A process and system for treating waste acid and alkali, and high-salt, recalcitrant waste liquid.

Abstract

This invention relates to a treatment process and system for waste acid and alkali, and high-salt, recalcitrant waste liquid, comprising: Step 1, acid-base compatibility and impurity removal of the waste liquid; Step 2, primary advanced oxidation treatment of the waste liquid; Step 3, heavy metal precipitation of the waste liquid; Step 4, secondary advanced oxidation treatment of the waste liquid; Step 5, desalination and ammonia removal treatment of the waste liquid; and Step 6, post-biochemical treatment of the waste liquid. This application provides a comprehensive treatment process for waste acid and alkali, and high-salt, recalcitrant waste liquid by homogenizing and removing impurities before oxidation, two-stage advanced oxidation pretreatment and coagulation sedimentation treatment during oxidation, evaporation desalination and ammonia nitrogen removal treatment after oxidation, and subsequent biochemical treatment. Specifically, by effectively pre-treating the target pollutants at the treatment end, it reduces the pressure on subsequent physicochemical and wastewater treatment processes, improves treatment efficiency, and ensures that the downstream treatment processes meet standards.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hazardous waste disposal, in particular to a treatment process and system for waste acid, alkali and high-salt refractory liquid waste. BACKGROUND

[0002] The disposal process of a comprehensive hazardous waste disposal enterprise generally includes physical and chemical disposal, incineration disposal, stabilization and solidification disposal, landfill, etc. Among them, the physical and chemical disposal, as the main process unit for inorganic waste liquid disposal, includes the disposal of waste acid, waste alkali, electroplating waste liquid, laboratory waste liquid and high-salt wastewater. Such waste is generally characterized by complex composition, wide source, high toxicity, high organic matter, ammonia nitrogen, TDS, heavy metal and other pollution indicators, high disposal difficulty and great difficulty in handling secondary pollutants generated during the disposal process.

[0003] At present, the process route of oxidation-reduction, neutralization precipitation, solid-liquid separation and wastewater treatment is mainly used in China for treating complex waste liquid containing waste acid and alkali. Through oxidation-reduction and neutralization precipitation, heavy metals and free acid and alkali in the waste liquid can be effectively removed, but the removal effect of organic matter, ammonia nitrogen, TDS and other pollutants in the waste liquid is very poor. These pollutants are transferred to wastewater through the process chain, resulting in problems such as high influent index, poor operation stability, large amount of concentrated liquid, difficulty in viscous salt separation, frequent heater fouling, low biochemical treatment efficiency and non-compliance, etc., which brings great difficulty to subsequent treatment. Moreover, due to the complex composition of organic matter in waste acid and alkali, such as a large amount of phenolic and biphenyl macromolecular refractory pollutants with strong toxicity and poor biodegradability, the salt content of the wastewater after neutralization is high, making it difficult to achieve treatment effect by using traditional wastewater treatment process. At the same time, due to the use of traditional neutralization method, it is difficult to well dispose of organic matter and ammonia nitrogen, which brings great difficulty to the end wastewater treatment.

[0004] Therefore, in order to ensure the stable and compliant operation of wastewater treatment, the removal of key limiting pollution factors such as COD and NH3-N should be realized as much as possible at the waste liquid disposal end, so as to ensure the compliance of subsequent process operation. At the same time, the waste liquid disposal and wastewater treatment should adopt a systematic and serial process combination to avoid the systematic operation problems caused by the incoherent connection of multiple process units. SUMMARY

[0005] Therefore, the present application provides a treatment process and system for waste acid, alkali and high-salt refractory liquid waste, which is used to solve the problem that the neutralization waste liquid treatment method in the traditional waste liquid disposal technology cannot well treat organic matter, ammonia nitrogen and TDS, resulting in increased difficulty in end wastewater treatment. The specific scheme is as follows:

[0006] A treatment process for waste acid, alkali and high-salt refractory liquid waste, comprising the following steps:

[0007] Step one, acid-base compatibility, impurity removal of waste liquid;

[0008] Step two, first-stage advanced oxidation treatment of waste liquid after impurity removal;

[0009] Step three, heavy metal precipitation of waste liquid after first-stage oxidation treatment;

[0010] Step four, second-stage advanced oxidation treatment of waste liquid after heavy metal removal;

[0011] Step five, desalination and ammonia removal treatment of waste liquid after second-stage advanced oxidation treatment;

[0012] Step six, biochemical post-treatment of waste liquid after desalination and ammonia removal treatment.

[0013] Preferably, the first-stage advanced oxidation treatment adopts Fenton-like oxidation;

[0014] The second-stage advanced oxidation treatment adopts ozone catalytic oxidation.

[0015] Preferably, in the first-stage advanced oxidation treatment, the pH value of the homogeneous system is 3-4, the HRT of the waste liquid in the oxidation tower is >60 min, the upflow velocity is ≤0.05 m / min; the ratio of H2O2 dosage to waste liquid influent COD is 0.6-1.2 mg H2O2 / mg COD, and the acid pickling waste liquid (in terms of M 2+ ) dosage is H2O2: M 2+ = 4.5-6:1.

[0016] Preferably, in the second-stage advanced oxidation treatment:

[0017] The pH of the system is 8-9;

[0018] The ratio of ozone dosage to waste liquid influent COD is 0.2-0.8 mg O 3 / mg COD;

[0019] The circulation stage of the influent is not less than 3 stages, and the particle size of the catalyst material is 5-8 mm.

[0020] Preferably, the heavy metal precipitation treatment includes coagulation sedimentation and first-stage solid-liquid separation;

[0021] The coagulation sedimentation rapidly precipitates the heavy metals in the waste liquid;

[0022] The first-stage solid-liquid separation separates the precipitated heavy metals from the remaining wastewater;

[0023] During coagulation and sedimentation, the pH value of the enhanced coagulation treatment is adjusted to pH 6-8, the dosage of calcium oxide is 30-50 g / L, the dosage of PFCS is 200-300 mg / L, and the hydraulic stirring rate is ≤90 r / min.

