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Effect of microplastic on anaerobic digestion of wasted activated sludge
Summary
This study investigated how varying doses of microplastics affect methane production during anaerobic digestion of waste activated sludge, testing concentrations from 0 to 100,000 particles per gram. Higher microplastic doses progressively inhibited methane production, suggesting that high microplastic loads in wastewater treatment sludge can impair biogas recovery.
Over 90% of microplastics that enter wastewater treatment plants end in the wasted activated sludge. The effect of microplastic abundance on the activated sludge anaerobic digestion has been rarely reported. This study investigated the methane production performance during anaerobic digestion with different abundance of microplastic doses (0, 1,000, 3,000, 6,000, 10,000, 30,000, 60,000, 100,000 and 200,000 polyester particle/kg activated sludge). The methane production was reduced to 88.53 ± 0.5%, 90.09 ± 1.2%, 89.95 ± 4.7%, 95.08 ± 0.5%, 90.29 ± 0.5%, 93.16 ± 0.8%, 92.92 ± 1.3%, and 92.72 ± 0.6% as compared with control after digestion for 59 days. The methane production of all conditions was fitted with the logarithm model (R > 0.95) and one-substrate model (R > 0.99). The predicted and actual methane production values of digestion for 59 days had high correlation in all conditions with R > 0.95. The analysis based on the biochemical methane potential test model indicated that the methane production potential (B) and hydrolysis coefficient (k) decreased at nearly all tested conditions. The reactor digestate with microplastics retained higher organic matter and nutrient concentration and had slightly lower dewaterability than the control. The inhibition of methane production potential could be attributed to the incomplete digestion with the existence of microplastics. The microbial community showed no significant difference with and without microplastics.
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