A multi-stage biological treatment process for N-methylpyrrolidone production wastewater based on VBBR

Abstract

The present invention relates to the technical field of wastewater treatment processes, and discloses a multi-stage biological treatment process for N-methylpyrrolidone production wastewater based on VBBR, comprising the following steps: step 1, measuring the concentration information of the raw wastewater; step 2, based on the raw wastewater concentration information, sequentially connecting at least two VBBR groups in series, each stage being sequentially connected in series by an anaerobic VBBR and an aerobic VBBR; step 3, sequentially transporting the raw wastewater to the multi-stage VBBR, and transporting the raw wastewater to the next or n-stage anaerobic VBBR in a bypass form at a ratio of 5% to 20% along the transport direction of the raw wastewater, while the sewage treated by the aerobic VBBR of the last stage is refluxed to the anoxic VBBR of the current stage or the previous stage or the n-stage at a ratio of 75% to 300% along the reverse direction of the transport direction of the raw wastewater. The present invention achieves the purpose of mineralization of industrial wastewater containing nitrogen heterocyclic compounds and removal of total nitrogen simultaneously through the multi-stage series VBBR operation.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment processes, in particular to a multi-stage biological treatment process for N-methylpyrrolidone production wastewater based on VBBR. Background Art

[0002] Since biological methods are the most economical methods in all sewage treatment fields, the mainstream process for various wastewater treatments is still biological methods.

[0003] For some industrial wastewaters with higher concentrations that can be biochemically treated or can be biochemically treated after pretreatment, most of the current treatment methods used at home and abroad are anaerobic plus aerobic combined processes to improve the treatment efficiency of wastewater. In the anaerobic stage, some macromolecular compounds are decomposed through a series of biological reaction processes such as acidification and hydrolysis, and then mineralized through subsequent aerobic processes. Ultimately, the purpose of industrial wastewater treatment is achieved. This anaerobic plus aerobic two-stage process combination has been widely used as a primary water treatment process in related fields. However, this primary treatment process still has some problems in removing total nitrogen from industrial wastewater containing some nitrogenous compounds or nitrogenous heterocyclic compounds. As a result, after this type of industrial wastewater is treated by the above process, the total nitrogen index is often difficult to meet the discharge or management standards. This is because in the process of anaerobic and aerobic biological treatment of nitrogenous compounds or nitrogenous heterocyclic compounds, the compounds in the wastewater are first ring-opened. In this process, the nitrogen elements in these nitrogenous compounds or nitrogenous heterocyclic compounds are mostly in the form of NH4 + Even after the subsequent aerobic process, only NH4 + Converted to NO3 – In the end, total nitrogen is still difficult to be effectively removed. In addition, some people consider using traditional A 2 / O process, through the internal reflux method, a part of NO3 – It is returned to the anaerobic or anoxic tank at the front end to be reduced through denitrification reaction. However, the problem with this method is that for nitrogen-containing heterocyclic compounds with higher concentrations, the microorganisms that open the rings of these organic compounds by acid hydrolysis are usually the dominant microorganisms in the anaerobic or anoxic stage. In this way, if both acid hydrolysis and denitrification are to be carried out in the same reactor, its efficiency is bound to be reduced. In addition, the discharge of industrial wastewater is closely related to production tasks, so the water quality and water volume fluctuate greatly. Using a first-stage A / O or A 2 The A / O process is more difficult to remove total nitrogen. Another important issue is the A / O or A 2 In the actual operation of the / O process, activated sludge and sewage circulate simultaneously. Over time, this leads to the distribution of microbial communities in pool A and pool O becoming similar, which greatly reduces the efficiency of the biological reaction.

[0004] Take the production wastewater of N-methylpyrrolidone (NMP for short) as an example. NMP is a nitrogen-containing heterocyclic compound with the molecular formula C5H9NO. The production wastewater mainly comes from the residues in the NMP distillation process, such as NMP, a small amount of monomethylamine and some other compounds. The main feature of this wastewater is the high COD concentration, generally above 5000 mgCOD / L, and the total nitrogen concentration is as high as 300-1200 mgN / L. At present, the treatment process for NMP production wastewater is mainly anaerobic plus aerobic. Taking the current treatment process of Maiqi Chemical Co., Ltd. as an example, the UASB process is used in the front section and the CASS process is used in the back section. Under normal circumstances, COD can meet the nanotube standard, but the total nitrogen concentration is difficult to meet the nanotube standard. Similar methods are also used for the treatment of other similar wastewaters. For example, like UASB+A / O or UASB+A 2 / O process, etc. Although the process is added to A / O or A / O in the UASB back end 2 / O, which can improve the removal efficiency of total nitrogen, but due to the traditional A / O or A 2 The internal circulation of the / O process uses sludge and water to circulate together, resulting in the microorganisms in both pool A and pool O being very similar. This results in low efficiency of denitrification and nitrification reactions. Achieving efficient removal of total nitrogen remains an important issue.

