Deep-well Injection Research Articles

A comprehensive assessment of the economic and technical viability of a zero liquid discharge (ZLD) hybrid desalination system for water and salt recovery

Brine, a by-product of desalination and industrial facilities, is becoming more and more of an environmental issue. This comprehensive techno-economic assessment (TEA), focusing on the technical and economic aspects, investigates the performance and viability of a novel hybrid desalination brine treatment system known as zero liquid discharge (ZLD). Notably, this research represents the first instance of evaluating the feasibility and effectiveness of integrating three distinct desalination processes, namely brine concentrator (BC), high-pressure reverse osmosis (HPRO), and membrane-promoted crystallization (MPC), within a ZLD framework. The findings of this study demonstrate an exceptional water recovery rate of 97.04%, while the energy requirements stand at a reasonable level of 17.53 kWh/m3. Financially, the ZLD system proves to be at least 3.28 times more cost-effective than conventional evaporation ponds and offers comparable cost efficiency to alternatives such as land application and deep-well injection. Moreover, the ZLD system exhibits profitability potential by marketing both drinking water and solid salt or solely desalinated water. The daily profit from the sale of generated water varies from US$194.08 to US$281.41, with Greece and Cyprus attaining the lowest and highest profit, respectively. When considering the sale of both salt and water, the profit rises by 8% across all locations.

Concentrate circularity: A comparative techno-economic analysis of membrane distillation and conventional inland concentrate management technologies

Inland desalination with reverse osmosis (RO) offers a promising alternative to increase potable water resources. However, large volumes of concentrated brine are generated as a byproduct of the process. Concentrate disposal for inland regions displaces valuable water resources and can make up to 33 % of the total cost of desalination. Conventional disposal systems are limited by location, hydrogeology, climate, and policies, and few place value on resource recovery, thus limiting the implementation of desalination facilities in water-stressed regions. Membrane distillation (MD) is an alternative technology that can minimize disposal volume while maximizing water recovery for beneficial reuse. MD uses thermal energy gradients to desalinate the concentrate stream achieving near zero-liquid discharge. Furthermore, several MD configurations include heat recovery, making MD an energy-efficient alternative. A techno-economic assessment (TEA) of air-gap MD (AGMD) for RO concentrate management was performed and compared to three conventional concentrate management systems: evaporation ponds, deep-well injection (DWI), and concentration-crystallization. TEA results indicate that compared to DWI at 1.09 $/m3, evaporation ponds at 1.47 $/m3, and concentrators at 6.2 $/m3, respectively, AGMD is a competitive concentrate management technology producing water at 0.90 $/m3 when operating conditions are optimized and low-grade heat is available. When operating at high salinity (>70 g/L) the selection of operating conditions, specifically module length and circulating flowrate, is critical. Results of this study support the economic viability of AGMD in contrast to current industry standards and highlight the importance of resource recovery to promote a circular water-energy economy for regions relying on reuse and desalination.

Numerical modeling of geological sequestration of brine wastewater due to coal mining in the Ordos Basin, China

The coal resources play an indispensable role in the development of heavy industry in China, and coal mining activity leads to brine wastewater drainage, causing major risks for the aquatic environmental system. Thus, the effective and economic treatment of coal mine wastewater is vital to mitigate the environmental burdens, and geological sequestration by deep-well injection is a promising treatment technique. This study elucidates the physical and geochemical processes of coal mine wastewater transport in deep reservoirs and proposes an optimized injection scheme to satisfy environmental and economic benefits simultaneously in the Ordos Basin, China. First, a variable density and variable parameter groundwater reactive transport model is constructed to simulate the long-term process of deep-well injection for coal mine wastewater treatment. Then, the environmental metrics, i.e., the percentage of permeability reduction, the total mass and spatial second moment of the wastewater plume, and the economic metric defined as achieving a higher concentration at a higher injection rate are proposed to evaluate the performance of the injection scheme. The simulation results show that the secondary mineral anhydrite dominates the reduction of reservoir permeability due to the precipitation reactions with SO42− in the brine wastewater, and the permeability in the reaction zone decreases by 0.66 % ~ 1.26 % after 10 years in the basic scenario. Moreover, higher concentrations negatively affect reservoir permeability and increase total dissolved solids, while higher injection rates decrease reservoir permeability and increase the brine wastewater plume. The study also identifies promising schemes that can achieve an optimal trade-off between the conflicting metrics. Based on the economic and environmental benefits demanded in this study, an injection scenario with a concentration of C4 and an injection volume of 800 m3/d is recommended to maximize environmental benefits. Overall, this numerical study offers significant implications for designing an economically and environmentally sustainable treatment injection scheme for coal mining wastewater drainage.

