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Oil Extraction of Microplastics from Communal Dewatered Sludge

2022
Griessler Bulc, Žgajnar Gotvajn, gajnar Gotvajn, C Anderson, B J Park, V Palace, A Andrady, S Blair R M, Waldron, C Gauchotte-Lindsay, S Carr, J Liu, A Tesoro, F Corradini, P Meza, R Eguiluz, F Casado, M Cole, H Webb, P Lindeque, E Fileman, E Crichton, P Ross, A Dehaut, A-L Cassone, L Frere, L Hermabessiere, A Dyachenko, J Mitchell, N Arsem, E Gies, J Lenoble, M Nol, A Etemadifar, J Gong, P Xie, X Han, X Lu, R Vogt, J Hanvey, P J Lewis, J L Lavers, N Crosbie, Hurley R R, A Liusher, M Olsen, L Nizzetto, H Imhof, K Schmid, J Niessner, R Ivleva, N, M Lares, M Ncibi, M Sillanp, X Li, L Chen, Ji Li, Ji Li, S M Mintenig, I Int-Veen, M G J Lder, S Primpke, P Ngo, L Pramanik, B Shah, K Roychand, R, M Nuelle, J Dekiff, Remy Fries, E, C Scopetani, D Chelazzi, J Mikola, V Leini, J Sun, X Dai, Q Wang, M Van Loosdrecht, M, J Talvitie, A Mikola, A Koistinen, O Setl, P Vermeiren, C Munoz, K Ikejima, Z Zhang, Y Chen, Q Zhou, H Zhang, C Fu, Y Zhou

Summary

Researchers tested whether canola oil could extract microplastics from dried municipal sewage sludge, finding the method effective at separating plastic particles from complex organic matrices. Sludge applied to agricultural land is a significant pathway for microplastics to enter soils, and better extraction methods are needed to assess the risk.

Polymers
Study Type Environmental

Microplastics (MPs) as solid particles are found all over in the environment. Plastic particles, smaller than 5 mm are defined as MP and smaller than 1 m as nanoplastic. One of main sources are communal wastewater treatment plants (WWTPs), that contribute to releasing MPs into the environment. Through outlet, MPs continue their way into surface waters and groundwaters or come in environment with sewage sludge that is disposed on farmland or other surfaces. There is still no standardized method for extracting plastic particles from environmental samples, so we investigated efficiency of oil extraction protocol (OEP). Since sludge consists of organic matter and it needs to be pre-treated before an extraction, Fenton's reagent was used to reduce organic matter. Before and after the extraction, particles were analysed with Fourier-transform infrared spectroscopy (FT-IR), where we discovered that a washing step after the extraction with 96% ethanol removes oil traces and other interferences. A recovery rate of MP particles was assessed by counting spiked plastic particles on filters after a vacuum filtration. The results showed that with OEP the recovery rate was on average 10% higher in pre-treated samples in comparison with samples without pre-treatment. We determined the highest recovery rate for bigger particles (1-5 mm) of polypropylene (PP), (86% 16% with OEP and 99% 4% with pre-treatment). The results reveal that the oil extraction can offer a cost-efficient, rapid and simple extraction method for MPs with high recovery rate especially for plastic particles with lower densities as PP and polystyrene (PS).

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