Deep denitrification process and system for PCB (printed circuit board) wastewater

Abstract

The invention provides a PCB wastewater deep denitrification process and system, and belongs to the technical field of wastewater treatment.The PCB wastewater deep denitrification process comprises the following steps that PCB wastewater is pretreated, and pretreated wastewater is obtained; the method comprises the following steps: firstly carrying out anaerobic treatment on the pretreated wastewater, then carrying out aerobic treatment to obtain nitrification effluent, carrying out mud-water separation on the nitrification effluent through precipitation, and carrying out sulfur autotrophic denitrification reaction on supernatant obtained through separation to obtain effluent. The invention provides a deep denitrification process and system for PCB (Printed Circuit Board) wastewater, which are used for realizing the purposes of reducing the cost and simply operating the process.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and in particular to a PCB wastewater deep denitrification process and system. Background Art

[0002] PCB (printed circuit board) is one of the important components of the electronics industry. Almost every electronic device, from electronic watches and calculators to computers, communication electronic equipment, and military weapon systems, as long as there are electronic components such as integrated circuits, must use printed circuit boards to make electrical interconnections between various components. Therefore, the application range of printed circuit boards is very large, and different steps in the production of printed circuit boards produce nitrogen-containing wastewater. The sources and conventional concentrations of nitrogen in PCB wastewater are shown in the table below.

[0003]

[0004] The total nitrogen in PCB wastewater includes organic nitrogen, ammonia nitrogen, nitrate nitrogen and nitrite nitrogen. The difficulty lies in the removal of nitrate nitrogen and nitrite nitrogen. The commonly used removal methods in the prior art include medium adsorption, ion exchange, reverse osmosis, electrodialysis, evaporation concentration, active metal catalytic reduction and biochemical method. Except for the biochemical method, the other methods are common, with large investment, high operating cost, high maintenance cost and by-products that require secondary treatment. It is not suitable for large-scale treatment. At present, the most widely used sewage treatment method is the biochemical method, and the main process is the AAO process.

[0005] The conventional AAO process classifies various types of wastewater. After pretreatment, the water is stored in the biochemical intermediate water tank, and then enters the anaerobic tank. Under anaerobic conditions, it is hydrolyzed and acidified to decompose organic nitrogen into ammonia nitrogen. It then enters the anoxic tank. Under anoxic conditions, denitrifying microorganisms use carbon sources to convert nitrate nitrogen and nitrite nitrogen into nitrogen gas for release. Ammonia nitrogen will not be eliminated at this stage, but will enter the aerobic tank of the next stage. After nitrification, it is converted into nitrate nitrogen and nitrite nitrogen. The nitrified liquid is returned to the anoxic tank to be converted into nitrogen gas for release.

[0006] However, the conventional AAO process often requires the addition of a large amount of carbon source in order to remove nitrate nitrogen in the anoxic tank stage, which increases the operating cost. On the other hand, since the total nitrogen in the influent will fluctuate, the amount of carbon source used is also unstable. A large amount will cause COD to exceed the standard, and a small amount will cause the total nitrogen removal to fail to meet the standard. Therefore, there are corresponding additional requirements for the operating process, and the operation is cumbersome. Summary of the invention

[0007] In view of this, the present invention provides a PCB wastewater deep denitrification process and system to achieve the purpose of reducing costs and simplifying process operation.

[0008] To achieve the above-mentioned purpose, the present invention provides a deep denitrification process for PCB wastewater, comprising the following steps: pre-treating PCB wastewater to obtain pre-treated wastewater; subjecting the pre-treated wastewater to anaerobic treatment and then to aerobic treatment to obtain nitrification effluent, subjecting the nitrification effluent to sedimentation for mud and water separation, and discharging the separated supernatant after sulfur autotrophic denitrification reaction.

[0009] Optionally, part of the sludge obtained from the mud-water separation is returned to the anaerobic treatment and the aerobic treatment, and the remaining sludge is collected and then harmlessly treated.

