Étude du comportement de l'azote dans un biofiltre à lit ruisselant traitant du lisier de porc
|Advisor:||Lessard, Paul; Buelna, Gérardo Ramon|
|Abstract:||In Quebec, an important increase in pig production, observed from years 1970 to 2000, led to pig slurry surpluses in some regions, because of insufficient land for application. As a consequence of these surpluses, water pollution occurred, such as the contamination of groundwater by nitrates (NO3-) and the eutrophication of surface water. A solution to overcome this pollution is to install, on the farm site, a pig slurry treatment system. Over the past 20 years, many technologies have been developed, one of them based on the principle of biofiltration. The aim of this study was to improve the knowledge regarding nitrogen behavior inside a trickling biofilter treating pig slurry. As a first step, the biodegradability of three types of pig slurry was studied. Respirometry and the ASM3 biological model were used to quantify the rapidly and slowly biodegradable organic fractions of these slurries. Parallel to this work, nitrogen removal performances of three pilot biofilters were evaluated under different operating conditions. Satisfactory removal efficiencies with regards to chemical oxygen demand (COD) and ammoniacal nitrogen (N-NH4+) were confirmed. Total nitrogen removal varied between 82 and 90%, proving the presence of denitrification inside the systems. These trials also showed that total nitrogen removal is favored at high C/N ratio (17 g COD/g N). In addition, investigation of the nitrogen behavior inside the biofilter led to the surprising conclusion that organic matter oxidation, nitrification and denitrification occurred mainly in the top 30 cm of biofilter. Finally, N2O production, inherent to any denitrifying system, must be followed considering the impact of this powerful greenhouse gas on climatic changes. Results suggested that the main factors favouring N2O production in the biofilter are related to water, dissolved oxygen and nitrate contents inside the filtering media. Consequently, the optimisation of nitrogen removal from pig slurry, while minimizing its impact on climatic changes, may require the study of an aeration diminution through the implantation of aerobic/anoxic cycles.|
|Document Type:||Thèse de doctorat|
|Open Access Date:||16 April 2018|
|Collection:||Thèses et mémoires|
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