1, printing and dyeing wastewater treatment technology
Printing and dyeing wastewater treatment method can be divided into physical method, chemical method and biological method of three categories. Physical methods mainly include grating and screening, conditioning, precipitation, air flotation, filtration, membrane technology, etc. Chemical methods include neutralization, coagulation, electrolysis, oxidation, adsorption, disinfection, etc. Biological methods include anaerobic biological methods, aerobic biological methods, and partially aerobic biological methods.
2, printing and dyeing wastewater treatment unit selection series
(1) regulation: water quality and quantity of wastewater changes in large, regulating pool should be considered longer residence time. In general the subsequent treatment unit for hydrolysis acidification or anaerobic treatment, regulation should not be used in aeration mixing.
(2) coagulation: when the wastewater contains more hydrophobic dyes, the coagulation process is placed in front of the biochemical to remove insoluble dyes and reduce the load of subsequent biological treatment. Coagulation chemicals can be selected according to the nature of the dye alkaline aluminum chloride (PAC), ferrous sulfate (FeSO4), etc., coagulation reaction using mechanical mixing is easy to adjust the hydraulic conditions to ensure that the reaction is sufficient to ensure that the reaction time should be between 25~30min. Considering the decolorization effect, the reaction time should be extended appropriately.
(3) neutralization: raw water pH is high, usually with H2S04 or HCl neutralization, in order to save the dosage of chemicals, can be adjusted later. If flue gas neutralization is used, desulfurization and ash removal should be considered.
(4) precipitation (air flotation): separation of physical and chemical dosing reaction due to a large amount of sludge, priority should be given to precipitation [inclined tube precipitation easy to clog should not be used), the usual spokes of the sedimentation tank for large amounts of water, vertical flow sedimentation tank for small amounts of water, when there is a plot of land can be utilized, advection sedimentation tank with suction mud can be used. When the dosage is large, the amount of mud is also large, and the spoke flow tank may cause heterogeneous heavy flow, and the novel peripheral inlet and outlet sedimentation tank can overcome this drawback. If the surfactant content in the wastewater is high, should choose the air flotation method, air flotation method in the pressure dissolved air flotation technology is mature, can be considered for selection.
(5) filtration: when the water requires clarification or reuse, sand filter or coal sand two-layer filtration should be used.
(6) Electrolysis: titanium-plated ruthenium inert electrode electrolysis to deal with acid dyes printing and dyeing wastewater decolorization effect is good, the removal of COD, sulfur dyes, reducing dyes, acid dyes, reactive dyes and so on have a high removal rate. Metal anode electrolysis method is less used due to the amount of mud.
(7) anaerobic hydrolysis: printing and dyeing wastewater organic content of COD is high, and B / C low, should consider hydrolysis acidification, and increase the filler hanging film, the bottom of the pool should be set up hydraulic mixer, to ensure that the suspended activated sludge in water with a wide range of organic contact. When the pool is large, a series system should be set up to avoid short circuits. Printing and dyeing wastewater less pure anaerobic technology, only when desizing wastewater and other high-concentration wastewater alone can be considered pure anaerobic treatment.
(8) aerobic biodegradation: large water volume, high concentration of printing and dyeing wastewater is prioritized to use activated sludge method, such as oxidation ditch, intermittent activated sludge (SBR), cyclic activated sludge method (CSTR) and so on. For small water volume, low concentration of wastewater can be considered biological contact oxidation method, but the filler should ensure the density and volume rate, and multi-stage series method is appropriate. Aeration methods such as blast aeration, should be selected with diaphragm type microporous aeration head or microporous aeration tube, etc., to ensure oxygenation efficiency.
(9) decolorization: the use of Cl2 need to ensure that the decolorization of oxidation time is not less than 1h, Cl2 decolorization and back to adjust the pH value of the function. Small-scale can choose ClO2, NaClO bleaching powder Ca (ClO) 2, ultraviolet light. Decolorization reaction pool can be used rotary partition or folding plate, should not use mechanical stirring or compressed air reaction.
(10) activated carbon adsorption: activated carbon has good adsorption performance for wastewater of water-soluble dyes such as cationic dyes, direct dyes, acid dyes, reactive dyes and so on (the effect of wastewater of insoluble dyes such as sulfur dyes and reducing dyes is poor). Bio-activated carbon (BAC) method is a derivative technology of activated carbon adsorption, which utilizes the exo-enzymes secreted by added microorganisms to penetrate into the microporous structure of the carbon, so that the organic matter adsorbed by the activated carbon is continuously decomposed into CO2, H2O or synthesized into new cells, and finally exudes out of the structure of the carbon to be removed.The BAC technology needs to ensure that there is a certain amount of dissolved oxygen in the influent water, and the microorganisms of the charcoal bed need to be cultivated by inoculation, so that the operation cycle of BAC is much higher than that of Activated carbon adsorption.
