A combination biocide including OPA, quaternary phosphonium biocide (TTPC), alcohol (preferably isopropyl alcohol), and functional excipients for use in the oil and gas recovery industry or for vessel ballast water treatment. The functional excipients for the oil and gas recovery industry are an optional cellulose type proppant, a poloxamer wetting agent, a friction-reducing pluronic block copolymer, a drag reducing agent such as polyethylene oxide, and a flocculating agent. The proppant is unnecessary for vessel ballast water treatment. In both applications the OPA is the dialdehyde C6H4(CHO)2 form. It will produce an inherent cidal effect and lower surface tension and thus aids in the spread of the TTPC on biofilm covered surfaces where it is readily absorbed by the negative surfaces of proteins and bacteria. It thus serves as a binding cidal agent between the TTPC and the application surface. The foregoing constituents are combined in preferred concentrations within acceptable ranges to provide a synergistic biological chemical complementarity system.
