Innovating Slow Sand Filtration: Exploring the Regeneration of a Traditional Technology for the 21st Century

The intensifying rate of global water stress is motivating the exploration of alternative water sources. This research aims to unlock conventionally unusable wastewater effluent for reuse with the aid of slow sand filtration (SSF). In this study, a traditional SSF reactor was constructed and later modified by replacing a section with sawdust, a sustainable material. The two filter configurations were asynchronously investigated to evaluate their potential capacity for the removal of antibiotics and common surface-water nutrients, i.e., nitrates and phosphates. Each filtration system was operated in a recirculating mode over four weeks to develop the biological component referred to as the “schmutzdecke”. Standard water-quality testing indicated that the SSF with an incorporated sawdust layer buffered shock events (e.g., turbidity spikes) while still cultivating a healthy schmutzdecke. Furthermore, the sawdust facilitated greater microbial activity, which is associated with the biodegradation of various contaminants and pathogens. Following filtration of a simulated wastewater effluent containing sulfamethoxazole (SMX) and trimethoprim (TMP) antibiotics (ca. 1 mg∙L−1), it was found that the TMP removal exceeded 93% in both configurations. The SMX removal rate was much lower and varied significantly, ranging from 1.2 to 38.6% and from 1.4 to 3.4% for the traditional and modified filters, respectively. These findings suggest that the proposed configuration has the potential to address some emerging contaminants but that refinements are needed to address other contaminants such as SMX.