Biotransformation of trace organic chemicals during groundwater recharge: How useful are first-order rate constants?

Abstract

This study developed relationships between the attenuation of emerging trace organic chemicals (TOrC) during managed aquifer recharge (MAR) as a function of retention time, system characteristics, and operating conditions using controlled laboratory-scale soil column experiments simulating MAR. The results revealed that MAR performance in terms of TOrC attenuation is primarily determined by key environmental parameters (i.e., redox, primary substrate). Soil columns with suboxic and anoxic conditions performed poorly (i.e., less than 30% attenuation of moderately degradable TOrC) in comparison to oxic conditions (on average between 70-100% attenuation for the same compounds) within a residence time of three days. Given this dependency on redox conditions, it was investigated if key parameter-dependent rate constants are more suitable for contaminant transport modeling to properly capture the dynamic TOrC attenuation under field-scale conditions. Laboratory-derived first-order removal kinetics were determined for 19 TOrC under three different redox conditions and rate constants were applied to MAR field data. Our findings suggest that simplified first-order rate constants will most likely not provide any meaningful results if the target compounds exhibit redox dependent biotransformation behavior or if the intention is to exactly capture the decline in concentration over time and distance at field-scale MAR. However, if the intention is to calculate the percent removal after an extended time period and subsurface travel distance, simplified first-order rate constants seem to be sufficient to provide a first estimate on TOrC attenuation during MAR.

Water Quality Monitoring in Northern India for an Evaluation of the Efficiency of Bank Filtration Sites

“…This is clear evidence for inadequate wastewater management in these areas. Caffeine, theophylline and cotinine are usually degradable to a high degree during RBF [37][38][39][40]. This fact was confirmed within this study for Delhi, Mathura and Agra (Appendix A Table A2), Haridwar, Srinagar and Karnaprayag (Appendix B Table A4).…”

The effect of feed water dissolved organic carbon concentration and composition on organic micropollutant removal and microbial diversity in soil columns simulating river bank filtration

“…This could be explained by either the lower active biomass on the soil in the current study (ATP ¼ 70 ng cm À3 ) compared to the previous study (ATP ¼ 109e135 ng cm À3 ), the different redox conditions (nitrate reducing versus oxic conditions in the previous study), or a combination of both. Regnery et al (2015b) demonstrated that acetaminophen removal was not affected by redox conditions, thus the most plausible explanation for the lower OMP biodegradation rates observed in this study is the lower quantity of active biomass.…”

Reactive Barriers for Renaturalization of Reclaimed Water during Soil Aquifer Treatment

“…Besides, the pathogen indicators (total coliforms and E. coli) were also measured along the reference system and compared to those obtained for the systems operating with the two reactive barriers to assess the efficiencies of these designs. Figure 3 shows the comparison among the estimated degradation rates, λ (A), and retardation coefficients, R (B), at Sant Vicenç dels Horts and those reported from other studies carried out both in laboratory experiments and at field sites [54][55][56][57][58][59][60][61][62]. Considering the typical maximum duration for columns (1-2 years) and field experiments (10-20 years), the minimum value for λ was allowed to be 10 −3 , and 10 −4 d −1 , respectively, following the approach from Greskowiak et al [63].…”