CN104803542A - Integrated treatment and reuse technology of esterification wastewater - Google Patents

Abstract

The invention relates to the field of esterification wastewater treatment technology, in particular to an integrated treatment and reuse technology of esterification wastewater. It includes the following steps: (1) Pretreatment: The esterification wastewater first passes through the adjustment tank to adjust the pH, and then enters the coagulation sedimentation tank to remove the tiny suspended particles and flocs in the esterification wastewater; (2) Biochemical treatment: After the steps ( 1) The treated esterification wastewater passes through the two-stage ABR reactor and the biological contact oxidation tank in turn, so that the COD of the wastewater is greatly reduced; (3) Advanced oxidation: the esterification wastewater treated in step (2) passes through UV/O ₃ Oxidation stage to remove refractory organic matter; (4) Membrane treatment: The esterification wastewater treated in step (3) is passed through multi-media filtration, activated carbon filtration and reverse osmosis membrane to obtain reusable clean water. The technology of the invention solves the problem that the prior art cannot discharge and reuse the esterification waste water up to the standard. The technology of the invention can widely solve the comprehensive treatment and reuse of esterification wastewater.

Description

An integrated treatment and reuse technology of esterification wastewater

technical field

The invention relates to the field of environmental science, in particular, the invention relates to an integrated treatment and reuse technology of esterification wastewater. The invention is suitable for wastewater treatment in the chemical industry, especially the efficient treatment of high-concentration esterification wastewater. the

Background technique

In recent years, under the conditions of national policy support and rapid social and economic progress, my country's chemical industry has developed rapidly, and the esterification wastewater discharged during the production process has continued to increase, posing a great threat to environmental safety. Esterification wastewater, that is, the wastewater generated in the esterification reaction, generally comes from the polyester production process. Because the esterification reaction process is reversible and the reaction is extremely slow, concentrated sulfuric acid is often used as a catalyst. The pH value of the wastewater is very low and the acidity is strong. At the same time, the wastewater contains diethylene glycol, acetaldehyde, ethylene glycol, 2-methyl-1 , 3-dioxolane and other organic substances, resulting in complex components of esterification wastewater, large relative molecular weight of pollutants, and containing benzene ring structure, difficult to biodegrade, high COD value, and difficult to treat. Data show that by the end of 2012, the world's polyester production capacity reached 70 million tons, and my country's polyester production capacity reached 38 million tons, accounting for 54% of the world's total production capacity. It has become the longest and most influential production in the global polyester industry chain. big country. For every ton of polyester product produced, the wastewater directly generated in the esterification reaction stage reaches 0.187 tons. Based on the annual production capacity of 38 million tons of polyester in my country, the discharged esterification wastewater reaches 7.106 million tons, accounting for the entire polyester chemical fiber industry sewage. more than 10% of the total emissions. the

At present, the "Comprehensive Wastewater Discharge Standard" (GB8978-1996) stipulates that for enterprises built after January 1, 1998, the first-level COD discharge standard should generally be ≤ 100mg/L, but for waste water recycling, "Recycled Cooling Water Recycled Water Quality Standard" (HG/T3923-2007) stipulates that CODcr should be ≤ 80mg/L. "Urban Sewage Recycling Industrial Water Quality" (GB/T19923-2005) stipulates that the COD of open circulating cooling water system make-up water, boiler make-up water, process and product water should be ≤60mg/L. With the country's emphasis on environmental protection, industrial sewage discharge standards and industrial reclaimed water quality standards will be improved, and higher requirements are also put forward for the esterification wastewater treatment process. At present, there are three main categories of esterification wastewater treatment methods: the first category is biochemical treatment, including biological contact oxidation technology, upflow anaerobic sludge bed reactor (UASB), A/O process, A ² /O process, etc.; The second category is advanced oxidation method, including Fenton oxidation method, supercritical water oxidation technology, etc.; the third category is physical and chemical treatment, including distillation, rectification, activated carbon adsorption, etc.

UASB processing technology. Catalana de Polimers Spain’s UASB esterification wastewater treatment facility in Barcelona has a reactor volume of 600m ³ , a flow rate of 0.5m/s, and a designed flow rate of 108m ³ /d for esterification wastewater and fiber wastewater (COD is 30g/L ) and 96m ³ /d (COD is 4.5g/L), reflux ratio R=5, organic load is 0.6gCOD per gram of VSS per day, little mud production, effluent COD is lower than 3g/L. Unable to meet discharge standards.

