THWRC Awarded Proposal 513UTA0038H

Project number:          513UTA0038H

Title:                             Saving Energy in Drinking-Water Biofilter Operation:  A Fundamental Study

                                     of the Relationship Among Nutrient Concentrations, EPS Production, and

                                     Headloss Accumulation

Lead PI:                       Mary Jo Kirisits

Awarded amount:      $43,177


Project Abstract

Biologically-active filters (biofilters) can remove an array of organic and inorganic contaminants in drinking water. Biofilters are prone to rapid headloss development, which translates to more frequent backwashing and higher energy demands. Bacteria require a variety of elements (such as carbon, nitrogen, and phosphorus) for growth, but the nutrients nitrogen and phosphorus might be limiting in a biofilter. Such nutrient-limited conditions can cause increased microbial production of extracellular polymeric substances (EPS), which likely contribute to filter fouling. We hypothesize that a nutrient limitation in a biofilter leads to increased EPS production and concomitant headloss accumulation.

The overall objective of the proposed work is to gain a fundamental understanding of the effects of nitrogen and phosphorus on EPS production in drinking-water biofilters. Specific objectives are to (1) optimize an EPS extraction protocol for granular biofilter media; (2) compare the EPS concentration and headloss in bench-scale biofilters under carbon-, nitrogen-, and phosphorus-limited conditions; and (3) explore cell-cell signaling and gene expression in the microbial community under carbon-, nitrogen-, and phosphorus-limited conditions.

To meet these objectives, a two-year project ($50,058) is proposed, which will be divided into three tasks. In Task 1, an EPS extraction protocol will be optimized to recover EPS from granular filter media. In Task 2, three parallel bench-scale biofilters will be constructed and run under several nutrient conditions; EPS and headloss will be quantified over time. In Task 3, the concentrations of intercellular signaling molecules will be quantified and the microbial transcriptome will be assembled de novo. Together, these data will show if a link exists among the influent molar ratio of carbon to nitrogen to phosphorus (C:N:P), EPS production, and headloss accumulation in drinking-water biofilters and will provide a mechanistic basis for that link. If this link exists, then nitrogen/phosphorus supplementation might be a practical strategy that utilities can adopt to increase filter run times and conserve energy.