Message Transféré De Shane
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Very good question! Yes, we actually quenched whenever we were doing kinetic work. I think it is discussed on our OS&E paper (see attached). We talk about the impacts of quenching agents in Trenholm et al. 2006 (attached). We did not test sulfite, but we did test thiosulfate, which we found to impact a few of our target compounds (i.e., prozac). We use sodium azide as a preservative, which reacts VERY quickly with ozone. So, we add azide to all our bottles and it can both quench and preserve; however, it reacts much slower with chlorine. Therefore, when we sample full-scale treatment plants, we add both azide and ascorbic acid (our preference for oxidant quenching). I attached another paper that may explain this a bit better.
I think you are looking at the Westerhoff paper where we did not quench ozone, perhaps. In that case, we were working with relatively small doses that had rapid decay. We usually do add a quenching agent/preservative.
Let me know if you have any other questions.
Cheers,
Shane
(See attached file: 2005 IOA17 EDC-keynote-proceedings.pdf)(See attached file: 2006-Snyder-Ozone-EDCs.pdf)(See attached file: 2006-Trenholm-methods.pdf)(See attached file: 2006-Trenholm-methods-supplemental.pdf)(See attached file: 2006-Vanderford-EST.pdf)(See attached file: 2007-WR-ozone-DBPs-Wert.pdf)
*********************************************** Shane Snyder, Ph.D. R&D Project Manager Applied Research and Development Center Southern Nevada Water Authority T: (702) 856-3668 F: (702) 856-3647 E: [email protected] W: www.snwa.com ************************************************* Michèle Prévost
Thanks Shane for the quick answer and too bad we missed each other. We have some kind of a lead crisis in Canada and I got stuck in that session.
We will try to stay away from the carrier. I would rather have losses as long as I can account for them. Did you quench your ozone when sampling? I read through the Huber paper and he used a fresh solution of sodium sulfite. I looked at one of your presentation that it said that you did not quench.
To quench or not to quench? with applied dosages of 3 mg/L ozone we need to quench to get removals vs CT. Have you heard about any impact of sulfite on the compounds? regards,
Michèle Prévost, Ph.D. Professeur Titulaire et Chercheur Principal Chaire Industrielle CRSNG en Eau Potable Génies Civil, Géologique et des Mines École Polytechnique de Montréal C.P. 6079, succ Centre-Ville Montréal, Québec, Canada H3C 3A7 www.polymtl.ca/chaireeau ______Tel: 514 340 4778 ou 514 340 4711 poste 5924 Fax: 514 340 5918 Email:[email protected]
[email protected] a écrit : > Greetings. Indeed I had a nice conversation with your student. My > suggestion on the methanol is to not use it at all. It is always going to > be a problem, or at least questioned by the ozone experts. I believe other > solvents to be better, but in future efforts we are going to try to use no > appreciable solvent carriers. We have thought to place the spike mixture > on glass petri dishes, then immerse/mix them with the water. As long as we > are measuring the before/after concentrations, some loss to evaporation is > not really an issue. Most of our new work is using "natural" matrices > where we do not need to spike at all, but of course, this is not ideal for > all situations. If you need to use solvent carriers, then I recommend > looking at the ozone rate constants and choosing the carrier with the > lowest rate constant (like dichloromethane). > > As far as the filtration, some plants filter before ozone (like the new > plant we are building now). Yes, filtration will lower the demand! In > our case, we shoot for ozone CT (residual) and as long as CT is constant, > the contaminant destruction is relatively constant among the waters tested. > In our most recent project, we are using UF before ozone. The UF filtered > water exhibited around 25-30% lower ozone demand. > > Well, I really need to run to a meeting. Please stay in touch and let me > know if you need any additional information. > > Best Regards, > > Shane > > *********************************************** > Shane Snyder, Ph.D. > R&D Project Manager > Applied Research and Development Center > Southern Nevada Water Authority > T: (702) 856-3668 > F: (702) 856-3647 > E: [email protected] > W: www.snwa.com > ************************************************* > >> Michèle Prévost
> > Hi Shane, > > I believe that you met my student in Toronto and that your are going > with online analysis as well. Liza (our post-doc) should be done with a > draft of her first paper soon and we will send it to you. > > We are preparing to conduct some ozonation spiking bench sacle tests in > parallel to our full scale measurements of pre and post ozonation water. > > I recall that you reported issues with methanol when using your spiking > concentrate in a 25L volumes > Any suggestions other than minimizing the concentration of methanol? > > We also noticed that you pre-filtered all samples on 0,7 and 0,45um > membranes. As we will be comparing our results with full scale plants, > we did not intend on filtering the samples. Any ozone demand and/or > adsorption will also occur in our samples. Any thoughts on that? > > Thanks > > Michèle > > > > -- > Michèle Prévost, Ph.D. > Professeur Titulaire et Chercheur Principal > Chaire Industrielle CRSNG en Eau Potable > Génies Civil, Géologique et des Mines > École Polytechnique de Montréal > C.P. 6079, succ Centre-Ville > Montréal, Québec, Canada -----