The effect of nutrient limitations on the production of extracellular polymeric substances by drinking-water bacteria

dc.contributor.advisorKirisits, Mary Jo
dc.creatorEvans, Ashley Nicholeen
dc.date.accessioned2013-10-29T19:47:18Zen
dc.date.accessioned2017-05-11T22:35:24Z
dc.date.available2017-05-11T22:35:24Z
dc.date.issued2013-05en
dc.date.submittedMay 2013en
dc.date.updated2013-10-29T19:47:19Zen
dc.descriptiontexten
dc.description.abstractBiological filtration (biofiltration) of drinking-water is gaining popularity due the potential for biodegradation of an array of contaminants not removed by traditional drinking-water processes. However, previous research has suggested that biomass growth on biofilter media may lead to increased headloss, and thus, greater energy and water requirements for backwashing. Research has suggested that the main cause of headloss might be due to extracellular polymeric substances (EPS) rather than the bacterial cells themselves. As EPS production has been shown to increase under nitrogen- and phosphorus-limited or -depleted conditions, the goal of this research was to add to the body of knowledge regarding biofiltration by studying the relationship between EPS production and nutrient limitations in drinking-water. Batch experiments with a synthetic groundwater were run with a mixed community of drinking-water bacteria under nutrient-balanced (a molar carbon to nitrogen to phosphorus ratio [C:N:P] of 100:10:1), nutrient-limited (e.g., C:N:P of 100:10:0.1), and nutrient-depleted conditions (C:N:P of 100:0:1 or 100:10:0). After 5 days, growth was measured as the optical density at 600 nanometers (OD600), and the concentrations of free and bound carbohydrates and proteins, the main components of EPS, were measured. In batch experiments with 2.0 and 0.2 g/L as carbon (mixture of acetic acid, mannitol and sucrose) increases in EPS production per OD600 and decreases in growth were noted under nutrient-depleted conditions. When the same experiments were conducted with a pure culture of Bacillus cereus, bound polysaccharides normalized to OD600 increased under nitrogen- and phosphorus-depleted conditions. Since previous research suggested that Bradyrhizobium would be an important player in EPS production in drinking-water biofilters, similar batch experiments were conducted with Bradyrhizobium. However, due to experimental challenges with Bradyrhizobium japonicum USDA 110, differences in EPS production under nutrient limitations could not be reliably assessed. Additional work is required with Bradyrhizobium. Recommendations for future work include the replication of these batch conditions in steady-state chemostats containing biofilm attachment media and in bench-scale columns. Additionally, future work should include experiments at carbon concentrations as low as 2 mg/L to match typical carbon concentrations in drinking-water biofilters.en
dc.description.departmentEnvironmental and Water Resources Engineeringen
dc.format.mimetypeapplication/pdfen
dc.identifier.urihttp://hdl.handle.net/2152/21794en
dc.language.isoen_USen
dc.subjectDrinking wateren
dc.subjectbiofiltrationen
dc.subjectbiologicalen
dc.subjectfilteren
dc.subjectwateren
dc.subjectEPSen
dc.subjectextracellular polymeric substancesen
dc.subjectheadlossen
dc.subjectbacteriaen
dc.subjectBradyrhizobiumen
dc.subjecttreatmenten
dc.subjectdrinkingen
dc.subjectnitrogenen
dc.subjectphosphorusen
dc.subjectnutrienten
dc.subjectlimitationen
dc.titleThe effect of nutrient limitations on the production of extracellular polymeric substances by drinking-water bacteriaen

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