Physicochemical-biological co-process for the treatment of high-salt, high-COD wastewater

Abstract

This invention discloses a physicochemical coupled biochemical treatment process for high-salt, high-COD wastewater, comprising the following steps: Step (1), adding a demulsifier, oxidant, and catalyst related to the wastewater to the high-salt chemical / dyeing / pharmaceutical wastewater and performing full aeration; Step (2), adding a flocculant to the aerated high-salt chemical / dyeing / pharmaceutical wastewater from Step (1) and stirring; Step (3), separating the solids and liquids in the high-salt chemical / dyeing / pharmaceutical wastewater from Step (2) and evaporating the liquid. The process and system of this invention effectively remove small molecule compounds that can synthesize tar during the evaporation process, increasing the evaporator's treatment efficiency by more than 80%, and achieving zero-discharge treatment of high-salt, high-COD wastewater.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, and in particular to a physicochemical coupled biochemical treatment process for high-salt, high-COD wastewater. Background Technology

[0002] Industries such as chemical, food, pharmaceutical, papermaking, and printing and dyeing generate large amounts of saline wastewater. This type of wastewater is characterized by complex pollutant composition, high salinity, poor biodegradability, drastic water quality fluctuations, and high treatment costs. Among these, the pollutant composition of high-salinity wastewater is particularly complex, making treatment more challenging. To minimize its environmental impact, achieving zero liquid discharge of high-salinity wastewater is imperative.

[0003] Zero Liquid Discharge (ZLD) is a wastewater management strategy that advocates minimizing wastewater discharge and maximizing water reuse. To achieve zero discharge, advanced water treatment technologies are integrated to purify and reuse wastewater and recover valuable byproducts. This type of wastewater, due to its high salt content, cannot be directly treated biologically and is currently typically treated using a "pretreatment + evaporation crystallization" process. Evaporation separates the wastewater into crystalline salt and condensate. The crystalline salt can be utilized as a resource, while the condensate is used for biological treatment, thus achieving zero discharge.

[0004] Wastewater, in particular, has a complex organic composition and high organic matter content. The crystals produced during evaporation contain not only salt but also some organic matter, which reduces the purity of the salt. This type of salt, with a high organic content, can only be treated as waste salt. Simultaneously, evaporation generates a mother liquor with significantly higher COD and TDS levels than the original wastewater, along with viscous oily substances. Therefore, effectively treating the mother liquor and improving evaporation efficiency remains a major challenge.

[0005] This includes high-salinity wastewater treatment equipment targeting chemical wastewater characterized by high COD, high salt content, high ammonia nitrogen, and high levels of aromatic aldehydes and other organic compounds. Directly introducing water into the evaporation system will result in a high influent load, and some small-molecule compounds in the wastewater may synthesize tar at higher temperatures, adhering to the inner wall of the evaporator and affecting mass and heat transfer efficiency, thereby reducing evaporation efficiency.

[0006] Currently, pretreatment methods for high-salinity wastewater mainly include wet oxidation, activated carbon adsorption, Fenton oxidation, membrane separation, ozone oxidation, and photocatalytic oxidation. These methods involve pretreatment to remove some organic matter before the wastewater enters an evaporator for crystallization. Wet oxidation has high treatment efficiency, but it requires high temperature and pressure, and demands high operational capabilities. Activated carbon adsorption is low-cost and effective, but it requires continuous regeneration, resulting in high operating costs. Fenton oxidation has high removal efficiency, but it produces a significant amount of iron sludge. Membrane separation has high retention rates, serving as a substitute for secondary sedimentation tanks, but membranes are prone to clogging and are costly. In summary, although there are many methods for treating single or multiple pollutants, they all have their limitations. For certain high-salinity chemical wastewaters, these methods cannot solve the core problem, and their actual treatment effect and economic efficiency are significantly lacking. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a physicochemical coupled biochemical treatment process for high-salt, high-COD wastewater. This process uses organic synthesis to synthesize water-insoluble substances from the organic matter in the wastewater, thereby removing them from the wastewater and achieving the goal of effectively removing organic matter from the wastewater. This significantly removes pollutants that affect the evaporation efficiency of the subsequent evaporator, increasing the evaporator's treatment efficiency by more than 80%.

[0008] To achieve the above objectives, the technical solution adopted by this invention is a physicochemical coupled biochemical treatment process for high-salt, high-COD wastewater, comprising the following steps:

[0009] Step (1): Add demulsifiers, oxidants, and catalysts related to the wastewater to the chemical / printing and dyeing / pharmaceutical wastewater and perform sufficient aeration;

[0010] Step (2): Add the flocculant to the chemical / printing and dyeing / pharmaceutical wastewater that has been aerated in step (1) and stir it.

