Reduction of greenhouse gas (GHG) emission in the vegetation-activated sludge process (V-ASP) involving decontaminated plants for decentralized wastewater treatment

Wastewater treatment plant (WWTP) is one of the important sources for anthropogenic greenhouse gases (GHGs) emission. The objective of this study was to evaluate vegetation-activated sludge process (V-ASP) that simultaneously achieved the improvement of decentralized wastewater treatment performance and reduction of GHGs emission, in contrast to conventional ASP. With the same organic and nitrogen loading rates and operational modes, V-ASP achieved a decreasing of 19.79% for total GHGs emission in comparison to ASP. From the microbial community analysis on activated sludge microbes and plant roots, V-ASP had a much lower abundance of Chloroflexi, and a comparable abundance of denitrifiers, in contrast to conventional ASP, which likely correlated with the differences of CH₄ production and emission. Specifically, it was noted that the relatively higher abundance of mcrA and nirS genes in the V-ASP would take a certain responsible for reducing CH₄ and N₂O emission, respectively. The V-ASP also demonstrated the increased enzymatic activities, such as ammonia monooxygenase (AMO) and hydroxylamine oxidoreductase (HAO), which could help to reduce GHGs emission flux. It was proved that V-ASP process, compared to the traditional ASP process, was an effective decentralized wastewater treatment technique for reducing GHGs emission.