Heavy metal tolerant sulfur autotrophic denitrification system

Abstract

The invention discloses a heavy metal tolerant sulfur autotrophic denitrification system, and relates to the field of sewage treatment. The sulfur autotrophic denitrification system comprises a wastewater supply unit, a strain supply unit and a biological membrane unit; the wastewater supply unit is connected with the biological membrane unit and supplies wastewater to the biological membrane unit; the strain supply unit adopts an independent culture mode, and strains are supplied to the biological membrane unit for use after being cultured to be mature; the biological membrane unit is loaded with filler; the filler comprises a sulfur-containing synthetic material and pelelith; the strain is mainly sulfur autotrophic denitrifying bacteria. According to the system, through domestication of low-concentration heavy metal ions, the heavy metal resistance of the system is effectively improved, and efficient denitrification performance can still be kept under the influence of high-concentration heavy metal ions. The bicarbonate present in the system plays a key role in removal of heavy metal ions.

Description

Technical Field

[0001] The invention relates to the field of sewage treatment, and in particular to a sulfur autotrophic denitrification system for biological denitrification of sewage containing heavy metals. Background Art

[0002] In recent years, nitrate pollution in water bodies has become increasingly serious, potentially threatening people's health and the sound operation of the ecosystem. Biological denitrification has always been an important method for denitrification of sewage. However, heavy metal pollution is becoming more and more serious. Heavy metal ions are highly mobile, especially in water bodies, and can easily cause wide-area pollution. In addition, heavy metals have high biological toxicity and can easily inhibit microbial activity, which makes it difficult to biologically denitrify some heavy metal-containing sewage. Therefore, it is necessary to take measures to deal with heavy metal pollution in sewage.

[0003] There are many methods for heavy metal treatment. For example: Patent CN 117985882 A (application publication number) uses sulfiding agents, gypsum and other agents to achieve the simultaneous removal of heavy metals and non-metallic oxides in multi-pollutant wastewater; Patent CN222593565 U (authorization announcement number) designs a membrane reactor separation device, combining the high permeability flux of membrane separation with the high separation efficiency of adsorption materials to achieve high-flux and high-efficiency separation of heavy metals in wastewater; Patent CN 104829058 A (application publication number) develops a process combining sludge adsorption, chemical desorption and autotrophic denitrification to achieve high-efficiency and low-consumption denitrification and heavy metal recovery of low carbon-nitrogen ratio heavy metal-containing and high ammonia nitrogen wastewater.

[0004] Existing heavy metal treatment methods have the following problems: (1) High cost. The production costs of chemical agents and membrane reactor components are high, and the operating costs should not be underestimated; (2) There is a risk of secondary pollution. Some chemical agents are toxic in themselves, such as sulfides, and if the adsorbed products are not properly handled, they may cause secondary pollution to the land, water, and atmosphere; (3) Single function. Most processes select and remove pollutants in steps, which complicates the treatment process.

[0005] Therefore, it is of great significance to develop a process with simple process, integrated operation and the ability to simultaneously remove heavy metals and nitrates for wastewater where nitrates and heavy metals coexist. Summary of the invention

[0006] The purpose of the present invention is to provide a sulfur autotrophic denitrification system that tolerates heavy metals to solve the problems encountered in the biological denitrification process of heavy metal-containing wastewater. The present invention improves the resistance of the autotrophic denitrification system to heavy metals through the principle of low-concentration heavy metal ion acclimation and adsorption precipitation, and efficiently removes heavy metals in wastewater while achieving efficient nitrate removal.

[0007] The solution adopted by the present invention is as follows:

[0008] The present invention provides a sulfur autotrophic denitrification system resistant to heavy metals, which is characterized in that the system consists of three units, namely a wastewater supply unit, a strain supply unit, and a biofilm unit; the wastewater supply unit is connected to the biofilm unit to supply wastewater to the biofilm unit; the strain supply unit adopts an independent culture mode, and after the strains are cultured and matured, they are supplied for use in the biofilm unit; the biofilm unit is loaded with packing materials; the packing materials include sulfur-containing synthetic materials and volcanic stones; the strains are mainly sulfur autotrophic denitrifying bacteria.

