Epoxypropane production wastewater treatment process

Abstract

The invention relates to the technical field of industrial wastewater treatment, in particular to an epoxypropane production wastewater treatment process which comprises the following steps: S1, pretreatment; s2, primary biochemical treatment; s3, carrying out secondary solid-liquid separation; s4, deep biochemical treatment; s5, final precipitation; according to the method, through the combined process of pretreatment, biochemical treatment, deep treatment and sludge treatment, technological parameter control is combined, and the polymeric silicate agent and the additive are matched, so that the problems of low biochemical efficiency, sludge bulking, unstable effluent quality and the like when the epoxypropane wastewater is treated by a traditional method are solved; through optimization of two additives and a biochemical system, metabolism and decomposition of specific pollutants by microorganisms are promoted, it is ensured that the chemical oxygen demand of effluent stably reaches the standard, and the yield of residual sludge is reduced through an optimized sludge backflow path.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial wastewater treatment, in particular to a propylene oxide production wastewater treatment process. BACKGROUND

[0002] Propylene oxide is an important petrochemical raw material, and a large amount of industrial wastewater with complex components and high biological toxicity is generated in its production process.

[0003] In the prior art, for the treatment of propylene oxide production wastewater, the conventional coagulation and sedimentation method using ordinary aluminum or iron coagulant has limited removal efficiency for small-molecule organic matter dissolved in wastewater, and a large amount of sludge is generated. Based on this, the present application provides a propylene oxide production wastewater treatment process. SUMMARY

[0004] The purpose of the present application is to provide a propylene oxide production wastewater treatment process. The treatment system constructed by the present application not only can effectively treat refractory organic matter, but also has good sludge settling and system stability performance, effectively realizing the standard discharge of wastewater.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme: A propylene oxide production wastewater treatment process, comprising the following steps: S1: Pretreatment: The high-temperature wastewater of 70-80 DEG C generated in the propylene oxide production workshop is introduced into a cooling tower, cooled to below 40 DEG C, then 0.03-0.07% of polymeric silicate agent by mass of wastewater is added, and then sent to a horizontal flow primary sedimentation tank for sludge-water separation treatment to obtain supernatant and sludge; S2: Primary biochemical treatment: The supernatant of the primary sedimentation tank is sent to an aeration oxidation tank, 0.03-0.05% of ferrous sulfate by mass of wastewater is added, and an additive is added, and the aerobic treatment is carried out under the condition that the dissolved oxygen concentration is 2-4 mg / L, wherein the mass of the additive is 0.002-0.01% of the wastewater; S3: Secondary solid-liquid separation: The effluent of the aeration oxidation tank is sent to a secondary sedimentation tank to obtain supernatant and sludge, a part of the sludge of the secondary sedimentation tank is backflowed to the front end of the primary sedimentation tank, and another part is backflowed to the front end of the aeration oxidation tank, wherein the surface load of the secondary sedimentation tank is ≤0.54 m 3 / (m 2 ·h); S4: Advanced biochemical treatment: The supernatant of the secondary sedimentation tank is sent to a contact oxidation tank, the dissolved oxygen concentration is controlled at 2-4 mg / L, the tank is filled with Φ80 mm suspended ball filler, the biofilm culture is carried out by using the backflow sludge of the secondary sedimentation tank, and after the biofilm culture is completed, the dissolved oxygen is controlled to be ≥2 mg / L; S5: Final precipitation: the effluent from the contact oxidation tank is sent to the final sedimentation tank to obtain supernatant and sludge, and the supernatant is metered through the Bartha tank and then discharged after reaching the standard; S6: Sludge treatment: the sludge obtained from the primary sedimentation tank, the secondary sedimentation tank and the final sedimentation tank is sent to the sludge storage tank for concentration, and after concentration, the sludge is conditioned and then subjected to pressure filtration treatment to obtain a mud cake, which is transported out for disposal.

[0006] Further, the polymeric silicate agent is prepared by the following method: mixing water glass and deionized water in a mass ratio of 1:(1.85-4.7), stirring at a speed of 300-600 rpm to obtain a water glass solution, adding dilute phosphoric acid aqueous solution to the water glass solution under stirring to adjust the pH to 10.5-11.5, and then stirring at a speed of 50-100 rpm, aging for 12-24 h to obtain an intermediate liquid, adding an additive to the intermediate liquid, stirring at a speed of 40-50 rpm at 25-40°C for 1-2 h, and standing for 12 h to obtain the polymeric silicate agent, wherein the mass concentration of the dilute phosphoric acid aqueous solution is 10%, and the mass ratio of the intermediate liquid to the additive is (20-30):1.

[0007] Further, the additive is prepared by the following method: adding magnetotactic bacteria to a liquid culture medium, and fermenting and culturing under micro-aerobic conditions at 28°C and pH 6.9-7.1, collecting the bacterial cells after fermentation, and purifying the bacterial cells by cell disruption and magnetic separation to obtain an intermediate product, mixing humic acid powder and sodium hydroxide solution in a mass ratio of (4.5-5.5):2, filtering, mixing the filtrate and the intermediate product in a mass ratio of (3-5):1, stirring at a speed of 80-90 rpm at room temperature and pH 7.2 for 2-3 h to obtain the additive, wherein the mass concentration of the sodium hydroxide is 0.4%.

