RU2329956C2 - Method of sewage water biological treatment - Google Patents

Abstract

FIELD: technological process.

SUBSTANCE: invention may be realised in operation of different treatment plants and in operation of small household sewage water treatment plants. Method of biological treatment of sewage water by means of active sludge in suspended condition includes supply of sewage water in activation reservoir with simultaneous supply of air in the same reservoir. Temperature of air that is supplied to activation reservoir is measured depending on ambient air temperature. If ambient air temperature is positive, air supplied to activation reservoir is cooled down to at least temperature equal to temperature of sewage water, and in case of negative temperature of ambient air, air that is supplied to activation reservoir is heated up to the temperature that is at least equal to temperature of sewage water.

EFFECT: simplification of sewage water treatment method and reduction of economical expenses for its implementation with increase of extent of sewage water treatment.

7 cl, 1 dwg

Description

The invention relates to a method for biological treatment of domestic wastewater using activated sludge and can be implemented during the operation of various treatment plants. The invention can find its widest application in the operation of small domestic wastewater treatment plants.

Methods of biological wastewater treatment using activated sludge are widely known [1, 2, 3]. Such cleaning is very effective and environmentally friendly. It is based on the fact that activated sludge is a mixture of various bacteria and the smallest microorganisms capable of consuming, as the nutrients necessary for life, organic compounds contained in wastewater. Suspended sludge treatment is especially effective when sludge flakes are uniformly mixed with wastewater. For the activation process to take place, continuous oxidation is required, which is ensured by forcing air into the activation tank.

Known methods of wastewater treatment using activated sludge can be divided into methods involving continuous and intermittent flow of wastewater through an activation tank.

During continuous supply of wastewater that has undergone a rough preliminary treatment to the activation tank, the wastewater, after a certain period of time in the activation tank, necessary for treatment, is discharged together with activated sludge into a secondary sump. Sludge is deposited in the sump, and clean water flows through the outlet either into the body of water or into the soil, or is used for some household needs. The use of continuous cleaning is advisable when servicing large enough and constantly functioning facilities.

In the case of intermittent supply, rough pretreatment wastewaters are either introduced into the activation tank immediately or pumped from the equalization tank. After cleaning, the activation process is interrupted, that is, the air supply and mixing of water in the activation tank are stopped and the sludge settles, and the purified water is discharged. Then the activation tank is refilled, and the cleaning cycle is repeated. Compared to continuous cleaning with intermittent cleaning, there is no need for a secondary sump.

In both cases, treatment plants and their operation are very expensive, requiring qualified maintenance personnel, mainly due to the fact that the plants include complex control systems [4]. With continuous cleaning, this is due to the need for regular and frequent pumping of sludge from the secondary sump to the activation tank. During intermittent cleaning, it is necessary to stop the air supply to the activation tank, and, accordingly, the process of mixing the mixture of sludge and waste water. Moreover, the process interruption time, on the one hand, is limited by the possibility of the development of autolysis of sludge, and on the other hand, should be sufficient to ensure sedimentation of sludge.

But in addition to achieving ease of management, there is a problem of increasing the degree of wastewater treatment, which, as a rule, is not up to standard. The latter circumstance, in particular, with an increase in the number of country houses threatens environmental pollution, most often pollution of nearby water bodies, in violation of the established ecological balance as a whole.

A known method of biological wastewater treatment [2], aimed at increasing the degree of purification, which carry out effective mixing of effluents with activated sludge due to the bubbling of compressed air. Moreover, when the level of wastewater in the equalizing tank is lowered, compressed air is supplied to the equalizing tank, and when the level of wastewater in the equalizing tank is increased, compressed air is supplied to the activation tank. Moreover, the air supply is carried out in a pulsating mode. Moreover, during the treatment process, wastewater is treated with a magnetic field.

However, trying to fight for an increase in the degree of purification, they again go to the complication of the method of wastewater treatment and control of the treatment process, and, accordingly, to increase the costs associated with wastewater treatment. Due to these drawbacks, this method does not seem optimal when treating low-power wastewater.

