A biological CANDAN "nitrogen-cutting" process for treating nitrogen-containing industrial wastewater

Abstract

The present invention discloses a biological CANDAN "nitrogen cutting" process for treating nitrogen-containing industrial wastewater. The specific steps of the process operation are as follows: 1) NH4 + -N industrial wastewater enters the pre-aeration reaction tank to remove most of the organic matter and suspended solids; 2) NO3 ‑ -N industrial wastewater enters the physicochemical treatment tank to remove heavy metals and other toxic and harmful substances to microorganisms; 3) The two types of wastewater enter the adjustment tank in a certain proportion to control the appropriate mass concentration ratio and pH of NO3 ‑ -N and NH4 + -N; 4) The mixed sewage in the adjustment tank and appropriate external organic matter enter the CANDAN "nitrogen cutting" reaction tank together to remove the inorganic nitrogen in the wastewater. The present invention can achieve synchronous and efficient denitrification of NH4 + -N and NO3 ‑ -N industrial wastewater under anaerobic conditions, solves the problems of low denitrification efficiency, large consumption of carbon sources, and high aeration energy consumption in the traditional biological denitrification process for treating nitrogen-containing industrial wastewater, and has important economic value and application prospects.

Description

Technical Field

[0001] The present invention relates to a biological CANDAN "nitrogen cutting" process for treating nitrogen-containing industrial wastewater, belonging to the field of industrial wastewater treatment. Background Art

[0002] Industrial wastewater is large in quantity, complex in composition, unstable in water quality and quantity, and contains abundant organic matter and nitrogen. Currently, common biological nitrogen removal technologies mainly include nitrification and denitrification, as well as the anaerobic ammonium oxidation technology that has developed rapidly in recent years.

[0003] Based on the traditional nitrification and denitrification process for treating industrial wastewater containing NH4 + -N and NO3 - -N, a large amount of aeration is required for the nitrification process, and external organic matter needs to be added as a carbon source for denitrification. The traditional nitrification and denitrification process can ensure stable operation and is applied in many water treatment plants worldwide. However, in the application process, it often faces problems such as being less economical and environmentally friendly and generating a large amount of greenhouse gases. Therefore, the research and development of more efficient and economical biological treatment processes are becoming one of the key issues of concern.

[0004] In recent years, the anaerobic ammonium oxidation technology that has received continuous attention is a nitrogen removal method in which anaerobic ammonium oxidizing bacteria convert NH4 + -N and NO2 - -N into N2 for removal under anaerobic conditions. As a new nitrogen removal process, the anaerobic ammonium oxidation process is attracting more and more attention due to its economic, efficient, and environmentally friendly advantages. Anaerobic ammonium oxidizing bacteria are relatively sensitive to changes in the living environment, and the concentration of anaerobic ammonium oxidation product NO3 - -N is relatively high under high-concentration substrate conditions. Multiple factors can cause difficulties such as unqualified effluent, which become the main problems hindering the application in the treatment of high-concentration substrate industrial wastewater.

[0005] Based on this, the present invention proposes to integrate short-cut denitrification and anaerobic ammonium oxidation in a single reactor for one-stage reaction. Under the premise of retaining the advantage of no aeration required for anaerobic ammonium oxidation, the short-cut denitrification process that requires less carbon source is coupled, enabling anaerobic ammonium oxidizing bacteria and short-cut denitrifying bacteria to react synchronously in a single reactor, thereby completely removing NH4 + -N, NO3 - -N, NO2 - -N (i.e., CANDAN, Complete Ammonium and Nitrate removal via Denitritation - Anammox over Nitrite). The short-cut denitrifying bacteria first use a small part of the carbon source in the water to convert NO3 - -N into NO2 --N, and then anaerobic ammonium oxidation bacteria remove NH4 in water + -N and NO2 - -N synchronously to generate N2 and a small amount of NO3 - -N, and NO3 - -N can participate in the short-cut denitrification process again. The CANDAN "nitrogen removal" process has the advantages of being able to treat various nitrogen species, high theoretical nitrogen removal rate, energy saving and consumption reduction, economic environmental protection, and environmental friendliness. Summary of the Invention

[0006] To solve the practical problems existing in the application of existing biological nitrogen removal technologies to industrial wastewater, a one-stage short-cut denitrification coupled with anaerobic ammonium oxidation process for nitrogen-containing industrial wastewater is provided, which realizes the complete removal of NH4 + -N, NO2 - -N and NO3 - -N (CANDAN) in the system. A pretreatment unit is set in the front section of this process to ensure that the effluent of the pretreatment unit is suitable for the growth of microorganisms, and the effluent then enters the CANDAN "nitrogen removal" reaction tank for biochemical treatment. It can not only retain the nitrogen removal advantage of anaerobic ammonium oxidation but also achieve deep nitrogen removal of wastewater by in-situ removing the NO3 - -N generated by anaerobic ammonium oxidation.

