In-site soil flushing and aeration are the typical synergetic remediation technology for contaminated sites.The surfactant present in flushing solutions is bound to affect the aeration efficiency.The purpose of this s...In-site soil flushing and aeration are the typical synergetic remediation technology for contaminated sites.The surfactant present in flushing solutions is bound to affect the aeration efficiency.The purpose of this study is to evaluate the effect of surfactant frequently used in soil flushing on the oxygen mass transfer in micro-nano-bubble(MNB)aeration system.Firstly,bio-surfactants and chemical surfactants were used to investigate their effects on Sauter mean diameter of bubble(dBS),gas holdup(ε),volumetric mass-transfer coefficient(kLa)and liquid-side mass-transfer coefficient(kL)in the MNB aeration system.Then,based upon the experimental results,the Sardeing's and Frossling's models were modified to describe the effect of surfactant on kL in the MNB aeration.The results showed that,for the twenty aqueous surfactant solutions,with the increase in surfactant concentration,the value of dBS,kLa and kL decreased,while the value ofεand gas-liquid interfacial area(a)increased.These phenomena were mainly attributed to the synergistic effects of immobile bubble surface and the suppression of coalescence in the surfactant solutions.In addition,with the presence of electric charge,MNBs in anionic surfactant solutions were smaller and higher in number than in non-ionic surfactant solutions.Furthermore,the accumulation of surfactant on the gas-liquid interface was more conspicuous for small MNB,so the reduction of kL in anionic surfactant solutions was larger than that in non-ionic surfactant solutions.Besides,the modified Frossling's model predicted the effect of surfactant on kL in MNB aeration system with reasonable accuracy.展开更多
Neonicotinoid insecticides(NNIs),including thiamethoxam(TMX),clothianidin,and imidacloprid,are widely used in agriculture to control pests.Consequently,they have been frequently detected in wastewater,posing significa...Neonicotinoid insecticides(NNIs),including thiamethoxam(TMX),clothianidin,and imidacloprid,are widely used in agriculture to control pests.Consequently,they have been frequently detected in wastewater,posing significant ecotoxicological risks.Conventional ozonation is widely applied for NNI removal but is limited by low mineralization efficiency and high effluent toxicity.However,the mechanisms of the performance limitations and increased toxicity remain unclear,hindering the effective application of ozonation in wastewater treatment.This study constructed a novel micro-nano-bubble ozonation(MNB-O_(3))system,which enhanced the degradation rate of TMX,a representative NNI,by 34.7%and the mineralization efficiency by 176.5%,compared to conventional bubble ozonation(CB-O_(3)).MNB-O_(3)also significantly reduced both acute toxicity and neurotoxicity in the ozonated effluents,addressing the issue of high toxicity associated with CB-O_(3).Mechanistically,the formation of hydroxyl radicals(·OH)and singlet oxygen(1O_(2))increased substantially and was identified as the primary contributor to TMX degradation.Transformation product(TP)analysis revealed that formaldehyde and acetaldehyde were the key contributors to effluent toxicity,both accumulating in the CB-O_(3)effluent.In contrast,MNB-O_(3)achieved significant reductions in formaldehyde(87.4%)and acetaldehyde(34.6%)concentrations,substantially lowering effluent toxicity.Furthermore,a large-scale MNB-O_(3)application demonstrated excellent performance in removing NNIs and reducing toxicity.This study provides valuable insights into the mechanisms underlying toxicity reduction in MNB-O_(3)and highlights its potential for low-carbon wastewater treatment.By addressing the limitations of CB-O_(3)and reducing the NNIs-related environmental risks,MNB-O_(3)represents a promising advancement in the field of wastewater treatment.展开更多
基金financially supported by the National Natural Science Foundation of China(41877240)National Key Research and Development Program of China(2018YFC1802300)Scientific Research Foundation of Graduate School of Southeast University(YBPY2154).
文摘In-site soil flushing and aeration are the typical synergetic remediation technology for contaminated sites.The surfactant present in flushing solutions is bound to affect the aeration efficiency.The purpose of this study is to evaluate the effect of surfactant frequently used in soil flushing on the oxygen mass transfer in micro-nano-bubble(MNB)aeration system.Firstly,bio-surfactants and chemical surfactants were used to investigate their effects on Sauter mean diameter of bubble(dBS),gas holdup(ε),volumetric mass-transfer coefficient(kLa)and liquid-side mass-transfer coefficient(kL)in the MNB aeration system.Then,based upon the experimental results,the Sardeing's and Frossling's models were modified to describe the effect of surfactant on kL in the MNB aeration.The results showed that,for the twenty aqueous surfactant solutions,with the increase in surfactant concentration,the value of dBS,kLa and kL decreased,while the value ofεand gas-liquid interfacial area(a)increased.These phenomena were mainly attributed to the synergistic effects of immobile bubble surface and the suppression of coalescence in the surfactant solutions.In addition,with the presence of electric charge,MNBs in anionic surfactant solutions were smaller and higher in number than in non-ionic surfactant solutions.Furthermore,the accumulation of surfactant on the gas-liquid interface was more conspicuous for small MNB,so the reduction of kL in anionic surfactant solutions was larger than that in non-ionic surfactant solutions.Besides,the modified Frossling's model predicted the effect of surfactant on kL in MNB aeration system with reasonable accuracy.
基金supported by National Natural Science Foundation of China(42227806)Natural Science Foundation of Jiangsu Province(BK20241241)+2 种基金China Postdoctoral Science Foundation(2024M761399)Postdoctoral Fellowship Program of CPSF(GZC20240680)Jiangsu Funding Program for Excellent Postdoctoral Talent(2024ZB295).
文摘Neonicotinoid insecticides(NNIs),including thiamethoxam(TMX),clothianidin,and imidacloprid,are widely used in agriculture to control pests.Consequently,they have been frequently detected in wastewater,posing significant ecotoxicological risks.Conventional ozonation is widely applied for NNI removal but is limited by low mineralization efficiency and high effluent toxicity.However,the mechanisms of the performance limitations and increased toxicity remain unclear,hindering the effective application of ozonation in wastewater treatment.This study constructed a novel micro-nano-bubble ozonation(MNB-O_(3))system,which enhanced the degradation rate of TMX,a representative NNI,by 34.7%and the mineralization efficiency by 176.5%,compared to conventional bubble ozonation(CB-O_(3)).MNB-O_(3)also significantly reduced both acute toxicity and neurotoxicity in the ozonated effluents,addressing the issue of high toxicity associated with CB-O_(3).Mechanistically,the formation of hydroxyl radicals(·OH)and singlet oxygen(1O_(2))increased substantially and was identified as the primary contributor to TMX degradation.Transformation product(TP)analysis revealed that formaldehyde and acetaldehyde were the key contributors to effluent toxicity,both accumulating in the CB-O_(3)effluent.In contrast,MNB-O_(3)achieved significant reductions in formaldehyde(87.4%)and acetaldehyde(34.6%)concentrations,substantially lowering effluent toxicity.Furthermore,a large-scale MNB-O_(3)application demonstrated excellent performance in removing NNIs and reducing toxicity.This study provides valuable insights into the mechanisms underlying toxicity reduction in MNB-O_(3)and highlights its potential for low-carbon wastewater treatment.By addressing the limitations of CB-O_(3)and reducing the NNIs-related environmental risks,MNB-O_(3)represents a promising advancement in the field of wastewater treatment.
