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A listing of webinars, symposia, and conferences relevant to this work.
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Groundwater Week
December 6-8 | Las Vegas, Nevada
Formally known as the Groundwater Expo, early bird registration for this event ends November 4.
2017 Annual Conference and Exhibit
January 22-25 | Boston, Massachusetts
Registration for this New Englakd Water Enivornment Association conference opens in November.
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Project Update from the DeRISK Center
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The Design of Risk-reducing, Innovative-implementable Small-system Knowledge (DeRISK) Center at the University of Colorado-Boulder is led by Dr. Scott Summers.
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The DeRISK Center’s overall objectives focus on applying principles of risk reduction, sustainability and new implementation approaches to innovative technologies that will reduce the risk associated with key contaminant groups and increase the chance of adoption and sustainable use in small systems.
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Progress to Nitrate Reduction in a Fiber-Optic/Light- Emitting Diode Photocatalytic Reactor
Kiril Hristovski and Paul Westerhoff, Arizona State University
Nitrate removal from contaminated sources via small-scale water treatment systems has primarily been conducted by employing physical-chemical treatment methods because of the risks and operational challenges associated with biological treatment of drinking water. The most common nitrate treatment technologies are ion exchange or reverse osmosis. Ion exchange processes may be tailored to selectively remove nitrate, but the media must be regenerated regularly, which generates concentrated high salinity brines. In contrast, reverse osmosis allows for unselective removal of dissolved constituents, stripping water of desired anionic and cationic minerals, while also generating concentrated brines. A transformative technology that could reduce nitrate to innocuous gaseous products would be desirable for nitrate reduction instead of translational approaches (aqueous to solid in same oxidation state). However, a major concern of transformative technologies is the undesired production of aqueous ammonium. Seeking a solution that provides nitrate reduction to innocuous gaseous products in lieu of aqueous ammonium generation at relatively low cost and energy requirement, our research group has focused on photocatalysis.
Photocatalysis is effective at destructive decontamination of organic constituents and some inorganic oxy-anions, in addition to reductive/sorption treatment of heavy metals. Photocatalysis is traditionally deployed in a slurry system with in-line immersed mercury lamps, similar to those utilized for UV-disinfection. The semiconductor catalyst, upon ultraviolet irradiation, produces aqueous radical species and promotes electrons (at irradiation energy greater than or equal to the bandgap) to the surface for aqueous phase reactions. Obstacles to implementation of slurry reactors are the separation of the nanoparticle catalysts, which require ultrafiltration membranes and may undergo some leaching into the supply water. Alternatives to discrete particles in a slurry are fixed-film processes, which combine a light-permeable substrate (often quartz for UV-applications), and catalyst coating on the surface. These are often at some distance from the irradiation source, which may cause efficiency losses in low transmittance water.
The evolution of fixed film processes has been significant in recent years in an effort to maximize photoactive surface area and light delivery to the catalyst while providing immobilization and higher emphasis on safe-by-design technologies. ASU is currently exploring the implementation a fiber optic/light emitting diode (FOLED) system (Figure 1) for reduction of nitrate from drinking water and ion exchange brine. This allows for catalyst immobilization onto the fiber optic substrate and fiber-LED pairing promotes direct photon delivery into the reactor via the fiber optics. Preliminary validation of this reactor design was completed with FOLED bleaching of methylene blue, a model organic contaminant dye with known quantum yield for comparative analysis. As radicals are formed at the catalyst-water interface, methylene blue becomes clear and the reduction in color can be measured using a spectrophotometer. The FOLED reactor outperforms a slurry system at equivalent catalyst dose by a factor of 7. Nitrate and nitrite reduction are far more complex than methylene blue, however, and provide the following challenges in treatment: nitrate to nitrite is kinetically rate limiting, undesired nitrogenous products such as ammonium must be properly avoided, and timescales for nitrate reduction to nitrogen gases are significant. Understanding how to best deliver sufficient light into the system has been identified as the greatest challenge. Secondarily, choosing a catalytic material with high kinetics for nitrate reduction to nitrite, which is readily reduced, is of primary focus. Nitrite was successfully removed in the FOLED system (Figure 2) at competitive kinetic rates and high quantum efficiency, with the 365nm LED outperforming the 318nm LED due to high quantum yield of nitrite in its acidic form, HONO, at 365nm (Φ=0.35-0.451). Nitrate reduction work is ongoing, but has been demonstrated utilizing UV-LEDs in a petri-dish with 1.5x enhanced removal than a medium pressure lamp on a per-photon basis.
