An anaerobic front-end pre-detoxification treatment method for sulfite lye waste water

Abstract

The present application belongs to the technical field of pulp and papermaking wastewater treatment, and particularly relates to an anaerobic front-end pre-detoxification treatment method for camphor wood mechanical pulp wastewater, comprising the following steps: 1) adding polyaluminum chloride and anionic polyacrylamide into the camphor wood mechanical pulp wastewater and mixing; the polyaluminum chloride is added in an amount of 0.05-0.4% by weight of the camphor wood mechanical pulp wastewater, and the anionic polyacrylamide is added in an amount of 0.002-0.01% by weight of the camphor wood mechanical pulp wastewater; 2) adjusting the pH value to 2-5, and adding an oxidizing agent into the wastewater, wherein the oxidizing agent is persulfate; the present application can effectively improve the removal rate of terpene pollutants in the camphor wood mechanical pulp wastewater, reduce the COD value, and eliminate the biological toxicity inhibition of subsequent anaerobic treatment.

Description

Technical Field

[0001] This invention belongs to the field of pulp and paper wastewater treatment technology, specifically relating to an anaerobic pre-detoxification treatment method for camphor wood chemical mechanical pulp wastewater. Background Technology

[0002] In the pulp and paper industry, the cost of timber raw materials, the stability of raw material supply, and the availability of regional resources are important factors affecting the raw material structure of enterprises. In recent years, influenced by factors such as rising prices of high-quality commercial wood chips, increased transportation costs for purchased timber, and increased demand for cost reduction and efficiency improvement, some chemimechanical pulp production enterprises have gradually increased their utilization of alternative timber resources that are readily available locally and have relatively low procurement costs. Camphor wood, as a local timber raw material with certain resource distribution advantages in some regions, can be used as a supplementary or alternative raw material in chemimechanical pulp production under certain conditions, thus forming a production model of camphor wood pulping alone or blending with conventional wood.

[0003] However, camphor wood differs significantly from conventional pulping wood in its natural organic composition. In the production of chemimechanical pulp using camphor wood as raw material or blended with a certain proportion of camphor wood, the natural volatile essential oils, terpenes, and oxygenated terpenes in the wood are released and enter the wastewater system during processes such as hot milling, extrusion, and washing. This results in wastewater that, in addition to exhibiting the typical characteristics of high organic load, high suspended solids, and high volatility found in papermaking wastewater, further displays complex pollutant composition, enhanced biological inhibition, and a sudden increase in localized toxicity. In other words, while the introduction of camphor wood as a raw material alleviates some of the pressure on raw material costs and resource security for enterprises, it also presents new challenges to the stable operation of wastewater treatment systems.

[0004] In camphor wood slurry wastewater treatment systems, the anaerobic unit typically undertakes the main functions of reducing organic load and recovering methanogenic energy, making it a crucial link in the stable operation of the entire process. Research and engineering practice have shown that when the proportion of camphor wood increases or influent fluctuations intensify, the anaerobic system often first exhibits phenomena such as decreased COD removal rate, inhibited gas production, suppressed intermediate metabolism, and deteriorated effluent, subsequently transferring the load and risks to subsequent aerobic and advanced treatment units, leading to increased system energy consumption, heavier sludge burden, and higher operating costs. Therefore, from the perspective of system stability and synergistic pollution and carbon reduction, targeted pre-detoxification control of the anaerobic system is significantly necessary.

[0005] Currently, publicly available pretreatment technologies for pulp and paper wastewater primarily aim to reduce total pollutants such as COD, SS, and color. Common methods include coagulation sedimentation, flotation, biological pretreatment, and combinations thereof. These technologies are effective in removing suspended, colloidal, or some recalcitrant organic matter. However, most solutions lack the identification and targeted control of characteristic inhibitory organic compounds, particularly failing to establish a "identification-reduction-recovery" technical chain for key pollutants in camphor wood chemical pulp wastewater that cause anaerobic inhibition.

