iPURSE 2016

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https://ir.lib.pdn.ac.lk/handle/20.500.14444/40

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Browsing iPURSE 2016 by Subject "Anaerobic ammonia- oxidizing"

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    Biological pathways of nitric oxide production in anaerobic ammonia- oxidizing bacterial granules
    (University of Peradeniya, 2016-11-05) Rathnayake, L.; Satoh, H.
    Nitric oxide (NO) is an important atmospheric trace gas, which has a direct effect on the ozone chemistry of the atmosphere. NO is a free radical and toxic to a wide range of organisms. Considering the toxicity of NO to humans, the Dutch government (MAC values, as of 1/1/2007) has defined the relatively low maximum 8-h exposure limit. Biological nitrogen removal from wastewaters via anaerobic ammonium oxidation (anammox) process is a sustainable treatment process due to its great advantages over the conventional methods and there are more than 120 full-scale treatment plants operated worldwide. According to some studies, 0.003-0.03%of nitrogen load is being removed as NO by an anammox process. In an anammox biofilm or granule, NO can be produced via mainly four microbiological pathways; namely i) anammox pathway by bacteria, ii) nitrification by Ammonia Odixing Bacteria (AOB), iii) nitrifier denitrification by AOB, and (iv) denitrification by heterotrophic denitriers. So far, no study has revealed the mechanism of NO emissions from anammox granules and it is still unclear which microorganisms and pathways are responsible for NO emissions in an anammox process. Therefore, the study investigated the microorganisms and pathways responsible for the NO production in the anammox granules taken from an anammox reactor. Using anoxic batch experiments, anammox reaction and NO emission from anammox granules were estimated. The anammox and the NO emission rates were 0.41 ± 0.16 μmolmg-BSA–1 h–1 and 51.6 ± 11.9 nmol mg-BSA–1 h–1, respectively. Furthermore, the anoxic batch experiments using labeled isotopic substrates for microorganisms with or without inhibitors of microorganisms were conducted to identify NO production pathways. In inhibition batch tests, it was likely that both anammox and heterotrophic denitrifiers contributed in NO production in the anammox granules. To the best of our knowledge, this is the first report demonstrating the bacterial species responsible for NO emissions from anammox granules.