Membrane pre-treatment by AFM

 

 

Dryden Aqua are marine biologists specialising in seawater filtration systems for the aquaculture industry over the last 25 years. It is absolutely essential to have the best possible filtration when trying to cultivate delicate marine fish.  It is also essential that the systems are a low cost and reliable, because system failure, even for a few minutes could result in loss of millions of juvenile fish.

Dryden Aqua in association with the European Commission under the Life Environment initiative have completed extensive research for the development of AFM  ( Activated Filter Media).  AFM  replaces the sand in your media bed filters. Simply by changing the sand and replacing it with AFM  media,  you will double the performance of your filters, and present a much better water quality to the membranes.  Typically, by changing the sand and anthracite in your filters to just AFM  you will reduce the SDI ( Silt Density Index) values by 50% to 80%. For example in a comparable trial with sand and AFM, the discharge from AFM  was 1.5 and from sand it was 3.5 on average, the influent SDI was actually too high to measure. Filter velocity was 8 cubm/hr/sqm   

Ultra filtration will give a better performance,  however the SDI does not give the full story. When AFM  is combined with pre-coagulation and flocculation using flocculants, or even if small quantities of ozone at 0.05mg/l  is used to create flocculation reactions,  AFM  will remove sub-micron particles below 0.01 microns as well as dissolved organics. This would be impossible using membranes,  so a relatively low cost procedure using AFM  can actually be much more efficient that Ultra Filtration.  AFM with pre-coagulation and flocculation using a ZPM and APF  will therefore provide better performance that UF, and protect the RO membranes from silica, phosphates and nutrients that would otherwise contaminate the membranes and cause bacterial growth.