Departmental Seminar
Microplastics (MPs) are synthetic polymer particles smaller than 5 mm that come from textiles, personal care items, plastic degradation, and industrial activities. The majority of MPs, as water pollutants, are retained in sludge produced at wastewater treatment plants (WWTPs), which serve as both a sink and a secondary source of these MPs. Since sludge is employed during anaerobic digestion (AD) for biogas recovery, the existence of MPs raises questions regarding their permanence and possible interference with microbial activities.
Literature has yielded discrepant results about their impact on the AD of sludge. A key factor influencing MP behavior is crystallinity, which controls environmental persistence, degradation resistance, and structural rigidity. Few studies, nonetheless, have examined the impact of MP crystallinity within the AD process. This study has used small-scale Biochemical Methane Potential (BMP) reactors under mesophilic conditions (35°C) to examine the fate and impacts of polystyrene (PS), a low crystallinity polymer, and polyethylene (PE), a high crystallinity polymer, during AD. To be able to address the discrepancies in literature and to investigate if there are any negative effects at increasing concentrations of MPs, higher doses compared to environmentally relevant doses are used in these BMP tests. Five MP doses have been tested: 10 mg/g TS, 100 mg/g TS, 200 mg/g TS, 300 mg/g TS, and 500 mg/g TS. It has been found that the addition of neither type of MPs into the AD reactors has caused a negative impact. Rather, overall increases in both cumulative biogas and methane production, ranging from 2.6% to 20.5% (with the highest increase seen within the 200 mg PS/g TS added dose) have been observed. Through the assessment of MP interactions with AD, this study will shed light on their impacts on sludge treatment efficiency and overall environmental consequences.