[0008] Further, the additive is prepared by the following method: mixing the reaction material, diammonium phosphate and urea in a mass ratio of 100:(3-8):(1-4), mixing at a speed of 15-35 rpm for 20-40 min to obtain a crude material, spraying a polyvinyl alcohol solution with a mass concentration of 5% on the crude material, and then feeding the material into a granulator to form 1-3 mm granules, and drying the granules at a temperature below 60°C to obtain the additive, wherein the mass of the polyvinyl alcohol solution is 8-15% of the mass of the crude material.

[0009] Further, the reaction material is prepared by the following method: malt dextrin and trehalose are mixed according to a mass ratio of (3-5):1 to obtain a mixture, the mixture is put into a reaction kettle, deionized water is added, p-toluenesulfonic acid is added, the reaction kettle is closed, the pressure is reduced to -0.08 to -0.1 MPa, and reaction is carried out at 85-100 DEG C. for 2-4 h, and then the reaction kettle is cooled to below 60 DEG C., a 10% sodium hydroxide solution is added to adjust the pH to 6.0-7.0, activated carbon powder is added, and stirring is carried out at 70-80 DEG C. for 30 min, and then filtration is carried out, and the filtrate is collected to obtain the reaction material, wherein the mass of the deionized water is 50-60% of the mass of the mixture, the mass of the p-toluenesulfonic acid is 1-2% of the mass of the mixture, and the mass of the activated carbon powder is 1-3% of the mass of the mixture.

[0010] Further, the liquid culture medium comprises the following components at the following concentrations: 1.0 g / L of sodium succinate, 1.2-1.6 g / L of yeast extract, 0.15-0.25 g / L of ferric ammonium citrate, 3.0-3.8 g / L of 4-hydroxyethylpiperazine ethanesulfonic acid, 0.10-0.18 g / L of magnesium sulfate heptahydrate, 0.010-0.018 g / L of ferrous sulfate, 0.002-0.004 g / L of cobalt chloride and 0.002-0.004 g / L of sodium molybdate, and the pH of the liquid culture medium is 6.9-7.1.

[0011] Further, the biofilm culture in the contact oxidation tank in S4 comprises the following steps: sludge from a secondary sedimentation tank is introduced into the contact oxidation tank, the aeration amount is controlled to prevent sludge from accumulating at the bottom of the tank, after the surface of the suspended filler is covered with a biofilm, sludge backflow is stopped, the aeration amount is increased to make the dissolved oxygen concentration greater than or equal to 3 mg / L, and stable operation is carried out for 3-5 days to complete the biofilm formation.

[0012] Further, the primary sedimentation tank is a horizontal flow type primary sedimentation tank, the primary sedimentation tank is configured to have a hydraulic load of less than or equal to 0.26 m³ / (m 2 ·h), a design super height of greater than or equal to 500 mm, and a hydraulic retention time of not less than 23 h.

[0013] Further, the sludge retention time of the aeration oxidation tank is 11 days, and the volume load is less than or equal to 0.75 kg / (m³·d).

[0014] Further, the sludge pressure filtration in S6 adopts a compartment type pressure filter, the working pressure of the pressure filter is 25 MPa, and the filter liquid of the pressure filter is backflowed to the primary sedimentation tank in S1.

[0015] Compared with the prior art, the present application has the following beneficial effects: 1. In this invention, by introducing a polymeric silicate agent, a polymeric hydroxyl iron silicate complex with a high positive charge is formed during hydrolysis. This complex can effectively compress the double electric layer of organic colloidal particles in wastewater and achieve efficient destabilization and flocculation through adsorption bridging. At the same time, the magnetic additive in the polymeric silicate agent endows the flocs with magnetic cores, increasing the floc density and size through micro-magnetic flocculation. This reduces the sludge volume in the primary sedimentation tank at the source, thereby surpassing the settling speed and separation efficiency of conventional coagulants and improving wastewater treatment efficiency.

[0016] 2. In this invention, the additives use maltodextrin, trehalose, etc. as reactants. Through granulation, they are slowly dissolved and released in the aeration oxidation tank, providing microorganisms with a stable and lasting source of energy and carbon skeleton. At the same time, the extracellular polymers of microorganisms stimulated by the additives combine with the hydrolysis products of ferrous sulfate to form dense flocs, which significantly improves the settling properties of sludge. The two work synergistically to improve the efficiency and stability of biochemical treatment, enabling the treatment system to operate stably and the effluent to meet standards.

[0017] 3. In this invention, through the combined process of "pretreatment synergistic sedimentation + segmented biochemical treatment", in the pretreatment stage, the polymer silicate agent and the subsequent biochemical unit work together to remove some salts in advance and break down and detoxify the recalcitrant organic matter, which significantly reduces the bioinhibitory properties of the wastewater. Subsequently, through the segmented design of "primary biochemical treatment + advanced biochemical treatment", microbial communities with different functional characteristics grow in their respective optimal environments, and are responsible for efficiently removing the main organic matter and deeply degrading specific recalcitrant pollutants. This division of labor and relay overcomes the shortcomings of single biochemical systems in adapting to complex wastewater components, and ultimately ensures that the effluent quality stably meets the standard discharge requirements. Attached Figure Description

[0018] Figure 1 The present invention provides a flowchart of a process for treating wastewater from propylene oxide production. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] It should be noted that the raw materials used in the following embodiments are all commercially available.

