The pretreatment scheme of using water from the Grand Canal as ingoing water of the reverse osmosis system has been studied. The main points are elimination of organics in the water

and reduction of the water turbidity

including: （1） determining the content of organics in raw water and the distribution range of its molecular weight; （2） selecting cogulant and its concentration; （3） defining the effects of cogulating aid and low turbidity additives; （4） considering the infuence of pH value in raw water upon the cogulating effectiveness; （5） conducting oxidation test for NaCIO; （6） performing test of organics abosorbing ability for activated carbon. Based on the results of test

an effective and practical pretreatment process has been put forward.