The Future of Water Purification?

The first self-cleaning, whole-house water filter

In the spring of 2000, heavy rains washed bacteria-laden livestock manure into an insecure well in Walkerton, Ontario, introducing E-coli into the town's water supply. Hundreds of people became seriously ill, and seven died. As an immediate measure to help Walkerton residents, the Ontario Clean Water Agency asked ZENON Environmental Inc. in Oakville, Ontario, to add its proprietary ZeeWeed ® ultra-filtration water treatment unit to one of the town wells to help clean the infected water.

 Like many municipalities, Walkerton already used chlorine to help kill deadly bacteria and parasites such as Cryptosporidium. But chlorine doesn’t kill everything.“Chlorine kills organisms, but there’s the potential that a small amount won’t be killed. And chlorine is relatively ineffective against Cryptosporidium,” says Mark Wiesner, Ph.D., P.E., director of the Environmental and Energy Systems Institute at Rice University in Houston, and an expert on water purification. ”Membranes actually remove the organisms.”

Since ZENON introduced its membrane technology in the early 1990s, thousands of municipal systems worldwide have used it to supplement chlorine treatment. Now this technology is available to homeowners for the first time. ZENON is manufacturing a new residential system that Maytag will sell as the Central Water Filtration System.

The system consists of a 4-foot-high cylinder installed near the home’s water meter, where it can treat all of the home’s water. Inside the cylinder is a membrane consisting of thousands of long fibers about twice the diameter of a string of dental floss. (Think of a fistful of spaghetti.) Pores in the fibers capture viruses and bacteria as small as .04 microns in diameter – about 99.999 percent of them, according to ZENON.There’s virtually no reduction in water pressure, and the fibers let essential minerals and fluoride pass freely. The system is driven by water pressure, so it uses no electricity.

And the membrane never has to be changed. In fact, this is the first self-cleaning, whole-house water filter. Once every 24 hours – typically, in the middle of the night – water pressure in the line compresses a diaphragm that expands and blows the nasty stuff off the membrane and down the drain. A high-capacity charcoal filter at the top of the unit removes any chlorine in the water. The charcoal filter has to be replaced yearly.

Not surprisingly, ZENON and Maytag tout the new system’s advantages over existing technologies. For instance, while an ultraviolet light filter will kill most bacteria and viruses, it won’t always get all of them, and it uses a lot of energy. Reverse osmosis (RO) systems strip everything out of the water, including essential minerals. RO systems also decrease water utilization to only 40 percent and typically only serve one faucet.

One disadvantage membrane technology has when compared to RO systems is that the membrane won’t remove chemicals. If there was a dissolved chemical in water, such as a heavy concentration of gas or arsenic, it would pass right through the filter. ZENON and Maytag see this as a minor shortcoming. “Most problems we see are caused by bacterial contamination, or by a virus or parasite of some sort,” says Paul Bognar, the Maytag manager in charge of introducing the Central Water Filtration System to the U.S. market.