Microbial peroxide producing cells (MPPCs) are a type of microbial electrochemical cells that are used to produce hydrogen peroxide (H2O2). Different catholytes were evaluated in biotic and abiotic reactors to determine their impacts on reactor performance. The abiotic reactor produced cathode efficiencies of less than 1%, leading us to investigate the potential causes of the low efficiency. An acid wash of the reactor parts was observed to significantly decrease the degradation rate of peroxide in the reactor, indicating that metal impurities in the catholyte solution was the driving cause of the low peroxide yields in the reactor. Diffusion testing confirmed that peroxide diffused across the anion exchange membrane (AEM) at a rate of 13.3 mg/L/hr, but had no significant impact on the overall peroxide produced in the reactor. We also confirmed that auto-decay of H2O2 was not responsible for the low observed yields.

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.

Optimizing cathodes for microbial fuel cells is important to maximize energy harvested from wastewater. Cathodes were made by modifying a recipe from previous literature and testing the current of the cathode using linear sweep voltammetry. The cathodes contained an Fe-N-C catalyst combined with a Polytetrafluoroethylene binder. Optimizing the power resulting from the microbial fuel cells will help MFCs be an alternative energy source to fossil fuels. The new cathodes did improve in current production from −16 𝐴/𝑚 to −37 𝐴/𝑚 at -0.4 V. When fitted using a Butler-Volmer model, the cathode linear-sweep voltammograms did not follow the expected exponential trend. These results show a need for more research on the cathodes and the Butler-Volmer model, and they also show that the cathode is ready for further and longer application in a microbial fuel cell.

The objective of this work is to perform LCAs three wastewater treatement alternatives at battalion-sized (500 soldier) FOBs. Three systems will be explored: traditional wastewater treatment of combined blackwater and graywater streams using activated sludge and anaerobic digestion (the status quo); MXC treatment of blackwater to produce H2O2 for disinfection of blackwater and graywater; a hybrid system of blackwater treatments with MXCs to produce electricity with graywater disinfection using H2O2 produced offsite. Environmental impacts are assessed using Impact 2002+ midpoint and endpoint categories, primarily reported for human health and environmental impacts. Uncertainity analysis is performed using two techniques. First, a pedigree matrix is developed to identify the highest areas of uncertainties in data. Second, a sensitivity analysis is used to explore the effects on endpoint categories from varying transportation distance, the percentage of wastewater that is reused as nonpotable water, and coagulant doses.

The Combined Activated Sludge-Anaerobic Digestion Model (CASADM) quantifies the effects of recycling anaerobic-digester (AD) sludge on the performance of a hybrid activated sludge (AS)-AD system. The model includes nitrification, denitrification, hydrolysis, fermentation, methanogenesis, and production/utilization of soluble microbial products and extracellular polymeric substances (EPS). A CASADM example shows that, while effluent COD and N are not changed much by hybrid operation, the hybrid system gives increased methane production in the AD and decreased sludge wasting, both caused mainly by a negative actual solids retention time in the hybrid AD. Increased retention of biomass and EPS allows for more hydrolysis and conversion to methane in the hybrid AD. However, fermenters and methanogens survive in the AS, allowing significant methane production in the settler and thickener of both systems, and AD sludge recycle makes methane formation greater in the hybrid system.