Benchmarking plant operation and instrumentation, control and automation in the wastewater industry

Benchmarking is an effective tool to compare the performance of full-scale wastewater treatment plant operation. In this study, 29 wastewater treatment plants from eight countries were surveyed with the aim of developing some key performance indicators, which may be used for benchmarking purposes. The level of utilisation of instrumentation, control and automation (ICA) has also been measured. The study of ICA utilisation revealed that on average only 23% of all sensors are used for online control. For most parameters, ICA is not the single dominant factor determining performance, although it is the factor that has the highest potential to improve performance. Eighty percent of the participating plants had implemented new control during the last five years leading to improvements in nitrogen and phosphorous removal, energy efficiency and ease of operation. The survey has quantified how "non-standardised" wastewater treatment plant operational practice is. Some simple key performance indicators are derived that relate the level of removal of ammonium, total nitrogen, phosphorous and suspended solids to the resources needed for their removal, i.e. volume, energy, organic matter and precipitation chemicals. Several indicators are suggested for each substance. The indicators show a great difference from the best to the poorest performance indicating that improvement potentials exist at many plants.