Removal of microplastics from water by coagulation of cationic-modified starch: An environmentally friendly solution

Mitigation of Dietary Microplastic Accumulation and Oxidative Stress Response in Rainbow Trout (Oncorhynchus mykiss) Fry Through Dietary Supplementation of a Natural Microencapsulated Antioxidant

Microplastic (MP) contamination in aquafeed poses a significant risk to fish health and safety. This study evaluated the effectiveness of a microencapsulated natural antioxidant, astaxanthin (AX), in mitigating the adverse effects of dietary MPs in rainbow trout fry. The microcapsules were composed of an organic wall matrix designed to preserve AX while limiting MP absorption in the intestine. During a 60-day feeding trial, fish were fed diets containing amino formaldehyde polymer fluorescent MP microbeads (1-5 µm; 50 mg/kg), either alone or in combination with microencapsulated AX. MP localization in tissues was assessed via confocal microscopy, and quantification was performed following chemical tissue digestion. Fish welfare was evaluated using histological and molecular analyses. No significant effects on growth or gut morphology were observed across experimental groups. However, MPs were mainly translocated to the liver, where they induced oxidative stress, as evidenced by the upregulation of sod1, sod2, and cat gene expression. The inclusion of microencapsulated AX significantly mitigated the oxidative stress response, and the microcapsules facilitated MP coagulation in the gut, reducing intestinal absorption. These findings highlight the potential of microencapsulated antioxidants to counteract MP-induced oxidative stress and reduce MP bioavailability in aquaculture species, contributing to improved fish welfare and product quality.

Mitigating Dietary Microplastic Accumulation and Oxidative Stress Response in European Seabass (Dicentrarchus labrax) Juveniles Using a Natural Microencapsulated Antioxidant

Aquafeed's contamination by microplastics can pose a risk to fish health and quality since they can be absorbed by the gastrointestinal tract and translocate to different tissues. The liver acts as a retaining organ with the consequent triggering of oxidative stress response. The present study aimed to combine the use of natural astaxanthin with natural-based microcapsules to counteract these negative side effects. European seabass juveniles were fed diets containing commercially available fluorescent microplastic microbeads (1-5 μm; 50 mg/kg feed) alone or combined with microencapsulated astaxanthin (AX) (7 g/kg feed; tested for half or whole feeding trial-30 or 60 days, respectively). Fish from the different dietary treatments did not evidence variations in survival and growth performance and did not show pathological alterations at the intestinal level. However, the microplastics were absorbed at the intestinal level with a consequent translocation to the liver, leading, when provided solely, to sod1, sod2, and cat upregulation. Interestingly, the dietary implementation of microencapsulated AX led to a mitigation of oxidative stress. In addition, the microcapsules, due to their composition, promoted microplastic coagulation in the fish gut, limiting their absorption and accumulation in all the tissues analyzed. These results were supported by in vitro tests, which demonstrated that the microcapsules promoted microplastic coagula formation too large to be absorbed at the intestinal level and by the fact that the coagulated microplastics were released through the fish feces.

Recent advances in microplastic removal from drinking water by coagulation: Removal mechanisms and influencing factors

Microplastics (MPs) are emerging contaminants that are widely detected in drinking water and pose a potential risk to humans. Therefore, the MP removal from drinking water is a critical challenge. Recent studies have shown that MPs can be removed by coagulation. However, the coagulation removal of MPs from drinking water remains inadequately understood. Herein, the efficiency, mechanisms, and influencing factors of coagulation for removing MPs from drinking water are critically reviewed. First, the efficiency of MP removal by coagulation in drinking water treatment plants (DWTPs) and laboratories was comprehensively summarized, which indicated that coagulation plays an important role in MP removal from drinking water. The difference in removal effectiveness between the DWTPs and laboratory was mainly due to variations in treatment conditions and limitations of the detection techniques. Several dominant coagulation mechanisms for removing MPs and their research methods are thoroughly discussed. Charge neutralization is more relevant for small-sized MPs, whereas large-sized MPs are more dependent on adsorption bridging and sweeping. Furthermore, the factors influencing the efficiency of MP removal were jointly analyzed using meta-analysis and a random forest model. The meta-analysis was used to quantify the individual effects of each factor on coagulation removal efficiency by performing subgroup analysis. The random forest model quantified the relative importance of the influencing factors on removal efficiency, the results of which were ordered as follows: MPs shape > Coagulant type > Coagulant dosage > MPs concentration > MPs size > MPs type > pH. Finally, knowledge gaps and potential future directions are proposed. This review assists in the understanding of the coagulation removal of MPs, and provides novel insight into the challenges posed by MPs in drinking water.

Rapid sand filtration for <10 μm-sized microplastic removal in tap water treatment: Efficiency and adsorption mechanisms

The omnipresence of microplastics (MPs) in potable water has become a major concern due to their potential disruptive effect on human health. Therefore, the effective removal of MPs in drinking water is essential for life preservation. In this study, tap water containing microplastic <10 μm in size was treated using constructed pilot-scale rapid sand filtration (RSF) system to investigate the removal efficiency and the mechanisms involved. The results show that the RSF provides significant capacity for the removal and immobilization of MPs < 10 μm diameter (achieving 98 %). Results showed that silicate sand reacted with MPs through a cooperative assembly process, which mainly involved interception, trapping, entanglement, and adsorption. The MPs were quantified by Flow cytometry instrument. A kinetics study underlined the pivotal role of physio-chemisorption in the removal process. MP particles smaller than absorbents, saturation of adsorbents, and reactor hydrodynamics were identified as limiting factors, which were alleviated by backwashing. Backwashing promoted the desorption of up to 97 % MPs, conducive for adsorbent active site regeneration. These findings revealed the critical role of RSF and the importance of backwashing in removing MPs. Understanding the mechanisms involved in removing microplastics from drinking water is crucial in developing more efficient strategies to eliminate them.

Effects and applications of surfactants on the release, removal, fate, and transport of microplastics in aquatic ecosystem: a review

Microplastics (MPs) and surfactants (STs) are emerging pollutants in the environment. While many studies have focused on the interactions of STs with MPs, there has not been a comprehensive review focusing on the effect of STs on MPs in aquatic ecosystems. This review summarizes methods for removal of MPs from wastewater (e.g., filtration, flotation, coagulation/flocculation, adsorption, and oxidation-reduction) and the interactions and effects of STs with MPs (adsorption, co-adsorption, desorption, and toxicity). STs can modify MPs surface properties and influence their removal using different wastewater treatments, as well as the adsorption-desorption of both organic and inorganic chemicals. The concentration of STs is a crucial factor that impacts the removal or adsorption of pollutants onto MPs. At low concentrations, STs tend to facilitate MPs removal by flotation and enhance the adsorption of pollutants onto MPs. High ST concentrations, mainly above the critical micelle concentrations, cause MPs to become dispersed and difficult to remove from water while also reducing the adsorption of pollutants by MPs. Excess STs form emulsions with the pollutants, leading to electrostatic repulsion between MPs/STs and the pollutant/STs. As for the toxicity of MPs, the addition of STs to MPs shows complicated results, with some cases showing an increase in toxicity, some showing a decrease, and some showing no effect.