Hillsboro City Council approved a study of ozone treatment to solve an issue with zebra mussels getting into the city’s water treatment plant. Invasive zebra mussels have become more of a problem at the city’s water treatment plant with workers having to remove a substantial number every two to three days at the pump house. Removing them by hand is a labor-intense process and not a long-term solution. The six-month study will be done in a lab to provide controlled conditions. Ozone has been studied at other facilities for the treatment of zebra mussels, particularly power plants where the problem can be severe.
Mitsui O.S.K. Lines, Ltd. (MOL) announced that an ozone-based ballast water treatment system earned a certificate of compliance from the Japanese government. The system was audited based on guidelines set out in the International Convention for the “Control and Management of Ships’ Ballast Water and Sediments (G8),” adopted by the International Maritime Organization (IMO).
Certification required a full-scale on-land test of the system and an onboard test. Both tests verified the system’s complete conformity to the ballast water treatment standard. The system also acquired the final approval under the “Procedure for Approval of Ballast Water Management Systems that Make Use of Active Substances (G9)” by the IMO.
Ozone is an extremely powerful biocidal agent that is produced on site by electric discharge using air. The ozone is mixed with the water to be treated and the micro organisms are killed by oxidation.
According to Singapore’s National water agency PUB the water treatment process at its Bedok plant takes six steps, two of which involve an enhanced disinfecting technology called ozonation. When infused with water, ozone kills bacteria and micro-organisms like algae and plankton which float on the water surface initially.
A coagulant called aluminium sulphate is then used to clump the dead particles. Due to their combined weight, the dead particles sink to the bottom of the tanks, leaving clarified water at the top. At this point, the water looks relatively clean, but it will go through three more steps to ensure it is safe to drink.
Ozone is introduced to the process once more, this time as a disinfectant. The ozonated water is then passed through filters to remove finer particles. To sustain the disinfection, chlorine is added, together with lime and fluoride.
This process provides multiple barrier water treatment system which is combined with monitors that follow the water from the source all the way to our tap.
Bedok Waterworks is one of two plants in Singapore that have been using ozonation for more than two decades.
Tokyo, Japan — Teijin Limited announced today that an advanced oxidation process has proven its effectiveness in decomposing 1,4-dioxane, a highly persistent organic solvent. With the Japanese government now considering the introduction of 1,4-dioxane discharge regulations, Teijin’s system could have promising applications in the Japanese market and beyond.
The process combines ozone and hydrogen peroxide to produce the hydroxyl radical, the most powerful oxidant available for water treatment. A joint development project now being conducted by Teijin and PUB, Singapore’s national water agency, has demonstrated that the process significantly reduces persistent pollutants such as pharmaceutical residue and endocrine-disrupting compounds.
The water-soluble organic solvent 1,4-dioxane dissolves numerous organic materials, making it suitable for a wide range of industrial applications. However, the World Health Organization’s International Agency for Research on Cancer has classified the solvent in category 2B (possibly carcinogenic), and in 2009 Japan’s Ministry of the Environment set the standard for 1,4-dioxane in wastewater at 0.05mg/l or less.
Both biologically and chemically stable, 1,4-dioxane requires the use of special degrading bacteria for biological treatment. Adsorption is difficult in treatments that use activated carbon, and the substance is hard to break down even with oxidation treatments that use ozone. In view of the extreme difficulty of treating 1,4-dioxane, the Japanese government is carefully considering the introduction of discharge regulations in the near future.
City and community leaders in Waco had a chance to tour the site of the new drinking water treatment facility. The plant began its water pretreatment process last summer, but officials said they only recently starting running the ozone disinfection process. Ozone is a well proven option for reducing taste and odor problems in drinking water. Since then, officials with Waco’s Water Utility Services said they have noticed a difference in the smell and taste of the city’s water. Waco has had problems with taste and odor for many years prior to the improvements.
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.