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UV Advanced Oxidation for Treatment of Taste and Odor and Algal Toxins

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Presentation on theme: "UV Advanced Oxidation for Treatment of Taste and Odor and Algal Toxins"— Presentation transcript:

1 UV Advanced Oxidation for Treatment of Taste and Odor and Algal Toxins
Ohio AWWA Annual Conference Research Workshop September 20, 2011 Erik Rosenfeldt, PE, PhD

2 Presentation Agenda Algae issues
Taste and Odor Toxic Substances Climate change impacts on algae events UV Advanced Oxidation Fundamentals Treatment of taste and odor, toxins Comparisons with other technologies Summary and Conclusions

3 Algae Issues Seasonal algae blooms present many problems for water utilities Depleted oxygen Turbidity Taste and Odor Cyanobacteria “Blue-green” algae Not quite algae, not quite bacteria Photosynthetic but lack well-defined nucleus Responsible for Taste and Odor compounds Create and may release toxic compounds

4 Algal Taste and Odor Compounds
Methylisoborneol (MIB) and geosmin Musty/earthy odor detectable at low (5-10 ng/L levels) Non-toxic Released by cyanobacteria Not regulated, but public perception rules

5 Cyanotoxins Some blue-green can produce one or more toxins
Do not produce toxins at all times Toxins can affect Fish and other aquatic life Livestock Pets Humans Exposure routes in humans Dermal Oral (water or food) Inhalation Dialysis Included on US EPAs CCL3 Produce toxins during genetic strain, growth phase, competition, environmental conditions

6 Cyanotoxins Species Dermatoxin (Irritant) Hepatoxin (Liver)
Neurotoxin (Nervous) Taste/Odor Compound Aphanacapsa spp. microcystins Microcystis spp. microcystins, nodularin anatoxins Snowella spp. Synechococcus spp. MIB, Geosmin Woronichinia spp. Lyngbya spp. Lyngbyatoxins saxitoxins MIB Oscillatoria spp. Aplysiatoxins anatoxins, saxitoxins Planktothrix agardhii Pseudoanabaena spp. Anabaena spp. microcystins, cylindrospermopsin Anabaenopsis elenkii Aphanizomenon spp. Geosmin Cylindrospermopsis raciborskii cylindrospermopsin Nordularia spp. Tedesco et al, 2011

7 Cyanotoxin Occurrence
Indiana data Yearly occurrence Occurs during algal blooms Late summer, early fall Toxins typically released during lysis Algae mitigation processes can make problem worse Tedesco et al, 2011

8 Cyanotoxins in Ohio Lake Erie and Grand Lake St. Marys Algal Blooms
Last year: Ohio EPA testing revealed 0.23 and 0.16 ppb Microcystin in two treated drinking waters Lake Erie Source: Potassium Permanganate, PAC, Lime Softening, Filtration, Chlorine Raw water filtration, Ozone, adsorption clarifier, chlorine disinfection

9 Cyanotoxins and Taste and Odor
USGS 2010 study (ES&T 44, 7361 – 7368) Sampled 23 Midwest lakes Multiple toxin classes co-occurred in 48% Toxins and T&O co-occurred in 91% No health risks during T&O outbreaks?

10 Climate Impacts on Algae
Temperature Warmer temperatures encourage blooms (Pearl and Huisman, 2008) Warmer temperatures increase the odor intensity of VOCs at very low concentrations, increasing consumer detection (Whelton et al., 2004) Precipitation Long antecedent dry periods increase nutrient content of runoff Low rainfall can cause stagnant conditions in the watershed Wind/storms Heavy storms and strong wind can mix reservoirs, reintroducing nutrients into the water column from bottom sediments

11 Northeast Climate Projections
Temperature 3° to 7°C temperature increase by 2100 (Frumhoff et al, 2007) More frequent days over 35°C (Karl et al, 2009) Precipitation 5 to 10% increase, mostly in fall and winter (Frumhoff et al, 2007) Storms Increasing trends in extreme precipitation (Spierre and Wake, 2010)

12 What will OH’s climate look like?
Lower Emissions Scenario Higher Emissions Scenario Adapted from Frumhoff et al, 2007

13 What can be done? Algae blooms are getting more prevalent and potentially more dangerous Fortunately, algae typically only occur in the summer months Several treatment processes are effective Activated Carbon GAC PAC Ozone UV Advanced Oxidation (UV AOP)

14 Advanced Oxidation Processes
An effective process for disinfection and chemical oxidation, capable of providing barriers for protecting public health and improving public perception Pharmaceuticals, Personal Care Products, EDCs Crypto, Viruses, E. coli, etc. AOPs work by creating hydroxyl radicals (•OH) •OH then blast away at organic chemicals Usually an expensive chemical process Complex chemistry UV Based AOPs UV/H2O2, UV/O3, UV/HOCl, etc. Ozone Based AOPs Ozone/H2O2, Ozone/NOM, Ozone/pH

15 UV/H2O2 AOP H2O2 absorbs UV energy and degrades to 2 OH radicals
Only 1 OH radical per UV photon Due to “water caging” H2O2 OH Org OH UV Absorbance of H2O2 Org H2O2 OH OH H2O H2O H2O2

