Applicability of Ozone and Biological Activated Carbon for Potable Reuse

The Upper San Gabriel Valley Municipal Water District in California is considering groundwater replenishment as a potential strategy to augment its potable water supply. This case study demonstrates the broad applicability of ozone and biological activated carbon (BAC) for such potable reuse systems based on recently developed criteria and models for bulk organics, trace organic contaminants, disinfection byproducts, and cost. Using an advanced treatment train composed of ozone (ozone to total organic carbon ratio of 1.0) and BAC (empty bed contact time of 20 min), a 10 million gallon per day potable reuse facility can achieve savings of $25–$51 million in capital costs, $2–$4 million per year in operations and maintenance costs, and 4–8 GWh per year in energy consumption in comparison to alternative treatment trains with reverse osmosis. This ozone-based treatment train is also capable of achieving public health criteria recently developed by the California Department of Public Health and the National Water Research Institute for potable reuse applications.     

Towards improved characterization of high-risk releases using heterogeneous indoor sensor systems

The sudden release of toxic contaminants that reach indoor spaces can be hazardous to building occupants. For an acutely toxic contaminant, the speed of the emergency response strongly influences the consequences to occupants. The design of a real-time sensor system is made challenging both by the urgency and complex nature of the event, and by the imperfect sensors and models available to describe it. In this research, we use Bayesian modeling to combine information from multiple types of sensors to improve the characterization of a release. We discuss conceptual and algorithmic considerations for selecting and fusing information from disparate sensors. To explore system performance, we use both real tracer gas data from experiments in a three-story building, along with synthetic data, including information from door-position sensors. The added information from door-position sensors is found to be useful for many scenarios, but not always. We discuss the physical conditions and design factors that affect these results, such as the influence of the door positions on contaminant transport. We highlight potential benefits of multisensor data fusion, challenges in realizing those benefits, and opportunities for further improvement.     

Effect of Contamination on Reinforcing Bar-Concrete Bond

Current specifications require the removal of reinforcing bar contaminants that reduce bond prior to placing concrete. This study focused on the interactions of contaminant type, bar size, epoxy coating, concrete strength, and test method (beam and direct pullout). The majority of the beam tests showed the bond strength was not significantly affected, with certain exceptions. However, the direct pullout tests revealed a significant reduction of bond strength in most situations. Although the bond strength was still greater than that required by code, it is recommended that specifications for removal of contaminants should not be relaxed until further study is performed.     

Influence of river discharge patterns on the hydrodynamics and potential contaminant dispersion in the Douro estuary (Portugal)

Freshwater input to estuaries is a fundamental feature of these ecosystems, which may be profoundly altered by river damming as human needs for water consumption, irrigation or energy production increase. The Douro estuary is limited upstream by a dam since 1985, which reduced its length by ca. 60%. Freshwater inputs to the estuary are now irregular and greatly dependent on hydroelectric power demand; values ranging from zero to over 1000 m³ s⁻¹, in a matter of hours, especially in summer are common. In the present study, a three-dimensional hydrodynamic model was applied to the Douro estuary. The model was calibrated and validated against water elevation, current velocity, salinity and temperature data. Thereafter, it was used to analyse the effects of different flow regimes and magnitudes on estuarine hydrodynamics and contaminant dispersion. Results obtained suggest that the highly variable flow regimes, currently observed in the Douro, tend to reduce water column stratification and to enhance seawater intrusion, when compared with flow discharges of similar average magnitude, but lower variability. Stable flows seem to be the most effective in dispersing contaminants eventually introduced into the estuary through its small river tributaries. Overall results suggest that flow management may have important effects on estuarine hydrodynamics through non-linear interactions between flow magnitude and variability.     

An experimental overview of the effects of hydrogen impurities on polymer electrolyte membrane fuel cell performance

Hydrogen quality is critical for increasing the reliability, stability, and durability of polymer electrolyte (PEM) fuel cells. In this work, several hydrogen impurities have been studied to understand their effects on PEM fuel cell performance at various operating concentrations. Our studies have shown that the following impurities suggested by industry stakeholders do not result in substantial fuel cell degradation when they are the sole impurity in hydrogen: 5 ppm formaldehyde, 2 ppm formic acid, 19 ppm chloromethane, 30 ppm acetaldehyde, 5% ethylene, 20 ppm toluene, and 10 ppm benzene. In addition, a specific mixture of impurities called the “specification concentration level cocktail” consisting of 0.2 ppm carbon monoxide, 4 ppb hydrogen sulphide, 0.2 ppm formic acid, 2 ppm benzene, and 0.1 ppm ammonia in hydrogen, also does not show significant effects on cell performance. In comparison, when a cocktail having five times the specification concentration is introduced into the cell, significant performance loss is evident.     

