19 research outputs found
Unravelling the reasons for disproportion in the ratio of AOB and NOB in aerobic granular sludge
In this study, we analysed the nitrifying microbial community (ammonium-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB)) within three different aerobic granular sludge treatment systems as well as within one flocculent sludge system. Granular samples were taken from one pilot plant run on municipal wastewater as well as from two lab-scale reactors. Fluorescent in situ hybridization (FISH) and quantitative PCR (qPCR) showed that Nitrobacter was the dominant NOB in acetate-fed aerobic granules. In the conventional system, both Nitrospira and Nitrobacter were present in similar amounts. Remarkably, the NOB/AOB ratio in aerobic granular sludge was elevated but not in the conventional treatment plant suggesting that the growth of Nitrobacter within aerobic granular sludge, in particular, was partly uncoupled from the lithotrophic nitrite supply from AOB. This was supported by activity measurements which showed an approximately threefold higher nitrite oxidizing capacity than ammonium oxidizing capacity. Based on these findings, two hypotheses were considered: either Nitrobacter grew mixotrophically by acetate-dependent dissimilatory nitrate reduction (ping-pong effect) or a nitrite oxidation/nitrate reduction loop (nitrite loop) occurred in which denitrifiers reduced nitrate to nitrite supplying additional nitrite for the NOB apart from the AOB
Standard of civilization, nomadism and territoriality in nineteenth-century international society
In this chapter, the encounter between the Russian Empire and the nomads of the Eurasian steppe in the nineteenth century is analyzed using the theoretical framework of the standard of civilization. The creation of the Westphalian state-model in Europe in the seventeenth century, linked to the later emergence of the notion of the standard of civilization led to the âotheringâ of the nomads of the Eurasian steppe as barbarians, as a threat to the borders of civilized Europe. The chapter presents also an argument to define âterritorialityâ as not only an institution of international society of the time but also as a distinctive quality and requirement for being considered âcivilizedâ. In this analytical framework, the nomads become the âotherâ, the âalienâ, the âmenaceâ, onto which projections of rationality and modernity were cast in order to prevent threats to Russiaâs European and civilized identity. The chapter sheds light on the encounter between âfixedâ and âmobileâ units in the course of expansion of international society; contextualizes the role played by nomadic tribes in resisting the application of Westphalian spatial categories in the Eurasian space; and scrutinizes what the role of nomads was in constructing a European, civilized identity.PostprintPeer reviewe