CN118307145A - Pentaerythritol production wastewater treatment system and application thereof - Google Patents

Abstract

The present invention belongs to the field of wastewater treatment, and specifically relates to a pentaerythritol production wastewater treatment system and its application. According to the characteristics of pentaerythritol wastewater, the present invention has the characteristics of high COD concentration, high formaldehyde content, lack of nutrients such as nitrogen and phosphorus, high toxicity and inhibition of microbial degradation, and belongs to high-concentration toxic and harmful wastewater. The wastewater is degraded by microorganisms and all the treated wastewater is reused. The present invention completely biochemically degrades pentaerythritol wastewater to achieve zero discharge of enterprise production wastewater, and the quality of the recycled water after treatment is better than tap water, and it is returned to the workshop for production. The biochemical sludge generated in the process is newly anaerobic digested and reduced before being filtered. The mud cake after the filtration can be sent to a solid waste incinerator for treatment or outsourced treatment. The concentrated liquid generated in the evaporation and crystallization process is first dried and reduced by a vacuum disc scraper and then sent to a solid waste incinerator for treatment or outsourced treatment, thereby minimizing the cost of enterprise sludge treatment.

Description

A pentaerythritol production wastewater treatment system and its application

Technical Field

The invention belongs to the field of wastewater treatment, and specifically relates to a pentaerythritol production wastewater treatment system and application thereof.

Background technique

Pentaerythritol is a polyol organic compound, which is widely used in the production of alkyd resins, synthetic lubricants, plasticizers, surfactants and other fields. The wastewater containing pentaerythritol produced in industrial production causes serious pollution, and the treatment process of pentaerythritol-containing wastewater has gradually attracted attention.

IC anaerobic reactor, namely IC internal circulation anaerobic reactor, is developed on the basis of the second generation anaerobic reactor (UASB). Structurally, it can be seen as two UASB reactors connected in series and overlapped with each other. The biogas produced by the anaerobic reaction is used as the power to lift the wastewater and sludge to the separation bag at the top of the reactor, and then return to the bottom of the reactor from the central return water pipe, thus realizing the internal circulation of the mixed liquid, buffering the impact of the bottom water on the sludge, and at the same time increasing the hydraulic load of the reactor, ensuring the full mixing of mud and water, so that the wastewater can obtain a stable treatment effect. The IC internal circulation anaerobic reactor currently developed overcomes the problems of low load, low gas production, and sludge loss of other anaerobic reactors.

The uniform distribution of gas production and influent as well as the internal circulation reflux of the IC anaerobic reactor make the sludge at the bottom "fluidized", and the influent (substrate) and activated sludge (bacteria) form a good contact, which increases the mass transfer effect between them; the protection of multiple sets of three-phase separators makes the sludge loss only less than 1/3 of that of UASB, thus ensuring that there is enough anaerobic sludge during the operation of the reactor, providing safety guarantee for the stable and high-load operation of the reactor; compared with the first and second generation anaerobic technologies, IC can reduce the land occupation by 1/2-1/3, the tank volume by 1/3-1/4, and the total project investment is also greatly reduced; there is a special separation package to make the biogas collection rate high; the effluent is stable and has strong resistance to load shock; the internal circulation system greatly reduces the consumption of power equipment and reduces the operation and maintenance costs; and solves the scaling and blockage problem that is most likely to be caused by the water inlet system.

MVR evaporator is a new type of high-efficiency and energy-saving evaporation equipment mainly used in the evaporation and crystallization industry. The equipment uses low-temperature and low-pressure steaming technology and clean energy as energy to generate steam and separate the water in the medium. It is an internationally advanced evaporation technology and an upgraded product to replace the traditional evaporator. After the brine is preheated, it enters the evaporator and partially evaporates in the evaporator. The secondary steam generated is compressed by the compressor to increase the pressure and then introduced into the heating side of the evaporator. After the steam is condensed, it is drawn out as product water, thus realizing the recycling of heat energy. MVR evaporator is different from ordinary single-effect falling film or multi-effect falling film evaporator. MVR is a monomer evaporator that integrates multi-effect falling film evaporator. It adopts segmented evaporation according to the required product concentration. That is, when the product cannot reach the required concentration after passing through the effect body for the first time, the product will be pumped to the upper part of the effect body through the vacuum pump at the bottom of the effect body through the external pipeline of the effect body after leaving the effect body, and then pass through the effect body again, and then reach the required concentration through this repeated passage through the effect body.

Summary of the invention

In order to solve the technical problems of pentaerythritol wastewater treatment and improve the efficiency of treatment, this application provides the following technical solutions:

The present invention provides a pentaerythritol production wastewater treatment system, comprising a wastewater treatment system, a sludge treatment system and a reclaimed water reuse system connected in sequence;

The wastewater treatment system comprises a comprehensive wastewater regulating tank, a pretreatment biochemical tank, a water distribution tank, an IC anaerobic reactor (internal circulation anaerobic reactor) and an oxidation ditch type activated sludge treatment tank which are connected in sequence;

The sludge treatment system comprises a secondary sedimentation tank and a tertiary coagulation reaction sedimentation tank connected in sequence;

The reclaimed water reuse system includes an intermediate water tank I, a multi-media filter, a cation exchanger, a UF ultrafiltration system, an intermediate water tank II, a primary RO reverse osmosis device, a secondary RO reverse osmosis device, an MVR evaporator and a vacuum disc scraper dryer connected in sequence;

The water outlets of the primary RO reverse osmosis device, the secondary RO reverse osmosis device and the MVR evaporator (Mechanical Vapor Recompression, steam mechanical recompression technology) are all connected to the water inlet of the recycling water tank.

Preferably, the secondary sedimentation tank and the tertiary coagulation reaction sedimentation tank are both connected to a sludge thickening tank); the discharge port of the sludge thickening tank is connected to a filter press.

Furthermore, the water outlet of the filter press is connected to the water inlet of the wastewater treatment system.

Preferably, the comprehensive wastewater regulating tank and the water distribution tank are both provided with an aeration and stirring device for homogenizing the water quality.

Furthermore, the aeration intensity of the aeration and stirring system is 2-4 m ³ /(m ² ·h).

Preferably, the oxidation ditch type activated sludge treatment tank is provided with a submersible stirring device, an anaerobic section, an aerobic section and a sedimentation tank; the anaerobic section and the aerobic section are alternately arranged, the mud outlet of the sedimentation tank is connected to the mud inlet of the anaerobic section, and the aerobic section is provided with a microporous aeration device.