[0021] Example 1: A process for treating wastewater from propylene oxide production includes the following steps: S1: Pretreatment: The high-temperature wastewater at 70 DEG C generated by the propylene oxide production plant is passed into a cooling tower, cooled to below 40 DEG C, then 0.03% of poly silicate agent by mass of the wastewater is added, then sent into a horizontal flow primary sedimentation tank, mud-water separation treatment is carried out, and supernatant and sludge are obtained; S2: Primary biochemical treatment: The supernatant of the primary sedimentation tank is sent into an aeration oxidation tank, 0.03% of ferrous sulfate by mass of the wastewater is added, an additive is added, and aerobic treatment is carried out under the condition that the dissolved oxygen concentration is 2 mg / L, wherein the mass of the additive is 0.002% of the wastewater; S3: Secondary solid-liquid separation: The effluent of the aeration oxidation tank is sent into a secondary sedimentation tank, supernatant and sludge are obtained, part of the sludge of the secondary sedimentation tank is backflowed to the front end of the primary sedimentation tank, and another part is backflowed to the front end of the aeration oxidation tank, wherein the surface load of the secondary sedimentation tank is ≤0.54 m 3 / (m 2 ·h); S4: Advanced biochemical treatment: The supernatant of the secondary sedimentation tank is sent into a contact oxidation tank, the dissolved oxygen concentration is controlled at 2 mg / L, the tank is filled with Φ80 mm suspended ball fillers, and biofilm culture is carried out by using the backflow sludge of the secondary sedimentation tank, after the biofilm is formed, the dissolved oxygen is controlled to be ≥2 mg / L; S5: Final sedimentation: The effluent of the contact oxidation tank is sent into a final sedimentation tank, supernatant and sludge are obtained, the supernatant is metered through a Bartha tank, and then discharged after reaching the standard; S6: Sludge treatment: The sludge obtained from the primary sedimentation tank, the secondary sedimentation tank and the final sedimentation tank is sent into a sludge storage tank for concentration, after concentration, the sludge is conditioned, then pressure filtration treatment is carried out, and a mud cake is obtained, which is transported out for disposal.

[0022] The raw material composition of the liquid medium is: sodium succinate 1.0 g / L, yeast extract 1.2 g / L, ferric ammonium citrate 0.15 g / L, 4-hydroxyethylpiperazine ethanesulfonic acid 3.0 g / L, magnesium sulfate heptahydrate 0.10 g / L, ferrous sulfate 0.010 g / L, cobalt chloride 0.002 g / L and sodium molybdate 0.002 g / L, and the pH of the liquid medium is 6.9.

[0023] Preparation of the additive: the magnetotactic bacteria are added into the liquid medium, and fermentation culture is carried out under the conditions of 28 DEG C, pH 6.9 and micro-aerobic conditions, after the fermentation is completed, the bacterial cells are collected, cell disruption and magnetic separation purification are carried out, and an intermediate product is obtained, which is used as needed, the humic acid powder and sodium hydroxide solution are mixed in a mass ratio of 4.5:2, filtration is carried out, the filtrate is mixed with the intermediate product in a mass ratio of 3:1, stirring is carried out at 80 rpm under the conditions of room temperature and pH 7.2 for 2 h, and the additive is prepared, wherein the mass concentration of the sodium hydroxide is 0.4%.

[0024] Preparation of the polymeric silicate agent: water glass and deionized water were mixed at a mass ratio of 1:1.85, and stirring was performed at a rotation speed of 300 rpm to obtain a water glass solution. Under stirring, dilute phosphoric acid aqueous solution was added to the water glass solution to adjust the pH to 10.5, and stirring was performed again at a rotation speed of 50 rpm. After aging for 12 h, an intermediate liquid was obtained. An additive was added to the intermediate liquid, and stirring was performed at a rotation speed of 40 rpm at 25-40℃ for 1 h. After standing for 12 h, the polymeric silicate agent was prepared. In the polymeric silicate agent, the mass concentration of the dilute phosphoric acid aqueous solution was 10%, and the mass ratio of the intermediate liquid to the additive was 20:1.

[0025] Preparation of the reaction material: malt dextrin and trehalose were mixed at a mass ratio of 3:1 to obtain a mixture. The mixture was put into a reaction kettle, deionized water was added, and p-toluenesulfonic acid was added. The reaction kettle was closed, the pressure was reduced to -0.08 MPa, and reaction was performed at 85-100℃ for 2 h. After cooling to below 60℃, a 10% sodium hydroxide solution was added to adjust the pH to 6.0, and activated carbon powder was added. Stirring was performed at 70℃ for 30 min, and the filtrate was collected by filtration to obtain the reaction material. In the reaction material, the mass of the deionized water was 50% of the mass of the mixture, the mass of the p-toluenesulfonic acid was 1% of the mass of the mixture, and the mass of the activated carbon powder was 1% of the mass of the mixture.

