Device for removing nitrate in sewage by using biodegradable material and use method of device

Abstract

The invention discloses a device for removing nitrate in sewage by using a biodegradable material and a use method of the device. The device comprises a first bioreactor and a second bioreactor, the water supply tank is communicated with the first bioreactor and the second bioreactor through a water inlet pipe; the peristaltic pump is mounted on the water inlet pipe; the water collecting tank is communicated with the first bioreactor and the second bioreactor through a water outlet pipe, the nitrate content in the nitrate nitrogen content (32-35 mg / L) of the V-class water quality can be reduced to the III-class water quality standard (4-10 mg / L), a filling medium belongs to a slow-release carbon source, the influence of the filling medium on organic carbon which cannot be purged in the water quality after the filling medium is used for a long time is very small, and secondary pollution is hardly generated.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and in particular relates to a device for removing nitrate in sewage by using biodegradable materials and a use method thereof. Background Art

[0002] In the process of implementing the present invention, the inventors found that the prior art has at least the following problems:

[0003] The world's freshwater resources are very scarce, and one-third of the world's population has no access to safe drinking water. Groundwater, as one of the main sources of freshwater, is seriously affected by human activities. The excessive use of fertilizers and the discharge of sewage or industrial wastewater have caused the excessive nitrate content in groundwater, which has gradually attracted people's attention. However, there are many factories around the world dedicated to removing nitrates from surface water, and there are far fewer facilities dedicated to groundwater remediation. Therefore, there is an urgent need for efficient and low-cost sustainable management technologies for groundwater resources.

[0004] A large number of studies on the removal of nitrate pollution in groundwater have been carried out at home and abroad. At present, the main methods for removing nitrate in water are physical methods (such as ion exchange, electrodialysis, reverse osmosis, etc.), chemical denitrification (such as active metal reduction method, catalytic denitrification, etc.), and biological denitrification. These methods can remove nitrate from groundwater to varying degrees, but the physical method has problems such as difficult operation and high cost. Chemical denitrification is not widely used in practical applications as biological denitrification due to its high cost and the defect of easily generating secondary pollution. There are also some problems with traditional bioremediation methods. For example, Chinese patent CN117303602A disclosed on October 10, 2023 discloses a method for purifying nitrate nitrogen in aquaculture wastewater using a pyrite biofilter. The pyrite in the patent can be used as an electron donor for denitrifying bacteria to carry out autotrophic denitrification. The invention has low wastewater treatment cost, less sulfate production in effluent water quality, and good nitrate removal effect, but the invention uses pyrite as an electron donor, which will cause a long start-up time and low removal efficiency. Chinese patent CN102992479A published on December 13, 2012 discloses a method for removing nitrate nitrogen from water using polyhydroxybutyrate-valerate copolyester (PHBV). The carbon source release of biodegradable solid PHBV has a slow release performance, which can avoid the problem of difficult control of liquid carbon source addition, and the effluent quality is good. The operation of the reactor is simple and easy to control. However, the solid carbon source PHBV added in the invention will have a high carbon content in the effluent after long-term operation. Therefore, how to effectively remove nitrate pollution in groundwater while controlling the effluent quality needs further study. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a device for removing nitrates from sewage using biodegradable materials and a method for using the device, which can reduce the nitrate content in Class V water quality nitrate nitrogen content (32-35 mg / L) to Class III water quality standards (4-10 mg / L). The filling medium is a slow-release carbon source, and after long-term use, its effect on the non-purgeable organic carbon in the water quality is very small, and almost no secondary pollution is generated.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a device for removing nitrates from sewage using biodegradable materials, comprising:

[0007] a first bioreactor and a second bioreactor;

[0008] A water supply tank, which is connected to the first bioreactor and the second bioreactor through a water inlet pipe;

[0009] A peristaltic pump, installed on the water inlet pipe;

[0010] A water collecting tank is connected to the first bioreactor and the second bioreactor through a water outlet pipe.

[0011] The water supply tank and the water collection tank are made of PVC; the bioreactor is cylindrical, with a total height of 55 cm and a diameter of 11 cm. A water inlet and a water outlet are respectively arranged at the bottom and the top of the bioreactor.

[0012] A water inlet and a water outlet are respectively arranged at the bottom and the top of the first bioreactor and the second bioreactor, wherein the water inlet is connected to the water inlet pipe and the water outlet is connected to the water outlet pipe.

