Abstract
Characteristics and performance of granular media filtration of eutrophicated moat water were studied in the bench-scale equipment to determine the design and operating parameters (AL/T, medium size, filtration rate) for optimum filter operation.
The reasonable aluminum/turbidity ratio (AL/T) was about 0.01 in both terms of achieving sufficient stability of the filter performance and lessening the influence of residual aluminum salt on fish and shellfish in the moat. The 1.2mm size medium had the highest SS removal ratio, but the weight of removed SS was the lowest due to clogging in the short term. The 2.4mm size medium was suited for the removal of the SS which were mostly particles larger than 20 μm and the VSS in influent, making long-term filtration possible. The filtration process of 2.4mm media was expressed in a filtrate equation by Mintz and a conservation equation. Higher filtration rates decreased the SS removal ratio more rapidly and reduced the ultimate deposit (σu). Judging from the calculation result, the filtration rate should be about 100m·d-1 at the high SS concentration of influent in summer and should be about 100-175m·d-1 at the low SS concentration of influent in winter.
