No abstract

We assessed the incremental lifetime risks due to groundwater contamination with benzene, toluene, ethylbenzene, and xylene compounds (BTEX) for residents living on the site of a former gas station. Five remedial processes were applied to examine the degradation pattern of groundwater samples under similar weather conditions in winter: H2O2/solar light (action 1), immobilized TiO2/solar light (action 2), TiO2 slurry/solar light (action 3), immobilized TiO2/solar light/H2O2 (action 4), and TiO2 slurry/solar light/H2O2 (action 5). None of the remedial actions satisfied the criteria of acceptable risk (1 × 10−6 for carcinogens) using point estimation with both central tendency exposure (CTE) and reasonable maximum exposure (RME) for all pathways via designated exposure scenarios. Regarding the total hazard index (HI) for noncarcinogens, only action 5 satisfied all the exposure scenarios, both CTE and RME, for toluene, ethylbenzene, and xylene compounds, whereas the total health risk for benzene was between 10−5 and 10−6 for carcinogens. Results of probabilistic estimation before and after the treatment of benzene with action 5 using a Monte Carlo simulation were 68.1% for males (95% CI: 5.0 × 10−7 to 3.9 × 10−6) and 74.2% for females (95% CI: 5.0 × 10−7 to 4.6 × 10−6), exceeding the criteria of acceptable risk (10−6 for carcinogens). However, no adverse health risk was posed if remedial action 5 or an increased reaction time were applied. This study is a new attempt to integrate issues of groundwater contamination based on concentration and health risk assessment associated with different ex situ remedial actions. © 2008 American Institute of Chemical Engineers Environ Prog, 2008

Microbiological reactions by sulfate reducing bacteria and ferrous oxidizing bacteria are critical in the passive treatment of acid mine drainage using constructed wetlands. A lot of research have been done to find better mixing strategy of different substrates to maximize viability of sulfate reducing bacteria and reactor performance. However, research efforts have been poorly made in their microbial ecology comprising community identification and their interactions though they are the main body of acid mine drainage treatment. Currently, to attain high degrees of treatability and sustainability in this wetland-based treatment facility, biotechnological approaches are necessary to improve oxic ponds and successive alkalinity producing systems, where most of microbiological reactions occur during the treatment. In this paper, we critically reviewed microbial community and physiological functions of sulfate reducing bacteria and ferrous oxidizing bacteria, and suggested perspectives regarding microbiological facility improvement for more sustainable and more efficient passive treatment of acid mine drainage.