Hydrophilic spongy biochar crosslinked with starch and polyvinyl alcohol biocarrier for nitrate, phosphorus, and cadmium removal in low carbon wastewater: Enhanced performance mechanism and detoxification.

This study aims to develop a functional biocarrier with hydrophilic spongy biochar crosslinked with starch and polyvinyl alcohol (WSB/starch-PVA) for simultaneous removal of NO3--N, total phosphorus (TP) and Cd2+ in low carbon wastewater. Results showed that the WSB/starch-PVA bioreactor achieved the maximum NO3--N removal efficiency in subphase 1.2 with 98.07 % (3.64 mg L-1h-1) versus control (75.30 %, 2.81 mg L-1h-1), and removed 54.84 % and 73.97 % of TP and Cd2+. Material characterization suggested that functional groups (related to C, N and O) on biocarrier and biofilm, and biogenic co-precipitation facilitated TP and Cd2+ removal. The WSB made the biocarrier pores larger and regular, and decreased fluorescent soluble microbial products. The predicted metagenome further suggested that central citrate cycle, oxidative phosphorylation of bio-community, and NO3--N removal were enhanced. Functions for microbial induced co-precipitation, Cd2+ transport/efflux, antioxidants, and enhanced biofilm formation favored the NO3--N/TP removal and Cd2+ detoxification.