Self-sustained ultrafiltration coupling vermifiltration for decentralized domestic wastewater treatment: Microbial community and mechanism

In this study, self-sustained ultrafiltration (SUF) without extra backwashing, aeration and chemical cleanings was investigated. To further improve removal performance and membrane permeability, vermifiltration (VF) was introduced, developing VF/SUF (VF coupling SUF without reflux) and RVF/SUF (VF coupling SUF with reflux). Synergism effects of contaminants removals were achieved with effective removals of dissolved pollutants (e.g., 95.97% of TOC and 45.25% of NH₃−N) via VF process, simultaneously with efficient rejections of particles, bacteria, protozoa and metazoan via SUF process, ensuring permeate safety. Notably, vermifilters improved the membrane flux by over 101% relative to the control, attributing to the synergetic effects among the modified bio-fouling layer structure by more prosperous eukaryotic communities, the reduction of extracellular polymeric substances and the increase of inorganics contents. With the usage of reflux, the membrane flux was further elevated by 181% since the reflux delivered more eukaryotes into SUF to increase the heterogeneity of the bio-fouling layer.