Enhancement of carbon sequestration via MIL-100(Fe)@PUS in bacterial-algal symbiosis treating municipal wastewater.

Bacterial-algal symbiosis (BAS) is a promising carbon neutrality technology to treat municipal wastewater. However, there are still non-trivial CO2 emissions in BAS due to the slow diffusion and biosorption of CO2. Aiming to reduce CO2 emissions, the inoculation ratio of aerobic sludge to algae was further optimized at 4:1 on the base of favorable carbon conversion. MIL-100(Fe) served as CO2 adsorbents was immobilized on polyurethane sponge (PUS) to increase the interaction with microbes. When MIL-100(Fe)@PUS was added to BAS in the treatment of municipal wastewater, zero CO2 emission was achieved and the carbon sequestration efficiency was increased from 79.9% to 89.0%. Most genes related to metabolic function were derived from Proteobacteria and Chlorophyta. The mechanism of enhanced carbon sequestration in BAS could be attributed to both enrichment of algae (Chlorella and Micractinium) and increased abundance of functional genes related to PS I, PS II and Calvin cycle in photosynthesis.