Preferably, a honeycomb filler is provided in the three-stage coagulation reaction sedimentation tank.

Preferably, the water outlet of the primary RO reverse osmosis device is also connected to the water inlet of the primary RO concentrated water tank, and the water outlet of the primary RO concentrated water tank is simultaneously connected to the water inlet of the UF ultrafiltration system and the secondary RO reverse osmosis device.

Preferably, a secondary RO concentrated water tank is provided between the secondary RO reverse osmosis device and the MVR evaporator.

In the pretreatment biochemical pool, formaldehyde-resistant fixed fillers are arranged in the pretreatment pool, and biofilm is formed. Under the multiple effects of influent dilution, microbial degradation, physical adsorption of fillers, etc., the formaldehyde concentration in the wastewater is reduced to an appropriate value.

Adjust the nutrients (nitrogen, phosphorus, etc.) of pentaerythritol wastewater and reduce the formaldehyde content entering the IC anaerobic reactor. Rely on the action of mechanical force (submersible flow propeller) to enhance the mass transfer effect of pretreatment, set formaldehyde-resistant fixed fillers in the pool, and reduce the formaldehyde concentration in the wastewater to an appropriate value under the multiple effects of influent dilution, microbial degradation, and physical adsorption of fillers.

Formaldehyde-resistant fixed filler, specific surface area ≥ 0.5m ² /g, height 3.0m. The formaldehyde concentration of the pretreatment pool effluent is controlled below 100mg/L.

Preferably, a submersible flow propeller is provided in the pretreatment biochemical pool to enhance the mass transfer effect of the pretreatment by mechanical force. The power configuration is 6-12 (W/ ^m3 pool body) to enhance the mass transfer effect of the pretreatment.

The IC anaerobic reactor is used to significantly remove COD in the water. The remaining COD in the wastewater is basically removed in the pool, and at the same time, the anaerobic-aerobic sections are alternately set in the oxidation ditch to remove ammonia nitrogen and total nitrogen in the water.

In the oxidation ditch type activated sludge treatment pool, in terms of hydraulic flow, the flow rate in the oxidation ditch can reach more than 0.3m/s, and there is a large proportion of self-recirculation in the ditch, so that the influent of the oxidation ditch is fully mixed with the mixed liquid in the ditch, which can quickly adsorb and dilute the organic matter at the inlet end, so that the organic matter concentration in each section of the ditch will not change significantly, and the ability to resist shock loads is enhanced.

The oxidation ditch includes an anaerobic section, an aerobic section, and a sedimentation tank. Most of the sludge precipitated in the sedimentation tank flows back to the anaerobic section to ensure a high sludge concentration in the anaerobic section. After the wastewater enters the anaerobic section of the oxidation ditch, the facultative microorganisms in the ditch can decompose and break the long-chain macromolecular organic matter that is difficult to degrade in the wastewater, and divide it into easily degradable small molecular substances, which can improve the biodegradability of the wastewater and facilitate the subsequent biochemical reactions in the aerobic section.

The dissolved oxygen in the aerobic section of the oxidation ditch is controlled at 3-5 mg/L, a microporous aerator is installed, and the aeration volume of aerobic treatment is 5-6 ^m3 /( ^m2 ·h); the dissolved oxygen in the anaerobic section of the oxidation ditch is controlled to be ≤0.2 mg/L, the carbon-nitrogen ratio is 4-5:1, a submersible stirring device is installed, and the power configuration is 6-12 (W/ ^m3 tank body).

In the secondary sedimentation tank, aerobic sludge is separated from water in the sedimentation tank, and the effluent is clarified to achieve the purpose of removing suspended solids (SS), and most of the precipitated sludge is returned to the anaerobic section of the oxidation ditch. The surface load of the secondary sedimentation tank is 0.6-0.8m ³ /(m ² ·h); wherein, the linear speed of the selected central drive scraper is 2-3m/min, and the rotation speed is 1-3r/h.

The precipitated sludge in the secondary sedimentation tank is returned to the anaerobic section and the aerobic section of the oxidation ditch at a certain return ratio to replenish the lost bacteria; the return ratio is preferably 150%-300%, and is returned to the anaerobic treatment and aerobic treatment processes.

The coagulation reaction is carried out in the three-stage coagulation reaction sedimentation tank. The coagulation reaction is divided into three stages, and the main purpose is to efficiently remove calcium and magnesium ions. In the first stage reaction, the pH is controlled within the range of 9-10, and liquid _alkali and _Na2CO3 are added to form precipitation with the reagent and the calcium and magnesium ions in the wastewater. PAC and PAM are continuously added in the subsequent two reaction tanks. The role of the coagulant PAC and the polymer coagulant aid PAM is to cause coagulation reaction of colloids, particulate matter, calcium precipitates, etc. in the wastewater through purification mechanisms such as electrical neutralization, adsorption bridging, net capture and co-precipitation, so that the pollutants are settled as sludge, and the mud and water are separated in the subsequent sedimentation tank, so that the calcium and magnesium ions are removed by the double alkali method.

Liquid alkali (sodium hydroxide), Na ₂ CO ₃ , PAC and PAM are added to the three-stage coagulation reaction sedimentation tank. The amount of PAC added is 0.35-0.45 kg/m ³ of wastewater, and the amount of PAM added is 0.005-0.01 kg/m ³ of wastewater.

Preferably, in step S7, the coagulant and flocculant are preferably polyaluminium chloride (PAC) coagulant and anionic polyacrylamide (PAM) flocculant, the Al ₂ O ₃ content in the PAC coagulant is preferably 24%, and the molecular weight of the PAM coagulant is preferably 12 million.

The produced water of the three-stage coagulation reaction sedimentation tank enters the intermediate water tank I and adds hydrochloric acid to adjust the pH to neutral. The three-stage coagulation reaction sedimentation tank is provided with honeycomb filler (i.e. inclined tube sedimentation) and uses the shallow sedimentation principle to shorten the particle sedimentation distance, thereby shortening the sedimentation time and increasing the sedimentation area of the sedimentation tank, thereby greatly improving the sedimentation efficiency of the sedimentation tank.

The multi-media filter removes suspended solids (SS) in water: removes suspended solids, particulate matter, colloids and other substances in raw water, and reduces the turbidity and color of raw water. It is entirely possible to filter out visible matter such as particles and algae brought by raw water. It ensures that the SDI value is no more than 3, and is a powerful protective screen for the subsequent membrane system.

Preferably, the filtered backwash water enters an oxidation ditch type activated sludge treatment tank for re-treatment.