[0006] Previous studies have shown that using coagulation sedimentation as an enhanced pretreatment method for anaerobic processes can improve the influent water quality of camphor wood chemical pulp wastewater to a certain extent and buffer the impact on subsequent anaerobic systems. Under optimized conditions, the influent COD decreased by 25.9% and SS decreased by 28.7%. The COD removal efficiency of the pretreated wastewater entering the anaerobic unit was 14.5% higher than that of direct treatment of raw water. This indicates that adding a physicochemical buffer unit is feasible. However, conventional coagulation sedimentation still has significant limitations: firstly, it has limited ability to remove dissolved, small molecule, and hydrophobic organic matter; secondly, it has a long retention time and high chemical consumption; and thirdly, it produces a large increase in sludge, resulting in high cost per ton of water treated, making it difficult to balance functionality and economy. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide an anaerobic pre-detoxification treatment method for camphor wood chemical pulp wastewater. The present invention can effectively improve the removal rate of terpene pollutants in camphor wood chemical pulp wastewater, reduce COD value, and eliminate the biotoxicity inhibition of subsequent anaerobic treatment.

[0008] This invention provides an anaerobic pre-detoxification treatment method for camphor wood chemical pulp wastewater, comprising the following steps: 1) Add polyaluminum chloride and anionic polyacrylamide to the camphor wood chemical pulp wastewater and mix them; The added polyaluminum chloride is 0.05-0.4% of the weight of the camphor wood chemical pulp wastewater, and the added anionic polyacrylamide is 0.002-0.01% of the weight of the camphor wood chemical pulp wastewater. 2) Adjust the pH value to 2-5 and add an oxidant, namely persulfate, to the wastewater.

[0009] The camphor wood chemical pulp wastewater originates from camphor wood chip washing water, wastewater from the extrusion section of the chemical machinery workshop, or influent from the pre-anaerobic settling tank; the camphor wood chemical pulp wastewater contains terpene pollutants, including one or more of α-pinene, eucalyptol, camphor, and terpineol.

[0010] Because the flocs formed by coagulation with polyaluminum chloride (PAC) in camphor wood chemical pulp wastewater have a surface more suitable for increasing particle size through long-chain bridging, and anionic polyacrylamide (PAM) is more conducive to forming stable large flocs with aluminum salt hydrolysis products, the combination of the two promotes the formation of separable flocs from hydrophobic terpene pollutants and colloidal and suspended organic components.

[0011] Adding the oxidant of this invention enables deep oxidative degradation of residual soluble and recalcitrant terpene pollutants in wastewater. It can effectively attack the unsaturated bonds and functional groups of terpene pollutants, and achieve degradation of toxic components through the free radical oxidation pathway, thus overcoming the limitations of coagulation pretreatment in removing soluble small molecule pollutants.

[0012] Compared to a single coagulation method, the treatment method of the present invention is more suitable for comprehensively reducing terpene pollutants of different properties, such as camphor, eucalyptol, terpineol, and α-pinene, and can achieve directional pre-detoxification at the anaerobic front end in a shorter time.

[0013] Preferably, the degree of hydrolysis of the anionic polyacrylamide is 10-30%, and the molecular weight is 5 million-18 million.

[0014] Preferably, the anionic polyacrylamide has a molecular weight of 8 million to 15 million.

[0015] Preferably, the mixing time in step 1) is 10-30 min.

[0016] Preferably, the weight of the polyaluminum chloride added is 0.1-0.3% of the weight of the camphor wood slurry wastewater, and the weight of the anionic polyacrylamide added is 0.004-0.008% of the weight of the camphor wood slurry wastewater.

[0017] Preferably, the weight of the polyaluminum chloride added is 0.2% of the weight of the camphor wood chemimetallurgical wastewater, and the weight of the anionic polyacrylamide added is 0.006% of the weight of the camphor wood chemimetallurgical wastewater.

