RU2758398C1 - Method and installation for biological wastewater purification - Google Patents

Abstract

FIELD: wastewater purification.

SUBSTANCE: invention relates to the biological purification of household wastewater and wastewater close to them in composition; it can be used to purify wastewater of individual residential buildings, cottages, recreation centers, health resorts, shift settlements. A method for deep biological purification of household wastewater is characterized by that wastewater is fed into a facility that includes a wastewater reception zone, in which wastewater is averaged, a zone of hydrolysis and fermentation of sediments for the extraction of easily oxidized organic matter, in which processing is carried out for three days, zones of denitrification, dephosphatization and nitrification processes in one compartment without partitions or in one compartment with partitions, while the denitrification stage is carried out before the nitrification stage, denitrification and dephosphatization processes are provided by precipitation and sludge formed during the purification process with a decrease in the amount of precipitation formed during wastewater purification, wherein water processing is carried out using activated sludge being suspended or using attached sludge, a zone of separating activated sludge and purified water, followed by recycling of sludge into the denitrification zone, zones of post-purification and disinfection of wastewater. A purification installation includes an averager, a primary settling tank, an aerotank with anaerobic-aerobic purification zones for denitrification, dephosphatization and nitrification processes, a secondary settling tank for separation of activated sludge and purified water, devices for recycling activated sludge into the denitrification zone, units for post-purification and disinfection of wastewater.

EFFECT: reduction in sediment and excess activated sludge formed during wastewater purification, ensuring high efficiency of removal of pollutants, reliable wastewater purification.

13 cl, 2 dwg

Description

The field of technology.

The field of technology to which the invention relates is the field of biological treatment of domestic wastewater and wastewater close to them in composition, can be used to treat sewage from individual residential houses, cottages, recreation centers, sanatoriums, rotational camps, is used to protect the environment environment and human health.

It is known from the state of the art that traditional activated sludge treatment systems are designed to remove organic matter, oxidize ammonium, remove nitrogen and phosphorus from wastewater, but with traditional biological treatment, nitrogen removal is 30-40%, phosphorus removal with a simultaneous nitri- denitrification reaches 15-25%. Also, with traditional aerobic biochemical wastewater treatment, a large amount of precipitation and excess sludge is formed, the removal of which causes difficulties, including placement in the environment. There is a need to reduce the amount of precipitation and excess silt.

Known patent "Method for biological wastewater treatment with activated sludge", RU 2424199 from 2009.12.28. The method for biological treatment of wastewater with activated sludge includes finding a sludge suspension in the anoxide, aerobic and anaerobic zones of the volume of treated water in the aeration tank. Further, the sludge suspension passes to the secondary settling tank, where it is separated into purified water and thickened activated sludge. In this case, the anaerobic zone of the aeration tank is combined with the process of sludge fermentation - the production of volatile fatty acids, in which part of the activated sludge flakes sink to the bottom, compacted to a concentration of about 40 g / l for several days, and after the fermentation process, the sludge is carried out by the flow of liquid from the anaerobic zone. As a result of the absence of forced mixing of activated sludge in this combined zone, this zone can be called a "ripening" zone. The disadvantages of this method include the fact that the fermentation of the sludge is carried out in the anaerobic zone due to the process of settling activated sludge flakes to the bottom, they are compacted within a few days. But the fermentation process for several days (especially in the summer) will lead to an uncontrolled fermentation process and the appearance of a strong odor in the treatment plant. The disadvantages include the lack of mixing in this anaerobic "ripening" zone, which will lead to an uncontrolled fermentation process. The surging of fermented sludge will occur continuously, which will lead to disruption of the treatment process, disruption of the settling process in secondary sedimentation tanks and a decrease in the efficiency of treatment for suspended and biogenic substances.

Known patent "Method of wastewater treatment", RU 2439001 from 2010.08.03. To implement the method, mechanical purification of the original waste water is preliminarily carried out with the extraction of dispersed mechanical impurities. The resulting water is subjected to anaerobic treatment with a dissolved oxygen content of not more than 1 mg / l, followed by aerobic treatment using free-floating activated sludge. After intermediate settling, the resulting water-sludge mixture is subjected to flotation in the presence of a bioreagent containing cultures of bacteria Zoogloea and algae of the genus Chlorella, immobilized on a metal carrier, followed by final settling. The disadvantage of this method is the low degree of wastewater treatment: since the method is aimed at purifying wastewater from nitrogen ammonium salts and nitrogen nitrates, and does not contribute to the removal of phosphorus and phosphates. The disadvantage of this method is the complexity of the design at the stage of separation of activated sludge: the use of flotation in the presence of a bioreagent, the use at this stage of immobilized cultures of bacteria Zoogloea and algae of the genus Chlorella on a metal carrier, which significantly increases the cost of the process due to the need for periodic regeneration of the load and the use of flotation.

