Organic wastewater treatment system and method

Abstract

The invention relates to the technical field of water treatment, and discloses an organic wastewater treatment system and method. The organic wastewater treatment system comprises a first anaerobic unit, a deamination unit and a second anaerobic unit which are connected in sequence, the first anaerobic unit comprises an anaerobic reactor, and the number of stages of the anaerobic reactor is 1 + N (N is an integer greater than or equal to 0); the second anaerobic unit comprises an anaerobic reactor, and the number of stages of the anaerobic reactor is 1 + M (M is an integer greater than or equal to 0). According to the organic wastewater treatment system provided by the invention, the deamination unit is additionally arranged between the anaerobic units, and the deamination unit can effectively remove free ammonia generated by primary anaerobic treatment, so that the influence of anaerobic treatment intermediate metabolites on methanation reaction is reduced, the methanation reaction in subsequent anaerobic treatment is ensured, and the yield of the organic wastewater is improved. The treatment effect of anaerobic treatment on organic wastewater is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular to a system and method for treating organic wastewater. Background Art

[0002] Nicotinamide, also known as vitamin B6 or nicotinic acid, is produced by oxidizing β-methylpyridine to nicotinic acid through air, then reacting with ammonium hydroxide, and then heating and dehydrating. The production wastewater mainly comes from the extraction and refining process. Most industrial wastewaters such as nicotinamide wastewater have defects such as high concentration of organic pollutants, high concentration of organic nitrogen, high content of difficult-to-biodegrade pollutants, difficulty in treatment, and poor treatment effect.

[0003] The existing treatment processes for industrial wastewater with high pollutant concentration and high organic nitrogen concentration mainly include: multiple-effect evaporation, advanced oxidation, aerobic contact oxidation and anaerobic treatment, among which anaerobic treatment has the advantages of low operating cost, high ammoniation efficiency and low investment, but it is found in practice that anaerobic treatment has the disadvantage of low COD removal rate (sometimes even less than 10%), and the low COD removal rate obviously limits the application of anaerobic treatment process in the field of wastewater treatment with high pollutant concentration and high organic nitrogen concentration. Discovering the main factors affecting the efficiency of anaerobic treatment and reducing its influence on the efficiency of anaerobic treatment is of great significance to promoting the application of anaerobic process in the treatment of high-concentration organic wastewater and improving the effect of organic wastewater treatment. Summary of the invention

[0004] The present invention aims to solve at least one of the above-mentioned technical problems existing in the prior art. To this end, one of the purposes of the present invention is to provide a system for treating organic wastewater; the second purpose of the present invention is to provide a method for treating organic wastewater; the third purpose of the present invention is to provide a system for treating organic wastewater, or the application of the method for treating organic wastewater.

[0005] The basic principle of the present invention is described as follows:

[0006] 1) The inventors have found through research that the intermediate metabolites of anaerobic treatment, especially the high concentration of ammonia produced by anaerobic ammoniation, are the main factors leading to the low anaerobic COD removal rate. High concentration of ammonia leads to an increase in the concentration of free ammonia in the wastewater, and the high concentration of free ammonia significantly inhibits the methanogenic reaction of anaerobic treatment, resulting in the anaerobic reaction mostly staying in the hydrolysis stage. The metabolic intermediates produced by hydrolysis cannot be effectively converted to inorganic form through methanogenesis, thereby limiting the removal of COD. Based on this, the present invention provides an organic wastewater treatment system comprising a first anaerobic unit, a deammoniation unit and a second anaerobic unit.

[0007] 2) The first anaerobic unit includes one or more anaerobic reactors, and the wastewater mainly undergoes ammoniation reaction and partial methanation reaction in the first anaerobic unit, so that organic nitrogen is metabolized into small molecular metabolites such as organic acids and ammonia nitrogen under anaerobic conditions;

[0008] 3) The deamination unit can denitrify wastewater, remove free ammonia that inhibits methanation, and ensure the smooth progress of subsequent methanation reactions;

[0009] 4) The second anaerobic unit also includes one or more anaerobic reactors. The methanogenic reaction is mainly carried out in the second anaerobic unit. The organic matter in the wastewater and the organic acid produced by the metabolism of the first anaerobic unit are further degraded and methanogenic under anaerobic conditions, thereby achieving deep removal of COD.