[0018] Preferably, the persulfate is a potassium peroxymonosulfate complex salt, potassium persulfate, or ammonium persulfate.

[0019] The potassium peroxymonosulfate complex salt includes potassium peroxymonosulfate (KHSO5), which is the main active ingredient and provides oxidation properties, and also includes potassium bisulfate (KHSO4) and potassium sulfate (K2SO4), which mainly play a stabilizing and buffering role. The molecular formula is represented as 2KHSO5·KHSO4·K2SO4.

[0020] Preferably, the persulfate is a potassium peroxymonosulfate complex salt, and ferrous ions are also added to the wastewater in step 2).

[0021] Preferably, in step 2), the pH value is adjusted to 3-4, and the amount of oxidant added is 0.1-5 g / L, preferably 0.1-0.2 g / L. The ferrous ions exist in the form of ferrous sulfate, and the concentration of ferrous sulfate in the camphor wood chemimechanical pulp wastewater is 1-2 mmol / L.

[0022] Preferably, after adding the oxidant, the mixing time is 10-60 minutes; then the pH value is adjusted to 6.5-7.5.

[0023] The beneficial effects of this invention are that, through the synergistic effect of coagulation and advanced oxidation technologies, it achieves efficient pretreatment of wastewater and a significant improvement in subsequent anaerobic performance.

[0024] This invention specifically targets terpene pollutants in camphor wood pulp wastewater, demonstrating significant industry relevance. Through the hydrolysis of PAC, polynuclear hydroxyl complexes compress the electric double layer and adsorb hydrophobic components. Combined with the long-chain bridging effect of anionic PAM, large-particle-size, highly stable flocs are formed. Simultaneously, sulfate and hydroxyl radicals generated during advanced oxidation processes are used to target the olefin bonds and oxygen-containing functional groups of terpene pollutants. This synergistic mechanism of coagulation-encapsulation combined with oxidative bond breaking effectively disrupts the chemical structure of recalcitrant organic matter, exhibiting particularly high degradation efficiency for eucalyptol and terpineol containing active groups such as hydroxyl groups. Partial degradation of structurally stable camphor and α-pinene can also be achieved through ring-opening and bond breaking.

[0025] This invention, through pre-detoxification, effectively reduces components that strongly inhibit anaerobic systems, solving the problem of directly and efficiently treating highly toxic wastewater through anaerobic processes. Its main features include: 1. After pretreatment by the present invention, the COD removal rate of the subsequent anaerobic system is significantly increased from 61% in the traditional high-toxicity raw water group to 79%.

[0026] 2. The system's cumulative methane production and specific methane production rate are both superior to the undetoxified group, achieving higher energy recovery efficiency.

[0027] 3. Pretreatment effectively mitigates the risk of accumulation of intermediate metabolites (such as VFA), making the VFA conversion process smoother and ensuring the stability of the anaerobic system.

[0028] This invention constructs a complete technical chain of characteristic pollutant identification, targeted oxidation detoxification, and anaerobic function restoration, achieving a significant reduction in wastewater toxicity at each stage. Even under highly toxic conditions with a total toxicity concentration of 30 mg / L, it can still significantly reduce various terpene pollutants; under low toxicity conditions of 6-7 mg / L, the removal rates of camphor, terpineol, and eucalyptol reach over 40%, 50%, and 65%, respectively. The relative luminescence of the raw water was only 40.38% (highly toxic), which increased to over 70% (mildly toxic or non-toxic) after coagulation-advanced oxidation pretreatment, and further increased to 86.43% after 8 hours of subsequent anaerobic treatment, completely eliminating biotoxicity inhibition.

[0029] Compared to traditional coagulation and sedimentation processes, this invention offers advantages in terms of reagent consumption and treatment efficiency. It features a reasonable reagent dosage, short retention time, and low overall operating costs. By prioritizing the reduction of characteristic pollutants detrimental to methanation, it lowers the aeration energy consumption and sludge treatment pressure in the subsequent aerobic stage. This method is particularly suitable for treating pulp and paper wastewater under fluctuating camphor wood raw material ratios, ensuring the long-term stable operation of the treatment system. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating the processing of an embodiment of the present invention. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments. For those skilled in the art, equivalent substitutions or simple modifications made without departing from the concept of the present invention should be considered to fall within the scope of protection of the present invention.

