A method for treating bamboo retting pulp waste liquid

Abstract

The application discloses a processing method of bamboo retting pulp waste liquid. The method comprises the following steps: collecting the bamboo retting pulp waste liquid into a homogenizing adjusting pool, performing homogenizing mixing and oxidation through nano aeration; performing twice flocculation and precipitation on the waste liquid after the nano aeration; allowing the supernatant after the flocculation and precipitation to flow into a self-electrolysis treatment pool for self-electrolysis for 1-2 hours; allowing the waste liquid after the self-electrolysis treatment pool to enter a salt-tolerant biochemical treatment system; allowing the effluent of the salt-tolerant biochemical treatment system to flow into an A / O biochemical system; allowing the effluent of the A / O biochemical system to enter a final sedimentation tank, performing solid-liquid separation on the waste liquid through an inclined tube, then allowing the effluent to flow into a discharge pool, and allowing the effluent to enter a comprehensive sewage treatment system. The method is suitable for treating high-concentration industrial waste water, especially the industrial waste water with a COD concentration of more than 40000 mg / L, provides a practical and feasible method for treating high-concentration retting pulp waste liquid of small scattered bamboo chips, and provides a solution for solving environmental pollution.

Description

Technical Field

[0001] This invention belongs to the field of environmental pollution control technology, specifically relating to a method for treating bamboo pulping waste liquid. Background Technology

[0002] Bamboo pulp can be used to replace part of paper pulp, and added to packaging paper to replace some waste paper pulp. The main steps of bamboo pulping include cutting raw bamboo into lengths according to the nodes, soaking the cut bamboo strips in an alkaline solution to make pulp, separating them into fine bamboo fibers using a shredder, and then mechanically grinding the pulp. The waste liquid from bamboo pulping is black, has a pungent odor, high dissolved solids content (TDS ≥ 10000 mg / L), high organic pollutant content, and contains impurities such as lignin and pectin. The waste liquid contains high concentrations of COD (40000 mg / L~80000 mg / L), is alkaline (pH 10~13), and has many suspended particulate matter, making it a difficult-to-treat high-concentration industrial waste liquid. Improper treatment of bamboo pulping waste liquid will pollute the environment and damage the surrounding ecosystem.

[0003] Chinese patent application CN 110713320 A discloses a system and method for deep treatment of papermaking wastewater. The influent COD of the papermaking wastewater treated in this method is <200mg / L. This method is a deep treatment process for the effluent of the secondary sedimentation tank of papermaking wastewater treatment. This process is only suitable for the treatment of low-concentration papermaking wastewater.

[0004] The waste liquid from bamboo pulping contains high concentrations of COD Cr (40,000 mg / L to 80,000 mg / L), so it is necessary to provide a process suitable for treating wastewater with high concentrations of COD. Summary of the Invention

[0005] To address the shortcomings and deficiencies of existing technologies, the present invention aims to provide a method for treating bamboo pulping wastewater, achieving effective treatment of high-salt, high-concentration bamboo pulping wastewater.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for treating bamboo pulping waste liquid includes the following steps:

[0008] (1) The bamboo pulping waste liquid enters the homogenization and conditioning tank after being collected in the collection tank. Nano-aeration is added to the homogenization and conditioning tank for homogenization and oxidation.

[0009] (2) The waste liquid after nano-aeration enters the primary flocculation sedimentation tank and flocculant is added for sedimentation; the filtered water after primary flocculation sedimentation enters the secondary flocculation sedimentation tank and flocculant is added.

[0010] (3) The supernatant after flocculation and sedimentation in the secondary sedimentation tank flows into the self-electrolysis treatment tank by gravity, and the pH of the wastewater is adjusted to 8-9, and the self-electrolysis time is 1-2 hours.

[0011] (4) The waste liquid after passing through the self-electrolysis treatment tank enters the salt-tolerant biochemical treatment system, which contains compound photosynthetic bacteria and EM bacteria;

[0012] (5) The effluent from the salt-tolerant biological treatment system flows by gravity to the A / O biological treatment system for further treatment;

[0013] (6) The effluent from the A / O biochemical system enters the final sedimentation tank, where the solid and liquid waste is separated by inclined tube sedimentation. After that, the effluent flows into the discharge tank and is then connected to the integrated sewage treatment system.

[0014] Preferably, the COD of the bamboo pulping waste liquid is ≥40000mg / L.

