[Drinking water safety from private wells in Zagreb]

Bacterial quality of water from private wells was examined seasonally during the year 2003 in 3 districts of Zagreb-Pesćenica, Trnje and Tresnjevka. The aim of the study was to estimate the quality of water consumed by 5% of citizens who are not connected to the public water supply system. Total coliforms, fecal coliforms and Enterococcer were determined by the multiple tube (most probable number) method, and the heterotrophic plate count by enumerating culturable microoorganisms. Samples taken from Trnje had the best water quality, and the worst were from Tregnjevka. 21 out of 34 examined samples were sanitarily unsatisfactory (61.8%). Only one private well had no bacterial contamination and was satisfactory in all four seasons. Total coliforms were detected in 24 samples and values were from 2 to >240/100 ml, and 16 samples had values above maximal allowed concentration (MAC). Fecal coliforms were detected in 17 samples and values were from 2 to >240/100 ml. Two samples contaminated by Enterococcus were taken from Tregnjevka (autumn) and Trnje (spring). Heterotrophic plate count (colony count) was present in all samples, values being from 1 to 1920/ml, but were above MAC in 8 samples.