Real-time monitoring of enhanced biological phosphorus removal in a multistage EBPR-MBBR using a soft-sensor for phosphates

Abhilash M Nair,Blanca M Gonzalez-Silva,Finn Aakre Haugen,Harsha Ratnaweera,Stein W Østerhus

doi:10.1016/j.jwpe.2020.101494

Abstract

Enhanced biological phosphorus removal (EBPR) from municipal wastewater has been achieved in a multistage Moving Bed Biofilm Reactor (MBBR) configuration. The process operations can be further optimized by real-time monitoring of water quality parameters in the individual chambers of the EBPR-MBBR process. This work presents a hybrid, soft-sensor as a cost-effective monitoring option for real-time estimation of phosphates (PO43−-P) and soluble COD (sCOD) concentrations in the anaerobic chambers of a multistage EBPR-MBBR pilot plant. The soft-sensor is developed by implementing an Extended Kalman filter on a reduced-order nutrient removal model. The hybrid model is constructed by combining mechanistic elements of phosphorus release kinetics in anaerobic conditions, and a statistical model correlating PO43−-P and sCOD concentration with conductivity measurements. A systematic method for developing, calibrating a reduced-order model and tuning of the Kalman filter parameters have been discussed in this work. The drift in soft-sensor performance was studied and practical solutions were suggested for re-calibrating the model utilizing data from periodic lab measurements. The estimation results are successfully validated against standardized lab measurements to demonstrate the accuracy of the soft-sensing algorithm.

Highlights

Enhanced biological phosphorus removal (EBPR) process is a treatment configuration designed for phosphorus removal from wastewater
The plots indicate an increase in conductivity measurements when the PO43−-P ions are released and soluble Chemical Oxygen Demand (sCOD) is consumed under anaerobic conditions, These observations are consistent with the results obtained from similar experiments [12,25,8]
A reduced-order model explaining the dynamics of phosphorus release during the anaerobic stage of biological wastewater treatment process was developed

Summary

Introduction

Enhanced biological phosphorus removal (EBPR) process is a treatment configuration designed for phosphorus removal from wastewater. The EBPR process consists of an anaerobic stage before the aeration stage, where a specific species of biomass called polyphosphate-accumulating organisms (PAO) is enriched [1]. A novel configuration was reported by [13] for achieving EBPR in a continuous moving bed biofilm reactor (MBBR) process. The reactor performance is currently monitored using off-line laboratory analysis of PO43−-P, soluble Chemical Oxygen Demand (sCOD) volatile fatty acids (VFA) ammonium (NH4+-N), nitrites (NO2--N) and nitrates (NO3--N). Off-line monitoring implies a low sampling frequency, leading to potential non-optimal conditions between the sampling instances, and a subsequent delay between sampling time, hampering adjusting of the process conditions, and data availability. Sample preparation, and lab analysis involve additional man-hours and costs associated with chemicals and kits required for lab analysis

Methods

Results

Conclusion