Building an EPA Class VI Permit Application

Summary To accelerate the commercialization of carbon capture and storage (CCS), the US Department of Energy (US DOE) is building on decades of characterization efforts and pilot-scale projects through their CarbonSAFE program. Administered through their National Energy Technology Laboratory, this program seeks to bring fully integrated projects to the sector that can store more than 50 million tonnes of CO2 over a 30-year period. The program, which was enacted before the enhancement of Internal Revenue Code Section 45Q, is in the capture assessment, characterization, and permitting phase. The objectives of this paper are to discuss (a) the injection permitting requirements of the CarbonSAFE projects; (b) information gathering in support of the permit; (c) the timelines of field development and permit-related activities; (d) the major technical components of the field development plan; and (e) early feedback from the regulators toward acceptance of the permit. In Mississippi, more than 30,000 acres have been characterized by six deep characterization wells, a deep groundwater well, and 92 line miles of 2D seismic as part of the CarbonSAFE Project ECO2S. During the acquisition of seismic data, all receiver lines were live, which resulted in the generation of a pseudo-3D seismic design. The incorporation of a 3D seismic survey was not included as part of this project due to logistical difficulties presented by the undulating, wooded surface terrain. A suite of openhole geophysical logs was taken from each well, allowing for a detailed interpretation of prospective storage reservoirs and confining intervals to complement the analysis carried out on the 290 ft of a whole core that was cut through the prospective confining zone and storage reservoir. The detailed geologic and reservoir data were assembled and entered into a 3D model to assess the injection capacity and the area of review (AoR). This information fed into the detailed corrective action, monitoring, testing, and postinjection site care (PISC) modeling. The results have been exceptional. The geologic assessment has revealed three primary storage targets, ranging in depth from 3,500 ft to 6,000 ft. These storage reservoirs net 1,300 ft of sandstone, with mean porosity and permeability of 29% and 3.6 darcies, respectively. Together, these reservoirs have storage capacities that may exceed 20 million tonnes per square mile, making this a gigatonne prospect. Forward modeling of the project resulted in an AoR of 16 sq miles, injecting about 8000 t/d, for 30 years, via two deep injection wells. The excellent confining characteristics of the caprock, relatively simple geologic structure, and lack of historical well drilling activity in this area provide excellent containment of the injected CO2. Based on this work, the project has proposed 20 years of PISC. To date, only two US CO2 injection permits have been granted. These projects relied on a singular capture point feeding a singular sequestration point (source to sink), and considerations have not been made to garner CO2 emissions from other industrial sources. The Kemper County Storage Complex is a first-of-its-kind storage hub concept that looks to develop an area capable of storing significant quantities of CO2 from the region. Also, this work will show how characterization efforts, geological and numerical modeling efforts, and plan development were constructed in support of permit and incentives acceptance.

Characterization of Reverse Osmosis Reject Wastewater Generated from Sulaibiya Wastewater Treatment Plant

Sulaibiya Wastewater Treatment Plant (Kuwait) is considered as one of the largest wastewater treatment plants that use Reverse Osmosis (RO) membranes in their processes to reclaim water from municipal wastewaters for indirect potable water reuse. This result in considerable wastewater treatment brine which needs to be further investigated before discharge. Samples were collected on daily basis from the RO reject wastewater (brine wastewater) for one month and analyzed in situ and in the laboratory. The results obtained showed that the brine wastewater met the requirements of the Kuwait Environment Public Authority with the exception of biochemical oxygen demand, total dissolved solids, and total phosphate. In Kuwait, the brine wastewater is either used for deep-well injection or is discharged to the seawater. Based on the monitoring results, potential reuse options of wastewater brine include surface water discharge, sewer disposal, deep-well injection, and land application. Treatment options via evaporation ponds using membrane filters will further enhance the quality of the brine wastewater.

