Granulation enhancement in anaerobic sequencing batch reactor operation

Abstract

Two laboratory-scale anaerobic sequencing batch reactors (anSBRs) were used to investigate the effectiveness of polymer addition for enhancing granulation. Mixed liquor volatile suspended solids (MLVSS) concentrations in R1 (with a polymer supplement) and R2 (control) were maintained at approximately 5 g/L. Granule development was measured by determination of the average bioparticle diameter of biosolids from the anSBRs. Addition of cationic polymer to R1 started on the 47th day after reactor start-up at a dosage of 1 ppm (on reactor volume) once per every two cycles. The cationic polymer had a beneficial effect on granulation. Compared to the control, it shortened the granulation process by approximately four months. Within the range investigated, food-to-microorganism (F/M) ratios at 0.5-0.6 g COD/g VSS d were also beneficial to granulation. After 300 days operation (at F/M ratio 0.5 g COD/g VSS d), the average bioparticle diameter of R1 was 0.78 mm, while R2 was only 0.39 mm. R1, aside from having a larger granule size, also had a higher methane production and lower soluble COD in effluent at F/M ratio 0.6 g COD/g VSS d compared to R2.