CN116693077A - Method for treating and recycling chemical wastewater containing oligomer - Google Patents

Abstract

The application provides a method for treating and recycling chemical wastewater containing oligomers, which comprises the following steps: 1) The chemical wastewater containing the oligomer to be treated, an initiator and a cross-linking agent are subjected to cross-linking reaction in a cross-linking unit; 2) Introducing the crosslinked wastewater from the crosslinking unit into an air floatation unit, adding a floatation agent, and performing air floatation treatment; 3) Introducing air-float effluent from the air-float unit into a biochemical unit for biochemical treatment; 4) Introducing the effluent from the biochemical unit into a deep treatment unit for treatment; 5) And introducing the effluent from the advanced treatment unit into a membrane treatment unit for membrane treatment, wherein the obtained membrane treatment water can be reused for preparing water from chemical water or supplementing water from circulating water. The application has the advantages of good treatment effect and low treatment cost, solves the problem of recycling the treated styrene-butadiene rubber wastewater, and saves water resources.

Description

A method for the treatment and reuse of chemical wastewater containing oligomers

technical field

The invention relates to a method for pretreatment of chemical wastewater, in particular to a method for treating and reusing oligomer-containing chemical wastewater.

Background technique

Synthetic rubber, such as styrene-butadiene rubber (styrene butadiene rubber), needs to add a large amount of coagulant aids, diffusing agents, regulators and polymerization inhibitors during production, resulting in a relatively high concentration of organic matter that is extremely difficult to degrade in its wastewater. Most of the organic matter is unreacted monomers and oligomers, and it is difficult to achieve satisfactory results by conventional methods, so it is difficult to perform advanced treatment and reuse.

At present, the treatment of wastewater from synthetic rubber production is basically a combination of pretreatment and biochemical treatment, and the research and development of related technologies also focuses on how to improve the efficiency of pretreatment and biochemical treatment. The pretreatment measures of synthetic rubber production wastewater mainly include coagulation sedimentation method, coagulation air flotation method, electrolytic flocculation method, catalytic oxidation method, etc., and the subsequent biochemical treatment measures mainly include hydrolysis acidification method, contact oxidation method, activated sludge method , the use of high-efficiency dominant bacteria, etc. From the engineering practice of synthetic rubber production wastewater treatment, although the combination of pretreatment and biochemical treatment can obviously remove pollutants, due to the existence of some non-biodegradable substances in the wastewater, the quality of the biochemical treatment effluent is poor. It will affect the standard discharge, and at the same time, due to the presence of oligomers in the wastewater, it is difficult to carry out desalination and reuse.

In terms of the advanced treatment and reuse of synthetic rubber production wastewater treated by secondary biochemical treatment, some methods such as coagulation sedimentation, activated carbon adsorption, and reverse osmosis treatment have been proposed. Insufficient stability and other constraints make it difficult to realize industrial applications.

Patent CN101723526 provides a membrane treatment method for synthetic rubber production wastewater that has undergone secondary biochemical treatment. This method adopts the treatment process of "catalytic oxidation + coagulation precipitation + ultrafiltration + reverse osmosis". Iron is used as a catalyst to carry out catalytic oxidation treatment of wastewater, mainly to remove refractory COD in wastewater, then remove iron and suspended solids through coagulation precipitation, then remove colloids and remaining particulate matter through ultrafiltration, and finally perform desalination treatment through reverse osmosis. Because pre-membrane pretreatment effectively removes organic matter that has a greater impact on the operation of the membrane system, this method has the characteristics of excellent effluent quality.

However, this method cannot effectively remove the oligomers in the wastewater, and cannot avoid the clogging of the membrane by the oligomers, and the membrane facility cannot be operated for a long period of time. Moreover, the use of Fenton's reagent to treat waste water has a large amount of waste residue, and the consumption of acid and alkali is large.

Therefore, it is necessary to adopt a practical method to treat the chemical wastewater containing oligomers, so that the treated wastewater can be recycled.

Contents of the invention

The purpose of the present invention is to provide a method for the treatment and reuse of chemical wastewater containing oligomers, especially a method for the treatment and reuse of synthetic rubber wastewater.

