WO2020192536A1 - Method for efficiently treating nitrogen-containing wastewater based on dnra-anammox immobilized pellets - Google Patents

Abstract

The present invention relates to a method for efficiently treating nitrogen-containing wastewater based on DNRA-Anammox immobilized pellets. The DNRA-Anammox immobilized pellets are formed by embedding DNRA bacteria and Anammox bacteria with a cross-linked polymerization product of polyvinyl alcohol, sodium alginate, and gelatinized starch as a carrier. The immobilized pellets used in the method of the present invention have the advantages of high biomass concentration, strong environmental toxicity resistance, recycling, and the like, and high bacterial concentration and bio-activity of the DNRA bacteria and Anammox bacteria in a system can be maintained, so that the total nitrogen removal rate of the system is increased. Both the DNRA bacteria and the Anammox bacteria are anaerobic bacteria, the DNRA-Anammox immobilized pellets block mass transfer of dissolved oxygen, so that the DNRA bacteria and Anammox bacteria in the DNRA-Anammox immobilized pellets are not easily affected by the dissolved oxygen, the stability of the system is enhanced, combined nitrogen removal is realized, and the total nitrogen removal rate of the system is increased.

Description

Method for efficiently treating nitrogen-containing wastewater based on DNRA-Anammox immobilized pellets Technical field

The invention relates to a method for efficiently treating nitrogen-containing wastewater based on DNRA-Anammox immobilized pellets, and belongs to the technical field of sewage treatment.

Background technique

With the progress of the times, people's living standards continue to improve, and excessive nitrogen is artificially discharged into the environment, causing nitrogen pollution. The "Announcement on the State of the Environment in China" issued in recent years shows that nitrogen pollution is one of the main causes of water pollution in my country. Denitrification treatment of nitrogen-containing wastewater has always been a research hotspot in sewage treatment, and biological denitrification is the most economical and effective method.

The traditional biological denitrification process is built around the nitrification-denitrification pathway. The process is complex and difficult to run, produces a large amount of excess sludge, and has a high operating cost. In recent years, the Anammox process has developed rapidly due to its short process flow, simple operation, low cost, and no N ₂ O generation, and has broad development prospects. ANAMMOX directly with ammonia to nitrite nitrogen into the process, the reaction ^{_{is: NH 4 + + 1.32NO 2 -}} + 0.066HCO 3 - + 0.13H + → 1.02N 2 + 0.26NO 3 - + 0.066CH ₂ O _0.5 N _0.15 +2.03H ₂ O. Due to the formation of nitrate nitrogen in the product, theoretically, the total nitrogen removal rate will be limited. Therefore, it needs to be combined with other processes to improve the total nitrogen removal rate.

In recent years, reduction of ammonium nitrate dissimilation (DNRA) growing concern during the process is the gradual reduction of nitrate to ammonia, the reaction of _{^{NO 3 - → NO 2 - →}} NH 4 +. However, this process retains nitrogen in the water body, so it cannot be promoted and applied as a denitrification technology alone. The coexistence of anammox bacteria and DNRA bacteria have been found in the sediments of various natural ecosystems such as oceans, estuaries, rice fields, mangroves, and urban water systems, indicating that they play an important role in the nitrogen cycle. The current research generally believes that DNRA coupled with anammox is the main contributor to ocean nitrogen. In addition, the DNRA process can consume the nitrate generated by the anammox process and reduce it to ammonium nitrogen, which can also be converted into nitrogen by anammox. The theoretical reaction _{^{is: 0.74NH 4 + + 1.32NO 2 -}} + 0.13H + + 0.52CH 2 O → 1.02N 2 + 0.066CH 2 O 0.5 N 0.15 + 1.77H 2 O + 0.454HCO 3 -. The theoretical maximum total nitrogen removal rate is 99%. This shows that the coupling of DNRA and Anammox process can improve the total nitrogen removal rate.

