In the present technical note, a simple methodology for identifying the source location of an accidental contamination in a water distribution network is formulated. Starting from measured solute concentration data and using the pollution matrix concept, the methodology first selects a group of candidate nodes, which are possible intrusion points. Among all candidate nodes, the source location is then identified, minimizing the differences between simulated and measured concentrations. The source location procedure, which incorporates a hydraulic network simulation model, is formulated as an optimization problem, linearized using the water fraction matrix concept. An example illustrates methodology effectiveness. An uncertainty analysis is performed in order to demonstrate the methodology robustness with respect to uncertainties in some input data, like concentration measurements and water demands.

Efficient management of a sewer system includes the control of the conveyed wastewater quality to adequately operate treatment plants and protect the receiving water bodies. Moreover, these systems are vulnerable to either accidental spills or intentional unauthorized discharges. To properly manage them, a limited number of sensors could be placed at different locations to monitor the water quality. In this paper, multiobjective and single-objective optimization procedures to optimally locate sensors in sewer systems are proposed, tested, and compared. The multiobjective procedures include objective functions related to information theory (IT procedure), detection time and reliability (DR procedure), and a combination of them (IT_DR procedure). The single-objective procedures include a greedy-based objective function (GR procedure) and a merged objective function (DR_IT_GR procedure). The procedures show a similar performance when applied on a small network, whereas in a real system, the results show that (1) the IT-based method can be effectively used as a filtering technique; (2) the DR_IT_GR procedure outperforms the other multiobjective ones; and (3) the GR procedure is very efficient in finding the Pareto extreme solutions.

Plastic pipes are widely used in pressurized water systems. Their viscoelastic behavior has to be taken into account in the design phase as well as in the interpretation of water-hammer signals for diagnostic purposes. The aim of the present paper is to experimentally investigate the transient waves’ transmission and reflection in branched networks of high density polyethylene (HDPE) pipes and to test the efficacy of a viscoelastic model for the interpretation of the results. Two laboratory Y-shaped systems were built in the Water Engineering Lab of the University of Cassino and Southern Lazio (Italy) and a set of water-hammer tests was conducted on them. A significant variation of transmission and reflection coefficients at the pipe junction is observed in comparison with the values suggested in classical textbooks. The strong agreement between the experimental pressure values and those obtained using the viscoelastic model suggests that the differences from the classical theory are due to the vi...

The impact of a dam-break wave on an erodible embankment with a steep slope is studied in the paper using both experimental and numerical approaches. The laboratory experiments have been specifically designed and performed for a range of the storage water levels and the embankment elevations and slopes. The simulations were carried out using a recently-developed two-phase depth-integrated model, supplemented with a geofailure operator to account for the possible occurrence of geotechnical collapses. A comparison between numerical and experimental results indicates that the two-phase model reproduces the experimental free surface elevation well, with or without the geofailure operator. On the other hand, especially for high embankment slopes, this operator appears to be important for predicting the observed morphological evolution. The results also show that, due to the geotechnical collapses, water and sediment velocities may have opposite signs. While the models based on equal direction of the liquid and the solid motions cannot reproduce this effect, the proposed two-phase approach easily accounts for such a peculiarity of the investigated process.

Chlorination is the most widely used method for disinfection of drinking water, but there are concerns about the formation of by-products, such as trihalomethanes (THMs), since the chronic exposure to them may pose risks to human health. For these reasons regulations fix maximum acceptable THMs levels throughout distribution networks, so it is very important to be able to correctly reproduce their formation. In the literature many models for predicting THMs formation have been developed, both based on empirical relationships and on kinetics involved during chlorine reactions. In this work the use of some of these models and their reliability in real situations is investigated through the application to the Aurunci-Valcanneto Water Supply System in Southern Lazio (Italy). The comparison of the performances of 18 selected literature empirical models furnishes interesting observations, indicating that the formula, developed using field data, results in being more suitable for reproducing THMs formation for the presented case study. Other considerations are also offered from the comparison with the results obtained using a simple first order kinetic model, calibrated using measured data.