Resumen en español

Two different systems of biological treatment were operated (anaerobic-anoxic-aerobic –A2O–, namely, arrangement I, and aerobic-anoxic, namely, arrangement II). After modification by the addition of AnoxKaldnes as a support medium for the aerobic chambers, they were used in the simultaneously elimination of organic material and two nutrients:nitrogen and phosphorus. The arrangements involved the growing of suspending biomass in anaerobic and anoxic chambers, and combined (suspended and attached) in the aerobic chambers. During the experiments, recirculation rates (aerobic-anoxic) within 100 and 300% were guaranteed, applied in the same experimental periods, from the secondary settler toward the anaerobic chamber in the arrangement I and toward the anoxic chamber in arrangement II, with rates of 100%. The hydraulic retention time (HRT) varied within 10 and 24 hours per arrangement, and the solids retention time (SRT) remained between 15 and 20 days. The processes were evaluated using synthetic residual water with composition similar to the found in the domestic residual water; it was prepared from milk powder whey with the addition of macro and micro-nutrients.