Dredged Marine Sediments Research Articles

Field Study of a Sustainable Land Reclamation Approach Using Dredged Marine Sediment Improved by Horizontal Drains under Vacuum Preloading

Field Study of a Sustainable Land Reclamation Approach Using Dredged Marine Sediment Improved by Horizontal Drains under Vacuum Preloading

Recycling single use surgical face mask waste for reinforcing cement-treated/untreated dredged marine sediments: Strength, deformation and micro-mechanisms analysis

To prevent the transmission of airborne infectious diseases (SARS, H1N1, COVID-19, and influenza), the use of disposable surgical face masks has increased dramatically in the past few years. To mitigate the environmental consequences associated with mask waste, implementing circular economy strategies with the reuse of mask waste is a sustainable method. This study explores an innovative way to reuse mask fiber (MF) with dredged sediment waste together as road construction materials. First, the MF was introduced into cement-treated/untreated dredged marine sediment mixtures with different content and lengths. Then, a variety of laboratory tests were carried out to explore the basic physical and chemical characterization of raw materials and the development of mechanical properties of mixtures. In addition, the intrinsic mechanism of MF inclusion on cement-treated sediments was analyzed by scanning electron microscope (SEM) test. The results show that the inclusion of MF significantly improves the unconfined compression strength (UCS) and splitting tensile strength (STS) of both treated and untreated specimens. The highest UCS and STS values are at the condition with an MF content of 0.25%, a length of MF of 2 cm, and a curing time of 28 days. The combined strength increase caused by cement-MF together inclusion is much greater than the strength increase caused by either of them separately. It was also found that the elastic modulus (E50) decreased with the inclusion of MF. Furthermore, the addition of MF changes the brittle behavior of the specimens, which also improves the ductility and residual strength of the specimens. The SEM analysis demonstrates the microstructure of MF and MF-reinforced specimens. The creation of a stable and interconnected microstructure is largely attributed to the bridging impact of MF and the binding effect of hydration products, which significantly improves the mechanical behavior of specimens. The MF-reinforced cement-treated sediment could be an innovative, environmentally friendly, and economical material for road construction.

Investigation of the transportation characteristics of marine dredged-sediment in pipelines based on experimental pipeline models

Marine dredged-sediment(DS) is often transported through pipelines, where factors such as the solid volume concentration and transport rate can significantly influence the efficiency of the process. Inadequate selection of transport rates for a given solid volume concentration can lead to substantial energy losses. The pressure loss Δ P L or pressure loss gradient Δ P L / L are critical parameters for assessing energy loss during pipeline transport. In this study, large-scale indoor experiments on DS pipeline transport were conducted to investigate the effects of the cross-sectional mean flow velocity Vavg and solid concentration ϕ on the transport characteristics of DS. The results show that at higher solid volume concentrations, Δ P L / L increases rapidly with the square of Vavg and then plateaus, followed by a linear growth phase. In addition, a linear relationship is observed between lgf and lgVavg when the flow velocity is below critical velocity (Vavg ) critical ; above (Vavg ) critical , the friction factor f stabilizes at f 0 . Formulas for calculating (Vavg ) critical , f 0 and ϕ were developed. Additionally, a method for determining the optimal transport velocity of DS at varying volume concentrations was established, enabling the identification of the most efficient flow velocity for DS pipeline transportation across different concentrations. HIGHLIGHTS Pipeline model tests were conducted on marine dredged sediments. A formula for predicting pressure loss on the basis of solid concentration was derived. The impact of the solid concentration on the Darcy friction factor was determined. A method for determining the optimal transport velocity was established.

Use of shells for the mechanical stabilisation of sediments: a valuable geomechanical perspective?

