Instructors Learn from Homework, too: Streamlining Data Collection to Facilitate Reteaching Before the Test

Whether it’s for accreditation or simply as a good teaching practice to inform future instruction, gathering and analyzing data can be time consuming. This is especially true for large classes. How can you streamline the process for quick evaluation?https://digitalscholarship.unlv.edu/btp_expo/1011/thumbnail.jp

Fostering Student Engagement: Four Strategies

In response to studies demonstrating that poor teaching was the cause of many students leaving math, science, and engineering programs, the American Society of Civil Engineers (ASCE) developed the ExCEEd(Excellence in Civil Engineering Education) Teaching Workshop. Several faculty from the UNLV Department of Civil & Environmental Engineering and Construction have attended the highly intensive five-day workshop. To evaluate the impact on student engagement, four basic instructional strategies from the ExCEEdworkshop, applicable to all fields, were tested and assessed during the Fall 2018 semester: Questioning techniques, physical models, instructor involvement, and group work.https://digitalscholarship.unlv.edu/btp_expo/1066/thumbnail.jp

Impact of Sludge Treatment Processes on Estrogen Concentration in Wastewater Sludge

Endocrine-disrupting compounds (EDCs), such as estrogen, are known to be present in the aquatic environment at concentrations that affect fish and other wildlife. For example, juvenile male fish exposed to estrogen will synthesize vitellogenin, which is a female-specific protein. Estrogen exposure is also linked to sex reversal, intersexuality, and inhibition of gonadal growth (Jobling et al., 1996). Wastewater treatment plants are major contributors of EDCs into the environment. EDCs end up in wastewater as a result of natural excretion from the body or being washed off the skin. WWTPs are not designed to remove these substances. As a result, EDCs are released via effluent discharge to rivers and lakes, as well as through solid waste placed in landfills or applied to fields (biosolids) as fertilizer. In both the effluent and sludge, the final concentration of a compound depends on the treatment processes, chemical properties of the compound, and environmental conditions. This study focuses on estrogen concentration in wastewater sludge as a result of sludge handling processes

New N-nitrosodimethylamine (NDMA) precursors that react with ozone: Implications for water reuse

Ozonation is a promising treatment step for water reuse. Compared to the “gold standard” with reverse osmosis and advanced oxidation, ozone requires less energy and does not result in a waste brine. This makes ozone more cost-effective. However, the formation of nitrosamines may be a significant barrier to the use of ozonation in water reuse applications, particularly for potable reuse

Ozonation in Water Reuse: Formation and Mitigation of N-~nitrosodimethylamine

Formation of N-nitrosodimethylamine (NDMA) is a substantial concern for drinking water and water reuse. NDMA, a probable human carcinogen, is formed when water is disinfected with chloramines and ozone. This research focused on three issues regarding NDMA formation and mitigation. The first issue involved understanding the compounds (i.e., precursors) present in water and wastewater that react with ozone to form NDMA. Model precursors were identified and molar yields for NDMA formation were determined. The model precursors form high amounts of NDMA with ozone, but form very little NDMA with chloramines, which means there are two distinct groups of NDMA precursors: ozone-reactive and chloramine-reactive. An investigation into factors that affect NDMA formation resulted in understanding that bromide enhances NDMA formation for some precursors and elimination of hydroxyl radicals, which are produced during ozonation, leads to higher NDMA formation. Comparison of three oxidants, molecular ozone, hydroxyl radicals and dissolved oxygen, revealed that molecular ozone is the agent responsible for NDMA formation. The second issue addressed the strategic use of disinfection oxidants, alone and in combination, to minimize disinfection byproduct (DBP) formation. This study compared the formation and reduction of NDMA and two groups of regulated drinking water DBPs (trihalomethanes (THMs) and haloacetic acids (HAAs)) in treated wastewaters using seven disinfection treatment schemes. The top two treatment schemes resulting in the lowest total DBP formation, after converting concentrations to an equivalent unit based on drinking water risk, were ozonation and ozonation-chloramination. Both treatment schemes also exhibit several advantages for application in water reuse situations. It was demonstrated that pre-chlorination can reduce NDMA formation by inactivating ozone-reactive NDMA precursors, but DBP trade-offs must always be addressed because chlorination causes THM and HAA formation. The third issue investigated non-optimized biofiltration to mitigate NDMA formation by removing NDMA precursors prior to disinfection with ozone or chloramines. NDMA precursor removal (ranitidine (RNTD), daminozide (DMZD), 2-furaldehyde dimethylhydrazone (2-F-DMH) and 1,1,1\u27,1\u27-tetramethyl-4,4\u27-(methylene-di-p-phenylene)disemicarbazide (TMDS)) and DBP formation potential (NDMA, THMs, HAAs) in treated wastewater were assessed before and after biofiltration using three anthracite-containing columns with different contact times. Precursor removal varied (RNTD: 6-7%; DMZD: 73-85%; 2-F-DMH: 15-27%; TMDS: 11-24%) and was correlated to dissolved oxygen concentration or correlated to contact time for some precursors. The investigated wastewater was phosphorus-limited and had low dissolved oxygen. NDMA, THM, and HAA precursor removal may be increased through optimization of the biofilter media and the nutrients available for bacteria growth

