40 / INSIGHT INSIGHT / 41 Emmanuelle Prest of PWNT: “Drinking water must remain of the same quality on its way to the consumers’ taps” A researcher at PWNT, Emmanuelle Prest shares her insight in the importance of maintain drinking water standardduring transportation from plant to consumers’ taps. mmanuelle Prest is a scientist at the water technology company, PWNT, in the Netherlands. Her research focuses on drinking water quality during the transport of water from treatment plant to consumers’ tap and its biological stability. In other words, how to prevent Ethe growth of micro-organisms and formation of sediments in the transport and distribution pipelines? Disadvantages of chemical disinfection “It is important for every drinking water producer that the drinking water quality remains the same on its way to the consumers’ tap, especially from a microbiological point of view,” explained Prest. “That is a global requirement and that is the idea behind biological stability. For instance, in the U.S. disinfectant chemicals, such as chlorine or monochloramine, are dosed into the distributed water. They keep the concentration high across the distribution system to prevent bacterial growth and activity. Most countries all over the world use chlorine in their distribution. That is their way to maintain microbiological safety in the water. However, the big disadvantage is that chlorine can react with molecules in the water and form reaction byproducts that affect human health. Emmanuelle Prest, a researcher at PWNT 40 / INSIGHT INSIGHT / 41 WATER & WASTEWATER ASIA July / August 2017 42 / INSIGHT INSIGHT / 42 The Dutch way of circumstances are. If a country’s The water produced in treatment average temperature is 10 degrees the treatment plant of Andijk is The Netherlands does not dose higher than the Netherlands, other transported through many pipes. disinfectant chemicals into the water kinds of bacteria can be found in It starts with big pipes that quickly distribution. The counterpart is, if the water. The famous saying here transport the water, which flows you do that, you need to treat your is ‘everything is everywhere, but the at a high speed. At the end of the water so well to limit the microbial environment selects’. distribution system, the pipes are growth in the distribution system. smaller. In fact, some distribution The objective in the Netherlands is Sediment research by pipes in Volendam and Edam do not to remove as much compounds as PWN/PWNT go any further and hits a dead end. possible from the water to minimise “Together with Dutch water supply And if there is a low consumption of the availability of food for bacteria. company and parent company water, there is no flow, which results The Netherlands are a specific case, PWN, I am doing research in the in stagnant water that remains in the as they treat, or ‘over treat’ the field of biological stability, because pipes for a long time. This causes water so extensively, particularly it is part of both water treatment biological instability, especially in for surface water treatment. This is (PWNT) and distribution where summer time. needed because the surface water PWN is responsible for,” said Prest. The high microbial activity in used in the Netherlands for drinking During distribution from the water the water combined with the rising water production is extremely treatment plant in Andijk to the temperatures is trouble in the polluted. The main source is the house taps of consumers, the water making. In the worst-case scenario, IJssel Lake, which is the ending goes through pipes of different sizes it results in the growth of pathogenic point of the river Rhine, hence, and materials. The water remains in bacteria, but fortunately, that is rare accumulating a lot of pollution these pipes for a certain amount of and well-controlled. However, the (pharmaceuticals, pesticides, and time and the water quality changes. growth of other bacteria can also more). By using extensive treatment This is because water is biological cause the formation of sediments, steps like suspended ion exchange and not static, and any change in a problem faced in Edam and and ceramic membrane filtration, the conditions has an impact on the Volendam. Based on intensive the country is able to obtain one of bacterial side. research, flushing the pipes regularly the best drinking water qualities in “What you want as a water and placing filter screens before the the world. Treatment trains usually supply company is to be able distribution to the taps helped the contain pre-treatments such as to control this change in water issue considerably. coagulation, sedimentation, rapid condition. It is important how water “We are still researching why we sand filtration, followed by an is perceived by consumers, in terms have that specific sediment growth oxidative treatment step such as of taste and colour. Our consumers in these areas as it does not happen ozonation or advanced oxidation must be pleased with the water they in other areas of PWN. This could (UV or peroxide) and a post drink,” said Prest. be because the areas use a different treatment such as activated carbon The quality of the treated water is type of treatment,” Prest analysed. filter or slow sand filtration. In many defined by being the same standard “We are researching the water cases, dune infiltration is also an as when the water was supplied. from the Andijk treatment plant; important part of the treatment. Biological instability means there from source to tap. I am also In comparison, other countries is activity in the water, hence, the researching this biological instability in Europe such as Switzerland or change in quality. For instance, on the treatment level and on Germany have access to better when there is not much movement the distribution level, and that quality surface water and do not in the pipes, small particles in the has shown some progressive and need to treat water so extensively, drinking water settle and form promising results to fully control this even without adding disinfection sediments. problem in the future.” WWA residuals in the water. The growth Sediments have been a big issue of microorganisms in the water for the past decade, especially in depend on several conditions, the areas of Volendam and Edam such as the type of source water, in north Holland where consumers how this water is treated and how complained about brown or turbid the environmental and climate coloured tap water. .