[0010] 5) The first anaerobic unit and the second anaerobic unit in the organic wastewater treatment system independently include one-stage or multiple-stage anaerobic reactors. When multiple-stage anaerobic reactors are used, due to the different concentrations and components of influent pollutants in each stage of the reactor, the microbial population suitable for the influent conditions can be domesticated and cultivated in the single-stage reactor to achieve single-stage optimized treatment and the effect of comprehensive optimal treatment.

[0011] In order to achieve the above object, the technical solution adopted by the present invention is:

[0012] A first aspect of the present invention provides an organic wastewater treatment system, comprising a first anaerobic unit, a deammoniation unit, and a second anaerobic unit connected in sequence;

[0013] The first anaerobic unit includes an anaerobic reactor, and the number of stages of the anaerobic reactor is 1+N (N is an integer greater than or equal to 0);

[0014] The second anaerobic unit includes an anaerobic reactor, and the number of stages of the anaerobic reactor is 1+M (M is an integer greater than or equal to 0).

[0015] Preferably, in the first and second anaerobic units, when the number of stages of the anaerobic reactors is greater than 1, the anaerobic reactors are connected in series.

[0016] Preferably, the hydraulic retention time of the organic wastewater in each stage of the anaerobic reactor is 1-120 hours; further preferably, the hydraulic retention time of the organic wastewater in each stage of the anaerobic reactor is 24-48 hours.

[0017] Preferably, the temperature in the anaerobic reactor is 35-40°C; further preferably, the temperature in the anaerobic reactor is 35-38°C.

[0018] Preferably, the pH value in the anaerobic reactor is 6.5-8.5; further preferably, the pH value in the anaerobic reactor is 6.8-8.2.

[0019] Preferably, the anaerobic reactor adopts a bottom water inlet and top water outlet mode.

[0020] Preferably, the anaerobic reactor is filled with biological carriers respectively; further preferably, the biological carriers include at least one of activated carbon, polyurethane foam, and ball rings; and the anaerobic organisms mainly grow on the biological carriers.

[0021] Preferably, the filling ratio of the biological carrier in the anaerobic reactor is selected from 5-100%; further preferably, the filling ratio of the biological carrier in the anaerobic reactor is selected from 50-70%.

[0022] Preferably, the biological carrier adopts a fixed bed or a fluidized bed.

[0023] Specifically, the biological carrier can be a regular or irregular filler. For industrial wastewater with simple pollutant composition but complex pollutant structure, it is generally difficult to generate granular sludge by anaerobic treatment. The use of biological carriers can increase the sludge concentration in the reactor on the one hand, and improve the reactor's ability to resist shock loads on the other hand. In addition, the use of biological carriers can reduce the loss of sludge in the anaerobic reactor, and the effluent from the reactor can be directly used for other subsequent treatments without considering the sludge return problem.

[0024] Preferably, in the first and second anaerobic units, a circulation pump is used to force the wastewater to circulate; the forced circulation can enhance the solid-liquid contact.

[0025] Preferably, the hydraulic retention time of the circulating water is 1-2 hours; further preferably, the hydraulic retention time of the circulating water is 1.5-2 hours.

[0026] Preferably, the deamination unit comprises an ammonia nitrogen stripping tower.

[0027] Preferably, the gas-liquid ratio in the ammonia nitrogen stripping tower is (1000-25000):1; further preferably, the gas-liquid ratio in the ammonia nitrogen stripping tower is (20000-25000):1.

[0028] Preferably, the length-to-diameter ratio of the ammonia nitrogen stripping tower is (8-12):1; further preferably, the length-to-diameter ratio of the ammonia nitrogen stripping tower is (9-11):1.

[0029] Preferably, the ammonia nitrogen stripping tower comprises an empty tower or a packed tower.

[0030] Preferably, the packed tower is filled with structured or non-structured packing to expand the gas-liquid contact area and improve the mass transfer efficiency.

[0031] Preferably, in the ammonia nitrogen stripping tower, wastewater enters from the top of the tower and flows to the bottom of the tower after water distribution, and air enters from the bottom of the tower and flows to the top of the tower, forming a countercurrent flow of gas and liquid.

[0032] Specifically, gas deammoniation is carried out at room temperature in an ammonia nitrogen stripping tower, and free ammonia in the downwardly flowing wastewater is transferred to the gas phase and flows out from the top of the tower with air, thereby achieving deammoniation of the wastewater.

[0033] The second aspect of the present invention provides a method for treating organic wastewater, comprising treating the organic wastewater using the organic wastewater treatment system according to the first aspect of the present invention.

