Formation and characterization of the micro-size granular sludge in denitrifying sulfur-conversion associated enhanced biological phosphorus removal (DS-EBPR) process.

Denitrifying Sulfur conversion-associated Enhanced Biological Phosphorus Removal (DS-EBPR) bioprocess has been recently developed for saline sewage treatment. This study investigated the applicability of granulation technology in DS-EBPR by long-term operation (272 days) of a lab-scale reactor to cultivate sludge granules, then analyzed important physicochemical and biological properties. The findings of this research showed that the net P removal and denitrification efficiencies in DS-EBPR were 80% and 98%, respectively. The average particle size was about 100 μm, and the ratio of SVI and SVI was <1.3, indicating the activated sludge was well aggregated as micro-granules. The dry density was between 32 and 56 mg/mL, and the specific surface area was 28 m/g, demonstrating good microporous structure. FISH reveals absence of PAOs, but enriched with SRB (predominant) and denitrifying bacteria in the DS-EBPR granular sludge. Overall, this study provided essential characterization information of DS-EBPR granular sludge which can be used for future development.