RU2255905C1 - Waste water biological treatment method - Google Patents

Abstract

FIELD: waste water treatment.

SUBSTANCE: method comprises sorption and activation in biocenosis of activated sludge or waste water/activated sludge mixture in pressure conduit in the process of aeration of waste water/activated sludge mixture performed at least twice in receiving tank of pumping unit and during pumping through pressure conduit with degree of air oxygen-in-water saturation at least 15-20 mg/L accompanied by low-intensity cavitation treatment performed in receiving tank of pumping unit with cavitation number G=0.1-0.4 and during pumping through pressure conduit with cavitation number G=0.02-0.04. Separation of treated water and retention of swelled sludge are effected in sedimentation tank mounted in outlet of conduit and incorporating plane modules with secured biological charge and connecting pipes for discharging clarified water, for exhausted sludge, and water-sludge mixture. Swelled sludge is recycled into aeration zone is accomplished by way of picking water-sludge mixture in amount at least 0.2 g/L from the middle part of sedimentation tank.

EFFECT: lowered treatment expenses, simplified equipment, diminished required areas, combined several process operations, and improved quality of treated water.

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Description

The invention relates to the biological treatment of wastewater.

A known method of wastewater treatment, including the oxidation of organic pollutants contained in wastewater during hydrodynamic cavitation treatment [see A.S. USSR No. 1708775, C 02 F 3/20, publ. 1992]. The cavitation number in this method of water treatment is 0.5-1.

The specified method is not effective, requires sophisticated equipment, does not allow to use microorganisms (activated sludge) with high oxidizing ability to a sufficient degree in the process of water purification, since with microflora cavitation numbers used, incl. and useful, dying.

A known method of biological wastewater treatment, including biological sorption and oxidation in the biocenosis of active, including swollen, sludge, by aeration of a mixture of wastewater and activated sludge, separation of purified water and retention of swollen sludge using a biological film and gravity deposition, return separated from purified swollen sludge water to the aeration stage for reuse as activated sludge [see A.S. USSR No. 1551660, C 02 F 3/12, publ. 03/23/1990]. In this case, separation from the purified water and the delay of the swollen sludge are carried out by two or multiple sequential processes of deposition of swollen sludge particles.

The disadvantages of this method include the fact that although it allows the use of swollen sludge, which has a high oxidizing ability and is formed during wastewater treatment, the proportion of swollen sludge in the total proportion of sludge used remains small, and the process of maintaining the working capacity of swollen sludge is uncontrollable.

Closest to the proposed method is a biological wastewater treatment, including sorption and oxidation in the biocenosis of activated sludge by aeration of a mixture of wastewater and activated sludge subjected to low-intensity cavitation treatment, separation of purified water and delayed swollen sludge by flocculation using a biologically active film and gravity sedimentation, return of activated sludge to the aeration stage [see Russian Patent No. 2146231, C 02 F 3/34, C 12 N 1/00, 1/20, 13/00, publ. 03/10/2000]

To implement the method requires complex and cumbersome equipment, containing both a sorption and oxidation zone, and a flocculation and deposition zone. In addition, the sorption and oxidation process takes place according to a countercurrent flow scheme, first in a spiral upward flow, which ensures complete mixing of waste water and activated sludge, and then also alternately in the flow paths in both vertical and horizontal directions. In some cases, with large degrees of water pollution and its large volumes, water purification devices according to this method occupy large urban areas. In addition, these devices, according to sanitary standards, must be distant from residential areas over considerable distances, which increases the required area occupied by water treatment equipment. All these factors lead to a significant increase in the cost of wastewater treatment. At the same time, the disposal of purified water uses long pipelines, the volume of which is quite sufficient to carry out the process of treating large volumes of wastewater, provided that they maintain the sorption and oxidizing ability of microflora in optimal condition.

The task of creating this technical solution and its technical result is to reduce the cost of water treatment by reducing the complexity of the equipment used, reducing the urban areas required for water treatment and combining several technological operations in the equipment used while maintaining and improving the quality of water treatment.