The traditional coupling process directly inoculates the sludge rich in different bacterial species for sewage treatment. The nitrate dissimilation reduces to ammonium bacteria and anammox bacteria that grow slowly, are sensitive to environmental elements, start slowly, and free bacteria are easy in the water environment. Loss and poor adaptability of bacteria, therefore, it is of great significance and significance to choose suitable carriers to embed and fix nitrate dissimilation and reduction into ammonium bacteria and anammox bacteria to reduce sludge loss and slow down the negative impact of environmental factors on microorganisms. Innovative exploration, and has greater economic benefits.

At present, it has been reported that polyvinyl alcohol and sodium alginate are used as embedding agents, and an aqueous solution containing calcium chloride and boric acid is used as a cross-linking agent. The embedding agent is solidified by the cross-linking agent to embed and solidify microorganisms to obtain a porous structure. However, the following problems have been found in the actual application of this kind of gel beads: (1) The network pores of the gel beads are too large, and bacteria are easy to leak from the network pores of the gel beads, resulting in entrapment The buried bacteria are partially lost, and the utilization rate is low. (2) The gel beads have low strength and toughness, and are easily softened and deformed by hydraulic shear, and their service life is greatly reduced.

Summary of the invention

In view of the shortcomings of the prior art, the present invention provides a method for efficiently treating nitrogen-containing wastewater based on DNRA-Anammox immobilized pellets. The DNRA-Anammox immobilized pellets are made of polyvinyl alcohol, sodium alginate and gelatinized starch. The co-polymerization product is the carrier, and the immobilized pellets formed by embedding DNRA and Anammox bacteria. The retention rate of DNRA and Anammox bacteria is good, and it is not easy to lose. At the same time, the shape is spherical, the strength and toughness are significantly improved, and it is more resistant to water erosion. Long service life, more conducive to the growth and enrichment of bacteria, DNRA-Anammox immobilized beads couple anammox and DNRA together, maintain a high biomass concentration and biological activity during the treatment process, and reduce dissolved oxygen The impact on the system, enhance the stability of the system operation, thereby increasing the total nitrogen removal rate of the system.

Term description:

Dissimilatory nitrate reduction to ammonium (DNRA): DNRA bacteria i.e. organic-electron donor, NO ^3- is an electron acceptor, which is eventually converted to through NO ^2- NH ^4+, reaction is NO ₃ ^- → NO ₂ ^- →NH ₄ ⁺ .

ANAMMOX (Anammox): The ammonia and nitrite nitrogen into the process, the reaction _{^{is: NH 4 + + 1.32NO 2 -}} + 0.066HCO 3 - + 0.13H + → 1.02N 2 + 0.26NO 3 ^- +0.066CH ₂ O _0.5 N _0.15 +2.03H ₂ O.

In order to achieve the above objective, the present invention is achieved through the following solutions:

A method for efficiently treating nitrogen-containing wastewater based on DNRA-Anammox immobilized pellets includes the following steps:

(1) DNRA-Anammox immobilized pellets are activated and cultured at 25℃-30℃ for one week to obtain activated DNRA-Anammox immobilized pellets, and DNRA-Anammox immobilized pellets are added to the submerged anaerobic bioreactor in;

(2) Use a peristaltic pump to pass the wastewater to be treated from the bottom of the reactor, adjust the water flow rate, adjust the temperature and pH, and carry out nitrogen aeration and magnetic stirring at the same time to maintain an anaerobic environment; to achieve efficient removal of nitrogen in the sewage except;

The DNRA-Anammox immobilized pellets are formed by embedding DNRA bacteria and Anammox bacteria with cross-linked polymer products of polyvinyl alcohol, sodium alginate, gelatinized starch and polyurethane as carriers.

