The sequence of the phases in the SBR cycle consisted of fill, aerobic reaction, anoxic reaction, settle, and decant. The aerobic and anoxic reaction length varied, depending on the nitritation/denitritation rates observed, from 130 to 160 min and from 40 to 50 min,respectively in periods I and II.
The influent was fed from a 100 L tank using a peristaltic pump. The external carbon source was
added during the last 3 min of the feeding phase using a peristaltic pump.
On-line submerged probes of DO, pH and oxidation–reduction potential (ORP) were used to monitor the process.
The SBR operated at room temperature. The probe signals were processed and stored by a programmable logic controller (PLC, Compact Field Point CF-2200, National Instruments).
Aeration was provided byblowers placed at the bottom of the SBR that were switched on and off based upon the DO set point.