The present study contributes to developing a novel eco-friendly solution for the mechanical stabilisation of dredged marine sediments by using mussel shells – another high-impact waste of marine origin – in the partial replacement of cements. What are the underlying chemo-mechanical interactions affecting the evolution of such mixtures? Can mussel shells replace cement without compromising useful geomechanical and geochemical properties of the stabilised sediments? Can such mixtures still be modelled as soils when it comes to their geotechnical design and analysis? The paper answers these questions by assessing the mechanical performance of mixtures formed by sediments stabilised with three types of cement and a mussel shell powder and comparing them with those of the same sediments treated with cement only. Multiple beneficial effects of the use of mussel shell powder, as a peculiar source of calcium carbonate from its biogenic origin, have been demonstrated: it acts as a void filler; enhances the electrolytic exchanges between sediment and cement, and increases the contact area between the mineral particles promoting the chemical hydration reactions. As a result, for fixed replacement ratios, the original mixtures still exhibit soil-like behaviour consistent with traditional geomechanics and even better performance than the control mixtures.

Management of dredged marine sediments in Southern France: main keys to large-scale beneficial re-use.

Fifty million cubic meters of marine sediments are dredged each year in France in order to maintain harbor activities and sustain the economy of littoral territories. Because of anthropogenic activities in and around harbors, sediments can contain significant amounts of chemical and organic pollutants whose behavior during dredging must be addressed in order to avoid releasing risks for humans and the environment. French regulations come to govern the management of dredged sediments, considering them "safe" and possible to be dumped at sea or "contaminated" and needed to be treated on land as waste. In recent years, new constraints have been pushed toward the management of land. This management is, however, challenging as few channels are proposed to reuse marine sediments, and elimination appears to be economically and environmentally unsustainable. This study provides an overview of the technical and regulatory aspects related to dredged marine sediment management in France and aims to identify and discuss the limits of their valorization. Dredged sediments are mainly composed of particles with heterogeneous grain size, some being known for many applications such as building materials and growing media. However, several reasons have been put forward to explain why these particles are not reused when extracted from dredged sediments. Several technical, socio-economic, and regulatory obstacles explain the low demand for dredged sediments. This demand can be stimulated by government incentives and a good regulatory framework. National regulations could help streamline their reuse by removing their "waste" status and creating a regulated market for dredged sediment.

Removal of heavy metals from dredging marine sediments via electrokinetic hexagonal system: A pilot study in Italy

Among the several treatment options, electrokinetic (EK) remediation is recognized as an effective technique for the removal of heavy metals from low-permeability porous matrices. However, most of the EK decontamination research reported was performed on linear configuration systems at a laboratory scale. In this study, a series of experiments were performed on a pilot-scale system where the electrodes were arranged in a hexagonal configuration, to assess the improvement of the EK process in the removal of inorganic contaminants from sediments dredged in the harbor of Piombino, Italy. HNO3 was used as acid conditioning and both pH effect and treatment duration time were investigated. Sediment characterization and metal fractionation were also presented, in order to understand how the bioavailability of metals affects the process efficiency. The increase in pH due to the buffering capacity of the sediment in the sections close to the cathode favored the precipitation and accumulation of metals. However, the results highlighted that longer treatment times, combined with an efficient pH reduction, can improve treatment performance, resulting in high removal efficiencies for all the target metals considered (a percentage removal greater than 50% was reached for Cd, Ni, Pb, Cu and Zn). Compared to different EK configuration systems, the hexagonal configuration arrangement applied in our study provides better results for the remediation of dredged marine sediment.

Phytoremediation of chloride from marine dredged sediments: A new model based on a natural vegetation recolonization

