煤化工含盐废水近零排放的预处理研究

Study on Near-zero Discharge Pretreatment of Salt-containing Wastewater in Coal Chemical Industry

研究了化学沉淀法对不同煤化工企业含盐废水的除硬预处理效果。研究发现,900 mg/L的NaOH可将废水(一)的出水总硬和钙硬分别控制到100mg/L和25mg/L,去除率分别为90.9%和96.4%;500mg/L的NaOH或者500 mg/L的Ca(OH)2都能够将废水(二)的出水总硬和钙硬分别控制在150 mg/L和60 mg/L以下,去除率分别高于80.0%和88.0%;但是,在废水(三)的研究中发现,在碱度足够的情况下,1 400 mg/L以下的NaOH或700 mg/L以下的Ca(OH)2都无法起到软化的效果,只有在pH大于12的情况下,外加700mg/L的Ca(OH)2和600 mg/L的Na2CO3或者外加200 mg/L的MgCl2·6H2O和400 mg/L的Ca(OH)2,可以将出水总硬维持在150mg/L以下。

The effect of hardness removal pretreatment for salt-containing wastewater from different coal chemical plants was studied. The results showed that, the total hardness and calcium hardness of the effluent were respectively 100 mg/L and 25 mg/L by adding 900 mg/L NaOH to No.1 wastewater, and the removal efficiencies were 90.9% and 96.4%, respectively. The total hardness and calcium hardness of the effluent were respectively maintained below 150 mg/L and 60 mg/L by adding either 500 mg/L NaOH or 500 mg/L Ca(OH)2 to No.2 wastewater, and the removal efficiencies were above 80.0% and 88.0%, respectively. However, even if the alkalinity was sufficient, NaOH below 1 400 mg/L or Ca(OH)2 below 7 00 mg/L could not remove the hardness of No.3 wastewater. Only when the pH was greater than 12, the total hardness of effluent was lower than 150 mg/L by adding 700 mg/L Ca(OH)2 and 600 mg/L Na2 CO3, or adding 200 mg/L MgCl2·6 H2 O and 400 mg/L Ca(OH)2 to No.3 wastewater.