Treatment Of Ni-EDTA Containing Wastewater By UV/H₂O₂ Process

Ni-EDTA containing wastewater is one of the typ ical metal complexed wastewater discharged by electroless plating industry.The disposal of Ni-EDTA containing wastewater mainly follows the principle of oxidation followed by alkaline precipitation.Fenton process is widely employed in the practical engineering project.However,it still suffered from the excessive metal sludge generated in the process and expensive cost.UV/H2O2 process,which is characterized by strong oxidation power and little sludge,is generally considered to be promising in solving the problems mentioned above.In this paper,the treatment performance of Ni-EDTA wastewater by a UV/H2O2 process was demonstrated in the lab scale.For the Ni-EDTA wastewater with higher pollutant concentration,the process of ozone enhancement was also s ystematically studied.The disposal strategy of real Ni-EDTA containing wastewater was also proposed.To start with,the working parameters of UV/H 2O2 process was optimized for Ni-EDTA stimulated wastewater.The results showed that,when Ni-EDTA wastewater,with the initial concentration at 50 mg/L,was treated for 60 min by a UV/H2O2 process,where the power of UV light is 100 W,initial p H is 3.0 and 30%H2O2 dosage is 2.0 m L/L,the concentration of nickel in the effluent is less than 0.1 mg/L,and meets the “Electroplating Pollutant Discharge Standard"(GB21900-2008).Moreover,the sludge production of UV/H2O2 process is only 1.64 kg/m3,which is 80 percentage less than that of the Fenton process.The treatment cost of UV/H2O2 process is 12.56 yuan/m3,much less than that of Fenton process.Secondly,using stimulated Ni-EDTA wastewater with the initail concentration of 1000 mg/L,the treatment performance by UV/H2O2 and ozone enhancement process was systematically investigated.The results showed after the treatment of UV/H2O2 and ozone enhancement process for 120 min,where the power of UV light is 750 W,initial p H is 3.0,50%H2O2 dosage is 15 m L/L and ozone dosage is 2000 mg/L,the nickel concentration in the effluent is less than 50 mg/L,which is nearly equal to that of the Ni-EDTA wastewater with low concentration.Finally,the disposal strategy of real Ni-EDTA wastewater was proposed.After the treatment of high concentration Ni-EDTA wastewater by UV/H2O2 and ozone enhancement process for 180 min,the nickel concentration in the effluent was less than 50 mg/L,and then would be mixed with low concentration wastewater.The UV/H2O2 process would be employed to treat the mixed wastewater for 75 min and adjusted the effluent p H at 11±0.3 using Ca O,the nickel and total phosphorus concentration in the effluent would meet the discharge standard.After that,the mixed wastewater was biodegraded for 12 hours and the effluent total nitrogen,ammonia and COD would meet the discharge standard.