Assessment of Drinking Water Quality from the Dobromierz Reservoir During the Treatment Process: Collection, Distribution and Future Challenges

Drinking water contamination during the treatment process remains a major problem for decision-makers responsible for the collection and supply of water to recipients. This article presents measurements of 33 parameters of drinking water quality in the years 2009–2023, taken from the Dobromierz reservoir in Poland, with particular emphasis on the stages of raw water, water undergoing treatment, and utility water. The results showed that the raw water tested is contaminated microbiologically (presence of coliform bacteria), organoleptically (worse turbidity, odor, color), and chemically (increased PAHs, nitrites, benzo(α)pyrene). This indicates improper maintenance of the areas around the reservoir, i.e., agricultural areas (the existing nutrient runoff), residential areas (the lack of stringent records of cesspools and septic tanks), and roadside (improper maintenance of ditch slopes). In most cases, water at the treatment stage and at the end recipients was effectively purified (in most cases, the analyzed parameters achieved a degree of compliance with drinking water standards of at least 95%). Only for the turbidity in the network, the standards did not reach the adopted minimum level. This suggests the need to conduct systematic investment activities in order to reduce failures in the network (average system failure rate of 34%). Moreover, the statistical analysis of the results showed significant changes in the parameters between raw water and water in the water supply network and at end recipients (p < 0.05). Therefore, it is necessary to focus on protecting the quality of raw water resources for more effective treatment and ensuring human health safety.