Activated sludge + biological contact oxidation method. Shanghai Petrochemical General Plant puts polyester production wastewater into the aeration tank after pH adjustment, and then enters the sedimentation tank. After that, the ordinary activated sludge method + biological contact oxidation method is adopted, and the COD removal rate can reach 82% to 92%. However, if the COD of the effluent is to be less than 100mg/L, the COD value of the influent must be controlled to be less than 1250mg/L, that is, the volume load of the aerobic treatment unit cannot be high. The disadvantages of this process are that it is sensitive to changes in water quality and water quantity, is not resistant to the impact of organic loads, produces a large amount of mud, consumes a lot of energy, and is difficult to reach the standard for water production. the

Pretreatment + anaerobic + aerobic. After the esterification wastewater is pretreated in the regulating tank, it enters the anaerobic biological filter with soft filler, then enters the biological contact oxidation tank, and finally enters the secondary sedimentation tank. After treatment, the COD value dropped from 20200mg/L to 260mg/L, and the BOD value dropped from 5000mg/L to 80mg/L. the

Stripping stripping + anaerobic + activated sludge process + facultative oxygen + aerobic. The pretreatment of esterification wastewater can greatly reduce the toxic and side effects of organic substances such as formaldehyde and acetaldehyde on biochemical reactions, and the acetaldehyde in the wastewater can be stripped through the stripping equipment in the workshop to improve the efficiency of subsequent treatment. All waste water is collected into the mixed water regulating tank and mixed evenly, and then all enter the anaerobic reaction tank for treatment to reduce the concentration of biochemical inhibitory substances in the waste water. The activated sludge method + facultative oxygen + aerobic treatment process has a good removal and decomposition effect on organic molecules and some macromolecular organic substances, and the COD value is reduced from 5000mg/L to below 100mg/L. the

Supercritical water oxidation technology. Cocero and others in Spain used supercritical water oxidation technology to treat PET polyester production wastewater from Catalana de Polimers. The total chemical oxygen demand (TOC) was 16g/L, and the wastewater mainly contained ethylene glycol with a mass fraction of 4%. In the experiment, the air flow rate is selected as 30-34kg/h, and the supercritical water oxidation is carried out under the supercritical zone pressure maintained at 23MPa. The results show that when the operating temperature is 630°C, the removal rate of TOC can reach 99.9% after only 50 seconds of reaction. However, this method has a large one-time investment and high operating costs. the

Distillation method + activated sludge method + Fenton oxidation method. The COD value of polyester wastewater from a chemical plant in Turkey is 180-230g/L, and the pH value is 2.3. The company first uses a distillation process to reduce the COD of raw water to 40g/L, and then uses ordinary activated sludge and Fenton oxidation for treatment. The study found that using the ordinary activated sludge method to treat the mixture of distilled esterification wastewater and domestic sewage, after waiting for 10 days after dilution, the sludge load was 0.1gCOD/gVSS, about 70% COD was removed, and the effluent COD was 12g/L About; but using the Fenton oxidation method, the COD removal rate can reach 67% in one day; using the activated sludge method + Fenton oxidation method, the COD value can be reduced to 5.8g/L. the

Stripping + hydrolysis + rectification. Zhejiang University adopts the method of "steam stripping + hydrolysis + rectification" to recover ethylene glycol and acetaldehyde from polyester wastewater, which has been patented. That is to say, after the esterification wastewater is concentrated by stripping, it is concentrated by evaporation and purified by rectification. The industrial application of this technology is limited by the long processing time and high cost. the

Condensed distillation + biological contact oxidation. At a certain pH value, use a flocculant to flocculate part of the non-water-soluble substances in the esterification wastewater, filter and then distill. After distillation, the COD is 1000-1200mg/L. After secondary biological contact oxidation, the effluent COD is 116mg/L. the

Aeration + activated carbon adsorption. The waste water produced by Luoyang Petrochemical Chemical Fiber Factory is mainly PTA and PET mixed waste water. Through the "double aeration + activated carbon adsorption technology", the COD of the influent water is between 7000-9500mg/L, and the COD value of the effluent water is reduced to 280-950mg/L . the