Impact of Secondary Treatment Types and Sludge Handling Processes on Estrogen Concentration in Wastewater Sludge

Endocrine-disrupting compounds (EDCs), such as estrogen, are known to be present in the aquatic environment at concentrations that negatively affect fish and other wildlife. Wastewater treatment plants (WWTPs) are major contributors of EDCs into the environment. EDCs are released via effluent discharge and land application of biosolids. Estrogen removal in WWTPs has been studied in the aqueous phase; however, few researchers have determined estrogen concentration in sludge. This study focuses on estrogen concentration in wastewater sludge as a result of secondary treatment types and sludge handling processes. Grab samples were collected before and after multiple treatment steps at two WWTPs receiving wastewater from the same city. The samples were centrifuged into aqueous and solid phases and then processed using solid phase extraction. Combined natural estrogens (estrone, estradiol and estriol) were measured using an enzyme-linked immunosorbent assay (ELISA) purchased from a manufacturer. Results confirmed that activated sludge treatments demonstrate greater estrogen removal compared to trickling filters and estrogen load (mass estrogen per mass solid) was measured for the first time on trickling filter solids. Physical and mechanical sludge treatment processes, such as gravity thickeners and centrifuges, did not significantly affect estrogen removal based on mass balance calculations. Dissolved air flotation demonstrated a slight decrease in estrogen concentration, while anaerobic digestion resulted in increased estrogen load on the sludge and a high estrogen concentration in the supernatant. Although there are no state or federally mandated discharge effluent standards or sludge application standards for estrogen, implications from this study are that trickling filters would need to be exchanged for activated sludge treatment or followed by an aeration basin in order to improve estrogen removal. Also, anaerobic digestion may need to be replaced with aerobic digestion for sludge that is intended for land application

The Return of Labor-based Grading Contracts

Despite best attempts, grading can be very subjective when it comes to determining quality. For certain courses, the process is just as important as the product, but often the grade is based mainly on the quality of the product and doesn’t take the labor or process into account. One alternative to standard grade systems is labor-based grading or contract grading. In this system, students meet certain requirements to earn a certain grade. If students meet the criteria for the assignment, it counts toward the contract. If not, they can revise, reflect and resubmit. With this format, students can focus on the process without constantly thinking about having to get 100% on every task in order to achieve their desired grade. When students miss out on a concept (as embedded criteria for an assignment), there is a pathway for metacognitive learning through reflection. Labor-based grading was applied to a lab section of EGG 202, a new course that counts for first-year seminar credits in the College of Engineering. This course is oriented toward projects and skills (i.e., no exams scheduled). Students need time to get used to this new grading format, but they appreciate the flexibility of the grading system (i.e., being able to resubmit if they “miss the mark” on the first try). In addition, this grading system reduces the penalty for students who come in less prepared than their peers. While they are still required to achieve the same criteria for an assignment, they can take advantage of the resubmittal process if they don’t reach the minimum criteria on the first try. Students self-reported that contract grading and rubrics caused them to reflect on assignments before submitting them and to recognize their ability to improve and grow as a learner.https://digitalscholarship.unlv.edu/btp_expo/1174/thumbnail.jp

