Disinfection of potable water sources on animal farms and their microbiological safety

The aim of this study was to examine drinking water on three farms in eastern Slovakia and to determine experimentally the optimum dose for adequate disinfection in terms of devitalisation of potential pathogens while observing the limit for residual active chlorine (0.3 mg/l) in drinking water. Our investigations included bacteriological examination focused on general contamination and indicator bacteria (bacteria cultivated at 22 and 37 °C, total coliforms, E. coli, enterococci), physico-chemical examination (pH, ammonium ions, nitrites, nitrates, chlorides, free chlorine, chemical oxygen demand CODMn and Ca + Mg), and EEM (excitation emission matrix) fluorescence spectroscopy which focused on the presence of natural organic matter (NOM). After determining the optimum single dose of Chloramine T for disinfection of water used for watering of animals, the bacteriological quality of water was checked on the 5th day after the disinfection. The results showed that water quality was better on Farm No. 3 than on Farms No. 1 and No. 2. The weather (precipitation) evidently affected the quality of water on all three farms and was associated with some risk to animals consuming this water. The experimentally determined doses of Chloramine T appeared relatively efficient on Farm No. 1 and Farm No. 3, while the Chloramine T dose estimated for adequate disinfection on Farm No. 2 had to be increased considerably but was still much lower than the dose recommended by the manufacturer of this preparation. It appeared effective to adjust the intervals between individual chlorine treatments according to weather conditions (heavy rain) instead of increasing the active chlorine dose.