In addition, the low degree of purification is mainly due to the low efficiency of the means for mixing wastewater with sludge and the low efficiency of saturating them with oxygen, and above all, the overflow of the purification plant with sludge, which leads to a violation of the course of the fine bubble aerobic reaction. Excess sludge must be removed from the treatment plant in a timely manner. In an intensive mode of operation, this operation should be performed quite often. Moreover, it requires interruption of the treatment plant, and the removal of sludge should be done by qualified personnel. In addition, special containers should be provided for storing and storing sludge removed from the plant, since not all the sludge can be immediately used, for example, as fertilizer [5].

A known method of wastewater treatment [3], which includes the supply of wastewater to an equalizing tank and the subsequent pumping of wastewater into an activation tank, the supply of treated wastewater to a secondary sump and the disposal of treated wastewater after sedimentation of the remaining sludge into the outlet. Moreover, in the event of a decrease in the level of wastewater in the equalizing tank below the set minimum level, the activation process is automatically interrupted. Excess sludge or a mixture of sludge with contaminated water is pumped from the activation tank to the equalization tank until the wastewater level in the equalization tank reaches the set operating level. Upon reaching the established operating level of wastewater in the equalization tank, the pumping of sludge from the activation tank is interrupted and the process is restored.

The method also provides for the removal of excess sludge after interrupting the activation process after a set time delay in the range from 30 to 90 minutes.

The advantage of this method is the absence of the need for frequent interruption of the treatment plant, as well as the ability to more easily control the cleaning process, without the constant presence of maintenance personnel.

In other words, according to the method [5], when the level of wastewater is reduced, the course of the oxidation reaction changes over time, giving it a periodic character by alternately pumping purified water from the equalization tank to the activation tank and vice versa. This technique allows you to not interrupt the operation of the installation as a whole. But in the absence of an influx of wastewater for 2-3 months, as suggested in the method, due to the gradual evaporation, the amount of liquid component in the mixture of treated wastewater and sludge will decrease, and the amount of nutrients necessary to maintain the vital activity of bacteria will also decrease. activated sludge. As a result, the cleaning ability of the equipment will be impaired.

In addition, the need for alternate pumping of the treated water in the mixture with sludge from the equalization tank to the activation tank and vice versa requires energy and does not allow to simplify the cleaning method so as to make it optimal for use in small house wastewater treatment plants.

It should also be noted that none of the known methods of biological wastewater treatment does not take into account the influence of the climatic factor on the quality of treatment. The climatic factor is taken into account only from the standpoint of ensuring the operability of the treatment plant, namely, to prevent freezing of wastewater, the tanks of the plant are usually located at an appropriate depth from the ground.

The objective of the invention is to simplify the method of wastewater treatment and reduce the economic costs of its implementation while increasing the degree of wastewater treatment.

The objective of the invention is also the creation of a method that can be most optimally used when operating small home wastewater treatment plants.

The problem is solved if the method of biological treatment of wastewater through activated sludge in suspension, including the supply of wastewater to the activation tank while simultaneously supplying air to this tank, is different in that the temperature of the air supplied to the activation tank is regulated depending on the capacity of the wastewater and / or ambient temperature.

The task is also solved if:

- at a positive ambient temperature and at low wastewater capacity, air is fed into the activation tank, cooled at least to a temperature equal to the temperature of the wastewater;

- if wastewater is supplied to the activation tank from the equalization tank, cooled air is supplied to the activation tank when the level of wastewater in the equalization tank is lower than the set minimum level;

- the air entering the activation tank is cooled to a temperature below the temperature of the wastewater by means of a refrigerator;

- the air entering the activation tank is cooled by passing through a pipeline, which in turn passes through an ice container located relative to the surface of the earth at a depth that prevents ice melting;

- tap water in a regulated amount is additionally supplied to the equalizing and / or activation tank;

- at minus ambient temperature, the air entering the activation tank is heated to a temperature at least equal to the temperature of the wastewater;

- air is heated by passing through a pipeline of a given length laid relative to the surface of the earth at or below the level of the pipeline for supplying wastewater;

- air is heated by means of a heater to a temperature above the temperature of wastewater by 15-20 ° C.