[0010] Optionally, the pretreatment is physical and chemical methods to treat PCB wastewater.

[0011] Optionally, the chemical method includes using complex breakers, cyanide breakers and flocculants; the physical method includes natural sedimentation.

[0012] Optionally, a sulfur autotrophic denitrification device is used to carry out the sulfur autotrophic denitrification reaction.

[0013] Optionally, the sulfur autotrophic denitrification equipment is a sulfur autotrophic denitrification filter.

[0014] In order to achieve the above-mentioned object, the present invention also provides a PCB wastewater deep denitrification system, including a pretreatment module, a denitrification module and a deep denitrification module; The denitrification module comprises an anaerobic tank, an aerobic tank, a biochemical sedimentation tank and a sludge collection device, wherein the anaerobic tank has an anaerobic water inlet, an anaerobic water outlet and a second sludge return port, the aerobic tank has an aerobic water inlet, an aerobic water outlet and a first sludge return port, the biochemical sedimentation tank has a biochemical sedimentation water inlet, a biochemical sedimentation water outlet and a sludge discharge port, the anaerobic water outlet is connected to the aerobic water inlet, the aerobic water outlet is connected to the biochemical sedimentation water inlet, the biochemical sedimentation water outlet is connected to the deep denitrification module, and the sludge discharge port is respectively connected to the first sludge return port and the second sludge return port and the sludge collection device; The deep denitrification module comprises a sulfur autotrophic denitrification filter tank, which has a sulfur autotrophic denitrification water inlet and a sulfur autotrophic denitrification water outlet, and the sulfur autotrophic denitrification water inlet is connected to the biochemical precipitation water outlet.

[0015] Optionally, the pretreatment module includes a physical and chemical pretreatment unit and a biochemical intermediate water tank. The wastewater passing through the physical and chemical pretreatment unit enters the biochemical intermediate water tank. The biochemical intermediate water tank includes a biochemical intermediate water tank water inlet and a biochemical intermediate water tank water outlet. The biochemical intermediate water tank water inlet is connected to the physical and chemical pretreatment unit, and the biochemical intermediate water tank water outlet is connected to the anaerobic water inlet.

[0016] The above technical solution of the present invention includes at least the following beneficial effects: In the technical solution provided by the present invention, the anoxic tank stage is eliminated, and the pretreatment effect on the total nitrogen treatment effect in the wastewater is not obvious. A large amount of total nitrogen is still contained in the wastewater. The organic nitrogen therein is decomposed into small molecules and ammonia nitrogen after hydrolysis and acidification in the anaerobic tank. After entering the aerobic tank, the ammonia nitrogen is converted into nitrate nitrogen and nitrite nitrogen through nitrification reaction, and mud and water are separated in the biochemical sedimentation tank. The supernatant enters the sulfur autotrophic denitrification tank. The autotrophic microorganisms such as denitrifying Thiobacillus in the sulfur autotrophic denitrification tank use inorganic carbon sources to denitrify and reduce them to nitrogen gas for release. There is no need to add additional carbon sources and adjust the usage of carbon sources, thereby reducing additional requirements for the operating process and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a process flow chart of wastewater denitrification according to Example 2 of the present invention; Figure 2 This is a process flow chart of wastewater denitrification in comparative example 1 of the present invention. DETAILED DESCRIPTION

[0018] To make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the following will be combined with the appended drawings of the embodiments of the present invention. Figure 1~2 , the technical scheme of the embodiment of the present invention is clearly and completely described. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0019] Example 1 A PCB wastewater deep denitrification system The PCB wastewater is passed through a pretreatment module to obtain pretreated wastewater. The pretreatment template includes a physical and chemical pretreatment unit and a biochemical intermediate water tank. The wastewater passing through the physical and chemical pretreatment unit enters the biochemical intermediate water tank. The biochemical intermediate water tank includes a biochemical intermediate water tank inlet and a biochemical intermediate water tank outlet. The biochemical intermediate water tank inlet is connected to the physical and chemical pretreatment unit, and the biochemical intermediate water tank outlet is connected to the anaerobic inlet. The physical and chemical pretreatment unit includes using a complex breaker, a cyanide breaker and a flocculant as well as a natural sedimentation method to treat wastewater.

