Study On Advanced Treatment Of Printing And Dyeing Wastewater

With the implementation of the new standard < Discharge standard of water pollutant for dyeing and finishing oftextile industry >?GB4287-2012?,the national emission requirements for printing and dyeing wastewater are increasingly stringent.As a gathering ground of textile printing and dyeing industry,the Pearl River Delta has a higher standard of emission up to prospective class ? standards of surface water in environmental sensitive area,the original secondary biochemical treatment is difficult to meet the new requirements of water emission standards.Therefore,it is urgent to look for an efficient,economic,practical and feasible treatment technique for advanced treatment of dyeing wastewater biochemical effluent.In this thesis,a combined process of multi-stage bio-filters with ozone oxidation were used for the advanced treatment of the secondary biochemical effluent of a textiles printing and dyeing Co.,Ltd.named Lian De in Dongguan city.The best process of the advanced treatment was explored,and a 4.8 m³/d pilot was carried out.The experiment results of the denitrification biofilter?DNBF?in laboratory showed that under the condition of 4⁵ mg/L of dissolve oxygen?DO?,the hydraulic load of 2 m³/?m²?h?,the water temperature of 26.5³4.8 ?,the optimal carbon and nitrogen ratio was 5 when methanol as carbon source.With the hydraulic residence time?HRT?? 27 min,the removal rates of NO₃^--N were higher than 90%,and the removal rates of total nitrogen?TN?were higher than 88%.A combined process of ozone catalytic oxidation/ biological aerated filter?BAF?/ozonebiological aerated filter?O₃-BAF?/deep bed anaerobic filter was used for treatment of dyeing wastewater after the secondary biochemical process.The operation practice showed that the TN of the effluent was less than 8 mg/L with a average value of 4 mg/L,the main indicaters except aniline and TN could meet the class ?standard of <Environmental quality standard for surface water >?GB3838-2002?.The removal rates of COD_Cr in BAF were about 70% and the removal efficiencies of NH₄⁺-N were more than 97%.The control of the COD_Cr /TN was the key factor for denitrification effect of denitrification biofilter.In the DNBF,with 27.5³6.9? inlet temperature,DO=3.2⁵.3 mg/L,initial p H=7.9⁸.6,and the dosing of methanol to TN = 3 5 g/g,the optimal average removal efficiencies of TN and NO₃^--N were both about 91%.A combined process of O₃-BAF/DNBF/BAF was used as programe II to optimize the pilot process,the control and adjustment of the aeration volume of O₃-BAF was the main influencing factor of the operation effect.To make a futher optimization of pilot process,the combined process of DNBF/BAF was proposed as programme III.The long-term operation results showed that when the reflux ratio was 100%²00%,the effluent concentration of COD_Cr,NH₄⁺-N and TP were less than 30 mg/L,0.8 mg/L,10 mg/L,0.3 mg/L respectively,basically achieving the preset target.The temperature and the carbon-nitrogen ratio were the key factors influencing the stability of operation.The molecular biology analysis of the pilot plant through high throughput sequencing presents that there are a large amount of denitrifying bacteria belong to Alphaproteobacteria,Betaproteobacteria and Gammaproteobacteria in the denitrifying biofilters,and anaerobic ammonium oxidation?Anammox?also exist.The dominant bacteria in the pre-and-back denitrification filter are different,which correspond to the respective denitrification effect.