The essence of the invention lies in the fact that by changing the temperature of the air supplied to the activation tank, the intensity of the oxidative aerobic reaction during the treatment of wastewater by activated sludge is controlled, in one case accelerating this reaction, and in the other, on the contrary, slowing it down. At the same time, the slowdown of the oxidation reaction, in comparison with the known method [3], allows not reducing the activation process in the event of a decrease in the level of wastewater in the equalizing tank, but eliminating the operation of alternately pumping purified water from the equalizing tank to the activating tank and vice versa. The value of the time required for the oxidation reaction to occur is determined taking into account the power of the wastewater and temperature by calculation or experiment. This value must be taken into account when the wastewater enters the treatment plant completely. Obviously, the lower the temperature of the air entering the activation tank, the longer the period of time for stopping the flow of wastewater into the activation tank. In particular, at a temperature of air entering the activation tank of about 0 ° C, the oxidation process, as well as autolysis of sludge, proceeds so weakly that the installation works without wastewater for about 30 days.

The technical essence of the considered method, as already noted, is based on ensuring the life of the simplest microorganisms. The intensity of the oxidation reaction necessary for this largely depends on the temperature of the wastewater. The treatment plants are located in pits whose depth is sufficient to prevent wastewater from freezing. The temperature of the wastewater in this case is 4-5 ° C in the winter season. If even colder air is introduced into such cold water, then the intensity of the oxidation reaction will be characterized by a very small value. In the volume of the activation tank, colder layers saturated with air will remain below. In the absence of mechanical mixing, for example using perforated drums [1] or air sparging [2], the cleaning will take place unevenly due to uneven saturation of the wastewater with air. The problem of increasing the degree of purification in this situation cannot be solved by increasing the residence time of wastewater in the activation tank. On the contrary, it is further exacerbated even with a slight increase in wastewater capacity. The problem is solved by supplying warm air to cold wastewater.

Experience shows that it is enough to lay an air supply pipeline underground at or below the level of the pipeline for supplying wastewater, choosing its length so that the air has time to warm up, at least to the temperature of the wastewater. In the same way, in the summer, you can cool the air, plus by passing the pipeline through a container filled with pieces of ice, for this it is enough to install the tank at the required depth. The implementation of such a design of the pipeline for air is low cost, and operation is generally economically inexpensive. Therefore, it seems to be most optimal for individual sparsely populated houses and cottages. For more intensive cooling of the air in summer, it is possible to use a refrigerator installed at the compressor inlet, through which air is supplied to the activation tank.

The best result in winter is observed when the air is heated to a temperature above the temperature of the wastewater by about 15-20 ° C. At the same time, convective exchange in the activation tank is enhanced, which contributes to uniform saturation of wastewater with air and supports a fine-bubble aerobic reaction, thereby contributing to better cleaning. Structurally, the problem is solved by the fact that the installation is equipped with a heater or several heaters, depending on the size of the installation and the capacity of the wastewater that heats the air supply pipe. Heaters are installed, as a rule, at the compressor outlet, by means of which air is supplied to the activation tank.

During a long break in the wastewater supply process in order to avoid lowering the level of wastewater in the equalizing and / or activation tank, in particular due to evaporation of the water, it is possible to supply tap water to the treatment plant. The water supply allows you to dilute the sludge and facilitate the removal of its excess from the installation. The use of this technique in other known methods, in the presence of a break in the supply of wastewater and at a normal intensity of the oxidative process, could lead, in particular, to a lack of nutrients necessary for the functioning of activated sludge bacteria. However, with a low intensity of the oxidation process, which can be provided in the proposed method, in the presence of a break in the supply of wastewater, the use of this technique does not lead to negative consequences.

