Pictures of the Future      Spring 2005

Solutions for a Thirsty Planet

As population rises, demand for clean water continues to grow. Advanced water treatment systems have an important role to play. Membrane filtering plants and ulraviolet water disinfection already offer particularly efficient solutions. Furthermore, exciting new technologies are just around the corner.

Last year’s tsunami disaster in southeast Asia highlighted a problem that seemed to have been long forgotten, at least in the industrialized countries: Contaminated drinking water can be just as deadly as killer waves.

According to Jan Egeland, UN coordinator for disaster relief, contaminated water could kill even more people than the original flood. As a matter of fact, unclean drinking water is literally a global killer and, according to the UN, causes over 80 percent of all diseases and more than a third of all deaths in developing countries. Clean water is therefore a vital resource. But one-sixth of the world’s population must do without it today—because of a lack of infra­structure, unequal distribution of reserves, or simply adverse geographic conditions that prevent access to clean water. Even in industrial countries such as Spain and Italy, water shortages are a serious issue (see  interview with Catherine Day).

And the problem is likely to become more acute. According to UN Environ­mental Program Executive Director Prof. Klaus Töpfer, two-thirds of the world’s population might be living in countries with moderate or severe water shortages by 2025. "That’s why water is in the focus of our millennium develop­ment targets," emphasizes Töpfer. The UN therefore plans to cut in half the number of people without access to clean drinking water by 2015.

It’s an ambitious goal, and the only hope of attaining it is by using powerful water treatment systems that can filter out a multitude of different substances. Many industrialized countries have accomplished this. Their river water still contains plenty of suspended matter, but far fewer germs and environmental toxins than are found in the rivers of developing countries—thanks to more effective water treatment (see Wastewater Purification) and tougher environ­mental regulations.

Without these safeguards, water can turn into a noxious soup of hepatitis viruses, bacteria such as cholera and typhus pathogens, agricultural poisons and heavy metals, such as lead.

Siemens offers solutions that include diverse water purification methods for even the most unappetizing fluid wastes. They range from disinfection systems using ultraviolet radiation to mechanical purification systems that may, for instance, employ sand particles or membrane filters. Often, several methods are used in combination, because not every method removes every different impurity.

The most effective methods include membrane systems made by Water Technologies, a Siemens business unit (see  Wastewater Purification). The most thorough of these systems use reverse osmosis (RO) filters, which can block objects less than one nanometer in size, allowing only water molecules to pass through. However, the RO process uses very high pressure to squeeze water through tiny pores and is therefore very energy-intensive. The choice of membrane system therefore depends on the desired water quality and on local conditions.

Effective Tsunami Help. The tsunami disaster in southeast Asia is a case in point. One of the companies that provided water treatment plants for the disaster region was Siemens, which installed seven of its Memcor AXIM systems. These systems use low-pressure membrane filters in linear arrays of multiple modules. Although each unit is only about the size of a passenger car, it can treat 100 m&3sup; of potable water per day—enough to supply a small town. "These membranes can filter out particles down to 0.1 µm in size," notes Stratton Tragellis, product manager at Water Technologies Memcor Products in Sturbridge, Massachusetts. "As a result, they can be relied upon to remove protozoa, bacteria, algae and other microorganisms."

In principle, a membrane module functions like a fine-meshed sieve. It consists of some 10,000 porous plastic fibers that form a web within a cylindrical housing. A pump propels contaminated water from the outside of the module through the membrane to the inside. Any particle that’s larger than 0.1 µm—which includes all bacteria—literally gets stuck. Only filtered water emerges from the module.

However, depending on the source, the product water may still contain some viruses. With dimensions of less than 100 nm, viruses are small enough to slip through even tiny pores. The filter systems are therefore coupled with a disinfection system. The result: top-quality potable water. In order to cleanse the membrane of collected particles, the system is periodically back-flushed with filtered water, while compressed air is simultaneously used to ensure that the surface is clean. In addition, the membrane surface is cleaned with chemicals at four- to six-week intervals.

The principal users of Water Technologies’ systems include municipal water utilities and industry. Among these users, the market share represented by membrane filters is growing rapidly because, compared to conventional filtration methods, this technology is more economical to operate. "Although the acquisition costs of membrane systems still exceed those of conventional systems," says Tragellis, "they meet increasingly stringent water quality standards, need less space, and cost less to install. Their operating costs are also lower, they use less energy than distillation systems, and require very few chemicals." Tragellis expects future water treatment plants to be universally equipped with membranes. "The trend continues to favor systems that have ever higher capacity, yet are increasingly compact," he says.

Portable and Potable. Smaller and, above all, flexible systems are already a Siemens specialty. The company’s Mobile Services include water treatment plants that are built into a truck trailer for use wherever there’s an urgent demand for the precious liquid. And the company can deliver these plants within 48 hours.

Such prompt service is one reason that Water Technologies (previously USFilter, see Wastewater Purification) has been the U.S. market leader for more than 20 years. Siemens has also been supplying communities for two years. A case in point is a Florida community. "In 2004, construction work at a retaining pond damaged a water line system that supplied drinking water to the resort town of Steinhatchee," relates Bob Newton of Siemens Municipal Services. "Following the accident, water was contaminated with fecal bacteria and discolored." At the town’s request, Siemens promptly dispatched two trucks equipped with reverse osmosis and activated carbon filtration to the site. "The water that was purified by these systems met all standards for potable water," recalls Newton. Such mobile systems can produce between 750 and 3,785 liters per minute and continue to operate for up to 18 months—until repairs have been completed or stationary treatment plants are built.