According to the present invention, preferably, DNRA-Anammox immobilized pellets are prepared as follows:

(1.1) Add polyvinyl alcohol and sodium alginate to water in sequence and heat and stir to dissolve and mix uniformly to obtain mixed solution 1;

(1.2) Add soluble starch to water and heat to gelatinize, and then cool to 70～80℃ to obtain mixture 2;

(1.3) Add the water-based polyurethane emulsion and the mixed solution 2 to the mixed solution 1 and mix to obtain a gel solution;

(1.4) After cooling the gel liquid to room temperature, mix DNRA and Anammox bacteria in a mass ratio of 1:1 to obtain DNRA-Anammox mixed bacteria. Add the mixed bacteria to the cooled gel liquid After mixing evenly, the fungus gum mixture is obtained;

(1.5) Dissolve boric acid and calcium chloride in water to prepare a mixed solution containing boric acid and calcium chloride, which is the coagulation liquid;

(1.6) Add the fungal gum mixture dropwise to the coagulation solution under stirring conditions for coagulation and shape, and then stand to make it fully crosslinked to obtain DNRA-Anammox immobilized pellets.

According to the present invention, preferably, in step (1.1), the mass percentage of polyvinyl alcohol in the mixed solution 1 is 8-20%, and the mass percentage of sodium alginate is 0.5-1.5%.

Preferably according to the present invention, in step (1.1), the polyvinyl alcohol is polyvinyl alcohol with a degree of polymerization of 1600-1800 and a degree of alcoholysis> 99%.

According to the present invention, preferably, in step (1.2), the mass volume ratio of soluble starch to water is 1: (40-60), unit: g/mL.

According to the present invention, preferably, in step (1.3), the solid content of the water-based polyurethane emulsion is 20%-40%, and the mass fraction of the water-based polyurethane in the gel liquid is 0.1%-1.2%; The volume ratio of liquid 1 is 1: (10-30).

According to the present invention, preferably, in step (1.4), the DNRA bacterial sludge is obtained by anaerobic sludge reduction by nitrate dissimilative reduction to ammonium bacteria enrichment culture and washing, and the water content of the DNRA bacterial sludge is 60-90wt%.

Nitrate dissimilation reduction to ammonium bacteria enrichment culture reference: Research on the environmental distribution and enrichment culture of dissimilation nitrate reducing bacteria (DNRA), Bu Cuina, "Shandong University" 2018, deionization for cleaning the sludge after enrichment culture After washing with water, centrifuge at 8000 rpm for 10 min to remove the supernatant.

According to the present invention, preferably, in step (1.4), the Anammox bacterial sludge is obtained by anaerobic ammonia oxidizing bacteria enrichment culture and cleaning, and the water content of the Anammox bacterial sludge is 60-70 wt%.

The enrichment culture of anammox bacteria is carried out according to the prior art. The sludge after washing for enrichment culture is washed with deionized water and centrifuged at 8000 rpm for 10 minutes to remove the supernatant.

Preferably, according to the present invention, in step (1.4), the mass-volume ratio of the DNRA-Anammox mixed bacterial sludge to the gel liquid is 1: (3-8), unit: g/mL.

According to the present invention, in step (1.5), the mass fraction of boric acid in the coagulation liquid is 3%-5%, and the mass percentage of calcium chloride is 2%-6%.

Preferably, according to the present invention, the activation is to place the DNRA-Anammox immobilized pellets in activated water at 25°C-30°C for a week of activation and culture, and the activated water composition is as follows: ammonium bicarbonate 190mg/L, phosphoric acid Potassium dihydrogen 25mg/L, magnesium sulfate 200mg/L, calcium chloride 300mg/L, glucose 12.2mg/L, trace element solution 1mL/L; the composition of the trace element solution is: ethylenediaminetetraacetic acid 20.0g/ L, zinc sulfate 0.43g/L, manganese chloride 0.99g/L, cobalt chloride 0.24g/L, nickel chloride 0.19g/L, copper sulfate 0.25g/L, sodium selenate 0.21g/L, molybdic acid Sodium 0.22g/L, boric acid 0.014g/L.

