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Microbiological Characterization and Ecological Control of Membrane Biofouling in Side Stream Municipal Sewage Treatment Reactors Operated for Nitrification

Daniel B. Oerther, Ph.E., PE, BCEE – Mathes Chair and Director of Environmental Research Center, Missouri University of Science and Technology

Increasingly stringent discharge regulations require conventional municipal sewage treatment plants to undertake operational upgrades to remove the nutrient nitrogen in addition to removing biochemical oxygen demand. Conceptually, reduced nitrogen species including protenaceous nitrogen, urea, and ammonia present in the influent sewage are converted sequentially to nitrite and then nitrate in the aeration basis before complete removal is accomplished through denitrification. A carefully examination of the materials balance within a typical plant demonstrates that more than 50 percent of the reduced nitrogen loading on the aeration basis originates from liquid recycle streams from the solids handling operations. Effectively treating these nitrogen rich side streams represents a major operational upgrade to many existing municipal sewage treatment plants to protect surface water quality from eutrophication. While membrane bioreactors offer a compact unit operation that can be cost effectively retrofitted into space constrained plant layouts, the operation and maintenance concerns associated with membrane biofouling represent the most substantial impediment to this technology.

To address this challenge, the primary research objective of this project is to prevent the initiation of membrane biofouling. This overall objective will be achieved through the specific aims of characterizing the bacterial populations associated with the initiation of membrane biofouling, and evaluating ecological control measures to prevent the initiation of membrane biofouling. The target unit operation of interest will be the side stream nitrifying membrane bioreactor.

To accomplish this objective, this project will examine the initiation of biofilm formation on membrane surfaces through a synergistic study of membrane properties, the chemical composition of side stream wastewater, and the ecology of nitrifying microbial communities. Four tasks will be performed, namely: (T1) lab-scale membrane bioreactors will be designed, constructed, and operated to treat a synthetic side stream wastewater; (T2) biofouling will be characterized through evaluation of transmembrane flux, physical inspection of membrane surfaces, and chemical characterization of biofouling constituents; (T3) microbiological characterization of membrane bound and planktonic bacterial populations will be performed using quantitative 16S ribosomal RNA targeted molecular signature methods; and (T4) the effectiveness of bioreactor operating conditions to control microbial community structure and therefore reduce the extent of biofouling will be evaluated