[0007] The technical problems to be solved by the present invention are achieved through the following technical solutions;

[0008] (1) NO3 - -N industrial wastewater enters the physicochemical treatment pool to remove heavy metals and other toxic and harmful substances for microorganisms, and the effluent enters the comprehensive wastewater regulation pool;

[0009] (2) NH4 + -N industrial wastewater enters the pre-aeration reaction tank to remove most of the organic matter and suspended solids, and the effluent enters the comprehensive wastewater regulation pool;

[0010] (3) Adjust the pH value of the comprehensive wastewater regulation pool to control the pH value within the range of 6.0 - 8.5;

[0011] (4) The mixed sewage in the comprehensive wastewater regulation pool and the organic matter in the carbon source reserve pool enter the CANDAN "nitrogen removal" reaction tank together to remove the inorganic nitrogen in the wastewater, and the effluent can reach the standard for discharge or further advanced reuse treatment.

[0012] During the operation of step (2), the NH4 + -N oxidation and removal rate in the pre-aeration reaction tank is controlled to be less than 20%, the COD / NH4 + -N mass concentration ratio of the effluent from the pre-aeration reaction tank is less than 2.0, and the suspended solid concentration is less than 1.0 g / L;

[0013] During the operation of step (3), by optimizing the volume ratio of NO3 - -N industrial wastewater and NH4 + -N industrial wastewater entering the integrated wastewater regulation tank, controlling the mass concentration ratio of NO3 - -N / NH4 + -N in the mixed wastewater of the regulation tank is 1.0 - 2.0;

[0014] During the operation of step (4), the organic matter in the carbon source reserve tank is the common denitrification commercial carbon sources such as sodium acetate, glucose or ethanol. Control the mass ratio of the organic matter in the carbon source reserve tank entering the CANDAN "nitrogen removal" reaction tank (COD / NO3 - -N) to the mass of NO3 - -N in the mixed sewage of the integrated wastewater regulation tank entering the CANDAN "nitrogen removal" reaction tank is 2.0 - 4.0;

[0015] During the operation of step (4), control the MLSS of the mixed sludge in the CANDAN "nitrogen removal" reaction tank within the range of 4.0 - 10.0 g / L;

[0016] During the operation of step (4), when the NH4 + -N and NO2 - -N in the effluent of the CANDAN "nitrogen removal" reaction tank is greater than 3.0 mg / L, extend the hydraulic retention time of the CANDAN "nitrogen removal" reaction tank; when the NH4 + -N and NO3 - -N in the effluent are greater than 3.0 mg / L, and NO2 - -N is less than 1.0 mg / L, increase the mass of the organic matter in the carbon source reserve tank entering the CANDAN "nitrogen removal" reaction tank; when the NH4 + -N in the effluent is greater than 5.0 mg / L, and NO2 - -N and NO3 - -N concentration sum is less than 3.0 mg / L, reduce the volume of NH4 + -N industrial wastewater entering the integrated wastewater regulation tank; when the NO3 - -N in the effluent is greater than 5.0 mg / L, and NH4 + -N is less than 1.0 mg / L, reduce the volume of NO3 - -N industrial wastewater entering the integrated wastewater regulation tank.

[0017] Integrating short-cut denitrifying bacteria and anaerobic ammonium oxidation bacteria in a single reaction tank, under appropriate regulation conditions, synergistic nitrogen removal can occur between the two. The short-cut denitrifying bacteria use the organic matter in the water to convert NO3 - -N into NO2 - -N, and the anaerobic ammonium oxidation bacteria convert the NO3 in the water- -N and NH4 + -N is converted to N2 for removal and a small amount of NO3 is generated. - -N, a small amount of NO3 generated by anaerobic ammonium oxidation bacteria - -N can participate in the reaction process in situ again, enabling the deep removal of organic matter and nitrogen in water.

