2.2: The use of bauxite residue as a phosphorus getter

EPA Funded Research Project at the University of Limerick

Bauxite Residue for Phosphorous Recovery from waste water-Current state of knowledge:

  • The sustainable use of phosphorus (p) is one of the major challenges of the 21st century (Sharpley and Tunney, 2000). Phosphorus is essential for life, and for global agricultural production. However, natural phosphorus resources (phosphate rock) are depleting and Cordell et al. (2009) postulated that “peak P” would occur around 2035. Recent phosphate rock reserve estimates by Cordell and White (2011) ranges from 60 to 130 years.

  • However, phosphorus has been recognized as the primary nutrient causing eutrophication and is a widespread global environmental issue. Whilst legislation is in place requiring low P emission limits in treated waters many of the biological and physicochemical techniques used for phosphorous removal have some limitations. The lack of solutions for the sustainable and cost-effective treatment of agricultural wastewater is a wide-spread problem, particularly across the European Union (Martinez et al., 2009). Production of excessive phosphorus-rich sludge, which requires further treatment for reduction of volume and stabilization before final disposal is one such issue. In addition, restrictions placed on land-spreading of corresponding wastewaters at certain times of the year and limitations in suitable land for spreading (Harrington and Scholz, 2010). It is also recognised that equipment such as membrane technology can place financial burdens on agricultural enterprises (Henkens and van Keulen, 2001).

  • Adsorption is an efficient process for the removal of environmental pollutants such as phosphorus from waste waters. Low cost and waste materials such as ochre (Fenton et al., 2009), pumice, steel slag (Barca et al., 2014) and other iron-rich minerals have been proposed to sequester P from wastewater. More recently the application of modified bauxite residues for improving conventional waste water streams has received attention (Huang et al., 2008; Klauber et al., 2011). Bauxite residue has recognised ability to sequester or adsorb phosphorous and other undesirable constituents of waste water through a variety of mechanisms. Modified bauxite residues aggregates exhibit good stability in aqueous solution with adsorption capacities of 50-100% for phosphorous, copper, zinc nickel, and cadmium (López et al., 1998).

  • However, with the exception of one company in Australia (Virotec), there has been limited promotion of bauxite residue-derived products for phosphorous and metal recoveries from waste waters (Klauber et al., 2011). Further, whilst P-recovery techniques are often technologically feasible, constraints to implementing techniques have been attributed to economic feasibility (Desmidt et al., 2014).

  • Al-source will investigate bauxite residue for its potential to adsorb and sequester phosphorus and to examine recovery and reuse of phosphorus from the bauxite residue filter systems.