Pretreatment process of high-ammonia-nitrogen wastewater

Abstract

The invention discloses a pretreatment process of high-ammonia-nitrogen wastewater, and relates to the field of environmental engineering, and the process comprises the following steps: step 1, pumping high-ammonia-nitrogen wastewater into a circulating system, and then adding a sodium hypochlorite solution with the concentration of 10% into the wastewater; 2, the wastewater is circulated to a retention tank, mixed gas of nitrogen and ozone is introduced into the lower end of the retention tank, the gas is discharged from the upper end of the retention tank, the wastewater continues to be circulated, and the volume ratio of the mixed gas of nitrogen and ozone is (3-5): (7-5); step 3, after the wastewater is separated and discharged through a material separation port, adding an excessive sodium sulfite solution with the concentration of 10% to neutralize the residual sodium hypochlorite with the concentration of 10%, and then discharging into a sewage pool; according to the process method disclosed by the invention, sodium hypochlorite, ozone and nitrogen can generate a synergistic effect, and ammonia nitrogen and COD (Chemical Oxygen Demand) in the wastewater are efficiently treated; meanwhile, no sodium hypochlorite residues exist, the treatment effect is good, follow-up biological treatment is not affected, and the cost is low.

Description

Technical Field

[0001] The present invention relates to the field of environmental engineering, in particular to a pretreatment process for high-ammonia nitrogen wastewater. Background Art

[0002] In recent years, with the improvement of environmental protection requirements, sewage treatment has become a major difficulty restricting the development of the chemical industry. The production capacity of most chemical companies is restricted by the sewage treatment capacity. The treatment of high-concentration ammonia nitrogen wastewater has always been a difficult problem in the chemical industry. The general biological and chemical methods are slow to treat ammonia nitrogen, and the removal effect is very limited. The content of this patent is a pretreatment process for high-concentration ammonia nitrogen wastewater. Breakpoint chlorination combined with ozone can quickly treat ammonia nitrogen and COD in wastewater, but this method generally adds excess sodium hypochlorite to the water body according to the ammonia nitrogen concentration. Although sodium hypochlorite is very effective in degrading ammonia nitrogen, the residual sodium hypochlorite will enter the sewage pool along with the sewage, causing a devastating blow to the bacterial flora in the sewage pool. Therefore, it is necessary to neutralize the residual sodium hypochlorite by other methods after the sodium hypochlorite neutralizes the ammonia nitrogen, and the method of removing sodium hypochlorite cannot affect the subsequent sewage treatment.

[0003] The market needs a pretreatment process for ammonia nitrogen wastewater that can efficiently treat ammonia nitrogen and COD in the wastewater without affecting subsequent biological treatment. The present invention solves this problem. Summary of the Invention

[0004] To address the deficiencies of the prior art, the present invention aims to provide a pretreatment process for high-ammonia nitrogen wastewater, which can produce a synergistic effect between sodium hypochlorite, ozone, and nitrogen to efficiently treat ammonia nitrogen and COD in the wastewater; at the same time, no sodium hypochlorite residue is left, which not only has a good treatment effect, but also does not affect subsequent biological treatment and has low cost.

[0005] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0006] A pretreatment process for high-ammonia nitrogen wastewater comprises the following steps:

[0007] Step 1: Pump high ammonia nitrogen wastewater into the circulation system, and then add a 10% sodium hypochlorite solution to the wastewater. 8%-12% of the wastewater is separated through the separation port and discharged, and the remaining 88%-92% continues to circulate. The filling rate of the sodium hypochlorite solution is 0.01% of the circulation speed of the circulation pump;

[0008] Step 2: The wastewater is circulated to the retention tank, and a mixed gas of nitrogen and ozone is introduced into the lower end of the retention tank. The gas is discharged at the upper end of the retention tank, and the wastewater continues to circulate. The volume ratio of the mixed gas of nitrogen and ozone is 3-5:7-5;

[0009] Step 3: After the wastewater is separated and discharged through the material separation port, an excess of 10% sodium sulfite solution is added to neutralize the remaining 10% sodium hypochlorite, and then the wastewater is discharged into the sewage pool.

[0010] In the aforementioned pretreatment process for high-ammonia nitrogen wastewater, in step 1, the high-ammonia nitrogen wastewater is pumped into the circulation system, the feed rate is set to 10-30 t / h, the circulation pump circulation rate is 100-300 t / h, and then a 10% sodium hypochlorite solution is added to the wastewater through the circulation system at a rate of 10-30 kg / h.

[0011] In the aforementioned pretreatment process for high-ammonia nitrogen wastewater, in step 1, 10% of the wastewater is separated and discharged through a separation port, and the remaining 90% is continuously circulated.