Known patent "Method for biological wastewater treatment with activated sludge", RU # 2633896 from 2015.09.08. The invention relates to biological wastewater treatment. The method provides for the combination of the anaerobic purification zone with the process of sludge fermentation - the creation of a "ripening" zone, characterized in that this "ripening" zone is removed from the aeration tank and is located in the primary sedimentation tanks. Waste water and part of the circulating activated sludge suspension enter the primary sedimentation tanks. Suspended substances of waste water and activated sludge settle to the bottom of the settling tanks and are compacted to a concentration of 30-40 g / l. The location of the "ripening" zone in the primary sedimentation tanks ensures the fermentation of 100% of the incoming wastewater sludge. The sediment from the primary settling tank is also fed into the upper channel of the aeration tank every two days. The disadvantage of this method is the supply of a suspension of circulating activated sludge to the primary settling tank and 100% fermentation of the sludge, which leads to the removal of easily oxidizable organic substances, a decrease in the cleaning efficiency and an increased removal of suspended solids from the primary sedimentation tanks, and, accordingly, to additional costs for air consumption and electricity. The supply of sediment from the primary sedimentation tank every two days into the upper channel of the aeration tank will lead to the suppression of nitrification processes in the aeration tank, which will cause a decrease in the efficiency of purification by nitrogen of ammonium salts and phosphate phosphorus, additional air consumption.

Known patent "Method for removing phosphorus from waste fluid", RU 2654969 from 2017.03.17. The method includes mechanical, biological, physicochemical treatment with the return of compacted activated sludge depleted in phosphorus from the sludge compactor-dephosphatizer to the aerotank. At the stage of physicochemical treatment, a complex of reagents is introduced into the sludge water from the sludge compactor-dephosphatizer, namely: lime from the ratio P: Ca ²⁺ = (1-1.5) and caustic soda in an amount that provides an increase in pH to 10.5- eleven. The disadvantages of this method are additional costs at the stage of physicochemical purification: the consumption of a large amount of a complex of reagents, namely: lime from the ratio P: Ca ²⁺ = (1-1.5) and caustic soda in an amount that provides an increase in pH to 10, 5-11; the formation of a large amount of chemical sludge, the cost of its removal and placement at specialized landfills.

The closest analogue adopted for the prototype is "Method for biological wastewater treatment with sludge", patent RU 2296110 from 2005.08.15. The method includes mechanical treatment of wastewater in a primary settling tank, after which the wastewater is fed into a bioactivator with microflora, in which the presence of zones with a medium dissimilar in oxygen content is maintained by means of controlled oxygen input, and then a mixture of wastewater with activated sludge enters the secondary settling tank for separation for purified waste water and activated sludge, which is constantly returned to the beginning of the bioactivator. The crude sludge after the primary settler is recirculated to the inlet of the primary settler to create conditions for the hydrolysis and heteroacetogenic process directly in the primary settler. In the secondary sedimentation tank, zones with a medium dissimilar in oxygen content are created by regulating the rate of recirculation of activated sludge from the secondary sedimentation tank to the inlet of the bioactivator. Zones with a medium heterogeneous in oxygen content in the bioactivator are distributed in the horizontal direction. Preferably, 1/3 of the useful volume of the bioactivator works as aerobic, 1/3 of the useful volume of the bioactivator works as a transitional one, 1/3 of the useful volume of the bioactivator works as anaerobic. The disadvantages of the prototype are:

- a long residence time of the raw sludge in the primary settling tank up to 20 days will entail a decrease in the settling efficiency and lead to the removal of the wet sludge into the bioactivator.

- the accumulation of a large amount of sediment in the primary sedimentation tank during the settling period of 20 days and its removal into the bioactivator will lead to a deterioration of the nitrification process and an increase in the amount of air, which increases the cost of electricity.

- insufficient efficiency of wastewater treatment, since the processes of nitrification and denitrification are carried out directly and in the secondary sedimentation tank, which will lead to a violation of the efficiency of treatment for ammonium nitrogen, phosphorus and will cause the removal of sludge from the secondary sedimentation tanks.

- acidification processes do not provide a significant reduction in sludge from treatment facilities and additional costs will be required for placement and disposal of sludge, because the method does not ensure a reduction in the amount of the formed sediment, which is removed from the bioreactor,

- an increase in the rate of recirculation of activated sludge will lead to additional costs for equipment and electricity consumption.