The specified technical result is achieved by the fact that in the method of biological wastewater treatment, including sorption and oxidation in the biocenosis of activated sludge by aeration of a mixture of wastewater and activated sludge, subjected to low-intensity cavitation treatment, separation of purified water and delayed swollen sludge by flocculation using biologically active films and gravity deposition, return of activated sludge to the aeration stage, there are differences, namely biological sorption and oxidation are carried out in pressure pipelines in the process pumping, aeration is carried out at least twice - in the receiving tank of the pumping station and during pumping by pipeline, with a degree of saturation of water with oxygen of at least 15-20 mg / l, the separation of purified water and the delay of the swollen sludge are carried out in the sedimentation device, installed at the outlet of the pipeline and containing planar modules with fixed biological loading and nozzles for the selection of clarified water, spent sludge and water-sludge mixture, cavitation treatment when pumping to a pump receiving tank the stations conduct with a cavitation number G = 0.1-0.4, and when pumping through a pipeline with a cavitation number G = 0.02-0.04, the oxidative and sorption capacity of activated sludge is maintained by selecting a water-sludge mixture with a sludge dose of 0 , 2-0.5 g / l from the middle part of the sedimentation device.

The proposed method allows to reduce the cost of wastewater treatment due to the reduction in the area occupied by treatment equipment through the use of a complex for pumping water as treatment tanks, reducing the complexity of the equipment used. The method simultaneously allows to improve the quality of water treatment due to the proposed modes of aeration and cavitation treatment.

Aeration carried out during processing at least twice, mixing wastewater and activated sludge with sufficient oxygen saturation of 15-20 mg / l in the receiving tank of the pumping station and during pumping through the pipeline allows for high oxidative and sorption capacity of activated sludge and its transition in flocculent form - swollen sludge, which, in combination with the proposed two-stage regime of cavitation treatment of low intensity, allows maintaining its oxidizing ability at a high level. The cavitation treatment used at the first stage of the process with a cavitation number G = 0.1-0.4 allows you to destroy the flocs supplied from the final stage (gravitational precipitation stage) in the water-sludge mixture of the flocculated, partially lost working sludge and transfer it to a flocculent working state . This solves the problem of regeneration of activated sludge. The cavitation mode used with the cavitation number G = 0.02-0.04, which is used in the subsequent stages when pumping through the pipeline, makes it possible to maintain its oxidative and sorption ability at the highest level.

The duration of treatment with the applied technological parameters should be sufficient for effective wastewater treatment, which is achieved due to the length of the pipelines used and the number of cavitation treatments and aeration during pumping. The separation of purified water and swollen sludge in a sedimentation device equipped with planar modules with biological film loading is also accompanied by a water treatment process, thereby increasing the efficiency of water treatment.

The method is as follows.

Wastewater freed from coarse mechanical impurities is supplied to the receiving tank of the pumping station. In the process of its supply, it is subjected to cavitation treatment with a cavitation number G = 0.1-0.4. In the receiving tank, water is aerated with a device for supplying air to saturate the water with atmospheric oxygen of at least 15-20 mg / l. In the receiving tank of the pumping station, along with wastewater, a water-sludge mixture is supplied from the sedimentation device with a sludge dose of not less than 0.2 g / l, which contains activated sludge flocs that have largely lost their working capacity. Under the influence of cavitation treatment with a cavitation number G = 0.1-0.4, the process of destruction of the flocs and the transition of activated sludge to the initial flocculent state, i.e. in essence, there is a process of regeneration of the growth of activated sludge involved in the oxidation of wastewater pollution due to low-intensity cavitation. At the same time, the growth of other microorganisms that are not involved in the oxidation and sorption is suppressed. Next, the wastewater is pumped into the pipeline. During pumping, it is processed by cavitation with a cavitation number G = 0.02-0.04 and aerated one or more times until the oxygen content in the water-sludge mixture is at least 15-20 mg / l. Cavitation treatment of this mode contributes to a significant increase in the oxidative and sorption ability of activated sludge. After the pipeline, the purified water is supplied to the sedimentation device installed at the outlet of the pipeline and containing planar modules with a fixed biological load (biofilm) and nozzles for the selection of clarified water, waste sludge and water-sludge mixture.

Under the influence of unlike charges of a biofilm and activated sludge, a swollen sludge and a biological film come into contact in a sedimentator, flocculation of swollen sludge and gravitational deposition of flocs. Swollen sludge flocs fall into the lower sludge part and are removed from there through a pipe to select the spent sludge for processing or to sludge sites. The clarified water is removed through the sediment pipe in the upper part of the device. In the middle part of the device there is a nozzle for the selection of water-sludge mixture, with which it is selected and fed into the wastewater supplied to the receiving tank of the pumping station, at the initial stage of processing. A sludge-water mixture with a sludge dose of 0.2-0.5 g / l is selected and fed to a receiving tank.

