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CE 421/521- Environmental Biotechnology

Bioremediation of Military Explosives in the Environment

 Yonghui Shi

 ABSTRACT

 An extensive literature review was conducted for biological treatment of explosive contaminated water and soil. Explosive contaminants present in the environment are discharged by many military facilities. The most common forms of explosives are 2,4,6-trinitrotoluene (TNT), Hexahydro-1,3,5-trinitro-1,3,5-triazine or Royal Demolition Explosive (RDX) and HMX. All of these nitroaromatic contaminants are recalcitrant to normal treatment.  As an efficient and cost effective approach, biological methods have attracted more attention recent years. Three main available biological approaches to degrade explosive contaminants, composting, bioreactor, and in-situ treatment methods are stated and their application and advancement are discussed.

 KEYWORDS

 explosives; bioremediation; composting; bioreactor; phytoremediation

 INTRODUCTION

Many army ammunition plants, weapon installation and dismantling places across the United States produce large quantities of waste from explosives. Contaminants often present in the environment include 2,4,6-trinitrotoluene (TNT), Hexahydro-1,3,5-trinitro-1,3,5-triazine or Royal Demolition Explosive (RDX) and HMX (Drzyzga et al., 1999; Freedman and Sutherland, 1998; Bhadra et al., 2001). The organic nitrogen compounds found in these contaminants, are toxic in nature as well as suspected carcinogenic. TNT has been shown to be able to affect the central nervous system and cause liver damage. RDX is even more toxic and has been used as a rat poison. These waste products, if released untreated, may result in contamination of the soil and ground water, thereby cause negative effect on the human health and may have a detrimental effect on the environment.

 Normally, the treatment methods available can be grouped into three categories, i.e., physical, chemical and biological methods. Lots of research has been made to develop efficient and cost-effective methods to remove these harmful pollutants from environment.  Biological methods, which have gained much attention in recent years, utilize bacteria, fungi or plants to degrade the recalcitrant nitro components into harmless inorganic ones.

 Compared to the former two methods, biological methods have long been favored for their advantages in their cost and efficiency. Different forms of these methods are discussed and both advantages and disadvantages are mentioned.

 PHYSICAL AND CHEMICAL METHOD 

 As a main physical method, granular-activated carbon (GAC) is a standard technology used for explosives-contaminated ground water treatment based on its adsorption ability. It can remove a wide range of explosive materials and their byproducts from wastewater efficiently. Moreover, the GAC treatment process is relatively simpler than other methods with its main component being a tank filled with GAC.

Although GAC is effective, it is more expensive compared with other methods, especially biological method. It also needs careful maintenance to keep the GAC treatment process work in an optimal status. Pretreatment must be adopted to remove the suspended solids from groundwater, and the GAC saturated with the explosive must periodically be regenerated or destructed by incineration.