[0034] Preferably, the processing method specifically comprises the following steps:

[0035] The organic wastewater is sequentially subjected to anaerobically treatment in the first anaerobic unit, physicochemical treatment in the deammoniation unit, and methanogenic reaction in the second anaerobic unit to obtain treated water.

[0036] Preferably, before the wastewater enters the deammoniation unit, a step of adjusting pH is also included.

[0037] Preferably, the pH of the wastewater is adjusted to be greater than 10 before entering the deamination unit; further preferably, the pH of the wastewater is adjusted to 12-13 before entering the deamination unit.

[0038] Preferably, before the wastewater enters the second anaerobic unit, a step of adjusting pH is also included.

[0039] Preferably, the pH of the wastewater is adjusted to 6-9 before entering the second anaerobic unit; further preferably, the pH of the wastewater is adjusted to 6.5-8.5 before entering the second anaerobic unit.

[0040] Preferably, the water quality parameters of the organic wastewater include at least one of the following: TKN>1000mg / L; TOC>5000mg / L; NH3-N>400mg / L; further preferably, the water quality parameters of the organic wastewater include at least one of the following: TKN=2000-5000mg / L; TOC=8000-11000mg / L; NH3-N=400-700mg / L.

[0041] The third aspect of the present invention provides the organic wastewater treatment system described in the first aspect of the present invention, or the use of the organic wastewater treatment method described in the second aspect of the present invention in the treatment of nicotinamide production wastewater.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1) The organic wastewater treatment system provided by the present invention has a deamination unit added between the anaerobic units. The deamination unit can effectively remove the free ammonia generated by the initial anaerobic treatment, reduce the influence of the intermediate metabolites of the anaerobic treatment on the methanogenesis reaction, ensure the methanogenesis reaction in the subsequent anaerobic treatment, and improve the treatment effect of the anaerobic treatment on the organic wastewater;

[0044] 2) Compared with the traditional anaerobic treatment, the method for treating organic wastewater provided by the present invention can significantly improve the treatment effect of wastewater with high organic nitrogen and high organic pollutant concentrations such as TKN>1000mg / L; TOC>5000mg / L; NH3-N>400mg / L;

[0045] 3) The method for treating organic wastewater provided by the present invention can achieve deep removal of TKN, NH3-N and TOC by preliminarily treating wastewater with high organic nitrogen and high organic pollutant concentrations and then combining it with aerobic biological treatment. Compared with the traditional anaerobic coupled aerobic biological treatment process, the removal effects of TKN, NH3-N and TOC are significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a schematic diagram of the structure of the organic wastewater treatment system of the present invention. DETAILED DESCRIPTION

[0047] The present invention is further described in detail below by specific examples. Unless otherwise specified, the raw materials, reagents or devices used in the examples and comparative examples can be obtained from conventional commercial sources or can be obtained by prior art methods. Unless otherwise specified, the experiments or test methods are conventional methods in the art.

[0048] Figure 1 It is a schematic diagram of the structure of the organic wastewater treatment system of the present invention, comprising Figure 1 It can be seen that the organic wastewater treatment system provided by the present invention comprises a first anaerobic unit, a deammoniation unit and a second anaerobic unit connected in sequence, and the first anaerobic unit and the second anaerobic unit contain anaerobic reactors. The organic wastewater treatment system is described below in combination with embodiments and comparative examples:

[0049] Example 1

[0050] In this example, nicotinamide wastewater is treated, and the water quality indicators of nicotinamide wastewater are shown in Table 1:

[0051] Table 1 Water quality indicators of nicotinamide wastewater

[0052] Water quality indicators TKN <![CDATA[NH3-N]]> TOC concentration 2640mg / L 456mg / L 9230mg / L

[0053] The organic wastewater treatment system used is composed of a first anaerobic unit, a deammoniation unit and a second anaerobic unit, wherein the first anaerobic unit contains a first-stage anaerobic reactor, in which ball rings and polyurethane foam biological carriers (volume ratio is 1:1) are filled, and the filling rate of the biological carrier is 60%; the reactor adopts the method of bottom water inlet and top water outlet, and a circulating pump is used for forced circulation of wastewater to strengthen solid-liquid contact; the temperature in the reactor is 35-38°C, the pH is 6.8-8.2, the hydraulic retention time of the inlet water is 1.5d, and the hydraulic retention time of the circulating water is 2h;

[0054] The deamination unit uses an empty ammonia nitrogen stripping tower with a length-to-diameter ratio of 10:1. A solid cone spiral nozzle is used on the top of the tower for water distribution, and the gas-liquid ratio is 23000:1.

