Pre-treatments minimizing membrane fouling are extensively studied, to extend membrane life span and decrease the operating costs. In this study, the effect of several pre-treatment options before tertiary membrane treatment was investigated with a submicron particle counter from Nanosight (UK). This device using the Nanoparticle Tracking Analysis method is able to measure the particle size distribution and the absolute particle concentration of particles between 50 and 1000 nm in secondary effluent. The goal of this study is to enhance the understanding of MF/UF membrane fouling by monitoring the submicron particle fraction in the water. Experiments were carried out at lab-scale. Reliability and reproducibility of the device were determined as well as the impact of the pre-filtration on the measurements. The impact of ozonation (0-15 mg O3/L) and/or coagulation (0-12 mg Fe3+/L) on particle size distribution and on the filtration performance was studied on a polyethersulfone ultrafiltration membrane. Results showed a clear relationship between the amount of nanoparticles below 200 nm and the filtration behavior. Lower particle concentrations in this size range resulted in lower flux decline due to reversible fouling. Coagulation and ozonation pre-treatment decreased the particle concentration below 200 nm. The combination of ozonation/coagulation shows synergistic effects and leads to an additional decrease of submicron particle content and further improvement of the filtration performance. Long term impact on hydraulic irreversible fouling still needs to be clarified.

Managed aquifer recharge (MAR) provides efficient removal for many organic compounds and sum parameters. However, observed in situ removal efficiencies tend to scatter and cannot be predicted easily. In this paper, a method is introduced which allows to identify and eliminate biased samples and to quantify simultaneously the impact of (i) redox conditions (ii) kinetics (iii) residual threshold values below which no removal occurs and (iv) field site specifics. It enables to rule out spurious correlations between these factors and therefore improves the predictive power. The method is applied to an extensive database from three MAR field sites which was compiled in the NASRI project (2002e2005, Berlin, Germany). Removal characteristics for 38 organic parameters are obtained, of which 9 are analysed independently in 2 different laboratories. Out of these parameters, mainly pharmaceutically active compounds (PhAC) but also sum parameters and industrial chemicals, four compounds are shown to be readily removable whereas six are persistent. All partly removable compounds show a redox dependency and most of them reveal either kinetic dependencies or residual threshold values, which are determined. Differing removal efficiencies at different field sites can usually be explained by characteristics (i) to (iii).

The capacity of drinking water abstraction wells, which is the yield for a given drawdown of the water level, is often decreasing after a certain time of operation. This well ageing can be caused in carbonate aquifers by a chemical process : calcite precipitation. Using an hydrogeochemical model developped during the internship, the quantity of precipitated calcite and the time required to fill up the bore are estimated. It is then showed that carbonate precipitation is enhanced by chemical and physical parameters (hydrogenocarbonate concentrations, temperature) as well as the operating of the well (pumping and resting).

In the future, advanced phosphorus removal will be necessary in many WWTP in order to meet the demands of the European water framework directive. The project OXERAM deals with the comparison of different technologies with regard to their efficiency and applicability in tertiary treatment. In the course of the project membrane and microsieve filtration are tested in pilot scale at the Ruhleben STP. In this thesis the optimization of coagulation and flocculation prior to microsieve filtration for advanced phosphorus removal (< 80 µg/L TP; total phosphorus) was investigated. For the optimization of the coagulation/ flocculation several test series were conducted with the aid of jar test and the mircosieve pilot plant. A direct comparison of jar tests and the pilot plant showed that jar tests are an appropriate method to predict the approximate outcome of optimization steps (e.g. variation of chemical doses) in the pilot plant. The pilot trials were able to demonstrate that the microsieve technology (10 µm pore size) in combination with chemical pre-treatment of 0.036 - 0.179 mmol/L coagulant (Fe or Al) and 2 mg/L cationic polymer could easily achieve good and reliable TP removal. The phosphorus removal was comparable to dual media filtration (< 80 µg/L TP) and partly even to membrane filtration (< 50 µg/L TP). The reduction of the residual coagulant contents in the filtrate was identified as the main challenge of this technology. High iron contents of about 1 mg/L were accompanied by floc formation behind the mircosieve in filtrate tank and pipe. In a microsieve the formed flocs have to endure high shear forces. Thus, the so-called post-flocculation was most probably caused by re-flocculation of floc fragments. Very low phosphorus values < 50 µg/L were possible at high metal dosing. But the higher suspended solid load reduced the filtration capacity of the microsieve. Coagulation with polyalumium chloride (PACl) produced better effluent quality compared to FeCl3 as less suspended solids and less residual coagulant were found in the microsieve effluent. Furthermore, the transmission of UV radiation through the water was improved from 47 up to 66 % by using PACl which is favorable if a downstream UV disinfection is considered. When using FeCl3 the transmission was not improved or even reduced. Due to the influence on the performance of the microsieve cationic polymers were preferred to anionic polymers. However, the tested anionic polymer proved to be not applicable in the given process configuration due to very low filtrate flows. When cationic polymer was applied the polymer dose had a high impact on the particle removal and moreover on the contents of phosphorus and coagulant residuals in the effluent. In most cases 2 mg/L polymer was necessary. In total, the microsieve technology in combination with chemical pre-treatment is a suitable option for advanced phosphorus removal. Through a dynamic adjustment of the chemical dosing to the influent water quality (e.g. ortho phosphate and turbidity online measurement) and the choice of polymer the process could be optimized in the future with regard to efficient chemical application.