Occurrence of geosmin and other odorous compounds of natural origin in surface and drinking waters. A case study

The concentrations of geosmin and other natural compounds in raw water from the Llobregat river and tap water from Barcelona (N.E. Spain) were measured by CLSA and GC-MS. From 1997 to mid 1999, average concentrations of 86 and 33 ng/l of geosmin were recorded in Llobregat river water at the entrance to the two main water treatment plants (WTP1, WTP2), whereas their treated waters contained 24 and <5 ng/l, respectively. Barcelona's tap water coming from the WTP3 supplied by Ter river had also an average value of <5 ng/l for geosmin. The presence of geosmin in Barcelona's tap water can be attributed to the blending of the two Llobregat WTPs and also to the blending of Llobregat and Ter river treated waters. Geosmin is one of the compounds responsible for complaints from consumers. Neither 2-methyl-isoborneol (MIB) nor 2-alkyl-3-methoxypirazines were detected among other compounds with low odor threshold concentrations (OTC).