Algae in lakes and reservoirs can create issues for drinking water plants including toxins, bad taste and unpleasant odors in the water. While there are a number of treatment methods used to deal with this problem, ozone treatment of the water has emerged as a proven and cost effective method.
Depending on where and how the ozone is applied to the process, the ozone can serve two purposes: primary disinfection and removal of algae related compounds that pose health or aesthetic risks to the drinking water plants customers.
The city of Oregon in Ohio was concerned about algae related issues from their intake in Lake Erie due to cyanobacteria that can produce microcystin, a toxin. Toledo had experienced a severe issue with this toxin that resulted in a 2014 temporary ban on the use of water from their drinking water plant. This cause Oregon to look for solutions before they experienced a similar problem.
In Oregon’s process, water from lake Erie will be treated with ozone and then go through biological filtration. The approach will remove algae-related toxins. The process works because ozone breaks down the toxins into molecules that are quickly digested by the biology living in the filter.
The process was first tested at the pilot scale for several months to prove that it worked well. The full scale system is expected to be in operation by the algae season of 2017. Other advantages include reduced use of chlorine, improved disinfection and reduced disinfection byproducts. Ozone also eliminates trace organic compounds.
The project is expected to cost $14 million, with funds mainly coming from the Ohio Environmental Protection Agency’s Water Supply Resolving Loan Account. Oregon’s water rates will increase about $2 to $3 more a month for the improved quality and safety.
The City of Tyler has released the results of an independent review of its water treatment process conducted by Enprotec/Hibbs & Todd, Inc. The study looked at the causes and possible remedies for high levels of haloacetic acids in the water. Haloacetic acids are a disinfection byproducts (DBP) which are regulated by the US EPA. They are formed when organic compounds in raw water react with chlorine to form chlorinated organic compounds such as haloacetic acids and trihalomethanes. In October of 2015 the city had received notification of high haloacetic acid levels in its drinking water.
The study recommended some operational changes to reduce the haloacetic acid levels, but some of the issues are due to the age of the water plant where the acid levels are the highest. The facility was constructed in 1950s before the onset of increased regulations on water quality. A newer facility uses ozone as a pre-treatment. The study recommends utilizing the ozone at the older water treatment plant, thereby reducing the amount of byproducts created by chlorine.
Ozone has been used extensively in the US and Europe to reduce the formation of chlorine based DBP’s.
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.
A recent market study by Persistence Market Research suggests that global market for ozone technology market was $715 million in 2013 and is expected to grow to 1,242 million in 2020.
Ozone technology is used for a wide variety of applications, but primarily for water purification, disinfection and the removal of organic and inorganic contaminants. Ozone technology equipment has promising growth rate in the waste water treatment equipment, in municipalities, and other water treatment segment which include swimming pools and spas. This growth is attributed to the many benefits associated with the technology. High oxidation potential, quicker processing time compared to other traditional disinfection techniques, with no harmful by-product.
The increasing global health concerns due to surge in urbanization, increasing water contamination and increasing level of industrialization are driving the ozone technology market globally. The government expenditure on upgrading water infrastructure has increased in the past decades across all regions., Municipalities are upgrading from traditional chlorine-based disinfection to UV and ozone technology based disinfection which has boosted ozone technology market. There is also an interest for both municipalities and industry to remove organic contaminants from water, ozone and ozone based advanced oxidation processes have been found to be useful in this regard. Water treatment related regulations in some of the countries are also compelling water and waste water service establishments to modify their water treatment techniques to improve safety level of water.
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 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.
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.
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.