Studies the Factors of the Simultaneous Removal of Nitrogen and Carbon on Membrane Aeration Bioreactor

A Membrane aerated bioreactor (MABR) capable of simultaneous nitrification and denitrification in a single reactor vessel was developed to investigate the factors of the simultaneous removal of nitrogen and carbon. The results showed that when the bubble point pressure of membrane modules is 25kPa, the relationship between oxygenation efficiency and intransmembrane pressure were not positively correlated, controlling the transmembrane pressure was 15kPa, oxygen supply rate (OSR) was the highest. During the earlier stage of operation, reducing the hydraulic retention time of MABR could improve the integral removal efficiency, when the HRT was 2h, the removal of COD and ammonia - nitrogen were respectively 70.29% and 52.3%. The dissolved oxygen in the reactor had a significant influence, with the dissolved oxygen （DO） concentration about 0.5mg/L, ammonia-nitrogen and total nitrogen removal efficiency was better, the removal rate were 79.5% and 63% respectively. The reaction tank had CO2 accumulation, and caused pH reduced to 5.8, the operation should maintain the pH at 7.5 by increasing the alkalinity of the raw water.

Quantitative Assessment of Oxygen Availability: Perceived Aerobiosis and Its Effect on Flux Distribution in the Respiratory Chain of Escherichia coli

ABSTRACT Despite a large number of studies on the role of oxygen in cellular processes, there is no consensus as to how oxygen availability to the cell should be defined, let alone how it should be quantified. Here, a quantitative definition for oxygen availability (perceived aerobiosis) is presented; the definition is based on a calibration with reference to the minimal oxygen supply rate needed for fully oxidative catabolism (i.e., complete conversion of the energy source to CO2 and water for glucose-limited conditions). This quantitative method is used to show how steady-state electron fluxes through the alternative cytochrome oxidases of Escherichia coli are distributed as a function of the extent of aerobiosis of glucose-limited chemostat cultures. At low oxygen availability the electron flux is mainly via the high-affinity cytochrome bd oxidase, and, at higher oxygen availability, a similar phenomenon occurs but now via the low-affinity cytochrome bo oxidase. The main finding is that the catabolic activities of E. coli (and specifically its respiratory activity) are affected by the actual oxygen availability per unit of biomass rather than by the residual dissolved oxygen concentration of the culture.