Methods of treating ground water and methods for reducing contaminants (e.g., chlorinated compounds in contaminated ground water) to harmless compounds in the presence of an elemental metal treatment composition. Said methods comprise injecting a treatment solution comprising a colloidal suspension of elemental metal particles (e.g., iron, a tin, a zinc, a palladium and mixtures thereof) having a nanoscale particle size and a carbohydrate in an organic liquid (e.g., dodecane, butyl acetate and polypropylene glycol ethyl ether acetate and mixtures thereof) into the ground, proximate to the contaminated ground water.