Quality-divided treatment and efficient purification system and purification process for printing and dyeing wastewater

Abstract

The invention discloses a quality-divided treatment and efficient purification system and a purification process for printing and dyeing wastewater, and relates to the field of printing and dyeing wastewater purification, and the key point of the technical scheme is that the process takes biological treatment as a core and organically combines physicochemical and biochemical treatment. The physicochemical methods mainly comprise grating filtration, precipitation, ultrafiltration (UF) + reverse osmosis (RO) double-membrane method, MVR and the like, and are mainly used for removing suspended solids and part of COD, separating, recycling resources and the like; the biochemical method mainly comprises a hydrolytic acidification method, a CAST process technology, an anaerobic method, an aerobic method and the like, and is mainly used for removing COD (Chemical Oxygen Demand), BOD (Biochemical Oxygen Demand), chromaticity and the like in the wastewater; an advanced treatment process, namely an A-A-O advanced nitrogen and phosphorus removal and near-zero discharge system, can be selected, so that the discharge capacity of the printing and dyeing wastewater system is further reduced, and resource recycling is realized.

Description

Technical Field

[0001] The invention relates to the field of printing and dyeing wastewater purification, and more specifically, to a quality-based treatment and high-efficiency purification system and a purification process for printing and dyeing wastewater. Background Art

[0002] Printing and dyeing wastewater contains suspended fiber particles, dyes, auxiliaries, slurries, finishing agents, etc., so the chromaticity is large, the organic content is high, and the wastewater contains a large amount of alkali and a high pH value. The main sources of pollutants in printing and dyeing wastewater are as follows: BOD comes from organic matter, such as dyes, slurries, surfactants, etc.; COD comes from dyes, reducing bleaching agents, aldehydes, reducing water purifiers, starch finishing agents, etc.; heavy metal poisons come from copper, lead, zinc, chromium, mercury, cyanide ions, etc.; chromaticity comes from the color of dyes and pigments in wastewater.

[0003] The raw materials, chemical reagents and technologies used in the printing and dyeing industry are quite different, but the basic processes are very similar. The typical printing and dyeing process has eight steps: desizing, refining, bleaching, mercerizing, dyeing, finishing, drying and finished products. The main sources of pollution include: the acid and alkali used in refining and dyeing will cause the pH value of the wastewater to be extreme; since the refining and dyeing processes are carried out at high temperatures, high-temperature wastewater is produced; the high suspended solids in the wastewater mainly come from the hair, fiber and impurities produced by the desizing and refining processes; the starch, glue and wax produced in the desizing increase the BOD value in the wastewater, and the commonly used acidifiers such as acetic acid will also increase the BOD value; the COD in the wastewater mainly comes from chemical slurries such as polyvinyl alcohol (PVA), various dyes and pigments.

[0004] The two major pollution sources of printing and dyeing wastewater are desizing and dyeing (printing) processes, which account for a very high proportion of the wastewater generated in the entire printing and dyeing process. The main pollutants in desizing wastewater are starch, PVA and some auxiliaries. Dyeing (printing) wastewater has the characteristics of high chroma and high concentration and is difficult to degrade. Therefore, reducing the organic pollutant load of these two wastewaters plays a key role in improving the water quality of terminal wastewater.

[0005] Therefore, new solutions need to be proposed to solve this problem. Summary of the invention

[0006] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a system and process for the quality-based treatment and efficient purification of printing and dyeing wastewater, so as to quantify, recycle and render harmless the wastewater.

[0007] The above technical purpose of the present invention is achieved through the following technical solutions: a system for quality-based treatment and efficient purification of printing and dyeing wastewater, including various quality-based water treatment systems, a main process treatment system and pipelines, wherein the various quality-based water treatment systems include a PVA desizing wastewater treatment structure, a starch desizing wastewater treatment structure, a scouring wastewater treatment structure, a bleaching and mercerizing wastewater treatment structure, a printing and dyeing wastewater treatment structure, and an alkali reduction wastewater treatment structure; the main process treatment system includes a fine grid, a primary sedimentation tank, a hydrolysis acidification system, and a CAST process system; the fine grid is arranged at the inlet of the primary sedimentation tank; the primary sedimentation tank uses pipelines in sequence including a hydrolysis acidification system and a CAST process system.

