Ozone and Wastewater Disinfection

14th Apr 2020

Ozone and Wastewater Disinfection

Wastewater Disinfection

The use of ozone for wastewater disinfection has been growing in popularity due to the strict regulations on fecal coliform and other pathogens. As chemical costs rise, ozone becomes a more cost effective solution for wastewater disinfection. Ozone can be produced on site using oxygen from the ambient air. Only electrical power is required for operation.

When discharge limits on pathogens are lowered, the natural solution is to add additional chemicals to meet these new limits. Adding more chemicals to a wastewater stream effluent for disinfection may seem like an easy solution at first; however, in many cases these chemicals must then be removed from the effluent wastewater prior to discharge due to limits on these chemicals. For example, if chlorine is used for the reduction of E.coli the chlorine must be removed using dechlorination prior to wastewater discharge. If 20% more chlorine is required to meet the new wastewater discharge limits, 20% de-chlorination must also be applied to this water. Over time, these costs can really add up.

Ozone is a Green Solution

Ozone is a green solution to wastewater disinfection. Ozone is produced on site and is all natural, formed from only oxygen. No by-products or waste products are formed in the creation of ozone.

  • The use of ozone eliminates the need to transport chemicals to the site
  • Ozone is produced on-site from air and electricity, all renewable resources
  • Ozone is a completely renewable resource
  • Potential hazardous storage of chemicals is removed with ozone use
  • After ozone is dissolved into water, ozone reverts to oxygen leaving no residual in the water

Action in Water Chlorine Ozone
Oxidation Potential (Volts) 1.36 2.07
Bacteria Disinfection Moderate Excellent
Virus Disinfection Moderate Excellent
Environmentally Friendly No Yes
Color Removal Moderate Excellent
Carcinogen Formation Likely Unlikely
Organics Oxidation Moderate High
Micro flocculation None Moderate
pH Effect Variable Lowers
Water Half-Life 2-3 Hours 20 Minutes

Operation Hazards

Skin Toxicity High Moderate
Inhalation Toxicity High High
Implementation Complexity Low High
Capitol Cost Low High
Monthly Use Cost Moderate-High Low
Air Pre-treatment None Extensive

The Ozone Advantage

Using ozone for wastewater disinfection offers many advantages in cost savings, space savings, labor savings and cleaner water. More and more wastewater plants are making the switch to ozone use to capitalize on these advantages.

  • Ozone leaves no residual, so only ozone injection is necessary. No second chemical for quenching is necessary.
  • Ozone is produced on site from renewable resources and requires no chemical storage.
  • Ozone is clean, safe and reliable; taking up less space and less equipment than many chemical treatment / storage systems.
  • Using ozone saves money by eliminating on-going chemical costs.
  • Ozone will destroy all bacteria without a preference to one type of organism. Ozone will also remove some BOD, COD and many other contaminates in the waste water stream. Many customers comment on the clarity of the water after switching to ozone.
  • Ozone is effective on wastewater with TDS and TSS levels that may not be acceptable with UV disinfection. Therefore, filtration will not be necessary for ozone use in many wastewater applications.
  • Fewer secondary by-products like tri-halomethones (THM's) are formed with the use of ozone.

Secondary Benefits of Ozone Use

The use of ozone in wastewater disinfection has gained popularity in recent years due to the secondary effects that ozone may offer in some applications. These secondary benefits have helped make ozone a cost-effective alternative and a necessary alternative in some applications.

  • Color removal with ozone is a common use of ozone. While ozone is used primarily for disinfection a secondary effect is color removal of the effluent water stream. Using ozone for disinfection may offer the elimination of a second technology used for color removal.
  • Oxidation of odor causing compounds in the water may also be a secondary effect of ozone use in wastewater. By eliminating these compounds odor control may be completed during the disinfection process.
  • Micro-pollutant removal from water using ozone is gaining interest at a rapid rate. Using ozone for wastewater disinfection may offer the secondary benefit of micro-pollutant removal and eliminate the need to add processes in the treatment stream with future regulations.
  • Suspended solids may also be removed or reduced with the use of ozone. Ozone is commonly used for the removal of suspended solids in drinking water, these same effects are achievable in wastewater.

History of Ozone and Wastewater Disinfection

Ozone used for wastewater disinfection became popular early on when the widespread use of ozone gained popularity in the 1970's and 1980's. Due to lack of equipment reliability and rising costs, the use of ozone almost completely disappeared from this application. In recent years however, ozone is getting another chance in many locations across the USA and Europe. This is partly due to improvement in equipment reliability and lower cost; however, the main reason for this revival is the secondary benefits that ozone offers along with the increased costs of chemicals creating an economic advantage. See the timeline.

Additional Resources

  • Ozone Effects on Pathogens

  • Ozone Disinfection

  • Effect of Ozone on Bacteria