Effect of zeolite-sponge iron combined substrate on microbial community in ecological floating bed

Substrate has been proven to be a useful way to enhance the purification effect of ecological floating bed (EFB), and it also affected the microbial community. While at cold temperature, there was a lack of research on the effect of substrates on plant growth and microbial communities. In this study, three EFBs, namely plant EFB (EFB-P), substrate EFB (EFB-S) and plant-substrate EFB (EFB-PS), were constructed. The effects of zeolite-sponge iron combined substrate on pollutant removal, plant growth and microbial community in the EFBs were investigated at low temperature (3.1 similar to 11.7 degrees C). Results showed that the removal efficiencies of total nitrogen, total phosphorus and nitrate nitrogen by EFB-PS (60.35%, 95.09% and 64.43%) was significantly better than that of EFB-P (47.71%, 88.59% and 51.65%), but the relative growth of the aboveground biomass of plants (50.41%) was less than that of EFB-P (81.16%). In addition, the microbial biomass in EFB-PS (69.14 mg/(g DW.day)) and EFB-S (68.76 mg/(g DW.day)) was much larger than that in EFB-P (50.69 mg/(g DW.day)). High throughput sequencing showed that the microbial diversity (Shannon (6.06 similar to 8.33) and Simpson (0.88 similar to 0.97)) and richness (Chao1(1621.7 similar to 2556.2) and Observed _ species (1437 similar to 2423.3)) of EFB with adding zeolite-sponge iron combined substrate were also higher than those of EFB-P. In addition, the addition of combined substrates changed the microbial community structure, some genera with denitrification and nitrogen fixation functions, including Rhodobacter (36.03 similar to 48.59%), Hydrogenopha (2.21 similar to 5.89%), were abundantly enriched in the EFB with adding zeolite-sponge iron combined substrate. These results improved the effects of substrate low temperature operation on plant growth and microbial characteristics in EFB, and provide a theoretical basis for strengthening the operation of the low temperature conditions of the EFB.