No abstract

A laminar flow reactor was designed that provides constant and reproducible growth conditions for the bioelectrochemical observation of electroactive bacteria (EAB). Experiments were performed using four reactors in parallel to enable the comparison of EAB growth behavior and bioelectrochemical performance under different hydrodynamic conditions while simultaneously keeping biological conditions identical. With regard to the moderate flow conditions found in wastewater treatment applications, the wall shear stress was adjusted to a range between 0.4 mPa to 2.9 mPa. Chronoamperometric data indicate that early stage current densities are improved by a moderate increase of the wall shear stress. In the same way, current onset times were increasing slightly towards higher values of the applied wall shear stress. Long‐term observations of EAB performance showed a decrease in current density and a leveling of the trend observed for the early stages of biofilm growth.

In this study, the performance of electroactive bacteria (EAB), cultivated inside tubular electrode ducts, is systematically investigated to derive predictions on the behavior of EAB under conditions limited by electrochemical losses. A modeling approach is applied to assess the influence of the electrochemical losses on the electrochemical performance and scaling characteristics of complex 3D structures, such as sponges and foams. A modular flow reactor is designed that provides laminar and reproducible flow conditions as a platform for the systematic electrochemical and bioelectrochemical characterization of 3D electrodes in bioelectrochemical systems (BES). The bioelectrochemical experiments are carried out in a set of reactors incorporating cylindrical electrodes exhibiting ducts of 1 cm length and different diameters ranging from 0.1 cm up to 1 cm. Single duct calculations are extrapolated to three dimensions through geometrical considerations; trends in 3D bioanode performance are demonstrated using the resulting simplified 3D structure. The combined experimental and modeling approach constitutes a framework for future studies on systematic electrode design.

A prominent example of unwanted accumulation in production plants is particulate fouling, which has been subject of many studies in apparatuses. However, pipe fittings have attracted little attention despite their large number in production plants. Here, the influence of process parameters and geometry factors on the fouling in pipe fittings is investigated under isothermal conditions that aims to an improved understanding of their fouling behavior. The variation of fitting type and size, the run time and particle mass fraction have the greatest impact on the fouling mass while the temperature does not influence the result.

To successfully deal with a complex fouling problem usually entails a good understanding based on a broad spectrum of additional data. Meanwhile, a huge amount of process data is recorded and may be utilized to create a better understanding and prediction of the fouling status of an apparatus or the entire production plant. We propose a systematic approach to generate training data in a pipe fitting as a pre-step before the potential use of the entire data set of the production plant, irrespective of the relevance for the fouling prediction. Therefore, a temperature-based detection of the heat transfer resistance of plastic discs (representing 'artificial’ fouling) and a particulate material deposition (representing ‘real’ fouling) was applied in a pipe fitting obtaining reproducible results. The parameter variation experiments exhibit linear fouling curves and are therefore very suitable for model training. The temperature measurements confirm a correlation between the obtained temperature drop and the layer thickness of the plastic discs as well as the deposited particle fouling mass.