Moderate Organic Content Research Articles

Geotechnical investigation of low-plasticity organic soil treated with nano-calcium carbonate

Soil stabilization using nanomaterials is an emerging research area although, to date, its investigation has mostly been laboratory-based and therefore requires extensive study for transfer to practical field applications. The present study advocates nano-calcium carbonate (NCC) material, a relatively unexplored nanomaterial additive, for stabilization of low-plasticity fine-grained soil having moderate organic content. The plasticity index, compaction, unconfined compressive strength (UCS), compressibility and permeability characteristics of the 0.2%, 0.4%, 0.6% and 0.8% NCC-treated soil, and untreated soil (as control), were determined, including investigations of the effect of up to 90-d curing on the UCS and permeability properties. In terms of UCS improvement, 0.4% NCC addition was identified as the optimum dosage, mobilizing a UCS at 90-d curing of almost twice that for the untreated soil. For treated soil, particle aggregation arising from NCC addition initially produced an increase in the permeability coefficient, but its magnitude decreased for increased curing owing to calcium silicate hydrate (CSH) gel formation, although still remaining higher compared to the untreated soil for all dosages and curing periods investigated. Compression index decreased for all NCC-treated soil investigated. SEM micrographs indicated the presence of gel patches along with particle aggregation. X-ray diffraction (XRD) results showed the presence of hydration products, such as CSH. Significant increases in UCS are initially attributed to void filling and then because of CSH gel formation with increased curing. • Optimum dosage of 0.4% NCC improved the UCS by 1.94 times with 90-d curing. • Permeability increased upto the optimum dosage and decreased for higher dosages and ageing. • Compression index reduced with NCC addition. • Early increase in strength was due to void filling and with ageing hydration products enhanced strength.

Pengaruh Dissolved Organic Carbon (DOC) pada Efektivitas Perbaikan Tanah Gambut dengan Metode Calcite Precipitation

The problems that are generally found in land preparation for infrastructure developments are the characteristics of soils that have low bearing capacity, such as peat soils. Calcite precipitation is a soil improvement method that utilizes biochemical reactions with the final product being calcite. Peat soil has different characteristics from other soils, that it has high levels of Dissolved Organic Carbon (DOC). The amount of DOC present in peat soil significantly affects the specific gravity, liquid limit, density, and strength of the soil. Therefore, it is necessary to evaluate whether DOC in peat soil can affect the effectiveness of the calcite precipitation method. The research was conducted on soil with high organic content (95.35%) and soil with moderate organic content (73,51%). The research was carried out through five stages, namely soil properties, test-tube experiment, soil samples treatment, Unconfined Compressive Strength (UCS) test, and evaluating the soil pH. The results of this study obtained in the form of high organic content have an additional strength of 76.47%. Medium organic content soil has an additional strength of 137.50. Thus, DOC has an effect on increasing soil strength in the calcite precipitation method.

Advanced Oxidation Processes as sustainable technologies for the reduction of elderberry agro-industrial water impact

World is facing an environmental crisis and industrial awareness regarding their wastewaters is gaining strength. By treating them, water footprint can be reduced allowing their recycle and reuse, as well as recovering substances with added value. This work reports the pre-treatment of non-biodegradable elderberry agro-industrial wastewater at pilot plant scale by different oxidative processes (solar photo-Fenton, solar electrochemistry and ozonation). An economical approach has been addressed for improving biodegradability for a subsequent lower-cost biological treatment. Solar photo-Fenton process attained biodegradability in 30 min entailing 0.22 € m−3 of operation costs. Solar photoelectro-Fenton treatment turned industrial wastewater biodegradable after 20 min costing 0.11 € m−3, while solar-assisted anodic oxidation required 60 min and 0.12 € m−3. Solar processes combined with electrooxidation showed to be more promising options than ozonation for reducing water footprint of biorecalcitrant industrial wastewaters and moderate organic content, if an engagement between treatment time and operating costs is prioritized.

