The efficiency of four biological aerobic treatment units was studied as regards nutrient removal performances and repartition of compounds (nitrogen, phosphorus, potassium, copper and zinc). Several type of separators were evaluated : press-auger separator and decanter centrifuge for the separation of the raw slurry and vacuum sieve-belt separator for the separation of the aerated slurry. Between 60 and 70 percent of the nitrogen was removed in gaseous form. The separation efficiency for the press-auger was 20-25 percent for phosphorus and 8-10 percent for copper and zinc. Efficiency was improved with the use of the decanter centrifuge and could raise 80 percent for phosphorus and 50-70 percent for copper and zinc. With the use of press-auger forthe separation of the raw slurry and vacuum sieve-belt for the separation of the aerated slurry, 90 percent of phosphorus and the totality of copper and zinc were concentrated in the solid phases. By-products characteristics were obtained during this study. Copper and zinc concentration up to 96 gCu/ton and 194 gZn/ton for the solid phase from the press-auger separator and 140 gCu/ton and 342 gZn/ton from the vacuum sieve-belt separator were obtained.
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