ALGAL PROBLEMS Taste and Odor T&O by diatoms

104 Pages·2011·4.51 MB·English

by  Ken Wagner

IDENTIFICATION, ECOLOGY AND
CONTROL OF NUISANCE
FRESHWATER ALGAE
KENNETH J. WAGNER, Ph.D, CLM
WATER RESOURCE SERVICES
PART 1: THE PROBLEMS
ALGAL PROBLEMS
Algal problems include:
• Ecological imbalances
• Physical impacts on the
aquatic system
• Water quality alteration
• Aesthetic impairment
• Taste and odor
• Toxicity
ALGAL PROBLEMS
Ecological Imbalances
High algal densities:
• Result from overly successful growth processes
and insufficient loss processes
• Represent inefficient processing of energy by
higher trophic levels
• May direct energy flow to benthic/detrital
pathways
• May actually reduce system productivity
(productivity tends to be highest at
intermediate biomass)
ALGAL PROBLEMS
Aesthetic Impairment
High algal densities lead
to:
• High solids, low clarity
• High organic content
• Fluctuating DO and pH
• “Slimy” feel to the water
• Unaesthetic appearance
• Taste and odor
• Possible toxicity
ALGAL PROBLEMS
Taste and Odor
• At sufficient density, all algae can
produce taste and odor by virtue of
organic content and decay
• Some algae produce specific taste and
odor compounds that are released into
the water
• Geosmin and Methylisoborneol (MIB)
are the two most common T&O
compounds; these can induce T&O at
very low concentrations
ALGAL PROBLEMS
Taste and Odor
T&O by blue-greens
• Anabaena, Aphanizomenon, Microcystis, and
Oscillatoria are most common T&O
producers, but many other genera produce
T&O as well
• Geosmin and MIB often produced
• Odors usually include musty, grassy, and
septic
• May be produced by planktonic or benthic
growths
ALGAL PROBLEMS
Taste and Odor
T&O by greens
• Chara, Cladophora, Chlorococcales
(Dictyosphaerium, Scenedesmus, Pediastrum,
Hydrodictyon), Volvocales (Chlamydomonas,
Volvox), and desmids (Staurastrum,
Closterium, Cosmarium, Spirogyra) are
primary greens causing T&O, but almost any
genus can induce T&O at high density
• Main odors are fishy, skunky, musty, grassy
and septic (wide range, species-specific)
• Not usually as severe as with blue-greens
ALGAL PROBLEMS
Taste and Odor
T&O by diatoms
• Melosira/Aulacoseira, Stephanodiscus,
Cyclotella, Asterionella, Fragilaria/Synedra,
and Tabellaria are primary diatoms causing
T&O, usually only at high density
• Main odors are geranium, spicy and fishy,
with occasional musty or grassy scent
• Not as severe as with blue-greens unless
diatom density is very high
ALGAL PROBLEMS
Taste and Odor
T&O by goldens
• Synura, Dinobryon, Mallomonas, Uroglenopsis,
and Chrysosphaerella are major T&O
producers, others impart odor at high density
Main odors are cucumber, violet, spicy and
fishy
• Can produce substantial T&O even at low
density