TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The peroxide source is carbamide peroxide, percarbonate, perborate and/or persulfate. The hydrogen peroxide generating enzyme is glucose oxidase. The enzyme substrate is glucose. The halide is in the form of a halide salt of an alkaline metal or alkaline earth metal. The halide is ammonium bromide, sodium bromide, potassium bromide, calcium bromide, magnesium bromide, sodium iodide, potassium iodide, ammonium iodide, calcium iodide, magnesium iodide, ammonium chloride, sodium chloride, potassium chloride, calcium chloride, and/or magnesium chloride. The halide and the ammonium source are provided by an ammonium halide, preferably ammonium bromide, quaternary ammonium halide, or polyquaternary ammonium halide. The halide and ammonium are both provided by benzalkonium chloride, (oxydiethylene glycol)bis(coco alkyl)dimethyl ammonium chloride, N,N-dichlorobenzene sulfonamide, N,N-diethyl-N-dodecyl-N-benzylammonium chloride, N,N-dimethyl-N-octadecyl-N-(dimethylbenzyl)ammonium chloride, N,N-dimethyl-N,N-dodecylammonium chloride, N,N-dimethyl-N,N-didodecylammonium chloride, N,N,N-trimethyl-N-tetrahexylammonium chloride, N-benzyl-N,N-dimethyl-N(ChlD 12-18C alkyl) ammonium chloride, N-(dichlorobenzyl)-N,-N-dimethyl -N-dodecylammonium chloride, N-hexadecylpyridinium chloride, N-hexadecylpyridinium bromide, N-hexadecyl-N,N,N-trimethylammonium bromide, N-dodecylpyridinium chloride, N-dodecylpyridinium bisulphate, N-benzyl-N-dodecyl-N,N-bis(beta-hydroxy-ethyl)ammonium chloride, N-dodecyl-N-benzyl-N,N-dimethylammonium chloride, N-benzyl-N,N-dimethyl-N-(12-18C alkyl)ammonium chloride, ethyl-n-hexadecyl dimethylammonium bromide, N-dodecyl-N,N-dimethyl-N-ethylammonium ethyl sulfate, N-dodecyl-N,N-dimethyl-N-(1-naphthylmethyl)ammonium chloride, N-hexadecyl-N,N-dimethyl -N-benzylammonium chloride or N-dodecyl-N,N-dimethyl-N-benzylammonium chloride. The halide and ammonium are preferably provided by poly(oxyethylene-(dimethyliminio)ethylene(dimethyliminio)-ethylene dichloride), or bis (2 -chloroethyl)ether-N,N,N',N'-tetramethylethylenediamine copolymer. The halide is lysozyme chloride or any enzyme in a halide buffer solution. The antialgal agent is provided to an aqueous system by adding the haloperoxidase, peroxide source, halide, and ammonium source to the aqueous system so that the haloperoxidase has a concentration in the aqueous system of 0.01-1000 ppm. The haloperoxidase is preferably 0.1-50 ppm. The peroxide source is present preferably at 0.1-200 ppm. The halide is preferably present at 1-500 ppm. The ammonium source is preferably present at 0-500 ppm. The peroxide source is preferably hydrogen peroxide. The peroxide source can also be an enzymatic hydrogen peroxide generating system that comprises a hydrogen peroxide generating enzyme and an enzyme substrate that is acted upon by the enzyme to produce hydrogen peroxide. The composition is maintained in a non-reacting form for a period of time by keeping the glucose oxidase physically separated from the haloperoxidase, glucose and quaternary or polyquaternary ammonium halide. The glucose oxidase is kept under anaerobic conditions. The material or medium is in the form of a solid, dispersion, an emulsion, or a solution.    TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Components: The aqueous system is a metal working system, a cooling water system, a waste water system, a food processing system, a dinking water system, a leather-processing water system, a white water system, a paper-making system or paper-processing system. The controlling growth of algae in an aqueous system is carried out by providing the antialgal agent to intake water of a metal working system, a cooling water system, a waste water system, a food processing system, a drinking water system, a leather-processing water system, a white water system for paper-making process, a paper-making system or a paper processing system. ACTIVITY - Antialgal.    MECHANISM OF ACTION - Algae growth inhibitor. The Pour Plate Count agar was prepared. The sample (1 ml) was placed on the center of a sterile petri dish by using a sterile pipette. Sterile, molten (44-46degreesC) plate count agar (pH 7) was added and mixed with the sample by swirling the plate. The samples were allowed to cool at room temperature until solidified and then were inverted and incubated at 35plus minus0.5degreesC for 48plus minus2 hours. Colonies formed in or on the plate count medium within 48plus minus2 hours were counted. The results were reported as CFU/ milliliter produced 90% kill at greater than 0.5-1.