Ludwig Dinkloh, Xylem Services GmbH
Authors: Steffen Rueting, Harald Stapel, Hans Wijers
8:30 AM - 9:00 AM

The Dunea Water Company provides drinking water to over 1.3 Mio customers with an average flow rate of ~ 9,000 m³/h (57 MGD). The water source is the River Meuse. In a dead end side stream of the Meuse River, iron sulfate is dosed for coagulation. This side stream is used as a natural reservoir for self-purification. Dunea abstracts the water from the river and micro sieve it, and then it is transported to the pretreatment. The water is filtered over dual layer rapid sand filtration, and is now clean enough to infiltrate it and it is transported to the dune area. After a residence time of 3 months in the dunes the water is recovered and at three post treatment locations drinking water is produced.

Some organic micropollutants (OMPs) such as MTBE, bentazone and 1.4-dioxane are still measurable at low concentrations after the managed aquifer recharge.

Dunea therefore went through an extensive pilot phase from 2009-2012 in Bergambacht with a pilot plant capacity of 5 m³/h. 6 months of testing with combined process of O₃/H₂O₂ and UV were conducted. Both medium pressure and low pressure UV systems were evaluated. The bromate concentration needed to be below 0.5 µg/l.

The paper presents the results of the tests which led to the full-scale specification for a 2,200 m³/h AOP system.

The paper will then present the full-scale solution and operational experiences of this exceptional innovative solution securing safe water for 1.3 Mio customers.

Fateme Barancheshme, University of North Carolina at Charlotte
Authors: Olya Keen, Ph.D.
9:00 AM - 9:30 AM

The aim of this study is to assess the change in molecular weight (MW) distribution of natural organic matter (NOM), including that of algal origin, during advanced oxidation processes (AOPs) and determine the correlation between molecular size and disinfection byproducts (DBPs) formation. High performance size exclusion chromatography (HPSEC) equipped with Sievers M9 dissolved organic carbon (DOC) detector was used to assess the MW distributions of organic matter in drinking water samples before and after UV/Cl₂ and UV/H₂O₂ treatment. By doing so, the effect of AOPs on MW distribution of organic matter was assessed, and the study investigated which organic matter fractions are likely responsible for DBPs formation. Drinking water samples were collected with no background algal organic matter. AOPs were conducted on bench-scale and samples were exposed to UV doses up to 2000 mJ/cm2 to simulate full-scale UV dose range in AOPs. Some samples were spiked with extracted algal organic matter. The MW distribution of organic matter in the water samples at different levels of treatment was assessed to determine any correlations with DBP formation. Formation of trihalomethanes and haloacetic acids was measured using EPA methods 551.1 and 552.3 after a uniform formation conditions test.

Gary Hunter, Black & Veatch
Authors: Bill Decker, Geoff Smith, James Powell,Julian Turbull
8:30 AM - 9:00 AM

UVC LED system have been developed for point of use application as well as for use in the potable drinking water market. Literature indicates that UVC LED systems have been relatively successful at smaller flows with high water quality requirements. LEDs use in wastewater provides some challenges that limit the overall throughput capacity. These challenges relate to not only water quality, design of the reactor, cooling of LEDs and hydraulics. Recent testing indicates that an understanding of the materials of the reactor construction may also play a role in the design of the system. This presentation provides results of modeling work conducted to enhance the efficiency of the UVC-LED system for wastewater. Modeling was conducted using FLUENT to ensure that the hydraulic design was optimized before the radiation model was incorporated into the design. Prototype reactors were developed and tested based on the results. The findings and recommendations of the modeling approach will be presented.

Shawn Verhoeven, GAP EnviroMicrobial Services Ltd.
Authors: Daniella Mosqueda, Linda Sealey, Jessica Patterson, Conrad Odegaard
9:00 AM - 9:30 AM

We have seen that the type of water used, whether de-chlorinated tap, ground, ultrafiltered, de-ionized, distilled or waste water, or certain water types mixed with UVT modifiers, can have a dramatic effect on the log reductions of MS2, and other bacteriophage, measured through ultraviolet (UV) reactors, in collimated beam experiments and in ultrafiltration (UF) flow through tests. This impact is important to understand while performing a validation of a water disinfection technology, including UV systems and ultrafilters, as enhanced inactivation of a surrogate microbe will result in in over stating the performance when compared to a real-life installation. Essentially, a flow through validation is an experiment to prove that a certain disinfection technology is effective in reducing harmful contaminates, and quality control is important to any experiment. Validation protocols do have quality control procedures in place such as prescribed in the UVDGM, NWRI, and NSF guidance, but the water used for testing is often not scrutinized enough. This is particularly concerning when looking at the 2019 revision of NSF 55 for UV LED systems where no collimated beam test is required, and the current NWRI guidance where a standard curve is used for stating a dose with wide QC bounds.

We will show how enhancing the quality control, through use of a UV collimated beam test, is essential for all flow through validation testing, not only UV disinfection systems. We will outline the various water interactions showing enhanced log removals compared standard curves for MS2 and the steps we suggest implementing as part of a quality control procedure prior to, and during, validation to ensure results obtained using a surrogate microbe translate to real-world results.

