Microplastic contamination in refilled drinking water: The impact of gallon washing frequency

Microplastic contamination in drinking water has become an increasing global concern due to its potential health impacts. This study aimed to assess the presence and characteristics of microplastics in refillable drinking water stored in gallon containers subjected to different washing frequencies. The research was conducted at a refillable water depot in Makassar City using a quasi-experimental design. Three washing treatments were applied – single wash (1×), moderate wash (50×), and frequent wash (100×) – each with three replicates. Microplastics were identified through membrane filtration and microscopic observation. A total of 56 particles were detected, with fiber-shaped particles being dominant (91.1%). The most frequently observed colors were transparent and red, and particle sizes ranged from 0.064 to 1.944 mm. The highest average microplastic count was found in the moderate wash group (8.33 particles/L), followed by the single wash group (5.33 particles/L), and the lowest in the frequent wash group (5.00 particles/L), although the differences among groups were not statistically significant. These find¬ings suggest that moderate washing frequency may increase microplastic release due to mechanical abrasion of the container surface. The study underscores the importance of evaluating washing procedures and selecting appropri¬ate cleaning tools to reduce microplastic contamination in refillable drinking water.