According to the present invention, the filling rate of the activated DNRA-Anammox immobilized pellets in the reactor is preferably 15%-25% of the reactor volume.

Compared with the prior art, the present invention has the following advantages:

1. The present invention uses polyvinyl alcohol, sodium alginate, gelatinized starch and polyurethane cross-linked polymer products as carriers to embed DNRA bacteria and Anammox bacteria. The embedded immobilized microorganisms have high biomass concentration and are resistant to environmental toxicity. Strong, reusable and other advantages, can make DNRA bacteria and Anammox bacteria maintain a higher bacterial concentration and biological activity in the system, thereby improving the total nitrogen removal rate of the system. Both DNRA bacteria and Anammox bacteria are anaerobic bacteria. The DNRA-Anammox immobilized pellets hinder the mass transfer of dissolved oxygen, so that the DNRA bacteria and Anammox bacteria in the DNRA-Anammox immobilized pellets are not susceptible to the influence of dissolved oxygen, which enhances the system The stability of the system can achieve joint denitrification and improve the total nitrogen removal rate of the system.

2. The DNRA-Anammox immobilized pellets of the present invention are not easy to cause sludge loss, and the obtained DNRA-Anammox immobilized pellets hinder the mass transfer of dissolved oxygen, thereby maintaining the anaerobic environment inside the DNRA-Anammox immobilized pellets, Can make the system run stably for a long time.

3. The DNRA-Anammox immobilized pellets of the present invention use soluble starch with swelling properties as a carrier, so that the bacterial sludge is attached between the porous soluble starch, avoiding the DNRA-Anammox immobilized pellets from being damaged due to excessive network pores. The embedded bacteria are partially lost and the utilization rate is low.

4. The DNRA-Anammox immobilized pellets of the present invention are dispersed independently, are not easy to bond together, have high toughness, are more resistant to hydraulic erosion, and have a long service life.

Description of the drawings

Figure 1 is an appearance photograph of DNRA-Anammox immobilized pellets prepared in Example 1 of the present invention.

Figure 2 is a schematic diagram of the structure of a submerged anaerobic bioreactor.

In Figure 2: 1. Reservoir 2. Water inlet pump 3. Water inlet 4. Air outlet 5. Aeration pipe 6. Water outlet 7. Liquid level gauge 8. DNRA-Anammox immobilized ball 9. Magnetic stirrer 10. Outlet pump 11. Outlet pool.

detailed description:

The present invention will be further specifically described below in conjunction with examples, but the large implementation of the present invention is not limited to this.

The submerged anaerobic bioreactor includes a reaction barrel. A sealing cover is arranged on the top of the reaction barrel. A water inlet 3, an air outlet 4 and a water outlet 6 are provided through the sealing cover. The water inlet 3 is connected with a water inlet pump through a water inlet pipe. 2 and the reservoir 1, the outlet 6 is connected with the outlet pump 10 and the outlet pool 11 through the outlet pipe. The bottom of the reaction barrel is filled with DNRA-Anammox immobilized beads 8, and the bottom of the reaction barrel is also equipped with a magnetic stirrer 9. An aeration head is arranged in the reaction tank body, the aeration head is connected to the aeration tube 5, and extends through the sealing cover to the reaction tank body and a level gauge 7 is also provided.

Example 1:

A method for efficiently treating nitrogen-containing wastewater based on DNRA-Anammox immobilized pellets includes the following steps:

(1) Add polyvinyl alcohol and sodium alginate to water in turn and heat and stir to dissolve and mix uniformly to obtain mixed solution 1. The mass percentage of polyvinyl alcohol in mixed solution 1 is 16%, and the mass percentage of sodium alginate The content is 1.2%, polyvinyl alcohol is polyvinyl alcohol with a degree of polymerization of 1600-1800 and a degree of alcoholysis >99%

(2) Add soluble starch to water for heating and gelatinization, and then cool to 70-80°C to obtain mixture 2. The mass volume ratio of soluble starch to water is 1:33, unit: g/mL;

