Testing Online Analyzers for Biological Nutrient Removal Process Control

Online analyzers were evaluated for monitoring and controlling a biological nutrient removal process at a demonstration-scale treatment facility. The instruments were tested at the Sacramento Regional County Sanitation District’s Advanced Treatment Technology Pilot plant, which is located at the Sacramento Regional Wastewater Treatment Plant in Elk Grove, California, USA. The pilot plant was constructed for the purpose of evaluating secondary and tertiary treatment technologies capable of meeting new discharge permit restrictions ; the evaluation of online instruments was a component of the overall pilot testing program to provide information for full-scale design and operation. The online instruments included ammonia/ammonium, nitrate, total suspended solids, and dissolved oxygen analyzers. Experience was gained in using the instruments for both monitoring and control of the treatment process. Results of the testing show confidence that the optical measurement technologies for dissolved oxygen, total suspended solids, and nitrate typically produce reliable and repeatable data within the ranges that were tested and can be used for process control. Testing of ammonia analyzers in this particular application showed that certain ion-selective electrode technologies can be used with confidence provided that adequate cleaning and calibration is performed, however, an ex-situ analyzer capable of lower level accuracy was preferred for process control.