Enhanced ability of 3D-printed bricks to treat wastewater under variable conditions

This study explores a sustainable and affordable approach to wastewater treatment by combining traditional slow sand filtration with 3D-printed bricks made from clay or a clay-crawfish shell composite. Building on the findings from a preliminary study using pre-UV treated wastewater as the influent, the current study implemented stress tests to assess how effectively and quickly the reactors could respond to sudden changes in influent composition potentially occurring in the presence of a spill, a malfunctioning treatment plant, and or in rural and underserved communities. Three stress tests (feed water: 50 % raw wastewater and 50 % pre-UV treated wastewater; average duration of each stress test: 2 d) followed by three recovery phases referred to baseline tests (feed water: 100 % pre-UV treated wastewater; average duration of each recovery phase: 5 d) were conducted using three reactors: 1) a reactor with composite bricks (90 % clay and 10 % crawfish shell waste by weight) and sand, 2) a reactor with clay bricks and sand, and 3) a reactor with only sand (control). The reactors' performance was evaluated in terms of turbidity, Chemical Oxygen Demand (COD), Total Organic Carbon (TOC), total coliforms, E. coli, and 46 contaminants of emerging concern (CECs). While turbidity removal efficiency remained stable throughout the study (∼90 %), higher COD and TOC removal efficiency were achieved during the stress tests (∼50 % and ∼80 %, respectively) compared to the baseline tests (∼40 % and ∼45 %, respectively), across the three systems. The crawfish reactor enhanced the removal of total coliforms and E. coli towards the end of the study. Among the detected CECs, fluoxetine, ketoconazole and miconazole were completely removed regardless of the nature of the reactor (clay bricks vs. clay and crawfish bricks vs. control). Enhanced removal in terms of trimethoprim (+6 %) was achieved in the presence of the reactor with clay bricks, while enhanced removal of labetalol (+22 %), iohexol (+31 %), lidocaine (+21 %), and carbamazepine (+20) was achieved in the presence of clay and crawfish bricks. Regarding the analytes' removal, there was no statistical difference among the three reactors, except for carbamazepine, which was significantly higher in the crawfish brick reactor compared to the clay brick reactor (p = 0.01) and the control (p = 0.02).