New Dutch water treatment plant is first to combine UV disinfection, oxidationOn October 21, the PWN Water Supply Company North Holland officially opened its state-of-the-art water treatment plant in Andijk, the Netherlands. Equipped with Trojan Technologies' TrojanUVSwift(TM) environmental contaminant treatment (ECT) system, the facility is the first of its kind in the world designed to combine UV disinfection with UV-oxidation to provide a barrier against microorganisms and micropollutants potentially present in the source water. The UV-oxidation process is based on the generation of hydroxyl radicals via the UV-photolysis of hydrogen peroxide.
The Andijk installation will ultimately treat more than 95,000 cubic metres (25 million gallons) of water per day, providing drinking water to approximately 500,000 people. As an added advantage, the TrojanUVSwift(TM)ECT system in Andijk does not require large contact basins in which to perform treatment as is the case with ozone. The system fits into a very compact space (approximately 7 metres by 7 metres). This is an important consideration in the Netherlands and results in both significantly reduced building capital costs and more efficient use of land area.
The TrojanUVSwift system employed at the facility uses a process known as UV-oxidation, in which hydrogen peroxide is added to the water. The water is then treated with UV light. In addition to the direct breakdown of some compounds by UV light, UV-oxidation produces hydroxyl radicals, powerful oxidizers that break down and eliminate contaminants.
"Our testing has demonstrated unequivocally that UV-oxidation technology is highly effective in destroying micropollutants such as pesticides, herbicides, endocrine disruptors, pharmaceuticals and algal toxins and at the same time eliminating many pathogens including E Coli, bacteria, viruses, cryptosporidium and giardia," said Peer Kamp, director of research and development for PWN.
PWN and Trojan have been working together since the spring of 2001 piloting and testing the technology. The first two phases, consisting of prototype development and the optimization and testing of a UV treatment system to destroy micropollutants found in contaminated drinking water supplies, were completed successfully in order to facilitate the completion of the third phase, full-scale equipment delivery. These initial phases enabled Trojan and PWN to determine the sizing and design of the UV equipment required to achieve the target levels of contaminant reduction.
Another important benefit of the process used at PWN is that it does not form bromate. Formed through the reaction of bromide with ozone, bromate is a regulated disinfection by-product and is a suspected human carcinogen. Although the current regulatory limit for bromate in drinking water is 10 parts per billion (ppb), the U.S. Environmental Protection Agency's Integrated Risk Information System (IRIS) database gives a one-in-a-million cancer risk concentration (the level on which most regulations are based) of 0.05 ppb.
Bromide is present in many water sources worldwide, and the formation of bromate from bromide presents a significant challenge for users of ozone in water treatment. Throughout North America and Europe, researchers have detected trace amounts of potentially carcinogenic substances in water supplies. These substances include N-nitrosodimethylamine (NDMA), 1,4-dioxane, pesticides, pharmaceuticals, personal care products and potential endocrine disruptor compounds.
"There is an increasing recognition that many water sources contain trace contaminants that cannot be removed by conventional technologies," said Trojan president and CEO Marvin DeVries. "The need for municipalities to provide multiple barriers to microorganisms and chemical pollutants is becoming more acute."
Since entering the ECT market four years ago, Trojan has won more than $40 million (Cdn) (Euro 26 million) in contracts. The European Environment Agency (EEA) reports that source water supplies in many European countries regularly exceed the maximum pesticide concentration of 0.1 ppb. The fact that it can take years for pesticides to seep into water supplies, together with heavy historical use of pesticides, suggests that this contamination problem is only just beginning to emerge. Pesticide contamination is forcing water providers to find new water supplies or more effective treatment methods in order to provide safe drinking water.
More information is available from Diana Cunningham at Trojan Technologies, 519/457-3400, Web site www.trojanuv.com.