As already noted above, compared with the method [3], the claimed method eliminates the need for pumping sludge from the activation tank to the equalization tank and vice versa. When reducing the capacity of wastewater more rarely there is a need to remove sludge from the treatment plant. Accordingly, there is no need for frequent and, it can be characterized, emergency call of qualified personnel to remove excess sludge from the installation. The latter circumstance is due to the fact that the amount of excess sludge can be reduced due to the possibility of reducing the intensity of the oxidative process. As a result, energy costs are significantly reduced, including electricity for maintaining the operability of the treatment plant. In the inventive method, cooling or heating the air supplied to the activation tank may also require energy, but they are incomparably small compared with the energy spent on pumping sludge from the activation tank to the equalization tank and vice versa. Moreover, the air entering the activation tank can be naturally heated or cooled, which seems, as noted above, generally cost-free. Particularly, depending on the power of the wastewater, a combination of cooling or heating by means of apparatuses and naturally is possible.

A hydraulic pump designed for pumping treated wastewater from an activation tank to a secondary sump works, as a rule, in a batch mode. The time period when the hydraulic pump is turned off is selected sufficient for cleaning. In the inventive method, with a decrease in wastewater capacity, the specified time period increases. This additionally reduces energy costs.

It should be noted that it is not possible to completely refuse the services of qualified personnel during the operation of any treatment plant. But when using the proposed method, it can only be scheduled maintenance work.

In any case, the control of the treatment plant and the cleaning method as a whole differ from the known plants and methods in their simplicity and cost-effectiveness. The design of the treatment plant is also not complicated, since it is not necessary to introduce additional sensors. Switching the unit to the mode of operation with cooled or heated air can be carried out either manually or automatically. Automatically or manually, you can change the intensity of heating or cooling, as well as the method of heating or cooling, namely using apparatus and / or in a natural way.

The most optimal is the use of the proposed cleaning method for individual houses and cottages. However, this does not exclude the use of the method for any wastewater capacity.

A solution is known [1], in which a sufficiently powerful heating system of a treatment plant is provided for conducting the process in anaerobic conditions at a temperature of 34-37 ° С. The solution is aimed at achieving such benefits as improving mass transfer processes, intensifying the process of biogas removal from the upper part of the treatment plant, since chromium-containing wastewater from galvanic plants are cleaned. This solution, in contrast to the proposed solution, is not aimed at adapting the treatment process to environmental conditions and to the capacity of wastewater. In addition, the entire unit operating under anaerobic conditions is heated, which is associated with much greater energy costs than heating the air supplied to the unit operating under aerobic conditions.

There is also known a solution aimed at improving the temperature regime of the cleaning process [6], but due to mechanical mixing of the mixture of wastewater and activated sludge, and not changing the temperature of the air supplied to the activation tank.

The proposed cleaning method can be implemented both with continuous and intermittent wastewater supply.

The proposed cleaning method can be implemented with any known design of the treatment plant.

Therefore, the following specific example of carrying out the invention does not exhaust all possible cases of its implementation in light of the designs of the treatment plants, the capacity of the wastewater and the type of wastewater supply to the treatment plant.

Specific Embodiment

The wastewater treatment plant contains an equalizing tank 1, an activation tank 2 and a secondary settling tank 3. In the bottom part of the activation tank there is an outlet pipe 4 of the compressor 5. At the outlet and inlet of the compressor 5, a heater 6 and an ejector type refrigerator 7 are installed. Item 8 is shown sewage supply pipeline to equalization tank 1. Pos. 9, 10 show sewage supply pipelines from the equalization tank to the activation tank. The hydraulic pump 11 is designed to supply treated wastewater from the activation tank to the secondary sump through line 12. The same hydraulic pump can be used to supply wastewater from the equalizing tank to the activation tank. Switching the hydraulic pump to perform the above functions is carried out using valves 13 and 14. The pipe 15 is designed to remove purified water from the secondary sump and, if necessary, accumulated sludge. During a long break during the supply of wastewater to the activation and equalization tanks, piped water can be supplied through pipelines 16 and 17. The air supplied to the compressor 5 and further to the activation tank can be cooled by passing through a pipe 18, passed through an underground chamber 19, filled with pieces of ice. In winter, the pipeline passing through the underground chamber can be equipped with a heater (not shown). Switching the installation to a mode of operation using natural devices for changing air temperature or special devices, such as an ejector-type refrigerator, or when used together, is carried out using taps 20, 21.

