Abstract
In the process of large-scale urban construction, large amounts of waste slurry are produced. The slurry has a high water content and is difficult to precipitate naturally, resulting in low treatment efficiency. To improve the treatment efficiency of slurry, a variety of inorganic and organic polymer flocculants were used to carry out flocculation settlement tests on the slurry. The changes in the slurry properties and the filtration dewatering effect after flocculation were tested. The results show that the addition of flocculant makes the slurry particles form aggregates, which leads to rapid precipitation of the slurry. The use of an inorganic flocculant significantly reduced the zeta potential of the slurry. Organic polymer flocculant, however, had little effect on the slurry potential, but did cause the slurry to produce larger size aggregates, resulting in a better flocculation effect than inorganic flocculant. Inorganic flocculants and organic flocculants can improve the pressure filtration dewatering performance of slurry. CPAM12 (cationic polyacrylamide, with a relative molecular weight of 12 million Daltons) had the best overall effect. The formation of aggregates after flocculation and the change in the nonuniformity coefficient (Cu) were the main cause of improvement of pressure filtration dewatering performance of the slurry. When Cu decreases from 11.85 to 8.75, the time required for pressure filtration stabilization is shortened by 70%. The nonuniformity coefficient of flocculated slurry can be used to evaluate flocculants, determine the optimal dosage, and predict the dewatering effect.
Highlights
Slurry is widely used in large-scale infrastructure construction in China because of its excellent wall protection and slag carrying characteristics, in addition to other advantages, such as its low cost and ready availability [1, 2]
Large amounts of waste slurry are unavoidably produced in the construction process. e slurry has a high water content, a very large volume, and a need to occupy a large amount of land for settlement treatment
Waste slurry stored in the Nanjing Comprehensive Disposal Center was used in this investigation. e basic physical properties of the slurry were determined according to the Standard of the Geotechnical Test Method (GB/T 50123-1999). e water content of the slurry was as high as 900%. e particle size distribution curve of the slurry was measured using a laser particle size analyzer (Malvern Mastersizer 2000)
Summary
Slurry is widely used in large-scale infrastructure construction in China because of its excellent wall protection and slag carrying characteristics, in addition to other advantages, such as its low cost and ready availability [1, 2]. E slurry has a high water content, a very large volume, and a need to occupy a large amount of land for settlement treatment. Geotextile bag method [4,5,6] and vacuum filtration [7, 8] are commonly used for separation of slurry and water. In vacuum suction filtration dewatering, a vacuum suction filter tube is installed in the slurry to accelerate the dewatering through negative pressure. To address the problem of geotextile blockages, engineers and Advances in Civil Engineering technicians periodically apply pressure and suction to the bottom slurry filter tube, which reduces the blockage, but does not significantly increase the drainage efficiency [7, 13]. To improve the dewatering efficiency, flocculants, such as polyacrylamide [16] and polyaluminium chloride [17], are added to pretreat the sludge, which can reduce the loss of fine particles [18] and accelerate the dewatering time [19,20,21,22]
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