Safety and Technical Feasibility of Sustainable Reuse of Shale Gas Flowback and Produced Water after Advanced Treatment Aimed at Wheat Irrigation

Treatment and reuse of flowback and produced water (FPW) from shale gas extraction for agricultural irrigation has often been proposed as a sustainable alternative to disposal via deep-well injection. Here, we investigate the effects of FPW on the germination period, macroscopic growth, element enrichment, and grain gene expression of wheat upon dilution and advanced membrane treatment of the liquid stream. Compared to tap water, irrigation with treated FPW shortened the germination time, slightly improved the seed vigor index, and ensured a similar germination rate. On the other hand, the biomass and grain yield of mature wheat irrigated with treated FPW and with FPW diluted to 5% groups decreased compared to tests using tap water. After a whole growth cycle of wheat, higher concentrations of nutrients, such as K, Ca, and Mg were enriched in mature wheat tissue irrigated with treated FPW. However, the Pb and Cr contents of mature wheat grains treated with three types of irrigation waters exceeded the standard to varying degrees. A total of 1973 differentially expressed genes were mainly related to binding, catalytic activity, cellular process, metabolic process, and cell part, more than half of which were upregulated and induced by irrigation with treated FPW. These findings provide critical guidance for the reuse of treated shale gas FPW for agricultural application from the perspective of plant uptake of toxic elements, as well as crop and human health risks.

Techno-economic assessment and feasibility study of a zero liquid discharge (ZLD) desalination hybrid system in the Eastern Mediterranean

The environmental consequences of brine disposal (i.e., marine pollution, soil salinization, and groundwater contamination) are a concern for desalination plants across the world. This techno-economic assessment and feasibility study explores for the first time both the performance and the feasibility of a zero liquid discharge (ZLD) desalination hybrid system for brine treatment and valorization in Eastern Mediterranean countries, namely, Greece, Cyprus, and Israel. The results revealed that the recovery rate (99.19%) is exceptional, while the energy demands are 20.23 kWh/m3, which is reasonable as three different desalination processes (namely, high-pressure reverse osmosis (HPRO), brine concentrator (BC), and brine crystallizer (BCr)) are integrated into the ZLD system. The ZLD system is at least 3.22 times less costly than evaporation ponds, and it is on par with deep-well injection and land application alternatives in terms of cost. Furthermore, the ZLD system is lucrative whether it markets only water or both water and solid salt. The profit gain from desalinated water sales ranges from US$196.36/day to US$285.63/day, with Cyprus and Greece having the highest and lowest profit gain, respectively. In respect of both desalinated water and salt sales, the profit gain increases by 7% for each location.

Deep Well Injection Induced Seismicity

Injection of fluid into subsurface geologic strata for geothermal energy, oil production, and waste disposal has been linked to induced seismic activity in the United States as well as in several other countries. According to the report of the National Research Council of United States of America thousands of induced earthquakes were reported at the numerous sites, where oil and gas recovery and waste disposal activities took place. Most of these induced earthquakes were small magnitude events (Moment Magnitude [Mw] < 4), although earthquakes of magnitude (Mw) 6.5 to 7 were also reported near the oil and gas production sites. This paper presents the results of a review of case histories on increased seismic events due to deep well injection (DWI) and oil extraction. Key factors that may lead or contribute to increased seismicity will also be discussed.

Flood Mitigation in Urban Areas through Deep Aquifer Recharge: The Case of the Metropolitan Area of Guadalajara.

