The necessity to limit water use and for using recirculating economy leads to much attention being devoted to the reuse of backwash from filter flushing in water treatment plants. Pre-treatment of backwash water, especially the elimination of harmful substances and microorganisms, is necessary for its reuse. This paper presents an evaluation of the possibility of achieving water backwash biostability from surface and infiltration water treatment plants by subjecting it to chlorination or irradiation with UV light. The results of this study have shown that it is necessary to use large chlorine and radiation doses, irrespective of the type of treated water. At the same time, the optimal disinfection process parameters were determined, which ensured an elimination of pathogenic microorganisms, and limiting the number of other microorganisms. Both analyzed disinfection methods allow for the recirculation of backwash water into the beginning of the water treatment process, yet physical disinfection requires larger investments and operating costs. The increased cost in treating backwash water with UV as compared to chlorine is small, yet it eliminates the problem of the creation of disinfection by-products, whose concentration were significant, but did not exceed the values allowed for drinking water. The disinfection of backwash water from treating surface and infiltration water allowed for a reduction in sourced water in the amount of about 4% of treated water volume.