Calibration of a whole of works process simulation model for the Mangere wastewater treatment plant

The Mangere Wastewater Treatment Plant (WWTP), situated on the Manukau Harbour, receives the wastewater flow from four municipalities of greater Auckland, treating a population equivalent of one million. The design average inflow to the plant is 390,000 m³/day and the current load to the plant consists of 120 tonnes/day of BOD5, 130 tonnes/day of total suspended solids (TSS), 18 tonnes/day of total nitrogen (TN), and 1.8 tonnes/day of total phosphorous (TP). This large plant provides primary, secondary and advanced level treatment for all flows up to 9 m 3 /s and primary treatment and UV disinfection for further storm flows of 9 - 16.5 m3 /s. The plant is designed to achieve an effluent standard of 15 mg/L TBOD5, 15 mg/L TSS and a total nitrogen of 9.5 mg/L (summer) and 35 mg/L (winter).

A “whole of works” BioWin model was calibrated using the protocols and suggested analytical testing contained in “Methods for Wastewater Characterization in Activated Sludge Modeling”, WERF 2003.

This paper presents a summary of the testing results versus model for each unit process and a discussion of the SBR protocol and its application to a complex treatment process such as Mangere. The paper also discusses some of the key factors influencing the model calibration and some o f the difficulties and uncertainties associated with collection, measurement and interpretation of analytical and SBR data for model calibration.