“Quality specification and safety in hydrogen production,commercialization and utilization”

For decades, the issue of hydrogen quality specification has been a source of complexity and confusion in particular for end users, especially because of the jargon spoken by different providers and clients in varied and diverse areas of application. Virtually every requirement was established within the customer–supplier relationship.     

Complementary uses of chlorine dioxide and ozone for drinking water treatment

Application of both chlorine dioxide (ClO₂) and ozone (O₃) at a single drinking water treatment plant is rare in the United States but not in other countries. European utilities that use both oxidants commonly add ozone at one or more points prior to filtration and then apply ClO₂ after filtration. In this mode, the oxidant demand is considerably reduced prior to ClO₂ addition, thus reducing the ClO₂ requirement for maintaining a concentration of 0.1 mg/L to 0.2 mg/L in the distribution system. The combined use of ClO₂ and O₃ has merit in many situations, but the way in which the oxidants are sequenced (e.g. pre‐ozonation followed by ClO₂ treatment or vice versa) is critical in terms of finished water quality. The objectives of this paper are: (1) to review the most common water‐treatment goals associated with ClO₂ and O₃, and (2) to discuss the potential consequences and benefits of applying both oxidants at various points in the treatment train.     

Numerical studies of indoor airflow and particle dispersion by large Eddy simulation

The indoor airflow and contaminant particle concentration in two geometrically different rooms have been investigated using the Large Eddy Simulation (LES) technique based on Renormalization Group (RNG) theory derived by Yakhot, Orszag, Yakhot and Israeli, Journal of Scientific Computing, 1989. The first room is without contaminant particles. Its simulated air phase velocity profiles are validated against the measurements of Posner, Buchanan and Dunn-Rankin, Energy and Buildings, 2003. A good agreement is achieved between the prediction and measured data. The LES model successfully captures the mean flow trends as well as instantaneous flow information, which is required for appropriate design and evaluation of a ventilation system. The second room has contaminant particles, which are simulated with a Lagrangian particle tracking model. In this case, the LES model provides acceptable prediction of the contaminant particle concentration, compared to the particle concentration decay measured by Lu, Howarth, Adam and Riffat, Building and Environment, 1996. The numerical results reveal that the particle-wall impact model has a considerable effect on the Lagrangian concentration prediction. It is proposed that further improvements to the particle-wall impact model are required to correctly predict the contaminant particle concentration through the Lagrangian model.     

Isolation, identification and monitoring of contaminant bacteria in Iranian Kefir type drink by 16S rDNA sequencing

Iranian Kefir type drink (IKTD) is a highly consumed, traditional Iranian, fermented milk product. To improve monitoring procedures for food safety 32 industrial Kefir type drinks from 4 brands and 8 different production dates as well as 32 samples from pasteurized milk of the same Kefir manufacturers and air of the production sites were analyzed for contaminations. 16S rDNA extraction from Kefir samples as well as 16S rDNA obtained from samples incubated on Columbia agar were analyzed using PCR/DGGE, cloning, sequencing and phylogenetic classification. Already DGGE analysis indicated contaminations including Bacillus strains. Subsequently analysis of cultured clones indicated contaminations with Bacillus sp. including Bacillus cereus, Bacillus thuringiensis and Paenibacillus sp. in 9 (28%) from all analyzed samples. Also 38% of pasteurized milk samples were contaminated with B. cereus. The average count of B. cereus was 74 ± 19 cfu/ml. B. cereus and B. thuringiensis were found as contaminant bacteria in the air of the all manufacturing sites. These results suggest that milk is one of the most important sources of contamination with Bacillus sp., especially B. cereus for Kefir products in Iran. But bacterial contamination in Kefir samples might also originate from the air of the production sites. 16S rDNA analysis accelerates monitoring strategies.