Enhanced ice slurry with low oxidant consumption for ultrafast in-situ removal of micropollutants sheltered in sediments of water supply pipelines

The cleaning of water supply pipelines represents an increasingly prevalent global practice with the aim of providing high-quality drinking water. Ice pigging, a widely-utilized pipe cleaning technique, can effectively remove substantial sediment sediments from pipe walls. During this process, micropollutants adsorbed to the sediments are inevitably released into the effluent, posing a potential threat to public health. Existing technologies can only address these micropollutants through various post-treatment methods. To improve pipeline cleaning efficiency and reduce costs, we have developed an enhanced ice slurry by adding a minute quantity of peroxymonosulfate (PMS) into the base ice slurry for ultrafast, in-situ removal of micropollutants within sediments. Comparative studies with the base ice slurry demonstrate a significant enhancement in the removal efficiency of the common micropollutant carbamazepine (CBZ) using the enhanced ice slurry. While the removal efficiency of CBZ ranged from 16 to 23 % with increasing NaCl content from 3 to 7 wt% over 10 min for the base ice slurry, nearly complete removal of CBZ was achieved within 1 min by introducing 10 μM PMS into the base ice slurry. The influence of operational parameters (e.g., PMS and Cl^- concentrations, cleaning flow velocity) and pipeline characteristics (e.g., CBZ and Fe²⁺ concentrations, turbidity, pipe sediment) on CBZ removal efficiency was comprehensively examined for the enhanced ice slurry. The enhanced micropollutant removal process was mainly driven by active species such as hydroxyl and sulfate. Remarkably, chlorinated byproducts were scarcely detected during ice pigging, and the degradation products exhibited minimal ecotoxicity. With a cost of 0.16 Euro per cubic meter of cleaned pipe, the enhanced ice slurry presents a notable economic advantage over alternative methods. Overall, the enhanced ice slurry offers an environmentally friendly, cost-effective, and efficient solution for reducing micropollutants in water supply systems.