Bubble Free Aeration & Nitrificantion Of Membrane Aerated Biofilm Reactor

Nitrogenous pollutants from domestic and industrial wastewater are promoting the entrophication effects in rivers and lakes. Thus, the removal of nitrogen from wastewater is of increasing importance. Microbial nitrification is a key process in the removal of ammonia nitrogen from wastewater. Due to slow growth rate and the relatively high O₂ consumption, nitrifying bacteria are generally outcompeted by heterotrophic bacteria for O₂. As a result, nitrification only occurs in conventional biofilm reactors when the organic carbon concentration is low.A membrane Aerated Biofilm Reactor(MABR) has been proposed as a promoting alternative to the conventional biofilm reactors. In the MABR system, the biofilm develops on the outside surface of a hollow fiber membrane, and the O₂ is supplied from the inside of the membrane to the bottom of the biofilm, whereas organic carbon in wastewater is supplied from the biofilm surface. Consequently, nitrification can occur at the bottom of the biofilm, where O₂ concentration is high and the organic carbon concentration is low due to diffusion limitation, resulting in high nitrification capacity of the reactor.In this study the whole work was divided into three aspects: study on pollution and its cleaning of hollow fiber membrane used in bubble free aeration; study on bubble free aeration using hollow fiber membranes; study on the nitrification capacity of MABR filled with synthetic wastewater high in ammonia nitrogen(80²28mg/L).By an evaluation of the recovery effect of the mass transfer coefficient with various cleaning method and observation of the surface after every step of cleaning, the characteristics of membrane pollution in MABR and its cleaning are studied. It could be conclude that the inorganic pollutant has a big contribution on the membrane pollution. An 80% recovery effect rate of the mass transfer coefficient was obtained finally.The influences of hydrologic condition and air pressure on oxygen transfer ability were studied. At an air pressure 0.025Mpa the effects of Sherwood numbers on the Reynolds numbers can be evaluated as follow Sh=1.7957·Re^0.3254·Sc^0.33。Sc0.33 High nitrification was achieved during the study. When operated as a completely mixed reactor, a 65% ammonia nitrogen removal and a 0.377 kgm^-3d^-1of volumetric nitrification rate were obtained at the highest nitrogen loading rate. During plug flow...