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在聚合氯化铝(PACl)投加量为4 mg/L条件下,通过调节原水的初始p H值,考察p H条件对混凝超滤组合工艺的净水性能及膜污染的影响。结果表明:当p H为7.5时,组合工艺对COD_(Mn)、UV_(254)、DOC的去除率分别为40.2%、35.4%和36.1%;当p H降至4.5时,对应的去除率分别增加至52.9%、52.1%和42.0%。酸性条件下,膜池内絮体的分形维数大,絮体结构密实,膜污染速率较快;当p H等于4.5时,絮体分形维数为1.75±0.15,尺寸大于500μm的絮体数占总絮体数的9%。中性及偏碱性条件下,絮体分形维数小,絮体结构松散多枝,膜污染速率缓慢;当p H等于7.5时,絮体分形维数为1.37±0.05,尺寸大于500μm的絮体占65%。针对该水库的水质状况,控制原水p H为7.5有利于混凝超滤膜组合装置的运行。
The effect of pH on the water purification performance and membrane fouling of the coagulation and UF process was investigated by adjusting the initial p H value of raw water under the condition of PAC1 dosage of 4 mg / L. The results showed that the removal rates of COD Mn and UV 254 and DOC were 40.2%, 35.4% and 36.1% respectively when p H was 7.5. When p H was reduced to 4.5, the removal rate of COD, Increased to 52.9%, 52.1% and 42.0% respectively. Under acidic conditions, the fractal dimension of the flocs in the membrane pool is large, the floc structure is compact, and the membrane fouling rate is relatively fast. When p H is equal to 4.5, the fractal dimension of the flocs is 1.75 ± 0.15 and the number of flocs whose size is larger than 500 μm 9% of the total number of flocs. Under the neutral and alkaline conditions, the fractal dimension of flocs was small, the flocs were loose and branched, and the rate of membrane fouling was slow. When p H was equal to 7.5, the floc fractal dimension was 1.37 ± 0.05 and the floc size was larger than 500μm Body accounted for 65%. In view of the water quality of the reservoir, controlling the raw water p H to be 7.5 facilitates the operation of the coagulation ultrafiltration membrane combination device.