Demonstrating organic contaminant removal in an ozone-based water reuse process at full scale

The 350 ML per d Eastern Treatment Plant (ETP) tertiary facility produces “Class A” water for the city of Melbourne, Australia, which is used for irrigation, dual reticulation and fire fighting. The ETP process utilizes ozone and biological media filtration as part of the advanced treatment train for secondary treated wastewater. An extensive sampling campaign was carried out to evaluate the removal of hundreds of contaminants of concern through various steps in the treatment train, as well as identify the formation of any byproducts of the treatment process. Degradation of contaminants throughout the treatment was mainly controlled by the ozone process. Chemicals with moderate to high reaction rates with ozone and/or ˙OH radical (10 M−1 s−1 ≤ kO3 or kO3 < 10 M−1 s−1 and k˙OH ≥ 5 × 109 M−1 s−1) were removed by the tertiary treatment to below the detection limit. However, the advanced treatment train resulted in some contaminants increasing in concentration (i.e. NDMA and desisopropyl atrazine) and other newly forming contaminants, such as trihalomethanes and chloral hydrate. The resulting levels of contaminants of concern remaining in the ETP final effluent were below levels of relevance based on guidelines for reuse in irrigation or discharge to the environment.