Total Dissolved Solids Concentration Research Articles

Relative contributions of organic and inorganic fouling during nanofiltration of inland brackish surface water

Bench-scale nanofiltration (NF) experiments were performed with two commercially available membranes having different ion rejection characteristics to assess dominant fouling mechanisms during inland brackish surface water desalination and the role of rejection on flux decline. The Foss Reservoir in the state of Oklahoma, USA was used as a representative natural brackish surface water source in these experiments. Both nanofilters rejected divalent cations to a very high extent (Mg>94% and Ca>92%) but exhibited substantially different rejections of monovalent cations (e.g. Na removals of 60% and 97%). A model solution formulated to have a similar ionic composition as the natural water but with no added natural organic matter (NOM) was also employed to isolate mineral scaling effects. The low monovalent ion rejecting membrane was predominantly fouled by NOM with only limited contributions from calcium carbonate scaling. In contrast, electron microscopy along with infrared and X-ray photoelectron spectroscopy revealed that both NOM and gypsum were major foulants for the membrane that highly rejected both mono- and divalent ions. The exacerbated flux decline for the more salt-rejecting nanofilter was attributed to the synergistic effects of NOM and gypsum on fouling coupled with the formation of a very compact organic foulant layer due to greater extent of Ca-NOM interactions and the higher ionic strength of the concentration polarization layer. These results demonstrate that the relative contributions of NOM and mineral scaling to flux decline during brackish surface water NF depends on membrane ion rejection characteristics. Hence, optimal membrane selection needs to balance total dissolved solids concentration of the product water with the need to minimize fouling.

Capacitive deionization (CDI) integrated with monovalent cation selective membrane for producing divalent cation-rich solution

In this study, a newly developed capacitive deionization (MCDI) integrated with a monovalent cation permselective exchange membrane was evaluated for selective removal of monovalent and divalent cations. A variety of solution chemistries including cation composition, total dissolved solids (TDS), and feedwater pH were investigated. The removal selectivity was worsened when TDS concentration increased and pH decreased. Based on the experimental observations in this study, the optimum operating conditions (i.e., time, voltage, and flow rate) were recommended for maximum selectivity. The energy consumption of MCDI process was compared with NF process by collecting NF plant data from the previous literature. It was found that the MCDI process was more effective for selective removal of monovalent cations, and used less energy than the NF process under optimum conditions. Based on the results, a novel concept of employing MCDI process producing Ca2+-rich water as a post-treatment integrated with typical NF/LPRO softening process was proposed for preventing the corrosion in the pipe distribution system.

Hydrological and environment tritium investigation to evaluate groundwater in capital territory of Pakistan

The capital territory of Pakistan constitutes twin cities, Islamabad and Rawalpindi. Islamabad is the capital city, located at the foot of the Margallah Hills, whereas Rawalpindi lies in the Potohar Plateau. Both cities are located in the semi-arid region of Pakistan, where the residents meet their basic need of water through groundwater resources. For the last many years, the quantity and quality of groundwater in these cities has been deteriorating very rapidly. In this study, the foremost recharge source for these cities was identified using tritium and major ion chemistry, and different physiochemical parameters were studied to find out the facts behind the quality deterioration of the groundwater. Tritium values and chemical data suggested that aquifers located in the territory of Islamabad were mainly recharged by upland areas (the Margalla Hills), which accounts for their low electrical conductivity and total dissolved solids contents. A higher sodium adsorption ratio (SAR) suggested an alteration in recharge patterns through soil compaction and cementation (from increased construction activity) that reduced the recharge inputs. The high SAR also disturbs the recharge pattern and had disturbed the natural equilibrium of the groundwater system, deteriorating the quality of the water.

Chemical weathering rates and atmospheric/soil CO2 consumption of igneous and metamorphic rocks under tropical climate in southeastern Brazil