[0008] Furthermore, the quality-differentiated water treatment system includes a coarse grid, a chemical sedimentation tank, a water collection tank 1, a boiler desulfurization and dust removal system, a water collection tank 2, a double membrane system, and an alkali reduction wastewater treatment system, and the double membrane system includes a curtain UF system and an RO system; The PVA desizing wastewater treatment structure includes a coarse screen and a chemical sedimentation tank in order of wastewater flow, and the chemical sedimentation tank is connected to the inlet of the primary sedimentation tank; The starch desizing wastewater treatment structure comprises a coarse screen, and the coarse screen is connected to the inlet of the primary sedimentation tank; The scouring wastewater treatment structure includes a coarse screen, a water collection tank, and a boiler desulfurization and dust removal system in order of wastewater flow, and the boiler desulfurization and dust removal system is connected to the inlet of the primary sedimentation tank; The bleaching mercerizing wastewater treatment structure includes a second water collection tank and a curtain UF system in order of wastewater flow, the sewage discharge port of the curtain UF system is connected to the inlet of the primary sedimentation tank, and the purified water discharge port of the curtain UF system is connected to the inlet of the RO system; The printing and dyeing wastewater treatment structure comprises a coarse grid, and the coarse grid is connected to the inlet of the primary sedimentation tank; The alkali reduction wastewater treatment structure comprises an alkali reduction wastewater treatment system, and the alkali reduction wastewater treatment system is connected to the inlet of the primary sedimentation tank.

[0009] Furthermore, the chemical precipitation tank recovers PVA in the PVA desizing wastewater by a coagulation method, and the chemical precipitation tank adds sodium sulfate and borax by a dosing device.

[0010] Furthermore, the alkali reduction wastewater treatment system recycles sodium terephthalate using a physical and chemical method.

[0011] Furthermore, the coarse grid and the fine grid each include a plurality of grid bars, and the spacing between the grid bars in the coarse grid is greater than the spacing between the grid bars in the fine grid.

[0012] Furthermore, the primary sedimentation tank is provided with a FeSO4 dosing device.

[0013] Furthermore, the main process treatment system also includes an AAO denitrification and phosphorus removal system, which includes an anaerobic tank, an anoxic tank, and an aerobic tank. The anaerobic tank is fed with the effluent of the CAST process system and the phosphorus-containing return sludge discharged from the secondary sedimentation tank, and the feed passes through the anaerobic tank, the anoxic tank, and the aerobic tank in sequence.

[0014] Furthermore, the main process treatment system also includes a near-zero emission system, which includes a double-membrane system and an MVR evaporator in sequence according to the flow direction of sewage.

[0015] A quality-based treatment and efficient purification process for printing and dyeing wastewater, comprising the following steps: S1, various quality-based water treatment processes, PVA desizing wastewater passes through the coarse screen and enters the chemical sedimentation tank for PVA recovery and then enters the primary sedimentation tank; Starch desizing wastewater, dyeing wastewater, and printing wastewater pass through the coarse screen and enter the primary sedimentation tank; The scouring wastewater passes through the coarse screen and enters the water collection tank 1, and then enters the primary sedimentation tank after being treated by the boiler desulfurization and dust removal system; Bleaching wastewater and mercerizing wastewater enter the second water collection tank. The muddy water produced after the treatment of the curtain UF system enters the primary sedimentation tank. The treated water produced after the treatment of the curtain UF system enters the RO system. The fresh water produced by the RO system is reused in the workshop with high water quality requirements, and the concentrated alkaline water produced by the RO system is reused in the scouring workshop. The sorted wastewater directly enters the primary sedimentation tank; Alkali reduction wastewater enters the primary sedimentation tank after being treated by physicochemical methods; S2, adding FeSO4 into the primary sedimentation tank to form FeS and Fe(OH)3 flocs for co-precipitation; S3, the wastewater after sedimentation in the primary sedimentation tank enters the hydrolysis acidification system, and adopts the completely mixed anaerobic digestion (CMAD) method to hydrolyze the large molecular insoluble complex organic matter into small molecular soluble organic matter under the action of extracellular enzymes; S4, the wastewater treated by the hydrolysis acidification system enters the CAST process system. The CAST process system is equipped with more than two reactors to achieve continuous water inflow and continuous drainage. The muddy water generated by the CAST process system flows back to the hydrolysis acidification system.

