Experimental studies of slag filter for drinking water treatment

Abstract

The study examined the use of granulated blast furnace slag, an industrial by-product from ferrous industries for drinking water treatment. A laboratory scale filter, 9 cm diameter and 40 cm with iron slag media supported on a gravel bed could completely remove turbidity, total suspended solids and colour for an average influent loading of 28.26 NTU, 128.85 mg/L and 177.05 PCU respectively at a filtration rate of 0.32 m3hr?1m?2. The average removal of hardness, sulphate, nitrate, chloride and iron were 35%, 83%, 71%, 28% and 94% for an average influent loading of 579.79 mgL?1, 367.72 mgL?1, 120.52 mgL?1, 355.67 mgL?1 and 1.49 mgL?1respectively. Doubling the filtration rate with slight increase in loading rate showed 100% removal for turbidity, suspended solids and colour whereas hardness, sulphate, nitrate, chloride and iron removals were 27%, 73%, 86%, 28% and 95% respectively. The maximum head loss for continuous operation without backwash was only 75 mm. Intermittent washing helped to improve the filtered water quality for various filtration and loading rates. An increase in the rate of filtration up to 1.28 m3hr?1m?2 did not have any impact on the quality of treated water except sulphate and nitrate. After backwashing, there was considerable improvement in chloride removal. The removal of physicochemical parameters was due to precipitation, adsorption and ion exchange with the formation of products both at the surface and within the slag media. FTIR and XRD results also confirmed the behaviour of slag as an anion exchange resin. The maximum head loss observed in slag filter was 190 mm at the highest loading level and filtration rate. 2019 Elsevier B.V.