[0009] Further, the sulfur autotrophic denitrifying bacteria are domesticated and enriched successively using thiosulfate and elemental sulfur as electron donors.

[0010] Further, the sulfur autotrophic denitrifying bacteria can be rapidly domesticated and enriched, and the period is 20 days.

[0011] Further, the mass ratio of elemental sulfur, calcium carbonate, and liquid sodium silicate in the sulfur-containing synthetic material is 5:2:14. After being mixed evenly, it is cured at 125°C for 12 hours.

[0012] Further, the sulfur-containing synthetic material and volcanic stones are mixed evenly and loaded into the biofilm unit, and the volume ratio is 9:1.

[0013] Further, the biofilm unit is carried in an upflow reactor at a constant temperature.

[0014] Further, the biofilm unit needs to be continuously started with wastewater and domesticated with low-concentration heavy metal wastewater.

[0015] The present invention also provides the application of the above sulfur autotrophic denitrification system in the biological denitrification of low carbon-nitrogen ratio wastewater containing heavy metals.

[0016] Further, the application includes maintaining stable operation, maintaining high denitrification efficiency, and high heavy metal removal rate in the presence of high-concentration heavy metal ions.

[0017] The present invention also provides a method for denitrifying heavy metal wastewater, which includes simultaneously removing nitrate and heavy metals through an integrated reactor.

[0018] Compared with the existing heavy metal wastewater treatment technologies, the technology of the present invention has the following advantages:

[0019] The main raw material of the packing material used in this technology is cheap elemental sulfur, the strain culture is simple, the occupied space of the reactor is small, and the cost is reduced; the integration of denitrification and heavy metal removal simplifies the operation; the reactor can operate for a long time with high stability. Description of the Drawings

[0020] Figure 1 Microbial composition map at the genus level for enriched microorganisms;

[0021] Figure 2 Schematic diagram of the structure of the sulfur autotrophic denitrification system of the present invention;

[0022] Figure 2 In which, 1 - reactor water outlet, 2 - feed port, 3 - exhaust port, 4 - sulfur-containing synthetic material, 5 - three-phase separator, 6 - sampling port, 7 - volcanic rock, 8 - reactor water inlet, 9 - peristaltic pump, 10 - silica gel hose, 11 - water inlet bottle;

[0023] Figure 3 Denitrification performance map of the sulfur autotrophic denitrification system under the influence of heavy metals;

[0024] Figure 4 Microbial community composition map of the biofilm unit during operation. Detailed implementation manners

[0025] The present invention will be further explained in detail below in conjunction with the drawings and specific implementation manners.

[0026] Example 1

[0027] Enriched medium for sulfur autotrophic denitrifying bacteria: 2.482 g / L Na 2 S 2 O 3 ·5H 2 O, 1.515 g / L KNO 3 , 0.84 g / L NaHCO 3 , 1.36 g / L KH 2 PO 4 , 0.342 g / L NH 4 Cl, 0.651 g / L MgCl 2 , 0.111 g / L CaCl 2 , 1 ml / L trace element solution.

[0028] Composition of the trace element solution: 50 g / L EDTA, 7.34 g / L CaCl 2 ·2H 2 O, 3.58 g / L FeCl 2 ·4H 2 O, 1.06 g / L ZnCl 2 , 0.5 g / L CoCl 2 ·6H 2 O, 0.5 g / L (NH 4 ) 6 Mo 7 O 24 ·4H2 O, 2.50 g / L MnCl 2 ·4H 2 O, 0.14 g / L CuCl 2 ·2H 2 O.

