EA049802B1 - METHOD OF PURIFYING MUNICIPAL WASTEWATER AND EQUIPMENT FOR ITS IMPLEMENTATION - Google Patents

Abstract

Wastewater is filled from a minimum to a maximum level in the storage tank. While the storage tank is filling, the bioreactor is aerated. Once the storage tank is full, aeration is stopped. After the activated sludge settles at the bottom of the bioreactor, purified water is pumped from the subsurface water layer to the discharge, while wastewater from the storage tank is simultaneously pumped into the settled sludge layer—that is, to the bottom of the bioreactor. This ensures a constant water level in the bioreactor while the purified water is being pumped out. Once the water level in the storage tank has dropped to the minimum level, both the pumping of purified wastewater and the pumping of wastewater into the bioreactor are simultaneously stopped. The storage tank is equipped with a wastewater pump, which pumps wastewater to the bottom of the bioreactor. The bioreactor has a safety overflow leading to the discharge of purified water, and the discharge is equipped with a pump for purified water. The hydraulic capacities of the wastewater pump and the purified water pump are set to maintain a stable water level in the bioreactor during the pumping period. Both pumps are preferably air-driven. Thus, the intermittent wastewater treatment system maintains a stable water level in the bioreactor, just like continuous systems.

Description

Scope of application

The invention relates to a method for purifying municipal wastewater based on the intermittent principle of wastewater purification, and to domestic biological treatment facilities.

State of the art

When purifying wastewater using a suspended activated sludge system, two methods of separating activated sludge from the water being purified are mainly used in practice.

The first method involves continuous passage of purified water through an activation tank, when a mixture of activated sludge together with purified water is constantly fed into a separate settling tank, where the sludge, heavier than water, settles - on the bottom and returns to the activation tank. Purified water flows from the surface of the settling tank of the treatment facilities to the discharge.

The second method, the so-called SBR system, with an intermittent flow through the activation tank, uses the interruption of activation to settle the sludge to the bottom of the activation tank, and then pump the treated water from the subsurface layer to the discharge, and then the activation tank is filled with wastewater again for a further activation cycle.

The disadvantage of the known SBR systems, periodic action, is first of all the method of pumping out purified water, in which the level of pumped out water in the reactor decreases. Various designs are known for pumping out purified water - decanters that are lowered into the water or kept afloat by floats, or submersible pumps on floats and other solutions are used. The general problem of these decanters is that sludge should not penetrate into them during aeration of the bioreactor, which leads to the structural complexity of the decanters and often to deterioration of the quality of water at the outlet of the treatment facilities. Another problem is associated with the gradual lowering of the decanting device when the level of pumped out purified water from the subsurface layer decreases, which, thus, approaches the zone contaminated with sludge. This also leads to the already described negative consequences in relation to the complexity of the decanter design and the quality of purified water.

The closest analogues for the application of the invention are:

invention PCT/CZ22O11/OOOO22, utility model 8662, Bulletin of UPR SR 02/2020.

The essence of the invention

The above disadvantages are eliminated by the method of wastewater treatment according to the invention, in which the wastewater is discharged from the minimum to the maximum level in the storage tank, during which time the bioreactor is aerated. After filling the storage tank, the aeration of the bioreactor is stopped. After subsequent settling of the activated sludge at the bottom of the bioreactor, the purified water is pumped from the subsurface layer to the discharge, and at the same time the wastewater from the storage tank is fed to the layer of settled sludge in the bioreactor, i.e. to the bottom. This will ensure a constant water level in the bioreactor during the entire time of pumping the purified water from the bioreactor. After the water level in the storage tank has decreased to the minimum level, both the pumping of purified wastewater and the pumping of wastewater into the bioreactor are simultaneously stopped. After this, the storage tank begins to fill with wastewater again and aeration in the bioreactor begins. Aeration of the bioreactor when filling the storage tank can be continuous or periodic, or alternate with mixing of wastewater. During aeration of the bioreactor, wastewater in the storage tank can also be aerated.

A biological treatment plant for domestic wastewater consists of at least two separate tanks of arbitrary shape: a storage tank with a wastewater inlet and a bioreactor equipped with an aeration device. The sludge tank may also be part of the treatment plant. The storage tank is equipped with a pump for pumping wastewater into the bioreactor, a measuring device for determining the drain level, the fill level and a safety overflow into the bioreactor with a protruding hole wall. This overflow is connected to the lower part of the bioreactor through vertical pipes. The bioreactor is also equipped with a safety overflow with a through wall before the discharge of purified water from the treatment facility. The discharge is equipped with a pump for purified water. The hydraulic capacities of the pump for pumping water into the bioreactor and the pump for purified water from the treatment facility are set such that a stable water level is maintained in the bioreactor. As a result, the inlet of the purified water pump can be set at a constant shallow depth below the water level in the bioreactor.

The solution according to the invention combines the above-described methods of continuous and intermittent wastewater treatment. In this case, the invention is aimed at an intermittent method with simultaneous maintenance of a constant water level in the bioreactor. At a constant level, as in the case of continuous action systems, the bioreactor is simultaneously filled, aerated, settled and pumped out purified water, which, however, is unique to the periodic action system.