Compared with other wastewaters, there are few researches on esterification wastewater at home and abroad, and the treatment effects are different, but almost none of the produced water can meet the quality requirements of industrial reuse water. In order to solve the market dilemma of esterification wastewater with complex components, strong acidity, high COD (>18000mg/L), poor biodegradability, and common treatment technologies that cannot achieve the ideal treatment effect, an efficient and reasonable integrated treatment and reuse technology is needed. the

Contents of the invention

The purpose of the present invention is to provide an integrated treatment and reuse technology of esterification wastewater. the

The present invention comprises the following technical steps:

1) Pretreatment: The esterification wastewater first passes through the adjustment tank to adjust the pH, and then enters the coagulation sedimentation tank, and uses the flocculant to remove the ester substances and micro suspended solids in the esterification wastewater. the

2) Biochemical treatment: The esterification wastewater treated in step 1) passes through the two-stage ABR reactor and the biological contact oxidation tank in sequence, so that the COD of the wastewater is greatly reduced and the biodegradability is improved. the

3) Sedimentation: The esterification wastewater treated in step 3) is passed through the secondary sedimentation tank to remove suspended particles in the wastewater, and the sedimentation sludge is discharged to the sludge tank. the

4) Advanced oxidation: The esterification wastewater treated in step 3) passes through the ultraviolet/ozone (UV/O ₃ ) oxidation stage to remove refractory organic matter.

5) Membrane treatment: After step 4), the esterified wastewater is processed through multi-media filtration, activated carbon filtration and reverse osmosis to obtain reusable clean water, and the obtained clean water is introduced into the industrial water system, and the concentrated water is directed to step 2 ) for further cycle processing. the

in,

The step 1) before the wastewater enters the flocculation and sedimentation tank, the pH of the wastewater is controlled to be between 7 and 9 through alkali treatment. the

Step 5) The operating pressure of reverse osmosis is between 0.6-1.4 MPa. the

According to the technology of the present invention, the step 1) uses the conventional pretreatment technology in the field, dosing coagulation and precipitation, but because the flocculant has an unsatisfactory flocculation effect under acidic conditions, the technology of the present invention is before flocculation and precipitation. The pH of the esterification wastewater is adjusted to between 7 and 9. In addition, because the technology of the present invention contains a membrane treatment process, in order to reduce membrane pollution, the flocculant adopts an inorganic flocculant. the

According to the technology of the present invention, wherein said biological treatment step comprises two-stage ABR reactor and biological contact oxidation tank. First, ABR has a series of advantages such as strong biological retention capacity, good hydraulic mixing conditions, simple structure, good hydraulic characteristics, less dead zone, stable operation, strong resistance to impact load, high treatment efficiency, and less mud production. A staged multiphase anaerobic process is realized. The COD removal rate of esterification wastewater by single-stage ABR is greater than 80%, and the two-stage ABR reactor can increase the COD removal rate to ensure that the incoming COD of the subsequent biological contact oxidation tank is less than 1000mg/L; second, the biological contact oxidation tank method It is a new type of wastewater biochemical treatment method developed on the basis of activated sludge method and biofilm method. Filling is installed in the aeration tank, and the activated sludge is attached to the surface of the filling. Through aeration, the biofilm is directly agitated by the updraft and is constantly renewed, thereby improving the purification effect, with short processing time, small volume and high purification effect. Good, good and stable effluent quality, sludge does not need to reflux and does not expand, low power consumption and other advantages. the

According to the technology of the present invention, the advanced oxidation step includes UV/O ₃ combined technology. Due to the poor ability to remove refractory organic matter by using UV or O ₃ alone, the advanced oxidation technology combined with UV and O ₃ can efficiently remove refractory organic matter in wastewater.

