activated sludge is mixed with sludge after flotation separation of the sludge mixture in the first stage, the mixture is saturated with air and fed to the first stage in an aerotank-flotator. 2. The method according to π. 1, with the fact that sludge after flotation separation before mixing with recirculated activated sludge aerate. 3. The method according to π. 1, characterized in that they saturate the mixture with oxygen.