Phosphorus recovery from calcium phosphate enriched activated sludge

Abstract

This study explores the potential of activated sludge from wastewater treatment plants (WWTP) as an alternative source of phosphorus, vital for fertilisers and other products, compared to large-scale phosphorus mining. The research focuses on analysing optimal conditions and the impact of activated sludge characteristics on phosphorus release from calcium phosphate compounds, particularly hydroxyapatite (HAP). Using batch reactor experiments with varying pH and contact time, the results reveal that lower pH values, particularly pH 4, result in higher phosphorus release. The study also finds that calcium, the predominant metal content in activated sludge, plays a vital role in bonding with phosphates and forming new compounds, effectively reducing phosphorus concentration in the solution. Moreover, the VSS/TSS value in the activated sludge has no significant effect on phosphorus release, but interventions occur at high VSS/TSS values. The reaction rate coefficient is calculated at 0.00033/min at pH 4. Overall, this research emphasises the potential of phosphorus recovery from calcium phosphate enriched activated sludge and underscores the importance of optimising pH and considering activated sludge characteristics for efficient phosphorus release.