[0026] Preparation of the additive: the reaction material, diammonium phosphate, and urea were mixed at a mass ratio of 100:3:1 to obtain a crude material. After spraying a 5% polyvinyl alcohol solution on the crude material, the mixture was transferred into a granulator to form 1 mm particles. The particles were dried at a temperature below 60℃ to obtain the additive. In the additive, the mass of the polyvinyl alcohol solution was 8% of the mass of the crude material.

[0027] In S4, the biofilm cultivation in the contact oxidation tank includes the following steps: the sludge from the secondary sedimentation tank is introduced into the contact oxidation tank, and the aeration amount is controlled to prevent the accumulation of impurities at the bottom of the tank. After the surface of the suspended filler is covered with a biofilm, the sludge backflow is stopped, and the aeration amount is increased to make the dissolved oxygen concentration ≥3 mg / L. After stable operation for 3 d, the biofilm cultivation is completed.

[0028] In S1, the primary sedimentation tank is a horizontal flow type primary sedimentation tank. The primary sedimentation tank is set to have a hydraulic loading of ≤0.26 m³ / (m 2 ·h), a design super height of ≥500 mm, and a hydraulic retention time of not less than 23 h.

[0029] In S5, the sludge retention time in the aeration oxidation tank is 11 d, and the volumetric loading is ≤0.75 kg / (m³·d).

[0030] In S6, the sludge pressure filtration uses a box-type pressure filter, and the working pressure of the pressure filter is 25 MPa. The filtrate of the pressure filter is returned to the primary sedimentation tank in S1.

[0031] Example 2: An isopropyl oxide production wastewater treatment process, comprising the following steps: S1: Pretreatment: The high-temperature wastewater of 75℃ generated by the isopropyl oxide production workshop is passed into a cooling tower, cooled to below 40℃, then a polymeric silicate agent with a mass of 0.05% of the wastewater is added, and then sent to a horizontal flow primary sedimentation tank for sludge-water separation treatment to obtain supernatant and sludge; S2: Primary biochemical treatment: The supernatant of the primary sedimentation tank is sent to an aeration oxidation tank, ferrous sulfate with a mass of 0.03-0.05% of the wastewater is added, an additive is added, and aerobic treatment is carried out under the condition of a dissolved oxygen concentration of 3mg / L, wherein the mass of the additive is 0.005% of the wastewater; S3: Secondary solid-liquid separation: The effluent of the aeration oxidation tank is sent to a secondary sedimentation tank to obtain supernatant and sludge, part of the sludge of the secondary sedimentation tank is backflowed to the front end of the primary sedimentation tank, and another part is backflowed to the front end of the aeration oxidation tank, wherein the surface load of the secondary sedimentation tank is ≤0.54m 3 / (m 2 ·h); S4: Advanced biochemical treatment: The supernatant of the secondary sedimentation tank is sent to a contact oxidation tank, the dissolved oxygen concentration is controlled at 3mg / L, the tank is filled with Φ80mm suspended ball fillers, and the secondary sedimentation tank backflow sludge is used for biofilm cultivation, and after the biofilm cultivation is completed, the dissolved oxygen is controlled to be ≥2mg / L; S5: Final sedimentation: The effluent of the contact oxidation tank is sent to a final sedimentation tank to obtain supernatant and sludge, and the supernatant is metered through a Bartha tank and then discharged after reaching the standard; S6: Sludge treatment: The sludge obtained from the primary sedimentation tank, the secondary sedimentation tank and the final sedimentation tank is sent to a sludge storage tank for concentration, and after concentration, the sludge is conditioned and then subjected to pressure filtration treatment to obtain a mud cake, which is transported out for disposal.

[0032] The raw material composition of the liquid medium is: sodium succinate 1.0g / L, yeast extract 1.4g / L, ferric ammonium citrate 0.20g / L, 4-hydroxyethylpiperazine ethanesulfonic acid 3.4g / L, magnesium sulfate heptahydrate 0.14g / L, ferrous sulfate 0.014g / L, cobalt chloride 0.003g / L and sodium molybdate 0.003g / L, and the pH of the liquid medium is 7.0.

[0033] Preparation of the additive: the magnetotactic bacteria are added to the liquid medium, and fermentation culture is carried out under the conditions of 28℃, pH 7.0 and micro-aerobic conditions, the bacterial cells are collected after fermentation, and cell disruption and magnetic separation purification are carried out to obtain an intermediate product, which is used as needed, the humic acid powder and sodium hydroxide solution are mixed in a mass ratio of 5:2, filtered, the filtrate is mixed with the intermediate product in a mass ratio of 4:1, stirred at a speed of 90rpm for 2.5h at room temperature and pH 7.2 to prepare the additive, wherein the mass concentration of the sodium hydroxide is 0.4%.

[0034] Preparation of the polymeric silicate agent: mix the water glass and deionized water in a mass ratio of 1:3.25, and stir at a speed of 500 rpm to obtain a water glass solution, add dilute phosphoric acid solution to the water glass solution under stirring to adjust the pH to 11.0, and then stir at a speed of 70 rpm for 16 h to obtain an intermediate liquid, add the additive to the intermediate liquid, and stir at 30℃ and a speed of 50 rpm for 1.5 h, and then stand for 12 h to obtain the polymeric silicate agent, wherein the mass concentration of the dilute phosphoric acid solution is 10%, and the mass ratio of the intermediate liquid to the additive is 25:1.