[0013] The method for using the above-mentioned device for removing nitrates from sewage using biodegradable materials comprises the following steps:

[0014] 1) Filling a uniform mixture of PBAT and ceramsite sand in a first bioreactor;

[0015] 2) Filling the second bioreactor with ceramsite sand as a control group;

[0016] 3) After filling, the first reactor and the second reactor are inoculated with domesticated sludge respectively;

[0017] 4) setting the simulated groundwater flow rate, and pumping the artificially synthesized groundwater with a nitrate nitrogen content that meets the Class V standard into the first bioreactor through a peristaltic pump;

[0018] 5) Determine the water quality of the purified groundwater at the outlet.

[0019] In the above step 1), the filling rate of PBAT is 50% to 65%.

[0020] The particle size of PBAT in the first bioreactor is 4-5mm; the particle size of ceramsite sand in the first bioreactor is 1-3mm. Smaller particle size means larger specific surface area, which makes microorganisms contact with materials more fully, thus maximizing the use of materials as carbon sources, which is conducive to the formation of biofilm on the surface of materials and the stable operation of the system.

[0021] In the above step 5), the groundwater quality parameters measured include nitrate nitrogen content, nitrite nitrogen content and non-purgeable organic carbon content.

[0022] The bioreactor is made of PVC material, with a sealed bottom and an open top.

[0023] The molecular formula of PBAT is (C 10 H 10 O4.C6H 10 O4.C4H 10 O2) X .

[0024] In the above step 4), the simulated groundwater flow rate is set, and the hydraulic retention time is 20 to 27 hours. In this time interval, the wastewater with nitrate content Class V water quality standard can be purified to Class III water quality standard. When the temperature is higher than 26°C, the wastewater can be purified to Class I water quality standard. The setting of this time interval can make the reactor fully react and effectively remove nitrate nitrogen in the water body.

[0025] One of the above technical solutions has the following advantages or beneficial effects: it can reduce the nitrate content in Class V water quality nitrate nitrogen content (32-35 mg / L) to Class III water quality standard (4-10 mg / L); the filling medium is a slow-release carbon source, and after long-term use, its impact on the non-purgeable organic carbon in the water quality is very small, and almost no secondary pollution is generated. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the structure of a device for removing nitrates from sewage using biodegradable materials provided in an embodiment of the present invention;

[0027] The markings in the above figures are: 1. water supply tank, 2. peristaltic pump, 3. water collecting tank, a. first bioreactor, b. second bioreactor. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Embodiment 1

[0030] See also Figure 1 , a device for removing nitrate from sewage using biodegradable materials, comprising: a first bioreactor a and a second bioreactor b; a water supply tank 1, which is connected to the first bioreactor a and the second bioreactor b through a water inlet pipe; a peristaltic pump 2, installed on the water inlet pipe; a water collecting tank 3, which is connected to the first bioreactor a and the second bioreactor b through a water outlet pipe. A uniform mixture of PBAT and ceramsite sand is filled in the first bioreactor a. The nitrate content in the nitrate nitrogen content of Class V water quality (32-35 mg / L) can be reduced to the Class III water quality standard (4-10 mg / L). The filling medium is a slow-release carbon source. After long-term use, its effect on the non-purgeable organic carbon in the water quality is very small, and almost no secondary pollution is generated.

[0031] The water supply tank 1 and the water collection tank 3 are made of PVC; the bioreactor is cylindrical, with a total height of 55 cm and a diameter of 11 cm. A water inlet and a water outlet are respectively arranged at the bottom and the top of the bioreactor. The water supply tank 1 and the water collection tank 3 are PVC plastic barrels with a size of 25 cm × 25 cm, which are used to hold artificial synthetic groundwater and treated synthetic groundwater. The flow range of the peristaltic pump 2 is 0.002-500 ml / min, which can supply water to two biological packed bed reactors at the same time.

[0032] A water inlet and a water outlet are respectively arranged at the bottom and the top of the first bioreactor a and the second bioreactor b. The water inlet is connected to the water inlet pipe, and the water outlet is connected to the water outlet pipe.

[0033] The method for using the above-mentioned device for removing nitrates from sewage using biodegradable materials comprises the following steps:

[0034] 1) Filling a first bioreactor a with a uniform mixture of PBAT and ceramsite sand;

[0035] 2) Filling the second bioreactor b with ceramsite sand as a control group;

[0036] 3) After filling, the first reactor and the second reactor are inoculated with domesticated sludge respectively;

[0037] 4) setting the simulated groundwater flow rate, and pumping the artificially synthesized groundwater with a nitrate nitrogen content that meets the Class V standard into the first bioreactor a through the peristaltic pump 2;

[0038] 5) Determine the water quality of the purified groundwater at the outlet.

[0039] In the above step 1), the filling rate of PBAT is 50% to 65%. If the filling rate is lower than 50%, the denitrification performance of the reactor will be significantly reduced, and the nitrate removal effect will be poor; if the filling rate is higher than 65%, it will affect the effluent DOC and cause secondary pollution.

