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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Vancouver adds UV to Complement Existing Ozone Disinfection for Drinking Water

The Coquitlam watershed treatment facility in British Columbia provides approximately 370 MLD, a third of the total water supply delivered in Metro Vancouver. The facility uses the process of ozonation as the primary disinfectant, but has added new UV disinfection equipment to complement the existing ozone and chlorination processes. Construction of the new facility started in spring 2011, and the technology cost under 100 million dollars to put in place.

Ultraviolet light at a wavelength of 254 nanometers passes through the water inactivating the micro organisms by disrupting the DNA of microorganisms preventing the organisms from reproducing. Since these organisms have a very short lifetime, without reproduction the population quickly dies away. UV radiation does not change the taste or color of the water.

The facility will continue to use ozone and chlorine as part of its multi barrier approach to disinfection. Each disinfection agent, ozone, UV and chlorine have their own unique advantages. Besides disinfection ozone can remove organic matter that can add color, taste or odor to the water. Ozone also can remove micro pollutants such as pesticides that may be present. UV is very effective against organisms that might require much higher doses of ozone or chlorine such as cryptosporidium. Chlorine provides a persistent residual in the water protecting the water distribution system from developing pathogens.

By employing all three approaches, Coquitlam is offering a significant layers of protection to the people of Vancouver.

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Yorkshire Water Adds Ozone Water Treatment for Pesticide Removal

The Acomb Landing water treatment plant with an output capacity of 35ML/day drinking water processes raw water from the River Ouse as part of Yorkshire Water. The principal contractor, AECOM, is working to update the plant to remove micro pollutatns, primarily pesticides. They have decided to use ozone water treatment combined with activated carbon to remove these contaminants.

Ozone is effective in breaking down complex micro pollutants, such as pesticides, into safer compounds.

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North Texas Municipal Water District completes $123 million Ozonation Project

The North Texas Municipal Water District (NTMWD) recently completed a $123 million ozonation project at their Wylie facility. The NTMWD’s Bonham and Tawakoni treatment plants also produce ozonated water. With the projects completion, the NTMWD’s four water treatment plants in Wylie are now the nation’s largest water treatment facility using ozone to treat 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.

The use of ozone as the primary disinfectant when treating water is expected to improve the taste and odor of drinking water. Ozonation removes many of the traditional harsh chemicals out of the treatment process and the taste and smell of the water is more consistent when using Ozonation.

The NTMWD began using ozone in the treatment process as a result of changes in regulatory requirements set by the United States Environmental Protection Agency’s Safe Drinking Water Act, which were strengthened, and to provide enhanced water quality for public water supplies. according to NTMWD.

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Natrona County Uses Ozone To Treat Drinking Water

Natrona County’s drinking water is taken from the North Platte River and is treated at the Central Wyoming Regional Water System (RWS) with the primary disinfectant being ozone. The facility produces up to 25 million gallons of water per day. RWS uses chloramines as their secondary disifectant to keep bacteria from growing in the delivery system, including the pipes in your house.

At the RWS plant, after raw water is drawn from a well field that’s under the influence of the river, water is filtered and then ozone is used as their primary disinfectant.

Ozone is used because it’s better at killing giardia and other protozoan parasites like cryptosporidium (crypto) than chlorine. Protozoan parasites have hard outside surfaces. When chlorine is used in the process it requires longer contact times to kill bacteria.

Both RWS’ water plants is located low in the valley by the river. Once water is processed, it’s pumped uphill to high capacity tanks for storage. RWS operates 22 tanks. The system of high capacity tanks sits above the populations they serve and employ gravity to provide water pressure.

RWS’ water plant uses closed-system computers to operate their plants. Operators are able to gather information in real time from water flow and chemical analysis sensors, and use the computers to operate valves, introduce chemicals and automatically fill tanks. Supervisory control and data acquisition (SCADA) systems are common in the industry. Because their SCADA systems are closed systems, there’s no remote access to them from the Internet and operators must be on site to manage the plant.

The cost of the RWS facility in the range of $40-$50 million not including tanks or the distribution system. Tanks start at more than $1 million. Add the cost of miles and miles of underground lines, lift pumps, taps and other plumbing to the cost of the water plant and the total cost is much higher.

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Ambient Ozone Measurement for Ozone Water Treatment

The use of ozone water treatment systems requires the measurement of ambient ozone levels as a safety measure. OSHA sets a 40 our exposure limit to ozone in spaces where people are present of 0.10 or less. Emissions from the ozone system or the down stream processes can exceed the OSHA levels. If this occurs, the ozone system should be shut down and the source of the ozone isolated. Normally, an ozone system will be interlocked with the ambient ozone monitor.

There are basically two different types of ambient ozone monitors: electrochemical and UV. The electrochemical sensors are less expensive and if there is not source of interference for these units, they are a good choice. They can see interference, especially from other oxidants that might be present, for example chlorine or one of its variants.

UV sensors are very accurate for low level ozone measurement, but much more expensive than electrochemical sensors. UV monitors are essentially UV spectrophotometers operating at 254 nm where ozone absorbs UV. They can also be affected by interferences, especially by aromatic hydrocarbons that also absorb UV at the 254 nm region. So, if these organic compounds are present UV monitors may not be a good choice for the application.

Because ambient ozone monitors are used for measuring ppb levels of ozone, it is a very challenging applications. Sometimes it is difficult to find the interference or to determine if there is an interfering compound. So, it is important to test the sensors against a known zero gas and calibrated ozone containing gas.

