H4-DV15-B drawing The following symbols some of which are Helical gear Reduction Boxes H4

Flender/Flender Gear Units/Helical gear Reduction Boxes H4

indicate theoretical optimal -recycle ratios ranging from 2.6 to 1xADWF for the observed mixed liquor temperature range of 1-2oC. The operating -recycle was therefore too low to fully utilize the denitrification potential of the anoxic zone. Consequently, the plant failed to comply with the fi nal effluent nitrate/nitrite licence limit. By moving the -recycle withdrawal point to the end of the last aerobic cell (Cell all the six installed -recycle pumps are available and can be utilized thus allowi ng the -recycle to be varied to maximum of 1Ml/ (1:1 .. 2 ADWF and 1:6 .. design ADWF) which is within the optimal range to fully utilize the denitrification potential of the anoxic zone. This evaluation shows that there is potential to reduce aeration energy requirements from the current baseline values by optimizing the operating sludge age and -recycle ratios while utilizing the existing aeration control strategy. The optimization will also improve denitrification and result in final effluent compliance with the nitrate/nitrite final effl uent limit which is currently not being met. 4-2 4.6.2 Advanced Process Control Global wastewater industry experience has shown th at implementing advanced process control (APC)1, combination of optimal process control and adva nced aeration control strategies rather than traditional feedback oxygen based real time control can save up to 2% in aeration energy. Literature reviews show that industry definitions of APC when applied to wastewater energy use reduction can differ from place to place. For the purposes of this report, APC is concurrent implementation of optimal process control (as outlined in 4.6. and advanced aeration control strategies other than traditional feedback DO based control. Some of the aeration control strategies that have been tested internationally and can be implemented at Zeekoegat WWTP include: 1. Ammonia Based Control Feedback (FB) cascaded ammonia/DO control Feedfor