Phytoremediation is a type of bioremediation process that involves the use of plants to remove or degrade contaminants from soil, water, or air. In most of the observed phytoremediation models, plants are introduced and planted on a polluted site to take up, absorb, or transform contaminants. This study aims to explore a new mixed phytoremediation approach that involves natural recolonization of a contaminated substrate, by identifying the species growing naturally, their bioaccumulation capacity, and by modeling annual mowing cycles of their aerial parts. This approach aims to evaluate the phytoremediation potential of such a model. Both natural and human interventions are involved in this approach, which is referred to as a mixed phytoremediation process. The study focuses on chloride phytoremediation from a chloride-rich and regulated substrate that is marine dredged sediments abandoned for 12 years and recolonized for 4 years. The sediments are colonized by a Suaeda vera dominated vegetation and possess heterogeneity in lixiviate chloride and conductivity. The study found that despite Suaeda vera is the well adapted species for this environment, it is not an effective species for phytoremediation as it has low bioaccumulation and translocation rates (9.3 and 2.6 respectively), and disturbs chloride leaching below in the substrate. Other identified species, such as Salicornia sp., Suaeda maritima, and Halimione portulacoides, have better phytoaccumulation (respectively 39.8, 40.1, 34.8) and translocation rates (respectively 7.0, 4.5, 5.6) and can successfully remediate the sediment in 2–9 years. The following species have been found to bioaccumulate chloride in aboveground biomass at the following rates: Salicornia sp. (181 g/kg DW), Suaeda maritima (160 g/kg DW), Sarcocornia perennis (150 g/kg DW), Halimione portulacoides (111 g/kg DW) and Suaeda vera (40 g/kg DW).

Effect of seawater on solidification/stabilisation treatment of marine soft soil slurry by lime-activated ISSA and GGBS

It is proposed to use dredged marine sediments as fill material in marine reclamation engineering by stabilisation/solidification (S/S) technology with sustainable binding materials, which can help the soft soil gain strength to solve the engineering geological problem of its insufficient bearing capacity. In this work, lime and two types of industrial wastes, i.e., incinerated sewage sludge ash (ISSA) and ground granulated blast-furnace slag (GGBS), were selected as the binding materials. Hong Kong marine deposits (HKMD) slurry with a high initial water content of 110% was mixed with 30% binders (30% lime and 70% (ISSA+GGBS) with ISSA: GGBS = 3). The seawater (SW) with salinity of 3.6% was employed as mixing solution in S/S treatment of HKMD. To detect the effect of each main composition in SW on the performance of S/S HKMD, the pure solutions of NaCl, MgCl2 and Na2SO4 were adopted in this study.The results show that the use of SW in the lime-activated ISSA and GGBS treated dredged HKMD slurry is effective in improving its strength. The X-ray diffraction, thermo-gravimetric analysis and scanning electron microscopy observations present the formation of calcium/magnesium silicate hydrate (C/M-S-H), Friedel's salt and ettringite, which fill into the pores and interlock the particles in the mixture increasing the strength of the treated HKMD. The chemical compositions of SW have significant and different impacts on the performance of treated HKMD samples. Na+ can help the samples gain higher strength and result in the cracking development in the S/S samples. Mg2+ will lead to the formation of M-S-H, which reduces the porosity of treated HKMD samples. However, the contribution of M-S-H to the soil strength is less than that of C-S-H. Cl− in the mixture would slow down the reaction speed and show slight impacts on the modulus. SO42− accelerates the reactions in the treated samples and has a more significant effect on nano-size porosity of bulk sample. Consequently, the seawater has positive effect on the S/S performance of HKMD slurry, suggesting potential application in the practical projects.

Effective thermal conductivity of a gypsum mortar using harbor sediments

For sustainable use of natural resources, marine sediments areregularly dredged. One of the valorization ways of thesesediments is to reuse them as raw materials for the formulation of civil engineering products.This paper presents a thermal homogenization methodology for the optimization of heat transfer in Gypsum Plaster Boards formulation using dredged marine sediments. An up-scaling or homogenization technique that links macro- to micro thermal conductivity is given. Effective homogenized thermal conductivity formulation could be presented for a composite material on which a periodic micro-scale heat flux was subjected. For that purpose, steady state balance equations and Fourier heat law were used. Then, a thorough characterization of grain size distributions of dredged sediments were carried out. This showed that the dredged sediments are mainly sandy. Finally, ANSYS Finite Element Code is used to numerically compute the effective homogenized thermal conductivity of Gypsum-sediment composite incorporating different volume fractions of sediments. These simulations, performed on the Representative Volume Element, allowed studying the influence of the sediment grain size. The numerical simulations results, compared to classical theoretical models, have demonstrated the reuse feasibility of investigated sediment in Gypsum Plaster applications.

