Reclaimed wastewater or surface water use in irrigation: Delineating potential fate and impacts of pharmaceuticals

The depletion of groundwater storage is being acknowledged as a progressively severe global issue. Around 69% of the total groundwater abstracted is used in the agricultural sector. Hence, it is imperative that we refrain from excessive abstraction of groundwater for irrigation and instead focus on utilizing surface water or reclaimed wastewater. However, these alternate sources can be contaminated with certain emerging contaminants (EOCs) that might raise concern in the future. Hence, this study aims to investigate the effect of surface water or reclaimed wastewater irrigation on rice (Oryza sativa), a water-intensive staple grain in the Asian region. A field experiment was carried out on rice, in which they were subjected to irrigation with water spiked with three commonly detected pharmaceuticals in the environment, namely sulfamethoxazole (SMX), carbamazepine (CBZ), and ibuprofen (IBP). The crops were irrigated at regular intervals for ten times throughout the growing period with three different pharmaceutical doses (0.5g), medium (1g), and high (5g). The control set was irrigated with uncontaminated water. Post-harvest agronomical analysis suggests that the grain yield remained unaffected by contaminant addition, whereas the straw yield was increased by up to 25%, 29% and 33% for SMX, CBZ, and IBP, respectively. The contaminant concentration in the rice grains was found to be greater than the limit of detection (LOD) for all the contaminants at different doses but was not > LOQ for some of them. The health quotient (HQ) for SMX and IBRU was <0.1, signifying lower risk, while for CAR, it ranged from 0.1 to 1, indicating medium risk. Overall, irrigation with reclaimed wastewater or surface water can be detrimental only if higher concentrations of certain pharmaceuticals, like CAR, are present. However, further studies are required as far as metabolites are concerned. Hence, this study will help in determining appropriate concentration thresholds for pharmaceuticals present in surface water or reclaimed wastewater that are considered safe for agricultural purposes.