[0011] Step (3) separates the solids and liquids in the chemical / printing and dyeing / pharmaceutical wastewater from step (2) and evaporates the liquid.

[0012] In one embodiment of the present invention, the following steps are included:

[0013] Step (1): The chemical / printing and dyeing / pharmaceutical wastewater is transported to the air flotation oxidation tank, and a removal agent related to the wastewater is added at the same time, and then a demulsifier is added to demulsify the wastewater;

[0014] Step (2), flocculation and sedimentation: The wastewater after demulsification in step (1) is passed into the inclined tube sedimentation tank and flocculant is added to remove suspended solids and sediments in the wastewater;

[0015] Step (3), preheating synthesis: The wastewater after flocculation and sedimentation in step (2) is passed into the preheating synthesis tower, and the small molecule compounds in the wastewater that have not been completely reacted are further synthesized organically;

[0016] Step (4), centrifugal separation: The wastewater preheated and synthesized in step (3) is passed into a centrifugal separation tower to separate the organic compounds;

[0017] Step (5): The wastewater separated by centrifugation in step (4) is fed into an evaporator for evaporation, crystallization and desalination.

[0018] Step (6) involves cooling and desalting the evaporation mother liquor that could no longer be concentrated in step (5), adding a demulsifier to demulsify and remove oily substances, and then returning it to the air flotation oxidation tank for further demulsification and oxidation of the evaporation mother liquor.

[0019] In step (7), the water-containing sludge formed in steps (2) and (6) is transported to the sludge dewatering room. After dewatering by pressure filtration, the filtrate is returned to the air flotation oxidation tank in step (1). The filter cake formed by pressure filtration is transported off-site as solid waste. The distilled water evaporated in step (5) is sent to the biological treatment system and discharged in compliance with standards.

[0020] This invention employs a pretreatment process that synthesizes and then removes organic matter from high-salt chemical, dyeing, and pharmaceutical wastewater. By utilizing the concept of organic synthesis, organic matter in the wastewater is synthesized into water-insoluble substances, which are then removed from the wastewater, thereby significantly reducing pollutants that affect the evaporation efficiency of subsequent evaporators.

[0021] In one embodiment of the present invention, in step (1), an oxidant, a catalyst, and liquid alkali need to be added to the air flotation oxidation tank; and the pH of the wastewater is adjusted to 8-10.

[0022] In one embodiment of the present invention, in step (1), the oxidant used is one or more of hydrogen peroxide, persulfate, and ozone, and the amount used is 0.1-10% of the wastewater volume.

[0023] In one embodiment of the present invention, in step (1), the catalyst is one or more of the following: iron series catalyst, manganese series catalyst, copper series catalyst, vanadium pentoxide, elemental metal (platinum, silver, lead), and graphene.

[0024] In one embodiment of the present invention, in step (1), the amount of demulsifier (by concentration) is 0.2-10‰ of the wastewater volume, the amount of oxidant (by concentration) is 0.1-10% of the wastewater volume, and the amount of catalyst (by concentration) is 0.001-0.01% of the wastewater volume.

[0025] In one embodiment of the present invention, in step (1), the aeration method is microporous aeration or micro-nano aeration, the aeration time is 3-10h, and the aeration temperature is 25-80 degrees.

[0026] In one embodiment of the present invention, in step (2), one or more of polyacrylamide, polyaluminum chloride, and polyferric sulfate are added to the inclined tube sedimentation tank, and the dosage is 1-100 ml / L of wastewater.

[0027] In one embodiment of the present invention, in step (2), polypropylene (PP) is used as the honeycomb inclined tube packing for the sedimentation tank.

[0028] In one embodiment of the present invention, the evaporator in step (5) is one or more of the following coupled together: MVR evaporator, thin film evaporator, single-effect evaporator, double-effect evaporator, triple-effect evaporator, and multi-media MVR evaporator.

