Experimental Study On Treatment Of LAS Wastewater By Coagulation Air Flotation-membrane Bioreactor

Anionic surfactant(LAS)has a good washing function and is widely used in all walks of life.The discharge of LAS sewage is increasing year by year,and the pollution of the water environment has also become aggravating trend.The foaming property increases the difficulty of treatment.Therefore,how to effectively treat LAS wastewater and ensure the quality of the effluent has attracted the attention of many researchers.This study is aimed at special wastewater of anionic surfactant(LAS).Based on membrane bioreactor,polyferric sulfate(PFS),polyacrylamide(PAM)and acid-modified fly ash are used for coagulation pretreatment to investigate coagulation sediment-Removal efficiency of organic pollutants by air flotation process.And the effects of pretreatment on the removal of LAS wastewater by the coagulation flotation-membrane bioreactor combined process are discussed.The mode of combining pilot experiments and process commissioning and start-up research is used to study the reliability of the system operation and analyze the membrane pollution.The main results and conclusions are listed below.(1)Sludge acclimation and reactor start-up.The inoculation sludge adopts the continuous domestication method.During the cultivation process,there is no abnormality in the activated sludge,which can meet the requirements of subsequent experiments.In the A / O-DMBR reactor,the researchers commissioned parameters such as LAS influent concentration,hydraulic retention time(HRT),and dissolved oxygen(DO).The experiment obtained the best operating parameters: LAS inlet concentration is 150mg/L,HRT=24,DO=2~3mg/L.Under the optimal working conditions,the removal rates of COD(influent concentration is about 995.37 mg / L)and LAS((influent concentration is about 156.05 mg / L removal rate))by the A / O-DMBR reactor reached 91.29% and 91.79%,respectively.The system effluent of COD and LAS are 86.31 mg / L and 12.79 mg / L respectively.(2)By comparing the effect of PFS and PAC on LAS wastewater treatment,PFS was determined to be the best coagulant.The coagulant helper PAM and the adsorbent acid modified fly ash were selected to further enhance the coagulation and precipitation effect.After the pilot test,the dosage of each additive was determined to be 0.4g/L,0.08 g /L and 0.08 g /L,respectively.In the stage of coagulation and air floatation,the best working condition parameter is determined by adjusting the process parameters.The dissolved air floatation is 0.35 Mpa,and the air floatation time is 25 min.The removal rates of COD and LAS in wastewater were increased to 82.01% and 41.46% respectively.(3)The experiment explored the delayed control of the coagulation air flotation-A / O-DMBR combined process on the removal efficiency of pollutants,the migration and transformation of dissolved organic matter,and membrane pollution.The experimental results showed that The removal rate of COD in LAS wastewater by the combined process can reach about 93.41%,and the removal rate of LAS can reach about 99.16%.Observing the operation of the A / O-DMBR process and the combined process,it was found that the addition of the pretreatment process can effectively reduce the growth of EPS in the system and delay the growth rate of TMP.The average TMP value of the combined process in the late stage of the reaction is compared to A / O-DMBR The process is reduced by about 5.9KPa.The MLSS and Zeta potentials showed a negative correlation during the operating period of the coagulation-air floatation-DMBR combined process,Rp=-0.89.The increase of protein and polysaccharide in the combined process during operation,and the analysis of sludge on the surface of the dynamic membrane by Fourier infrared spectroscopy,further proved that protein and polysaccharide are the main factors causing membrane pollution.At the same time,observe the changes of the three-dimensional fluorescence spectrum of the combined process in a process cycle.It can be seen from the graph analysis that there are mainly three kinds of fluorescence peaks of high excitation wavelength tryptophan,fulvic acid in the ultraviolet region,and fulvic acid in the visible light in the wastewater.Fluorescence parameter analysis showed that during the treatment of LAS wastewater in the coagulation air flotationA / O-DMBR combined process,DOM biological source increased,microbial metabolism increased,and biodegradability increased.Figure[17] table[22] reference[97]...