ADVANCES IN UV TECHNOLOGY AND THE OPTION TO USE UV FOR 4-LOG VIRUS DISINFECTION DURING PRIMARY DISINFECTION OF GROUNDWATER BEFORE DISTRIBUTION

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1 ADVANCES IN UV TECHNOLOGY AND THE OPTION TO USE UV FOR 4-LOG VIRUS DISINFECTION DURING PRIMARY DISINFECTION OF GROUNDWATER BEFORE DISTRIBUTION Scott Bindner, Trojan Technologies* Greg Warkentin, Trojan Technologies Adam Festger, Trojan Technologies * Trojan Technologies, 3020 Gore Road, London, Ontario, Canada, N5V 4T7 INTRODUCTION Groundwater is an important source of municipal drinking water in Ontario. In the province, over 140 million cubic liters of groundwater were delivered for municipal use in Due to its natural filtration, water from groundwater aquifers is generally considered to contain fewer pathogens than surface waters. However, there are concerns that groundwater supplies are becoming increasingly exposed to pathogens (including bacteria and viruses) due to aging and expanding wastewater collection systems as well as failing septic systems. In partial response to these concerns, drinking water guidelines including the United States Environmental Protection Agency s (USEPA) Groundwater Rule (GWR) and the Canadian Drinking Water Guidelines suggest, and in many cases require, that extracted groundwater be treated to ensure 4-log (99.99%) disinfection of enteric viruses. Supporting the hypothesis that such treatment will lead to tangible health benefits, recent epidemiological studies (Lambertini, et al., 2011) detected various viruses, including adenovirus, in non-disinfected groundwater and have linked these pathogens to gastrointestinal illnesses in small communities relying on groundwater resources. The increasing risk of exposed groundwater supplies to pathogenic contaminants is leading some public water systems (PWS) which extract groundwater to enhance the level of treatment, in particular primary disinfection, before the treated water enters distribution systems. Primary disinfection of groundwater, in particular virus disinfection, is commonly carried out with chlorine. Ultraviolet (UV) technology up until now has not traditionally been used due to the relatively high UV doses required to accomplish 4-log virus disinfection. Adenovirus in particular has demonstrated UV resistance such that the USEPA, which used adenovirus as its target virus, requires validated UV doses of greater than 186 mj/cm 2 to achieve 4-log disinfection of all enteric viruses. Validated doses of this magnitude often require calculated reduction equivalent doses (RED) of greater than 250 mj/cm 2 to be achieved during thirdparty bioassay validation of the UV reactor in order to account for the validation factor (described in greater detail in USEPA 2006). Comparatively, UV doses used for more traditional drinking water treatment applications often require calculated REDs of 40 mj/cm 2 or less.

2 Recent advances in UV technology have resulted in third-party-validated UV systems designed for 4-log inactivation of virus (including adenovirus) with a single low-pressure high-output (LPHO) UV system. This was accomplished by carrying out UV reactor validation using the spore Aspergillus brasiliensis (Petri et al., 2011) as a surrogate organism. A. brasiliensis like adenovirus, is resistant to UV and measured REDs when using A. brasiliensis were accurately calculated to be as high as 400 mj/cm 2 during bioassay validation. More commonly utilized surrogates such as MS2-bacteriophage are more difficult to culture to high enough titers to demonstrate these high REDs. However, similar to MS2-bacteriophage, A. brasiliensis meets the requirements of a suitable surrogate organism as outlined by the USEPA s Ultraviolet Disinfection Guidance Manual (UVDGM) in that it is easily cultured, validation results can be easily repeated, it is stable over long periods of time, and is also non-pathogenic. This paper reviews the rationale used by PWSs in small communities dependent on groundwater to install UV technology as their exclusive treatment technology for primary disinfection of their groundwater. METHODOLOGY This paper s focus primarily centers on a PWS located in rural Pennsylvania. The system in question was designed to treat 5.7 megaliters per day (MLD) of groundwater extracted from the Piedmont and Blue Ridge crystalline-rock aquifers. This site was required to install primary disinfection equipment capable of achieving 4-log virus inactivation in response to legislation set by the Pennsylvania Department of Public Health (PADEP) which stated all groundwater providers install primary disinfection equipment regardless of the quality of groundwater available. The PWS installed two (2) TrojanUVSwift SC (Small Community) low-pressure high-output (LPHO) UV reactors to carry out primary treatment. These UV systems were third-party validated to inactivate 4-log virus in accordance with the validation protocol established in the UVDGM and using the A.brasiliensis surrogate described in Petri et al., The decision to utilize UV disinfection for primary treatment was made as a result of three main drivers: reduced footprint, non-chemical disinfection and safety. RESULTS Reduced Footprint Chlorine and chlorine-based chemicals such as chloramines have arguably been the most common disinfection approach taken by PWSs for both primary and secondary (residual) disinfection. However, one of the drawbacks associated with chemical-based disinfection is the contact time (CT) required to achieve the necessary disinfection credits. Often, achieving the necessary CT requires extensive infrastructure such as large contact tanks or extensively meandering channels and pipes. In the case of the Pennsylvania site, it was evaluated that an

