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Project title

From a ?waste? into useful material: identifying adsorption capacity of dewatered alum sludge for phosphorus removal

Primary Funding Agency

Environmental Protection Agency

Co-Funding Organisation(s)

n/a

Lead Organisation

University College Dublin (UCD)

Lead Applicant

Yaqian Zhao

Project Abstract

The future development of the economy is closely connected with the contributions achieved by sustainable development including more efficient utilisation of resources and the reduction of the negative impacts of these processes on humans and the ecosystem by supporting resource conservation and recycling. The sludge derived from the drinking-water treatment is an inescapable by-product and has been historically reviewed as a -waste for landfill. Alum sludge refers to the water treatment residual when aluminum sulphate was employed as chemical coagulant to be added to raw waters. The raw alum sludge contains flocs of humic matter and metal hydroxide in which the impurities removed from the natural water are entrapped adsorbed or chemically bounded. It is noted that due to the feature of generation of alum sludge aluminium hydroxides become the important composition of the sludge once it has been dewatered. This makes a possibility of reusing such kind of sludge as a valuable raw/source material in wastewater treatment as the ions enhance adsorption and chemical precipitation processes that remove various pollutants especially phosphorus (P).Groups of experiments in this study were designed to explore the P adsorption characteristics especially the adsorption capacity by dewatered alum sludge collected from the local water treatment plants namely Ballymore Eustace Water Treatment Plants and Leixlip Water Treatment Plant. Extensive batch adsorption tests followed by a series of alum sludge-column experiments were conducted with artificial and real P-enriched wastewater. The results have demonstrated that dewatered alum sludge has the potential to be used as raw material for a wide range of P species removal in simulated and real P-enriched wastewater. Considerable amounts of P can be adsorbed onto a relatively low mass of dewatered alum sludge. The adsorption capacities obtained from the Langmuir isotherm vary for the different types of P species as well as the pH of the P suspension. The highest adsorption capacity is obtained for orthophosphate (say KH2PO4) followed by polyphosphate (say (NaPO3)6) and finally organic phosphate (say C10H14N5O7Pi?H2O). P adsorption favours acidic suspensions rather than alkaline suspensions for all the three P species tested. Long term P-adsorption tests have revealed the adsorption capacity of the two alum sludge studied which is given in the following Table.

Grant Approved

�29,100.00

Research Hub

Natural Environment

Research Theme

Protecting our Water Resources

Start Date

01/10/2005

Initial Projected Completion Date

n/a