title: Effects of thiocyanate on the formation of free cyanide during chlorination and ultraviolet disinfection of publicly owned treatment works secondary effluent.
abstract: Cyanide has been detected in effluent of some publicly owned treatment works (POTWs) at levels exceeding influent concentration. Thiocyanate (SCN-) is a cyanide-related compound encountered in most POTW influents and may be decomposed to free cyanide (CN-) under some circumstances. Effects of SCN- on the formation of cyanide during chlorination and UV disinfection were studied through a laboratory study with synthetic solutions and POTW secondary effluent. Results indicated that CN- was detected in SCN- solutions after chlorination in which the chlorine dose or reaction time was not sufficient to destroy SCN-completely, thus ensuring no residual chlorine to destroy any CN-produced. It was also found that SCN can be broken down to yield cyanide by UV irradiation. In addition, SCN- was observed to cause significant positive error in the conventional total cyanide analysis technique involving acidic distillation and colorimetric measurement when nitrate was present in the sample.
authors.affiliation: Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Anping
authors.initials: A
authors.lastname: Zheng
authors.forename: David A
authors.initials: DA
authors.lastname: Dzombak
authors.forename: Richard G
authors.initials: RG
authors.lastname: Luthy
mesh_terms: D002623:Chemistry Techniques, Analytical; D002713:Chlorine / Q000737:chemistry; D003486:Cyanides / Q000032:analysis / Q000737:chemistry*; D004203:Disinfection / Q000379:methods*; D013861:Thiocyanates / Q000737:chemistry*; D014466:Ultraviolet Rays; D014865:Waste Disposal, Fluid / Q000379:methods*; D014867:Water / Q000737:chemistry
chemical_list: D003486:Cyanides; D013861:Thiocyanates; D014867:Water; D002713:Chlorine; C031760:thiocyanate