A good evaluation of polymer performance for
application in belt and filter presses, in sludge dewatering, will depend
on free drainage filtrate volume, filtrate clarity and sludge cake characteristics.
The best polymer results would yield the greatest filtrate volume, best
clarity, and a compressible dry sludge cake. The experimentally determined
dosage may not necessarily be the precise dosage needed on the press, but
this dose will aid in the selection process and serve as a starting dosage.
- Required Equipment
- Graduated cylinder 250 mL
- Bucket for sample collection: 5 gallon capacity
- Buchner Funnel Apparatus (90 mm dia.), with
- Fabric screen, like that used in the filter
press or Whatman #40 filter paper.
- Beakers: 250 mL, two
- Syringes: 1cc, 5 cc
- Mechanical vacuum pump or connection to
laboratory or plant vacuum source.
- Test Procedure
- Assemble Buchner funnel apparatus.
- Collect 5 gallons of sludge to be tested.
This sludge should not have any polymer in it, however, it should contain
whatever substances are typical of the system to be treated.
- Fill the 250 mL cylinder with 200 mL of
- Add polymer solution, according to the second
- Pour this into one of two beakers. Pour
back and forth between the two beakers six times. Consistent mixing is
- Start the vacuum on the Buchner funnel and
pour the sludge into the funnel
- Start the timer. Note the filtrate volume
at ten second intervals, until the drainage stops. Note the final volume
of the filtrate and its clarity.
- Look into the funnel to observe the cake
characteristics. A dull cake indicates a dry cake. As shiny surface indicates
a wet cake. Determine the percentage moisture content by weighing the wet
cake, then drying it overnight in an oven set at 100 degrees C, and weighing
- A crude pressibility test can
be run by squeezing the cake in one hand. If the sludge is compressible
and the runoff is clear, the sludge should run well on the press. If the
sludge runs through the fingers, it is not likely to run well on the press.