Nitrosamines in pilot-scale and full-scale wastewater treatment plants with ozonation

Ozone-based treatment trains offer a sustainable option for potable reuse applications, but nitrosamine formation during ozonation poses a challenge for municipalities seeking to avoid reverse osmosis and high-dose ultraviolet (UV) irradiation. Six nitrosamines were monitored in full-scale and pilot-scale wastewater treatment trains. The primary focus was on eight treatment trains employing ozonation of secondary or tertiary wastewater effluents, but two treatment trains with chlorination or UV disinfection of tertiary wastewater effluent and another with full advanced treatment (i.e., reverse osmosis and advanced oxidation) were also included for comparison. N-nitrosodimethylamine (NDMA) and N-nitrosomorpholine (NMOR) were the most prevalent nitrosamines in untreated (up to 89ng/L and 67ng/L, respectively) and treated wastewater. N-nitrosomethylethylamine (NMEA) and N-nitrosodiethylamine (NDEA) were detected at one facility each, while N-nitrosodipropylamine (NDPrA) and N-nitrosodibutylamine (NDBA) were less than their method reporting limits (MRLs) in all samples. Ozone-induced NDMA formation ranging fro

Altered gene expression in asymptomatic SHIV-infected rhesus macaques (Macacca mulatta)

Simian-Human immunodeficiency virus is a chimeric virus which, in rhesus macaques (Macacca mulatta) closely imitates immunodeficiency virus infection in human (HIV). A relatively new way to study pathogenesis of viral infection is to study alterations in host gene expression induced by the virus. SHIV infection with certain strains does not result in clinical signs. We hypothesized that alterations in gene expression relating to the immune system would be present in SHIV-infected animals despite the lack of clinical signs. Splenic tissue from four adult male Indian-origin Rhesus monkeys serologically positive for non-pathogenic SHIV 89.6 was processed by cDNA microarray analysis. Results were compared with the corresponding outcome using splenic tissues from four unexposed adult male Rhesus monkeys. Subsequent gene analysis confirmed statistically significant variations between control and infected samples. Interestingly, SHIV-infected monkeys exhibited altered expression in genes related to apoptosis, signal transduction, T and B lymphocyte activation and importantly, to immune regulation. Although infected animals appeared asymptomatic, our study demonstrated that SHIV-infected monkeys cannot reliably be used in studies of other infectious agents as their baseline gene expression differs from that of normal Rhesus monkeys. The gene expression differences in SHIV-infected animals relative to uninfected animals offer additional clues to the pathogenesis of altered immune function in response to secondary infection

A Study on Modified Biochars for the Removal of Trichloroethylene (TCE)

Biochar (BC), a biomass-derived black carbon with interconnected networks of micropores, is an economical substitute for conventional adsorbents, such as activated carbon. In this study, we investigated the effect of acid modification on the functional groups and adsorptive capacity of the biochar. The BC used here is prepared through pyrolysis at temperatures in the range between 700 °C and 900 °C in an argon gas inert environment from three different biomasses: walnut shells, pecan shells, and loblolly pine. Then, the BCs are modified using hydrochloric acid (HCl) and used for the remediation of chlorinated hydrocarbons such as trichloroethylene (TCE). The results can advance the understanding of different modification effects on BCs’ properties, aiming at the wide adoption of cost-effective and eco-friendly adsorbents.https://digitalscholarship.unlv.edu/durep_posters/1011/thumbnail.jp