[0015] Preferably, the nano-aeration bubbles have a particle size of 70nm to 100nm and a density of 30 million to 40 million bubbles / mL; the hydraulic retention time of the waste liquid in the homogenization tank is 0.5 to 2 hours.

[0016] Preferably, both the primary flocculation sedimentation tank and the secondary flocculation sedimentation tank are vertical flow sedimentation tanks, and the flocculation sedimentation time is 2 to 10 hours.

[0017] Preferably, the dosage of flocculant in both the primary flocculation sedimentation tank and the secondary flocculation sedimentation tank is 0.1–0.2 mg / L.

[0018] Preferably, the flocculant is PAC.

[0019] More preferably, the flocculant is composed of aluminum oxide and mineral adsorbents, wherein the aluminum oxide content is above 26%, and the mineral adsorbents include zeolite and kaolin.

[0020] Preferably, the self-electrolysis treatment cell uses pure iron as the anode and iron carbide as the cathode.

[0021] Preferably, the salt-tolerant biochemical system can be one of a biofilm reactor, an SBR reactor, an intermittent aerated biofilter reactor, or a UASB anaerobic reactor, with the most preferred being an intermittent aerated biofilter reactor.

[0022] Preferably, the composite photosynthetic bacteria include a variety of Bacillus species; the hydraulic retention time of the waste liquid in the salt-tolerant biochemical treatment system is 144–192 hours.

[0023] More preferably, the composite photosynthetic bacteria are BioPower 600 salt-tolerant bacteria (the main components are various salt-tolerant Bacillus species, purchased from Wuhan Water Kingdom Environmental Protection Technology Co., Ltd.).

[0024] Preferably, the mass ratio of the composite photosynthetic bacteria to EM bacteria is 7:3 to 8:2; the dosage of the composite photosynthetic bacteria and EM bacteria is 0.005-0.01‰ of the mass of the waste liquid after the self-electrolysis treatment tank.

[0025] Preferably, the composite photosynthetic bacteria and EM bacteria are acclimatized and cultured before treating the waste liquid. The method is as follows: in an anaerobic environment, using the effluent from the electrolysis treatment tank as the water source, the acclimatization is carried out for 7 days by sequential batch influent at 10%, 20%, 30%, 40%, 50%, 70%, and 100%, or by continuous acclimatization at 10% influent for 10 days.

[0026] Preferably, in the A / O biological treatment system: the dissolved oxygen content is 4 mg / L to 6 mg / L; the hydraulic retention time is ≤24 h for section A and ≤16 h for section O; the temperature is 10℃ to 40℃; and the COD of the effluent after treatment by the A / O biological system is ≤1000 mg / L.

[0027] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0028] 1. The process of this invention is suitable for treating high-concentration industrial wastewater, especially industrial wastewater with a COD concentration of ≥40000mg / L;

[0029] 2. The process of this invention is suitable for treating high-salinity wastewater with TDS ≥ 10000 mg / L;

[0030] 3. The process of this invention has a very good high-efficiency flocculation and sedimentation effect. When the COD of the raw water is ≥40000mg / L, the COD removal rate can reach more than 70% after two flocculation stages.

[0031] 4. The process of this invention provides a practical and feasible process for the treatment of high-concentration fermentation waste liquid from small bamboo chips, and provides a solution to environmental pollution. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to embodiments, but the embodiments of the present invention are not limited thereto. All raw materials involved in the present invention can be purchased directly from the market. For process parameters not specifically specified, conventional techniques can be referred to.

[0033] This invention provides a method for treating bamboo pulping wastewater, comprising the following steps:

[0034] (1) The bamboo chip pulping waste liquid is collected in a collection tank and then enters a homogenization and conditioning tank. Nano-aeration is added to the homogenization and conditioning tank for homogenization, mixing, and oxidation. The nano-aeration bubbles have a particle size of 70nm–100nm and a density of 30–40 million bubbles / mL. In this step, the concentration of the collected bamboo chip pulping waste liquid is adjusted to be uniform through nano-aeration to facilitate subsequent treatment. The hydraulic retention time of the waste liquid in the homogenization and conditioning tank is 0.5–2 hours.

