UV Advanced Oxidation for Treatment of Taste and Odor and Algal

28 Pages·2011·1.82 MB·English

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TTrreeaattmmeenntt ooff TTaassttee aanndd OOddoorr
aanndd AAllggaall TTooxxiinnss
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2
Presentation Agenda
•
Algae issues
(cid:1)
Taste and Odor
(cid:1)
Toxic Substances
••
CClliimmaattee cchhaannggee iimmppaaccttss oonn aallggaaee eevveennttss
•
UV Advanced Oxidation
(cid:1)
Fundamentals
(cid:1)
Treatment of taste and odor, toxins
(cid:1)
Comparisons with other technologies
•
Summary and Conclusions
3
Algae Issues
•
Seasonal algae blooms present many problems
for water utilities
(cid:1)
Depleted oxygen
(cid:1)
Turbidity
(cid:1)
Taste and Odor
•
Cyanobacteria
(cid:1)
“Blue-green” algae
(cid:1)
Not quite algae, not quite bacteria
•
Photosynthetic but lack well-defined nucleus
(cid:1)
Responsible for Taste and Odor compounds
(cid:1)
Create and may release toxic compounds
4
Algal Taste and Odor Compounds
•
Methylisoborneol (MIB) and geosmin
(cid:1)
Musty/earthy odor detectable at low (5-10 ng/L levels)
(cid:1)
Non-toxic
(cid:1)(cid:1)
RReelleeaasseedd bbyy ccyyaannoobbaacctteerriiaa
(cid:1)
Not regulated, but public perception rules
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Cyanotoxins
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Some blue-green can produce one or more toxins
(cid:1)
Do not produce toxins at all times
•
Toxins can affect
(cid:1)
Fish and other aquatic life
(cid:1)
Livestock
(cid:1)(cid:1)
PPeettss
(cid:1)
Humans
•
Exposure routes in humans
(cid:1)
Dermal
(cid:1)
Oral (water or food)
(cid:1)
Inhalation
(cid:1)
Dialysis
•
Included on US EPAs CCL3
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Cyanotoxins
Species Dermatoxin Hepatoxin (Liver) Neurotoxin Taste/Odor
(Irritant) (Nervous) Compound
Aphanacapsaspp. microcystins
Microcystisspp. microcystins, nodularin anatoxins
Snowella spp. microcystins
Synechococcus spp. microcystins MIB, Geosmin
Woronichinia spp. microcystins
LLyynnggbbyyaa sspppp.. LLyynnggbbyyaattooxxiinnss ssaaxxiittooxxiinnss MMIIBB
anatoxins,
Oscillatoria spp. Aplysiatoxins microcystins MIB, Geosmin
saxitoxins
Planktothrix agardhii Aplysiatoxins microcystins saxitoxins MIB, Geosmin
Pseudoanabaenaspp. MIB, Geosmin
microcystins, anatoxins,
Anabaena spp. MIB, Geosmin
cylindrospermopsin saxitoxins
Anabaenopsis elenkii microcystins
microcystins, anatoxins,
Aphanizomenon spp. Geosmin
cylindrospermopsin saxitoxins
Cylindrospermopsis
cylindrospermopsin saxitoxins
raciborskii
Nordularia spp. microcystins, nodularin
Tedesco et al, 2011
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Cyanotoxin Occurrence
Indiana data
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Yearly occurrence
•
Occurs during algal
bblloooommss
(cid:1)
Late summer, early fall
•
Toxins typically released
during lysis
(cid:1)
Algae mitigation processes
can make problem worse
Tedesco et al, 2011
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Cyanotoxins in Ohio
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Lake Erie and Grand Lake
St. Marys Algal Blooms
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Last year: Ohio EPA testing
revealed 0.23 and 0.16 ppb
MMiiccrrooccyyssttiinn iinn ttwwoo ttrreeaatteedd
drinking waters
(cid:1)
Lake Erie Source:
•
Potassium Permanganate, PAC, Lime Softening,
Filtration, Chlorine
(cid:1)
Lake Erie Source:
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Raw water filtration, Ozone, adsorption clarifier,
chlorine disinfection
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Cyanotoxins and Taste and Odor
•
USGS 2010 study (ES&T
44, 7361 – 7368)
•
Sampled 23 Midwest lakes
(cid:1)(cid:1)
MMuullttiippllee ttooxxiinn ccllaasssseess ccoo--
occurred in 48%
(cid:1)
Toxins and T&O co-occurred
in 91%
•
No health risks during T&O
outbreaks?
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Climate Impacts on Algae
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Temperature
(cid:1)
Warmer temperatures encourage blooms (Pearl and
Huisman, 2008)
(cid:1)
Warmer temperatures increase the odor intensity of VOCs at
very low concentrations, increasing consumer detection
((WWhheellttoonn eett aall..,, 22000044))
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Precipitation
(cid:1)
Long antecedent dry periods increase nutrient content of
runoff
(cid:1)
Low rainfall can cause stagnant conditions in the watershed
•
Wind/storms
(cid:1)
Heavy storms and strong wind can mix reservoirs,
reintroducing nutrients into the water column from bottom
sediments