Azo dye and condensation dye production wastewater combined treatment method

Abstract

The invention relates to the field of wastewater treatment, in particular to a combined treatment method for azo dye and condensation dye production wastewater. The integrated process of enhanced Fenton oxidation, the IC anaerobic reactor, the anoxic tank, the aerobic tank (AO) and the membrane bioreactor (MBR) developed by the invention realizes efficient removal of organic matters, gives consideration to economical efficiency and stability, and breaks through the bottlenecks of high energy consumption and low efficiency of the traditional process.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wastewater treatment, in particular to a combined treatment method for azo dye and condensation dye production wastewater. BACKGROUND

[0002] Azo dye and condensation dye production wastewater is a typical high-concentration and refractory organic wastewater, which has the characteristics of high concentration of organic pollutants, deep color, poor biodegradability, and strong toxicity. This type of wastewater mainly contains acrylonitrile, xylene, styrene, acrylic acid, p-aminoazobenzene, and naphthalene sulfonate sodium, etc. The chemical stability is strong and it is not easy to be degraded by microorganisms. The COD is as high as 30000~100000 mg / L, the color is more than 5000 times, and it is accompanied by high salinity and some heavy metal ions.

[0003] At present, many printing and dyeing and dye enterprises use "advanced oxidation + biochemical treatment" process to treat production wastewater, but due to the presence of benzene ring, azo bond (-N=N-) and sulfonic acid group in dye molecules, the structure is stable and it is difficult to open ring and break bond, which leads to the inhibition of microorganisms in conventional aerobic system, and it is difficult to reduce the COD of effluent to the standard level. Specifically, the existing technology has the following problems: 1. The "advanced oxidation + biochemical treatment" process commonly used by printing and dyeing and dye enterprises at present has single structure, limited pollutant removal depth, and is difficult to deal with complex wastewater with high concentration, high color and poor biodegradability.

[0004] 2. The traditional Fenton process has poor oxidation effect on refractory organic matter such as azo bond and aromatic ring, needs acidic conditions, has large amount of reagents and sludge, and the catalyst is difficult to recover, which has high operation cost.

[0005] 3. The traditional biochemical system is easily inhibited by toxic and harmful components in high-concentration dye wastewater, the microbial activity decreases, the reaction efficiency is unstable, and sludge loss and poor settling are easily occurred.

[0006] 4. The existing process has low overall integration, the system is easy to be impacted, has weak resistance to high salt and high toxicity, and weak water quality fluctuation ability, the effluent is unstable, has high energy consumption and poor resource utilization efficiency.

[0007] The traditional process has low treatment efficiency, high energy consumption, poor stability and difficulty in reaching the standard, and a new combined treatment process that takes into account efficient degradation and economic operation needs to be developed. SUMMARY

