54 LIMNOLOGY, WATER SUPPLY AND WASTE DISPOSAL 



must take into account these water volumes with the resulting complica- 

 tions relating to economics. 



Various attempts have been made to impound these wastes in reser- 

 voirs, sometimes for extended periods. For example, Crawford (1946) 

 was able to provide adequate stream protection by storing in a lagoon 

 (for periods up to 90 days) the more concentrated wastes from a typical 

 kraft mill. The objective of this installation was to provide storage space 

 during periods of low water for subsequent release when the river was high. 

 The work demonstrated that, during the time the wastes were impounded, 

 their pollutional properties were greatly reduced. A somewhat similar 

 installation, described by Gehm (1947), has been made in Texas with satis- 

 factory results. 



The construction and successful operation of lagoons involve a number 

 of requirements not always available on a pulp mill premises. For example, 

 in order to operate successfully, the contents of a lagoon must be held at 

 a level higher than that of the receiving body of water. In mills located 

 on or near tide water, this primary requirement cannot be met without 

 great capital outlay. Furthermore, lagoons, over a sustained period of 

 operation, will fill with solids and must be dredged or otherwise cleared. 

 Depending on the type of operation, this might have to be done often 

 enough to make lagooning operations unfeasible. 



Several studies have been made to remove the sulphur compounds 

 from kraft wastes of kraft mills by special processes. Bergstrom and 

 Trobeck (1945) have suggested that water pollution can be abated by 

 removing the sulphur compounds in wooden absorption towers. The 

 towers contain fillers of a type to afford a maximum absorbing surface. 

 The wastes are passed downward over the filler and waste stack gases are 

 forced upwards through the tower. It is claimed that this process will 

 remove most of the sulphides contained in the condensates. If this type 

 of installation can be made to work, it will reduce considerably the amount 

 of sulphides and other sulphur compounds which ordinarily pass to the 

 stream. One objection, however, becomes apparent. The apparatus may 

 prevent the sulphur compounds from passing to the stream and pass them 

 to the air instead. This would result in an air pollution problem which 

 might be considered worse than possible effects on the stream. 



Actually, the feasibility of the Bergstrom and Trobeck development 

 remains to be demonstrated in our country. 



Summary 



Under normal circumstances, kraft pulp mill operation depends, for 

 its economic feasibility, on the recovery and utilization of the components 

 of its spent liquor. If the mill is well operated and adequate stream dis- 

 charge is available, the effluent from the mill should not cause a serious 

 stream pollution problem. Certain sulphur components in the wastes, 

 particularly those in the condensed blowdown and evaporator condensates. 