Solidification/stabilization treatment of Hong Kong marine deposits slurry at high water content by ISSA and GGBS

Soft soils have been adopted as a conventional fill material in land reclamation projects, which is quite promising in Hong Kong with a huge mass of dredged marine sediments produced per year. It is proposed to use Hong Kong marine deposits (HKMD) as fill material treated by stabilisation/solidification (S/S) technology with sustainable binding material. In this work, lime, incinerated sewage sludge ash (ISSA) and ground granulated blast furnace slag (GGBS) were selected as the binding materials. The S/S performance of the binders on HKMD slurry was investigated. The results showed that the use of ISSA and GGBS as part of the binder is effective in promoting the strength of HKMD slurry with a high initial water content of 200%. The HKMD slurry treated by 30% binders (30% lime and 70% (ISSA + GGBS) with ISSA: GGBS = 3) gains strength, which became higher with increasing curing time. The results from X-ray diffraction (XRD), thermo-gravimetric (TG) analysis and scanning electron microscopy-energy dispersive spectrometer (SEM-EDS) presented the formations of calcium (aluminium) silicate hydrate (C-(A)-S-H), Friedel’s salt, and ettringite, which are mainly responsible for the strength increase of treated HKMD with their phases filling into the pores, interlocking and reinforcing the particles in the mixture. The porosity of the treated HKMD in bulk and powder state was determined by mercury intrusion porosimetry technique (MIP) and nitrogen adsorption/desorption isotherms (NAI), it is found that the bulk porosity of treated HKMD samples reduces with curing time due to the neoformations, especially the ettringite crystal by SEM results. This work indicates the potential application of lime-activated recycling wastes (i.e., ISSA and GGBS) for S/S treatment of HKMD slurry.

Valorization of uncontaminated dredged marine sediment through sand substitution in marine grade concrete

Marine sediment disposal is an important economic and environmental issue worldwide. In order to minimize these discharges and optimize resources through a circular economy approach, this study discusses the potential use of fine marine sediments without treatments as a sand substitute in the marine concrete class (XS2, C30/37). The Dreux-Gorisse method was applied to find the concrete formulation containing 10, 20, 30, 40 and 50% sediment by weight. The results show that an XS2 concrete C30/37 with a water to binder ratio of 0.55 could be designed with 10% of sediment replacement content without significantly affecting the concrete properties. However, the optimization of concrete mix design shows that marine concrete (XS2, C30/37) could be designed with 30% of sediment replacement content without significantly affecting the potential durability and the estimated lifetime of the concrete structure.

Study on the early strength characteristics and source mechanism of solidified dredged marine sediment based on moisture transformation

Context Large land areas are occupied by dredged sediments with which the strength of the solidified soil develops slowly, and this has become an instant problem in geotechnical engineering. Aims This study was designed to investigate the performance of solidified dredged deposits treated by sulfoaluminate cement for sludge solidification, and whether the mechanism for early strength development is based on water transfer. Methods With sediments dredged from Dalian Bay as the research objects, the strength, deformation and amount of moisture transferred by the solidified sludge were measured and analysed and referred to the data for Portland cement. Key results Sulfate aluminium cement is characterised by great early strength. Conclusion The mechanism for early strength development relies on reactions that form crystalline calcium vanadium stone. Implications Our study showed that calcium vanadium stone plays a critical role in early strength development, and this was measured quantitatively for the mineral water form.

Paradigm shifts in incinerator ash, sediment material recovery and landfill monitoring

The current paper discusses some selected developments for efficient management of the globally increasing quantity of waste. Incinerator bottom ash (IBA), the heavier ash generated during incineration of municipal waste, is currently utilised in two distinct ways. One pathway is not to fragment IBA and use it as a building material in road construction. This results in reduced landfilled residual but low metal recovery. The other way is to crush the mineral aggregate, thus maximising metal recovery but resulting in higher landfilled, end material. Here emphasis is placed on the second approach as implemented in Switzerland together with the economics and need for improvement of metal recovery from IBA and fly ash. The second theme reports on the viability of recycling mussel shells as a partial substitute for cement to stabilise dredged marine sediments mechanically. This can reduce the consumption of natural resources and lower the amount of binders used in sediment stabilisation practices. Finally, the adequacy of EU’s requirements regarding monitoring of groundwater pollution from landfills is assessed, and recommendations are provided to use bioindicators to determine the impact of landfills on surrounding vegetation.

