Formation and Characterization of Aerobic Granules in Sewage Treatment

Abstract

Aerobic granulation is an emerging technology for wastewater treatment. However, long start-up periods are required for the development of granules. In this study, aerobic granules were developed in ambient conditions in four identical sequencing batch reactors (SBRs). The reactors were fed with a mixture of domestic wastewater and leachate from the acidification reactor of two-phase anaerobic digester treating food waste. They were seeded with three different inert nuclei to compare their effect on the process of granulation. The results show that when the reactor is seeded with large flocs and selective discharge of the microbial consortia is allowed, the presence of inert nuclei is not essential for the formation of granules, neither has it has any major influence on the properties of the granules. The SEM images show absence of filamentous organisms in all the reactors. Organic removal efficiency has been found to be highest (90%) in the reactor inoculated with commercial activated carbon. The results indicate that the reactor without any particle addition formed the granule with the highest EPS content and protein, which is essential for bacterial agglomeration. The granules were found to be very well settling with settling velocity of 40m/h and SVI of around 20mL/g in all the four reactors. The integrity coefficient and hydrophobicity of the sludge in all the reactors were found to be similar.