Could you identify what caused the variation in ACSF among different water types? This seems to occur even when UVT is constant.

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1 Question Answer Could you identify what caused the variation in ACSF among different water types? This seems to occur even when UVT is constant. With polychromatic MP UV reactors, the UV dose is the integrated affect of wavelengths from 200 to 300 nm. The contribution to UV dose at each wavelength is affected by the UV absorbance of the water at that wavelength. For a given UVT at 254 nm, one can have different UV absorbance at other wavelengths. For example, the UV absorbnace at wavelengths below 240 nm can be very different for a fixed UVT at 254 nm because of varying nitrate concentrations. One also gets a different spectral UV absorbance for a given UVT at 254 nm whenusing the UV absorbers LSA or Super Hume during UV validation. How would you use the tables if the validation was done with a mix of different aquifer types? The guidance recommends that all water qualities be compared to the assumed values for each water source in the generic tables. If a validation included a mix of aquifers types, the UV absorbance of the mix should be compared to the assumed water quality and the most appropriate water source can be selected. What parameters are used for water quality in the CFD I modeling if UVT/UVA is evaluated across the spectrum? The UV intensity is predicted through out the reactor at wavelengths from 200 to 300 nm, typcially in 1 to 5 nm increments. Increments larger than 5 nm should not be used, since that starts to cause errors in the calculation of integrated UV dose. Would ASCFs be used in combination with a sleeve that blocks out low wavelengths? How do you know how your water interacts with those low wavelengths? If the sleeve selection is able to reduce the ASCF 1.0, the ASCF can be defaulted to 1.0. The guidance recommends that an ASCF value be used for all medium pressure disinfection applications even if the ASCF is less than the UVDGM cut off of 1.05 or The influence of the low wavelengths for a given application depend on the output of the lamps, the absorbance of the sleeves, and the absorbance of the water. If the ASCF modeling assumes the target pathogen has no action below 240 nm, the site specific water quality will not have a large influence on the ASCF calculations. If the site specific water quality and action below 240 nm are used in the modeling, the UV absorbance of the water and the output of the lamps below 240 nm must be monitored to determine how the lower wavelength influence disinfection performance.

2 Why would a we want to reduce/eliminate the lower wavelengths? Seems conservative to keep them, even if they are not accounted for in the ASCF. Validations that reduce or eliminate the lower wavelength are an option to reduce the ASCF to close to 1.0, depending on the sleeve and water type selection and validation microbes. Some validations are completed with sleeves that block the lower wavelengths for other water quality reasons (e.g., to prevent the photolysis of nitrate to nitrite). In general, the presence of the low wavelengths will provide disinfection benefits even if the benefits are not accounted for in the ASCF calculations. To the knowledge of the speakers, We did not evaluate the economics of using the ASCF tables vs. is there a plant size where the validation-specific or site-specific ASCF calculations. Likely, the main reduction of power consumption of UV venders will conduct validation-specific calculations so that they UV reactors would begin to be maximize their ability to compete. Site-specific calculations could significant so this evaluation would lower the ASCF values by about 5 to 10 percent, depending on the UV be worthwhile or is it worthwhile spectra at the site. However, the opposite could also occur, for all plant size? depending on UV sensor placement relatiev to the lamps. If credit can be obtained for adenovirus at low wavelengths, what is the most resistant common virus of concern and does it is the response of that virus require less UV than crypto for the same target inactivation? There are some MP UV systems that have received credit for virus inactivation by validating their system with adenovirus directly and taking advantage of the low wavelengths emitted from the MP UV source. However, talking advantage of low wavelengths does require a low wavelength UV sensor. Other systems using LP UV (not emitting low wavelengths) have been validate by using a surrogate that can demonstrate higher doses. Adenovirus is the most resistant common virus of concern with all other viruses showing lower resistance to UV. Cryptosporidium is one of the most sensitive organisms to UV and is very easily killed. There are not any viruses that require less UV than Crypto for the same target inactivation. Do I understand correctly by saying that the main gain of the low wavelengths would be to improve virus log reduction with lower UV dose? Yes - the reason MP UV is more effective for adenovirus inactivation is due to the increased action at the low wavelengths. Because all virus log inactivation credit are based on adenovirus response to UV, virus log reduction would be improved (lower doses required for the same effect) in the presence of low wavelengths. Note that all other viruses of know waterborne health concern require about 1/4 of the dose required for adenoviruses for the same level of inactivation. Also note that realizing these benefits requires proper monitoring using low wavelength UV sensors, and those sensors are currently being developed by the UV system manufacturers. Is the uvdgm being revised with this - e.g. addition of these tables? The United States Environmental Protection Agency (USEPA) was a cosponsor of this guidance report, and at the time of publication does not plan to issue a revised UVDGM to include the ASCF calculations.

3 When may the report be available with all of the guidance that was discussed? How did the study confirm that low wavelengths were prevalent if sensors cannot measure wavelengths below ~220? Is the SBA regen waste a hazardous waste? Is the backwash solids from the ferrous addition a hazardous waste? We expect the report to be available at the end of July Please direct specific inquiries to the Water Research Foundation Staff. We can confirm UV output below 240 nm using a spectral radiometer that measures down to 200 nm. Yes, SBA regen waste is a hazardous waste. Backwash solids, if unsettled, are not hazardous (if settled, they may be depending on water quality). Does Biological Filtration has any room in Cr6 removal? Some recent studies have started to evaluate chromium removal with biological treatment, but testing has not been extensive. It may be of interest as a technology under some circumstances (e.g., co-occuring constituents removable with biological treatment, where brine disposal is challenging and use of the water source is not intermittent). More research would be needed to develop system design information. Other than Cr6, what Water Quality parameter interferes with removal of Cr6? What are the Cr(VI) concentrations in groundwater? What are the major ion chemistries of the Glendale and Livermore groundwaters? SO4-2 and CrO4-2 have same charge and coordination, so they are competing anions? Sorry I haven't read the study yet - but based on the presentation, it seems like the WBA resin is the most cost effective solution in conditions where ph adjustment is not a huge cost driver. Is that a fair statement? For SBA, sulfate is the primary water quality parameter that impacts removal of Cr6 (i.e., time to regeneration). Cr(VI) concentrations included ppb at Glendale and 10 ppb at Livermore for resins. RCF testing was 15 ppb influent. Major ion chemistries are shown in slide 32. They are both ions removed by SBA resin, although chromate is more selectively retained on resin. Cost effectiveness of the technologies requires analysis based on water quality and waste disposal options. What is the chloride concentration in the product water for SBA treatment? Sodium concentration? Resin is rinsed before being placed into service to remove sodium and chloride. No appreciable increase with respect to secondary MCLs was observed in the testing.

4 Compared to chlorine/chloramine, This wasn't tested in the Glendale/Livermore studies. A literature how effective is hydrogen peroxide review and/or testing would be needed to answer. is reoxidizing Cr(III)? Formaldehyde was found leaching while WBA was used. Did you anticipate the leaching before the study or you found out this during the study? How did you find out formaldehyde was leaching? thanks We did not anticipate the leaching based on discussions with the manufacturer, but the resin has a formaldehyde backbone so we analyzed for this in the VOC/SOC suite and tentatively identified compounds analyses. Is ph control or adjustment required for the RCF process? No ph control was necessary based on testing at Glendale.

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