[0016] Furthermore, the following optional steps are included: S5, the wastewater treated by the CAST process system can be processed through the AAO denitrification and phosphorus removal system to obtain clean water for reuse in the boiler workshop and printing workshop; S6, the clean water obtained by the AAO denitrification and phosphorus removal system can pass through the near-zero emission system, and the clean water passes through the curtain UF system, the RO system and the MVR evaporator in turn. The muddy water produced after the curtain UF system is treated is returned to the hydrolysis acidification system, and the fresh water produced by the RO system is reused in the workshop with high water quality requirements. The concentrated brine produced by the RO system enters the MVR evaporator, and the solid salt obtained by evaporation and crystallization of the MVR evaporator can be reused in the printing and dyeing workshop. In summary, the present invention has the following beneficial effects: The present invention adopts wastewater cleaning and pollution diversion, and treats wastewater with different pollution levels in various process flows of the dyeing factory by quality, recycles solutions, and treats high-concentration wastewater and low-concentration wastewater separately, reducing the cost of terminal wastewater treatment and improving the safety of the process system. With the biological treatment system (CAST process system) as the core, it has a good treatment effect on printing and dyeing wastewater, saves infrastructure investment, and has low maintenance costs. In particular, this process has certain denitrification and phosphorus removal functions. If the nitrogen and phosphorus content in the raw water is high, the AAO treatment process can be selected to perform deep denitrification and phosphorus removal on the effluent of the CAST process so that the wastewater meets the national emission standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a flow chart of a quality-based treatment and efficient purification process for printing and dyeing wastewater. DETAILED DESCRIPTION

[0018] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0019] Embodiment: A system for treating and purifying printing and dyeing wastewater by quality separation, including various quality separation water treatment systems, a main process treatment system and pipelines, wherein each quality separation water treatment system includes a PVA desizing wastewater treatment structure, a starch desizing wastewater treatment structure, a scouring wastewater treatment structure, a bleaching mercerizing wastewater treatment structure, a printing and dyeing wastewater treatment structure, and an alkali reduction wastewater treatment structure, wherein the main process treatment system includes a fine grid, a primary sedimentation tank, a hydrolysis acidification system, and a CAST process system, wherein the fine grid is arranged at the inlet of the primary sedimentation tank, and the primary sedimentation tank uses pipelines for the hydrolysis acidification system and the CAST process system in sequence, wherein the quality separation water treatment system includes a coarse grid, a chemical precipitation tank, a water collection tank 1, a boiler desulfurization and dust removal system, a water collection tank 2, a double membrane system, and an alkali reduction wastewater treatment system, wherein the double membrane system includes a curtain UF system and an RO system; When starch and starch derivatives are used as sizing agent, the BOD5 of desizing wastewater is high and can be sent to the biological treatment system; when PVA is used as sizing agent, the COD5 of desizing wastewater is high. Cr High and BOD5 low, must be collected and recovered separately. This patent adopts the coagulation method, that is, the chemical precipitation method of adding sodium sulfate and borax is used to recover the PVA in the desizing wastewater.

[0020] The scouring wastewater is highly alkaline, BOD5, COD Cr , and chroma are high. In order to reduce the pH value of the scouring wastewater, the scouring wastewater is collected through a collection well and used for desulfurization and dust removal of boiler smoke. This can not only improve the desulfurization efficiency and reduce the total sulfur dioxide emissions of the factory, but also neutralize part of the alkali solution and reduce the amount of acid used.

[0021] The bleaching wastewater has a lighter color, BOD5 and COD Cr The content is not very high, and a large part of it is cleaning water, which contains few impurities and is below the discharge standard. The bleaching wastewater directly enters the reuse system.

[0022] Mercerizing wastewater has low chroma, high alkalinity, and not too high BOD5 and COD Cr This wastewater contains a large amount of alkali, which can be recycled. This patent mixes mercerizing wastewater with bleaching wastewater and enters a double membrane system for water reuse and concentrated alkali reuse (directly reused in the scouring process).

[0023] Dyeing wastewater is a kind of dye used in dyeing, and there are many chemical raw materials and additives used. This wastewater is highly variable, complex, colored, and has COD Cr High, poor biodegradability, must enter a biological treatment system including hydrolysis and acidification.

[0024] Printing wastewater is similar to dyeing wastewater, containing a variety of dyes, auxiliaries, chemical raw materials, detergents and printing pastes. The water quality is the most complex, with high chromaticity and large changes. COD Cr The BOD5 is also high and must enter the biological treatment system.

[0025] Finishing wastewater contains a variety of additives, resins, chemicals and detergents. The wastewater composition is complex and must be treated in a biological system.

