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Case Studies

Drinking Water Put Under the Microscope

How Pure Is Our Water?

When it comes to water hygiene, we tend to think of developed countries with safe water distribution systems and poor, third world countries where lots of people do not have access to drinking water. In the highly developed industrial countries of “the West”, we take it for granted that we can drink tap water without considering any health issues. It is true that authorities have set up high standards for water quality. Municipalities and water suppliers go to great lengths to make sure these standards are met. So why are there still drinking water-related infections in highly developed countries such as Europe, Britain, or the U.S.? And are there ways to increase tap water quality?

Fighting the Invisible Threats with UV Radiation

Beyond Borders

Contaminated water is one the main causes for many deadly epidemics such as cholera, dysentery, or typhoid fever. It was not until the mid and late 1800s scientists and physicians like John Snow, Robert Koch, or Louis Pasteur discovered the importance of water hygiene. Since then, an ever-increasing amount of effort has been put into hygiene and sanitation. Authorities such as the EU, the U.S. Environmental Protection Agency (EPA), and the World Health Organization (WHO) issue strict quality guidelines for drinking water. In most first world countries water-induced infections have been more or less irradicated, but still occasional outbursts occur – especially when the public water supply is interrupted by natural disasters such as floods, landslides, or hurricanes.

One of the Best-Controlled Foods

Beyond Borders

Most of the drinking water that is supplied to our homes comes from natural sources such as lakes, rivers, and groundwater – sometimes even from protected natural reserves. Nonetheless, this water undergoes elaborate purification treatment at water treatment plants before being distributed to the consumers. The exact process differs from case to case, but in most cases, it includes the following steps1:

  • Coagulation and Flocculation: Chemicals with a positive charge are added to neutralise the negative charge of particles that are dissolved in the water. Both react with each other to form larger particles called floc.
  • Sedimentation: Due to its weight, the floc settles at the bottom of the water supply.
  • Filtration: The clear water at the top is sent through various filters (e.g., sand, gravel, and charcoal) to remove finer particulate matter such as dust, organisms, and even dissolved chemicals.
  • Disinfection: Remaining parasites, bacteria, and viruses are killed by disinfecting chemicals or UV radiation.

To avoid the risks that come with the use of toxic chemicals, many large-scale plants use UV light treatment as part of the purification process. The most effective wavelengths are in the UVC part of the ultraviolet spectrum, which ranges from 100 to 280 nm. They are absorbed by DNA and RNA strands of viruses and microbes and break down the chemical bonds that form the double-or single-helix structure respectively. The germs are thereby destroyed or at least no longer able to replicate.

So far, sources for the highly effective UVC light were limited to low-pressure mercury lamps. Given their size and shape, these light sources are only fit for use in larger facilities. In addition to that, they are fragile, difficult to operate, and the disposal of toxic mercury is complex and expensive. With the emergence of high-power UVC LEDs, UV treatment is now also available for everyday use in homes.

Germ-Free Tap Water

Beyond Borders

Why is there any need for water treatment at home, if drinking water undergoes all these purification measures? The problem is that local authorities are only responsible for the water delivered to your home. Whatever happens on the customers’ premises is their own responsibility, and there is a lot going on in the pipes and reservoirs of every private household and company facilities.
As long as the water is in motion, it is most likely to remain as clean as it was provided by the local utilities. As soon as it stands still for some time, microorganisms begin to group together in slimy, glue-like substances, which allow them to stick to surfaces. These so-called biofilms consist of a wide variety of bacteria, fungi, and single-celled organisms. They are most likely to be found on the inner surfaces of water pipes, water storage tanks, or water heaters.

The biofilms themselves are not dangerous. Scientists even found out that they contain many organisms that contribute to keeping the water clean. On the other hand, biofilms also serve as a breeding ground for many dangerous pathogens and their slime “shield” protects them against chemical disinfectants such as chlorine. Biofilms in the water piping system may release germs into the otherwise clean water. Therefore, additional disinfection is recommended.

A highly effective method is to use UVC close to the consumer – just before the water leaves the tap. LEDs allow for space-saving, affordable and environmentally neutral solutions such as the Aegina Purifier line, developed by British manufacturer PRP Optoelectronics. The UVC sources used by the company comply to the NSF 55 Class A Standard which covers inactivation of microorganisms, including bacteria, viruses, Cryptosporidium oocysts, and Giardia cysts, from water. This kind of radiation is also harmful to other lifeforms including humans.

The LEDs in the Aegina system are therefore placed within the closed piping, so that they pose no harm to humans or their pets. For increased safety, the UV light will automatically switch off if there is any alteration or damage to the system. The water is led through a U-turn in order to provide the time and amount of radiation necessary to destroy all germs. It also remains in motion during the whole process to avoid new contamination. With these measures the Aegina modules are able to deliver 99.99% clean water. With their low power consumption, the devices are designed for residential and mobile use. Depending on the model, they offer outputs of 3, 6, 12 and 18 litres of high-quality drinking water per minute.

Did you know?²

Beyond Borders

  • … that one third of the global population does not have access to safe drinking water.
  • … that almost 6 billion people could be living in areas with temporary water shortage by 2050
  • … that the lives of more than 360,000 infants could be saved every year, if they had access to climate-resilient water supply and sanitation.
  • … that climate-induced water stress can be reduced by up to 50%, if global warming is reduced to 1.5°C above pre-industrial levels.

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