Avoiding Sewer Fires with Vapor Space Organics Monitoring

Regulation of flammable gases released from wastewater discharges is facilitated by the use of the Vapor Space Organics test method. Such regulation can reduce the risk of a flash sewer fire, resulting damage and potential injury. The updated 2003 VSO process developed by Severn Trent Laboratories produced data that was equivalent to the 1990 VSO process developed and used by the Cincinnati Metropolitan Sewer District. The similarity of the VSO results was apparent when the data were compared statistically with 99% and 95% confidence intervals and when compared graphically. Overall, the average difference was 6.8%. The precision, as estimated by the average RSD, is about 5% for VSO 2003 and 11% for VSO 1990. This represents a significant and expected improvement in precision when comparing the automated 2003 process to the manual 1990 process.