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Discipline: Biological Sciences
Subcategory: Water
Philip M. Roveto - University of New Mexico
Co-Author(s): Chase Stearnes and Andrew J. Schuler, University of New Mexico, Albuquerque, NM
Biofilms form through planktonic adhesion and conglomeration to fixed surfaces, yielding consortia with dramatically increased lifespans and biocide resistance. Nitrifying biofilms are increasingly used in wastewater treatment plants for ammonium removal, as biofilms are conducive to the survival of slow growing heterotrophs. Biofilm strength, dependent on secretion of glue-like extracellular polysaccharides (EPS), is important in high-shear, high-variability environments, intrinsic to natural systems and wastewater plants. Our team is developing a better understanding of biofilm strength and metabolic capability with variations in surface morphology and chemistry. We are evaluating separate 3DP surfaces composed of exposed and protected Nylon-6,6 plastic, as well as Nylon surface-treated with activated carbon. We also investigate the effects of a laminated, azlactone-based, polymer system overlaid on both morphologies. Mature biofilms grown under uniform conditions will be structurally dependent on the surfaces they inhabit. Grown under a constant aeration rate, with a shear force of 0.1 N/m^2, each biofilm will experience a decrease in attached biomass and a change in metabolic efficiency when confronted with a dramatically higher aeration rate, and a shear force of 0.3 N/m^2. Metabolism of ammonium is directly related to biofilm integrity, and will serve as an analytic marker towards the overall health of each biofilm as it undergoes a low-shear to high-shear conversion. Due to higher surface area, activated carbon-treated surfaces are expected to provide a stronger anchor, promote EPS formation, and yield biofilm stability, while smoother Nylon surfaces will undergo major sloughing events and diminished metabolic activity. Polymer laminations are expected to produce lesser, but additive stability due to their physiochemical properties. Seven different Nylon and modified-Nylon substrates (Flat, Millimeter-Indented [MI], MI Activated Carbon [AC], Azlactone MI, Azlactone MI AC, Polyamine MI, Polyamine MI AC) were inoculated in activated sludge for 24h and were grown under identical conditions in batch reactors with aeration-based oxygen delivery and mixing. Buffered synthetic wastewater imparted 125 ppm ammonia as N, as well as essential trace metals and nutrients to mature biofilms. Under these conditions, ammonium oxidation flux ranged from 6.5-7.0 g/m^2/d. After introduction of increased shear, activated carbon surface-biofilms showed enhanced ammonium removal, 8.5-9.0 g/m^2/d despite losing 1/3 of attached biomass. Nylon surfaces demonstrated sloughing events without increased shear, demonstrating a likely dissolution of biofilm integrity, particularly in the case of the experimental control, flat Nylon, under increased shear force. Despite losing biomass, increased mixing influences deeper nutrient and oxygen penetration into the biofilm interior, producing superior N removal in a thinner, more efficient system.
Funder Acknowledgement(s): This material is based upon work supported by the National Science Foundation under Grant Number 1345169. Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
Faculty Advisor: Andrew J. Schuler, schuler@unm.edu
Role: I was responsible for experimental design, material construction, data collection, and data analysis/interpretation for this research.
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