Triggers for taste and odour events

265 Pages·2013·4.91 MB·English

by  Ian England

Triggers for taste and odour events:
A study of microbial production of
geosmin and
2-methylisoborneol

Heather Karen Uwins
B.Sc. Hons

School of Biomolecular and Physical Sciences,
Science, Environment, Engineering and Technology
Griffith University

Submitted in fulfilment of the requirements of the degree of
Doctor of Philosophy

December 2011

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.

Sixteen Actinobacteria isolates from the Hinze Dam and Nerang River water samples
were examined for geosmin and MIB production and identified using 16S rRNA
analysis. A significant number of these isolates (69%) produced geosmin or both
geosmin and MIB and were identified as Streptomyces species. The laboratory study
with Streptomyces coelicolor A3(2) demonstrated that geosmin production was
influenced by temperature, incubation time and nutrient concentration. In general,
more geosmin was produced by S. coelicolor A3(2) at higher temperatures and after
longer incubation times. It was demonstrated that manganese and iron, at
concentrations found in the dam, may not influence geosmin production by S.
coelicolor A3(2), whilst nitrogen, at concentrations found in the dam, stimulated
geosmin production. S. coelicolor A3(2) was able to produce geosmin under limited
phosphorus conditions, similar to those found in the dam, but optimal geosmin
production occurred with higher concentrations of phosphorus. This study revealed
that, unlike many cyanobacteria, geosmin production in S. coelicolor A3(2) was most
typically released extracellularly although some geosmin was retained intracellularly.
Geosmin production in S. coelicolor A3(2) was not readily correlated with biomass
production but was correlated with ATP production, thus revealing that geosmin
production is not necessarily coupled with growth. The results from the field study
and the laboratory study reveal that there is potential for Actinobacteria in the Hinze
Dam to contribute to taste and odour events but there appears to be environmental
factors controlling or impeding the production of geosmin and MIB in the water
column. Analysis of data and literature suggests that temperature, dissolved oxygen
and concentration of phosphorus are likely to be the key factors that prevent or inhibit
the production of geosmin and MIB by Actinobacteria in the dam.

Based on the findings of this research and current literature, a framework has been
developed to assist water storage managers to systematically examine all factors and
complex interactions that may contribute to taste and odour events. The framework
has been applied to the Hinze Dam water storage, catchment, treatment and
distribution system and a conceptual model developed to provide a visual aid to help
understand the complex interactions occurring in the system that may influence the
potential for microbially derived taste and odour events.

This work has not previously been submitted for a degree or diploma in
any university. To the best of my knowledge and belief, the thesis
contains no material previously published or written by another person
except where due reference is made in the thesis itself.

…………………………………………………..
Heather K Uwins
i
Table of Contents

Acknowledgements ....................................................................................................... i
Abbreviations ............................................................................................................. iii
Glossary of terms ........................................................................................................ iv

Chapter 1 – Introduction and objectives ................................................................... 1

Chapter 2 - The Issue of taste and odour compounds in drinking water ............... 5
2.1 Introduction ....................................................................................................... 5
2.2 Geosmin and 2-methylisoborneol ..................................................................... 6
2.3 Source water studies of taste and odour events ................................................ 7
2.4 Geosmin and 2-methylisoborneol-producing microorganisms ......................... 9
2.4.1 The cyanobacteria ...................................................................................... 9
2.4.2 Algae ........................................................................................................ 11
2.4.3 Fungi ........................................................................................................ 11
2.4.4 The Actinobacteria ................................................................................... 12
2.5 Metabolic pathways of geosmin and MIB production .................................... 15
2.5.1 The correlation of geosmin and MIB production with photo-pigments .. 17
2.6 Factors affecting microbial production of geosmin and MIB ......................... 18
2.7 Water treatment approaches for removing taste and odour compounds ......... 21
2.7.1 Studies on the effects of treatment chemicals .......................................... 21
2.8 Potential sources of geosmin & MIB post treatment ...................................... 23
2.9 Predictive tools................................................................................................ 23
2.10 Gaps in knowledge .......................................................................................... 24

Chapter 3 – Field Study 1 - Presence, perseverance and sources of geosmin and
MIB in the Hinze Dam ............................................................................................... 25
3.1 Introduction ..................................................................................................... 25
3.2 Aims ................................................................................................................ 25
3.3 Materials and methods .................................................................................... 26
3.3.1 Sampling sites and sampling processes ................................................... 26
3.3.2 Analysis.................................................................................................... 30
3.3.2.1 Parameters measured ........................................................................ 30
3.3.2.2 Algal counts ...................................................................................... 32
3.3.2.3 Bacterial counts ................................................................................. 32
3.3.2.4 Actinobacteria isolation and counts .................................................. 34
3.3.2.5 Geosmin and MIB ............................................................................. 35
3.3.2.6 Carbon ............................................................................................... 35
3.3.2.7 Data analysis ..................................................................................... 36
3.4 Results ............................................................................................................. 36
3.4.1 Investigation one – Hinze Dam depth profile .......................................... 36
3.4.1.1 Occurrence of geosmin in the dam ................................................... 36
3.4.1.2 Occurrence of 2-methylisoborneol (MIB) in dam ............................ 36
3.4.1.3 Physical parameters .......................................................................... 39
3.4.1.4 Bacterial numbers ............................................................................. 45
3.4.1.5 Nitrogen ............................................................................................ 50
3.4.1.6 Phosphorus ........................................................................................ 50
3.4.1.7 Iron .................................................................................................... 50
3.4.1.8 Manganese ........................................................................................ 51
3.4.1.9 Carbon ............................................................................................... 51
3.4.1.10 Dry weather and wet weather sampling .......................................... 53
3.4.2 Investigation two – surface profile of Hinze Dam ................................... 54
3.4.2.1 Geosmin and MIB ............................................................................. 54
3.4.2.2 Water temperature ............................................................................. 54
3.4.2.3 Anabaena counts and total algal counts ............................................ 55
3.4.2.4 Actinobacteria numbers .................................................................... 56
3.4.2.5 Rainfall and dam capacity ................................................................. 56
3.4.2.6 Nitrogen ............................................................................................ 56
3.4.2.7 Phosphorus ........................................................................................ 56
3.4.2.8 Analysis............................................................................................. 58
3.5 Discussion ....................................................................................................... 59
3.5.1 Presence and perseverance of geosmin .................................................... 59
3.5.2 Presence and perseverance of MIB .......................................................... 61
3.5.3 Potential sources of geosmin and MIB in dam ........................................ 61
3.5.4 Potential triggers for geosmin and MIB................................................... 66
3.6 Conclusions ..................................................................................................... 70