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SEPTEMBER 2016 WET NEWS 23 ONSITE RENEWABLE ENERGY do it safe with axedo JDP - Integrated solutions in drainage & water management w www.jdpipes.co.uk e contact@jdpipes.co.uk t 0800 195 1212 Features & Benefits • Lighter than concrete • Can be installed manually without wet trades • No heavy machinery • No working in confined spaces • Estimated 42% savings on total install costs Exceed your expectations with Axedo Inspection Chambers Do it safe with Axedo from JDP, the state-of-the-art inspection chamber system providing adaptable, reliable and safe drainage access. Axedo guarantees savings on installation time and safety without compromising the need for a durable, leak-free, easily maintained and modern drainage system. For more information on Axedo systems and solutions go to www.jdpipes.co.uk Visit the Axedo web portal to download the Axedo brochure or contact our Technical Team to discuss your project. Axedo - The can do Inspection Chamber from JDP Axedo is one of the most flexible ranges of inspection chambers available in the UK. do it safe with axedo do it safe with axedo JDP Axedo H/P Ads WET NEWS_Layout 1 10/08/2016 10:42 Page 2 TECHKNOW • The FSM4000 magnetic flowmeters measure and control the flow of sludge between the tanks • The flowmeters use AC excitation, producing a much less noisy signal • Two ABB temperature transmitters are mounted on the THP tank • Data from the meters is relayed to the plant's SCADA system NEED TO KNOW 1 THP is used in conjunction with mesophilic anaerobic digestion to treat and dewater sewage sludge 2 The Basingstoke plant incorporates an additional intermediate stage into the process 3 Sludge from the MAD is heated to 165°C for 30 minutes under 6.5 barg pressure 4 Pressure and level transmitters have been used to measure sludge levels inside the digestion tanks THE VERDICT "The data from the instruments is a valuable part of this, as it shows not only the impact of any changes we make in the operation of the process, but also gives us an idea of which instruments deliver the best results in terms of accuracy and the delivery of useful data" Ester Rus Perez, senior research engineer, Thames Water The inclusion of pressure, temperature and level devices around the plant has helped to identify other challenges that can arise and how to solve them The SCADA system can also be remotely accessed to enable conditions to be monitored off- site at any time of the day. "A few times, I have found myself dialling into the system late at night and even in the early hours to see what's going on at the plant, especially when things haven't been running as they should," admits Rus Perez. To maximise the efficiency of the thermal hydrolysis stage, the sludge from the mesophilic anaerobic digester is heated to 165°C for 30 minutes under 6.5 barg pressure. Using an ABB swirl meter enables the flow of steam to the process to be accurately monitored to help ensure that the correct amount is being supplied, with the treatment temperature itself being measured by two ABB temperature transmitters mounted on the THP tank. The inclusion of pressure, temperature and level devices around the plant has helped to identify other challenges that can arise and how to solve them, including knowing which instrument is best at detecting particular occurrences.One example is the issue of foaming in the digestion tanks. "Increased surface tension caused by sudden changes in temperature or starting and stopping of the feeding process has frequently led to the formation of foam," says Perrault. "We have to make sure we can detect and measure this as soon as it happens. The presence of foam not only causes problems if it gets into the biogas stream, but it can also reduce the overall efficiency of the process." It is therefore important to be able to detect and assess the extent of foaming and to use the data to put in place anti- foaming measures. During the trial, both pressure and level transmitters have been used to measure sludge levels inside the digestion tanks. Comparison of the two trends from the devices has shown that the difference between the two values was a good estimation of the foam level in the digester, which helped avoid further problems more than once. "If it is shown that ITHP can work on a larger scale, all of the lessons we learn from this installation will be factored into the design of future plants," says Rus Perez. "The data from the instruments is a valuable part of this, as it shows not only the impact of any changes we make in the operation of the process, but also gives us an idea of which instruments deliver the best results in terms of accuracy and the delivery of useful data." The Basingstoke ITHP plant is just one of a number of projects being undertaken by Thames Water's Innovation team to optimise its water and wastewater treatment operations. If the plant is successful, it will form part of the company's drive to increase its generation and use of renewable energy. "It has been a slow and challenging process to get to this point, but one which has also been very revealing, producing valuable lessons and information for building and running future ITHP plants," says Perrault. "For both myself and Ester, it has been great to be involved in developing and testing what could be a ground-breaking approach to producing biogas from sludge."

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