Potentials of Different Water-Storage Mats Treating Greywater from a Canteen: From Laboratory to Pilot-Scale Testing

Water scarcity is an increasingly urgent global challenge, prompting the development of new water purification technologies that surpass conventional solutions. Decentralized greywater treatment is emerging as a viable option for enhancing water reuse in multifunctional systems that contribute to microclimate regulation, cooling, and urban climate adaptation. In this context, water-storage mats have been identified as a form of decentralized, roof-based biofilter for greywater treatment. The aim of this study was to assess the performance of newly developed, innovative, bio-based textile mats and assess their effectiveness in treating pre-treated greywater from a canteen (CGW) with a high organic content, in both laboratory- and pilot-scale experiments. The findings from the lab-scale testing revealed that the mats made from polyethylene terephthalate (PET) nonwoven fabric materials had the highest water storage capacity and dried out more slowly in outdoor conditions than mats made from polylactide (PLA) spunbonded fabric and polyhydroxyalkanoate (PHA) spunbonded nonwoven fabric. The PET hydroentangled nonwoven fabric mat (PET-WS) performed better than the other sample mats in the lab-scale experiment, and also outperformed the PHA mat consistently in the pilot-scale experiment when treating CGW. Apparent reductions in the concentration of the macro-pollutant parameters were observed at the outflow of the PET-WS mat compared to the inflow (p < 0.05) at the pilot-scale. Mean concentration reductions were comparatively higher for the five-day biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total nitrogen (TN), and total suspended solids (TSS), with mean reductions of 64%, 54%, 39% and 60%, respectively. This indicated the superior treatment performance of the PET-WS mat compared to the PHA mat, with mean reductions of only 36%, 25%, 6%, and 32%, respectively. However, the lower E. coli counts of 1.1 and 0.5 log reduction for the PET-WS and PHA mats, respectively, indicated that an additional disinfection unit was necessary. The findings of this study may help to determine the performance, stability and reliability of using lightweight, nonwoven fabric mats to treat high-strength GW, which is currently considered as an intermediate treatment step. The study also provides recommendations for process optimization. Additional post-treatment steps are required to produce high-quality treated effluent for non-potable reuse, particularly in urban areas facing high water scarcity, provided that the relevant reuse regulations or discharge criteria are met.