复配混凝剂去除地下水中溶解性硅酸盐的试验研究

Experimental Investigation into Removal of Soluble Silicate in Groundwater by Using Compound Coagulants

为有效去除水中的溶解性硅酸盐,以某溶解性硅酸盐含量高达50~60mg/L的地下水为对象,开展复配混凝剂去除水中溶解性硅酸盐的试验研究.结果表明:当Ca(OH)_2投加量为450 mg/L时,对水中溶解性硅酸盐和浑浊度的去除率分别为51.16%和74.8%;进一步增加Ca(OH)_2投加量可进一步强化溶解性硅酸盐的去除,但会引起出水pH值的大幅升高;FeCl_3对水中溶解性硅酸盐的去除率低于12.55%,但其对出水浑浊度具有明显的控制优势;MgO对水中溶解性硅酸盐的最优投加量为400 mg/L,此时去除率为14.53%,处理后出水浑浊度较高;FeCl_3复配Ca(OH)_2时,对水中溶解性硅酸盐的去除率超过60%,并且出水浑浊度低于0.65 NTU;FeCl_3复配MgO时,对水中溶解性硅酸盐的去除率可达75%以上;Ca(OH)_2复配MgO时,对水中溶解性硅酸盐的去除率最高达73.76%,较单独使用Ca(OH)_2除硅时(81.41%)有所下降.3种复配方案中,以FeCl_3复配MgO的方案为佳,在此方案下,当Fe^(3+)质量浓度为16.8 mg/L、MgO质量浓度为500 mg/L时,硅的去除率达76.67%,滤后浑浊度为0.83 NTU,同时出水pH值最低,可节省后续调整pH时的酸用量.

In order to effectively remove the soluble silicate in water, by taking the groundwater with a soluble sili- cate content of 50 -60 mg/L as the research objective, coagulation experiments for the soluble silicate removal by using different compound coagulants were performed. The results show that （1） when the dosage of Ca（OH）2 is 450mg/L, the removal of soluble silicate and the turbidity reaches 51.16% and 74. 8%, respectively; （2） with the increase of Ca（OH） z dosage （more than 450 mg/L）, the removal of soluble silicate slightly increases while the pH value of the effluent greatly increases, too; （3） FeC13 has a poor removal on soluble silicate （less than 12. 55% ） but has an advantage in turbidity control; （4） MgO possesses poor efficiency for both soluble silicate removal （less than 14. 53% ） and turbidity control, and the optimal MgO dosage is 400mg/L; （5） the compound of FeC13 and Ca（OH）2 possesses good performance on both soluble silicate removal and turbidity control, more than 60% of soluble silicate is removed and the effluent turbidity is less than 0. 65 NTU; （6） the compound of FeC13 and MgO also possesses good performance on both soluble silicate removal and turbidity control, more than 75 % of solu- ble silicate is removed; （7） the compound of Ca （OH）2 and MgO results in a soluble silicate removal up to 73.76%, which is relatively less than that contributed by Ca（ OH）2 only （81.41%） ; and （8） among the three above-mentioned compound approaches, the compound of FeCl3 and MgO with a Fe3＋ dosage of 16.8 mg/L and a MgO dosage of 500 mg/L is the best because it results in a soluble silicate removal of 76. 67% and an effluent turbidity of 0. 83 NTU, and because it helps to obtain effluent with the lowest pH value, which saves the acid added in the later process.