A Comprehensive Modeling of Microplastic Emission from Wastewater Treatment Plants to the Sea via Rivers in China

Wastewater treatment plants (WWTPs)
are significant sources of
microplastic (MP) emissions. In order to quantify the potential MP
emission from WWTPs, a database of more than 10,000 WWTPs in China
with an estimated MP emission rate was built. The MP riverine retention
after emission was also estimated based on Stokes’ law for
both fragments and fibers. The results show that the mass of MPs discharged
from WWTPs is (4.48 ± 7.48) × 107 kg, yet the
amount of MPs released from untreated sewage is (4.55 ± 3.00)
× 107 kg, which is comparable to that of treated wastewater,
indicating the capacity of wastewater treatment should be further
strengthened. The flux of MPs into the sea after river interception
is between 4.08 × 107 kg and 8.20 × 107 kg with 14–27% being directly discharged to the sea within
20 km from the shore.

污水处理厂（Wastewater Treatment Plants, WWTPs）是微塑料（Microplastic, MP）排放的重要来源。为量化污水处理厂的潜在微塑料排放量，本研究构建了涵盖中国1万余座污水处理厂、包含估算微塑料排放速率的数据库。本研究还基于斯托克斯定律，对排放后微塑料在河流中的滞留量进行了估算，涵盖碎片态与纤维态两种微塑料形态。研究结果显示，污水处理厂排放的微塑料总质量为(4.48±7.48)×10^7 kg，而未经处理的污水所释放的微塑料总量为(4.55±3.00)×10^7 kg，二者规模相当，表明当前污水处理能力仍有待进一步提升。经河流截留后进入海洋的微塑料通量介于4.08×10^7 kg至8.20×10^7 kg之间，其中14%~27%的微塑料会在距岸线20公里范围内直接排放入海。