title: Degradation of anionic surfactants during drying of UASBR sludges on sand drying beds.
abstract: Anionic surfactant (AS) concentrations in wet up-flow anaerobic sludge blanket reactor (UASBR) sludges from five sewage treatment plants (STPs) were found to range from 4480 to 9,233 mg kg(-1)dry wt. (average 7,347 mg kg(-1)dry wt.) over a period of 18 months. After drying on sand drying beds (SDBs), AS in dried-stabilized sludges averaged 1,452 mg kg(-1)dry wt., a reduction of around 80%. The kinetics of drying followed simple first-order reduction of moisture with value of drying constant (k(d))=0.051 d(-1). Reduction of AS also followed first-order kinetics. AS degradation rate constant (k(AS)) was found to be 0.034 d(-1) and half-life of AS as 20 days. The order of rates of removal observed was k(d)>k(AS)>k(COD)>k(OM) (drying >AS degradation>COD reduction>organic matter reduction). For the three applications of dried-stabilized sludges (soil, agricultural soil, grassland), values of risk quotient (RQ) were found to be <1, indicating no risk.
authors.affiliation: Department of Chemical Engineering, Sardar Vallabhbhai National Institute of Technology, Surat 395007, India. akm@ched.svnit.ac.in
authors.forename: Arvind Kumar
authors.initials: AK
authors.lastname: Mungray
authors.forename: Pradeep
authors.initials: P
authors.lastname: Kumar
mesh_terms: D000838:Anions; D007700:Kinetics; D012722:Sewage; D012822:Silicon Dioxide; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D000838:Anions; D012722:Sewage; D013501:Surface-Active Agents; D012822:Silicon Dioxide