Geothermal Wastewater Research Articles

Wetland system for geothermal wastewater management

The SFS-Wetland model used is the wastewater treatment tank belonging to Pertamina Geothermal Lahendong. Based on the slope of the existing land, it is possible to design twin gravity wetlands of a certain size. This study aimed to develop a Surface Flow System Constructed Wetland design model using Monocaria vaginalis, Salvania molesta and Colocasia esculenta, analyze stakeholder perceptions of the SFS-Wetland Model, and refine this model based on stakeholder perceptions. Stakeholders' perception of the SFS-Wetland model based on a priority scale is that the geothermal waste management system is acceptable and accountable from an environmental perspective, waste management is socially and culturally acceptable, accountable and economically feasible. The components of the SFS-Wetland Model that must be improved are land availability, utilization of other local plant potentials, final geothermal wastewater temperature ranging from 33-35oC, ease of operation/maintenance, and low and environmentally friendly operational costs. The SFS-Wetland model suggested by stakeholders to improve is the existing SFS-Wetland model by taking into account the stakeholders' perceptions of the components that must be improved, namely the expansion of land for wetland ponds as much as 2x8 = 16 pool plots with a size of 35x60m = 33600 M2.

Geological and environmental implications of the utilisation of geothermal energy in the Lahendong working area, Indonesia

This study presents the characteristics of the Lahendong geothermal working area (GWA) in terms of the geological, geophysical, geochemical, and environmental implications. The investigated area is located in the Sulawesi North Arm, where the volcanic arc extends from Sangihe Island to Minahasa with two major strike-slip faults. NE–SW (northeast-southwest) trending faults control the thermal surface manifestation. The geothermal field is grouped into two hydrochemical systems: acid-sulphate-chloride (acid reservoir) and chloride (closer to neutral) types. The environmental implication analysis shows that the North Sulawesi province is experiencing water shortages due to excessive mining activities, inadequate wastewater management, and periods of drought. Although geothermal wastewater is being re-injected, the possibility of water contamination by hazardous materials from geothermal power plant activity is still evident. This study reviews the actual geothermal utilisation in the form of the 120 MWe power plant, the 500 kWe binary power plant, while the heat from geothermal energy is used for palm sugar production. Furthermore, the article also analyses the potential of the rational use of geothermal resources in this area. As a result of the high salinity and silica concentration of the brine, the geothermal wastewater should be treated before further utilisation and it potentially benefits both local communities and geothermal companies.

Innovative desalination of geothermal wastewater supported by electricity generated from low-enthalpy geothermal resources

The integration of renewable energy generation with water treatment techniques, based on geothermal water and energy resources, represents a new and interesting research direction. This paper presents a model study aimed at evaluating the twofold utilisation of geothermal water potential: as an energy resource necessary for the desalination process and as a source of wastewater used in the desalination process. The key objective of this work is to critically evaluate the feasibility of integrating electricity generation and technological processes based on membrane techniques solely on the basis of the potential of low-enthalpy geothermal waters. The results of the use of two steps of BWRO on a semi-production scale showed a high quality of permeate in accordance with physical, chemical, microbiological, potential organic and toxic substance contents and also its radiological characteristics. With respect to the feasibility of implementing the organic Rankine cycle or the Kalina cycle, an analysis was carried out that focused on using geothermal water extracted in the temperature range of 80–95 °C. The mass flow rate of geothermal water directed to the power plant was assumed to be in the range 10–150 kg/s. The mineral content of the geothermal water used in the model was 3 g/L.

