Efficacy of natural coagulants in reducing water turbidity under future climate change scenarios

There is a growing need for sustainable solutions to mitigate poor water quality with the uncertainty of climate change. Natural coagulants, substances derived from organic materials that help to bind together particulate matter in water, have arisen as potential alternatives to synthetic coagulants, which typically contain harmful chemicals such as aluminum sulfate. The objective of our research was to 1) determine the effects of temperature on the efficacy of natural coagulants and synthetic coagulants in reducing water turbidity, and 2) model how natural coagulation efficacy could vary across various segments of a watershed under future climate change scenarios. We hypothesized that both natural coagulants and their synthetic counterparts would have an inverse relationship between temperature and reduction in turbidity. Utilizing water samples from the Tennessee River Watershed, we conducted experiments that estimated the impact of water temperature on turbidity reduction efficiency of four coagulants. We found that turbidity reduction was higher at lower temperatures for only two of the coagulants. The eggshells, one of the natural coagulants, had a stronger association for increased turbidity reduction at lower temperatures out of those two. We then projected and mapped turbidity reductions under two climate change scenarios and three future time spans for eggshells. There were spatiotemporal variations of turbidity reduction for eggshells and a clear depreciation in natural coagulation efficacy with the progression of climate change. Our results suggest that site-specific and time-varying turbidity reductions utilizing natural coagulants under future climate change conditions can be vital for optimal water treatment plans.