Fate of chlorination byproducts and nitrogen species during effluent recharge and soil aquifer treatment (SAT)

Abstract

A pilot-scale study was conducted under field conditions to determine the potential role of soil aquifer treatment (SAT) in renovating wastewater effluent to potable water quality. Instrumented test basins were used to evaluate water quality transformations through the upper vadose zone during effluent recharge. Samples of either chlorinated secondary or reclaimed (tertiary) effluent were obtained from suction samplers situated in two separate test basins at depths of up to 6.1 m (20 ft). Samples were characterized according to dissolved organic carbon (DOC), a measurement of dissolved organic matter, and total organic halide (TOX), a measurement of chlorination byproducts. Average DOC and TOX removals were 50% and 40%, respectively, for secondary source water; slightly higher removals were observed for tertiary source water. Performance was found to be affected by operational factors; variations in DOC and TOX removal were observed within a wetting cycle as well as from cycle to cycle. Significant nitrification occurred during drying cycles between flooding cycles, resulting in an initial wave of high nitrate in the percolating water. Water Environ. Res., 65, 726 (1993).Southwestern municipalities faced with impending water shortages recognize the need to reuse treated effluent. Recharge and recovery of effluent balances out seasonal needs for nonpotable irrigation water. Also, when combined with soil aquifer treatment (SAT), groundwater recharge becomes an adjunct to standard treatment technologies, potentially leading to potable reuse. A major concern in SAT schemes is the fate and transport of trace organics during deep percolation of wastewater. A secondary concern relates to nitrogen species. This paper will review the results of a short-term study of fate and transport processes during deep percolation of chlorinated secondary and tertiary effluent applied to instrumented pilot-scale test basins at Tucson, Arizona, and discuss implications for potable water recovery. ObjectivesThe general objective of the research reported below was to determine the fate of wastewater effluent organic matter, as measured by dissolved organic carbon (DOC), and chlorinated organics, as measured by total organic halide (TOX) through a SAT system. Specific objectives were to:• delineate the potential role of SAT in the potable reuse of effluent;• develop well-characterized, instrumented, pilot-scale test basins to evaluate SAT through the vadose zone;• develop time-dependent depth profiles of DOC and TOX;• evaluate the effects of wetting/drying cycles on performance and, within a given wetting cycle, evaluate the effects of time;• contrast secondary versus tertiary effluent as a source water, and provide a qualitative understanding of sorption versus microbiological phenomena; and• define variations in infiltration rates from cycle to cycle and within a given cycle.

Wastewater-Derived Dissolved Organic Nitrogen: Analytical Methods, Characterization, and Effects—A Review

“…Humic substances in the source water that ultimately becomes municipal wastewater probably contribute to wastewater DON. The concentration of humic substances, in wastewater effluent is estimated to range between 1 and 5 mg C/L (Amy et al, 1993;Barber et al, 2001;Ma et al, 2001). Although it is hard to give a specific formula for humic substances, the average composition of humic acid (C 187 H 186 O 89 N 9 S; Sposito, 1989) can be used to calculate the DON contribution of humic substances in the wastewater effluent.…”

Natural Organic Matter Removal During Riverbank Filtration: Current Knowledge and Research Needs

“…Steady infiltration conditions in RBF systems generate a special bioactive filtration layer at the water/sediment interface (Matthess, 1990). Amy et al (1993), Kivimaeki et al (1998), and Drewes and Fox (1999) observed the highest removal of DOC and TOX within the first meter of infiltration. Wang (2002) also reported that the majority of NOM removal occurred within the first 15 m of infiltration.…”

Surface Area and Travel Time Relationships in Aquifer Treatment Systems

“…Soil Aquifer Treatment and Bank Filtration. Soil aquifer treatment (SAT) is a process whereby wastewater effluent from treatment plants is applied to infiltration basins and transported through the subsurface environment, where further purification occurs (Amy et al, 1993;Bouwer, 1985;Bouwer and Rice, 1984;Drewes and Jeckel, 1998;Wilson et al, 1995). The SAT provides water-quality benefits during percolation through vadose zone sediments and subsequent groundwater storage.…”