Preliminary Study of Reduction of Microplastics Contained in Salt Produced in Padang, Indonesia

Document Type : Original Research Paper


1 Department of Chemistry, Faculty of Mathematics and Natural Science, Andalas University, P.O.Box 25163, Padang, Indonesia

2 Department of Medical Laboratory Technology, Syedza Saintika College of Health Sciences, P.O.Box 25132, Padang, Indonesia

3 Department of Fisheries Resources Utilization, Faculty of Fisheries and Marine Sciences, Bung Hatta University, P.O. Box 25133, Padang, Indonesia


Salt produced from seawater evaporation contains harmful microplastics (MP). For this reason, a technology that can remove MP from seawater using coagulation and filtration techniques is needed. The purpose of this study is to utilize alum as a coagulant and sand as a filtration media to reduce MP pollution in seawater as a source of raw material for salt making. Seawater from Buo Bay, Padang City, Indonesia was taken as raw material for salt production. The MP abundance of salt made from seawater without alum and sand treatment was found to be 400 particles/kg. To reduce the abundance of MP in the salt, we varied the alum concentration (0.1; 0.3; and 0.5 g/L) and sand particle size (≥2, ≥1-<2, and <1 mm). From the results obtained, the optimal condition is an alum concentration of 0.5 g/L and sand particle size is <1 mm. The optimal condition of salt made from seawater in treatment H obtained MP abundance from 400 particles/kg to 30 particles/kg with an MP reduction efficiency of 92.5%. Visual analysis using optical trinocular microscopy found 4 forms of MP, namely: fragments (51.13%), fibers (28.95%), films (15.41%), and pellets (4.05%). Rewith the most dominant MP size found was >100-300 µm. The results of ATR-FTIR analysis identified the types of MP as Polyethylene (14.28%), Polyethylene Terephthalate (42.85%), Polypropylene (14.28%), and Polyamide (28.57%).


