Water & Wastewater Treatment Magazine
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18 | AUGUST 2017 | WWT | www.wwtonline.co.uk Sewage contains a lot of material that can potentially be recycled. It is estimated that each year, the wastewater from a single person in Europe could provide 6kg of cellulose, 3.3kg of biopolymers, 0.9kg of phosphorus, 4.6kg of nitrogen, 12.8kg of methane, 9.1kg of organic fertiliser and 91 cubic metres of reusable water. Most of the cellulose present in wastewater comes from toilet paper, which is 80% cellulose. Removing it from the wastewater stream at the fi rst opportunity improves the effi ciency of the rest of the wastewater treatment process, as well as giving a product which can be sold to make plastics, construction materials such as asphalt. Phosphorus is one of the nutrients that can be recovered using the new technologies, and can be used to make fertiliser. European utilities are under pressure to remove phosphorus from wastewater to help meet stricter environmental water quality standards in watercourses resulting from the Water Framework Directive. However, there is also an ecological imperative to recover P, which is a fi nite and diminishing resource. Biopolymers, or polyhydroxyalkanoates (PHA) are linear polyesters created in nature by bacterial fermentation, and are valuable as alternatives to using petroleum in the production of plastic. Bioplastics created in this way have the big advantage of being biodegradable, as well as being less carbon-intensive, meaning they are in demand for a host of eco-friendly products. One of the UK-based partners in the SMART-Plant project is EcoDek, which makes environmentally-friendly composite decking boards. Methane extracted from sewage as a result of anaerobic processes (biogas) can be used to generate energy, making the entire treatment process cheaper and using less fossil fuels THE RESOURCES WATER COMPANY VIEW The Works: resource recovery Severn Trent is one of the UK partners in the SMART-Plant project, and recently hosted the regular update meeting for the 25 partners in the project at its headquar- ters in Coventry. Speaking at this event, Bob Stear, Sev- ern Trent's Head of Innovation, explained why resource recovery is an exciting ‡ eld for the utility: "Predicting the future is hard work, but we put concrete in the ground that lasts for 50, 60 or 70 years, so as a compa- ny we have got to be good at it. Five years ago, we went on a journey with our inno- vation strategy where we aimed to focus our e' orts on those approaches that made sense whatever happens in the future - plotting a course that would work for the maximum number of possible worlds. We decided then that our strategy was to re- ally go a" er the circular economy. "Many of our 1000 wastewater treat- ment works are small and located in using less fossil fuels "Our mindset is that we are open to recovering as much from the treatment process as we can." rural areas, but we also have a number of large urban works, and it is here that the 'conveyor belt' of the circular economy, re- covering resources which can be re-used, really makes sense. We already recycle energy: we have been operating anaerobic digestion plants for more than 40 years, and today, 35% of our total power comes from renewable sources. So the obvi- ous next step is to see what else we can recover. That ‡ ts in with our innovation needs document, which contains eight priorities, with protecting the environ- ment being one of those eight. "Some of the technologies and tech- niques in the SMART-Plant project are those that we are already know about - we have done a lot of interesting work on phos- phorus recovery, for example – but others, such as cellulose recovery, are newer. Our mindset is that we are open to recovering as much from the wastewater treatment process as we can. As an innovation team, with a limited budget, we are only able to invest in a limited number of initiatives at any one time, which is why the consortium approach adopted by SMART-Plant is such a good thing. It's a great way for us to keep in touch with all the latest technologies that are on the conveyor belt. Some of them will be ready for adoption quickly and some might take longer, but over time this collaborative approach is likely to pay o' and we will be in the best position to take advantage." and regenerates products and materials at the end of each service life. In the water industry, we can play an important role in the emerging circular economy - we re- ceive huge amounts of 'waste' water that is full of material that can be recovered and regenerated." All the technologies in the project are proven, but the large pilot scale instal- lations will reveal a great deal of useful information about how they can best be deployed and combined in order to give the best value, he adds. Many of the technologies also have multiple bene‡ ts. For example, upstream cellulose recovery reduces the load experienced in the main activated sludge plant, so it not only gives you usable cel- lulose, but makes the whole wastewater treatment process more eœ cient. Tertiary nutrient removal helps meet ež uent discharge standards as well as giving nutrients that can be used for commercial fertiliser; and the anaerobic treatment of sewage makes for a cheaper treatment process at smaller plants while also pro- viding energy-producing biogas. While European utilities may initially adopt individual technologies involved in the project, the thinking behind the pro- gramme is that in time they will want to use them in concert, with operations that make the most of multiple resources.