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Definition English:
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It objectives mainly the organic matter removal, possibly microorganisms and nutrients such as nitrogen and phosphorus, with a predominance of biological mechanisms in these processes. Substantial reduction in organic matter in fine suspension is achieved, which was not removed in the primary treatment, and organic matter in the form of solids not liable to sedimentation, dissolved (BOD soluble). A removal percentage of 60 to 99 percent in BOD and coliforms, and 10 to 50 percent of the nutrients can be achieved. The natural biological treatment processes applied at this stage, consisting of a single treatment unit that produces satisfactory quality effluent for the final release, are facultative lagoons and optional aerated lagoons. In this stage there are numerous biological treatment systems, formed by the treatment unit layouts; and the highest efficiencies in the pollutants removal are obtained by placing an aerobic treatment unit as a posttreatment anaerobic unit. (Free translation from the original: Brasil. FUNASA, 2018) |