References:
Vione, D., Maurino, V., Minero, C. & Pelizzetti, E. Reactions Induced in Natural Waters by Irradiation of Nitrate and Nitrite Ions. Environ. Photochem. Part II 2M, 221–253 (2005).
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Figure 1. Schematic sketch of fiber optic/light emitting diode system.
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Figure 2. Quantum efficiency, Φ, of nitrite reduction in FOLED system with 318nm or 365nm UV-LED irradiation and 0.02mg catalyst coating (1x) or 0.1mg catalyst coating (5x). Performed at 100mg-N/L initial NO2- and 40mM HCOOH with reactor volume of 10mL.
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Biomass Evolution in Full-Scale Anthracite-Sand Drinking Water Filters Following Conversion to Biofiltration
Stoddart, A.K., Schmidt, J.J., and Gagnon, G.A. (2016). Biomass evolution in full-scale anthracite-sand drinking water filters following conversion to biofiltration. Journal of the American Water Works Association, 108:12 (In Press). doi:10.5942/jawwa.2016.108.0154.
Why it's interesting: This study determined that the use of adenosine triphosphate has the potential to address the need for monitoring tools in biofiltration design, operation, and optimization.
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Full-Scale Implementation of Second-Stage Contactors for Manganese Removal
Bazilio, Arianne A., Kaminski, G.S., Larsen, Y., Mai, X., and Tobiason, J.E. (2016). Full-scale implementation of second-stage contactors for manganese removal. Journal of the American Water Works Association, 108:12 (In Press). doi:10.5942/jawwa.2016.108.0184.
Why it's interesting: In this study, second stage contactors successfully removed Mn at hydraulic loading rates of up to 10 gpm/ft2 with little head loss accumulation and effluent Mn concentrations typically ≤ 0.01 mg/L.
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University Lab Seeks Solution for Pesky PFCs
Public health researchers at the University of Minnesota are looking for a method of solidifying PFCs to make them easier to remove from drinking water.
Replacing All Lead Water Pipes Under EPA Consideration
A white paper released by U.S. EPA on October 26 states that the agency is considering lead service line replacement as part of its upcoming revisions to the lead and copper rule.
Researcher Developing Cost-Effective Water Treatment Technologies to Meet Industrial, Agricultural and Domestic Needs
New technology from Texas A&M researchers can help protect source water by removing a wide array of toxic metals from wastewater.
Clean Water-Treatment Option to Target Sporadic Outbreaks
A scientist at the University of Cincinnati has engineered an protein-based photocatalyst that generates hydrogen peroxide to eliminate E. coli, Listeria, and other outbreak-causing microbes.
As Drought Persists, Collaboration Seeks to Advance Technology that Helps Generate New Water Supply
The National Science Foundation has awarded University of California, Riverside professor Haizhou Liu $300,000 to help advance water reuse technologies for drinking water supplies.
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The two National Centers for Innovation in Small Drinking Water Systems, based at the University of Colorado - Boulder and the University of Massachusetts - Amherst, are collaborative research groups charged with examining and reducing the barriers of innovative treatment technology implementation at small drinking water systems. The funding for the centers comes from the U.S. Environmental Protection Agency as part of its Science to Achieve Results (STAR) program.
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