Water purification Frequently Asked Questions (FAQ ).
What is water purification?
Water purification generally means freeing water from any kind of impurity it contains, such as contaminants or micro organisms.
Water purification is not a very one-sided process; the purification process contains many steps. The steps that need to be progressed depend on the kind of impurities that are found in the water. This can differ very much for different types of water.
How can bacteria be removed from water?
Bacteria and other microorganisms are removed from water through disinfection. This means that certain substances are added to kill the bacteria, these are called biocides. Sometimes disinfection can also be done with UV-light.
How are fertilizers removed from water?
Fertilizers such as phosphate are removed through addition of another chemical, usually iron. The substances than become solid precipitates, that can be filtered from the water.
The removal of ammonium and nitrates is a little bit more complicated; it is a purification process that takes both aerobic and anaerobic conversion to remove them.
In the aerobic conversion stage there are two bacterial species involved. Nitrosomonas bacteria that convert ammonia to nitrite and Nitrobacter bacteria that convert nitrite to nitrate after that. Although nitrate does not represent a direct health threat to most fish, high levels are still undesirable. Apart from encouraging abnormal extensive algal growth, it is now believed that high nitrate levels are implicated in some fish diseases. This means that the process cannot be stopped here. The anaerobic bacteria take over; they convert nitrate to atmospheric nitrogen gas. This process only occurs in the absence of oxygen. The first stage is the reverse of the nitrification process, it converts nitrate back to nitrite. The second stage of denitrification converts nitrite to nitrogen gas (N2). This gas can be freely released into the atmosphere without causing environmental damage.