Physiochemical Studies of Biofilm Growth on 3-D Printed Nanosurfaces Towards Improved Wastewater Treatment

Tuesday, February 23, 2016
Philip Roveto , Civil Engineering, University of New Mexico, Albuquerque, NM

Bacterial conglomerations, or biofilms, are of utmost concern in many fields, including material manufacture, biomedicine, and water and wastewater treatment. Biofilms form through the processes of adhesion, growth, and dispersal, yielding communities with dramatically increased lifespans and biocide resistance. Municipal wastewater and natural waterways both can contain high concentrations of ammonia and phosphorus that can provide nutrients for algal growth, leading to ecosystem asphyxiation. Nitrifying biofilms are increasingly used in wastewater treatment plants for ammonia removal, as biofilms are conducive to the survival of these slow growing heterotrophs.

Our research is focused on developing a better understanding of how attachment surface geometry and chemistry affects biofilm structure and function. We are evaluating high surface-area surfaces composed of acrylonitrile butadiene styrene (ABS), poly-lactic acid (PLA), and nylon plastics fabricated with 3-D printing technology, which include hundreds of miniature wells (1 mm)3 for bacterial colonies to grow. The plastic surfaces were laminated with a series of covalently cross-linked polymeric layers, alternating between commercially available polyethyleneimine (PEI) and synthesized poly-dimethylazlactone (PDMA). A terminal layer containing residual azlactone rings was then further modified by attaching spermine, a long-chain nitrogen-rich substrate, to create a physio-chemical nanosurface potentially capable of increasing bacterial adhesion.

A series of bioreactors were designed to provide consistent environmental conditions for untreated and modified surfaces. Constant aeration provided sufficient dissolved oxygen levels, and a well-buffered synthetic nutrient source provided inorganic carbon in the form of bicarbonate, ammonia, a metabolic energy source for the nitrifying bacteria, and additional biologically necessary nutrients. Colony health was measured by nitrification rates, based on ammonia removal. Early results show the corresponding rate of chemical transformation per unit of surface area increased 3-4 times over the course of one month to 3 g/m2/d of ammonia.

Philip Roveto, Civil Engineering, University of New Mexico, Albuquerque, NM
Philip Roveto grew up in New Mexico and the issues of water scarcity and treatment inherent in this region have led him towards the research he is undertaking today. He earned a bachelor’s degree in chemistry from Boston University, and entered the pharmaceutical industry as a medicinal chemist. While there, he worked on small-molecule target projects that focused on Alzheimer’s and cancer. While designing effective medicine is an important goal, providing clean water to the world’s population, regardless of socio-economic status, is a pursuit that Roveto wanted to dedicate himself to. It is his hope that the work he does will translate into a valued benefit to the environment.