Optimization of the simultaneous removal of nitrogen and organic matter from fishery wastewaters

Anaerobic treatment of saline and protein-rich effluents reduces the organic concentration but forms ammonium that binders nitrogen removal in a later aerobic treatment. The goal of this work was to optimize the design of a denitrifying-nitrifying system for the simultaneous removal of organic matter and nitrogenous compounds from fishery effluents to meet the Chilean legal standards and to compare pre and post-denitrfication processes in the biological treatment of high-strength effluents to minimize the total volume of biological reactors required. A predenitfifying system, that included three reactors-acidifying anaerobic filter, denitrifying (anoxic) filter, and aerobic-active sludge (nitrifying reactor) with recycle to the denitrifying reactor-reduced nitrogen to 0.33 g of total ammonia nitrogen (TAN) L-1, well above the allowed 0.05 g total nitrogen L-1. The predenitrifying system with a second denitrifying reactor, to which organic matter was added, met the legal organic matter and nitrogen emission concentrations (0.042 g TAN L-1). Conversions were 99.0, 92.5, 90.9, and 99.0% for the anaerobic digestion, first denitrification, nitrification, and second denitrification, respectively.