EA004338B1 - Method treatment of sewage water by biological way and a unit for realization of the method - Google Patents

Abstract

1. Method of sewage treatment, wherein crude sewage without a mechanical pre-treatment is supplied into the compensative tank, then into the activation tank, where the biological treatment takes place, and at least, to the settling tank, where activated sludge is separated from purified water, characterized in that in compensative tank rough sewage is crushed by means of periodical air injection and mixing. 2. Method of sewage treatment, according to claim 1, characterized in that air supplying to the compensative tank is realized when obtaining a minimal level on the surface in compensative tank. 3. Method of sewage treatment, according to claim 1, characterized in that air supplying to the compensative tank is finished when obtaining a working level of the surface in compensative tank. 4. Method of sewage treatment, according to claim 1, characterized in that air supplying to the compensative tank is realized in rigidly adjusted time intervals. 5. Method of sewage treatment, according to claim 1, characterized in that air is supplied to the activation tank and sludge tank, when pumping of sewage from compensative tank, to which air is not supplied, and where the hold-up of rough sewage is done. 6. Method of sewage treatment, according to claim 1 or 5, characterized in that while air supplying into the activation tank, the activation mixture is supplied from the activation tank to the settling tank, the activated sludge is going back through the opening on the bottom of the settling tank to the activation tank, and purified water is raising to outlet from treating unit and/or to the sand filter. 7. Method of sewage treatment, according to claim 1-6, characterized in that water is running from up to down, and filtrated water is pressed out to outlet by hydrostatic increased pressure, formed by the difference of water surface levels over sand filter and water surface on the drain, or by independent pump. 8. Method of sewage treatment, according to claim 1, characterized in that while air supplying into the compensative tank, the pumping of sewage from compensative tank to activation tank is stopped, and thereby the discharge of water from the treating unit. 9. Method of sewage treatment, according to claims 1-8, characterized in that while air supplying into the compensative tank, air is passing through the sand filter, activation tank, and transforming to quiescent state, the settler tank filling is stopped and the pump of removing of sludge of activation tank is turned on. 10. Method of sewage treatment, according to claims 1-9, characterized in that the inlet of the pump for removing the sludge in activation tank is located on such height over the bottom, that to leave under the inlet such quantity of settled activated sludge, that is optimal for biological treatment process. 11. Method of sewage treatment, according to claims 1-9, characterized in that, when air is supplied to the sand filter, polluted water is leaving from the filter surface. 12. Activation unit of sewage with activated sludge in suspension state, consisting of compensative tank with air pump of pre-treated water, activation tank with air pump of sludge removing, settling tank with the outlet of treated water, sludge tank, and sand filter, characterized in that the compensative tank (1) is provided with air supplying equipment (12), connected with the system of air supplying of the compensative tank (33), float breaker of minimal water level (10) and float switch of working level of working level (11), when the activation tank (2) is provided with air pump of sludge removing (15) and supplying equipment (13), connected on the air supplying system of activation tank (32), which is connected to air supplying through three-way electric valve (30) and/or through independent straightway electric valve. 13. Activation treating unit, according to claim 12, characterized in that the air supplying system of compensative tank (33) consists of air supplying equipment of compensative tank (12), air supplying to the pump of sludge removing (15), air supplying to the equipment purging the settling tank (19), air supplying to the air pump of purge removing of the sand filter (34), air supplying to the air pump of floating sewage of the settling tank (16) and to the air sprayer. 14. Activation treating unit, according to claim 12, characterized in that the air supplying system of activation tank (32) consists of air supplying equipment of activation tank (13), equipment for supplying air of sludge tank (20), air supplying to air pump of crude water (7) and air supplying to the air pump of settling tank (14). 15. Activation treating unit, according to claim 12, characterized in that the system of air supplying of treating unit consists of compressor (29) three-way electric valve (30) and/or 2 straightway electric valves/for switching over the air purging system of activation tank (33) depending on the water level in compensative and/or timer switch. 16. Activation treating unit, according to claim 12 or 15, characterized in that the system of air supplying of the unit consists of 2 independent compressors, system of air supplying of compensative tank (33) and the system of air supplying of activation tank. 17. Activation treating unit, according to claim 12 or 15, characterized in that on the water level decreased for a level of float switch of minimal surface (9), the purging system of compensative tank (33) is switched on till the time, required for obtaining of working surface, which is signaled by float breaker of working surface (10), wherein the system of air supplying to the activation tank is not still activated. 18. Activation treating unit, according to claim 12 or 15, characterized in that the air supplying system of activation tank (32) is activated on the time, required for decreasing of the surface level in compensative tank (1) from the water level, signaled by floating switch of working surface (10) and/or level higher on water level, signaled by floating switch of minimal surface level (9). 19. Activation treating unit, according to claim 12 or 13, characterized in that the inlet of air pump of sludge removing (15) is located on such height over the bottom of the activation tank (2), that is required for maintaining the optimal layer of activated sludge, settled at the bottom of activation tank (2) while the air supplying system of compensative tank is working. 20. Activation treating unit, according to claim 12 or 18, characterized in that polluted water of flushing of the sand filter (22) in time of air supplying to compensative tank (1) is pumped by air pump of sludge removing of the sand filter (34) in compensative tank.