In the cation exchanger, the metal cations in the wastewater are exchanged with the hydrogen ions on the cation exchange resin, so that the metal cations in the solution are transferred to the resin, and the hydrogen ions on the resin are transferred to the solution (the same as the anion exchange), thereby removing the salt in the water and preventing scaling and clogging of the subsequent membrane system.

In the UF ultrafiltration system, solute particles of 10-100A are separated from the surrounding medium containing particles. The basic principle is to filter in a cross-flow manner at a certain pressure and flow rate at room temperature, using an asymmetric microporous structure and a semipermeable membrane medium, relying on the pressure difference on both sides of the membrane as a driving force, so that solvents and small molecules pass through, and macromolecules and microparticles such as proteins, water-soluble polymers, bacteria, etc. are retained by the filter membrane, thereby achieving the purpose of separation, classification, purification, and concentration.

Preferably, the UF ultrafiltration system uses a hollow fiber membrane.

The first-stage RO reverse osmosis device utilizes the reverse osmosis principle and adopts a reverse osmosis membrane with high selective permeability, which can achieve an inorganic salt removal rate of 99% in water. At the same time, it can also remove various organic matter and particles in the water, greatly improving the product cleaning qualification rate, and is pollution-free, so it is widely used in pure water preparation.

The reverse osmosis system uses imported Dow Membrane Energy low-pressure anti-pollution membrane elements. At the same time, the system's water inlet, water production and concentrated water pipelines are equipped with a series of control valves, flow, conductivity, pressure gauges and other monitoring instruments and program-controlled operating systems, which will achieve long-term quality and quantity guaranteed systematic operation of the equipment through the PLC control system.

After pretreatment, qualified raw water enters the membrane assembly placed in the pressure vessel. Water molecules and a very small amount of small molecular organic matter pass through the membrane layer, and after being concentrated in the collection pipe, they are led to the water production pipe and then injected into the reuse water tank. This process requires pretreatment of the raw water entering the primary RO reverse osmosis device, specifically including adding scale inhibitors, reducing agents, non-oxidizing bactericides, etc. to the raw water. The reducing agent can neutralize the oxides in the raw water to prevent the reverse osmosis membrane from being oxidized, the non-oxidizing bactericide can eliminate microorganisms in the water and prevent microorganisms from attaching and growing on the membrane, and the addition of scale inhibitors can prevent the membrane from scaling and clogging.

After pretreatment, qualified raw water enters the membrane assembly placed in the pressure vessel. Water molecules and a very small amount of small molecular organic matter pass through the membrane layer, are concentrated through the collection pipe, and then lead to the water production pipe and injected into the reuse water tank.

When the primary RO reverse osmosis device produces water, fresh water with a yield of 80% enters the recycled water tank for standby use, the remaining 20% of the primary RO concentrated water enters the primary RO concentrated water tank for temporary storage, part of the primary RO concentrated water enters the secondary RO reverse osmosis device for treatment, and the remaining primary RO concentrated water is used as ultrafiltration backwash water. The backwash water and ultrafiltration effluent enter the primary RO reverse osmosis device together.

When the secondary RO reverse osmosis device produces water, fresh water with a yield of 75% enters the recycled water tank for standby use, and the remaining 25% of the secondary RO concentrated water enters the secondary RO concentrated water tank for temporary storage.

When the MVR evaporator discharges water, 98% of the evaporated condensate enters the reuse water pool for standby use, and the remaining 2% of the concentrated liquid enters the vacuum disc scraper dryer for drying and crystallization outsourcing, thereby minimizing the company's sludge treatment costs.

The vacuum scraper dryer is a new type of horizontal concentration equipment based on heat conduction. It is mainly used for evaporation, concentration, drying and crystallization. The heat conduction part of the equipment includes the inner wall of the main machine and the disc. Since the equipment adopts the heat conduction method, the gas emitted is very small, so the heat required is very low, which is very suitable for materials that require solvent recovery or tail gas treatment. The jacketed spiral with special internal design can accurately control the flow state of the material and the residence time inside the equipment, so that continuous production or batch production can be achieved. The equipment adopts the jacket and hollow disc conduction method, so the material can be heated or cooled. This equipment has good sealing performance and can be operated in vacuum or normal pressure according to different process requirements. This product breaks the limitation of the previous equipment with only a single function, so this product is a multifunctional energy-saving and environmentally friendly equipment.

The recycled water tank pump is returned to the enterprise workshop for production use.

The residual sludge from each biochemical pool and the precipitated sludge from the tertiary coagulation reaction are discharged into the sludge thickening tank for temporary concentration and storage. The sludge from the sludge thickening tank is pumped into the filter press room for filtration and dehydration. The mud cake is outsourced for disposal and the filtrate is returned to the front end of the system for further treatment.

Specifically, the pentaerythritol production wastewater treatment system comprises a series-connected wastewater treatment system and a series-connected reclaimed water reuse system: wherein the outlet of the integrated wastewater regulating tank effluent lift pump is connected to the water inlet of the pretreatment tank; the water outlet of the pretreatment tank is connected to the water inlet of the water distribution tank; the outlet of the water distribution tank effluent lift pump is connected to the water inlet of the IC anaerobic reactor; the water outlet of the IC anaerobic reactor is connected to the water inlet of the oxidation ditch; the water outlet of the oxidation ditch is connected to the water inlet of the secondary sedimentation tank; the water outlet of the secondary sedimentation tank is connected to the water inlet of the tertiary coagulation reaction sedimentation tank; the water outlet of the tertiary coagulation reaction sedimentation tank is connected to the water inlet of the intermediate water tank I; the outlet of the intermediate water tank I effluent lift pump is connected to the water inlet of the multi-media filter; the water outlet of the multi-media filter is connected to the water inlet of the cation exchanger; The water outlet of the exchanger is connected to the water inlet of the UF ultrafiltration system; the water outlet of the UF ultrafiltration system is connected to the water inlet of the intermediate water tank II; the water outlet of the intermediate water tank II is connected to the water inlet of the primary RO reverse osmosis device; the water outlet of the primary RO reverse osmosis device is connected to the water inlet of the reuse water tank and the primary RO concentrated water tank; the outlet of the primary RO concentrated water tank water outlet lift pump is connected to the water inlet of the ultrafiltration backwash water and the water inlet of the secondary RO reverse osmosis system; the water outlet of the UF ultrafiltration backwash water is connected to the water inlet of the intermediate water tank II; the water outlet of the secondary RO reverse osmosis is connected to the water inlet of the reuse water tank and the water inlet of the MVR evaporator; the evaporation condensate outlet of the MVR evaporator is connected to the water inlet of the reuse water tank; the concentrated liquid outlet of the MVR evaporator is connected to the feed inlet of the vacuum disc scraper dryer.