Desalination of geothermal wastewaters by membrane processes: Strategies for environmentally friendly use of retentate streams

The paper presents the results of research on the desalination of geothermal wastewater for further environmentally friendly use of the concentrate streams obtained. Three geothermal waters previously used for heating purposes were desalinated. They are 1) lightly mineralised geothermal water (LM-GT), 2) moderately mineralised geothermal water (MM-GT) and 3) heavily-mineralised (HM-GT) geothermal water. The analysis is based on six technical experiments. The results indicated that geothermal wastewater desalination system can provide satisfactory fresh water which can be used for drinking or economic purposes. At the same time high-quality concentrate was obtained which can potentially be used for: 1) balneotherapy treatment – all concentrates; 2) drinking and inhalations – LM-GT; 3) therapeutic purposes – MM-GT. The raw MM-GT product can, for instance, also be considered as medicinal solution, like silica water, due to the high metasilicic acid content. Other concentrates analysed can also be recommended for the treatment of various diseases or cosmetic purposes based on their specific composition. The high boron concentration and elevated chromium content in MM-GT and HM-GT concentrates require additional treatment due to the requirements of some therapeutic instructions and this may limit the possibility of their use as base substance for cosmetic or therapeutic product.

Biodegradability and Adaptability Studies of Geothermal Wastewater in a Biological Treatment Plant

The purpose of this study was to identify the optimal conditions for the operation of biological treatment plant by carrying out biodegradability tests for geothermal wastewaters with high salt content. The biodegradation tests for geothermal wastewaters were carried out in a discontinuous flow bioreactor. The phases of the biodegradation process were: adaptation of the biological sludge, control of the biological treatment process, experiments in the laboratory bioreactors (BATCH). The results of the biodegradability tests revealed that geothermal waters with high salt content influence the treatment process. The dilution of these waters with domestic water up to chlorine concentrations below 800 mg L-1, makes the purification process to have a good biodegradation yields for CCO-Cr (about 75%) and CBO-5 (about 72%). If these geothermal wastewaters are not diluted to concentrations lower than 800 mg L-1, the biological sludge after 6 days is mineralized, which makes the use of biological treatment plant to be impossible.

Application of metallurgical slag to treat geothermal wastewater with high concentrations of arsenic and boron

The reuse of geothermal wastewater for irrigation is an attractive alternative for supplying water demand in agriculture, due to the high volumes generated in geothermal plants. This application is limited by the presence of toxic semimetals such as arsenic and boron, which generally require high-cost commercial adsorbents for removal. This work studies the removal mechanism and process optimization of arsenic and boron, present in high concentrations in synthetic solutions and in geothermal wastewater, using metallurgical slags. The effect of pH, initial concentration of arsenic and boron and slag dose were investigated using a 33 factorial experimental design and response surface method to optimize the operating conditions of the removal of pollutants. Scanning electron microscope analysis showed that the removal mechanism consisted in a dissolution–precipitation reaction rather than adsorption. The effluent produced from wastewater at the optimal operating conditions in a two-step process meets the criteria proposed for both metalloids by the US Environmental Protection Agency for water used for irrigation.

Injection-induced surface deformation and seismicity at the Hellisheidi geothermal field, Iceland

Induced seismicity is often associated with fluid injection but only rarely linked to surface deformation. At the Hellisheidi geothermal power plant in south-west Iceland we observe up to 2 cm of surface displacements during 2011–2012, indicating expansion of the crust. The displacements occurred at the same time as a strong increase in seismicity was detected and coincide with the initial phase of geothermal wastewater reinjection at Hellisheidi. Reinjection started on September 1, 2011 with a flow rate of around 500 kg/s. Micro-seismicity increased immediately in the area north of the injection sites, with the largest seismic events in the sequence being two M4 earthquakes on October 15, 2011. Semi-continuous GPS sites installed on October 15 and 17, and on November 2, 2011 reveal a transient signal which indicates that most of the deformation occurred in the first months after the start of the injection. The surface deformation is evident in ascending TerraSAR-X data covering June 2011 to May 2012 as well. We use an inverse modeling approach and simulate both the InSAR and GPS data to find the most plausible cause of the deformation signal, investigating how surface deformation, seismicity and fluid injection may be connected to each other. We argue that fluid injection caused an increase in pore pressure which resulted in increased seismicity and fault slip. Both pore pressure increase and fault slip contribute to the surface deformation.