Olya Keen, UNC Charlotte
Authors: Justine Gleason, Daniel Burbes
10:30 AM - 11:00 AM

Quenching of residual hydrogen peroxide (H₂O₂) after advanced oxidation processes is one of the biggest operational challenges, especially for UV/H2O2 processes where high concentrations of H₂O₂ are necessary due to its low UV absorbance. Effective quenching is particularly important for drinking water treatment, as residual H₂O₂ has a high chlorine demand

Use of chlorine or granular activated carbon are two of the main alternatives currently in practice, both of which have their drawbacks.

This study investigated the possibility to use solid inorganic materials known to react with hydrogen peroxide as alternative quenching agents. While many transition metals fall into this category, the study focused on materials that are naturally abundant, commercially available, and would be safe to use in drinking water treatment. A preliminary batch study identified aluminum oxide and iron oxide as promising options. In a comparative column test with granular activated carbon (GAC), aluminum oxide was not competitive with GAC, but iron oxide showed superior results. This work was followed up by a rapid small-scale column test (RSSCT) study with commercially available granular iron oxide and showed potential for full-scale use. The RSSCT column was operated for the equivalent of 3 years of a full-scale column and showed >90% removal of H₂O₂ at 18,000 bed volumes treated. Iron leaching and formation of hydroxyl radicals in the quenching reactions were evaluated as well.

Sofia Semitsoglou-Tsiapou, Biology Centre CAS
Authors: Travis B. Meador, David Kahoun, Pavla Fojtikova, Bo Peng, Lihini Aluwihare
11:00 AM - 11:30 AM

Organic molecules in the ocean store as much carbon (C) as exists in the atmosphere, thus their reactivity has important implications for the global C budget. Studies suggest that a substantial fraction of the complex, presumably recalcitrant, marine dissolved organic carbon (DOC) comprises of molecules rich in highly oxygenated, aliphatic functionalities. Although there may be multiple pathways by which these molecules are produced, we propose that photochemical degradation of algal metabolites via solar light in the presence of reactive radicals is a crucial source. Such abiotic formation of recalcitrant DOC can be tested using carotenoids and related structures as model compounds. This work aimed to characterize radical-assisted, solar degradation of known antioxidants as well as carotenoid-like compounds produced by a variety of organisms, including fungi and algae. The antioxidant activity of molecules harvested from culture media of five species of Ascomycota was assessed via the ABTS radical scavenging assay, exhibiting up to 45 mM Trolox equivalent, roughly 20-fold higher than that of b-carotene. A preliminary screening of both biomass and medium samples via liquid chromatography-mass spectrometry (LC-MS) revealed known antioxidants, such as semiquinones, carotenoids (canthaxanthin), and b-carotene degradation products (beta-apo-4'-carotenal and retinal). Consequently, five representative antioxidant standards were selected and their organic solvent-water aggregates were irradiated under solar light assisted by a constant dose of H₂O₂, mimicking OH-radical formation in the ocean’s euphotic zone. Degradation kinetics determined via UV-Vis spectroscopy revealed orders of magnitude differences in the reaction rate constants (fucoxanthin > b-carotene > astaxanthin > coenzyme Q10 > vitamin K₂), suggesting that heterogeneity in the aliphatic chain and headgroup linkage play important roles in reactivity and may yield distinct oxidation products. LC-QTOF (Quadrupole Time-of-Flight)-MS protocols were applied to identify the structures of reaction products, which were hypothesized to represent short-chain, water-soluble, hydroxylated, alicyclic, putative biomarkers of recalcitrant DOC.

Pao Chen, Violumas
Authors: Pratibha Sharma, PhD
10:30 AM - 11:00 AM

UVC LEDs: How heat dissipation influences reliability & optical output

All LEDs exhibit thermal behavior which directly relates their heat dissipation to expected performance. As the junction temperature of the LEDs increase, efficiency can decrease, specifically at higher driving currents, leading to a saturation in the optical output. This implies that LEDs with less thermal decay will exhibit more stable radiant flux over time, leading to better reliability.

For LEDs in the UVC range, where at least 95% of energy may be dissipated as heat rather than radiant flux, the importance of thermal management cannot be overstated. Lower thermal resistance values indicate longer package durabilities to thermal shock and superior optical performance. Hence, effective thermal management methodologies are required to maintain as well as improve lifetimes, critical for maximizing the potential of UV LEDs.

To combat the thermal challenges in the deep UV range, Violumas has developed an integrated thermal technology at both the chip and at the package level, which allows for maximum thermal dissipation and improved reliability. With the addition of a “thermal” pad, the unique thermal structure proposed by Violumas shows the benefits of optimal thermal management at the package level, which can be effectively utilized, specifically for higher power UV applications.

In this paper, we discuss important thermal characteristics (thermal decay, thermal droop) of UV LEDs, emphasizing the importance of optimal thermal management at the package level. Experimental results that exhibit the benefits of this integrated thermal technology will be presented for high performing UVC LEDs.