Aeration Energy Utilization and Optimization Approach for Thermophilic Activated Sludge Process

Even though aeration energy utilization is more efficient in thermophilic compared to mesophilic activated sludge systems, optimization and efficient energy utilization should be a major objective of thermophilic aeration systems. Based on several years of design and operational experience, an effective approach to energy utilization and optimization has been developed. This approach is based on the basic concept of matching energy utilization for oxygen transfer with oxygen demand. Two key process control parameters of oxidation reduction potential (ORP) and temperature within the thermophilic reactor are closely monitored on-line and used through a PLC control system for aeration system control and optimization. Secondary process control parameter monitoring in both the bulk liquid and reactor off-gas can also be used for fine-tuning the optimization approach. This process control system is utilized to control both aeration energy utilization and reactor temperature. Target values are initially established, and routine and continuous on-line monitoring trends are developed for optimized aeration system process control. Automated aeration system operational changes are routinely made as a function of the ORP and temperature trend analyses as the primary control parameters. The secondary process control parameters are also useful for fine-tuning the process. This approach has been implemented at full-scale. The methodology, approach, and implementation of this control scheme are addressed herein.