Identification of 2-methoxy-3,5-dimethylpyrazine as the obnoxious compound at trace levels in water supplies.

摘要

A study of organic compounds causing several odor problems in water supplies from NW Spain was conducted. Sour dish-cloths, potato bin and musty were the main descriptors associated to these events. Closed loop stripping analysis (CLSA) was employed as preconcentration method combined with sensory-GC and GC/MS detection. The compound responsible of the first odor events was identified as 2-methoxy-3,5-dimethylpyrazine. Concentration levels were 2010 and 300 ng/L in the influent and effluent from an activated sludge WWTP to 3 ng/L in finished water. Although 2-methoxy-3,5-dimethylpyrazine has been previously reported as the malodorous compounds in wine corks and old machine cutting-fluid emulsions, it is the first time that is identified as the compound responsible of odor incidents in finished water. 2-isobutyl-3-methoxypyrazine and other alkyl methoxypyrazines were the compounds responsible for the odor in another event occurred several months later. Concentration levels in the mg/L range were measured in the activated sludge of the WWTP.