Chemical weathering rates and atmosphere/soil CO2 consumption of igneous and metamorphic rocks under tropical climate in southeastern Brazil were evaluated using the chemical composition of surface waters and fresh rocks and soil (horizon C) in the Upper Sorocaba River basin. Surface water samples were collected between June/2009 and June/2010, and analyses were performed to assess pH, electrical conductivity (EC), temperature and total dissolved solids (TDS), including Na+, K+, Ca2+, Mg2+, Cl−, SO42−, PO43−, NO3− and SiO2. Fresh rocks and C horizon samples were also collected, taking into account their geological context, abundance and spatial density, to analyze major elements and mineralogy. The concentration of TDS and dissolved cations, anions and silica increased during the dry period in relation to the wet period, and the same behavior was observed for pH, EC and temperature. After corrections of anthropogenic contributions (ca. 21t/km2/yr) and atmospheric inputs (ca. 19t/km2/yr), the annual flux due to chemical weathering involving the igneous and metamorphic rocks was ca. 29t/km2/yr. The CO2 atmospheric/soil consumption in the Upper Sorocaba River basin was ca. 0.2×106mol/km2/yr, and when extrapolated to the entire Mantiqueira Orogenic Belt, accounted an estimated consumption of 0.07×1012mol/yr, representing 0.6% of the total CO2 consumption flux derived from global average silicate weathering. The chemical weathering rates of igneous and metamorphic rocks in the Upper Sorocaba River basin were estimated at 15m/My, respectively. The main weathering process in this watershed was the monossialitization, with partial hydrolyses of bedrock minerals, except quartz, which was not weathered and remained in the soil profile. The annual specific flux derived from igneous and metamorphic rocks at Upper Sorocaba River basin could be compared with watersheds in tropical climates. However, this value is higher than in other North American, European, Asian and African granitoid watersheds, and lower than in montane watersheds.

Produced water disposal injection in the southern San Joaquin Valley: No evidence of groundwater quality effects due to upward leakage

Upward migration of brine because of pressurization resulting from injection is a risk of disposal of water produced with oil and geologic carbon storage. Analysis of the net production in each zone associated with oil production activities in the southern San Joaquin Valley, California, determined that net injection caused by disposal of water produced with oil occurred in zones above the shallowest zone with net production in several oil fields. The zones with net injection are also variously at depths just greater than the shallowest depths for geologic carbon storage or at depths intermediate between more typical geologic carbon storage depths and overlying groundwater with a total dissolved solids concentration appropriate for domestic use. As such, these net injections provide analogs for brine pressurization caused by geologic carbon storage, either in the injection zone around the CO2 plume or in overlying zones caused by vertical leakage of brine or CO2. Hundreds of newspaper articles regarding groundwater contamination in the main newspaper in the southern San Joaquin area collectively reported on effects on groundwater from tens of sources at tens of locations. These effects resulted in the closure of about 100 water supply wells. However, no effects caused by upward migration of brine were reported. Of the shallowest zones with oil production–related activity in each field, the Fruitvale field, Main area, Etchegoin pool had the largest cumulative net injection volume. This pool is also intersected by numerous faults and approximately 900 wells related to oil production, each providing a potential pathway for upward fluid migration. Total dissolved solids and nitrate concentration data are available from greater than 100 water supply wells overlying this pool. Analysis of these data determined there was no significant groundwater quality change likely attributable to upward migration of brine (p < 0.05). It is not known if this is because the application of current underground injection control regulations is effective or because upward migration of brine, which is a dense phase, to groundwater is unlikely. The different engineering and economic implications of these two hypotheses suggest the need for future work to ascertain which is correct under different conditions.

Development of a predictive model to determine the temporal variability in mine feed water quality towards informing and forecasting plant operating strategy – a South African coal mine water treatment plant case study

The feed water quality associated with mine water treatment is typically characterised by a dynamic variability resulting from the fact that the final feed water to the water treatment plant (WTP) can be an amalgamation of water streams emanating from a number of sources. Consequently, the ability to deal with the dynamic nature of the feed water quality towards successful and sustainable mine water treatment goes beyond a proactive approach and requires a systemic, predictive approach. This paper discusses the development of an unsteady state mass balance model on a surface dam located on a coal mine towards predicting the dynamic fluctuations in total dam volume and its total dissolved solids (TDS) concentration in the feed water to a NuWater 20 MLD mobile WTP, comprising chemical conditioning, ultrafiltration and reverse osmosis (RO). The unsteady state mass balance, incorporated water entering the dam via the opencast pits, underground compartments, seasonal rainfall and the RO brine return. Water leaving the dam comprised the feed water to the WTP, partial brine treatment, surface evaporation and seepage. Validation of the model using actual data over an 8-month period showed excellent results. The model showed that without water treatment, the dam would overflow in 218 days. Although the dam's volume could be sustained at the ideal volume by treating 14.2 MLD, its TDS would exceed the maximum environmental limit in 197 days. Consequently, the combination of a 13.2 MLD WTP with a 1 MLD brine treatment plant provided the optimal water treatment strategy to sustainably maintain the dam's TDS concentration and volume within acceptable limits over the 5-year investigation period. This paper demonstrates the importance of using a predictive methodology for forecasting feed water characteristics and as an early warning system for most water treatment systems that are subjected to dynamic conditions.

