Hybrid processes utilizing powdered activated carbon adsorption and filtration for the removal of micropollutants and efficient water management

The steady increase of human population and activity on earth is associated with a strong increase of water consumption. This is leading to localized imbalances between water availability and fresh water demand as well as decreasing fresh water qualities. The resulting water scarcity in certain regions and stricter legislations on wastewater treatment and drinking water production, require a continuous investigation and exploration of new water treatment schemes and processes. In this thesis, two specific examples of the abovementioned development are addressed by the combination of powdered activated carbon (PAC) adsorption and filtration processes. The modified Swiss Water Protection Act and Water Protection Ordinance which target the removal of micropollutants from municipal wastewater is the latest example of the increasing demands put on wastewater treatment processes by legislative changes. The process combination of PAC adsorption and filtration was investigated in two case studies in technical- and pilot scale for its suitability and performance for micropollutant removal from municipal wastewater. In one study ultrafiltration was used as filtration process to retain PAC particles from entering into the receiving water body, while deep-bed filtration was applied in the other. The combination of porous membrane filtration and PAC adsorption showed general applicability with superior permeate water quality while economic aspects remain a drawback in comparison to competing technologies. The combination of adsorption and deep-bed filtration proved to be a robust and economic process combination for the removal of micropollutants with economic advantages over membrane filtration. PAC retention over the filter bed was generally very high and considered sufficient but was shown to depend on PAC conditioning with flocculants while ultrafiltration provides complete PAC retention independent of conditioning or process parameters. Acute water scarcity in Europe was addressed in a case study, which aimed for industrial wastewater reuse through reverse osmosis (RO) desalination. In this scope, the application of the PAC/UF process was explored as potential pre-treatment step for reverse osmosis and compared to other conventional pre-treatment options. The process combination proved superior to other conventional pre-treatment technologies with respect to removal of fouling causing substances upstream the RO. Drawbacks of the process combination such as PAC waste handling and economic aspects, however, currently prevent its full scale application in the specific case. The investigations performed within the scope of this thesis specifically broaden the knowledge and understanding of the process combination with respect to optimal process configuration and long term operation for best process performance and further contribute towards the technical realization of the processes for other treatment tasks