Advanced Treatment Process of Printing and Dyeing Wastewater
Printing and dyeing wastewater refers to the wastewater discharged from printing and dyeing factories that mainly process cotton, hemp, chemical fiber and their blended products. Its characteristics are: large amount of water, high concentration of organic pollutants, deep color, large changes in alkalinity and pH value, and drastic changes in water quality. Due to the different dyeing and finishing requirements of dyes, auxiliaries and fabrics, the pH value, CODCr, BOD5 concentration and color of dyeing and finishing wastewater are also different, but one of their common characteristics is that the M (BOD5)/M (CODcr) values are very low, generally around 0.2, and their biodegradability is poor. Another common feature is high chroma, some as high as 4,000 times. At present, the secondary treatment processes for printing and dyeing wastewater are mainly physical and chemical methods and biological methods.
Biological method is mainly aimed at organic pollutants, but the removal of chromaticity is not ideal, the removal rate is generally only 50% ~ 60%, so the removal of chromaticity is mainly physical and chemical method. At present, the effluent quality of the secondary treatment of printing and dyeing wastewater still cannot meet the requirements of the discharge and reuse standards. The main problem is that the CODCr remaining in the secondary treatment effluent is an organic matter that is difficult to biodegrade. However, it is difficult to completely remove chroma by common coagulation, adsorption, air flotation and other methods, so the object of advanced treatment is difficult to biodegrade organics and chroma. At present, the main technological processes for advanced treatment of printing and dyeing wastewater include physical method, advanced oxidation method, biological method, etc.
Advanced oxidation technology (AOPs) is a chemical oxidation technology that involves a large amount of OH in the reaction process. Taking Fenton catalytic oxidation process and ozone catalytic oxidation as examples, this paper introduces the application of AOPs in advanced treatment of printing and dyeing wastewater.
Fenton catalytic oxidation process
Fenton catalytic oxidant can effectively oxidize and remove refractory organics which cannot be removed by traditional wastewater treatment technology. LAT-F01 series heterogeneous Fenton catalyst produced by our company is a high-efficiency catalyst specially developed for improving traditional Fenton technology aiming at the problems of narrow applicable pH range, large sludge yield and the like. The catalyst takes porous composite materials as carriers. A variety of precious metals, rare earth metal oxides and transition metal oxides are used as catalytic components, and are refined through carrier doping, extrusion molding, mixed impregnation, high-temperature roasting and other processes, thus improving the generation of hydroxyl radicals, avoiding the generation of iron mud, reducing secondary pollution, and having the characteristics of high catalytic activity, long service life and the like.
Its essence is that organic matter and hydrogen peroxide diffuse from the solution body to the vicinity of the active site on the catalyst surface and adsorb, then hydrogen peroxide decomposes to produce OH under the catalysis of the catalyst components of the catalyst, thus initiating a free radical chain reaction to oxidize and degrade the organic matter, and finally the degradation products desorb from the catalyst surface and diffuse into the solution body.
Longantai environmental protection uses Fenton catalytic oxidation filler to treat the effluent from the secondary sedimentation tank of a printing and dyeing wastewater treatment plant in Jiangsu Province. The removal rates of COD, TP and chromaticity are 84%, 75% and 83% respectively. The effluent quality meets the requirements of DB 32 ／1072—2012 " Emission Limits of Major Water Pollutants from Urban Sewage Treatment Plants and Key Industrial Industries in Taihu Region"
Ozone catalytic oxidation process There are two ways for ozone to oxidize organic matter: direct reaction and indirect reaction. Direct reaction is that ozone directly reacts with pollutants through cycloaddition, electrophilic or nucleophilic action. Indirect reaction is that ozone generates OH with stronger oxidation under the action of alkali, light or other factors. LAT-CY01 ozone catalytic oxidation filler developed by Longantai aims at the problems of poor mass transfer effect, low ozone utilization rate, high investment and operation cost and the like of the traditional ozone oxidation technology, improves the generation of hydroxyl radicals and greatly enhances the ozone oxidation capability.
Ozone oxidation is mainly used for decolorization of printing and dyeing wastewater. Ozone can destroy the chromophoric groups of dyes and the cyclic compounds such as benzene, naphthalene, anthracene, etc. which constitute chromophoric groups, thus decolorizing the wastewater.
Longantai advanced treatment of low-concentration printing and dyeing wastewater after biochemical treatment in a printing and dyeing wastewater treatment plant by ozone catalytic oxidation method. The results show that the removal rates of COD and chromaticity are 79.65% and 95.83%, respectively, meeting the requirements of DB 32 ／1072—2012.
Shandong Longantai Environmental Protection Technology Co., Ltd. has accumulated rich experience in the pretreatment and advanced treatment of high-concentration and refractory organic wastewater for many years, and is a professional provider of overall environmental protection schemes in China. The company has accumulated numerous cooperation cases in the research and development and engineering of electrochemical catalysis, multiphase fluidized catalysis, ozone catalysis, membrane concentration and extraction technologies. Products include new micro-electrolysis catalytic fillers, heterogeneous catalytic oxidation fillers and high-efficiency ozone catalytic oxidation fillers, and provide complete sets of equipment such as electrolytic catalytic oxidation, ozone catalytic oxidation, organic waste gas recovery and treatment integration, sludge disposal, etc. The company has a full-stage service flow from product development, product production, process design, engineering construction, process debugging, after-sales tracking, etc., which provides a strong guarantee for the efficient implementation of the project and the reasonable application of the process.
