The discharged excess sludge treated by Oligochaeta

Area of Science:

• Environmental Engineering
• Wastewater Treatment
• Ecology

Background:

• Unstable worm growth poses challenges in biological wastewater treatment.
• Oligochaetes are effective in sludge reduction but require stable conditions.
• Activated sludge systems generate excess sludge requiring efficient management.

Purpose of the Study:

• To develop and evaluate a novel worm-reactor for enhanced sludge reduction.
• To investigate the effectiveness of Oligochaeta in treating excess sludge from activated sludge systems.
• To assess the impact of worm growth on sludge characteristics and nutrient release.

Main Methods:

• A bench-scale worm-reactor (Reactor 1) was inoculated with Tubifex tubifex.
• A control reactor (Reactor 2) was maintained without specific worm inoculation.
• Excess sludge from a pilot activated sludge system was treated in both reactors.
• Sludge reduction, settling characteristics, and nutrient levels were monitored.

Main Results:

• Reactor 1 achieved an average sludge reduction of 59%, significantly higher than the control.
• Tubifex tubifex successfully established and thrived in the worm-reactor.
• Free-swimming oligochaetes naturally colonized both reactors.
• Sludge settling characteristics showed minor improvement; nutrient release (nitrogen and phosphorus) was observed but not excessive.
• High ammonia nitrogen concentrations inhibited worm growth.

Conclusions:

• The developed worm-reactor demonstrates significant potential for effective sludge reduction.
• Oligochaete-mediated treatment offers a viable biological approach to wastewater sludge management.
• Optimizing conditions to mitigate ammonia toxicity is crucial for maximizing worm growth and treatment efficiency.