Economic Evaluation of the Precipitation of Phosphate as Struvite at Pilotscale E. Desmidt*, K. Ghyselbrecht*, A. Monballiu*, B. Maes*, W. Verstraete*** and B.D. Meesschaert* / ** * Department of Industrial Science and Technology, Katholieke Hogeschool Brugge-Oostende, Associated to the Katholieke Universiteit Leuven, Zeedijk 101, Ostend, Belgium ** Centre for Surface Chemistry and Catalysis, Department of Microbial and Molecular Systems (M 2 S), Faculty of Bio-engineering Sciences, Katholieke Universiteit Leuven, – Heverlee, Belgium *** Laboratory of Microbial Ecology and Technology (LabMET), Faculty of Bio-engineering Sciences, University of Ghent, Belgium Abstract A novel approach using ureolytic induced MAP formation, for the recovery of phosphate, has been economically evaluated. The ureolytic MAP crystallizationon has been tested on anaerobic effluent of a potato processing company in a pilot plant, with MgCl 2 .6H 2 O as magnesium source. The pilot plant showed a high phosphate removal efficiency of 82 ± 9 %, resulting in a final effluent concentration of 13 ± 7 mg/L PO 4 -P. XRD analyses confirmed the presence of struvite in the precipitate. During operation pH and the molar magnesium : ammonium : phosphate ratio are the most important operational parameters influencing MAP crystallization. Results show that for high phosphate concentrations in wastewater (e.g. 100 mg/L PO 4 -P) the ureolytic phosphate precipitation is a cost effective method (6.1 € kg -1 P removed ). Moreover, the technique is competitive with the chemical phosphate precipitation of struvite (6.2 € kg -1 P removed ). Keywords: Phosphate removal; nutrient recovery; ureolytic activity INTRODUCTION Phosphorus is an important element, making a major contribution to agricultural and industrial development, but its release to natural water bodies is one of the main causes of eutrophication. It is desirable that water treatment facilities remove phosphorus from the wastewater before it is returned to the environment. In most countries, total removal or at least a significant reduction of phosphorus is obligatory, but is not always fulfilled. In recent times two new processes have been developed for P precipitation from wastewater, the calcium phosphate crystallization process and the magnesium ammonium phosphate (MAP) crystallization process. (Doyle and Parsons, 2002). The recovered products can be used as the alternative of agricultural fertilizer or as the phosphate rock for phosphate industry (Li and Zhao, 2003; de-Bashan and Bashan, 2004). Anaerobically treated wastewater mostly contains large amounts of phosphate and ammonium. For the recovery of phosphate as struvite an increase of pH and the addition of a magnesium source is necessary. When dealing with anaerobically treated wastewaters, pH increase can be achieved by simple air stripping. If air stripping does not suffice, additional alkaline reagent must be added, e.g. sodium hydroxide, although this alkaline addition can be combined with the supplementation of magnesium using either MgO or Mg(OH). Corresponding authors, Tel: +32 59 56 90 53; fax: +32 59 56 90 01 E-mail address: boudewijn.meesschaert@khbo.be ; evelyn.desmidt@khbo.be