Direct addition of powdered activated carbon (PAC) to the inlet of a deep bed filter represents an energy- and space-saving option to remove organic micropollutants (OMPs) during advanced wastewater treatment or drinking water purification. In this lab-scale study, continuous dosing, preconditioning a filter with PAC and combinations thereof were investigated as possible dosing modes with respect to OMP adsorption efficiency. Continuous dosing resulted in decreasing effluent concentrations with increasing filter runtime due to adsorption onto accumulating PAC in the filter bed. Approximately constant removal levels were achieved at longer filter runtimes, which were mainly determined by the dose of fresh PAC, rather than the total PAC amount embedded. The highest effluent concentrations were observed during the initial filtration stage. Meanwhile, preconditioning led to complete OMP adsorption at the beginning of filtration and subsequent gradual OMP breakthrough. PAC distribution in the pumice filter was determined by the loss on ignition of PAC and pumice and was shown to be relevant for adsorption efficiency. Preconditioning with turbulent upflow led to a homogenous PAC distribution and improved OMP adsorption significantly. Combining partial preconditioning and continuous dosing led to low initial effluent concentrations, but ultimately achieved concentrations similar to filter runs without preconditioning. Furthermore, a dosing stop prior to the end of filtration was suitable to increase PAC efficiency without affecting overall OMP removals.

Due to rapid economic development and population growth, China is facing severe water problems that include sea-level rise and increasing salinization, floods, water pollution, water shortage, soil erosion and ecosystem deterioration, as well as biodiversity loss. In recent decades, China is progressively more concerned with its water issues that are now at the center of social and political attention. Having to overcome similar challenges, Germany has taken a leading role in the field of water sciences and technology. In particular, China can benefit from the lessons learnt in Germany concerning the rehabilitation of water resources in areas heavily affected by chemical industry and mining after the reunification in 1989. German-Chinese cooperation in water sciences started over 25 years ago and dealt with increasing challenges in the 21st century. Following the open space workshop during the Water Research Horizon Conference in Berlin 2014, this article provides a view of some of the challenges and potential opportunities of German-Chinese cooperation in water science and technology.

To sustain good harvests, each year more than one million tonnes of mineral phosphorus have to be imported to the European Union (van Dijk et al., unpublished data), while the potential to recover and recycle this essential resource remains untapped or is just inefficiently used as in the case of sewage sludge, manure and food waste. In recent years various technical solutions have been developed to recover phosphorus providing mineral compounds suitable as raw material for fertiliser production or even as ready-to-use fertiliser. Regarding the implementation of these technologies, operational benefits for plant operators like the water utilities in the case of P recovery from wastewater and/or sewage sludge are the strongest argument for their market penetration. Without the provision of direct operational benefits, implementation needs to be motivated or even enforced by suitable and reliable policies. In order to realise a circular economy, it is important not just to focus on the recovery itself. The recovered materials need to match the requirements and needs of their intended users. Therefore, full value-chain solutions have to be promoted instead of isolated technology-focused approaches. Following our principles of sustainability and resource efficiency, the assessment of innovations must also include their environmental impact. This review provides an overview of recently developed and promising technologies for phosphorus recovery from wastewater and discusses aspects regarding their wide-spread application, along with their limitations. It will focus on recovery and recycling from sewage sludge. Not only the technologies themselves, also the recovered materials and their valorisation options are addressed. Results of the EU FP7 funded project P-REX entitled 'Sustainable sewage sludge management fostering phosphorus recovery and energy efficiency' and other recent initiatives will be included. Since innovation always needs an enabling environment for market penetration, barriers set by the existing legal framework and measures to resolve them will be reviewed. Finally, Goethe's words are true more than ever: 'Knowing is not enough, we must apply! Willing is not enough, we must do!'

The theoretical work presented here analyses various process chains for the energetic utilisation of municipal sewage sludge in their energy and greenhouse gas balance taking into account the hydrothermal carbonisation (HTC), based on the operating data of an HTC pilot plant. In the comparison with reference processes for sewage sludge dewatering (centrifuge, chamber filter press) the HTC with this offers energetic advantages with the treatment of digested sludge through high energy credit notes in the incineration and relatively small additional expenditure if the process can be operated via waste heat. For raw sludges without digestion the HTC offers no advantages as the energe tic advantage of the high calorific value are balanced out through additional outlays (natural gas, increased return loading). Decisive factors with the energetic evaluation of the HTC process are here the internal heat management and the biogas yield from the HTC process water. To be noted is, however, that the refractory COD in the process water can lead, via the return loading of the wastewater treatment plant, to considerably increased COD discharge values, which the introduction of an HTC in many cases would prevent. Along with the energy balance the HTC technology for sewage sludge should therefore be comprehensively evaluated in large-scale trials in order to investigate more accurately the economic efficiency and environmental relevance of the process.