Aerobic granular sludge – Microbial and morphological characterization

Abstract

Biological wastewater treatment processes have a crucial importance to the modern world, due to the ever increasing need of sanitation and pollution control in urbanized areas. Aerobic granular sludge represents an alternative for the conventional biological system. Recent studies have greatly expanded the vision on aerobic granular sludge morpho-functional and microbiological peculiarities and their influence on wastewater treatment performance and behavior. The microbial composition of the granules obtained in a sequencing batch reactor – SBR, were characterized using microscopy and molecular biology techniques. Scanning electron microscopy investigations,revealed in sights into the granules morphology and structure: size, pore dimensions, presence of filamentous bacteria. Molecular biology techniques were used to determine the presence and abundance of biotechnologically useful bacteria (nitrifiers, denitrifiers) in the sludge granules samples. The samples were subjected to PCR amplification using the following primers: specific for ammonium oxidizing bacteria; specific for nitrite oxidizing bacteria; universal bacteria primers. The results indicated the presence of nitrifying bacteria specific genes belonging to Nitrosomonas sp., Nitrospira sp., and Nitrobacter sp., species responsible for nitrification. The abundance and diversity of identified microbial species were correlated with the treatment performances registered for the operational sequencing batch reactor.