Optimizing the integration of pollution control and water transfer for contaminated river remediation considering life-cycle concept

The approaches of pollution control (i.e. wastewater collection and treatment) and water transfer (i.e. flowing river water by inducing clean water) have been proved to be effective for contaminated river remediation, but at the same time they will inevitably result in environmental burden associated with resource consumptions and pollution emissions. To quantify the environmental impacts and optimize the integration of the two approaches for contaminated river remediation, a comprehensive framework was proposed by using response surface methodology based on the life cycle assessment (LCA) results of 81 scenarios, in which different pollution levels and the self-purification capacities of a river were considered. According to the LCA results, which are presented as six categories, i.e., Climate Change (CC), Terrestrial Acidification (TA), Freshwater Eutrophication (FE), Marine Eutrophication (ME), Human Toxicity (HT), and Freshwater Ecotoxicity (FET), pollution control performed better for ME, FET, and HT, whereas water transfer performed better for CC and TA, highlighting the need to optimize the combined approaches for different river characteristics. The further optimization results showed that the pollutant interception rate and pumping time should be as high as possible when the self-purification coefficient of the river was below 0.005 and the chemical oxygen demand (COD) was over 80 mg/L. However, neither a very high pollutant interception rate nor a very high pumping time was able to improve the water quality at minimal environmental impact when the self-purification coefficient was above 0.005 and the COD was from 50 to 80 mg/L. Thus, the optimal integration for achieving the minimal environmental impact could be determined based on the local pollution concentration and self-purification coefficient of river. This study quantified the effects of river characteristics on the integration of pollution control and water transfer for the first time, which could provide a scientific basis for the improvement of remediation strategies for polluted rivers.