Water Supply System Performance for Different Pipe Materials Part I: Water Quality Analysis

The quality of potable water has been a major issue in the water industry for the last few decades. The deterioration of treated water can be due to physical, chemical or microbiological changes that occur in the water during distribution. In addition, pipe material and decay of a disinfectant agent can affect the quality of the water being distributed. In this study the purpose was to simulate the decay of chlorine in two networks, one made of old cast iron (CI) pipes and another of polyethylene (PE) pipes. In addition the performance of the network considering chlorine concentration, velocity, water age, and an intrusion of a contaminant – in this case organic material – into the network was evaluated. The simulations were performed with EPANET software using as the simulation network an example network from the program. It was found that the CI network requires higher initial chlorine concentrations than the PE network to maintain the required minimum chlorine concentration throughout the whole network. To maintain the chlorine concentrations required by WHO (Cl must be greater than 0.2 mg/l and lesser than 0.5 mg/l) re-chlorination stations were necessary to add into both networks. The performance of both networks before re-chlorination was low due to high initial chlorine concentrations, but after the addition of the re-chlorination stations it was 100% throughout the networks. The performance of the velocities was good in both networks. The performance of the water age was dependent mainly on the tank usage, and the performance of contamination by organic material depended on the coefficient that defines the decay rate of the organic material in the bulk phase.     

Energy efficiency in a water supply system:Energy consumption and CO2 emission

This paper presents important fundamentals associated with water and energy efficiency and highlights the importance of using renewable energy sources.A model of multi-criteria optimization for energy efficiency based on water and environmental management policies,including the preservation of water resources and the control of water pressure and energy consumption through a hybrid energy solution,was developed and applied to a water supply system.The methodology developed includes three solutions:(1)the use of a water turbine in pipe systems where pressures are higher than necessary and pressure-reducing valves are installed,(2)the optimization of pumping operation according to the electricity tariff and water demand,and(3)the use of other renewable energy sources,including a wind turbine,to supply energy to the pumping station,with the remaining energy being sold to the national electric grid.The use of an integrated solution(water and energy)proves to be a valuable input for creating benefits from available hydro energy in the water supply system in order to produce clean power,and the use of a wind source allows for the reduction of energy consumption in pumping stations,as well as of the CO2 emission to the atmosphere.     

Wave-front retrieval from Hartmann test data

In the classical Hartmann test the wave front is obtained by integration of the transverse aberrations, joining the sampled points by small straight segments, in the so-called Newton integration. This integration is performed along straight lines joining the holes on the Hartmann screen. We propose a modification of this procedure, considering the cells of four holes of the Hartmann screen to fit a small second-power wave front recovering each square. This procedure has some important advantages, as described here.