Simultaneous Nitrification and Denitrification with Low Dissolved Oxygen Level and C/N ratio

The Orbal process for the treatment of waste waters, claims simultaneous nitrification and denitrification in the outer lane in the presence of a dissolved oxygen concentration of 1.5 mg/l. The potential of this process is to offer both a reduced cost and simplified operation for nitrogen removal in the Mediterranean environment. The objective of this work was to investigate these claims and attempt to describe a mechanism for the experimental verifications. Using mixed cultures grown in chemostats, simultaneous nitrification and denitrification was observed under oxic/anoxic cycling. A reduced pathway, or ‘nitrite shunt’ could not be demonstrated but it was possible to explain the observations based on the lag time of the denitrifiers under oxic conditions. Denitrification continued for some time before oxygen replaced nitrate as the terminal electron acceptor and the length of the lagged response was a function of the duration of the anoxic conditions.

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Impact of Dissolved Oxygen and Anoxic Decay on the Longterm OModeling of Simultaneous Nitrification and Denitrification (SNdN) in a Pilot Scale MBR

Proceedings of the Water Environment Federation ◽

10.2175/193864709793954998 ◽

2009 ◽

Vol 2009 (14) ◽

pp. 2711-2729

Author(s):

M. Sarioglu ◽

G. İnsel ◽

D. Orhon

Keyword(s):

Dissolved Oxygen ◽

Pilot Scale ◽

Simultaneous Nitrification And Denitrification ◽

Nitrification And Denitrification

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Some Effects of Temporary Exposure to Low Dissolved Oxygen Levels on Pacific Salmon Eggs

Journal of the Fisheries Research Board of Canada ◽

10.1139/f58-013 ◽

1958 ◽

Vol 15 (2) ◽

pp. 229-250 ◽

Cited By ~ 91

Author(s):

D. F. Alderdice ◽

W. P. Wickett ◽

J. R. Brett

Keyword(s):

Oxygen Consumption ◽

Dissolved Oxygen ◽

Oxygen Demand ◽

Oxygen Availability ◽

Oncorhynchus Keta ◽

Hatching Rate ◽

Oxygen Level ◽

Low Oxygen ◽

Low Dissolved Oxygen ◽

Oxygen Levels

Eggs of the chum salmon (Oncorhynchus keta) were exposed to various constant levels of dissolved oxygen for a period of seven days. The procedure was repeated with fresh egg samples at various developmental stages. Temperatures were constant at 10 °C. from fertilization to hatching. Estimates of oxygen consumption uninhibited by low dissolved oxygen levels were obtained at various stages of egg development for whole eggs and also on the basis of the weight of larvae, excluding the yolk. Eggs were most sensitive to hypoxia between 100–200 Centigrade degree-days and compensated for reduced oxygen availability by reducing the oxygen demand and rate of development. Very low oxygen levels at early incubation stages resulted in the production of monstrosities. At about the time the circulatory system becomes functional the compensatory reduction in rate of growth under hypoxial conditions is reduced, but eggs no longer survive extreme hypoxial conditions. Eggs subjected to low dissolved oxygen levels just prior to hatching hatch prematurely at a rate dependent on the degree of hypoxia. The maximum premature hatching rate corresponded approximately with the median lethal oxygen level. Estimated median lethal levels rose slowly from fertilization to hatching. Oxygen consumption per egg rose from fertilization to hatching while the consumption per gram of larval tissue declined from a high to a low level at about the time of blastopore closure. Subsequently, a slight rise in the rate occurred up to a level which was more or less constant to hatching. "Critical" dissolved oxygen levels were calculated and they appear to define the oxygen level above which respiratory rate is unmodified by oxygen availability. Critical levels ranged from about 1 p.p.m. in early stages to over 7 p.p.m. shortly before hatching.

