Clogging reduction and removal of hormone residues with laboratory-scale vertical flow organic-based filter and hybrid wetland

Abstract

A laboratory-scale, intermittently fed, organic-based vertical flow filter was tested as a pre-treatment of high-strength urban wastewater to reduce the risk of clogging in treatment wetlands. At an average hydraulic loading rate of 815 L/m2 day and average surface loading rates of biological oxygen demand of 458 g/m2 day, chemical oxygen demand of 594 g/m2 day and suspended solids of 310 g/m2 day, the organic-based vertical flow filter achieved removal efficiencies of 48 % of biological oxygen demand, 45 % of chemical oxygen demand, 69 % of suspended solids and 51 % of turbidity. For this unit, removals were significantly correlated with organic surface loading rates but not with hydraulic loading rate. Additionally, the organic-based vertical flow filter removed almost completely the hormone residues studied: estrone, 17β-estradiol, 17β-ethynyl estradiol, diethylstilbestrol, estriol, norethisterone and testosterone, most probably by the combination of adsorption onto the organic substrate and biodegradation. The efficiency of the combined system was remarkable for biological oxygen demand (97 %), chemical oxygen demand (89 %), suspended solids and turbidity (99 %), fecal coliforms and E. coli (99.9 %) and fecal enterococci (99 %).