High Sulfate Concentrations Research Articles

Cambios temporales y espaciales en la química del agua superficial en un río mediterráneo de Chile central: el caso del río Mataquito (~35°S)

Spatial and temporal changes in water chemistry were evaluated using surface water extracted from a Mediterranean river basin, i.e., The Mataquito River, central Chile. The processes that control water chemistry dynamics in the basin were determined by assessing the relationship between hydrologic events (rainfall, river flow, runoff rates), physical-chemistry properties, and major ion concentrations/distributions along the river. During the rainy period, major ion levels were controlled predominantly by weathering (rainfall). During the dry period, seawater intrusion was the main factor controlling water chemistry. Unusually high chlorine and sulfate concentrations suggested anthropogenic sources of the ions entering the basin. Thus, pollution from industrial and agricultural activities in the basin might be quantitatively important and should be considered in future studies of this area.

Near Quantitative Removal of Selenate and Sulfate Anions from Wastewaters by Cocrystallization with Chelating Hydrogen-Bonding Guanidinium Ligands.

Selenium (Se) has become an environmental contaminant of aquatic ecosystems as a result of human activities, particularly mining, fossil fuel combustion, and agricultural activities. By leveraging the high sulfate concentrations relative to Se oxyanions (i.e., SeO n 2-, n = 3, 4) present in some wastewaters, we have developed an efficient approach to Se-oxyanion removal by cocrystallization with bisiminoguanidinium (BIG) ligands that form crystalline sulfate/selenate solid solutions. The crystallization of the sulfate, selenate and selenite, oxyanions and of sulfate/selenate mixtures with five candidate BIG ligands are reported along with the thermodynamics of crystallization and aqueous solubilities. Oxyanion removal experiments with the top two performing candidate ligands show a near quantitative removal (>99%) of sulfate or selenate from solution. When both sulfate and selenate are present, there is near quantitative removal (>99%) of selenate, down to sub-ppb Se levels, with no discrimination between the two oxyanions during cocrystallization. Reducing the selenate concentrations by 3 orders of magnitude or more relative to sulfate, as found in many wastewaters, led to no measurable loss in Se removal efficiencies. This work offers a simple and effective alternative to selective separation of trace amounts of highly toxic selenate oxyanions from wastewaters, to meet stringent regulatory discharge limits.

The characteristics of ultraviolet absorption and electronic excitation of sulfate at high concentrations

The variation of spectra and the characteristics of electronic excitation are critical for establishing a model for quantifying sulfate at high concentrations. The absorption characteristics of sulfate are affected by the optical pathlength and sulfate concentration. The absorption coefficient declines by approximately 86.09–96.20% with an increasing concentration (0–130 g/L) at different optical pathlengths (1–100 mm). Moreover, a high sensitivity and accuracy can be achieved at weak absorption wavelengths or at lower optical pathlengths when high concentrations of sulfate are detected. In addition, the maximum absorption wavelength of sulfate redshifts by approximately 0–10 nm with an increasing concentration and optical pathlength, which is significantly affected by the optical pathlength. The (H2SO4)n‧(H2O)4-n models were established at the PBEPBE/6–311++G(d, p) level of theory. There absorption spectra were calculated by the time-dependent density functional theory (TD-DFT) method. As a result, the maximum absorption wavelength redshifted from 180.16 nm to 192.71 nm with an increasing sulfate concentration, and the corresponding absorption coefficient demonstrated a declining trend. Furthermore, the electron-hole and natural bond orbital (NBO) analysis indicate that the type of electronic excitation changes from a n(O) → σ*(S-O) localized excitation to n → σ* charge-transfer excitation as the sulfate concentration increases. This study provides a theoretical foundation for understanding the spectral behavior of sulfates and constructing the quantification models or methods that can also be applied to analyze the spectroscopy of other chemicals.

Microbial sensitivity to temperature and sulfate deposition modulates greenhouse gas emissions from peat soils.

