Fate and effect of Polyamide-6 microplastics in mesophilic and thermophilic anaerobic digestion

Şimşek İ., SANİN F. D.

Environmental Pollution, cilt.361, 2024 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 361
  • Basım Tarihi: 2024
  • Doi Numarası: 10.1016/j.envpol.2024.124855
  • Dergi Adı: Environmental Pollution
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, PASCAL, Aerospace Database, Aqualine, Aquatic Science & Fisheries Abstracts (ASFA), BIOSIS, Biotechnology Research Abstracts, CAB Abstracts, Chemical Abstracts Core, Chimica, Communication Abstracts, Compendex, EMBASE, Environment Index, Food Science & Technology Abstracts, Geobase, Greenfile, MEDLINE, Metadex, Pollution Abstracts, Veterinary Science Database, Civil Engineering Abstracts
  • Anahtar Kelimeler: Carbonyl index, Crystallinity, Mesophilic digestion, Microplastic, Polyamide-6, Thermophilic digestion
  • Orta Doğu Teknik Üniversitesi Adresli: Evet

Özet

Research has demonstrated that depending on the type and concentration, microplastics affect anaerobic digestion (AD). Owing to the high abundance of polyamide-6 (PA6) in wastewater treatment plants and limited understanding of its behavior, this study investigates PA6 microplastics' effect in AD. Biochemical methane potential experiments were performed under mesophilic (35 °C) and thermophilic (55 °C) conditions using PA6 at concentrations from 0 to 200 particles/g total solids (TS). Under both conditions, methane production increased in the highest (200 particles/g TS) PA6-dosed reactors, with thermophilic conditions having a statistically significant effect. Methane yield increased from 403.1 ± 5.3 mL/g VS to 436.6 ± 9.2 mL/g VS under thermophilic and from 332.1 ± 1.5 to 340.6 ± 6.6 mL/g VS under mesophilic conditions for the 200 particles/g TS dose, corresponding to increases of 8.3% and 2.6% respectively. PA6 crystallinity decreased from 32.8% to 27.1% and 26.8%, corresponding to decreases of 17.4% in mesophilic and 18.2% in thermophilic reactors compared to pristine control. Similarly, crystallinity decreased in PA6 microplastics collected from abiotic reactors, with thermophilic conditions showing a greater effect. The carbonyl index (CI) values were similar between biotic and abiotic reactors, but PA6 from all reactors had significantly higher CI than pristine PA6, suggesting abiotic factors also affect carbonyl bonds. Additionally, an increase in average PA6 mass was observed for mesophilic and thermophilic conditions by 22.0 % and 23.0 %, respectively. The study shows that temperature and other abiotic factors, like sludge chemistry, significantly influence the fate and effect of PA6 microplastics in digesters. Including abiotic reactors seems crucial for a full understanding of the impact of microbial and non-microbial factors in microplastic studies in the AD process. Studying the effects of microplastics on AD is only one part of the picture, whereas simultaneously examining their fate in digestion is necessary for a complete understanding.