Degradation Of High Concentration Liquid Crystal Wastewater With Fenton-SBR-Fenton Hybrid Process

The liquid crystal washing wastewater contains more than ten kinds of components,the main components are alkyl glucoside,perfluorooctanoic acid,polyvinyl alcohol,toluene and ethanol,etc,which have complex pollutant components,high CODCr concentration,strong toxicity,poor biodegradability and different batches of water quality.The characteristics of emissions into the environment will bring serious pollution problems.Only using one method of physical method,chemical method or biological method is difficult to achieve the treatment effect of liquid crystal washing wastewater.At present,there are few studies on its treatment in China.With the development of the liquid crystal production industry,how to treat liquid crystal washing wastewater efficiently and stably has become a hot topic of research.The experimental wastewater treated in this paper is the equipment washing wastewater of a liquid crystal factory in Qingdao.It is characterized by high concentration of CODCr,strong toxicity and poor biodegradability.It is processed by Fenton pretreatment-SBR-Fenton advanced treatment process,and the Fenton pretreatment is optimized.The treatment conditions in the SBR system were determined,and the optimal operating parameters were determined.The SBR system was also tested for optimal conditions and impact load tests to verify its feasibility in practical engineering applications.The iron pyrolysis is carried out by microwave pyrolysis,which produces better economic and environmental benefits.The main research results are as follows:Single factor experiment and response surface curve experiment were carried out on Fenton pretreatment process.The effects of initial p H,H₂O₂ and Fe²⁺ ratio and Fe²⁺ concentration on COD removal rate were studied.The optimal reaction conditions were found to be initial p H of 7 and H₂O₂ and Fe²⁺ ratio.3,Fe²⁺ concentration 0.15mol/L,CODCr removal rate of high concentration liquid crystal washing wastewater with COD of 3000mg/L is 90%,and the effect of CODCr removal rate is ranked as: pre-reaction p H,c(Fe²⁺),c（H₂O₂）/c(Fe²⁺).The Fenton iron mud resource treatment after centrifugation was carried out,and the optimal reaction power and reaction time were determined by microwave pyrolysis experiment.The XRD was detected by the pyrolysis and the main product was γFe2O3.The conversion of contaminants in Fenton and SBR reactions was analyzed by liquid chromatography and gas chromatography.It is speculated that the liquid crystal washing wastewater was first degraded by Fenton to produce CO₂,organic acids,alcohols and other organic products,and then organic acids and alcohols.After SHF aerobic biodegradation,it was finally mineralized into CO₂ and H₂ O.The aerobic rate experiment showed that the biodegradability of wastewater was improved after Fenton reaction.After 49 days of activated sludge domestication,the SBR system was successfully started,and the effluent CODCr was stable at about 450 mg/L,and the removal rate was 85%.MLSS stability is 3.8g/L,SV30 is 22%,and its operating parameters are initially determined: aeration time is 20 h,precipitation time is 4h,reaction temperature is 27°C,influent p H is 7,sludge age is 10 days,influent water volume It is 350 ml.The parameter optimization experiment was carried out on the SBR system,and the optimal parameters were determined as follows: aeration reaction time was 10 h,aeration gas flow was 3.6L/min,sedimentation time was 2h,HRT was 120 h,and water exchange rate was 10%.The impact load test of the SBR system shows that the SBR system can withstand 2.5 times its volume in a short period of time,and the SBR system recovers to the effluent level before impact in 5 cycles.The optimal conditions for Fenton advanced treatment were determined by single factor experiment: p H before reaction,H₂O₂ and Fe²⁺ ratio of 3,Fe²⁺ concentration of 0.065mol/L,and effluent CODCr of less than 30mg/L.SBR was operated for 12 cycles under optimal operating conditions.The removal rates of CODCr,N-NH3,and TP were 85%,96.5%,and 74%,respectively.The effluent concentrations were 450 mg/L,10.5 mg/L,and 2.9 mg/L,respectively.Left and right;the whole process runs for 12 cycles according to the optimal parameters,the effluent CODCr is stable below 30mg/L,and the removal rate is over 99.9%.The Fenton pretreatment-SBR-Fenton advanced treatment treatment of liquid crystal washing wastewater meets the urban miscellaneous water quality standard（GB/T18920-2002）,and the treatment cost is estimated to be 217.58 yuan/ton,which has high environmental and economic benefits..