Soil Buffering Capacity Can Be Used To Optimize Biostimulation of Psychrotrophic Hydrocarbon Remediation

Effective bioremediation of hydrocarbons requires innovative approaches to minimize phosphate precipitation in soils of different buffering capacities. Understanding the mechanisms underlying sustained stimulation of bacterial activity remains a key challenge for optimizing bioremediation—particularly in northern regions. Positron emission tomography (PET) can trace microbial activity within the naturally occurring soil structure of intact soils. Here, we use PET to test two hypotheses: (1) optimizing phosphate bioavailability in soil will outperform a generic biostimulatory solution in promoting hydrocarbon remediation and (2) oligotrophic biostimulation will be more effective than eutrophic approaches. In so doing, we highlight the key bacterial taxa that underlie aerobic and anaerobic hydrocarbon degradation in subarctic soils. In particular, we showed that (i) optimized phosphate bioavailability outperformed generic biostimulatory solutions in promoting hydrocarbon degradation, (ii) oligotrophic biostimulation is more effective than eutrophic approaches, and (iii) optimized biostimulatory solutions stimulated specific soil regions and bacterial consortia. The knowledge gleaned from this study will be crucial in developing field-scale biodegradation treatments for sustained stimulation of bacterial activity in northern regions

In Situ Warming and Soil Venting to Enhance the Biodegradation of JP-4 in Cold Climates: A Critical Study and Analysis

Numerous bioremediation projects have proven effective in accelerating contaminant biodegradation by injecting oxygen into the vadose zone with a technique called bioventing. In cold climates, bioremediation is limited to the summer when soil temperatures are sufficient to support microbial growth. Laboratory studies directly correlate increased biodegradation rates with temperature. By raising soil temperatures, in situ jet fuel remediation can be accelerated which was shown by a bioventing project conducted in 1991 at Eielson AFB, Alaska, where three soil warming techniques were used. Two methods actively warmed the soil - warm water circulation and heat tape; the other passively warmed the plot with insulatory covers. All plots were compared to an uncontaminated area and an unheated contaminated control plot. This study critically analyzes the project data to determine its effectiveness in enhancing biodegradation. This study also models the temperature-biodegradation relationship at the test plots using the van\u27t Hoff-Arrhenius equation. Using paired oxygen consumption rates and temperatures, application of the equation was valid only for the warm water and passive warming plots. This study demonstrates that bioremediation is feasible in cold climates and can be enhanced by soil warming. Soil warming can significantly decrease remediation time with acceptable cost increases

Attenuation of Nitrate from Simulated Agricultural Wastewater Using an Immobilized Anaerobic Biofilm

A number of methods are currently in use for attenuating nitrates from wastewater with varying degrees of efficiency. Bioremediation using bacteria may be an efficient and cost effective method. In an anaerobic bioremediation system, nitrate can replace carbon dioxide as an electron acceptor and aids in nitrate attenuation by assimilatory reduction. The purpose of this study was to investigate nitrate attenuation in a hyperfiltration system using a pure culture of strictly anaerobic, facultative Methanobrevibacter ruminantium bacteria. Filtration experiments were conducted using amalgamated Na- montmorillonite clay-glass beads compacted at 500 psi differential hydraulic pressure with or without a biofilm. A simulated agricultural wastewater of 3.105×10-4 moles/L of NO3- was bioremediated. The use of bacteria in attenuating nitrates offers promising results on a bench-scale