Alternative treatment for wastewater destined for agricultural use

An Advanced Primary Treatment (APT) system commercially known as ACTIFLO(R) , coupled with a system of filtration and chlorination are described. The s ystem used microsand grains in the coagulation phase. This allowed an almos t 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 draina ge system, which typically varies in water quality and quantity. The ACTIFL O(R) 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 qua lity 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 me dia are compared. In both cases the HE were reduced to <1.0 HE/L for filtra tion rates of up to 40 m/h. In the disinfection phase 10 mg Cl-2/L were use d to reduce the number of fecal coliforms from 6.5 x 10(8) to 340 MPN/100 m t. (C) 1999 IAWQ Published by Elsevier Ltd. All rights reserved.