rate of ofa is adjusted to provide a concentration thereof of from about 0 5 to about 20 ppm in the mother suspension to obtain satisfactory granulation according to the instant process it is preferred to increase the concentration of suspended solids at least threefold over the concentration thereof in the untreated mother suspension liquor in other words in the granulation separation apparatus of the present invention the lower limit of the internal concentration within the blanket layer must be maintained at about at least 3 times higher than the concentration of the suspended solids in the mother suspension liquor otherwise granulation and separation do not satisfactorily occur generally satisfactory results are achieved when the solids concentration is within the range of from about 1 g l to about 150 g l the upward flow rate also substantially influences the above mentioned critical internal concentration within the granulation section therefore the upward flow rate must be adjusted to satisfy the critical solids concentration level the upward flow rate is also dependent upon the type of mother suspension liquor to be treated in a granulation separation apparatus of the type illustrated in fig1 and 2 satisfactory results are obtained when the suspension upward flow rate is adjusted to from about 200 mm min to about 2 000 mm min however the optimum upward flow rate is to be experimentally determined for each suspension the speed of the impellers varies also with types of mother suspensions in the apparatus of the present invention preferably the speed of the impellers at the distal end.