[0024] Preferably, the desalination and ammonia removal process includes removal of hardness ions, a second solid-liquid separation, evaporation and crystallization, and ammonia nitrogen removal;

[0025] First, the hardness ions in the wastewater are precipitated using sodium hydroxide and carbon dioxide to remove the hardness of the wastewater.

[0026] Secondly, hardness ion precipitates are separated from wastewater through a second solid-liquid separation process; then, TDS in the high-salt wastewater is precipitated out by triple-effect evaporation and heating.

[0027] Finally, NH3-N in the wastewater was removed by stripping.

[0028] Preferably, during the process of removing hardness ions:

[0029] The influent pH is 8.5–10.5, the ratio of CO2 addition to the concentration of calcium and magnesium ions in the influent is 1:1.2–2.2, and the CO2 content in the CO2 or exhaust gas is 50–90%.

[0030] In triple-effect evaporation, the influent pH is 6.5–9, the concentration is 10–15% (based on sodium chloride), the steam pressure is 0.3–0.4 MPa, the live steam temperature is 125–135℃, and the output concentration is 55–60%.

[0031] In ammonia nitrogen removal, the influent pH is 8–10.5; the influent temperature is 40–50℃; the gas flow rate is 6–8 L / min; the particle size of the packing material is 30–35 mm; and sulfuric acid absorption is used.

[0032] Preferably, the biochemical post-treatment process includes ASBR anaerobic treatment and two-stage contact oxidation treatment, MBR membrane reactor, and disinfection treatment;

[0033] In the ASBR anaerobic treatment process:

[0034] MLSS 40000~50000mg / L, volumetric loading 8~12kgCOD / m³ 3 • d, sludge content 40-50%, system temperature 26-30℃, pH 7.0-7.5, CODcr:N:P=200:5:1, influent COD not less than 6000mg / L;

[0035] During the two-stage contact oxidation process: MLSS 8000~10000mg / L; CODcr:N:P=120:5:1; packing volumetric load 2.5kgBOD / m³ 3 ·d, the PFCS dosage is 10-15 mg / L;

[0036] Composite fiber fillers with a specific surface area of ​​500–1200 m² 2 / m 3 The diameter of the composite fiber filler is 120mm;

[0037] The air-to-water ratio is 15–22:1, and the influent pH is 7–7.5.

[0038] In the primary contact oxidation treatment, DO > 4.0 mg / L, HRT = 6 h; in the secondary contact oxidation treatment, DO > 2.2 mg / L, HRT = 2 h.

[0039] In the MBR membrane reactor, the concentration of the submerged activated sludge flat sheet membrane is 5000-6000 mg / L, the water temperature is 15-22℃, the influent pH is 6-9, and the DO is 0.8-2.2 mg / L.

[0040] A waste acid and alkali, high-salt and recalcitrant waste liquid treatment system, the system comprising, in sequence:

[0041] The impurity removal system includes a first homogenizing tank;

[0042] A primary advanced oxidation system performs the first oxidation pretreatment on the waste liquid after impurity removal, including a Fenon tower and an aeration and dosing system, wherein the Fenon tower is connected to the output end of the homogenizing tank;

[0043] A heavy metal precipitation system includes a coagulation sedimentation tank, the input end of which is connected to the output end of the Fenon tower, and the output end of the coagulation sedimentation tank is sequentially connected to a first filter press and a first water tank.

[0044] A secondary advanced oxidation treatment system is used to perform secondary oxidation on the waste liquid after sedimentation. The secondary advanced oxidation treatment system includes a catalytic oxidation tower and a circulation system. The catalytic oxidation tower is connected to the output end of the first water tank.

[0045] The desalination and ammonia removal system includes a hardening reaction tank, a second filter press, a second water tank, a triple-effect steam evaporator, and an ammonia nitrogen removal device connected in sequence.

[0046] The input end of the hardening reaction tank is connected to the output end of the catalytic oxidation tower, and the output end of the hardening reaction tank is also connected to a second water tank;

[0047] The biochemical post-treatment system includes an ASBR reaction tower, an anaerobic sedimentation tank, a second homogenization tank, a two-stage contact oxidation tank, an MBR membrane tank, and a disinfection tank connected in sequence.

[0048] The output end of the homogenization tank is connected to the domestic water tank;

[0049] The ASBR reactor, anaerobic sedimentation tank, two-stage contact oxidation tank, and MBR membrane tank are respectively connected to the sludge thickening tank.

[0050] The disinfection tank is connected to a ClO2 generator.

[0051] Preferably, the ammonia nitrogen removal device includes an ammonia absorption tower, a third water tank, and a stripping tower;

[0052] H2SO4 is added to the ammonia absorption tower. The input end of the third water tank is connected to the output end of the triple-effect evaporator. The output end of the third water tank is connected to the input end of the ammonia stripping tower. The output end of the ammonia stripping tower is connected to the input ends of the ammonia absorption tower and the ASBR reaction tower, respectively.

[0053] The output end of the stripping tower is connected to the input end of the ASBR reaction tower, and the stripping tower, the two-stage contact oxidation tank, the MBR membrane tank, the Fenton tower, and the catalytic oxidation tower are respectively connected to an air / ozone generator;

[0054] The first homogenizing tank, the Fenton tower, the coagulation sedimentation tank, the second filter press, the two-stage contact oxidation tank, and the ammonia absorption tower are respectively connected to a reagent storage tank;

[0055] CO2 is introduced into the hardening reaction tank.

[0056] Compared with the prior art, the beneficial effects of this application are as follows:

[0057] This application provides a comprehensive treatment process for waste acid and alkali, high-salt and recalcitrant waste liquids. This process involves homogenization and impurity removal before oxidation, two-stage advanced oxidation pretreatment and coagulation sedimentation during oxidation, followed by evaporation desalination and ammonia nitrogen removal, and subsequent biochemical treatment. By employing optimized material ratios and a combination of various advanced oxidation technologies, the process effectively removes and destroys target pollutants at the front end of the treatment process. This ensures the stability of the subsequent evaporation and concentration unit, resulting in low concentrate production, good salt separation performance, and avoids frequent heater failures. Simultaneously, it guarantees stable influent parameters, low treatment pressure, and high treatment efficiency in the wastewater biochemical treatment section, ensuring that the downstream treatment processes meet standards.

