Walk out the front door of a house under construction in Santa Monica, California, and the bridge over a koi pond in the front yard leads to stepping stones, then a meditation deck that appears to float in the water.
To the casual observer, the pond merely looks like pretty landscaping. But when construction is completed, it also will be the filtration system for a backyard swimming pool that will use plants, gravel and mechanical filters instead of chlorine or other chemicals to clean the water.
It's called a natural swimming pool or swimming pond, and it's an idea that some in the industry believe will be the next big thing in health-and environment-conscious Southern California.
Chlorine has long been the industry standard to keep pool water clean and clear, but consumer demand for alternatives has prompted the emergence of new technologies, including the saltwater systems that came into vogue a few years ago and the copperand-silver ionization and ozone-gas systems that are increasingly popular.
"I don't like the stuff that goes into swimming pools," said Philip Daughtry, a Topanga Canyon poet who often swims in the koi pond he refers to as his "backcountry swimming hole."
Daughtry's swimming pond was constructed by Environmental Sculpturing in Topanga Canyon, the outfit that also helped to design and install the Santa Monica pond being built in a Zeninfluenced, Minimalist style.
Natural swimming ponds take many shapes. Some look like traditional pools with poured concrete foundations, hard edges and straight lines. Others take forms that more closely mimic nature, with gently sloping and planted edges.
Natural swimming ponds are relatively new to the U.S., but more than 20,000 have been built globally, according to a spokesman for BioNova Natural Pools, a German company with North American headquarters in New Jersey and three natural swimming pools built or under construction on the East Coast.
Next year BioNova will install what will be the first public natural swimming pool in the country at Webber Park in Minneapolis.
"A lot of people are interested in leading a chemicalfree lifestyle. We're not using any devices, sterilizers or chemicals of any kind," said Alan Weene, spokesman for BioNova, which has partnerships to build natural swimming ponds in more than 30 countries.
The BioNova system uses shallow-and deepwater plants in conjunction with filters to keep the water clear. The system only works to a temperature of 86 degrees, so it isn't suitable for Jacuzzis.
BioNova pools, as well as those designed locally by Environmental Sculpturing, are biologically active. That means unlike chemically treated pools, which are sterile, natural swimming pools contain plants and beneficial micro-organisms that outcompete algae and harmful bacteria for nutrients, leaving water safe for swimming. In these natural pools, water is circulated with pumps to prevent mosquitoes from laying eggs.
Although installation costs are slightly higher for a natural swimming pond compared with a traditional pool, the level of maintenance is roughly the same.
Both types of pools require vacuuming and hand skimmers to pick off surface debris. Natural swimming ponds do not need biweekly visits from a pool professional to add chemicals, but they do require occasional weeding and replanting.
"One of the reasons why chlorine is the most popular swimming pool disinfectant is that it provides a longlasting residual in the water," said Mary Ostrowski, director of chlorine issues for the American Chemistry Council in Washington, D.C. In response to rising consumer interest, Ostrowski said, the group is working with an advisory council to determine ways pool owners could reduce their chlorine use in conjunction with other technologies, such as ozone gas, ionization and ultraviolet light.
Many of those chlorinecomplementary systems are already in use. Nature2 from Zodiac Pool Systems in Vista, California, dissolves traces of silver and copper into the water to disinfect it and prevent algae.
The system, approved by the Environmental Protection Agency, allows pools to operate using just 0.5 parts per million of chlorine, compared with the recommended one to four ppm for conventional pools.
PRIMER ON POOL SANITATION SYSTEMS
Chlorine: Inexpensive and easily available, chlorine is the chemical most commonly used in swimming pools and hot tubs to kill bacteria that can spread disease.
Used in concentrations of 1 to 4 parts per million, chlorine helps keep pool water at the recommended pH level of 7.2 to 7.8.
However, chlorine breaks down into different chemicals that have been blamed for itchy skin, difficulty breathing, asthma and other ailments. If released into the environment, chlorine can cause lowlevel harm to organisms living in the water and soil, according to the U.S. Environmental Protection Agency.
Ozone gas: More expensive than chlorine, ozone is a short-term disinfectant that rids pool water of organic material to keep it clear. Ozone gas is generated by combining oxygen with electricity. It's added to pool water after it goes through the filter and heater.
Ionizer: This device uses a low electric current to create copper and silver ions that attract and kill algae, bacteria and viruses.
Ultraviolet light: Pool water circulates through a chamber that destroys or inactivates microorganisms by exposing them to UV light. The system reduces the need for chlorine and other chemical sanitizers.
Bio-filtration: A chemical-free system that circulates water through rooted aquatic plants and a fine-mesh filter that helps break down contaminants in the water. Beneficial micro-organisms keep down algae and harmful bacteria.
