Phosphorus removal characteristics of granular and flocculent sludge in SBR

Aerobic granulation technology has become a novel biotechnology for wastewater treatment. However, the distinct properties and characteristics of phosphorus removal between granules and flocculent sludge are still sparse in enhanced biological phosphorus removal process. Two identical sequencing batch reactors (SBRs) were operated to compare phosphorus removal performance with granular sludge (R1) and flocculate activated sludge (R2). Results indicated that the start-up period was shorter in R2 than R1 for phosphorus removal, which made R2 reach the steady-state condition on day 21, while R1 was on day 25, and R2 released and took up more phosphorus than R1. As a result, the phosphorus removal was around 90% in R2 while 80% in R1 at the steady-state system. The special phosphorus release rate and special phosphorus uptake rate were 8.818 mg P/g volatile suspended solids (VSS)/h and 9.921 mg P/g VSS/h in R2, which were consistently greater than those (0.999 and 3.016 mg P/g VSS/h) in R1. The chemical oxygen demand removal in two reactors was similar. The granular SBR had better solid-separation performance and higher removal efficiency of NH (4) (+) -N than flocculent SBR. Denaturing gradient gel electrophoresis of PCR-amplified 16S rDNA fragment analysis revealed that the diversity and the level of phosphorus-accumulating bacteria in flocculent sludge were much more than those in the granular sludge.