Water & Wastewater Treatment

www.wwtonline.co.uk | WWT | MARCH 2016 | 27 T oday's innovative water companies are shiing their focus from sewage disposal to energy generation: processing waste in new ways can transform it from Mark Neal UK SALES MANAGER SAxLUNd INTERNATIoNAL a bigger slice of cake With utilities seeking to get the most value from sludge, it's vital to ensure sludge is dewatered, transported and stored in an optimal way In the know Getting to grips with... sludge cake optimisation Truck loading systems for transferring sludge need to run smoothly being a costly overhead to a source of revenue. Water companies can apply new technology to address the combined challenges of a rapidly growing population which is producing more sewage, the need to reduce overhead costs, and the need to meet environmental targets. Generating gas from sludge at large water treatment sites using anaerobic digestion and thermal hydrolysis infrastructure is a key part of the solution. Sludge can be dewatered into a cake to minimise its bulk, thus reducing transportation and storage costs by up to 75% - sludge cake optimisation is therefore an essential factor in managing waste. What are the key challenges in exploiting sludge through advanced digestion? There are several issues water companies face in building new advanced digestion facilities. Obtaining planning permission to build large industrial structures in the countryside is oen cited as a key issue, along with concerns over unpleasant odours and disruptive truck movements. Population growth requires wastewater treatment technology to keep pace with ever- increasing volumes of sewage sludge, while grid connection and certainty over continuous industrial fuel supply and consumer fuel demand are essential in the long term. The spread of landmass available to receive waste from water companies (as well as from food, drink, and biofuel manufacturers) is limited, so an alternative solution is required. Why do water companies need to transfer sludge between sites? Economy of scale means the default model is a large digestion hub serviced by smaller satellite storage units. Large treatment sites in towns and cities (hubs) can receive sludge transported from smaller storage stations (satellites). The alternative is for multiple smaller treatment works to cover demographics, but to date these have not proved cost effective. In order to maintain economy of scale investment in advanced anaerobic digestion (AAD) efficiency at each installation, indigenous waste needs to be topped-up, which means transferring sludge between sites. Davyhulme (United Utilities) and Colchester, Cliff Quay and Pyewipe (Anglian Water) are examples of hubs being served by satellites. What methods are available for transporting it? Existing transport options include

• Cover