Joint effect of triclosan and copper nanoparticles on wastewater biological nutrient removal

Triclosan (TCS) is widely used in household and personal care products, and its release into wastewater might have impact on wastewater biological treatment for its antibacterial property. Besides, emerging pollutant such as copper nanoparticles (CuNPs) will also release from nanoparticle-containing products, showing a joint effect with TCS on biological nutrient removal. The TCS of 1 and 10 mg/L inhibited the nitrosification and nitrification stage, and the first step of denitrification was suppressed as well, causing a decline in final TN removal efficiency. Additionally, the phosphorus uptake was inhibited seriously, leading to a remarkable decrease in phosphorus removal efficiency. When they were co-existed, the TCS concentration decreased due to the absorption by CuNPs, and the released Cu²⁺ from CuNPs increased. Further investigation revealed that when 5 mg/L CuNPs and 1 mg/L TCS were immediately added to the activated sludge, the final joint toxicity was similar to the individual effect of 1 mg/L TCS, while 10 mg/L CuNPs contributed to the final stronger toxicity. When TCS was sufficiently reacted with CuNPs in wastewater, their final toxicity to activated sludge was enhanced because the extent of toxicity relief caused by decrease in TCS concentration was less than the degree of deteriorating effect due to the promotion of Cu²⁺ release from CuNPs.