[0008] The "enhanced Fenton oxidation + IC anaerobic reactor + anoxic tank-aerobic tank (AO) + membrane bioreactor (MBR)" integrated process developed by the present application realizes efficient removal of organic matter, takes into account economy and stability, breaks through the bottleneck of high energy consumption and low efficiency of traditional process, and the specific scheme is as follows: A method for treating wastewater from azo dyes and condensed dye production, comprising the following steps: Step one, high concentration wastewater enters Fenton oxidation tank, sulfuric acid is added to adjust pH, then ferrous sulfate and hydrogen peroxide are added for Fenton reaction; Step two, wastewater after Fenton reaction enters flocculation tank, and alkali, PAC and PAM are added; Step three, flocculated wastewater enters primary sedimentation tank, and mud and water are separated by gravity sedimentation, the supernatant flows into the conditioning tank, and the sludge is discharged into the sludge tank for centralized treatment; Step four, the effluent from the primary sedimentation tank and low concentration wastewater enter the conditioning tank, and the water quality and quantity are stabilized by hydraulic stirring and homogenization, the pH is adjusted to 6.5-7.5, and stable influent is provided for the subsequent biochemical reaction system, and a grid is arranged in the conditioning tank; Step five, then enter the coagulation sedimentation tank, add alkali, PAC and PAM, further remove residual suspended solids and part of soluble organic matter, and the effluent enters the water distribution tank; Step six, balance the flow through the water distribution tank to control the hydraulic load and residence time of the wastewater entering the anaerobic system; Step seven, wastewater enters two-stage IC anaerobic reactors in series, wastewater, granular sludge and reflux liquid are mixed in the mixing zone to preliminarily degrade organic matter; first, wastewater enters the first anaerobic zone, high concentration sludge bed converts most of the organic matter into biogas under intense disturbance, and biogas drives internal circulation of the mixed liquid through the riser; then, wastewater enters the second anaerobic zone, and the remaining organic matter is further degraded by low concentration sludge; Step eight, the effluent from the IC anaerobic reactor enters the anoxic tank, and under the action of facultative bacteria, the nitrate in the internal reflux nitrification liquid is used as an electron acceptor for denitrification reaction to remove total nitrogen and decompose part of the organic matter; Step nine, the effluent from the anoxic tank flows into the aerobic tank, oxygen is supplied by the aeration system to promote further oxidation and decomposition of organic matter and nitrification of ammonia nitrogen, and the system adopts intermittent aeration mode; Step ten, the effluent from the aerobic tank enters the MBR tank, and the hollow fiber membrane assembly is used for solid-liquid separation of the mixed liquid; Step eleven, the effluent from the MBR enters the final sedimentation tank for final sedimentation.

[0009] In step one, the pH is adjusted to 2.5-3.5, the mass ratio of hydrogen peroxide to COD is 1:1, the molar ratio of ferrous sulfate to hydrogen peroxide is 1:1, and the reaction time is 30-60 min.

[0010] The PAC dosage in the step two is 1.0-1.5 g / L, and the PAM dosage is 10-20 mg / L; the PAC dosage of the coagulation sedimentation tank reagent in the step five is 100-500 mg / L, and the PAM dosage is 1-10 mg / L; the PAC dosage of the final sedimentation tank reagent in the step eleven is 10-100 mg / L, and the PAM dosage is 0.5-5.0 mg / L.

[0011] The sludge concentration in the flocculated wastewater in the step three is controlled to be 2-5 g / L, and the sedimentation time is 30-60 min.

[0012] The residence time of the anoxic tank in the step eight is 2-4 h.

[0013] The dissolved oxygen in the aerobic tank in the step nine is controlled to be 2-3 mg / L, the residence time is 6-10 h, and the reflux ratio is 200%-300%.

[0014] The membrane pore size of the hollow fiber membrane assembly in the step ten is 0.1-0.3 μm, and the membrane flux is 10-20 L / (m 2 h).

[0015] The sludge in the preliminary sedimentation tank, the MBR tank and the final sedimentation tank in the steps three, ten and eleven enters the sludge tank, and solid-liquid separation is carried out through a plate-and-frame filter press.

[0016] The present application has the following advantages: 1. In view of the problem that the existing process has single structure and is difficult to deal with high-concentration and high-colority wastewater, the present application constructs a deep integration process of "enhanced Fenton oxidation + IC anaerobic reactor + AO + MBR", realizes the staged treatment from oxidative chain breaking, anaerobic degradation to membrane separation and purification, and improves the adaptability of the system to high-concentration organic matter and complex dyes; 2. In view of the problem that the traditional Fenton technology consumes a large amount of reagents, produces a large amount of sludge and has limited removal efficiency, the present application sets a cyclonic Fenton reactor at the front end, realizes pH adjustment, uniform mixing and efficient ·OH oxidation, improves the reagent utilization rate and pretreatment efficiency; 3. In view of the problem that the traditional biochemical system is inhibited by toxic and harmful components, has low microbial activity and unstable effluent, the present application designs a multi-stage biochemical system of IC anaerobic reactor + AO + MBR, improves the microbial tolerance and system stability, and realizes efficient removal of organic matter and nitrogen; 4. In view of the problem that the existing process has low integration degree and low treatment efficiency, the present application optimizes the coupling of each unit through homogeneous adjustment and a multi-stage reflux system, constructs an integrated reaction system with adjustable load, energy and material circulation, improves the impact resistance and stability of the system, realizes the standard discharge of high-salt and high-toxicity wastewater and energy resource utilization. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 A flow chart of a combined treatment method for azo dye and condensation dye production wastewater of the present application. DETAILED DESCRIPTION Example 1

