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Behavioral Dynamics of Primary Microplastics in Sand Filtration
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Researchers found that when tiny plastic particles build up in the sand filters used to clean drinking water, they actually form a dense layer that traps even more contaminants—making the water clearer. But there's a catch: this plastic buildup clogs the filters faster and could release trapped microplastics and other pollutants back into the water when the filters are cleaned. This matters because it shows water treatment plants may need to rethink filter design to keep our drinking water both clean and free of plastic contamination.
Primary microplastics (MPs) pose significant risks in drinking water treatment plants, yet their removal behavior and hydraulic implications during sand filtration remain poorly understood. This study investigates the fate, retention mechanisms, and operational implications of industrially derived polyvinyl chloride and high-density polyethylene primary MPs during sand filtration, one of the most widely applied drinking treatment processes. More than 300 filtration runs were conducted with sands of varying grain sizes and specific filter depths. The results showed that cake filtration dominated MP removal, with an efficiency of over 95%, while the contribution from depth filtration was minimal. MP retention promoted the formation of a dense cake layer at Dsand/DMP ratios of 3.22–10.67, which enhanced suspended solid capture and improved effluent turbidity to <1 nephelometric turbidity unit (NTU), compared to conventional sand filtration. However, cake formation induced progressive head loss by up to 150%, particularly in filters with finer media, highlighting trade-offs between enhanced particle removal and operational sustainability. Scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM–EDX) analysis revealed that suspended solids were immobilized on MP layers via straining, entrapment within surface depressions, and adsorption, confirming MPs as active sites for retaining secondary particles. Modeling results showed that filtration dynamics were well described by a declining rate (DR) model (R2=0.96), suggesting that sand filters (SF) exposed to primary MP-rich effluents should be designed as DR filters. Although these findings show that primary MP accumulation enhances particle removal and alters filter hydraulics, they also highlight the risk of MPs as long-term contaminant carriers and the potential for their release during backwashing.
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Scientists coated ordinary sand with a special water-repelling chemical and found it captured tiny plastic particles from water far better than regular sand—staying nearly 99% effective even after treating hundreds of batches of water, while plain sand's performance dropped by half almost immediately. Since sand filters are already widely used at water treatment plants, this upgrade could be a practical way to reduce the microplastics that end up in our drinking water without requiring costly new equipment.
Investigations and comparison of a conventional sand filter and a modified sand filter for water purification.
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This study compared the performance of conventional sand filters and modified sand filters for purifying drinking water. Improving the efficiency of sand filtration is relevant to microplastics research since enhanced sand filters have shown potential for removing microplastic particles from drinking water supplies.
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Researchers discovered that the plastic membrane filters used to purify drinking water can actually release microplastics into the treated water. The particles came not just from the membrane itself but also from plastic equipment in the system, meaning that water treatment technology designed to remove contaminants may inadvertently be adding new plastic particles to our drinking water.
Unraveling the Interactions between Nanoplastics and Biofilms on Dense Filtration Membrane Surfaces.
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Scientists studied how tiny plastic particles (nanoplastics) get trapped by bacterial slime layers (biofilms) that form on water filtration membranes, like those used in water treatment systems. They found that plastic buildup increased significantly when bacteria and plastics grew together over several days, and that water chemistry—especially calcium levels and natural organic matter—affected how much plastic got stuck. This matters because it helps engineers understand whether current water filtration systems effectively trap nanoplastics before they reach our drinking water, though this lab study used higher plastic concentrations than typically found in nature.
Performance of Rapid Sand Filter Dual Media for Microplastic Removal in the Water: The Effect of Microplastic Size and Effective Size of Filter Media
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This study tested how well rapid sand filters with dual media can remove microplastics from drinking water, examining the effects of different microplastic sizes and filter media configurations. Researchers found that filter performance varied depending on the size of the plastic particles and the effective size of the filter media, providing practical insights for improving drinking water treatment systems.
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When a large batch of papers lands in the Atlas, we read through it and send a short write-up of what stood out.