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Published on: December 25, 2015
Nitrogen removal optimization in a sequencing batch reactor treating sanitary landfill leachate
Alessandro Spagni1, M Cristina Lavagnolo, Carlotta Scarpa
1ENEA, Italian National Agency for New Technologies, Energy and the Environment-Water Resource Management Section, Bologna, Italy. alessandro.spagni@bologna.enea.it
Summary
Biological nitrogen removal via nitrite is effective for landfill leachate, even with low biodegradable COD/TKN ratios. Monitoring dissolved oxygen, pH, and ORP optimizes this process, though it can impact sludge settling.
Area of Science:
- Environmental Microbiology
- Wastewater Treatment Engineering
Background:
- Biological nitrogen removal via nitrite is a promising strategy for optimizing nitrogen removal, especially with low biodegradable Chemical Oxygen Demand (COD) to Total Kjeldahl Nitrogen (TKN) ratios.
- Landfill leachates present challenges for nitrogen removal due to low biodegradability of organic matter.
Purpose of the Study:
- To evaluate dissolved oxygen (DO), pH, and oxidation-reduction potential (ORP) as monitoring parameters for optimizing nitrogen removal via nitrite in a lab-scale sequencing batch reactor (SBR).
- To assess the effectiveness of nitrogen removal via nitrite from landfill leachate and identify the impact of process parameter control on efficiency and operational costs.
Main Methods:
- A lab-scale sequencing batch reactor (SBR) was operated for approximately two years to treat landfill leachate.
- Continuous monitoring of DO, pH, and ORP was performed to correlate these parameters with nitritation and denitritation efficiency.
- Manual adjustments to SBR phase lengths were made to optimize nitrogen removal via nitrite.
Main Results:
- The SBR achieved over 99% nitrification efficiency.
- COD removal was approximately 40%, necessitating external COD addition for denitrification.
- Monitoring DO, pH, and ORP proved reliable for tracking nitritation and denitritation in SBRs treating landfill leachate.
- Manual phase adjustments led to a 20% saving in external COD addition, but also caused process instability.
- Low DO concentrations during oxic phases potentially impaired activated sludge settling characteristics.
Conclusions:
- Nitrogen removal via nitrite is feasible and efficient for landfill leachate treatment using SBRs.
- DO, pH, and ORP are valuable real-time monitoring tools for optimizing nitrogen removal via nitrite processes.
- While process control can reduce operational costs, careful management is needed to avoid instability and negative impacts on sludge properties.
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