Specific conductance–stage relationships in Appalachian valley fill streams

Surface coal mining impacts on water resources in the Appalachian region, USA, are widely studied. Total dissolved solids (TDS), which are estimated in situ by the proxy variable specific conductance (SC), are of interest due to potential aquatic macroinvertebrate effects. Prior studies have documented the hydrochemical impacts of surface mining on streams, but research on the relationships between SC and discharge is limited. SC–Stage relationships can help infer potential hydrologic flow paths, as well as source water TDS concentrations in mining-influenced watersheds. The objectives of this study were to compare baseflow and stormflow hydrochemistry and determine SC–Stage relationships in valley fill (VF) streams. Five VF streams of varying ages in Virginia were equipped with continuous SC and stage data loggers for up to 12 months (December 2013–November 2014). Data analyses included baseflow and stormflow hydrochemistry, and SC–Stage regressions and storm hysteresis patterns. Data were analyzed seasonally. Stages were generally highest in winter and lowest in summer, while SCs were generally highest in summer and lowest in winter. All SC–Stage regressions indicated SC dilution during stormflow, but significance differed seasonally. Storm SC–Stage hysteresis patterns varied with storm precipitation amounts, season, and vegetative period, implying climatic controls on VF stream storm responses. Counterclockwise storm hysteresis likely occurred in response to high rainfall amounts exceeding the mine soil infiltration capacity. Clockwise storm hysteresis likely resulted from precipitation dissolving salts brought to the surface by evapotranspiration, but may have also resulted from rapid flow through pseudokarst features within the VF.

Determining the Salt Tolerance Threshold for Biological Treatment of Salty Wastewater

Background: Wastewaters with high salt content disturb the metabolic function of microorganisms causing plasmolysis or activity loss in microorganisms, so the efficiency of biological treatment of saline wastewater by conventional microorganisms will decrease. Objectives: This study aimed to find the outbreak of disorder in the biological wastewater treatment process and how much salt leads to low efficiency in the wastewater treatment plant. Methods: A study unit consisting of two aeration and sedimentation parts was used in this pilot research. Initially, 2 to 10 gr of NaCl was added to wastewater (WW) then aerated and settled for six and two hours, respectively. During a 10-weeks period, 10 samples were obtained and, the parameters of biological oxygen demand in 5 (BOD5), chemical oxygen demand (COD), total suspended solids (TSS), pH, turbidity, total dissolved solids (TDS) and mixed liquor suspended solids (MLSS), were measured. All experiments were done according to standard methods. Results: Removal efficiency of qualitative parameter including BOD, COD, TSS and turbidity showed a reduction of about 79.7, 73.9, 67.6 and 66%, respectively by addition of 8 gr/L of NaCl to wastewater. By increasing TDS by more than 4000 mg/L, biological treatment was done at a low efficiency and was disturbed with TDS of about 8000 mg/L, with efficiency of the treatment system strongly decreasing. Conclusions: For wastewater with high TDS content, modification such as dilution, collection system sanitation, application of halophytic organisms, the use of non-biological methods and so on is recommended.

