Tertiary Treatment of Wastewater by Phosphorus Precipitation – Pilot Scale Test of Flotation Utilization for Suspension Separation

• Main Authors: L. Houdková, M. Cmaradová, P. Strnadel, H. Chládková, J. Borán
• Format: Article
• Language: English
• Published: AIDIC Servizi S.r.l. 2014-08-01
• Series: Chemical Engineering Transactions
• Online Access: https://www.cetjournal.it/index.php/cet/article/view/5509

A research published in this paper is focused on a phosphorus removal from municipal wastewater. A technology consisting of chemical precipitation and flotation was tested to simulate a tertiary stage of wastewater treatment plant. Biologically treated wastewater with a very low concentration of total phosphorus (approx. 1.2 mg/L) was used. The ferric sulphate solution was used as a precipitant. The precipitate was removed by dissolved air flotation which took place in a pilot scale flotation unit Kunst-i-flot. This is an experimental device that was designed for thickening of sewage sludge (inlet pump flow ranges from 0.7 to 5.0 m3/h). The target of the experiments was to determine whether this technology is applicable in case of low inlet concentration of total phosphorus in the wastewater. The influence of the ratio Fe3+/P, the amount of air used for flotation and the hydraulic retention time in the tank for slow mixing were studied. The significantinfluence of ratio Fe3+/P was proved, while increasing of air fed in flotation unit had no positive effect. It was found an optimum dose of ferric sulphate solution approx. 2 g Fe3+/g P. The phosphorus removalefficiency was 50 %. Increasing of ferric sulphate dose did not decrease the phosphorus concentration in wastewater effluent, which was usually approx. 0.4 mg/L and higher.