| The process An AFM filtration system has recently been commission for
a UK water company. The system was installed on a small rural sewage works typical of many sewage works around the country.
The site is approximately 30 years old and has seen a steady increase in loading over recent years, to such an extent that the works is trying to
cope with up to three times the initial design hydraulic loading. Consequently the works is struggling to maintain water quality.
A decision was taken by the water company to retrofit an AFM pressure filtration system. The photograph shows the stainless steel control and
pumping system, two black buffer tanks and the light blue pressure filter. |
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| Effluent water quality The AFM filtration system filters the water
immediately after the percolating filters but before the humus tanks.
The final effluent water quality normally ranged between 40 and 100mg/l suspended solids. After the AFM filtration the discharge level was reduced
to around 5mg/l
Flocculation
If flocculation is used on the system, discharge water quality can be improved to less than 1 mg/l
Phosphate removal
AFM systems can virtually eliminate final effluent phosphate by using ferric chloride or lanthanum chloride flocculation
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| Sludge and chemical recovery The AFM filter is
back-flushed automatically at regular intervals, a mass balance can then be conducted on the quantity of solids removed by the filter and back-flushed
back out of the filter.
The back-flushed water has a solids content between 2000 and 4000 mg/l. The sludge is kept in an active aerobic condition and can either be
recycled back to the beginning of the works, or de-watered for sludge disposal.
We have found that removal of the bacterial sludge by AFM before it is subjected to the anoxic conditions in the humus tank, prevents the release
of prescribed substances back into the water. This aspect of AFM process technology is protected by our IPR and for the first time
provides us with an effective relatively inexpensive tool to prevent the discharge of toxins to the environment. |
AFM filtered water, and discharge taken directly from the percolating filters
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| The system The system is housed in a self contained enclosed skid,
comprising of the run phase variable speed controlled pump, back-flush pump and air blower. The process is controlled by a plc which continually monitors water flowrate, pressure, and tank water levels.
The system has been designed to be completely automatic and requires no operator intervention.
AFM turns sewage effluent into clear bright water..
AFM filtered water, and discharge taken directly from the percolating filters
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