[0018] The experimental water was azo and condensation dye high-concentration wastewater generated in the production process of a certain material technology Co., Ltd., with COD = 74620 mg / L, color about 5,000 times, pH = 7.2. A continuous flow pilot system was used for the experiment, with a daily treatment capacity of 0.04 m 3 / d. The wastewater entered the Fenton oxidation tank-flocculation sedimentation tank-coagulation sedimentation tank-IC anaerobic reactor-AO tank-MBR tank in turn. Each unit was connected by constant flow pump and pipeline.

[0019] A combined treatment method for azo dye and condensation dye production wastewater, comprising the following steps: Step one, high-concentration wastewater enters the Fenton oxidation tank, sulfuric acid is added to adjust the pH, and ferrous sulfate and hydrogen peroxide are added for Fenton reaction. The mixed effluent from the Fenton reactor enters the flocculation sedimentation tank.

[0020] Step two, the wastewater after Fenton oxidation enters the flocculation-coagulation tank, and alkali, PAC and PAM are added. The effluent from the flocculation-coagulation tank enters the primary sedimentation tank.

[0021] Step three, the flocculated wastewater enters the primary sedimentation tank, and mud and water are separated by gravity sedimentation. The supernatant flows into the adjustment tank, and the sedimented sludge is discharged into the sludge tank for centralized treatment.

[0022] Step four, the effluent from the primary sedimentation tank and low-concentration wastewater enter the adjustment tank, which stabilizes the water quality and quantity through hydraulic stirring and homogenization, and adjusts the pH. The adjustment tank is provided with a device for removing large particles of suspended solids and floating matter.

[0023] Step five, coagulation sedimentation tank, add alkali, PAC and PAM, further remove residual suspended solids and part of soluble organic matter, effluent into water distribution tank.

[0024] Step six, through the water distribution tank to balance the flow, control the hydraulic load and residence time of the wastewater entering the anaerobic system, prevent the impact load from affecting the efficiency of anaerobic reaction.

[0025] Step seven, the wastewater enters the two-stage IC anaerobic reactor in series, the wastewater, granular sludge and reflux liquid are mixed in the mixing zone to preliminarily degrade organic matter.

[0026] Step eight, the IC effluent enters the anoxic tank, under the action of facultative bacteria, uses nitrate in the internal reflux nitrification liquid as electron acceptor for denitrification reaction to remove total nitrogen and decompose part of organic matter.

[0027] Step nine, the anoxic effluent flows into the aerobic tank, oxygen is supplied by the aeration system to promote the further oxidation and decomposition of organic matter and the nitrification of ammonia nitrogen.

[0028] Step ten, the effluent from the aerobic tank enters the MBR tank, and the hollow fiber membrane assembly is used to separate the mixed liquid, effectively intercepting suspended solids and microorganisms, achieving mud-water separation and high-quality effluent.

[0029] Step eleven, the MBR effluent enters the final sedimentation tank for final settlement.

[0030] The results show that the process units run smoothly and well connected, the system as a whole has a significant removal effect on organic pollutants and color, and the effluent meets the discharge standard. The process structure is compact and energy-saving, and is suitable for efficient treatment and engineering popularization of high-concentration azo and condensed dye wastewater.

[0031]

[0032] [Control 1] (without Fenton oxidation) Remove the Fenton oxidation unit, only use the flocculation sedimentation tank-coagulation sedimentation tank-IC anaerobic reactor-AO tank-MBR tank combined process. The experimental results show that the overall COD removal rate of the system is only 45.43%, and the microorganisms in the biochemical section are inhibited by high organic load, and the final effluent COD is still as high as 40718 mg / L. Without Fenton oxidation pretreatment, the azo bond and aromatic ring in the wastewater are not destroyed, and the macromolecular organic matter is difficult to biodegrade, resulting in a significant decrease in the treatment efficiency of the subsequent system.

