The Katadyn Pocket Filter purifies water from bacteria and protozoa using a long-life ceramic filter (up to 50,000 litres). An optional activated carbon additive can be used to remove odours, taste and chemicals. The activated carbon cartridge costs around CHF 20-25 and lasts for around 200 litres or 6 months. The additive is not mandatory, but significantly improves the water quality of contaminated or chlorinated water.