Jeff Roberts is a Senior Manager at SiREM with extensive technical experience in the laboratory assessment and field implementation of soil, sediment and groundwater remediation technologies at sites containing contaminants including chlorinated solvents, petroleum hydrocarbons and other recalcitrant compounds. Over the past fourteen years he has conducted and managed hundreds of bench-scale batch and column treatability studies and also has technical experience in the growth, scale up and field implementation of several anaerobic microbial cultures for bioremediation remedies.
PLATFORM PRESENTER – Biological Treatment: Strength in Small Packages
Optimizing Injection Methods Using High Quality Anaerobic Injection Water and Dealing with Low pH Groundwater During Bioremediation of Chlorinated Solvents
Successful enhanced in-situ bioremediation (EISB) remedies rely on the effective delivery of amendments to create conditions where microbial populations can thrive and degrade the contaminants of concern. Common challenges encountered during EISB include, difficulties preparing high quality anaerobic injection water to disperse amendments, oxidizing redox conditions in the aquifer, low pH and the absence of critical microbial populations. Increasingly, technical innovations are available to effectively deal with these obstacles.
Creating anaerobic conditions in aquifers was traditionally completed in advance of bioaugmentation through addition of electron donors. While effective, the development of reducing conditions can require weeks to months and often results in pH declines prior to bioaugmentation. In order to save time and mobilization costs, co-injection of electron donor and bioaugmentation cultures is increasingly being performed. For single mobilization injection events, the rapid preparation of anaerobic injection water from potable water supplies was facilitated at several sites by the use of chemical reductant mixtures that reduce water (ORP >-75 mV) without negatively impacting pH or otherwise inhibiting the bioremediation performance.
Modifying aquifer pH using buffering agents is challenging and alternate strategies to achieve complete dechlorination at lower pH are worth considering. In certain cases, especially where pH is near or slightly below 6.0, the use of bioaugmentation cultures acclimated to lower pH could reduce the need for aquifer neutralization. A low pH acclimated Dehalococcoides bioaugmentation culture has been applied at several sites to date. Results will be presented and lessons learned discussed.
Bioaugmentation Approaches for Anaerobic Benzene Remediation
Benzene and other gasoline range petroleum hydrocarbon compounds typically have faster degradation kinetics under aerobic conditions than anaerobic systems. However, aerobic bioremediation is not universally applicable, and anaerobic approaches may be more appropriate to address benzene contamination in anaerobic aquifers. Over the past 15 years, anaerobic enrichment cultures that are capable of complete degradation of benzene, toluene, o-xylene to carbon dioxide and methane (if methanogenic) have been developed by Dr. Edwards’ lab at the University of Toronto, and have recently been thoroughly characterized using next-generation sequencing technologies. This detailed characterization has clearly identified the organisms responsible for BTEX degradation (Luo et al, 2015).
The objectives of this new project include scaling up an anaerobic benzene bioaugmentation culture, demonstrating its effectiveness in laboratory treatability studies and ultimately testing the culture in field pilot trials. The culture will be used in laboratory treatability studies to evaluate the performance of the culture on contaminated materials from field sites. Information provided from this testing will include cell density requirements, degradation rates and the range of geochemical conditions for optimal performance, which will be used to design future field pilot trials. This presentation will focus on the scale up and performance of the culture in laboratory treatability studies and discuss lessons learned to apply the culture in the field.