We can't find the internet
Attempting to reconnect
Something went wrong!
Hang in there while we get back on track
Hydraulic and chemical cleaning efficiency for the release of microplastics retained during coagulation/flocculation-ultrafiltration
Summary
Researchers studied how effectively ultrafiltration membranes used in drinking water treatment can capture microplastics, and whether standard cleaning procedures release them back into treated water. They found that while the membranes effectively retained microplastics during filtration, chemical cleaning with sodium hypochlorite released a significant portion of the trapped particles. The study raises important questions about whether routine membrane cleaning in water treatment plants may inadvertently reintroduce microplastics into the drinking water supply.
Microplastics (MPs) are ubiquitous in global drinking water sources (lakes, rivers), with reported concentrations ranging from 0.5 to >7,500 particles/L. Ultrafiltration (UF), widely applied in drinking water treatment, is anticipated to represent an effective barrier to MPs due to its pore size (0.01-0.1 µm), which can retain MPs of potential health concern. To-date limited studies have reported that MPs may contribute to UF fouling, albeit when considering concentrations up to 10 orders of magnitude higher than those typically observed in source waters. The present study evaluated the retention of MPs by UF membranes when incorporating coagulation/flocculation pre-treatment, as well as their release during hydraulic and chemical cleaning. Polyethylene (PE) fragments, representing a range of environmentally relevant sizes (1-50 µm) and concentrations (907 ± 293 particles/L), were spiked into untreated lake waters prior to coagulation/flocculation-UF. Results suggest that in the absence of coagulant (alum) addition, only 50% of MPs retained during UF permeation were subsequently released during hydraulic cleaning. The release of MPs during hydraulic cleaning decreased (<20%) at medium and high (8 mg/L, 15 mg/L) alum dosages when compared to the absence of coagulant addition. Chemical cleaning with sodium hypochlorite (500 mg/L) was only capable of releasing 20% to 60% of retained MPs. Both hydraulic and chemical cleaning were less effective for the release of MPs when compared to reversible fouling resistance, organic matter, and aluminum. As such, future research is required to determine if the accumulation of MPs leads to increased UF fouling over extended operating periods, in addition cleaning practices which specifically target MPs should be further examined. Low and medium alum dosages (2 mg/L, 8 mg/L) were observed to increase the release of retained MPs during chemical cleaning, suggesting that incorporation of coagulation pre-treatment is useful to increase the release of MPs and minimize potential long-term accumulation on membranes.
Sign in to start a discussion.
More Papers Like This
Release of microplastics from polymeric ultrafiltration membrane system for drinking water treatment under different operating conditions
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.
Fate and Behavior of Microplastics in Ultrafiltration Membrane Systems for Water Treatment: Fouling, Releasing, and Organic Leaching
Researchers investigated the fate and behavior of microplastics in ultrafiltration membrane systems used for water treatment, examining three key phenomena: membrane fouling caused by microplastic deposition, release of microplastics through membrane failure or bypass, and leaching of organic additives from microplastics. The work provides mechanistic understanding of how microplastics interact with ultrafiltration systems in drinking water treatment contexts.
Effect of Sodium Hypochlorite Disinfection on Polyvinylidene Fluoride Membranes in Microplastic Ultrafiltration
Researchers studied how sodium hypochlorite disinfection, commonly used in water treatment plants, affects the ability of ultrafiltration membranes to remove microplastics. They found that while pre-chlorination improved water flow through the membrane, it significantly reduced the microplastic removal rate from 36.6% to 22.6%. The study also showed that prolonged chlorine exposure damaged the membrane structure, raising concerns about the long-term effectiveness of this approach.
Occurrence and removal of microplastics by advanced and conventional drinking water treatment facilities
Researchers evaluated the performance of both advanced and conventional drinking water treatment processes for removing microplastics, finding that advanced methods such as ultrafiltration substantially outperform standard coagulation and filtration. Most conventional treatment plants leave a meaningful fraction of microplastics in finished drinking water.
Membrane fouling characteristics and mechanisms in coagulation-ultrafiltration process for treating microplastic-containing water
This study investigated how microplastics affect membrane fouling during a common water treatment process that combines coagulation with ultrafiltration. Researchers found that while microplastics initially worsen membrane fouling, adding the right amount of coagulant can actually turn the plastics into an advantage by creating a looser filter cake that improves water flow.