[0012] In the aforementioned pretreatment process for high-ammonia nitrogen wastewater, the ammonia nitrogen content of the high-ammonia nitrogen wastewater in step 1 is ≤60ppm, and the chemical oxygen demand (COD) of the wastewater is ≤8000mg / L.

[0013] In the aforementioned pretreatment process for high-ammonia nitrogen wastewater, the nitrogen content of the mixed gas of nitrogen and ozone in step 2 is 30%-50%, and the ozone content is 50%-70%.

[0014] In the aforementioned pretreatment process for high-ammonia nitrogen wastewater, the pressure of the mixed gas of nitrogen and ozone in step 2 is 1-3 MPa, and the flow rate of the mixed gas of nitrogen and ozone is controlled at 167-500 L / min.

[0015] In the aforementioned pretreatment process for high-ammonia nitrogen wastewater, the internal pressure of the retention tank in step 2 is controlled at 3 MPa, the retention time is controlled at 30-90 seconds, and the pressure of the mixed gas of nitrogen and ozone introduced into the lower end of the retention tank is set to 1-3 MPa.

[0016] In the aforementioned pretreatment process for high-ammonia nitrogen wastewater, after the wastewater in step 2 is separated and discharged through the material separation port (4), the rate of adding sodium sulfite is 17-51 kg / h.

[0017] In the aforementioned pretreatment process for high-ammonia nitrogen wastewater, the injection rate of the sodium sulfite solution in step 2 is 1.7 times the injection rate of the sodium hypochlorite solution.

[0018] The present invention is beneficial in that:

[0019] The method provided by this patent can produce a synergistic effect of sodium hypochlorite, ozone and nitrogen, and effectively treat ammonia nitrogen and COD in wastewater;

[0020] While efficiently treating ammonia nitrogen and COD in wastewater, it can prevent sodium hypochlorite from remaining, thus not affecting the subsequent biological treatment of sewage pools and improving the treatment effect of the overall sewage treatment system;

[0021] The device involved in the method provided by this patent is relatively simple to install, the accessories are easy to purchase, and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the pretreatment process and equipment system of the present invention;

[0023] The meaning of the reference numerals in the figures:

[0024] 1 High ammonia nitrogen wastewater feed port, 2 Sodium hypochlorite solution, 3 Circulation pump; 4 Material separation port, 5 Retention tank, 6 Nitrogen and ozone mixed gas, 7 Gas outlet, 8 Sodium sulfite solution, 9 Wastewater discharge port. DETAILED DESCRIPTION

[0025] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Depend on Figure 1 It can be seen that the working process of the process system of the present invention is:

[0027] After high-ammonia nitrogen wastewater enters the circulation system from the high-ammonia nitrogen wastewater feed port (1), sodium hypochlorite solution (2) is added, and after circulation through the circulation pump (3), it reaches the material separation port (4). Part of the material continues to circulate to the retention tank (5), and a mixed gas (6) of nitrogen and ozone is introduced to increase pressure, and then the gas is discharged from the gas outlet (7). After passing through the retention tank (5), the wastewater continues to circulate, and the other part of the wastewater is separated from the material separation port (4) and discharged. Before discharging, sodium sulfite solution (8) is added to neutralize excess sodium hypochlorite in the wastewater, and finally the wastewater is discharged from the wastewater discharge port (9).

[0028] Example 1

[0029] The initial ammonia nitrogen content of the high ammonia nitrogen wastewater is 40 ppm, and the COD is 6000 mg / L. The wastewater is pumped into a circulation system, the feed rate is set to 10 t / h, the circulation pump circulation rate is 100 t / h, and the sodium hypochlorite solution addition rate is 10 kg / h. 10% of the wastewater is separated and discharged through the separation port, and the remaining 90% continues to circulate. The internal pressure of the retention tank (5) is controlled at 1 MPa, and the retention time is controlled at 90 seconds. A mixed gas of nitrogen and ozone is introduced into the retention tank (5), wherein nitrogen accounts for 50% and ozone accounts for 50%, and the pressure of the mixed gas is set to 1 MPa. After the wastewater is separated and discharged through the material separation port (4), the sodium sulfite is added at a rate of 17 kg / h.

[0030] After treatment by this process, the ammonia nitrogen content in the wastewater dropped to 1ppm, COD dropped to 320mg / L, and sodium hypochlorite was not detected. It can be directly pumped into the sewage pool for subsequent treatment.

