Using mathematical models to track phosphorus in a full-scale wastewater treatment plant

The challenges associated with pollution, declining nutrients and water shortage, resulted in the need for strategies towards cost effective recovery of nutrients from waste types fed to wastewater treatment systems, to forms that are usable and possibly marketable, while ensuring maintenance of good effluent quality from the plant. To address these challenges, the plant wide model (PWM_SA) of Ikumi et al. (2015) was utilized to evaluate and propose operational strategies for Zeekoegat WWTW of the City of Tshwane to help with future design or optimized operation of the system. This goal was achieved by (i) acquisition of all necessary data from Zekoegat WWTP, (ii) Reconciliation of measured data and subsequent characterization of the influent WW using widely documented protocol to run an excel steady state model which uses explicit mass balanced equations and (iii) setting up Zeekoegat WWTW virtually within the WEST® dynamic simulation environment and ensuring that confidence is achieved in virtual replication of the plant before testing operational scenarios. The two operational strategies were simulated and evaluated using performance indices (PI's: operational cost index (OCI) and effluent quality index (EQI)) derived from a previous investigation by the International Water Association (IWA) benchmark simulation modelling task group (Copp, 2002, Nopenset al., 2010). These PI's were modified by De Ketele et al. (2018) and later extended by Coothen (2021) and they proved to be a useful approach to evaluating the environmental (EQI) and economic (OCI) impact of a WWTP based on any operational strategy implemented i.e., optimizing water resource recovery (WRRFs) and troubleshooting problems to improve our wastewater treatment systems in South Africa