Performance of volcanic tuff in soil aquifer treatment for wastewater reuse

Soil Aquifer Treatment (SAT) is a sustainable and low-cost approach for wastewater reclamation and groundwater recharge, with performance strongly influenced by the filtration medium. This study compares sand and volcanic tuff as filtration media in a laboratory-scale SAT system treating secondary wastewater from Chennai, India. Two identical columns were operated under controlled hydraulic conditions during three seasons (summer, monsoon, and post-monsoon) to assess seasonal variability in treatment performance. Total Organic Carbon (TOC) and Total Nitrogen (TN) were monitored together with microbial indicators, including bacterial production, respiration, and abundance. Scanning Electron Microscopy and 16S rRNA-based microbial analysis were used to examine biofilm development and microbial habitat suitability. The volcanic tuff-based SAT column consistently showed higher overall treatment performance than sand, achieving up to 45% TOC and 52% TN reduction. Enhanced microbial retention and more pronounced biofilm formation were observed in volcanic tuff due to its high porosity and complex internal structure. Although seasonal variations affected both systems, volcanic tuff maintained more stable performance under fluctuating conditions. The results indicate that volcanic tuff enhances SAT performance through combined physical retention, adsorption, and biological conditions.