Peatlands are among the largest natural sources of atmospheric methane (CH4 ) worldwide. Microbial processes play a key role in regulating CH4 emissions from peatland ecosystems, yet the complex interplay between soil substrates and microbial communities in controlling CH4 emissions as a function of global change remains unclear. Herein, we performed an integrated analysis of multi-omics data sets to provide a comprehensive understanding of the molecular processes driving changes in greenhouse gas (GHG) emissions in peatland ecosystems with increasing temperature and sulfate deposition in a laboratory incubation study. We sought to first investigate how increasing temperatures (4, 21, and 35°C) impact soil microbiome-metabolome interactions; then explore the competition between methanogens and sulfate-reducing bacteria (SRBs) with increasing sulfate concentrations at the optimum temperature for methanogenesis. Our results revealed that peat soil organic matter degradation, mediated by biotic and potentially abiotic processes, is the main driver of the increase in CO2 production with temperature. In contrast, the decrease in CH4 production at 35°C was linked to the absence of syntrophic communities and the potential inhibitory effect of phenols on methanogens. Elevated temperatures further induced the microbial communities to develop high growth yield and stress tolerator trait-based strategies leading to a shift in their composition and function. On the other hand, SRBs were able to outcompete methanogens in the presence of non-limiting sulfate concentrations at 21°C, thereby reducing CH4 emissions. At higher sulfate concentrations, however, the prevalence of communities capable of producing sufficient low-molecular-weight carbon substrates for the coexistence of SRBs and methanogens was translated into elevated CH4 emissions. The use of omics in this study enhanced our understanding of the structure and interactions among microbes with the abiotic components of the system that can be useful for mitigating GHG emissions from peatland ecosystems in the face of global change.

Research and demonstration on reclaimation of chemical industrial wastewater with high salinity and hardness and purification of reverse osmosis concentrates

The demonstration is specifically designed to achieve the reclaimation of integrated chemical industry park wastewater (CIPWW) with high levels of hardness and salinity and the standardized discharge of concentrates generated during the reclaimation period by effectively composing dual-membrane technology combined by microfiltration (MF) and reverse-osmosis (RO) with multiple water treatment techniques. Concerning the concentrates generated by RO, the full-scale calcium-sulfate (CaSO4) crystallizer is creatively applied as the pretreatment unit for hardness removal with doubled catalytic ozonation-high performance biological aerated filter (O3-HBAF) and ultrafiltration (UF) as subsequent treatment technologies. Considering the characteristics of RO concentrates as high permanent hardness, high sulfate concentration and high refractory organic matter (ROM) content, pilot tests were conducted particularly focusing on the CaSO4 crystallizer and O3-HBAF unit which verified the reasonability of the technological process, and relevant operating parameters were optimized including flocculant dosage, catalyst dosage, etc. A series of adjustments were also made for the agent-addition devices of RO in order to stabilize the differential pressure facing variable influent circumstances. During over one-year of full-scale operation, the treated CIPWW was innovatively supplied for chemical fiber factories which established rigorous limitations on the impurity content of reuse water, and the water quality of purified RO concentrates partially met the requirements of class IV of Environmental Quality Standard for Surface Water (GB3838–2002, China). The application of CaSO4 crystallizer approximately saved the operation cost by 57.04 % compared with that of Na2CO3 softening process, and sufficiently recycled calcium ions from RO concentrates as CaSO4·2H2O products.

Effective biosorption of As(V) from polluted water using Fe(III)-modified Pomelo (Citrus maxima) peel: A batch, column, and thermodynamic study

Pomelo, Citrus maxima, peel was chemically modified with lime water and then loaded with Fe(III) to develop anion exchange sites for effective sequestration of As(V) from water. Biosorbent characterizations were done by using FTIR, SEM, XRD, EDX, and Boehm's titration. The batch biosorption studies were carried out at various pHs using modified and non-modified biosorbents and optimum biosorption of As(V) occurred at acidic pH (3.0–5.0) for both the biosorbents. A kinetic study showed a fast biosorption rate and obtained results fitted well with the pseudo-second-order (PSO) model. When isotherm data were modeled using the Langmuir and Freundlich isotherm models, the Langmuir isotherm model fit the data better and produced maximal As(V) biosorption capacities of 0.72 ± 03, 0.86 ± 06, and 0.95 ± 05 mmol/g at temperatures 293± 1K, 298± 1K and 303± 1K, respectively. Desorptionof As(V) was effective using 0.1 M NaOH in batch mode. Negative values of ΔG° for all temperatures with positive ΔH° confirmed the spontaneous and endothermic nature of As(V) biosorption. The existence of co-existing chloride (Cl−), nitrate (NO3−), sodium (Na+), and calcium (Ca2+) showed insignificant interference whereas a high concentration of sulphate (SO42−) and phosphate (PO43−) significantly lowered As(V) biosorption percentage. Arsenic concentrations in actual arsenic polluted groundwater could be reduced to the WHO drinking water standard (10 μg/L) by using only 1 g/L of investigated Fe(III)-SPP. The dynamic biosorption of As(V) in a fixed bed system showed that Fe(III)-SPP was effective also in continuous mode and different design parameters for fixed bed system were determined using Thomas, Adams-Bohart, BDST, and Yoon-Nelson models. Therefore, from all of these results it is suggested that Fe(III)-SPP investigated in this study can be a potential, low cost and environmentally benign biosorbent material for an effective removal of trace amounts of arsenic from polluted water.

