Triggers for Taste and Odour Events: A study of Microbial Production of Geosmin and 2-Methylisoborneol

Abstract

The research presented in this thesis was initiated and supported by Gold Coast Water (Queensland Australia) in response to severe taste and odour issues experienced during a prolonged dry period that impacted on its drinking water service. The intent of this research project was to gain a better understanding of the presence, source and perseverance of geosmin and MIB within the Hinze Dam and the treated water distribution system and to explore potential environmental and physiological triggers for the microbial production of geosmin and MIB. Both field-based and laboratory-based research was undertaken to achieve this goal. The outcomes of this research have contributed to the knowledge of factors influencing taste and odour events and have provided further guidance, management options and research to understand and manage taste and odour events. A 13-month sampling program of the Hinze Dam was undertaken, during which time a significant taste and odour event occurred. High concentrations of geosmin were detected in the surface water of Gold Coast Water’s raw water source, Hinze Dam, during the Summer months and were strongly correlated with an increase in numbers of the cyanobacterium Anabaena sp. The increase in these cyanobacterial cells occurred immediately after a significant rainfall event and an accompanying pulse in nutrients during a time of warmer water temperatures. However, high rainfall and a pulse of nutrients did not render the same effect during colder months. Thus it was concluded that temperature and nutrient concentrations are important parameters involved in the microbial production of geosmin and MIB. This study also revealed that geosmin is present throughout the depth of the dam at most times throughout the year, albeit at concentrations not likely to cause aesthetic concerns for Gold Coast Water. This study did not find evidence to support the supposition that the taste and odour compounds, geosmin and MIB, were being produced by biofilm-attached or free Actinobacteria, post-treatment, in the reticulation system.