[0058] This process employs a main removal unit targeting various pollutants, including organic matter, ammonia nitrogen, TDS, heavy metals, and acids / alkalis, supplemented by other units throughout the entire process. The front-end utilizes the strong oxidizing power of advanced oxidation technology to partially remove and thoroughly pre-treat pollutants that are difficult to treat, have high concentrations, and significantly impact the evaporation unit. The middle stage removes toxic pollutants that have a significant impact on biochemical treatment, ensuring the stable operation of the biochemical section. The entire process, encompassing pretreatment, intermediate treatment, post-treatment, and advanced treatment, is balanced, avoiding the problems of overloading the evaporation and biochemical units and increasing operational difficulty. Furthermore, the process design fully considers the nature of the enterprise's main industry, making good use of waste acid, waste alkali, waste hydrogen peroxide, and metal catalytic ions, significantly reducing raw material consumption and lowering treatment costs.

[0059] In this application, primary and secondary advanced oxidation treatments can effectively decompose organic matter, break down long-chain macromolecules, improve the biodegradability of wastewater, and reduce the content of organic matter and ammonia nitrogen. The primary and secondary advanced oxidation treatments respectively employ Fenton-like oxidation and ozone catalytic oxidation, both of which have strong oxidation capabilities and are non-selective in oxidizing targets, further reducing the content of organic matter and ammonia nitrogen in the waste liquid.

[0060] Heavy metal ions and trace amounts of organic matter are removed by adding neutralizing agents, coagulants, and heavy metal chelating agents through flocculation and sedimentation. Hardness in wastewater is removed by using sodium hydroxide and carbon dioxide.

[0061] The triple-effect evaporation unit rapidly removes TDS from the wastewater through evaporation and concentration, ensuring the biochemical reaction proceeds. Due to the high ammonia nitrogen content in the wastewater, an ammonia nitrogen stripping device is installed at the end of the triple-effect evaporation unit to remove ammonia nitrogen. The ASBR anaerobic process, with its highly controllable sequential batch reactor, can further decompose organic matter. The aerobic unit further decomposes organic matter and ammonia nitrogen.

[0062] Meanwhile, this process makes full use of resources such as acids, alkalis, metal ions in hazardous waste, heat sources from triple-effect evaporation, and waste gas from the plant area. It realizes the implementation of processes such as pH adjustment, catalytic reaction, coagulation and sedimentation in the reaction system. The process system is highly efficient and economical. While ensuring the high efficiency of the treatment process, it greatly reduces the cost of reagents and achieves the goal of treating waste with waste, which is in line with the policy requirements of circular economy. Attached Figure Description

[0063] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0064] In the attached diagram:

[0065] Fig. 1This is a process flow diagram of a treatment process for waste acid and alkali and high-salt, recalcitrant waste liquid in an embodiment of the present invention;

[0066] Fig. 2 This is a schematic diagram of a waste acid, alkali, and salt recalcitrant waste liquid treatment system according to an embodiment of the present invention. Detailed Implementation

[0067] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0068] According to the appendix Figs. 1-2 The process for treating waste acid and alkali, and high-salt, recalcitrant waste liquid includes the following steps:

[0069] Step 1: Prepare the waste liquid with acid and alkali and remove impurities;

[0070] Step 2: Perform primary advanced oxidation treatment on the waste liquid after impurity removal;

[0071] Step 3: Precipitate heavy metals from the waste liquid that has undergone primary oxidation treatment;

[0072] Step 4: Perform secondary advanced oxidation treatment on the waste liquid after heavy metal precipitation;

[0073] Step 5: Desalinate and remove ammonia from the waste liquid after the secondary advanced oxidation treatment;

[0074] Step 6: Perform biochemical post-treatment on the waste liquid after desalination and ammonia removal.

[0075] Furthermore, the primary advanced oxidation treatment employs a Fenton-like oxidation process;

[0076] The secondary advanced oxidation treatment employs ozone catalytic oxidation.

[0077] Furthermore, in the primary advanced oxidation process, the pH of the homogenized system is 3–4, the HRT of the waste liquid in the oxidation tower is >60 min, and the upflow velocity is ≤0.05 m / min; the ratio of H2O2 dosage to COD of the waste liquid influent is 0.6–1.2 mg H2O2 / mg COD, and the pickling waste liquid (in M... 2+ The calculated dosage is H2O2:M 2+ = 4.5~6:1.

[0078] Furthermore, in the secondary advanced oxidation process:

[0079] The pH of the system is 8–9;

[0080] The ratio of ozone dosage to COD in the influent is 0.2–0.8 mg O. 3 / mgCOD;

[0081] The number of water circulation stages should be no less than 3, and the particle size of the catalyst material should be 5-8 mm.

[0082] Furthermore, the heavy metal precipitation treatment includes coagulation precipitation and a first solid-liquid separation;

[0083] The coagulation and sedimentation process rapidly precipitates heavy metals in the waste liquid.

[0084] The first solid-liquid separation separates the precipitated heavy metals from the remaining waste liquid;

[0085] During coagulation and sedimentation, the pH value of the enhanced coagulation treatment is adjusted to pH 6-8, the dosage of calcium oxide is 30-50 g / L, the dosage of PFCS is 200-300 mg / L, and the hydraulic stirring rate is ≤90 r / min.

[0086] Furthermore, the desalination and ammonia removal process includes the removal of hardness ions, a second solid-liquid separation, evaporation and crystallization, and ammonia nitrogen removal;

[0087] First, sodium hydroxide and carbon dioxide are used to precipitate the waste liquid to remove hardness ions from the waste liquid;

[0088] Secondly, hardness ion precipitates are separated from waste liquid through a second solid-liquid separation process; then, TDS in the high-salt wastewater is evaporated and precipitated through triple-effect evaporation.

[0089] Finally, NH3-N in the wastewater was removed by ammonia stripping.

[0090] Furthermore, in the process of removing hardness ions:

[0091] The influent pH is 8.5–10.5, the ratio of CO2 addition to influent calcium ion concentration is 1:1.2–2.2, and the CO2 content in CO2 or exhaust gas is 50–90%.

