Abstract: The refinery special wastewater has become an environmental problem for enterprises due to its poor water quality and difficulty of treatment. Aiming at the water quality characteristics of the special wastewater, a set of enhanced pretreatment process and pilot plant of “oil separation-flotation-electrochemical oxidation-neutralization- filtration” were designed. The results of 186 days on-site operation showed that the compliance rate of effluent COD, petroleum, and suspended solids concentration was 100%, the compliance rate of ammonia nitrogen concentration was 97.8%, and the average B/C increased to 0.334, and the water quality could meet the acceptance requirements of the integrated wastewater treatment plant. The removal rates of ammonia nitrogen and total nitrogen in the electrochemical oxidation unit were up to 96.5% and 93.3%, respectively, and the B/C value of the wastewater was increased by 67.0%. The processing cost was low, and an average operating cost was 4.56 yuan/m³.

Key words: refinery special wastewater, electrochemical oxidation, biodegradability, COD, ammonia nitrogen