Microbial activity in soils following steam treatment

Area of Science:

• Environmental Science
• Microbiology
• Soil Science

Background:

• Steam enhanced extraction (SEE) is effective for volatile contaminants but less so for low-volatility compounds like PAHs.
• Understanding the impact of SEE on soil microbial communities is crucial for assessing post-treatment biodegradation potential.

Purpose of the Study:

• To evaluate the effects of steam injection on soil microbial activity, community structure, and biodegradation potential.
• To assess microbial recovery and metabolic capabilities in soils treated with steam.

Main Methods:

• Direct epifluorescent microscopy (DEM) with CTC and DTAF to quantify microbial numbers and activity.
• Enrichment cultures to assess metabolic capabilities and biodegradation potential.
• Fluorescent in situ hybridization (FISH) with rRNA probes to identify microbial domains (Archaea and Bacteria).

Main Results:

• Microbial activity was below detection in hot, freshly steamed soils but comparable to pre-steamed levels in slowly cooled soils.
• Field-scale steaming also showed high microbial activity post-cooling.
• Surviving mesophilic populations demonstrated biodegradation capabilities, with both Archaea and Bacteria detected post-treatment.

Conclusions:

• Soil microbial activity and community structure can recover following steam enhanced extraction.
• Biodegradation potential exists within the surviving microbial populations after steam treatment.
• SEE can be a viable remediation technique when considering microbial recovery and subsequent bioremediation.