絮凝剂对电渗处理河道疏浚淤泥的影响

河道疏浚淤泥含水量高,流动性大,运输和处置较难,且易对环境造成二次污染,需要对其进行脱水处理,而且脱水后的疏浚淤泥可以作为道路路基的主要填充材料,提高资源利用率。因此为了更好地提高疏浚淤泥的脱水效果,利用自制的电渗试验装置,对疏浚淤泥进行了无机絮凝剂电渗排水试验。先将疏浚淤泥进行初步脱水,使其含水量保持在75%左右,作为待用土样;再根据无机絮凝剂FeCl3和Al2(SO4)3的不同掺入比配制溶液,与待用土样充分混合,静置24h后装填土样启动电渗试验。电渗过程中监测排水量和电流强度,试验后测量土体的含水量和pH。试验结果表明:絮凝剂对疏浚淤泥电渗排水效果有着明显的影响,并存在最佳掺入比使得排水效果最好,其中FeCl3与Al2(SO4)3的最佳掺入比均为0.1%;当掺入比高于最佳值时,将会降低电渗排水效果;与纯电渗试验相比,随着絮凝剂掺入比的增大,电流会增大,电渗能耗也随之增大;试验后,土体的含水量有明显降低但分布不均,主要表现在FeCl3作用时阳极区域高于阴极区域,而对照组和Al2(SO4)3作用时阴极区域优于阳极区域;由于试验过程中絮凝剂的水解以及电化学反应,在试验前后土体均保持酸性,且随着絮凝剂掺入比的增加,土体pH会随之降低,电导率会随之增加。

Effect of Flocculants on Electro-osmotic Treatment of River Dredged Sludge

River-dredged sludge is characterized by a high water content and great fluidity. Its transport and disposal are difficult, and this may easily lead to secondary pollution of the environment. It therefore appears necessary to dewater the sludge prior its transport and disposal. Moreover, if properly treated, the sludge could easily be used as the main filling material in road construction, thereby optimizing the utilization of resources. In order to improve the drainage of the dredged sludge, a series of tests were carried out-using a self-made electro-osmotic test device-in which electro-osmosis and the use of inorganic flocculants were combined. Firstly, the dredged sludge was preliminarily drained to reach 75% used as the soil sample. Then, FeCl₃ and Al₂(SO₄)₃ were mixed with the soil in different proportions to promote flocculation. After 24 hours, electro-osmosis was performed, and the amount of water drained and the current intensity were monitored. The results showed a significant influence of the flocculant on the electro-osmotic drainage of the sludge. The optimal mixing ratios of both FeCl₃ and Al₂(SO₄)₃ were found to be 0.1%. Higher-than-optimal ratios were found to reduce the effect of the electro-osmotic drainage. Compared with electro-osmosis in absence of flocculant, the electric current and energy consumption were found to increase with the mixing ratio increasing. After the tests, the water content of the soil was found to have decreased significantly; however, the spatial distribution of such decrease was uneven, as it mainly occurred in the anode region in the case of FeCl₃, and in the cathode region in the case of Al₂(SO₄)₃. Due to the hydrolysis of the flocculant and electrochemical reactions, the soil remained acidic before and after the tests. With the mixing ratio increasing, the pH of the soil decreased, while the conductivity increased.