[0055] The second anaerobic unit contains a first-stage anaerobic reactor, which is filled with ball rings and polyurethane foam bio-carriers (volume ratio is 1:1), and the filling rate of the bio-carrier is 60%; the reactor adopts the method of bottom water inlet and top water outlet, and uses a circulating pump to force the wastewater to circulate in order to strengthen the solid-liquid contact; the temperature in the reactor is 35-38°C, the pH is 6.8-8.2, the hydraulic retention time of the inlet water is 3d, and the hydraulic retention time of the circulating water is 1.5h.

[0056] The treatment of nicotinamide wastewater includes the following steps:

[0057] S1, the wastewater enters the first anaerobic unit for anaerobic treatment, and the TKN content in the effluent is 2595mg / L, the NH3-N content is 2483mg / L, and the TOC content is 8166mg / L;

[0058] S2. After sodium hydroxide was added to the effluent of the first anaerobic unit to adjust the pH to 12.5, the wastewater was fed into the top of the ammonia nitrogen stripping tower, and air was fed into the tower from the bottom. The free ammonia in the wastewater flowing downward was transferred to the gas phase and flowed out from the top of the tower with the air. The TKN content in the effluent of the ammonia nitrogen stripping tower was 273 mg / L, the NH3-N content was 152 mg / L, and the TOC content was 7920 mg / L.

[0059] S3. After adding hydrochloric acid to the effluent of the ammonia nitrogen stripping tower to adjust the pH to 6.8-8.2, the wastewater enters the second anaerobic unit for methanation reaction. The TKN content in the effluent is 264 mg / L, the NH3-N content is 227 mg / L, and the TOC content is 1860 mg / L.

[0060] Comparative Example 1

[0061] This comparative example uses the traditional anaerobic process to treat nicotinamide wastewater. The water quality indicators are shown in Table 1. The treatment steps are as follows:

[0062] A two-stage series anaerobic reactor was used for treatment. The reactors were filled with ball rings and polyurethane foam bio-carriers (volume ratio of 1:1), and the filling rate of the bio-carrier was 60%. The reactor adopted the method of bottom water inlet and top water outlet, and a circulating pump was used for forced circulation of wastewater to enhance solid-liquid contact. The temperature in the reactor was 35-38°C, the pH was 6.8-8.2, the hydraulic retention time of the inlet water was 1.5d, the hydraulic retention time of the circulating water was 2h, the TKN content in the effluent was 2613mg / L, the NH3-N content was 2566mg / L, and the TOC content was 7985mg / L.

[0063] Comparative Example 2

[0064] This comparative example uses a process combining anaerobic and aerobic activated sludge methods to treat nicotinamide wastewater, wherein the aerobic activated sludge method is a commonly used treatment method for nicotinamide wastewater. The water quality indicators are shown in Table 1. The treatment steps are as follows:

[0065] S1. The treated water in Comparative Example 1 was diluted 10 times with distilled water and then treated with an aerobic activated sludge method. The water treatment conditions were: microporous aeration was used to control the dissolved oxygen concentration to be greater than 2 mg / L, the activated sludge concentration was 3-4 g / L, the temperature was 25-30°C, the pH was 6.5-8.5 (pH was adjusted using sodium bicarbonate), and the inlet hydraulic retention time was 24 h; the TKN content in the effluent of the aerobic reactor was 252 mg / L, the NH3-N content was 121 mg / , and the TOC content was 153 mg / L.

[0066] Comparative Example 3

[0067] The water treated in Example 1 was diluted 10 times with distilled water and then treated with an aerobic activated sludge method. The water treatment conditions were: microporous aeration was used to control the dissolved oxygen concentration to be greater than 2 mg / L, the activated sludge concentration was 3-4 g / L, the temperature was 25-30°C, the pH was 6.5-8.5 (pH was adjusted using sodium bicarbonate), and the inlet hydraulic retention time was 24 h; the TKN content in the effluent of the aerobic reactor was 25 mg / L, the NH3-N content was 0.3 mg / L, and the TOC content was 15 mg / L.

