Full Description

This powerpoint presentation looks at a problem that the Massachusetts Water Resources Authority (MWRA) had with how hits for cyanide in ozone-treated water samples. MWRA set up a study on whether cyanide was really in the samples, or was itforming in the sample containerduring preservation and storage. A literature search found thatthere is growing evidence, especially on thewastewater side, that cyanide can form in thebottle. The hypothesis as stated in the presentation was thatpreservation interrupts a series ofchemical reactions betweenformaldehyde, an ozone disinfection byproduct (DBP), andchlorine/chloramines that normallyconvert formaldehyde into CN- tocyanogen chloride (CNCl), and on tonon-toxic cyanate (CNO-). A bench-scale experiment and results are presented, that showed: unspiked and spiked samples formeddetectable cyanide over 2 to 10 daysof storage;this happened with both Thiosulfateand Ascorbic acid dechlorination; and,Thiosulfate had twice as many hits,and higher concentration hits, thanAscorbic Acid. The on-site experiment is presented, using a Micro Dist Tube, with results indicating that only the samples handled in theconventional way had detectableamounts of cyanide. Conclusion from these studies:cyanide can form in preserveddrinking water samples;formaldehyde appears to stimulatecyanide formation; and,stabilizing samples in MICRO DISTtubes on-site, without raising to pH12 appears to avoid cyanideformation. Includes figures.

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Edition: Vol. - No. Published: 01/01/2008 Number of Pages: 36File Size: 1 file , 710 KB