Zero valent 
metal composite, manufacturing thereof, using thereof, and 
system including thereof, for (in-situ or ex-situ) catalytically treating 
contaminated water, such as sub-
surface water, 
surface water, above-
surface water, 
water vapor, or / and gaseous water. Composite includes powdered diatomite matrix incorporated with nanometer (1-1000 nm) sized particles of a zero valent (transition) 
metal (iron, 
cobalt, 
nickel, 
copper, 
zinc, 
palladium, 
platinum, or / and gold) and at least one 
electron transfer 
mediator (catalyst) from porphyrinogenic organometallic complexes (e.g., metalloporphyrins (chlorophylls, hemes, cytochromes) or metallocorrins (e.g., 
vitamin B12), and optionally, includes 
vermiculite. 
System includes composite and in-situ or / and ex-situ unit containing the composite, enabling 
exposure of 
contaminated water thereto. Applicable to in-situ sub-surface permeable reactive barriers (PRBs). Treatable 
water contaminants are organics (halogenated organic compounds), or / and inorganics (
metal elements, metal element containing inorganic species, 
nonmetal elements, and 
nonmetal element containing inorganic species). Applicable to non-aqueous fluids (liquids, vapors, gases), for removing contaminants therefrom.