2. Methodology
2.1. Case study description
The case study was carried out in a sector of the drinking water transmission system that supplies eastern Algarve, Portugal. It comprises a 23 km long, large-diameter trunk main with 6 delivery points. At each point, water is delivered to service storage tanks that are managed by municipal water utilities. The system is supplied by the Tavira Water Treatment Plant (WTP) and carries water to Cabeço service tank at the downstream end (Figure 1). Pipe diameters range from 1500 mm to 450 mm in the main line, with delivery branches ranging from 100 mm to 400 mm. Water flows by gravity and uni-directionally. Flow is controlled by water levels in the tanks and, therefore, depends on the demand patterns at the delivery points. Tavira WTP is supplied with water from the Beliche reservoir through a raw water transmission pipeline. Water is treated by a conventional process for superficial waters consisting of pre-oxidation with ozone, followed by coagulation/flocculation/sedimentation, sand filtration and final disinfection with gaseous chlorine. Average chlorine content is 0.83 mg/L at the WTP outlet and 0.6 mg/L at the inlet of Cabeço tank. Water has relatively low, organic (1.5 mg C/L as total organic carbon) and inorganic contents (iron, ammonia and manganese concentrations below detection limits) and therefore, low chlorine demand is expected. Predominant pipe materials are ductile iron with aluminous cement lining and steel. Average infrastructure service age is about 15 years.