[0029] 1. Acclimation and enrichment culture of sulfur autotrophic denitrifying bacteria

[0030] Acclimatize and enrich sulfur autotrophic denitrifying bacteria from the anaerobic activated sludge obtained from the secondary sedimentation tank of the sewage treatment plant. The method is as follows:

[0031] Use a sequencing batch reactor to enrich sulfur autotrophic denitrifying bacteria. Add activated sludge to the reactor. The sludge is taken from the secondary sedimentation tank of the sewage treatment plant and is washed three times with deionized water before being added to the reactor. The enrichment process is divided into two stages. In the first stage, Na 2 S 2 O 3 is used as the electron donor because Na 2 S 2 O 3 is easily soluble and has a high reaction rate, so the speed of enriching bacteria is faster. The specific enrichment operation is as follows: (1) In the first stage, add about 1 L of washed sludge to a 2 L biological feeding bottle, pump in the liquid nutrient medium using a peristaltic pump, control the temperature at 30 - 35 °C using an intelligent temperature controller, and provide stirring with a magnetic stirrer. Replace the medium every 5 days; (2) In the second stage, replace Na 2 S 2 O 3 with 2 g of elemental sulfur, and regularly add it to the sequencing batch reactor to further acclimatize and enrich sulfur autotrophic denitrifying bacteria using elemental sulfur as the electron donor. The two stages last for 20 days in total.

[0032] 2. Microbial community analysis

[0033] Use high-throughput sequencing technology to detect the sludge in the two enrichment stages, evaluate the enrichment of bacterial species, and obtain the relative abundance map of the microbial species composition in the two stages. The results are as Figure 1 shown.

[0034] Among them, sample B1 is taken from the first stage of enrichment, and sample B2 is taken from the second stage. At the genus level, Thiobacillus is a common sulfur autotrophic denitrifying bacterium that plays an important role in sulfur oxidation and nitrate reduction. Its relative abundance reaches 51% and 66% in the two stages respectively, indicating that Thiobacillus has been rapidly enriched in the sequencing batch reactor.

[0035] Example 2

[0036] The synthetic wastewater used in this case simulates the nitrate pollution concentration in groundwater, and its composition is as follows: 0.46 g / L KNO 3 、0.14 g / L KH 2 PO 4 、0.07 g / L MgCl 2 、0.01 g / L CaCl 2 and 1 ml / L trace element solution.

[0037] Composition of the trace element solution: 50 g / L EDTA, 7.34 g / L CaCl 2 ·2H 2 O, 3.58 g / L FeCl 2 ·4H 2 O, 1.06 g / L ZnCl 2 、0.5 g / L CoCl 2 ·6H 2 O, 0.5 g / L (NH 4 ) 6 Mo 7 O 24 ·4H 2 O, 2.50 g / L MnCl 2 ·4H 2 O, 0.14 g / L CuCl 2 ·2H 2 O.

[0038] 1. Operation of the sulfur autotrophic denitrification system

[0039] The sulfur autotrophic denitrification system constructed in this case includes a wastewater supply unit, a strain supply unit and a biofilm unit, and its structure is as Figure 2 shown. The wastewater supply unit consists of a water inlet bottle 11, a peristaltic pump 10 and a silica gel hose 9. The strain supply unit adopts an independent culture mode, and after the strains are cultured and matured, they are supplied for use in the biofilm unit. The biofilm unit uses a sulfur autotrophic denitrification reactor, which is an upflow plexiglass reactor. It is fed from the reactor water inlet 8 and drained from the reactor water outlet 1. A three-phase separator 5 and an exhaust port 3 are also provided therein. The reactor is 400 mm high, with an effective volume of 200 ml, the filler diameter is 80 mm, the height is 250 mm, and a sulfur-containing synthetic material 4 and volcanic stones 7 are filled. The filler is added through the feed port 2, evenly loaded in the biofilm unit, and the volume ratio is 9:1. Then 150 ml of sulfur autotrophic denitrification sludge (obtained by domestication and enrichment from Example 1) is added.

