An Advanced Primary Treatment (APT) system commercially known as ACTIFLO®, coupled with a system of filtration and chlorination are described. The system used microsand grains in the coagulation phase. This allowed an almost immediate start-up as well as an increase in loading in the sedimentation tank to rates far higher than those previously described (up to 180 m/h). The process was shown capable of treating wastewater from a combined drainage system, which typically varies in water quality and quantity. The ACTIFLO® process reduced TSS from 354 to 27 mg/L, helminth eggs from 24.8 to 1.2 HE/L, COD from 460 to 198 mg/L, TKN from 21.7 to 18.3 mg/L, and TP-P from 8.7 to 3.2 mg/L. To comply with WHO, 1989 recommendations regarding HE quality in water destined for irrigation of crops eaten raw it is necessary to add to the APT a system of filtration. In the paper two types of filter media are compared. In both cases the HE were reduced to <1.0 HE/L for filtration rates of up to 40 m/h. In the disinfection phase 10 mg Cl2/L were used to reduce the number of fecal coliforms from 6.5 × 108 to 340 MPN/100 mL.

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