[0092] In triple-effect evaporation, the influent pH is 6.5–9, the concentration is 10–15% (based on sodium chloride), the steam pressure is 0.3–0.4 MPa, the live steam temperature is 125–135℃, and the output concentration is 55–60%.

[0093] In ammonia nitrogen removal, the influent pH is 8–10.5; the influent temperature is 40–50℃; the gas flow rate is 6–8 L / min; and the particle size of the packing material is 30–35 mm.

[0094] Furthermore, the biochemical post-treatment process includes ASBR anaerobic treatment and two-stage contact oxidation treatment, MBR membrane reactor, and disinfection treatment.

[0095] In the ASBR anaerobic treatment process:

[0096] MLSS 40000~50000mg / L, volumetric loading 8~12kgCOD / m³ 3 • d, sludge content 40-50%, temperature 26-30℃, system pH 7.0-7.5, CODcr:N:P=200:5:1, influent COD not less than 6000mg / L;

[0097] During the two-stage contact oxidation process: MLSS 8000~10000mg / L; CODcr:N:P=120:5:1; packing volumetric load 2.5kgBOD / m³ 3 ·d, the PFCS dosage is 10-15 mg / L;

[0098] Composite fiber fillers with a specific surface area of ​​500–1200 m² 2 / m 3 The diameter of the composite fiber filler is 120mm;

[0099] The air-to-water ratio is 15–22:1, and the influent pH is 7–7.5.

[0100] In the primary contact oxidation treatment, DO > 4.0 mg / L, HRT = 6 h; in the secondary contact oxidation treatment, DO > 2.2 mg / L, HRT = 2 h.

[0101] In the MBR membrane reaction system, the concentration of activated sludge submerged flat sheet membrane is 5000-6000 mg / L, the water temperature is 15-22℃, the influent pH is 6-9, and the DO is 0.8-2.2 mg / L.

[0102] A waste acid and alkali, high-salt and recalcitrant waste liquid treatment system, the system comprising, in sequence:

[0103] The impurity removal system includes a first homogenizing tank;

[0104] A primary advanced oxidation system performs the first oxidation pretreatment on the waste liquid after impurity removal, including a Fenon tower and an aeration and dosing system, wherein the Fenon tower is connected to the output end of the homogenizing tank;

[0105] A heavy metal precipitation system includes a coagulation sedimentation tank, the input end of which is connected to the output end of the Fenon tower, and the output end of the coagulation sedimentation tank is sequentially connected to a first filter press and a first water tank.

[0106] A secondary advanced oxidation treatment system is used to perform a second oxidation on the waste liquid after sedimentation. The secondary advanced oxidation treatment system includes a catalytic oxidation tower and a circulation system. The catalytic oxidation tower is connected to the output end of the first water tank.

[0107] The desalination and ammonia removal system includes a hardening reaction tank, a second filter press, a second water tank, a triple-effect steam evaporator, and an ammonia nitrogen removal device connected in sequence.

[0108] The input end of the hardening reaction tank is connected to the output end of the catalytic oxidation tower, and the output end of the hardening reaction tank is also connected to a second water tank;

[0109] The biochemical post-treatment system includes an ASBR reaction tower, an anaerobic sedimentation tank, a second homogenization tank, a two-stage contact oxidation tank, an MBR membrane tank, and a disinfection tank connected in sequence.

[0110] The output end of the homogenization tank is connected to the domestic water tank;

[0111] The ASBR reactor, anaerobic sedimentation tank, two-stage contact oxidation tank, and MBR membrane tank are respectively connected to the sludge thickening tank.

[0112] The disinfection tank is connected to a ClO2 generator.

[0113] Furthermore, the ammonia nitrogen removal device includes an ammonia absorption tower, a third water tank, and a stripping tower;

[0114] H2SO4 is added to the ammonia absorption tower. The input end of the third water tank is connected to the output end of the triple-effect evaporator. The output end of the third water tank is connected to the input end of the stripping tower. The output end of the stripping tower is connected to the input end of the ammonia absorption tower and the input end of the ASBR reaction tower, respectively.

[0115] The output end of the stripping tower is connected to the input end of the ASBR reaction tower, and the stripping tower, the two-stage contact oxidation tank, the MBR membrane tank, the Fenton tower, and the catalytic oxidation tower are respectively connected to an air / ozone generator;

[0116] The first homogenizing tank, the Fenton tower, the coagulation sedimentation tank, the second filter press, the two-stage contact oxidation tank, and the ammonia absorption tower are respectively connected to a reagent storage tank;

[0117] CO2 is introduced into the hardening reaction tank.

[0118] It should be noted that:

[0119] In this application, a two-stage advanced oxidation pretreatment process is used, combined with physicochemical treatment and biochemical treatment, to comprehensively treat waste acid and alkali solutions, thereby achieving efficient treatment of industrial waste acid and alkali solutions. Specifically:

[0120] (1) Discharge the waste acid and alkali solution into the first homogenization tank, and perform M based on the COD in the first homogenization tank. 2+ Prepare the solution while ensuring the pH of the waste acid / alkali solution system to be treated is 3-4.

[0121] (2) Pump the prepared waste acid and alkali solution in the first homogenizing tank to the Fenton tower, and add H2O2 to the Fenton tower for oxidation reaction;

[0122] (3) The waste liquid after primary oxidation treatment flows into the coagulation sedimentation tank by gravity. Waste alkali or CaO is added to the coagulation sedimentation tank to adjust the pH. Coagulation agents are added to coagulate and settle the waste liquid. The coagulated sediment and waste liquid are separated by the first filter press. The separated liquid is pumped to the catalytic oxidation tower or hardening reaction tank according to the index.

[0123] (4) Introduce ozone into the catalytic oxidation tower to perform secondary oxidation pretreatment on the waste liquid in the catalytic oxidation tower;

[0124] (5) Pump the waste liquid in the first water tank or the waste liquid that has been pretreated by the secondary oxidation of the catalytic oxidation tower to the hardness removal reaction tank. Introduce CO2 into the hardness reaction tank and add PFCS, PAM and NaOH to form hardness ions in the waste liquid. Then separate the hardness ion precipitate and the waste liquid through the second filter press. Send the waste water to the second water tank and pump the waste liquid into the triple-effect evaporator through the second water tank.

