Effect of Phosphorus Limitation on the Production of Extracellular Polymeric Substances (EPS) by Drinking-Water Bacteria

摘要

The drinking-water industry is increasingly interested in the optimization of biofiltration. The control of extracellular polymeric substances (EPS) in biofilters might be one such area for optimization. Heterotrophic bacteria are often cited as requiring a carbon:nitrogen:phosphorus (C:N:P) molar ratio of 100:10:1 for growth. However, the literature documents increased production of EPS when the nitrogen and/or phosphorus concentrations are limiting. If nitrogen or phosphorus limitation leads to increased EPS production, this could lead to increased headloss in a biofilter. Consequently, increased headloss will translate to increased backwash frequency and energy consumption. The goal of the current work was to examine EPS production by drinking-water bacteria under balanced nutrient conditions (C:N:P of 100:10:1) and nutrient-limited conditions. The pilot-scale data show that exopolysaccharides in the EPS decreased substantially in the phosphorus-supplemented biofilter as compared to the phosphorus-limited biofilter. The pilot-scale data also showed that phosphorus addition caused a significant change in the microbial community composition. Batch experiments, inoculated with a mixed community of drinking-water bacteria, demonstrated increased production of exopolysaccharides in the EPS (normalized to bacterial biomass) under nitrogen- and phosphorus-limited conditions.