Utilization of alum sludge as adsorbent for phosphorus removal in municipal wastewater: A review

Aluminium sulphate is the commonest and most widely used coagulant for water treatment worldwide. Aluminium is a well-known adsorbent for phosphorous (P), a nutrient highly associated with eutrophication in most water bodies. Thus, this paper provides a review on P adsorption from aqueous media using alum sludge waste material generated by water treatment plants that use aluminium sulphate as sole coagulant. A meta-analysis of data on characteristics of various alum sludges was done. The hindrance factors and adsorption capacities, under varying operating conditions are presented, including future direction. It is evident from literature survey that there is the emerging shift from reuse and recycling of raw alum sludge towards synthesis of value-added alum sludge based adsorbents. Possibilities to improve efficacy as both filter media and adsorbent but at the same time reducing metal leaching are highlighted. Value-added products may also offer an added advantage of acting as source of phosphorous for possible reuse in agricultural soils.