[0035] Preparation of the reaction material: mix the malt dextrin and trehalose in a mass ratio of 4:1 to obtain a mixture, put the mixture into a reaction kettle, add deionized water, add p-toluenesulfonic acid, close the reaction kettle, reduce the pressure to-0.09 MPa, and react at 90℃ for 3 h, then cool to below 60℃, add a 10% sodium hydroxide solution to adjust the pH to 6.5, then add activated carbon powder, stir at 75℃ for 30 min, filter, and collect the filtrate to obtain the reaction material, wherein the mass of the deionized water is 55% of the mass of the mixture, the mass of the p-toluenesulfonic acid is 1.5% of the mass of the mixture, and the mass of the activated carbon powder is 2% of the mass of the mixture.

[0036] Preparation of the additive: mix the reaction material, diammonium phosphate, and urea in a mass ratio of 100:5:2, and mix at a speed of 25 rpm for 30 min to obtain a crude material, spray a 5% polyvinyl alcohol solution on the crude material, then transfer the mixture into a granulator to form 2 mm particles, and dry the particles at a temperature below 60℃ to obtain the additive, wherein the mass of the polyvinyl alcohol solution is 12% of the mass of the crude material.

[0037] In S4, the biofilm cultivation in the contact oxidation tank comprises the following steps: passing the sludge backflowed from the secondary sedimentation tank into the contact oxidation tank, controlling the aeration amount to be free of pool bottom impurities, stopping the sludge backflow after the surface of the suspended filler is covered with a biofilm, increasing the aeration amount to make the dissolved oxygen concentration ≥3 mg / L, and stably operating for 4 d to complete the biofilm cultivation.

[0038] In S3, the primary sedimentation tank is a horizontal flow type primary sedimentation tank, the primary sedimentation tank is set to have a hydraulic loading ≤0.26 m³ / (m 2 ·h), a design super height ≥500 mm, and a hydraulic retention time not less than 23 h.

[0039] In S5, the sludge retention time in the aeration oxidation tank is 11 d, and the volume loading is ≤0.75 kg / (m³·d).

[0040] In S6, the sludge pressure filtration adopts a box-type pressure filter, the working pressure of the pressure filter is 25 MPa, and the filter liquor of the pressure filter is backflowed to the primary sedimentation tank in S1.

[0041] Example 3: An isopropyl oxide production wastewater treatment process, comprising the following steps: S1: Pretreatment: The high-temperature wastewater of 80 DEG C generated by the isopropyl oxide production workshop is passed into a cooling tower, and after being cooled to below 40 DEG C, a poly silicate agent with a mass of 0.07% of the wastewater is added, and then sent to a horizontal flow primary sedimentation tank for sludge-water separation treatment to obtain supernatant and sludge; S2: Primary biochemical treatment: The supernatant of the primary sedimentation tank is sent to an aeration oxidation tank, and ferrous sulfate with a mass of 0.05% of the wastewater is added, and an additive is added, and under the condition of a dissolved oxygen concentration of 4 mg / L, aerobic treatment is carried out, wherein the mass of the additive is 0.01% of the wastewater; S3: Secondary solid-liquid separation: The effluent of the aeration oxidation tank is sent to a secondary sedimentation tank to obtain supernatant and sludge, and part of the sludge of the secondary sedimentation tank is backflowed to the front end of the primary sedimentation tank, and another part is backflowed to the front end of the aeration oxidation tank, wherein the surface load of the secondary sedimentation tank is ≤0.54 m3 / (m2.h); S4: Advanced biochemical treatment: The supernatant of the secondary sedimentation tank is sent to a contact oxidation tank, and under the condition that the dissolved oxygen concentration is controlled at 2-4 mg / L, the tank is filled with Φ80 mm suspended ball fillers, and the secondary sedimentation tank backflow sludge is used for biofilm cultivation, and after the biofilm cultivation is completed, the dissolved oxygen is controlled to be ≥2 mg / L; S5: Final sedimentation: The effluent of the contact oxidation tank is sent to a final sedimentation tank to obtain supernatant and sludge, and the supernatant is metered through a Bartha tank and then discharged outside after reaching the standard; S6: Sludge treatment: The sludge obtained from the primary sedimentation tank, the secondary sedimentation tank and the final sedimentation tank is sent to a sludge storage tank for concentration, and after concentration, the sludge is conditioned and then subjected to filter pressing treatment to obtain a mud cake, which is transported out for disposal.

[0042] The raw material composition of the liquid medium is: sodium succinate 1.0 g / L, yeast extract 1.6 g / L, ferric ammonium citrate 0.25 g / L, 4-hydroxyethylpiperazine ethanesulfonic acid 3.8 g / L, magnesium sulfate heptahydrate 0.18 g / L, ferrous sulfate 0.018 g / L, cobalt chloride 0.004 g / L and sodium molybdate 0.004 g / L, and the pH of the liquid medium is 7.1.

