PAC is not a single product,
but an entire spectrum of versatile inorganic polymers. PAC's are characterized
by two primary numbers: their strength (usually in % alumina, or Al2O3), and
their basicity. Basicity gives a general idea of the amount or degree of
polynuclear material in the PAC. At the low end of the basicity scale is ACS,
with 0% basicity (which means it is not a PAC). The lowest basicity commercial
PAC's are about 10%; most PAC's are in the medium to high basicity range
(50-70%). At the top of the scale is aluminum chlorhydrate (ACH): at 83%, it is
the highest stable basicity PAC available. (ACH is simply a special species of
PAC - more about ACH in the next section).
PAC's can offer a number
of advantages over traditional coagulants such as alum or iron salts. Because
PAC's are pre-neutralized and have a higher charge density than traditional
coagulants, they coagulate via a more efficient mechanism, called charge
neutralization. This allows PAC's to be effective at lower doses than alum or
iron salts, when one compares the actual metal being added by the coagulant to
the system. Resulting benefits can include:
- Less pH
depression and alkalinity depletion, reducing lime or caustic
requirements
- Reduced
chemical sludge volumes.
- Sludge
density is increased.
- Improved
results in higher pH systems.
- Better
performance in cold water.
And because PAC does
function so differently, there are many applications where it will provide
finished water quality that the traditional coagulants can't achieve.
By matching the right PAC
to the stream being treated and the mechanics of the treatment system, these
benefits can be optimized. GEO understands the relationships between basicity,
alumina content and the way a PAC will perform. We also have the capability to
produce PAC's across the entire spectrum of basicity; our standard line includes
low, medium, high and maximum basicity products. Combine our applications and
manufacturing expertise, and GEO can find the optimal PAC product for you.