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Increasing use of silver nanoparticles (AgNPs) in consumer products has raised concerns about the potential impacts of AgNPs on the environment. This study aimed to assess the potential release of AgNPs from textiles due to sequential washing. Different types of fabrics including cotton, polyester (PES), and cotton blended with PES (called TC) were coated with 4-5 nm AgNPs and used in the sequential washing experiments with Milli-Q water at neutral pH and with commercial detergent at alkaline pH. Similar experiments were also run-on consumer textile products washed with Milli-Q water. The percent Ag remaining on the products after washing was also investigated. The initial Ag contents ranged from 254 to 350 μg Ag/g of the product in lab-prepared fabrics and from 1.2 to 44 μg Ag/g of the product in consumer products. After 20 wash cycles, 48 to 72 % of Ag was lost from the prepared fabrics washed with Milli-Q water, while a greater loss of 84-94 % of Ag occurred after washing the prepared fabrics with commercial detergent. The Ag released during the washing process is present dominantly in particulate form. In the consumer products after 20 washes with Milli-Q water, the percent Ag remaining was found to be around 46 to 70 %. Statistical analysis of the Ag release rate between consumer products and lab-prepared fabrics in Milli-Q washing water by independent t test showed no significant difference after 20 washing cycles (p > 0.05).

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Dissolved organic matter (DOM) and phosphorus promote microbial regrowth in water distribution networks. Ferrihydrite (Fh) has a high adsorption affinity with DOM and phosphate. Hence, a lab-scale unit of the hybrid Fh-MF/UF membrane filtration system was used to evaluate membrane fouling and the removal efficiency of DOM and phosphate. Suwannee River natural organic matter (SRNOM) was used as a surrogate for DOM in natural water. The Fh-membrane system demonstrated removal rates of dissolved organic carbon (DOC), UV254 and phosphate up to 50%, 80% and 90%, respectively, at the Fh dose of 17.5 mg/L. The effect of phosphate on the removal of DOM was different without or with the addition of Fh; namely, phosphate increased the DOM removal without Fh by interacting with the UF membrane made of regenerated cellulose (RC), but phosphate decreased the DOM removal by Fh due to the strong affinity of phosphate with Fh. Size exclusion chromatography revealed that phosphate mainly competed against smaller DOM molecules for Fh adsorption sites. Although the addition of Fh caused only a moderate flux decline with the RC membranes, the deposition of positively charged Fh on the surface of a negatively charged high-flux membrane, i.e., polyethersulfone (PES), caused a rapid decline of the permeation flux.