Experimental Investigation On Optimal Soil Column Depth For Efficient Soil Aquifer Treatment

Abstract

Water scarcity and the rapid increase in wastewater generation associated with urbanization have intensified the need for sustainable and decentralized water reuse solutions. Soil Aquifer Treatment (SAT) is a nature-based technology that improves wastewater quality through integrated physical filtration, chemical adsorption, and biological degradation processes occurring within soil-aquifer systems. In this study, the performance of SAT systems was experimentally evaluated using laboratory-scale layered soil columns operated under different hydraulic retention times (HRTs). Experiments were conducted to evaluate the efficiency of different soil column depths. Raw sewage wastewater was applied to ten soil columns consisting of fine and coarse sand layers, operated under short (4 hrs) and long (24 hrs) HRTs over a continuous period of 45-100 days. Key water quality parameters, including biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), nitrogen species, phosphorus, total dissolved solids (TDS), and pH, were systematically monitored. The results demonstrate substantial improvements in effluent quality, with BOD and TSS removal efficiencies reaching up to 80% and 75-80%, respectively. Treatment performance was strongly influenced by soil depth and retention time, with longer HRTs and layered soil configurations enhancing organic matter degradation, nutrient removal, microbial activity, and system stability while reducing clogging risks. These findings confirm that SAT systems represent a low-energy, cost-effective, and environmentally sustainable solution for decentralized wastewater reuse and can play a significant role in achieving net-zero water cycles in rapidly urbanizing regions.