[0033]

[0034] [Control 2] (without IC anaerobic reactor) Remove the IC anaerobic reactor, only use the Fenton oxidation tank-flocculation sedimentation tank-coagulation sedimentation tank-AO tank-MBR tank combined process. The experimental results show that although the front-end oxidation and physical treatment units can effectively reduce part of the COD, the lack of anaerobic deep degradation stage, the overall organic matter removal rate of the system decreases significantly, and the final effluent COD is still as high as 12397 mg / L.

[0035] The IC anaerobic reactor plays a core role in linking and energy conversion in the process of the application, which realizes the efficient degradation of organic matter under high load conditions through the high-concentration granular sludge bed and the biogas internal circulation system. The IC anaerobic reactor can convert complex aromatic and condensed organic matter into small-molecule volatile fatty acids (VFA), thereby significantly improving the biodegradability of the wastewater and providing high-quality carbon source for the subsequent AO reaction system.

[0036] In the control 2, the IC anaerobic reactor is not set, and the AO system directly receives the wastewater containing high molecular and intermediate products, which causes the nitrifying bacteria to be inhibited by the toxicity, the carbon source for denitrification reaction to be insufficient, and the carbon and nitrogen removal efficiency of the system to be significantly reduced.

[0037] Therefore, the IC anaerobic reactor not only undertakes the main degradation task of high-concentration organic matter, but also maintains the carbon source balance and energy recovery of the system by producing methane and VFA, and is a key unit for realizing stable and efficient treatment of high-concentration azo and condensation dye wastewater.

[0038] Example 2

[0039] In this embodiment, the dye production wastewater of a material technology company in Quzhou is taken as the treatment object, and the daily treatment scale of the high-concentration wastewater is 9 t / d, including 6 t / d of azo dye wastewater and 3 t / d of condensation dye wastewater. The wastewater is mainly derived from the synthesis and washing process of azo dyes and condensation dyes, and has characteristics such as high organic load, high colority and strong inhibition. After mixing and homogenization, the COD is 75032 mg / L, and the colority is greater than 5,000 times.

[0040] A combined treatment method for azo dye and condensation dye production wastewater, comprising the following steps: Step one, the high-concentration wastewater enters the Fenton oxidation tank, sulfuric acid is added to adjust the pH, and ferrous sulfate and hydrogen peroxide are added for Fenton reaction. The mixed water from the cyclone Fenton reactor enters the flocculation sedimentation tank.

[0041] Step two, the wastewater treated by Fenton oxidation enters the flocculation tank, and alkali, polyaluminum chloride (PAC) and polyacrylamide (PAM) are added, and the effluent from the flocculation tank enters the primary sedimentation tank.

[0042] Step three, the flocculated wastewater enters the primary sedimentation tank, and mud and water are separated by gravity sedimentation, the supernatant flows into the adjustment tank, and the sludge is discharged into the sludge tank for centralized treatment.

[0043] Step four, the effluent from the primary sedimentation tank and the low-concentration wastewater enter the adjustment tank, and the water quality and quantity are stabilized by hydraulic stirring and homogenization, and the pH is adjusted. A grid is provided in the adjustment tank for removing large particles of suspended solids and floating matter.

[0044] Step five, the coagulation sedimentation tank, alkali, PAC and PAM are added to further remove residual suspended solids and part of soluble organic matter, and the effluent enters the water distribution tank.

[0045] Step six, the water distribution tank balances the flow, controls the hydraulic load and residence time of the wastewater entering the anaerobic system, and prevents the impact load from affecting the efficiency of the anaerobic reaction.

[0046] Step seven, the wastewater enters the two-stage IC anaerobic reactor in series, and the wastewater is mixed with the granular sludge and the reflux liquid in the mixing area to preliminarily degrade the organic matter. First, the wastewater enters the first anaerobic zone, and the high-concentration sludge bed converts most of the organic matter into biogas under intense disturbance, and the biogas drives the internal circulation of the mixed liquid through the riser to realize the full contact of the sludge and the water. Then, the wastewater enters the second anaerobic zone, and the remaining organic matter is further degraded by the low-concentration sludge, the biogas production is reduced, and the disturbance is smaller, which is beneficial to the sludge settlement.

