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- Creators: Barrett, The Honors College
- Creators: Chemical Engineering Program
This outlines a mathematical model created in MATLAB for the purposes of predicting nitrous oxide emissions from wastewater treatment plants with updated an updated understanding of AOB metabolic pathway.
Anaerobic Digestion (AD) typically stabilizes 40-60% of influent wastewater sludge. Improving the methane yield in wastewater may produce enough energy to power some wastewater treatment processes, while the production of volatile-fatty acids (VFAs) generates economic incentives for yard waste pre-fermentation. In this research, pre-fermenters consisting of inocula composed of media; cellulose, lantana, or grass; and rabbit cecotrope were fed various concentrations of plant matter. The contents of these pre-fermenters were the influent for respective anaerobic digesters. The microbial consortium derived for the lignocellulosic pretreatment with common yard waste in Arizona successfully increased methane production in AD, while producing additional VFAs during pretreatment in all systems. The performance of the system appeared to depend on plant matter loading and operating time, with a higher plant loading increasing the VFA production and a longer operating time increasing soluble chemical oxygen demand (COD) in pre-fermentation, and therefore the methane production in AD increased. The pre-fermenter with the highest plant matter loading and longest operating time –1.44 g plant matter per day at a 9.6% influent concentration and 193 days of total operating time– produced 10,000 mg COD/L of VFA, and its reactor produced about 460 mL methane (CH4) per day, which was almost twice the production of the control AD at 250 mL CH4 per day. This research uses yard waste that would previously be disposed of in landfill to increase valuable product production in AD. The potential value added to wastewater treatment plant (WWTP) processes by these methods could incentivize the expansion of wastewater treatment, thereby increasing sanitation access. The use of net-neutral biogas as a fuel source for WWTPs is additionally an incremental solution for reducing carbon equivalents present in the atmosphere, thereby reducing the greenhouse gas effect.
The combined use of methamphetamine and opioids has been reported to be on the rise throughout the United States (U.S.). However, our knowledge of this phenomenon is largely based upon reported overdoses and overdose-related deaths, law enforcement seizures, and drug treatment records; data that are often slow, restricted, and only track a portion of the population participating in drug consumption activities. As an alternative, wastewater-based epidemiology (WBE) has the capability to track licit and illicit drug trends within an entire community, at a low cost and in near real-time, while providing anonymity to those contributing to the sewer shed. In this study, wastewater was collected from two Midwestern U.S. cities (2017-2019) and analyzed for the prevalence of methamphetamine and the opioids oxycodone, codeine, fentanyl, tramadol, hydrocodone, and hydromorphone. Monthly 24-hour time-weighted composite samples (n = 48) from each city were analyzed using isotope dilution liquid chromatography tandem mass spectrometry. Results showed that methamphetamine and total opioid consumption (milligram morphine equivalents) in City 1 were strongly correlated only in 2017 (Spearman rank order correlation coefficient, ρ = 0.78), the relationship driven by fentanyl, hydrocodone, and hydromorphone. For City 2, methamphetamine and total opioid consumption were strongly positively correlated during the entire study (ρ = 0.54), with the correlations driven by hydrocodone and hydromorphone. In both cities, hydrocodone and hydromorphone mass loads were highly correlated, suggesting a parent and metabolite relationship. WBE provides important insights into licit and illicit drug consumption patterns in near real-time as they evolve; important information for community stakeholders in municipalities across the U.S.