A method for the treatment and reuse of chemical wastewater containing oligomers, comprising the steps of:

1) Make the chemical wastewater containing oligomers to be treated and the initiator and the crosslinking agent carry out crosslinking reaction in the crosslinking unit;

2) passing the cross-linked waste water from the cross-linking unit into the air flotation unit, adding a flotation agent, and performing air flotation treatment;

3) passing the air flotation effluent from the air flotation unit into the biochemical unit for biochemical treatment;

4) Pass the effluent from the biochemical unit to the advanced treatment unit for treatment.

5) Pass the effluent from the advanced treatment unit to the membrane treatment unit for membrane treatment, and the obtained membrane treated water can be reused for chemical water production or circulating water replenishment.

In the step 1 crosslinking unit of the present invention, the initiator can be persulfate, hydrogen peroxide, sodium hypochlorite, preferably persulfate, such as potassium persulfate, and the dosage of the initiator can be 50-1000ppm, preferably 100-500ppm.

The cross-linking agent can be N,N'-dimethylene bisacrylamide, hydroxyethyl acrylate, dibenzoyl peroxide, glutaraldehyde, etc., preferably N,N'-dimethylene bisacrylamide Acrylamide; the dosage of the crosslinking agent can be 0.1-80ppm, preferably 1-10ppm; the reaction time of the crosslinking reaction can be 2-200 minutes, preferably 10-100 minutes. The reaction temperature can be greater than 15°C, preferably 30°C-80°C

In the air flotation unit in step 2 of the present invention, the air flotation treatment may adopt one or more of dissolved air flotation, aerated air flotation, and electrolytic air flotation, preferably dissolved air flotation. The conditions for the air flotation treatment may be: the dissolved air pressure is 0.2-0.4 MPa, and the air-water volume ratio is 0.04-0.08:1.

The flotation agent can be one or more of commonly used flotation agents such as aluminum salt, iron salt, polyaluminum, polyiron, polyacrylamide, preferably a combination of polyaluminum chloride and polyacrylamide. The dosage of polyaluminum chloride is 1-5000mg/L, preferably 10-200mg/L; the dosage of polyacrylamide is 0.05-100mg/L, preferably 1-20mg/L.

In step 3 of the biochemical unit of the present invention, the biochemical unit is preferably a treatment process of hydrolytic acidification + denitrification + MBBR. Specifically, it is hydrolytic acidification tank + denitrification tank + MBBR tank + secondary sedimentation tank. The temperature of the biochemical unit is 10-40°C, the condition of the hydrolytic acidification tank can be that the dissolved oxygen is less than 1mg/L, and the hydraulic retention time is 3-16h; the condition of the denitrification tank can be that the dissolved oxygen is less than 1mg/L, and the hydraulic retention time 2-12h, sludge concentration 2-4g/L; MBBR conditions can be dissolved oxygen 2-4mg/L, hydraulic retention time 30-80h, sludge concentration 2-4g/L; The hydraulic retention time is 1-4h. Wherein, part of the mixed liquid at the outlet of the MBBR tank flows back to the inlet of the denitrification tank, and the reflux ratio of the mixed liquid is 100%-400%. The sludge at the bottom of the secondary settling tank is partially returned to the denitrification tank, and the sludge return is 50%-150%.

In step 4 of the advanced treatment unit of the present invention, the advanced treatment unit is preferably a treatment process of ozone oxidation + BAF. Among them, the ozone oxidation section is equipped with an ozone reaction pool and an ozone buffer pool. The hydraulic retention time of the ozone reaction tank is 0.1-2h, the hydraulic retention time of the ozone buffer tank is 0.5-4h, and the concentration of ozone is 20-200mg/L. The residence time of the BAF reaction pool is 0.2-16h, preferably 0.5-8h.

In the membrane treatment unit in step 5 of the present invention, the main process is preferably a combination of ultrafiltration + reverse osmosis, specifically sand filtration + multimedia filtration + ultrafiltration + security filter + reverse osmosis. The sand filter adopts quartz sand filtration, and the filtration rate is less than 15m/h; the multi-media filtration adopts two kinds of media, anthracite and quartz sand, and the filtration speed is less than 10m/h; the ultrafiltration adopts ceramic membrane with a flux of 18-30L/m ² h, clean water backwashing time is 15-20min:1min, security filter precision is 5μm; reverse osmosis operating flux is 18-20L/m ² h, recovery rate is 65-75%.

Compared with the prior art, the invention has the advantages of good treatment effect and low treatment cost, solves the problem of reuse of synthetic rubber wastewater after treatment, and saves water resources.

