Optimizing wastewater treatment: Algae-mediated calcite formation and carbon sequestration through bicarbonate control

The growing emphasis on sustainability in environmental health, climate change, and water usability has driven the exploration of economically and environmentally friendly approaches to enhance wastewater quality. Algae-mediated natural precipitation of minerals in wastewater, driven by these organisms' carbon utilization in photosynthesis, has emerged as a promising wastewater treatment (WWT) method due to its sustainability and cost-efficiency benefits. This study examines the impact of varying carbon content in bicarbonate forms on algae activity in mediating CaCO3 precipitation and how pH in algae-mediated solutions influences calcite precipitation. Solutions with different Ca2+ and HCO3- concentrations were prepared, and algae growth curves were established to ensure solution suitability. The experiments, conducted in two sets, employed ANOVA and t-test analyses for samples with common calcium concentration. Results indicated that increasing HCO3-concentration positively correlates with algae mediation and CaCO3 precipitation, while elevating pH from 9.8 to 11.0 negatively correlates with calcite precipitation. In conclusion, HCO3 additions were effective in enhancing algae-mediated calcite precipitation in wastewater. Recommendations include ensuring proportionate HCO3- additions to calcium content to optimize mineral precipitation without detrimental effects on algae.