Removal of microplastics from secondary wastewater treatment plant effluent by coagulation/flocculation with iron, aluminum and polyamine-based chemicals

WATER RESEARCH

卷:183

Article

Rajala, Katriina¹  Gronfors, Outi¹  Hesampour, Mehrdad^1,3  Mikola, Anna² 

[1] Kemira Oyj, Luoteisrinne 2, Espoo 02270, Finland

[2] Aalto Univ, Dept Built Environm, POB 15200, FI-00076 Aalto, Finland

[3] Lappeenranta Univ Technol, LUT Sch Engn Sci, Lappeenranta 53851, Finland

关键词: Microplastic;    Removal;    Coagulation/flocculation;    Wastewater treatment;    Flow cytometry;   

DOI  :  10.1016/j.watres.2020.116045

来源: Elsevier

【 摘 要 】

Microplastic (MP) removal by coagulation/flocculation followed by settling was studied in a secondary wastewater treatment plant (WWTP) effluent matrix. MP concentration in size range <10 mm in wastewater is currently unknown due to the exclusion of this size range in many studies and due to difficulties in MP quantification. WWTP effluent samples were spiked with a known amount of polystyrene spheres of two different sizes 1 mm and 6.3 mm. The samples were treated with inorganic and organic coagulants typically used in WWTPs, i.e., ferric chloride, polyaluminum chloride, and polyamine. The effect of pH was studied with ferric chloride by changing the pH from 7.3 to 6.5. In this study, MP removal was monitored using flow cytometry. The role of chemicals in MP removal at WWTPs has not been in the focus of previously reported MP studies. Our results showed that all tested coagulants enhanced the removal of MPs with dosages applicable to tertiary treatment. The highest removal efficiency obtained was 99.4%, and ferric chloride and polyaluminum chloride were more efficient than polyamine. Performances of ferric chloride and polyaluminum chloride were close to each other, with a statistically significant difference at a certain dosage range. Our findings suggest that chemical coagulation plays a key role in the removal of MPs, and the process can be optimized by selecting the right coagulant and pH. (c) 2020 Elsevier Ltd. All rights reserved.

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