Disinfecting Water with Light. Another Siemens company has also made a commitment to the cause of pure water: Radium, an Osram subsidiary in the German state of North Rhine-Westphalia, has developed a UV source for sterilizing drinking water. These UV lamps can, for instance, be used to irradiate wastewater in sewage plants or to sterilize drinking water for apart­ment buildings.

A new Radium product is a small, mobile UV system for camping or Third World applications. "We’ve developed a low-pressure UV lamp that works like an immersion heater," reports Radium marketing specialist Hans-Jürgen Streppel. "The user simply suspends it in a container holding about 20 l of water and turns it on. The emitted short-wavelength UV radiation penetrates the nuclei of any bacteria and destroys their genes." Streppel adds that it takes about 15 minutes to sterilize the water completely. The UV source is about 25 cm long and is best suited for treating water that can’t be entirely trusted—for instance, water that’s been stored at a campsite.

Radium has also developed a version for developing countries that’s powered by solar cells. The germicidal UV source was introduced to the market in Spring 2005. While it’s deadly for bacteria, the system is harmless to users—a fact that can’t be taken for granted with ultraviolet lamps. "We’ve included a safety switch that turns the power off the instant the system is removed from a container," reports Streppel. "There’s no comparable UV system available anywhere at this time." But the sterilizer kills only microorganisms. It isn’t able to eliminate environmental toxins such as pesticides. "At least it can’t do that just yet," Streppel adds. "But we’re working on Xeradex lamps that emit UV radiation of much shorter wavelengths. These can even break up chemical compounds and render them harmless."

Electric Water. An entirely different method of processing water for human consumption is being developed by a team led by Dr. Werner Hartmann of Siemens Corporate Technology (CT) in Erlangen, Germany. The researchers are experimenting with pulsed electrical fields to convert wastewater into potable water. The first such system may be ready in two to four years.

Here’s the idea behind it: "The water flows through a chamber that contains two electrodes placed a few centimeters apart. We’re applying pulsed high voltage to these electrodes—about 100 kV with a pulse length of less than 1 µs—which produces very high electric field strengths," Hartmann explains.

This high-voltage approach sets two processes in motion that swiftly kill bacteria, viruses, algae and even mussel larvae, Hartmann adds: "It causes all cell walls to become more porous and eventually destroys them completely. And it creates free radicals, such as ozone, which have an additional germicidal effect and in turn break down chemical impurities." Hydrocarbons, plant poisons and hormones are rendered harmless as if by magic.

Although this pulse technology is still in its infancy compared to other methods and no such water treatment systems exist as yet, Hartmann is confident that such systems will play an important role within 15 years. Here’s why: He expects this technology to have a long service life and to be very easy to maintain. That would make it more cost-efficient than UV treatment systems, for instance. However, he thinks the key advantage will be that this system requires no chemicals. "Such a treatment facility would operate entirely without chemistry. Germs would not be able to develop resistance and you wouldn’t need to store or transport disinfectants," he says. What Hartmann likes most about this method is this: "You might say that the water purifies itself."

Autonomous Water Analyzer. Just as important as pure water from the faucet are clean rivers and lakes, because that’s where many communities get most of their water. In Germany, for instance, the water quality in such sources is checked every four weeks by taking samples, which are then sent to large accredited laboratories for extensive analyses. It usually takes one or two days before the results are available. What’s more, these tests are complex and expensive.

A more economical and much faster solution is provided by a mobile water analysis system developed by Siemens as part of an EU project in collaboration with partners including the University of Tübingen and the Water Technology Center in Karlsruhe. No larger than a suitcase, AWACSS (Auto­mated Water Analyzer Computer Supported System) can automatically identify 32 substances and transmit its findings to water authorities online or via text message (SMS). "It takes 15 minutes at most to detect a few nanograms of pesticide in a liter of water," says Dr. Joachim Kaiser of Siemens Corporate Technology in Erlangen. "No other system like this exists anywhere in the world today."

The core of AWACSS is a biochip that captures molecules of environmental toxins. The water sample is first mixed with synthetic antibodies that are attached to a fluorescent pigment. If the sample contains matching molecules, such as those of plant poisons, the antibodies bind to and "mark" the toxic particles. A pump then propels the liquid across a biochip—a matchbox-sized glass plate coated with a layer of binder molecules. These molecules capture all marked toxic molecules. Unmarked particles are then rinsed from the chip by a shot of clear water.

"You can then identify the type and quantity of environmental poisons by causing these molecules to fluoresce," explains Kaiser. The chip is therefore equipped with an optical-fiber waveguide, along which a laser beam is directed. The laser light causes the captured toxic particles to glow, which makes them detectable by an optical sensor. "After each measurement the chip is rinsed with what we call an SDS solution, which splits off all the captured antibodies without destroying the binder molecules. Thus, a chip can be used for as many as 300 analyses," explains Kaiser.

Sex Hormones in Water? In addition to antibiotics, pesticides and other toxic substances, AWACSS is also capable of detecting hormones, such as estrogen from birth control pills. Kaiser believes that hormone detection may become compulsory in coming years in the European Union. Indeed, the EU is currently investigating the potential risks associated with these substances.

At present, however, the AWACSS is facing regulatory obstacles, at least in Germany. Only accredited laboratories are authorized to analyze water samples in the Federal Republic. The use of independent monitoring instruments has not yet been approved. But Kaiser is confident. "You can absolutely count on AWACSS becoming important in the next few years," he says.
                                                                                                                   Florian Martin