New Applications of Ordinary Portland and Calcium Sulfoaluminate Composite Binder for Recycling Dredged Marine Sediments as Road Materials

In this study, systematic investigations were conducted to solidify dredged marine sediments using the low-carbon composite binder made by mixing Ordinary Portland and calcium sulfoaluminate cement (OPC–CSA). A series of tests to evaluate physical and mechanical properties of samples, which indicated that the OPC–CSA composite binder could effectively improve the engineering characteristics of solidified dredged marine sediments, such as the immediate California Bearing Ratio (I-CBR) index, unconfined compressive strength, splitting tensile strength, and elastic modulus. In addition, simple models were proposed to correlate the unconfined compressive and splitting tensile strength with the elastic modulus of treated sediments. Importantly, the elastic modulus of treated sediments was defined by the local small-strain sensor method. In addition, the correlation between the strength and the three kinds of failure mode of the specimens was revealed. Lastly, simplified carbon footprint analysis indicated that OPC–CSA composite binder offers potential CO2 emissions savings of 14%–41%. The laboratory tests have revealed that the mechanical and environmental behaviors of solidified dredged marine sediments meet the environmental and engineering requirements of the standards and regulations. Low-carbon and sustainable OPC–CSA composite binder-solidified dredged marine sediments could be reused as subbase or roadbed infill materials for low traffic.

Leaching Remediation of Dredged Marine Sediments Contaminated with Heavy Metals

There are more than 150 ports in China and a considerable proportion of dredged sediments in ports and waterways are contaminated with heavy metals as the typical contaminants. It is mandatory to remediate the contaminated dredged sediments prior to further resource utilization. The over-arching objective of this study was to use natural organic acids (oxalic acid, citric acid, tartaric acid, and malic acid) as leaching agents to remove heavy metals (Cu, Cd, and Pb) from contaminated dredged sediments. Batch experiments were conducted to investigate the factors governing the removal rate of heavy metals and leaching kinetics. Citric acid had the best leaching effect on heavy metals Cu, Cd, and Pb with an optimal leaching concentration of 20 mmol/L and a solid-to-liquid ratio of 1:20. The average removal rates of Cu, Cd, and Pb were 85%, 73%, 56%, and 35% for citric acid, malic acid, tartaric acid, and oxalic acid, respectively. The leaching kinetics showed that the removal of heavy metals increased rapidly with time and then gradually reached the maximum value which was best described by the Elovich equation model. The outcomes of this study suggest that citric acid is an effective and environmentally friendly leaching agent for removing heavy metals from marine dredged sediments.

Enhanced Electroremediation of Metals from Dredged Marine Sediment under Periodic Voltage Using EDDS and Citric Acid

The electrokinetic remediation (EKR) method has been extensively considered for the removal of inorganic pollutants from contaminated dredged sediment. In addition, the use of chelating agents as electrolyte solutions has been beneficial in increasing the mobility of metals. This study investigated the metals’ (Cd, Cr, Cu, Pb, and Zn) mobilities by assessing the effect of two environmentally friendly chelating agents, ethylenediaminedisuccinic acid (EDDS) and citric acid (CA), in enhancing the EKR efficiency under a periodic voltage gradient. The results showed that, for the same concentration (0.1 mol L−1), CA is more suitable for enhancing the removal of Cr (67.83%), Cu (59.77%), and Pb (32.05%) by chelating and desorbing them from the sediment matrix and concentrating them in the electrode compartments. EDDS provided efficiency to improve the Cd extraction percentage (45.87%), whereas CA and EDDS had comparable improvement removal impacts on Zn EKR (39.32% and 41.37%, respectively). From the comparison with previous results obtained with a continuous voltage, applying a periodic voltage gradient associated with a low concentration of chelating agents led to a promising result.

