Natural granulation in sequencing batch reactor: granules characteristics and performance for domestic wastewater treatment

ABSTRACT

Sequencing batch reactor (SBR) with aerobic granular biomass is a compact and promising technology in wastewater treatment. However, its use for sanitary sewage is still a challenge due to the instability and disintegration of the aggregates. The present work evaluated the biomass granulation in a pilot SBR, without addition of inoculum, for sanitary sewage treatment. The study was divided into three operational strategies with cycles composed by the phases of: filling, anoxic, aerobic, settling, effluent withdrawal and idle. The variations in the operational cycle time were: 4 hours (strategies I and II) and 6 hours (strategy III); and anoxic phase of 13, 30 and 90 minutes in strategies I, II and III, respectively. The granules development occurred in a natural way, without inoculation, and the reactor treated the sanitary wastewater meeting the national requirements of effluent discharge standards. The characteristics of the aerobic granular sludge and the reactor’s performance improved with the anoxic phase increase. Granules (200-400 µm) were more than 80% of the biomass with good sedimentation characteristics (SVI₃₀/SVI₁₀ ratio between 0.7-1.0), in strategy III. The greatest relevance variables for the process were SVI₃₀/SVI₁₀ and COD Effluent/COD_S Anoxic ratios, polysaccharides and temperature, indicating the importance of these parameters for the maintenance of the operational stability of granular SBR.

Keywords:
natural aerobic granulation; sequencing batch reactor; sanitary sewage treatment