Nitrogen removal in a two-stage, re-circulating waste stabilisation pond system.

Area of Science:

• Environmental Engineering
• Microbiology
• Wastewater Treatment Technologies

Background:

• Waste stabilization ponds are widely used globally for domestic and industrial wastewater treatment, particularly in rural areas.
• Existing ponds often require upgrades to meet stringent nutrient removal standards.
• Conventional biological nutrient removal processes can be costly to implement in existing infrastructure.

Purpose of the Study:

• To evaluate a novel two-stage, re-circulating waste stabilization pond system incorporating algal-bacterial biofilm.
• To assess the system's efficiency in nitrogen removal compared to conventional methods.
• To determine the economic viability of this approach for upgrading existing facilities.

Main Methods:

• A laboratory-scale, two-stage, re-circulating system was designed using "Bio-Tube" plastic modules as attached growth medium.
• The system was tested using synthetic wastewater with controlled influent conditions.
• Nitrogen removal mechanisms under complete mix conditions were investigated.

Main Results:

• The system demonstrated high removal efficiencies for ammonia nitrogen (90-95%) and total nitrogen (65-85%).
• Nitrification-denitrification was identified as the primary nitrogen removal mechanism.
• Influent conditions were approximately 600 mg/L COD and 70 mg/L total nitrogen.

Conclusions:

• The two-stage, re-circulating system with algal-bacterial biofilm is a viable and economical option for enhancing nitrogen removal in existing waste stabilization ponds.
• This technology offers a significant improvement over traditional wastewater treatment methods for nutrient management.
• The findings support the adoption of this innovative approach for sustainable wastewater treatment in rural and small communities.