Pilot-scale Study On Tertiary Treatment Of Emulsion Wastewater From Cold Rolling

Because of the poor biodegradability and high pollutant concentration of emulsion wastewater from cold rolling mill, emulsion wastewater is one of the refractory wastewater produced in iron and steel plants. As the normal treatment methods have unsatisfied effect on treating emulsion wastewater, this paper proposes a combined process of hydrolysis-acidification/ activated sludge process/constructed wetland to treat emulsion wastewater. Lab research and pilot test have been done to study this advanced treatment, and the conclusions are as following:(1) From the lab research, the feasibility and treatment effect of the combined process of hydrolysis-acidification/activated sludge process on treating emulsion wastewater was investigated .The results show the combined process has nice feasibility and treatment effect on treating emulsion wastewater.(2) From the pilot test of the advanced treatment by hydrolysis-acidification/activated sludge process/constructed wetland, the appropriate operating condition of this advanced treatment are concluded: influent pH is7~9, temperature is 18～30℃, volume loading of hydrolysis-acidification reactor, activated sludge reactor is 1.07～2.04kgCOD/(m~3·d), 0.84～1.97kgCOD/(m~3·d), the DO concentration of activated sludge process is near 3 mg/L, and the COD concentration of influent for constructed wetland is below 400 mg/L.. Under this operating condition, the combined process has good treatment effect, the effluent COD concentration is reduced from 953～2251mg/L to 31～145mg/L, as the removal rates of COD is 91.3%～98.2%, and the effluent SS concentration is reduced from 651～1128 mg/L to 29～54mg/L, as the removal rates of SS is 92.3%～96.1%.