North Texas Municipal Water District Begins Operating Nations Largest Ozone Drinking Water Facility

The North Texas Municipal Water District (NTMWD) began using ozone as the primary disinfectant at its Wylie Water Treatment Plants in 2014. As a result of the $123 million ozone project, a significant improvement in the taste and odor of the drinking water produced is expected. The NTMWD selected ozone in the treatment process because of changes in US Environmental Protection Agency’s Safe Drinking Water Act.

Now operating the nation’s largest water treatment facility using ozone, the NTMWD implemented extensive planning efforts, modifications, construction and project management at the four Wylie Water Treatment Plants. In addition to the Wylie location, the Bonham and Tawakoni Water Treatment Plants also produce ozonated water. Cumulatively, NTMWD has the capability to treat and deliver 806 million gallons per day of high- quality, safe drinking water to the region served.

Ozone is a good choice for municipal drinking water treatment because it offers multiple benefits to the plant operators. In the case of NTMWD, it allowed them to meet more stringent US EPA regulations for disinfecting drinking water while also improving the waters taste and odor profile. Using another primary disinfectant would have required a second process or chemical to deal with the taste and odor.

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Ozone Effective for Hydrogen Sulfide and Color Removal from Texas Well Water

The Four Way Special Utility District (SUD) operates multiple potable water plants, including Water Plant Number 3 in Eastern Angelina County, Texas. Plant Number 3 was having problems with Hydrogen Sulfide (H2S) and color due to the presence of tannic acids in the source water. The current process, aeration/chlorination was not successfully treating the problem, so SUD asked their consulting engineer for options. They suggested ozone could resolve all of the problems.

Testing showed that an ozone system would reduce color, taste and odor concerns while avoiding the formation of regulated disinfection by-products. The process design presentation was supported by laboratory testing which confirmed no excessive disinfection by-product formation. In addition to color, taste and odor control that ozone treatment provides, the treatment process enhancement allowed for reduced chlorine dosage and discontinuation of the air stripping process. The ozone system was adopted and is now in operation at Plant Number 3.

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Barriers to Water Reuse for Drinking Water in the US

It has been demonstrated that existing technologies for advanced water treatment can successfully upgrade wastewater to drinking water quality in large scale. There are installation for water reuse/water reclaim in California that are treating municipal wastewater to drinking water quality in volumes over 70 MGD.

These technologies employed include membrane filtration, RO, UV and ozone. Despite the technology there are a number of barriers from keeping this from happening. The first issue is that while water resources are being depleted and lower quality sources are increasingly being used, most of the US has ample supplies of water. Second, advanced treatment technologies cost more money that conventional treatment technologies. Simply put, treating dirtier water with higher technology costs more. It is difficult to justify diversifying the water resource given the higher costs.

However, even in areas where water is scarce and governments are interested in exploring new approaches, there are challenges. Schemes for water reuse up till now have used indirect water reuse for potable water. Wastewater is treated and then injected into the ground for later use. Direct reuse, connecting the sewage plant to the drinking water plant is creates the “yuck” factor. People are more comfortable with the water passing through the environment prior to going directly from wastewater treatment to drinking water treatment.

Even if the “yuck” factor is overcome, there is a regulatory gap that needs to be addressed. There are no federal regulations in place covering this area, thus no guidance to the states. California, the most advanced in this area, hopes to have regulations in place by 2016. Many states just have guidelines. Without clear rules, it is difficult for planners and governments to decide how to proceed.

Finally, there is no one solution for all locations. RO systems for example produce concentrated waste streams that need to be disposed of. Some location have the ability to do so economically and other do not. So, solutions have to be crafted for each location and water source. This involves engineering that adds to the cost and complexity of each project.

In all likelihood, it will take many years for direct reuse of reclaimed water for direct potable use to become a mainstream application. Nonetheless, many intermediate projects are moving forward to increase the overall supply of clean water.

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Los Angeles Expands Ozone Treatment of Drinking Water

The Los Angeles Metropolitan Board of Directors has authorized construction of $140.4 million of new ozone facilities at the district’s oldest treatment plant. The new facilities will use ozone to replace chlorine as the primary disinfectant at Metropolitan’s F.E. Weymouth Water Treatment Plant in La Verne.

20 years ago, Los Angeles identified ozone disinfection as a more effective treatment process. The board has a plan to convert all five Metropolitan treatment plants to ozone technology because it is the most beneficial and cost-effective way to improve and protect the quality of drinking water served to 19 million Southern Californians.

The Weymouth plant is among the largest water filtration facilities in the nation. The plant treats a blend of waters from the district’s Colorado River Aqueduct and the State Water Project for the central area of Metropolitan’s distribution system in Los Angeles and Orange counties.

Metropolitan will construct the initial phase of facilities at Weymouth, with a capacity to treat 260 million gallons a day with ozone, and up to 345 million gallons per day under certain conditions. The phasing of the ozone processes will allow the district to expand the plant’s ozone treatment capabilities in the future.

Metropolitan initiated the changeover to ozone treatment in 1994 to comply with anticipated federal regulations and to offer a greater margin of safety in its imported supplies. A colorless gas, ozone has been used as a water disinfectant in Europe and parts of the United States for more than a century.

The Metropolitan Water District of Southern California is a cooperative of 26 cities and water agencies serving nearly 19 million people in six counties. The district imports water from the Colorado River and Northern California to supplement local supplies, and helps its members to develop increased water conservation, recycling, storage and other resource-management programs.

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Winnipeg to Start Up Water Plant with Ozone

Several months ago we mentioned that Winnipeg was building a water treatment plant that would use ozone to treat their water. Now the start up of that plant is only days away, turning on the taps at a $300-million water-treatment facility.

In the new plant ozone will break down organic chemicals into smaller, more easily destroyed chains. This will improve the look, smell and taste of the water. Fewer organic chemicals in the drinking water means fewer trihalomethanes — potentially carcinogenic compounds created when chlorine comes into contact with organics.

THE WINNIPEG WATER TREATMENT PLANT

Cost: $300 million

Under construction: 2005 to 2009

Capacity: 105 MGD

Benefits: Will reduce summer odor from algae, improve water clarity and reduce the amount of potentially carcinogenic compounds called trihalomethanes, which are created when chlorine comes into contact with organic chemicals

New water-treatment processes: Coagulation and flocculation, dissolved air flotation, ozone water treatment and biologically activated carbon filtration

Existing water-treatment processes: Chlorination and ultraviolet-radiation disinfection

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