The tasks to be solved by the present invention are to eliminate the above disadvantages. The main tasks to be solved are:

- increasing the efficiency of cleaning due to additional extraction of organic substances and ensuring the processes of denitrification and dephosphatization due to zones of different aerobicity.

- increasing the efficiency of settling, reducing the removal by improving the sedimentation rate of activated sludge.

- Reduced air volume and reduced energy costs.

- reducing the volume of sludge and reducing the cost of its processing due to the processes of fermentation of sludge and due to dehydration.

The technical result of the proposed method and wastewater treatment plant is, simultaneously with minimizing the volumes of raw sludge and reducing the volumes of raw sludge and excess activated sludge generated in the process of wastewater treatment, ensuring a high degree of wastewater purification for pollutants with an ammonium ion removal efficiency of up to 99, 5%, total nitrogen up to 80% and phosphorus up to 99%; increasing the degree of wastewater treatment from suspended solids, organic substances, nitrogen and phosphorus compounds to maximum permissible concentrations (MPC) established for fishery reservoirs, reuse of treated water for domestic needs, use of sewage sludge as fertilizers, cost reduction for the operation of treatment facilities. The technical result is achieved due to the fact that the proposed invention, with the implementation of methods for averaging wastewater flows in the first chamber of the installation and ensuring the mode of pre-fermentation of sediments in an acidifier, ensures the extraction of easily oxidized organic matter for denitrification and dephosphatization processes, complete oxidation of ammonium ions and organic contaminants after the stage of removing nitrates with the help of aeration, settling, subsequent filtration on filters with loading and disinfection at the installation. A deep biological treatment method, in which water treatment is carried out using suspended activated sludge, or a method of cleaning with attached sludge is used; with carrying out the processes of denitrification, dephosphatization and nitrification in one structure without partitions or in a structure with partitions, while maintaining optimal aerobic conditions at each stage of the process. The advantages of the proposed technical solution in comparison with the known are as follows:

1. Reducing the amount of precipitation formed in the process of wastewater treatment due to the extraction of easily oxidized organic matter necessary for the removal of nitrogen nitrates and phosphorus phosphates and reducing the amount of precipitation due to the use of dewatering equipment.

2. Reducing the cost of reagents required to ensure the removal of nitrogen and phosphorus due to:

- the implementation of the denitrification stage before the nitrification stage, which contributes to the production of alkalinity, which ensures the nitrification processes.

- provision of denitrification and dephosphatization processes with easily oxidized organic matter due to sediments and sludge formed during the purification process.

3. Reducing energy costs by reducing the amount of oxygen required under normal conditions during the cleaning process in the facility.

4. The implementation of the denitrification stage includes staying in the anoxic and anaerobic zone within 1-3 hours, in the aerobic zone of the nitrification stage in the range of 4-9 hours, depending on the wastewater flow rate. Carrying out the processes of denitrification, dephosphatization and nitrification in one structure without partitions provides a reduction in material and operating costs.

5. Improving the cleaning efficiency due to:

- providing conditions for carrying out the processes of denitrification and dephosphatization.

- prevention of crust formation and sludge caking in the sludge pre-fermentation unit.

- the use of a thin-layer clarifier, or fabric filters, or feed materials, or a combination of feeds, as devices for the purified water purification.

- the use of chlorine-containing preparations of prolonged action or UFO in the device for disinfection of purified water.

6. Improvement of activated sludge sedimentation indices due to the following units: sludge pre-fermentation unit, homogenizer and primary settling tank, aeration tank with anaerobic - aerobic treatment zones, activated sludge and purified water separation tank, devices for recycling and returning activated sludge, post-treatment and effluent disinfection units ...

7. Possibility of using sediments formed during cleaning as fertilizers by processing them with quicklime.

8. Possibility of using purified water for household and technical needs due to the high degree of purification and complete biological disinfection of effluents.

Analysis of the patent and scientific and technical literature did not reveal technical solutions with a similar set of essential features, which allows us to conclude that the criterion of "novelty" of the claimed invention is met

The method is implemented in installations (figure 1, figure 2). Installations for averaging and anaerobic - aerobic purification of domestic wastewater, additional purification and disinfection of purified water to the norms of discharge into fishery water bodies, in the process of purification, which reduces the amount of precipitation formed, the sedimentation rate of activated sludge improves. The installations include the following units: a homogenizer, a primary settler 1 (sludge pre-fermentation unit), an aeration tank with anaerobic - aerobic treatment zones, a settling tank for separating activated sludge and purified water, devices for recycling and returning activated sludge, additional treatment and decontamination of effluents.

