Abstract
Abstract In regions facing water scarcity, optimising existing treatment infrastructure is increasingly important. In the São Paulo Metropolitan Region, low per capita water availability and declining reservoir levels have increased reliance on the São Lourenço water treatment system. The system, however, operates below full capacity because pumps are shut down on peak-tariff hours to cut electricity costs. This study proposes an integrated hydraulic, economic, and environmental framework combining mass balance, tariff-based operational expenditures (OPEX) savings, Net Present Value (NPV) analysis, and comparative Life Cycle Assessment to support decisions on increasing treatment throughput. Economic and environmental dimensions explored sensitivity in discount rate, capital expenditure (CAPEX), pump degradation, coagulant dose, construction allocation and parameters, complemented by Monte Carlo simulation of tariff variation. Two scenarios were compared: operating existing pumps on-peak, and constructing an additional raw-water reservoir to avoid on-peak pumping one business day per week. Both achieved similar maximum treatment throughput (< 1.7% difference). Under the modelled assumptions, scenarios showed no material differences in environmental performance (< 1.7% difference), as pipeline construction dominated construction-phase impacts (91–96%), and intake specific energy consumption remained nearly constant (1.3126–1.3185 kWh/m³). Economic assessment indicated negative net NPV under base CAPEX and 8% discount rate (− R$34.29 to − R$11.93 million); CAPEX, pump degradation, and tariff escalation emerged as the main variables capable of shifting viability, restricted to the three-pump on-peak configuration. Among the explored scenarios, the pumping-based strategy proved more attractive than storage expansion in most configurations. The framework offers a transferable approach for evaluating storage- and pumping-based strategies trade-offs.