Description

The invention relates to a method and installation of wastewater treatment by biological means using an activated sludge activation system in suspension, which is used mainly for small home wastewater treatment plants.

State of the art

Biological treatment of wastewater uses activated sludge, which is a mixture of various bacteria and small microorganisms. This sludge requires the nutrients contained in the wastewater to live, and when these nutrients are consumed from the wastewater, they are cleaned. The activation process is possible only with a sufficient supply of oxygen, which, as a rule, is carried out by forcing air into the activation tank.

The previously known activation installations for wastewater treatment with sludge in suspension can be generally divided into systems with continuous flow of wastewater through activation tanks and into systems with intermittent flow.

In a continuous system, wastewater after coarse pretreatment is introduced into the activation tank and after the necessary, from the technological point of view, the time for purification is discharged together with the activated sludge into a separate secondary clarifier. Sludge is deposited in this sump, and clean water is discharged to the outlet.

In a system with intermittent flow, the wastewater is fed into the activation tank cyclically, usually from a surge tank. After filling the activation tank, a cleaning cycle occurs, which is interrupted by stopping the supply of air, by settling sludge at the bottom of the activation tank and ending with pumping purified water to the outlet. After the release of the activation tank, the cycle ends and the next cycle begins by re-filling the activation tank. In this case, the cleaning system does not contain a secondary clarifier.

In small domestic wastewater treatment plants, wastewater is unevenly generated and the quality of wastewater is uneven. For these reasons, it is better to install a separate surge tank before the treatment plant itself.

A major operational problem is the removal of coarse impurities (hard excrement, toilet paper, etc.), which in large types of treatment plants are removed mechanically or with special equipment (various mechanical sieves, grids, etc.). But for small domestic wastewater treatment plants, these engineering products are too expensive and are not used. The usual solution to this issue is to install a preliminary sedimentary tank, where substances are captured, both floating on the surface of the tank and deposited on the bottom, and only in this way the previously purified water is fed into the activation system. In these cases, the problem is that large volumes of these reservoirs of primary sedation are necessary, which leads to anaerobic decay of the organic mass, which creates a source of unpleasant odor. The sludge deposited here at the bottom is not stabilized and belongs to the category of primary sludge, which according to waste classification is waste that is especially hazardous.

In other systems without primary sedimentation tanks, lattice baskets or various types of dishes with openings are used to trap solids. These devices must be cleaned regularly, which causes the problem of where to put these unhealthy and strongly smelling remnants, and, in addition, it requires frequent maintenance of the cleaning installation.

Summary of Invention

The above disadvantages are eliminated using the wastewater treatment method in accordance with the present invention, in which wastewater without the need to install devices of coarse mechanical pre-treatment comes in a separate inlet tank, which serves instead of equipment for coarse pretreatment and simultaneously has the function of an equalizing and leveling tank, where homogenization of wastewater. Coarse impurities, both floating and besieged, linger here. Floating impurities remain on the surface of the surge tank, and precipitated sludge - at the bottom of the tank. During treatment, wastewater is pumped from the surge tank into the activation tank, where it is biologically cleaned, and then transferred to a secondary settling tank, where biologically active sludge is separated from the treated water, which is fed to the outlet.