[0040] The reactor adopts a continuous influent mode, with the hydraulic retention time controlled at 8 h. The nitrate, nitrite, and total nitrogen contents in the effluent are detected daily to judge the start-up situation of the reactor. After 30 days of continuous influent, the nitrate removal rate of the reactor reaches 96.9%, with almost no nitrite accumulation, and the total nitrogen removal rate reaches 90%, indicating the completion of the reactor start-up.

[0041] After the reactor start-up is completed, it continues to operate under the same conditions for 10 days. The reactor operates well and can maintain a stable denitrification efficiency, with the total nitrogen removal rate being 90.23±2.36%.

[0042] After 40 days of reactor operation, representative heavy metal ions (copper ions) are added to the influent, and the copper ion concentration is gradually increased in five stages. The influent copper ion concentrations are 1, 2, 5, 10, and 20 mg / L respectively. The reactor operates for 50 days under the influence of copper ions. The reactor operates for a total of 90 days and is divided into P 0 、P 1 、P 2 、P 3 、P 4 、P 5 Six stages according to the influent copper ion concentration. The changes in the denitrification performance of the reactor in these six stages are as Figure 2 shown.

[0043] Under the influence of copper ions, the denitrification performance of the sulfur autotrophic denitrification system is not significantly affected as a whole. Copper ions at 1-2 mg / L have no obvious effect on the denitrification performance of the reactor, and the average total nitrogen removal rate remains at about 90%. The denitrification efficiency of the reactor decreases significantly at the initial stage of influent with 2 and 5 mg / L copper ions, and the total nitrogen removal rates drop to 77.41% and 75.57% respectively, and recover after a period of time. Copper ions at 5 mg / L have a certain impact on the denitrification performance of the reactor. Obvious continuous nitrate accumulation is observed during the influent of 5 mg / L copper ions, and the average total nitrogen removal efficiency drops to 85.35%. When the influent copper ion concentration is increased to 10 mg / L, the nitrate accumulation gradually decreases, and the average total nitrogen removal efficiency increases to 91.59%. When the influent copper ion concentration is increased to 20 mg / L, no nitrate and nitrite accumulation is observed, and the average total nitrogen removal efficiency is as high as 95.53%. These results indicate that the copper ion resistance of the sulfur autotrophic denitrification system is improved after being domesticated and adapted to low-concentration copper ions.

[0044] 2. Microbial community analysis

[0045] Samples were collected from sampling port 6 of the reactor for P 0 、P 2 、P 3 、P 5The microbial samples at the end of each stage, named S11, S12, S13, and S14 respectively, were analyzed by high-throughput sequencing technology to study the changes in the microbial community composition in the reactor under the influence of copper ions, and the relative abundance diagrams of the species composition at each stage were obtained. The results are as Figure 4 shown.

[0046] From Figure 4 it can be seen that under the influence of 2 and 5 mg / L copper ions, the relative abundance of the key sulfur autotrophic denitrifying bacterium Thiobacillus in the reactor decreased significantly, from 12.8% in the P 0 stage to 9.5% and 10.5%, while it increased to 15.4% in the P 5 stage. The change trend of the relative abundance of Thiobacillus was consistent with the change trend of the denitrification performance of the reactor, indicating that domestication and adaptation to low-concentration copper ions can improve the resistance of Thiobacillus to copper ions, so that the reactor can still maintain high-efficiency denitrification performance under the influence of high-concentration copper ions.

[0047] 3. Copper ion transformation process

[0048] In this case, shake-flask batch experiments were used to reveal the possible copper ion transformation process in the reactor. The specific settings are shown in Table 1. After all the experimental flasks were prepared, they were placed in a shaker and cultured at 150 r and 30 °C. Samples were taken regularly to measure the concentration of copper ions in the water body.

