MICROBIOLOGICAL CONTAMINATION OF DRINKING-WATER IN A COMMERCIAL HOUSEHOLD WATER FILTER SYSTEM

The microbiological quality of filtered water in a commercial water fi lter system (Brita) was tested in households and in two laboratories. In 24 of 34 filters used in households, bacterial counts increased in the filtered water up to 6,000 cfu/ml, In 4 of 6 filters tested in the laboratory, bacterial counts in the fresh filtrate were higher than i n tap water after approximately one week of use both at room temperatu re and at 4 degrees C, suggesting growth or biofilm formation in the f ilter material, In some cases colony counts in the filtered water were 10,000 times those in tap water. The filter material of 5 of 13 new c ommercial filters was contaminated with bacteria or moulds. National o r international regulatory agencies should ensure that water filters m arketed for domestic use do not allow deterioration in the microbiolog ical quality of drinking water.