The paper evaluates drinking water quality on selected dairy farms on the territory of the Czech Republic. The drinking water samples were collected in the farm milk storage rooms of 30 farms with subsequently made analyses. The pre – selected chemical and microbiological indicators were stated according to the regulation No. 252/2004 Coll. (pH, conductivity, chemical oxygen demand, colour, turbidity, Fe, ammonia ions, nitrites, nitrates, colony count growing at 36 °C, colony count growing at 22 °C, coliform bacteria, Escherichia coli, Ca, Mg, Na, K, Zn, Cu, Mn, Pb, Cr and Ni). The statistical evaluation was performed in the obtained data file and these data were compared with the limit values given by the regulation. The nitrate content ranged between 1 and 40.7 mg L−1 with an average of 15.6 mg L−1. The pH values varied from 5.71 to 8. The chloride concentration geometrical means was 7.57 mg L−1 1. The Ca average concentration 58.5 mg L−1 was in the middle of the recommended interval 40–80 mg L−1. The geometric means in Mg content was 7.9 mg L−1 being under the recommended value 20–30 mg L−1. The Cu, Pb, Cr and Ni limit values were not exceeded. The limit values in microbiological analyses were exceeded 18x in coliform bacteria, 10x in enterococci, 5x in Escherichia coli. The microbiological colonies growing at 36 °C exceeded limit 9x, those growing at 22 °C 5x.Further, differences are compared between the organic and conventional farms, and between farms producing milk in different type of LFAs (less favourable areas) and farms not included in these areas. The difference found out between the chloride concentrations in organic (6.56 mg L−1) and conventional farms (18.2 mg L−1; p < 0.05) was statistically significant. Locality or altitude, where a given far is situated, were another classifying criterion. A significant dependence was only found out in nitrate content, which decreased (p < 0.05) with increasing altitude (the correlation coefficient value −0.39). It can correspond with the soil use decrease – a lesser fertilization intensity. Statistically significant differences were found out in hardness value as well as in Ca, Mg contents connected with that in all reference criterions. The hardness was clearly lower (1.13 mmol L−1) in organic farms as compared with concentration 2.27 mmol L−1 in conventional ones. It is, however, only a supplementary indicator according to the respective regulation. No statistical significance was found among microbiological finding values in any case.
Change in dissolved oxygen concentrations during aeration and mixing using a combined system