where C is the concentration of filtrate and C0 is the concentration of the furnish.
In the microparticle retention test, the cationic polymer was added into the pulp suspension, and stirred at the speed of 1400 rpm for 30 s. Then, the stirring speed was reduced to 750 rpm and NCC was added. The drainage rate and the FPR could be calcu- lated according to the formula (3).