Wastewater, an underexploited resource
Processing urban wastewater is typically limited to cleaning it up for release into the environment. This is a shame, because it contains compounds that could be put to good use - as could the water itself. EU-funded researchers have tested promising innovations to advance resource-efficient processing, recovery of substances, and re-use.
© Stefania - fotolia.com
The joint coordinators of the R3Water project are proposing a future without wastewater treatment plants. Instead, the vision set out by Uwe Fortkamp and Klara Westling of the IVL Swedish Environmental Research Institute involves what they refer to as resource recovery facilities, where wastewater would be processed to extract useful substances and prepare it for further use.
Resource efficiency would be a defining feature of such facilities. By optimising the processes that are already widely used to produce biogas from sewage sludge, plants could generate the energy they need to power their operation potentially, with a surplus to spare for other applications.
A variety of innovations will be needed to take this vision forward. R3Water tested a dozen promising technologies in real-life conditions, at demonstration sites located in Belgium, Spain and Sweden. All 12 were developed by members of the consortium, enabling these partners, which include a number of SMEs, to refine their technologies and take them closer to commercialisation.
Reduce, reuse, recover
The innovations examined by R3Water included methods linked to the generation of usable energy or the extraction of phosphorous for use in agriculture, solutions for the re-use of the water itself, and ways to make wastewater treatment more resource-efficient. To provide an example, Fortkamp describes a method for the production of bio-coal from sewage sludge. Both the substance, which is also known as bio-char, and the process itself can be used in various ways.
Notable technologies the project tested in water re-use include a system that checks for signs of microbial contamination continually and in real time. In water plants, water quality is currently monitored by sampling, every four hours or so, Fortkamp explains.
An early warning system such as this would thus be a significant improvement, helping to safeguard the quality of water for applications as varied as street cleaning, irrigation or even human consumption, says Westling. Depending on the proposed use, different threshold values could be set, she adds.
Towards optimised processes
Innovation could thus help not just to recover useful compounds and water fit for other purposes, but also to make facilities considerably more resource-efficient potentially enabling them to cover their own energy needs, and then some. The treatment process uses energy, which can be obtained from the biomass in the wastewater, says Fortkamp. In fact, he adds, this resource might yield more than an optimised plant requires, and so it might even be possible to make energy available for additional applications.
The production of biogas from sewage sludge, for example, is a well-established process, says Westling. R3Water looked into possible improvements, and it also helped to fine-tune a number of other innovations designed to make the treatment process more efficient.
These solutions include services such as model-based energy audits and a system designed to help operators optimise the aeration of the wastewater in their plant a process that typically accounts for up to 60 % of the facilitys energy consumption and that has to be adjusted on an ongoing basis in line with varying conditions.
R3Water gave particular attention to helping the participating SMEs to take their innovations to the market. The partners carried out environmental technology verification, organised workshops and study visits enabling potential clients to discover the proposed technologies at the demonstration sites, and also supported its private sector members with training.
Reflecting on the outcomes of R3Water as its end-date in June 2017 approaches, Fortkamp and Westling highlight another significant result. The project advanced 12 promising technologies, supported prospective innovators and fulfilled the various objectives it had set itself, they note but just as importantly, they conclude, it generated real benefits for the environment.