vertECO® vertical green wall system demonstration for domestic wastewater treatment and on-site reuse in an Austrian eco-village

Abstract

In recent years, various green wall systems for on-site wastewater treatment have been developed and investigated. One of them, the vertECO®, was created by alchemia-nova and consists of aerated basins aligned stepwise vertically in series having a subsurface horizontal flow hydraulic regime. The system has proven effective for treatment of greywater and the liquid fraction of blackwater in previous studies. To the authors knowledge this study is the first to demonstrate the treatment efficiency of a full-scale green wall system receiving all fractions of domestic wastewater. Four parallel vertECO® system modules were used, with 2 m long basins, receiving a total of 500 L/d of mechanically pre-treated wastewater from an eco-village in Austria. vertECO® purified water is stored in integrated tanks underneath the system and ozonated three times per day while being recirculated in the treated water tanks, aiming at water and nutrient reuse in the local agriculture. Wastewater feeding started in May 2022 and the sampling period extends from November 2022 till July 2023. The organic loading rate based on the cross-sectional surface area (OLR_cs) of the systems amounts to 57 g BOD₅/m²d and 48 g TN/m²d. vertECO® effluent results show that average values are already below EU water reuse regulation thresholds for reclaimed water quality class C (only drip irrigation), and the average effluent values after vertECO® and ozonation combined are below thresholds for class B (BOD₅ ≤ 25 mg/L, TSS ≤ 35 mg/L Legionella <1000 CFU/L and E. coli ≤ 100 CFU/100 mL) and meet Austrian local permit requirements with an average of BOD₅ < 3 mg/L, TSS 1.3 mg/L, Legionella <1 CFU/L and E. coli result of 65 CFU/100 mL, whereas singular sampling event results even reach EU reuse class A (e.g., additional raw eaten vegetables and more can be irrigated).