Prelimer suspended solids can be separated. - ASSBT Proceedings

tests. The variability in operating conditions and the short test time, along with any
changes beet quality and/or testing variations, resulted in enatic result . At times it
appeared that there may have been improvement in settling and filtration, but at ti mes no
improvement was indicated. The plant personnel did not notice any adverse effect of any
kind they could contribute to the test. At any rate we were encouraged by the results.
Over the time frame from the first tests at Hereford in 1992 until the present a numb r of
tests were made at several beet sugar plants: Imperial HolJy Sugar plants at Worland
Wyoming and Hereford, Texas ~ Western Sugar Co. plants at Scottsbluff, Nebraska,
Billings, Montana, and Ft. Morgan Colorado' American Crystal Sugar Co. plant at East
Grand Forks, Minn esota ~ Southern Minnesota Sugar Co. plant at Renville, Mi nn so t~
and Minn-Dak Farmers Cooperative plant at Wahpeton, North Dakota. At Billings, East
Grand Forks, Renville, and Wahpeton only laboratory testing was conducted. Plant tests
were run at all other plants listed, most tests being of short duration (a couple of days or
so). Also, most ofthe tests were only involved with polymer treatment at the Preli mer
and evaluation of the settling and filtration qualities of the resulti ng Prelim r effl uent.
In order to properly evaluate the improvement in pJant operation realized from the
Prelimer treatment it is necessary that the full plant stream must be treated with all of the
suspended solids removed therefrom. To accomplish tIllSthe plant must be capable of
settling and filtering both the Prelimer effluent and also the 1 st Carb effluent. The plant
will nonnaJly run with separation of 1 st Carb soLids, but must be able to switch over to
separation at the Prelimer for the test period. If the plant personnel were willing to risk
starting out with and using the polymer system, only separation equipment at the
Prelimer would be needed. However, that is a risk that few would wish to take.
At any rate, to properly test the polymer technology, tRe plant needs the capability of
settling suspended solids both at the Prelimer and 1st Carb--usually a clarifier, though
other equipment could be utilized. The plant would al so require the capability of
switching on the run from filtering concentrated 1st Carb sludg to filtering concentrated
Prelimer sludge. Since there will continue to be suspended solids generat d at 1st Carb
when the solids are settled and remo ed at the Preiimer, disposition thereof is requir d.
Cone ntrated sludg from 1st Carb couJd either partially or wholJy sent dire tly to the
fIlter supply tank (for Prelimer sl udge) or recycled to the Prelimer to provide seed
crystals and bulk for improved settling and filtration. The latter option is sur Iy the
better, especially when lime addition is cut back to decrease costs. Witb th vast bulk of
precipitable material having been removed from the Prelimer effluent, particular! the
fluffy and sticky colloidal types, about all that is precipitated in 1st Carb is rather pure
calcium carbonate crystals having excellent surface characteristics to help gi e good
settling and filtration. The volume of recycle sludge from 1 st Carb to the Prelimer
should, of course, be minimal.
In all testing at the various plants we consistently found that the use of cationic Mafloc
2009 improved both the settling and filtering characteristics of the suspended solids in
Prelimer effluent. Because of the similar results obtained at each plant, we will no
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