Modelling and simulation of a hydropower system using wastewater discharged from Marine outfalls

Abstract

Municipal or industrial wastewater from the treatment plant is discharge by marine outfalls through the use of a pressurized pipeline scheme. The wastewater is discharged deep under the sea surface at a distance from the coast. During discharging of the wastewater, the excess pressure is applied to push the wastewater deep under the sea. The operation of allowing the wastewater to be discharge far away from the coast, takes the environmental perspective into consideration. However, from engineering perspective, significant amount of energy is wasted during discharging of wastewater and can be recovered. Hence, the aim of this paper is to model and simulate an energy recovery system able recover some of the energy wasted, using a hydro-turbine and generator in a hydropower scheme. The simulation results, for the South African Green Point outfall, have demonstrated that the marine outfalls have the potential to generate electrical energy during discharging of the wastewater. Using a 16-kW permanent magnet synchronous generator, the load demand of a 16 kW resistive load was met at a nominal voltage of 313 Vrms. Given the constant discharge flowrate of 28.4 × 106 litres of wastewater per day at Green Point outfall site, a significant amount of electrical energy can be generated.