Nitrogen removal from digested slurries using a simplified ammonia stripping technique.
Giorgio Provolo1, Francesca Perazzolo1, Gabriele Mattachini1
1Department of Agricultural and Environmental Sciences, Universitá degli Studi di Milano, Via Celoria 2, 20133 Milano, Italy.
Waste Management (New York, N.Y.)
|August 13, 2017
Summary
This study shows a new method to remove ammonia from digested waste using air and mixing. It effectively removes nitrogen from livestock manure at typical biogas plant conditions with low energy use.
Area of Science:
- Environmental Science
- Biotechnology
- Waste Management
Background:
- Nitrogen removal from digested organic waste is crucial for environmental protection.
- Anaerobic digestion of livestock manure produces digestate requiring nutrient management.
- Ammonia stripping is a potential method for nitrogen removal.
Purpose of the Study:
- To assess a novel slow-rate air stripping technique for ammonia removal from digested organic waste.
- To evaluate the impact of temperature and pH on nitrogen removal efficiency.
- To determine the suitability of the technique for livestock manure digestate.
Main Methods:
- Three 10-day experiments using two 50-L reactors.
- Continuous mixing of digestate and air stream delivery across the liquid surface.
- Testing different temperatures (30°C, 40°C, 50°C) and pH levels (adjusted and unadjusted).
Main Results:
- Highest ammonia removal efficiency (87%) achieved at 40°C with pH adjustment.
- Significant nitrogen removal (69% ammonia, 47% total nitrogen) at 40°C without pH adjustment.
- Effective ammonia removal (approx. 85%) at 50°C without pH adjustment, even with varying digestate characteristics.
Conclusions:
- The slow-rate air stripping technique is effective for removing nitrogen from livestock manure digestate.
- The method is viable at natural pH (≈8) and 40°C, common in biogas plants.
- The process has low energy requirements (estimated 3.8 kWh/m³ digestate) and potential for further improvement.
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