[0020] The pretreated wastewater passes through a denitrification module, which includes an anaerobic tank, an aerobic tank, a biochemical sedimentation tank and a sludge collection device. The anaerobic tank has an anaerobic water inlet, an anaerobic water outlet and a second sludge return port. The aerobic tank has an aerobic water inlet, an aerobic water outlet and a first sludge return port. The biochemical sedimentation tank has a biochemical sedimentation water inlet, a biochemical sedimentation water outlet, and a sludge discharge port. The anaerobic water outlet is connected to the aerobic water inlet, the aerobic water outlet is connected to the biochemical sedimentation water inlet, the biochemical sedimentation water outlet is connected to the deep denitrification module, and the sludge discharge port is respectively connected to the first sludge return port, the second sludge return port and the sludge collection device.

[0021] The deep denitrification module comprises a sulfur autotrophic denitrification filter tank, which has a sulfur autotrophic denitrification water inlet and a sulfur autotrophic denitrification water outlet, and the sulfur autotrophic denitrification water inlet is connected to the biochemical precipitation water outlet.

[0022] Example 2 A deep denitrification process for PCB wastewater PCB wastewater is mixed with complex breakers, cyanide breakers and flocculants to produce flocculation precipitation. After natural sedimentation, the wastewater is passed into the biochemical intermediate water tank for storage, and then into the anaerobic tank. The organic nitrogen in the wastewater is hydrolyzed and acidified in the anaerobic tank, decomposed into small molecular substances and ammonia nitrogen, and then enters the aerobic tank. After nitrification, the ammonia nitrogen is converted into nitrate nitrogen and nitrite nitrogen. After the aerobic tank treatment, nitrification effluent is obtained, and the nitrification effluent enters the biochemical sedimentation tank for mud and water separation. The mud and water separation obtains sludge and supernatant. The supernatant enters the sulfur autotrophic denitrification filter for denitrification reaction. Since the sulfur autotrophic denitrification filter contains autotrophic microorganisms such as denitrifying thiobacillus, it can use CO 2 , CO 3 2- , HCO 3 - The inorganic carbon source is used for denitrification, and nitrate nitrogen and nitrite nitrogen are reduced to nitrogen gas, and nitrogen is deeply removed. Therefore, no additional carbon source is needed, which reduces the cost on the one hand and simplifies the operating conditions of the process on the other hand, making the process simple and easy to operate. The process flow chart of Example 2 is shown in Figure 1 .

[0023] Comparative Example 1 Conventional AAO process in the prior art: Compared with Example 2, the difference is that the wastewater is treated in an anoxic tank after being treated in an anaerobic tank. In the anoxic tank, denitrifying microorganisms use an external carbon source to convert nitrate nitrogen and nitrite nitrogen into nitrogen gas for release, and the wastewater after the anoxic tank enters the aerobic tank for treatment. Ammonia nitrogen is converted into nitrate nitrogen and nitrite nitrogen after nitrification reaction in the aerobic tank. The nitrified liquid in the aerobic tank is returned to the anoxic tank for treatment to remove nitrate nitrogen and nitrite nitrogen. The nitrified liquid treated in the anoxic tank enters the biochemical precipitation tank. The remaining steps and raw materials are consistent with those in Example 2. The process flow chart of Comparative Example 1 is shown in FIG. Figure 2 .

