On-line monitoring of the enhanced biological phosphorus removal process using respirometry and titrimetry

Enhanced biological phosphorus removal (EBPR) requires alternating anaerobic and aerobic (or anoxic) conditions to favour polyphosphate accumulating organisms (PAO) against other bacteria. Due to its economical and ecological relevance, EBPR is currently a focus of interest in many environmental labs. A sequencing batch reactor (SBR) is used in most lab-scale EBPR systems in order to enrich the sludge with PAO. The management of these reactors is mostly based on off-line measurements such as volatile fatty acids and phosphorus and, if available, intemal storage polymer measurements (polyhydroxyalkanoates or glycogen). However, off-line monitoring of the SBR cycle implies low frequency data sampling and delay between sampling and availability of the results. This is an obstacle for a proper process monitoring and makes difficult the application of control strategies to the process. For this reason, the on-line monitoring of the SBR cycle would improve the daily process management, as well as facilitate the "on-time" detection of abnormal situations and the implementation of new control strategies. This work illustrates that titrimetry and respirometry provide enough information to monitor the EBPR process in lab-scale SBR. For this aim, the effect of EBPR on respirometry and titrimetry is theoretically discussed and several monitoring examples using a lab-scale SBR with a highly PAO-enriched sludge are shown. (C) 2007 Elsevier B.V. All rights reserved.