(512d) Effects on Incubating Functional Bacteria with Different-Sizes Microplastics: An Unexpected Increase of COD Removal Rate with Presence of Microplastics

Nowadays, microplastics(MPs) debris in natural water system is being more and more a concern for the environment. To observe the effects of different sizes of MPs particles have on the functional bacterial used in the waste water treatment, a research was conducted using chemical oxygen demand (COD) as an indicator to discuss the issue. In the research, we used pure tetrahydrofuran(THE) to dissolve commercial PS plastic balls, prepared two solution with different concentrations and used water to extract different sizes of the MPs particles. After filtering, the MPs particles, the functional bacteria and the nutrient solution were mixed and incubated in the temperature controlled shaker incubator under an optimal temperature. The COD was then tested after 24 hours. The results showed that with averagely MPs sizes 0.75 μm, the COD has a 1.62%~13.68% removal rate. We then repeated the best-removal-rate set with higher concentrated nutrient solution five more times. Though the removal rate data shows high diversity, generally it is all lower than the blank sample, and averagely has a 12% better removal. We concluded that the MPs particles do have a positive effect on COD removal during the process. A possible explanation would be that the MPs adsorbed some bigger particles of the nutrient solution due to its large surface area.