This report concerns some methods whereby the liquid waste from plants using the Clark hot water process to extract bitumen from tar sands is rendered clean. This report describes some novel experiments on liquid tailings from the G. C. O. S. plant, which may lead to an economically feasible tailings treatment process. The majority of the said novel experiments consist basically of adding carbon dioxide to the tailings. After this treatment the fines in the tailings settle out leaving the water part of the tailings clean and with an environmentally acceptable pH value. In some variations of the carbon dioxide treatment method it is possible to recover some of the bitumen in the tailings. The non carbon dioxide experiments consist of simply adding a readily available compound to the tailings. In this case similar sedimentation results as with this report describes some novel experiments on liquid tailings from the G. C. O. S. plant, which may lead to an economically feasible tailings treatment process.