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Hydrothermal carbonization as a promising approach towards the removal of polyethylene microplastics and trace organic contaminants from wastewater sludge
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Scientists found that heating sewage sludge with water under pressure (a process called hydrothermal carbonization) removed about 71% of microplastics and completely eliminated drug residues like caffeine and carbamazepine. This matters because sludge is often used as fertilizer, so cutting down on these contaminants could reduce how much plastic and medication residue ends up in soil, water, and eventually our food supply.
Microplastics from sludge need to be eliminated since they can enter the environment through agronomic utilization and threaten the organisms as well as water quality. This study provides novel insights into the concurrent removal of polyethylene microplastics and trace organic contaminants (TrOCs) from two types of sludges (oxidation ditch sludge (ODS) and aerated lagoon sludge (ALS)) using hydrothermal carbonization (HTC), a low-energy process, by analyzing the impacts of temperature and time on removal efficiency. HTC at 220°C (± 3 °C) for 3 hours removed about 71% (± 7.52%) of microplastics from sludge. Temperature and contact time were observed to have a significant effect ( p < 0.05) on microplastic removal efficiency. Morphological characterizations of residual microplastics after HTC revealed that exposure to subcritical water under hydrothermal conditions caused surface deterioration and structural changes. Several TrOCs were detected in sludges, and caffeine exhibited the highest concentration (16.34 µg/g) in the solid phase of ODS, whereas carbamazepine showed the highest concentration (0.695 µg/L) in the aqueous phase. Furthermore, caffeine had the highest concentration (0.240 µg/L) in the aqueous phase of ALS, whereas carbamazepine was the most concentrated (19.96 µg/g) in the solid phase. The initially observed TrOCs were not detected in the aqueous phase nor the solid phase after the HTC, irrespective of varying temperatures and contact times, which signifies their complete removal. These findings demonstrated that HTC is a sustainable sludge management strategy since it can effectively eliminate microplastics and TrOCs from sludge and thus minimize their detrimental effects on the environment.
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Microplastic Degradation in Sewage Sludge by Hydrothermal Carbonization: Efficiency and Mechanisms
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Researchers evaluated hydrothermal carbonization as a method for degrading microplastics in sewage sludge. The study found that treatment at 260 degrees Celsius achieved a 79% reduction in microplastic concentrations, and investigated the decomposition mechanisms for different polymer types. The findings suggest that hydrothermal carbonization could be an effective approach for removing microplastics from sewage sludge before environmental disposal.
Current understanding on the fate of contaminants during hydrothermal treatment of sewage sludge
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This review examines how hydrothermal treatment of sewage sludge handles various contaminants including microplastics, heavy metals, and pharmaceuticals. While the high-temperature water treatment can break down many pollutants, its effectiveness against microplastics specifically is still being studied. Since sewage sludge is often spread on farmland, understanding how well treatment destroys microplastics is important for preventing them from entering the food supply.
Replication data for: Microplastic degradation during hydrothermal carbonization
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Sewage sludge (leftover waste from treating wastewater) often contains tiny plastic bits called microplastics, and when this sludge is spread on farmland as fertilizer, those plastics can end up in our food. This study tested a heat-and-pressure treatment method called hydrothermal carbonization to see if it can break down microplastics in sludge before it's used as fertilizer, offering a possible way to keep plastic pollution out of the food chain and reduce risks to human health.
Changes in physicochemical and leachate characteristics of microplastics during hydrothermal treatment of sewage sludge
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Researchers examined hydrothermal treatment of sewage sludge containing microplastics and found that while the process degraded polyethylene, polystyrene, and PET to varying degrees, it also generated potentially harmful leachates, highlighting trade-offs in this treatment approach.
Hydrothermal carbonization of PET and PS microplastics under conditions relevant to sewage sludge treatment
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Scientists tested whether a heat-based sewage treatment method (hydrothermal carbonization) can break down two common microplastics, PET (used in bottles) and polystyrene (used in foam packaging). PET broke down much more easily than polystyrene, which stayed largely intact, suggesting this treatment may not fully eliminate all microplastic types from sludge before it's reused, such as in fertilizer.
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