Pretreatment method for removing oil by gas-making wastewater

The invention discloses a pretreatment method for removing oil by gas-making wastewater, which adopts a combined process of 'a heavy medium loaded coagulation oil remover, a round floatation tank and PTFE membrane micro-filtration'. The method comprises the following steps: firstly, adding acid and a demulsifying agent to enable emulsified tar to be unstable, precipitating, and carrying out preliminary oil-water separation; then, adding surface-modified heavy medium magnetic powder as a carrier in the heavy medium loaded coagulation oil remover to adsorb heavy oil suspending in water, wherein the hydraulic load can be more than 20m/h; enabling the effluent water to enter the round floatation tank so as to remove a great deal of precipitated light oil through the action of round floatation; and intercepting slightly-soluble disperse emulsified oil by the PTFE membrane micro-filtration through the action of a hydrophilic PTFE membrane. The combined process of 'the heavy medium loaded coagulation oil remover, the round floatation tank and the PTFE membrane micro-filtration', adopted by the invention, is capable of removing oil in water in a step-by-step and classified way, the removal rate of non-soluble oil can be more than 99%, the hydraulic load is high, and the floor area is small.