[0043] Preparation of the additive: the magnetotactic bacteria are added to the liquid medium, and under the conditions of 28 DEG C, pH 7.1 and micro-aerobic conditions, fermentation culture is carried out, and after the fermentation is completed, the bacterial cells are collected, subjected to cell disruption and magnetic separation purification to obtain an intermediate product, which is used as needed, the humic acid powder and sodium hydroxide solution are mixed in a mass ratio of 5.5:2, filtered, and the filtrate is mixed with the intermediate product in a mass ratio of 5:1, stirred at a speed of 90 rpm for 3 h at room temperature and pH 7.2 to prepare the additive, wherein the mass concentration of the sodium hydroxide is 0.4%.

[0044] Preparation of the polymeric silicate agent: mix the water glass and deionized water in a mass ratio of 1:4.7, stir at a speed of 600 rpm to obtain a water glass solution, add dilute phosphoric acid solution to the water glass solution under stirring to adjust the pH to 11.5, and then stir at a speed of 100 rpm, mature for 24 h to obtain an intermediate liquid, add the additives to the intermediate liquid, stir at a speed of 50 rpm at 40℃ for 2 h, and stand for 12 h to obtain the polymeric silicate agent, wherein the mass concentration of the dilute phosphoric acid solution is 10%, and the mass ratio of the intermediate liquid to the additives is 30:1.

[0045] Preparation of the reaction material: mix the malt dextrin and trehalose in a mass ratio of 5:1 to obtain a mixture, put the mixture into a reaction kettle, add deionized water, add p-toluenesulfonic acid, close the reaction kettle, reduce the pressure to-0.1 MPa, react at 100℃ for 4 h, cool to below 60℃, add a 10% sodium hydroxide solution to adjust the pH to 7.0, then add activated carbon powder, stir at 80℃ for 30 min, filter, and collect the filtrate to obtain the reaction material, wherein the mass of the deionized water is 60% of the mass of the mixture, the mass of the p-toluenesulfonic acid is 2% of the mass of the mixture, and the mass of the activated carbon powder is 3% of the mass of the mixture.

[0046] Preparation of the additive: mix the reaction material, diammonium phosphate, and urea in a mass ratio of 100:8:4, mix at a speed of 35 rpm for 40 min to obtain a crude material, spray a 5% polyvinyl alcohol solution on the crude material, transfer the mixture into a granulator to form 3 mm particles, and dry the particles at a temperature below 60℃ to obtain the additive, wherein the mass of the polyvinyl alcohol solution is 15% of the mass of the crude material.

[0047] In S4, the biofilm cultivation in the contact oxidation tank comprises the following steps: passing the sludge backflowed from the secondary sedimentation tank into the contact oxidation tank, controlling the aeration amount to prevent the accumulation of impurities at the bottom of the tank, stopping the sludge backflow after the surface of the suspended filler is covered with a biofilm, increasing the aeration amount to make the dissolved oxygen concentration ≥3 mg / L, and stably operating for 3-5 days to complete the biofilm cultivation.

[0048] In S1, the primary sedimentation tank is a horizontal flow type primary sedimentation tank, the primary sedimentation tank is set to have a hydraulic loading ≤0.26 m³ / (m 2 ·h), a design super height ≥500 mm, and a hydraulic retention time not less than 23 h.

[0049] In S5, the sludge retention time in the aeration oxidation tank is 11 days, and the volume loading is ≤0.75 kg / (m³·d).

[0050] In S6, the sludge pressure filtration adopts a box-type pressure filter, the working pressure of the pressure filter is 25 MPa, and the filtrate of the pressure filter is backflowed to the primary sedimentation tank in S1.

[0051] Comparative Example 1, the difference between this comparative example and Example 1 is that this comparative example does not contain polymeric silicate agent.

[0052] Comparative Example 2, the difference between this comparative example and Example 1 is that this comparative example does not contain additives.

[0053] Comparative Example 3, the difference between this comparative example and Example 1 is that this comparative example cancels the deep biochemical treatment unit, i.e. cancels the contact oxidation tank.

[0054] Comparative Example 4, the difference between this comparative example and Example 1 is that this comparative example cancels the path of the secondary sedimentation tank sludge backflow to the front end of the primary sedimentation tank, and all the secondary sedimentation tank sludge is backflowed to the front end of the aeration oxidation tank.

[0055] Performance test: the performance test of the propylene oxide production wastewater treated by the processes of Examples 1-3 and Comparative Examples 1-4 is carried out, and the test data obtained are recorded in the following table: Table 1

[0056] In the performance test, the chemical oxygen demand test refers to HJ828-2017, the suspended solids test uses a glass fiber filter with a pore size of 0.45 μm to filter the water sample, the filter is dried at 105°C to a constant weight, and the weight difference is calculated, and the adsorbable organic halogen test refers to passing the water sample through an activated carbon adsorption column to adsorb and enrich organic halogens, and then performing high-temperature combustion hydrolysis in a microcoulometric titration system, and calculating by measuring the halide ion content.