(3) Add the water-based polyurethane emulsion with a solid content of 30% and the mixed liquid 2 to the mixed liquid 1 in turn to obtain a gel liquid. The mass fraction of the water-based polyurethane in the gel liquid is 0.6%; the mixed liquid 2 and the mixed liquid The volume ratio of liquid 1 is 1:25, unit: g/mL;

(4) The anaerobic sludge is reduced to ammonium bacteria enrichment culture by nitrate dissimilation, and then washed with deionized water and centrifuged at 8000 rpm for 10 minutes to remove the supernatant to obtain highly active DNRA bacterial sludge.

The anaerobic sludge is enriched and cultured with anammox bacteria, then washed with deionized water and centrifuged at 8000 rpm for 10 minutes to remove the supernatant to obtain highly active Anammox bacterial sludge;

Mix the DNRA bacteria mud and Anammox bacteria mud in a mass ratio of 1:1 to obtain DNRA-Anammox mixed bacteria mud. Take 30g of DNRA-Anammox mixed bacteria mud and 100ml of the gel solution cooled to room temperature and mix well to obtain a mixture of bacteria gum liquid;

(5) Dissolve boric acid and calcium chloride in water to prepare a mixed solution containing boric acid and calcium chloride, which is the coagulation liquid; the mass fraction of boric acid in the coagulation liquid is 4%, and the mass percentage of calcium chloride is 3%;

(6) Add the fungus gum mixture dropwise to the coagulation solution under stirring conditions for coagulation and shape, and then stand for full cross-linking to obtain DNRA-Anammox immobilized pellets.

(7) Place the DNRA-Anammox immobilized pellets in activated water at 26°C for activation and culture for one week, so that the microorganisms inside the DNRA-Anammox immobilized pellets are fully recovered, and the activated DNRA-Anammox immobilized pellets are obtained. DNRA-Anammox immobilized pellets were added to the submerged anaerobic bioreactor at a volume filling rate of 20%, and the effective volume of the reactor was 6L, as shown in Figure 2;

(8) Water is fed into the reactor through the water inlet pump. In order to make the reactor water evenly distributed, it can fully contact with the DNRA-Anammox immobilized pellets. A magnetic stirrer is installed at the bottom of the anaerobic reactor; An aeration head is installed in the reactor to aerate nitrogen to maintain the anaerobic environment in the reactor. A liquid level controller is installed in the reactor to adjust the effluent water, so that the reactor can maintain the balance of inlet and outlet water, and realize the efficient removal of nitrogen in the sewage. .

The appearance photo of the DNRA-Anammox immobilized pellets prepared in this example is shown in FIG. 1.

Claims (10)

1. A method for efficiently treating nitrogen-containing wastewater based on DNRA-Anammox immobilized pellets includes the following steps:

   (1) DNRA-Anammox immobilized pellets are activated and cultured at 25℃-30℃ for one week to obtain activated DNRA-Anammox immobilized pellets, and DNRA-Anammox immobilized pellets are added to the submerged anaerobic bioreactor in;

   (2) Use a peristaltic pump to pass the wastewater to be treated from the bottom of the reactor, adjust the water flow rate, adjust the temperature and pH, and carry out nitrogen aeration and magnetic stirring at the same time to maintain an anaerobic environment; to achieve efficient removal of nitrogen in the sewage except;

   The DNRA-Anammox immobilized pellets are formed by embedding DNRA bacteria and Anammox bacteria with cross-linked polymer products of polyvinyl alcohol, sodium alginate, gelatinized starch and polyurethane as carriers.
2. The method for efficiently treating nitrogen-containing wastewater according to claim 1, wherein the DNRA-Anammox immobilized pellets are prepared as follows:

   (1.1) Add polyvinyl alcohol and sodium alginate to water in sequence and heat and stir to dissolve and mix uniformly to obtain mixed solution 1;