[0018] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0019] (1) Realize the synergistic deep biological denitrification of high-concentration NO3 - -N wastewater and NH4 + -N wastewater. Utilize the synergistic effect of anaerobic ammonium oxidation bacteria and short-cut denitrifying bacteria to denitrify in an anaerobic environment and remove the NO3 - -N produced by anaerobic ammonium oxidation in situ. Achieve the deep and efficient treatment of nitrogen in high-concentration NH4 + -N, NO3 - -N mixed industrial wastewater, reduce the capital construction cost of the process, and is an economical and efficient biological denitrification process;

[0020] (2) Compared with the traditional nitrification-denitrification process, the CANDAN process reduces the addition of external carbon sources, does not require aeration to provide an aerobic environment, and reduces the investment in operating funds. At the same time, it produces fewer greenhouse gas by-products. It is an economical and environmentally friendly biological denitrification process;

[0021] (3) The process has relatively simple and controllable operating conditions. By controlling the mass concentration of COD / NO3 - -N, a stable and easily controllable NO2 - -N source can be obtained for anaerobic ammonium oxidation. Control the mass concentration of NO3 - -N / NH4 + -N to regulate the population quantity relationship between short-cut denitrifying bacteria and anaerobic ammonium oxidation bacteria, and achieve a stable synergistic treatment effect of the bacteria;

[0022] The present invention is applicable to the mixed and synergistic treatment of industrial wastewater such as photovoltaic wastewater, stainless steel pickling wastewater, leather-making wastewater, and coking wastewater. Description of the Drawings

[0023] Figure 1 is the process flow chart of the present invention.

[0024] Figure 2 is the schematic diagram of the device of the present invention. Detailed Embodiments

[0025] The following clearly describes the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. However, the technical solutions of the present invention are not limited to the embodiments.

[0026] Example 1. Refer to Figure 1 , a biological CANDAN "nitrogen cutting" process for treating nitrogen-containing industrial wastewater, which co-treats stainless steel pickling wastewater and coking wastewater. The NH4 + -N content in coking wastewater is 201.2 mg / L, COD is 1000.3 mg / L, and pH is 7.5; the NO3 - -N content in stainless steel pickling wastewater is 461.0 mg / L, COD is 65.2 mg / L, and pH is 2.0.

[0027] The coking wastewater and stainless steel pickling wastewater are respectively introduced into a pre-aeration reaction tank and a physico-chemical treatment tank for pretreatment, and then introduced into a comprehensive wastewater regulation tank according to a volume ratio of 2:1. Homogenization of the mixed wastewater and pH adjustment are carried out in the comprehensive wastewater regulation tank. The mass concentrations of NH4 + -N, NO3 - -N and COD are 122.1 mg / L, 151.0 mg / L, and 210.5 mg / L respectively, and pH is 7.2.

[0028] Subsequently, the mixed wastewater and sodium acetate are pumped into the CANDAN "nitrogen cutting" reaction tank together. Under the condition that the mass concentration ratio of the sodium acetate dosage to the NO3 - -N entering the reaction tank (COD / NO3 - -N) is 2.2, and the MLSS of the mixed sludge in the reaction tank is 5.0 g / L. Under the operating conditions that the reaction tank temperature is 22.0 - 28.0 °C and the hydraulic retention time is 4.0 h, the concentrations of NH4 + -N, NO2 - -N and NO3 - -N in the effluent of the long-term operating CANDAN "nitrogen cutting" reaction tank are 2.3 mg / L, 1.4 mg / L, and 1.3 mg / L respectively.

[0029] Example 2. Refer to Figure 1 , a biological CANDAN "nitrogen cutting" process for treating nitrogen-containing industrial wastewater, which co-treats tannery wastewater and photovoltaic wastewater. The NH4 + -N content in tannery wastewater is 113.1 mg / L, the NO3 - -N content is 6.6 mg / L, COD is 563.7 mg / L, and pH is 7.5. The NO3 - -N content in photovoltaic wastewater is 1202.8 mg / L, COD is 200.9 mg / L, and pH is 6.0.

