Assessment of the performance of intermittent planted filters in treating urban wastewater under arid climate

Abstract

Intermittent planted filters are extensive biological purification techniques aimed at oxidizing and decontaminating urban wastewater at a low cost and with minimum environmental impacts. The main purpose of this study was to evaluate the performances of intermittent planted filters in treating urban wastewater under arid conditions of southern Tunisia. The experimental study was carried out on a pilot scale plant comprising five constructed gravel-sand basins. Screened urban wastewater effluent was intermittently applied with a daily hydraulic load of 400 L/m2. Several water quality parameters were monitored at the inlet and outlet of this treatment plant. The average removal rate were 94.8%, 92.3%, 99.3%, 89.9% and 93.3% for chemical and biological oxygen demand, total suspended solids, ammonium nitrogen and orthophosphate, respectively. Additionally, results demonstrated that this treatment system is capable of removing 3.67, 3.22 and 2.44 log units of total and faecal coliforms, and faecal streptococci, respectively. Results showed that Phragmites australis allowed the development of biofilm in the sand filter beds, improving their purification efficiency. Furthermore, no bio-sludge production, no mechanical aeration, low energy requirement (0.02 kW/m2) and green aesthetic ambience are the additional particular strengths of the proposed pilot plant. HIGHLIGHTS Planted filters are efficient in treating urban wastewater under arid conditions.; Results showed that Phragmites australis improved the purification efficiency of the planted filters.; Planted filters accomplished significant removal rates of organic and nitrogen matter.; This treatment system led a significant abatement of pathogens.; The treated wastewater can be reused in irrigation.;

Keywords

• arid climate
• assessment
• efficiency
• planted filters
• treatment
• urban wastewater