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Yoon, Sukhwan,Nissen, Silke,Park, Doyoung,Sanford, Robert A.,Loffler, Frank E. American Society for Microbiology 2016 Applied and environmental microbiology Vol.82 No.13
<P>Bacteria capable of reduction of nitrous oxide (N2O) to N-2 separate into clade I and clade II organisms on the basis of nos operon structures and nosZ sequence features. To explore the possible ecological consequences of distinct nos clusters, the growth of bacterial isolates with either clade I (Pseudomonas stutzeri strain DCP-Ps1, Shewanella loihica strain PV-4) or clade II (Dechloromonas aromatica strain RCB, Anaeromyxobacter dehalogenans strain 2CP-C) nosZ with N2O was examined. Growth curves did not reveal trends distinguishing the clade I and clade II organisms tested; however, the growth yields of clade II organisms exceeded those of clade I organisms by 1.5- to 1.8-fold. Further, whole-cell half-saturation constants (K(s)s) for N2O distinguished clade I from clade II organisms. The apparent Ks values of 0.324 +/- 0.078 mu M for D. aromatica and 1.34 +/- 0.35 mu M for A. dehalogenans were significantly lower than the values measured for P. stutzeri (35.5 +/- 9.3 mu M) and S. loihica (7.07 +/- 1.13 mu M). Genome sequencing demonstrated that Dechloromonas denitrificans possessed a clade II nosZ gene, and a measured Ks of 1.01 +/- 0.18 mu M for N2O was consistent with the values determined for the other clade II organisms tested. These observations provide a plausible mechanistic basis for why the relative activity of bacteria with clade I nos operons compared to that of bacteria with clade II nos operons may control N2O emissions and determine a soil's N2O sink capacity.</P>
Yoon, Hyun,Song, Min Joon,Yoon, Sukhwan American Chemical Society 2017 Environmental science & technology Vol.51 No.18
<P>N2O is a potent greenhouse gas and ozone-depletion agent. In this study, a biofiltration system was designed for removal of N2O emitted at low concentrations (<200 ppmv) from wastewater treatment plants. The proposed biofiltration system utilizes untreated wastewater from the primary sedimentation basin as the source of electron donor and nutrients and energy requirement is minimized by utilizing gravitational force and pressure differential to direct liquid medium and gas through the biofilter. The experiments performed with laboratory-scale biofilter in two different configurations confirmed the feasibility of the biofiltration system. The biofilter operated with cycling of raw wastewater exhibited up to 94% and 53% removal efficiency with 100 ppmv N2O in N-2 and air, respectively, as the feed gas, corroborating that untreated wastewater can serve as a robust Inflow source of electron donor and nutrients.The laboratory-scale biofilter operated with a continuous flow-through of synthetic wastewater attained >99.9% removal of N2O from N-2 background at the gas flow rate up to 2,000 mL.min(-1) and >50% N2O removal from air background at the gas flow rate of 200 mL.min(-1) nosZ-containing bacterial genera including Flavobacterium (5.92%), Pseudomonas (4.26%) and Bosea (2.39%) were identified in the biofilm samples collected from the oxic biofilter, indicating these organisms were responsible for N2O removal.</P>
Yoon, Hyun,Song, Min Joon,Kim, Daehyun D.,Sabba, Fabrizio,Yoon, Sukhwan American Chemical Society 2019 Environmental science & technology Vol.53 No.4
<P>Wastewater treatment plants (WWTPs) are among the major anthropogenic sources of N<SUB>2</SUB>O, a major greenhouse gas and ozone-depleting agent. We recently devised a zero-energy zero-carbon biofiltration system easily applicable to activated sludge-type WWTPs and performed lab-scale proof-of-concept experiments. The major drawback of the system was the diminished performance observed when fully oxic gas streams were treated. Here, a serial biofiltration system was tested as a potential improvement. A laboratory system with three serially positioned biofilters, each receiving a separate feed of artificial wastewater, was fed N<SUB>2</SUB>O-containing gas streams of varied flow rates (200-2000 mL·min<SUP>-1</SUP>) and O<SUB>2</SUB> concentrations (0-21%). Use of the serial setup substantially improved the reactor performance. Fed fully oxic gas at a flow rate of 1000 mL·min<SUP>-1</SUP>, the system removed N<SUB>2</SUB>O at an elimination capacity of 0.402 ± 0.009 g N<SUB>2</SUB>O·m<SUP>-3</SUP>·h<SUP>-1</SUP> (52.5% removal), which was approximately 2.4-fold higher than that achieved with a single biofilter, 0.171 ± 0.024 g N<SUB>2</SUB>O·m<SUP>-3</SUP>·h<SUP>-1</SUP>. These data were used to validate the mathematical model developed to estimate the performance of the N<SUB>2</SUB>O biofiltration system. The Nash-Sutcliffe efficiency indices ranged from 0.78 to 0.93, confirming high predictability, and the model provided mechanistic insights into aerobic N<SUB>2</SUB>O removal and the performance enhancement achieved with the serial configuration.</P> [FIG OMISSION]</BR>