| AFM
( Active Filtration Media) is a simple media bed filtration system
that replaces sand in sand filters. However AFM works a great deal better
than sand and has many additional benefits;
Basic qualities
- AFM does not biofoul
- The filter bed is resistant to coagulation and
wormhole channeling
- The organic load or SS load does not affect AFM,
however from a physical perspective, influent solids load should be kept
below 200mg/l
- AFM has a high surface negative Zeta potential,
which allows AFM to adsorb some heavy metals and organics, back-washing
removes the chemicals (can reduce load by 50% on activated carbon, and
with development we will be able to replace carbon with AFM
- Catalytic surface causes dissociation of oxygen and
production of free radicals. Regular AFM will crack some organics,
decolourise the water and adsorb heavy metals
Advanced AFM systems
Hydrocarbons, PCB`s & list 1 chemicals
Hydrocarbons can often be treated by biofiltration, if
this is practical then a fixed film reactor or a fluidised bed may be used.
The effluent from the biofilter goes directly to AFM with no flocculation.
The solids load from the biofilter will normally be below 200mg/l, however
if the levels are higher then a simple inclined tube clarifier may be used.
The important point is that we do not want to expose the discharged aerobic
bacterial cell biomass to the anaerobic conditions in a humus tank.
The specialised adapted bacteria in the system are important for the
operation of the process, the AFM filter will capture these bacteria and
return them to the bio-reactor.
List 1 chemicals and bio-accumulated toxic substances
will tend to become concentration in the bacterial cell biomass. If the
biomass is exposed to anaerobic conditions in a humus tank, the bacteria may
succumb, or leachate out the list 1 chemicals. By using AFM, bypassing the
humus tank and keeping the system aerobic. The discharge of list 1
toxic chemicals can be reduced by up to 90%.
Heavy metals
AFM will remove some heavy metals directly,
however it is important that there is oxygen in the water to insure that the
catalytic reactions will progress. In some situation it may be
necessary to adjust the pH and use flocculation prior to AFM filters. No-Phos
has proved to be very efficient in this respect.
Iron & Manganese
a specific schematic for iron and manganese
click here for details
Phosphates
Phosphate will form an insoluble precipitate with PAC
and to some degree with calcium. However when NoPhos is used the
reactions are stoichiometric and a very high percentage of the phosphate
will precipitate out of solution. The precipitate will have a positive
charge and is easily removed by the high negative surface potential on AFM.
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- 2 to 10 cubm/hr AFM skid mounted system
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Quaternary Treatment
After AFM filtration the water will be of a high quality, suitable in most
cases for direct discharge. However it very pure water is required for
a gray water recirculation system, or even drinking water treatment, then
extra treatment will be required. The AFM system will have reduced
most of the loading on the final Quaternary step and makes the installation
and use of the the following processes a much lower cost and practical
proposition;
- membrane filtration
- UVc and advanced photo oxidation
system
- Ultra and sub-sonic treatment
- Ozonation
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AFM filters yeast directly out of
brewery effluent ( 8 microns) 98% removal efficiency, no coagulation
or flocculation used
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