Study On Dredged Sediments Dewatering And Drying By Two-step Chemical Dosing Combined With Negative Pressure And Air Transmission

Recent years, rivers, lakes, reservoirs are badly polluted in our country, which results in phenomenon of eutrophication frequently, it is a Serious threaten to the residents about safe drinking water. In order to improve water quality, we have to not only control the pollution not to go into the river, but also eliminate the impact of internal pollution sources. Sediment is the main accumulation place for the pollution, a lot of heavy metals, refractory organics, nitrogen and phosphorus material deposit here. Environmental dredging is the most direct way to remove the internal pollution sources from the water. So far, environmental dredging project has not started a nationwide large-scale .The key factor is that dredged sediment is unable to rapid dehydration and reduction, The mud occupies sediment yard for a long time, which result in large quantity of land not restoring the original function,if precipitation climatology comes, it is possible that secondary pollution may happen in dredged sediment yard.This research included laboratory studies and field trials. Simulating dredging mud to the separation of mud and water in the lab, chosing a proper kind of dehydration, dehydration agent, improver types, determining the appropriate dosage, which can improve the performance of mud dewatering, Improve the speed of mud and water separation, reduce seepage resistance, and improve water quality with the way of two-step chemical dosing; which can also enhance the overall permeability of the sediment yard and be helpful to the water discharging after the dewatering sediment in the drying Stage. Propose the parameters which is proper to speed up dewatering speed of Taihu dredged sediment with the detection of moisture content, bulk density, capacity in the different depth of the yard. Setting the enhanced dewatering facilities in the late stage of drying, with the way of setting The bottom of the drainage system, negative pressure vertical, the bottom of the ventilation, negative pressure combined the bottom of the ventilation,which can enhance the pressure of drainage in the yard, increase air circulation, discharge the dredged mud water yimely. In the condition of testing in dredged sediment yard of taihu, further research for acceleration of the separation of the mud and water and the improvement of the bearing capacity of soil layers with dehydration, dehydration agent; In the demonstration project, chose a method of dosing dehydration, dehydration agent combine with negative vertical, which can verify the effect of the bearing capacity of dredged sediment from this technology, and provide theoretical support for the practical engineering applications of this technology.The results of the experiment in the lab and simulation yard show that in the dosage of Fe-dehydrating 100mg/L, dehydration agent 10mg/L can improve the speed of mud and water separation, as well as keep water quality to meet national emission standards; in the drying stage,because of the improver types, The overall permeability of the simulation yard is improved, average capacity of the yard that took slag as a modifier enhanced 73.4%; the method of negative pressure vertical, the bottom of the ventilation, negative pressure combined the bottom of the ventilation can respectively enhance the capacity of the sediment for 42.7%,38.0%,59.1%.The data of demonstration project yard of dredged sediment in taihu show that dosing Fe-dehydrating and dehydrating agent, combined with negative vertical can be able to achieve good effect on dredged sediment dewatering and drying, and the sediment yard achieved the desired goal of capacity.