Two continuous-feed decanter centrifuges were deployed for
carrying out field tests in a wastewater treatment plant that processed
a mixed sludge with 52% waste activated sludge from secondary
treatment and 48% primary sludge from primary
treatment. The cake solids have dry matter content between 29%
and 30% [13]. A polymer solution was prepared from dissolving
Percol 789 polymer (powder) in deionized water to produce a solution
with concentration of about 0.3%. One machine referred as HS
has diameter 427 mm by length 1372 mm for which operating
parameters were varied for testing purposes, while the smaller
machine DS with diameter 429 mm by length 1257 mm was run
at fixed condition as a referee machine. When feed sludge properties
changed during testing for a given day, they affected both
machines and a fair comparison could be made between the two
machines.