Monitoring ditch water quality using OTT ecoN, Hydrolab HL4 and XLink 500

The RIVM in the Netherlands is using the OTT ecoN and the Hydrolab HL4, connected to an XLink 500 datalogger, to monitor the temporal variation of nutrients in ditch water. The data is sent to Hydromet Cloud.

The goal of this project (WaterSNIP) is to improve the efficiency of the monitoring using water quality sensors and to monitor the water quality on a smaller scale (from regional to local). In the Minerals Policy Monitoring Programme (LMM) RIVM samples the ditch water 7 times a year. These samples are analyzed in the laboratory on a wide range of parameters, for the WFD-standards, total-N and total-P are important. RIVM measures at a high frequency to calculate a more accurate average of the concentrations in the ditch. Also, it improves the understanding of the leaching of nutrients from farm lands to the ditch and the chemical and biological processes that are involved.

Measuring Total-N and Total-P in real time is only possible using an expensive and power-hungry analyzer (lab-in-a-can). The ecoN can measure NO3.

The Hydrolab HL4 measures, Temperature, Conductivity, pH, Dissolved oxygen and Turbidity. RIVM is investigating the relation of these parameters with the variation of nutrients (from lab analyses and ecoN) in the ditch. In this way they examine whether the parameters of the HL4 can be used as a proxy (derivative parameter) for Total-P and Total-N. The ecoN and HL4 take readings every 15 minutes. The data is sent to HydrometCloud webserver. The complete system is powered by a 20 Wp solar panel. The XLink 500 is equipped with an internal Solar regulator that charges the integrated 7 Ah battery.