[0049] Table 1 Experimental group serial number Component composition Z1 100 mL pure water Z2 <![CDATA[100 mL synthetic wastewater (lacking NaHCO 3 )]]> Z3 <![CDATA[100 mL synthetic wastewater (lacking KH 2 PO 4 )]]> Z4 100 mL pure water + sulfur-containing synthetic material

[0050] The changes in the copper ion concentration of each experimental group in the batch experiment are shown in Table 2 (unit: mg / L):

[0051] Table 2

[0052] Comparing Z2 and Z1, it can be seen that KH 2 PO 4 has a weak copper ion removal ability. Comparing Z3 and Z1, it can be seen that the copper ion removal ability of NaHCO 3 is significant, and it can remove 87.19% of the copper ions. Comparing Z4 and Z1, it can be seen that the sulfur-containing material has a strong copper ion removal ability and can remove 41.13% of the copper ions.

[0053] From the above experimental results, it can be seen that the constructed sulfur autotrophic denitrification system has excellent nitrogen removal performance. After adaptation to low-concentration copper ions, its resistance to copper ions has been improved, and it can tolerate the influence of up to 20 mg / L copper ions. Bicarbonate and sulfur-containing materials in the system have made important contributions to the removal of copper ions. Especially bicarbonate can remove 87.19% of copper ions alone.

[0054] The above is only a preferred embodiment of the present invention, and thus the scope of implementation of the present invention cannot be limited thereby. For those skilled in the art, equivalent changes and modifications made according to the scope of the present invention patent and the content of the specification are all within the protection scope of the present invention.

Claims

1. A heavy metal-tolerant sulfur autotrophic denitrification system, characterized in that: The system consists of three units, namely a wastewater supply unit, a bacterial strain supply unit and a biofilm unit; the wastewater supply unit is connected to the biofilm unit to supply wastewater to the biofilm unit; the bacterial strain supply unit adopts an independent cultivation mode, and the bacterial strain is supplied to the biofilm unit for use after being cultivated to maturity; the biofilm unit is loaded with fillers; the fillers include sulfur-containing synthetic materials and volcanic rocks; the bacterial strains are mainly sulfur autotrophic denitrifying bacteria.

2. The sulfur autotrophic denitrification system according to claim 1, characterized in that: The sulfur autotrophic denitrifying bacteria are obtained by domestication and enrichment by successively using thiosulfate and elemental sulfur as electron donors.

3. The sulfur autotrophic denitrification system according to claim 1, characterized in that: The sulfur autotrophic denitrifying bacteria can be rapidly domesticated and enriched within a period of 20 days.

4. The sulfur autotrophic denitrification system according to claim 1, characterized in that: The mass ratio of elemental sulfur, calcium carbonate and liquid sodium silicate in the sulfur-containing synthetic material is 5:2:

14. After being evenly mixed, the material is cured at 125° C. for 12 hours.

5. The sulfur autotrophic denitrification system according to claim 1, characterized in that: The sulfur-containing synthetic material and volcanic rock are mixed and loaded into the biofilm unit at a volume ratio of 9:

1.

6. The sulfur autotrophic denitrification system according to claim 1, characterized in that: The biofilm unit is supported in a thermostatic upflow reactor.

7. The sulfur autotrophic denitrification system according to claim 1, characterized in that: The biofilm unit needs to be started by continuously passing wastewater and acclimated with low-concentration heavy metal wastewater.

8. Use of the sulfur autotrophic denitrification system as claimed in any of claims 1 to 7 in biological denitrification of low carbon-nitrogen ratio wastewater containing heavy metals.

9. The use according to claim 8, characterized in that: The applications include maintaining stable operation, high denitrification efficiency, and high heavy metal removal rate in the presence of high concentrations of heavy metal ions.

10. A method for denitrification of heavy metal wastewater, characterized in that: The method achieves the removal of nitrates and heavy metals simultaneously through an integrated reactor.

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