Under‐ice blooms and source‐water odour in a nutrient‐poor reservoir: biological, ecological and applied perspectives

1. Algal taste and odour is usually associated with open water blooms and eutrophic systems. However, some algal species can produce high biomass under ice-cover, even at low nutrient concentrations, that can impact water quality. This paper describes a winter odour outbreak in oligotrophic Glenmore Reservoir (Calgary, Alberta, Canada), the major algal species, volatile organic compounds (VOCs) and some treatment implications. 2. Using sensory, chemical and microscope analyses, we monitored odour, algal biomass and taxa, bacteria and major nutrients. In a preliminary assessment of the effectiveness of standard water treatment with this type of algal biomass and odour, we used bench-scale tests and sampled raw water from the Glenmore treatment plant at successive treatment stages. 3. In the winter of 1999–2000 Glenmore ice-cover was delayed, nutrients were characteristically low (TP < ∼5 μg L–1), but organic carbon and bacteria were higher than in previous years. 4. During this period there was an increase in algal biomass dominated by the mixotrophic chrysoflagellate Dinobryon divergens. Temporal dynamics of this species were inversely correlated with bacteria, and biomass declined following the establishment of ice-cover, while depth profiles showed the highest abundance at subsurface layers. This suggested that the population outbreak was triggered by high bacteria abundance but depended on a minimum amount of light, consistent with in vitro studies of other mixotrophic chrysophytes. 5. Other non-bactiverous taxa were also numerous, notably Asterionella formosa, cryptomonads, dinoflagellates and the synurophyte Synura petersenii. 6. Raw water odour was characteristically fishy, mainly caused by the VOCs 2,4,7-decatrienal, 2,4-heptadienal and 2,4-decadienal. Based on algal population and VOC dynamics, these compounds were attributed to Dinobryon. Trace amounts of 2,6-nonadienal (S. petersenii) and 1,3,5 and 1,3,6-octatriene (A. formosa) were also detected. It was concluded that 2,4,7-decatrienal was the major source of the raw water odour. 7. Sensory and microscopic analyses of pre- and post-treatment samples in the treatment plant indicated a complete removal of odour, but only a 30–60% removal of algal biomass and evident rupture of residual algal cells. Laboratory experiments showed that using standard treatment, chlorination rapidly oxidized 2,4,7-decatrienal and 2,6-nonadienal but had little effect on 2,4-hepta- and decadienal.

[1]  S. Watson,et al.  Quantitative analysis of trace levels of geosmin and MIB in source and drinking water using headspace SPME , 2000 .

[2]  D. Millie,et al.  EVALUATING THE RELATIONSHIP BETWEEN PHOTOPIGMENT SYNTHESIS AND 2‐METHYLISOBORNEOL ACCUMULATION IN CYANOBACTERIA , 1999 .

[3]  Takehito Yoshida,et al.  EFFECTS OF PHOSPHORUS SUPPLY ON PHAGOTROPHY BY THE MIXOTROPHIC ALGA UROGLENA AMERICANA (CHRYSOPHYCEAE) , 1999 .

[4]  D. Stoecker,et al.  Conceptual models of mixotrophy in planktonic protists and some ecological and evolutionary implications , 1998 .

[5]  S. Watson,et al.  Drinking water treatment options for taste and odor control , 1996 .

[6]  P. Persson.  Cyanobacteria and off-flavours , 1996 .

[7]  F. Jüttner,et al.  Lipoxygenase-mediated formation of hydrocarbons and unsaturated aldehydes in freshwater diatoms , 1996 .

[8]  W. F. Young,et al.  Taste and odour threshold concentrations of potential potable water contaminants , 1996 .

[9]  J. Smol,et al.  CHRYSOPHYTE POPULATION AND ENCYSTMENT PATTERNS IN TWO CANADIAN LAKES 1 , 1995 .

[10]  J. Ward,et al.  Winter phytoplankton dynamics in a subalpine lake, Colorado, U.S.A , 1993 .

[11]  D. Caron,et al.  Mixotrophic algae in three ice‐covered lakes of the Pocono Mountains, U.S.A. , 1992 .

[12]  Gary A. Burlingame,et al.  Cucumber flavor in Philadelphia's drinking water , 1992 .

[13]  I. Gustafsson,et al.  FATTY ACID CONTENT AND CHEMICAL COMPOSITION OF FRESHWATER MICROALGAE 1 , 1992 .

[14]  F. Azam,et al.  Phytoplankton and Bacterial Production and Biomass in Subalpine Eastern Brook Lake, Sierra Nevada, California. II. Comparison With Other High-Elevation Lakes , 1991, Arctic and Alpine Research.

[15]  H. Gardner.  Recent investigations into the lipoxygenase pathway of plants. , 1991, Biochimica et biophysica acta.

[16]  A. Konopka.  Metalimnetic cyanobacteria in hard‐water lakes: Buoyancy regulation and physiological state , 1989 .

[17]  H. Ito,et al.  Water Blooms of Uroglena Americana and the Identification of Odorous Compounds , 1988 .

[18]  F. Jüttner,et al.  SEASONAL ANALYSIS OF VOLATILE ORGANIC BIOGENIC SUBSTANCES (VOBS) IN FRESHWATER PHYTOPLANKTON POPULATIONS DOMINATED BY DINOBRYON, MICROCYSTIS AND APHANIZOMENON 1 , 1986 .

[19]  Stuart W. Krasner,et al.  Production of 2-Methyliso-Borneol by Two Benthic Cyanophyta , 1983 .

[20]  F. Jüttner,et al.  Volatile Excretion Products of Poterioochromonas malhamensis Identification and Formation , 1981 .

[21]  F. Jüttner.  Detection of Lipid Degradation Products in the Water of a Reservoir During a Bloom of Synura uvella , 1981, Applied and environmental microbiology.

[22]  T. Galliard.  Lipolytik and Lipoxygenase Enzymes in Plants and their Action in Wounded Tissues , 1978 .

[23]  E. Mccauley,et al.  The use of solid phase microextraction (SPME) to monitor for major organoleptic compounds produced by chrysophytes in surface waters , 1999 .

[24]  F. Jüttner,et al.  High lipoxygenase activities in epilithic biofilms of diatoms , 1997 .

[25]  F. Jüttner.  Physiology and biochemistry of odorous compounds from freshwater cyanobacteria and algae , 1995 .

[26]  H. Hardisty.  Phytoplankton community dynamics and taste and odour events in Glenmore Reservoir Calgary, Alberta , 1993 .

[27]  D. Bird,et al.  Phagotrophic sustenance of a metalimnetic phytoplankton peak , 1989 .

[28]  A. E. Greenberg,et al.  Standard methods for the examination of water and wastewater : supplement to the sixteenth edition , 1988 .