Papers by Keyword: Dewatering

Abstract: The active mining of the Mátraszentimre (Hungary) underground base-metal mine was halted in 1985. So far enormous research and efforts have been taken for the final closure of the mine. The technology of fly-ash based hydraulic backfilling was selected. About 95 000 tons of fly-ash backfilling is necessary to close the mine. A suitable technology have been developed, installed and put into operation. So far about 14 400 tons fly ash have been backfilled.This paper summarizes the main results and elements of the process engineering part of this work. The pozzolanic activity of fly-ash from the Mátra Power Station was examined in order to develop a new hydraulic binder with the addition of lime. As results of the different examinations it had been decided that the backfilling material should be lignite fly-ash from the tailings pond of the nearby Mátra Power Plant. The fly-ash hydraulic transport system of the Mátra Power Station was designed by our institute back in 1998. This system is still operating and now serving the material for backfilling. The knowledge of designing the power station pipeline system was utilized at designing the hydraulic backfilling system. The main technical parameters of the solid – liquid pipe flow were designed based on the Tarján – Faitli: coarse mixture flow in fine suspension flow model then and now as well. The design covered many other aspects of the task such as material characterization and mixing, settling behavior of the backfill, dewatering and mechanical properties of the backfill, water permeability and so on...

Abstract: With Chinese continuous improvement of the urbanization and industrialization level, water pollution has becoming more and more serious, and the by-product —sludge has caught the focus of public attention. The total amount of sewage sludge produced in Beijing in 2010 is about 3,700t/d (wet base), 2,500t/d of which is from the urban area and 1,200t/d is from country side. Such a large amount of sludge with abundant water brought great difficulties to the subsequent processing. However, the cost of sludge treatment amounts to almost half of the sewage plant running cost while the consumption of drug covered more than half of the sludge treatment expenditure. Another aspect is that the water content of the dewatered sewage sludge is not stable, because of the variation of inlet amount and quality. Without knowing the relationship between the characteristics of sewage sludge and conditioning reagent, the operator just try to add more reagent, which in the end increase the cost of sludge treatment. Meanwhile, cationic polyacrylamide (C-PAM) is currently the most widely used sludge conditioning reagent. This research is to find out the relationship between the characteristics of sewage sludge and adding dosage of CPAM, which can be the first step to discuss how to adjust the conditioning reagent according to sewage sludge with different characteristics.Polyacrylamide (PAM) of different cationic (15%,35%,45%,60%), molecular weight (8 million, 10million, 12million) and dosage (2‰,3‰,4‰,5‰,6‰) are under testing in the experiment considering the index of capillary suction time (CST).Experimental material is the sludge from digestion tank in one of Beijing sewage plants. According to the experiment, it was found that the 8million-10million molecular weight, 4‰-6‰ adding dosage perform the best.

Abstract: The extracellular polymeric substances (EPS) are susceptible to microbial degradation, highly efficient, non-toxic, no secondary pollution, etc, and are considered to be the most promising biological polymers. At present, EPS have been considered by many researchers as a potential flocculent for their applications in various water, wastewater and sludge treatment process. They are insoluble organic matter adhesive to the cell surface, and they mainly derive from microbial metabolism and cell autolysis, which are mainly composed of polysaccharides, proteins, extracellular DNA. Based on illustrating content, function and structure composition of EPS, the paper reviews the action mechanism of EPS on flocculation and settlement of activated sludge and those flocculation, settlement and dewatering properties in the sewage treatment system. In addition, it summarizes the development trend and application prospect of EPS, which would provide valuable references for further research and application of EPS.

Abstract: With the environment problems more and more emerged the matters caused by dewatering are set out to be probed and the rule that the ground settlement around a dewatering well presents a funnel shape , is acquainted usually. But in the case of special geology and hydrology due to this paper a new ground settlement pattern presents according to the buildings failure status and the subsequently monitoring results analysis. Namely the ground settlement along the transverse direction to the underground runoff presents V-shape flute profile in the area around the predominant underground runoff. The results also demonstrate that: 1 The foundation type in main building is as same as in the podium building .The main building kept stable while the podium building presented large settlement and inclination and went to failure in final during the construction of the pit. 2 The difference of affecting degree due to dewatering in the environment around the pit is variable and the main affecting zone appears locality and directivity. According to the investigation the most possible main resource of dewatering originates from the river system around to the pit pass by the podium building. 3 Combining the construction process of the pit and the time points of deformation in the building , associability is confirmed between buildings deformation and dewatering on the pit on the ground of excluding the other artificial factors around the building.

Abstract: Sewage sludge proves to be difficult to dewater due to its composition and biological nature, and it is unsuitable for disposal with high moisture content. In the present work, sewage sludge is dewatered by the thermal compression, which shows unique separation advantages of various materials, and the effects of applied temperature and pressure on the dewatering performance are investigated. The filtrate SCOD reveals that higher temperature benefits the disruption of sludge flocs, resulting in the release of organic content. According to the accumulative filtrate volume, higher temperature and pressure facilitate the dewatering process, obtaining sludge cake with lower moisture content.

Abstract: Microwave drying characteristics of Xilingol lignite were investigated with microwave drying testing equipment at 2450 MHz. Effects of particle size has been carefully studied. Mass losses of the samples were measured during drying. Drying rates were then obtained through the trends of drying curves. Results show the 0.6-1mm sample has low drying rate. Changing the stacking superficial area and size composition has been tested and resulted that only mixed with fine coal can increase the drying rate of 0.6-1mm. But classification experiment shows sieving 0-6mm sample into fine sample and coarse sample cannot advance the drying rate obviously.

Abstract: In recent years accidents in deep excavation have frequently occurred, which brought a heavy loss in lives and property. The past cases of accident indicated water was a key one of accident resource. In this paper, water-control and its influencing factors in deep excavation were researched from sealing, draining and dewatering, and then fault tree of waterproofing was set up. The probability of waterproofing failure was calculated using Fuzzy Mathematics, and importance degrees for basic events were analyzed to find the events which would lead to the occurrence of the top event. The analysis can be used to make safety measures.

Abstract: Abstract: During excavation in deep foundation pit, the deformation of soil and earth surface caused by engineering dewatering is an important factor to affect engineering safety. In this paper, according to the data provided by the detailed survey report of route 1 subway in Shenyang, the subsidence laws of the ground and around buildings caused by the dewatering of route 1 subwaywere analyzed by using Coupling System of Flow & Solid in FLAC-3D which is based on poroelasticity theory and consolidation theory, and preliminary results were obtained.

Abstract: Foundation excavations support and dewatering method have been full-grown after years of development. However, during the excavation of polluted soil in special sites, dewatering scheme should not simply based on the experience and form of excavation but should be combined with the characteristics of contaminated sites so as to choose a reasonable dewatering method which meets the construction requirement of soil excavation on one hand and prevents the spread of contamination on the other hand. This paper design and analysis the dewatering of soil excavation in contaminated sites combined with specific project example.

Abstract: The studies application of deep foundation pit decompression technology focusing on special engineering geological and hydrogeological conditions. Taking foundation pit dewatering of certain rail transit station as an example, designs deep foundation pit decompression precipitation technology scheme with hydrogeological parameters obtained through pumping test, and assesses and monitors its impacts on surrounding environment according to measured data on project site, which has achieved good results in practical engineering application and provides foundation for construction of rail transit lines.