Dual application of lotus stem in fabricating a bioreactor for the remediation of nitrate, plumbum, and carbamazepine in industrial wastewater

Addressing the treatment of complex industrial wastewater continues to be a substantial challenge within the realm of water treatment. A biofilm reactor was engineered, integrating lotus stem biochar, lotus stem biological filler, and the ZW5 strain for enhanced wastewater treatment. The removal efficiencies of nitrate (NO₃⁻-N), calcium (Ca²⁺), chemical oxygen demand (COD), phosphorus (PO₄^3--P), plumbum (Pb²⁺), and carbamazepine (CBZ) were 98.46, 81.08, 91.79, 96.63, 97.75, and 99.26% when HRT was 3 h, pH was 7.0, Pb²⁺, CBZ, and influent salinity contents were 15.0, 3.0, and 1500 mg L⁻¹. The reactor effectively fixed the microorganisms and provided a good microenvironment and niche, which was conducive to the adsorption of Pb²⁺ and CBZ by microorganisms and biominerals. Furthermore, the modified biochar in the reactor filler facilitated microbial metabolism and enabled indirect electron transfer. Microorganisms altered their dominant community structure in response to Pb²⁺ and CBZ exposure. Microorganisms maintained efficient activity through synergy and direct electron transfer through nanowires. The reactor serves as a model for pollutant removal from complex industrial wastewater, leveraging the multifaceted use of lotus stems and microbial-induced calcium precipitation.