Water & Wastewater Treatment Magazine
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meet zero waste by 2050," adds Fergus- son. For Severn Trent, collaborating with academia and other stakeholders is key to driving innovation in this area. As well as working with Cranfield University to develop anaerobic technology [see case study], the company is also collaborating on a new development with Coventry Uni- versity that will produce hydrogen from waste materials using renewable energy produced at its sites. Looking ahead The future sustainability of the water industry is heavily dependent on the way wastewater is managed. But shiƒing towards a more circular approach is about more than just delivering an alternative source of clean water to meet rising de- mand. Wastewater is a largely untapped resource, with the potential to have wide- ranging impact in areas such as energy production, agriculture and industrial development. With the emergence of new technolo- gies, increased collaboration will be key for the industry as it forges ahead into a new era of wastewater management. Working closely with research partners to harness the potential value of wastewater, while engaging with communities, could help secure the sustainability of the water system to 2050 and beyond. www.wwtonline.co.uk | WWT | NOVEMBER 2019 | 17 • UKWIR'S BIG QUESTION How do we maximise recovery of useful resources and achieve zero waste by 2050? UKWIR aims to establish what wastes have value that is not currently being recovered. It will be crucial to assess the value of these wastes, as well as any environmental impact, to provide evidence to influence the way they are regulated as well as raising awareness of these opportunities amongst customers. UKWIR's approach to answering this Big Question is expected to cover some high-level outcomes, including: • Zero waste to landfill • Minimising use of finite resources • Securing reuse routes that will maximise value for society • Recovery at the most economic point is normal practice and is promoted • Value of waste is reflected by regulation Severn Trent has recently opened a new multi-million pound demonstra- tion test-bed site at Spernal STW in Redditch and will be using this to validate technologies and flowsheets that can be used to upgrade its waste- water treatment works to resource recovery factories. The test-bed offers the opportunity to evaluate energy neutral wastewater treatment and to recover valuable materials contained in wastewater. Energy neutral sewage treatment The initial focus of the trial programme will be on low energy treatment con- sisting of enhanced primary treatment and mainstream anaerobic treat- ment. An enhanced primary treatment stage removes more suspended solids and more organic load than conven- tional primary settlement tanks. This directs more of the organic load to the energy generating anaerobic sludge di- gesters and less to the energy consum- ing wastewater secondary treatment process. Severn Trent has been developing the anaerobic technology over the last 10 years with one of its research partners, Cranfield University. Anaero- bic treatment is already successfully used in warm countries like Brazil, but recent research breakthroughs with anaerobic membrane bioreactors (AnMBRs) have developed a process capable of efficient treatment in tem- perate climates like the UK's. In 2020 the company plans to commission the largest demonstration scale AnMBR system in Europe, capable of treat- ing up to 500m3/d. The AnMBR will degrade the organic material in sewage without the need for air and in doing so will produce methane that can generate renewable electricity. Nutrient recovery In most of Severn Trent's wastewater treatment plants the company also removes nutrients – nitrogen and phosphorus – to protect the streams and rivers it discharges into. Nutrients, however, are an essential resource, they are a component of all living cells and without them it is impossible to grow crops, fruit or vegetables. Nitro- gen fertilisers are manufactured by the energy intensive Haber-Bosch process which chemically converts nitrogen from the air to ammonia. Phosphorus is a non-renewable, finite resource that is mined and incorporated into fertilisers. Consequently, the Earth's phosphate rock reserves are becoming rapidly depleted. There is a compelling argument, therefore, to recover both nitrogen and phosphorus from sewage. Severn Trent already has a full-scale plant that recovers phosphorus in the form of struvite (magnesium ammo- nium phosphate) at its Nottingham sewage treatment works. Mainstream anaerobic treatment will not remove nitrogen and phosphorus from the sew- age, which in the context of nutrient recovery is yet a further advantage. The effluent from an AnMBR will be rela- tively rich in nitrogen and phosphorus, but crucially it is free from solids and hence very suitable for adsorption and ion exchange based nutrient recov- ery technologies that the company will also evaluate at Spernal. These technologies, developed by Cranfield University, use a media – mesolite for ammonia recovery and an iron nano- particle embedded ion exchange bead for phosphorus recovery. Future opportunities This work in developing resource recovery from sewage has been strongly supported by the company's involvement in a number of EU research projects. The EU's Horizon 2020 Innovation Fund has provided ap- proximately £450,000 worth of funding for the AnMBR demonstration plant through the "NextGen" project. This European consortium, consisting of over 30 world-leading partners from across the EU, is setting out a four-year programme to evaluate and champion circular economy solutions and sys- tems in the water sector. • CASE STUDY: SPERNAL STW TEST BED WASTEWATER QUALITY Severn Trent's testbed site at Spernal STW.