The experiment was conducted in three model drinking water distribution systems (DWDSs) made of unplasticized polyvinyl chloride (PVC), silane cross-linked polyethylene (PEX) and high density polyethylene (HDPE) pipes to which tap water was introduced. After 2 years of system operation, microbial communities in the DWDSs were characterized with scanning electron microscopy, heterotrophic plate count, and denaturing gradient gel electrophoresis. The most extensive biofilms were found in HDPE pipes where bacteria were either attached to mineral deposits or immersed in exopolymers. On PEX surfaces, bacteria did not form large aggregates; however, they were present in the highest number (1.24 × 10⁷ cells cm⁻²). PVC biofilm did not contain mineral deposits but was made of single cells with a high abundance of Pseudomonas aeruginosa, which can be harmful to human health. The members of Proteobacteria and Bacteroidetes were found in all biofilms and the water phase. Sphingomonadales and Methylophilaceae bacteria were found only in PEX samples, whereas Geothrix fermentans, which can reduce Fe(III), were identified only in PEX biofilm. The DNA sequences closely related to the members of Alphaproteobacteria were the most characteristic and intense amplicons detected in the HDPE biofilm.

Designing of District metered areas (DMA) schemes is a key element in developing a technique for detecting and removing unreported leaks in a water distribution system (WDS) called active leakage control. The design of DMA is very specific to individual networks’ hydraulic and often constitutes one area with pressure managed zones. This paper presents the division of a selected water supply network zone into DMA areas. Based on the spatial distribution of the flow rate and the geometrical structure of the network (routes, pipe diameters, existing gate valves) in the analyzed water supply zone, the main transmission trunks were separated (DN150 ÷ DN500 diameter range) and were excluded from the division into metering areas. DMA areas were separated from the remaining parts of the network, using the district metered areas module, supporting the division of water supply networks into metering zones, available in the WaterGEMS software by Bentley. The number of nodes in the area was 200 as the main criterion for separating DMAs. The separated areas were combined into 3 main DMA zones, in which the sum of the pipe lengths varied between 2500 ÷ 3800 m. For each of the DMAs, the water supply route was determined individually, seeking a one-sided inflow to the isolated area. In two out of three cases, this goal has been achieved. In the third case, it turned out necessary to provide two-sided water inflow. The analysis of the correct operation of DMAs was based on the hydraulic modeling of WDS.

The process of shaping distribution network structures is one of the most fundamental design tasks, and determines the delivery certainty of media transported by them. It is especially crucial with reference to network elements of a critical character, such as roads or water supply, sewage, or electrical networks. In urban conditions, the geometric shaping of these structures has a quasi-chaotic character that is individual for each network and city. The complexity of these networks increases significantly with the size of a city, and therefore the evaluation of water delivery certainty is also a difficult issue. Despite many years of research, there is no universal method to evaluate this certainty. The objective of this paper is to present two original approaches: the number of minimal efficiency paths from a water source to reference consumption nodes, and the relation of this number to the fractal dimension of a network’s geometric structure. The developed methods were tested in the conditions of a few real water supply networks. The obtained results indicate that the analyzed methods can be used for the preliminary and relatively rapid evaluation of water delivery certainty.