Main Subjects

Cheval, N., Gindy, N., Flowkes, C., & Fahmi, A. (2012). Polyamide 66 microspheres metallised with in situ synthesised gold nanoparticles for a catalytic application. Nanoscale Res. Lett., 7(1), 182.
Deswati, Sutopo, J., Putra, A., & Suparno. (2023). Mikroplastik; sampling dan analisisnya (1st ed.). Graha Ilmu.
Edzwald, J. K., & Haarhoff, J. (2011). Seawater pretreatment for reverse osmosis: Chemistry, contaminants, and coagulation. Water Res., 45(17), 5428–5440.
Fajar, M., Sembiring, E., & Handajani, M. (2022). The Effect of Filter Media Size and Loading Rate to Filter Performance of Removing Microplastics using Rapid Sand Filter. J. Eng. Technol. Sci., 54(5).
Falahudin, D., Cordova, M. R., Sun, X., Yogaswara, D., Wulandari, I., Hindarti, D., & Arifin, Z. (2020). The first occurrence, spatial distribution and characteristics of microplastic particles in sediments from Banten Bay, Indonesia. Sci. Total Environ., 705, 135304.
Ha, D. T. (2021). Microplastic Contamination in Commercial Sea Salt of Viet Nam. Vietnam J. Sci. Technol., 59(3), 333–344.
Hidalgo-Ruz, V., Gutow, L., Thompson, R. C., & Thiel, M. (2012). Microplastics in the marine environment: A review of the methods used for identification and quantification. Environ. Sci. Technol., 46(6), 3060–3075.
Huisman, L. (1974). Slow Sand Filtration. In Encyclopedia of Microfluidics and Nanofluidics (pp. 1711–1712).
Iñiguez, M. E., Conesa, J. A., & Fullana, A. (2017). Microplastics in Spanish Table Salt. Sci. Rep., 7(1), 1–7.
Ioakeimidis, C., Fotopoulou, K. N., Karapanagioti, H. K., Geraga, M., & Zeri, C. (2016). The degradation potential of PET bottles in the marine environment : An ATR-FTIR based approach. Sci. Rep., October 2015, 1–8.
Jung, M. R., Horgen, F. D., Orski, S. V., Rodriguez C., V., Beers, K. L., Balazs, G. H., Jones, T. T., Work, T. M., Brignac, K. C., Royer, S. J., Hyrenbach, K. D., Jensen, B. A., & Lynch, J. M. (2018). Validation of ATR FT-IR to identify polymers of plastic marine debris, including those ingested by marine organisms. Mar. Pollut. Bull., 127(November 2017), 704–716.
Karami, A., Golieskardi, A., Choo, C. K., Larat, V., Galloway, T. S., & Salamatinia, B. (2017). The presence of microplastics in commercial salts from different countries. Sci. Rep., 7(March), 1–11.
Karami, A., Golieskardi, A., Choo, C. K., Romano, N., Ho, Y. Bin, & Salamatinia, B. (2017). A high-performance protocol for extraction of microplastics in fish. Sci. Total Environ., 578, 485–494.
Kim, J. S., Lee, H. J., Kim, S. K., & Kim, H. J. (2018). Global Pattern of Microplastics (MPs) in Commercial Food-Grade Salts: Sea Salt as an Indicator of Seawater MP Pollution. Environ. Sci. Technol., 52(21), 12819–12828.
Kim, S. K., & Song, N. S. (2021). Microplastics in edible salt: a literature review focusing on uncertainty related with measured minimum cutoff sizes. Curr. Opin. Food Sci., 41, 16–25.
Lee, P. S., & Jung, S. M. (2022). Quantitative analysis of microplastics coagulation-removal process for clean sea salt production. Int. J. Environ. Sci. Technol., 19(6), 5205–5216.
Liebezeit, G., & Dubaish, F. (2012). Microplastics in beaches of the East Frisian Islands Spiekeroog and Kachelotplate. Bull. Environ. Contam. Toxicol., 89(1), 213–217.
Lin, Z., Jin, T., Zou, T., Xu, L., Xi, B., Xu, D., He, J., Xiong, L., Tang, C., Peng, J., Zhou, Y., & Fei, J. (2022). Current progress on plastic/microplastic degradation: Fact influences and mechanism. Environ. Pollut., 304(November 2021).
Lippiatt, S., Opfer, S., & Arthur, C. (2013). Marine Debris Monitoring and Assessment : Recommendations for Monitoring Debris Trends in the Marine Environment. NOAA Tech. Memo., NOS-OR&R-46, 88.
Lu, S., Liu, L., Yang, Q., Demissie, H., Jiao, R., An, G., & Wang, D. (2021). Removal characteristics and mechanism of microplastics and tetracycline composite pollutants by coagulation process. Sci. Total Environ., 786, 1–11.
Mao, R., Lang, M., Yu, X., Wu, R., Yang, X., & Guo, X. (2020). Aging mechanism of microplastics with UV irradiation and its effects on the adsorption of heavy metals. J. Hazard. Mater., 393(March), 122515.
Masura, J., Baker, J., Foster, G., & Arthur, C. (2015). Laboratory Methods for the Analysis of Microplastics in the Marine Environment: Recommendations for quantifying synthetic particles in waters and sediments (Issue July).
Mudunkotuwa, I. A., Minshid, A. Al, & Grassian, V. H. (2014). ATR-FTIR spectroscopy as a tool to probe surface adsorption on nanoparticles at the liquid-solid interface in environmentally and biologically relevant media. Analyst, 139(5), 870–881.
Ng, M., Liana, A. E., Liu, S., Lim, M., Chow, C. W. K., Wang, D., Drikas, M., & Amal, R. (2012). Preparation and characterisation of new-polyaluminum chloride-chitosan composite coagulant. Water Res., 46(15), 4614–4620.
Peixoto, D., Pinheiro, C., Amorim, J., Oliva-Teles, L., Guilhermino, L., & Vieira, M. N. (2019). Microplastic pollution in commercial salt for human consumption: A review. Estuar. Coast. Shelf Sci., 219(February), 161–168.
Ravikumar, S., Jeyameenakshi, A., Syed Ali, M., & Ebenezer, K. S. (2023). Assessment of microplastics in edible salts from solar saltpans and commercial salts. Total Environ. Res. Themes, 6(July 2022), 100032.
