Phosphorus removal from swine wastewater using aluminum-based water treatment residuals

Aluminum water treatment residuals (Al-WTR), a waste product created during drinking water treatment, is generated in large quantities globally and typically landfilled; alternative, uses are desperately required. Inorganic phosphorus (P) is proven to be quickly and irreversibly sorbed by Al-WTR, rendering P unavailable for subsequent environmental use.

However, little work has been done to characterize how Al-WTR interacts with organic P sources (e.g., wastewaters) to both sorb and later release P. Experiments characterized Al-WTR's ability sorb and subsequently desorb swine wastewater organic P, and to ascertain Al-WTR's potential for agricultural wastewater treatment and to return organic P to systems (e.g., soils) for beneficial use. Al-WTRs were shaken with swine wastewater (2.5:1;w/w) and solution total/inorganic/organic P were monitored over 21 days. The Al-WTR sorbed almost 100% (~ 16,500 mg kg⁻¹) of swine wastewater organic P within a 1-h timeframe. X-ray absorption near-edge spectroscopy showed that P was primarily sorbed by Ca phases present in Al-WTR during the initial 1-h sorption phase. In a subsequent study, the newly generated organic P-laden Al-WTR was shaken in 0.01M KCl along with an anion membrane-probe to capture desorbed P. Approximately 17% (~ 3000 mg kg⁻¹) of the organic P sorbed onto Al-WTR was desorbed. Findings suggest that Al-WTR can remove excessive organic P from agricultural waste streams, with the Al-WTR-organic P-containing material potentially having the ability to supplement agricultural soils with P for plant use. By following such an approach, this could provide municipalities with an alternative and beneficial utilization strategy as compared to landfilling.