Improving the Dewatering of Marine Sediment Using a Combination of Geo-Textile and Electrokinetic Treatment

2017 ◽  
Author(s):  
Silja Kostia ◽  
Janika Tuomi ◽  
Martin Romantschuk
Keyword(s):  
Water Column ◽  
Direct Current ◽  
Marine Sediment ◽  
Clay Content ◽  
Water Layer ◽  
Control Treatment ◽  
Dredged Material ◽  
Dredged Sediment ◽  
Electric Treatment ◽  
Electro Osmosis

The purpose of this study was to test whether electro-osmosis can be used to increase the effectiveness of dewatering of dredged sediment being drained in geo- textile tubes. The marine sediment used in the study had a high proportion of clay known to be problematic in geo-tube treatment. The laboratory set-ups were performed using sediment-filled sacks (approximately 5-7 liters / sack) sewn from geo-textile (TenCate Geotube® GT500), and plastic columns (approximately 1.6 liters / column) closed at the bottom with geo-textile, both supplied with electrodes for applying direct current. In the sack set-ups, a seven-hour electric treatment led to the same result as the 72-hour control treatment. The volume of the sediment decreased in column set-ups by 32 % due to electric treatment while only a 14 % decrease was obtained in the controls after 189 hours. The water layer on top of the sediment treated with electro-osmosis decreased by up to one-fifth, as compared to the control columns. We can conclude that electro-osmosis is an effective approach to boost the dewatering of the dredged sediment treated in geo-textile tubes. When draining sediment with a high clay content, electric treatment can prevent the formation of a water column on top of the sediment. This in turn accelerates dewatering of the dredged material.

Characterising the effect of submarine iceberg melting on glacier-adjacent water properties

2021 ◽  
Author(s):  
Ben Davison
Keyword(s):  
Water Column ◽  
Ocean Circulation ◽  
Ice Sheet ◽  
Circulation Model ◽  
Water Layer ◽  
Atlantic Water ◽  
Temperature Gradients ◽  
Vertical Temperature ◽  
Water Properties ◽  
Adjacent Water

<p>Ocean-driven retreat of Greenland’s tidewater glaciers remains a large uncertainty in predictions of sea level rise, partly due to limited constraints on glacier-adjacent water properties. Icebergs are likely important modifiers of fjord water properties, yet their effect is poorly understood. Here, we use a 3-D ocean circulation model coupled to a submarine iceberg melt module to investigate the effect of submarine iceberg melting on glacier-adjacent water properties in a range of idealised settings. Icebergs can modify glacier adjacent water properties in three principle ways: (1) substantial cooling and modest freshening in the upper ~50 m of the water column; (2) warming of Polar Water due to iceberg-induced upwelling of warm Atlantic Water, and; (3) the Atlantic Water layer warms on average when vertical temperature gradients through the Atlantic Water layer are steep (due to vertical mixing of warm water at depth), but cools on average when vertical temperature gradients are shallow. When icebergs extend to-or-below sill depth, they can cause cooling throughout the entire water column. All of these effects are more pronounced in fjords with higher iceberg concentrations and deeper iceberg keel depths. These results characterise the important role of icebergs in modifying ice sheet – ocean interaction and highlight the need to improve representations of fjord processes in ice sheet-scale models.</p>

Influence of thermal effect on vacuum electro-osmosis of Taizhou dredged sediment

2021 ◽  
pp. 1-16
Author(s):  
Yang Shen ◽  
Wencheng Qi ◽  
Wen Shi ◽  
Shaoyu Li ◽  
Junhong Xu
Keyword(s):  
Thermal Effect ◽  
Dredged Sediment ◽  
Electro Osmosis

Influence of Uniform Electric Field in Bioremediation of Oil-Contaminated Soils

2013 ◽  
Vol 777 ◽  
pp. 253-257
Author(s):  
Jin Lan Xu ◽  
Dong Dong Sun ◽  
Ting Lin Huang ◽  
Long Fei Han
Keyword(s):  
Electric Field ◽  
Direct Current ◽  
Contaminated Soil ◽  
Contaminated Soils ◽  
Control Treatment ◽  
Uniform Electric Field ◽  
Direct Current Electric Field ◽  
Inoculation Treatment ◽  
Current Electric Field ◽  
Electric Field Treatment

Electrokinetic remediation is an effective technology to enhance bioremediation of oil-contaminated soil as the transport process of non-polar organic contaminants in soil was promoted under low-power direct current electric fields. In this study three treatments including the application of electric field treatment alone, inoculation treatment alone, and combination of the application of electric field and inoculation treatment were carried out. The results indicated that highest removal efficiency was 83% in couple of the application of electric field and inoculation treatment. TPH concentration decreased from 6000 mg.kg-1 to 2000 mg.kg-1 when a 30 voltage direct current electric field was applied to oil-contaminated soil for 10 min after 4 days. It was observed that dehydrogenase activity had no increase after application direct current electric field. However, the TPH degradation efficiency was 52% higher than the control treatment. GC analysis showed that n-alkanes (C14-C31) were preferentially degraded, and soil remaindered more low quality compounds after the application of electric field treatment applied 52 days. These results indicated that the application of electric field improved degradation of inoculated bacteria through promoting the transport of nutrients, such as nitrogen and phosphorous and electron acceptors.