The basis of the invention is that waste water is supplied to an activation tank without coarse impurities that float on the surface of the surge tank from the layer of water between the surface and the sludge bed deposited on the bottom, while coarse organic matter from the waste water is mechanically destroyed, and partially and biologically decompose during the minimum intake of water into the treatment plant, when the filling of the activation tank is stopped, and air is supplied to the surge tank. When air is supplied, intensive mixing of the leveling tank content occurs. Under the action of the activated sludge on the content of the surge tank and in parallel with the intensive mechanical mixing with air under pressure, at periodic intervals of time mechanical and partial biological decomposition of coarse organic substances occurs. The remains of these organic substances then pass through a coarse filter, which protects the pump, which supplies water from the surge tank to the activation tank, while this filter is not clogged, and full biological decomposition takes place in the activation tank. The result of this cleaning method and the chosen design is that the cleaning installation made according to this invention does not contain any mechanical equipment to delay coarse impurities and at the same time produces only aerobically stabilized sludge, which is accumulated in a separate collection of sludge in the cleaning installation and can serve as high-quality organic fertilizer. In this case, the cleaning unit does not require maintenance of equipment for coarse pretreatment and does not produce primary sludge as particularly hazardous waste, which is usually the case with other types of wastewater treatment plants.

The activation installation of wastewater treatment biologically with activated sludge in suspension in accordance with the present invention consists of a surge tank with a wastewater inlet, an activation tank, a secondary clarifier, a sludge collector and usually another sand filter for the final treatment of waste water.

There is air supply equipment and a water level switch in the surge tank. After this rough treatment, the wastewater from this tank is usually pumped by an air pump to the activation tank. The air pump is protected from clogging by the coarse filter, which does not have a hole in the lower part, so that at rest, when air is not pumped into the surge tank, prevent the influx of activation sludge to the raw water pump. Thus, a sufficient amount of activated sludge is provided for the biological degradation of coarse impurities during the air injection phase into the surge tank.

In the activation tank biological treatment of wastewater occurs with activated sludge. The mixture of purified water and activated sludge goes to the secondary clarifier, usually pumped by an air pump when the sludge returns through the hole in the bottom of the clarifier to the activation tank, and the evacuated water rises to the drain. A gravity sand filter can also be placed on the drain for the purification of waste water from sludge residues. An integral part of the purification plant is usually also an independent sump settling tank, into which air is forced during the air supply phase to the activation tank. The activation tank further contains a pump for deactivating activation - maintaining the optimal amount of sludge in the activation tank. This pump is turned on while air is being supplied to the surge tank. The inlet to the pump is located above the bottom of the activation tank at a height that is necessary to maintain the optimum amount of activated sludge. The pump is switched on either at the moment of supplying air to the surge tank, or after the passage of time necessary for sedimentation of the sludge in the activation tank.

When sewage enters the surge tank, the level of the water surface in the surge tank is above the set minimum level. At this time, the pumped wastewater enters the activation tank and at the same time the purified water is drained from the treatment plant. Air injection into the surge tank, and thus the elimination of coarse contaminants, occurs during minimal inlets into the treatment plant, which is indicated by a decrease in the surface level in the surge tank to the prescribed minimum level. At this point, the pumping of raw water to the activation tank stops and at the same time the air enters the surge tank. Usually the technical solution is that one compressor is used as an air source, and with the help of a triple electric fan, air is diluted into two independent systems, one of which is to supply air to the surge tank, and the other to supply air to the activation tank. When the minimum surface level in the surge tank is reached, the float switch switches the three-way electrical valve and this will start to supply air to the aeration system of the surge tank, and at the same time the air supply to the aeration system of the activation tank will stop. The time it takes for the air to be supplied to the surge tank is determined either by the set time or by reaching the set maximum operating level of the surface. The maximum working level of the surface is reached either by the inflow of raw sewage or by pre-treated water from the activation reservoir, which in a strictly fixed amount is pumped out together with excess sludge to the sludge pit, where the sludge is deposited, and the remaining water gravitationally flows into the surge tank.

The main advantages of this technical solution of a biological purification plant with activated sludge in a suspended state are, in addition to the simple and reliable elimination of coarse impurities, also ensuring automatic removal of sludge from the activation tank, denitrification of water nitrified in the activation phase by its gradual pumping through the sludge tank to the surge tank with oxygen deficiency, and last but not least - an exceptionally high quality of water at the outlet when the dog is turned on Full-time filter as the third phase of cleaning, when the sand filter is cleaned by supplying air during the phase of supplying air to the surge tank, when no water is released from the cleaning unit. Water polluted by washing the sand filter is returned to the surge tank, where denitrification occurs again. The sand filter is not an obligatory part of the purification plant, but is installed where increased requirements are imposed on the quality of wastewater. When using all these cleaning elements in an installation from this one installation, a product of high utility and value arises, which meets both the requirements for high reliability and the minimum requirements for operation and maintenance and, when equipped with a sand filter, the requirements for maximum water quality at the drain .