(11) diatomaceous earth adsorption: diatomaceous earth in the printing and dyeing wastewater both coagulation and adsorption, play a good decolorization effect. Usually, activated diatomaceous earth has different effects on decolorization of hydrophilic dyestuffs, and better effects on hydrophobic dyestuffs. When there are more surfactants and leveling agents in the wastewater, the effect will be significantly reduced.
(12) Oxidation: Ozone oxidation decolorizes hydrophilic dyestuffs such as direct dyestuffs, acid dyestuffs, basic dyestuffs, reactive dyestuffs, etc. with fast speed and good effect; for hydrophobic dyestuffs such as reducing dyestuffs, ice dyestuffs (naftal), oxidizing dyestuffs, sulfuric dyestuffs, dispersed dyestuffs, etc., the decoloration effect is poorer, and the ozone dosage is also large. Ozone decolorization will not produce "trichrome", which can guarantee the safety index of wastewater effluent.Fenton catalytic oxidation method has remarkable efficiency in removing residual COD, which can be used for smaller water volume.TiO2 catalytic oxidation method can remove residual chromaticity of effluent, which is a promising photocatalytic oxidation technology.
(13) membrane separation technology
① ultrafiltration: ultrafiltration membrane has precise fine holes, can retain large molecules and other particles in the water, and the operating pressure is low, the equipment is simple, and can be used for the recovery of dyes or the depth of treatment of water. The use of acetate fiber semi-permeable membrane ultrafiltration method to recover dyes has been achieved.
② nanofiltration: a new technology to retain pollutants with nanofiltration membrane, separation pressure is generally 0.5~2.0MPa, to deal with water-soluble (hydrophilic) dyes wastewater, can be recovered useful dyes. The use of nanofiltration membrane to recover direct black, activated brilliant red, acid orange Ⅱ and acid big red dye wastewater has achieved results.
Xiamen Visbon has been focusing on the research and development and application of technologies related to the metallurgy and reuse of printing and dyeing wastewater. 2008 April, based on the "Flow Split?SMFTM + HAP ROTM" dual membrane technology, Shenghong Group's 10,000-ton reuse system for printing and dyeing wastewater was the first to be completed and passed the acceptance of the relevant parts of the HuanTaihu Lake basin. Passed the relevant part of the acceptance. The completion of the project has changed the negative reputation of printing and dyeing enterprises as large water-consuming, large drainage and large polluters, and has played a vital role in demonstrating for other printing and dyeing enterprises around Taihu Lake and across the country, and formally declared that the printing and dyeing industry has entered into a new era of water conservation, emission reduction and resource reuse.
3, printing and dyeing wastewater treatment process
Summarize the treatment process of printing and dyeing wastewater, adequate conditioning time is necessary, physical and chemical, biochemical combination of treatment processes is currently used in a reasonable process. Physical method is mainly used to remove suspended solids, color and part of the COD, dosing coagulation reaction is an important part of the physical treatment, separation process of air flotation has outstanding advantages, biochemical method mainly uses anaerobic hydrolysis - aerobic oxidation tandem process, anaerobic hydrolysis process is to solve the problem of printing and dyeing wastewater with high COD value, poor biochemical and chromaticity problems of the effective antecedent technology, most of the difficult degradation of organic matter after anaerobic hydrolysis has been After anaerobic hydrolysis, most of the non-degradable organic matter has been decomposed into easily biodegradable small molecule organic matter, which can improve the biochemistry of wastewater and guarantee the efficiency of aerobic biological treatment of wastewater and effluent water quality. Aerobic oxidation process has a variety of ways, such as oxidation ditch, intermittent activated sludge method, biological contact oxidation, etc., the latter due to easy management, less sludge production, sludge is not easy to expand the phenomenon and low operating costs and so on, it is one of the commonly used aerobic biological treatment of small-scale printing and dyeing wastewater, but each printing and dyeing enterprises should make preferences according to their own wastewater characteristics when choosing the aerobic method, and take the integrated treatment technology as much as possible if necessary. Comprehensive treatment technology. Here are a few typical processes.
