Effects of COD/N ratio and DO concentration on simultaneous nitrification and denitrification in an airlift internal circulation membrane bioreactor.

Key Laboratory of Industrial Ecology and Environmental Engineering, MOE, School of Environmental and Biological Science and Technology, Dalian University of Technology, Dalian 116024, China.
Journal of Environmental Sciences (Impact Factor: 1.92). 02/2008; 20(8):933-9. DOI: 10.1016/S1001-0742(08)62189-0
Source: PubMed

ABSTRACT The effects of chemical oxygen demand and nitrogen (COD/N) ratio and dissolved oxygen concentration (DO) on simultaneous nitrification and denitrification (SND) were investigated using an airlift internal circulation membrane bioreactor (AIC-MBR) with synthetic wastewater. The results showed that the COD efficiencies were consistently greater than 90% regardless of changes in the COD/N ratio. At the COD/N ratio of 4.77 and 10.04, the system nitrogen removal efficiency became higher than 70%. However, the nitrogen removal efficiency decreased to less than 50%, as the COD/N ratio shifted to 15.11. When the operating DO concentration was maintained at 1.0 mg/L in AIC-MBR, a satisfying SND was achieved. Either low or high DO concentration could restrain SND.

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    ABSTRACT: In this study, simultaneous nitrification and denitrification (SND) from synthetic wastewater were performed to evaluate dissolved oxygen(DO) effects on chemical oxygen demand(COD) and nitrogen removal in a single membarne bio-reactor(MBR). DO levels in MBR at Run 1, 2, and 3 were 1.9~2.2, 1.3~1.6, and 0.7~1.0 mg/L, respectively. Experimental results indicated that DO had an important factor to affect COD and total nitrogen(TN) removal. SND were able to be accomplished in the continuous-aeration MBR by controlling ambient DO concentration. It is postulated that, because of the oxygen diffusion limitation, an anoxic micro-zone was formed inside the flocs where the denitrification might occur. From the results of this study, 96% of COD could be removed at DO of 0.7mg/L. At run 2 72.92% of nitrogen was removed by the mechanisms of SND (7.75mg-TN/L in effluent). In this study, SND was successfully occurred in a MBR due to high MLSS that could help to form anoxic zone inside microbial floc at bulk DO concentrations of 1.3~1.6mg/L.
    Korean Journal of Environmental Agriculture. 01/2009; 28(4).
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    ABSTRACT: Background The post-denitritation sequencing batch reactor (SBR) is widely-used and can achieve high levels of nitrogen removal. In this study the effect of influent COD/TN (total nitrogen) ratio (i.e. C/N ratio) on nitrogen removal performance was investigated. ResultsThe experimental results showed that polyhydroxybutyrate (PHB) was the internal carbon source for denitritation, so PHB degradation rate following first-order kinetics was the rate-limiting step both for simultaneous nitritation–denitritation (SND) in the substrate famine period of the oxic stage and endogenous denitritation in the anoxic stage. Higher influent C/N ratio resulted in more PHB fractions in microorganisms, which facilitated a higher efficiency of SND and a faster endogenous denitritation rate (DNR). Consequently, mean TN removal ratio in oxic stage dropped from 32.81% to 8.61%, and average endogenous DNR in the anoxic stage fell from 1.50 to 0.27 mgN h-1 gVSS-1, when influent C/N ratio changed from 6.82 to 1.89. Furthermore, PHB fraction in the biomass did not drop drastically when influent C/N ratio dropped for a short-term period, which facilitated better resistance to shock loads. Conclusion High influent C/N ration benefits nitrogen removal in this process, and an influent C/N ratio of 4.00 was suitable for advanced nitrogen removal. © 2013 Society of Chemical Industry
    Journal of Chemical Technology & Biotechnology 10/2013; 88(10). · 2.50 Impact Factor
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    ABSTRACT: Simultaneous nitrification and denitrification (SND) occurs concurrently in the same reactor under micro dissolved oxygen (DO) conditions. Anaerobic zone was applied for phosphorus release prior to an aerated membrane bio-reactor (MBR), and anoxic zone was installed by placing a baffle in the MBR for enhancing denitrification even in high DO concentration in the MBR. Phosphorus removal was tested by alum coagulation in the anaerobic reactor preceding to MBR. DO concentration were 2.0, 1.5, 1.0, 0.75 mg/L in the MBR at different operating stages for finding optimum DO concentration in MBR for nitrogen removal by SND. pH was maintained at 7.0~8.0 without addition of alkaline solution even with alum addition due to high alkalinity in the raw sewage. Both TCODcr and -N removal efficiency were over 90% at all DO concentration. TN removal efficiencies were 50, 51, 54, 66% at DO concentration of 2.0, 1.5, 1.0, 0.75 mg/L, respectively. At DO concentration of 0.75 mg/L with addition of alum, TN removal efficiency decreased to 54%. TP removal efficiency increased from 29% to 95% by adding alum to anaerobic reactor. The period of chemical backwashing of the membrane module increased from 15~20 days to 40~50 days after addition of alum.
    Journal of Korean Society of Environmental Engineers. 10/2013; 35(10).

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