Method for treating catalyst wastewater by combined biochemical denitrification

Abstract

The invention discloses a method for treating catalyst wastewater by a combined biochemical denitrification method, which adopts fluidized bed anaerobic denitrification (ADFB), two-stage AO, a secondary sedimentation tank and a biological filter, the wastewater enters an ADFB anaerobic denitrification fluidized bed system after the water quality is balanced by a regulating tank, and after most of total nitrate radicals in the water are removed, the wastewater enters a two-stage A / O system to further remove organic matters and SS (suspended solids) in the water; the wastewater, backwashing water of the reverse osmosis system, concentrated water and the like jointly enter a biological aerated filter system for treatment, and finally the wastewater reaches the standard and is discharged.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental engineering, and in particular relates to a method for treating catalyst wastewater by a combined biochemical denitrification process. Background Art

[0002] In the catalyst production process, the deionized water used to rinse the intermediate products will produce a large amount of nitrate-containing rinse wastewater, in which excessive nitrogen will cause eutrophication of the water body, affecting water quality and water ecology. Due to the implementation of the local standard "Chemical Industry Water Pollutant Discharge Standard" (DB32 / 939-2020), as shown in Table 1, especially the requirement of total nitrogen ≤15mg / L, catalyst wastewater can no longer be incorporated into the comprehensive wastewater station for treatment.

[0003] Table 1 Effluent indicators of the Chemical Industry Water Pollutant Discharge Standard

[0004] Common denitrification methods include physical denitrification, chemical denitrification and biochemical denitrification. The removal effect of physical denitrification technology is not ideal and the cost is high. The chemical denitrification technology uses chemical agents, the waste liquid generated is difficult to treat, the operating cost is high, and it is very likely to cause secondary pollution to the environment. Therefore, biological denitrification technology is widely used in wastewater treatment as a relatively economical and efficient method for treating wastewater.

[0005] Currently, most of the more mature and reliable biological denitrification processes use the traditional A / O activated sludge denitrification process. Part of the nitrogen in the effluent is nitrate nitrogen or nitrite nitrogen that has not been completely denitrified, resulting in the total nitrogen in the effluent failing to meet the standard. Summary of the invention

[0006] The purpose of the present invention is to provide an improved combined biochemical denitrification method for treating catalyst wastewater so as to meet the discharge standards.

[0007] The technical solution adopted by the present invention is: a method for treating catalyst wastewater by combined biochemical denitrification, characterized in that high-concentration nitrate catalyst wastewater is treated in sequence by a fluidized bed anaerobic denitrification ADFB unit, a two-stage activated sludge denitrification A / O unit, a secondary sedimentation tank and an aerated biological filter, and finally meets the discharge standards; the nitrate catalyst wastewater COD≤50 mg / L, TN1500-1800 mg / L, SS≤10000 mg / L, and the flow rate is 50m 3 / h.

[0008] Generally, the high-concentration nitrate-nitrogen catalyst wastewater of the present invention enters the ADFB anaerobic denitrification fluidized bed system after the water quality is balanced in the regulating tank, and most of the nitrate ions are removed, and the total nitrogen value TN is ≤200 mg / L. Then it enters the two-stage activated sludge denitrification A / O unit and the secondary sedimentation tank to further remove organic matter and SS in the water, and the total nitrogen value TN is ≤15 mg / L. Finally, it enters the aerated biological filter for treatment, COD≤50 mg / L, TN≤15 mg / L, SS≤330 mg / L, and finally meets the discharge standards.

[0009] Furthermore, the anaerobic denitrification fluidized bed (ADFB) unit: The entire system is a treatment tank, including a biological fluidization treatment tower, a circulating reflux device and a gas-liquid-solid three-phase separator. Under anaerobic conditions, the tank is filled with fine high-density carriers to provide a huge surface area for denitrifying bacteria to attach, greatly increasing the sludge concentration in the system, and utilizing a rapid rising water flow to fluidize the biofilm carrier, increasing the substrate transfer rate and removing a large amount of nitrate ions.

[0010] Furthermore, the two-stage A / O unit and the secondary sedimentation tank: the anoxic section and the aerobic section are connected in series. In the anoxic section, heterotrophic bacteria can utilize organic matter in the water during the denitrification process to convert NO 3- Reduction to molecular nitrogen N 2 , completing the cycle of C, N, and O in the ecology, the anoxic effluent enters the aerobic zone, and with the participation of aerobic microorganisms in the aerobic zone, the organic matter in the wastewater is degraded and transformed, thereby gradually achieving the effect of removing COD; Pool A pH = 7.5-8; Pool O pH = 7; Mixed liquor reflux 300-400%.