Organic-carbon-rich sediments: benthic foraminifera as bio-indicators of depositional environments

Abstract. Fjords have been described as hotspots for carbon burial, potentially playing a key role within the carbon cycle as climate regulators over multiple timescales. Nevertheless, little is known about the long-term fate of the carbon that may become stored in fjordic sediments. One of the main reasons for this knowledge gap is that carbon arriving on the seafloor is prone to post-depositional degradation, posing a great challenge when trying to discriminate between an actual change in the carbon deposition rate and post-depositional carbon loss. In this study, we evaluate the use of modern benthic foraminifera as bio-indicators of organic carbon content in six voes (fjords) on the west coast of Shetland. Benthic foraminifera are known to be sensitive to changes in organic carbon content in the sediments, and changes in their assemblage composition therefore reflect synchronous variations in the quantity and quality of carbon reaching the seafloor. We identified four environments based on the relationship between benthic foraminiferal assemblages and organic carbon content in the sediments: (1) land-locked regions influenced by riverine and/or freshwater inputs of organic matter, namely the head of fjords with a restricted geomorphology; (2) stressed environments with a heavily stratified water column and sediments rich in organic matter of low nutritional value; (3) depositional environments with moderate organic content and mild or episodic current activity; and (4) marginal to coastal settings with low organic content, such as fjords with an unrestricted geomorphology. We conclude that foraminifera potentially provide a tool to disentangle primary organic carbon signals from post-depositional degradation and loss of organic carbon because of their environmental sensitivity and high preservation potential in the sedimentary record.

Infaunal macrobenthos in the Porcupine Bank (NE Atlantic)

Infaunal macrobenthos in the Porcupine Bank (NE Atlantic)

Multi-criteria analysis for site selection for the reuse of reclaimed water and biosolids

Low pH soils with insufficient organic matter can benefit from the application of reclaimed water (RW) and biosolids. The presence of nutrients also aids plant growth. This paper presents the results of two integrated research studies, both carried out in the Beira Interior Region (Covilha, Portugal); one used RW for irrigation, the other applied paper mill sludge to agricultural land. In both cases, multiple criteria based on GIS tools were used for site selection. In the first study, the characteristics of RW analyzed over 2 years were found suitable for crop irrigation. The RW had moderate organic content, low electrical conductivity (CE), high nutrient content (N, P), and low concentrations of nitrate, metals and phytotoxic elements (Al, B, Cl and Na). The multi-criteria analysis was carried out taking into account environmental, technical and economic criteria and a suitable area of 30.5 ha was found for RW irrigation. In the second work, the paper mill sludge was considered suitable for application to agricultural land. Its concentrations of N, P and heavy metals did not a present risk for soil contamination and were suitable for soil improvement and crop production. A multi-criteria analysis based on similar criteria was conducted and a suitable area of 253 ha was found for sludge application.

Insights into real cotton-textile dyeing wastewater treatment using solar advanced oxidation processes

Different advanced oxidation processes (AOPs) were applied to the treatment of a real cotton-textile dyeing wastewater as a pre-oxidation step to enhance the biodegradability of the recalcitrant compounds, which can be further oxidized using a biological process. Tests were conducted on a lab-scale prototype using artificial solar radiation and at pilot scale with compound parabolic collectors using natural solar radiation. The cotton-textile dyeing wastewater presents a lilac color, with a maximum absorbance peak at 641 nm, alkaline pH (pH = 8.2), moderate organic content (DOC = 152 mg C L(-1), COD = 684 mg O2 L(-1)) and low-moderate biodegradability (40 % after 28 days in Zahn-Wellens test). All the tested processes contributed to an effective decolorization and mineralization, but the most efficient process was the solar-photo-Fenton with an optimum catalyst concentration of 60 mg Fe(2+) L(-1), leading to 98.5% decolorization and 85.5% mineralization after less than 0.1 and 5.8 kJUV L(-1), respectively. In order to achieve a final wastewater with a COD below 250 mg O2 L(-1) (discharge limit into water bodies imposed by the Portuguese Legislation-Portaria no. 423/97 of 25 June 1997), considering the combination of a solar-photo-Fenton reaction with a biological process, the phototreatment energy required is 0.5 kJUV L(-1), consuming 7.5 mM hydrogen peroxide, resulting in 58.4% of mineralization [Formula: see text].

