Source and release mechanism of arsenic in aquifers of the Mekong Delta, Vietnam

In order to elucidate the arsenic source and its release mechanism into groundwater in the Mekong Delta, Vietnam, groundwater samples were collected from wells at different depths (20 to 440 m) and core samples (from 20 to 265 m depth) were analyzed. Based on the analytical results for groundwater and core samples, the As source in groundwater is considered to be pyrite (FeS 2 ) in acid sulfate soil (ASS) under oxidizing conditions and hydrous ferric oxide (Fe(OH) 3 ) under reducing conditions. Geochemical modeling demonstrated that As (III) is the dominant species and the presence of As-bearing sulfides, Fe-bearing sulfides and oxides phases may locally act as potential sinks for As. From variation between Fe and As concentrations in groundwater samples, the release mechanism of As is: dissolution of Fe(OH) 3 containing As under reducing conditions and oxidative decomposition of FeS 2 containing As under oxidizing conditions

Geochemical Assessment of Vulnerability of Groundwater to Contaminant at Phuoc Hiep Landfill Site, Ho Chi Minh City, Vietnam

Abstract A geochemical assessment on vulnerability of groundwater quality and shallow aquifer in the vicinity of the Phuoc Hiep landfill site was carried out with a hydro-chemical approach for identifying various geochemical processes and understanding the impacts of landfill leachate on groundwater quality. Results indicate that hardness, nitrate, fluoride, iron in groundwater and heavy metal in surface water are above the standard for drinking water. Leachate seepage from the landfill is a main contaminant source of groundwater of Na-Cl water type with electrical conductivity (EC) values of 4,275 to 4,575 μS/cm. The pH values of the leachate are between 5.8 and 6.6. Concentrations of Al, Fe and Mn and heavy metals (Pb, Zn and Cu) in the leachate are above the drinking water standards. As a result, the waste leachate has a high content of contaminant that affects groundwater quality in highly productive zones. Two main zones of the aquifer were determined to be most vulnerable using GOD vulnerability model. Thus, these vulnerable zones are not suitable for waste disposal and the aquifer should be protected from leachate

Hybrid Geothermal and Wind Power Generation System Using Geothermal Waste Water as a Heat Source

ABSTRACT Increasing demand and cost for energy and declining fossil fuels in near future make researches and developments on renewable energies feasible. Utilization of renewable energy sources are limited by their availability and efficiency. There is absolute exergy loss in most of geothermal power plants from separated brine; low temperature geothermal fields are also widely distributed worldwide. Several attempts have been made to utilize low temperature geothermal fields. In this paper the novel idea of hybrid power generation system has been proposed as a simple and renewable method to achieve sustainable utilization of renewable resources. The new hybrid system will benefit from solar chimney to produce electricity with windmill, and geothermal heat will be used as a heat source to achieve desirable air speed inside the chimney. Results promise, and it seems that suggested idea is competitive with other renewable energy sources. Further studies are necessary to achieve more realistic results to start actual projects. INTRODUCTION Increases in energy demand, declines in energy resources, and potential environmental impacts of conventional energy resources development underscore needs for a sustainable approach to the development and management of earth's energy resource

Conceptual Model of Hydrothermal System at Kotamobagu Geothermal Field, North Sulawesi, Indonesia

AbstractA conceptual model that is proposed here is based on the interconnections of the geological and chemical characteristics of the hydrothermal system of Kotamobagu. Chemical analyses were performed on thirty water samples collected from hot spring, river, and shallow well on the southern and northern parts of Mt. Muayat at Kotamobagu geothermal field. The acidic water samples with pH of about 2, which come from a steaming ground and are discharging near the summit of Mt. Muayat, are identified to have a water chemistry of SO4 type. Hot springs discharging at the lower elevation of Mt. Muayat, on the other hand, are determined to be of bicarbonate water type while acidic hot springs discharging at cliff on the slope of Mt. Muayat and at Makaroyen at 7km NE of Mt. Muayat are Cl-SO4 type. On the foot of Mt. Wuluramatus, at the west of Makaroyen are alkaline chloride water types and hot springs discharge at the west and south west of Mt. Muayat are hybrid type. Temperature of 130 -160°C, 180-230°C and 210-320°C were also estimated using different geochemical geothermometers such as quartz geothermometer, Na-K-Ca-Mg and Na-K geothermometers, respectively

