NSPs rely on a combination of hydraulic design techniques in conjunction with a finefilter. Materials such as leaves, pollen, dust or suntan lotion commonly found floating on the water's surface are removed by a specialized skimmer or overflow channel. These specially designed devices allow optimal skimming of the water surface and reduce silting. Downstream, a bioreactive biological filter removes and retains additional particulate matter down to a particle size of 100 micrometres. Pumps different from those found in conventional pools hydraulically optimize water flow rates and volumes, thereby accelerating the cleaning process even further. This mechanically enhanced natural filtration produces clear, clean water. In fact, when NSPs are installed in Europe, pool owners and builders will ceremoniously wrap up an installation with a ceremonial drink of water collected directly from the pool.
A biofermenta system is the latest form of filtration for NSPs reducing the need for large plantation areas and filtration beds.European and European-style NSP builders follow the EEC bath waters guideline 2006/7/EG concerning the quality of bath waters and their management. Specific health guidelines are also clearly established in the German FLL Guidelines, which are adhered to by NSP builders throughout Europe. On March 4, 2006, new pool water standards were published in the Official Journal of the European Union. These standards, enacted throughout Europe within two years, outline the methods of monitoring pool water quality. Unlike conventional North American swimming pools whose sanitation levels are monitored by testing for proper pool chemical balance, European-style NSPs maintain strict standards for bacterial levels. Peter Petrich, an originator of natural swimming pools in Austria, has said that the risk of swimmers becoming sick is "very low." [6]
Properly built public NSPs in Europe, some that see up to 3,000 swimmers per day, are able to meet these high sanitation standards.[14][15] The first public Natural Swimming Pool in North America has been designed to accommodate over 1,000 bathers per day. Thus, the efficacy of the NSP cleaning process remains in little doubt, even though no guidelines for natural pool water quality currently exist in the United States
