Assessment of Microplastics Contamination along the Stretch of Wang Chhu of Thimphu, Bhutan under Marine Plastics Abatement Program

Plastics, in particular the single-use plastics are cheap, portable and easy to manufacture and  therefore, conventional benefits of plastic are undeniable. Only a tiny fraction of plastic waste is  recycled and about 13 million tons of plastic leak into the environment and water bodies. It is  reported that most plastic polluted rivers are in Asia. Freshwater bodies as a pathway of plastic  pollution, particularly microplastics, have been least studied compared to marine system. 

Therefore, this research studied the concentration of microplastics at the upstream location 1- Dechencholing and downstream location 2 -Babesa of the Wangchhu river flowing before and  after Wastewater Treatment Plant (WWTPs) in Thimphu Municipality in Bhutan. Primary data  was collected through water and sediment sample collections in May 2022, and the secondary data  was generated through literature review. The study identified WWTPs as one of the potential  sources of microplastic pollution in Wangchhu River. The downstream of Wangchhu River  selected as sampling location 2 -Babesa validated abundant presence of microplastics compared  to upstream of Wangchhu River, location 1-Dechencholing. The most dominant size of the  microplastics were from the range of 600-1800 micrometer. Fibers and fragment shapes of  microplastics were present ubiquitously in water and sediment samples, respectively. Yellow  colour was found abundantly in both water and sediment samples. It is recommended to conduct  in depth research on influent of waste water into the WWTPs to quantify the microplastics,  compare with effluent quantity and type of plastics and its sources to improve the removal  efficiency of WWTPs. On policy frontier, this study recommends to include microplastics as one  of the water quality parameters to conserve freshwater bodies, aquatic and human health. 

Currently, the Environmental Standards 2020 of Bhutan lacks microplastics in the parameters for  any ambient water quality criteria, industrial effluent discharge standard and sewage treatment  plant discharge standards. Other standards including Bhutan Drinking Water Quality Standard  2016 lacks to include microplastics in its parameters. Therefore, this is first study assessing  microplastics contamination in freshwater river of Bhutan. Due to time limitation of allocated to  conduct research for academic fulfilment of master in Marine Plastics Abatement, it is  recommended to include seasonal variations to understand factors affecting the concentration of  microplastics.