Surface Water Quartz Sand Filter Black Into The Cause And Control Technology Research

Factors causing sandy filter-media darken, darken-controliing technology, and influence of darkened and regenerated sandy media on filtration in surface water plants are studied in this thesis. Results indicated that Mn, Fe, Al were the main elements consisting in the darkened coating of the sand media. The adhesive coating could effectively cleaned by soaking in 1. 5-3% HCl solution for 30 minutes with 100-150rpm stirring. The darkened sand, the sands regenerated from the darkened sand with acid-wash cr base-wash, and the new sand, have not much difference in filtrate quality according to removal of Mn, Fe and turbidity, as well as in hydraulic loss. After 8 months of operation, 15 inspected quality indexes of the filtrate from filtration with the media met the Standards for Drinking Water (GB5749-85), indicating that either darkened sand or its regenerated sands could be used as filter media as the new sand. Further, economic analysis showed that using the darkened sand could reduce operation cost. However, it is suggested that strict inspecting of water quality should be applied for the blacked sand, and preliminary filtrating time should be prolonged in order to ensure water quality. In addition, adding potassium permanganate before coagulating can remove manganese at efficiency of more than 60%, which will reduce enrichment of manganese on the sand so that sand darkening can be retarded.