## 1 Introduction  
The quality of tap water is important for the functioning of households and industry. When the source of a water supply is a river, water quality is determined by both natural factors (geological conditions, forest cover, and climate in the river basin) and anthropogenic factors (pollutions from agriculture, households, industry, hospitals, etc., in the form of sewage and surface runoff) [1]. Common water pollutants include pathogenic bacteria and viruses, mainly originating from domestic sewage and agricultural activities [1]. A sudden, uncontrolled increase in the number of pathogens may occur as a result of water treatment plant failure, the overflow of the sewage system due to heavy rainfall, and other crisis situations [2]. The microbiological purity of water is usually determined by the content of _Escherichia coli_ (_E. coli_) and fecal coliform bacteria.  
Disinfection is an important step in the preparation of drinking water and wastewater treatment. A commonly used and economical method of disinfection is chlorination, which effectively inactivates bacteria and other pathogens. However, molecular chlorine reacts with dissolved organic matter to form chlorinated by-products that are hazardous to human health [3,4]. Typical examples of toxic halogenated by-products are trihalomethanes and haloacetic acids [5]. An alternative to chlorination may be ozonation or UV radiation. These techniques are very effective for primary disinfection, but long-lasting chlorine remains superior for secondary disinfection of water distribution systems [4]. The main disadvantage of ozonation and UV radiation is their high energy consumption [6].  
Hydroxyl radicals are also very effective disinfectants. Due to their high oxidizing potential, hydroxyl radicals easily damage cell membranes and DNA, leading to the death of bacteria [7]. Compared to chlorine, hydroxyl radicals are more environmentally friendly because they destroy bacteria without leaving toxic by-products. Catalytically generated hydroxyl radicals have been successfully tested on real samples from municipal wastewater treatment plants [8,9]. The Fenton process has been proven to provide effective disinfection, especially when used after coagulation/flocculation of wastewater [9].  
Compared to the homogeneous Fenton catalyst, heterogeneous catalysts (Fenton-like catalysts) have the advantage that they can be used for a long time. Fenton-like catalysts effectively produce hydroxyl radicals from hydrogen peroxide [8,10]. Typical Fenton-like catalysts are oxides of transition metals [11]. Among metal oxide catalysts, compounds with a spinel crystal structure are of particular interest due to their adjustable properties [12]. Changing the elemental composition and annealing can cause a transition from the normal spinel structure to the inverse spinel structure. As a result, oxygen vacancies and other structural defects are created that act as catalytic sites [13]. Recently, hydrogen peroxide has been tested for bacterial inactivation in continuous-flow mode using hematite [14] and cobalt ferrite [15] catalysts. The effect of H\({}_{2}\)O\({}_{2}\) and inorganic anion concentrations was investigated.  
This paper examines in detail the kinetics of H\({}_{2}\)O\({}_{2}\) decomposition and bacterial inactivation. Disinfection tests were conducted using bacterial counts similar to those found in natural river water.