Managing taste and odour metabolite production in drinking water reservoirs: The importance of ammonium as a key nutrient trigger

R.G Perkins,E.I Slavin,T.M.C Andrade,C Blenkinsopp,P Pearson,T Froggatt,G Godwin,J Parslow,S Hurley,R Luckwell,D.J Wain

doi:10.1016/j.jenvman.2019.04.123

Abstract

Taste and odour (T&O) compounds (most commonly 2-MIB and Geosmin) in drinking water are becoming an increasingly global problem for water management. Here, the trigger(s) for 2-MIB and Geosmin production were investigated in Plas Uchaf reservoir (North Wales, UK) with detailed water sample analysis between 2015 and 2016. Historical abstraction data from this reservoir and 4 reservoirs in Somerset (England, UK) were compared statistically using Self-Organising Map (SOM) analysis. In-reservoir measurements (2015–2016) revealed an 85% reduction in ammonium from the primary external loading source led to lower 2-MIB and Geosmin concentrations, with peak concentrations of 2-MIB declining from 60 to 21 ng l−1 and Geosmin declining from 140 to 18 ng l−1. No other measured water chemistry parameter showed a significant difference between years. The SOM results support the in-reservoir findings, revealing 2-MIB and Geosmin to be associated with high ammonium relative to nitrate for all 5 reservoirs. We conclude that ammonium is key for stimulating cyanobacterial productivity and production of T&O compounds. Whilst it is well understood that adequate availability of phosphorus is required for rapid growth in cyanobacteria, and hence should still be considered in management decisions, we suggest that monitoring sources and concentrations of ammonium is key for managing T&O outbreaks in drinking water reservoirs.

Highlights

Taste and odour (T&O) problems in drinking water supply associated with the secondary metabolites 2-Methylisoborneol (2-MIB) and 1,10-dimethyl-trans-9-decalol (Geosmin) are increasing in frequency and magnitude globally (Winter et al, 2011). 2-MIB and Geosmin are naturally occurring tertiary alcohols that produce strong musty and earthy odours (Rogers, 2001), and impart unfavourable tastes in drinking water
The same relationship between Total Nitrogen (TN):Total Phosphorus (TP) and 2MIB/Geosmin concentrations was observed in Durleigh from 2013 to 2017 (Supplementary Fig. S2), the inverse relationship is much clearer for 2-MIB concentrations compared to Geosmin
This study has shown that 2-MIB and Geosmin production correlated with ammonium concentration in Plas Uchaf reservoir both spatially, and temporally correlating with external loading of ammonium

Summary

Introduction

Taste and odour (T&O) problems in drinking water supply associated with the secondary metabolites 2-Methylisoborneol (2-MIB) and 1,10-dimethyl-trans-9-decalol (Geosmin) are increasing in frequency and magnitude globally (Winter et al, 2011). 2-MIB and Geosmin are naturally occurring tertiary alcohols that produce strong musty and earthy odours (Rogers, 2001), and impart unfavourable tastes in drinking water. Taste and odour (T&O) problems in drinking water supply associated with the secondary metabolites 2-Methylisoborneol (2-MIB) and 1,10-dimethyl-trans-9-decalol (Geosmin) are increasing in frequency and magnitude globally (Winter et al, 2011). The T&O thresholds in water are very low at 6.3 ng l−1 for 2-MIB and 1.3 ng l−1 for Geosmin (Wert et al, 2014). These compounds are one of the principal causes of customer complaints to water utilities worldwide and over recent years the number of consumer complaints have been growing (Bai et al, 2017). T&O producing cyanobacteria can be planktonic (Jüttner and Watson, 2007), or form benthic biofilms

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