Abstract: The present invention relates to systems and methods for the on-site generation (for example at oil well drilling operations, oil well hydraulic fracturing operations, makeup water pipeline transportation systems, and oil and gas refining operations) of haloamine chemistry such as chloramines and/or bromamines. The invention also relates to the application of the generated haloamines to control microorganisms such as bacteria as well their harmful byproducts such as hydrogen sulfide and other undesired substances found in oil and gas industries.