[0040] The particle size of PBAT in the first bioreactor a is 4-5 mm; the particle size of ceramsite sand in the first bioreactor a is 1-3 mm. The bioreactor wall is filled with biodegradable material PBAT, which can be used as a solid carbon source for denitrification due to its slow-release properties. According to laboratory leaching experiments, the carbon released by PBAT is about 0.03-0.05 mg / g per day, which can provide a carbon source for the physiological activities of denitrifying microorganisms while ensuring the quality of purified groundwater without causing secondary pollution.

[0041] In the above step 5), the groundwater quality parameters measured include nitrate nitrogen content, nitrite nitrogen content and non-purgeable organic carbon content.

[0042] The bioreactor is made of PVC material, with a sealed bottom and an open top.

[0043] The molecular formula of PBAT is (C 10 H 10 O4.C6H 10 O4.C4H 10 O2) X .

[0044] In step 4) above, the simulated groundwater flow rate is set and the hydraulic retention time is 20 to 27 hours.

[0045] After adopting the above scheme, the nitrate content in Class V water quality nitrate nitrogen content (32-35 mg / L) can be reduced to Class III water quality standard (4-10 mg / L). The filling medium is a slow-release carbon source. After long-term use, its impact on the non-purgeable organic carbon in the water quality is very small, and almost no secondary pollution is generated.

[0046] Embodiment 2

[0047] Use Figure 1The water treatment system is used to simulate the removal of nitrates during the flow of groundwater. The above-mentioned PBAT and ceramsite sand uniform mixture is filled in the first bioreactor a, and the filling rate of PBAT is about 63%. The ceramsite sand is filled in the second bioreactor b as a control group, and the filling height is 45 cm. After filling, the reactors a and b are inoculated with domesticated sludge. The simulated groundwater flow rate is set, and the hydraulic retention time is 20 to 27 hours. The artificially synthesized nitrate nitrogen content that meets the Class V standard (32 to 36 mg / L) is pumped into the first bioreactor a through a peristaltic pump. By measuring the purified groundwater at the outlet, it can be obtained that its nitrate nitrogen content is reduced to the Class III water quality standard (4 to 10 mg / L), the nitrite nitrogen content meets the Class III water quality standard (0.004 to 0.03 mg / L), and the non-purge organic carbon content is less than 3 mg / L, and almost no secondary pollution is generated.

[0048] The second bioreactor was filled with pure expanded clay sand and was inoculated with domesticated sludge before being connected to artificial synthetic wastewater. During the experimental stage, the influent nitrate-nitrogen content was 32-36 mg / L. Under the same environmental conditions as the upflow reactor, the hydraulic retention time was kept consistent, and the effluent nitrate-nitrogen content was 31-35 mg / L.

[0049] Polybutylene adipate / terephthalate (PBAT) was purchased from Shanghai MacLean Biochemical Technology Co., Ltd., molecular formula: (C 10 H 10 O4.C6H 10 O4.C4H 10 O2) X , specification purity: Mn~120,000.

[0050] Sludge domestication: The sludge is taken from the bottom mud of rivers and lakes and domesticated under laboratory conditions. After the domestication is completed, biofilm formation is started in the reactor.

[0051] The main body of the present invention is a permeable biological reaction wall with a filling medium added, and the filling medium is composed of a uniform mixture of polybutylene adipate / terephthalate (PBAT) with a particle size of 4 to 5 mm and ceramsite sand with a particle size of 1 to 3 mm. A permeable biological reaction wall is set up in an area where groundwater is contaminated with nitrate. The contaminated groundwater passes through the biological reaction wall along the direction of the water flow. The PBAT in the reaction wall is used as an electron donor for denitrification, which can effectively remove nitrates from the groundwater. The nitrate content of the groundwater after this treatment is lower than the Class III standard in the Groundwater Quality Standard GB / T 14848-2017.

[0052] The bioreaction wall is filled with biodegradable material PBAT, which can be used as a solid carbon source for denitrification due to its slow-release properties. According to laboratory leaching experiments, the carbon released by PBAT is about 0.03-0.05 mg / g per day, which can provide a carbon source for denitrifying microorganisms to carry out physiological activities while ensuring the quality of purified groundwater without causing secondary pollution. Figure 1 A water treatment system is used to simulate a method for removing nitrates during groundwater flow, the system comprising a water supply tank 1, a peristaltic pump 2, a water collecting tank 3, a first bioreactor a, and a second bioreactor b. The water supply tank 1 and the peristaltic pump 2 are connected via a water supply pipeline, the peristaltic pump 2 is connected to the first bioreactor and the second bioreactor b via a drain pipeline, and the two bioreactors are connected to the water collecting tank 3 via an outlet pipeline.