[0035] (2) The wastewater after nano-aeration enters the primary flocculation sedimentation tank and flocculants are added for sedimentation; the filtered water after primary flocculation sedimentation enters the secondary flocculation sedimentation tank and flocculants are added; neither the primary nor secondary flocculation sedimentation tanks require pH adjustment, and the flocculation sedimentation time is 2-10 hours. The COD removal rate in the wastewater after two flocculation sedimentations is approximately 70%. The flocculants consist of alumina and mineral adsorbents, with the alumina content exceeding 26%, and the mineral adsorbents including zeolite and kaolin.

[0036] (3) The supernatant after flocculation and sedimentation in the secondary sedimentation tank flows by gravity into the self-electrolysis treatment tank, adjusting the pH of the wastewater to 8-9; using pure iron as the anode and iron carbide as the cathode, the self-electrolysis time is 1-2 hours; the COD of the wastewater after self-electrolysis treatment is ≤12000mg / L, and the total salt concentration is 10000mg / L≤25000mg / L. The self-electrolysis materials (pure iron, iron carbide) can generate an electrolysis voltage of about 1230mV in the wastewater, and electrode reactions occur in the self-electrolysis treatment tank, which open the rings and break the chains of cyclic and long-chain macromolecular organic matter, and break the toxic functional groups of toxic and harmful organic pollutants, effectively removing color and heavy metal ions from the wastewater. Fe generated after iron discharge 2+ Further release of electrons to oxidize into Fe 3+ When the pH is adjusted to 8-9, a flocculant Fe(OH)3 is formed, which has a strong adsorption-flocculation effect. This allows residual suspended solids, toxic organic matter, heavy metal ion hydrates and organic macromolecules in wastewater to be adsorbed, flocculated and separated, thus achieving wastewater purification.

[0037] (4) The wastewater after the electrolysis treatment tank enters the salt-tolerant biological treatment system, which contains a complex of photosynthetic bacteria composed of various Bacillus species and EM bacteria. The hydraulic retention time of the wastewater in the salt-tolerant biological treatment system is 144–192 hours. The salt-tolerant biological treatment system is characterized by its tolerance to high concentrations and high salinity, high pollutant removal efficiency, and ability to decompose large organic molecules into smaller molecules, and to decompose substances that are difficult to degrade into substances that are easy to degrade, further degrading substances that inhibit microorganisms, increasing the B / C ratio and reducing the pressure on subsequent treatment. At the same time, a large portion of the organic matter is converted into carbon dioxide and water. The COD of the effluent precipitated from the salt-tolerant biological treatment system is 3000 mg / L to 5000 mg / L.

[0038] Before treating the waste liquid, the composite photosynthetic bacteria and EM bacteria are first acclimatized and cultured. The method is as follows: in an anaerobic environment, using the effluent from the electrolysis treatment tank as the water source, the acclimatization is carried out for 7 days by sequential batch influent at 10%, 20%, 30%, 40%, 50%, 70% and 100%, or by continuous acclimatization at 10% influent for 10 days.

[0039] (5) The effluent from the salt-tolerant biological treatment system flows by gravity to the A / O biological treatment system for further treatment. The COD of the effluent after treatment by the A / O biological treatment system is ≤1000mg / L. In this step, the dissolved oxygen content is 4mg / L~6mg / L, the hydraulic retention time is ≤24h for section A and ≤16h for section O, the temperature is 10℃~40℃, and the pH does not need to be adjusted.

[0040] (6) The effluent from the A / O biochemical system enters the final sedimentation tank, where the solid and liquid waste is separated by inclined tube sedimentation. After that, the effluent flows into the discharge tank and is then connected to the integrated sewage treatment system.

[0041] In one preferred embodiment, both the primary flocculation sedimentation tank and the secondary flocculation sedimentation tank are vertical flow sedimentation tanks.

[0042] In one preferred embodiment, the dosage of flocculant in both the primary and secondary flocculation sedimentation tanks is 0.1–0.2 mg / L.

[0043] In one preferred embodiment, the mass ratio of the composite photosynthetic bacteria, EM bacteria, and waste liquid entering the salt-tolerant biochemical treatment system is 9:1:90.

[0044] In one of the preferred technical solutions, the salt-tolerant biochemical system can be one of a biofilm reactor, an SBR reactor, an intermittent aerated biofilter reactor, or a UASB anaerobic reactor, with the intermittent aerated biofilter reactor being the most preferred.