Impact of Brine Composition on Calcite Wettability: A Sensitivity Study

Summary Brine composition change has a significant demonstrated impact on the recovery of oil in laboratory corefloods. Although low-salinity waterflood in clastics has been studied extensively, the impact of brine composition on the wettability and recovery in carbonates is relatively less understood and studies are more recent. Wettability measurements by use of contact angles can reflect the surface energy changes caused by adsorption of compounds present in crude oil and the electrostatic, structural components caused by the formation of the double layer. In this study, the impact of ion composition on the contact angles and interfacial tensions (IFTs) between crude oil, brine, and restored/aged calcite-mineral surface is studied by use of a drop-profile-analysis method. A 13-factor experimental design is used to quantify the impact of six salts and seven interactions. This experimental method design, following the Taguchi method (Roy 1990), is used to identify the combination of different salts that leads to the lowest oil-wetness and highest water-wetness as measured through the contact angles. In addition, the impact of the total dissolved solids (TDS) on both the wettability and the IFT is studied for the selected crude oil/brine system. The analysis of variance of the measurements shows that the Alkali/Alkaline Earth metal chloride concentration has a significant impact on the wettability measured with static contact angles. The interactions between sodium chloride and sodium sulfate concentration; between sodium chloride and magnesium chloride salt concentration; and between sodium chloride and calcium chloride concentration are significant. The most-favorable interaction response is obtained at the highest sodium sulfate concentration along with lower sodium chloride, calcium chloride, and magnesium chloride concentrations. Therefore, a combination of higher concentration of sulfate anions with lower cation concentration and reduced salinity can lead to more-water-wet conditions. This composition is found to lead to the lowest contact angle or the most-water-wet condition. It is interesting to note that the lowest contact angle of approximately 29 ° (highly water-wet) is obtained with a relatively high TDS content of 134.5 g/L. This observation is in line with some of the recent studies reported in the literature on carbonate-rock corefloods and offers a fundamental explanation.

Ecology-oriented groundwater resource assessment in the Tuwei River watershed, Shaanxi Province, China

In arid and semi-arid regions, a close relationship exists between groundwater and supergene eco-environmental issues such as swampiness, soil salinization, desertification, vegetation degradation, reduction of stream base flow, and disappearance of lakes and wetlands. When the maximum allowable withdrawal of groundwater (AWG) is assessed, an ecology-oriented regional groundwater resource assessment (RGRA) method should be used. In this study, a hierarchical assessment index system of the supergene eco-environment was established based on field survey data and analysis of the supergene eco-environment factors influenced by groundwater in the Tuwei River watershed, Shaanxi Province, China. The assessment system comprised 11 indices, including geomorphological type, lithology and structure of the vadose zone, depth of the water table (DWT), total dissolved solids content of groundwater, etc. Weights for all indices were calculated using an analytical hierarchy process. Then, the current eco-environmental conditions were assessed using fuzzy comprehensive evaluation (FCE). Under the imposed constraints, and using both the assessment results on the current eco-environment situation and the ecological constraint of DWT (1.5–5.0 m), the maximum AWG (0.408 × 108 m3/a or 24.29 % of the river base flow) was determined. This was achieved by combining the groundwater resource assessment with the supergene eco-environmental assessment based on FCE. If the maximum AWG is exceeded in a watershed, the eco-environment will gradually deteriorate and produce negative environmental effects. The ecology-oriented maximum AWG can be determined by the ecology-oriented RGRA method, and thus sustainable groundwater use in similar watersheds in other arid and semi-arid regions can be achieved.

Chemical and strontium isotopic characteristics of the rivers around the Badain Jaran Desert, northwest China: implication of river solute origin and chemical weathering

The chemical and strontium isotopic compositions of four major rivers (Heihe, Shule, Beida, and Shiyang) around the Badain Jaran Desert, northwestern China, were measured to understand the solute sources of surface water and rock weathering in the arid region. These rivers have high total cationic charge (TZ+) and total dissolved solids (TDS), averaging at 7379 μEq and 511 mg l−1, which are significantly higher than the global river average. The increase in TDS and major ions (Na+, Cl−, and SO4 2−) and TDS concentrations from upper to lower reaches is ascribed to the evaporite dissolution and the effect of evaporation in the arid and semiarid areas. 87Sr/86Sr isotopic ratios of these rivers range between 0.71019 and 0.71628, with an average of 0.71328. The chemical and 87Sr/86Sr isotopic analyses indicate that three reservoirs (evaporites, carbonates, and silicates) contribute to the total dissolved loads. The contributions of the different reservoirs to the dissolved load are first calculated using a forward method in this area. The calculated results show that the dissolved cation load is dominated by carbonates weathering and evaporites dissolution, and their contribution account for about 80 % of the total dissolved cations for the rivers around the Badain Jaran Desert. The proportion of the dissolved cations from silicates weathering is 23.5, 10.8, 12.1, and 18.2 %, and the weathering rate of silicates is 0.81, 0.76, 2.04, and 0.93 ton km−2 a−1 for Heihe, Shule, Beida, and Shiyang, respectively.

