Top-Feed Vacuum Filtration of Waste-Activated Sludge

摘要

A side-by-side comparison of a conventional bottom-feed vacuum filter and a prototype top-feed vacuum filter was conducted. Thickened, waste-activated sludge at approximately 1.8 percent feed solids concentration and conditioned with ferric chloride was dewatered on two filters 12 ft (3.66 m) in diameter and 16 ft (4.88 m) long. One operated in the bottom-feed mode and the other in the top-feed mode. As expected, the top feed filter was more efficient when forming a filter cake because of its basic design configuration (resulting in a longer drying time even at similar cycle times). The results of a statistical analysis (two-tailed t-test with a 95-percent confidence interval) of data from the top- and bottom-feed filters during operation at an equivalent loading rate (1.5 lb/hr per sq ft (7.3 kg/hr per sq m) and cycle time (3 minutes and 40 seconds) indicates that the difference between the average cake solids was statistically significant and that the top-feed filter produced a drier filter cake than the bottom-feed filter (15.0 versus 14.4 percent). A total cost comparison based on the above amortized costs indicates that there is no significant cost difference between the two filters ($2,682 per year per filter for the top-feed filter versus $2,434 for the bottom-feed filter).