Enhancing slow sand filtration with 3D-printed eco-friendly bricks

Wastewater reuse after adequate treatment represents a sustainable approach and a valuable alternative source to mitigate the current water scarcity. In wastewater treatment, low-cost and low-tech approaches draw attention as small/rural communities struggle to achieve the anticipated water quality standards due to insufficient funds, or expert knowledge in implementing and maintaining high-tech treatment methods. This study evaluated the ability of two low-cost and sustainable materials, clay and crawfish shell waste to produce 3D-printed bricks to remove turbidity, Chemical Oxygen Demand (COD), Total Organic Carbon (TOC), total coliforms and E. coli. Additionally, the study included an investigation of their ability to remove contaminants of emerging concern (CECs). Three different bench-scale reactors were built for the study, 1) a reactor with 3D-printed crawfish shell waste bricks (90 % clay and 10 % crawfish shell waste by weight) with sand, 2) a reactor with 3D-printed clay bricks with sand, and 3) a control (without 3D printed bricks) with only sand. All three systems, including the control, effectively removed turbidity (up to 96 %), total coliforms (up to 99 %) and E. coli (up to 99 %). Although the changes in removal efficiencies were not statistically different, the sand filter with clay bricks showed the highest removal rates for turbidity (87.1 % ± 7.1), COD (55 % ± 18.6) and TOC (47 % ± 27). Among the different CECs analyzed, the highest removal rates were recorded for fluoxetine (100 % removal), diphenhydramine (>90 % removal) and erythromycin (60 % – 100 % removal) regardless of the reactor used. However, the reactor with crawfish bricks outperformed the other two in removing CECs exhibiting a 40 % – 80 % removal such as trimethoprim, tramadol, irbesartan, guaifenesin, gabapentin and losartan, as well as CECs exhibiting a relatively low removal (10 – 40 %) including lidocaine and sucralose. Sucralose is the only emerging contaminant with a statistically significant difference among the reactors, with the crawfish bricks showing significantly higher removal compared to the clay bricks (p = 0.026).