 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
Environmental Impacts of Bleaching With Chlorine
As soon as pulp is exposed to chlorine or chlorine dioxide during the bleaching process, the concentration of chloride ions in the waste water makes it too corrosive to be recirculated to the recovery system where the organic waste is stripped from the water and burned for energy in the recovery boiler. The organic waste in the effluent must be discharged to the effluent treatment system and ultimately rivers and lakes.
Pollution Prevention Strategies
Low Effluent TCF
Replace chlorine bleaching stages with oxygen based chemicals so that all of the effluent can be recirculated to the recovery system
Pulp mill effluent contains a large mixture of organic substances. At this point, 415 have been identified - 315 of these contain chlorine. We will continue to see concerns about different substances in the effluent as scientific research continues. A reasonable long term strategy would be to install technologies that will eliminate the discharge of any effluent from the mill.
75% of effluent is sent to the recovery system (Q-stage is discharged)
Low Effluent ECF
Mill-Scale Demonstration
Remove chloride ions from bleach plant effluent and burn organic waste in the recovery boiler
Champion International is currently [1996] testing this system at its Canton, NC mill.
Champion claims that they have demonstrated a technology on a laboratory scale that will allow them to remove the corrosive chloride ions from the effluent. The remaining water and organic waste can then be sent to the recovery system where the organic waste can be burned.
Champion assumes that they will be able to burn small quantities of chlorinated organics in the recovery boiler without generating any dioxins. Air emissions from the recovery boiler and recovery boiler ash will have to be tested for dioxin content.
NOTE: Reach for Unbleached! does not endorse the movement of mills to this system. While it may lead to reduced effluent, testing still has not been done to show that chlorinated organics do not end up in the air and ash instead of the water. It also does not address the worker and community safety concerns of using chlorine dioxide. As shown below, it is also likely to be more expensive. For the cost, mills should do the right thing and move to Totally Chlorine Free. For further information on our reasons see our report, Zero Discharge in the Library.
NOTE 2005: This mill has been sold and the testing of this system discontinued.
See also Zero Discharge: Technological Progress Towards Eliminating Kraft Pulp Mill Liquid Effluent, Minimising Remaining Waste Streams And Advancing Worker Safety