During WELLMA-DNA, 13 diploma and bachelor theses along with several internships have been completed. A sampling system for biofilm samples as well as a sampling device for water samples have been designed and tested. More than 400 DNA samples of different well sites have been collected and analyzed. Microbiological and molecular methods have been combined to gain a better understanding of the community composition of the ochre forming biofilms inside the wells. Molecular methods included PCR, DGGE, cloning and sequencing. During the project, the bacterial populations of an unprecedented number of wells have been analyzed and several indicator bacteria for iron-related well clogging have been identified. Alongside iron-oxidizing bacteria, iron-reducing bacteria have been found in the wells and their potential for ochre-solubilization was confirmed. Alongside the molecular experiments, microbiological trials included the isolation of pure cultures, microscopic analysis and physiological tests. The morphology of the encountered iron bacteria could be classified into four different groups, which may have an impact on the rigidity of the biofilms on a macroscopic level. We were able to cultivate several of these indicator organisms, which could play an important role in the formation of ochreous deposits in the Berlin wells. During experiments utilizing microscopic flow cells, differences in growth rate and patterns of these ochre-forming bacteria have been observed. For several of the identified indicator bacteria, primers have been calculated. These primers will allow for the first time to quantify the amount of indicator bacteria in a water sample and to derive operational pointers. In addition, several experiments regarding the effect of hydrogen peroxide on ochre forming biofilms have been conducted and the effect of an additional electron donor (ethanol) on the communities has been tested. For future data acquisition and documentation, a guideline for classifying the degree of pump clogging has been developed.

The assessment of methods for the diagnosis and distinction of well ageing types and processes with the aim to recommend methods and tools for further fieldwork was part of work package 1 of the preparatory phase WellMa1. Therefore, field tests were carried out at selected well sites with a variety of methods covering standard monitoring methods to assess the constructive state of a well (TV inspections, borehole geophysical methods) and its performance (pump tests) as well as methods aiming at a better process understanding such as the hydrochemical and microbiological analysis of the raw water and clogging deposits. Altogether ten methods were applied at 21 different wells of the Berliner Wasserbetriebe (BWB) covering (i) exposure of object slides during operation and rest periods for microbiological investigations, (ii) BART with test kits for iron-related bacteria (IRB) and slime-forming bacteria (SLYM), (iii) water sampling for the investigation of pristine groundwater organisms, (iv) online measurements of chemical parameters O2, Eh, pH and T and water sampling for chemical analyses (main cations and anions), (v) TV inspections, (vi) three-step pumping tests, (vii) borehole geophysics with Gamma-Gamma-Density scan (GG.D), NeutronNeutron log (NN), Flowmeter (Flow) and Packer-Flowmeter measurement and (ix) Particle countings. The assessment and comparison should originally be completed by a horizontally directed core sampling from different depths from the screen sections of three of the chosen wells. Due to technical difficulties, this was not achieved during this phase of the project. The investigations led to a development and refinement of the methods and approaches. Because of their limited accessibility to the different parts of a well, a combination of methods is always necessary. Especially for the indirect methods like borehole geophysics, an initial assessment of the well condition directly subsequent to construction is essential to provide a basis for the assessment of the well performance development. Generally, the applied standard monitoring methods and diagnosis tools provided the expected identification of a performance deterioration and evidence for the presence of starting materials for clogging processes such as iron, oxygen, iron-related bacteria and particles. Room for improvement could be identified with regard to the reliability, information value and comparability of the tested methods, e.g. by a stepwise combination and extension of the methods to determine the interacting processes from the composition of the deposits. Further investigations should aim at method validation, especially for well monitoring during routine operation (e.g. use of delta h, development of standards for Qs-measurements and TV inspections), and further method development for the ongoing project with scientific investigations to obtain deeper process understanding, e.g. investigating shares of deposits resulting from the different processes (chemical, biological, physical) and relations between the rate of clogging or the location of deposits to well characteristics and site conditions to separate the different well ageing processes. This will then lead to the identification of key parameters that may be influenced to slow down well ageing and keep the well performance and water quality at an optimum.

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).