Process Model for Ammonia Volatilization from Anaerobic Swine Lagoons Incorporating Varying Wind Speeds and Gas Bubbling
2008
Ro, Kyoung S. | Szogi, Ariel A. | Vanotti, Matias B. | Stone, Kenneth C.
Ammonia volatilization from treatment lagoons varies widely with the total ammonia concentration, pH, temperature, suspended solids, atmospheric ammonia concentration above the water surface, and wind speed. Ammonia emissions were estimated with a process-based mechanistic model integrating ammonia chemistry of the lagoon and interfacial transport characteristics between air and water. This improved model incorporated the effect of internal bubble production and continuously variable wind speed on ammonia volatilization measured at 10 m above the liquid surface (U 10 ). Model simulations were compared to ammonia emission rates measured simultaneously at three contrasting lagoon scenarios: non-treated lagoon (13,633 kg ha -1 year -1 ), partially pre-treated manure using solid-liquid separation (3,699 kg ha -1 year -1 ), and treated manure using combined solid-liquid separation with nitrogen and phosphorus removal from the liquid (1,311 kg ha -1 year -1 ). The simulations only using average U 10 with bubble enhancement or U 10 distributions without bubble enhancement produced fluxes 42% and 44% below observed fluxes, respectively. However, the simulated fluxes using the U 10 distributions along with bubble enhancement for the non-treated lagoon during warm seasons closely matched the observed fluxes (y = 1.04x, with R 2 = 0.76). Ammonia emissions would be significantly underpredicted if bubbling-enhanced mass transport was not taken into account during warm seasons, as demonstrated by the improved process model and evidenced by the observed fluxes.
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