Mobile Sources Mixing Model Implementation for a Better Quantification of Hydrochemical Origins in Allogenic Karst Outlets: Application on the Ouysse Karst System

On the edge of sedimentary basins, karst aquifers can be fed by several water sources from both autogenic and allogenic recharge. In some cases, assessing water origins can be hard and cause some difficulties for water resource management. The main goal of this study is to show the implementation of the mobile sources mixing model approach. More precisely, this research develops how a monitoring method using a multi-proxy approach can be used to quantify waters sources contributions from several origins at the outlets of a karst system. The study site is the Ouysse karst system, located in western France. The site offers the opportunity to understand the mixing processes between allogenic and autogenic water recharges. The karst system covers a 650 km² watershed, and is fed by three different chemical facies: (i) Autogenic water from the direct infiltration on the karstified limestones with high HCO3− values (median: 436 mg.L−1); (ii) Water coming from sinking rivers fed by spring coming from igneous rocks with low mineralization but relatively higher K+ values (median: 4.2 mg.L−1); (iii) Highly mineralized water coming from deep evaporitic layers and feeding another sinking river with very high sulfate concentrations (median: 400 mg.L−1). Sliding window cross-correlation analyses and hydrochemical analyses during a flood event are performed to implement a mobile source mixing model approach. This approach shows significant differences with a simple fixed source mixing model and appears more reliable but requires more time and money to carry out. The results and conclusion of this study will be used for forecasting and managing operational actions for resource management.

Effect of copper sulphate on Cryptocaryon irritans based on metabolome analysis.

Cryptocaryon irritans is one of the most harmful marine parasites in mariculture. Copper sulphate is often used to kill parasites and the influence of copper sulphate on the tomont stage of C. irritans was explored in this study. The results showed that excystment rate was not significantly affected when tomonts were exposed to 5 mg/L (76.7%) and 10 mg/L (78.9%) of copper sulphate for 3 h. However, excystment rate was significantly inhibited when exposed to 15 mg/L (33.3%) for 3 h and 5 mg/L (28.9%), 10 mg/L (33.3%) and 15 mg/L (33.3%) for 6 h. After treatment with high concentrations of copper sulphate, the interior of the tomonts was fuzzy under the microscope, and the division process could not be observed. Metabolomic results combined with preliminary transcriptome analysis results showed that the tomonts were induced to produce linoleate, riboflavin, inositol and other substances under the stress of Cu2+ , which affected the antioxidant mechanism of the body. Using MDA content determination and antioxidant enzyme activity analysis, copper sulphate was found to cause oxidative damage to tomonts by affecting the generation of metabolites, leading to the death of tomonts.

Electrochemical Corrosion in Bars of AISI 304 Embedded in Concrete Immersed in Marine-Sulfated Environment

The electrochemical behavior of the corrosion resistance of AISI 304 embedded in concrete manufactured as indicated by the ACI 211.1 method was evaluated. The specimens were exposed for more than 150 days to highly aggressive marine-sulfated environment, solution with a concentration of 5% NaCl and 5% Na2SO4. The electrochemical technique of Resistance to Linear Polarization (Rp) was used for to determine the corrosion rate (Icorr) and monitoring of corrosion potential (Ecorr). The Ecorr and Icorr results indicate a high level of corrosion for AISI 1018 steel, on the contrary, the electrochemical behaviour of AISI 304 steel according to the values of Ecorr and Icorr, indicate a corrosion resistance of up to 10 times higher when exposed to an environment with a high concentration of chlorides and sulfates.

