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Water Science & Technology Vol 65 No 11 pp 1954–1962 © IWA Publishing 2012 doi:10.2166/wst.2012.092 Evaluation and thermodynamic calculation of ureolytic magnesium ammonium phosphate precipitation from UASB effluent at pilot scaleE. Desmidt, K. Ghyselbrecht, A. Monballiu, W. Verstraete and B. D. MeesschaertDepartment of Industrial Science and Technology, Katholieke Hogeschool Brugge-Oostende, Associated to the Katholieke Universiteit Leuven as faculty of Industrial Sciences, Zeedijk 101, B-8400 Ostend, Belgium E-mail: evelyn.desmidt@khbo.beLaboratory of Microbial Ecology and Technology (LabMET), Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium Centre for Surface Chemistry and Catalysis, Department of Microbial and Molecular Systems (M2S), Faculty of Bio-engineering Sciences, Katholieke Universiteit Leuven, Kasteelpark Arenberg 23, B-3001 Heverlee, Belgium ABSTRACT The removal of phosphate as magnesium ammonium phosphate (MAP, struvite) has gained a lot of attention. A novel approach using ureolytic MAP crystallization (pH increase by means of bacterial ureases) has been tested on the anaerobic effluent of a potato processing company in a pilot plant and compared with NuReSys® technology (pH increase by means of NaOH). The pilot plant showed a high phosphate removal efficiency of 83 ± 7%, resulting in a final effluent concentration of 13 ± 7 mg · L−1 PO4-P. Calculating the evolution of the saturation index (SI) as a function of the remaining concentrations of Mg2+, PO4-P and NH4+ during precipitation in a batch reactor, resulted in a good estimation of the effluent PO4-P concentration of the pilot plant, operating under continuous mode. X-ray diffraction (XRD) analyses confirmed the presence of struvite in the small single crystals observed during experiments. The operational cost for the ureolytic MAP crystallization treating high phosphate concentrations (e.g. 100 mg · L−1 PO4-P) was calculated as 3.9 € kg−1 Premoved. This work shows that the ureolytic MAP crystallization, in combination with an autotrophic nitrogen removal process, is competitive with the NuReSys® technology in terms of operational cost and removal efficiency but further research is necessary to obtain larger crystals. Keywords: nutrient recovery; phosphate removal; struvite; urease activity eProduct: Buy this article for £24.00 (IWA MEMBER PRICE: £18.00) All prices include VAT. For customers where VAT should not be applied, the VAT amount will be removed upon payment |
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