Design of intelligent control strategies for full-scale wastewater treatment plants with struvite unit

Abstract

In this study, intelligent (fuzzy logic) control strategy is designed for plant-level wastewater treatment plants (WWTP) with an aim to reduce the operational cost and improve the effluent quality. Benchmark simulation model (BSM2PSFe) with an additional resource recovery unit (Struvite unit) is considered as a working platform. Binary-level control topology is designed in which lower-level PI controllers are implemented to control dissolved oxygen (DO) in the first, second, and third aerobic reactor and fuzzy logic controller (FLC) is designed at the supervisory level. This supervisory level considers the ammonia (NH3) in the second and third aerobic reactor to alter the DO set-points in the lower level. Six control approaches (CA1, CA2, CA3, CA4, CA5, and CA6) are developed by using different combinations of PI and FLC Both operational cost index (OCI) and effluent quality index (EQI) were improved by 9.9 % and 1.14 % respectively in the case of CA2 when compared with the existing open-loop. Nevertheless, EQI was improved by 7.1 % with a slightly higher OCI in the case of CA5. In most cases, greenhouse gas emissions were also decreased. The ammonia, total nitrogen, and total phosphorus concentration removal rates were improved by 87.14 %, 5.6 %, and 5.8 % respectively.