[0125] (6) In the triple-effect evaporator, the countercurrent evaporation process is adopted. The TDS in the high-salt wastewater is precipitated as the solubility decreases through heating and evaporation, thereby achieving the purpose of efficient salt separation. The triple-effect evaporator discharges the wastewater with salt removed into the third water tank.

[0126] (7) Add H2SO4 into the ammonia absorption tower. The third water tank and the ammonia absorption tower are connected to the stripping tower. Add air into the stripping tower. Remove NH3-N from the wastewater by stripping in the stripping tower. Pump the wastewater with removed NH3-N into the ASBR reaction tower.

[0127] (8) In the ASBR tower, anaerobic microorganisms decompose the organic matter in the wastewater, remove most of the organic matter in the wastewater, and the growing activated sludge is periodically discharged into the sludge thickening tank, while the wastewater flows into the anaerobic sedimentation tank by gravity.

[0128] (9) In the anaerobic sedimentation tank, the fine sludge and dead sludge flowing out with the wastewater are separated by sedimentation, and then the sludge is discharged into the sludge thickening tank. The wastewater after sedimentation is pumped into the second homogenizing tank;

[0129] (10) The second homogenizing tank is connected to the domestic water tank. Domestic wastewater is metered and sent into the second homogenizing tank for homogenization and adjustment. The homogenized wastewater is then pumped into the two-stage contact oxidation tank.

[0130] (11) After entering the two-stage contact oxidation tank, the wastewater is further decomposed into organic matter and ammonia nitrogen by aerobic microorganisms. The DO value of the wastewater is controlled by the aeration system, and PFC is added according to the sludge condition. The wastewater after two-stage aerobic treatment is pumped into the MBR membrane tank, and the remaining sludge is periodically pumped to the sludge thickening tank.

[0131] (12) Air is introduced into the MBR membrane tank to further remove organic matter, while removing suspended solids, microorganisms and other impurities in the wastewater to perform solid-liquid separation, thereby achieving wastewater treatment and purification. The remaining sludge is then returned or pumped into the sludge thickening tank. The wastewater enters the disinfection tank after membrane filtration and is discharged after disinfection in compliance with standards.

[0132] Among them, the Fenton-like oxidation method utilizes metal ions under acidic conditions to catalyze the generation of hydroxyl radicals, which in turn trigger more free radicals to attack the internal bonds of organic molecules, thereby achieving the goal of completely mineralizing or breaking down organic matter into smaller molecules, reducing the content of organic matter and ammonia nitrogen, and improving the biodegradability of wastewater. The Fenton-like reaction utilizes active metal ions in waste acid, including Fe... 2+ Ni contained in the ionic system 2+ Zn 2+ When metal ions generate catalytic properties, the Fenton reaction can be carried out efficiently, reducing the amount of reagents used while harmlessly disposing of waste acids and alkalis, thus achieving the goal of treating waste with waste.

[0133] The precipitation method involves adjusting the pH to 7-9 by adding calcium oxide, followed by the addition of a self-developed heavy metal chelating agent to generate heavy metal precipitates. These precipitates are then rapidly settled through charge neutralization and adsorption precipitation using PFCS and PAM flocculants, removing heavy metal pollution while adsorbing some organic matter. This unit utilizes the large amount of iron ions in the wastewater to achieve a coagulation effect similar to that of PFS coagulants, reducing the need for chemical reagents.

[0134] The ozone catalytic oxidation unit employs an external circulation multi-stage heterogeneous catalytic oxidation process. Generally, ozone oxidation exhibits a certain degree of selectivity, often oxidizing small-molecule hydroxy acids, ketones, and aldehydes, making it difficult to completely degrade organic matter into CO. 2 H2O and inorganic matter. The external circulation multi-stage heterogeneous catalytic oxidation technology combines a highly efficient ozone catalyst with ozone oxidation. Through multi-stage circulation reaction, enrichment, catalytic activation, and oxidative degradation, it can significantly improve the degradation rate and efficiency of organic matter in wastewater.

[0135] The triple-effect evaporation process employs countercurrent evaporation. By fully pretreating the organic matter in the front end and setting up a filtration and hardening reaction tank at the feed end, the stable operation of the triple-effect evaporation can be ensured. Through heating and evaporation, the TDS in the high-salt wastewater precipitates out as the solubility decreases, thereby achieving the purpose of efficient salt separation.

[0136] Ammonia stripping utilizes the difference between the actual and equilibrium concentrations of volatile substances such as ammonia nitrogen in wastewater. Under alkaline conditions, air is used for stripping. As gas is continuously released during the stripping process, the ammonia concentration in the gas phase changes, ensuring that the actual concentration remains lower than the equilibrium concentration under those conditions. Ultimately, dissolved ammonia in the wastewater continuously crosses the gas-liquid interface, allowing NH3-N to be removed. This application cleverly places the ammonia stripping unit after triple-effect evaporation, utilizing the waste heat from the condensate to provide the system temperature, reducing the need for a heat source and enabling more effective ammonia nitrogen stripping.

[0137] In this application, the anaerobic reactor unit decomposes organic matter through anaerobic microbial metabolic reactions. The anaerobic digestion process is divided into three stages: hydrolysis and fermentation, acetic acid and hydrogen production, and methanogenesis. In the hydrolysis and acidification stage, complex macromolecules and insoluble organic matter in wastewater are hydrolyzed into smaller molecules and soluble organic matter under the action of extracellular enzymes, producing volatile organic acids, alcohols, and aldehydes. In the hydrogen and acetic acid production stage, various organic acids are decomposed into acetic acid, hydrogen, and carbon dioxide under the action of hydrogen-producing and acid-producing bacteria. In the methanogenesis stage, methanogenic bacteria convert acetic acid, hydrogen, and carbon dioxide into methane. The anaerobic reactor unit adopts the ASBR process, and the sequencing batch reactor (SBR) influent is suitable for wastewater with unstable flow and quality, high organic matter content, and complex water quality. The reaction process is clearly divided into influent, reaction, sedimentation, and effluent stages, with simple operation, high activated sludge concentration, and a volumetric loading rate of up to 12 kg / (m³) after stable operation. 3 ·d).