[0031] Example 2

[0032] The initial ammonia nitrogen content of the high ammonia nitrogen wastewater is 45ppm, and the COD is 6300mg / L. The wastewater is pumped into a circulation system, the feed rate is set to 30t / h, the circulation speed of the circulation pump (3) is 300t / h, and the sodium hypochlorite solution is added at a rate of 30kg / h. 10% of the wastewater is separated and discharged through the separation port, and the remaining 90% continues to circulate. The internal pressure of the retention tank (5) is controlled at 3Mpa, and the retention time is controlled at 30s. A mixed gas of nitrogen and ozone is introduced into the retention tank (5), wherein nitrogen accounts for 30% and ozone accounts for 70%, and the pressure of the mixed gas is set to 3Mpa. After the wastewater is separated and discharged through the material separation port (4), the sodium sulfite is added at a rate of 51kg / h.

[0033] After treatment by this process, the ammonia nitrogen content in the wastewater dropped to 2ppm, COD dropped to 560mg / L, and sodium hypochlorite was not detected. It can be directly pumped into the sewage pool for subsequent treatment.

[0034] Comparative Example 1

[0035] The initial ammonia nitrogen content of the high ammonia nitrogen wastewater is 35ppm, and the COD is 5600mg / L. The wastewater is pumped into a circulation system, the feed rate is set to 20t / h, the circulation speed of the circulation pump (3) is 200t / h, and the sodium hypochlorite solution is added at a rate of 20kg / h. 10% of the wastewater is separated through a separation port and discharged, and the remaining 90% continues to circulate. The internal pressure of the retention tank (5) is controlled at 2Mpa, and the retention time is controlled at 60s. A mixed gas of nitrogen and ozone is introduced into the retention tank (5), wherein nitrogen accounts for 40% and ozone accounts for 60%, and the pressure of the mixed gas is set to 2Mpa. After the wastewater is separated through the separation port, it is directly discharged without adding sodium sulfite.

[0036] After treatment by this process, the ammonia nitrogen content in the wastewater dropped to 2ppm, COD dropped to 530mg / L, and sodium hypochlorite residue was detected. Sodium hypochlorite will affect the bacterial flora of the sewage pool and cannot be directly pumped into the sewage pool for subsequent treatment.

[0037] Comparative Example 2

[0038] The initial ammonia nitrogen content of the high-ammonia nitrogen wastewater is 30 ppm, and the COD is 5000 mg / L. The wastewater is pumped into a circulation system, the feed rate is set to 20 t / h, the circulation speed of the circulation pump (3) is set to 200 t / h, and the sodium hypochlorite solution is added at a rate of 20 kg / h. 10% of the wastewater is separated and discharged through the separation port, and the remaining 90% continues to circulate. The internal pressure of the retention tank (5) is controlled at 2 MPa, and the retention time is controlled at 60 seconds. Air is introduced into the retention tank (5) and the air pressure is set to 2 MPa. After the wastewater is separated and discharged through the material separation port (4), the sodium sulfite is added at a rate of 34 kg / h.

[0039] After treatment by this process, the ammonia nitrogen content in the wastewater dropped to 15ppm, COD dropped to 4200mg / L, and sodium hypochlorite was not detected. However, since the ammonia nitrogen content and COD were still relatively high, directly pumping the wastewater into the sewage pool for treatment would put greater pressure on the sewage pool.

[0040] Comparative Example 3

[0041] The initial ammonia nitrogen content of the high ammonia nitrogen wastewater is 50 ppm, and the COD is 8000 mg / L. The wastewater is pumped into a circulation system, the feed rate is set to 20 t / h, the circulation speed of the circulation pump (3) is 200 t / h, and the sodium hypochlorite solution is added at a rate of 20 kg / h. 10% of the wastewater is separated and discharged through the separation port, and the remaining 90% continues to circulate. The internal pressure of the retention tank (5) is controlled at 2 MPa, and the retention time is controlled at 60 seconds. A mixed gas of nitrogen and ozone is introduced into the retention tank (5), wherein nitrogen accounts for 70% and ozone accounts for 30%, and the ozone pressure is set to 2 MPa. After the wastewater is separated and discharged through the material separation port (4), the sodium sulfite is added at a rate of 34 kg / h.

[0042] After treatment by this process, the ammonia nitrogen content in the wastewater dropped to 20ppm, COD dropped to 3500mg / L, and sodium hypochlorite was not detected. However, since the ammonia nitrogen content and COD were still relatively high, directly pumping the wastewater into the sewage pool for treatment would put a lot of pressure on the sewage pool.

[0043] Comparative Example 4

[0044] The initial ammonia nitrogen content of the high-ammonia nitrogen wastewater is 40 ppm, and the COD is 6500 mg / L. The wastewater is pumped into the circulation system, the feed rate is set to 20 t / h, and the circulation speed of the circulation pump (3) is set to 200 t / h. No sodium hypochlorite solution is added this time. A mixed gas of nitrogen and ozone is introduced into the retention tank (5), wherein nitrogen accounts for 40% and ozone accounts for 60%. The pressure of the mixed gas is set to 2 MPa. After the wastewater is separated at the separation port, it is directly discharged without adding sodium sulfite.