The Metropolitan Area of Guadalajara (MAG) experiences water shortage and overexploitation of aquifers. In addition, it suffers from seasonal flooding that is channeled towards inadequate sanitary drainage, creating a strong negative environmental impact. These problems are rooted in the waterproofing of the urban surface. Many cities around the world have used deep injection wells to recover aquifers and remove surface waters. Certain geohydrological conditions are required for the implementation of these deep injection wells, deeper than 30 m, such as significant surface runoff, acceptable water quality for infiltration, considerable depth in the phreatic levels, and good subsoil permeability. All of these conditions exist in the MAG or could be achieved without significant investment. An assessment is presented exploring the viability for a solution based on this technology, as a strategy to recover aquifers and reduce flooding. The first step was to identify, through map algebra, a micro-basin suitable for this technology. Then, mean runoff volumes were obtained and a stratigraphic profile was carried out based on 19 standard penetration tests (SPT). With these data, a numerical simulation of deep injection wells of different dimensions was performed, providing recommendations for a solution based on these calculations. The results show that both problems can be solved with this relatively simple and cheap technology supporting public health.

Deep well injection for the waste brine disposal solution of potash mining in Northeastern Thailand

Under the pressure of the existing world population growth trends, the dercreasing pastoral fields and the increasing duration and incidences of drought and heat stress, the potash fertilizers demand dramaticly increase to enhance the world food production. Asia currently consumes 40% of the world's potash market, yet 70% of world potash exports come from mines in Canada and Europe. Weak collective efforts to produce potassium fertilizers economically pose the risk of global shortages of potash goods and threatening global food security. While the Khorat Plateau in Northeastern Thailand is noted to contain active and promising regional potash deposits, developing a proper potash industry in the region has largely been unsuccessful due to major constraints such as the challenge of establishing a brine disposal solution. This study demonstrates the performance of deep well injection (DWI) as an environmentally friendly alternative to secure waste brine production from the potash mine. The groundwater numerical model demonstrates the movement and penetration of the concentrate during and after deep well injection. The boundary condition was utilized from the regional hydrogeology data. The waste brine injection is based on the waste products of the mine factory. Our simulation shows that the DWI can isolate waste brine with freshwater by injecting it into the deep formation based on the geologic structure and properties analysis. With high porosity and low specific yield, the Khok Kruat formation within Khrat Basin shows a high potential injection rate of 200,000 m3/day, which is 200 times higher than current water brine production rates. Moreover, the salinity can easily dissolve into the target domain with specific formation properties. Hence, the DWI not only boosts the potash industry's image in the long term but also enable sustainable potash mining development in the region. Finally, we recommend that government agencies with regulatory oversight over the DWI must promote further research associated with site characterization, well construction and injection technologies, and monitoring tools in the long term.

Mitigating membrane wetting in the treatment of unconventional oil and gas wastewater by membrane distillation: A comparison of pretreatment with omniphobic membrane

The treatment of unconventional oil and gas (UOG) wastewater by membrane distillation (MD) is a promising alternative to disposal via deep-well injection for UOG wastewater management. However, MD has been constrained by membrane pore wetting, which could be induced by surfactants that are commonly used in hydraulic fracturing fluids. Herein, we investigated and compared two strategies, namely pretreatment via coagulation-adsorption and the use of omniphobic membranes, for wetting mitigation in MD treatment of UOG wastewater from the Denver-Julesburg Basin, Colorado. Both strategies were able to mitigate membrane wetting, but pretreatment exhibited better treatment efficiency than the use of omniphobic membranes that was subject to significant membrane fouling. Membrane characterization using scanning electron microscopy, energy dispersive X-ray spectroscopy, and attenuated total reflectance-Fourier transform infrared spectroscopy demonstrated the effective reduction of membrane fouling and scaling after pretreatment. Further, ultrahigh pressure liquid chromatography (UHPLC) coupled with quadrupole time-of-flight mass spectrometry (LC/QToF/MS) was performed to investigate the efficacy of pretreatment in removing surfactants. Pretreatment was found to be highly efficient at removing polyethylene glycol (PEG) and polypropylene glycol (PPG) surfactant classes, which were likely responsible for membrane wetting. Our findings suggest that pretreatment could have comparable or even better effectiveness than omniphobic membranes for improving MD treatment of UOG wastewater with high wetting potential. Comparative investigations on these two wetting mitigation strategies are valuable for rational selection of appropriate strategies to promote practical applications of MD to industrial wastewater treatment. • Membrane wetting occurs in MD treatment of UOG wastewater. • Pretreatment and omniphobic membranes as wetting mitigation strategies. • Pretreatment outperforms omniphobic membranes. • Key surfactant classes removed by pretreatment are identified.

