From "fills" to filter : insights into the reuse of dewatered alum sludge as a filter media in a constructed wetland

Dewatered alum sludge, a by-product of drinking water treatment plants, hitherto consigned to landfills was used to develop a novel bio-filter in form of a constructed wetland. Performance results have demonstrated the benefits of the alum sludge cakes in a lab-scale system in enhancing phosphorus (P) removal from an animal farm wastewater. Although P and organic matter were concurrently removed in the system, there was a probable “one off” release of organics from the system, and this coincided with an increase in inlet P concentration from 39.2 mg-P/l to 163.0 mg-P/l. A conceptual model was then proposed to explain and discuss this.