Fluorimetric determination of nitrite in water using a novel fluorescent dye

A simple, sensitive and selective fluorimetric method for the determination of trace amounts of nitrite in different water samples (e.g., underground water, geothermal waste water, domestic waste water and drinking water) was proposed. The fluorimetric determination is based on the diazotization reaction of nitrite with a fluorescent dye, tetraamino zinc (II) phthalocyanine in an acidic medium. Under the optimum experimental conditions, nitrite can be determined in the range 10−6–10−4mol·L−1 with the detection limit 2.04×10−8mol·L−1. The proposed method has been successfully applied to the determination of nitrite in various water samples. The results compared favorably with the results from a standard isocertified method.

Assessment of stream water chemistry and impact of geothermal fluid in the up-Buyuk Menderes Basin, Turkey.

The discharge of geothermal fluid into the natural water environment may lead to serious damages. In this study, the impact of geothermal waste water on surface water has been investigated in the up-Buyuk Menderes River, Turkey. Thermal return water from district heating and from thermal bath in the Sandıklı region were the most important source of major solutes and trace elements to the up-Buyuk Menderes River and tributaries. The thermal contribution causes a drastic increase in Na, SO4 ions, EC, and temperature of surface waters. The concentrations of As, Al, B, Fe, Cr, Li, S, P, Pb, U, Mn, and Zn are increasing dramatically downstream of thermal water inputs in the Kufi Creek tributary. In addition to natural thermal water inputs, water quality was impacted by anthropogenic trace and major element inputs from surface waters. The increased of some trace elements (Al, As, B, Cu, Cd, Fe, Mn, P, U) in surface water are related to anthropogenic activities such as agricultural activities, sewage effluents, and stockyards in the study area. Additionally, surface water quality of the up-Buyuk Menderes River and tributaries was evaluated according to standards given by the Environmental Protection Agency of both Turkey and USA. Our study demonstrates the influence of thermal water inputs on water quality of surface waters.

Reinjection of cooled water into sandstone geothermal reservoirs in China: a review

Low injectivity of sandstone geothermal reservoirs during reinjection of geothermal waste water is a problem generally encountered in China, and has become a main obstacle for sustainable development of the geothermal resources. Over the last few decades, researchers have made much efforts to solve it based on the studies of reinjection schemes, hydrogeology of the reservoirs, well completion, reinjection water disposal techniques, and water-rock interactions focused on precipitation/dissolution reactions during reinjection. These studies have been very helpful in improving the injectivity. However, there are still many problems remaining for further investigations, among which characterization of the complete process of water-rock interactions during reinjection with the change in redox conditions, CO2 partial pressure, non-isothermal transport process of the reinjection water, and the mechanism of release, transport and sedimentation of colloidal particles on reservoir permeability being taken into account are considered to be the most necessary. This paper gives a brief review of the history and state of the art of the research works on reinjection of cooled water into sandstone geothermal reservoirs, and outlooks the research demands in water-rock interactions during reinjection in the future.

Natural attenuation of geothermal arsenic from Yangbajain power plant discharge in the Zangbo River, Tibet, China

The Yangbajain geothermal field located in central Tibet is characterized by the highest measured reservoir temperature among all hydrothermal systems in China. The high-temperature geothermal fluid extracted from Yangbajain has been used for electricity generation for over 30years. The geothermal wastewater generated by the Yangbajain power plants, with arsenic (As) concentrations up to 3.18mg/L, drains directly into the Zangbo River, the major surface water at Yangbajain, which has elevated arsenic concentrations in the segments downstream of wastewater discharges. However, along the flow direction of the river, the arsenic concentration decreases sharply. Further inspection reveals that the concentrations of weakly bound arsenic, strongly adsorbed arsenic and total arsenic in riverbed sediment were affected by the drainage of geothermal wastewater, indicating that the sediment serves as a sink for geothermal arsenic. A logarithmic relationship between the integrated attenuation coefficients (IAC) for three river segments and the corresponding adsorption distribution coefficients of riverbed sediment samples also suggests that besides the dilution of geothermal arsenic in the Zangbo River, natural attenuation of arsenic may be caused by sorption to riverbed sediment, thereby reducing its health threat to local residents using the Zangbo River as a drinking water source.