Dredged Material Quality in Anthropogenically Exploited Catchment Area

2020 ◽  
Vol 838 ◽  
pp. 118-124
Author(s):  
Natalia Junakova ◽  
Eva Šelingova ◽  
Lenka Demkova
Keyword(s):  
Heavy Metals ◽  
Water Quality ◽  
Catchment Area ◽  
Anthropogenic Activity ◽  
Dredged Material ◽  
Mining Activities ◽  
Dredged Sediment ◽  
Limit Values ◽  
Long Time ◽  
Reservoir Watershed

The paper is focused on the research of pollutants in dredged material and water in the watershed of the Sigord reservoir (Eastern Slovakia), which is influenced by anthropogenic activity. The monitored area extends to the cadastral area of ​​Zlatá Baňa, which has been used for a long time and intensively for mining of gold, antimony and mercury. After the end of mining activities (at the beginning of the 20th century) the territory remained devastated by numerous remains of mining activities and no attention has been paid to this area in terms of scientific research. Therefore, the monitoring of dredged sediment and water quality has been carried out. The results show that the limit values ​​of selected heavy metals (such as Sb, As, Hg, Pb, Cu, Zn, Ni, Fe and Al) are exceeded in both sediments and water in the reservoir watershed, as a result of the former mining activities around Sigord.

scholarly journals Community Shift from Phototrophic to Chemotrophic Sulfide Oxidation following Anoxic Holomixis in a Stratified Seawater Lake

2014 ◽  
Vol 81 (1) ◽  
pp. 298-308 ◽  
Author(s):  
Petra Pjevac ◽  
Marino Korlević ◽  
Jasmine S. Berg ◽  
Elvira Bura-Nakić ◽  
Irena Ciglenečki ◽  
...  
Keyword(s):  
Water Column ◽  
Sulfide Oxidation ◽  
Water Layer ◽  
Tight Coupling ◽  
Phototrophic Sulfur Bacteria ◽  
Community Shift ◽  
Sulfur Bacteria ◽  
Microbiological Methods ◽  
Culture Independent ◽  
The Impact

ABSTRACTMost stratified sulfidic holomictic lakes become oxygenated after annual turnover. In contrast, Lake Rogoznica, on the eastern Adriatic coast, has been observed to undergo a period of water column anoxia after water layer mixing and establishment of holomictic conditions. Although Lake Rogoznica's chemistry and hydrography have been studied extensively, it is unclear how the microbial communities typically inhabiting the oxic epilimnion and a sulfidic hypolimnion respond to such a drastic shift in redox conditions. We investigated the impact of anoxic holomixis on microbial diversity and microbially mediated sulfur cycling in Lake Rogoznica with an array of culture-independent microbiological methods. Our data suggest a tight coupling between the lake's chemistry and occurring microorganisms. During stratification, anoxygenic phototrophic sulfur bacteria were dominant at the chemocline and in the hypolimnion. After an anoxic mixing event, the anoxygenic phototrophic sulfur bacteria entirely disappeared, and the homogeneous, anoxic water column was dominated by a bloom of gammaproteobacterial sulfur oxidizers related to the GSO/SUP05 clade. This study is the first report of a community shift from phototrophic to chemotrophic sulfide oxidizers as a response to anoxic holomictic conditions in a seasonally stratified seawater lake.

scholarly journals Past environmental and climatic changes during the last 7200 cal yrs BP in Adamawa Plateau (Northern-Cameroun) based on fossil diatoms and sedimentary <sup>13</sup>C isotopic records from Lake Mbalang

2011 ◽  
Vol 7 (1) ◽  
pp. 305-345 ◽  
Author(s):  
V. F. Nguetsop ◽  
I. Bentaleb ◽  
C. Favier ◽  
C. Martin ◽  
S. Servant-Vildary ◽  
...  
Keyword(s):  
Water Column ◽  
Vegetation Type ◽  
Stable Carbon Isotope ◽  
Water Layer ◽  
Trade Winds ◽  
Vegetation Landscape ◽  
Stable Conditions ◽  
Millennial Time Scale ◽  
Climatic Event ◽  
Isotopic Records