The sludge treatment system includes: the outlet of the sludge pump of the secondary sedimentation tank and the coagulation sedimentation tank is connected to the inlet of the sludge thickening tank.

The system design of the pentaerythritol production wastewater treatment system adopts a dual-line operation mode, which serves as a backup for each other and is easy to maintain.

The present invention also provides a method for treating wastewater from pentaerythritol production, which uses the above-mentioned wastewater treatment system from pentaerythritol production, and comprises the following steps:

S101: passing the pentaerythritol wastewater into a comprehensive wastewater regulating tank, and after aeration and stirring, entering the pretreatment biochemical tank for pretreatment; the pretreatment method includes water dilution, microbial degradation and physical adsorption of fillers;

S102: passing the wastewater pretreated in step S101 into a water distribution tank for aeration and stirring, and then passing it into an IC anaerobic reactor to adjust COD (chemical oxygen demand);

S103: passing the wastewater after COD adjustment in step S102 into an oxidation ditch type activated sludge treatment tank to adjust COD, ammonia nitrogen and total nitrogen, and then passing it into a secondary sedimentation tank for mud-water separation;

S104: passing the supernatant obtained after the mud-water separation in step S103 into a three-stage coagulation reaction sedimentation tank for coagulation reaction; the coagulation reaction is divided into three stages, the first stage reaction method is to add alkali solution to make the pH value 9-10, the second stage reaction method is to add coagulant PAC (polyaluminum chloride), and the third stage reaction method is to add polymer coagulant PAM (polyacrylamide);

S105: passing the wastewater after the coagulation reaction in step S104 into the intermediate water tank I to adjust the pH to neutral and then passing it into a multi-media filter to remove suspended solids (SS);

S106: passing the wastewater from step S105 where suspended solids are removed into a cation exchanger to remove salts and then into a UF ultrafiltration system for ultrafiltration;

S107: passing the wastewater after ultrafiltration in step S105 into the intermediate water tank II for pretreatment and then into the primary RO reverse osmosis device for reverse osmosis to obtain primary reverse osmosis concentrated water and primary reverse osmosis fresh water; the pretreatment method is: adding a scale inhibitor, a reducing agent and a non-oxidizing bactericide;

S108: passing the primary reverse osmosis concentrated water into a secondary RO reverse osmosis device to obtain secondary reverse osmosis concentrated water and secondary reverse osmosis fresh water;

S109: passing the secondary reverse osmosis concentrated water into an MVR evaporator for evaporation and concentration to obtain evaporation condensate and concentrated liquid;

S110: the concentrated liquid is passed into a vacuum disk scraper dryer for drying and crystallization, and the obtained crystals are outsourced for treatment, thereby completing the method for treating pentaerythritol production wastewater.

Preferably, in step S108, part of the primary reverse osmosis concentrated water is passed into the secondary RO reverse osmosis device, and the remaining part is refluxed to the UF ultrafiltration system.

Preferably, the primary reverse osmosis fresh water, secondary reverse osmosis fresh water and evaporation condensate are all introduced into a recycling water tank for recovery.

Preferably, in step S103, the secondary sedimentation tank is a radial flow sedimentation tank with peripheral water outlet, and a scraper is provided in the secondary sedimentation tank, and the scraper is a central transmission scraper.

Preferably, the sludge after the mud-water separation in step S103 and the precipitate obtained by the coagulation reaction in step S104 are passed into a sludge concentration tank for concentration and then filtered and dehydrated using a filter press to obtain a mud cake and a filtrate; the mud cake is outsourced for disposal, and the filtrate is returned to the wastewater treatment system.

The technical solution of the present invention has the following advantages over the prior art:

The object of the present invention is to provide a pentaerythritol wastewater treatment and reclaimed water reuse system. According to the characteristics of this type of wastewater, the present invention adopts the device provided by the present invention to solve the problems of high organic matter content, high formaldehyde content and poor biodegradability in the pentaerythritol wastewater. The wastewater treatment system has the advantages of rapid process, stable and reliable operation, small footprint, high removal efficiency, simple operation and maintenance, etc.

The invention provides a pentaerythritol production wastewater treatment and reclaimed water reuse system. According to the characteristics of pentaerythritol wastewater, the wastewater has the characteristics of high COD concentration, high formaldehyde content, lack of nutrients such as nitrogen and phosphorus, high toxicity and inhibition of microbial degradation, and is high-concentration toxic and harmful wastewater. A new set of ^2400m3 /d sewage treatment and reclaimed water reuse facilities is built. The COD of the wastewater is about 7000mg/L and the formaldehyde is about 1200-1500mg/L. The treated wastewater is degraded by microorganisms and all is reused.

The present invention mainly adopts the process route of "comprehensive regulating tank + pretreatment tank + IC anaerobic reactor + aerobic tank + secondary sedimentation tank + tertiary coagulation reaction precipitation + ion exchange + UF ultrafiltration + secondary RO reverse osmosis + MVR evaporation + vacuum disc scraper drying", and completely biodegrades pentaerythritol wastewater, realizes zero discharge of enterprise production wastewater, and the quality of the treated recycled water is better than tap water, and it is returned to the workshop for production. The biochemical sludge generated in the process is newly anaerobic digested and reduced before being filtered. The mud cake after filtering can be sent to a solid waste incinerator for treatment or outsourced treatment. The concentrated liquid generated in the evaporation and crystallization process is first dried and reduced by a vacuum disc scraper and then sent to a solid waste incinerator for treatment or outsourced treatment, which minimizes the cost of sludge treatment in the enterprise.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic diagram of a pentaerythritol wastewater treatment system.

FIG. 2 is a schematic diagram of a process flow of a pentaerythritol wastewater treatment system according to an embodiment of the present invention.

FIG3 is a schematic flow diagram of a pentaerythritol water recycling system according to an embodiment of the present invention.