The advantage of the solution according to the invention is the simplicity of the design without moving parts and, therefore, the increase in the reliability of the treatment plant. Another advantage is that the operation of the treatment plant can be controlled both by a single float in the storage tank and by a complex electronic control unit. The advantage over known systems

- 1 049802 SBR topics are that the bioreactor is aerated throughout the entire accumulation filling phase up to the maximum depth of the bioreactor, which leads to better use of the oxygen energy from the supplied air. The most significant advantage, on which the other described advantages are based, is the simplicity of the decanter design, consisting, for example, of an air pump, and the failure-free provision of the required water quality. Due to the simplicity of the technical solution, this technology is also very convenient for the reconstruction of old, or even the construction of new, as well as problematic domestic wastewater treatment plants. Due to its structural simplicity, it is especially suitable for small biological treatment plants for domestic wastewater.

Description of drawings

Fig. 1 shows a plan of one of the possible design solutions for small treatment facilities for domestic wastewater, consisting of two round tanks.

Fig. 2 shows a rectangular treatment plant.

Fig. 3 shows a section A-A of the treatment plant according to Fig. 1 at the stage of filling the bioreactor.

Fig. 4 shows section A-A in the precipitation phase.

Fig. 5 shows section A - A in the unloading phase.

Examples of implementation of the invention

The wastewater enters the storage tank 1 through the pipe 2. The wastewater level in the storage tank 1 rises from the minimum level 5 to the maximum level 6, and these levels are recorded by the measuring device 4, consisting of, for example, a float or a pressure sensor, ultrasound and other detection devices. The bioreactor 8 is filled to a level of 18 and is aerated by the aeration system 14. At this stage of purification, it is also advisable to aerate the storage tank 1 by the aeration system 22. After reaching the maximum level 6, the aeration of the bioreactor 8 ends and the sedimentation phase occurs when the sludge in the bioreactor 8 settles to the bottom and subsequently forms a sludge layer 12, which is separated from the purified water layer 13. After the time required for settling, which usually exceeds 20 minutes, the discharge phase begins, when the wastewater pump 3 is switched on, which pumps water from the storage tank 1 into the connecting pipe 7, and then through the vertical pipe 9 the wastewater enters the lower level of the reactor 8. The water level in the storage tank 1 gradually decreases to the minimum level 5, the pumped out wastewater pushes the already purified water upward to the clean water pump 10 and thus replaces the already pumped out purified water from the bioreactor 8, thereby maintaining a stable water level 18 in the bioreactor 8 for the entire pumping period.

The purified water is fed by pump 10 from the subsurface layer to discharge 16. In case of a large inflow from the storage tank 1 into the bioreactor, the discharge of purified water also occurs through the safety discharge 11, which is equipped with a slotted wall 17. This prevents impurities floating on the surface 18 of the water in the bioreactor 8 from leaking into the already purified water. A slotted wall 19 is also installed in front of the safety overflow 20, preventing coarse floating impurities from entering the bioreactor 8.

The pump 10 for clean water is usually an air pump, as is the pump 3 for waste water. The water level 18 in the bioreactor 8 is maintained at a constant level during the draining phase, or fluctuates slightly at the safe overflow level 11. Before the draining phase ends and the next filling phase begins, it is necessary that the water level 18 in the reactor 8 must fall below the safe overflow level 11.

During the filling phase, it is advisable to aerate the storage tank 1 using the aeration device 22. After the sedimentation phase is completed and before the next filling phase of the bioreactor 8, excess sludge is pumped out using the sludge pump 21 into the storage tank 1 or into a separate tank - sludge collector 23.

Claims (3)

1. A method for purifying wastewater with suspended activated sludge with aeration at domestic treatment facilities, comprising an inflow of wastewater, filling a storage tank from a minimum to a maximum level, pumping the accumulated water into a reactor, settling or draining the purified water, characterized in that the bioreactor together with the storage tank are aerated simultaneously during filling of the storage tank, wherein after filling the storage tank to the maximum level, aeration of the bioreactor and the storage tank is stopped and after subsequent settling of the activated sludge at the bottom of the bioreactor, wastewater from the storage tank is fed by a tube (7) to the bottom of the reactor through a vertical part (9) into a layer of settled sludge in the bioreactor, thereby pushing purified water to the outlet, maintaining a constant water level in the bioreactor, and after the water level in the storage tank has decreased to the minimum level, pumping of wastewater into the bioreactor from the storage tank and the discharge of purified water from bioreactor, after which aeration of the bioreactor and storage tank is resumed. - 2 049802 voirs until the storage tank is filled with wastewater to the maximum level. 2. A device for implementing the method according to paragraph 1, comprising at least a storage tank (1) with an inflow (2) of waste water, with a pump (3) for pumping waste water into a bioreactor (8) by means of a tube (7) to the bottom of the reactor through a vertical part (9) and a bioreactor (8) equipped with aeration equipment (14) and an outlet (16) of purified waste water, characterized in that the storage tank (1) is equipped with aeration equipment (22), a measuring device (4) for determining the minimum level (5) and the maximum level (6) with a control unit, a connecting tube (7) connected to a pipe (9) that ends at the bottom of the bioreactor (8), in addition, the bioreactor (8) is equipped with an overflow (11) leading to an outlet (16) of purified water. 3. The device according to item 2, characterized in that the bioreactor (8) is equipped with a sludge pump (21) leading to a storage tank.