A substantial part of the energy that is used in the watercycle is the thermal energy for heating the water that is used in buildings. Per Dutch inhabitant about 94 W is used for heating water, while only 26.5 W per Dutch inhabitant is needed for the rest of the watercycle (drinking water production and distribution; wastewater collection and treatment). Water saving techniques and heat recovery are therefore obvious measures to make the watercycle climate neutral. Furthermore, in theory, enough organic energy can be recovered from the watercycle, to provide the primary energy for the watercycle companies.
However, these organics are present in relatively low concentrations. This means that there is a lot of water in wastewater which can actually be potentially recovered and reused. In our Sewer Mining project we extract water from sewage by means of forward osmosis (FO) in combination with a reconcentration system e.g. reverse osmosis (RO), to produce high-quality water and to convert the subsequent concentrated sewage into a renewable energy source (i.e. biogas). The effectiveness of FO membranes in the recovery of water from sewage has been evaluated. Stable FO water flux values were obtained with settled sewage (screened, not treated) as a feed solution. Sewer Mining could lead to a more economical and sustainable treatment of wastewater, facilitating reuse of water and energy from sewage.
State-of-the-art wastewater treatment plants (WWTP) with a primary settler collect only about 30% of the wastewater organics. Direct collection of suspended solids from wastewater by innovative fine sieving of influent can result in the removal of approximately 50% of the organics. The rest of the organic matter is currrently converted in an aerobic process and used for nutrient removal from wastewater. Aeration energy represents approximately 60% of the total energy use of a WWTP. With the 'Adsorption-Belebung' system (AB-process), developed at the University of Aachen during the energy crisis in the nineteenseventies, more organics can be collected. More than 70% of the organic matter can be trapped in the first adsorption step (A-stage). Whereas the present AB-process is equipped with intermediate settling tanks a new separation technology is put forward to collect these organics by use of dynamic filtration. Dynamic filtration is a process in which on a coarse support material (typical pore size from 3 to 500 μm), a filtering cake layer is built-up with smaller pore sizes. In the DynaFil project we work on the optimization of process conditions in the A-stage, development of sludge separation based on dynamic filtration and study digestion with dynamic filtration. The results of the project are expected to contribute to an increased sustainable energy production at WWTP plants, reduced greenhouse gas emissions, and savings in energy use, costs and space. The latest results are presented, including results from dynamic filtration experiments. The presented projects show innovative possibilities for water reuse, energy and nutrient recovery from wastewater.
Partners The Sewer Mining project is initiated by KWR and together with the TU Delft, Waternet, Triqua, and US-based Hydration Technology Innovations an international Innowator grant from AgentschapNL has been obtained. The DynaFil project, in which KWR (project leader), TU Delft, Waternet, STOWA, Logisticon Water Treatment, Waterboard Brabantse Delta and Bert Daamen participate, is partly funded by AgentschapNL under the Energy and Innovation Grant, Effective and Efficient Digestion chain.
Kees Roest Kees Roest completed his MSc in medical biology and his PhD in environmental sciences, focused on the microbiological aspects of anaerobic wastewater treatment systems (combining culture-dependent and culture-independent approaches). As a Marie Curie research fellow, he arranged new microbiology laboratories for the investigation of environmental bioreactor processes in Spain (Department of Chemical Engineering and Environmental Technology of the Universidad de Valladolid) and in the UK (Sustainable Environment Research Centre (SERC) of the University of Glamorgan). Currently he is working as a scientific researcher at KWR watercycle research institute in Nieuwegein, the Netherlands. His research focuses mainly on innovative wastewater & reuse technologies.
More information:
kees.roest@kwrwater.nl