Effects of groundwater abstraction and desalination brine deep injection on a coastal aquifer

As a result of climate change, population increase and improvement of living standards, the water demand is annually growing drawing worldwide attention on seawater desalination to face water crisis. The total global desalination capacity is dominated by Reverse Osmosis (RO) and, often, this desalination process is fed with the brackish water extracted from coastal aquifers. After this process the desalted freshwater is obtained at a recovery factor of ca. 50%, while concentrate byproduct, named brine, is disposed back to coastal aquifers, seas, oceans or evaporative ponds, determining detrimental effects on the surrounding environment. A common approach to clean out the brine is the deep-well injection into coastal aquifers, exacerbating the seawater intrusion. The ultimate result is a reduction of the available water both in terms quantity and quality hampering the benefits of the desalination.The aim of this study is to investigate the effects of brine water injection in the Nile coastal aquifer, one of the largest underground freshwater reservoirs in the world, and to find a way to minimize and manage the environmental impact of the RO process. In order to simulate the effects of the brackish water extraction and the brine deep-injection on the Nile coastal aquifer, a combined seawater intrusion, numerical models for flow and salt transport model in aquifers and the solution-diffusion in RO practices were implemented. Different management scenarios were considered and their consequences on salt mass storage in the Nile coastal aquifer evaluated.According to the numerical results, the salinization of the coastal aquifer can be mitigated by reducing the concentration of the water feeding the reverse osmosis plant, i.e., mixing the extracted brackish water with a lower salinity water. Besides, low feed salinity leads to significant gains by decreasing the specific energy consumption of the desalination process.

Energetic, economic and environmental assessment of zero liquid discharge (ZLD) brackish water and seawater desalination systems

The discharge of brine (saline wastewater) from brackish water and seawater desalination plants poses a major threat to the natural environment. This research study presents an energetic, economic and environmental assessment of zero liquid discharge (ZLD) desalination systems in the Eastern Mediterranean. Two scenarios are considered: (i) ZLD brackish water and (ii) ZLD seawater systems, both aimed at producing saleable freshwater and mixed solid salt. Results showed that the energy consumption in scenario 1 (9.48 kWh/m3) is 2.38 times lower than in scenario 2 (22.55 kWh/m3) due to the 7 times lower feed salinity. The differentiation in energy demands is also translated to costs since scenario 2 (US$1.04/m3) is 1.24 times more expensive than scenario 1 (US$0.84/m3). Both scenarios are 3.18 times cheaper than the disposal method of the evaporation pond, while they are in the same cost range as the land application and deep-well injection. Whether only freshwater is sold or both freshwater and mixed solid salt are sold, both scenarios are profitable as the profit ranges from US$215.05/day to US$302.55/day. Concerning CO2 emissions, scenario 1 (5.91–6.45 kg CO2/m3) has lower values than scenario 2 (14.05–15.33 kg CO2/m3) as the energy demanded in scenario 1 is significantly lower.

Geologic characterization of nonconformities using outcrop and core analogs: hydrologic implications for injection-induced seismicity

Abstract. The occurrence of induced earthquakes in crystalline rocks kilometers from deep wastewater injection wells poses questions about the influence nonconformity contacts have on the downward and lateral transmission of pore-fluid pressure and poroelastic stresses. We hypothesize that structural and mineralogical heterogeneities at the sedimentary–crystalline rock nonconformity control the degree to which fluids, fluid pressure, and associated poroelastic stresses are transmitted over long distances across and along the nonconformity boundary. We examined the spatial distribution of physical and chemical heterogeneities in outcrops and core samples of the Great Unconformity in the midcontinent of the United States, capturing a range of tectonic settings and rock properties that we use to characterize the degree of past fluid communication and the potential for future communication. We identify three end-member nonconformity types that represent a range of properties that will influence direct fluid pressure transmission and poroelastic responses far from the injection site. These nonconformity types vary depending on whether the contact is sharp and minimally altered (Type 0), dominated by phyllosilicates (Type I), or secondary non-phyllosilicate mineralization (Type II). Our observations provide geologic constraints for modeling fluid migration and the associated pressure communication and poroelastic effects at large-scale disposal projects by providing relevant subsurface properties and much needed data regarding common alteration minerals that may interact readily with brines or reactive fluids.

