沉淀回流对石灰软化法去除地下水硬度的影响

Influence of sediment recirculation on hardness removal from groundwater by lime softening process

针对地下水硬度去除问题,在传统石灰软化法基础上,通过静态实验对比研究了沉淀回流过程对石灰软化法处理效果的影响。结果表明:在进水硬度385 mg/L,Ca O投加量200 mg/L条件下,经"沉淀回流-石灰软化"处理后,出水滤后总硬度为140 mg/L,比传统石灰软化法低40 mg/L;出水滤前浊度在20 NTU以下,比传统石灰软化法低100 NTU;石灰有效利用率为88%,比传统石灰软化法高25%。这表明通过沉淀回流有效提高了石灰有效利用率,降低了出水浊度。在Ca O投加量200 mg/L,Fe Cl_3投加量3.6 mg/L条件下,通过"沉淀回流-石灰软化/Fe Cl3混凝"处理12 min,静沉30 min后,出水滤后总硬度可维持在140 mg/L左右,浊度低于1 NTU,达到《生活饮用水卫生标准》(GB 5749-2006),加热煮沸后无沉淀和漂浮物产生。

To improve the removal of hardness in groundwater,a modified process,the lime softening coupling sediment recirculation process,was compared with the traditional lime softening process using a static test.The results indicated that the treatment effect of the modified process was better than the traditional process at385 mg / L hardness and at a Ca O content of 200 mg / L in the influent. The filtered hardness in the effluent of the modified process was 140 mg / L,which was approximately 40 mg / L lower than the traditional process. The unfiltered turbidity in the effluent of the modified process was below 20 NTU,which was 100 NTU lower than the traditional process. In addition,the effective utilization of lime was 88% in the modified process,which was about25% higher than in the traditional process. This illustrates that the sediment recirculation process can improve the effective utilization of lime and effluent turbidity. Using the modified process with a further Fe Cl3 coagulation treatment of 12 minutes and precipitation for 30 minutes,then the filtered hardness can be maintained at 140 mg /L with a Ca O content of 200 mg / L and a Fe Cl3 content of 3. 6 mg / L. The filtered turbidity was below 1 NTU.There was no precipitation and floating after the filtered effluent had being boiled,which meets the Drinking Water Sanitary Standard（ GB 5749-2006）.