Water Purification

Water contaminated with the parasite Cryptosporidium can make people ill. Healthy people may suffer diarrhoea, nausea, vomiting, abdominal cramps, headaches and a mild fever for one to two weeks. For people with weakened immune systems, including people living with HIV, cancer patients having chemotherapy, infants and the elderly, it can be life-threatening.

Giardia is another waterborne protozoan cyst and a common cause of diarrhoea. Unlike Cryptosporidium, Giardia (about 5 to 6 microns in diameter) can be killed by long contact with chlorine. Filtration also traps and removes it. In healthy people it can cause severe diarrhoea, nausea, loss of appetite and fever for days to weeks, and people with weakened immune systems need antibiotics to clear it.

The good news is that treated tap water is very unlikely to contain Cryptosporidium or Giardia, because it has been filtered and disinfected before it reaches you. Ozone and filtration together remove at least 99.9% of Giardia cysts. A combination of treatments works best.

In rare cases microorganisms can still enter the water supply despite treatment, for example through animal activity in the catchment or sewage entering the supply. Treated water stored in open reservoirs can also be contaminated by storm runoff.