Relating ions concentration variations to conductivity variations in a sequencing batch reactor operated for enhanced biological phosphorus removal

In this paper a deterministic relationship between ionic conductivity and phosphorus concentration variations in an enhanced biological phosphorus removal (EBPR) process is established. Conductivity shows a strong correlation with phosphorus in both anaerobic and aerobic stages, increasing or decreasing when phosphorus is released or taken up, respectively. Since the end of these processes can be detected by examining the conductivity profile in a cycle, useful information on the EBPR performance and stability is available. This information can be used for adjusting the length of the anaerobic and aerobic stages. Therefore, online process control based on inexpensive and easy to maintain sensors could be applied. Laboratory scale experiments were conducted to study the most significant ions concentration behaviour in a sequencing batch reactor (SBR) operated for EBPR as well as the conductivity and pH profiles. Statistical analysis of the experimental data also showed a strong correlation between metal cations and phosphorus concentrations (0.28 mol K mol P−1 and 0.36 mol Mg mol P−1). The model used in the simulation stage (BNRM1) takes account of all the ions that play an important role in the EBPR process as well as the pH value. Model predictions accurately reproduced the experimental data.