Overview of Drawings

The attached drawings show one of the possible technical versions of the activation purification plant according to the invention.

FIG. 1 shows a design solution for a cleaning unit in a horizontal section; FIG. 2 shows a flow chart for injecting air into the equalizing tank, and FIG. 3 shows the flow chart for air supply to the equalizing tank.

Designation of drawings

- equalizing tank

- activation tank

- secondary clarifier

- silt settler

- sand filter

- wastewater inlet

- raw water air pump

- coarse dirt filter

- float switch minimum water level

- water level float switch

- the maximum level of activated sludge

- air supply equipment in equalizing tank

- equipment for supplying air to the activation tank

- air pump of the secondary clarifier

- air sludge removal pump

- air pump for floating sediment

- gas removal cylinder

- release of purified water

- air supply to the sump

- air supply to the sludge pit

- septum water with silt

- filter sand

- interzone space

- filtration nozzles

- air nozzles 26 - protective spillway

- release of purified water

- release of filtered water

- compressor

- three-way electric valve

- switchboard

- air supply system in the activation tank

- air supply system in equalizing tank

- sand filter sludge air pump

An embodiment of the invention

The wastewater treatment plant in accordance with FIG. 1, 2 and 3 consists of equalizing tank 1, activation tank 2, secondary clarifier 3, sludge tank 4, sand filter 5. Equalizing tank 1 contains waste water inlet 6, raw water air pump 7, coarse sewage filter 8, which has inlets raw water above the maximum surface level of activated sludge 11, the minimum level float switch 9, the working surface level float switch 10, the air supply equipment 12 and the protective spillway 26 with the release of purified water 27. In activation In the tank 2, the air supply equipment, the secondary sump pump 14, the sludge removal air pump 15, the sump floating sewage air pump 16 are placed. The cylinder for gas removal 17, the discharge of purified water 18 and the air supply to the secondary sump 19 are placed in the secondary sump. Sludge trap 4 is equipped with equipment for air supply 20 and a septum of water with sludge 21. Sand filter 5 contains filter sand 22, inter-space 23, inlet filtration nozzles 24, air nozzles 25, filter release water 28. The cleaning plant in FIG. 1 and 2 further comprises a compressor 29 with a three-way electric fan 30 and / or 2 pcs. compressors without electric valves and / or compressor 29 with 2 pcs. direct ventilator, which divides the tube for air into two separate systems. One system is for forcing air into the equalizing tank 1, and the second system is for forcing air into the activation tank.

2. The cleaning plant also contains a conventional electrical switch for controlling the valve 30, depending on the surface of the water level in the equalizing tank 1.

Wastewater flows through inlet 6 to equalizing tank 1, in which the water surface level is higher than the minimum water surface level specified by the float sensor 9. A three-way electric fan 30 directs air into the air supply system of the activation tank 32. This system 32 simultaneously supplies air to the engines air pump for raw water 7, air pump for secondary sedimentation tank 14, equipment for supplying air to the activation tank 13 and equipment for supplying air to the siphon 20. In equalizing tank 1 on sedmintiruyutsya heavier particles from the waste water. Floating pollutants remain on the surface, and the pre-treated wastewater flows through the inlet ports of the coarse sewage filter 8 to the raw water air pump 7, which is pumped into the activation tank 2. Air is pumped into the activation tank 2, and thereby mixing with active sludge followed by biological wastewater treatment.

The mixture of purified water and activated sludge is pumped by the air pump of the secondary clarifier 14 into the secondary clarifier 3 through a gas removal cylinder 17. The silt that is heavier than water gradually descends to the hole at the bottom of the clarifier 3 and falls back into the activation tank 2. Purified water rises to release 18, which leads to sand filter 5 and / or to the release of clean water from unit 27, if the installation is not equipped with a sand filter. The sand filter is in a submerged state, water flows through the filter sand 22 from top to bottom through the inlet filtration nozzles 22 into the inter-space 23 and this mechanically refines. The filtered water is squeezed out into the outlet 28 by the hydrostatic difference of the water surface levels above the sand filter 5 and the flow of purified water from the purification unit 27 and / or the pump not shown in the figures.