[0032] Example 1 An anaerobic pre-detoxification treatment method for camphor wood chemical pulp wastewater includes the following steps: 1) Pre-treat the camphor wood chemical pulp wastewater by coagulation; the specific steps are: add polyaluminum chloride (PAC) and anionic polyacrylamide (PAM) to the camphor wood chemical pulp wastewater, mix them to form flocs; The added polyaluminum chloride is 0.2% of the weight of the camphor wood slurry wastewater, and the added anionic polyacrylamide is 0.006% of the weight of the camphor wood slurry wastewater. The mixing time is 20 minutes. 2) Then, use dilute acid (such as 10% dilute sulfuric acid) to adjust the pH of the wastewater after coagulation pretreatment to 2-5 (preferably 3-4, specifically 3.5 in Example 1) for advanced oxidation treatment; the specific steps are: add an oxidant to the wastewater after coagulation pretreatment, the oxidant is potassium persulfate, the amount of oxidant added is 2g / L, and the mixing time after adding is 30min.

[0033] After pre-detoxification treatment, the pH of the oxidized wastewater is adjusted to 6.5-7.5 using liquid alkali (such as a 10% NaOH solution). The effluent is then sent to an anaerobic biological treatment unit for further treatment. Specific process details... Figure 1 As shown.

[0034] Example 2 Compared with Example 1, Example 2 is the same as Example 1 except that the oxidant is potassium persulfate complex salt (PMS complex salt).

[0035] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the oxidant is Fenton's reagent, specifically H2O2 / Fe. 2+ H2O2 and Fe 2+ The molar ratio was 2:1, the dosage of hydrogen peroxide with a mass concentration of 27.5% was 25 mL / L, and the dosage of ferrous sulfate heptahydrate with a purity of 85% was 36.4 g / L. Everything else was the same as in Example 1.

[0036] Comparative Example 2 Compared with Example 1, Comparative Example 2 differs in that the oxidant is ozone (O3), an ozone generator is used to supply ozone, oxygen is used as the gas source, the ozone production rate is 8 g / h, it is introduced into 1 L of water, and the oxidation time is 60 minutes. Everything else is the same as in Example 1.

[0037] Comparative Example 3 Compared with Example 1, Comparative Example 3 differs in that polyaluminum chloride (PAC) is replaced with polyferric sulfate (PFS). Everything else is the same as in Example 1.

[0038] Comparative Example 4 Comparative Example 4 differs from Example 1 in that polyaluminum chloride (PAC) is replaced with aluminum sulfate. Everything else is the same as in Example 1.

[0039] Comparative Example 5 Compared with Example 1, Comparative Example 5 differs in that step 2 is removed, and only step 1 is retained. Everything else is the same as Example 1.

[0040] Comparative Example 6 Compared with Example 1, Comparative Example 6 is different in that step 1 is removed and only step 2 is retained. Otherwise, it is the same as Example 1.

[0041] Example 3 The wastewater was taken from the extrusion section of the camphor wood chemical pulp workshop, with a COD value of 12000 mg / L and a total concentration of characteristic pollutants of 30 mg / L. The effects of Examples 1-2 and Comparative Examples 1-6 on the removal rate of terpenoid characteristic pollutants and the acute toxicity of the wastewater (characterized by the relative luminescence of luminescent bacteria) in camphor wood chemical pulp wastewater were compared, and the results are shown in Table 1 below.

[0042] Table 1 Comparison of the removal effects of different pre-detoxification combination processes on terpene pollutants

[0043] The relative luminescence intensity was assessed for acute toxicity using the luminescent bacteria method, according to the national standard GB / T 15441-1995.

