A STUDY ON THE QUALITY OF DRINKING WATER DISINFECTION IN SMALL SETTLEMENTS FROM STARA ZAGORA REGION, BULGARIA

Abstract

Introduction: Providing safe drinking water is an integral part of public health and a major task for water supply companies and health control agencies alike. Poor quality disinfection of drinking water significantly increases the risk of water-borne epidemics. In Bulgaria, villages and small towns are affected more often by failures in the disinfection due to negligence from water supply employees and technological limitations. Aims: To determine the quality of drinking water disinfection by measuring significant indicators (free chlorine, E.coli and coliforms) in samples from villages in Stara Zagora region. Materials and Methods: Water s amples were taken according to protocol directly from water taps in 50 villages in Stara Zagora region. Levels of free chlorine were measured using HACH DR/850 colorimeter and compatible reagents. 100 mL samples were inoculated with the medium Readycult ® Coliforms 100. The samples were incubated in a thermostat at 37°C for 24 hours and E.coli were identified using Kovac’s reagent. Results: Only in 5 samples (10%) free chlorine was adequate to the established norm of 0.3-0.4 mg/L. In 30 villages the levels of free chlorine were below 0.3 mg/L and cannot guarantee drinking water safety. In 15 villages (30%) were found coliforms above the acceptable norms (0/100 mL). Nine of these samples were positive for E. coli. Conclusion: The results showed significant deviation from the legally established norms for drinking water safety. More tests will be done to determine whether these problems are incidental or permanent.