Do I need to control internal recycle?
For maximum nitrogen removal, yes. The internal recycle in a Carrousel® system is free and is not limited by pumping capacity and can approach 15-20Q . While this high recycle rate is good for nitrate delivery to the anoxic zone, this large recycle amount can dilute the incoming BOD and anoxic zone detention times, suppressing overall nitrogen removal. A control system on the internal recycle allows you to have unlimited nitrate recycle capacity and allows you to make adjustments based on ORP measurements to deliver the optimum nitrate recycle at any given time.