Geochemical behaviors of boron and its isotopes in aqueous environment of the Yangbajing and Yangyi geothermal fields, Tibet, China

Fifty-two samples including geothermal well water, hot spring water, cold groundwater and river water were collected from the Yangbajing and Yangyi geothermal fields to determine their boron concentrations and δ11B values. The results show that the concentrations of boron in the geothermal waters range from 38.5 to 165.4mg/L, much higher than those of cold groundwaters and river waters (0.3–0.7 and 0.1–3.9mg/L respectively). The δ11B values are between −11.4 and −12.3‰ for the Yangbajing geothermal waters and between −5.0 and −9.7‰ for the Yangyi geothermal waters, while those of the cold groundwaters are from −2.6 to −4.8‰. The δ11B values and B/Cl ratios indicate that boron in geothermal water is mainly leached from reservoir host rocks, whereas magma degassing is possibly another source of boron. Although the dissolution of tourmaline-rich granitic rocks is the primary factor controlling the boron concentrations and δ11B values of the Yangbajing and Yangyi geothermal waters, other secondary processes, e.g. CO2 degassing as well as subsequent pH increase and precipitation of carbonate minerals, also affect the boron isotope fractionation occurring in the reservoirs. In addition, the geothermal exploitation for electricity generation at Yangbajing had a significant impact on geothermal water chemistry, which may have relations to boron isotopic fractionation as well. For the Zangbo River flowing through the Yangbajing field, the boron isotopic geochemistry of river waters was significantly influenced by geothermal wastewater near its drainage exit. However, the recharge of the tributaries of the Zangbo River and the desorption of boron from river-bed sediments are major processes affecting the δ11B values of river waters at the far downstream of the drainage exit. The results of this study validate that boron and its isotopes can be used to trace the origin of geothermal water and to identify contamination induced by geothermal wastewater drainage.

Impact of Geothermal Wastewater Drainage on Arsenic Species in Environmental Media: A Case Study at the Yangbajing Geothermal Field, Tibet, China

The high temperature geothermal fluids from the Yangbajing geothermal field, Tibet, have been used for electricity generation. The geothermal wastewater generated by the Yangbajing power plants, with arsenic (As) concentrations up to 3.18mg/L, was drained immediately into the Zangbo River, which markedly increased the arsenic concentration of river water downstream from the wastewater discharges. However, along the flow direction of the river, arsenic concentrations in water declined sharply. Further inspection shows that the concentrations of weakly- bound As, strongly-adsorbed As, and total As in riverbed sediment were also affected by the drainage of geothermal wastewater, indicating that the sediment may serve as a sink for arsenic from the geothermal source. After arsenic from geothermal wastewater entered the Zangbo River, the adsorption of arsenic on riverbed sediment lowers the arsenic concentrations in the river water, reducing the health threat of arsenic to local residents using the river as a drinking water source.

Criterion for the discharge of geothermal waste water into surface water sources in Hungary

Hungary’s potential in geothermal energy is quite remarkable. In order to protect the quantity and the quality of the surface and sub-surface water sources and the soil as well it is important to find an environmental friendly way for the discharge of the geothermal waste water. If this problem is solved from an environmental and legal point of view, thermal water is going to be the most promising energy source of Hungary. The aim of this study was to work out a system of criteria, the fulfillment of which would allow the discharge of utilized thermal water.

