An evaluation of the feasibility of ammonia stripping for ammonia recovery from waste liquid resulting from an in-house belt separation system is presented. The liquid stream produced is a low-volume stream with a high concentration of ammonia and relatively low suspended solids. These characteristics make this waste stream favorable for recovery of the ammonia using physical/chemical processes. Immediate separation of liquids and solids greatly reduces ammonia volatilization, and the majority (77%) of excreted nitrogen remains in the liquid stream. This liquid also has high alkalinity, which means that a large amount of base is needed to raise the pH to a high enough level to achieve ammonia stripping. The need to raise pH can be reduced by raising the temperature. A countercurrent stripping tower process was tested at laboratory scale. The laboratory reactor used in this research was a PVC column of 0.15 m (6 in) diameter and 1.2 m (4 ft) height, packed with plastic media. Operating conditions of pH 8.0 – 10.5, temperatures of 45 – 60 degrees C, and gas:liquid flow ratio of 80 were evaluated. The trade-off between increasing pH and temperature are discussed in relation to the cost of the process. Results indicate that increasing the temperature to 50 – 60 degrees C will significantly reduce the amount of pH adjustment needed for efficient stripping.
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