Surface water quality monitoring of an agricultural watershed for nonpoint source pollution control

Water pollution is a major environmental problem in the United States. To improve the surface water quality of the 2,493 ha (6,160 ac) Coulee Baton watershed in Louisiana, a collaborative nonpoint source pollution control study was initiated in 2004. Conservation measures and best management practices (BMPs) including cross-fencing of pasturelands (726.9 m [2,385 ft]), irrigation land leveling (12.9 ha [32 ac]), grade stabilization structures (two), irrigation water pipeline (975.4 m [3,200 ft]), and a livestock well covering a total of 92.7 ha (229 ac) of agricultural land, and repair or replacement of 80 septic systems in the watershed were voluntarily implemented by landowners and homeowners. Water samples were collected from seven monitoring sites for 66 rain events from September 24, 2009, to August 9, 2011. Laboratory determinations of water samples included total suspended solids (TSS), total dissolved solids (TDS), total solids (TS), five-day biological oxygen demand (BOD5), nitrate/nitrite-nitrogen (NO3/NO2-N), soluble reactive phosphate (SRP), total phosphorus (TP), total Kjeldahl N (TKN), chloride (Cl), fluoride (Fl), sulfate (SO4), and fecal coliform counts. Surface water temperature, dissolved oxygen (DO), turbidity, conductivity, and pH were determined in the field using YSI Sonde (YSI Incorporated, Yellow Springs, Ohio). For the watershed, DO, BOD5, and TS concentrations and fecal coliform count ranged, respectively, between 1.2 and 14.1 mg L−1 (ppm), 2 and 40.1 mg L−1, 35 and 5,719 mg L−1, and 400 × 106 and 17 × 106 most probable number (MPN) per 100 mL. The months of March, April, June, and September showed, on average, higher concentrations of TS and TDS, fecal coliform count, NO3/NO2-N, and SRP and TP, respectively. As compared to the ongoing BMPs, the post-BMPs, TSS, NO3/NO2-N, SRP, and BOD5 concentrations, on average, were lower by 56.2%, 23.1%, 82.5%, and 27.4%, respectively. Developed land use types and the failed septic systems were identified as major sources of fecal coliform pollution. These results suggest comprehensive strategies are necessary for effective nonpoint source pollution control in agricultural watersheds.

Assessment of the Hydrogeochemical Processes Affecting Groundwater Quality in the Eocene Limestone Aquifer at the Desert Fringes of El Minia Governorate, Egypt

El Minia Governorate is within the Nile Valley and is surrounded by the Eocene limestone plateaus from the east and west. The present study focuses on the hydrogeochemistry of the Eocene limestone aquifer in both the eastern and western desert fringes of El Minia. Thirty groundwater samples from the Eocene aquifer (east and west of the Nile) and seven samples from post-Eocene aquifers in this area were analyzed to assess the groundwater geochemistry, isotopic compositions and the subsurface hydrology. Samples obtained from depths of 24–120 m were measured for major components, nutrients, oxygen-18, deuterium and carbon-13. The groundwater TDS (total dissolved solids) concentrations ranged from 530 to 2788 and 453 to 1903 mg/l at the western and eastern desert fringes, respectively. Values of Eocene aquifer water δ18O ranged from −8.31 to −0.44 and −2.07 to 0.55 ‰, and those of water δD ranged from −63.6 to −2.32 and −9.03 to 5.03 ‰ for the Eocene aquifer at the western and eastern side, respectively. Chemical analysis shows that the main chemical facies of the Eocene water are Ca–Mg–HCO3 and Ca–SO4. The chemical and isotopic data show that water–rock interaction (calcite dissolution and silicate weathering) and mixing between different water types control the major ion chemistry of Eocene aquifer water. The chemical composition of Eocene water has also evolved by evaporation and ion exchange. The present study indicates the need for regional chemical and isotopic study for the Eocene aquifer along the Nile Valley region to delineate the sources of recharge to this important aquifer.

