Piggery waste treatment by using down-flow anaerobic fixed bed reactors.

Area of Science:

• Environmental Engineering
• Biotechnology
• Wastewater Treatment

Background:

• Down-flow anaerobic fixed-bed reactors (DFAFBR) are crucial for treating piggery waste.
• Understanding the role of reactor depth is key to optimizing performance.
• Hydraulic retention time (HRT) significantly influences biological activity and contaminant removal.

Purpose of the Study:

• To investigate the impact of reactor depth on DFAFBR performance using piggery waste.
• To analyze the relationship between nominal hydraulic retention time (HRT(N)), influent concentration, and reactor activity.
• To characterize the hydraulic behavior and soluble chemical oxygen demand (SCOD) removal efficiency.

Main Methods:

• Laboratory-scale DFAFBRs were operated at varying HRT(N) and influent COD concentrations (2-8 g/L).
• Profiles of SCOD, organic nitrogen, ammonia nitrogen, pH, and electrical conductivity were measured across reactor depths.
• Hydraulic tests were conducted to determine dispersion numbers and real contact times (Theta).

Main Results:

• An initial highly active zone was observed in the first half of the reactor, decreasing in depth with increased HRT(N).
• Higher influent concentrations led to steeper concentration gradients within the active zone.
• SCOD decreased exponentially with increasing real contact time (Theta), with influent concentration significantly affecting removal in the initial reactor stages.

Conclusions:

• Reactor depth plays a critical role in anaerobic digestion performance, with activity concentrated in the upper sections.
• Optimizing HRT and influent concentration is essential for maximizing SCOD removal efficiency in DFAFBRs.
• The hydraulic pattern approaches plug-flow, with dispersion increasing at longer HRT(N).