Research Project Full Title: Saving energy in drinking-water biofilter operation: A fundamental study of the relationship among nutrient conditions, EPS production, and biofilter headloss
2-4 Word Description: Saving energy in drinking-water biofilter operation
Principal Investigator(s): Dr. Mary Jo Kirisits and Ms. Sarah Keithley
Full Abstract: Biological water treatment is receiving increased interest in the United States because it can transform organic and inorganic contaminants, including natural organic matter, nuisance taste and odor compounds, pharmaceuticals and personal care products, and heavy metals (Zhu et al. 2010, Zearley et al. 2012). One operational concern with biofilters is the potential for excessive headloss, shortening filter run times and increasing the energy demands for backwashing. Extracellular polymeric substances (EPS) likely play a critical role in headloss accumulation by occupying void space. EPS are mainly high molecular weight compounds excreted by microorganisms or produced by cellular lysis. They aid in microbial adhesion to surfaces and provide the structure for a biofilm (Flemming & Wingender 2010). Nutrients (e.g., N and P) are essential for biological growth, and nutrient availability can affect microbial growth rate and production of EPS. The literature often cites a C:N:P molar ratio of 100:10:1 as necessary for microbial growth (e.g., LeChevallier et al. 1991), but nitrogen or phosphorus could be limiting in a biofilter because the biodegradable organic carbon concentration is increased by ozonation (commonly used upstream of biofilter) or because phosphorus is removed during coagulation (Nishijima et al. 1997). Lauderdale et al. (2012) observed longer filter run times and less EPS in pilot-scale biofilters receiving influents amended with ammonium and phosphate, but they did not conclusively show the role of EPS in the performance of the filters.
This research seeks to improve the hydraulic performance of biofilters by lengthening filter run times. The primary objectives are as follows:
- Develop and optimize an EPS extraction protocol for biofilters.
- Examine the relationship among C:N:P molar ratios, EPS concentrations, and headloss accumulation in bench-scale biofilters.
- Fundamentally interrogate the activity of the microbial community by monitoring gene expression.