A step forward in the in-line river monitoring of nitrate by means of a wireless sensor network

Abstract

This paper is based on our previous work consisting of the development and deployment of a wireless sensor network for the continuous in-line monitoring of the content of nitrates in a river in Eastern Spain. We present new contributions that significantly enhance its applicability, improve its features, and increase its reliability and useful life.

For this purpose, an expert system has been developed in order to improve the features of the whole system operation in an intelligent, flexible, user friendly way. This expert system offers several policies to optimize the times at which measurements are to be carried out (and sent), sampling frequency being altered according to the system evolution, the user preferences and the application features. The implemented policies are as follows: (a) periodic transmission; (b) gradient transmission; (c) user request and (d) peer request.

Additionally, in order to increase the reliability of the system, a triple modular redundant transducer in each sensor has been implemented, increasing dependability of the system with a very small affection of cost and consumption. Prior to the field trials, some laboratory experiments have been performed for parameter adjustment and checking purposes. As in the previous work, the proposed system has been deployed along a certain stretch of the river, its operation being studied and validated.