Fate and partitioning of copper nanoparticles in a model septic system
Authors:Aaron Coyoca, Alicia Taylor
Mentor:Sharon Walker, Associate Professor of Chemical & Environmental Engineering, UC Riverside
With growing popularity of the nanotechnology industry, increasing amounts of nanoparticles may be produced and introduced into the environment through uses of consumer products. This is of concern because preliminary toxicity studies demonstrate that nanoparticles may be toxic to bacteria, which regulate many environmental processes. Septic tanks are a form of onsite wastewater treatment in 20% of American households; an improperly functioning tank can lead to contamination of groundwater. Here, a model septic system was dosed with three types of copper particles (micro Cu, nano Cu, Cu(OH)2) at 10 ppm to determine if a deviation from baseline function will occur. Copper is known to be toxic to bacteria; hence the particles may cause a disruption in the fermentation process inside the septic tank regulated by bacteria, leading to the incomplete breakdown of waste. Deviations from baseline performance may indicate a septic tank not functioning optimally, which can suggest the release of higher concentrations of total suspended solids, fecal coliforms, and copper nanoparticles into the groundwater. Septic effluent samples underwent weekly analyses including pH, alkalinity, biological oxygen demand, and total suspended solids without and with copper for baseline and experimental conditions, respectively. Tools used for detecting copper nanoparticles in the septic tank effluent included a cupric ion specific electrode and inductively coupled plasma optical emission spectrometry (ICP-OES). Low concentrations of copper were found in the septic tank effluent (0-0.6 ppm) using ICP-OES. Concentrations of nanoparticles released from a septic tank depend on how the particles partition and speciate in the septic tank (aggregation, dissolution, and precipitation).Results regarding copper concentrations found in the biofilm will be further discussed; data suggests high amounts of copper in the sludge with all three copper particle experiments. Further research will give insight to the potential toxicity of copper released into the environment through the effluent.