[0138] The aerobic unit employs a two-stage contact oxidation process. Contact oxidation is a biological wastewater treatment method derived from the biofilm method. It involves filling a biological contact oxidation tank with a certain amount of packing material. Utilizing the biofilm adsorbed on the packing material and a sufficient supply of oxygen, the organic matter in the wastewater is oxidized and decomposed through biological oxidation. This process combines characteristics of the activated sludge process. Furthermore, the high-efficiency biological packing material used has a large specific surface area, resulting in excellent oxygenation conditions within the tank. The biological solids content per unit volume in the aerobic tank is higher than that in activated sludge aeration tanks and biological filters. Therefore, the aerobic tank has a high volumetric loading rate, high treatment efficiency, strong adaptability to sudden changes in water quality and quantity, strong resistance to shock loads, short treatment time, small equipment requirements, and a small footprint. It can also be acclimatized to wastewater with relatively high salinity.

[0139] In one embodiment of this application, during the ASBR anaerobic treatment process, the MLSS is 40,000–50,000 mg / L, and the volumetric loading rate is 8–12 kg COD / m³. 3• d, sludge content 40-50%, temperature 26-30℃, influent pH control range 7.5-8.0 (or wastewater system pH 7.0-7.5), CODcr:N:P = 200:5:1, influent COD not less than 6000mg / L. Strictly control each stage of influent, reaction, sedimentation, and effluent.

[0140] In the two-stage contact oxidation tank treatment process, the influent pH is 7–7.5; MLSS is 8000–10000 mg / L; CODcr:N:P = 120:5:1; and the packing volumetric loading is 2.5 kg BOD / m³. 3 • PFCS dosage is 10–15 mg / L; the specific surface area of ​​the composite fiber packing is 500–1200 m². 2 / m 3 The packing material has a diameter of 120 mm; the air-to-water ratio is 15–22:1; during the first-stage contact oxidation treatment, DO > 4.0 mg / L and HRT = 6 h; during the second-stage contact oxidation treatment, DO > 2.2 mg / L and HRT = 2 h.

[0141] In the MBR membrane tank treatment process, submerged flat sheet membranes with activated sludge concentration (MLSS) of 5000-6000 mg / L are used, the water temperature is required to be 15-22℃, the influent pH is 6-9, and the DO is 0.8-2.2 mg / L.

[0142] In one embodiment of this application, the anaerobic reaction treatment employs the ASBR process. The sequencing batch reactor (SBR) is suitable for wastewater with unstable flow rates, unstable water quality, high organic matter content, and complex water characteristics. The reaction process is clearly divided into influent, reaction, sedimentation, and effluent stages. The operation is simple, the activated sludge concentration is high, and the volumetric loading rate can reach 12 kg / (m³) after stable operation. 3 •d). The reactor adopts a gas-air hybrid design, without a three-phase separator, with a low height-to-diameter ratio and small footprint, resulting in low equipment operation and maintenance costs and low energy consumption.

[0143] In one embodiment of this application, during the desalination process of the triple-effect evaporator, the influent pH is 6.5-9, the concentration is 10-15% (based on sodium chloride), the steam pressure is 0.3-0.4 MPa, the live steam temperature is 125-135°C, and the output concentration is 55-60%. This application cleverly sets the ammonia stripping after the triple-effect evaporator, using the residual heat of the condensate to provide the system temperature, reducing the use of heat sources and allowing ammonia nitrogen to be stripped more effectively.

[0144] In one embodiment of this application, during the ammonia nitrogen removal process, the pH of the influent is controlled to be 8-10.5, with the optimal pH being 9.5-10; the influent temperature is 40-50℃, with the optimal temperature being 47℃; the air flow rate is 6-8 L / min; and the packing material is multi-faceted hollow spheres with a diameter of 30-35 mm.

[0145] In one embodiment of this application, during the secondary oxidation pretreatment of wastewater in a catalytic oxidation tower, and / or by adding alkaline solution to control the pH of the influent to 8-9; wherein the ratio of ozone dosage to COD of the influent wastewater is 0.2-0.8 mgO3 / mgCOD, and a preferred ratio of ozone dosage to COD of the influent wastewater is 0.4-0.6 mgO3 / mgCOD;

[0146] The number of circulation stages should be set according to the influent, with no less than 3 circulation stages; the particle size of the catalyst material should be 5-8 mm.

[0147] In one embodiment of this application, during the coagulation and sedimentation process, the pH of the enhanced coagulation system is adjusted to 6-8, the CaO dosage is 300-5000 g / L, the PFCS dosage ratio is 200-300 mg / L, and the optimal dosage ratio is 250-300 mg / L; the hydraulic stirring rate is ≤90 r / min.

[0148] In one embodiment of this application, during the Fenton-like oxidation process, the HRT of the wastewater in the oxidation tower is >60 min, with the optimal HRT being 60-90 min and the upflow velocity ≤0.05 m / min;

[0149] The ratio of H2O2 dosage to COD in the influent wastewater is 0.6–1.2 mg H2O2 / mg COD, with a preferred ratio of 0.8–1.0 g H2O2 / g COD. (The acid pickling wastewater is expressed as M...) 2+ The dosage of (calculated) and the ratio of H2O2 are: H2O2:M 2+ = 4.5 to 6:1, with the optimal ratio being 4.5:1.

[0150] In one embodiment of this application, M containing catalytic properties is added to the first homogenizing tank. 2+ The substances include, but are not limited to, iron ions, zinc ions and nickel ions, with iron ions being the most preferred, and the source of iron ions is FeSO4.

