Using bio-based CaCO3 functionalized sediment to simultaneously remove algae and COD through adsorption and sedimentation in water source reservoirs
Abstract
In-situ turbidity enhancement can suppress algal growth in reservoirs but often exacerbates chemical oxygen demand (COD) accumulation due to incomplete organic removal. This study presents a biologically synthesized bio-CaCO3-modified sediment, engineered via Bacillu s-induced carbonate precipitation, to simultaneously control algae and reduce COD. The material forms 15–30 nm core–shell clusters with enriched –OH/–COOH groups and mesopores (~19.76 nm), confirmed by SEM, XRD, FTIR, and BET (+1.02 m2 g-1). Adsorption tests against Microcystis aeruginosa, Chlorella, and Limnothrix showed Langmuir-type monolayer binding (R2 > 0.97) and pseudo-second-order kinetics. XDLVO theory and DFT analysis revealed strong EPS–Bio-CaCO3 interactions (\(\Delta E_\text{AB}\) = 31.28 mJ m-2; \(\Delta E_\text{ads}\) = –1.07 ev). Optimal conditions (7.5 wt% CaCO3, 56% residual Ca2+, 85 min) achieved 93.8% Chl-a removal, 88.6% COD reduction, and 87.5% turbidity control (R2 = 0.98), with minimal Ca2+ leaching. By integrating chemisorption, interfacial adhesion, and pore confinement, this material provides a stable, eco-friendly strategy for dual pollutant control and in-situ sediment remediation.