[0057] From the data in the table obtained by the performance test, it can be seen that the chemical oxygen demand, suspended solids and adsorbable organic halogens of the effluent treated by Examples 1-3 are significantly lower than those of Comparative Examples 1-4, which shows that the polymeric silicate agent not only removes colloids and suspended solids in the pretreatment stage through its magnetic flocculation and specific adsorption capacity, but also captures and detoxifies the dissolved small molecule toxic substances in the wastewater, creating favorable conditions for the low toxicity load of the subsequent biochemical treatment unit, and at the same time, the synergistic effect of the agent and the subsequent biochemical unit effectively prevents the inhibition of toxic substances on the microbial community, solving the problem of low removal efficiency of traditional coagulants for dissolved pollutants. The chemical oxygen demand and adsorbable organic halogen concentration of Comparative Example 1 are significantly higher than those of Examples due to the absence of polymeric silicate agent.

[0058] In addition, the additive is synergized with ferrous sulfate in the primary biochemical treatment, not only maintains the sustainability of microbial metabolism as a slow-release carbon source, but also activates the enzyme activity of functional flora through its specific components, promotes the co-metabolic process for refractory organic matter, and the water quality indicators of Comparative Example 2 without the additive are deteriorated, which shows that the absence of the additive or the incompleteness of the process chain leads to the insufficient degradation ability of the characteristic toxic substances, and the presence of the additive in the present application opens the metabolic pathway of microbial degradation of toxic halogenated substances, effectively blocking the persistent residues of these substances in the environment.

[0059] Comparative Example 3 cancels the deep biochemical treatment, and the chemical oxygen demand and the adsorbable organic halogen concentration values of the effluent are poor, which proves that the refractory organic matter cannot be effectively removed after the primary biochemical treatment, and Comparative Example 4 changes the sludge reflux path, and the effluent effect is better than that of other comparative examples but still far inferior to the embodiment, which shows that the optimized reflux strategy can maintain the balance and functional division of the microbial community in the system, and although the change does not cause the system to collapse, it will restrict the performance of the whole process.

[0060] Through comparison and analysis of the related data in the table, it can be known that the propylene oxide production wastewater treatment process provided by the present application realizes the whole-chain optimization from physical and chemical pretreatment to biological enhanced degradation through the synergistic design of polysilicate agent and additive and the combined process of "pretreatment synergistic precipitation + staged biochemical treatment"; and the precise sludge reflux and deep biochemical membrane formation technology further ensures the long-term biological phase stability and treatment efficiency of the system. Therefore, the process of the present application has significant advantages in efficient removal of comprehensive pollutants, guaranteeing stable operation of the system and controlling environmental risks, and provides a reliable technical solution for solving the problem of treating highly toxic and refractory propylene oxide production wastewater, and is more suitable for popularization and application.

[0061] In the description of the present specification, the description of the terms "one embodiment", "example", "specific example" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0062] The preferred embodiments of the application disclosed above are only to facilitate the elucidation of the application. The preferred embodiments do not describe all the details of the application and limit the application to the specific embodiments described. Obviously, many modifications and variations can be made in light of the teachings above. The description is chosen and described in order to best explain the principles of the application and its practical application to thereby enable others skilled in the art to best utilize the application and get the best results from the application. The application is only limited by the claims and their full scope and equivalents.

Claims

1. A process for the treatment of propylene oxide production wastewater, characterized in that, The method comprises the following steps: S1： Pre-treatment: high-temperature wastewater (70-80 DEG C) generated in a propylene oxide production plant is passed into a cooling tower, cooled to below 40 DEG C, then a polymeric silicate agent with a mass of 0-0.07% of the wastewater is added, then sent into a horizontal flow primary sedimentation tank, for sludge-water separation treatment, to obtain supernatant and sludge; S2: primary biochemical treatment: the supernatant of the primary sedimentation tank is sent into an aeration oxidation tank, ferrous sulfate with a mass of 0.03-0.05% of the wastewater is added, an additive is added, and aerobic treatment is carried out under the condition that the dissolved oxygen concentration is 2-4 mg / L, wherein the mass of the additive is 0.002-0.01% of the wastewater; S3: secondary solid-liquid separation: sending the effluent from the aeration oxidation tank to a secondary sedimentation tank to obtain supernatant and sludge, and returning part of the sludge from the secondary sedimentation tank to the front end of the primary sedimentation tank and part of the sludge from the secondary sedimentation tank to the front end of the aeration oxidation tank, wherein the surface load of the secondary sedimentation tank is ≤0.54 m 3 / (m 2 ·h); S4: advanced biochemical treatment: the supernatant of the secondary sedimentation tank is sent into a contact oxidation tank, the dissolved oxygen concentration is controlled at 2-4 mg / L, the tank is filled with Φ80 mm suspended ball fillers, and biofilm cultivation is carried out by using the backflow sludge of the secondary sedimentation tank, after the biofilm cultivation is completed, the dissolved oxygen is controlled to be greater than or equal to 2 mg / L; S5: final sedimentation: the effluent of the contact oxidation tank is sent into a final sedimentation tank, to obtain supernatant and sludge, the supernatant is metered through a Bartha tank and then discharged outside after reaching the standard; S6: sludge treatment: the sludge obtained from the primary sedimentation tank, the secondary sedimentation tank and the final sedimentation tank is sent into a sludge storage tank for concentration, after the concentration, the sludge is conditioned and then subjected to pressure filtration treatment, to obtain a sludge cake, and the sludge cake is transported out for disposal.