In the first chamber, the primary settling of effluents takes place with the simultaneous averaging of the wastewater flow by means of an equalizer 7. Excess biomass is fed into the primary settler 1 (acidifier) from the biological treatment unit, in the lower part of which anaerobic stabilization of the resulting sediments occurs. Periodic supply of air and loosening of the sludge are provided in order to prevent the formation of a dense crust on the surface in the acidifier. Acidification is used for hydrolysis and fermentation of the sediment in order to reduce the sediment by transferring this mass into a soluble substrate. The longer the hydraulic retention time, the higher the COD yield (optimally 3 days). In this case, the runoff is provided by easily oxidized organic matter (VFA - volatile fatty acids) obtained as a result of acidification. The constant supply of new portions of raw sediments ensures a uniform supply of easily oxidized organic matter to the denitrification zone 2. The introduction of easily oxidizable organic matter in the form of VFA allows you to provide:

- increased feeding of activated sludge;

- no rotting of sludge and wet sediment;

- to reduce the toxic effect of pollutants due to their anaerobic decomposition during fermentation;

- to increase the efficiency of removing nitrogen pollution and phosphorus.

The effluent, enriched with easily oxidizable organic matter, flows by gravity into the biological treatment unit in the denitrification zone 2. The stage of denitrification by reducing nitrate nitrogen from a liquid with suspended sludge to gaseous nitrogen includes staying in an oxygen-free and anaerobic zone within 1-3 hours, depending on the flow rate of waste water. The denitrification stage is carried out before the nitrification stage, which ensures the production of alkalinity, which ensures the nitrification processes, thus reducing the cost of reagents required to ensure the removal of nitrogen and phosphorus: the cost of alkalinizing the effluents, easily oxidized organic matter required to remove nitrogen from nitrates and phosphorus. Further purification of the effluent takes place in the aerated zone 3 of nitrification.

To ensure the process of vital activity of microorganisms, air from the compressor is constantly supplied to the nitrification zone 3, the device for generating air bubbles is made using membranes. The nitrification stage is provided with a hydraulic residence time in the range of 4-9 hours. The use of attached biomass at this stage makes it possible to increase the efficiency of the installation, and on the other hand, to make the installation less susceptible to possible interruptions in the flow of wastewater, salvo water inflows. To ensure stable cleaning and to completely remove nitrogen in the form of nitrates, the pumping of return sludge from the secondary clarifier 4 to the denitrification zone 2 is provided. Providing the sludge fermentation mode and maintaining optimal aerobic conditions at each stage allows for wastewater treatment with a reduction in the amount of precipitation, a decrease in odor during cleaning and minimal energy costs. Based on the data obtained as a result of the implementation of this technology, the implementation of this biological treatment scheme ensures the efficiency of removing 99.5% of ammonium ions, up to 80% of total nitrogen and up to 99% of phosphorus. In the process of sludge fermentation, its pre-fermentation, the amount of precipitation is reduced. Treated wastewater is fed to stage 5 of post-treatment using a thin-layer clarifier, or fabric filters, or feed materials, or a combination thereof; in zone 6 of the installation, the effluents are disinfected using chlorine-containing preparations of prolonged action or ultraviolet irradiation. After treatment, the water can be used for garden irrigation or other technological needs. The implemented method of purification at the installation guarantees the purification of waste water to the norms of discharge into fishery reservoirs and the decontamination of the purified water. At the same time, odorlessness is ensured and additional ventilation is not required at the installation location.

In the installation, gravity drainage of purified water, if necessary, forced removal of purified water, the installation can be equipped with a pump. Excess sludge is accumulated in the compartment 8 for sludge and after dehydration using a bag dehydrator 9, for agrotechnical use of the resulting sludge from treatment facilities as fertilizers, they are processed, additionally mixed with 30% quicklime. Installation conditions - underground or above ground.

Features of the installation:

- all processes proceed due to the use of a minimum amount of air (maintaining optimal aerobic conditions at each stage).

- the system of airlifts provides the necessary recirculation of the wastewater and the efficient course of nitri-denitrification processes.

- the use of an inert plastic nozzle with an attached biocenosis ensures maximum cleaning efficiency and small overall dimensions of the installation.

- to smooth out the unevenness of the flow of wastewater in the design of the installation, the required amount of averaging is provided.

- the unit provides a constant flow of purified water and, as a result, uniform dissolution of the pelleted chlorine reagent and reliable water disinfection.