[0045] Example 1

[0046] A paper mill performs pre-pulping treatments on raw bamboo, including slicing, soaking, and shredding. The bamboo slices are soaked in a 30wt% caustic soda solution for 3 days, generating 300 tons of waste liquid. After soaking in the caustic soda solution, the bamboo slices are rinsed in clean water for 2 days, generating 200 tons of rinsing waste liquid. The bamboo slices are then rinsed again in clean water for 2 days, generating another 200 tons of rinsing waste liquid. A total of 700 tons of combined waste liquid is generated over 7 days. The combined waste liquid has a COD ≤ 50000 mg / L, a pH of 10–13, a TDS of 13880 mg / L, and SS ≤ 6000 mg / L.

[0047] The method for treating the above-mentioned combined wastewater using the bamboo pulping wastewater method described in this invention comprises the following specific steps:

[0048] (1) The 700 tons of comprehensive waste liquid generated in 7 days are mixed in the collection tank and then enter the homogenization and conditioning tank. Nano-aeration is added to the homogenization and conditioning tank for homogenization and oxidation. The nano-aeration has a particle size of 70nm to 100nm, a density of 30 to 40 million particles / mL, and a hydraulic retention time of 0.5 hours.

[0049] Table 1. Test results of raw wastewater after mixing in the collection tank

[0050] Testing items Results (mg / L) COD 45300 SS 3500 TDS 13880 pH (dimensionless) 11

[0051] (2) The wastewater after nano-aeration enters the primary flocculation sedimentation tank and flocculants are added for sedimentation. Flocculation sedimentation lasts for 2 hours. After primary flocculation sedimentation, the filtered water enters the secondary flocculation sedimentation tank and flocculants are added for sedimentation. Flocculation sedimentation lasts for 2 hours. The amount of flocculants added in the two flocculation sedimentation processes is the same. The flocculants are composed of aluminum oxide and mineral adsorbents. The content of aluminum oxide is above 26%. The mineral adsorbents include zeolite and kaolin. Both the primary and secondary flocculation sedimentation tanks are vertical flow sedimentation tanks.

[0052] In this step, four water samples were taken for flocculant dosage experiments. The flocculant dosage and COD removal rate for the two experiments are shown in Table 2.

[0053] Table 2. COD removal rate after flocculation and sedimentation

[0054]

[0055] As shown in Table 2, the flocculation and sedimentation effect was best when the flocculant dosage for both flocculation and sedimentation was 0.12 mg / L, indicating that more flocculant dosage is not necessarily better. To demonstrate the overall treatment effect of the process of this invention, in this embodiment, the effluent treated with the flocculant dosage with the worst flocculation effect (0.18 mg / L) was used for subsequent self-electrolysis and other steps.

[0056] (3) The supernatant after secondary flocculation and sedimentation flows into the self-electrolysis treatment tank by gravity, and the pH of the wastewater is adjusted to 8-9 and self-electrolyzed for 2 hours.

[0057] Table 3. Wastewater parameters after electrolysis treatment

[0058]

[0059] (4) The waste liquid after electrolysis in the self-electrolysis treatment tank for 2 hours enters the salt-tolerant biochemical treatment system (specifically, an intermittent aerated biological filter reactor) with a hydraulic retention time of 144 hours; the salt-tolerant biochemical treatment system contains compound photosynthetic bacteria and EM bacteria (EM bacteria purchased from Guangzhou Mubang Technology Co., Ltd.), and the compound photosynthetic bacteria are BioPower 600 salt-tolerant bacteria (the main components are various salt-tolerant Bacillus species, purchased from Wuhan Shuizhiguo Environmental Protection Technology Co., Ltd.);

[0060] The mass ratio of the compound photosynthetic bacteria to EM bacteria is 7:3; the dosage of the compound photosynthetic bacteria and EM bacteria is 0.005‰ of the mass of the waste liquid after the self-electrolysis treatment tank; the compound photosynthetic bacteria and EM bacteria are acclimatized and cultivated before treating the waste liquid. The method is as follows: in an anaerobic environment, using the effluent from the self-electrolysis treatment tank as the water source, the acclimatization is carried out for 7 days through a sequential batch influent of 10%, 20%, 30%, 40%, 50%, 70%, and 100%.

[0061] The influent of the salt-tolerant biological treatment system has a B / C ratio > 0.3, COD < 10000 mg / L, total nitrogen ≤ 100 mg / L, and TDS ≤ 25000 mg / L; the effluent has a COD < 1000 mg / L, total nitrogen ≤ 70 mg / L, and ammonia nitrogen ≤ 40 mg / L.

