Year Established: 2016 Start Date: 2016-03-01 End Date: 2017-02-28
Total Federal Funds: $5,000 Total Non-Federal Funds: $11,138
Principal Investigators: Wen Zhang
Abstract: Engineered nanoparticles (ENPs) incorporated into consumer products have shown to negatively impact vital ecosystems once released into the environment. Wastewater treatment plants, an important barrier between consumers and their surroundings, are not designed specifically for the removal of ENPs. As wastewater influent complexity increases, treatment plants should be re-evaluated for their processing efficiency. Likewise, as competing demands increase upon limited freshwater resources, reuse practices of treated wastewater will increase across the United States. Smaller, decentralized treatment plants provide the benefit of keeping reclaimed water supplies local for recycling practices. Consequently, there is a pressing need for economical yet effective regionalized wastewater treatment. Biofilm systems are easy to maintain and convenient for small communities. The proposed research will investigate the role of wastewater biofilms in the removal of ENPs from waste streams. A commonly used model ENP, silver nanoparticles (Ag-NPs), will be exposed to wastewater bacteria under changing variables. Common to wastewater, the experiments will be conducted in the sequence of using bacterial biofilm of a single species (Acinetobacter calcoaceticus), dual species (Acinetobacter calcoaceticus and Comamonas testosteroni), and mixed species (Acinetobacter calcoaceticus, Comamonas testosteroni, and Delftia acidovorans). Three major interactions between ENPs and biofilm are attachment, diffusion, and detachment. The proposed study breaks down into 3 tasks to explore these interactions. First, it is expected that ENPs within wastewater can attach to biofilms without significantly altering nutrient reduction capacity. Over 5 days, environmental parameters (influent and effluent conductivity, total dissolved solids, COD, total nitrogen, and total phosphorous) will be monitored along with reactive oxygen species generation to reveal inhibition of nutrient processing or biofilm stress. Second, Ag-NP accumulation within the biofilm matrix will be investigated with initial ENP quantities of 0.1, 10, 50, and 200 mg L-1. Diffusion into the biofilm may vary depending on biofilm density and EPS composition. This step will explore threshold conditions by varying biofilm age and investigating the impact of EPS composition. The transition from single species, A. calcoaceticus, to dual species experiments (A. calcoaceticus, C. testosteroni) isolates EPS as a variable. Third, we predict that biofilm will become a source of ENPs when biofilm detachment or sloughing occurs. Increased stress upon the biofilm such as elevated levels of ENPs or wastewater fluctuations may cause re-release of trapped ENPs. Detachment will be quantified from confocal laser scanning microscopy imaging and significant changes in Ag-NP concentrations will be monitored as biofilm stress occurs. This research will provide an essential initial understanding of ENP impacts on biofilm systems for wastewater processing.