Numerical evaluation of community-scale aquifer storage, transfer and recovery technology: A case study from coastal Bangladesh

Aquifer storage, transfer and recovery (ASTR) may be an efficient low cost water supply technology for rural coastal communities that experience seasonal freshwater scarcity. The feasibility of ASTR as a water supply alternative is being evaluated in communities in south-western Bangladesh where the shallow aquifers are naturally brackish and severe seasonal freshwater scarcity is compounded by frequent extreme weather events. A numerical variable-density groundwater model, first evaluated against data from an existing community-scale ASTR system, was applied to identify the influence of hydrogeological as well as design and operational parameters on system performance. For community-scale systems, it is a delicate balance to achieve acceptable water quality at the extraction well whilst maintaining a high recovery efficiency (RE) as dispersive mixing can dominate relative to the small size of the injected freshwater plume. For the existing ASTR system configuration used in Bangladesh where the injection head is controlled and the extraction rate is set based on the community water demand, larger aquifer hydraulic conductivity, aquifer depth and injection head improve the water quality (lower total dissolved solids concentration) in the extracted water because of higher injection rates, but the RE is reduced. To support future ASTR system design in similar coastal settings, an improved system configuration was determined and relevant non-dimensional design criteria were identified. Analyses showed that four injection wells distributed around a central single extraction well leads to high RE provided the distance between the injection wells and extraction well is less than half the theoretical radius of the injected freshwater plume. The theoretical plume radius relative to the aquifer dispersivity is also an important design consideration to ensure adequate system performance. The results presented provide valuable insights into the feasibility and design considerations for community-scale ASTR systems but installation of systems in different hydrogeological contexts (i.e. high regional hydraulic gradient and aquifer TDS concentration) may require re-evaluation of the system design.

An optimization framework for the integration of water management and shale gas supply chain design

This study presents the mathematical formulation and implementation of a comprehensive optimization framework for the assessment of shale gas resources. The framework simultaneously integrates water management and the design and planning of the shale gas supply chain, from the shale formation to final product demand centers and from fresh water supply for hydraulic fracturing to water injection and/or disposal. The framework also addresses some issues regarding wastewater quality, i.e., total dissolved solids (TDS) concentration, as well as spatial and temporal variations in gas composition, features that typically arise in exploiting shale formations. In addition, the proposed framework also considers the integration of different modeling, simulation and optimization tools that are commonly used in the energy sector to evaluate the technical and economic viability of new energy sources. Finally, the capabilities of the proposed framework are illustrated through two case studies (A and B) involving 5 well-pads operating with constant and variable gas composition, respectively. The effects of the modeling of variable TDS concentration in the produced wastewater is also addressed in case study B.

Assessment of the toxicity of wastewater from the metalworking industry treated using a conventional physico-chemical process.

This article presents results from a toxicity reduction evaluation program intended to describe wastewater from the metalworking industry that was treated using a conventional physico-chemical process. The toxicity of the wastewater for the microcrustacean Daphnia magna was predominantly expressive. Alkaline cyanide wastewater generated from electroplating accounted for the largest number of samples with expressive toxicity. When the raw wastewater concentrations in the batches were repeated, inexpressive toxicity variations were observed more frequently among the coagulated-flocculated samples. At the coagulation-flocculation step, 22.2% of the treatments had reduced acute toxicity, 30.6% showed increased toxicity, and 47.2% remained unchanged. The conductivity and total dissolved solids contents of the wastewater indicated the presence of salts with charges that were inappropriate for the survival of daphnid. The wastewaters treated by neutralization and coagulation-flocculation had average metallic compound contents that were greater than the reference toxic concentrations reported in other studies, suggesting that metals likely contributed to the toxic effects of the wastewater on freshwater microcrustaceans. Thus, alternative coagulants and flocculants should be assessed, and feasible doses should be determined to improve wastewater treatment. In addition, advanced treatment processes should be assessed for their abilities to remove dissolved toxic salts and ions.

High recovery, low fouling, and low energy reverse osmosis

Desalination and water reuse using reverse osmosis (RO) are viable new water supply resources; however, traditional RO systems often create excess brine waste, do not fully utilize source water supplies, and consume too much energy. Newly emerging closed-circuit RO processes improve RO performance and reduce its cost by increasing recovery, reducing fouling and scaling, and reducing energy consumption. This performance has been documented in dozens of RO installations in a range of applications. In particular, a closed-circuit RO unit operated on groundwater with a silica concentration of 59 ppm at recovery rates of up to 93.5%, producing brine silica concentrations exceeding 900 ppm. This recovery rate was sustained at neutral pH, with modest anti-scalant dosing and no scaling-related CIP requirements. A traditional RO system operating in feedwater with this concentration of silica would be limited to 76% recovery or less, corresponding to more than 3 times the production rate of brine concentrate. At another site, seawater with a total dissolved solids content of 35,329 ppm was desalinated with 5.5 kWh/1,000 gal (1.45 kWh/m3) of RO pump energy. This represents the lowest energy consumption ever reported for seawater RO at a comparable recovery rate and flux.