Resource recovery from tannery wastewater using an integrated biological system: Towards a circular bioeconomy and net positive tannery operations

Anaerobic digestion (AD) of tannery effluents generated by beamhouse processes is limited by ammonia and sulfur species. High sulfate concentrations in beamhouse effluents (BHE) promote sulfidogenesis during AD, and the hydrogen sulfide that is generated inhibits methanogenesis. The feasibility of using a novel integrated biological system that comprised of hybrid linear flow channel reactor/s (HLFCR/s) and an anaerobic sequential batch reactor (AnSBR) connected in series mainly for the pre-treatment and recovery of elemental sulfur (S0) and methane (CH4) was investigated. The application of single-stage and two-stage HLFCR topology operating at 8 and 4 days’ hydraulic retention times (HRT), respectively, produced effluents that were ideal for AD. Single-stage HLFCR (8-days HRT) recovered 21% of the inlet sulfur and the downstream effluent treatment in continuously mixed AnSBR at 50 rpm achieved 238 mL CH4/gCODadded). The full-scale application of the system at a local medium sized tannery treating 2258 m3 of BHE would produce a floating sulfur biofilm with 33% S0, 3420 m3 of CH4, 50 m3 of irrigation water and 31 tonnes of biofertiliser. The sale of recovered resources and potential savings from a 72% reduction in electricity demand and 62% in sludge disposal had a potential revenue of US$5559. This study demonstrated the feasibility of a circular bioeconomy and net positive tannery operations through the conversion of tannery wastewater treatment plants into bio-refineries.

Monitoring and PH Analysis of Tailings from the Effluents of the Cerro De Pasco Mining Company in the Years 2017-2021

Currently, mining operations in Peru, such as in the province of Pasco, require water consumption for metallurgical mining processes, supply for personnel, among other operations. The purpose of this study is to determine whether the mining company located in Cerro de Pasco has reduced its pH values over the years and whether they are within the Maximum Permissible Limits established by Peru. The impacts of mining activities cause damage to water bodies and the health of the population, so water monitoring is carried out at certain discharge points called cell1, cell2 and cell3, where pH measurements were taken. The results of the monitoring, with respect to the tailings from the mine, are acidic pH values containing suspended solids as well as high concentrations of sulphates and metals. The contributions of the study, which is carried out in the city of Cerro de Pasco located at 4338 m.a.s.l., show practical results as they are used for a diagnosis and analysis for the years 2017-2021 with respect to the mine tailings.

Spontaneous fractures and hypocuprosis in pen-backgrounded Holstein calves

Bone fractures are a frequent cause of limp in cattle, being pre-existing bone lesions among the predisposing factors. However, there is scant information about the natural occurrence of bone disease. This report aimed to describe an outbreak of spontaneous fractures associated with hypocuprosis in pen-backgrounded calves. Hind limp and irreversible recumbency were noticed in 9-month-old calves of a dairy farm from Córdoba province (Argentina). The issue was only evident in males fed a diet composed (DM) of 57% wet corn, 24% dry corn distiller grains, and 19% corn silage. No mineral mix was supplied. Accumulated morbidity and fatality rates were 5.8 and 100%, respectively. Two autopsies were performed, observing multiple femoral and rib fractures. Severe hypocupremia, very low copper levels in the liver and plasma, deficient dietary copper levels, normocalcemia, marginal hypophosphatemia, and high sulfate concentrations in the water supply were determined. Except for the decreased bone quantity and the multiple fractures, no bone lesion was observed, confirming osteoporosis as the pathological diagnosis, and hypocuprosis as the etiology.

Fate of Sulfate in Municipal Wastewater Treatment Plants and Its Effect on Sludge Recycling as a Fuel Source

Wastewater sludge is used as an alternative fuel due to its high organic content and calorific value. However, influent characteristics and operational practices of wastewater treatment plants (WWTPs) can increase the sulfur content of sludge, devaluing it as a fuel. Thus, we investigated the biochemical mechanisms that elevate the sulfur content of sludge in a full-scale industrial WWTP receiving wastewater of the textile dyeing industry and a domestic WWTP by monitoring the sulfate, sulfur, and iron contents and the biochemical transformation of sulfate to sulfur in the wastewater and sludge treatment streams. A batch sulfate reduction rate test and microbial 16S rRNA and dsrB gene sequencing analyses were applied to assess the potential and activity of sulfate-reducing bacteria and their effect on sulfur deposition. This study indicated that the primary clarifier and anaerobic digester prominently reduced sulfate concentration through biochemical sulfate reduction and iron–sulfur complexation under anaerobic conditions, from 1247 mg/L in the influent to 6.2~59.8 mg/L in the industrial WWTP and from 46.7 mg/L to 0~0.8 mg/L in the domestic WWTPs. The anaerobic sludge, adapted in the high sulfate concentration of the industrial WWTP, exhibited a two times higher specific sulfate reduction rate (0.13 mg SO42−/gVSS/h) and sulfur content (3.14% DS) than the domestic WWTP sludge. Gene sequencing analysis of the population structure of common microbes and sulfate-reducing bacteria indicated the diversity of microorganisms involved in biochemical sulfate reduction in the sulfur cycle, supporting the data revealed by chemical analysis and batch tests.

