Effect of Limited-Aeration in AnMBR Operation

Abstract

The scarcity of water is a major global concern in the modern times. Hence, the judicial use of water must be coupled with water reuse to counteract the water depletion. To reuse water, we eye on available treatment technologies which can guide us to circular use and reuse of water and nutrients. Anaerobic digestion, is known for producing better quality effluent with a possibility of energy generation through biogas. It can also be coupled with post-treatment techniques to extract nutrients. Anaerobic membrane bioreactors have been used to treat high-strength wastewater to obtain higher particle and organic removal. Introducing limited aeration to such an anaerobic environments have been studied earlier to enhance the degradation process. Depending on the quantity of aeration added and the mechanism of aeration, studies have reported both positive and negative effects on the organic degradation. The existing studies only cover the effects of the applied aeration on the Anaerobic Digestion process. Little is talked about its effect on the sludge characteristics such as particle size and sludge rheology. This research focuses on studying the effect of applied aeration on the AnMBR performance, based on the effect of aeration on substrate degradation and on sludge characteristics. To study this, an AnMBR is operated with laboratory-made synthetic blackwater treating 5gCOD/l. A 2% increase in oxygen with respect to the sludge VSS is introduced through added air. The effect of this added aeration to the system is studied. The organic removal was enhanced by 11% when compared to the observed removal during the non-aerated phase. Ammonium concentration increased by 24% and sulphate concentration reduced by 12% in the effluent. The size of the coarser fraction of sludge, D90 increased by 13% and that of the finer fraction D10 increased by 15%. The viscosity profile of the sludge after aeration also increased. Inhibition caused to the Methanogenic activity of the sludge reduced as the sludge started adapting to the applied aeration. Activity changes to higher sets of aeration matching that of a Dissolved Aeration and Flotation system was studied. The feasibility of such a system is still a work in progress for the future. The obtained results are for an adapting sludge, and has to be continued for a better adapted sludge. Recommendations based on this study to future works on the same line, is given.