Simultaneous removal of COD, nitrogen and phosphorus and the tridimensional microbial response in a sequencing batch biofilm reactor: with varying C/N/P ratios

•Simultaneous nutrients removal in SBBRs were evaluated at varying C/N/P ratios.•Lower C/N/P inhibited S-SBBR more severely in terms of TP removal.•Both the microbial diversity and richness were effected by C/N/P ratios.•Microorganism in suspended sludge and biofilm showed different characteristics.•PAOs and DNPAOs enriched at the C/N/P of 33.3:8.3:1.