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). • The performance of sustainable 3D-printed bricks was compared to a slow sand filter. • Low-cost materials, clay and crawfish shell waste were used to print 3D bricks. • Clay bricks showed the highest average removals in terms of turbidity, COD, and TOC. • Crawfish bricks slightly increased the removal of bacteria (+2 %). • Crawfish bricks outperformed the other two systems for most of the CECs targeted.