Effect of substrate N/COD ratio on the formation and characteristics of aerobic granules developed in sequencing batch reactors

With increasing demands on water quality, advanced and cost-effective techniques for nitrogen removal from wastewater become more and more important. Water industry has very strong demand for development of novel biotechnology for efficient removal of nitrogen from industrial and municipal wastewaters. This research work attempted to develop aerobic granules for simultaneous organic carbon and nitrogen removal. For this purpose, four sequencing batch reactors (SBR) were operated at different substrate N/COD ratios in the range of 5/100 to 30/100 by weight. Results showed that aerobic granules could be formed over the substrate N/COD ratios of 5/100 to 30/100, i.e. aerobic granulation would be independent of the substrate N/COD ratios applied, However, the substrate N/COD ratio showed a significant effect on microbial and physicochemical characteristics of aerobic granules. It was found that the activity of nitrifying bacteria was enhanced with the increase of substrate N/COD ratio. The cell hydrophobicity was improved significantly, while the production of extracellular polysaccharides showed a decreasing trend as the substrate NKOD ratio was increased.Doctor of Philosophy (CEE