The present study proposes a chlorination schedule calibrated for the Drinking Water Distribution Network (DWDN) of Buzau  a medium sized city, in South-Eastern Romania. The numerical model of Buzau's DWDN was set up in EPANET, considering the main pipes of the network that interconnect 4 pumping stations and 45 booster stations (viewed here as end-users). The calibration of the numerical model was based on real-time recordings available for January and July 2014. The chlorination scheduling was simulated at each reservoir supplying a pumping station, by a variable injection pattern added to the EPANET DWDN model. The injected amount of chlorine was determined by values of the chlorine concentration obtained at 4 key monitoring points, spread over the network. The simulations were performed over an extended time period of 72 hours. The system behaviour has been analysed for two cases: with all pumping stations in operation, and with the biggest pumping station shutdown. For each case, the proposed schedule corresponds to the injection in the network of less chlorine than the corresponding recorded values for January and July 2014, and yet obtaining at the 4 key points a chlorine concentration variation similar to the recorded one, while the chlorine concentration at the end users was within the admissible range, across the whole DWDN.

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We focus on the operation of a real centre pivot irrigation system. The system encountered problems in 2016 and did not operate for several weeks due to the low level of the Danube (its water source). In that period, water level in the Danube went below the most probable minimal level during summer, with a return period of 30 years. With a natural desire to solve the problem, the owner of the system added a new pump near the water intake. This new, double-entry vertical axis pump, coupled in series with the existing pumping station situated further downstream, added roughly 1 bar to the pressure in the system. Things went well till the end of summer 2017 when, due to a pressure surge in the pumping station (most likely at shutoff head), one of the anti- vibration joints detached suddenly from the discharge pipe, and the pumping station was entirely flooded. The performed analysis helped understand the reasons of the accident and provided solutions (including pumping operating rules and schedule for pivots that can be operated simultaneously) that will hopefully avoid reoccurrences in the future, without affecting the day to day operation of the system.

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