A framework to determine the optimum contact time and organic micropollutant removal efficiency of the ozone process applied in the context of Cape Flats Managed Aquifer Recharge Water Reclamation Plant

Final wastewater treatment plant effluent is widely recognised as a hazardous water source for human consumption as it may contain organic micmpollutants and pathogens. The advanced processes required to adequately remove them are costly, and consequently, it is crucial to investigate how the associated costs can be optimised. One of the key treatment steps in the treatment train of the Cape Flats Managed Aquifer Recharge (MAR) water reclamation plant (WRP) is the advanced ozonation (O-3) treatment process. The O(3 )process was assessed using the T-10 and CSTR methods. The O-3/TOC dose ratio was used as the main parameter to compare and relate various O(3 )treatment objectives and assessment methods. Furthermore, an O(3 )contact time optimisation was performed on the Cape Flats O(3 )process using capital and operation and maintenance (O&M) costing models, as well as process performance regression models. The optimum contact time, in terms of cost for 2-4 Log virus inactivation by ozone and 1-3 Log giardia inactivation by ozone, was determined to be between 5 and 7 min by the CSTR method, and 5 min by the T-10 method. The optimum contact time, in terms of cost for 1-3 log inactivation of cryptosporidium by ozone, was determined to be between 8 and 18 min by the CSTR method, and between 6 and 13 min by the T-10 method, depending on the treatment objective and O(3 )transfer efficiency. The O(3 )process of the Cape Flats MAR WRP can theoretically reduce more than 87% of the organic micmpollutants in the Cape Flats Wastewater Treatment Works (WWTW) final effluent.

Automated summary

Final wastewater treatment plant effluent is recognized as a hazardous water source for human consumption due to potential contamination. This article investigates how to optimize the costs of advanced ozonation treatment process to adequately remove contaminants.