Occurrence and distribution of microplastic particles and the concentration of Di 2-ethyl hexyl phthalate (DEHP) in microplastics and wastewater in the wastewater treatment plant

Wastewater treatment plant (WWTP) is one of the significant sources of Microplastics (MPs) release to the environment. Di 2-ethyl hexyl phthalate (DEHP) is used as an additive for more flexibility of plastics. In this study, we determined the number, size, shape, and color distribution of MPs as well as the concentration of DEHP in MPs and wastewater during the wastewater treatment process in WWTP. Samples were collected from 4 stations of different treatment stages of WWTP. The microplastic particles and the concentration of DEHP were detected via the fluorescence and polarized light microscopy and GC/MS instrument, respectively. The number of MPs decreased from 9.2 (station 1) to 0.84 MP/L (the final treated effluent) during the wastewater treatment process. Also, the size of MPs at the last station was smaller than the other stations. The mean concentrations of DEHP in MPs in stations 1, 2, 3 and 4 had the respective values of 83.3, 61.05, 30.62 and 17.49 mu g/g, while the mean concentrations of DEHP in wastewater in stations 1, 2, 3 and 4 were 30.08, 25.07, 9.56, and 8.13 mu g/L, respectively. This study shows that despite the removal of high amounts of MPs and DEHP in the final effluent of WWTP, due to the high volume of this effluent (2.828 x 10(8) L/d), significant amount of MPs (2.419 x 10(7) MP/day) and DEHP enter the aquatic environment daily, which may threaten the health of the fish and aquatic organisms and ultimately on the health of the local population.

Automated summary

The wastewater treatment plant is a significant source of microplastics release, with DEHP being commonly used. This study found a decrease in the number and size of microplastics and DEHP concentrations in the treated effluent, but highlighted the ongoing threat to aquatic health due to the large volume of effluent entering the environment daily.