Apprehending the complex transport and fate behavior of Pharmaceuticals and Personal Care Products in Silty Saturated Porous media - A Numerical Study

The Pharmaceuticals and Personal Care Products, PPCPs, a category of Emerging Contaminants are omnipresent in the environment. These PPCPs have allured significant importance globally over two decades. Because of the lack of efficient treatment systems concerning to their varying Spatio-temporal effects, they impose chronic toxicity on the environment. Therefore, understanding the fate and transport behavior of PPCPs is of prime importance for the successful accomplishment of remediation operations.  In the study, three different PPCPs viz. Metformin, Triclosan and Erythromycin were modeled using numerical techniques in the silty saturated porous media using the software- COMSOL Multiphysics. A fate and transport model considering advection, dispersion, degradation, and adsorption is conceptualized as imitating the real soil column scenario. The column was fed with continuous injection of the contaminants in consideration. Further, sensitivity analysis is carried out by varying flow and transport parameters (longitudinal dispersivity, Darcy’s velocity, adsorption coefficient (K_d), and degradation coefficient) by three orders of magnitude. The degradation and adsorption delayed the process of transport of the three ECs, thereby taking more time to travel through the column. Erythromycin having comparatively less K_d is detected in the column outlet before metformin and triclosan. The results depicted a denoting effect of adsorption, Darcy’s velocity, and degradation co-efficient, thereby highlighting the importance of adsorption, advection and degradation being important factors in the transportation of PPCPs via saturated silty soil. Moreover, the longitudinal dispersivity tends to have a negligible effect on the concentration modeled, thus proving to be a less significant parameter influencing the transport of PPCPs in the environment. The results of the simulation may serve as a foreboding tool for prior identification of the ever-increasing ECs in the environment. Furthermore, the results may prove to be useful in policymaking and risk assessment due to the PPCPs.