[0005] For example, a Chinese patent, publication number CN102040315A, discloses a two-stage A / O process for treating high-ammonia nitrogen wastewater. The circulation between the A tank and the O tank is a mixed circulation of mud and water, which ultimately results in the microbial community distribution of the sludge in the four tanks being very similar, resulting in low nitrification and denitrification efficiency. Summary of the Invention

[0006] The present invention is intended to provide a multi-stage biological treatment process for N-methylpyrrolidone production wastewater based on VBBR to solve the problems described in the background technology.

[0007] In order to achieve the above object, the basic scheme of the present invention is as follows: a multi-stage biological treatment process for N-methylpyrrolidone production wastewater based on VBBR, comprising the following steps:

[0008] Step 1: measuring the concentration information of the original wastewater;

[0009] Step 2: anoxic VBBR and aerobic VBBR are connected in series to form a primary VBBR;

[0010] Step 3: Based on the original wastewater concentration information, at least two VBBR stages are connected in series;

[0011] In step 4, the raw wastewater is transported to the VBBR group in series, and the raw wastewater is transported to the next or n-th anaerobic VBBR in a bypass form at a certain ratio along the transport direction of the raw wastewater, and the wastewater treated by the VBBR group is returned to the anaerobic and anoxic VBBR of the same level or the anaerobic VBBR of the previous level in a certain ratio in the reverse direction along the transport direction of the raw wastewater.

[0012] Furthermore, the VBBR group includes an anaerobic VBBR and an aerobic VBBR, the anaerobic VBBR and the aerobic VBBR are connected in series, and the anaerobic and aerobic VBBRs are connected in series as one level.

[0013] Furthermore, in step 4, the bypass mode is determined to be transported to one or more anaerobic VBBRs separated by one stage or more according to the α ratio of the total influent volume.

[0014] Furthermore, the value of the α ratio is determined according to the COD concentration and reaction progress in the VBBR at the front end of the raw sewage conveying direction, and the value of the α ratio is 5% to 20%.

[0015] Furthermore, in step 4, the position of the reverse reflux is determined according to the β ratio of the total amount of influent water.

[0016] Furthermore, the value of the β ratio is determined according to the water quality in the VBBR at the end of the raw sewage transportation direction, and the β value is between 75% and 300%.

[0017] Principle and beneficial effects of the present invention: (1) In the prior art, industrial wastewater with high concentration of nitrogen-containing heterocyclic compounds formed by the residual liquid in the NMP distillation process is mostly treated by anaerobic + aerobic process. This process is to first treat the wastewater with a concentration of up to 5000 mgCOD / L anaerobically and then use aerobic treatment. The disadvantages of this process are: ① Since the COD removal amount of the wastewater needs to be as high as several thousand mgCOD / L in a single reactor, the distribution of microbial communities at this time will lead to a decrease in bioconversion efficiency; ② Due to the lack of reflux, the NH3 released from the NMP and the converted NO3 – , cannot be effectively removed, so the total nitrogen removal effect has always been poor. The present invention achieves the purpose of mineralization of industrial wastewater containing nitrogen heterocyclic compounds and removal of total nitrogen at the same time through multi-stage series VBBR operation.

[0018] (2) In the present invention, since the carbon source is insufficient during denitrification in the VBBR group, the position of the bypass stage is determined according to the α ratio of the total influent volume, and 5% to 20% of the original wastewater is directly transported to the anaerobic VBBR that requires a carbon source, providing sufficient carbon source as an electron donor to convert NO3 – reduction, thereby improving the efficiency of the denitrification reaction.

[0019] (3) In the present invention, due to different NMP production processes, the COD concentration of NMP production wastewater sometimes fluctuates to a certain extent. This process can adopt multi-stage series connection according to the change of its COD concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the process of multi-stage biological treatment of N-methylpyrrolidone production wastewater based on VBBR in an embodiment of the present invention.

[0021] Figure 2 Graph showing the degradation of NMP under anaerobic / aerobic alternating conditions in an embodiment of the present invention.

[0022] Figure 3 In the embodiment of the present invention, NMP is used as an electron donor to reduce NO3 – Situation diagram. DETAILED DESCRIPTION

[0023] The following is further described in detail through specific implementation methods:

[0024] Basically as attached Figure 1 As shown:

[0025] The present application provides a multi-stage biological treatment process for N-methylpyrrolidone production wastewater based on VBBR, comprising the following steps:

[0026] Step 1: Measure the concentration information of the raw wastewater, which mainly includes the COD concentration and the total nitrogen concentration. The concentration information can be obtained by using existing monitoring equipment, such as COD concentration detection equipment and total nitrogen concentration detection equipment.

[0027] Step 2: Based on the concentration information of the original wastewater, at least two VBBR groups are connected in series. In this embodiment, a two-stage VBBR group is taken as an example. Each VBBR includes an anaerobic VBBR and an aerobic VBBR connected in series. In this embodiment, since the two-stage VBBRs are connected in series, the anaerobic VBBR is located at an odd position and the aerobic VBBR is located at an even position. Figure 1 As shown, the two-level VBBR groups in this embodiment are a first-level VBBR group, a second-level VBBR group, and a third-level VBBR group, and are connected in sequence from left to right.

