PATHOGEN AND NUTRIENT REMOVAL DURING WASTEWATER TREATMENT AT A 21 ST CENTURY WASTEWATER TREATMENT PLANT

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1 PATHOGEN AND NUTRIENT REMOVAL DURING WASTEWATER TREATMENT AT A 21 ST CENTURY WASTEWATER TREATMENT PLANT Abstract Schmitz, B., 1 Gerba, C., 1 and Pepper, I. 1 1 The University of Arizona Corresponding Author Tel ; ipepper@ag.arizona.edu A new wastewater treatment plant (WWTP) was commissioned in Tucson in January This plant, Agua Nueva is unique in the United States in that it has dissolved air flotation instead of conventional primary sediment, and also a 5-stage Bardenpho process for nutrient removal (N&P) from the effluent. Finally, it has a large contact chamber for chlorination that allows for a large Ct value for disinfection. A second modern WWTP (Tres Rios) contains modified Bardenpho and Ludzack-Ettinger basins. In this presentation we will report the influence of these new treatment trains on effluent quality with respect to nutrient (N&P) content and pathogen removal (virus and fecal coliform). These two parameters have important implications for both ecological and human health. Keywords Bardenpho process; virus removal; wastewater treatment Agua Nueva and Tres Rios Water Reclamation Facility In 2013, Tucson Arizona had two major conventional WWTPs: Roger Rd WWTP and Ina Rd WWTP. Due to a need to reduce total nitrogen concentrations in effluent discharged into the Santa Cruz River, the Pima County Regional Wastewater Reclamation Department implemented a Regional Optimization Master Plan (ROMP). Implementation of ROMP (a $673m project) comprised of several components: Decommissioning Roger Rd WWTP in December 2013 Commissioning the new Agua Nueva WWTP (32 mgd) in January 2014 Upgrading and expanding Ina Rd WWTP into the newly named Tres Rios WWTP (50 mgd) Building a new interconnect sewer pipeline to allow transfer of solids from Agua Nueva to Tres Rios and subsequent anaerobic digestion Figure 1: Agua Nueva and Tres Rios Water Reclamation Facility

2 Objectives Evaluate efficacy of modern WWTPs (Agua Nueva and Tres Rios) to inactivate/remove human pathogenic viruses during treatment Compare removal with conventional WWTPs (Ina Rd and Roger Rd) Evaluate 5 model viruses as potential indicators of sewage contamination Study #1 Monitoring at Conventional WWTPs In a previous study 7 viruses were monitored at two conventional WWTPs for a 1 year period utilizing qpcr. The Roger Rd plant utilized a trickling filter process for secondary treatment. The old Ina Rd plant activated sludge for secondary treatment. Analysis of influent and effluent collected from Roger Rd and Ina Rd WWTPs allowed for estimates of the abundance of the viruses in wastewater; any seasonal effects on incidence; and efficacy of treatment for virus removal. These parameters were used to evaluate which of the 7 viruses would be best suited to be a model indicator of sewage contamination. Data were collected from August 2011 to July The treatment trains of the two plants are shown in Figure 2. Figure 2: Ina and Roger Rd WWTP trains The viruses monitored were: - Enterovirus - Adenovirus - GI, GII, GIV, Norovirus - Aichi virus - Pepper mild mottle virus Data shown in Figure 3 illustrate that the Pepper Mild Mottle Virus proved to be the best candidate for a model indicator of sewage contamination. This is a plant virus that infects chile and bell peppers. The fact that a large percentage of any community ingests peppers on a somewhat regular basis, results in a high incidence of the plant virus in sewage at any point in time. Thus seasonal effects are low. In addition, the virus passes

3 intact through the human gut, and is likewise resistant to wastewater treatment. All of these factors make the Pepper Mild Mottle Virus a conservative tracer of sewage contamination. Figure 3: Incidence of the Pepper Mild Mottle Virus in the influent and effluent of Ina Rd and Roger Rd WWTPs (From Kitajima et al., Sci. Tot. Environ. 488: ) Study #2 Monitoring at Modern WWTPs The Roger Rd plant was decommissioned in December The new Agua Nueva plant was commissioned in January At this same time, the old Ina Rd plant was upgraded with new technologies and renamed Tres Rios. Included in the upgrade was the development of two treatment trains, the East and West trains. Thus Agua Nueva and Tres Rios now provide the opportunity for the evaluation of three new treatment trains with respect to efficacy of virus removal (Figure 4a&b).

4 a. b. Figure 4a&b: Treatment trains at the Tres Rios and Agua Nueva Plants

5 Thus a second study was initiated in July The second study has involved monitoring the incidence of viruses in the influent and effluent of Agua Nueva and Tres Rios WWTPs for a 1 year period. Since the sewage provided to these two plants came from the same community and location as the sewage in the first study, then the data from both studies are directly comparable. Based on the data from the first study the viruses chosen to be monitored were: - Enterovirus - Adenovirus - GIV Norovirus - Aichi virus - Pepper Mild Mottle Virus These viruses are being monitored monthly in influent and effluent for a 1 year period via qpcr. To date we have five monthly sample sets from both treatment plants. These preliminary data suggest that the Tres Rios West Train is the most efficient with respect to virus removal followed by the Tres Rios East Train. These trains removed more viruses from the effluent than Agua Nueva or the old Ina Rd and Roger Rd WWTPs. However, it is important to note that treatment at Agua Nueva is still being optimized with respect to carbon inputs into the Bardenpho process. With respect to nutrient removal, Tres Rios and Agua Nueva are much more efficient for N removal than the older conventional plants. Thus overall, for the 21 st Century WWTPs, both nutrient and virus removal must be considered.