Enhanced biosolubilization of mid-low grade phosphate rock by formation of microbial consortium biofilm from activated sludge

Mid-low grade phosphate rock (PR) is a potential source of free phosphate to facilitate crop growth, but a cost effective and environmentally responsible extraction process is required. In this study, the capacity of a microbial consortium from activated sludge to solubilize PR in a laboratory-scale column reactor was investigated. The microbial consortium proved capable of efficiently releasing soluble phosphate in the reactor effluent over the 90-day trial. The microbial consortium grew well in the column system as evidenced by reduced chemical oxygen demand (COD) in the reaction solution. Biofilm formation was identified as critical for biosolubilization of the mid-low grade PR. Imaging of the biofilm by scanning electron microscopy (SEM) revealed a dense network of microbial cells embedded in extracellular polymeric substances (EPS). The biofilm contained both oxic and anoxic zones. The pH decreased significantly in both the biofilm and the reaction solution during operation, indicating healthy growth of the microbial consortium with corresponding acid generation and subsequent enhancement of phosphate solubilization.