| Liquid dairy farm wastes put water quality at risk if improperly managed. Waste management systems are therefore used, including two components: constructed wetlands, and liquid manure storages. These systems negatively affect air quality, however, by producing greenhouse gases and ammonia. Thus, water quality is improved at the expense of air quality. Since the trade-off is undesirable, this thesis investigates ways of reducing emissions while maintaining water quality. Specifically, the focus is on the mitigation potential of floating covers on the surface of liquid manure storages, and differences between subsurface flow and surface flow wetlands.;From liquid manure storages, CH4 accumulated in the liquid and was released during spring agitation---partially explaining inaccuracy of winter emission models. Two cover types were tested: straw covers (an inexpensive option), and synthetic covers (Biocap(TM); an engineered option). Straw reduced GHG emissions by 20-21% (due to reduced CH4), and NH 3 emissions by 78-90%. Thicker covers performed best. Agitation data indicated straw did not merely trap CH4 in the liquid; however, NH3 emissions increased, negating some benefits. Biocap(TM) reduced NH3 emissions by ∼90% but did not reduce GHG emissions. Data suggest Biocap(TM) impeded transport of CO2 and NH 3, but not CH4.;From constructed wetlands, SSF wetlands had similar wastewater N-removal while emitting less NH3 than SF wetlands, but a similar amount of N2O. SSF wetlands removed as much C from the wastewater, while emitting less CH4. Overall, SF wetlands had 180% higher GHG emissions. Thus, SSF wetlands are preferable on the basis of emissions.;Considering both components of dairy wastewater treatment and storage, most CH4 reductions can be made at the manure storage, whereas meaningful reductions in NH3 and N2O can be made at either location.;Research was conducted in Truro, Nova Scotia, Canada, at a unique facility where replicated, pilot-scale (6.6 m2) experimental units were monitored quasi-continuously for four years. Concentrations were measured using acid traps (NH3), an infrared gas analyzer (CO2), and tunable diode lasers (CH4, N2O). Fluxes were determined using large transparent steady-state chambers that encompassed the entire experimental unit (manure storage or constructed wetland). |