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Simultaneous Nitrification and Denitrification in Biofilm-Electrode Reactor

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.652-654.1633 ◽

2013 ◽

Vol 652-654 ◽

pp. 1633-1636 ◽

Cited By ~ 1

Author(s):

Xiao Liu ◽

Mei Yang ◽

Xian Huai Huang

Keyword(s):

Dissolved Oxygen ◽

Electric Current ◽

Removal Efficiency ◽

Nitrogen Removal ◽

Simultaneous Nitrification And Denitrification ◽

Autotrophic Denitrification ◽

Effluent Recirculation ◽

Removal Efficiencies ◽

Nitrification And Denitrification ◽

Limited Oxygen

To study the nitrification and denitrification in compartmented biofilm-electrode reactor (C-BER) under limited oxygen, influence of mild electrolysis on nitrogen removal was investigated under low C/N (mole ratios) with dissolved oxygen about 1mg/ L. It was found that nitrogen removal was mainly through simultaneous nitrification and denitrification (SND). C/N ratio was 1, average total nitrogen (TN) removal efficiencies were 33% and 45% for electric current of 5 and 15mA. C/N was 0.5, electric current was 25mA and effluent was recirculated, TN removal efficiency increased to 60%, within which autotrophic denitrification accounted for about 51%. There was about 50% NH3-N reduced under 15mA when C/N ratio was 1, this increased to 70% for 25mA when C/N ratio was 0.5. Nevertheless, TN reduced between anode and cathodes accounted for 64% in all. The experimental results show that both higher electric current and effluent recirculation are good for SND process under oxygen-limited condition, nitrogen removal can be activated by mild electrolysis.

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The presence of ammonium facilitates nitrite reduction under PHB driven simultaneous nitrification and denitrification

Water Science & Technology ◽

10.2166/wst.2004.0639 ◽

2004 ◽

Vol 50 (10) ◽

pp. 181-188 ◽

Cited By ~ 8

Author(s):

B.M. Gibbs ◽

L.R. Shephard ◽

K.A. Third ◽

R. Cord-Ruwisch

Keyword(s):

Dissolved Oxygen ◽

Wastewater Treatment Plants ◽

Reducing Power ◽

Nitrite Reduction ◽

Synthetic Wastewater ◽

Batch Reactors ◽

Simultaneous Nitrification And Denitrification ◽

Low Oxygen ◽

Total N ◽

Nitrification And Denitrification

For economic and efficient nitrogen removal from wastewater treatment plants via simultaneous nitrification and denitrification the nitrification process should stop at the level of nitrite such that nitrite rather than nitrate becomes the substrate for denitrification. This study aims to contribute to the understanding of the conditions that are necessary to improve nitrite reduction over nitrite oxidation. Laboratory sequencing batch reactors (SBRs) were operated with synthetic wastewater containing acetate as COD and ammonium as the nitrogen source. Computer controlled operation of the reactors allowed reproducible simultaneous nitrification and denitrification (SND). The oxygen supply was kept precisely at a low level of 0.5 mgL−1 and bacterial PHB was the only electron donor available for denitrification. During SND little nitrite or nitrate accumulated (< 20% total N), indicating that the reducing processes were almost as fast as the production of nitrite and nitrate from nitrification. Nitrite spiking tests were performed to investigate the fate of nitrite under different oxidation (0.1–1.5 mgL−1 of dissolved oxygen) and reduction conditions. High levels of reducing power were provided by allowing the cells to build up to 2.5 mM of PHB. Nitrite added was preferentially oxidised to nitrate rather than reduced even when dissolved oxygen was low and reducing power (PHB) was excessively high. However, the presence of ammonium enabled significant reduction of nitrite under low oxygen conditions. This is consistent with previous observations in SBR where aerobic nitrite and nitrate reduction occurred only as long as ammonium was present. As soon as ammonium was depleted, the rate of denitrification decreased significantly. The significance of the observed strongly stimulating effect of ammonium on nitrite reduction under SND conditions is discussed and potential consequences for SBR operation are suggested.

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