Multistage wastewater treatment using separated storage driven denitrification and nitrification biofilms

Area of Science:

• Environmental Engineering
• Microbiology
• Wastewater Treatment

Background:

• Traditional biological nitrogen removal systems face challenges with low carbon-to-nitrogen (C/N) ratios.
• Simultaneous nitrification and denitrification (SND) systems have limitations in efficiency and removal rates.

Purpose of the Study:

• To assess the feasibility of integrating a storage-driven denitrification biofilm with a nitrification reactor for complete biological nitrogen removal.
• To evaluate the system's performance at low C/N ratios and high nitrogen removal rates.

Main Methods:

• A combined reactor system utilizing a storage-driven denitrification biofilm (converting acetate to poly-beta-hydroxybutyrate/PHB) and a nitrification reactor (submerged or trickling filter) was employed.
• The system's efficiency and nitrogen removal rates were measured using waste streams with a C/N ratio as low as 3.93 kg COD/kg N-NH3.

Main Results:

• The integrated system demonstrated complete biological nitrogen removal at a high rate of 1.1 mmole NH3/L/h.
• The system outperformed traditional and SND systems in nitrogen removal efficiency and rates.
• Challenges identified include incomplete reactor draining leading to ammonia retention and pH drifts affecting nitrification rates.

Conclusions:

• The combined storage-driven denitrification and nitrification system shows significant potential for effective biological nitrogen removal from low C/N ratio wastewater.
• Further optimization is needed to address issues of incomplete draining and pH stability for enhanced overall performance.