   (1.2) Add soluble starch to water and heat to gelatinize, and then cool to 70～80℃ to obtain mixture 2;

   (1.3) Add the water-based polyurethane emulsion and the mixed solution 2 to the mixed solution 1 and mix to obtain a gel solution;

   (1.4) After cooling the gel liquid to room temperature, mix DNRA and Anammox bacteria in a mass ratio of 1:1 to obtain DNRA-Anammox mixed bacteria. Add the mixed bacteria to the cooled gel liquid After mixing evenly, the fungus gum mixture is obtained;

   (1.5) Dissolve boric acid and calcium chloride in water to prepare a mixed solution containing boric acid and calcium chloride, which is the coagulation liquid;

   (1.6) Add the fungal gum mixture dropwise to the coagulation solution under stirring conditions for coagulation and shape, and then stand to make it fully crosslinked to obtain DNRA-Anammox immobilized pellets.
3. The method for efficiently treating nitrogen-containing wastewater according to claim 2, wherein in step (1.1), the mass percentage of polyvinyl alcohol in the mixed solution 1 is 8-20%, and the mass percentage of sodium alginate The content is 0.5-1.5%.
4. The method for efficiently treating nitrogen-containing wastewater according to claim 2, wherein in step (1.1), the polyvinyl alcohol is polyvinyl alcohol with a degree of polymerization of 1600-1800 and a degree of alcoholysis> 99%.
5. The method for efficiently treating nitrogen-containing wastewater according to claim 2, characterized in that, in step (1.2), the mass volume ratio of soluble starch to water is 1: (40-60), unit: g/mL.
6. The method for efficiently treating nitrogen-containing wastewater according to claim 2, wherein in step (1.3), the solid content of the aqueous polyurethane emulsion is 20%-40%, and the mass of the aqueous polyurethane in the gel liquid The fraction is 0.1%-1.2%; the volume ratio of the mixed solution 2 to the mixed solution 1 is 1: (10-30).
7. The method for high-efficiency treatment of nitrogen-containing wastewater according to claim 2, characterized in that the DNRA bacterial sludge is obtained by anaerobic sludge after nitrate dissimilative reduction to ammonium bacteria enrichment culture and cleaning, and the water content of the DNRA bacterial sludge is 60-90wt%, Anammox bacterial sludge is obtained by anaerobic ammonia oxidizing bacteria enrichment culture and cleaning, and the water content of Anammox bacterial sludge is 60-70wt%.
8. The method for efficiently treating nitrogen-containing wastewater according to claim 2, wherein in step (1.4), the mass-volume ratio of DNRA-Anammox mixed bacterial mud and gel liquid is 1: (3-8), unit : G/mL; in step (1.5), the mass fraction of boric acid in the coagulation liquid is 3%-5%, and the mass percentage of calcium chloride is 2%-6%.
9. The method for high-efficiency treatment of nitrogen-containing wastewater according to claim 1, characterized in that the activation is to place the DNRA-Anammox immobilized pellets in activated water and activate and culture for one week at 25°C-30°C. The composition of activated water is as follows: ammonium bicarbonate 190mg/L, potassium dihydrogen phosphate 25mg/L, magnesium sulfate 200mg/L, calcium chloride 300mg/L, glucose 12.2mg/L, trace element solution 1mL/L; the trace elements The composition of the solution is: ethylenediaminetetraacetic acid 20.0g/L, zinc sulfate 0.43g/L, manganese chloride 0.99g/L, cobalt chloride 0.24g/L, nickel chloride 0.19g/L, copper sulfate 0.25g /L, sodium selenate 0.21g/L, sodium molybdate 0.22g/L, boric acid 0.014g/L.
10. The method for efficiently treating nitrogen-containing wastewater according to claim 1, wherein the filling rate of the activated DNRA-Anammox immobilized pellets in the reactor is 15%-25% of the volume of the reactor.

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