Simulation of heavy metal leaching from cement-stabilized polluted sediments : geochemical modelling

A lot of concern has been raised by individuals and organizations regarding the menace associated with heavy metal contamination of marine sediments in Norway. This has necessitated the remediation of heavy metal contaminated areas. Stabilization and solidification is one of the techniques used to immobilize heavy metals in marine sediments. Laboratory leaching tests are generally used to assess the effectiveness of stabilization and solidification. Results of laboratory leaching tests are, however, used only on short term basis. Geochemical models have evolved into invaluable tools that can be used as a substitute for laboratory leaching experiments. Results from geochemical modelling can be used for future predictions and also help in management options. Previous studies have revealed that several leaching experiments have been successfully simulated with geochemical models. This study, which is in connection with a larger project being carried out by NGI, has been designed with the intent of using geochemical modelling code, PHREEQC to simulate the binding and release of Pb and Cu and their long-term behaviour in cement-stabilized polluted sediments from three Norwegian harbours namely: Hammerfest, Grenland and Bergen. The Freundlich empirical adsorption isotherm was utilized in this study to describe the behaviour of the heavy metals in the three stabilized sediments. Results showed that the Freundlich empirical isotherm could be used to describe the adsorption characteristics of the stabilized sediments for Cu and Pb as the isotherm fitted rather well to experimental data from the three sediments. The sorption capacities of the stabilized sediments for the heavy metals were determined using the nonlinear Freundlich equation. Stabilized sediments from Hammerfest demonstrated the least sorption capacity for both metals with stabilized sediments from Bergen showing the highest capacity to sorb the two heavy metals. The sorption capacity of the stabilized sediment from Grenland was between that of Bergen and Hammerfest. In general, results indicated that the sorption capacities of the sediments were higher for Pb than for Cu. A 1-dimensional transport based on PHREEQC using diffusion and a non-linear sorption was employed to simulate heavy metal releases from the cement-stabilized sediment into sea water and to predict their long-term behaviour using time spans of 2, 10 and 20 years. It followed thus from the results of the fluxes calculated that stabilized sediment from Bergen was effective in retaining the heavy metals and consequently reduced their diffusive transport for all the time spans studied. The fluxes of both metals from Hammerfest stabilized sediment for all the time spans were relatively high due to the inability of the sediment to retain the metals. Fluxes of both metals from Grenland sediments were between those of Bergen and Hammerfest sediments

Permeable biosorbent barrier for wastewater remediation

Chromium is one of the heavy metals that significantly affect water quality in Mongolia. The present study is focused on the remediation of surface water contaminated with chromium (III) by a permeable barrier in order to prevent sediment pollution. The adsorption capacity of the selected materials (13X zeolite and vermiculite) was investigated at different sorbent dosages, pH and initial Cr(III) concentration. The equilibrium adsorption studies showed that vermiculite has a higher Cr(III) removal efficiency in comparison with 13X zeolite. A fungal isolate obtained from the sediment samples collected near Tuul River (Mongolia) was selected from enriched Luria-Bertani medium, showing a good performance for Cr(III) removal (78.2\% for an initial concentration of 50 mg/L). The fungal isolate was genetically typed by DNA sequencing and was identified as belonging to the Alternaria alternata species. 13X zeolite showed the best performance for Cr removal in the permeable barrier assays compared to vermiculite, achieving a total removal of 96\\% and a global uptake of 2.49 mg/g. After 13 days of operation none of the barriers reached saturation with chromium.A previous version of the paper has been presented in the 2nd EWaS International Conference: BEfficient & Sustainable Water Systems Management toward Worth Living Development^, Chania, Crete, Greece, 1-4 June 2016. This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte. Bruna Silva is thankful to the FCT for the concession of a Post-Doc grant (SFRH/BPD/112354/2015). Sampling process was supported by the collaborative research grant of National Academy of Sciences of Taiwan and Science and Technology Foundation of Mongolia, project code NCS-NECS2013003 and co-funded by the Young Scientist Grant (SEAS-2015075) of National University of Mongolia. E. Tuuguu would like to acknowledge the Erasmus-Mundus AREAS+ program for the opportunity to conduct research at CEB-University of Minho.info:eu-repo/semantics/publishedVersio

Hydrogeochemical Studies to Assess the Suitability of Groundwater for Drinking and Irrigation Purposes: The Upper East Region of Ghana Case Study