[0030] The tannery wastewater and photovoltaic wastewater are respectively introduced into the pre-aeration reaction tank and the physicochemical treatment tank for pretreatment, and then introduced into the comprehensive wastewater regulation tank according to a volume ratio of 9:1. Homogenization of the mixed wastewater and pH adjustment are carried out in the comprehensive wastewater regulation tank. The concentrations of NH4 + -N, NO3 - -N and COD are 96.3 mg / L, 112.4 mg / L and 32.3 mg / L respectively, and the pH is 7.3.

[0031] Subsequently, the mixed wastewater and sodium acetate are pumped into the CANDAN "nitrogen removal" reaction tank together. Under the conditions that the mass concentration ratio of the sodium acetate dosage to the NO3 - -N entering the reaction tank (COD / NO3 - -N) is 2.5, the mixed sludge MLSS in the reaction tank is 6.0 g / L, the reaction tank temperature is 25 - 28 °C, and the hydraulic retention time is 3.0 h. During long-term operation, the average concentrations of NH4 + -N, NO2 - -N and NO3 - -N in the effluent of the CANDAN "nitrogen removal" reaction tank are 1.1 mg / L, 1.2 mg / L and 2.1 mg / L respectively.

[0032] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A biological CANDAN "nitrogen-cutting" process for treating nitrogen-containing industrial wastewater, the nitrogen-containing industrial wastewater including NO3 - -N industrial wastewater and NH4 + -N industrial wastewater, characterized in that, It includes the following steps: (1)NO3 - The industrial wastewater containing -N enters the physicochemical treatment tank to remove heavy metals, and the effluent enters the comprehensive wastewater regulation tank; (2)NH4 + The (2)NH4-N industrial wastewater enters the pre-aeration reaction tank to remove organic matter and suspended solids, and the effluent enters the comprehensive wastewater regulation tank; (3) Adjust the pH value of the comprehensive wastewater regulation tank to be within the range of 6.0 - 8.5; (4) Let the mixed sewage in the comprehensive wastewater regulation tank and the organic matter in the carbon source reserve tank enter the CANDAN "nitrogen cutting" reaction tank together to remove the inorganic nitrogen in the wastewater, and the effluent is discharged or further reused for treatment; In the operation process of step (2), the NH4 + -N oxidation and removal rate in the pre-aeration reaction tank is less than 20%, and the mass concentration ratio of COD / NH4 + -N in the effluent of the pre-aeration reaction tank is less than 2.0, and the suspended solid concentration is less than 1.0 g / L; The operation process of step (3) optimizes NO3 - -N industrial wastewater and NH4 + -N industrial wastewater entering the volume ratio of the integrated wastewater regulation tank, controlling the NO3 of the mixed wastewater in the regulation tank - -N / NH4 + -N mass concentration ratio is 1.0 - 2.0; During the operation of step (4), the organic matter in the carbon source reserve pool is sodium acetate, glucose or ethanol. Control the mass ratio of the organic matter in the carbon source reserve pool entering the CANDAN "nitrogen cutting" reaction tank to the NO3 - -N mass of the mixed sewage in the comprehensive wastewater regulation tank entering the CANDAN "nitrogen cutting" reaction tank, that is, COD / NO3 - -N is 2.0 - 4.0; During the operation of step (4), control the MLSS of the mixed sludge in the CANDAN "nitrogen cutting" reaction tank to be within the range of 4.0 - 10.0 g / L; During the operation of step (4), when the NH4 + -N and NO2 - -N in the effluent of the CANDAN "nitrogen cutting" reaction tank is greater than 3.0 mg / L, extend the hydraulic retention time of the CANDAN "nitrogen cutting" reaction tank; when the NH4 + -N and NO3 - -N in the effluent is greater than 3.0 mg / L and NO2 - -N is less than 1.0 mg / L, increase the COD mass of the organic matter in the carbon source storage tank entering the CANDAN "nitrogen cutting" reaction tank; when the NH4 + -N in the effluent is greater than 5.0 mg / L and NO2 - -N and NO3 - -N concentration sum in the effluent is less than 3.0 mg / L, reduce the volume of the NH4 + -N industrial wastewater entering the integrated wastewater regulation tank; when the NO3 - -N in the effluent is greater than 5.0 mg / L and NH4 + -N is less than 1.0 mg / L, reduce the volume of the NO3 - -N industrial wastewater entering the integrated wastewater regulation tank.

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