Ozonation in wastewater treatment has emerged as a well-established and highly effective alternative to enhance conventional approaches. Traditionally, chlorine has been utilized for disinfection in wastewater treatment due to its efficacy and affordability. Nevertheless, a pivotal study conducted in 1970 discovered that chlorine interacts with organic matter, resulting in the formation of disinfection by-products (DBPs). These DBPs can have detrimental effects on public health and aquatic ecosystems. Moreover, incidents of fish mortality were observed in water bodies that received wastewater disinfected with chlorine. To address these concerns, the US Environmental Protection Agency (US EPA) has actively advocated for research into alternative disinfection methods, such as ozonation and UV light disinfection technology.
Ozonation, a widely employed technique in both industrial and municipal wastewater treatment, has proven to be highly effective. This process involves the generation of ozone, a molecule composed of three oxygen atoms, using an ozone generator. The ozone gas is then dissolved in water to eradicate microorganisms and eliminate organic and inorganic pollutants. Acting as a potent oxidizing agent, ozone facilitates the breakdown of organic compounds and safely neutralizes harmful bacteria and viruses through chemical reactions.
Upon entering the water, ozone molecules readily bind to pollutants or microorganisms, initiating oxidation processes that effectively destroy them. Ozonation offers wastewater treatment plants significant flexibility as it can be applied at various stages of the process. Additionally, ozone can be combined with other oxidants, such as hydrogen peroxide, to create Advanced Oxidation Processes (AOPs) in any water purification system.
Ozonation in Wastewater Treatment: How It Works?
The wastewater treatment process encompasses several essential stages, including pretreatment, primary treatment, secondary treatment, tertiary treatment, and disinfection. The primary objective of wastewater treatment is to eliminate pollutants and contaminants from water, ensuring its safe release into the environment. In the industry, both bio and mechanical filtration methods are employed for significant reduction of BOD/COD (Biochemical Oxygen Demand/Chemical Oxygen Demand). Through filtration, the BOD/COD levels are reduced from 115,000 mg/L to approximately 50-100 mg/L. However, the utilization of bio and mechanical filtration methods becomes costly when aiming to achieve further reduction of BOD/COD to lower levels. To address this challenge, numerous Water Treatment Plants (WTPs) have implemented ozonation as an effective solution.
Ozone serves as a highly efficient water polisher and can be utilized as the final step in the wastewater treatment process. In terms of economic feasibility, ozonation offers a cost-effective means to reduce BOD/COD levels to safe thresholds before discharge into the receiving water (To learn how to size an ozone generator, refer to this article). By incorporating ozone systems, not only are processing costs decreased, but penalties associated with the disposal of contaminated water can also be eliminated. Moreover, this clean and environmentally friendly technology brings additional advantages such as increased oxygen demand and improved aesthetic characteristics through the reduction of turbidity.
Importance of Ozonation in Wastewater Treatment
Ozone surpasses chlorine in its effectiveness against viruses and bacteria, offering enhanced disinfection capabilities. The ozonation process requires a relatively short contact time of approximately 10 to 30 minutes. Ozone decomposes rapidly and completely, leaving behind no harmful residues. Additionally, after ozonation, microorganism regrowth is significantly inhibited, with exceptions limited to those protected by particulates present in the wastewater stream. Furthermore, the production of ozone onsite reduces safety concerns associated with shipping and handling, making it a safer option overall.
Advantages of Ozonation in Wastewater Treatment
- The process of oxidizing wastewater effluents offers numerous benefits. These include an elevation in dissolved oxygen levels, a decrease in chemical usage, and a reduction in both turbidity and color.
- Ozonation can be applied as an effective antimicrobial oxidizing agent, disinfectant, and sanitizer.
- Ozone is highly cost-effective.
- Ozone is a natural and environmentally friendly sanitizer that microorganisms cannot develop immunity to.
- While chlorine may not have an impact on Cryptosporidium parvum, ozonation has proven effective in addressing this microorganism.
- Ozone possesses a brief half-life and readily reverts back to oxygen atoms.