Seasonality in negative removal of pharmaceutical and personal care products at the Himalayan foothills wastewater treatment plants

Seasonal trends in negative removal, where effluents concentrations exceeded influent levels, were predominantly observed while monitoring seven pharmaceuticals and personal care products (PPCPs) in the Himalayan capital city of Uttarakhand, India. The findings showed consistent presence of Diclofenac and Caffeine in the influent samples, with significant seasonal variations. Higher mean PPCP levels were observed during spring, followed by the monsoon and summer. Specifically, Caffeine reached its peak concentration (71,000 ng/L) during the monsoon, while Ciprofloxacin levels were highest (17,000 ng/L) in the spring. The normality tests showed that the data distribution for all wastewater PPCPs samples, except for Caffeine influents, was non-normal (p >0.05). A significant difference in PPCPs concentration between influent and effluent samples (p <0.001) strongly indicated unequal means. The PPCPs reduction rates/removals in the WWTPs were observed in the ranges of 68.55-100 %. In terms of total PPCPs, average removal efficiencies of WWTPs were recorded in the range of 42-71 %. Acetaminophen and Ketoprofen had the highest positive removal rates, while Ciprofloxacin, Carbamazepine, and Caffeine had the most substantial negative removal rates. The highest PPCPs removal efficiency was observed in aeration and fluidized media oxidation (AFMO) based WWTPs, followed by the cyclic activated sludge technology (C-Tech), and sequencing batch reactor (SBR) processes. Due to negative removal, WWTPs have been identified as substantial contributors to PPCP pollution, posing a serious threat to ecological integrity. This study presses an urgent need for surveillance, and consequent regulation of emerging contaminants, especially in the biodiverse and ecologically sensitive hilly landscapes.