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Nitrous oxide (N2O) is a powerful greenhouse gas emitted from wastewater treatment, as well as natural systems, as a result of biological nitrification and denitrification. While denitrifying bacteria can be a significant source of N2O, they can also reduce N2O to N2. More information on the kinetics of N2O formation and reduction by denitrifying bacteria is needed to predict and quantify their impact on N2O emissions. In this study, kinetic parameters were determined for Paracoccus pantotrophus, a common denitrifying bacterium. Parameters included the maximum specific reduction rates, , growth rates, , and yields, Y, for reduction of NO3− (nitrate) to nitrite (NO2−), NO2− to N2O, and N2O to N2, with acetate as the electron donor. The values were 2.9 gN gCOD−1 d−1 for NO3− to NO2−, 1.4 gN gCOD−1 d−1 for NO2− to N2O, and 5.3 gN gCOD−1 d−1 for N2O to N2. The values were 2.7, 0.93, and 1.5 d−1, respectively. When N2O and NO3− were added concurrently, the apparent (extant) kinetics, , assuming reduction to N2, were 6.3 gCOD gCOD−1 d−1, compared to 5.4 gCOD gCOD−1 d−1 for NO3− as the sole added acceptor. The was 1.6 d−1, compared to 2.5 d−1 for NO3− alone. These results suggest that NO3− and N2O were reduced concurrently. Based on this research, denitrifying bacteria like P. pantotrophus may serve as a significant sink for N2O. With careful design and operation, treatment plants can use denitrifying bacteria to minimize N2O emissions.Electronic supplementary materialThe online version of this article (doi:10.1186/s13568-016-0258-0) contains supplementary material, which is available to authorized users.

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Active and experiential learning activities are highly regarded for delivering engineering content. This paper explores an inexpensive hands-on activity where students purified lake water using backpacking systems as a way to introduce water treatment concepts in an Introduction to Environmental Engineering course. Teams of two students were given one of the following methods of water purification: membrane filtration, membrane filtration coupled with an activated carbon adsorption, ultra violet disinfection, iodine tablet disinfection, solar water disinfection (SODIS), or disinfection via boiling. As part of this assignment, students evaluated the treatment methodologies in terms of their cost, ease-of-use, energy requirements, time of treatment and efficacy. They made observations about the effectiveness of their particular method by inspecting the reduction color, turbidity, and odor. In addition, they kept track of the time it took to purify one liter of water. Students also calculated the amount of time it would take to purify the minimum amount of water necessary for sustaining a person in one day as recommended by the World Health Organization and assessed the appropriateness of using each of the technologies in the developing world. Following this class session, students researched their respective purification technique and reported back to the class on its mechanism for removing contaminants as well as its limitations. The students then collectively discussed the tradeoffs of each method and debated which one would be most effective under a range of conditions such as turbidity, volume needed, availability, and cost of materials. This activity was followed by in class lectures on water quality and conventional drinking water treatment methods, which were related back to the backpacking water purification techniques. Overall, these activities were successful in providing a meaningful and engaging way to introduce physical and chemical treatment processes while concurrently examining water quality issues in the developing world. Student feedback from these activities was positive, and students demonstrated proficiency of water treatment concepts on subsequent exams. Numerous students reported that the activity helped them understand the principles behind water treatment while also challenging their preconceived notions about water treatment technologies in the developing world.

interests in biomechanics include developing clinical instruments for rehabilitation. Dr. DeGoede teaches upper-level undergraduate mechanical engineering and design courses and the first-year introduction to engineering course. He is also developing a collaborative study abroad program in West Africa built around social enterprise initiatives.

Research has shown that biological nutrient removal (BNR) processes may be significant sources of nitrous oxide (N 2 O) and nitric oxide (NO) emissions. However, most research has focused on suspended growth systems. Little is known about emissions from biofilm systems, where substrate gradients and microbial stratifications within the biofilm can complicate predictions of aggregate behavior. This research presents a preliminary biofilm model that includes the sequential reduction of nitrate (NO 3 -), nitrite (NO 2 -), NO, and N 2 O by heterotrophic bacteria, as well as autotrophic nitrification and denitrification processes. The model demonstrated that biofilms are likely to produce NO and N 2 O when the bulk liquid is aerobic. For the simulated conditions with combined heterotrophic and autotrophic processes, a maximum of 0.78% of nitrogen removed was emitted as N 2 O. The results should be used with caution, as the calculated N 2 O and NO emissions were sensitive to bulk substrate concentrations and to several assumed kinetic parameters that were not available in the literature.

This Complete Evidence-Based Practice paper explores the advantages and impact of techniques used to improve teamwork in an introduction to engineering course. The main goal of this study is to evaluate the effectiveness of methods used to develop and assess teamwork skills based on student performance and perception. This study integrates, interprets and contrasts quantitative and qualitative data obtained through a mixed-methods approach. Results indicate that students' attitudes toward teamwork and their perceptions of their own teamwork skills improved over the semester.

Given the concerns over nitrous oxide (N 2 O) formation during biological nutrient removal, a better and more quantitative understanding of N 2 O reduction by denitrifying bacteria is needed to predict the fate of N 2 O in wastewater treatment processes. In this research, kinetic parameters and yields were determined for a mixed culture of denitrifying bacteria. The effects of N 2 O on the microbial community structure were also assessed. A key finding was that denitrifying bacteria utilized N 2 O concurrently with either NO 3 -or NO 2 -. Concurrent utilization provided higher growth rates than on NO 3 -or NO 2 -alone, and caused shifts in the community structure. This result suggests that the presence of N 2 O selects for bacteria that grow faster in the presence of N 2 O.