TY - JOUR

T1 - Heat and Bleach

T2 - A Cost-Efficient Method for Extracting Microplastics from Return Activated Sludge

AU - Sujathan, Surya

AU - Kniggendorf, Ann Kathrin

AU - Kumar, Arun

AU - Roth, Bernhard

AU - Rosenwinkel, Karl Heinz

AU - Nogueira, Regina

N1 - Funding information: The authors thank Karin Kock and Benjamin Schwanda for their technical assistance to their work. The work of Dr. Kniggendorf was funded by the Federal Ministry of Education and Research (BMBF) of Germany within the project of OPTIMUS (Project Number: 13N13811). The work of Surya Sujathan was funded by the DAAD Sandwich Model Scholarships for Master’s Students of the IITs and IIMs, 2015 (Personal Ref No: 91590631).

PY - 2017/11

Y1 - 2017/11

N2 - The extraction of plastic microparticles, so-called microplastics, from sludge is a challenging task due to the complex, highly organic material often interspersed with other benign microparticles. The current procedures for microplastic extraction from sludge are time consuming and require expensive reagents for density separation as well as large volumes of oxidizing agents for organic removal, often resulting in tiny sample sizes and thus a disproportional risk of sample bias. In this work, we present an improved extraction method tested on return activated sludge (RAS). The treatment of 100 ml of RAS requires only 6% hydrogen peroxide (H2O2) for bleaching at 70 °C, followed by density separation with sodium nitrate/sodium thiosulfate (SNT) solution, and is completed within 24 h. Extracted particles of all sizes were chemically analyzed with confocal Raman microscopy. An extraction efficiency of 78 ± 8% for plastic particle sizes 20 µm and up was confirmed in a recovery experiment. However, glass shards with a diameter of less than 20 µm remained in the sample despite the density of glass exceeding the density of the separating SNT solution by 1.1 g/cm3. This indicates that density separation may be unreliable for particle sizes in the lower micrometer range.

AB - The extraction of plastic microparticles, so-called microplastics, from sludge is a challenging task due to the complex, highly organic material often interspersed with other benign microparticles. The current procedures for microplastic extraction from sludge are time consuming and require expensive reagents for density separation as well as large volumes of oxidizing agents for organic removal, often resulting in tiny sample sizes and thus a disproportional risk of sample bias. In this work, we present an improved extraction method tested on return activated sludge (RAS). The treatment of 100 ml of RAS requires only 6% hydrogen peroxide (H2O2) for bleaching at 70 °C, followed by density separation with sodium nitrate/sodium thiosulfate (SNT) solution, and is completed within 24 h. Extracted particles of all sizes were chemically analyzed with confocal Raman microscopy. An extraction efficiency of 78 ± 8% for plastic particle sizes 20 µm and up was confirmed in a recovery experiment. However, glass shards with a diameter of less than 20 µm remained in the sample despite the density of glass exceeding the density of the separating SNT solution by 1.1 g/cm3. This indicates that density separation may be unreliable for particle sizes in the lower micrometer range.

UR - http://www.scopus.com/inward/record.url?scp=85019740025&partnerID=8YFLogxK

U2 - 10.1007/s00244-017-0415-8

DO - 10.1007/s00244-017-0415-8

M3 - Article

C2 - 28550340

AN - SCOPUS:85019740025

VL - 73

SP - 641

EP - 648

JO - Archives of Environmental Contamination and Toxicology

JF - Archives of Environmental Contamination and Toxicology

SN - 0090-4341

IS - 4

ER -