Dissolved organic carbon transformations during laboratory-scale groundwater recharge using lagoon-treated wastewater

Reuse of treated wastewater through groundwater recharge has emerged as an integral part of water and wastewater management in arid regions of the world. Aerated-lagoon wastewater treatment followed by surface infiltration offers a simple low-tech, low-cost treatment option for developing countries. This study investigated the fate of dissolved organic carbon (DOC) through laboratory-scale soil aquifer treatment (SAT) soil columns over a 64-week period. Aerated-lagoon wastewater (average DOC=17 mg/l) and two soils were collected near the USA/Mexico border near Nogales, AZ. Laboratory-scale SAT columns exhibited three phases of ‘agingʹ where infiltration rates and DOC removals were delineated. DOC removal ranged from 39% to greater than 70% during the study, with DOC levels averaging 3.7 and 5.8 mg/l for the SAT columns packed with different soils. Soil with a higher fraction of organic carbon content had higher effluent DOC levels, presumably due to leaching of soil organic matter. UV absorbance data indicated preferential biodegradation removal of low molecular weight, low aromatic DOC. Overall, SAT reduced the potential towards forming trihalomethanes (THMs) during disinfection, although the reactivity (μg THM/mg DOC) increased. SAT and groundwater recharge would provide a high degree of DOC removal in an integrated low-tech wastewater reuse management strategy, especially for developing countries in arid regions of the world.