A reassessment of TBT action levels for determining the fate of dredged sediments in the United Kingdom

As part of reviewing the United Kingdom (UK) action levels (ALs) of contaminants for managing the disposal of dredged marine sediment material, tributyl tin (TBT) has been reassessed. TBT is a banned biocide capable of causing severe harm to the marine environment. Its presence is routinely screened for prior to marine disposal of dredged sediment material. Dredged sediment TBT concentrations have been studied using UK monitoring data obtained between 2000 and 2018. The changes in these TBT concentrations have guided the reassessment of ALs. Recent toxicity studies have also guided the reassessment of TBT ALs. This study, which itself forms part of a larger review by the Department for Environment, Food and Rural Affairs, has concluded that current UK TBT ALs may no longer be fit for purpose. A more environmentally protective approach for controlling release of TBT into the marine environment is recommended.

The Use of Dredged Marine Sediment in the Formulation of Air–Foam Concrete

The Use of Dredged Marine Sediment in the Formulation of Air–Foam Concrete

Evaluation of Different Binder Combinations of Cement, Slag and CKD for S/S Treatment of TBT Contaminated Sediments

Abstract The seabed in the ports needs to be regularly cleaned from the marine sediments for safe navigation. Sediments contaminated by tributyltin (TBT) are environmentally harmful and require treatment before recycling. Treatment methods include leaching, stabilisation and solidification to remove toxic chemicals from the sediments and improve their strength for reuse in the construction works. This study evaluated the effects of adding three different binder components (cement, cement kiln dust (CKD) and slag) to treat sediment samples collected in the port of Gothenburg. The goal of this study is to assess the leaching of TBT from the dredged marine sediments contaminated by TBT. The various methods employed for the treatment of sediments include the application of varied ratios of binders. The project has been performed by the Swedish Geotechnical Institute (SGI) on behalf of the Cementa (HeidelbergCement Group) and Cowi Consulting Group, within the framework of the Arendal project. An experiment has been designed to evaluate the effects of adding CKD while reducing cement and slag for sediment treatment. Methods that have been adopted include laboratory processing of samples for leaching using different binder combinations, followed by statistical data processing and graphical plotting. The results of the experiment on leaching of TBT for all samples are tested with a varied ratio of cement, slag, CKD and water. Specimens with added binders ‘cement/CKD’ have demonstrated higher leaching compared to the ratio ‘cement/slag/CKD’ and ‘cement/slag’. The ‘CKD/slag’ ratio has presented the best results followed by the ‘cement/slag/CKD’, and can be used as an effective method of s/s treatment of the sediments. The results have shown that the replacement of cement and slag by CKD is effective at TBT leaching for the treatment of toxic marine sediments contaminated by TBT.

Sewage sludge ash-incorporated stabilisation/solidification for recycling and remediation of marine sediments

Finding suitable disposal sites for dredged marine sediments and incinerated sewage sludge ash (ISSA) is a challenge. Stabilisation/solidification (S/S) has become an increasingly popular remediation technology. This study sheds light on the possible beneficial use of ISSA together with traditional binders to stabilise/solidify marine sediments. The performance of the binders on S/S of sediment 1 (clean) and sediment 2 (contaminated) was also compared. The results showed that the use of ISSA as part of the binder was effective in promoting the strength of the sediment with a high initial moisture content due to ISSA porous and high water absorption characteristics. The sediments treated with 10% cement and 20% ISSA attained the highest strength. Also, cement hydration as well as pozzolanic reactions between ISSA and Ca(OH)2 made contributions to the strength development. This was supported by the microstructural analysis, in particular the porosity results. In terms of environmental impacts, two leaching tests (toxicity characteristic leaching procedure and synthetic precipitation leaching procedure) found that all the S/S treated sediment by 10% lime and 20% ISSA resulted in the lowest leachate concentrations under the on-site reuse scenario or under simulative acidic rainfall conditions. Therefore, recycling waste ISSA with lime can be used as an appealing binder to replace cement to stabilise/solidify dredged marine sediments for producing fill materials.