Attenuation of Aqueous Naphthalene through a Constructed Wetland System Employing Lightweight Expanded Clay Aggregate

Abstract

Naphthalene (NAPH), a common polyaromatic hydrocarbon from the petrochemical and pharmaceutical industries, significantly contaminates water bodies due to its resistance to degradation. This study investigated the use of the lightweight expanded clay aggregate (LECA) in attenuating aqueous NAPH in wastewater. The methodology involved batch adsorption, vertical column experiments, and laboratory-scale constructed wetland tests validated by the HYDRUS 2.05 (2D/3D) numerical model. Batch adsorption tests achieved a maximum efficiency of 96.48% at 12 mg/L NAPH concentration. In this regard, two models were tested: Langmuir and Freundlich models. The Freundlich model [coefficient of regression R2 = 0.99, isotherm coefficient Kf = 0.07914 (mg/g) (L/mg)] and the pseudo-second-order kinetic model [K2 = 0.395 (g/mg min), R2 = 0.98] best described the observed data. Sorption decreased with increasing pH (84% at pH 2 to 47% at pH 10) and was minimally affected by temperature. Vertical column tests showed bed exhaustion at 36 h, while the constructed wetland system incorporating LECA reduced NAPH concentration by up to 97.5%, corroborated by HYDRUS model results. Recyclability tests demonstrated 100% removal efficiency for up to 120 cycles, declining to 0 by the 270th cycle. These results indicated that LECA-based constructed wetlands are an efficient and sustainable method for mitigating NAPH contamination, supporting Sustainable Development Goal 6 for clean water and sanitation. The research on using lightweight expanded clay aggregate (LECA) for naphthalene (NAPH) removal from wastewater highlights a cost-effective and sustainable solution with significant practical applications. LECA, with its exceptional compound stability and massive surface area, serves as an effective sorbent for NAPH, a hazardous polyaromatic hydrocarbon commonly found in industrial effluents. Incorporating the LECA into constructed wetlands enhances their ability to treat contaminated water, making it a valuable option for wastewater treatment plants. These LECA-based constructed wetlands can effectively remove NAPH from industrial effluents, remediate polluted sites, and protect groundwater. This approach is particularly beneficial in developing countries where industrial pollution is prevalent, and resources for advanced treatment are limited. Additionally, LECA-based systems can be used in rural and urban areas to treat domestic wastewater and stormwater runoff, ensuring compliance with regulatory standards and safeguarding public health. By leveraging the LECA in constructed wetlands, this research contributes toward attaining Sustainable Development Goal 6 for proper sanitation and clean water.