the dispersion composition includes a nonionic polymeric surfactant preferably the polymeric surfactant is an acrylic graft copolymer having a poly methyl methacrylate methacrylic acid backbone and polyethylene oxide side chains more preferably the acrylic graft copolymer is a copolymer of methyl 2 methyl 2 propenoate and alpha 2 methyl 1 oxo 2 propenyl omega methoxypoly oxy 1 2 ethanediyl one especially preferred acrylic graft polymer is commercially available from crodia international of cowick hall yorkshire england previously uniqema under the tradename atlox 4913 the dispersion composition additionally includes an ionic surfactant which is an alkoxylated polyarylphenol phosphate ester or a salt or an acid form thereof for example the ionic surfactant may enter the water based solvent in the form of a sodium an ammonium or a potassium salt and subsequently dissociate in the course of dissolving tristyrylphenolethoxylate phosphate ester and its salt and acid forms are preferred the potassium salt of tristyrylphenolethoxylate phosphate ester hereinafter referred to as u201c tsppe u201d which is commercially available from rhodia inc under the tradename soprophor flk is especially preferred examples of relatively water insoluble antimicrobially active materials which are useful as bactericides fungicides or algaecides in the present invention include 1 2 benzisothiazol 3 2h one bit 2 octyl 2h isothiazol 3 one oit 2 methyl 2h 5 chloro 2 methyl 2h isothiazol 3 one cit and isothiazol 3 one mit pyrithione zinc zpt 3 iodo 2 propynyl butylcarbamate ipbc 2 methylthio 4 ethylamino 6 tert butylamino s triazine terb and 3 4 isopropylphenyl 1 1 dimethylurea ipu further the following are possible examples for the use of the invention carbendazim bcm dichloroctylisothiazolinone dcoit thiabendazole tbz cybutryn diuron dazomet chloracetamide tebuconazole ortho.