Extracellular polymeric substances(EPS)form a stable gel-like structure to combine with water molecules through steric hindrance,making the mechanical dewatering of wastewater sludge considerably difficult.Coagulation...Extracellular polymeric substances(EPS)form a stable gel-like structure to combine with water molecules through steric hindrance,making the mechanical dewatering of wastewater sludge considerably difficult.Coagulation/flocculation has been widely applied in improving the sludge dewatering performance,while sludge properties(organic fraction and solution chemistry conditions)are highly changeable and have important effects on sludge flocculation process.In this work,the alkalinity effects on sludge conditioning with hydroxy-aluminum were comprehensively investigated,and the interaction mechanisms between EPS and hydroxy-aluminum with different speciation were unraveled.The results showed that the effectiveness of hydroxy-aluminum conditioning gradually deteriorated with increase in alkalinity.Meanwhile,the polymeric hydroxy-aluminum(Al 13)and highly polymerized hydroxy-aluminum(Al 30)were hydrolysed and converted into amorphous aluminum hydroxide(Al(OH)3),which changed the flocculation mechanism from charge neutralization and complexing adsorption to hydrogen bond interaction.Additionally,both Al 13 and Al 30 showed higher binding capacity for proteins and polysaccharides in EPS than monomeric aluminum and Al(OH)3.Al 13 and Al 30 coagulation changed the secondary structure of proteins in EPS,which caused a gelation reaction to increase molecular hydrophobicity of proteins and consequently sludge dewaterability.This study provided a guidance for optimizing the hydroxy-aluminum flocculation conditioning of sludge with high solution alkalinity.展开更多
基金the National Natural Science Foundation of China(Nos.51678546 and 41630318)the Chinese Universities Scientific Fund of China University of Geosciences(Wuhan)the Major Science and Technology Program for Water Pollution Control and Treatment(No.2018 ZX 07110004)。
文摘Extracellular polymeric substances(EPS)form a stable gel-like structure to combine with water molecules through steric hindrance,making the mechanical dewatering of wastewater sludge considerably difficult.Coagulation/flocculation has been widely applied in improving the sludge dewatering performance,while sludge properties(organic fraction and solution chemistry conditions)are highly changeable and have important effects on sludge flocculation process.In this work,the alkalinity effects on sludge conditioning with hydroxy-aluminum were comprehensively investigated,and the interaction mechanisms between EPS and hydroxy-aluminum with different speciation were unraveled.The results showed that the effectiveness of hydroxy-aluminum conditioning gradually deteriorated with increase in alkalinity.Meanwhile,the polymeric hydroxy-aluminum(Al 13)and highly polymerized hydroxy-aluminum(Al 30)were hydrolysed and converted into amorphous aluminum hydroxide(Al(OH)3),which changed the flocculation mechanism from charge neutralization and complexing adsorption to hydrogen bond interaction.Additionally,both Al 13 and Al 30 showed higher binding capacity for proteins and polysaccharides in EPS than monomeric aluminum and Al(OH)3.Al 13 and Al 30 coagulation changed the secondary structure of proteins in EPS,which caused a gelation reaction to increase molecular hydrophobicity of proteins and consequently sludge dewaterability.This study provided a guidance for optimizing the hydroxy-aluminum flocculation conditioning of sludge with high solution alkalinity.