Explanation of the accompanying drawings: 1-integrated wastewater regulating tank, 2-pretreatment biochemical tank, 3-water distribution tank, 4-IC anaerobic reactor, 5-oxidation ditch type activated sludge treatment tank, 6-secondary sedimentation tank, 7-tertiary coagulation reaction sedimentation tank, 8-intermediate water tank I, 9-multi-media filter, 10-cation exchanger, 11-UF ultrafiltration system, 12-intermediate water tank II, 13-primary RO reverse osmosis device, 14-secondary RO reverse osmosis device, 15-MVR evaporator, 16-vacuum disc scraper dryer, 17-sludge thickening tank, 18-recycled water tank, 19-primary RO concentrated water tank, 20-secondary RO concentrated water tank, 21-filter press.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

Example 1

A pentaerythritol production wastewater treatment system, comprising a wastewater treatment system, a sludge treatment system and a reclaimed water reuse system connected in sequence;

The wastewater treatment system comprises a comprehensive wastewater regulating tank 1, a pretreatment biochemical tank 2, a water distribution tank 3, an IC anaerobic reactor 4 and an oxidation ditch type activated sludge treatment tank 5 which are connected in sequence; both the comprehensive wastewater regulating tank 1 and the water distribution tank 3 are provided with an aeration stirring device.

The sludge treatment system includes a secondary sedimentation tank 6 and a tertiary coagulation reaction sedimentation tank 7 connected in sequence; the secondary sedimentation tank 6 and the tertiary coagulation reaction sedimentation tank 7 are both connected to a sludge concentration tank 17; the discharge port of the sludge concentration tank 17 is connected to a filter press 21. The water outlet of the filter press 21 is connected to the water inlet of the wastewater treatment system.

The reclaimed water reuse system includes an intermediate water tank Ⅰ 8, a multi-media filter 9, a cation exchanger 10, a UF ultrafiltration system 11, an intermediate water tank Ⅱ 12, a primary RO reverse osmosis device 13, a secondary RO reverse osmosis device 14, an MVR evaporator 15 and a vacuum disc scraper dryer 16 connected in sequence;

The water outlets of the primary RO reverse osmosis device 13 , the secondary RO reverse osmosis device 14 and the MVR evaporator 15 are all connected to the water inlet of the recycled water tank 18 .

The oxidation ditch type activated sludge treatment tank 5 is provided with a submersible stirring device, an anaerobic section, an aerobic section and a sedimentation tank; the anaerobic section and the aerobic section are alternately arranged, the mud outlet of the sedimentation tank is connected to the mud inlet of the anaerobic section, and the aerobic section is provided with a microporous aeration device. The three-stage coagulation reaction sedimentation tank 7 is provided with a honeycomb filler. The water outlet of the primary RO reverse osmosis device 13 is also connected to the water inlet of the primary RO concentrated water tank 19, and the water outlet of the primary RO concentrated water tank 19 is simultaneously connected to the water inlet of the UF ultrafiltration system 11 and the secondary RO reverse osmosis device 14. A secondary RO concentrated water tank 20 is provided between the secondary RO reverse osmosis device 14 and the MVR evaporator 15.

Example 2

Referring to Fig. 2 and Fig. 3, which are schematic diagrams of the structure of an embodiment of the present invention, a system for treating wastewater from pentaerythritol production and reclaimed water reuse is provided. The present invention first analyzes the types, concentrations and characteristics of pollutants in pentaerythritol wastewater. The pentaerythritol wastewater has a COD of about 7000 mg/L and formaldehyde of about 1200-1500 mg/L. It has the characteristics of high COD concentration, high formaldehyde content, lack of nutrients such as nitrogen and phosphorus, high toxicity and inhibition of microbial degradation, and is a high-concentration toxic and harmful wastewater. A new set of ^2400m3 /d sewage treatment and reclaimed water reuse facilities is built, and all the treated sewage is reused through microbial degradation.

The pentaerythritol production wastewater treatment and water reuse system includes the following steps:

Wastewater treatment system:

S1: Pentaerythritol wastewater is collected in a comprehensive wastewater regulating pool and homogenized and equalized. An aeration and stirring system is set in the pool; the aeration and stirring system has an aeration intensity of 2-4m ³ /(m ² ·h).

S2: The wastewater from the comprehensive wastewater regulating pool is pumped into the pretreatment biochemical pool, where the nutrients (nitrogen, phosphorus, etc.) of the pentaerythritol wastewater are adjusted and the formaldehyde content entering the IC anaerobic reactor is reduced. The mass transfer effect of the pretreatment is enhanced by the action of mechanical force (submersible flow propeller), and formaldehyde-resistant fixed fillers are set in the pool. Under the multiple effects of influent dilution, microbial degradation, and physical adsorption of fillers, the formaldehyde concentration in the wastewater is reduced to an appropriate value;

A submersible mixer is installed in the pretreatment tank to enhance the mass transfer effect of the pretreatment, and the power configuration is 4.3 (W/ ^m3 tank body). In step S2, a formaldehyde-resistant fixed filler is installed in the pretreatment tank, with a specific surface area of ^≥0.5m2 /g and a height of 3.0m. In step S2, the formaldehyde concentration of the effluent from the pretreatment tank is controlled below 100mg/L.

S3: The effluent from the pretreatment tank enters the water distribution tank, where it is temporarily stored before being pumped into the next level of treatment unit. An aeration and stirring system is set up in the water distribution tank to homogenize the water quality; an aeration and stirring system is set up in the water distribution tank, and the aeration intensity is 2-4m ³ /(m ² ·h).

S4: The effluent from the water distribution tank is pumped into the IC anaerobic reactor, and the COD in the water is largely removed in the system; The effluent from the water distribution tank is pumped into the IC anaerobic reactor, and the COD in the water is largely removed in the system.

S5: The effluent from the IC anaerobic reactor enters the oxidation ditch type activated sludge treatment pool, where the remaining COD in the wastewater is basically removed. At the same time, the oxidation ditch is equipped with an alternating anaerobic-aerobic section to remove ammonia nitrogen and total nitrogen in the water.

The effluent from the IC anaerobic reactor enters the oxidation ditch type activated sludge treatment pool, where the remaining COD in the wastewater is basically removed. At the same time, an anaerobic-aerobic section is alternately set in the oxidation ditch to remove ammonia nitrogen and total nitrogen in the water.

The dissolved oxygen in the aerobic section of the oxidation ditch is controlled at 3-5 mg/L, a microporous aerator is installed, and the aeration volume of aerobic treatment is 5-6 ^m3 /( ^m2 ·h); the dissolved oxygen in the anaerobic section of the oxidation ditch is controlled to be ≤0.2 mg/L, the carbon-nitrogen ratio is (4-5):1, a submersible stirring device is installed, and the power configuration is 3.2 (W/ ^m3 tank body).

S6: The effluent from the aerobic section of the oxidation ditch enters the secondary sedimentation tank, where the aerobic sludge is separated from the water and the effluent is clarified to achieve the purpose of removing SS. Most of the precipitated sludge is returned to the anaerobic section of the oxidation ditch.