The technical result achieved by the installation and the method used in the installations is to achieve the highest possible efficiency of removing pollutants in domestic wastewater, reliable wastewater treatment, reduction of precipitation generated during treatment, environmental safety of humans and the environment.

Documents cited in the search report:

1. Patent RU 2424199 from 2009.12.28. Author Kell Lev Sergeevich (RU). Method for BIOLOGICAL PURIFICATION OF WASTE WATER WITH ACTIVE SILT.

2. RU 2439001 from 2010.08.03 Authors: Skvortsov Lev Serafimovich (RU), Gracheva Raisa Semyonovna (RU), Shmatova Valentina Vasilievna (RU), Konygin Alexander Alexandrovich (RU). WASTE WATER PURIFICATION METHOD.

3. RU 2633896 from 2015.09.08. Author Kell Lev Sergeevich (RU). METHOD FOR BIOLOGICAL PURIFICATION OF WASTE WATER WITH ACTIVE SILT

4. RU 2654969 from 2017.03.17. METHOD FOR REMOVING PHOSPHORUS FROM WASTE LIQUID. Authors: Ambrosova Galina Tarasovna (RU), Matyushenko Evgeny Nikolaevich (RU), Belozerova Elizaveta Sergeevna (RU), Geisaddinov Tabriz Ilyaz ogly (RU), Nagornaya Tatyana Vyacheslavovna (RU), Funk Anna Aleksandrovna (RU)

5. RU 2296110 from 2005.08.15. Authors: Khalemsky Aron Mikhailovich (RU) Shvets Eduard Moiseevich (RU) METHOD FOR BIOLOGICAL WASTE WATER PURIFICATION WITH SILT

Claims (13)

1. A method of deep biological treatment of domestic wastewater, characterized in that wastewater is supplied to a structure including a wastewater intake area, in which wastewater is averaged, a zone of hydrolysis and fermentation of sediments to extract easily oxidized organic matter, in which processing is carried out in within three days, the zones of denitrification, dephosphatization and nitrification processes in one compartment without partitions or in the same compartment with partitions, while the denitrification stage is carried out before the nitrification stage, the denitrification and dephosphatization processes are provided due to precipitation and sludge formed during the cleaning process with a decrease in the amount of sludge formed in the process of wastewater treatment, and water treatment is carried out using activated sludge in a suspended state, or with the help of attached sludge, separation zone of activated sludge and purified water with subsequent recirculation of sludge to the denitrification zone, post-treatment zone and disinfection of effluents. 2. The method according to claim 1, characterized in that the stage of denitrification by reducing nitrate nitrogen from a liquid with suspended sludge to gaseous nitrogen includes staying in an oxygen-free and anaerobic zone within 1-3 hours depending on the flow rate of waste water. 3. The method according to PP. 1, 2, characterized in that the stage of denitrification provides the production of alkalinity, which ensures the processes of nitrification. 4. The method according to PP. 1-3, characterized in that the stage of nitrification is provided with a hydraulic residence time in the range of 4-9 hours. 5. The method according to PP. 1-4, characterized in that in the zone of post-treatment of purified water, cleaning is carried out using loads. 6. The method according to PP. 1-5, characterized in that in the zone of purified water disinfection, treatment with chlorine-containing preparations of prolonged action is carried out. 7. The method according to PP. 1-6, characterized in that it includes the stage of processing the sediments formed during cleaning with quicklime for agrotechnical use of sediments as fertilizers. 8. Installation for deep biological treatment of domestic wastewater according to PP. 1-7, including an averaging tank, a primary settling tank, aeration tank with anaerobic-aerobic treatment zones for carrying out denitrification, dephosphatization and nitrification processes, a secondary settling tank for separating activated sludge and purified water, devices for recirculating activated sludge to the denitrification zone, post-treatment and waste water decontamination units. 9. Installation according to claim 8, characterized in that it includes a device that prevents the formation of a crust and sludge caking in the primary settler. 10. Installation according to claim. 8, characterized in that it includes a device for generating air bubbles, made with the use of membranes. 11. Installation according to PP. 8-10, characterized in that the post-treatment unit is made in the form of a thin-layer clarifier, or fabric filters, or feed materials, or a combination thereof. 12. Installation according to PP. 8-11, characterized in that it provides a constant flow rate of purified water, and disinfection in the waste water disinfection unit is carried out with uniform dissolution of the tableted chlorine reagent. 13. Installation according to PP. 8-12, characterized in that it includes the stage of mixing the sediments formed in the process of wastewater treatment with quicklime (at least 30%), which allows them to be used as fertilizers for agrotechnical use.

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