Municipal Water Treatment with ozone for small to mid-sized plants

Ozone has been used for municipal drinking water continuously in the USA since 1940. Ozone use for drinking water treatment is one of the oldest and most well known uses for ozone worldwide.

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As of 2013, at least 277 Water Treatment Plant’s (WTP’s) operating in the USA utilize ozone. This number only includes plants larger than 1 MGD capacity. These plants have a combined combined capacity of 14.5 billion gallons per day with ozone production greater than 600,000 lb/day. Since 1993 at least 55 of these plants have been upgraded, again using ozone technology. Proving that ozone was cost effective and a good solution for the application.

Most ozone use for municipal water is in large water treatment plants. Of the 277 WTP’s of record less than 30 are plants with a capacity of less than 2 MGD. The median WTP implementing ozone is expected to grow from 5 MGD capacity at the end of 1984 to 80 MGP at the end of 2020.

Future of ozone use in municipal drinking water

The future of ozone in WTP’s in the USA is great. The EPA estimates there are over 150,000 municipal WTP’s in the USA. Only ~300 of these WTP’s are using, or planning on using ozone. Most of these plants are large, or very large. Opportunity for ozone use in WTP’s in the USA is untapped.

puplic water system size in the USA

Small to Medium sized WTP’s growth potential in the USA is the greatest. The largest WTP’s are targeted for ozone implementation. Also, the majority of ozone implementation is in large WTP’s. There are many small to medium WTP’s in the USA that could also benefit from ozone use, but are not targeted by the traditional ozone industry. This is the benefit of working with Oxidation Technologies. Our history of industrial and agricultural system integration lends us a great deal of experience integrating medium and large ozone systems that are well suited for medium sized municipalities.

 

Ozone drinking water plants past and future
* planned WTP’s using ozone, actual future plants expected to be higher (click on image to enlarge)

Image shows that WTP’s started in 10 year spans shown by water treatment capacity

  • It is clear that the average size of WTP using ozone has grown over time
  • Emphasis on small and medium WTP’s has diminished

 

* planned WTP’s using ozone, actual future plants expected to be higher.(click on image to enlarge)

Image shows that WTP’s started in 10 year spans shown by ozone production.

  • The average size ozone system has grown over time
  • Emphasis on small and medium WTP’s has diminished

 

Where and why is ozone implemented?

Ozone is used in 42 of the 50 states in the USA. Ozone is used all over the USA for a variety of applications. Ozone use does follow the population trends. The states of California, and Texas are the two largest users of ozone for municipal WTP’s.

Ozone is used to replace traditional oxidations

  • Disinfection (Giardia & viruses)
  • Taste and odor control
  • Reduction of chlorinated DBP’s
  • Removal of color
  • Sulfide oxidation, TOC reduction, Iron and Manganese oxidation
  • Enhance coagulation processes

 

Municipal water treatment plant with ozone
Other = Hydrogen sulfide oxidation, Oxidation of unnamed materials, enhancing coagulation, iron and/or manganese oxidation, TOC, and “other”

 

Image shows WTP’s using ozone and the purpose for ozone implementation

 

  • Ozone use for municipal WTP’s is diverse, and continues to be diverse
  • Only the use of ozone for Disinfection has grown consistently in each decade
  • Ozone use for “Other” has also grown over time, however this is a large group of uses for ozone in one category.

Summary – Ozone use for drinking water is diverse.  Many WTP’s throughout the USA will benifit from ozone in some way.

 

 

Will your city or project benefit from ozone use?

This is tough to answer. The best answer we can give, is call our application engineers for more information.

If pre-oxidation is required for water treatment, then yes, ozone would be a great alternative to those chemicals. If disinfection by products are a concern, then yes ozone would be a great alternative to chemicals producing those DBP’s. However, most applications are not this simple, give us a call, we would be glad to help,

Drinking water treatment with ozone

Water treatment approaches for algal toxins in drinking water

BIRMINGHAM — In Water Technology’s “Professor POU/POE – October 2014” Technical Editor Dr. Joseph Cotruvo discusses algal toxins in drinking water as a result of algal blooms and various water treatment options available.

In the article, Cotruvo offers the following water treatment approaches including physical removal, chemical conversion and adsorption:

  • Conventional treatment that includes coagulation, flocculation, sedimentation and chlorine disinfection can remove most of the algal cells, but toxin removal is more problematic. It is essential to remove the algal cells by filtration prior to the addition of any oxidant such as chlorine. The oxidant will lyse the cells and release the toxins into the drinking water.
  • Oxidants/disinfectants such as chlorine, chloramine, chlorine dioxide, ozone, potassium permanganate and ultraviolet (UV) light are frequently available in a water treatment facility, or can be added, and provide a range of efficacies against the toxins. The following relate to Microcystin-LR, which is a common form of an algal toxin and among the most potent:
    • Ozone will rapidly lyse the cells; it is effective against the toxin at ozone doses of five ppm or less and at very low concentration-time values (CT in mg-min/l). CT means concentration in mg/l x time in minutes, so for example, a concentration of one mg/l for 10 minutes would be the same as 10 mg/l for one minute. Elimination of Microcystin-LR is virtually instantaneous.
    • Potassium permanganate will lyse the cells and is also a very effective, rapid treatment for the toxin. The CT value for complete elimination is about 25 mg-min/l.
    • Free chlorine will lyse the cells and it is very effective, achieving nearly complete elimination at CT of about 60 mg-min/l. Chlorine is present in almost every surface water treatment plant and probably functions both as an oxidizing and chlorinating agent.
    • Chlorine dioxide is a good disinfectant and lyses cyanobacteria cells, but it has no reactivity toward the toxin.
    • Monochloramine has some reactivity against the cells but not towards the toxin.
    • UV light irradiation at high doses has a destructive effect on the cells but does not affect toxin concentrations.
  • Membranes such as reverse osmosis (RO), nanofiltration, ultrafiltration and microfiltration are all effective for the removal of cells. Pretreatment and frequent cleaning could be necessary. RO and nanofiltration, but not microfiltration, would be effective for toxin removal.
  • Adsorptionusing powdered activated carbon is a short-term technique for the removal of geosmin, 2-methylisoborneol and toxins. However, the efficacy is variable and is affected by water quality factors. Granular activated carbon (GAC) is effective if the filter is of sufficient depth and condition but it is subject to exhaustion and exceeding capacity. Only a few GAC systems are in place in the U.S. that are regularly/frequently reactivated; most applications are in shallow fixed beds for routine taste and odor control and not reactivated for years, so their performance is not generally predictable in a sustained algal bloom. Biological activated carbon filters would be more likely to have sustained performance without frequent reactivation, because they usually incorporate ozone that would react with the toxins and provide the opportunity for microbial degradation of chemicals on the GAC surface.

You can find the October issue’s entire Professor POU/POE feature here.