[0028] In step 3, the raw wastewater is transported in series toward the secondary VBBR group, and 5% to 20% of the raw wastewater is transported in a bypass manner along the direction of transport of the raw wastewater. For example, the bypass pipe is connected from the water inlet position to transport the raw wastewater directly to the anaerobic VBBR of the second-stage VBBR. In this embodiment, the position of the bypass-type inter-stage transport is determined according to the α ratio of the total amount of influent. The value of the α ratio is determined according to the COD concentration and reaction progress in the VBBR at the front end of the raw sewage transport direction. The value of the α ratio is between 5% and 20%. In this embodiment, the raw wastewater is directly transported to the second-stage anaerobic VBBR to make up for the lack of carbon source, so as to ensure that the denitrification reaction in the second-stage anaerobic VBBR proceeds smoothly. In addition, in order to improve the removal efficiency of total nitrogen, the NO3 – The sewage is refluxed in the reverse direction of the original wastewater delivery direction. For example, according to the β ratio of the total influent, it is refluxed to the anaerobic VBBR of the same level or even the previous level. The β ratio value is determined according to the water quality of the VBBR at the end of the original sewage delivery direction. The β value is between 75% and 300%. In this embodiment, the sewage treated by the second-stage aerobic VBBR group is refluxed to the anaerobic VBBR of the same-stage VBBR group, so that the generated NO3 – Can be effectively restored.

[0029] In this embodiment, the main biological reaction in the first-stage anaerobic VBBR is mainly acidification and hydrolysis. At this time, the main reaction is the ring opening of most of the NMP in the wastewater to form organic acids, converting large-molecule organic acids into small-molecule organic acids, and releasing the nitrogen in its structure in the form of NH3. The main biological reaction in the first-stage aerobic VBBR is aerobic oxidation reaction, which further oxidizes the remaining NMP to form organic acids, oxidizes part of the organic acids, and oxidizes the generated NH3 to NO3. – The main reaction in the second stage anaerobic VBBR is denitrification, which is to oxidize NO3 – Reduced to N2, the electron donor in this process is provided by NMP, and NMP releases electron donor (H) and NH3 at the same time. The chemical reaction formula is: C5H9NO+9H2O→5CO2+NH3+24H; the second stage aerobic VBBR mainly oxidizes the NH3 released in the first and second stage anaerobic VBBR to NO3 – Then, it returns to the second-stage VBBR anaerobic VBBR through reflux and further denitrifies NO3 – Converted to N2.

[0030] Below is Figure 2 Take the multi-stage VBBR series coupling process as an example to illustrate the necessity. Figure 2The figure shows the change of NMP concentration during biodegradation. In the first 2 hours, anaerobic degradation was used, and after 2 hours, aerobic degradation was used. As can be seen from the figure, after 4 hours of biodegradation, as the COD of NMP wastewater decreased, NH4 + -N concentration gradually increased until the 4th hour, and when aerobic treatment continued, NH4 + -N concentration began to decrease, along with NH4 + -N concentration began to decrease NO3 – -N gradually increases. If this treatment continues, the total nitrogen concentration will basically not be degraded. For this reason, we generate NO3 – -N solution, NMP was added and then placed in an anaerobic environment for denitrification.

[0031] The results are as follows Figure 3 As shown in the figure, when NMP is used as an electron donor for denitrification, although a small amount of NH4 + Generate NO3 – -N is effectively reduced. In general, the concentration of total nitrogen is decreasing. This experimental result shows that NMP production wastewater has good biodegradability, but NH4 + By alternating aerobic and anaerobic processes, COD can be degraded and total nitrogen can be removed.

[0032] The above are only some embodiments of the present invention, and the common knowledge such as the specific structure and / or characteristics of the scheme are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A multi-stage biological treatment process for N-methylpyrrolidone production wastewater based on VBBR, characterized by: The steps include: Step 1, measuring the concentration information of raw wastewater; Step 2: anoxic VBBR and aerobic VBBR are connected in series to form a primary VBBR; Step 3: Based on the original wastewater concentration information, at least two VBBR stages are connected in series; Step 4: The raw wastewater is transported to the at least two VBBRs connected in series, and the raw wastewater is transported in a bypass manner to an anoxic VBBR one or more stages away in a certain proportion along the direction of the raw wastewater transport. The wastewater treated in each VBBR is refluxed in a certain proportion in the reverse direction of the raw wastewater transport to the anoxic VBBR of the same stage or the anoxic VBBR of the previous stage; the wastewater is bypassed to the anoxic VBBR one or more stages away according to a proportion α of the total influent volume; the value of the α ratio is determined according to the COD concentration and reaction progress in the VBBR at the front end of the raw wastewater transport direction, and the value of the α ratio is 5% to 20%.

2. The process for multi-stage biological treatment of N-methylpyrrolidone production wastewater based on VBBR according to claim 1, characterized in that: In step 4, the β ratio of the total influent volume determines whether the reverse flow is to the anoxic VBBR of the same level or the anoxic VBBR of the previous level. The value of the β ratio is determined by the water quality in the VBBR at the end of the original wastewater transport direction, and the β value is between 75% and 300%.

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