A new look on old data: Usability of continuously measured discharge rates to monitor the ageing of drinking water abstraction wells.
Approximately 70% of the drinking water in Germany (BGR) and about 50% worldwide (IGREC 2011) are abstracted 2 from groundwater using filter wells. Their implementation and operation are major factors contributing to the costs of drinking water production. Within the joint research project ANTIOCKER , funded by the German Ministry of Research and Education, and coordinated at the Dept. of Applied Microbiology of the Technical University Berlin, the partners Berliner Wasserbetriebe (BWB) and the Berlin Centre of Competence for Water (KWB) focus on the efficient operation of drinking water abstraction wells. One major reason for inefficient wells is so-called well ageing, i.e. the increase in drawdown at constant discharge rate due to biological, chemical and / or physical processes in and around the well. In Berlin, approximately 80% of clogging deposits are described to be of biochemical nature involving iron-related bacteria. Previous studies, i.e. in the scope of the KWB research project WELLMA have revealed that such well ageing phenomena are determined by multiple correlated biological and chemical processes. For this reason, it is the sound understanding of the main processes and key parameters that will provide the basis for the systematic control of iron bacteria occurrence by an optimized well operation. A new approach to a large variety of data from well construction and maintenance of the Berlin drinking water wells focused on the determination of key parameters for monitoring and the identification of hidden variables for ageing by means of probabilistic statistics. Cumulative distribution plots are used to visualize large data amounts and frequency distribution plots filter correlations between e.g. maintenance events in the lifetime of a well and monitoring data. First results indicate that small changes in the discharge rate Q on a daily basis could be used to monitor the well performance on a much higher frequency than the currently used evaluation of the specific capacity. In addition, the electric conductivity proved to be a key variable for clogging. Both parameters are now being verified in field investigations and further data analyses within the research project ANTIOCKER and about 50% worldwide are abstracted 2 from groundwater using filter wells. Their implementation and operation are major factors contributing to the costs of drinking water production.