Comparative analysis of macrofiltration processes used as pre-treatment for municipal wastewater reuse

Three macrofiltration processes were evaluated as a first stage of tertiary treatment of municipal wastewater. The processes studied were pressure sand filter (PSF), disc filter (DF) and mesh filter (MF). The performance of each process was assessed by analysing the effluent for suspended solids, turbidity, E. coli, nematode eggs and particle distribution analysis. In all processes, the quality of the effluent with respect to suspended solids and turbidity was found to be dependent on the influent, with the PSF achieving the best results. The effluent particle analysis likewise indicated a superior retention capacity by PSF, while the DF and MF presented an increase in small particles. All effluent contained E. coli and pathogenic nematode eggs were not detected. However, other types of nematode eggs were observed, so the presence of this pathogen in effluents cannot be discarded. Costs analysis reveal than DF and MF present a higher cost than PSF, owing to the high power consumption. These technologies may be applied as pre-treatment of tertiary disinfection process, pointing up the PSF as the most effective process, allowing direct water reuse for uses with lower quality demands.