A pilot scheme in ireland is treating agricultural wastewater using waste alum sludge from water - treatment

alum sludge is the main residual by-product from drinking-water-treatment processes including coagulation, flocculation, clarification and filtration, followed by dewatering in plants using aluminium salt as a coagulant. It is the most widely generated water-treatment residual worldwide – and is mostly sent to landfill being perceived as a waste of little known reuse value. In Ireland, an annual total of 18 000 t dry solids of alum sludge is generated from the largest water-treatment plant alone, with landfill disposal costs of about £2·6 million. In the uk, about 182 000 t dry solids of waterworks sludge is generated each year, with disposal to landfill as the predominant disposal route. however, due to increasing environmental awareness, escalating costs, dwindling landfill space and the need for sustainability, efforts have been geared towards either minimising the generation of the sludge or finding alternative reuse options. the latter appears to be more feasible, with several studies being conducted to develop alternative end-uses.