Environmental triggers for geosmin and 2-MIB production in drinking water reservoirs

Hooper, Annalise Sara 2023. Environmental triggers for geosmin and 2-MIB production in drinking water reservoirs. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

The presence of taste and odour compounds (T&O) in drinking water lead to numerous complaints to water companies worldwide. Geosmin and 2-MIB are common T&O compounds, with Cyanobacteria being the primary biological source in drinking water reservoirs. Both compounds have low odour thresholds in humans and require expensive additional treatment. This thesis used molecular and statistical analysis of water from Welsh Water reservoirs, to provide a framework for predicting and monitoring T&O events and understanding their causes. Elevated T&O concentrations were confined to warmer months, except for a one geosmin event in winter 2019. There was no correlation between cyanobacterial abundance and T&O concentrations, but qPCR analysis based on eDNA sampling demonstrated that geosmin synthase (geoA) was a suitable proxy for predicting geosmin concentrations. Abundances of geoA and 2-MIB cyclase (mic) were significantly non-linearly associated with high ammonium-to-nitrate ratios, identifying thresholds for heightened T&O risk. The ratio of total inorganic nitrogen to total phosphorous was significantly non-linearly associated with increases in geoA. Increased geoA was also significantly negatively associated with temperature and dissolved reactive silicate in all reservoirs. Next-generation sequencing of bacterial and algal communities showed that community compositions clustered according to T&O concentrations. Bacterial and algal co-occurrence networks uncovered significant positive and negative associations, highlighting cyanospheres in all reservoirs. Random Forest models were developed for geosmin (Alaw) and 2-MIB (Pentwyn) using significantly co-occurring taxa exposing indicative T&O taxa and the probable Cyanobacteria causing the T&O. Cyanobacteria had more negative than positive associations in their cyanospheres. This thesis illustrates the importance of nutrient ratios in triggering potential geosmin and 2-MIB events. It also indicates that Cyanobacteria subjected to environmental stress (negative biotic interactions and low temperatures) increase their T&O-production. These findings provide a useful framework for water monitoring to enable the prediction and possible prevention of T&O events.

Item Type:	Thesis (PhD)
Status:	Unpublished
Schools:	Earth and Environmental Sciences
Date of First Compliant Deposit:	31 May 2023
Last Modified:	31 May 2023 11:24
URI:	https://orca.cardiff.ac.uk/id/eprint/160074

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