Effect of Stirring on Organic Matter Conversion in Horizontal Biodigesters

Area of Science:

• Environmental Engineering
• Biotechnology
• Waste Management

Background:

• Horizontal flow anaerobic biodigesters are crucial for treating swine wastewater.
• Sludge accumulation can impede biodigester efficiency and longevity.
• Optimizing biodigester performance requires understanding the impact of operational parameters.

Purpose of the Study:

• To investigate the effect of localized mechanical stirring on anaerobic biodigesters treating swine wastewater.
• To compare the performance of a mechanically stirred reactor (HFw) with a non-stirred reactor (HFw/o).
• To analyze organic matter conversion pathways and sludge accumulation under different mixing conditions.

Main Methods:

• Two parallel bench-scale horizontal flow anaerobic biodigesters were operated for 150 days.
• One reactor (HFw) was equipped with mechanical stirring; the other (HFw/o) was not.
• Identical hydraulic retention time (25 days) and volumetric organic loading rate (0.3-0.5 g TVS L-1 day-1) were maintained.

Main Results:

• No significant differences in hydrolysis, methanogenesis, biogas production, or composition were observed between the stirred and non-stirred reactors.
• Mechanically stirred biodigesters accumulated significantly less sludge (5.5% of applied COD) compared to non-stirred ones (13.6% of applied COD).
• Mass balance analysis confirmed reduced solid accumulation in the stirred reactor.

Conclusions:

• Localized mechanical stirring effectively mitigates sludge accumulation in horizontal flow anaerobic biodigesters.
• Mechanical stirring does not compromise overall treatment performance or biogas generation.
• This technique presents a viable strategy for enhancing the operational efficiency of swine wastewater biodigesters.