The influence UV/chlorination process on changes of biodegradable fraction in water

The aim of the research was to assess changes in the content of biodegradable dissolved organic carbon and assimilable organic carbon after disinfection process in groundwater from a backyard well and in surface water from a dam reservoir, from which a water supply company collects and treats water. Two types of disinfection processes were carried out, chlorination and UV enhanced chlorination, respectively. Sodium hypochlorite was applied as the disinfectant used in the tested water treatment plant. The content of selected forms of organic carbon, i.e. total organic carbon, dissolved organic carbon, biodegradable dissolved organic carbon and assimilable organic carbon, was determined in the waters before and after disinfection processes. The studies have shown that the applied disinfection processes significantly reduce the biodegradable dissolved organic carbon and assimilable organic carbon content in surface water sampled from the dam reservoir. Assimilable organic carbon concentration in water after 30 min and 24 h of contact decreased by 75.0 and 81.3%, respectively, biodegradable dissolved organic carbon by 50.0 and 55.3%. The results obtained in this study provide valuable information on the impact of the chemical oxidants most commonly used for disinfection on the content of biodegradable organic matter. This will allow to select appropriate disinfection methods to prevent secondary development of microorganisms in the distribution system. In these studies, the usage of monitoring of biodegradable dissolved organic carbon and assimilable organic carbon content after disinfection processes to assess the risk arising from a secondary microbial growth was considered. The proposal of a new approach to the content of biodegradable dissolved organic carbon and assimilable organic carbon after disinfection processes is aimed at encouraging the extension of research assessing the risk associated with water consumption depending on the content of biodegradable matter.