Environmental Engineering Reference
In-Depth Information
(NKN), total phosphorous (TP), and total organic carbon (TOC)), and head-
space oxygen concentration. Additionally, initial characterization included
particle size distribution (PSD), Atterberg properties, metals concentration,
particle surface area, and soil leachability. These characteristics were ana-
lyzed again at the end of the experiment. Routine soil/slurry samples were
collected every month for PCB concentration, microbial biomass, nutrient
analysis, soil moisture, and pH. Soil/slurry temperature and headspace oxy-
gen concentration were monitored biweekly to check anaerobic conditions
in the reactors. To ensure quality control of analytical results, samples were
analyzed in composite replicates of seven for high solids, five for medium
solids, and three for low solids reactors. Higher replicates were used in high
solids reactors because of the level of heterogeneity and variability, compared
to the well-mixed low solids reactor.
6.5.5 Analytical methods
Particle size distribution (PSD) was measured by using a Coulter LS 100Q
particle counter according to instrument specifications. The Atterberg limits
test was performed according to the
Corps of Engineers Laboratory Testing
Manual
, EM-1110-2-1906, “Appendix III: Liquid and Plastic Limits.” Bulk
density of the contaminated soil was measured by weighing a known volume
of soil at field conditions. Soil pH was determined by a soil-distilled water
slurry (1:10, w/w) using a Cole-Parmer® pH meter and was reported as pH
in water (pHw).
PCB concentrations in soil samples were determined by high-resolution
gas chromatography with electron capture detection (ECD). Total Kjeldahl
nitrogen (TKN) and total phosphorous (TP) analyses were performed by a
Lachat 8000 Flow Injection Analyzer (FIA). The preparation methods were
modified versions of EPA-600/4-79-020 (1983 revision) 365.1 and 351.2,
respectively. Total organic carbon (TOC) was determined by the Zellweger
Analytic TOC analyzer, according to the instrument protocol. Moisture con-
tent of soil samples was analyzed by oven drying at 105˚C for 24 h. Oxygen
concentration was measured in the headspace by using an LMSx Multigas
Analyzer®.
Surfactant analysis for Tween 80 concentrations in aqueous samples was
done by a Hewlett Packard 1100 series. Detection of Tween 80 was achieved
using a diode array selection HPLC controlled by a HP Vectro Pentium
computer.
Soil leachability was assessed by two alternative leachability methods.
The Sequential Batch Leaching Test (SBLT) consists of four repeat extractions
of the same sample using deionized water in a 4:1 (water:solid) ratio. The
slurry was mixed for 24 h, centrifuged, and filtered, and the filtrate was
analyzed for contaminants. The Synthetic Precipitate Leaching Procedure
(SPLP) was performed according to SW846, EPA Method 1312. Being a
nonvolatile extraction, a “bottle extraction vessel” such as an amber jar (1 l)
with sufficient capacity to hold the sample and the extraction fluid will be
