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.

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.