Mobilization of recalcitrant phosphorus from soil using citric acid wastewater

Abstract

Citric acid wastewater is recalcitrant wastewater with high levels of chemical oxygen demand and large quantities of citric acid. Numerous studies have certified that citric acid is a potential enhancement agent to mobilize phosphorus (P) in soils. In this study, the modified Hedley fractionation was conducted to evaluate the capability of citric acid wastewater to reduce P sorption from the soil and its impact on the soil properties including pH and organic matter. The results indicate that the citric acid wastewater with original concentration induced the most Olsen P and extractable P from soils. Besides, the processing time lasting for 30 days was generally satisfactory. Moreover, the process of P mobilization was explored. We concluded that the labile P, Al/Fe–P and Ca-P derived from the mobilization of residual P after the CAW application. It can be also observed that the dominant purging components in citric acid wastewater to mobilize P is citric acid. The addition of citric acid wastewater in soils decreased the soil pH but it recovers with the extension of time. Besides, it increased the soil organic matter during the processing time. Our results implied that citric acid wastewater could be a favourable soil amendment for the mobilization of soil P.