[0044] The data above demonstrates that this invention is significantly more effective than other combinations (such as Fenton, PMS, ozone, etc.) in targeted detoxification (removal of characteristic pollutants) and toxicity reduction (improvement of relative luminescence). Its particularly high efficiency in removing camphor, a highly toxic and structurally stable pollutant, is a key advantage. The superior performance of this invention compared to coagulation or oxidation alone indicates a synergistic effect, rather than a simple additive effect.

[0045] Example 4 This embodiment uses camphor wood chemical pulp wastewater under low-toxicity conditions as the treatment object, simulating a total toxic substance content of approximately 6.767 mg / L in the entire camphor wood wastewater, and conducts research on coagulation pretreatment-advanced oxidation pre-detoxification and subsequent anaerobic enhancement. The dosage ratios of the four characteristic toxic substances (α-pinene, eucalyptol, camphor, and terpineol) are set according to the measured concentration ratios in the camphor wood chemical pulp wastewater.

[0046] First, dichloromethane liquid-liquid extraction combined with GC-MS was used to identify potential inhibitory components in camphor wood chemical pulp wastewater, confirming that the main characteristic pollutants were α-pinene, eucalyptol, camphor, and terpineol. The concentrations of each pollutant in different processes are shown in Table 2 below.

[0047] Table 2. Concentrations of characteristic terpenoid pollutants at various stages of the camphor wood chemical pulp wastewater treatment process.

[0048] As shown in Table 2, the characteristic pollutants are significantly enriched at the drainage point of the pulping workshop, with a total concentration of over 30 mg / L. The anaerobic unit is the main reduction link and the core unit that withstands the toxic impact.

[0049] The toxicity of the above-mentioned characteristic pollutants was identified using a luminescent bacteria method. The results showed that the toxicity intensity was ranked as follows: camphor > terpineol > pinene > eucalyptol. Camphor and terpineol were determined to be extremely toxic, while pinene and eucalyptol were determined to be highly toxic. A mixed concentration of 72-108 mg / L was considered highly toxic.

[0050] In the anaerobic pre-detoxification process, coagulation pretreatment is first performed: the pH of the wastewater is adjusted to 6.5-7.5, and polyaluminum chloride (PAC) and anionic polyacrylamide (PAM) are added to the reaction tank. Through experimental optimization, the PAC dosage is set to 0.5‰, 1‰, 2‰, 3‰, and 4‰, while the PAM dosage is fixed at 60 ppm. The preferred molecular weight of PAM is 8 million-15 million. The coagulation reaction time is 15-20 minutes.

[0051] After coagulation pretreatment, the effluent enters the advanced oxidation treatment unit. This embodiment employs an advanced oxidation process based on persulfate. Potassium persulfate complex salt (PMS complex salt) is added to the oxidation reaction tank as an oxidant at a dosage of 50-200 mg / L. Simultaneously, the system pH is adjusted to 3-4 and / or trace amounts of transition metal ions (such as Fe²⁺) are added. + (0.5-2 mM) to activate persulfate, generating sulfate free radicals (SO4• - It uses hydroxyl radicals (•OH) to efficiently degrade soluble, recalcitrant toxic organic compounds that cannot be removed by coagulation. The advanced oxidation reaction takes 30-60 minutes.

[0052] During parameter optimization, in the coagulation pretreatment stage, a PAC dosage of 2‰ showed the best overall effect on the removal of characteristic pollutants and subsequent oxidation efficiency. In the advanced oxidation stage, a persulfate dosage of 100 mg / L, pH=3.5, and 1 mM Fe²⁺ were optimal. + The highest degradation efficiency for residual toxins is achieved when ferrous sulfate is completely dissolved (referring to the instantaneous molar concentration of ferrous ions in the advanced oxidation reaction system). The synergistic effect of these two methods enables broad-spectrum removal of both hydrophobic (through coagulation) and hydrophilic (through oxidation) toxic substances.

