Volatilization of Nitrogen from Dewatered Biosolids

Abstract

AbstractVolatilization of N from biosolids applied to land lessens the risk of ground water contamination and reduces the amount available for plant uptake. This study determined rates of volatilization of NH+4−N from biosolids after surface‐application. Biosolids from three sewage treatment plants (Cronulla, Liverpool, and Quakers Hill) in Sydney, Australia, were applied under controlled conditions to exclude leaching and plant uptake, and volatilization was calculated using a mass balance approach. Application rates supplied 100 to 168 g m−2 of total N including 20 to 67 g m−2 of NH+4‐N. Most loss of N occurred within 1 wk of application; within 3 wk 71 to 81% of the NH+4−N applied had been lost. Subsequent changes in NH+4−N were small and there was little loss of organic N. The rapidity and magnitude of loss in both NH+4−N and total N suggests that N was primarily lost by volatilization, and that denitrification losses, involving slower biological processes, were minimal. Amounts of NH+4−N volatilized were proportional to amounts applied. Loss of applied NH+4−N did not increase with regular re‐wetting, although loss of total N was increased, suggesting mineralization of organic N followed by gaseous loss. Volatilization, an important pathway for loss of N applied in biosolids, needs to be considered when calculating rates of biosolids application to protect ground water while providing nutritional benefit.