The most common cause of diseases in swimming pools is the lack of sanitary control of water quality; water may contain microbiological and chemical contaminants. Among the people most at risk of infection are children, pregnant women, and immunocompromised people. The origin of the problem is a need to develop a system that can predict the formation of chlorine water disinfection by-products, such as trihalomethanes (THMs). THMs are volatile organic compounds from the group of alkyl halides, carcinogenic, mutagenic, teratogenic, and bioaccumulating. Long-term exposure, even to low concentrations of THM in water and air, may result in damage to the liver, kidneys, thyroid gland, or nervous system. This article focuses on analysis of the kinetics of swimming pool water reaction in analytical device reproducing its circulation on a small scale. The designed and constructed analytical device is based on the SIMATIC S7-1200 PLC driver of SIEMENS Company. The HMI KPT panel of SIEMENS Company enables monitoring the process and control individual elements of device. Value of the reaction rate constant of free chlorine decomposition gives us qualitative information about water quality, it is also strictly connected to the kinetics of the reaction. Based on the experiment results, the value of reaction rate constant was determined as a linear change of the natural logarithm of free chlorine concentration over time. The experimental value of activation energy based on the directional coefficient is equal to 76.0 $[kJ\times {mol}^{-1}]$. These results indicate that changing water temperature does not cause any changes in the reaction rate, while it still affects the value of the reaction rate constant. Using the analytical device, it is possible to constantly monitor the values of reaction rate constant and activation energy, which can be used to develop a new way to assess pool water quality.

The article presents selected elements of the research task realized within the project “OHT Intelligent HVAC optimizer as a function of the THM potential for indoor siwmming pools - a new method of electricity and heat management that adjusts ventilation, heating and cooling control (HVAC) to carcinogenic chlorogenic hydrocarbon concentrations such as THMs and their removal from indoor pools.” The authors focused on the presentation of test stand, the control of which has been adapted to the needs of research into the characteristics of the amperometric probes used to determine the free chlorine concentration in aqueous solutions. Implemented control system is based on Siemens PLC controller. Performing the research allowed to optimize the working conditions of the system, implement the first part of industrial research and to draw important conclusions allowing to understand and describe the quantitative determination of chlorine in aqueous solutions by means of amperometric methods.