[0053] Under the above optimized conditions (coagulation pretreatment: addition of 2‰ PAC + 60 ppm PAM for coagulation; advanced oxidation treatment: adjustment of pH to 3.5, addition of 100 mg / L PMS + 1 mM Fe²), + After being processed in series, the system showed a significant targeted reduction effect on terpene-characteristic pollutants.

[0054] The total toxic content of camphor wood wastewater was obtained by quantitatively detecting four characteristic terpene pollutants—α-pinene, eucalyptol, camphor, and terpineol—using GC-MS, and then summing the concentrations of the four pollutants. The calculation formula is as follows:

[0055] For example, if the concentrations of the four pollutants in the wastewater from the laboratory camphor wood chip pressing are 2.85 mg / L, 7.21 mg / L, 8.29 mg / L, and 11.66 mg / L, then the total toxic concentration is 30.01 mg / L, approximately 30 mg / L. The 6.767 mg / L concentration under low-toxicity conditions in Example 4 was also obtained by summing the concentrations of the four pollutants using the same method.

[0056] Example 4 actually includes three steps: coagulation pretreatment optimization, advanced oxidation optimization, and subsequent anaerobic validation. In the coagulation stage, the PAC dosage was set at 0.5‰, 1‰, 2‰, 3‰, and 4‰, and the PAM dosage was 60 ppm, with a reaction time of 15-20 min. In the advanced oxidation stage, the initial pH was adjusted before adding the oxidant, followed by the addition of persulfate oxidant and Fe²⁺. + Activator, examining the dosage of oxidant and Fe² + The effects of concentration, pH and reaction time on the removal of COD and four toxins.

[0057] The total toxic substance removal rate refers to the removal rate of the total concentration of the four terpene pollutants, and the calculation formula is as follows:

[0058] Single pollutant removal rate is calculated as follows:

[0059] The toxic substance removal rate was calculated based on the concentrations before and after treatment as determined by GC-MS. The total COD removal rate was calculated based on the measured COD values ​​before and after treatment.

[0060] The COD removal rate is the total COD removal rate relative to the raw water after the two steps of coagulation and advanced oxidation are completed.

[0061] The VFA and methanogenesis experiments employed a batch anaerobic reactor system. Both the untreated raw water and the pre-treated effluent were adjusted to a COD of 6000 mg / L, inoculated with stable anaerobic sludge, and reacted for 8 h under nitrogen purging and sealed conditions at 35 ± 1 ℃, pH 6.8–7.2. COD, total VFA, acetic acid, propionic acid, butyric acid, gas production, and methane content were measured at 0, 2, 4, 6, and 8 h. Cumulative methanogenesis was calculated by multiplying gas production by the methane volume fraction, and the specific methanogenesis rate was calculated as the amount of methane produced per unit VSS per unit time. Based on the 8-h endpoint data, the cumulative methanogenesis and specific methanogenesis rate in the pre-treated group were more than 30% higher than those in the untreated group.

[0062] Under the above optimized conditions (coagulation pretreatment: addition of 2‰ PAC + 60 ppm PAM for coagulation; advanced oxidation treatment: adjustment of pH to 3.5, addition of 100 mg / L PMS + 1 mM Fe²), + The rest is the same as in Example 1.

[0063] For the wastewater containing approximately 6.767 mg / L of toxic substances from camphor wood, the COD removal rate was approximately 41%, the α-pinene removal rate was 89%, the eucalyptol removal rate reached 95%, the camphor removal rate was 90%, the terpineol removal rate reached 92%, and the subsequent anaerobic COD removal rate was 85%.

[0064] The pre-detoxified wastewater was adjusted to a COD of 6000 mg / L and then fed into an anaerobic system for 8 hours of treatment. The results showed that the anaerobic metabolic continuity of the pre-detoxified group was significantly better than that of the unpre-detoxified group, the conversion of volatile fatty acids (VFA) was smooth and no accumulation was observed, and the methanogenesis rate and cumulative methanogenesis were both increased by more than 30%.