3.1 Hydrolytic acidification - biological contact oxidation - biochar printing and dyeing wastewater treatment process
The treatment of printing and dyeing wastewater is usually hydrolytic acidification - biological contact oxidation - biochar-based treatment process, see Figure 3-1. This treatment process has been used in recent years in the printing and dyeing wastewater treatment more, more mature process. The purpose of hydrolysis acidification is to degrade certain macromolecule substances and insoluble substances in printing and dyeing wastewater with poor biochemistry into small molecules and soluble substances through hydrolysis acidification, so as to improve the biochemistry and B/C. The value of hydrolysis acidification creates the conditions for subsequent aerobic biochemical treatment. At the same time, the residual sludge produced by aerobic biochemical treatment is returned to the anaerobic biochemical section through the sedimentation tank to carry out anaerobic digestion, which reduces the residual sludge discharge of the whole system, i.e., it achieves its own sludge equilibrium. Anaerobic hydrolysis and acidification tank and biological contact oxidation tank are installed filler, is a biofilm method of treatment; biochar pool installed activated carbon and oxygen supply, both suspended growth and attached growth method characteristics; pulse water intake is the role of anaerobic hydrolysis and acidification tank for mixing.
The hydraulic retention time of each part is generally as follows. Conditioning tank: 8~12h; anaerobic hydrolysis acidification tank: 8~10h; biological contact oxidation tank: 6~8h; biological charcoal tank: 1~2h; pulse generator interval: 5~10min.
The treatment process system, for CODcr ≤1000mg/L printing and dyeing wastewater, the treated effluent can meet the national emission standards, such as further deep treatment can be reused. The system can be reused if further deep treatment is provided.
3.2 Hypoxic hydrolysis - biological aerobic - coagulation combined process for printing and dyeing wastewater
Wastewater volume of 26,000m3/d. Wastewater quality is: BOD 200~250mg/L, COD 750~850mg/L, pH 9~11, chromaticity 850 times. Wastewater quality requirements are: BOD ≤ 30mg/L, COD ≤ 100mg/L, pH value of 6~9, chromaticity ≤ 100 times.
Combined process for treatment of festival dyeing wastewater process flow is shown in Figure 3-2.
The combined process flow is characterized by; ① anoxic hydrolysis tanks are used before the aerobic biological treatment structures to improve the biochemical properties of wastewater (such as woven blended fabrics or synthetic fabrics based on poor degradation of printing and dyeing wastewater); ② coagulation and oxidation tank is set up after the sedimentation tank as a tertiary treatment, which can obtain a better effluent quality. better effluent quality, to meet the treatment requirements; ③ wastewater SS is low, do not set up the primary sedimentation tank; ④ anoxic hydrolysis tank is set up in the filler.
The operation data of this combined process is shown in Table 3-6.
3.3 Electrochemical + air flotation + hydrolysis acidification + two-stage contact oxidation + two-stage biochar tower + filtration treatment of printing and dyeing wastewater
The process is a combination of biochemical, chemical and deep treatment, and the process flow is shown in Fig. 3-3.
The process is designed for 5000m3/d. The main water quality indicators are as follows The main water quality indicators are: COD 1000~1500mg/L, BOD 300~500mg/L, S2-≤35mg/L, color ≤1000 times. Requirements for the treated effluent: COD ≤ 100mg / L, BOD ≤ 30mg / L, chromaticity ≤ 50 times, S2- ≤ 0.5mg / L.
The main parameters are: acid neutralization to pH = 6~9; hydrolysis and acidification tank hydraulic retention time of 4.3h, the surface loading rate of 1m3 / (m2.h), with YDT elastic three-dimensional packing; -, two biological contact oxidation pool hydraulic retention time of 4.8h and 2.3h, gas-water ratio of 20:1 and 15:1, respectively, the intermediate sedimentation tank supernatant according to 1:1 back to the beginning of a biological contact oxidation tank; intermediate sedimentation tank surface loading rate of 4m3 / (m2.h), the second sedimentation tank surface loading rate of 3m3 / (m2.h); generalized filtration pool (clear pool located below the filter pool, effective volume 95m3), flow rate 10m/h, backwash intensity 15L, (m2.s), flushing time 5min; biochar pool for the two tandem, the front stage for the ascending-flow type, the back stage for the descending-flow type, filtration speed of 3m/h, gas-water ratio of 5:1, backwash intensity 9L / (m2.s), backwash time 5min, 3 ~ 5d rinse once; Total adjustment pool hydraulic retention time of 11.5h, the bottom of the set of 7 sludge discharge ditch, each ditch set 1 DN300mm perforated sludge pipe 'sludge discharged into the collection of sludge wells with a submersible pump pumped to the sludge thickening tank.