The wastewater from coal coking process (gas liquid) is usually treated in the activated sludge after ammonia stripping. The two types of the gas / liquids, that were liquid (A) produced in a convensional ones and the other one (B) produced in a developing oven were treated in the activated sludege. Their biological reactivity and their chemical characteristics were compared. B liquid was found to carry so large quantities of organic compounds, especially the high molecular weight compounds, and the poisonous compounds (S2-, CN, SCN, etc.) for the biological treatment than A liquid. Hence B liquid was 4∼5 times more toxic than A one. B treated still carried larger quantities of organic compounds which included the high molecular weight ones than A treated effluent.
On the activated sludge treatment, A liquid could be treated by 3 time dilution, whereas, the 12.5 time dilution in the treated water was not enough with B liquid, increaseing of COD, SS and SCN values with foaming in the aeration tank. After some days of operation the ORP suddenly became out of contorol, digestion of SCN becoming very poor. Damaged activated sludge was regenerated by the addition of rice bran and the high dilution of feed for 4 months. The SCN digestion ability was restored or even improved after the regeneration.
