Silica and titania nanoparticles impact on water quality: Experiments involving Ralstonia pickettii in nutrient-rich and poor media

According to CDC, the public is being bombarded with ads for cleansers, soaps, toothbrushes, and hand lotions, all containing antibacterial agents. Nanoparticles, which are materials at length scales less than 100 nm, have previously demonstrated antibacterial and antimicrobial properties. One of the hardiest bacteria is a Ralstonia pickettii species isolated from an ultrapure water (UPW) facility. These bacteria survive in water that only contains parts per trillion levels of organic and inorganic contaminants. The focus of this article is to demonstrate the effects of silica and titania nanoparticles on Ralstonia pickettii bacteria in term of growth and yields. Solutions of nanoparticles and calcium fluoride were researched for their effects on the growth rate and cell yield of Ralstonia sp. bacteria in a protein-rich and protein-poor media. The collective effect of CaF₂ and 15 nm silica nanoparticles reduces the growth rate by 57% and the cell yield by 29% in protein-rich media. Titania nanoparticles returned similar results, where in nutrient-poor environments little to no growth occurred but in nutrient-rich media, the titania and CaF₂ reduced the growth rate by 64% and the cell yield by 34%. Conversely, larger silica nanoparticles in nonprotein-rich media have negligible effects on cell yield and growth rate. The diminished bacterial growth rate provides paralleled insight into the long-term effects of nanotechnology effluent on the United States' wastewater treatment processes, which utilize several species of bacteria. Extrapolation of these results to current toxicological studies suggests that unregulated industrial nanoparticles' expulsion may lead to degradation in water quality.