WMI, in association with a local partner, is in charge since February 2019 of optimizing the hydraulics sectorization (zoning) and reducing the physical losses (leakage) of the 3rd metropolis of Colombia, Santiago de Cali (2.5 million inhabitants).
The project, which is initially scheduled for 2 years with an initial amount of US$ 10 Mn, covers the entire distribution network (approximately 3,000 km of pipelines and 600,000 service connections), from DN50mm to 1500mm. It employs up to 100 people.
The sectorization activities are broken down into a diagnostic phase, which includes a comprehensive review of the network inventory and assets, hydraulic measurements, Zero Pressure Test (ZPT), hydraulics modeling, model calibration and proposal of optimization alternatives. In most cases, a better sectorization allows to homogenize the operating pressure in each distribution zone, helping to better regulate day and night pressure. In simplified terms, when the consumption of a sector decreases at night, the pressure tends to increase and to generate more leakage flow. Specialized equipment (Active Control Pressure systems – ACP), installed by WMI, allows to reduce the night pressure or off-peak pressure and save water from those background and non-visible leaks.
The leakage control activities include the systematic search for invisible leaks by traditional acoustic methods (approximately 1.5 times the length of the network, ie. 4,500 km), and the repair of all detected leaks. A dedicated construction budget allows WMI to repair detected leaks and reinstate sidewalks and roads, thus controlling the entire process (6,000 expected leaks), in a very short time.
In parallel with the sectorization and leakage control activities, the contract allows for regular evaluation of results through the standardized protocol of the IWA – International Water Association. This protocol consists in precisely performing an initial baseline (determination of the initial level of losses of a sector), then an evaluation of the water savings at the end of each phase of intervention, using the method of the Minimum Night Flow (MNF).
In order to improve the real-time knowledge of network behavior, the project also involves the tele-transmission of information to a control and data acquisition system (SCADA). The flows and the pressure in more than 300 points of the network will thus be progressively connected to the control center of EMCALI.
Finally, a general envelope of hydraulic works also allows to give flexibility to the contract, for example to renew sections of deteriorated pipelines, or to achieve reinforcements or interconnections necessary for the optimization of sectorization. In this context, WMI has implemented trenchless techniques to limit disturbances on public roads.
At first approach, the project estimates that it will be able to recover 15 million m3 (3300 iMG) of water in accumulated volume over the initial contract period, but it is likely that the real gains in m3/day (iMGD) at the end of the initial construction period allow for a higher outlook, especially if a phase of sustainability and maintenance is put in place at the end of the 2 years of initial contract. The first results are very encouraging.