We are proud to provide a sustainable, affordable, clean and safe water supply and to manage and treat the waste water returned to us in a way that protects the environment.
We are continuously working to develop beneficial disposal routes for the sludge remaining after sewage treatment and our latest scheme will convert green energy into power which will supply our treatment works at Bran Sands.
It is the biggest single plant of its kind in the UK and uses the emerging new technology of ‘thermal hydrolysis advanced digestion’, putting us at the forefront of the industry.
Sludge is squeezed to further reduce water content before being loaded into giant steam pressure cookers and then cooled before being fed into tanks for bacteria to digest. The methane given off by the bugs eating the waste is collected in biogas storage bags before being used to fuel engines to create enough renewable electricity to power about half of the entire treatment works site. Heat and steam generated is also captured and used efficiently elsewhere in the process.
The digested sludge cake remaining after the process is a safe and low odour product containing no detectable levels of pathogens, such as E-coli, and is used as a valuable agricultural fertiliser.
Since sludge was initially introduced in August 2009, the commissioning programme has been a gradual process, greatly dependant upon the complex biological system within the three digesters. The site is now treating approximately half of all NWL sludges actually produced and is generating 3.1MW electricity on site at Bran Sands.
The sludges which have been introduced so far are sludges produced from the on-site effluent treatment works, liquid sludges from local satellite sites and sludge cake from various sludge treatment centres.
The process will improve efficiency and reduce our carbon footprint. It will reduce more than 500,000 tonnes of sludge – from the treatment of domestic sewage and industrial effluent from a population equivalent of 1,900,000 people – to about 60,000 tonnes and will generate five megawatts of green electricity.
Operations Director, Graham Neave, said: “This is another leading development at our Bran Sands works which has already won international awards for innovation. Development of this sustainable process to re-use and recover valuable resources from sludge and create renewable energy puts Bran Sands once again in the national spotlight as a centre of environmental excellence”.
The plant has now been commissioned as being operated by NWL staff. The final stage of the project is to carry out intensive testing to confirm plant performance and to ensure that operations are able to operate and optimise this plant so that best performance can be achieved and maintained.