Wastewater sludge is a complex raw material that can support growth and protease production by Bacillus licheniformis. In this study, sludge was treated by different thermo-alkaline pre-treatment methods and subjected to Bacillus licheniformis fermentation in bench scale fermentors under controlled conditions. Thermo-alkaline treatment was found to be an effective pre-treatment process in order to enhance the proteolytic activity. Among the different pre-treated sludges tested, a mixture of raw and hydrolysed sludge caused an increase of 15% in the protease activity, as compared to the untreated sludge. The benefit of hydrolysis has been attributed to a better oxygen transfer due to decrease in media viscosity and to an increase in nutrient availability. Foam formation was a major concern during fermentation with hydrolysed sludge. The studies showed that addition of a chemical anti-foaming agent (polypropylene glycol) during fermentation to control foam could negatively influence the protease production by increasing the viscosity of sludge.

Nitroglycerin (NG) is often present in soils and sometimes in pore water at antitank firing positions due to incomplete combustion of propellants. Various degradation processes can contribute to the natural attenuation of NG in soils and pore water, thus reducing the risks of groundwater contamination. However, until now these processes have been sparsely documented. This study aimed at evaluating the ability of microorganisms from a legacy firing position to degrade dissolved NG, as well as NG trapped within propellant particles. Results from the shake-flask experiments showed that the isolated culture is capable of degrading dissolved NG but not the nitrocellulose matrix of propellant particles, so that the deeply embedded NG molecules cannot be degraded. Furthermore, the results from column experiments showed that in a nutrient-poor sand, degradation of dissolved NG may not be sufficiently rapid to prevent groundwater contamination. Therefore, the results from this study indicate that, under favorable soil conditions, biodegradation can be an important natural attenuation process for NG dissolving out of fresh propellant residues. In contrast, biodegradation does not contribute to the long-term attenuation of NG within old, weathered propellant residues. Although NG in these old residues no longer poses a threat to groundwater quality, if soil clean-up of a legacy site is required, active remediation approaches should be sought.