In order to obtain the fundamental conditions for the percolation through activated carbon columns for kraft pulp lignin, the fixed-bed column tests on the bench scale were attempted.
The results obtained are summarized as follows :
1. When the effect of flow direction for column tests was expressed by carbon usage, in terms of volume of effluent treated up to breakthrough point per weight of carbon, the carbon usage for downflow operation was more 15-30% than for upflow operation.
2. Non boiling and boiling treatments for carbon in water were investigated to drive out the air in pore of carbon as the pretreatment method of column test, and the carbon usage for the former was 72-75% of the carbon usage of the latter.
3. The relation between contact time and carbon usage was developed theoretically and it was verified experimentally that the same carbon usage was obtained at the same contact time in any column test of activated carbon and the graphical solution of the relation between contact time and carbon usage was given as a certain hyperbola.
4. Samples of the effluents from the carbon column at regular intervals were collected and analyzed for lignin, the chemical oxygen demand (COD) and the total organic carbon (TOC), and the COD/lignin and TOC/lignin ratios were 1.12 : 1 and 0.73 : 1 respectively.
The results of this work can be useful when column tests of pulp mill waste water on activated carbon are attempted.

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Dissolved-air flotation has been applied as a separation technique to recover suspended solids from the paper mill white water system. Polyelectrolytes are generally used to facilitate the flotation.
Main components of the white water are pulp, filler and size, though their contents differ according to the kind of paper to be manufactured.
The purpose of this study is to determine various factors involved in flotation with Polyethylenimine (PEI) and Polyacrylamide (PAM), and to evaluate their applicabilities.
Laboratory tests were conducted with artificially prepared white water samples, simulating pulp alone, pulp-filler, pulp-aluminum sulfate or pulp-filler-aluminum sulfate systems to compare the effectiveness between PEI and PAM for the above each system.
For the flotability of pulp the following results were obtained ; Flotability of pulp fibers varied with the kind of pulp, and that of coniferous wood pulp fiber was poor. Floating velocity increased when white water contained filler up to about 50% of pulp but the quality of treated water degraded in these cases. Flotability was particularly impeded by the presence of aluminum sulfate.
For the effects of PEI and PAM, it was found that, the affectiveness of PEI and PAM for the same kind of deciduous wood pulp differed depending on the manufacturers. PAM was more effective than PEI when filler was contained. PEI was superior to PAM when aluminum sulfate content was less than about 11 ppm (as Al), while PAM was better at the content more than that. When both filler and aluminum sulfate were contained other than pulp, the flotability of pulp was poor but most clear treated water was obtained at aluminum content of about 11 ppm. PAM was better for this system.
In conclusion, aluminum sulfate has significant effect on flotability and either PEI or PAM should be carefully chosen according to the composition of white water to be treated.

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As previously reported, the extractives contained in eucalyptus woods increase viscosity of concentrated black liquor abnormally and make troubles at burning. However, such extractives are known to be easily dissolved in alkaline cooking liquor and partly decomposed. The authors have applied wet combustion process for the oxidative decomposition of extractives in black liquor in order to improve the properties at evaporation and combustion.
Different from an ordinary Zimmermann process, the partial wet combustion, of which COD reduction is about less than 20%, was found to be effective for lowering the viscosity of concentrated black liquor and the swelling volume, preserving the sufficient calorific value of black liquor, which enables the chemical recovery for the kraft process.
Moreover, the changes of black liquor on the partial wet combustion were examined by gel filtration methods and found the fraction of higher molecular weight was decomposed easily as well as lignin.

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