Efficacy Assessment of Silty–Sandy Soil as Bed Material in Constructed Wetland to Treat Naphthalene-Laden Wastewater: Physical and Numerical Modeling

Abstract

Naphthalene is a common polycyclic aromatic hydrocarbon that is widely present in aquatic environments and has colossal negative health effects on living beings. Thus, the removal of naphthalene from wastewater using sustainable, low-cost geomaterials and novel technologies is of prime importance. In this study, the efficacy of a locally available silty–sandy soil in attenuating aqueous naphthalene was assessed using a laboratory-scale constructed wetland. The hydraulic conductivity of the soil was found to be 1.66 × 10−5 cm/s. Batch adsorption data showed that the Langmuir and pseudo-second-order models were the best fitting isotherm and kinetics models, with coefficient of determination values of 0.98 and 0.99, respectively. A one-dimensional vertical-column study using the tested soil on naphthalene showed that the exhaustion time of a 40-mm-deep soil bed was about 1.6 days. A laboratory-scale rectangular-tank test conducted using that soil, with the same test numerically modeled using HYDRUS solute-transport software, revealed that 90% of the initial concentration of naphthalene would reach the outlet in 102 days. The wetland constructed using the selected soil indicated a reduction in the naphthalene concentration of up to 92.8%, which corroborated the results from the CW2D HYDRUS module.