Effect of filtration rates on the performance and head loss development in granular filters during the post-treatment of anaerobic reactor effluent.

This study investigated the performance of a granular filtration system (GFS) composed of a rock filter (RF), a rapid sand filter (RSF), and an activated carbon filter (ACF), applied to the post-treatment of an anaerobic reactor effluent. Four filtration rates (FR) were applied to the GFS (in m³·m⁻²·d⁻¹): 100–60-60, 100–90-90, 200–120-120, and 200–160-160, for RF-RSF-ACF, respectively. A clarified final effluent with low turbidity (~ 10 NTU), solids (~ 6.5 mg TSS.L⁻¹), and organic matter content (~ 40 mg COD.L⁻¹) was obtained when the GFS worked with FR up to 100–90-90 m³·m⁻²·d⁻¹. For higher FR, the effluent quality was a little poorer. Principal component analysis showed when the RSF operated at 120 or 160 m³·m⁻²·d⁻¹, it presented an effluent with higher turbidity which did not affect negatively the ACF performance. The hydraulic load limits in the RSF were reached in periods of 45, 30, and 24.5 h for the FR of 60, 120, and 160 m³·m⁻²·d⁻¹, respectively, and head loss analysis depicted a more distributed solid retention through the sand depth with the lower FR. Thus, the results revealed that the RF-RSF-ACS system is a promising alternative for effluent polishing of anaerobic reactor, especially when the FR is set at 90 m³·m⁻²·d⁻¹ or even higher. [ABSTRACT FROM AUTHOR]