Repurposing Reverse Osmosis Concentrate as a Low-Cost Thermal Energy Storage Medium

The reject of the reverse osmosis water treatment process (aka brine, concentrate, ROC) is a mixture of salts that are dissolved in high salinity water. The ROC is classified as an industrial waste by the U.S. Environmental Protection Agency and can face regulatory limitations on disposal. State-of-the-art of ROC disposal includes deep-well injection, surface discharge to rivers, discharge to the ocean, and evaporation ponds. In this study, the feasibility of using Reverse Osmosis Concentrate as a low-cost Thermal Energy Storage (TES) medium is explored by a techno-economic analysis. The normalized cost of TES (cost per unit volume of stored thermal energy) is estimated through a series of cost analyses and is compared to the cost targets of the U.S. Department of Energy for low-cost thermal energy storage. It was shown that the normalized cost of TES using ROC salt content is in the range of $6.11 to $8.73 depending on ROC processing methods.

Increasing net water recovery of reverse osmosis with membrane distillation using natural thermal differentials between brine and co-located water sources: Impacts at large reclamation facilities

Maximizing water recovery and minimizing the volume of RO concentrate (i.e., brine) produced is a growing challenge, especially for inland communities that lack ocean disposal options. In such regions, transitioning towards zero liquid discharge (ZLD) can avoid detrimental impacts associated with salt disposal via regional sewer discharge or deep-well injection. On-site ZLD energy requirements are proportional to the RO brine flowrate. Thus, system-level strategies that reduce RO brine flows will lower ZLD costs while simultaneously increasing the overall water recovery for beneficial reuse in reclamation facilities. We investigated a membrane distillation (MD) system operating using co-located, cooler source water to treat warmer wastewater RO brine. Using experimentally-quantified MD fluxes based on observed monthly water temperatures of co-located water and RO brine at a facility in central Arizona, and based on the previously reported performance of large-scale MD systems, energy consumption and operating cost were estimated to evaluate the potential capabilities of MD to treat RO brine at full scale facilities. When the RO unit was combined with MD brine treatment, net water recovery at the full-scale facility can increase from 85% to up to 91% while brine flow can be reduced by 26%. A 25% lower thermal energy was required to achieve RO net water recovery of 95% when using co-located water, compared against conventional MD without using co-located water. Overall, this work demonstrates the potential to use local thermal gradients to reduce RO brine volumes, thereby reducing ZLD costs.

Excavation based enhanced geothermal system (EGS-E): introduction to a new concept

The current technology for enhanced geothermal system (EGS) typically involves drilling of deep injection and production wells to inject cold water into the injection well to the EGS reservoir depth, to extract heat by permeating through the fractured hot rock masses, collected by the production well and return to the surface as heated water. In this article, a new approach is proposed to develop EGS based excavation technology (EGS-E). This method consists of (1) excavation to deep rocks, including a deep shaft from surface to the EGS depth, a room-and-pillar mined cavern complex to be filled with water to become a large underground heated water reservoir in the hot rocks; (2) enhanced heat extraction from rock, aided by additional drillholes spreading out and down from the caverns, and induced fracturing of the surrounding rocks for enhanced rock–water heat transfer; (3) enclosed heat transmission from heated water reservoir to the power plant by using independent heat conducting pipes running between them, continuously supplying the heat for power generation, without water movement in the reservoir. EGS-E offers the following advantages: (1) utilizing mechanized rock excavation technology for large volume energy production; (2) greatly increasing heat extraction volume by easily extending vertically and horizontally; (3) maximize the energy transfer from hot rock to the water reservoir; and (4) separated heat transmission from heated water reservoir in EGS to power plant to minimize environmental pollution.

