Promoting heterotrophic denitrification of Pseudomonas hunanensis strain PAD-1 using pyrite: A mechanistic study

Abstract

Denitrification is critical for removing nitrate from wastewater, but it typically requires large amounts of organic carbon, which can lead to high operating costs and secondary environmental pollution. To address this issue, this study proposes a novel method to reduce the demand for organic carbon in denitrification. In this study, a new denitrifier, Pseudomonas hunanensis strain PAD-1, was obtained with properties for high efficiency nitrogen removal and trace N2O emission. It was also used to explore the feasibility of pyrite-enhanced denitrification to reduce organic carbon demand. The results showed that pyrite significantly improved the heterotrophic denitrification of strain PAD-1, and optimal addition amount was 0.8–1.6 g/L. The strengthening effect of pyrite was positively correlated with carbon to nitrogen ratio, and it could effectively reduce demand for organic carbon sources and enhance carbon metabolism of strain PAD-1. Meanwhile, the pyrite significantly up-regulated electron transport system activity (ETSA) of strain PAD-1 by 80%, nitrate reductase activity by 16%, Complex III activity by 28%, and napA expression by 5.21 times. Overall, the addition of pyrite presents a new avenue for reducing carbon source demand and improving the nitrate harmless rate in the nitrogen removal process.