GOT SULFUR? Analytical Methods in the Odor Threshold Range

Hydrogen sulfide is often mentioned as equal to total odor at publicly owned treatment works POTWs. Hydrogen sulfide is actually only one of a number of reduced sulfur compounds that are prevalent at POTWs and can cause an adverse olfactory reaction. Reduced sulfur compounds are often the source of many odor complaints from POTWs due to their low odor thresholds and their persistence.It is often desirable to know the quantity of these compounds to estimate off-site impacts and to determine odor control design parameters. Unfortunately, the human nose is significantly better at detecting reduced sulfur compounds than either of the primary toxic organic methods used today (TO-14A, or TO-15). Another method, ASTM method D-5504 has been employed that uses a sulfur chemiluminescence detector to reduce the reporting limit for reduced sulfur compounds. This test method, although effective, requires a significant additional laboratory expense that serves only one function and therefore makes it cost prohibitive for many laboratories to employ. In contrast, there are a number of commercial laboratories that have the capability to conduct TO- 14A and TO-15 analysis.This paper discusses an analytical procedure to better examine sulfide and thiol (mercaptan) compounds with modifications to EPA Method TO-15. A sensitivity study was conducted in both the full scan and selective ion-monitoring (SIM) mode to examine if there is any increase in sensitivity for these compounds via SIM. Reporting limits will be documented utilizing both approaches.Reactivity of reduced sulfur compounds has been a concern in all types of sampling media and has been evaluated before. In many of the earlier studies the reactivity of the samples was linked to variability in the Summa canister deactivation process or uncoated valves and fittings. This paper reexamines canister and Tedlar® bag hold times based on the recent advances in stainless steel canister coating technology, i.e. fused silica lining (FSL). An evaluation of canister and Tedlar® bag hold time was conducted. Different modifications to the canister deactivation process were also evaluated and observed effects on hold time were documented.