High Total Dissolved Solids Water Treatment by Charged Nanofiltration Membranes Relating to Power Plant Applications.

Selective desalination through nanofiltration (NF) is of great interest for many industrial applications including reuse of power plant scrubber wastewater and treatment of water containing high concentrations of TDS (total dissolved solids). This work seeks to understand the effect ion interactions at the membrane interface have on rejection and flux performance of charged NF membranes. NF membranes were also effective for low energy desalination of scrubber wastewater from Georgia Power Plant Bowen, composed primarily of Ca2+, Mg2+, Cl-, and SO4 2-. As NF membranes have the capability for selective separations, 80% water recovery was achieved experimentally while maintaining an overall rejection of over 60% for Ca2+ and Cl-. The occurrence of CaSO4 precipitation at high water recovery was observed. The effect of precipitation on osmotic pressure and the effect of Cl- counterions on increasing gypsum solubility were explored for water recovery operation. This work expands on a previous work on the topics of desalination of multi-ionic solutions by incorporating the use of large scale membrane modules (0.59 m2) with several synthetic solutions as well as actual scrubber water containing precipitating elements, Ca2+ and SO4 2-. It was observed that the spiral wound membrane modules maintained a stable water permeability over the 144 day course of tests.

Hydrogeochemical characterization and groundwater quality assessment in a coal mining area, India

The present study determines major and trace element chemistry of groundwater in the West Bokaro coalfield to assess the hydrogeochemical processes and groundwater quality for drinking and irrigation uses. For this purpose, 33 groundwater samples from different mining areas of the West Bokaro coalfield were collected and analysed for pH, electrical conductivity (EC), total dissolved solid (TDS), dissolved silica (SiO2), major cations (Ca2+, Mg2+, Na+, K+), anions (F−, Cl−, HCO3−, SO42− and NO3−) and trace metals (Mn, Cu, Pb, Zn, Ni, Co, As, Se, Al, Cd, Cr, Ba and Fe). The analytical results show the slightly acidic to alkaline nature of groundwater and dominance of HCO3− and SO42− in anionic and Ca2+ and Na+ in cationic abundance. High SO42− concentrations are attributed to the oxidative weathering of pyrite and gypsum dissolution. Supersaturation condition with respect to dolomite and calcite for most samples may result from the dissolution of gypsum after the water is saturated with respect to the carbonate minerals. The data plot on the Gibbs and Piper diagrams revealed that the groundwater chemistry is mainly controlled by rock weathering with secondary contribution from anthropogenic sources. In a majority of the groundwater samples, alkaline earth metals exceed alkalies and strong acids dominate over weak acid. Ca-Mg-HCO3, Ca-Mg-SO4-Cl and Ca-Mg-SO4 were the dominant hydrogeochemical facies. A comparison of groundwater quality parameters in relation to specified limits for drinking water shows that the concentrations of TDS, SO42−, NO3−, total hardness (TH), Fe and Ni are exceeding the desirable limits in many groundwater samples. Quality assessment for irrigation uses reveal that the groundwater is of good to suitable category. Higher salinity and magnesium hazard values at some sites restrict the suitability of groundwater for irrigation purposes.

Novel industrial wastewater treatment integrated with recovery of water and salt under a zero liquid discharge concept.

Conventional industrial effluent treatment systems are designed to reduce biochemical oxygen demand (BOD), chemical oxygen demand (COD) but not total dissolved solids (TDS), mainly contributed by chlorides. In addition to the removal of TDS, it is necessary to recover water for reuse to meet the challenges of shortage of quality water. To recover water, the wastewater needs to be further treated by adopting treatment systems including microfilters, low pressure membrane units such as ultrafiltration (UF), membrane bioreactors (MBR), etc., for the application of reverse osmosis (RO) systems. By adopting the RO system, 75%-80% of quality water with <500 mg/L of TDS is recovered from treated effluent. The management of 20%-25% of the saline water rejected from the RO system with high TDS concentration is being addressed by methods such as forced evaporation systems. The recovery of water from domestic and industrial waste for reuse has become a reality. The membrane system has been used for different applications. It has become mandatory to achieve zero liquid discharge (ZLD) in many states in India and other countries such as Spain, China, etc., and resulted in development of new treatment technologies to suit the local conditions.