[0062] (5) The effluent from the salt-tolerant biological treatment system enters the A / O treatment system. The COD of the effluent after treatment by the A / O biological system is ≤1000mg / L. In the A / O treatment system, the dissolved oxygen content is 4mg / L~6mg / L; the hydraulic retention time is 24h for section A and 12h for section O; the temperature is 30℃; and the pH does not need to be adjusted. In this step, organic matter undergoes carbonization and nitrification / denitrification reactions under the action of facultative and aerobic bacterial communities, removing most of the organic matter, ammonia nitrogen, and total nitrogen.

[0063] (6) The effluent from the A / O biochemical system enters the final sedimentation tank, where the solid and liquid of the waste liquid are separated by inclined tube sedimentation. After that, the effluent flows into the discharge tank and is then connected to the integrated sewage treatment system.

[0064] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for treating bamboo pulping wastewater, characterized in that, Includes the following steps: (1) The bamboo chip pulp waste liquid is collected in the collection tank and then enters the homogenization and conditioning tank. Nano-aeration is added to the homogenization and conditioning tank for homogenization and oxidation. The COD of the bamboo chip pulp waste liquid is ≥40000 mg / L, TDS is ≥10000 mg / L, and pH is 10-13. (2) The waste liquid after nano-aeration enters the primary flocculation sedimentation tank and flocculant is added for sedimentation; the filtered water after primary flocculation sedimentation enters the secondary flocculation sedimentation tank and flocculant is added; the bubble size of the nano-aeration is 70-100 nm and the density is 30-40 million bubbles / mL; the flocculant is composed of aluminum oxide and mineral adsorbent, the aluminum oxide content is above 26%, and the mineral adsorbent includes zeolite and kaolin. (3) The supernatant after flocculation and sedimentation in the secondary sedimentation tank flows into the self-electrolysis treatment tank by gravity, and the pH of the wastewater is adjusted to 8~9. Pure iron is used as the anode and iron carbide is used as the cathode. The self-electrolysis time is 1~2h. (4) The waste liquid after passing through the self-electrolysis treatment tank enters the salt-tolerant biochemical treatment system, which contains compound photosynthetic bacteria and EM bacteria; the mass ratio of compound photosynthetic bacteria to EM bacteria is 7:3 to 8:2; the compound photosynthetic bacteria are BioPower 600 salt-tolerant bacteria; Before treating the waste liquid, the composite photosynthetic bacteria and EM bacteria are first acclimatized and cultured. The method is as follows: in an anaerobic environment, using the effluent from the electrolysis treatment tank as the water source, the acclimatization is carried out for 7 days by sequential batch influent at 10%, 20%, 30%, 40%, 50%, 70% and 100%, or by continuous acclimatization at 10% influent for 10 days. (5) The effluent from the salt-tolerant biological treatment system flows by gravity to the A / O biological treatment system for further treatment; in the A / O biological treatment system: dissolved oxygen content is 4mg / L~6mg / L, hydraulic retention time is ≤24h for section A and ≤16h for section O; temperature is 10℃~40℃; COD of the effluent after treatment by the A / O biological treatment system is ≤1000mg / L; (6) The effluent from the A / O biochemical system enters the final sedimentation tank, where the solid and liquid of the waste liquid are separated by inclined tube sedimentation. After that, the effluent flows into the discharge tank and is then connected to the integrated sewage treatment system.

2. The method according to claim 1, characterized in that, The hydraulic retention time of the waste liquid in the homogenization tank is 0.5 to 2 hours.

3. The method according to claim 1, characterized in that, Both the primary and secondary flocculation sedimentation tanks are vertical flow sedimentation tanks, and the flocculation sedimentation time is 2 to 10 hours. The dosage of flocculant in both the primary and secondary flocculation sedimentation tanks is 0.1 to 0.2 mg / L.

4. The method according to claim 1, characterized in that, The salt-tolerant biochemical system is selected from one of the following: biofilm reactor, SBR reactor, intermittent aerated biofilter reactor, and UASB anaerobic reactor.

5. The method according to claim 1, characterized in that, The composite photosynthetic bacteria are BioPower 600 salt-tolerant bacteria; the hydraulic retention time of the waste liquid in the salt-tolerant biochemical treatment system is 144~192 hours.

6. The method according to claim 1, characterized in that, The dosage of the compound photosynthetic bacteria and EM bacteria is 0.005-0.01‰ of the mass of the waste liquid after the self-electrolysis treatment tank.

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