[0026] Alkali reduction wastewater mainly contains polyester hydrolyzate sodium terephthalate, ethylene glycol, etc., accompanied by mixed wastewater of spinning oil and other stains. The terephthalic acid content is as high as 75%, the pH value is high (generally > 12), and the organic matter concentration is high. COD Cr It can reach 90 g / L, containing high molecular weight organic matter and some dyes, and is a high-concentration organic wastewater that is difficult to degrade. Sodium terephthalate is a hydrocarbon organic salt with a benzene ring structure that is difficult to purify. The existing technology is a physical and chemical treatment method, and the COD removal rate can reach more than 75%. The remaining ethylene glycol in the wastewater is an alcohol organic matter that is more easily biodegradable and can enter the biological treatment system.

[0027] The present invention adopts wastewater cleaning and pollution diversion, and treats wastewater with different pollution degrees in various process flows of the dyeing factory according to their qualities, recycles the solution, and separately treats high-concentration waste liquid and low-concentration waste liquid, thereby reducing the terminal wastewater treatment cost and improving the safety of the process system.

[0028] The PVA in the PVA desizing wastewater is recovered by the coagulation method, and the PVA is recovered by the chemical precipitation method of adding sodium sulfate and borax, so that the PVA is recycled and utilized, and the treatment load of the PVA desizing wastewater on the subsequent processes is reduced.

[0029] The double membrane system (UF+RO) is used to recover the alkali in the bleaching wastewater and mercerizing wastewater, prepare concentrated alkaline water for reuse in the scouring process, and the fresh water is reused in the workshop to achieve zero emissions.

[0030] The scouring wastewater contains light alkali, which is collected in the collection pool and used for desulfurization and dust removal of boiler smoke. It can not only improve the desulfurization efficiency and reduce the total sulfur dioxide emissions of the factory, but also neutralize the alkali solution in the scouring wastewater and reduce the amount of acid used in the subsequent acid addition system.

[0031] The sodium terephthalate in the alkali reduction wastewater is recovered by physical and chemical methods, and the remaining ethylene glycol provides a carbon source for the biological treatment system, creating good water quality conditions for subsequent purification treatment.

[0032] With biological treatment system (CAST process system) as the core, it has good treatment effect on printing and dyeing wastewater, saves capital investment and low maintenance cost, especially this process has certain denitrification and phosphorus removal functions. If the nitrogen and phosphorus content in the raw water is high, the AAO treatment process can be selected to deeply denitrify and remove phosphorus from the effluent of the CAST process, so that the wastewater meets the national discharge standards.

[0033] The water in the terminal clear water tank meets the requirements of the national sewage discharge standards. The water quality sewage is recycled and can be used for spraying the water film dust collector of the boiler, flushing the slag of the boiler, and can also be used for flushing the guide belt of the printing machine, washing the pulp mixing barrel and printing plate, etc. Long-term use will not damage the equipment and can save a lot of process water.

[0034] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A system for quality-based treatment and efficient purification of printing and dyeing wastewater, characterized by: It includes various quality-based water treatment systems, a main process treatment system and pipelines. The various quality-based water treatment systems include PVA desizing wastewater treatment structure, starch desizing wastewater treatment structure, scouring wastewater treatment structure, bleaching and mercerizing wastewater treatment structure, printing and dyeing wastewater treatment structure, and alkali reduction wastewater treatment structure. The main process treatment system includes a fine screen, a primary sedimentation tank, a hydrolysis acidification system, and a CAST process system. The fine screen is arranged at the inlet of the primary sedimentation tank. The primary sedimentation tank uses pipelines in sequence including a hydrolysis acidification system and a CAST process system.

2. The system for quality-based treatment and efficient purification of printing and dyeing wastewater according to claim 1, characterized in that: The water treatment system includes a coarse grid, a chemical sedimentation tank, a water collection tank 1, a boiler desulfurization and dust removal system, a water collection tank 2, a double membrane system, and an alkali reduction wastewater treatment system. The double membrane system includes a curtain UF system and an RO system. The PVA desizing wastewater treatment structure includes a coarse screen and a chemical sedimentation tank in order of wastewater flow, and the chemical sedimentation tank is connected to the inlet of the primary sedimentation tank; The starch desizing wastewater treatment structure comprises a coarse screen, and the coarse screen is connected to the inlet of the primary sedimentation tank; The scouring wastewater treatment structure includes a coarse screen, a water collection tank, and a boiler desulfurization and dust removal system in order of wastewater flow, and the boiler desulfurization and dust removal system is connected to the inlet of the primary sedimentation tank; The bleaching mercerizing wastewater treatment structure includes a second water collection tank and a curtain UF system in order of wastewater flow, the sewage discharge port of the curtain UF system is connected to the inlet of the primary sedimentation tank, and the purified water discharge port of the curtain UF system is connected to the inlet of the RO system; The printing and dyeing wastewater treatment structure comprises a coarse grid, and the coarse grid is connected to the inlet of the primary sedimentation tank; The alkali reduction wastewater treatment structure comprises an alkali reduction wastewater treatment system, and the alkali reduction wastewater treatment system is connected to the inlet of the primary sedimentation tank.

