不同混凝剂处理低温低浊水

针对低温低浊水处理难度大的问题进行了一系列的混凝实验,实验结果表明,随着混凝剂投加量的增加,剩余浊度呈现先降低后升高的趋势,单独使用HPAC时,剩余浊度在投加量为14 mg/L时达到最低(2.39 NTU)。pH值对余铝含量具有重要的影响,3种铝系混凝剂均在pH=7.0时余铝含量达到最低。AlCl3对水中有机物的去除率较其他3种混凝剂低。絮体形成与破碎受搅拌强度的影响很大,当破碎强度增加到50 r/min,使用PACl、HPAC、FeCl3作混凝剂时絮体粒径下降不明显,当破碎强度增加到100 r/min时,絮体粒径有明显的下降。破碎结束后,絮体粒径有所恢复,但是并不能增长到破碎前的粒径。PACl、HPAC以及FeCl3形成的絮体的沉降性较好,上覆水浊度下降较快,经过3 h的沉降后,剩余浊度分别达到1.82、1.44和0.97 NTU。

Treatment of raw water with low turbidity and low temperature using different coagulants

The raw water with low turbidity and temperature was hard to be treated, and the coagulation performances under different conditions were investigated to solve this problem. The results indicated that when the coagulant dosage was 14 mg/L using HPAC, the residual turbidity reached the lowest point (2.39 NTU). When the coagulant dosage was larger than 14 mg/L, the residual turbidity increased due to charge reversal. Solution pH had large effects on the residual Al using three Al-based coagulants, and the residual Al reached the lowest point when the solution pH was adjusted to 7.0. The removal efficiency for organic matter using AlCl3 was smaller than other three coagulants. It was found that floc formation and breakage were affected by stirring rate, and when the stirring rate increased to 50 r/min, floc size decreased slightly using PACl, HPAC, FeCl3 as coagulants. When the stirring rate increased to 100 r/min and above, a significant drop in floc size could be observed. The flocs began to re-grow again when the shear was reduced, but the flocs could not re-grow to the former sizes. The sedimentation of flocs performed better using PACl, HPAC and FeCl3, and the residual turbidity was below 2.0 NTU after three hour sedimentation.