3 Added Footprint (m 3 ) Chemical Disinfection 3 UV Disinfection FIGURE 1: REQUIRED FOOTPRINT TO INSTALL PRIMARY DISINFECTION EQUIPMENT AT THE PENNSYLVANIA SITE additional 130 meters of 900 millimeter diameter pipe would have been required to achieve a CT great enough for 4-log virus credited primary treatment. This additional infrastructure would have resulted in over 80 cubic meters of increased footprint. Conversely, the two LPHO UV systems installed only required 3 cubic meters of footprint, including both the reactors and necessary controls (Figure 1). Non-Chemical Disinfection Interactions between free chlorine and natural organic matter (NOM) as well as other possible inorganic compounds potentially leads to the formation of unwanted disinfection by-products (DBP), the most highly regulated of which are trihalomethanes (THM) and haloacetic acids (HAA). Specifically, the Canadian Drinking Water Guidelines require that treated drinking water sent to end-users contain less than 100 μg/l of THMs and less than 80 μg/l of HAAs. Formation of DBPs is a concern as prolonged exposure in particular to THMs and HAAs has been linked to some forms of cancer with the strongest data suggesting heightened risks for bladder cancers (Villanueva et al., 2004; Villanueva et al., 2003) as well as data for colon, rectal and kidney cancers (Hildesheim et al., 1998; Mills et al., 1998). Reducing the quantity of chlorine used for disinfection by incorporating a nonchemical-based method of disinfection like UV technology is a recognized approach to reducing levels of DBPs delivered to end-users (Becker et al., 2013). Decreases in THMs and HAA resulting from a switch to non-chemical-based disinfection are site dependent and their magnitude depends on a number of factors which influence DBP production including but not limited to levels of total organic carbon (TOC), water temperature and ph. However, sample data taken from sites which have fully or partially replaced chlorine-based primary disinfection with UV disinfection have shown that the overall quantity of THMs can decrease by over 50% (Figure 2).

4 100% Sum of THM Concentration Ratios (Actual/Regulated) 80% 60% 40% 20% 0% Chemical Disinfection UV Disinfection FIGURE 2: THM CONCENTRATIONS AS PERCENTAGE OF THE LOCAL REGULATORY LIMIT Safety Chemical-based disinfection is commonly carried out using gaseous chlorine stored in high-pressure chambers. Operation of these chambers generally requires extensive monitoring in an effort to prevent accidental leakage of chlorine gas or possible explosions. Studies have been carried out which have assessed the possible risks of unwanted emissions of chlorine gas and possible effects on workers, the local population and environment (Artimani, et al., 2012). Chemical alternatives to using chlorine gas such as the use of liquid sodium hypochlorite are also options to reduce the risks of potential industrial accidents. However, storage of sodium hypochlorite is difficult as it takes up more footprint than chlorine gas and has a shorter half-life and cannot be stored for long periods of time. As a result, PWSs relying on bulk deliveries of sodium hypochlorite require frequent replacements and higher operating costs. Performance The installation in Pennsylvania has been in operation since July 2012 and performance data collected throughout the remainder of that year demonstrated that the UV systems maintained USEPA validated doses of greater than 186 mj/cm 2 (Figure 3) and met the requirements of the PADEP to achieve 4-log virus inactivation and eliminate the need to use chlorine gas to carry out the required primary disinfection of groundwater.

