WET News

14 WET NEWS JULY 2014 Construction at the Taunton sewage treatment facility has included removing one lagoon and four filters in order for the new works to be accommodated Optimising energy savings through real-time control • An upgrade of its Taunton STW has provided an ideal opportunity to lower energy costs and carbon footprint. TECHKNOW • Optical LDO sensors for measuring dissolved oxygen in each of 12 zones within four activated sludge lanes • AMTAX ammonium analysers continuously monitorASP influent and effluent • Two SOLITAX probes measure MLSS in the aeration lanes and the solids content of the RAS • Nitrification Real Time Controller (N-RTC) monitors ammonium load and adjusts DO set-point accordingly. This reduces energy consumption and improves efficiency significantly • Later in the year when the plant has been fully commissioned the ammonia control system will be brought into full auto-operation. W essex Water is invest- ing around £20M at Taunton (Ham) sew- age treatment works to improve the facilities for wastewater and sludge treatment in a project that is due for completion by the end of March 2015. The upgrade to the works under the DWF (dry weather flow) Improvements Scheme will increase the site's treatment capacity whilst also improving the efficiency and quality of the treatment process, lowering energy costs and re- ducing the site's carbon foot- print. Prior to the implementation of the DWF scheme, the treat- ment works comprised an inlet pumping station and balance tank; coarse and fine screens; grit removal (detritor); primary settlement tanks; a conven- tional Activated Sludge Process (ASP) and biological filter beds; final and humus tanks; and final effluent lagoons. The construction work involves the creation of a new four-lane ASP to replace the existing 16 biological filters. To facilitate this, one of the lagoons and four filters are being taken out of service to create space for the new works. This has allowed all development to remain within the existing site bounda- ries, enabling most works to be constructed under permitted development rights. Parameters Process optimisation of the new ASP stage will be achieved through implementation of Hach Lange's Real-Time Control (RTC) system, which monitors PROJECT SPECS • The Dry Weather Flow Improvements Scheme will increase treatment capacity whilst improving the efficiency and quality of the treatment process • Construct a new four-lane ASP to replace the existing 16 biological filters • Remove one lagoon and four filters • Implement a Real-Time Control system for process optimisation THE VERDICT • The equipment has been manufactured to programme and delivered to site in readiness for installation. • The development of the N-RTC system for Taunton and its integration with the new build has required a collaborative approach with Hach Lange, Nomenca and Wessex Water's Automation Team. • The construction element of the project is forecast to be complete within the project timescales and the instrumentation is being installed ready for initial commissioning during August 2014 • Having already seen 25% energy reduction from real-time control at the Holdenhurst WwTW near Bournemouth, the project team is confident that this refurbishment will result in a substantial saving in energy costs ONSITE Energy efficiency influent ammonium concentra- tion and dissolved oxygen con- centrations along the aeration lanes, providing more efficient control of the fine bubble dif- fused aeration. The measure- ment of other quality parame- ters in the process train provides feedback to the RTC. A reduc- tion of up to 15% energy usage is anticipated as a result. Balfour Beatty Regional Civil Engineering has provided the civil works and Nomenca is responsible for the supply, installation, commissioning, and performance testing of the mechanical and electrical com- ponents of the new works. Contracts manager Trevor Farrow says: "Nomenca's repu- tation is built on a track record of successfully delivered pro- jects, and the relationships that we develop with both clients and suppliers are key to this success. We have already worked with Hach Lange's instrumentation on a wide vari- ety of projects, so we are confi- dent that this project will be a further success." As project manager for Wes- sex Water, Garry Orford says: "The drivers for this works upgrade include an increased treatment capacity requirement and a tightening of the consent, taking in to account longer-term requirements that may be imple- mented in AMP6. We have already implemented Hach Lange's RTC process optimisa- tion systems at our Holdenhurst plant near Bournemouth, and this has delivered energy sav- ings of around 25%. We are con- fident that we can repeat this Nomenca is installing and testing the mechanical and electrical components of the new works Optimising energy savings through real-time control "The power generation of the AD plants is fairly stable, but the energy demand of the treatment plant varies according to the load" Garry Orford. Wessex Water success at Taunton." Following completion of the new works, the site will meet the following consent conditions: • Dry Weather Flow (DWF) 30,595m 3 /d • Sanitary parameters BOD:SS: AmmN 15:30:3mg/l In addition to the upgrade of the sewage treatment facilities, a third anaerobic digester (AD) is also being built at the Taun- ton works. "This will increase our capacity to generate renew- able energy and further reduce our electricity bill," says Orford. "The power generation of the AD plants is fairly stable, but the energy demand of the treat- ment plant varies according to the load, so there will be occa- sions where we can sell energy back to the grid, and others where we will continue to have a power requirement. It is essen- tial therefore that we use this power as efficiently as possible." Real-Time Control in indus- trial processes is commonplace. However, wastewater monitor- ing represents a greater chal- lenge because of its physical and chemical variability. Health status Historically, wastewater moni- toring technology was prone to dri' (especially galvanic dis- solved oxygen monitors) and required a high level of mainte- nance, so RTC was not feasible. However, the latest sensors offer much higher levels of reliability than was possible in the past, with substantially lower levels of maintenance and recalibration. This has been a major fac- tor in enabling the development of RTC in wastewater treatment. Also, many of the latest sensors provide a 'health status' output in addition to the readings. As a result, if any problems arise they can be quickly reme- died, and control systems can ignore data from sensors that are not performing to their tar- get specification. The capital outlay for the addition of RTC to a treatment plant is relatively small; the most significant extra cost is the requirement for extra sensors plus the RTC unit. The Taunton build includes the installation of the latest sensors for dis- solved oxygen, ammonium and turbidity, controlled by an sc1000 network, providing reli- able data on the influent, and from within the treatment process. The LDO sc dissolved oxygen sensor employs an optical lumi- nescence method for www.evoquawater.co.uk info.uk@evoqua.com © 2014 Evoqua Water Technologies Ltd Key benefits of upgrading your Activated Sludge Plant to a BioMag™ System • Simplicity and reliability • Enhanced nutrient removal (ENR) • 3X activated sludge capacity without new tankage • 5X hydraulic capacity • TN < 3.0 mg/L and TP < 0.2 mg/L embrace gravity. defy convention. The BIOMAG™ SYSTeM Increase plant throuput, eliminate clarifier bottlenecks and improve secondary effluent quality by retrofitting your Activated Sludge Plant with BioMag™ System. 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