Nitrogen behavior during sludge ozonation: a long-term observation by pilot experiments

Area of Science:

• Environmental Engineering
• Water Treatment Technologies
• Wastewater Management

Background:

• Excess sludge treatment and disposal pose significant challenges.
• Nitrogen behavior during sludge ozonation and biological removal requires clarification.

Purpose of the Study:

• To investigate nitrogen behavior during sludge ozonation and subsequent biological treatment.
• To determine optimal operational conditions for sludge ozonation.
• To assess the feasibility and stability of oxidizing organic nitrogen in a bioreactor.

Main Methods:

• Long-term observation of nitrogen behavior under varying sludge ozonation conditions.
• Analysis of soluble organic nitrogen oxidation to ammonia.
• Monitoring of nitrification and denitrification processes in a combined anaerobic/oxic system.

Main Results:

• Increasing ozone concentration and decreasing ozonation time reduced soluble organic nitrogen oxidation to ammonia (from 66.1% to 18.7%).
• Biological processes, specifically nitrification, were restored within three weeks after organic nitrogen shock loading.
• Nitrogen in excess sludge decreased with increasing sludge reduction rate, primarily via denitrification, without significantly increasing effluent nitrogen.

Conclusions:

• Optimized sludge ozonation conditions can reduce operational costs by minimizing ammonia formation.
• Sludge ozonation followed by biological treatment is a feasible approach for excess sludge management.
• Nitrogen removal is achieved through denitrification, with minimal impact on effluent quality.