The effluent from the oxidation ditch enters the secondary sedimentation tank, where the aerobic sludge is separated from the mud and water, and the effluent is clarified to achieve the purpose of removing SS. The surface load of the secondary sedimentation tank is ^0.5m3 /( ^m2 ·h); the linear speed of the selected central drive scraper is 2-3m/min, and the rotation speed is 1-3r/h. The precipitated sludge in the secondary sedimentation tank is returned to the anaerobic section and aerobic section of the oxidation ditch at a certain return ratio to replenish the lost bacteria; the return ratio is preferably 150%-300%, and is returned to the anaerobic treatment and aerobic treatment processes. Among them,

Recycled water reuse system:

S7: The supernatant of the secondary sedimentation tank enters the tertiary coagulation reaction sedimentation tank: The coagulation reaction is divided into three stages, the main purpose of which is to efficiently remove calcium and magnesium ions. In the first stage reaction, the pH is controlled within the range of 9 to 10, and liquid alkali and Na ₂ CO ₃ are added to form precipitation with the reagent and the calcium and magnesium ions in the wastewater. PAC and PAM are added in the subsequent two reaction tanks. The role of the coagulant PAC and the polymer coagulant PAM is to cause colloids, particulate matter, calcium precipitates, etc. in the wastewater to undergo coagulation reactions through purification mechanisms such as electrical neutralization, adsorption bridging, net capture and co-precipitation, so that the pollutants settle as sludge, and the mud and water are separated in the subsequent sedimentation tank, so that calcium and magnesium ions are removed by the double alkali method, and the produced water enters the intermediate water tank 1 and hydrochloric acid is added to adjust the pH to neutral. The tertiary coagulation reaction sedimentation tank uses honeycomb fillers (i.e. inclined tube sedimentation) and the shallow sedimentation principle to shorten the sedimentation distance of the particles, thereby shortening the sedimentation time and increasing the sedimentation area of the sedimentation tank, greatly improving the sedimentation efficiency of the sedimentation tank;

The supernatant of the secondary sedimentation tank enters the tertiary coagulation reaction sedimentation tank: the coagulation reaction is divided into three stages, the main purpose is to efficiently remove calcium and magnesium ions. In the first stage reaction, the pH is controlled within the range of 9 to 10, and liquid alkali and Na ₂ CO ₃ are added to form precipitation with the reagent and the calcium and magnesium ions in the wastewater. PAC and PAM are added in the subsequent two reaction tanks. The role of the coagulant PAC and the polymer coagulant PAM is to cause colloids, particles, calcium precipitates, etc. in the wastewater to undergo coagulation reactions through purification mechanisms such as electrical neutralization, adsorption bridging, net capture and co-precipitation, so that the pollutants are settled as sludge, and the mud and water are separated in the subsequent sedimentation tank, so that calcium and magnesium ions are removed by the double alkali method, and the produced water enters the intermediate water tank 1 and hydrochloric acid is added to adjust the pH to neutral. The tertiary coagulation reaction sedimentation tank uses honeycomb fillers (i.e. inclined tube sedimentation) and shallow sedimentation principles to shorten the sedimentation distance of particles, thereby shortening the sedimentation time, increasing the sedimentation area of the sedimentation tank, and greatly improving the sedimentation efficiency of the sedimentation tank. Add PAC and PAM reagents into the reaction tank.

Liquid alkali (sodium hydroxide), Na ₂ CO ₃ , PAC and PAM are added to the reaction tank. The amount of PAC added to the wastewater is 0.35-0.45 kg/m ³ of wastewater, and the amount of PAM added is 0.005-0.01 kg/m ³ of wastewater.

The coagulant and flocculant preferably use polyaluminium chloride (PAC) coagulant and anionic polyacrylamide (PAM) flocculant. The Al ₂ O ₃ content in the PAC coagulant is preferably 24%, and the molecular weight of the PAM coagulant is preferably 12 million.

In steps S1-S7, the system is designed with a dual-line operation mode, which serves as a backup for each other and is easy to maintain.

S8: The outlet water of the intermediate water tank 1 is pumped into the multi-media filter to remove SS in the water: it removes suspended matter, particulate matter, colloids and other substances in the raw water, and at the same time reduces the turbidity and color of the raw water. It is entirely possible to filter out visible matter such as particles and algae brought by the raw water. It ensures that the SDI value is no more than 3, which is a powerful protective screen for the subsequent membrane system. The filtered backwash water enters the aerobic tank for further treatment;

The outlet water of the intermediate water tank 1 is pumped into the multi-media filter to remove SS in the water: it removes suspended solids, particulate matter, colloids and other substances in the raw water, and at the same time reduces the turbidity and color of the raw water. It is entirely possible to filter out visible particles, algae and other substances brought by the raw water. It ensures that the SDI value is no more than 3, which is a powerful protective screen for the subsequent membrane system. The filtered backwash water enters the aerobic tank for further treatment.

S9: The effluent from the multi-media filter enters the cation exchanger: the metal cations in the wastewater exchange with the hydrogen ions on the cation exchange resin, so that the metal cations in the solution are transferred to the resin, and the hydrogen ions on the resin are transferred to the solution (the same as the anion exchange), so as to remove the salt in the water and prevent scaling and clogging of the subsequent membrane system;

The effluent from the multi-media filter enters the cation resin exchanger: the metal cations in the wastewater exchange ions with the hydrogen ions on the cation exchange resin, so that the metal cations in the solution are transferred to the resin, and the hydrogen ions on the resin are transferred to the solution, thereby removing the salt in the water and preventing scaling and clogging of the subsequent membrane system.

S10: The effluent from the cation exchanger enters the UF ultrafiltration system: solute particles of 10 to 100A are separated from the surrounding medium containing particles. The basic principle is to filter in a cross-flow manner at a certain pressure and flow rate at room temperature, using an asymmetric microporous structure and a semipermeable membrane medium, relying on the pressure difference on both sides of the membrane as a driving force, so that solvents and small molecules pass through, and large molecules and microparticles such as proteins, water-soluble polymers, bacteria, etc. are retained by the filter membrane, thereby achieving the purpose of separation, classification, purification, and concentration. The ultrafiltration effluent enters the intermediate water tank 2 for temporary storage;

The effluent from the cation exchanger enters the UF ultrafiltration system: solvents and small molecules pass through, while large molecules and microparticles such as proteins, water-soluble polymers, bacteria, etc. are retained by the filter membrane, thereby achieving the purpose of separation, classification, purification, and concentration. The ultrafiltration effluent enters the intermediate water tank 2 for temporary storage. The UF ultrafiltration membrane uses a hollow fiber membrane.

