Investigating the application of novel filling materials in Vertical Subsurface Flow Constructed Wetlands for the treatment of anaerobic effluents originating from domestic wastewater.

Vertical subsurface flow constructed wetlands (VSSF CWs) were employed to investigate the use of biochar that could be produced with local agricultural biomass through pyrolysis, recycled glass from local recycling companies and gel beads with decreased packing volume and shipping cost as substrate alternatives to sand. The materials were assessed in terms of granulometry, porosity, adsorption capacity and hydraulic conductivity and were used for the treatment of an upflow anaerobic sludge blanket (UASB) reactor, treating domestic wastewater, effluent. Granulometry was a major factor impacting TSS removal that ranged from 81% ± 10% to 97% ± 2%. The COD removal was affected by granulometry, porosity and the active biofilm formation, since biochar removal was slightly higher (up to 93% ± 3%) than that of sand and recycled glass (up to 86% ± 4% and 85% ± 5%, respectively) and significantly higher than that of gel beads (up to 68% ± 8%). The higher porosity of biochar affected NH-N removal in which adsorption had a greater and longer effect. The overall NH-N removal ranged between 84% ± 11% and 99% ± 1% for all materials. Sand, biochar and glass achieved an 80% average removal of selected contaminants of emerging concern (CECs), including ibuprofen (IBU), naproxen (NPX), triclosan (TCS), bisphenol A (BPA), diclofenac (DCF) and ketoprofen (KFN). The biochar and recycled glass are effective in treating UASB effluent and enable the treated wastewater reuse, since, high compliance rates with the EU Regulation 2020/741 - Class A were achieved (>98% for TSS, >88% for BOD and 100% for turbidity).