OPTIMIZATION OF AN AERATION SYSTEM AT AN INDUSTRIAL WASTEWATER TREATMENT PLANT

The Rohm and Haas Company wanted to reduce O&M costs at their Industrial Wastewater Treatment Plant in Bristol, PA. Like most activated sludge facilities, the greatest opportunities for costs savings and optimization revolved around the Aeration System. It was clear the existing Aeration Blowers were well oversized and the existing instrumentation was not reliable. Therefore, Rohm and Haas embarked on a program to systematically review the entire Aeration System and answer the following key questions:How much air is really required for the process?Are the existing blowers correctly sized and operating efficiently?Do we have accurate data for Dissolved Oxygen (D.O.), air flow, blower amps and other key parameters? If not, should we install any new instruments?Should we modify the Aeration System controls?What else can we do to improve the operability of the systemHow can our experiences benefit other Rohm and Haas Facility's and other WWTPs?Rohm and Haas applied Reliability Engineering principles and basic common sense to try and answer the above questions and reduce costs. As a result, the following major changes were implemented:Interconnected the Aeration and Sludge Storage Tank Air Headers and eliminated the need to run two 40 HP blowers.Replaced the eight D.O. sensors and transmitters with new instruments.Replaced the eight annubars and differential pressure transmitters for air flow with new mass flow devices.Repaired and adjusted the eight motor operated air control valves and three blower inlet throttling valves.Removed half of the fine bubble diffusers in each aeration tank.Instituted new control schemes for the Aeration System in the computer control system in order to minimize energy usage while maintaining the process.These changes have already resulted in operating cost savings of over 40,000 per year. The optimization work continues, primarily related to the three (3) 300 HP Aeration Blowers which are considerably oversized and therefore operating very inefficiently.The Authors believe this work can be applied at many activated sludge plants (both industrial and municipal) to optimize operations and save costs. Furthermore, engineers should keep in mind operating flexibility and efficiency when designing new plants or upgrading existing facilities.