[0065] The closed-loop toxicity evaluation showed that after coagulation-advanced oxidation pre-detoxification, the wastewater toxicity decreased from "highly toxic" to "slightly toxic"; after subsequent anaerobic treatment, the system toxicity further decreased to "non-toxic". This indicates that the method of the present invention forms an effective detoxification closed loop, significantly improving the anaerobic system's resistance to shock loads and operational stability.

[0066] Example 5: Anaerobic pre-detoxification and anaerobic enhancement under highly toxic conditions This embodiment takes camphor wood chemical pulp wastewater under highly toxic conditions as the treatment object and conducts research under the simulated working conditions of approximately 30-33 mg / L of total toxic substances in laboratory camphor wood chip extrusion wastewater.

[0067] The same coagulation pretreatment-advanced oxidation treatment tandem process as in Example 1 was employed. Under high toxicity loads, the dosage of oxidant was appropriately increased to cope with the higher toxicity load. The optimized conditions were: 2.5‰ PAC + 60 ppm PAM added during the coagulation stage; pH adjusted to 3.0 during the advanced oxidation stage, with the addition of 150 mg / L PMS + 1.5 mM Fe²⁺. + .

[0068] The COD removal rate was 38%, the α-pinene removal rate was 87%, the eucalyptol removal rate was 94%, the camphor removal rate increased to 92%, the terpineol removal rate increased to 93%, and the subsequent anaerobic COD removal rate was 83%.

[0069] The results show that this tandem process exhibits stronger adaptability under highly toxic conditions.

[0070] In terms of methanogenic performance, although the initial gas production of the pre-detoxification group was slightly slower due to the oxidation of some easily degradable organic matter in the early stage, the cumulative methanogenic amount at the end of 8 hours was more than 40% higher than that of the direct treatment group, and the methanogenic rate was also significantly improved, proving that the method effectively restored the suppressed anaerobic methanogenesis function.

[0071] Meanwhile, the VFA conversion process in the pre-detoxified group was stable, effectively avoiding the accumulation of intermediate products such as propionic acid and butyric acid, and ensuring the integrity of the anaerobic metabolic chain.

[0072] The toxicity verification results of the luminescent bacteria method are shown in Table 3, which demonstrates the excellent detoxification ability of this method for highly toxic wastewater.

[0073] Table 3. Toxicity changes during the pre-detoxification-anaerobic tandem process.

[0074] Comparison of this invention with single coagulation sedimentation or individual advanced oxidation processes highlights the synergistic effect. The method of this invention achieves more thorough detoxification and superior subsequent anaerobic effects with lower overall chemical consumption and shorter residence time.

[0075] Comparative Example 7: Low-toxicity raw water was directly introduced into anaerobic treatment without pre-detoxification. This comparative example uses camphor wood chemical pulp wastewater with a total toxicity content of approximately 6.767 mg / L under low toxicity conditions. No pre-detoxification treatment such as coagulation-advanced oxidation is performed. The wastewater is directly diluted to a COD of 6000 mg / L according to the experimental settings and then sent into the anaerobic system.

[0076] The results showed that, under conditions without pre-detoxification, although the anaerobic system could maintain a certain treatment capacity, the VFA conversion and methanation processes were more easily suppressed than in the pre-detoxification group when continuously affected by characteristic pollutants, and the gas production recovery capacity was weaker in the later stage. This indicates that even under low-toxicity conditions, directional detoxification at the front end of the anaerobic system is still beneficial to improving the operational stability of the anaerobic system.

[0077] Comparative Example 8: Highly toxic raw water was directly introduced into anaerobic treatment without pre-detoxification. This comparative example uses camphor wood chemical pulp wastewater with a total toxicity content of approximately 33.835 mg / L under highly toxic conditions. Without anaerobic pre-detoxification treatment, it is directly diluted to a COD of 6000 mg / L according to the same ratio as in Example 5 before being sent into the anaerobic system.