[0068] Table 2 Pollutant removal rates in Example 1 and Comparative Examples 1-3

[0069] TKN <![CDATA[NH3-N]]> TOC Example 1 90.0％ 50.2％ 79.8％ Comparative Example 1 1.0％ -462.7％ 13.5％ Comparative Example 2 90.5％ 73.5％ 98.3％ Application Example 1 99.1％ 99.9％ 99.8％

[0070] Table 2 shows the pollutant removal rates in Example 1 and Comparative Examples 1-3. It can be seen from Table 2 that in Comparative Example 1, only a series of anaerobic reactors were used to treat nicotinamide wastewater with high organic nitrogen concentration and high organic pollutant concentration. The removal rates of organic nitrogen and organic pollutants were low, and due to anaerobic ammoniation, the NH3-N concentration in the wastewater increased sharply.

[0071] The treatment method in Example 1 is actually based on Comparative Example 1, in which a deammoniation unit is added between the two-stage anaerobic reactors, and an ammonia nitrogen stripping tower is used to remove free ammonia in the original wastewater and produced by the primary anaerobic treatment, and then a secondary anaerobic treatment is carried out. Since the free ammonia that is inhibitory to methanogenesis is removed in large quantities, the concentrations of TKN, NH3-N and TOC in the effluent of the secondary anaerobic treatment are greatly reduced. Compared with Comparative Example 1, the removal rates of TKN, NH3-N and TOC are significantly improved, indicating that the wastewater treatment system and method provided by the present invention significantly reduce the influence of the intermediate metabolites of anaerobic treatment on the COD removal effect, and ensure the smooth progress of the subsequent methanogenesis reaction.

[0072] In Comparative Example 2, the wastewater treated in the two-stage series anaerobic reactor was diluted and then treated by aerobic activated sludge method. It can be seen that the removal effects of TKN and TOC are good, with removal rates reaching more than 90%, but the removal effect of NH3-N is relatively poor, with a removal rate of only 73.5%.

[0073] In Comparative Example 3, the effluent treated by the device and method provided by the present invention was diluted and then treated by an aerobic activated sludge method. When the operating conditions of the aerobic activated sludge method were exactly the same as those in Comparative Example 2, the removal effects of TKN, NH3-N and TOC were improved, and the removal rates all reached more than 99%, achieving deep treatment of nicotinamide wastewater with high organic nitrogen concentration and high organic pollutant concentration.

Claims

1. A system for treating organic wastewater, characterized in that: It includes a first anaerobic unit, a deammoniation unit and a second anaerobic unit connected in sequence; The first anaerobic unit includes an anaerobic reactor, and the number of stages of the anaerobic reactor is 1+N (N is an integer greater than or equal to 0); The second anaerobic unit includes an anaerobic reactor, and the number of stages of the anaerobic reactor is 1+M (M is an integer greater than or equal to 0).

2. The processing system according to claim 1, characterized in that In the first and second anaerobic units, when the number of stages of the anaerobic reactors is greater than 1, the anaerobic reactors are connected in series; And / or, the hydraulic retention time of the organic wastewater in each stage of the anaerobic reactor is 1-120h; and / or, the temperature in the anaerobic reactor is 35-40° C.; And / or, the pH value in the anaerobic reactor is 6.5-8.

5.

3. The processing system according to claim 1, characterized in that The anaerobic reactor is filled with biological carriers respectively; Preferably, the bio-carrier comprises at least one of activated carbon, polyurethane foam and Pall ring.

4. The processing system according to claim 3, characterized in that The filling ratio of the biological carrier in the anaerobic reactor is selected from 5-100%.

5. The processing system according to claim 1, characterized in that The deamination unit comprises an ammonia nitrogen stripping tower.

6. The processing system according to claim 5, characterized in that The gas-liquid ratio in the ammonia nitrogen stripping tower is (1000-25000):

1.

7. A method for treating organic wastewater, characterized in that: The method comprises using the organic wastewater treatment system according to any one of claims 1 to 6 to treat organic wastewater.

8. The processing method according to claim 7, characterized in that: The processing method specifically comprises the following steps: The organic wastewater is sequentially subjected to anaerobically treatment in the first anaerobic unit, physicochemical treatment in the deammoniation unit, and methanogenic reaction in the second anaerobic unit to obtain treated water.

9. The processing method according to claim 7, characterized in that: The water quality parameters of the organic wastewater include at least one of the following: TKN>1000mg / L; TOC>5000mg / L; NH3-N>400mg / L.

10. Use of the organic wastewater treatment system according to any one of claims 1 to 6, or the organic wastewater treatment method according to any one of claims 7 to 9 in the treatment of nicotinamide production wastewater.

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