5 Validated Dose (mj/cm 2 ) mj/cm Flow (liters/second) Operating Dose Target Dose Flow Rate (L/s) Jul-12 Aug-12 Sep-12 Oct-12 Nov-12 Dec-12 0 FIGURE 3: REAL-TIME PERFORMANCE DATA DEMONSTRATING UV DOSES AT AN LPHO UV INSTALLATION DESIGNED FOR 4-LOG VIRUS DISINFECTION. CONCLUSIONS Despite the fact that groundwater resources are considered to be of higher purity, municipalities dependent on groundwater often require extensive primary disinfection before distribution to remove pathogens which could potentially enter groundwater due to deteriorating wastewater infrastructure and septic systems. Enteric viruses are arguably the most significant pathogens of concern and are frequently targeted in primary disinfection. PWS which are required to install primary disinfection for viruses as a result of local regulations or the detection of fecal coliforms as per the GWR and Canadian Drinking Water Guidelines could benefit from the incorporation of UV technology as opposed to alternative chemical-based disinfection approaches. Specifically, installation of UV technology requires much less footprint then what s required to establish the necessary CT using chlorine. In addition, chemical-free disinfection methods prevent the formation of potentially unwanted DBPs and improve overall site safety. REFERENCES AND CITATIONS Artimani, J.S., M. Arjmand, and M.R. Kalaei Modeling and Assessing Risk Analysis of Chlorine Gas in Water Treatment Plants. 2(6): pp Becker, W., B. Stanford, and E.J. Rosenfeldt Guidance on Complying with Stage 2 D/DBP Regulation. Water Research Foundation. Denver, CO, United States.

6 Hildesheim, M.E., K.P. Cantor, C.F. Lynch, M. Dosemeci, J. Lubin, M. Alavanja and G.G. Craun Drinking Water Source and Chlorination Byproducts: Risk of Colon and Rectal Cancers. Epidemiology. 9(1): pp Lambertini, E., S.K. Spencer, B.A. Kieke Jr., F.J. Loge, and M.A Borchardt Virus contamination from operation and maintenance events in small drinking water distribution systems. Mills, C.J., R.J. Bull, K.P. Cantor, J.S. Reif, S.E. Hrudey and P. Huston Workshop Report. Health Risks of Drinking Water Chlorination by-products: Report of an Expert Working Group. Chronic Disease in Canada. 19(3): pp Petri, B., S. Hayes, A. Festger, O.K. Schieble, C. Shen, P. Patil, C. Odegaard and I. Gobulukoglu Use of a High-Resistance Challenge Organism for Validation of Low Pressure, High Output UV Reactors for Virus Inactivation; North American Conference on Ozone, Ultraviolet and Advanced Oxidation Technologies, Toronto, Ontario, Canada. September 18-20, Villanueva, C.M., K.P. Cantor, S. Cordier, J.J.K. Jaakkola, W.D. King, C.F. Lynch, S.Porru and M. Kogevinas Disinfection By-products and Bladder Cancer a Pooled Analysis. Epidemiology. 15(3): pp Villanueva, C.M., F. Fernandez, N. Malats, J.O. Grimalt and M. Kogevinas Meta-Analysis of Studies on Individual Consumption of Chlorinated Drinking Water and Bladder Cancer. Journal of Epidemiology and Community Health. 57: pp