[0047] Step eight, the IC effluent enters the anoxic tank, and under the action of facultative bacteria, the nitrate in the internal reflux nitrification liquid is used as an electron acceptor to carry out denitrification reaction to remove total nitrogen and decompose part of the organic matter.

[0048] Step nine, the anoxic effluent flows into the aerobic tank, and oxygen is supplied through the aeration system to promote the further oxidation and decomposition of the organic matter and the nitrification conversion of ammonia nitrogen. The system adopts an intermittent aeration mode to strengthen the microbial community diversity and reaction stability.

[0049] Step ten, the effluent of the aerobic tank enters the MBR tank, and the hollow fiber membrane assembly is used to separate the mixed liquid to effectively intercept the suspended solids and microorganisms, realize the separation of sludge and water, and obtain high-quality effluent.

[0050] Step eleven, the MBR effluent enters the final settling tank for final settlement.

[0051] In step one, the Fenton oxidation tank adopts a cyclone Fenton reactor to improve the mass transfer effect. The reaction zone of the cyclone Fenton reactor is provided with a rotary cutter mixer, so that the H2O2 and FeSO4·7H2O solution is changed from a columnar flow into a sheet flow, improving the mass transfer effect and the efficiency of the use of reagents.

[0052] In steps seven, eight and nine, a multi-stage biochemical treatment unit is formed. The IC anaerobic reactor is operated in series through two-stage anaerobic zones, and a biogas riser and a gas-liquid separator are additionally arranged inside to form an internal circulation system; after the separation of the sludge and the water, the supernatant is discharged, and the granular sludge is returned to the reaction zone. The AO tank is composed of an aeration tank, a secondary settling tank, a reflux system, a residual sludge discharge system and an oxygen supply system.

[0053] In step ten, the MBR membrane bioreactor is composed of an MBR membrane assembly system, a reflux system, a backwashing system, a cleaning system and an aeration system. The system is provided with a backwashing and chemical cleaning module to prevent membrane pollution.

[0054] In steps three, ten and eleven, the sludge in the primary settling tank, the MBR tank and the final settling tank enters the sludge tank, and is subjected to solid-liquid separation through a plate-and-frame filter press, so that the moisture content of the dewatered sludge is reduced to 76%, realizing sludge reduction and facilitating subsequent disposal.

[0055] The system is designed with multiple reflux mechanisms to realize efficient treatment of azo dyes and condensation dyes production wastewater. The internal circulation occurs in the lower reaction chamber of the IC anaerobic reactor, the fermentation liquor is separated from biogas in the gas-liquid separation chamber through the riser, the biogas is refluxed to the lower reaction chamber, and the continuous circulation of the fermentation liquor is formed. In the AO system, the nitrification liquid and sludge in the aerobic tank are refluxed to the anoxic tank through internal circulation, and 52% of the alkalinity consumed in the nitrification reaction is compensated. The sludge in the MBR tank is refluxed to the anoxic tank and the aerobic tank through external circulation, the sludge concentration and activity in the system are maintained, the denitrification and organic matter degradation processes are strengthened, and the overall nitrogen and organic matter removal efficiency is improved.

[0056]