S11: The water from the intermediate water tank 2 is pumped into the 1st-stage RO reverse osmosis system: using the reverse osmosis principle and a highly selective reverse osmosis membrane, the inorganic salt removal rate in the water can reach 99%. At the same time, it can also remove various organic matter and particles in the water, greatly improving the qualified rate of product cleaning, and it is pollution-free and widely used in the preparation of pure water. After pretreatment, qualified raw water enters the membrane assembly placed in the pressure vessel. Water molecules and a very small amount of small molecular organic matter pass through the membrane layer, and after being concentrated through the collection pipe, they are led to the water production pipe and then injected into the reuse water tank. This process requires pretreatment of the raw water entering the first-stage RO reverse osmosis system, specifically including adding scale inhibitors, reducing agents, non-oxidizing bactericides, etc. to the raw water. The reducing agent can neutralize the oxides in the raw water to prevent the reverse osmosis membrane from being oxidized. The non-oxidizing bactericide can eliminate microorganisms in the water and prevent microorganisms from attaching and growing on the membrane. Adding scale inhibitors prevents membrane scaling and clogging;

The water from the intermediate pool 2 is pumped into the 1st-level RO reverse osmosis system: using the reverse osmosis principle and a highly selective reverse osmosis membrane, the inorganic salt removal rate in the water can reach 99%. At the same time, it can also remove various organic matter and particles in the water, greatly improving the product cleaning qualification rate.

The reverse osmosis system uses imported Dow membrane energy low-pressure anti-pollution membrane elements. At the same time, the system's water inlet, water production and concentrated water pipelines are equipped with a series of control valves, flow, conductivity, pressure gauges and other monitoring instruments and program-controlled operating systems, which will achieve long-term quality and quantity guaranteed systematic operation of the equipment through the PLC control system.

The raw water entering the primary RO reverse osmosis system is pretreated, specifically including adding antiscaling agents, reducing agents, non-oxidizing bactericides, etc. to the raw water. The reducing agent can neutralize the oxides in the raw water to prevent the reverse osmosis membrane from being oxidized. The non-oxidizing bactericide can eliminate microorganisms in the water and prevent them from attaching and growing on the membrane. Adding antiscaling agents can prevent the membrane from scaling and clogging.

S12: First-stage RO reverse osmosis effluent: 80% of the fresh water enters the reuse water tank for standby use, the remaining 20% of the first-stage RO concentrated water enters the first-stage RO concentrated water tank for temporary storage, part of the first-stage RO concentrated water enters the second-stage RO reverse osmosis system for treatment, and the remaining first-stage RO concentrated water is used as ultrafiltration backwash water. The backwash water and ultrafiltration effluent enter the first-stage RO system together;

80% of the fresh water in the first-stage RO reverse osmosis effluent enters the reuse water tank for standby use, the remaining 20% of the first-stage RO concentrated water enters the first-stage RO concentrated water tank for temporary storage, part of the first-stage RO concentrated water enters the second-stage RO reverse osmosis system for treatment, and the remaining first-stage RO concentrated water is used as ultrafiltration backwash water. The backwash water and ultrafiltration effluent enter the first-stage RO system together.

S13: Secondary RO reverse osmosis effluent: 75% of the fresh water enters the reuse water tank for standby use, and the remaining 25% of the secondary RO concentrated water enters the secondary RO concentrated water tank for temporary storage;

75% of the fresh water in the secondary RO reverse osmosis effluent enters the reuse water tank for standby use, and the remaining 25% of the secondary RO concentrated water enters the secondary RO concentrated water tank for temporary storage.

S14: The water from the secondary RO concentrated water tank enters the MVR evaporator: The MVR evaporator is a new type of high-efficiency and energy-saving evaporation equipment mainly used in the evaporation and crystallization industry. The equipment uses low-temperature and low-pressure steaming technology and clean energy as energy to generate steam and separate the water in the medium. It is an internationally advanced evaporation technology and an upgraded product to replace the traditional evaporator. After the brine is preheated, it enters the evaporator and partially evaporates in the evaporator. The secondary steam generated is compressed by the compressor to increase the pressure and then introduced into the heating side of the evaporator. After the steam is condensed, it is drawn out as product water, thus realizing the recycling of heat energy. The MVR evaporator is different from ordinary single-effect falling film or multi-effect falling film evaporators. MVR is a single evaporator that integrates a multi-effect falling film evaporator. It adopts segmented evaporation according to the required product concentration. That is, when the product cannot reach the required concentration after passing through the effect body for the first time, the product will be pumped to the upper part of the effect body through the external pipeline of the effect body by the vacuum pump at the bottom of the effect body after leaving the effect body, and then pass through the effect body again through this repeated passage through the effect body to reach the required concentration;

The water from the secondary RO concentrated water tank enters the MVR evaporator for evaporation and concentration.

S15: MVR evaporator outlet water: 98% of the evaporated condensate enters the reuse water pool for standby use, and the remaining 2% of the concentrate enters the vacuum disc scraper dryer for drying and crystallization outsourcing, which minimizes the company's sludge treatment costs;

Vacuum scraper disc dryer: Vacuum scraper dryer is a new type of horizontal concentration equipment based on heat conduction. It is mainly used for evaporation, concentration, drying and crystallization. The heat conduction part of the equipment includes the inner wall of the main machine and the disc. Since the equipment adopts heat conduction, the gas emitted is very small, so the heat required is very low, which is very suitable for materials that require solvent recovery or tail gas treatment. The jacketed spiral with special internal design can accurately control the flow state of the material and the residence time inside the equipment, so that continuous production or batch production can be achieved. The equipment adopts the jacket and hollow disc conduction method, so the material can be heated or cooled. This equipment has good sealing performance and can be operated in vacuum or normal pressure according to different process requirements. This product breaks the limitation of the previous equipment with only a single function, so this product is a multifunctional energy-saving and environmentally friendly equipment.

98% of the evaporated condensate from the MVR evaporator outlet water enters the recycling water tank for standby use, and the remaining 2% of the concentrated liquid enters the vacuum disc scraper dryer for drying and crystallization outsourced.

S16: The above-mentioned recycled water tank pump is returned to the enterprise workshop for production use.