[0029] This invention proposes a physicochemical coupled biochemical treatment process for high-salt, high-COD wastewater. The wastewater enters an air flotation oxidation tank, where oxidants, demulsifiers, catalysts, and liquid alkali are added. Phenolic and aldehyde compounds in the wastewater undergo organic synthesis, and most of the COD, suspended solids, and phenolic compounds are removed. The effluent from the air flotation oxidation tank enters an inclined tube sedimentation tank, where a series of flocculants are added to further remove suspended solids and sediments. Sludge from the inclined tube sedimentation tank is periodically discharged and dewatered by a filter press. The filtrate is returned to the air flotation oxidation tank, and the dewatered sludge cake is transported off-site for solid waste treatment. The effluent from the inclined tube sedimentation tank enters a preheating synthesis tower, where unreacted small-molecule compounds continue to undergo organic synthesis. The effluent from the preheating synthesis tower enters a centrifugal separation tower, where the organic compounds are separated by centrifugation. The centrifugal separation tower requires periodic cleaning. After the above treatment, the small-molecule organic compounds of synthetic tar in the chemical / dyeing / pharmaceutical wastewater are largely removed, without affecting the desalination efficiency of the MVR evaporator. After the mother liquor that the MVR evaporator can no longer concentrate is cooled and desalinated, it is returned to the air flotation oxidation tank for the same repeated steps.

[0030] Compared to other existing processes, this invention removes small molecule compounds from wastewater that can synthesize tar at high temperatures, improves the heat and mass transfer efficiency of MVR, thereby increasing the evaporation efficiency of MVR evaporators by more than 80% and greatly reducing operating costs.

[0031] The principle of the pretreatment process proposed in this invention for the internal synthesis and subsequent removal of organic matter in high-salt chemical / dyeing / pharmaceutical wastewater is as follows: phenolic condensation reaction. Since the high-salt chemical / dyeing / pharmaceutical wastewater contains organic compounds such as phenols and aldehydes, under the action of catalysts and oxidants, the two hydrogen atoms at the adjacent positions of the hydroxyl groups of phenol are relatively active and combine with the oxygen atoms on the aldehyde groups of formaldehyde to form water molecules. The remaining parts connect to form the polymer compound phenolic resin. Phenolic resin is removed because it is insoluble in water. Attached Figure Description

[0032] Figure 1 This is a process flow diagram of an embodiment of the present invention. Detailed Implementation

[0033] The following is a description of the embodiments and appendices. Figure 1 The present invention will be further described below.

[0034] Example 1

[0035] Dissolve 50 parts of demulsifier in 1000 parts of water to obtain solution B, and then stir solution B at room temperature for 1 hour. Add 50 parts of solution B and 10 parts of 30% hydrogen peroxide to 1000 parts of wastewater, and then aerate thoroughly at 60 degrees Celsius for 3 hours. Increase the amount of oxidant and catalyst.

[0036] Dissolve 50 parts of flocculant A in 1000 parts of water and stir thoroughly for 1 hour to obtain solution C. Dissolve 1 part of flocculant E in 1000 parts of water and stir at room temperature for 4 hours to obtain solution D. Then, add 40 parts of solution D and 40 parts of solution C to the wastewater that has undergone the above aeration treatment and stir for 1 hour.

[0037] The wastewater was filtered, and the filtrate was placed in a rotary evaporator for evaporation. The resulting cooling water had a COD of less than 3000 mg / L, NH3-N of less than 200 mg / L, and was salt-free. Compared with the original wastewater (COD 100000 mg / L, NH3-N 25000 mg / L, total salt 180000 mg / L), the removal rates in this embodiment were as high as 95%, 99.2%, and 100%, respectively. Furthermore, the effluent was very white, and the mother liquor contained no tar and would not adhere to the flask (the method of judgment is: evaporate the treated wastewater to dryness and observe the adhesion to the evaporator, and observe whether the substances on the flask wall dissolve after adding water). This does not affect the heat and mass transfer efficiency and is beneficial for evaporation.

[0038] Example 2

[0039] according to Figure 1As shown in the process flow diagram, high-salinity wastewater and MVR evaporators from Fujian Dolphin Pharmaceutical Technology Co., Ltd., as well as air flotation oxidation tanks and inclined tube sedimentation tanks from Hangzhou Haoyue Environmental Technology Development Co., Ltd., and other equipment were used for batch testing. The treatment method includes the following steps:

[0040] Pharmaceutical wastewater containing ammonium sulfate was introduced into an air flotation oxidation tank. Hydrogen peroxide, an AR-type demulsifier, a catalyst containing C, H, O, Mn, Fe, S, P, and N, and sodium hydroxide were added. The reaction was carried out under aeration at 50℃-80℃ for 3-6 hours. The dosage of hydrogen peroxide was 1%, the AR-type demulsifier was 2‰, and the catalyst was 0.005%. Phenolic and aldehyde compounds in the chemical pharmaceutical wastewater underwent organic synthesis. National standard testing showed that most of the COD, suspended solids, and phenolic compounds in the wastewater were removed.