[0024] The same batch of PCB wastewater was tested using the process flow of Example 2 and Comparative Example 1, respectively, and the nitrate nitrogen load of the sulfur autotrophic denitrification filter was 0.8-1.5 kg N / (m³·d), and the nitrate nitrogen load of the anoxic tank was 0.2-0.6 kgN / (m³·d). It can be seen that the process provided by the present invention is more than twice the nitrate nitrogen removal capacity of the prior art.

[0025] Compared with the process flow of Comparative Example 1, Example 2 has a high denitrification load, the tank capacity of the anoxic section can be reduced, and the construction cost is reduced; the backflow of the nitrification liquid is avoided, and there is no need to add additional carbon source, so the operating cost is reduced; there is no need to adjust the usage of the carbon source according to the fluctuation of the influent, which reduces the risk of excessive COD in the effluent, reduces the additional requirements for the process operation, and the process is easy to operate.

[0026] In the present invention, unless otherwise clearly stipulated and limited, for example, it can be a fixed connection, a detachable connection, or an integrated one; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, for ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0027] The above are preferred embodiments 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 principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A PCB wastewater deep denitrification process, characterized in that: The following steps are involved: Pre-treating PCB wastewater to obtain pre-treated wastewater; The pre-treated wastewater is first subjected to anaerobic treatment and then to aerobic treatment to obtain nitrified effluent, the nitrified effluent is subjected to sedimentation to separate mud and water, and the separated supernatant is discharged after sulfur autotrophic denitrification reaction.

2. The PCB wastewater deep denitrification process according to claim 1, characterized in that: Part of the sludge obtained from the mud-water separation is returned to the anaerobic treatment and the aerobic treatment, and the remaining sludge is collected and then harmlessly treated.

3. The PCB wastewater deep denitrification process according to claim 1, characterized in that: The pretreatment is physical and chemical methods to treat PCB wastewater.

4. The PCB wastewater deep denitrification process according to claim 3, characterized in that: The chemical method includes using complex breakers, cyanide breakers and flocculants; the physical method includes natural sedimentation.

5. The PCB wastewater deep denitrification process according to claim 1, characterized in that: The sulfur autotrophic denitrification reaction is carried out using a sulfur autotrophic denitrification device.

6. The PCB wastewater deep denitrification process according to claim 5, characterized in that: The sulfur autotrophic denitrification equipment is a sulfur autotrophic denitrification filter.

7. A PCB wastewater deep denitrification system, characterized in that: It includes pretreatment module, denitrification module and deep denitrification module; The denitrification module comprises an anaerobic tank, an aerobic tank, a biochemical sedimentation tank and a sludge collection device, wherein the anaerobic tank has an anaerobic water inlet, an anaerobic water outlet and a second sludge return port, the aerobic tank has an aerobic water inlet, an aerobic water outlet and a first sludge return port, the biochemical sedimentation tank has a biochemical sedimentation water inlet, a biochemical sedimentation water outlet and a sludge discharge port, the anaerobic water outlet is connected to the aerobic water inlet, the aerobic water outlet is connected to the biochemical sedimentation water inlet, the biochemical sedimentation water outlet is connected to the deep denitrification module, and the sludge discharge port is respectively connected to the first sludge return port and the second sludge return port and the sludge collection device; The deep denitrification module comprises a sulfur autotrophic denitrification filter tank, which has a sulfur autotrophic denitrification water inlet and a sulfur autotrophic denitrification water outlet, and the sulfur autotrophic denitrification water inlet is connected to the biochemical precipitation water outlet.

8. The PCB wastewater deep denitrification system according to claim 7, characterized in that: The pretreatment module includes a physical and chemical pretreatment unit and a biochemical intermediate water tank. The wastewater passing through the physical and chemical pretreatment unit enters the biochemical intermediate water tank. The biochemical intermediate water tank includes a biochemical intermediate water tank water inlet and a biochemical intermediate water tank water outlet. The biochemical intermediate water tank water inlet is connected to the physical and chemical pretreatment unit, and the biochemical intermediate water tank water outlet is connected to the anaerobic water inlet.

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