Chemical Characteristics of Rainwater at Motooka, Fukuoka

Rainwater was collected with bulk samplers for two years from September 1998 to June 2000 at Motooka, Fukuoka, where a new campus of Kyushu University is under construction. Two rainwater samplers of open-air type for bulk sampling were set in the area. The rainwater stored in the tank was collected and chemically analyzed at an interval of two weeks during this monitoring period. Lowest pH of 4.0 was observed once, and relatively low pH, lower than the average pH of rainwater in Japan (pH 4.7), were measured 17 times out of 45 times in total. Concentrations of NO^-_3 and non-sea salt (nss) SO^_4 showed seasonal variations such that higher values during wintertime compared with other three seasons. Deposited amounts of these ions were calculated to be relatively constant for NO^-_3 when precipitation for one observation period, two weeks, exceeded 40 to 50 mm, but varied in a wide range for SO^_4 regardless of precipitation

Geothermal energy resources and development in Iran

Interest in geothermal energy originated in Iran when James R. McNitt, a United Nations geothermal expert, visited the country in December 1974. In 1975, a contract among the Ministry of Energy, ENEL (Entes Nazionale per L'Energia Elettrica) of Italy and TB (Tehran Berkeley) of Iran was signed for geothermal exploration in the north-western part of Iran. In 1983, the result of investigations defined Sabalan, Damavand, Khoy-Maku and Sahand regions as four prospected geothermal sites in north-western Iran. From 1996 to 1999, a countrywide geothermal energy resource exploration project was carried out by Renewable Energy Organization of Iran (SUNA) and 10 more potential areas were indicated additionally. Geothermal potential site selection using Geographic Information System (GIS) was carried out in Kyushu University in 2007. The results indicated 8.8% of Iran as prospected geothermal areas in 18 fields. Sabalan as a first priority of geothermal potential regions was selected for detailed explorations. Since 1995, surface exploration and feasibility studies have been carried out and five promising areas were defined. Among those prospective areas, Northwest Sabalan geothermal filed was defined for detailed exploration to justify exploration drilling and to estimate the reservoir characteristics and capacity. From 2002 to 2004, three deep exploration wells were drilled for evaluation of subsurface geological conditions, geothermal reservoir assessment and response simulation. Two of the wells were successful and a maximum temperature of 240 °C at a depth of 3197 m was recorded. As a result of the reservoir simulation, a 55-MW power plant is projected to be installed in the Sabalan field as a first in geothermal power generation. To supply the required steam for the geothermal power plant (GPP) 17 deep production and reinjection wells are planned to be drilled this year.Iran SUNA Geothermal Sabalan Direct use

Characterization of Solid Deposits formed in Geothermal Surface Facilities

Novel Carbon Resource SciencesSilica scaling has been one of the major problems in geothermal engineering. Scale prevention, monitoring and removal are necessary to counter excessive silica scaling in geothermal surface facilities and the reservoir. This study aims to characterize silica scales in terms of physical properties and chemical components. For this, the deposits are examined on the difference in density and porosity of silica scales formed in aging tank, canal and surface pipelines in the Otake and Tiwi geothermal fields, both of water-dominated system, as a measure to help in the mitigation process. Density has been found to not vary significantly across layers of the deposit for all samples. Average density of solid deposits from these two fields ranges from 2.15-2.20 g/cm^3. Apparent porosity, on the other hand, showed different 1rends in the result depending on the location of the sample in the surface facility. A homogenous porosity was observed for samples collected in surface pipelines. An increasing porosity was obtained for subaqueous solid deposits found near the aging tank. Similar trend in porosity was observed for samples obtained within the surface level of the aging tank. Iron and aluminum was detected in the sample but in very low composition compared to the amorphous silica that dominat.es the deposits