Ammonia Removal from Swine Wastewater by Microwave-Assisted Stripping

This study detetmined optimal microwave irradiation (MI) conditions for removal of ammonia nitrogen (${\mathrm{NH}}_3\text{-}\mathrm{N}$) from swine wastewater. The wastewater was treated using a laboratory-scale industrial microwave unit (2,450-MHz frequency). The removal of ${\mathrm{NH}}_3\text{-}\mathrm{N}$ increased with the increase of pH (9.5–12.5), final temperature (FT) ($50°\mathrm{C}\le FT\le 100°\mathrm{C}$), and MI time (MIT) ($0\le MIT\le 140\min$). Compared with conventional heating (CH), MI removed more ${\mathrm{NH}}_3\text{-}\mathrm{N}$. The calculated ${\mathrm{NH}}_3\text{-}\mathrm{N}$ half-lives decreased as FT and pH increased. FT (80°C–100°C) and MIT (2.5–5.5 min) significantly affected the ${\mathrm{NH}}_3\text{-}\mathrm{N}$ removal. Within the design boundaries, optimal conditions for ${\mathrm{NH}}_3\text{-}\mathrm{N}$ removal (94.9%) were $FT=100°\mathrm{C}$, $MIT=5.5\min$, and pH 10. This work shows the potential of MI as an effective method to reduce the ${\mathrm{NH}}_3\text{-}\mathrm{N}$ content in swine wastewater.