Using a mixture of perlite and sponge bio-carriers as substrate material in vertical flow-constructed wetlands for...

Using conventionally constructed wetlands filled with gravel or sand as a substrate material is often problematic for efficiently treating heavily organic-polluted agro-industrial wastewater. Consequently, exploring more advantageous materials to enhance the removal efficiency of these nature-based systems is of significant interest. In this context, this study aimed to investigate, for the first time, a mixture of perlite and sponge biocarriers as substrate material in vertical flow constructed wetlands (VFCWs) for the treatment of cheese production wastewater. Two lab-scale VFCWs, planted both with Atriplex halimus, and were filled the first one with conventional gravel (VFCW1) and the other with the newly examined mixture (VFCW2), were operated and monitored for a period of 250 days, two different hydraulic retention times were tested (period 1: 14.1 days, period 2: 7.05 days). Results showed that the use of the perlite and biocarrier mixture achieved significantly higher mean removal efficiencies compared to the conventional gravel-filled system for turbidity (95 % and 85 %, respectively), total suspended solids (86 % and 82 %, respectively), and organic matter (84 % and 74 %, respectively). In contrast, both systems exhibited similarly low removal of total phosphorus. The analysis of the bacterial communities in the rhizosphere of the examined VFCWs indicated minor differences. However, slightly higher relative abundance was recorded for Firmicutes (24.5 %) and Proteobacteria (19.2 %) in the system containing the perlite and biocarrier mixture compared to the conventional system (22.0 % and 16.8 %, respectively). Overall, using perlite and sponge biocarriers as porous materials in VFCWs could improve the effluent quality in the treatment of cheese production wastewater.