Phosphorus recovery from urine using cooling water system effluent as a precipitant

Abstract

Phosphorus (P) recovery from wastewater has been recognized as a critical technology for solving the sustainable supply of this indispensable and non - renewable natural resource. In this study, the cost - free magnesium and calcium sources of using the cooling water system effluent (CWSE) in two thermal power plants were proposed (Z - CWSE and G - CWSE) and the P recovery performance from source - separated urine was investigated. About 90% P recovery efficiency was achieved from the hydrolyzed urine when Z - CWSE and G - CWSE were added at the Ca: Mg: P molar ratios of 3.1 : 4.0: 1 and 3.6 : 3.4: 1, respectively. More than 95% P recovery performance was obtained from the fresh urine as the initial pH of the CWSE - FU mixtures was adjusted to over 9.5 and 10.0, respectively. The precipitates obtained contain 10.84–17.04% Ca, 6.22–9.58% P, 0.75–3.76% Mg and 0.13–0.23% N. XRD analysis confirmed the presence of struvite in the precipitates. The reuse of precipitates is secure due to extremely low contents of heavy metals. The feasibility of using CWSEs as the flushing water in urinals and toilets was assessed. Besides, we proposed CWSEs could be invoked as precipitants in various wastewaters as long as it contains considerable phosphate, e.g. P concentration more than 100 mg/L and 50 mg/L for Z - CWSE and G - CWSE, respectively.