Investigation of the microplastics profile in sludge from China’s largest Water reclamation plant using a feasible isolation device

Sewage sludge, which is widely applied to land as a fertilizer, is a key source of microplastics in the environment. We sought to develop a feasible device for isolation of microplastic from sewage sludge for further understanding their fates in the environment. In the present study, an effective isolation device, consisting of a fritted glass funnel and a glass filtration apparatus, was constructed to extract microplastics from sludge with nearly 100% recovery efficiency. Then, a high abundance of microplastics was detected in sludge sampled from China's largest sewage treatment plant. Among the 25 types of microplastic polymers confirmed by Fourier transform infrared spectroscopy, poly(11-bromoundecyl acrylate) (PBA) and poly(11-bromoundecyl methacrylate) (PBMA) accounted for 23.63% of total microplastics detected. Rayon, polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), and copolymers, such as PP/PE and poly(styrene:acrylonitrile:butadiene) (ABS), were also detected. The shapes of these microplastics consisted of pellets, fragments, films, and microfibers. Characterization of the isolated microplastics revealed that domestic applications and vehicle products were the major sources of microplastic in sewage treatment sludge. Some priority recommendations were issued based on these results. In conclusion, the present study demonstrate that the device is effective for the isolation of microplastics from sludge.