3. The system for quality-based treatment and efficient purification of printing and dyeing wastewater according to claim 2 is characterized by: The chemical precipitation tank recovers PVA in the PVA desizing wastewater by a coagulation method, and the chemical precipitation tank adds sodium sulfate and borax by a dosing device.

4. The system for quality-based treatment and efficient purification of printing and dyeing wastewater according to claim 2 is characterized by: The alkali reduction wastewater treatment system adopts a physical and chemical method to recycle sodium terephthalate.

5. The system for quality-based treatment and efficient purification of printing and dyeing wastewater according to claim 2 is characterized by: The coarse grid and the fine grid both include a plurality of grid bars, and the spacing between the grid bars in the coarse grid is greater than the spacing between the grid bars in the fine grid.

6. The system for quality-based treatment and efficient purification of printing and dyeing wastewater according to claim 1, characterized in that: The primary sedimentation tank is provided with a FeSO4 dosing device.

7. The system for quality-based treatment and efficient purification of printing and dyeing wastewater according to claim 1 is characterized by: The main process treatment system also includes an AAO denitrification and phosphorus removal system, which includes an anaerobic tank, an anoxic tank, and an aerobic tank. The anaerobic tank is fed with the effluent of the CAST process system and the phosphorus-containing return sludge discharged from the secondary sedimentation tank, and the feed passes through the anaerobic tank, the anoxic tank, and the aerobic tank in sequence.

8. The system for quality-based treatment and efficient purification of printing and dyeing wastewater according to claim 2 is characterized by: The main process treatment system also includes a near-zero emission system, which includes a double-membrane system and an MVR evaporator in sequence according to the flow direction of sewage.

9. The purification process of the printing and dyeing wastewater separation treatment and high-efficiency purification system according to claims 1-8, characterized in that: The steps include: S1, various quality-based water treatment processes, PVA desizing wastewater passes through the coarse screen and enters the chemical sedimentation tank for PVA recovery and then enters the primary sedimentation tank; Starch desizing wastewater, dyeing wastewater, and printing wastewater pass through the coarse screen and enter the primary sedimentation tank; The scouring wastewater passes through the coarse screen and enters the water collection tank 1, and then enters the primary sedimentation tank after being treated by the boiler desulfurization and dust removal system; Bleaching wastewater and mercerizing wastewater enter the second water collection tank. The muddy water produced after the treatment of the curtain UF system enters the primary sedimentation tank. The treated water produced after the treatment of the curtain UF system enters the RO system. The fresh water produced by the RO system is reused in the workshop with high water quality requirements, and the concentrated alkaline water produced by the RO system is reused in the scouring workshop. The sorted wastewater directly enters the primary sedimentation tank; Alkali reduction wastewater enters the primary sedimentation tank after being treated by physicochemical methods; S2, adding FeSO4 into the primary sedimentation tank to form FeS and Fe(OH)3 flocs for co-precipitation; S3, the wastewater after sedimentation in the primary sedimentation tank enters the hydrolysis acidification system, and adopts the completely mixed anaerobic digestion (CMAD) method to hydrolyze the large molecular insoluble complex organic matter into small molecular soluble organic matter under the action of extracellular enzymes; S4, the wastewater treated by the hydrolysis acidification system enters the CAST process system. The CAST process system is equipped with more than two reactors to achieve continuous water inflow and continuous drainage. The muddy water generated by the CAST process system flows back to the hydrolysis acidification system.

10. The process for quality-based treatment and efficient purification of printing and dyeing wastewater according to claim 9, characterized in that: The following optional steps are also included: S5, the wastewater treated by the CAST process system can be processed through the AAO denitrification and phosphorus removal system to obtain clean water for reuse in the boiler workshop and printing workshop; S6, the clean water obtained by the AAO denitrification and phosphorus removal system can pass through the near-zero emission system, and the clean water passes through the curtain UF system, RO system and MVR evaporator in turn. The muddy water produced after treatment by the curtain UF system is returned to the hydrolysis acidification system, and the fresh water produced by the RO system is reused in the workshop with high water quality requirements. The concentrated brine produced by the RO system enters the MVR evaporator, and the solid salt obtained by evaporation and crystallization through the MVR evaporator can be reused in the printing and dyeing workshop.

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