According to the technology of the present invention, the membrane treatment step includes multimedia filtration, activated carbon filtration and reverse osmosis processes. (1) The pretreatment of reverse osmosis includes the use of multi-media filter, activated carbon filter, disc filter, ultrafiltration and microfiltration. The method of the present invention preferably uses a multi-media filter and an activated carbon filter. The multi-media filter can remove large suspended particles in water, thereby reducing the SDI value of water and meeting the water quality requirements of deep purification. The equipment has low cost and low operating cost. , easy to operate, the filter material can be used many times after backwashing, and the filter material has a long service life. Activated carbon filter can remove peculiar smell, organic matter, colloid, iron and residual chlorine in water. It also has a good effect on reducing turbidity and color of water, purifying water quality and reducing pollution to subsequent systems (reverse osmosis). This equipment has It has the characteristics of low investment, high efficiency, low operation and maintenance costs, loose water quality requirements for influent water, and stable water quality for effluent water. The multi-media filter and activated carbon filter are connected in series as the pretreatment of reverse osmosis, which can further ensure that the influent water quality of reverse osmosis is stable and up to standard. When the filter is used for a certain period, due to the interception of the surface layer of the filter material or the adsorption of a certain amount of sundries or stains on the outer surface, the filtered water quality will deteriorate, the flow rate will decrease, and the pressure difference between the inlet and outlet pipes will increase. At this point, the filter should be backwashed. Backwashing is to use the water flow to reversely pass through the filter layer to make the filter layer swell and suspend, to clean the filter layer by the shear force of water flow and particle collision friction, and to discharge the dirt in the filter layer. (2) Reverse osmosis (RO) is a separation process that uses a permeable membrane (semipermeable membrane) to selectively pass through a solvent (usually water) and intercept a solute. RO is a pressure-driven membrane separation technology, using reverse osmosis membrane as the filter medium to intercept various inorganic ions, colloidal substances, bacteria and macromolecular solutes in the water, so as to obtain purified water. The reverse osmosis concentrated water is discharged to the first-level ABR water inlet. _On the one hand, it can dilute the COD concentration of the esterification wastewater after flocculation and precipitation. Degraded organic matter is concentrated by reverse osmosis, and then enters the biochemical system for recycling, and finally decomposes.

The invention discloses an integrated treatment and reuse technology of esterification wastewater. The present invention removes suspended matter and colloidal macromolecules from the esterification wastewater through pretreatment, then further reduces the COD in the raw water through a two-stage ABR reactor and a biological contact oxidation tank, and then utilizes UV/O ₃ advanced oxidation technology depth The organic matter in the raw water is removed, and the treated liquid passes through a multi-media filter, activated carbon filter and reverse osmosis to further reduce the COD in the water, and then directly recycles it. The technology of the invention solves the problem that the COD concentration of the final effluent is difficult to reach the discharge standard and cannot meet the industrial water standard after the esterification wastewater is treated in the prior art. The technology of the invention can widely solve the comprehensive treatment and utilization of esterification wastewater.

Description of drawings

Fig. 1 is a flow chart of the integrated treatment and reuse technology of esterification wastewater according to an embodiment of the present invention. the

Detailed ways

Below in conjunction with accompanying drawing 1 and embodiment the present invention will be further described:

Example 1

Utilize the concrete steps of the esterification waste water comprehensive treatment and reuse technology involved in the present invention to purify waste water:

1) Pretreatment: The COD of the initial esterification wastewater is 50000mg/L, the BOD is 12000mg/L, and the SS is 750mg/L. After adjusting the pH of the esterification wastewater through the adjustment tank, it enters the coagulation and sedimentation tank, and the flocculant is added through the dosing pipe, and the esters and suspended matter in the wastewater are fully flocculated and precipitated by stirring. The main indicators of the wastewater after flocculation and sedimentation are: COD is 27000mg/L, BOD is 6500mg/L, SS is 220mg/L. the

2) Biochemical treatment: pass the esterification wastewater treated in step 1) through two-stage ABR reactors to reduce the COD of the wastewater and improve the biodegradability. The main indicators of the wastewater after anaerobic deflection treatment are: COD is 1100mg/L, BOD is 300mg/L, and SS is 155mg/L. Subsequently, the COD of the wastewater is further reduced through the biological contact oxidation tank. The main indicators of the wastewater after biological contact oxidation treatment are: COD is 170mg/L, BOD is 80mg/L, SS is 95mg/L. the

3) Sedimentation: The esterification wastewater treated in step 2) is passed through the secondary sedimentation tank to remove suspended particles in the wastewater, and the sedimentation sludge is discharged to the sludge tank. The main indicators of the effluent of the secondary sedimentation tank are: COD is 145mg/L, BOD is 70mg/L, and SS is 40mg/L. the

4) Advanced oxidation: The esterification wastewater treated in step 3) is oxidized by UV/O ₃ to effectively remove refractory organic matter. The main indicators of wastewater oxidized by UV/ _O3 are: COD is 83mg/L, BOD is 55mg/L, and SS is 30mg/L.