Hydrogeochemistry of high-temperature geothermal systems in China: A review

As an important part of the Mediterranean-Himalayas geothermal belt, southern Tibet and western Yunnan are the regions of China where high-temperature hydrothermal systems are intensively distributed, of which Rehai, Yangbajing and Yangyi have been investigated systematically during the past several decades. Although much work has been undertaken at Rehai, Yangbajing and Yangyi to study the regional geology, hydrogeology, geothermal geology and geophysics, the emphasis of this review is on hydrogeochemical studies carried out in these geothermal fields. Understanding the geochemistry of geothermal fluids and their environmental impact is critical for sustainable exploitation of high-temperature hydrothermal resources in China. For comparison, the hydrogeochemistry of several similar high-temperature hydrothermal systems in other parts of the world are also included in this review. It has been confirmed by studies on Cl− and stable isotope geochemistry that magma degassing makes an important contribution to the geothermal fluids from Rehai, Yangbajing and Yangyi, though meteoric water is still the major source of recharge for these hydrothermal systems. However, the mechanisms of magma heat sources appear to be quite different in the three systems, as recorded by the 3He/4He ratios of escaping geothermal gases. A mantle-derived magma intrusion to shallow crust is present below Rehai, although the intruding magma has been heavily hybridized by crustal material. By contrast, the heat sources below Yangbajing and Yangyi are inferred to be remelted continental crust. Besides original sources, the geochemistry of characteristic constituents in the geothermal fluids have also been affected by temperature-dependent fluid–rock interactions, boiling and redox condition changes occurring in the upper part of hydrothermal systems, and mixing with cold near-surface waters. The geothermal fluids from Rehai, Yangbajing and Yangyi contain very high concentrations of some toxic elements. Since local drinking water sources may be mixed with geothermal water, and irrigation with water containing geothermally-derived harmful elements, possibly leading to accumulation in crops consumed by human beings, the natural geothermal spring discharge or anthropogenic geothermal wastewater drainage of these fields poses a threat to the environment and human health. Future research work should focus on estimation of stable O and H isotope compositions of magmatic water related to high-temperature hydrothermal systems in China, which is of significance for the quantitative source study of geothermal fluid recharged by degassed magmatic waters. Attention should also be paid to some constituent species in geothermal fluid of strong environmental significance, such as thioarsenate that is crucial for the fate of As discharged from geothermal springs, especially sulfidic hot springs.

The Comprehensive Test for Geothermal Tail-Water Disposal

Geothermal reservoirs and groundwater resources in layered porous media in large sedimentary basins have enormous exploitation potential because of their extensive distribution, great quantity, and feasible temperatures and drilling depths. The discharge of geothermal wastewater (i.e. tail-water) on the surface is a serious environmental issue because of its high salinity content, so the Bureau of Geology Exploration and Mineral Resources Exploitation in Shandong Province, China called for the study of the disposal technique of the geothermal tail-water. The disposal test process is as follows: take the waste of geothermal water to make physics-chemistry preparative disposal; filtration with manganese-sand set and/or double-medium equipment; filtration with ion exchange resins; nanofiltration membrane separation; and reverse osmosis separation. After separation, the cheap, clean water can be used as a material for chemical plants. However, in the case of deeply embedded geothermal groundwater resources, connate water(buried water), or bad recharge conditions, must be dried up for a long time exploitation, causing ground depression. Therefore, it is concluded that systems utilizing reinjection, i.e. closed-circuit cycle mode injection, in sandstone reservoirs are ideal for the realization of sustainable exploitation of the geothermal groundwater resources with favorable environmental conditions on the surface.

The geochemistry and sequestration of H 2S into the geothermal system at Hellisheidi, Iceland

The geochemistry and mineralization of H 2S in the geothermal system hosted by basaltic rock formation at Hellisheidi, SW Iceland, was studied. Injection of mixtures of H 2S with geothermal waste water and condensed steam into the > 230 °C geothermal aquifer is planned, where H 2S will hopefully be removed in the form of sulphides. The natural H 2S concentrations in the aquifer average 130 ppm. They are considered to be controlled by close approach to equilibrium with pyrite, pyrrhotite, prehnite and epidote. Injection of H 2S will increase significantly the reservoir H 2S equilibrium concentrations, resulting in mineralization of pyrite and possibly other sulphides as well as affecting the formation of prehnite and epidote. Based on reaction path modelling, the main factors affecting the H 2S mineralization capacity are related to the mobility and oxidation state of iron. At temperatures above 250 °C the pyrite mineralization is greatly reduced upon epidote formation leading to the much greater basalt dissolution needed to sequestrate the H 2S. Based on these findings, the optimum conditions for H 2S injection are aquifers with temperatures below ~ 250 °C where epidote formation is insignificant. Moreover, the results suggest that sequestration of H 2S into the geothermal system is feasible. The total flux of H 2S from the Hellisheidi power plant is 12,950 tonnes yr − 1 . Injection into 250 °C aquifers would result in dissolution of ~ 1000 tonnes yr − 1 of basalt for mineralization of H 2S as pyrite, corresponding to ~ 320 m 3 yr − 1 .