16 Fundamentals – UV/H2O2 AOP
16 Fundamentals – UV/H2O2 AOP Pollutant or Constituent OH radical rate constant (M-1 s-1) Reference MTBE Atrazine NDMA MIB Geosmin Bisphenol-A 17-b-Estradiol 17-a-Ethinyl Estradiol 4-Nonylphenol Para-Chlorobenzoic Acid Nitrobenzene Methanol NOM (TOC) HCO3- CO3-2 H2O2 1.9x109 3x109 3.3x109 8.2x109 1.4x1010 1.02x1010 1.41x1010 1.08x1010 5.65x109 5x109 3.9x109 9.7x109 2.5x104 (L mg-1 s-1) 8.5x106 3.9x108 2.7x107 Acero et al., 2001 Acero et al., 2000 Wink and Desrosiers, 1991 Glaze et al., 1990 Rosenfeldt and Linden, 2004 AWARF, 2006 Elovitz and von Gunten, 1999 Buston et al., 1988 Buxton et al., 1988 Larson and Zepp, 1988 Hoigne et al., 1985; Buxton et al, 1988 Hoigne et al., 1985; Buxton et al., 1988 AOP  High powered oxidation of contaminants via OH radical intermediate OH radical is very reactive with “targets” OH radical is also reactive with “scavengers”

17 Differences between UV disinfection and AOP
Some fundamental differences in Levels of Applied UV Energy Fundamental Mechanisms UV Dose (ie what does it mean?) Different “Targets” Disinfection Photolysis AOP

18 UV AOP for Taste and Odor
UV Photolysis UV Advanced Oxidation Rosenfeldt and Linden, 2005 UV Advanced Oxidation for Geosmin Oxidation at Cornwall, ON TrojanUV, 2010

19 UV AOP for Algal Toxins UV and UV AOP for m-LR destruction
UV AOP for MIB and algal toxins at Cornwall, ON Alvarez et al, 2010 Approximate Geosmin removal UV and UV AOP for m-RR destruction Faster due to photolysis of Microcystin and Anatoxin TrojanUV, 2010 Qiao et al, 2005

20 Taste and Odor as a surrogate for toxin oxidation?
Characteristics of a good surrogate Co-occurrence (Graham et al, 2010) Microcystin co-occurred with geosmin in 87% of blooms, with MIB in 39%. Anatoxin-a co-occurred with geosmin in 100% of blooms, with MIB in 43%. Similar trends of occurrence (Graham et al, 2010) Although toxins and T&O frequently co-occurred, concentrations were not strongly correlated (r < 0.4, p > 0.1) Not surprising because they are not produced by the same biochemical pathways Surrogate is conservative Microcystin LR and Anatoxin degraded faster than MIB, but not geosmin

21 Why UV AOP makes some sense
“Instant-on” technology Effective Disinfection / Innovative Technology Comparable replacement for other T&O treatment processes Pantin, 2009

22 Why UV AOP makes some sense
Cornwall, ON Trojan UV SwiftTM ECT Reactors (MP technology) UV system serves in disinfection mode” most of the year (4 of 8 lamps running) Can “ramp-up” to AOP conditions seasonally (8 lamps running, add H2O2) 5 operational levels  UV dose ~ 400 – 60 mJ/cm2 H2O2 varies 1, 2, 4, 8, 15 mg/L UV AOP replaces GAC filter caps for T&O control ($100,000/yr for GAC replacement). UV provides excellent disinfection barrier Cornwall relies on ad-hoc “odor panel” – municipal employees and research scientists – in the service area to determine when to “ramp-up” to AOP conditions. Pantin, 2009

23 Why UV AOP makes some sense
Neshaminy Water Treatment Plant Civardi and Lucca, 2010 (OAWWA and Tricon) compared costs and carbon footprint for 20 year design life 15 MGD Plant, Desired 1 log removal of “Geosmin and MIB” Assume 90 days per year of use (each is “instant-on”) UV-H2O2 AOP PAC Capital $2.5 mil $2.2 mil O&M $200,000 $310,000 Equivalent Uniform Annual Cost (4%) $384,000 $475,000 1 log Geosmin oxidation only 0.5 log MIB oxidation Civardi and Lucca, 2010

24 Why UV AOP makes some sense
Byproducts? In most cases, this is a major impact on AOP feasibility Eg: Estrogenic activity of BPA goes away slower than BPA BPA

25 Byproducts In the case of UV AOP treatment of taste and odor and toxins, the story is simpler… Taste and odor and toxic action are very dependent on molecular structure Small changes in structure (ie oxidation, phototransformation, etc.) will likely diminish toxicity significantly Anatoxin-a 250 mg/kg Anatoxin-a(S) 20 mg/kg MIB No toxicity

26 Wrap Up Algal toxins and algae related taste and odor outbreaks are both caused by seasonal, cyanobacteria outbreaks Recent research has indicated that presence of taste and odor (geosmin particularly), correlates well with presence of algal toxins UV Advanced Oxidation effectively degrades both T&O and algal toxins In general, MIB < Geosmin ~ Anatoxin << Microcystin Cost and carbon footprint similar to Activated Carbon “Instant-on” Technology

27 Parting thought… “Drinking water purveyors frequently tell customers during taste-and-odor outbreaks that there are no health risks. In our study, however, taste-and-odor causing compounds were always accompanied by cyanotoxins, highlighting the need for water purveyors to increase cyanotoxin surveillance during taste-and-odor outbreaks so that treatment can be modified accordingly, and to verify that cyanotoxins are not present at or above thresholds of potential health risk.” Graham et al, 2010

28 Questions? Erik Rosenfeldt, P.E., PhD Hazen & Sawyer Fairfax

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