S17: The residual sludge from each biochemical pool is discharged into the sludge thickening tank together with the tertiary coagulation reaction sedimentation sludge for temporary storage. The sludge from the sludge thickening tank is pumped into the filter press room for filtration and dehydration. The mud cake is outsourced for disposal and the filtrate is returned to the front end of the system for further treatment.

The residual sludge from each biochemical pool is discharged into the sludge thickening tank together with the tertiary coagulation reaction sedimentation sludge for temporary storage. The sludge from the sludge thickening tank is pumped into the filter press room for filtration and dehydration. The mud cake is outsourced for disposal and the filtrate is returned to the front end of the system for further treatment.

Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims (10)

1. A pentaerythritol production wastewater treatment system is characterized by comprising a wastewater treatment system, a sludge treatment system and a reclaimed water recycling system which are sequentially connected;

The wastewater treatment system comprises a comprehensive wastewater regulating tank (1), a pretreatment biochemical tank (2), a distribution tank (3), an IC anaerobic reactor (4) and an oxidation ditch type activated sludge treatment tank (5) which are connected in sequence;

the sludge treatment system comprises a secondary sedimentation tank (6) and a tertiary coagulation reaction sedimentation tank (7) which are connected in sequence;

The reclaimed water recycling system comprises a middle water tank I (8), a multi-medium filter (9), a cation exchanger (10), a UF ultrafiltration system (11), a middle water tank II (12), a primary RO reverse osmosis device (13), a secondary RO reverse osmosis device (14), an MVR evaporator (15) and a vacuum disc scraper dryer (16) which are sequentially connected;

The water outlets of the primary RO reverse osmosis device (13), the secondary RO reverse osmosis device (14) and the MVR evaporator (15) are connected with the water inlet of the recycling water tank (18).

2. The pentaerythritol production wastewater treatment system according to claim 1, wherein the secondary sedimentation tank (6) and the tertiary coagulation sedimentation tank (7) are connected with a sludge concentration tank (17); and a discharge hole of the sludge concentration tank (17) is connected with a filter press (21).

3. The pentaerythritol production wastewater treatment system according to claim 2, characterized in that the water outlet of the filter press (21) is connected with the water inlet of the wastewater treatment system.

4. The pentaerythritol production wastewater treatment system according to claim 1, wherein aeration stirring devices are arranged in the comprehensive wastewater regulating tank (1) and the distribution tank (3).

5. The pentaerythritol production wastewater treatment system according to claim 1, wherein a submersible stirring device, an anaerobic section, an aerobic section and a sedimentation tank are arranged in the oxidation ditch type activated sludge treatment tank (5); the anaerobic section and the aerobic section are alternately arranged, a mud outlet of the sedimentation tank is connected with a mud inlet of the anaerobic section, and the aerobic section is provided with a microporous aeration device.

6. The pentaerythritol production wastewater treatment system according to claim 1, wherein a honeycomb filler is arranged in the three-stage coagulation reaction sedimentation tank (7).

7. The pentaerythritol production wastewater treatment system according to claim 1, wherein the water outlet of the primary RO reverse osmosis device (13) is also connected with the water inlet of the primary RO concentrated water tank (19), and the water outlet of the primary RO concentrated water tank (19) is simultaneously connected with the water inlets of the UF ultrafiltration system (11) and the secondary RO reverse osmosis device (14).

8. The pentaerythritol production wastewater treatment system according to claim 1, characterized in that a secondary RO concentrate tank (20) is arranged between the secondary RO reverse osmosis device (14) and the MVR evaporator (15).

9. A method for treating waste water from pentaerythritol production, characterized in that the waste water treatment system for pentaerythritol production according to any one of claims 1 to 8 is used, comprising the steps of:

s101: introducing pentaerythritol wastewater into a comprehensive wastewater regulating tank (1), and introducing the wastewater into a pretreatment biochemical tank (2) for pretreatment after aeration and stirring; the pretreatment method comprises the steps of water dilution, microbial degradation and physical adsorption of filler;

S102: introducing the wastewater pretreated in the step S101 into a distribution tank (3), aerating and stirring, and introducing the wastewater into an IC anaerobic reactor (4) to regulate COD;

S103: introducing the wastewater subjected to COD adjustment in the step S102 into an oxidation ditch type activated sludge treatment tank (5) to adjust COD, ammonia nitrogen and total nitrogen, and then introducing into a secondary sedimentation tank (6) to perform mud-water separation;

S104: introducing the supernatant obtained after the mud-water separation in the step S103 into a three-stage coagulation reaction sedimentation tank (7) for coagulation reaction; the coagulation reaction is divided into three stages, wherein the first stage reaction method is to add alkali liquor to enable the pH value to be 9-10, the second stage reaction method is to add coagulant PAC, and the third stage reaction method is to add high molecular coagulant aid PAM;

s105: introducing the wastewater subjected to the coagulation reaction in the step S104 into an intermediate water tank I (8), regulating the pH value to be neutral, and introducing into a multi-medium filter (9) to remove solid suspended matters;

S106: introducing the wastewater from which the solid suspended matters are removed in the step S105 into a cation exchanger (10) to remove salt, and introducing the wastewater into a UF ultrafiltration system (11) to carry out ultrafiltration;

S107: introducing the wastewater subjected to ultrafiltration in the step S105 into an intermediate water tank II (12) for pretreatment, and then introducing into a first-stage RO reverse osmosis device (13) for reverse osmosis to obtain first-stage reverse osmosis concentrated water and first-stage reverse osmosis fresh water; the pretreatment method comprises the following steps: adding a scale inhibitor, a reducing agent and a non-oxidizing bactericide;

s108: introducing the first-stage reverse osmosis concentrated water into a second-stage RO reverse osmosis device (14) to obtain second-stage reverse osmosis concentrated water and second-stage reverse osmosis fresh water;

s109: introducing the second-stage reverse osmosis concentrated water into an MVR evaporator (15) for evaporation concentration to obtain evaporation condensate and concentrated solution;

S110: and (3) introducing the concentrated solution into a vacuum disc scraper dryer (16) for drying and crystallizing, and performing external treatment on the obtained crystals to finish the treatment method of the pentaerythritol production wastewater.

10. The method for treating pentaerythritol production wastewater according to claim 9, wherein the sludge obtained after the sludge-water separation in the step S103 and the precipitate obtained by the coagulation reaction in the step S104 are introduced into a sludge concentration tank (17) for concentration, and then are subjected to filter pressing dehydration by using a filter press (21) to obtain a mud cake and a filter pressing liquid; and the mud cake is treated outside the water treatment system, and the filter pressing liquid flows back to the water treatment system.