A phosphate-free, highly-concentrated aqueous dispersion composition comprising at least one biocide, sulfosuccinate based surfactant, block copolymer, suspending agent, and optionally an antifoaming agent and desired additives if any. The composition of the present application is significantly stable against heat, cold, transit, storage and dilution for at least 18 months. The preferred biocides of the dispersion composition are 2-meth-4-isothiazolin-3-one (MIT), 1,2-Benzisothiazolin-3-one (BIT), 5-Chloro-2-methyl-4-isothiazolin-3-one (CMIT), 2-Octyl-4-isothiazolin-3-one (Off) 3-Iodo-2-propynylbutyl carbamate (IPBC), oxyfluorfen, thiabendazole, terbutryn, zinc pyrithione (ZnPy), bronopol, folpet, diiiron, dehydroacetic acid (DHA), dazomet and carbendazim alone or in combination. Also disclosed is a process for preparing the dispersion composition and appropriate applications thereof.