Direct Aqueous Injection Gas Chromatographic Method for Measuring Reduced Sulfur Compounds in Pulp Mill Effluents, 2002 Environmental Conference Proceedings

A. Gholson, D. Hoy and L. Chambers -- Reduced sulfur compounds (RSCs) are byproducts of kraft pulping operations, and their release from process vents and wastewater treatment systems are often associated with nuisance odors from these facilities. One of the more difficult sources to assess for the release of RSCs has been the waste treatment system. To better understand the factors that influence this release, a simple, accurate, and sensitive method to measure RSC in wastewater streams is needed. The technique previously used by NCASI, PAPRICAN, and others required purging of a liquid sample, collecting the purge gas in a bag, and analyzing the gas by GC with a flame photometric detector. This technique is labor intensive and time consuming, and its accuracy is difficult to assure because of the multiple steps involved. A method has been developed using the more sensitive and selective pulsed flame photometric detector, allowing the sample to be directly injected into a GC with no sample preparation steps. Hydrogen sulfide, methyl mercaptan, dimethyl sulfide, carbon disulfide, dimethyl disulfide, and dimethyl trisulfide have been calibrated to a concentration of 20 µg/L. Samples collected throughout a treatment system have been analyzed with a precision of less than 15% and recoveries greater than 80%. Although hydrogen sulfide was found to be unstable is some matrices, a sample preservation technique was found that was effective for all the other RSCs in all the effluent samples encountered.