Microbial remediation of insensitive munitions compounds and their transformation products: from biodegradation mechanisms to engineered strategies

Insensitive munitions compounds (IMCs), such as 2,4-dinitroanisole (DNAN), 3-nitro-1,2,4-triazol-5-one (NTO) and nitroguanidine (NQ), are replacing conventional explosives due to their higher detonation temperatures and greater resistance to mechanical shocks, making them safer for handling and storage. IMCs can contaminate the environment through the dissolution of undetonated residues in military training ranges or the discharge of wastewater from IMCs manufacturing. Developing remediation strategies has become imperative, given the toxicity and, in some cases, carcinogenicity of IMCs or their transformation products. Bioremediation offers a cost-effective method to treat IMCs, potentially converting hazardous contaminants into harmless products. Recent years have seen a surge in research focused on various strategies for IMCs bioremediation. Thus, a review becomes imperative to consolidate findings and guide future research in this field. This work aims to provide the first comprehensive guidelines for the microbial remediation of IMCs and their transformation products. It starts by explaining the mechanisms involved in anaerobic biotransformation and aerobic mineralization of IMCs. It then explores different types of bioreactor systems used for treating both individual IMCs and their mixtures. Finally, it provides potential bioremediation approaches for handling wastewater from munitions manufacturing facilities and addressing groundwater and soil contaminated by IMCs. The focus is to support scientists, engineering consultants, and site remediation managers in developing and optimizing effective microbial remediation strategies for IMCs contamination.