Chlorine is a strong oxidizing agent and is the conventional chemical used in the disinfection process for water purification, reducing the risk of pathogenic infection. However, it may represent a chemical threat to human health due to waste and hazardous disinfection by-products formed as trihalomethanes, nitrosamines, chlorophenols, among others. This paper aims is to assess and monitor the concentration of free chlorine and chloramines in drinking water distributed in the city of Arequipa, to establish whether it is within the parameters set by the competent authority. Three monthly monitoring were performed in the distribution network of the three water treatment plants, performing the DPD spectrophotometric method, the experimental values to first order kinetic model were adjusted using the value of k = 0.0018 as decay constant. The values of free chlorine and chloramines, showed s...