Effect of vacuum degree and aeration rate on sludge dewatering behavior with the aeration-vacuum method |
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| Authors: | Yu-feng Gao and Yuan Zhou |
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| Institution: | (1) Department of Mechanical and Power Engineering, Nanjing University of Technology, 210009 Nanjing, China |
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| Abstract: | Due to large-scale dredging operations, a large amount of sludge is inevitably produced. Large areas of land are occupied
when the dredged sludge is discarded in the disposal site as waste material. The sludge dewatering with aeration-vacuum (SDAV)
method is suit for treating the sludge with high water content and high clay content in the disposal site. The water in the
sludge can be discharged out. The volume of the sludge can be reduced quickly, and the recycling of the land can be accelerated
by this method. Most importantly, this technique is an efficient way to deal with clogging problems when pumping water from
high water content, high clay content dredged sludge. Vacuum degree range tests, the aeration rate range tests, and the influencing
factors of sludge dewatering behavior tests were conducted with a self-developed SDAV model test device. Sludge samples were
taken from the South-to-North Water Diversion East Line Project in Huai’an White-Horse Lake disposal site, Jiangsu Province,
China. The optimal range of vacuum degree and aeration rate were obtained through the test results, and the mechanisms for
how the two factors work and how they affect the sludge dewatering behavior were analyzed. The suitable vacuum degree range
in SDAV is below 50 kPa, and the suitable aeration rate is about 1.0 m3/h. The low-vacuum degree contributes to reduce the adsorption effect of micro-channels on soil particles in filter material
and to maintain the arch structures. Aeration has the effects of expansion, disturbance, changing Reynolds number, and dynamic
sieve separating. The pump quantity of water per meter of filter tube (Δm) has different change rules as the vacuum degree changes under different aeration rates. The reason is that the formed arch
structures’ conformation and permeability differ greatly under different combined-conditions of vacuum degree and aeration
rate. The optimal combined-condition for dewatering the sludge is 35 kPa with 1.0 m3/h. |
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