Electrical resistivity tomography applied for monitoring backwash efficiency in drinking water filters

Abstract

Sustainable production of drinking water requires safe and efficient production, operation, and maintenance of the entire production line. Rapid gravity granular filters in water production require periodic backwash to ensure water quantity and quality. Therefore, an efficient backwash strategy plays a key role in ensuring a sustainable operation of the filters. In this study, a real-time monitoring method based on electrical resistivity tomography has been developed and tested at full scale for a period of six months in a rapid gravity granular filter during drinking water production. It provides proof of concept for a developed equipment and monitoring strategy within the given production environment. The time series of collected data, with different depth sensitivities of the upper 40 cm filter bed, demonstrates the temporal and spatial resolution capability of the method. Results show temporal development related to dynamic operation and backwash which in this study is combined with snapshot diagnostic tools and operational parameters to increase the spatial understanding of the active processes within the filter. These results suggest electrical resistivity tomography to be a suitable method for monitoring backwash efficiency. HIGHLIGHTS Spatial variation within rapid sand filtration is monitored in real time.; The applied electrical resistivity tomography monitoring strategy reveals vertical and temporal variations directly related to the operational and physical state of the filter.; Good and bad backwash efficiency can be differentiated based on the real-time monitoring data.;

Keywords

• backwash efficiency
• biofiltration
• electric resistivity tomography
• rapid sand filtration
• real-time monitoring