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Siphon downflow hanging sponge reactor with influent bypass system for improved simultaneous
Shehani Sharadha Maheepala1, Masashi Hatamoto2, Takahiro Watari2
1Department of Civil Engineering and Bioengineering, Nagaoka University of Technology, Nagaoka 940-2188, Japan.
Bioresource Technology
|January 22, 2026
Summary
This study improved wastewater treatment by modifying the siphon downflow hanging sponge (siphon DHS) reactor. The enhanced design boosts nitrification and total nitrogen removal, offering a cost-effective solution.
Area of Science:
- Environmental Engineering
- Microbiology
- Wastewater Treatment Technologies
Background:
- The conventional siphon downflow hanging sponge (siphon DHS) reactor has limitations in nitrification efficiency due to insufficient aerobic volume.
- Enhanced denitrification requires specific conditions often not met by standard DHS designs.
Purpose of the Study:
- To improve nitrification and denitrification rates in the siphon DHS reactor.
- To enhance simultaneous nitrification-denitrification (SND) through reactor modification and an influent bypass system.
- To evaluate the cost-effectiveness and microbial community shifts in the optimized reactor.
Main Methods:
- Modified the siphon DHS reactor volume ratios to 50:25:25 (aerobic:anoxic:anaerobic).
- Integrated a 20% influent bypass system to the anoxic zone.
- Conducted microbial analysis to assess changes in bacterial populations, particularly denitrifiers.
Main Results:
- Achieved 76% nitrification and 20% total nitrogen (TN) removal, a threefold improvement over conventional DHS.
- Maintained 86% soluble chemical oxygen demand (sCOD) removal.
- Observed increased denitrifier abundance (Comamonadaceae: 14%) and reduced nitrite accumulation.
- Demonstrated a 44% cost reduction for nitrogen removal.
Conclusions:
- The modified siphon DHS reactor with an influent bypass system significantly enhances nitrogen removal efficiency.
- The improved design offers a sustainable and cost-effective decentralized wastewater treatment solution.
- Microbial community shifts support the enhanced performance of the integrated system.
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