Effect of ammonia content in the biodegradability of the salmon industry wastes

Lately, efforts put into solving the serious environmental problems caused by the accumulation of liquid, gaseous or solid industrial residues, have been greatly increased, being solid wastes the last ones to be considered. This work studies the anaerobic biodegradation of salmon waste produced by death in the farming process. The results obtained: 61.99% degradation (expressed in volatile solids abatement), with a methane productivity of 535.66 1 CH₄/kg(d.k.) in studies done to samples with 1% w/v of dry residue, show that the anaerobic technology is adequate to treat these wastes. Runs performed with higher solid contents (7, 13 and 20% w/v) showed an ammonia accumulation, coming from protein degradation. They represent an upper limit of the system studied at a maximum value of ammonia nitrogen of 3.5 g/l attained, amount which hinders the further increase of solid matter in the tests. With the results obtained during this study, two inhibition models were analyzed (the Luong model and one proposed by the authors), which allow the prediction of the performance of the system studied.