[0151] To further verify the treatment effect of this invention on waste liquid, waste acid and alkali were treated based on COD content and M... 2+After homogenization and compatibility testing of the concentration and pH, comparative experiments were conducted on the treatment effects of wastewater with concentrations of 20000 mg / L ≤ COD ≤ 50000 mg / L and ammonia nitrogen ≤ 5000 mg / L, 50000 mg / L ≤ COD ≤ 100000 mg / L and ammonia nitrogen ≤ 8000 mg / L, and 100000 mg / L ≤ COD ≤ 150000 mg / L and ammonia nitrogen ≤ 10000 mg / L. Details are as follows:

[0152] Experiment 1 shows that when the COD in the waste liquid is 20000 mg / L ≤ COD ≤ 50000 mg / L and the ammonia nitrogen is ≤ 5000 mg / L, the treatment effect of this invention is as follows:

[0153]

[0154] Experiment 2: When the COD in the waste liquid is 50000 mg / L ≤ COD ≤ 100000 mg / L and the ammonia nitrogen is ≤ 8000 mg / L, the treatment effect of the present invention is as follows:

[0155]

[0156]

[0157] Experiment 3 shows that when the concentrations of COD and ammonia nitrogen in the waste liquid are 100,000 mg / L ≤ COD ≤ 150,000 mg / L and ≤ 10,000 mg / L, the treatment effect of this invention is as follows:

[0158]

[0159] The comparative experiments above demonstrate that this invention is suitable for treating comprehensive industrial wastewater, especially hazardous waste disposal industry wastewater containing heterocyclic compounds, hydrocarbons, or benzene series compounds, characterized by high levels of acid and alkali, high ammonia nitrogen, high salt content, poor biodegradability, and difficulty in degradation. Examples include the comprehensive treatment of complex wastewater such as electroplating wastewater, pharmaceutical wastewater, dyeing and printing wastewater, fine chemical wastewater, and laboratory wastewater. Compared to traditional chemical and biochemical methods, which have low tolerance to strong acids, alkalis, and salts, poor biodegradability, and the traditional Fenton method which requires large amounts of reagents and has low processing efficiency (no more than 40% removal rate) at high COD levels, with poor ammonia nitrogen removal, and ozone oxidation treatment which also has a COD and ammonia nitrogen removal rate of less than 30%, this application achieves better removal of organic matter, ammonia nitrogen, free acids, alkalis, and salts through a complete process of pretreatment, intermediate treatment, and posttreatment. At the same time, the two-stage advanced oxidation pretreatment process ensures the stability of the evaporation unit process, reduces the amount of concentrate generated, avoids frequent scaling of the heater, and greatly improves the biodegradability of the biochemical influent, ensuring that the biochemical unit treatment meets the standards and is stable.

[0160] Among them, the Fenton-like method uses a combination of catalytic oxidation tower and catalytic reagent to achieve continuous, efficient and stable operation. At the same time, it utilizes the catalytic effect of metal ions in waste acid and alkali, with a small amount of reagent used. The Fenton-like oxidation (enhanced coagulation) has a COD removal rate of more than 60% and an ammonia nitrogen removal rate of 25-30%; the precipitation method has a heavy metal removal rate of more than 98%.

[0161] The ozone catalytic oxidation method, which adopts the utility model "A Catalytic Oxidation Device for Recalcitrant Wastewater" published under authorization announcement number CN218810782U, achieves a COD removal rate of more than 45% and an ammonia nitrogen removal rate of more than 35% for raw water and / or a COD removal rate of more than 35% and an ammonia nitrogen removal rate of more than 30% for secondary advanced oxidation (Fenton-like treatment of reclaimed water).

[0162] The "sodium hydroxide plus carbon dioxide" process is adopted to collect waste gas from the plant area for use as process gas source, which reduces carbon dioxide emissions and complies with the "carbon neutrality" policy requirements. While reducing carbon emissions for the enterprise, it also removes hardness ions from wastewater, with a hardness ion removal rate of more than 99%.

[0163] Designing the ammonia stripping unit after the evaporation unit can effectively utilize the waste heat of the condensate, reduce energy consumption and lower treatment costs. The ammonia stripping unit has an ammonia nitrogen removal rate of over 90% and an ammonia recovery rate of over 97% in the wastewater.

[0164] In this application, the anaerobic unit adopts a sequencing batch process, which can better adapt to changes in water quality and quantity and the characteristics of intermittent water inflow. It has strong resistance to shocks, low operating costs, and a high degree of automation. The volumetric loading rate of the ASBR anaerobic reactor can be increased to 12 kg COD / m³. 3 During stable operation, the volumetric loading rate is 8–10 kg COD / m³·d, with a COD removal rate greater than 85%. The two-stage contact oxidation unit achieves a COD removal rate greater than 70%, ammonia nitrogen removal rate greater than 75%, total phosphorus removal rate greater than 90%, and SS removal rate greater than 95%. The entire process achieves a COD removal rate greater than 99.5%, ammonia nitrogen removal rate greater than 97%, total phosphorus removal rate greater than 90%, SS removal rate greater than 99%, salt content removal rate greater than 95%, and heavy metal removal rate greater than 98%.

[0165] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A process for treating waste acid and alkali, and high-salt, recalcitrant waste liquid, characterized in that, Includes the following steps: Step 1: Use waste acid and waste alkali to perform acid-base compatibility and impurity removal on the waste liquid; Step 2: Perform primary advanced oxidation treatment on the waste liquid after impurity removal; Step 3: Precipitate heavy metals from the waste liquid that has undergone primary oxidation treatment; Step 4: Perform secondary advanced oxidation treatment on the waste liquid after heavy metal removal; Step 5: Desalinate and remove ammonia from the waste liquid after the secondary advanced oxidation treatment; Step 6: Perform biochemical post-treatment on the waste liquid after desalination and ammonia removal; The primary advanced oxidation treatment employs a Fenton-like oxidation process. The secondary advanced oxidation treatment employs ozone catalytic oxidation. The desalination and ammonia removal process includes removal of hardness ions, a second solid-liquid separation, evaporation and crystallization, and ammonia nitrogen removal. First, the waste liquid is precipitated using sodium hydroxide and carbon dioxide to remove hardness ions from the waste liquid; Secondly, hardness ion precipitates are separated from waste liquid through a second solid-liquid separation process; then, TDS in the high-salt wastewater is evaporated and precipitated through triple-effect evaporation. Finally, the wastewater is treated by stripping. It can be removed; By placing the ammonia stripping unit after the triple-effect evaporator, the residual heat of the condensate is used to provide the system temperature, reducing the use of heat sources and allowing ammonia nitrogen to be stripped more effectively. Fenton-like reactions utilize active metal ions, including Fe, from waste acid. 2+ Ni contained in the ionic system 2+ Zn 2+ Metal ions exhibit catalytic properties; The biochemical post-treatment process includes sequential ASBR anaerobic treatment and two-stage contact oxidation treatment, MBR membrane reactor, and disinfection treatment.