If there is insufficient flow of wastewater, the level of the water surface in the equalizing tank 1 will decrease to the level of the minimum level 9 float switch, which will give instructions to switch the three-way electric fan 30, and / or two direct electric valves not indicated on the figures, and / or two independent ones indicated on the figures of compressors. This closes the injection of air under pressure into the air supply system of the activation tank 32 and at the same time opens the air supply to the air system of the equalizing tank 33. In this phase of the purification plant in accordance with the invention, the raw sewage from the surge tank 1 to the activation tank 2 will end using the raw water air pump 7, and at the same time, the equalizing tank 1 is intensively pumped with air and mixed with the help of the air supply equipment 12. It occurs by direct mechanical and partly biodegradation coarse impurities accumulated in the equalizing tank during the previous phase of operation the sewage treatment plant. At the same time, this phase does not release water from the treatment plant, since its pumping from the equalizing tank was stopped. This is used to remove sludge from the activation tank 2, to clean the surface of the secondary clarifier 3, and to clean the surface of the sand filter 5. The air sump pump 14, the air supply equipment to the activation tank 13, and the air supply equipment to the sedimentation tank 20 are off. which is heavier than water, is gradually sinking at the bottom of the activation tank 1. The pump for floating waste from the sump 16 is operated, the air is fed into the sump 19, the air sludge removal pump 15 is air The pump for removing the sludge from the sand filter 34 and the air supply to the sand filter 5 using air nozzles 25. The air pump for removing the sludge 15 has an inlet located above the bottom of the activation tank 2 at such a height that in the activation tank 2 always remains at the end of this phase purification plant works the optimal amount of activated sludge. The sludge removal air pump first pumps a mixture of purified water and sludge into the siphon 4, then gradually only sludge and in the final phase, when the sludge has settled and the excess sludge has been pumped out, only clear water.

The duration of this phase, while sewage does not flow into the equalizing tank 1, is determined by the capacity of the raw water air pump 15 and usually lasts about 60 minutes with a frequency of 1 to 6 times a day depending on the hydraulic load of the purification plant. Excessive water from the sludge collector 4 gravitationally flows into the equalizing tank 1, and in this tank the level of the water surface gradually increases. When the water reaches the level of the float switch of the working surface 10, the three-way electric fan 30 will switch again, which will direct the air from the air supply system of equalizing tank 33 to the air system of the activation tank 32. The wastewater treatment plant of the invention thus optimally uses the period of reduced inflow for treatment of coarse sewage in the equalizing tank 1 and at the same time to remove sludge from the activation tank 2, cleaning the surface of sludge nick sandscreen 3 and 5.

With a sufficiently large equalizing tank 1, the wastewater treatment plant according to the invention can be operated without taking into account the level of the water surface in the equalizing tank 1 signaled by surface level sensors (float switch of the minimum level of the surface height 9 and float switch of the working surface 10), with the help not shown in the figures a time relay switch that regularly switches the three-valve fan 30 at regular intervals and / or 2 pcs. direct valves, and / or 2 pcs. independent compressors, and thereby pressurized air is alternately supplied to the air supply system of the activation tank 32 and to the air supply system of equalizing tank 33. Usually, the time switch not shown in the figures is set to 5 hours of air supply to the activation tank 2 and 1 to equalizing tank 1. Other functions and equipment of the cleaning plant remain unchanged.

Claims (20)

