Water is a natural product that is needed in many industrial uses, but some processes like washing or cooling do not require drinking water. In this work we investigated the efficiency of an electrolytic treatment of surface waters in order to increase their quality. The waters were taken from a river and in a pond and they were treated by electrocoagulation-electroflotation with an aluminum soluble anode. Vital nutriments for the bacteria development were consumed during the electrolysis. This treatment led to great decreases of molecular oxygen, phosphate and nitrate anions and dissolved organic compounds. Each of these decreases may explain the disinfection effect that was observed for the total flora. Moreover, the X-ray diffraction of the electro-generated solid showed the presence of nanocrystallites that could be involved in a bactericidal effect. After the electrocoagulation-electroflotation treatment, the investigated waters exhibited an increased quality for a cooling use.