Lessons learnt from the application of a multi-variable controller for nitrogen removal in the Mekolalde wastewater treatment plant: good simulation practices in control

Abstract

Although often perceived as tools for use by scientists, mathematical modelling and simulation become indispensable when control engineers have to design controllers for real-life wastewater treatment plants (WWTPs). Nonetheless, the design of effective controllers in the wastewater domain using simulations requires effects, such as the nonlinearity of actuators, the time response of sensors, plant model uncertainties, etc. to have been reproduced beforehand. Otherwise, control solutions verified by simulation can completely underperform under real conditions. This study demonstrates that, when all the above effects are included at the outset, a systematic use of simulations guarantees high quality controllers in a relatively short period of time. The above is exemplified through the Mekolalde WWTP, where a comprehensive simulation study was conducted in order to develop a control product for nitrogen removal. Since its activation in May 2011, the designed controller has been permanently working in the plant which, from this time onwards, has experienced significant improvements in the quality of water discharges combined with a lower utilization of electricity for wastewater treatment.

Sewage Treatment Plants

“…In practice, the most implemented solution consists of the regulation of the internal flow-rate between the oxic and the anoxic reactors so that the nitrate concentration at the end of the anoxic zones is kept at a low value (e.g., 0.4 g N/m 3 ). Such a control strategy has been successfully implemented in the Galindo-Bilbao WWTP (Ayesa et al 2006) and in the Mekolalde WWTP (Irizar et al 2014). Such a control strategy has been successfully implemented in the Galindo-Bilbao WWTP (Ayesa et al 2006) and in the Mekolalde WWTP (Irizar et al 2014).…”

Modeling, Instrumentation, Automation, and Optimization of Water Resource Recovery Facilities

“…investigated the sensitivity of wastewater treatment plant model performance to the selection of one-dimensional secondary settling tanks (1-D SST) models with first-order and second-order mathematical structures. Based on the parameter sensitivity rankings obtained in this study, the settling parameters were found to be as influential as the biokinetic parameters on the uncertainty of plant model predictions, particularly for biogas production and treated water quality Irizar et al (2014). demonstrated that, when effects such as the nonlinearity of actuators, the time response of sensors, plant model uncertainties, etc.…”