According to the diagram shown in the drawing, a prototype installation was made, which had the following overall dimensions:

- length 1.0 m;

- width 1.0 m;

- height 2.4 m.

The installation was deepened into the ground about 1 m from the surface.

The installation and the cleaning method were tested in natural conditions, namely, the method and the cleaning installation were used to treat wastewater in a country house, in which the number of permanent residents was 6 people. In the summer period, for two months the number of residents decreased to 2 people, of which the house was empty for two to three weeks. And during one of the summer months, the number of people reached 10 people. The same number of people was in the winter, during the Christmas and school holidays.

In the summer, while reducing the number of inhabitants of the house, cooling of the air entering the activation tank was used by passing air through a pipeline passing through an underground chamber filled with ice. When all residents left, a refrigerator was connected for this purpose. At the same time, tap water was supplied to the unit practically in the drip mode. At the same time, the hydraulic pump 11 was set to the operating mode with the appropriate frequency.

In winter, the air entering the activation tank was heated to 25 ° C, i.e. 18-20 ° C higher than the temperature of the wastewater, which averaged 5 ° C.

Operations to switch the operating cranes of the installation were carried out manually. With further replication of the installation and improvement of its design, the introduction of appropriate automation is possible.

The start-up of the treatment plant with the establishment of the concentration of activated sludge necessary for treatment was carried out by qualified personnel. Preventive inspection of the installation with the removal of excess sludge from the activation tank, as well as the secondary sump, was carried out by qualified personnel three times a year. In winter, water samples were taken to determine the degree of its purification, which showed an increase in the degree of purification of approximately 1.5-2 times in comparison with the methods of purification without heating the air supplied to the activation tank. As noted, the proposed method can be widely used in the operation of small domestic wastewater treatment plants.

Information sources

1. Patent RU 21005730, IPC C02F 3/00, C02F 3/08, 1998

2. Patent RU 2233247, IPC C02F 3/12, 2004

3. Patent RU 2162062, IPC C02F 3/00, C02F 3/12, 2001

4. Patent for utility model RU 369 А01К 63/04, 2004

5. Patent RU 2121981, IPC C02F 3/00, 1998

6. Copyright certificate SU 1368268, IPC C02F 3/08, 1988

Claims (7)

1. The method of biological treatment of wastewater by means of activated sludge in suspension, comprising supplying wastewater to an activation tank while simultaneously supplying air to this tank, characterized in that the temperature of the air supplied to the activation tank is changed depending on the ambient temperature, and plus ambient temperature, air is fed into the activation tank, cooled at least to a temperature equal to the temperature of the wastewater, and at minus temperatures The ambient air entering the activation tank is heated to a temperature at least equal to the temperature of the wastewater. 2. The method according to claim 1, characterized in that, in the case of supplying wastewater to the activation tank from the equalizing tank, the cooled air is supplied to the activation tank while lowering the level of wastewater in the equalizing tank below the set minimum level. 3. The method according to claim 1, characterized in that the air entering the activation tank is cooled to a temperature below the temperature of the wastewater by means of a refrigerator. 4. The method according to claim 1, characterized in that the air entering the activation tank is cooled by passing through a pipeline that, in turn, passes through an ice container located relative to the surface of the earth at a depth that prevents ice melting. 5. The method according to claim 1, characterized in that the equalizing tank and / or activation tank additionally serves tap water in an amount that compensates for the amount of evaporated water. 6. The method according to claim 1, characterized in that the air is heated by passing through a pipeline laid relative to the surface of the earth at or below the level of the pipeline for supplying wastewater. 7. The method according to claim 1, characterized in that the air is heated by means of a heater to a temperature above the temperature of the wastewater by 15-20 ° C.