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 wor ld, Aerated-lagoon wastewater treatment followed by surface infiltration of fers 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 wer e collected near the USA/Mexico border near Nogales, AZ. Laboratory-scale S AT columns exhibited three phases of 'aging' where infiltration rates and D OC 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 biodegrad ation removal of low molecular weight, low aromatic DOC. Overall, SAT, redu ced the potential towards forming trihalomethanes (THMs) during disinfectio n, although the reactivity (mu g THM/mg DOC) increased. SAT and groundwater recharge would provide a high degree of DOC removal in an integrated low-t ech wastewater reuse management strategy, especially for developing countri es in arid regions of the world. (C) 2000 Elsevier Science Ltd. All rights reserved.