2. The propylene oxide production wastewater treatment process of claim 1, wherein, The polymeric silicate agent is prepared by the following method: water glass and deionized water are mixed in a mass ratio of 1:(1.85-4.7), stirring is carried out at a speed of 300-600 rpm to obtain a water glass solution, under the stirring state, dilute phosphoric acid aqueous solution is added to the water glass solution to adjust the pH to 10.5-11.5, then stirring is carried out at a speed of 50-100 rpm, and aging is carried out for 12-24 h to obtain an intermediate liquid, an additive is added to the intermediate liquid, stirring is carried out at a speed of 40-50 rpm at 25-40 DEG C for 1-2 h, and standing is carried out for 12 h, to prepare the polymeric silicate agent, wherein the mass concentration of the dilute phosphoric acid aqueous solution is 10%, and the mass ratio of the intermediate liquid to the additive is (20-30):

1.

3. The propylene oxide production wastewater treatment process of claim 2, wherein, The additive is prepared by the following method: magnetotactic bacteria are added into a liquid culture medium, fermentation culture is carried out at 28 DEG C, pH 6.9-7.1 and micro-aerobic conditions, after the fermentation is completed, the bacterial bodies are collected, cell disruption and magnetic separation purification are carried out, to obtain an intermediate product, humic acid powder and sodium hydroxide solution are mixed in a mass ratio of (4.5-5.5):2, filtration is carried out, the filtrate is mixed with the intermediate product in a mass ratio of (3-5):1, stirring is carried out at a speed of 80-90 rpm at room temperature and pH 7.2 for 2-3 h, to prepare the additive, wherein the mass concentration of the sodium hydroxide is 0.4%.

4. The propylene oxide production wastewater treatment process of claim 1, wherein, The additive is prepared by the following method: a reaction material, diammonium phosphate and urea are mixed in a mass ratio of 100:(3-8):(1-4), mixing is carried out at a speed of 15-35 rpm for 20-40 min to obtain a crude material, polyvinyl alcohol solution with a mass concentration of 5% is sprayed on the crude material, then the crude material is transferred into a granulator to prepare 1-3 mm granules, and the granules are dried at a temperature below 60 DEG C, to prepare the additive, wherein the mass of the polyvinyl alcohol solution is 8-15% of the mass of the crude material.

5. The propylene oxide production wastewater treatment process of claim 4, wherein, The reaction material is prepared by the following method: malt dextrin and trehalose are mixed in a mass ratio of 3-5:1 to obtain a mixture, the mixture is put into a reaction kettle, deionized water is added, p-toluenesulfonic acid is added, the reaction kettle is closed, the pressure is reduced to-0.08 to-0.1 MPa, and reaction is carried out at 85-100 DEG C for 2-4 h, and then cooled to below 60 DEG C, and then a 10% sodium hydroxide solution is added to adjust the pH to 6.0-7.0, and then activated carbon powder is added, and stirred at 70-80 DEG C for 30 min, and then filtered, and the filtrate is collected to obtain the reaction material, wherein the mass of the deionized water is 50-60% of the mass of the mixture, the mass of the p-toluenesulfonic acid is 1-2% of the mass of the mixture, and the mass of the activated carbon powder is 1-3% of the mass of the mixture.

6. The propylene oxide production wastewater treatment process of claim 3, wherein, The liquid culture medium comprises the following components at the following concentrations: sodium succinate 1.0 g / L, yeast extract 1.2-1.6 g / L, ferric ammonium citrate 0.15-0.25 g / L, 4-hydroxyethylpiperazine ethanesulfonic acid 3.0-3.8 g / L, magnesium sulfate heptahydrate 0.10-0.18 g / L, ferrous sulfate 0.010-0.018 g / L, cobalt chloride 0.002-0.004 g / L, and sodium molybdate 0.002-0.004 g / L, and the pH of the liquid culture medium is 6.9-7.

1.

7. The propylene oxide production wastewater treatment process of claim 1, wherein, The biofilm culture of the contact oxidation tank in the S4 comprises the following steps: the sludge of the secondary sedimentation tank is introduced into the contact oxidation tank, the aeration amount is controlled to prevent the accumulation of impurities at the bottom of the tank, after the surface of the suspended filler is covered with a biological membrane, the sludge reflux is stopped, the aeration amount is increased to make the dissolved oxygen concentration greater than or equal to 3 mg / L, and stable operation is carried out for 3-5 days to complete the biofilm culture.

8. The propylene oxide production wastewater treatment process of claim 1, wherein, The primary sedimentation tank is a horizontal flow primary sedimentation tank, the primary sedimentation tank is provided with a hydraulic load ≤0.26 m³ / (m 2 ·h), a design super height ≥500 mm, and a hydraulic retention time not less than 23 h.

9. The propylene oxide production wastewater treatment process of claim 1, wherein, The sludge retention time of the aeration oxidation tank is 11 days, and the volume load is less than or equal to 0.75 kg / (m3·d).

10. The propylene oxide production wastewater treatment process of claim 1, wherein, The sludge pressure filtration in the S6 adopts a van-type pressure filter, the working pressure of the pressure filter is 25 MPa, and the filtrate of the pressure filter is returned to the primary sedimentation tank in the S1.

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