WWEM - Abstract

Abstract Information :

Wessex Water is continuously seeking new opportunities to improve wastewater treatment plant efficiency and environmental performance. At Holdenhurst WRC, near Bournemouth 180,000 pe, the company originally operated the activated sludge plant ASPs by feeding dissolved oxygen data to the PLC, which controlled the blowers to maintain DO at specific levels approximately 2.5 mgl but with variations across treatment zones. The site had a good record for maintaining a low ammonium discharge, but had a high power amp; aeration requirement, particularly after storm events, with valves manually opened to 100 as the fixed setpoint was often not high enough. Hach Nitrification Real Time Controller N-RTC was installed to optimise the aeration system. The critical input parameters for the N-RTC are the influent NH4-N load and the NH4-N concentration at the outlet of the aeration lanes. Based on these parameters, the N-RTC continuously calculates set points for dissolved oxygen DO required to meet treatment objectives, determining the most efficient level of aeration intensity and continuously feeding DO set points to the PLC in order to control the blowers. This means that DO set points are no longer fixed, but instead vary according to the load. The RTC combines both energy saving, by reducing DO concentrations and hence blower power during low loads, but also increasing DO set points to above normal levels during periods of high loading to ensure ammonium compliance. Site operators have measured a notable reduction in blower power demand since the RTC was installed of circa 25, while improving the sites ammonium compliance.