Water clarification is an essential stage in the treatment process. Its management is particularly important nowadays given the latest requirements concerning the removal of parasitic micro-organisms such as Cryptosporidium and Giardia.
Filtration media (Drinking water)
Their small size (4 to 7 μm and 5 to 12 μm respectively) makes their removal difficult.
Only a well managed clarification process whose effectiveness relies on the existence of a series of multiple barriers will ensure that these parasites are removed.
Depending on the filtering media being used, filtration is one of those barriers that assists in removing turbidity, iron, aluminum and (particulate) manganese as well as colour, suspended matter and organic matter.
Filtration improves the effectiveness of the final disinfection process by reducing the suspended solids.
Moreover, it assists in reducing the possibility of disinfection by-products forming as a result of the effect of the chlorine on the organic matter (THM).
All existing prior treatment stages need to be properly managed in order to achieve optimal effectiveness from the filtration process.
This effectiveness, once achieved, makes it possible to :
- reduce clogging of the filter medium and prolong filter run cycles (hydraulically speaking)
- reduce the risk of the filters failing to maintain the parameters already mentioned with regard to quality (turbidity, particle content, bacterial and parasitic contamination, colour, iron etc.)
Used for centuries, the filtration technique is always evolving.
Employed in numerous areas, this technique has primarily been adapted for use in top quality drinking water production.
Sometimes used on its own, filtration has become a key treatment stage, which, despite its reliability, is constantly being improved upon in order to perfect the quality of filtered water.
In addition to its principal function of separation or clarification, filtration also enables biological treatment processes to be carried out.
In this case the filter medium is not limited to acting merely as a sieve for suspended matter, but also acts as a support which ensures the attachment and growth of the active biomass.
This feature of the filters makes biological treatments such as iron and manganese removal, nitrification of ammonia-nitrogen, denitrification, or even the assimilation of biodegradable organic carbon possible.
More and more attention is being paid to the design and use of filters, and even today numerous areas are still being found that can be improved upon.
New microfiltration and ultrafiltration techniques constitute an alternative solution to conventional filtration techniques.
With regard to the risk of infection from the microbiological quality of drinking water, the regulatory stipulated parametric value for a water supply's turbidity is by no means sufficient to be considered as a good enough quality target.
As a result, many treatment plants justifiably aim and also produce water quality which is a lot higher than turbidity limits.
Filtration affects numerous other parameters, such as physical-chemical and bacteriological parameters, and the quality of a filtration process needs to be judged by its overall removal capabilities.