Enhancement of granulation and start‐up in the anaerobic sequencing batch reactor

Abstract

The phenomenon of granulation was studied in anaerobic sequencing batch reactors (ASBRs) treating a synthetic sucrose wastewater. The objective was to study methods of minimizing the time typically required for start‐up of anaerobic processes, such as the ASBR. Specifically, it was hypothesized that development of a granular biomass soon after initial start‐up of the ASBR would significantly decrease the overall time required to achieve given organic and hydraulic loading rates. Laboratory‐scale ASBRs were seeded with anaerobically digested municipal biosolids and operated until granulation was observed or for a period of 5 months without granule development, whichever occurred first. Granule development was measured by determination of the average particle diameter of a representative sample of biosolids from the ASBRs. Granulation enhancements were added to the ASBRs to initiate early granule development and to aid in start‐up. Enhancements included powdered activated carbon, granular activated carbon, silica sand, garnet, polymers, and ferric chloride. The cationic polymer had the most beneficial effects on granulation enhancement, reducing the time required to form granules by approximately 75% compared to an un enhanced control ASBR.