The PFT meter has been developed by
WRc to measure Pressure Filtration Time.
It is a bench top instrument which is controlled by compressed
air. The meter uses a 100 ml sample of sludge which is poured
into a pressure vessel/filter assembly. This assembly is then
placed below a rubber covered block, which clamps and seals the
pressure vessel before pressurisation. It may be pressurised at
any pressure from zero to 140 psi. The PFT is measure using
a calibrated filtrate collection vessel containing level detecting
electrodes which are connected to a suitable timer, the Compact
100, [the timer is described on a separate sheet].
Typical applications for the meter
1. It can be used to characterise, in terms
of dewaterability, for example, either a raw untreated sludge
or digested sludge in order to produce a base line standard. It
would then be possible to utilise this information to compare
different methods of treatment and so help determine the best
possible process.
2. It may be used to test samples of flocculated
sludge prepared on the bench. Such tests have shown that the efficacy
of polyelectrolytes depend not only on their own properties but
also on the nature of the sludge and on the way the polyelectrolyte
is actually mixed into the sludge. The meter can be used to identify
the best polyelectrolyte for any particular sludge andthe optimum
mixing conditions. Since PFT can be related to plant performance,
the required dose of the polyelectrolyte can also be determined.
Such information is useful for improving the operation of dewatering
plants. For example, performance can be improved and costs reduced
by changing the polyelectrolyte or by controlling the mixing conditions
at the dosing point.
3. The meter can also be used for controlling
dewatering processes. In this case a sample of flocculated sludge
is taken from the process stream and the PFT measured. Operators
can relate the PFT value to plant performance and adjust polyelectrolyte
dose or make other process adjustments when necessary.
Endorsements
PFT meters
have been installed in over thirty different locations including
such prestigious organisations as Thames Water, East Hydes STW,
Luton, and Arjo Wiggins Fine Paper Limited, Stoney Wood Mill,
Aberdeen.
At East Hyde STW, a change was made from Copperas [Ferrous Sulphate] dosing to Polymer dosing to flocculate the sludge. Initially a Capillary Suction Time ( CST ) meter was used but it was found to be unreliable. The PFT meter has been used to select the best Polymers for the operating conditions and then to optimize the dose on a daily basis, as a result, considerable cost savings have been made.
Without the PFT Meter this could not
have been easily obtained.
Arjo Wiggins
are always looking for ways of improving the dewatering of their
waste solids, and they turned to the PFT Meter to improve
the efficiency of their plant. The meter was first used to select
the best polymers to flocculate the sludge and since then it has
been used for daily monitoring of the sludge condition. The meter
has been a great success and has contributed to improved efficiency.
TECHNICAL SPECIFICATION
Meter Contents
Case with pressure gauge
Overall Dimensions :- Base 250 x 270 mm, Height
580 mm
Pressure Vessel/Filter Assembly
Filtrate Collection Vessel ( which must be
connected to timer , Compact 100 )
Power Source
Compressed Air
Maximum Pressure 150 psi ( 10 bar )
Minimum Pressure 110 psi ( 7.5 bar )
This gives a maximum vessel pressurisation
of 140 psi (9.5 bar)
Contact
Richard Matthews Enterprises Ltd.,
17 Tansy Close,
Northampton,
NN4 9XW,
England..
Tel: (0) 1604 765197
Fax: (0) 1604 765868