In general, electrochemical sensors are widely deployed for a variety of industrial and municipal drinking water applications. If problems develop a UV monitor might be a good option for checking the environment if calibration of the electrochemical sensors does not indicate the nature of the high ozone readings.

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Burleson, TX Faces Water Taste and Odor Challenge

Burleson, TX residents are having taste and odor problems with their drinking water which is purchased from Fort Worth. While the water has been determined to be safe to drink, officials have acknowledged that it does have an “earthy smell and taste”.

Tests indicated an increase in the levels of a substance called geosmin in Lake.
Geosmin is a type of bicyclic alcohol produced by actinobacteria and released when those organisms die. City officials have said that colder-than-usual temperatures in December and January killed off the actinobacteria and released the geosmin into Lake Benbrook. Geosmin levels there are the highest seen in years.

Fort Worth uses ozone as a primary disinfectant which has the side benefit of removing taste and odor compounds like geosmin from the water. To combat the increased level of geosmin, the water department has increased the dose of ozone injected into the water. In addition city has also started blending the water from Lake Benbrook with water from Cedar Creek Lake.

Many factors such as seasonal variations and weather can result in changes in the level of taste and odor compounds in surface water sources such as lakes an reservoirs. It is difficult to predict these changes and develop counter measures. Ozone has been found to be one of the more effective and economical agents for this purpose since it not only removes the taste and odor compounds, but also disinfects the water.

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Ozone Used for New Shrimp Farming Process

A shrimp company in Texas has developed and commercialized a technology to produce fresh, gourmet-grade shrimp reliably and economically in an enclosed, recirculating, saltwater system. NaturalShrimp, located in La Coste, Texas, uses ozone to disinfect the water.

Ozone is increasingly used in aquaculture due to its numerous advantages over traditional water treatment methods. The primary application is removal of fish pathogens. It also effectively removes organics, pesticides, discoloration, and nitrates and unconsumed ozone reverts back to oxygen, leaving no harmful residuals behind. Ozone oxidizes long chain molecules, which are unaffected by bio filtration and involves far lower risk of accidental pollution in comparison to other water treatment methods. Finally, ozone improves the effectiveness of biological and particulate filtration

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Ozone Drinking Water Authority Wilfred LePage Passes

Wilfred LePage, age 83 of Monroe, MI died Monday, January 27, 2014 in his home after a year long period of declining health.

Following service with the Marines during the Korean Conflict, he studied at Wayne State University. While in college he entered his career field of drinking water purification at the Mount Clemens Water Filtration Plant. In 1959 he accepted a supervisory position with the Monroe Water Department from which he retired in 1995.

Wilfred rose to international prominence in the water industry. He authored and published numerous technical papers largely on the application of ozone to drinking water treatment and, following invasion of the water system by the non-indigenous zebra mussel, on mussel mitigation. He traveled extensively at home and abroad while presenting his work.

He held leadership positions in several technical and scientific societies and received numerous high honors including the water industry’s coveted George Warren Fuller Award for his innovative work with ozone.

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The Six Reasons Ozone Water Treatment Systems Fail

Ozone water treatment systems convert the oxygen in air or other feed gas into ozone and mixed it with water for the specific water treatment applications, e.g. disifection. Many applications are critical and reliability is important in the design of these systems.

There are a number of factors that can cause these an ozone water treatment system to fail. This article tries to group them into six basic categories based on my ten years of experience building and servicing this type of system. The typical failure mechanisms include:

• Back Flow of Water into the Generator
• Poor Feed Gas Quality
• Under sizing the system for the application
• Poor ozone transfer efficiency
• Ozone generator cooling issues
• Incorrect materials of construction

We will briefly discuss each here.

Back flow of water is possible since many application call for injecting ozone into a water system with higher pressure than the ozone generator, as a result, under the right conditions, water could flow into the generator. Because of the nature of the generator, this would result in sever damage and significant repair time. Well designed systems employ multiple barriers to prevent this condition including both passive devices and active controls.

The ozone generator requires a clean dry source of oxygen or air. Failure to deliver a high quality gas feed will result in both damage to the generator and a reduction in generator efficiency. Well designed systems employ gas dryers, filters and instruments to monitor gas quality with interlocks to shut down the system if poor gas quality is discovered.

If the ozone system is under designed, it will not have sufficient capacity to meet the requirements of the application. The sizing of the system will require laboratory and pilot studies prior to committing to a system size. It is usually not possible to predict without such studies the proper size of an ozone water treatment system.

Another design factor that must be considered is the efficiency of dissolving ozone into water for a given system. Only ozone that dissolves into water is useful for treatment. Since ozone has limited solubility in water, it is important to design the system to achieve a high degree of efficiency, normally greater than 90%. Well designed pilot studies can confirm the expected transfer efficiency.

Ozone generator output is a function of operating temperature. Whether cooled by water or air, the generator capacity declines with increasing cooling medium temperature. So, the design of the system must take into account ambient conditions on site.

The final area where problems occur is materials of construction. Ozone is a strong oxidizer and can damage materials not appropriate for the application. The incorrect materials will result in leaks and failure of various down stream equipment.

During the design or purchase of an ozone water treatment system, each of these factors should be carefully considered.

For more information on ozone water treatment system design visit www.SpartanWaterTreatment.com of contact us at info@spartanwatertreatment.com.

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