Pilot-scale study on treatment of nitrate nitrogen in electroplating wastewater by denitrifying granular sludge
Denitrifying granular sludge cultivated by flocculent sludge was used to treat nitrate nitrogen in actual electroplating wastewater,through gradually increasing denitrifying load and cultivating denitrifying granular sludge,the denitrification effect and the property changes of the denitrifying granular sludge were evaluated,and then,the practical application potential of the said sludge in the denitrification treatment of electroplating wastewater was explored.The experimental results showed that,under the condition that the mass concentrations of COD,NO3--N and NO2--N were 400～520,50～100 and 0.2～2.3 mg/L respectively,the pH value was 6.5～7.2,the mass concentration of dissolved oxygen in the reactor was lower than 0.2 mg/L,and the ascending velocity was 2～6 m/h,when the nitrogen removal load was increased to 3.4 kg[NO3--N]/(m3·d),the removal rate of nitrate nitrogen was higher than 95％,and the average value of Δρ(COD)/Δρ(NO3--N)was only 3.85∶1.The stable operation time of the system was up to 30 days,and the nitrate nitrogen concentration in the treated water was less than 5 mg/L.In addition,the contents of Ca,Cu,Ni and Fe in the denitrifying granular sludge increased significantly after the treatment of electroplating wastewater.At the same time,the VSS/SS value of the mature granular sludge was significantly reduced,and the particle size of granular sludge mainly concentrated in the range of 1.0～2.8 mm.Denitrifying granular sludge shows characteristics of high denitrifying load,low nitrate nitrogen concentration,low Δρ(COD)/Δρ(NO3--N)value and stable denitrification effect in treatment of electroplating wastewater,which can significantly improve the efficiency of NO3--NN removal from electroplating wastewater.
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