[0078] The results showed that the COD removal rate of the untreated, highly toxic raw water group was 61%, significantly lower than the over 85% achieved after pre-detoxification in Example 3. Furthermore, in the single-pollutant shock experiment, when the dosage was 200 mg / L, the COD removal rate of the control group was 57%, while it decreased to 39%-46% in the shock group, and the cumulative methane production decreased from 270 mL to 175-215 mL, further demonstrating that directly introducing highly toxic raw water into the anaerobic system causes a significant inhibitory effect.

[0079] The toxicity of the highly toxic raw water was evaluated by luminescent bacteria. The relative luminescence of the raw water + highly toxic mixture was 40.38%, classifying it as severely toxic. Compared with Example 3, highly toxic raw water that has not undergone anaerobic pre-detoxification is unlikely to effectively mitigate the toxicity impact in a short period of time, and is also detrimental to the stable operation of the subsequent system and energy recovery.

[0080] In summary, this invention addresses the characteristic terpene pollutants in camphor wood chemical pulp wastewater by constructing a synergistic anaerobic pre-detoxification enhancement method combining coagulation pretreatment and advanced oxidation treatment. This method preferentially removes hydrophobic particulate and colloidal toxic substances through coagulation, followed by deep degradation of soluble and recalcitrant toxic substances through advanced oxidation, achieving graded and targeted removal of inhibitors with different forms and properties. This method significantly reduces the acute toxicity of the wastewater, improves the continuity of subsequent anaerobic metabolism and methanogenesis capacity, and demonstrates significant advantages in treatment effect, operational stability, and engineering economy, exhibiting excellent synergistic benefits in pollution reduction and carbon reduction.

[0081] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of protection of this application is limited to these examples; within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of one or more embodiments of this application as described above, which are not provided in detail for the sake of brevity.

[0082] One or more embodiments in this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments in this application should be included within the protection scope of this application.

Claims

1. An anaerobic front-end pre-detoxification treatment method for a sulfidic pulp mill effluent, characterized by, Includes the following steps: 1) Add polyaluminum chloride and anionic polyacrylamide to the camphor wood chemical pulp wastewater and mix them; The added polyaluminum chloride is 0.05-0.4% of the weight of the camphor wood chemical pulp wastewater, and the added anionic polyacrylamide is 0.002-0.01% of the weight of the camphor wood chemical pulp wastewater. 2) Adjust the pH value to 2-5 and add an oxidant, namely persulfate, to the wastewater.

2. The method of claim 1 wherein, The anionic polyacrylamide has a degree of hydrolysis of 10-30% and a molecular weight of 5 million-18 million.

3. The method of claim 2, wherein, The anionic polyacrylamide has a molecular weight of 8 million to 15 million.

4. The method of claim 1 wherein, The mixing time in step 1) is 10-30 minutes.

5. The method of claim 1 wherein, The added polyaluminum chloride is 0.1-0.3% of the weight of the camphor wood chemical pulp wastewater, and the added anionic polyacrylamide is 0.004-0.008% of the weight of the camphor wood chemical pulp wastewater.

6. The method of claim 5 wherein, The added polyaluminum chloride is 0.2% of the weight of the camphor wood chemical pulp wastewater, and the added anionic polyacrylamide is 0.006% of the weight of the camphor wood chemical pulp wastewater.

7. The method according to any one of claims 1 to 6, wherein the method is characterized by, The persulfate is a potassium peroxymonosulfate complex salt, potassium persulfate, or ammonium persulfate.

8. The method of claim 7 wherein, The persulfate is a potassium peroxymonosulfate complex salt, and ferrous ions are also added to the wastewater in step 2).

9. The method of any one of claims 1-6, wherein, Step 2) Adjust the pH value to 3-4 and add 0.1-5 g / L of oxidant.

10. The method of any one of claims 1-6, wherein, After adding the oxidant, mix for 10-60 minutes; then adjust the pH to 6.5-7.5.

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