Abstract
The enhanced biological phosphorus removal process makes the phosphorus recovery feasible from the dewatering streams of biological sludge. The physicochemical properties of these sidestreams, as an input to a crystallizer, are different before and after anaerobic digestion. In this study, phosphorus recovery by calcium phosphate is proposed for pre-digestion sidestreams and by struvite precipitation for post-digestion sidestreams. The thermodynamic modeling followed by experimental tests was performed to evaluate the recovery efficiency and product properties of struvite and calcium phosphates. The variations in phosphorus recovery potential, reaction kinetics and particle size distribution emphasize the importance of the adjustment of initial supersaturation and pH of the reaction. The optimum pH, considering the economics and recovery efficiency, for both calcium phosphate and struvite precipitation was found to be pH = 8.5, whereas further increase of pH will not improve the overall efficiency of the process. In the case of calcium phosphate precipitation, it was shown that possible phase transformations should be considered and controlled as they affect both process efficiency and product properties. The economic evaluation indicated that the optimized operational condition should be determined for the phosphorus recovery process and that chemical costs for the production of calcium phosphates is lower than for struvite.
Highlights
Phosphate rocks are the main source of phosphorus for most phosphorus fertilizers in modern agriculture
Adaption of final product to the physicochemical properties of the targeted sidestream is necessary for an effective phosphorus recovery process
Pfinal is determined by the solubility of struvite and HAP, which is the thermodynamically most stable phase in the corresponding pH range and is constant under constant temperature
Summary
Phosphate rocks are the main source of phosphorus for most phosphorus fertilizers in modern agriculture. The sidestreams of the sludge handling line in the EBPR process, both before and after anaerobic digestion, are rich in. The precipitation of struvite and different calcium phosphate compounds is widely studied for phosphorus recovery from wastewater (Mehta et al ; Melia et al ). In these studies, input material is the liquid phase of anaerobically digested sludge and P-recovery from phosphate-rich sidestreams of undigested sludge is not fully elucidated. Adaption of final product to the physicochemical properties of the targeted sidestream is necessary for an effective phosphorus recovery process
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
