Primary sludge fermentate as carbon source for mainstream partial denitrification-anammox (PdNA)
Priyanka Ali1,2, Nadezhda Zalivina2,3, Tri Le2,4
1Department of Civil and Environmental Engineering, The George Washington University, Washington, DC, USA.
Summary
Primary sludge fermentate shows promise as a sustainable carbon source for partial denitrification-anammox (PdNA) wastewater treatment. While batch tests achieved 93% efficiency, pilot studies showed 49%, indicating potential cost savings over methanol.
Area of Science:
- Environmental Engineering
- Wastewater Treatment Technologies
- Microbial Ecology
Background:
- Conventional wastewater treatment faces challenges with nitrogen removal efficiency and operational costs.
- Methanol is a common external carbon source for partial denitrification-anammox (PdNA) processes, but its cost and supply chain can be limiting.
- Primary sludge fermentate offers a hydrolyzed wastewater carbon source that could be a sustainable alternative.
Purpose of the Study:
- To evaluate primary sludge fermentate as an alternative carbon source for mainstream partial denitrification-anammox (PdNA).
- To assess PdNA efficiency, nitrogen removal contributions, and effluent quality using fermentate.
- To estimate potential cost savings compared to methanol-based PdNA.
Main Methods:
- Suspended growth activated sludge process.
- Fermenter operation at 1-2 day sludge retention time (SRT) to optimize fermentate yield.
- Batch experiments to determine partial denitrification (PdN) efficiency with fermentate.
- Pilot-scale deammonification reactor studies comparing fermentate and acetate as carbon sources.
Main Results:
- Fermenter operation at 2-day SRT yielded 0.14 ± 0.05 g sCOD/g VSS without excessive ammonia/phosphorus release.
- Batch experiments achieved 93 ± 14% PdN efficiency with fermentate, comparable to acetate.
- Pilot studies showed 49 ± 24% PdN efficiency with fermentate, lower than acetate (66-70%), possibly due to kinetics.
- Estimated methanol cost savings of 30-55% are achievable with fermentate-based PdNA.
Conclusions:
- Primary sludge fermentate is a viable alternative carbon source for mainstream PdNA.
- Optimized fermenter operation (1-2 day SRT) maximizes yield without nutrient release.
- While pilot PdN efficiency was lower than acetate, significant cost savings are possible.
- Further research may optimize fermentate utilization for enhanced PdNA performance.
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