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Published on: April 26, 2024
Revealing How Polyvinyl Chloride Microplastic Physicochemically Affect the Anaerobic Digestion of Waste Activated
Yi Cheng1, Xiaoqing Hu2,3, Yuxuan Gao2,3
1Department of Environmental Science and Engineering, Fudan University, Shanghai, 200082, China.
Abstract:
Recent studies have shown that the microplastics in waste activated sludge (WAS) can directly reduce the microbial activity and influence the performance of anaerobic digestion. Unfortunately, few studies paid attention on the interactions between WAS and MPs, since MPs could impact the contact between sludge flocs and microorganisms. We found that PVC-MP changed the interfacial energy properties of the WAS surface and affected methane production. Low concentration (40 mg/L) of PVC-MP changed the water affinity and greatly reduced the energy barrier of interfacial reaction. Simultaneously, WAS surface charge characteristics changed with increasing MPs concentration, which made the sludge difficult to contact with microorganisms. The change process of WAS surface functional groups also indicated that PVC-MP first cover the sludge surface to prevent from being utilized by microorganisms, and then affect the surface protein structure before toxic substances leaching. Our study provides new insights into how MPs affect anaerobic digestion.
Insights
Microplastics in waste activated sludge (WAS) alter surface properties, reducing microbial contact and methane production during anaerobic digestion. This study reveals how PVC microplastics impact sludge interactions and digestion performance.
Area of Science:
- Environmental Science
- Microbiology
- Chemical Engineering
Background:
- Microplastics (MPs) in waste activated sludge (WAS) are known to inhibit microbial activity and anaerobic digestion.
- The specific interactions between MPs and WAS, particularly their impact on sludge floc structure and microbial accessibility, remain under-investigated.
Purpose of the Study:
- To investigate the effects of PVC microplastics on the interfacial properties of WAS.
- To elucidate the mechanisms by which MPs influence microbial activity and methane production in anaerobic digestion.
Main Methods:
- Analysis of WAS surface energy properties and water affinity with varying PVC-MP concentrations.
- Characterization of WAS surface charge and functional group changes.
- Assessment of methane production rates under different MP exposure conditions.
Main Results:
- PVC microplastics (MPs) at low concentrations (40 mg/L) altered WAS surface water affinity, reducing interfacial reaction energy barriers.
- Increasing MP concentration led to changes in WAS surface charge, hindering microbial-sludge contact.
- Functional group analysis indicated MPs initially coat sludge surfaces, followed by protein structure alteration and potential toxic substance leaching.
Conclusions:
- PVC microplastics significantly modify the physicochemical properties of WAS, negatively impacting anaerobic digestion performance.
- The interaction mechanism involves altered surface energy, reduced microbial accessibility, and potential toxicity, providing new insights into MP-sludge dynamics.
