The influence of the contact zone configuration on the performance of a DAF pilot plant applied to water treatment

Abstract

This paper presents the results of a study carried out aiming not only to characterize the flow structure into different contact zone (CZ) configurations of a 4.6 m3/h rectangular dissolved air flotation (DAF) pilot plant (DAFPP) fed with synthetic water but also to verify the influence of these changes on the color and turbidity removal efficiencies. MicroADV equipment was used to characterize the flow pattern into different CZ configurations. The CZ shaft wall was maintained in a vertical position and eight different configurations of the CZ were investigated in order to fit different values of hydraulic surface loadings (HSLCZ), hydraulic detention time (TCZ) and cross-flow velocity (VCF) in the CZ of the DAFPP. It was concluded that TCZ ranging from 34 to 65 s associated with HSLCZ ranging from 67 to 180 m/h led to satisfactory turbidity (>91%) and color (>87%) removal efficiencies; but the highest DAFPP performance was verified when applying higher values of HSLCZ (up to 180 m/h) associated with TCZ of 34 s and VCF of 45 m/h, thus resulting in 98.3% turbidity removal (residual of 0.21 NTU) and 96.4% color removal (residual < 2 CU).