Leachate flush strategies for managing volatile fatty acids accumulation in leach-bed reactors

Area of Science:

• Environmental Science
• Biotechnology
• Chemical Engineering

Background:

• Anaerobic leach-bed reactors (LBRs) are vital for waste treatment and biogas production.
• Co-digestion of diverse substrates influences reactor performance.
• Leachate recirculation is a key operational parameter in LBRs.

Purpose of the Study:

• To investigate the impact of leachate flush rates on volatile fatty acid (VFA) dynamics in LBRs.
• To determine optimal leachate injection strategies for both initial VFA extraction and subsequent VFA consumption.
• To enhance biogas production efficiency through controlled VFA management.

Main Methods:

• Experimental setup using LBRs co-digesting easily and slowly degradable substrates.
• Testing three leachate flush-rate conditions (0.5, 1, and 2 Lkg⁻¹TSd⁻¹) during the acidification phase.
• Injecting leachate with specific acetic acid concentrations (5-10 gL⁻¹) into mature reactors.

Main Results:

• Increased leachate flush rates during acidification significantly enhanced degradation kinetics.
• Leachate injection became less critical after the initial acidification phase.
• Optimal VFA consumption and sustained biogas production were achieved by injecting VFAs 6-7 hours after the methane production peak.

Conclusions:

• Leachate flush rate management is crucial for optimizing VFA extraction and degradation in LBRs.
• Strategic timing and frequency of VFA injection are essential for maximizing biogas yield in mature reactors.
• Understanding VFA dynamics allows for improved operational control of anaerobic digestion processes.