BOD

Biochar effectively reduces Biological Oxygen Demand (BOD) in wastewater by adsorbing organic pollutants, acting as a filter, and enhancing microbial activity, with treated biochars (especially from invasive weeds or specific feedstocks like water hyacinth) showing high removal efficiencies (80-95%+) by increasing surface area and porosity, making it a sustainable, low-cost solution for improving water quality. 

How Biochar Reduces BOD

• Adsorption: Its porous structure and large surface area trap organic matter causing BOD.
• Filtration: Biochar acts as a physical filter, removing suspended solids.
• Enhanced Microbial Activity: It provides a habitat for beneficial microorganisms that break down pollutants.
• Nutrient Recovery: It can also remove other pollutants like phosphorus and nitrogen, creating a potential biofertilizer. 

Factors Influencing Effectiveness

• Feedstock: Biochar from invasive weeds (like C. burhia) or agricultural biomass shows excellent results.
• Pyrolysis Conditions: Higher temperatures and longer times generally increase surface area and pore volume, improving performance.
• Treatment: Chemical activation (e.g., with NaOH) can significantly boost BOD removal.
• Integration: Combining biochar with other methods like vermifiltration or ozonation further increases efficiency. 

Real-World Examples

• Invasive Weeds: Biochar from certain weeds achieved up to 88% BOD removal in municipal wastewater.
• Dairy Wastewater: Biochar filters reduced BOD, COD, and TSS significantly, turning waste into a potential resource.
• Septic Effluent: Softwood pine biochar was highly effective at reducing BOD in septic systems. 

Conclusion