[0011] Furthermore, the purification process of activated sludge is divided into an adsorption stage, an oxidation stage, and a floc formation and coagulation sedimentation stage.

[0012] Furthermore, in the adsorption stage, pollutants in sewage are adsorbed and adhered to flocs formed by the microorganisms during contact with the activated sludge microorganisms.

[0013] Further, the oxidation stage: under aerobic conditions, microorganisms use part of the organic matter absorbed and taken into the body as nutrition to synthesize cellular substances, and the other part of the organic matter is decomposed and metabolized to release energy.

[0014] Further, floc formation and coagulation sedimentation stage: the bacteria synthesized in the oxidation stage flocculate to form flocs, which are separated from the water by gravity sedimentation, thereby purifying the water.

[0015] Furthermore, aerated biological filter: filter speed 2-8m 3 / (m 2 .h); aeration rate 4-8m 3 / (m2 .h) Microorganisms attach to the surface of the carrier. When sewage flows through the surface of the carrier, it oxidizes and decomposes pollutants through the adsorption of organic nutrients, the diffusion of oxygen into the biofilm, and the biological oxidation in the biofilm, removing SS, COD, BOD, nitrification, denitrification, phosphorus removal, and AOX, etc. It has strict requirements on the influent SS (SS≤100 mg / L), so it is placed after the A / O process.

[0016] Compared with other technologies, the present invention has the following advantages: By adopting the combined biochemical treatment process of the present invention, the key indicators such as COD and TN of the catalyst wastewater can meet the emission standards, effectively solving the problems existing in the traditional treatment technology. Compared with the traditional activated sludge denitrification process, the aerated biological filter has a high organic load, a small footprint, low investment, no sludge bulking, high oxygen transmission efficiency, good effluent quality, low operating energy consumption, and low operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the process flow of the method according to an embodiment of the present invention.

[0018] In the figure: 1-regulating tank, 2-ADFB unit, 3-primary A / O unit, 4-secondary A / O unit, 5-secondary sedimentation tank, 6-aerated biological filter, 7-sludge tank, 8-sludge filter pressing and drying, 9-high nitrate catalyst wastewater, 10-sludge return, 11-sludge discharge. Implementation

[0019] The present invention is further described in detail below with reference to the accompanying drawings and embodiments. Example

[0020] A combined biochemical denitrification method for treating catalyst wastewater Figure 1 , the specific process is as follows: The high nitrate catalyst wastewater 9 enters the regulating tank 1 to adjust the pH and balance the water quality and quantity. The wastewater passing through the regulating tank 1 enters the ADFB unit 2. Under the condition of anoxicity, the tower is filled with fine high-density carriers to provide a huge surface area for the attachment of denitrifying bacteria, which greatly increases the sludge concentration of the system. The biofilm carrier is fluidized by the rapid rising water flow, which increases the substrate transfer rate and removes a large number of nitrate ions. The wastewater passing through the ADFB unit 2 then enters the primary A / O unit 3 and the secondary A / O unit 4, and a carbon source is added to the A / O unit. In the A / O unit, the anoxic heterotrophic bacteria can use the organic matter in the water to convert NO 3- Reduction to molecular nitrogen (N 2), the anoxic effluent enters the aerobic zone, and with the participation of aerobic microorganisms in the aerobic zone, the organic matter in the wastewater is degraded and transformed, thereby gradually achieving the effect of removing COD. The effluent enters the secondary sedimentation tank 5. The purification process of activated sludge is divided into adsorption stage, oxidation stage and flocculent formation and coagulation sedimentation stage.

[0021] Adsorption stage: During the contact process between the pollutants in the sewage and the activated sludge microorganisms, they are adsorbed and adhered to the flocs formed by the microorganisms.

[0022] Oxidation stage: Under aerobic conditions, microorganisms use part of the organic matter absorbed and taken into the body as nutrition to synthesize cellular substances, and the other part of the organic matter is decomposed and metabolized to release energy.

[0023] Floc formation and coagulation sedimentation stage: The bacteria synthesized in the oxidation stage flocculate to form flocs, which are separated from the water by gravity sedimentation, thereby purifying the water.

[0024] Part of the sludge in the secondary sedimentation tank 5 is returned 10 to the primary A / O unit 3 and the secondary A / O unit 4, and part of it is discharged 11 into the sludge tank 7, and the sludge is filtered and dried 8.

[0025] The effluent passes through the aerated biological filter 6, and the microorganisms attach to the surface of the carrier. When the sewage flows through the surface of the carrier, the pollutants are oxidized and decomposed through the adsorption of organic nutrients, the diffusion of oxygen into the biofilm, and the biological oxidation occurring in the biofilm, and further remove SS, COD, BOD, nitrification, denitrification, phosphorus removal, AOX removal, etc., to achieve the target emission.

