Well biofouling is a complex and not yet sufficiently understood process. Water wells represent a unique habitat, since they create a link between the anaerobic ground water containing Fe(II) and the aerobic surface. This groundwater is rich in soluble Fe(II) and the presence of trace amounts of free oxygen in the well screens presents ideal conditions for the growth of iron bacteria. The ochreous deposits produced block not only the filter area, but also the adjacent gravel pack or even parts of the aquifer, and result in a steady decrease of well performance. In this project, the bacterial communities of several Berlin wells have been compared using standard microscopic techniques and molecular techniques like DGGE. The aim of this study is to identify the responsible bacteria and associated processes that lead to well clogging. The sampling system allows easy and effective collection of undisturbed biofilm samples with minimal impact on normal well operation. Fingerprinting analysis indicates the presence of bacterial populations that are ubiquitous in the wells and certain indicator bacteria which can be found in only few wells. Free water and biofilm populations show distinct similarities. Some well populations can be grouped in clusters, depending on the location of the well. Further comparison with chemical data of the wells is planned to asses the impact of chemical conditions of the respective groundwater on the bacteria responsible for clogging. A sampling device was designed and built for exposure of carrier materials into different Berlin drinking water abstraction wells. In addition, samples from well components (pumps and pipes) and water samples were collected. The DNA was extracted using the FastDNA SPIN Kit for Soil (MP). 16S rDNA polymerase chain reaction (PCR) of the V3 region and denaturing gradient gel electrophoresis (DGGE) analyses were performed on the DNA samples (Muyzer et al., 1993).

Well biofouling is a complex and yet not sufficiently understood process. Water wells represent a unique habitat, since they create a link between the anaerobic ground water, containing Fe(II) and the aerobic surface. These special conditions set ideal conditions for the growth of iron bacteria (Stuetz and McLaughlan, 2004). Some of these bacteria are known to be responsible for well clogging by precipitation of iron hydroxides (Cullimore, 1999). The consistency of the ochres can range from soft and bulky to solid and compact. The type of deposit strongly depends on the dominant species of bacteria at the well screen and inside the gravel pack. Within this project (WellMa) a sampling system was created, which allowed the collection of unaffected biofilm samples from inside the wells. The samples were microscopically examined, DNA was extracted and community profiles were created.

Bacterial induced well clogging is a common problem in water wells. The well represents a unique habitat by creating a link between the anaerobic ground water, containing Fe(II) and the aerobic surface. The presence of trace amounts of free oxygen in the well screens, sets ideal conditions for the growth of iron bacteria (Stuetz and McLaughlan, 2004). These bacteria precipitate iron hydroxides (Cullimore, 1999), that not only block the filter area, but also the adjacent gravel pack or even parts of the aquifer and result in a steady decrease of well performance. Each well has it’s own distinct chemical conditions, which impact the type of bacterial community that forms in the gravel pack. Within this project a novel sampling system was developed, which allowed the collection of intact biofilm samples from a selected range of Berlin water wells. The resulting biofilms were microscopically examined to gain a first rough overview of the different sampling sites. Subsequently, the bacterial DNA was extracted and used for a population comparison utilizing denaturing gradient gel electrophoresis, cloning and sequencing.