Experimental Study On Adcanced Treatment For Biologically Treated Coking Wastewater

The coking wastewater treated by biochemical treatment process was named as biologically treated coking wastewater(BTCW). Its values of CODCr, NH₃-N and chroma in the wastewater could not come up to the national discharge standard, and it presented yellowish-brown with slight pungent smell and poor biochemical purification ability. This thesis adopted activated carbon adsorption, Fenton oxidation, air stripping and combined processes of Fenton oxidation-activated carbon adsorption and of Fenton oxidation-air striping to treat this wastewater. Removal efficiency of target pollutants and treatment cost of these kinds of treatment process were investigated. Finally the best process route for treating BTCW was obtained.The operation conditions, such as pH, activated carbon powder dose, reaction time and temperature influencing the removal rate of target pollutants, were researched respectively. When the values of CODCr, NH₃-N and chroma were 150²00 mg/L, 45⁶0 mg/L and 20⁴0 respectively, under the optimum adsorption conditions, the removal rate of CODCr, NH₃-N and chroma were 53.1%, 30.4% and 92.3% respectively.The main factors, such as pH, H2O2 dose, FeSO4 dose, reaction time and temperature, influencing the removal rate of Fenton oxidation were studied respectively. Under the optimum reaction conditions, the removal rate of CODCr, NH₃-N and chroma were 65.2%, 30.4% and 85.3% respectively.The optimum reaction condition for the combined process of Fenton oxidation-activated carbon adsorption was further discussed. Under the optimum reaction conditions, the removal rate of CODCr, NH₃-N and chroma were 70.7%, 35% and 97.1% respectively.The operation parameters of air stripping, such as pH, reaction time and temperature, influencing the removal rate of NH₃-N were investigated respectively. Under the optimum operation conditions, the removal rate of NH₃-N was 62.2% and the concentration of NH₃-N was below the national discharge standard.The treatment effect of BTCW by the combined process of Fenton oxidation-air stripping was also researched. After treatment, the values of CODCr, NH₃-N and chroma were 64 mg/L, 13 mg/L and 5 respectively, and achieved the first grade of the national discharge standard.In view of the factors such as simple techniques, small occupation area, low operating cost and easy control and so on, under the premise of meeting the discharge standard, the combined process of Fenton oxidation and air striping was selected for treating BTCW. The overall running cost was about 6 yuan/t.