Sari, S. H. J., Kirana, J. F. A., & Guntur, G. (2017). Analisis Kandungan Logam Berat Hg dan Cu Terlarut di Perairan Pesisir Wonorejo, Pantai Timur Surabaya. J. Pendidik. Geogr., 22(1), 1–9.
Selvam, S., Manisha, A., Venkatramanan, S., Chung, S. Y., Paramasivam, C. R., & Singaraja, C. (2020). Microplastic presence in commercial marine sea salts: A baseline study along Tuticorin Coastal salt pan stations, Gulf of Mannar, South India. Mar. Pollut. Bull., 150(October 2019), 110675.
Seth, C. K., & Shriwastav, A. (2018). Contamination of Indian sea salts with microplastics and a potential prevention strategy. Environ. Sci. Pollut. Res., 25(30), 30122–30131.
Shahi, N. K., Maeng, M., Kim, D., & Dockko, S. (2020). Removal behavior of microplastics using alum coagulant and its enhancement using polyamine-coated sand. Process Saf. Environ. Prot., 141, 9–17.
Song, S., Rong, L., Dong, K., Liu, X., Le Clech, P., & Shen, Y. (2020). Particle-scale modelling of fluid velocity distribution near the particles surface in sand filtration. Water Res., 177, 115758.
Suteja, Y., Atmadipoera, A. S., Riani, E., Nurjaya, I. W., Nugroho, D., & Cordova, M. R. (2021). Spatial and temporal distribution of microplastic in surface water of tropical estuary: Case study in Benoa Bay, Bali, Indonesia. Mar. Pollut. Bull., 163(January), 111979.
Talvitie, J., Mikola, A., Koistinen, A., & Setälä, O. (2017). Solutions to microplastic pollution – Removal of microplastics from wastewater effluent with advanced wastewater treatment technologies. Water Res., 123, 401–407.
Tanaka, K., & Takada, H. (2016). Microplastic fragments and microbeads in digestive tracts of planktivorous fish from urban coastal waters. Sci. Rep., 6(March), 1–8.
Tang, W., Li, H., Fei, L., Wei, B., Zhou, T., & Zhang, H. (2022). The removal of microplastics from water by coagulation: A comprehensive review. Sci. Total Environ., 851(August), 158224.
Thi Ha, D. (2021). Microplastic contamination in commercial sea salt of Vietnam. Vietnam J. Sci. Technol., 59(3), 333.
Tsang, Y. Y., Mak, C. W., Liebich, C., Lam, S. W., Sze, E. T. P., & Chan, K. M. (2017). Microplastic pollution in the marine waters and sediments of Hong Kong. Mar. Pollut. Bull., 115(1–2), 20–28.
Vidyasakar, A., Krishnakumar, S., Kumar, K. S., Neelavannan, K., Anbalagan, S., Kasilingam, K., Srinivasalu, S., Saravanan, P., Kamaraj, S., & Magesh, N. S. (2021). Microplastic contamination in edible sea salt from the largest salt-producing states of India. Mar. Pollut. Bull., 171(July), 112728.
Viršek, M. K., Palatinus, A., Koren, Š., Peterlin, M., Horvat, P., & Kržan, A. (2016). Protocol for Microplastics Sampling on the Sea Surface and Sample Analysis. J. Vis. Exp., December, 1–9.
Wei, H., Gao, B., Ren, J., Li, A., & Yang, H. (2018). Coagulation/flocculation in dewatering of sludge: A review. Water Res., 143(2015), 608–631.
Xu, B., Ye, T., Li, D. P., Hu, C. Y., Lin, Y. L., Xia, S. J., Tian, F. X., & Gao, N. Y. (2011). Measurement of dissolved organic nitrogen in a drinking water treatment plant: Size fraction, fate, and relation to water quality parameters. Sci. Total Environ., 409(6), 1116–1122.
Xu, J. L., Thomas, K. V., Luo, Z., & Gowen, A. A. (2019). FTIR and Raman imaging for microplastics analysis: State of the art, challenges and prospects. TrAC - Trends Anal. Chem., 119, 115629.
Xu, Q., Huang, Q. S., Luo, T. Y., Wu, R. L., Wei, W., & Ni, B. J. (2021). Coagulation removal and photocatalytic degradation of microplastics in urban waters. Chem. Eng. J., 416(February), 129123.
Xue, J., Peldszus, S., Van Dyke, M. I., & Huck, P. M. (2021). Removal of polystyrene microplastic spheres by alum-based coagulation-flocculation-sedimentation (CFS) treatment of surface waters. Chem. Eng. J., 422, 1–11.
Yang, D., Shi, H., Li, L., Li, J., Jabeen, K., & Kolandhasamy, P. (2015). Microplastic Pollution in Table Salts from China. Environ. Sci. Technol., 49(22), 13622–13627.
Yang, R., Li, H., Huang, M., Yang, H., & Li, A. (2016). A review on chitosan-based flocculants and their applications in water treatment. Water Res., 95(2015), 59–89.
Yu, Y., Mo, W. Y., & Luukkonen, T. (2021). Adsorption behaviour and interaction of organic micropollutants with nano and microplastics – A review. Sci. Total Environ., 797(July), 149140.
Zaman, N. K., Rohani, R., Yusoff, I. I., Kamsol, M. A., Basiron, S. A., Izzati, A., & Rashid, A. (2021). Eco-Friendly Coagulant versus Industrially Used Coagulants : Identification of Their Coagulation Performance , Mechanism and Optimization in Water Treatment Process. Int. J. Environ. Res. Public Health, 18, 21.
Zhang, Y., Zhou, G., Yue, J., Xing, X., Yang, Z., Wang, X., Wang, Q., & Zhang, J. (2021). Enhanced removal of polyethylene terephthalate microplastics through polyaluminum chloride coagulation with three typical coagulant aids. Sci. Total Environ., 800(2), 149589.
Zhao, C., Zhou, J., Yan, Y., Yang, L., Xing, G., Li, H., Wu, P., Wang, M., & Zheng, H. (2021). Application of coagulation/flocculation in oily wastewater treatment: A review. Sci. Total Environ., 765, 142795.
Zhao, M., Huang, L., Babu Arulmani, S. R., Yan, J., Wu, L., Wu, T., Zhang, H., & Xiao, T. (2022). Adsorption of Different Pollutants by Using Microplastic with Different Influencing Factors and Mechanisms in Wastewater: A Review. Nanomaterials, 12(13).
Zhao, S., Zhu, L., & Li, D. (2015). Microplastic in three urban estuaries, China. Environ. Pollut., 206, 597–604.