Flux de phosphore et collecte des boues d'une pisciculture de moyenne taille

The production of Quebec's freshwater fish farm industry was reduced due to imposed environmental constraints. By 2014, this industry aims to reduce phosphorus (P) discharge to 4.2 kg of P released/ton of fish produced within the framework of an agreement called "Quebec's freshwater aquaculture development strategy (STRADDAQ)". In Quebec, 91% of the fish farms use at least one pond for fish rearing and culture, which indicates the importance to establish an integrated management system for pond fish farms. However, not enough data is available on the dynamics of P.;The purpose of this study was to establish an annual P balance in fish farm ponds and to identify the main factors for P release in fish farms based on the P mass measured in annual aquaculture sludge removal.;For this purpose, one Quebec fish farm was studied during two years of production. The analysed parameters were: the mass of P in the pond sludge, in the distributed feed and in the fish produced in relation with the hydraulic retention time, the surface overflow load and the fish density. Two similar shotcrete ponds (;The monthly characterization of sludge in the studied ponds showed that between 63 and 91% and between 19 and 83% of P in sludge accumulated under the floating surface aerator in shotcrete pond 2 and earthen pond 3 respectively. Moreover, results of annual sludge removal indicated that the earthen pond, which recovered an estimated 31% of P not taken up by fish, appeared to be more efficient in P retention in comparison with the shotcrete ponds which recovered between 8 to 17% of P not taken up by fish. However, it is possible that removed sludge from the bottom of the earth pond would be taking phosphorus accumulated from previous years of operations and thus, the efficiency of P removal would have been overestimated. A higher hydraulic retention time (HRT), a lower surface overflow rate (SOR) and a lower fish density (f d), as well as stronger P sorption mechanisms in the earthen pond favoured a high efficiency in P removed in sludge.;Results of P balances in ponds showed that from the 100% of P added by distributed feed, between 5 and 19% (8 to 31% of P not taken up by fish) was removed in the annual sludge removal. Between 40 and 57% was released from these ponds, which represented from 3.8 to 6.3 kg of P released per ton of fish produced. Finally, the HRT, the SOR, the fish density (fd ) and the P sorption were the most important factors to improve the efficiency of P removed from aquaculture ponds.;More in-depth studies of these parameters should be carried out and ponds with lower P retention efficiency could increase their sludge removal frequency to at least twice per year.