Dissertation/Thesis Abstract

Microbial stringent response and phosphorus cycling in wastewater
by Al-Najjar, Muamar, Ph.D., University of California, Davis, 2010, 48; 3443995
Abstract (Summary)

The excess discharge of soluble reactive phosphorus into water streams often enhances the growth of algae, which can lead to eutrophication. Enhanced biological phosphorus removal (EBPR) unit processes have been widely and successfully used in full-scale wastewater treatment plants (WWTP) to remove phosphorus from wastewater. Facilities use EBPR systems because of their lower capital and sludge handling costs, relative to chemical or physical processes. The EBPR process is believed to be facilitated by polyphosphate-accumulating organisms (PAOs).

EBPR inherently imposes stressful environmental conditions on bacteria, and the microbial stringent response (MSR) is a microbial response to stress that also involves phosphorus cycling. Thus, the goal of the study reported herein was to evaluate the role of the MSR in biological phosphorus cycling by activated sludge fed synthetic wastewater. To our knowledge, such a study has not been reported elsewhere. By expanding the current focus on PAOs to also include the MSR, findings from this research may lead to further optimization of existing treatment technologies and perhaps the development of new treatment methods for the biological removal of phosphorus from wastewater.

Major findings included: (1) Phosphorus removal to undetectable levels was achieved in the fully oxic and conventional anoxic-oxic EBPR processes, with an increase in the levels of MSR indicator, ppGpp. (2) Phosphorus cycling was associated with the MSR in four reactors. (3) The presence of Rhodocyclus related PAOs or Accumulator Phosphatis in four reactors was insignificant, suggesting the MSR is likely a central element in the biological cycling of phosphorus within wastewater. (4) The genetic diversity of microorganisms varied considerably between reactors. The extent of microbial diversity may suggest that engineering a system to elicit a specific structure of a mixed microbial consortium may not be as important as a particular function, namely the MSR, for the biological removal of phosphorus from wastewater. In conclusion, the MSR associated with the biological phosphorus cycling and is, most likely, responsible for phosphorus removal in a mixed culture EBPR system.

Indexing (document details)
Advisor: Loge, Frank
Commitee: Darby, Jeannie, Loge, Frank, Nelson, Doug
School: University of California, Davis
Department: Civil and Environmental Engineering
School Location: United States -- California
Source: DAI-B 72/05, Dissertation Abstracts International
Subjects: Civil engineering
Keywords: Anoxic-oxic EBPR, Microbial stringent response, Phosphorus cycling, Phosphorus removal, Wastewater
Publication Number: 3443995
ISBN: 978-1-124-50826-9
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