Detailed ways

Below in conjunction with embodiment the present invention is described in further detail, but the scope of protection of the present invention is not limited to the scope that embodiment represents.

Table 1 shows the water quality of styrene-butadiene rubber wastewater in a petrochemical enterprise.

Table 1 Water quality of styrene-butadiene rubber wastewater

From the data in Table 1, it can be seen that the COD of wastewater is high, the biodegradability is poor, the total nitrogen of wastewater is high, and the content of oligomeric suspended matter is high.

For this waste water, some enterprises adopt a long-term biochemical treatment process to make the waste water discharge up to the standard, but due to the existence of oligomers, it is impossible to use double-membrane treatment for desalination and reuse, but the method of the present invention can achieve reuse.

Example 1

The water samples were taken from the styrene-butadiene rubber wastewater in the homogenization tank of a refining and chemical enterprise, and the water quality is shown in Table 1.

1) Introduce wastewater into the crosslinking unit, add persulfate 100ppm, N,N'—— dimethylenebisacrylamide 3ppm, and react at 60°C for 60min.

2) The waste water after the cross-linking reaction enters the air flotation unit and adds 30ppm of polyaluminium chloride and 2ppm of polyacrylamide to carry out the dissolved air flotation reaction. The dissolved air pressure is controlled to be 0.3MPa, and the air-water volume ratio is 0.06:1;

3) The wastewater after the air flotation reaction enters the biochemical unit, which is: hydrolytic acidification tank + denitrification tank + MBBR tank + secondary sedimentation tank. The control conditions of the biochemical unit are: the dissolved oxygen in the hydrolysis acidification tank at a temperature of 20-35°C is less than 0.5mg/L, and the hydraulic retention time is 10h; the dissolved oxygen in the denitrification tank is less than 1mg/L, the hydraulic retention time is 8h, and the sludge concentration is 2- 4g/L; the dissolved oxygen in the MBBR tank is 2-4mg/L, the hydraulic retention time is 50h, and the sludge concentration is 2-4g/L; the hydraulic retention time in the secondary sedimentation tank is 2h. Part of the mixed liquor at the outlet of the MBBR pool flows back to the inlet of the denitrification pool, and the reflux ratio of the mixed liquor is 200%. The sludge at the bottom of the secondary settling tank is partially returned to the denitrification tank, and the sludge return ratio is 100%.

4) The wastewater after the biochemical reaction enters the advanced treatment unit, and the advanced treatment unit adopts the treatment process of ozone oxidation + BAF. Among them, the ozone oxidation section is equipped with an ozone reaction pool and an ozone buffer pool. The hydraulic retention time of the ozone reaction tank is 0.5h, the hydraulic retention time of the ozone buffer tank is 1.5h, and the dosing concentration of ozone is 50mg/L. The residence time of the BAF reaction pool is 3h.

5) The wastewater treated by the advanced treatment unit enters the membrane treatment unit, and the membrane treatment unit adopts the combination of "sand filter + multi-media filter + ultrafiltration + security filter + reverse osmosis". Among them, the sand filter adopts quartz sand filtration, and the filtration rate is 10m/h; the multi-media filtration adopts two kinds of media, anthracite and quartz sand, and the filtration rate is 8m/h; the ultrafiltration adopts ceramic membrane with a flux of 20L/m ² h The clean water backwashing time is 20min:1min, the precision of the security filter is 5μm; the operating flux of reverse osmosis is 18L/m ² ·h, and the recovery rate is 70%.

The double-membrane device in implementation 1 has been running stably for 3 months, the membrane flux does not drop, and the effluent can be used as circulating water and chemical water to make up water. The water quality of the treated wastewater is shown in the table below.

Table 1 embodiment 1 processing effect

Example 2

The water samples were taken from the styrene-butadiene rubber wastewater in the homogenization tank of a refining and chemical enterprise, and the water quality is shown in Table 1.

1) Introduce wastewater into the crosslinking unit, add persulfate 150ppm, N,N'—— dimethylenebisacrylamide 5ppm, and react at 60°C for 60min.

