Environmental Engineering Reference
In-Depth Information
5.3.2.3 Evaluation of preinjection natural attenuation
potential ............................................................................. 75
5.3.2.4 Well description ................................................................ 75
5.3.2.5 Groundwater flow characterization .............................. 79
5.4 Materials and methods ............................................................................... 82
5.4.1 Laboratory evaluations ................................................................. 82
5.4.1.1 Molecular ecology ............................................................ 82
5.4.1.2 Ethanol toxicity ................................................................. 82
5.4.2 Field studies ..................................................................................... 83
5.4.2.1 Groundwater sampling and analysis ............................ 83
5.4.2.2 Core material collection................................................... 84
5.4.2.3 Cosolvent flush and partitioning tracer tests .............. 85
5.4.2.4 Hydrogen gas analysis .................................................... 86
5.5 Accomplishments......................................................................................... 86
5.5.1 Solvent extraction (SE) pilot test .................................................. 86
5.5.2 Residual biotreatment (RB) monitoring and assessment ......... 89
5.5.3 Microbial ecology assessment ..................................................... 129
5.5.4 Ethanol toxicity assessment......................................................... 134
5.5.5 Evaluation of system performance ........................................... 136
5.5.5.1 Electron donor evaluation............................................. 136
5.5.5.2 Estimates of transformation rates ................................ 137
5.5.5.3 Single-well rate constants.............................................. 137
5.5.5.4 Total mass removal......................................................... 138
5.6 Conclusions on utility in remediation.................................................... 140
5.7 Technology transfer ................................................................................... 142
5.8 Notice ........................................................................................................... 142
References............................................................................................................. 143
5.1 Project background
Chlorinated solvents were used and released to the environment in massive
amounts during the 1950s, 1960s, and 1970s. These contaminants have
migrated through the subsurface and impacted groundwater at more than
1000 Department of Defense (DOD) sites. Their widespread use and the
physical and chemical properties of these compounds have resulted in the
chloroethenes being the most commonly detected class of organic contami-
nants in groundwater. Parent chloroethenes can become human health haz-
ards after being processed in the human liver or via reductive dehalogena-
tion in the environment. This has generated a high degree of interest in
efficient and cost-effective technologies to remediate soils and groundwater
contaminated with tetrachloroethylene (PCE) and trichloroethylene (TCE).
Remedial technologies for chlorinated solvents have progressed in three
major phases since the environmental challenge they present was recognized
during the 1970s. Until the late 1980s, physical-based technologies such as
pump and treat for dissolved phase contaminants and excavation (where
