The Emporia City, KS Commission approved a request authorizing the Public Works Department to proceed with an Ozone Equipment purchase Wednesday afternoon during an active session. The current equipment at the Water Treatment Plant uses atmospheric air and bubble diffusers and was installed in 1995, with an expected life of 15 to 20 years. The Ozone equipment and process is the primary disinfection action at the Water Treatment Plant. The equipment, which is slated to be installed in 2016, with a project construction cost estimate of $2.6 million.
Ozone equipment installed 20 years ago was primary based on air feed as the source of oxygen for ozone generation. Using air as the feed gas results in lower concentration ozone of 1-3 percent ozone. Newer oxygen fed ozone generators produce ozone at 10 percent concentration. Higher concentration ozone dissolves more readily in water for more efficient use of the ozone produced.
There is also a reduction in the size of the generator to produce the same mass of ozone, normally indicated in pounds/day. The reduction in the nitrogen levels also minimizes damage tot he generator due to the formation of nitric acid.
As a result of these advantages newer ozone systems have shifted to some form of oxygen feed, either from liquid oxygen supplied by gas companies or made on site using oxygen concentrators. The latter take air and remove the nitrogen to get to oxygen levels of 93%.
The first ozone systems were installed 20-30 years ago and are now being upgraded as the one in Emporium is later next year.
According to Kormorant news papers the upgrading of the Brits Water Treatment Plant at a cost of R578 million could help alleviate the water problems the Madibeng Local Municipality. The upgrade will not only improve the capacity of water provision, but quality as well. As part of the project, the Ozone Purification System which could see the municipality receiving a Blue Drop status, will be installed. The Ozone Purification System is a system used to kill bacteria, i.e. disinfect water and is used by many municipalities throughout the world.
Recent news regarding the algae related water quality problems in Toledo have raised issues about the potential for algae blooms and the release of toxic chemicals from the algae elsewhere in the US and especially in Northwest Ohio.
Celina, another town in Ohio, uses Grand Lake as its water source, which has encountered problems with the algae blooms and the toxins they release since 2009. Celina, however, has updated treatment system to deal with these issues.
The city uses two methods of water treatment to make its water safe, ozone and granular activated carbon treatments. Ozone is a powerful oxidant and highly effective disinfectant. It is a technology that has been in continual commercial use for more than 100 years and has distinct properties that allow disinfection of even heavily compromised water streams.
The GAC treatment is an extremely versatile technology and in many cases has proved to be a cost effective option. GAC absorption is particularly effective in treating low concentration waste streams and in meeting stringent treatment levels. GAC is known to remove a wide variety of toxic organic compounds to non-detectable levels.
As with any water treatment technology, suitability on a specific application normally depends on costs as they relate to the amount of carbon consumed.
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.
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.
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.
20 years ago Cryptosporidium passed through a Milwaukee water treatment plant. The microorganism caused an estimated 400,000 cases of gastrointestinal illness and at least 69 deaths. It was the largest waterborne desease outbreak recorded in U.S. history.
Since the outbreak, the city’s water utility, which draws its supply from Lake Michigan, has invested $417 million in improvements to infrastructure, monitoring and treatment.
Beginning in 2004, Milwaukee Water Works launched an aggressive program to monitor for emerging contaminants including estrogen and testosterone, flame retardants, pesticides, explosives and pharmaceuticals. Milwaukee Water Works tests for more than 500 chemicals annually, and posts its monitoring results online. The majority of water systems in the US focus only on a standard list of 91 contaminants regulated by the U.S. Environmental Protection Agency.
Since the Cryptosporidium outbreak of 1993, Milwaukee has made numerous improvements to its drinking water treatment. An $11 million project extended the Howard Avenue water intake 4,200 feet to a distance of two miles off Lake Michigan’s shoreline, beyond the path of contamination from the city’s industrial harbor. The water enters a nine-step treatment process that includes ozone disinfection, sedimentation and filtration.
At the other end of the city’s water system, the Milwaukee Metropolitan Sewerage District tested a state-of-the-art sewage filtration system. The goal was to catch emerging contaminants resistant to removal by conventional wastewater treatment along with phosphorus, a nutrient that contributes to algae blooms and fish kills.