Desalination brine disposal methods and treatment technologies - A review.

Brine, also known as concentrate, is the by-product of the desalination process that has an adverse impact on the environment due to its high salinity. Hence, viable and cost-effective brine management systems are needed to reduce environmental pollution. Currently, various disposal methods have been practiced, including surface water discharge, sewer discharge, deep-well injection, evaporation ponds and land application. However, these brine disposal methods are unsustainable and restricted by high capital costs and non-universal application. Nowadays, brine treatment is considered one of the most promising alternatives to brine disposal, since treatment results in the reduction of environmental pollution, minimization of waste volume and production of freshwater with high recovery. This review article evaluates current practices in brine management, including disposal methods and treatment technologies. Based upon the side-by-side comparison of technologies, a brine treatment technology framework is introduced to outline the Zero Liquid Discharge (ZLD) approach through high freshwater recovery and wastewater volume minimization. Furthermore, an overview of brine characteristics and its sources, as well as its negative impact on the environment is discussed. Finally, the paper highlights future research areas for brine treatment technologies aiming to enhance the effectiveness and viability of desalination.

Characterization of Biofilms and Mineralogical Scale in Underground Injection Well Disposal of Landfill Leachate and Industrial Wastewater Streams

Deep-well injection is a cost-effective alternative for industrial wastewater disposal, given the appropriate geology. Fouling of injection well tubing by biofilm or scale is common and reduces the effective diameter of the pipe, which results in increased wellhead pressure and lower injectivity. A detailed microbiological composition of biofilms and abiotic fingerprints use of mineral scale from an injection well has not been reported before. Therefore, biofilm and mineral scale samples from three depth intervals within a deep injection well (surface zone, D1= 0 - 61 m; intermediate zone, D2 = 62 - 457 m; and above the injection zone, D3 = 458 - 884 m) with recurrent biofilm development were collected to characterize the mineral composition and microbial community DNA. X-ray diffraction (XRD) analysis of the solids confirms the composition of the solids collected was mostly calcium carbonate (CaCO3) with minor contributions from common mineral salts. Microbiological fingerprinting suggests that methanogenic archaea and sulfate-reducing bacteria both of which are anaerobic biofilm producers were the most prevalent members of the prokaryotic community at all sampled depths. Methanosarcinae spp. increased with increasing depths, unlike other archaea. A non-pathogenic biofilm-producing Entamoeba dispar was the most prevalent member of the microbial domain (>30%) in all samples but was highest at the middle depth. The Chao alpha diversity indices for bacteria, viruses, and protozoans were highest at the shallow depth and gradually declined with increasing depth. The prevalent species above the injection zone depth are not barophilic organisms that thrive at high pressures, rather they are sulfate-reducing bacteria involved in anaerobic dissimilatory sulfate metabolism.

Deoxygenation Prevents Arsenic Mobilization during Deepwell Injection into Sulfide-Bearing Aquifers.

Coal seam gas (CSG) extraction generates large volumes of coproduced water. Injection of the excess water into deep aquifers is often the most sustainable management option. However, such injection risks undesired sediment-water interactions that mobilize metal(loid)s in the receiving aquifer. This risk can be mitigated through pretreatment of the injectant. Here, we conducted a sequence of three push-pull tests (PPTs) where the injectant was pretreated using acid amendment and/or deoxygenation to identify the processes controlling the fate of metal(loid)s and to understand the treatment requirements for large-scale CSG water injection. The injection and recovery cycles were closely monitored, followed by analysis of the observations through reactive transport modeling. While arsenic was mobilized in all three PPTs, significantly lower arsenic concentrations were observed in the recovered water when the injectant was deoxygenated, regardless of pH adjustment. The breakthrough of arsenic was commensurate with molybdenum, but distinct from phosphate. This allowed for the observed and modeled arsenic and molybdenum mobilization to be attributed to a stoichiometric codissolution process during pyrite oxidation, whereas phosphate mobility was governed by sorption. Understanding the nature of these hydrochemical processes explained the greater efficiency of pretreatment by deoxygenation on minimizing metal(loid) mobilization compared to the acid amendment.