The filtration parameter developed by the Water
Research Centre ( WRc) , UK..
The economical and reliable operation of dewatering
plant depends on having equipment which accurately measures a
filtration parameter that can be related to process performance.
When a sludge is dewatered, by filter press, belt filter or in a centrifuge, the filterability of the sludge has to be improved by the addition of a flocculent. If too little flocculent is
added the dewatering process proceeds too slowly,
where as, adding excessive flocculent is not only wasteful, it
can have a detrimental affect on the ultimate water content of
the sludge due, for example to the hydroscopic nature of polyelectrolytes.
A low water content in the dewatered sludge
has several economical advantages when considering further treatment
or disposal, for example:
Landfill
Low water content will result in less sludge to transport and a longer life for the
landfill site.
Incineration
A low water sludge will burn at a much higher
temperature, requiring less fuel to start and maintain the burn.
Thermal Drying
Less water will result in quicker drying times
and lower heating fuel consumption.
It is therefore important to be able to measure
accurately a filtrate parameter that can be used to determine
the correct dose of flocculent to produce the required plant performance.
The most pertinent measure of filterability
is the specific resistance of filtration [SRF], a fundamental
parameter which however is rarely used, due to the difficulty
in its measurement. As a result, other parameters have been developed;
the PFT being one of these. It was developed to overcome the problems
and limitations of the widely used CST which obtained results
by empirical means and was insensitive to changes in filterability.
Whereas PFT is sensitive, as it is directly proportional to SRF
and therefore can be related to the performance of dewatering
plant.
A PFT meter has been developed to measure this parameter.
Contact
E-Mail:
Richard Matthews Enterprises Ltd.,
17 Tansy Close,
Northampton,
NN4 9XW,
England..
Tel: (0) 1604 765197
Fax: (0) 1604 765868