COMPARATIVE ASSESSMENT OF DISINFECTION ALTERNATIVES FOR MEDIUM-SCALE WATER TREATMENT PLANTS

Abstract

Disinfection is an essential step in drinking water treatment, with conventional chlorination being the most widely adopted method in Water Treatment Plants (WTPs) in Brazil. This study presents a comparative analysis between conventional chlorination and alternative disinfection methods applicable to medium-sized WTPs, based on a case study conducted at the ETA Nova, located in the municipality of Barra Mansa, Rio de Janeiro, Brazil. The plant supplies approximately 110.000 inhabitants and operates with an average treatment flow rate of about 350 L/s. The evaluation was performed through a qualitative and comparative approach, considering criteria related to microbiological efficiency, operational feasibility, costs, occupational safety, and maintenance requirements, supported by the GUT Matrix (Gravity, Urgency, and Trend) and operational risk assessment tools. The results indicate that conventional chlorination provides adequate disinfection efficiency and low direct costs; however, it involves significant operational risks associated with the handling and storage of chlorine gas. Ultraviolet disinfection demonstrated high microbiological inactivation efficiency but does not ensure a disinfectant residual in the distribution network, requiring complementary processes. Ozonation showed high disinfection performance but presented greater operational complexity and higher implementation and operational costs. In contrast, on-site sodium hypochlorite generation achieved the best overall performance, combining effective disinfection, reduced occupational risks, simplified operation and maintenance, lower operational costs, and compliance with residual disinfectant requirements. Overall, the findings indicate that on-site hypochlorite generation represents the most suitable disinfection alternative for medium-sized WTPs under similar operational conditions.