CLAIM 1. Wastewater treatment method, when raw wastewater without mechanical pretreatment enters an equalizing tank, then into an activation tank, where biological purification takes place, and finally into a septic tank, where activated sludge is separated from purified water, characterized in that In the tank, periodic sewage is crushed by periodic air injection and mixing. 2. The method of wastewater treatment according to claim 1, characterized in that the air supply to the equalizing tank is carried out when the minimum level of the surface in the equalizing tank is reached. 3. The method of sewage treatment according to claim 1, characterized in that the air supply to the equalizing tank ends when the working level of the surface in the equalizing tank is reached. 4. The method of sewage treatment according to claim 1, characterized in that the air supply to the equalizing tank is carried out in tightly tuned time intervals. 5. The method of sewage treatment according to claim 1, wherein air is pumped into the activation tank and the siphon at a time when pumping sewage from the equalizing tank into which air is not supplied and where the coarse sewage delay occurs. 6. The method of sewage treatment according to claims 1 and 5, characterized in that when air is supplied to the activation tank, the activation mixture enters the activation tank into the settling tank, while activated sludge is returned through the hole in the bottom of the settling tank to the activation tank. Purified water rises to release from a purification unit and / or sand filter. 7. The method of sewage treatment according to claims 1-6, characterized in that water flows from the top down through the flooded sand filter, and filtered water is discharged into the outlet by hydrostatic overpressure, which is created by the difference in water surface levels above the sand filter and the water surface on the drain and / or independent pump. 8. The method of wastewater treatment according to claim 1, characterized in that when air is supplied to the equalizing tank, the pumping of the waste water from the equalizing tank to the activation tank and thereby the discharge of water from the treatment plant stops. 9. The method of sewage treatment according to claims 1-8, characterized in that when air is supplied to the equalizing tank, the air passes through the sand filter, the activation tank goes into a state of rest, filling of the sump will stop and the sludge removal pump of the activation tank will turn on. 10. The method of sewage treatment according to claims 1-9, characterized in that the inlet of the pump to remove sludge in the activation tank is located at such a height above the bottom, so that under this inlet there is always the amount of precipitated activated sludge that is optimal for the biological process cleaning up. 11. Wastewater treatment method according to claims 1-9, characterized in that when air is supplied to the sand filter, polluted water leaves the surface of the filter. 12. Activated installation of wastewater with activated sludge in suspension, consisting of a leveling tank with an air pump of pre-treated water, an activation tank with an air pump for removing sludge, a sump with a release of purified water, a sludge trap and a sand filter, characterized in that the leveling tank (1 ) is equipped with air supply equipment (12) connected to the equalizing tank air supply system (33), a float switch of the minimum level of the water surface (10) and a float switch The surface operating level switch (11), while the activation tank (2) is equipped with an air sludge removal pump (15) and supply equipment (13) connected to the air supply system of the activation tank (32), which is connected to the air supply through three-way electric valve (30) and / or through an independent pass-through electric valve. 13. Activation treatment plant in accordance with Claim 12, characterized in that the air supply system of the equalizing tank (33) consists of equipment for supplying air to the equalizing tank (12), supplying air to the sludge removal pump (15), supplying air to the sump blowing equipment ( 19), the air supply to the air pump for removal of sand filter sludge (34), the air supply to the air pump of the floating sewage sump (16) and to the air nozzles (25). 14. Activation treatment plant in accordance with Claim 12, characterized in that the air supply system of the activation tank (32) consists of equipment for supplying air to the activation tank (13), equipment for supplying air to the sump (20), supplying air to the raw water air pump (7 ) and supply air to the sump air pump (14). 15. Activation purification plant according to item 12, characterized in that the air supply system of the purification plant consists of a compressor (29), a three-way electrical valve (30) and / or 2 pcs. flow-through electric fans for alternating switching of the air purge system of the activation tank (33) depending on the level of the water surface in the equalizing tank and / or depending on the switch of the time relay. 16. Activation installation according to claims 12 and 15, characterized in that the installation air supply system consists of 2 pieces. independent compressors, equalizing tank air supply system (33) and activation tank air supply system (32). 17. Activation unit according to claims 12 and 15, characterized in that, when the water surface level is reduced to the level of the minimum surface float switch (9), the equalization tank purge system (33) is activated to the time required to reach the working surface, which signaled by the float switch of the working surface (10), and all this time the air supply system to the activation tank is not activated. 18. Activation cleaning installation according to claims 12 and 15, characterized in that the air supply system of the activation tank (32) is activated for the time required to reduce the surface level in the equalization tank (1) from the surface level of the water signaled by the float switch of the working surface ( 10), and / or higher level, to the level of the surface of the water, signaled by a float switch with a minimum surface level (9). 19. Activation installation according to claims 12 and 13, characterized in that the inlet of the sludge removal air pump (15) is located at such a height above the bottom of the activation tank (2), which is necessary to maintain an optimal layer of activated sludge deposited at the bottom of the activation tank ( 2) at the time when the equalizing tank air supply system (33) is operating. 20. Activation treatment plant according to Claims 12-18, characterized in that the polluted water from washing the sand filter (22) while supplying air to the equalizing tank (1) is pumped by the sand filter sludge removal air pump (34) to the equalizing tank (1 ).