Optimizing Ozone Treatment for Safe Drinking Water and Disinfection Control

Jim Crocker
20th August, 2024

Optimizing Ozone Treatment for Safe Drinking Water and Disinfection Control

Image Source: Natural Science News, 2024

Key Findings

  • The study by the Federal University of Rio Grande do Sul investigated ozonation conditions to effectively remove pathogens from reclaimed water
  • Ozonation significantly reduced pathogens, including total coliforms, E. coli, PMMoV, ToBRFV, and HNoV, with varying log reductions
  • Higher ozone doses increased harmful byproducts like bromate and NDMA, indicating a need for additional treatment steps to control these byproducts
Reclaimed water, which is treated wastewater intended for reuse, poses environmental and human health risks due to the presence of residual organic micropollutants and pathogens. The ozonation of reclaimed water is a crucial step in advanced water treatment systems for potable reuse, aiming to control pathogens and trace organics. However, ensuring efficient pathogen reduction while controlling disinfection byproducts remains a significant challenge. A recent study by the Federal University of Rio Grande do Sul aimed to investigate ozonation conditions using a plug flow reactor (PFR) to achieve effective pathogen removal/inactivation while minimizing the formation of harmful byproducts like bromate and N-Nitrosodimethylamine (NDMA)[1]. The study was conducted on a pilot scale using three different doses of ozone (0.7, 1.0, and 1.4 ozone/total organic carbon (O3/TOC) ratio) to determine the disinfection performance using actual reclaimed water. The efficiency of disinfection was assessed by measuring the reduction in concentrations of total coliforms, Escherichia coli (E. coli), Pepper Mild Mottle Virus (PMMoV), Tomato Brown Rugose Fruit Virus (ToBRFV), and Norovirus (HNoV). The ozone CT values, which represent the product of the concentration of ozone and the contact time, ranged from 1.60 to 13.62 mg.min L-1. The results showed significant reductions in pathogens and indicators, with concentration reductions of 2.46-2.89 log for total coliforms, 2.03-2.18 log for E. coli, 0.46-1.63 log for PMMoV, 2.23-2.64 log for ToBRFV, and greater than 4 log for HNoV. The study also found that after ozonation, the concentrations of bromate and NDMA increased, reaching levels between 2.8-12.0 μg L-1 for bromate and 28-40.0 ng L-1 for NDMA. These increases were more pronounced with higher ozone dosages, indicating a potential need for additional removal or control steps in subsequent treatment processes in some potable reuse applications. The findings from this study align with and expand upon previous research. For example, a study on the detection of SARS-CoV-2 RNA in wastewater highlighted the need for effective disinfection methods to mitigate the risks posed by pathogens in treated water[2]. The current study's focus on multiple pathogens, including viruses, broadens the scope of pathogen control beyond what was previously addressed. Additionally, the use of PMMoV as a performance indicator for viral reduction in wastewater treatment plants was supported by earlier research, which found PMMoV to be a promising indicator due to its persistence and detectability[2]. Moreover, the study's investigation into bromate and NDMA formation during ozonation builds on findings from a Swiss study on advanced treatment for micropollutant abatement in wastewater treatment plants[3]. The Swiss study recommended specific ozone doses to ensure effective micropollutant removal while highlighting the need for biological post-treatments to address potential negative effects generated during ozonation. The current study's observations on the formation of bromate and NDMA underscore the importance of considering disinfection byproducts in the design of ozonation processes, reinforcing the need for comprehensive treatment strategies. The use of sequential ozone-chlorine disinfection has been shown to improve the efficiency of pathogen inactivation compared to single disinfection methods, as demonstrated in a study on reclaimed water disinfection[4]. The current study's focus on optimizing ozone doses to minimize byproducts while achieving effective pathogen reduction provides valuable insights into enhancing the overall efficiency and safety of reclaimed water treatment processes. In summary, the study by the Federal University of Rio Grande do Sul contributes to the understanding of ozonation conditions necessary for effective pathogen removal in reclaimed water while addressing the challenges of disinfection byproduct formation. By building on previous research and exploring the interplay between ozone dosage and byproduct formation, the study offers practical guidance for optimizing advanced water treatment systems to ensure the safety and sustainability of potable water reuse.

EnvironmentHealthSustainability

References

Main Study

1) Optimizing ozone treatment for pathogen removal and disinfection by-product control for potable reuse at pilot-scale.

Published 17th August, 2024

https://doi.org/10.1016/j.chemosphere.2024.143128

Related Studies

2) Reduction of SARS-CoV-2 by biological nutrient removal and disinfection processes in full-scale wastewater treatment plants.

https://doi.org/10.1016/j.scitotenv.2023.165097

3) Evaluation of a full-scale wastewater treatment plant upgraded with ozonation and biological post-treatments: Abatement of micropollutants, formation of transformation products and oxidation by-products.

https://doi.org/10.1016/j.watres.2017.10.036

4) An insight to sequential ozone‑chlorine process for synergistic disinfection on reclaimed water: Experimental and modelling studies.

https://doi.org/10.1016/j.scitotenv.2021.148563


Related Articles

An unhandled error has occurred. Reload 🗙