This article summarizes the author's 30+ year journey in the field of chemical oxidation processes for water treatment. Initially, the efficiency of chemical oxidants for micropollutant abatement was assessed based on the removal of target compounds, which is controlled by reaction kinetics and second-order rate constants. Today, with extensive experimental data, predictions can be made for compounds without experimental data using Quantitative Structure Activity Relationships and quantum chemical computations. However, chemical oxidation processes are economically limited, leading to incomplete transformation of micropollutants and the formation of transformation products. These products may be less active, more toxic, or more biodegradable than the original compounds. Chemical oxidants also react with water matrix components like dissolved organic matter (DOM), bromide, and iodide, consuming most of the oxidant and forming disinfection byproducts. The formation of transformation products and disinfection byproducts is inherent to oxidation processes, and their biological effects, toxicity, and biodegradability are important factors to consider. Chemical oxidation processes are complex to understand and manage, but research has led to a good understanding of the underlying processes, allowing their optimized application in water treatment. The article discusses the kinetics, mechanisms, toxicity, and biodegradability of transformation products, as well as the formation of disinfection byproducts. It also highlights the role of bromide and iodide in oxidation processes and the formation of inorganic DBPs like bromate and iodate. The article concludes that chemical oxidation processes require careful consideration of various factors to ensure their effectiveness and safety in water treatment.This article summarizes the author's 30+ year journey in the field of chemical oxidation processes for water treatment. Initially, the efficiency of chemical oxidants for micropollutant abatement was assessed based on the removal of target compounds, which is controlled by reaction kinetics and second-order rate constants. Today, with extensive experimental data, predictions can be made for compounds without experimental data using Quantitative Structure Activity Relationships and quantum chemical computations. However, chemical oxidation processes are economically limited, leading to incomplete transformation of micropollutants and the formation of transformation products. These products may be less active, more toxic, or more biodegradable than the original compounds. Chemical oxidants also react with water matrix components like dissolved organic matter (DOM), bromide, and iodide, consuming most of the oxidant and forming disinfection byproducts. The formation of transformation products and disinfection byproducts is inherent to oxidation processes, and their biological effects, toxicity, and biodegradability are important factors to consider. Chemical oxidation processes are complex to understand and manage, but research has led to a good understanding of the underlying processes, allowing their optimized application in water treatment. The article discusses the kinetics, mechanisms, toxicity, and biodegradability of transformation products, as well as the formation of disinfection byproducts. It also highlights the role of bromide and iodide in oxidation processes and the formation of inorganic DBPs like bromate and iodate. The article concludes that chemical oxidation processes require careful consideration of various factors to ensure their effectiveness and safety in water treatment.