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

Abstract

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 ~ 11.7℃). 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 ~ 8.33) and Simpson (0.88 ~ 0.97)) and richness (Chao1 (1621.7 ~ 2556.2) and Observed _ species (1437 ~ 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 ~ 48.59%), Hydrogenopha (2.21 ~ 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.