[0057] The above are only preferred embodiments of the present application, and are not used to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art will appreciate that modifications, equivalent replacements and improvements can be made to the technical solutions recorded in the foregoing embodiments, or some technical features can be replaced equivalently. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for combined treatment of wastewater from the production of azo dyes and condensation dyes, characterized in that, Includes the following steps: Step 1: High-concentration wastewater enters the Fenton oxidation tank, sulfuric acid is added to adjust the pH, and then ferrous sulfate and hydrogen peroxide are added to carry out the Fenton reaction. Step 2: The wastewater that has undergone the Fenton reaction enters the flocculation and coagulation tank, where alkali, polyaluminum chloride and polyacrylamide are added. Step 3: The flocculated wastewater enters the primary sedimentation tank, where gravity sedimentation separates the sludge from the water. The supernatant flows into the equalization tank, and the deposited sludge is discharged into the sludge tank for centralized treatment. Step 4: The effluent from the primary sedimentation tank and the low-concentration wastewater enter the equalization tank. Through hydraulic stirring and homogenization, the water quality and quantity are stabilized, and the pH is adjusted to 6.5~7.5 to provide stable influent for the subsequent biological reaction system. The equalization tank is equipped with a screen. Step 5: After that, the water enters the coagulation sedimentation tank, where alkali, polyaluminum chloride and polyacrylamide are added to further remove residual suspended solids and some soluble organic matter. The effluent then enters the distribution tank. Step 6: Balance the flow rate through the water distribution tank to control the hydraulic load and residence time entering the anaerobic system; Step 7: Wastewater enters a two-stage IC anaerobic reactor in series. The wastewater, granular sludge, and return liquid are mixed in the mixing zone, where organic matter is initially degraded. First, the wastewater enters the first anaerobic zone, where the high-concentration sludge bed is violently disturbed, converting most of the organic matter into biogas. The biogas drives the internal circulation of the mixed liquid through the riser. Then, the wastewater enters the second anaerobic zone, where the remaining organic matter is further degraded by the low-concentration sludge. Step 8: The effluent from the IC anaerobic reactor enters the anoxic tank. Under the action of facultative anaerobic bacteria, the nitrate in the internal reflux nitrification liquid is used as an electron acceptor to carry out denitrification, removing total nitrogen and decomposing some organic matter. Step 9: The effluent from the anoxic tank flows into the aerobic tank, where oxygen is supplied through the aeration system to promote further oxidation and decomposition of organic matter and nitrification of ammonia nitrogen. The system adopts an intermittent aeration mode. Step 10: The effluent from the aerobic tank enters the MBR tank, where the hollow fiber membrane module is used to perform solid-liquid separation of the mixed liquor. Step 11: The MBR effluent enters the final sedimentation tank for final settling.

2. The method for combined treatment of wastewater from the production of azo dyes and condensation dyes as described in claim 1, characterized in that: In step one, the pH is adjusted to 2.5-3.5, the mass ratio of hydrogen peroxide to COD is 1:1, the molar ratio of ferrous sulfate to hydrogen peroxide is 1:1, and the reaction time is 30-60 min.

3. The method for combined treatment of wastewater from the production of azo dyes and condensation dyes as described in claim 1, characterized in that: In step two, the dosage of PAC is 1.0~1.5 g / L and the dosage of PAM is 10~20 mg / L; in step five, the dosage of PAC in the coagulation sedimentation tank is 100~500 mg / L and the dosage of PAM is 1~10 mg / L; in step eleven, the final sedimentation tank agent is used, which includes PAC and PAM, with the dosage of PAC being 10~100 mg / L and the dosage of PAM being 0.5~5.0 mg / L.

4. The method for combined treatment of wastewater from the production of azo dyes and condensation dyes as described in claim 1, characterized in that: In step three, the sludge concentration in the flocculated wastewater is controlled at 2-5 g / L, and the settling time is 30-60 min.

5. The method for combined treatment of wastewater from the production of azo dyes and condensation dyes as described in claim 1, characterized in that: The residence time in the anoxic pool in step eight is 2-4 hours.

6. The method for combined treatment of wastewater from the production of azo dyes and condensation dyes as described in claim 1, characterized in that: In step nine, the dissolved oxygen in the aerobic tank is controlled at 2-3 mg / L, the residence time is 6-10 h, and the reflux ratio is 200%-300%.

7. The method for combined treatment of wastewater from the production of azo dyes and condensation dyes as described in claim 1, characterized in that: In step ten, the hollow fiber membrane module has a membrane pore size of 0.1~0.3 μm and a membrane flux of 10~20 L / (m²). 2 ▪h).

8. The method for combined treatment of wastewater from the production of azo dyes and condensation dyes as described in claim 1, characterized in that: In steps three, ten, and eleven, the sludge from the primary sedimentation tank, MBR tank, and final sedimentation tank enters the sludge tank and undergoes solid-liquid separation using a plate and frame filter press.

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