Imaging Stratigraphy of Pontian Peatland, Johor Malaysia with Ground Penetrating Radar

Peat's stratigraphic sequence contains information related to humification, hydrology, nutrient content and formation history of the bog. These are vital information needed for effective assessment of the deposit's economic potentialities and environmental impact. This research is aimed at developing a model for delineating stratigraphic sequences of Pontian Peatland with ground penetrating radar. The study involves imaging of prominent reflection layers within the subsurface of the deposit and laboratory determination of organic content of the soil samples collected at various depth intervals on the study area. Four Ground Penetrating Radar (GPR) transects were scanned at regular interval spacing. Comparison of the processed radar image with the experimental data leads to the identification of three prominent stratigraphic layers: Top soil fabric with high ash content (low organic content), hemic layer of low ash content (high organic content) and kaolinitic clay with moderate organic content. The study could therefore serve as a means of assessing and monitoring fertility level and hydrological pattern of the deposit.

Treatment of textile wastewaters by solar-driven advanced oxidation processes

Abstract Heterogeneous (TiO2/UV, TiO2/H2O2/UV) and homogenous (H2O2/UV, Fe2+/H2O2/UV) solar advanced oxidation processes (AOPs) are proposed for the treatment of recalcitrant textile wastewater at pilot-plant scale with compound parabolic collectors (CPCs). The textile wastewater presents a lilac colour, with a maximum absorbance peak at 516 nm, high pH (pH = 11), moderate organic content (DOC = 382 mg C L−1, COD = 1020 mg O2 L−1) and high conductivity (13.6 mS cm−1), associated with a high concentration of chloride (4.7 g Cl− L−1). The DOC abatement is similar for the H2O2/UV and TiO2/UV processes, corresponding only to 30% and 36% mineralization after 190 kJUV L−1. The addition of H2O2 to TiO2/UV system increased the initial degradation rate more than seven times, leading to 90% mineralization after exposure to 100 kJUV L−1. All the processes using H2O2 contributed to an effective decolourisation, but the most efficient process for decolourisation and mineralization was the solar-photo-Fenton with an optimum catalyst concentration of 100 mg Fe2+ L−1, leading to 98% decolourisation and 89% mineralization after 7.2 and 49.1 kJUV L−1, respectively. According to the Zahn–Wellens test, the energy dose necessary to achieve a biodegradable effluent after the solar-photo-Fenton process with 100 mg Fe2+ L−1 is 12 kJUV L−1.

Validation of a Hybrid “Two-Site Gamma” Model for Naphthalene Desorption Kinetics

Three models for sorption/desorption of polycyclic aromatic hydrocarbon (PAH) contaminants from soil were compared for their ability to predict the transport of PAH in soil: a “gamma” model, a “two-site/two-region” nonequilibrium model, and a “hybrid” model. In the “hybrid” model, soil organic matter was conceptually divided into two compartments; a fraction with rapid sorption/desorption kinetics and a compartment with mass-transfer-limited kinetics. Contaminant sorbed in the rapid compartment was assumed to be in instantaneous equilibrium with the aqueous phase, while the release of contaminant from the slow fraction was assumed to be governed by a gamma distribution of rate coefficients. The “hybrid” model successfully described the initial rapid release of a model PAH contaminant, naphthalene, from a sieved soil sample of moderate organic content (≅2.3%) as well as the following slow release observed over 25 days in batch desorption experiments. Other necessary model parameters, such as the hydrodyna...

Influence of marine organic compounds on the engineering properties of a remoulded sediment

Rashid, M.A. and Brown, J.D. 1975. Influence of marine organic compound on the engineering properties of a remoulded sediment. Eng. Geol., 9: 141–154 The effect of low to moderate organic content on the engineering properties of a remoulded marine sediment was investigated by classificatin tests, undrained shear-strength tests, consolidation tests and triaxial compression tests. Sediment with a naturally occuring organic content of 2%, was treated to provide 0, 3, and 4% organic matter; first by reaction with hydrogen peroxide to remove the organic matter and then by addition of a naturally occuring humic compound in the latter two cases. In its natural state the sediment was classified as an organic sediment of low plsticity. Addition of the stated amounts of organic content did not result in the sediment being classified as organic; however, the remoulded undrained shear stregnth, the compressability, and the rheological behaivior of the sediment were significantly affected by ht evariations in the organic content. By contrast, the effects of these variations on the specific gravity, permeability, rate of consolidation and consolidated-undrained shear stregnth were not very marked.