Ozone, a form of oxygen, also works as an added barrier against viruses. A new building had to be erected to house ozone contact chambers, and half the cost of the total project went to the ozonation system. Switching to liquid chlorine will boost plant safety. Chlorine gas is an effective disinfectant, but also a highly dangerous chemical. The project also included new, Olympic swimming pool-sized filters that use granulated activated carbon and sand, replacing filters that used sand and anthracite.

The plant, which went online in 1985, produces about 5.5 million gallons of potable water daily and serves most of the town.

The problem came from algae growing in Lake Waco, the city’s main water source. Officials said when the algae die after being deprived of sunlight, they release a chemical compound called Geosmin which can affect the smell and taste of the water.

The addition of the dissolved air flotation (DAF) pretreatment plant means more of the algae can be removed before the water reaches the water treatment plant. Ozone then removes the dissolved compound Geosmin via oxidation. Officials said the pretreatment plant has brought the cost of water treatment down between 20 and 30 percent, because fewer chemicals are now needed at the main treatment plant. While costs have gone down, capacity has gone up from approximately 60-million gallons to 90-million gallons a day.

The ozone water treatment process reduces disinfection byproducts as well as taste and odor compounds. As part of the project, McCarthy will construct 11 ozone contactors and install side stream injection systems, ozone-quenching and filter backwash chemical feed systems.

The current water treatment facility has a capacity to treat 770-million gallons of water per day and serves more than 1.6 million residents in North Texas. The engineer on the project is Black and Veatch of Dallas. The project is scheduled for completion in January 2014.

The city treats about 4.3 million gallons of water a day. Red River water enters the system at a site near Elm Park in south Moorhead. Moorhead takes about 85 percent of its water from the Red River and 15 percent from wells.It takes about two hours for the water to make the three-mile journey to the treatment plant, where it is given its shot of ozone. Besides disinfecting, ozone breaks down organic material in river water that might cause taste and odor.

During the rehabilitation the existing plant will receive new lime feed equipment to soften the water and an ozone injection system to provide a more efficient way to remove bacteria and improve the taste and odor of the water.

The original water treatment facility was constructed in 1958 and supported six million gallons of water per day, an amount that has grown over the years to support increases in water demands. It currently supports 25 million gallons per day.

Ozone was recommended because it is capable of addressing emerging concerns about currently unregulated contaminants. It was determined that adding ozone as an additional treatment barrier would best protect public health in the long term. Ozone would pro actively ensure the best taste year round and would reduce the amount of chlorine used for disinfection, among other benefits.

The cities plan on beginning the system upgrades in the 2012-2013 fiscal year.

McKinney is served by the North Texas Municipal Water District (NTMWD) receives raw water supplies from: Lavon Lake, Jim Chapman Lake, Lake Texoma, Lake Tawakoni, and Lake Bonham for treatment and distribution to the region served. NTMWD is pursuing the implementation of ozonation, a process that uses ozone as a disinfectant, to meet new state and federal guidelines going into effect in 2012, and the new treatment method will also will also significantly reduce and/or eliminate taste and odor issues caused by algal blooms. Dallas, Fort Worth and Arlington have all had success with ozone for algal taste and odor issues. The organization’s current treatment process can only lessen these issues.

Ozonation is very effective for inactivating Cryptosporidium, bacteria and other naturally-occurring organisms. Ozonation also can reduce the formation of trihalomethanes (THMs), which result from the interaction of chlorine and naturally-occurring organic material in the source water. Additional benefits of this process is that it helps to alleviate taste and odor issues in treated drinking water, such as those experienced during algal blooms in Lavon Lake.

A preliminary engineering study for the utilization of ozonation as a primary disinfectant at the NTMWD Wylie Water Treatment Plants has been completed by the NTMWD staff and consulting engineer. The study provides the framework for the engineering design of ozonation facilities to be constructed at the Wylie Water Treatment Plant to meet the Texas Commission on Environmental Quality Stage 2 Disinfection Byproducts rules. A design contract has been executed with a consulting engineer, and the design has commenced. A purchase order has been issued for procurement of ozone generation equipment. The NTMWD anticipates completion of the design to allow for construction bids to be brought to the NTMWD Board of Directors for consideration in the fall of 2010. The project is estimated to cost $140-$150 million and will take several years to construct and place into operation. The current schedule includes implementation of the ozonation treatment process taking place in stages during the latter part of 2013 and early 2014.

Though the Cape Fear Public Utility Authority pulls its water from the same source, residents on that side of the river didn’t experience the same taste and odor problems. This is because Cape Fear Public Utility treats its water with ozone instead of chlorine dioxide.

New Hanover had experienced the same problem as Brunswick County is now. When the department was looking to expand its treatment plant at that time, officials decided to spend a little more money and go with the ozone system. Since then, they’ve had no trouble with odor or taste.

Brunswick County is now looking at ozone, along with other options to prevent future taste and odor occurrences. Taste and odor control is an important application for ozone in the treatment of drinking water.

The project was driven by drinking water regulatory compliance issues. These were caused by pollution of the source water. Better protection of the reservoir would have probably resulted in a less costly solution, but the process improvements at the plant will bring the drinking water into compliance.

The upgrade included a new ozone system, which will reduce the energy needed to disinfect and remove unwanted tastes and odors from the water. Ozone is widely used in situations where both disinfection and taste/odor problems are present. The facility previously used ozone, so the investment shows that this method of water treatment worked well.