Configuration of multi-stage membrane process towards effective separation of C, N and P from real-life biogas slurry: Design, optimization and analysis

Efficient separation and concentration of C, N, and P into three distinct streams from real-life biogas slurries remains a challenge. In this study, a three-stage membrane separation device was developed to address these challenges. Key discoveries revealed that the deployment of the UF1 membrane in the second-stage separation for C concentration was crucial for improving the separation efficiencies of N and P in the third-stage separation, leading to an improvement in selectivity towards N/P from 10.2 to 17.2 and achieving their distinguished separation/concentration. The eXtreme Gradient Boosting model revealed that the biomass raw material and pH dominantly determined the eventual separation efficiency of N/P. Building upon comprehensive cost and environmental analyses, the designed multi-stage membrane filtration process can be deployed to source nutrients from authentic biogas slurries at an ultralow cost of $10.8/m³. This work offers an avenue for processing authentic biogas slurries regardless of their sources.