2. The process for treating waste acid and alkali, and high-salt, recalcitrant waste liquid according to claim 1, characterized in that, In the primary advanced oxidation process, the pH of the homogenized system is 3-4, the HRT of the waste liquid in the oxidation tower is greater than 60 min, and the upflow velocity is ≤0.05 m / min; the ratio of H2O2 dosage to COD of the waste liquid influent is 0.6-1.2 mg H2O2 / mg COD.

3. The process for treating waste acid and alkali, high-salt, and recalcitrant waste liquid according to claim 1, characterized in that, In the secondary advanced oxidation process: The pH of the system is 8–9; The ratio of ozone dosage to COD in the influent is 0.2–0.8 mgO3 / mgCOD; The number of water circulation stages should be no less than 3, and the particle size of the catalyst material should be 5-8 mm.

4. The process for treating waste acid and alkali, and high-salt, recalcitrant waste liquid according to claim 1, characterized in that, The heavy metal precipitation treatment includes coagulation precipitation and a first solid-liquid separation. The coagulation and sedimentation process rapidly precipitates heavy metals in the waste liquid. The first solid-liquid separation separates the precipitated heavy metal sludge from the remaining waste liquid.

5. The process for treating waste acid and alkali, and high-salt, recalcitrant waste liquid according to claim 1, characterized in that, During the process of removing hardness ions: The influent pH is 8.5–10.5, and the ratio of CO2 dosage to influent calcium ion concentration is 1:2–2.

2. In triple-effect evaporation, the pH of the influent is 6.5–9, the feed concentration (based on sodium chloride) is 10–15%, the steam pressure is 0.3–0.4 MPa, the live steam temperature is 125–135℃, and the discharge concentration is 55–60%. In ammonia nitrogen removal, the influent pH is 8–10.5; the influent temperature is 40–50℃; the gas flow rate is 6–8 L / min; and the particle size of the packing material is 30–35 mm.

6. The process for treating waste acid and alkali, and high-salt, recalcitrant waste liquid according to claim 1, characterized in that, During ASBR anaerobic treatment: MLSS 40000~50000mg / L, volumetric loading 8~12kgCOD / m³ 3 • d, sludge content 40-50%, temperature 26-30℃, system pH 7.0-7.5, CODcr:N:P=200:5:1, influent COD not less than 6000mg / L; During the two-stage contact oxidation process: MLSS 8000~10000mg / L; CODcr:N:P=120:5:1; packing volumetric load 2.5kgBOD / m³ 3 ·d, the PFCS dosage is 10-15 mg / L; Specific surface area of ​​composite fiber fillers The diameter of the composite fiber filler is 120mm; The air-to-water ratio is 15–22:1, and the influent pH is 7–7.

5. In the primary contact oxidation treatment, DO > 4.0 mg / L, HRT = 6 h; in the secondary contact oxidation treatment, DO > 2.2 mg / L, HRT = 2 h. In MBR filtration, the concentration of activated sludge submerged flat sheet membrane is 5000-6000 mg / L, the water temperature is 15-22℃, the influent pH is 6-9, and the DO is 0.8-2.2 mg / L.

7. A waste acid and alkali, high-salt, and recalcitrant waste liquid treatment system employing the waste acid and alkali, high-salt, and recalcitrant waste liquid treatment process according to any one of claims 1 to 6, characterized in that, The system includes the following components configured sequentially: The impurity removal system includes a first homogenizing tank; A primary advanced oxidation system is used to perform primary advanced oxidation treatment on the waste liquid after impurity removal. It includes a Fenton tower and an aeration and dosing system. The Fenton tower is connected to the output end of the first homogenizing tank. A heavy metal precipitation system includes a coagulation sedimentation tank, the input end of which is connected to the output end of the Fenton tower, and the output end of the coagulation sedimentation tank is sequentially connected to a first filter press and a first water tank. A secondary advanced oxidation treatment system is used to perform secondary advanced oxidation treatment on the waste liquid after sedimentation. The secondary advanced oxidation treatment system includes a catalytic oxidation tower and a circulation system. The catalytic oxidation tower is connected to the output end of the first water tank. The desalination and ammonia removal system includes a hardness removal reaction tank, a second filter press, a second water tank, a triple-effect steam evaporator, and an ammonia nitrogen removal device connected in sequence. The input end of the hardness removal reaction tank is connected to the output end of the catalytic oxidation tower, and the output end of the hardness removal reaction tank is also connected to a second water tank. The biochemical post-treatment system includes an ASBR reaction tower, an anaerobic sedimentation tank, a second homogenization tank, a two-stage contact oxidation tank, an MBR membrane tank, and a disinfection tank connected in sequence. The output end of the second homogenizing tank is connected to the domestic water tank; The ASBR reactor, anaerobic sedimentation tank, two-stage contact oxidation tank, and MBR membrane tank are respectively connected to the sludge thickening tank. The disinfection tank is connected to a ClO2 generator.

8. The waste acid and alkali, high-salt and difficult-to-degrade waste liquid treatment system according to claim 7, characterized in that, The ammonia nitrogen removal device includes a stripping tower, an ammonia absorption tower, and a third water tank; H2SO4 is added to the ammonia absorption tower. The input end of the third water tank is connected to the output end of the triple-effect evaporator. The output end of the third water tank is connected to the input end of the stripping tower. The output end of the stripping tower is connected to the input end of the ammonia absorption tower and the input end of the ASBR reaction tower, respectively. The stripping tower, the two-stage contact oxidation tank, the MBR membrane tank, and the Fenton tower are each connected to an air generator; The catalytic oxidation tower is connected to an ozone generator; The first homogenizing tank, the Fenton tower, the coagulation sedimentation tank, the second filter press, the two-stage contact oxidation tank, and the ammonia absorption tower are respectively connected to a reagent storage tank; CO2 is introduced into the hardness removal reaction tank.

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