Wireless sensors as an efficient way to improve sustainability in water management by a significant reduction of water wasting

Abstract

Introduction: This paper presents an ICT solution to overcome the problem of water dispersion in water distribution networks. Leakage prevention and breaks identification in water distribution networks are fundamental for an adequate use of natural resources. Nowadays, all over the world, water wasting along the distribution path reaches untenable percentages (up to 80 % in some regions). Since the pipes are buried within the terrain, typically only relevant breaks are considered for restorations: excavations are very expensive and consequently the costs to identify the position of the leakage or just the position of the pipe itself are too high. To address this problem, and simplify the leakage identification process, the authors have designed a wireless network system making use of mobile wireless sensors able to detect breaks and reveal unknown tracks and monitor the pressure spectrum of the fluid flowing in the pipe. The sensors transmit the acquired data from the terrain to the surface by use of a wireless connection. On the surface ground there are stations that receive the signal, process it, and communicate with a central unit where necessary intelligent signal processing techniques are used to detect leakage sources. Compared to other leakage detection solutions already available in the market (such as: Ground penetrating radar (GPR), pure acoustic techniques and tracer gases), the proposed technique appears very efficient and much more inexpensive than the previous ones. Description of the system: The proposed new solution is based on the use of a mobile wireless sensor capabable of detecting breaks and revealing unknown tracks, by monitoring the pressure spectrum of the fluid flowing in the pipe and the relative speed within the fluid. The sensor transmits the sensed data via a wireless channel, hence it does not require a physical connection to the surface. The sensor gives an accurate detection of the leakage location and it allows an easy and repeatable identification of the track. The application of the wireless concept to the water leakage detection field allows the realization of mobile sensors able to flow together with the fluid removing the constraint that characterizes the traditional inspection techniques: the necessity of a wire between the sensor and the surface. In particular, the sensor has been realized by means of acoustic techniques, which are the most efficient in terms of leakage identification, but also strongly limited in terms of distance of application. Thanks to the mobility, the application range has been extended significantly. The proposed sensor is realized by means of a hydrophone that makes an analysis of the fluid pressure within the pipe, which is further used to recognize pipe damages or leakages, according to well known methods reported in the literature [2]. The data collected by the hydrophone is processed electronically, digitalized, stored on a flash memory and transmitted to the ground surface, thanks to a dedicated antenna design that allows wireless transmissions primarily out of the water and then within the ground. The on-board antenna and microwave circuit is designed by an innovative optimization process that takes into account the water and the pipe itself as they were antenna components. The wireless transmission is realized by means of a radio working between 200 MHz and 2500 MHz and compatible either with the IEEE 802.11 or the IEEE 802.15 standards. Thanks to the implementation of such components, the power consumption is kept within very low values and the survey can be extended over long ranges (at least 5 kilometers). The sensor is waterproofed and isolated from the water, thanks to a dedicated manufacturing process. The system design involves the minimization of the power consumption, thanks to a dedicated transmission protocol and the pre-processing of the data on-board that optimize the amount of data to be transmitted. The proposed new solution is based on the use of very low cost wireless technology: in this way the final product is cheap, as a mobile phone of average cost can be. Results: Some prototypes are being realized and tested in real environments, introducing the sensors within pipes located at different depths in the ground. Experimental data show excellent performance and optimum reliability.