By-products in surface and reclaimed water disinfected with various agents

Pollution of natural water resources and water shortages make it difficult to cope with the total demand for water (potable, industrial, agricultural uses). As a consequence, the interest for alternative resources, such as reclaimed wastewater, is growing. In this field, new needs are coming to the attention of researchers, especially with respect to compounds potentially toxic for the environment and human health. Disinfection by-products (DBPs) formation is therefore a subject to be closely examined since the disinfection process is the final step of nearly all post-treatment schemes. Information on DBPs formation, when biologically treated and filtered wastewater is disinfected with sodium hypochlorite (NaClO), peracetic acid (PAA) or UV irradiation, is given with reference to the results of long-term pilot-scale research on disinfection for wastewater reclamation and reuse. When NaClO was used, total trihalomethanes (TTHMs) concentration did not comply with the new Italian law for direct agricultural reuse, despite the good quality of the effluent to be reclaimed. On the contrary, the use of PAA, quite frequently utilised as a NaClO substitute in Italy, led to no significant DBPs formation. A set of tests using UV irradiation confirmed, also in this field, the overall safety of this disinfection agent with respect to DBPs formation. This work deals also with drinking water treatment, giving information on the risk of DBPs formation when PAA is used for surface water pre-disinfection. In this case, very low concentrations of aldehydes were observed and no formation of halogenated by-products was evidenced, even at high TOC content.