As a result of the improvements, Milwaukee has become a leading municipality with respect to drinking water treatment.
The Portland Water District (Maine) announced an upgrade to the Sebago Lake Water Treatment Facility with the addition of ultraviolet (UV) disinfection unit at the district’s facility in Standish. It is part of a $12.8 million project. When it becomes fully operational in 2014, the district’s UV water treatment system will be the second-largest in New England, behind the Massachusetts Water Resources Authority’s in Boston.
The process sends water through a reactor that is equipped with ultraviolet lamps. As water is exposed to the light, the light penetrates micro-organisms damaging their DNA so they can not reproduce and thus stoping the life cycle of the organism.
The improved disinfection system was mandated by the federal government. The U.S. Environmental Protection Agency (EPA) requires surface water treatment facilities to improve drinking water quality and provide additional protection from disease-causing micro-organisms and contaminants. To meet EPA standards, the district must operate two disinfection systems — its current ozone water treatment system and the new UV system. While EPA considers UV technology to be the most effective against cryptosporidium and giardia, they also promote multiple barriers for treating water. This means using two to three methods of disinfection in case any one of the systems fail.
The U.S. Centers for Disease Control and Prevention say cryptosporidium is a microscopic parasite that can cause diarrhea. Resistant to chlorine treatments, it is one of the most common causes of waterborne disease in humans.
Ann Arbor’s Drinking Water Treatment Plant’s primary source of water comes from the Huron River. Ann Arbor is one of only seven facilities using an inland river as a drinking water source in Michigan. About 85 percent of the water comes from the river, while 15 percent comes from wells located at the city’s airport. The plant pumps on average more than 15 million gallons of water per day to some 125,000 city water customers.
Because the city uses surface water as it primary source, the water goes through a complete treatment process that consists of rapid mixing for quick dispersion of chemicals being added, flocculation to give the chemical reaction time it needs, settling to allow the removal of solids by gravity, and filtration.
The city also softens the water using lime, removing calcium and magnesium. Ozone is used as the primary disinfectant and chloramines as a secondary disinfectant. Fluoride is added to the water for dental protection, and phosphate is added to stabilize the water.
City officials are evaluating replacing portions of the plant that date back to the 1930s, and which could cost tens of millions of dollars.
Spartan periodically posts information about water plants around the world that use ozone. Most people, and even some water professionals, are not aware of the widespread use of ozone in drinking water treatment as well as other applications.
Before a new water main or one that has recently under gone repair can be placed back into service, it must be flushed and disinfected. The conventional approach is to use high concentrations of chlorine for an extended period of time to kill the bacteria living in the biofilms attached to the water main surface. The disadvantage of this approach is that hypochlorite solutions need to be transported, stored and handled. These solutions are considered hazardous in some jurisdictions. In addition, the treated water must be dechlorianted prior to discharge, which requires another set of chemicals.
Ozone has been used in drinking water treatment for over 100 years and is a proven drinking water disinfectant. It has not been used extensively for the disinfection of water mains. The advantage of ozone use is that it can be generated on site from air and does not require any treatment prior to discharge. A question regarding the use of ozone for treating biofilms on water main surfaces is whether the ozone will penetrate the biofilm to inactivate all of the bacteria present.
Stantec Consulting and EPCOR Water Service Inc. of Edmonton, alberta, Canada conducted a laboraotry study to see if ozone would be effective against these biolfilms (Ozone Science and Engineering, 34: 243-251, Li Chang and Steve Craik). The study looked at HPC bacteria grown on concrete mortar substrates to simulate water main surfaces.
Ozone appears to be able to achieve a 1.7 log reduction of the biofilm at a CT value of 120 mg-min/l. Higher CT values did not appear to improve teh log reduction significantly. the study concluded that log reductions of less than 2.0 should be expected with ozone.
In the September 2006 issue of Opflow magazine published by the AWWA, ozone was also studied in treating water mains in Denver. In these tests the CT values were only 10-24 mg-min/l and the results were not as effective.
So, it appears that ozone may be an effective treatment for water mains that offers easier and safer application, but the ozone CT probably needs to be in the 120-240 mg-min/l range.