2) The waste water after the cross-linking reaction enters the air flotation unit and adds 30ppm of polyaluminium chloride and 2ppm of polyacrylamide to carry out the dissolved air flotation reaction. The dissolved air pressure is controlled to be 0.3MPa, and the air-water volume ratio is 0.06:1;

3) The wastewater after the air flotation reaction enters the biochemical unit, which is: hydrolytic acidification tank + denitrification tank + MBBR tank + secondary sedimentation tank. The control conditions of the biochemical unit are: temperature 20-35°C, dissolved oxygen in the hydrolytic acidification tank is less than 0.5mg/L, hydraulic retention time is 10h; dissolved oxygen in the denitrification tank is less than 1mg/L, hydraulic retention time is 8h, and the sludge concentration is 2 -4g/L; the dissolved oxygen in the MBBR tank is 2-4mg/L, the hydraulic retention time is 50h, and the sludge concentration is 2-4g/L; the hydraulic retention time in the secondary sedimentation tank is 2h. Part of the mixed liquor at the outlet of the MBBR pool flows back to the inlet of the denitrification pool, and the reflux ratio of the mixed liquor is 200%. The sludge at the bottom of the secondary settling tank is partially returned to the denitrification tank, and the sludge return ratio is 100%.

4) The wastewater after the biochemical reaction enters the advanced treatment unit, and the advanced treatment unit adopts the treatment process of ozone oxidation + BAF. Among them, the ozone oxidation section is equipped with an ozone reaction pool and an ozone buffer pool. The hydraulic retention time of the ozone reaction tank is 0.5h, the hydraulic retention time of the ozone buffer tank is 1.5h, and the dosing concentration of ozone is 50mg/L. The residence time of the BAF reaction pool is 3h.

5) The wastewater treated by the advanced treatment unit enters the membrane treatment unit, and the membrane treatment unit adopts the combination of "sand filter + multi-media filter + ultrafiltration + security filter + reverse osmosis". Among them, the sand filter adopts quartz sand filtration, and the filtration rate is 10m/h; the multi-media filtration adopts two kinds of media, anthracite and quartz sand, and the filtration rate is 8m/h; the ultrafiltration adopts ceramic membrane with a flux of 20L/m ² h The clean water backwashing time is 20min:1min, the precision of the security filter is 5μm; the operating flux of reverse osmosis is 18L/m ² ·h, and the recovery rate is 70%. The water quality of the treated wastewater is as follows

Table 2 embodiment 2 processing effect

Example 3

The water samples were taken from the styrene-butadiene rubber wastewater in the homogenization tank of a refining and chemical enterprise, and the water quality is shown in Table 1.

1) Introduce waste water into the crosslinking unit, add 200ppm persulfate, 8ppm N,N'—methylenebisacrylamide, and react at 60°C for 80min.

2) The waste water after the cross-linking reaction enters the air flotation unit and adds 30ppm of polyaluminum chloride and 2ppm of polyacrylamide for dissolved air flotation reaction. The dissolved air pressure is controlled at 0.3MPa, and the air-water volume ratio is 0.06:1.

3) The wastewater after the air flotation reaction enters the biochemical unit. The biochemical unit is: temperature 20-35°C, hydrolytic acidification tank + denitrification tank + MBBR tank + secondary sedimentation tank. The control conditions of the biochemical unit are: the dissolved oxygen in the hydrolytic acidification tank is less than 0.5mg/L, and the hydraulic retention time is 10h; the dissolved oxygen in the denitrification tank is less than 1mg/L, the hydraulic retention time is 8h, and the sludge concentration is 2-4g/L; MBBR The dissolved oxygen in the tank is 2-4mg/L, the hydraulic retention time is 50h, and the sludge concentration is 2-4g/L; the hydraulic retention time of the secondary sedimentation tank is 2h. Part of the mixed liquor at the outlet of the MBBR pool flows back to the inlet of the denitrification pool, and the reflux ratio of the mixed liquor is 200%. The sludge at the bottom of the secondary settling tank is partially returned to the denitrification tank, and the sludge return ratio is 100%.

4) The wastewater after the biochemical reaction enters the advanced treatment unit, and the advanced treatment unit adopts the treatment process of ozone oxidation + BAF. Among them, the ozone oxidation section is equipped with an ozone reaction pool and an ozone buffer pool. The hydraulic retention time of the ozone reaction tank is 0.5h, the hydraulic retention time of the ozone buffer tank is 1.5h, and the dosing concentration of ozone is 50mg/L. The residence time of the BAF reaction pool is 3h.