[0041] The effluent from the air flotation oxidation tank enters the inclined tube sedimentation tank, where polyaluminum chloride, polyacrylamide, and polyferric sulfate are added to further remove suspended solids and sediments. Sludge from the inclined tube sedimentation tank is periodically discharged and dewatered by a filter press; the filtrate is returned to the air flotation oxidation tank, and the dewatered sludge cake is transported off-site for solid waste treatment.

[0042] The effluent from the inclined tube sedimentation tank enters the preheating synthesis tower, where unreacted small molecule compounds continue to undergo organic synthesis. The effluent from the preheating synthesis tower then enters a centrifugal separator, which separates the organic compounds. The centrifugal separator requires regular cleaning.

[0043] The effluent from the centrifugal separator enters the MVR evaporator for evaporation. After the above treatment, the small-molecule organic compounds of synthetic tar in the wastewater are basically removed, and the desalination efficiency of the evaporator is not affected. The mother liquor that can no longer be concentrated in the evaporator is cooled and desalinated, and then returned to the air flotation oxidation tank for the above-mentioned repeated steps. In this example, the technology used in this invention achieves removal rates of 97% for COD, 99.3% for NH3-N, and 99.5% for total salt. The presence of a small amount of salt in the distilled water is due to flooding. Compared with the original process, this process improves the evaporation efficiency of the MVR evaporator by more than 80%.

[0044] The specific embodiments described above are only used to explain and illustrate the present invention, and are not intended to limit the present invention. Any changes and substitutions made to the present invention without creative effort within the scope of the inventive concept and claims shall fall within the protection scope of the present invention patent.

Claims

1. A physicochemical coupled biochemical treatment process for high-salt, high-COD wastewater, characterized in that, Includes the following steps: Step (1): The wastewater is transported to the air flotation oxidation tank. A demulsifier, oxidant, and catalyst related to the wastewater are added to the wastewater. Liquid alkali is added and the pH of the wastewater is adjusted to 8-10. Demulsification is performed and the wastewater is fully aerated. The oxidant is one or more of hydrogen peroxide, persulfate, and ozone. The catalyst is one or more of iron-based catalysts, manganese-based catalysts, copper-based catalysts, and vanadium pentoxide. The dosage of the demulsifier is 0.2-10‰ of the wastewater volume, the dosage of the oxidant is 0.1-10% of the wastewater volume, and the dosage of the catalyst is 0.001-0.01% of the wastewater volume. Step (2): The wastewater after aeration in step (1) is fed into the inclined tube sedimentation tank and flocculant is added to remove suspended solids and sediments from the wastewater. Step (3): The wastewater after flocculation and sedimentation in step (2) is passed into the preheating synthesis tower to continue the organic synthesis of the small molecule compounds in the wastewater that have not been completely reacted. Step (4): The wastewater preheated and synthesized in step (3) is passed into a centrifugal separator to separate the organic compounds; Step (5): The wastewater separated by centrifugation in step (4) is fed into an evaporator for evaporation, crystallization and desalination. Step (6) involves cooling and desalting the evaporation mother liquor that could no longer be concentrated in step (5), adding a demulsifier to demulsify and remove oily substances, and then returning it to the air flotation oxidation tank for further demulsification and oxidation of the evaporation mother liquor. In step (7), the water-containing sludge formed in steps (2) and (6) is transported to the sludge dewatering room. After dewatering by pressure filtration, the filtrate is returned to the air flotation oxidation tank in step (1). The filter cake formed by pressure filtration is transported off-site as solid waste. The distilled water evaporated in step (5) is sent to the biological treatment system and discharged in compliance with standards.

2. The physicochemical coupled biochemical treatment process for high-salt, high-COD wastewater according to claim 1, characterized in that, In step (1), the aeration method is microporous aeration or micro-nano aeration, the aeration time is 3-10h, and the aeration temperature is 25-80 degrees.

3. The physicochemical coupled biochemical treatment process for high-salt, high-COD wastewater according to claim 1, characterized in that, In step (2), one or more of polyacrylamide, polyaluminum chloride, and polyferric sulfate are added to the inclined tube sedimentation tank, with a dosage of 1-100 ml / L of wastewater.

4. The physicochemical coupled biochemical treatment process for high-salt, high-COD wastewater according to any one of claims 1 to 3, characterized in that, In step (2), polypropylene (PP) is used as the honeycomb inclined tube packing for the sedimentation tank.

5. The physicochemical coupled biochemical treatment process for high-salt, high-COD wastewater according to any one of claims 1 to 3, characterized in that, In step (5), the evaporator is one or more of the following coupled together: MVR evaporator, thin film evaporator, single-effect evaporator, double-effect evaporator, triple-effect evaporator, and multi-media MVR evaporator.

Images