Water & Wastewater Treatment Magazine
Issue link: https://fhpublishing.uberflip.com/i/515382
16 | JUNE 2015 | WWT | www.wwtonline.co.uk Project focus: wastewater treatment under normal operation parameters reducing power consumption by up to 60%, while minimising sludge output. System control The highly automated approach to mechanical and electrical control of treatment at Stoke Bardolph has been a step-change for the technology provider in the way their systems are operated. All previous installations have been at more heavily manned sites, while in Nottingham the plant runs itself, flagging operational issues through an automated system. NMCNomenca and Paques worked closely to deliver and optimise the operation and control system. One of the challenges was matching treatment with the characteristics of the waste stream itself, which changed as the project progressed. A pilot test was carried out a few years ago to prove the process. This showed that fundamentally the process would work at Stoke Bardolph. a successful ANAMMOX installation of at Minworth sewage treatment works, its largest, in 2012. In the ANAMMOX reactor, ammonium is converted to nitrogen gas by two coexisting species of bacteria. Nitritation bacteria oxidize about half of the ammonium to nitrite, while anammox bacteria convert the ammonium and nitrite into nitrogen gas. The treated wastewater leaves the reactor by passing the biomass retention system at the top of the reactor. The granular biomass is separated from the cleaned wastewater, assuring high biomass content in the reactor. Together with the dense conversion properties typical for granular biomass, the high biomass content provides for high conversion rates and therefore a small reactor volume. The use of heat-exchange technology means the temperature in the ANAMMOX reactor is self-sustaining "It's by far the most complex control system we've worked with," says Simon Kuitert, Paques process engineer. "We've never automated Phospaq like this before. It's been a learning process." Process benefits The new plant stacks up some major benefits. In terms of footprint, the highly efficient pre-treatment process brings it in at 25% of the size of a conventional ASP plant. This has removed the necessity for a further ASP plant and associated treatment tanks, achieving major savings on the total expenditure (totex). A saving of 40% capex was achieved compared to the alternative solution. Further, the installed system demands only 50% of the air of a standard ASP, so power consumption and energy costs are slashed too. The plant also uses surplus heat from CHP production and the exothermic process within the ANAMMOX to recycle its own internal heat. Some 1,000MWh per year is produced on site. Further operational expenditure (opex) savings are made when the new processes are compared with conventional nitrification and denitrification. Operational costs are reduced by over 50%, as are CO2 emissions. Each element of the innovative technology is suitable for use either independently or combined, where similar waste streams exist. This is applicable on many of the major treatment plants across the UK particularly in areas with industrial waste streams and those with phosphorus discharge consents. Magnesium-oxide dosing pumps feed the PHOSPAQ reactors to enable precipitation of struvite Partnership working was key to the project. Le to right: John Jenkins, Teresa Jeffcoat (both NMCNomenca); Simon Kuitert (Paques); Paul Bejar (NMC- Nomenca) Dylan Thorley (Severn Trent Water). Simon Kuitert, Process Engineer at Paques, and John Jenkins, Site Manager for NMCNomenca, inspect the pipes which take air to the reactors.