[0053] The water supply tank 1 and the water collection tank 3 are PVC plastic barrels with a size of 25 cm×25 cm, which are used to contain artificial synthetic groundwater and treated synthetic groundwater.

[0054] The manufacturer of peristaltic pump 2 is Baoding Lange Constant Flow Pump Co., Ltd., and its flow range is 0.002-500 ml / min, which can supply water to two biological packed bed reactors at the same time.

[0055] The first bioreactor, b, is made of PVC material, sealed at the bottom and open at the top. The bioreactor is cylindrical in shape, with a total height of about 55 cm and a diameter of about 11 cm. A water inlet and a water outlet are set at the bottom and top respectively. The filling rate of reactor a is 50% to 65% for PBAT. If the filling rate is lower than 50%, the denitrification performance of the reactor will be significantly reduced, and the nitrate removal effect will be poor; if the filling rate is higher than 65%, it will affect the effluent DOC and cause secondary pollution.

[0056] Beneficial effects of the present invention:

[0057] (1) The permeable bioreactor wall of the present invention can reduce the nitrate content of Class V water quality (32-35 mg / L) to Class III water quality standard (4-10 mg / L).

[0058] Table 1 Nitrate nitrogen content of each component during the experimental period

[0059]

[0060] (2) The filling medium of the permeable bioreactor wall of the present invention is a slow-release carbon source. After long-term use, its impact on the non-purgeable organic carbon in the water quality is very small, and almost no secondary pollution is generated.

[0061] In the description of the present invention, it is necessary to understand that the terms "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inside", "front", "center", "both ends" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0062] In the present invention, unless otherwise clearly stipulated and limited, the terms such as "installation", "setting", "connection", "fixation" and "screw-on" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, ordinary technicians in this field can understand the specific meanings of the above terms in the present invention according to the specific circumstances.

[0063] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A device for removing nitrates from sewage using biodegradable materials, characterized in that: have: a first bioreactor and a second bioreactor; A water supply tank, which is connected to the first bioreactor and the second bioreactor through a water inlet pipe; A peristaltic pump, installed on the water inlet pipe; A water collecting tank is connected to the first bioreactor and the second bioreactor through a water outlet pipe.

2. The device for removing nitrate from sewage using biodegradable materials according to claim 1, characterized in that: The water supply tank and the water collection tank are made of PVC; the bioreactor is cylindrical, with a total height of 55 cm and a diameter of 11 cm. A water inlet and a water outlet are respectively arranged at the bottom and the top of the bioreactor.

3. The device for removing nitrate from sewage using biodegradable materials as claimed in claim 2, characterized in that: A water inlet and a water outlet are respectively arranged at the bottom and the top of the first bioreactor and the second bioreactor, wherein the water inlet is connected to the water inlet pipe and the water outlet is connected to the water outlet pipe.

4. The method for using the device for removing nitrate from sewage using biodegradable materials according to any one of claims 1 to 3, characterized in that: The steps include: 1) Filling a uniform mixture of PBAT and ceramsite sand in a first bioreactor; 2) Filling the second bioreactor with ceramsite sand as a control group; 3) After filling, the first reactor and the second reactor are inoculated with domesticated sludge respectively; 4) setting the simulated groundwater flow rate, and pumping the artificially synthesized groundwater with a nitrate nitrogen content that meets the Class V standard into the first bioreactor through a peristaltic pump; 5) Determine the water quality of the purified groundwater at the outlet.

5. The device for removing nitrate from sewage using biodegradable materials as claimed in claim 4, characterized in that: In the above step 1), the filling rate of PBAT is 50% to 65%.

6. The device for removing nitrate from sewage using biodegradable materials as claimed in claim 5, characterized in that: The particle size of PBAT in the first bioreactor is 4-5 mm; the particle size of ceramsite sand in the first bioreactor is 1-3 mm.

7. The device for removing nitrate from sewage using biodegradable materials as claimed in claim 6, characterized in that: In the above step 5), the groundwater quality parameters measured include nitrate nitrogen content, nitrite nitrogen content and non-purgeable organic carbon content.

8. The device for removing nitrate from sewage using biodegradable materials as claimed in claim 7, characterized in that: The bioreactor is made of PVC material, with a sealed bottom and an open top.

9. The device for removing nitrate from sewage using biodegradable materials as claimed in claim 8, characterized in that: The molecular formula of PBAT is (C 10 H 10 O4.C6H 10 O4.C4H 10 O2) X .

10. The device for removing nitrate from sewage using biodegradable materials as claimed in claim 9, characterized in that: In step 4) above, the simulated groundwater flow rate is set and the hydraulic retention time is 20 to 27 hours.

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