(469g) Exploring Potential of Recycled Glass Sand As Water Filtration Medium

Each year, the United States dumps over 7.6 million tons of waste glass into landfills. At the same time, news headlines warn of sand shortages. Sand is not only the raw material for glass but is also used for construction, recreation, environmental restoration, and filtration, among other applications. Apart from recycling old glass into new glass, there are many other applications for crushed glass (or recycled glass sand) for which this vastly underutilized resource could be used, which would simultaneously reduce landfill waste and alleviate sand shortages. This study is evaluating recycled glass sand as a water filtration medium. This research involves a comprehensive examination of glass sand's permeability as a function of particle size distribution to elucidate its filtration capabilities for probe particles (<100 microns) and removal of E. coli. Laboratory scale filtration experiments were conducted using three different size sand particles. The particle sizes used for the experiment were L2 (3.4-1.7 mm), L3/L4 (1.7-0.4 mm), and L5-100 (0.4-0.1 mm). To attain a starting turbidity level of 75 NTU, 0.75 g of the probe material (glass sand particles < 100 microns) was suspended in 1000 mL of deionized water. As expected, we see a trade-off between turbidity reduction and permeability, with L5-100 providing the greatest turbidity reduction (3 NTU) but unacceptably low permeability (9x10^-10 m²) and L2 providing an acceptable permeability (2.8x10^-8 m²) but little turbidity reduction (50 NTU). This trade-off can be mitigated by layering the different glass sand sizes from largest (L2, top) to smallest (L5-100, bottom), resulting in turbidity reduction to 2 NTU and permeability of 4.8x10^-9 m²). For E. Coli treatment, natural water samples were spiked with E. Coli to an initial concentration of approximately 400 colony-forming units per 100 mL (CFU/100mL). After filtration through the layered glass sand configuration, concentrations were less than 2 CFU/100 mL for all three replicates, representing log 2 removal (99.9% E. coli reduction). These findings show that recycled glass sand is a sustainable and effective filtration medium for contaminated water. Furthermore, the filter can be configured with different particle sizes and/or layers to meet application-specific requirements. This research is funded by the NSF Convergence Accelerator Program, Grant# 2230769.