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Secure a sustainable, regional phosphorus supply: Development of a strategic phosphorus reserve through recovery from wastewater
Civil and Environmental Engineering
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Phosphorus (P) is vital to all living things. As the global population increases, so does the P demand. However, as a limited resource that can only be extracted by mining phosphate rock (PR), P has no substitute. This prompted the need to examine the recovery of P from water resource recovery facilities (WRRFs) as the majority of P consumed by humans ends up in WRRFs. Although the importance of P recovery has been established in the wastewater industry, the focus has been on recovery as struvite fertilizer for immediate use. The high implementation costs of struvite recovery coupled with low PR and chemical fertilizer prices make for an inadequate justification of the current approach of P recovery at WRRFs. There are three major streams in WRRFs where P can be recovered: sludge liquor, biosolids, and sludge ash. Using a simple payback, a 20-year present worth, and a Triple Bottom Line (TBL) analysis, this research systematically demonstrated that a promising way to encourage and justify WRRFs of all sizes to recover P is to establish a centralized facility where dewatered, undigested sludge from WRRFs of all sizes, within a region, would be transported to the facility for mono-incineration. Phosphorus would be extracted from the sludge ashes and precipitated to form calcium phosphate (Ca-P). The Ca-P, which has essentially the same composition as mined PR, would be deposited in a monofill as P reserve to be used in the future for diverse applications. One can argue that as of now, there is plenty of PR to be mined and the mining costs are inexpensive. Nevertheless, with more than 70% of the Earth’s known reserves of PR located in Morocco and West Sahara, it is risky to jeopardize the nation’s future P supply due to the possibility of geopolitical risks and supply chain interruptions in/from these regions. By creating regional localized P reserves, the dependency on PR imports from foreign countries can be minimized.