Trace Element Hydrochemistry Indicating Water Contamination in and Around the Yangbajing Geothermal Field, Tibet, China

Thirty-eight water samples were collected at Yangbajing to investigate the water contamination resulting from natural geothermal water discharge and anthropogenic geothermal wastewater drainage. The results indicate that snow or snow melting waters, Yangbajing River waters and cold groundwaters are free from geothermal water-related contamination, whereas Zangbo river waters are contaminated by geothermal wastewaters. Moreover, there may exist geothermal springs under the riverbed of a tributary stream of Zangbo River as shown by its Cd, Li, Mo and Pb concentrations. The efforts made in this study show trace element hydrochemistry can well indicate water quality degradation related to geothermal water exploitation.

Effects on Environment and Agriculture of Geothermal Wastewater and Boron Pollution in Great Menderes Basin

Boron toxicity is an important disorder that can be limit plant growth on soils of arid and semi arid environments through the world. High concentrations of Boron may occur naturally in the soil or in groundwater, or be added to the soil from mining, fertilizers, or irrigation water. Off all the potential resources, irrigation water is the most important contributor to high levels of soil boron, boron is often found in high concentrations in association with saline soil and saline well water. Although of considerable agronomic importance, our understanding of Boron toxicity is rather fragment and limited. In this study, Boron content of Great Menderes River and Basin was researched. Great Menderes Basin is one of the consequence basins having agricultural potential, aspect of water and soil resources in Turkey. Great Menderes River, water resource of the basin was to be polluted by geothermal wastewater and thermal springs including Boron element. Great Menderes Basin has abundant geothermal water resources which contain high amounts of Boron and these ground water are brought to surface and used for various purposes such as power generation, heating or thermal spring and than discharged to Great Menderes River. In order to prevent Boron pollution and hence unproductively in soils, it is necessary not to discharged water with Boron to irrigation water. According to results, it was obtained that Boron content of River was as high in particular Upper Basin where there was a ground thermal water reservoir. Boron has been accumulated more than plant requirement in this area irrigated by this water. Boron content of River was relatively low in rainy months and irrigation season while it was high in dry season. Boron concentration in the River was to decrease from upstream to downstream. If it is no taken measure presently, about 130,000 ha irrigation areas which was constructed irrigation scheme in the Great Menderes basin will expose the Boron pollution and salinity. Even though Boron concentration of river water is under 0.5 ppm limit value, Boron element will store in basin soils, decrease in crop yields, and occur problematic soils in basin.

Responses of Shortfin Eel (Anguilla Australis) Exposed In Situ to Pulp and Paper Effluent

The responses of shortfin eel (Anguilla australis) to discharges from two pulp and paper mills, municipal wastewater, and a geothermal power plant wastewater were examined. Eels were caged at 3 sites along the Tarawera River, North Island, New Zealand, to explore effects of a 3-wk exposure down a contamination gradient (Ref → D1 → D2). Most of the observed effects were seen in eels caged at the furthest downstream site (D2), below all the discharge areas. General hematology in eels was unaffected, as measures did not differ markedly at the two downstream sites compared with the reference site. At D2, eels were significantly lighter per unit length (reduced condition factor), although liver and spleen size (LSI and SSI) were unaffected. Significantly elevated circulating sex steroid concentrations (testosterone and estradiol) were measured in D2 eels and increasing sex steroid levels at both sites downstream of the reference site were observed. Significant ethoxyresorufin O-deethylase (EROD) activity induction was seen in D2 eels and bile chemistry showed significant accumulation of pyrene and retene equivalents. However, significantly greater concentrations of total resin acids were found in the bile of eels from the intermediate site (D1), between the two pulp and paper mills. The higher polycyclic aromatic hydrocarbon (PAH) equivalents found in the bile of D2 eels suggest that resin acid neutrals, particularly retene, are responsible for some of the effects observed in eels at the furthest downstream exposure site. Levels of pulp and paper mill extractives in sediment, including the PAH retene, support this conclusion.