Pressure-induced taste and odour deviations within the high-pressure drinking water distribution system

Taste and odour (T&O) issues in tap water decrease the willingness of consumers to drink it. Production and/or release of odour compounds during drinking water distribution should be avoided as the water is directly delivered to consumers without further treatment. Odours can be caused by leaching of compounds from pipe materials, microbial metabolism, disinfection reactions, or diffusion of odour compounds or precursors from external sources. Increasing knowledge of T&O origins is needed to better solve future problems. Therefore, this research focuses on odour linked to changes in pressure because of maintenance work at the high-pressure (HP) drinking water distribution system. A trace analytical method targeting 45 T&O compounds is further optimized by including derivatisation to improve halophenol detection. Next, in a field section of a real HP pipe (± 3 km), three scenarios were systematically investigated. Lowering the overpressure in the HP pipe from 10 to 5 bar resulted in an observed bitumen/asphalt odour, that further increased in intensity after a subsequent sudden pressure drop to 2 bar. Based on the odour threshold and profile, two halophenols were detected that may have contributed to this odour observation. When the section was partially emptied, 6 halophenols and 5 other T&O compounds were identified. Our results indicate that pressure changes induce the leaching of T&O compounds from sealing materials connecting the 6m-pipe sections. This is further supported by the detection of similar T&O compounds in a water extract of the sealing materials and in an odorous household sample collected after maintenance work in the HP-network.