Water resource recovery facilities often implement process automation to improve treatment performance and decrease operational costs. However, successful automation requires robust and reliable instrumentation, and many utilities lack the resources to test and confirm before purchase. For this reason, a study that tested different online analyzers was conducted at the Sacramento Regional County Sanitation District’s 946-m3/d (0.25-mgd) Advanced Treatment Technology Pilot Plant in Elk Grove, Calif. The pilot facility evaluated secondary and tertiary treatment technologies capable of meeting new discharge permit restrictions. Testing online instruments was one component of the pilot program and included ammonia/ammonium, nitrate, total suspended solids, and dissolved oxygen analyzers. The analyzers were evaluated for monitoring and controlling a biological nutrient removal (BNR) process at the demonstration-scale treatment facility. Results confirm that the optical measurement technologies for dissolved oxygen, total suspended solids (TSS), and nitrate typically produce reliable and repeatable data within the ranges that were tested and can be used for process control. Ammonia analyzers in this particular application showed that certain ion-selective electrode technologies can be used with confidence with adequate cleaning and calibration; however, an ex situ analyzer capable of lower-level accuracy was preferred for process control.