Multivariate analysis of mixed contaminants (PAHs and heavy metals) at manufactured gas plant site soils

Biodegradation of perchloroethylene and chlorophenol co-contamination and toxic effect on activated sludge performance

This study investigated the effects of PCE and 2-CP co-contamination on growth of microbial community in terms of enzymatic activity and microbial diversity in activated sludge. Results showed that the activities of three key enzymes (dehydrogenase, phosphatase and urease) decreased significantly when PCE (in the range of 5-150 mg/L) was mixed with 2-CP (in the range of 25-150 mg/L). Especially, activity of dehydrogenase decreased by more than 93% as the concentration of PCE and 2-CP both reached 150 mg/L. PCR-DGGE revealed that short-term exposure with PCE and 2-CP did not lead to shift in the microbial community structure, while clone library demonstrated a significant change in the microbial diversity after long-term exposure. As the population of Alphaproteobacteria and Gamaproteobacteria decreased, with Actinobacteria eventually disappeared, species including Firmicutes, Bacteroidetes and Synergistetes became dominating groups. This study demonstrated that co-contamination with PCE and 2-CP affected the performance of activated sludge in a significant way.

An approach for assessing potential sediment-bound contaminant threats near the intake of a drinking water treatment plant

To assist in assessing a potential contaminated sediment threat near a drinking water intake in a large lake, a technique known as the fingerprint analysis of leachate contaminants (FALCON), was investigated and enhanced to help draw more statistically significant definitive conclusions. This represents the first application of this approach, originally developed by the USEPA to characterize and track leachate penetration in groundwater and contaminant migration from waste and landfill sites, in a large lake from the point-of-view of source water protection. FALCON provided valuable information regarding contaminated sediment characterization, source attribution, and transport within a surface water context without the need for knowledge of local hydrodynamic conditions, potentially reducing reliance on complicated hydrodynamic analysis. A t-test to evaluate the significance of correlations was shown to further enhance the FALCON procedure. In this study, the sensitivity of FALCON was found to be improved by using concentration data from both conserved organics and heavy metals in combination. Furthermore, data analysis indicated that it may be possible to indirectly assess the success of remediation efforts (and the corresponding need to plan for a treatment upgrade in the event of escalating contaminant concentrations) by examining the temporal change in correlation between the source and intake sediment fingerprints over time. This method has potential for widespread application in situations where conserved contaminants such as heavy metals and higher molecular weight polycyclic aromatic hydrocarbons (PAHs), are being or have previously been deposited in sediment somewhere in, or within range of, an intake protection zone.