Land application of alum sludge from water purification plant to acid mineral soil treated with acidic water

Abstract

Land application of alum sludge has been considered to be an economical disposal method. However, its negative effects on the environment have been a cause for concern. In one example, an acid soil was treated with alum sludge from a water purification plant at 0 to 18% rate. Indian mustard was grown on the treated soil in a greenhouse for 5 weeks, and irrigated with pH 4 water during growth. Changes in the soil properties, leachate chemistry, plant growth, and plant uptake of elements by the sludge treatment were determined. The sludge treatment increased the buffer capacity to acidity, hydraulic conductivity, water-holding capacity, and phosphate adsorption of the soil and decreased the bulk density and mobility of small particles. The sludge treatment reduced the leaching of Al, Mg, K, Na, and Mn but increased leaching of Ca. The sludge treatment also increased the amount of biomass and enhanced root elongation. The plant absorbed a lower amount of cations and P, but a larger amount of Ca with the sludge treatment.