Groundwater is increasingly being used to help meet the Sustainable Development Goals (SDGs) 2 and 6 in many parts of the world, including Ghana. Against this background, hydrogeochemical and multivariate statistical studies were conducted to determine the physicochemical characteristics and suitability of groundwater in some agrarian communities in the Upper East Region of Ghana for drinking and irrigational farming. Additional analyses were also performed to identify potential health risks associated with the groundwater use and to better understand the hydrogeochemical processes controlling groundwater evolution for its effective management. The results showed that the groundwater is typically fresh; moderate to very hard in character; undersaturated with calcite, dolomite, halite, and gypsum; and supersaturated with quartz and amorphous silica. The physicochemical characteristics of the groundwater are controlled by both anthropogenic and natural activities/processes, such as fertilizer application, irrigation return flows, rock weathering, and forward/reverse cation exchange. The total dissolved solids (TDS) (165–524 mg/L), electrical conductivity (EC) (275–873 μS/cm), sodium percentage (Na%; 9.05–17.74%), magnesium ratios (MR) (29.25–53.3%), permeability index (PI) (36.6–74.6%), and sodium adsorption ratio (SAR) (0.20–0.51) point to the possibility of using the groundwater for irrigation, however, with some salinity control. The water quality and health risk analysis also revealed that the groundwater can be used for drinking; however, the high concentrations of fluoride, which can cause noncarcinogenic health issues such as dental and skeletal fluorosis in both adults and children, must be reduced to the WHO required level of 1.5 mg/L

Chemical drinking water quality in Ghana : water costs and scope for advanced treatment

To reduce child mortality and improve health in Ghana boreholes and wells are being installed across the country by the private sector, NGO's and the Ghanaian government. Water quality is not generally monitored once a water source has been improved. Water supplies were sampled across Ghana from mostly boreholes, wells and rivers as well as some piped water from the different regions and analysed for the chemical quality. Chemical water quality was found to exceed the WHO guidelines in 38% of samples, while pH varied from 3.7 to 8.9. Excess levels of nitrate (NO3−) were found in 21% of the samples, manganese (Mn) and fluoride (F−) in 11% and 6.7%, respectively. Heavy metals such as lead (Pb), arsenic (As) and uranium (U) were localised to mining areas. Elements without health based guideline values such as aluminium (Al, 95%) and chloride (Cl, 5.7%) were found above the provisional guideline value. Economic information was gathered to identify water costs and ability to pay. Capital costs of wells and boreholes are about £1200 and £3800 respectively. The majority of installation costs are generally paid by the government or NGO's, while the maintenance is expected to be covered by the community. At least 58% of the communities had a water payment system in place, either an annual fee/one-off fee or “pay-as-you-fetch”. The annual fee was between £0.3–21, while the boreholes had a water collection fee of £0.07–0.7/m3, many wells were free. Interestingly, the most expensive water (£2.9–3.5/m3) was brought by truck. Many groundwater sources were not used due to poor chemical water quality. Considering the cost of unsuccessful borehole development, the potential for integrating suitable water treatment into the capital and maintenance costs of water sources is discussed. Additionally, many sources were not in use due to lack of water capacity, equipment malfunction or lack of economic resources to repair and maintain equipment. Those issues need to be addressed in combination with water quality, coordinated water supply provision and possible treatment to ensure sustainability of improved water resources

Hydrogeochemical Studies to Assess the Suitability of Groundwater for Drinking and Irrigation Purposes: The Upper East Region of Ghana Case Study

Groundwater is increasingly being used to help meet the Sustainable Development Goals (SDGs) 2 and 6 in many parts of the world, including Ghana. Against this background, hydrogeochemical and multivariate statistical studies were conducted to determine the physicochemical characteristics and suitability of groundwater in some agrarian communities in the Upper East Region of Ghana for drinking and irrigational farming. Additional analyses were also performed to identify potential health risks associated with the groundwater use and to better understand the hydrogeochemical processes controlling groundwater evolution for its effective management. The results showed that the groundwater is typically fresh; moderate to very hard in character; undersaturated with calcite, dolomite, halite, and gypsum; and supersaturated with quartz and amorphous silica. The physicochemical characteristics of the groundwater are controlled by both anthropogenic and natural activities/processes, such as fertilizer application, irrigation return flows, rock weathering, and forward/reverse cation exchange. The total dissolved solids (TDS) (165–524 mg/L), electrical conductivity (EC) (275–873 μS/cm), sodium percentage (Na%; 9.05–17.74%), magnesium ratios (MR) (29.25–53.3%), permeability index (PI) (36.6–74.6%), and sodium adsorption ratio (SAR) (0.20–0.51) point to the possibility of using the groundwater for irrigation, however, with some salinity control. The water quality and health risk analysis also revealed that the groundwater can be used for drinking; however, the high concentrations of fluoride, which can cause noncarcinogenic health issues such as dental and skeletal fluorosis in both adults and children, must be reduced to the WHO required level of 1.5 mg/L