Effect of pipe materials on disinfection by-products and bacterial communities during sulfamethazine chlorination in a pilot-scale water distribution system

Abstract

Water research is usually done using simplified devices, e.g., beakers, in laboratory glassware, and thus may yield results that are not representative of real wastewater treatment plants that use complex pipe systems made of various materials. Therefore, here we studied for the first time the effect of different pipe materials on sulfamethazine chlorination and formation of disinfection by-products. We also studied the relationships between bacterial communities, pipe materials, sulfamethazine degradation, free chlorine decay and formation of disinfection by-products. Results show that the degradation of sulfamethazine was faster in pipes than in batch tests, due to the influences of sediment, iron and bacterial communities. Specifically, the total concentration of disinfection by-products after 22 h followed the order: 49.43 μg/L for stainless-steel pipe, 46.76 μg/L for ductile iron pipe, 39.12 μg/L for polyethylene pipe, and 19.22 μg/L for batch tests. 16S rRNA microbial analysis showed that ductile iron and stainless-steel pipes had the highest operational taxonomic unit (OTU) richness. Microbial communities between polyethylene and ductile iron pipe had a relatively higher similarity. Sphingomonas and Actinobacteria slowed down the decay of free chlorine in the stainless-steel pipe, which promoted the degradation of sulfamethazine. Mycobacterium and Pseudomonas are the dehalogenation-related bacteria, which reduced the formation of distribution by-products in polyethylene pipe.