[0026] The present invention will be further described below in conjunction with specific embodiments. Example 1

[0027] A company producing copper-based catalysts selected the combined biochemical denitrification process of the above embodiment of the present invention to treat a large amount of high-concentration nitrate nitrogen wastewater. The influent indicators are shown in Table 2, and all indicators do not meet the emission standards of the "Emission Standards for Water Pollutants in the Chemical Industry" (DB32 / 939-2020).

[0028] Table 2 Influent water quality parameters

[0029] After 2 months of operation, the stable water inflow of the denitrification tower is 15-17 m 3 / h, the effluent indicators all meet the discharge requirements, ammonia nitrogen, TP, SS sampling and testing all meet the discharge requirements, the average COD value of the filter effluent is 41 mg / L, and the average TN value of the A / O effluent is 11.8 mg / L, which meets the indicator requirements.

[0030] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A combined biochemical denitrification method for treating catalyst wastewater, characterized in that The high-concentration nitrate catalyst wastewater is treated in sequence by the fluidized bed anaerobic denitrification ADFB unit, the two-stage activated sludge denitrification A / O unit, the secondary sedimentation tank and the aerated biological filter, and finally meets the discharge standards; the high-concentration nitrate catalyst wastewater COD≤50 mg / L, TN1500-1800 mg / L, SS≤10000 mg / L, the flow rate is 50m 3 / h.

2. The method according to claim 1, characterized in that The high-concentration nitrate catalyst wastewater enters the fluidized bed anaerobic denitrification ADFB unit after the water quality is balanced in the regulating tank to remove most of the nitrate ions, and the total nitrogen value TN≤200 mg / L. It then enters the two-stage activated sludge denitrification A / O unit and the secondary sedimentation tank to further remove organic matter and SS in the water, and the total nitrogen value TN≤15 mg / L. Finally, it enters the aerated biological filter for treatment, COD≤50 mg / L, TN≤15 mg / L, SS≤30 mg / L, and finally meets the discharge standards.

3. The method according to claim 1 or 2, characterized in that The fluidized bed anaerobic denitrification ADFB treatment tank adopts a tower form. The system includes a biological fluidization treatment tower, a circulating reflux device and a gas-liquid-solid three-phase separator. Under anaerobic conditions, the small high-density carriers filled in the treatment tank are used to provide a huge surface area for denitrifying bacteria to attach, increase the sludge concentration in the system, and use the rapid rising water flow to make the biofilm carrier fluidized, increase the substrate transfer rate, and remove most of the nitrate ions.

4. The method according to claim 1 or 2, characterized in that The two-stage activated sludge denitrification A / O unit has an anoxic section and an aerobic section connected in series. In the anoxic section, heterotrophic bacteria use organic matter in the water to convert NO 3 - Reduced to molecular nitrogen N2, completing the cycle of C, N, and O in the ecology. The anoxic effluent enters the aerobic section. With the participation of aerobic microorganisms, the organic matter in the wastewater is degraded and transformed, thereby gradually removing COD. The pH of pool A is 7.5-8; the pH of pool O is 7; the mixed liquor reflux is 300-400%.

5. The method according to claim 1 or 2, characterized in that In the secondary sedimentation tank, sludge return is 100-200%; the purification process of activated sludge is divided into adsorption stage, oxidation stage and floc formation and coagulation sedimentation stage.

6. The method according to claim 5, characterized in that Adsorption stage: During the contact process between the pollutants in the sewage and the activated sludge microorganisms, they are adsorbed and adhered to the flocs formed by the microorganisms.

7. The method according to claim 5, characterized in that Oxidation stage: Under aerobic conditions, microorganisms use part of the organic matter absorbed and taken into the body as nutrition to synthesize cellular substances, and the other part of the organic matter is decomposed and metabolized to release energy.

8. The method according to claim 5, characterized in that Floc formation and coagulation sedimentation stage: The bacteria synthesized in the oxidation stage flocculate to form flocs, which are separated from the water by gravity sedimentation, thereby purifying the water.

9. The method according to claim 1 or 2, characterized in that Aerated biological filter, filtration rate 2-8m 3 / (m 2 .h); aeration rate 4-8m 3 / (m 2 .h), microorganisms attach to the surface of the carrier. When the sewage flows through the surface of the carrier, the pollutants are oxidized and decomposed through the adsorption of organic nutrients, the diffusion of oxygen into the biofilm, and the biological oxidation occurring in the biofilm, removing SS, COD, BOD, nitrification, denitrification, phosphorus removal, and AOX.

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