These modes provide the necessary performance of activated sludge and effective wastewater treatment.

Example 1

For the treatment of wastewater in an amount of 15,000 m ³ / day, a pressure pipeline with a diameter of 800 mm and a length of 17,200 m is used. In pumping the indicated amount of wastewater, two pumping pumping stations are used. The amount of contaminants in the waste water supplied for pumping according to BOD ₂₀ (biological oxygen demand in a twenty-day sample) is 214 mg / l. Before being fed to the receiving tank, the water to be purified passes through a mechanical cleaning process. The first stage of wastewater treatment consists in treating it with low-intensity cavitation with a cavitation number G = 0.3 and saturation of it with atmospheric oxygen of 15 mg / l using combined aeration. Then purified water pre-saturated with atmospheric oxygen is subjected to repeated treatment with low intensity cavitation with a cavitation number G = 0.04. During the passage of the treated water through a section of the pipeline with a length of 9500 m to the next pumping station, the amount of contaminants in the BOD ₂₀ decreased to 42 mg / l; at the second pump station, a similar operation is carried out to treat the treated water with low-intensity cavitation and aeration. As a result of the passage of purified water through the second section of the 7700-meter-long pipeline, the amount of pollution decreased by BOD ₂₀ from 42 mg / l to 14 mg / l. In the sedimentation device, the amount of contaminants according to BOD ₂₀ decreased to 3 mg / l. Next, the purified water is removed through a pipe in the upper part of the sedimentation device. The spent sludge is removed, and a water-sludge mixture is taken from the middle part of the sedimentator into the tanks with a sludge dose of 0.2 g / l, which is transported by road to the initial stage of the process. Permissible BOD ₂₀ for reservoirs of fisheries for use is 3 mg / l, and this degree of purification is achieved in the proposed method.

Examples 1-6 are shown in table

They illustrate the effect of treatment parameters on the degree of water purification.

TABLE No. Ref. overseas BOD₂₀
mg / l The length of two sections of the pipeline, m The degree is saturated. oxygen. Air mg / L Cavitation number The number of cavitation treatments, units Dose of silt, return. to the receiving tank g / l BOD degree of purification₂₀
mg / l In reception. reservoir II When pumping 1 2 3 4 5 6 7 8 nine 1 214 17200 fifteen 0.3 0.04 4 0.2 3.0 2 214 17200 19 0.1 0.02 4 0.4 2.1 3 214 17200 21 0.4 0,03 4 0.5 2.9 4 214 17200 eighteen 0.2 0.05 4 0.6 3.3 5 214 17200 17 0.5 0.05 4 0.6 3.3 6 214 17200 14 0.3 0,03 4 0.1 7.0

The proposed method allows to reduce the cost of water purification in comparison with the prototype by 1.5-2 times by reducing the area occupied by treatment plants by 3-4 times, simplifying the equipment used, and also to improve the degree of water purification.

Claims (1)

A method of biological wastewater treatment, including sorption and oxidation of activated sludge in the biocenosis by aeration of a mixture of wastewater and activated sludge subjected to low-intensity cavitation treatment, separation of purified water and retention of swollen sludge by means of biologically active film and gravitational deposition, return of swollen sludge into the aeration zone, characterized in that biological sorption and oxidation are carried out in the pressure pipe during the pumping process, aeration is carried out at least twice - in reception ohm tank of the pumping station and during pumping through a pipeline with a degree of saturation of water with atmospheric oxygen of at least 15-20 mg / l, the separation of purified water and the delay of swollen sludge are carried out in a sedimentation device installed at the outlet of the pipeline and containing planar modules with fixed biological loading and pipes for the selection of clarified water, waste sludge and water-sludge mixture, cavitation treatment of wastewater when pumping to the receiving tank of the pumping station is carried out with a cavitation number G = 0.1-0.4, and when pumping through a pipeline - with a cavitation number G = 0.02-0.04, the necessary oxidizing and sorption activity of activated sludge is supported by the selection of a water-sludge mixture with a dose of at least 0.2 g / l from the middle part of the sedimentation device.