The five zones — anaerobic, anoxic, aerobic, anoxic, and aerobic — each require dedicated tank space, which is the critical component and cost of the Bardenpho process. Municipalities that experience high flows due to storm events and inflow and infiltration (I&I) require even further capacity.
In addition to tanks and aeration blowers, anoxic mixers are necessary for the zones that aren’t aerated, and a recycle pump is needed to return the mixed liquor back to the front of the cycle for denitrification, as shown in the diagram above.
The importance of the recycle pump, and of backup equipment, was impressed upon the FRWRD staff in March of 2013, when a faulty wire shut the pump down and sent effluent nitrogen levels up to 18 mg/L. With no nitrogen mandate in place, the experience merely served as a valuable lesson for when regulations could be in play. “With that knowledge now, we will make sure that we have additional equipment available,” Trueblood vowed. “So if this occurs in the future, we can take temporary measures to continue to denitrify and to meet the demands.”
Mostly, however, the Bardenpho process is easy to operate and maintain. FRWRD does it with just two full-time operators — in addition to shared maintenance personnel — but they also get help from their supervisory control and data acquisition system (SCADA).
“If you’re going to do Bardenpho, or any type of advanced system, I think you really need to make sure that you have a good SCADA system there,” advised Trueblood, “particularly if you aren't staffed 24 hours a day. If you have an alarm condition, can you dial in with a laptop and take care of it? I think SCADA is fairly critical for any type of process like this.”