[0045] After treatment by this process, the ammonia nitrogen content in the wastewater dropped to 38ppm and the COD dropped to 6000mg / L. However, since the ammonia nitrogen content and COD are still relatively high, directly pumping the wastewater into the sewage pool for treatment will put greater pressure on the sewage pool.

[0046] The test results of the above 6 embodiments are shown in Table 1:

[0047] Table 1 Product test data of Examples and Comparative Examples

[0048]

[0049] From the comparative analysis of the product test data of the embodiment and the comparative example in Table 1 above, comparative example 1 shows that the sewage after the circulation system discharge still contains a certain amount of sodium hypochlorite, and sodium sulfite is required to enter the next step of treatment; comparative examples 2 and 3 show that the type and ratio of the mixed gas introduced into the retention tank (5) have a decisive influence on the properties of the final sewage; comparative example 4 shows that sodium hypochlorite plays a decisive role in the effect of the process.

[0050] In summary, the addition of sodium hypochlorite and the volume ratio of ozone and nitrogen play a decisive role in the performance data of the final wastewater. The special ratio and combination of these three materials have a synergistic effect in quickly treating the ammonia nitrogen content and COD in the wastewater without sodium hypochlorite residue.

[0051] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form, and any technical solutions obtained by equivalent replacement or equivalent transformation fall within the scope of protection of the present invention.

Claims

1. A pretreatment process for high-ammonia nitrogen wastewater, characterized in that: The steps include: Step 1: Pump high ammonia nitrogen wastewater into the circulation system, and then add a 10% sodium hypochlorite solution to the wastewater, separate 8%-12% of the wastewater through the separation port, and the remaining 88%-92% continues to circulate. The filling rate of the sodium hypochlorite solution is 0.01% of the circulation rate of the circulation pump; Step 2, the wastewater is circulated to the retention tank, a mixed gas of nitrogen and ozone is introduced into the lower end of the retention tank, the gas is discharged from the upper end of the retention tank, and the wastewater continues to circulate, and the volume ratio of the mixed gas of nitrogen and ozone is 3-5:7-5; Step three, after the wastewater is separated and discharged through the material separation port, an excess of 10% sodium sulfite solution is added to neutralize the remaining 10% sodium hypochlorite, and then the wastewater is discharged into the sewage pool.

2. A pretreatment process for high-ammonia nitrogen wastewater according to claim 1, characterized in that: In the step 1, high ammonia nitrogen wastewater is pumped into the circulation system, the feed rate is set to 10-30 t / h, the circulation pump circulation rate is 100-300 t / h, and then a 10% sodium hypochlorite solution is added to the wastewater, and the sodium hypochlorite solution is added through the circulation system at a rate of 10-30 kg / h.

3. A pretreatment process for high-ammonia nitrogen wastewater according to claim 1, characterized in that: In the step 1, 10% of the wastewater is separated through the separation port and discharged, and the remaining 90% continues to circulate.

4. A pretreatment process for high-ammonia nitrogen wastewater according to claim 1, characterized in that: The ammonia nitrogen content of the high ammonia nitrogen wastewater in the step 1 is ≤60ppm, and the chemical oxygen demand (COD) of the wastewater is ≤8000mg / L.

5. A pretreatment process for high-ammonia nitrogen wastewater according to claim 1, characterized in that: In the mixed gas of nitrogen and ozone in step 2, the nitrogen accounts for 30%-50%, and the ozone accounts for 50%-70%.

6. A pretreatment process for high-ammonia nitrogen wastewater according to claim 1, characterized in that: The pressure of the mixed gas of nitrogen and ozone in step 2 is 1-3Mpa, and the flow rate of the mixed gas of nitrogen and ozone is controlled at 167-500L / min.

7. A pretreatment process for high-ammonia nitrogen wastewater according to claim 1, characterized in that: The internal pressure of the retention tank in step 2 is controlled at 3 MPa, the retention time is controlled at 30-90 s, and the pressure of the mixed gas of nitrogen and ozone introduced into the lower end of the retention tank is set to 1-3 MPa.

8. A pretreatment process for high-ammonia nitrogen wastewater according to claim 1, characterized in that: After the wastewater in step 2 is separated and discharged through the material separation port (4), the rate of adding sodium sulfite is 17-51 kg / h.

9. A pretreatment process for high-ammonia nitrogen wastewater according to claim 2, characterized in that: The filling speed of the sodium sulfite solution in the step 2 is 1.7 times the filling speed of the sodium hypochlorite solution.

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