Abstract. Past limnological conditions of Lake Mbalang (7°19´ N, 13°44´ E, alt: 1130 m) and vegetation type were reconstructed from diatoms and sedimentary stable carbon isotope records (δ13C) since 7200 cal yrs BP. The data showed that before 3600 yrs cal BP the water column was preferentially cold and stable except around 5000–5300 cal yrs BP where diatom evidenced mixed upper water layer, δ13C data suggest more forested vegetation in the landscape. These stable conditions can be explained by a strong monsoonal flux and correlatively northern position of the ITCZ that entailed high/low rainfall well distributed over the year to allow the development mountainous forest taxa. The decreasing trend of the monsoonal flux towards mid-Holocene was however affected by several centennial to millennial time scale abrupt weakening at 6700, 5800–6000, 5000–5300, 4500 and 3600 cal yrs BP although their impact on vegetation is not visible probably because rainfall distribution was favourable to forest maintenance or extension. After 3600 cal yrs BP, water column became very mixed as a result of more intense NE trade winds (Harmattan) that led at ~3000 cal yrs BP to the instalment of savana in the vegetation landscape. At that time, rainfall was probably reduced following the southwards shift of the ITCZ and the distribution of yearly rainfall was no more favourable to forest development. Thus a strong seasonality with a well marked dry season was established, conditions that maintained the savana vegetation till today. Diatom data suggest the lake did not dried during the last 7200 cal yrs BP, however, a low lake level observed at 2400–2100 cal yrs BP is contemporaneous to a climatic event evidenced in several areas of tropical Africa and could correspond to the southernmost position of the ITCZ. Other low lake levels are observed at 1800 and 1400 cal yrs BP, after which lake rose to its present level.

scholarly journals Modelling the effect of submarine iceberg melting on glacier-adjacent water properties

2021 ◽  
Author(s):  
Benjamin Joseph Davison ◽  
Tom Cowton ◽  
Andrew Sole ◽  
Finlo Cottier ◽  
Pete Nienow
Keyword(s):  
Water Column ◽  
Ocean Circulation ◽  
Ice Sheet ◽  
Water Layer ◽  
Atlantic Water ◽  
Temperature Gradients ◽  
Vertical Temperature ◽  
Water Properties ◽  
Adjacent Water ◽  
Polar Water

Abstract. The rate of ocean-driven retreat of Greenland’s tidewater glaciers remains highly uncertain in predictions of future sea level rise, in part due to poorly constrained glacier-adjacent water properties. Icebergs and their meltwater contributions are likely important modifiers of fjord water properties, yet their effect is poorly understood. Here, we use a 3-D ocean circulation model, coupled to a submarine iceberg melt module, to investigate the effect of submarine iceberg melting on glacier-adjacent water properties in a range of idealised settings. Submarine iceberg melting can modify glacier-adjacent water properties in three principle ways: (1) substantial cooling and modest freshening in the upper ~50 m of the water column; (2) warming of Polar Water at intermediate depths due to iceberg melt-induced upwelling of warm Atlantic Water, and; (3) warming of the deeper Atlantic Water layer when vertical temperature gradients through this layer are steep (due to vertical mixing of warm water at depth), but cooling of the Atlantic Water layer when vertical temperature gradients are shallow. The overall effect of iceberg melt is to make glacier-adjacent water properties more uniform with depth. When icebergs extend to, or below, the depth of a sill at the fjord mouth, they can cause cooling throughout the entire water column. All of these effects are more pronounced in fjords with higher iceberg concentrations and deeper iceberg keel depths. These iceberg melt-induced changes to glacier-adjacent water properties will reduce rates of glacier submarine melting near the surface, but increase them in the Polar Water layer, and cause typically modest impacts in the Atlantic Water layer. These results characterise the important role of submarine iceberg melting in modifying ice sheet-ocean interaction, and highlight the need to improve representations of fjord processes in ice sheet-scale models.

scholarly journals Vacuum filter and direct current electro-osmosis dewatering of fine coal slurry

2009 ◽  
Vol 1 (1) ◽  
pp. 685-693 ◽  
Author(s):  
Dong Xian-shu ◽  
Hu Xiao-jie ◽  
Yao Su-ling ◽  
Ren Wei-peng ◽  
Wang Zhi-zhong
Keyword(s):  
Direct Current ◽  
Coal Slurry ◽  
Vacuum Filter ◽  
Fine Coal ◽  
Electro Osmosis
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