Recently, alternative water treatment systems have been implemented due to the eutrophication of reservoirs, in which high concentrations of organic matter prevent the use of conventional water treatment methods. This paper presents a study on the electrolytic process for water treatment using an alternating current. A reactor with iron and stainless steel electrodes was built and introduced into a water treatment system equipped with conventional coagulation with alum and direct descending filtration. Factors such as pH levels, turbidity, colour, and reductions in the specific UV absorbance were evaluated. The results showed a significant reduction in the specific UV absorbance between raw water and treated water (19.51–26.45%). Furthermore, the reactor did not significantly change the pH of the water. The average turbidity of the treated water was less than or equal to 0.5 NTU, and the average colour reached 2 HU, classifying the treated water as drinking water according to the current ordinance in Brazil. The cost of the electricity used by the reactor was $0.10 per cubic metre of water produced.