The implementation of a pretreatment unit before existing upward filter, to condition the eutrophic raw waters to its capacity, is an option which runs into a problem of technical nature, the need of a pretreatment unit with enough hydraulic load to properly feed the existing filter. Typically, the available studies on double filtration present upward filters followed by descendant ones. In this study, the installation of a pressure filter downflow adapted the raw water with high algae concentration to the upward direct filtration system limitations, improving the quality of water produced and reducing losses by washing. The pressure filter with better efficiency was the PFP1 filter showed a removal of 50% of apparent color and 63% of turbidity. The overall efficiency of the PFP/FA system was satisfactory, presenting final turbidity of less than 0.5 uT, apparent color around 5 uH and reducing losses from 11.7 to 4.5% of the total treated water.
double filtration; raw water pre conditioning; pressure filters; eutrophic water treatment
