In today's era, the issue of water quality in many regions of Greece causes the concern of more and more consumers. The distribution network in many cases is outdated and inadequate. Although city water supply systems employ water purification processes (such as filtration and chlorination) many contaminants can eventually pass through the household water supply. The unpleasant taste, smell of chlorine, solid particles (soil, rust, sand, mud) and cloudiness are typical examples of this condition. However, what we see in the water is not as serious as what we don't see. The substances with the greatest risk to our health, such as organic chemicals, heavy metals, microorganisms, are invisible, odorless and tasteless.
Water filters are systems used to remove a wide range of water contaminants, such as sediment, chlorine, chlorine derivatives, asbestos, nitrates, lead, copper, arsenic, iron, cadmium, mercury, organic compounds, pesticides, herbicides, and pathogenic microorganisms (bacteria, viruses, Cryptosporidium and Giardia cysts).
There are many ways to filter water. The most common method of filtering water is by using filters activated carbon. Activated carbon filters work through absorption that takes place due to intramolecular attraction between the surface of the carbon and the substance being absorbed. There are many types of activated carbon used in water filtration. The most well-known materials used to produce activated carbon are wood, lignite, coal and coconut.
The main pollutants that activated carbon can and does reduce are: chlorine, MTBE (Methyl-Tertiary-Butyl-Ether from oxygenated car fuels), cysts, volatile organic compounds (VOCs), i.e. chemicals, pesticides and disinfection by-products, tastes, smells, and lead.
Another technology that has been established on a global scale as the most effective method for drinking water filtration is the method of reverse osmosis. This method uses a semi-permeable membrane to filter out contaminants. Water is forced through the membrane. Only the pure water molecules pass through the membrane, while a large percentage of water and all impurities cannot pass and are then removed by simultaneous washing of the membrane. The permeability of the membrane reaches up to 0.0001 μm while the "thinnest" activated carbon can reach 0.1 μm.
The reverse osmosis method is at best effective for the following contaminants: dissolved minerals, suspended solids, dissolved chemicals, nitrates, nitrites, arsenic, heavy metals such as lead, barium, cadmium, hexavalent chromium, etc. For the latter, reverse osmosis achieves up to 96% rejection, while for the widest range of harmful substances and parasites it achieves up to 99% rejection.
The combination of these two ways of filtration, i.e. an array, which includes a carbon pre-filter and the main purification unit, reverse osmosis, gives the best solution for city dwellers and not only.