5) The wastewater treated by the advanced treatment unit enters the membrane treatment unit, and the membrane treatment unit adopts the combination of "sand filter + multi-media filter + ultrafiltration + security filter + reverse osmosis". Among them, the sand filter adopts quartz sand filtration, and the filtration rate is 10m/h; the multi-media filtration adopts two kinds of media, anthracite and quartz sand, and the filtration rate is 8m/h; the ultrafiltration adopts ceramic membrane with a flux of 20L/m ² h The clean water backwashing time is 20min:1min, the precision of the security filter is 5μm; the operating flux of reverse osmosis is 18L/m ² ·h, and the recovery rate is 70%.

The double-membrane device in implementation 3 has been running stably for 3 months, the membrane flux does not drop, and the effluent can be used as circulating water and chemical water to replenish water. The water quality of the treated wastewater is shown in the table below.

Table 3 embodiment 3 processing effect

Comparative example 1

Others are the same as Example 3, the difference is that there is no step 1, and the double-membrane device of Comparative Example 1 has been operated for 1 month, and the membrane flux has dropped significantly, and the membrane flux cannot be recovered by chemical cleaning. The water quality of the treated wastewater within one month is shown in the table below.

Table 4 Comparative Example 1 Treatment Effect

Comparative example 2

Others are as embodiment 3, and difference is that step 1 adopts the method for following catalytic oxidation:

Adjust the pH of the wastewater to 3, add 200ppm of persulfate and 200ppm of ferrous sulfate, react for 80 minutes, adjust the pH to 7 and settle for 2 hours.

The dual-membrane device in Comparative Example 2 was operated for one month, and the membrane flux decreased significantly, and the membrane flux could not be restored by chemical cleaning. The water quality of the treated wastewater within one month is shown in the table below.

Table 5 comparative example 2 processing effect

Claims (12)

1. A method for treating and recycling chemical wastewater containing oligomers comprises the following steps:

1) The chemical wastewater containing the oligomer to be treated, an initiator and a cross-linking agent are subjected to cross-linking reaction in a cross-linking unit;

2) Introducing the crosslinked wastewater from the crosslinking unit into an air floatation unit, adding a floatation agent, and performing air floatation treatment;

3) Introducing air-float effluent from the air-float unit into a biochemical unit for biochemical treatment;

4) Introducing the effluent from the biochemical unit into a deep treatment unit for treatment;

5) And (3) introducing the effluent from the advanced treatment unit into a membrane treatment unit for membrane treatment, and recycling the obtained membrane treatment water.

2. The method according to claim 1, wherein the initiator is selected from one or more of persulfate, hydrogen peroxide, and sodium hypochlorite.

3. The process according to claim 1, wherein the initiator is added in an amount of 50 to 1000ppm, preferably 100 to 500ppm.

4. The method according to claim 1, wherein the cross-linking agent is selected from one or more of N, N' -dimethylene bisacrylamide, hydroxyethyl acrylate, dibenzoyl glutaraldehyde.

5. The method according to claim 1, wherein the crosslinker is added in an amount of 0.1-80ppm, preferably 1-10ppm.

6. The method according to claim 1, wherein the reaction time of the crosslinking reaction is 2 to 200 minutes, preferably 10 to 100 minutes.

7. The method according to claim 1, wherein the air-float treatment adopts one or more of a dissolved air-float method, an aeration air-float method and an electrolysis air-float method, and the air-float treatment conditions are as follows: the gas dissolving pressure is 0.2-0.4 MPa, and the gas-water volume ratio is 0.04-0.08:1.

8. The method according to claim 1, wherein the flotation agent is selected from the group consisting of polyaluminium chloride and polyacrylamide, the polyaluminium chloride being added in an amount of 1-5000mg/L, preferably 10-200mg/L; the addition amount of the polyacrylamide is 0.05-100mg/L, preferably 1-20mg/L.

9. The method of claim 1, wherein the biochemical unit is a hydrolytic acidification + denitrification + MBBR treatment process.

10. The method of claim 1, wherein the advanced treatment unit is an ozone oxidation + BAF treatment process.

11. The method of claim 1, wherein the membrane treatment unit is an ultrafiltration + reverse osmosis treatment process.

12. The method according to claim 1, wherein the chemical wastewater containing the oligomer is wastewater generated in a synthetic rubber production process.