Experimental Research And Engineering Design For Printing And Dyeing Wastewater Treatment In Industrial Park With Ozone+BAF Combined Process

Printing and dyeing industry is the main industrial water user in China, meanwhile, it isalso basic industry. Nowadays, economic construction is the center of China, so printing anddyeing industry plays an important role."Chinese environment statistics annual report2012"shows, CODcr emissions of textile industry ranks fourth in the39major industries of China,total wastewater emissions ranked third and annual wastewater emissions is about25tons. InOctober of2012, the Ministry of Environmental Protection issued a "Discharge Standard ofWater Pollutants from Dyeing and Finishing of Textile Industry"(GB4287-2012), thedischarge of waste water of dyeing and finishing industry should abide by following standard:CODcr concentration is200mg/L and the CODcr direct discharge quantity is less than orequal to80mg/L since January of2013. At present, high concentration, difficult degradationand high chroma are the main characteristics of printing and dyeing wastewater. Theconventional biochemical and physico-chemical treatment process only can reduce COD crconcentration to200mg/L, which can’t meet the current requirements of discharge standards.So advanced treatment process research of printing and dyeing wastewater should bestrengthened.The use of ozone oxidation and biological aerated filter combination technology(O3+BAF) is for treatment of hardly biodegradable waste water, namely at first ozoneoxidation technology is used as pre-treatment process for this kind of waste water in order tochange the molecular structure of organic matter and improve the biodegradability of wastewater, and then use the biological aerated filter process for further degradation.We take the outlet water from flotation tank as raw water in Shaoxing printing anddyeing industrial park with a600000m3/d waste water treatment plant (mainly includedyeing and printing waste water) and compare the treatment effect by testing ozonationprocess alone and O3+BAF combination process. Through pilot test on wastewater ozonationalone, we research the removal effect of the organic pollution by using ozone. The removal rate of CODcr is25%and removal amount of CODcr with the unit dosage of ozone is about0.48gCODcr/gO3. When the ozone dosage was50mg/L, the removal rate of CODcr is higher.The organics removal rate becomes slowly beyond this range, so it will be meaningless ifdosage of ozone is increased continuously at this moment. Significant effect on removingUV254and chrom shows ozone has obvious decomposition and destructive effect on benzene,carbon carbon double bond and other organic matter. Inlet and outlet B/C of ozone contacttank respectively are0.092,0.105, which means the improvement effect of ozone on gasfloating outlet water B/C of printing and dyeing waste water is not obvious. Analyze theremoval effect to CODcr, UV254, chroma, biodegradability and other indexes under differentdosage of ozone, we confirmed it has better removal rate on all water quality indexes whenthe ozone dosage is50mg/L. so the ozone dosage of this test is50mg/L. When the ozonedosage is50mg/L, we analyze removal rate of alone ozone oxidation treatment process tooutlet floating water pollutants CODcr and chroma in printing and dyeing waste water and getthe preliminary determination of45min ozone reaction time.Through the test of O3+BAF combined process, COD cr is reduced for a further step.After "Ozone-Volcano Rock Biological Aerated Filter " treatment process, average CODcrvalue is reduced from95.3mg/L to56.1mg/L, removal rate is40.8%. Ozone oxidation and thevolcano rock ceramsite biological aerated filter treatment process separately remove amountof CODcr are24mg/L and15.2mg/L.According to the test, we do design and analysis of ozone+aeration biological filterprocess. Through the analysis to the ozone generator with air, liquid oxygen and PSA oxygenfeed gas and comparison to VPSA and PSA oxygen generation ways, VPSA site oxygengeneration way is confirmed to be used for providing feed gas for ozone generation. Ozonecontact tank consists of two seats, each seat is divided into six corridors and then enter twobiological aerated filters. Application of microporous aeration dose ozone gas from ozonecontact tank bottom into the ozone contact tank so that reverse contact of ozone and water canimprove the mixing efficiency. The effect of volcano rock as biological aerated filter mediafor pollutant removal of printing and dyeing waste water is slightly better than that of active carbon as the media and the investment is lower, so the volcano rock as biological aeratedfilter media is confirmed. Analyze the direct operation cost, the result is as follows: first phaseproject operation cost of advanced treatment is0.338yuan/m3; if second phase is constructed,total direct operation cost of two phases is0.426yuan/m3. As the printing and dyeing wastewater with high processing difficulty, the advanced treatment process has bigger superioritycompared to other treatment process on operation cost.In a word, the ozone+biological aerated filter combination process for advancetreatment of printing and dyeing waste water are feasible in aspects of economy andtechnology, which also have great reference function to other industrial waste wateradvanced treatment.