Landfill Leachate Treatment Through Coagulation-flocculation with Lime and Bio-sorption by Walnut-shell

Area of Science:

• Environmental Engineering
• Water Treatment Technologies
• Waste Management

Background:

• Landfill leachate poses environmental risks due to chemical oxygen demand (COD) and heavy metal contamination.
• Conventional treatment methods often generate substantial sludge and incur high material costs.
• Developing cost-effective and efficient leachate treatment is crucial for environmental protection.

Purpose of the Study:

• To optimize a sequential treatment process for landfill leachate using lime and walnut shells.
• To maximize COD and heavy metal removal efficiencies.
• To minimize sludge volume and material consumption rate.

Main Methods:

• Investigated the combined effects of lime treatment and walnut-shell adsorption.
• Employed response surface methodology to optimize lime dosage, walnut-shell dosage, and pH.
• Introduced a new metric, OSVLDR (observed sludge volume to lime dosage ratio), to assess efficiency.

Main Results:

• Achieved 43.24% COD removal under optimal conditions (pH 6, 6.83 g/L lime, 25 g/L walnut shell).
• Demonstrated high removal rates for heavy metals: Ni (98.17%), Cd (67.45%), Zn (91.03%), and Pb (88.02%).
• Identified that reducing initial pH to 3.50 could decrease costs by 10% and lower OSVLDR.

Conclusions:

• The sequential lime and walnut-shell treatment is a cost-effective approach for leachate remediation.
• Optimization of process variables significantly impacts removal efficiency and cost-effectiveness.
• Utilizing inactive, crushed walnut shells offers a cheaper alternative to activated shells.