5) The esterification wastewater treated in step 4) is filtered through quartz sand, activated carbon and reverse osmosis, and the purified water obtained is introduced into the production water system, and the concentrated water is led to step 1) for circular purification. The main indicators of water purification after the above steps are: COD is 45mg/L, BOD is 10mg/L, SS is 15mg/L, which meets the industrial reuse water standard. the

Example 2

Utilize the concrete steps of the esterification waste water comprehensive treatment and reuse technology involved in the present invention to purify waste water:

1) Pretreatment: The COD of the initial esterification wastewater is 70000mg/L. After adjusting the pH of the esterification wastewater through the adjustment tank, it enters the coagulation sedimentation tank. The flocculant is added through the dosing pipe, and the ester substances in the wastewater are made And the suspended solids are fully flocculated and precipitated. The main indicators of the wastewater after flocculation and sedimentation are: COD is 39000mg/L. the

2) Biochemical treatment: pass the esterification wastewater treated in step 1) through two-stage ABR reactors to reduce the COD of the wastewater and improve the biodegradability. The COD of the wastewater after anaerobic deflection treatment is 1500mg/L, and then passes through the biological contact oxidation tank to further reduce the COD of the wastewater. The COD of wastewater after biological contact oxidation treatment is 240mg/L. the

3) Sedimentation: The esterification wastewater treated in step 2) is passed through the secondary sedimentation tank to remove suspended particles in the wastewater, and the sedimentation sludge is discharged to the sludge tank. The main indicators of the effluent from the secondary sedimentation tank are: COD is 200mg/L. the

4) Advanced oxidation: The esterification wastewater treated in step 3) is oxidized by UV/O ₃ to effectively remove refractory organic matter. The main indicators of wastewater after UV/ _O3 oxidation are: COD is 80mg/L.

5) The esterification wastewater treated in step 4) is filtered through quartz sand, activated carbon and reverse osmosis, and the purified water obtained is introduced into the production water system, and the concentrated water is led to step 1) for circular purification. The main indicators of water purification after the above steps are: COD is 40mg/L, which meets the industrial reuse water standard. the

Claims (7)

1. an integrated treatment and reuse technology of esterification wastewater, characterized in that: the method comprises the steps: 1) Pretreatment: The esterification wastewater first passes through the adjustment tank to adjust the pH, and then enters the coagulation sedimentation tank, and uses the flocculant to remove the ester substances and micro suspended solids in the esterification wastewater. the 2) Biochemical treatment: The esterification wastewater treated in step 1) passes through a two-stage anaerobic baffle reactor (ABR) and a biological contact oxidation tank in sequence, so that the COD of the wastewater is greatly reduced and the biodegradability is improved. the 3) Sedimentation: The esterification wastewater treated in step 3) is passed through the secondary sedimentation tank to remove suspended particles in the wastewater, and the sedimentation sludge is discharged to the sludge tank. the 4) Advanced oxidation: The esterification wastewater treated in step 3) passes through the UV/O ₃ oxidation stage to remove refractory organic matter. 5) Membrane treatment: The esterification wastewater treated in step 4) is passed through multi-media filtration, activated carbon filtration and reverse osmosis to obtain reusable clean water, and the obtained clean water is introduced into the industrial water system, and the concentrated water is directed to step 2 ) cycle processing. the in, The step 1) pH is controlled between 6 and 9; The step 2) temperature is controlled between 25 ~ 35 ℃; The operating pressure of the step 5) reverse osmosis is 0.6-1.4 MPa. the 2. The integrated treatment and reuse technology of esterification wastewater according to claim 1, characterized in that the flocculant used in step 1) can effectively reduce COD in raw water. the 3. The integrated treatment and reuse technology of esterification wastewater according to claim 1, characterized in that: the anaerobic treatment in step 2) adopts two-stage ABR reactors, with high treatment efficiency and low sludge production. the 4. The integrated treatment and reuse technology of esterification wastewater according to claim 1, characterized in that: the biological contact oxidation tank used in step 2) has a high volume load and a low sludge production rate. the 5. The integrated treatment and reuse technology of esterification wastewater as claimed in claims 2 and 3, characterized in that: the sludge structure and biological phase of the anaerobic section and the aerobic section are optimized. the 6. The integrated treatment and reuse technology of esterification wastewater as claimed in claim 1, characterized in that: in step 4), an advanced oxidation technology combining UV and O ₃ is used. 7. The integrated treatment and reuse technology of esterification wastewater according to claim 1, characterized in that: in step 5), the reverse osmosis concentrated water is returned to the first-stage ABR. the