Cyanide generation during preservation of chlorinated wastewater effluent samples for total cyanide analysis.
Dechlorinating agents and pH adjustment are often used to preserve wastewater samples for cyanide analysis. The effects of four approved preservation protocols on the results of the total cyanide analysis of effluents from four water reclamation plants were examined. The results differed widely, and a clear pattern emerged. Immediate analysis without pH adjustment generally gave total cyanide concentrations below the reporting limit of 5 microg/L, irrespective of the dechlorinating agents used. When the pH was adjusted to > or =12, a slight increase in the measured total cyanide concentration was observed when thiosulfate was used to dechlorinate the samples, and a significant increase (>10 microg/L) was observed when arsenite was used as the dechlorinating agent. These results provide evidence that approved preservation protocols may give rise to cyanide formation in chlorinated wastewater effluent matrices.
Khoury
Joseph
J
Joint Water Pollution Control Plant Water Quality Laboratory, Carson, California, USA.
Pang
Maria
M
Young
Connie
C
Pandit
Anita
A
Carr
Steve
S
Fischer
Dwayne
D
Stahl
James
J
D002713:Chlorine; D003486:Cyanides / Q000032:analysis* / Q000138:chemical synthesis*; D006863:Hydrogen-Ion Concentration; D013048:Specimen Handling / Q000379:methods; D014865:Waste Disposal, Fluid / Q000379:methods*; D014876:Water Pollution / Q000032:analysis*
D003486:Cyanides; D002713:Chlorine