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AD in the water industry


However, Mohamed warns against a ‘one size fits all’ approach – while water companies are setting the standard for operational efficiency, their approach may not be suitable for all AD facilities. “While there is an established R&D base for AD in the water sector, and there has been much effort and investment in understanding the wastewater treatment process in AD, it is important that we do not assume that what we know from one sector transposes directly to another. Fundamentally, even though many principles at the heart of food waste and wastewater treatment are similar, they are still very different – despite the knowledge from the water industry’s research we do not have all the answers when it comes to different AD processes.”


Increasing efficiency through development


and innovation Veolia has recently reported on an innovative new system which reduces the costs and increases the gas production of anaerobic digestion. Its team has developed an existing technology, used in the processing of food waste, to increase biogas quality and generate more renewable electricity and heat. The fully automated system accurately tracks biogas quality parameters to treat sludge, resulting in an 80 per cent reduction in hydrogen sulphide (H2


S),


and thereby helping to increase biogas output and maintain plant efficiency. The company’s pilot project has now demonstrated a 14 per cent increase in renewable electricity generation. With an estimated payback on investment of less than two years, Veolia claims it is a better commercial option than biological or chemical dosing systems.


Commenting on the development, Veolia’s John Abraham said: “Recent estimates indicate that the water industry could be self-sustaining for electricity by harnessing the 11 billion litre annual flow of wastewater. Our technology demonstrates how we can help deliver greater sustainability for the industry using wastewater to energy systems, and also meet water industry carbon reduction targets. By providing an additional 14 per cent of renewable energy from an existing resource it also takes us a step closer to the circular economy objectives recently agreed at the World Economic Forum in Davos.”


While large scale R&D and novel processing frequently attract the headlines, small-scale process improvements have been no less important in helping to boost energy output. Northumbrian Water recently replaced four pumps at its Howdon Sewage Treatment Works with new Börger rotary lobe units. According to Colin Davison, Mechanical Maintenance Team Leader at Northumbrian Water, the big advantage is the ability of the pumps to cope with the tough conditions associated with moving sludge from a holding tank to the AD plant. “We wanted to improve this part of our process with a pump that would perform with suitable effectiveness, but also be far more reliable


GENeco, the AD arm of Wessex Water group, operates a food waste plant at Avonmouth


and easier to service than what we were already using,” he explained. “Over a sustained six-month period, the Börger FL776 proved conclusively that it is more than capable of handling this tough application, with the added bonus that its maintenance-in-place design makes it much easier and far less time consuming to service than other pumps.”


Maintenance and monitoring to maximise returns “The latest innovations are linked to the improvement and enhancement of the digestion process, and the use of the gas; be it to generate electricity and


heat, injection into the gas grid and now the use of elements such as CO2 from within the gas,” explains Dr Stephen Wise. “Operators are looking at how they can maximise every pound spent to generate additional revenue or reduce operating costs.”


Monitoring output is a key part of such performance improvement and Geotech has extensive experience in supplying gas monitoring equipment that aids water companies in the treatment and management of wastewater sludge through AD. Geotech’s BIOGAS 5000 is used by Southern Water in digesters on 18 sites across Hampshire, the Isle of Wight, Sussex and Kent. Treating and recycling 1.4m litres of wastewater from nearly two million households, Southern Water needs to ensure that its sewage sludge digesters are secured and working at optimum levels.


(CO2


By using Geotech’s equipment as their field instrument, Southern Water is able to measure the concentration levels for methane (CH4


monitor the temperature of these gases, providing consistent data collection for improved analysis and accurate reporting. Having better data means it is able to produce the optimal amount of biogas to power its CHP engines; generating its power needs internally. As a result of reducing its energy dependency on the grid, Southern Water has managed to reduce its operational costs and increase its revenue. The company now aims to enhance its power generating capacity through AD, in order to become fully self-sufficient in the near future.


), oxygen (O2 ) and H2


Water 2020 The recent Water 2020 report, published by the regulator Ofwat, is designed to kick-start a market for treated sewage sludge, also referred to as biosolids. Many in the AD sector hope the proposed changes could provide opportunities for the AD supply chain, as well as for research and innovation. Speaking at the conference at UK AD & Biogas 2016, Ofwat’s Principal Engineer, Alison Fergusson, explained the thinking behind the new programme: “We have a duty to protect consumers by promoting effective competition, and that is what we’re getting at with our proposals on sludge. It is very much our vision that there is trust in this sector and also in what this sector does with its resources, including sewage sludge.”


Geotech's BIOGAS 5000 analyser is used by Southern Water www.adbioresources.org adbioresources.org Continued>> SEPTEMBER 2016 | AD & BIORESOURCES NEWS 13 ), carbon dioxide S. The equipment also enables Southern Water to


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