Interface engineering enables stable and reversible zinc anode for high-performance Zn–I2 battery

Aqueous Zn-based batteries have been regarded as a promising energy storage system due to their high energy/power density, safety, and cost-effectiveness. However, their performance have been severely hindered by the dendrite growth of zinc and water-induced side reactions. Herein, a facial strategy of electrolyte modification with a high concentration of zinc sulfate and lithium iodide (LiI) as additives is proposed to guide the preferential growth along with the Zn (002) plane for the smooth Zn deposition. Compared to the pure zinc sulfate electrolyte, the Zn anode in the modified electrolyte exhibited the ultralong cycling stability for 3000 h at a capacity of 1 mAh cm−2 and 400 h at a higher capacity of 5 mAh cm−2, with low reversible deposition potentials of around 30 and 40 mV, respectively, demonstrating the stable plating/stripping behaviors. More importantly, the cycling stability of the Zn–I2 battery with the modified electrolyte can still deliver a large specific capacity after 5000 cycles. The strategy presented that the LiI as additive could not only provide an iodine-rich environment to induce the preferential growth of Zn (002) plane, but also eliminate the side corrosion reactions with the help of additional Li-ions, thus leading to the high-performing Zn–I2 battery.

Two problems in one shot: Vinasse and glycerol co-digestion in a thermophilic high-rate reactor to improve process stability even at high sulfate concentrations

Anaerobic co-digestion (AcoD) of sugarcane vinasse and glycerol can be profitable because of the destination of two biofuel wastes produced in large quantities in Brazil (ethanol and biodiesel, respectively) and the complementary properties of these substrates. Thus, the objective of this study was to assess the effect of increasing the organic loading rate (OLR) from 2 to 20 kg COD m−3 d−1 on the AcoD of vinasse and glycerol (50 %:50 % on a COD basis) in a thermophilic (55 °C) anaerobic fluidized bed reactor (AFBR). The highest methane production rate was observed at 20 kg COD m−3 d−1 (8.83 L CH4 d−1 L−1), while the methane yield remained stable at around 265 NmL CH4 g−1 CODrem in all conditions, even when influent vinasse reached 1811 mg SO42− L−1 (10 kg COD m−3 d−1). Sulfate was not detected in the effluent. Bacterial genera related to sulfate removal, such as Desulfovibrio and Desulfomicrobium, were observed by means of shotgun metagenomic sequencing at 10 kg COD m−3 d−1, as well as the acetoclastic archaea Methanosaeta and prevalence of genes encoding enzymes related to acetoclastic methanogenesis. It was concluded that process efficiency and methane production occurred even in higher sulfate concentrations due to glycerol addition.

Approaches for filtrate utilization from synthetic gypsum production.

Waste recycling and industrial wastewater treatment have always been of interest. A green approach was developed for the filtrate of synthetic gypsum production from water treatment coagulation sediments and spent sulfuric acid. Due to the high concentration of iron sulfate, concentrated filtrate showed good coagulation results, which were 5% lower than pure iron sulfate. In addition, a high concentration of iron facilitates its use as a precursor for synthesizing magnetic sorbents and photocatalysts. Such materials were synthesized by the solution combustion synthesis method. Oil sorption capacity reached 1.8g/g, comparable to some synthetic materials and higher than sorption materials based on natural materials. Photodegradation of acid telon blue dye after 90min of irradiation time was 82.7% with catalyst derived from filtrate compared to the just dye solution with 17.6% efficiency. The reaction rate constant for the photocatalyst sample was up to 11.4-fold higher compared with only UV treatment. The neutralized filtrate containing sulfur, calcium, magnesium, and sodium has been tested as a complex fertilizer. The results of bioindication for oil radish showed up to a 15% increase in the shoot length. A number of techno-economic indicators show that such an approach is advantageous from a technological, environmental, and economic point of view.

The Relationship of Uremic Toxin Indoxyl Sulfate and Intestinal Elimination Mechanisms in Hemodialysis Patients

Introduction: High indoxyl sulfate (IS) concentration is a serious problem for patients with CKD increasing the risk of cardiovascular diseases and CKD progression. Thus, the methods of decreasing the toxin concentrations are highly desired. The study aimed to discover the role of selected intestine-related factors on IS concentration. Methods: We evaluated the impact of ABCG2 and ABCC2 polymorphisms influencing activity and protein intake by normalized protein catabolic rate. Additionally, we examined the relation of IS and uric acid (UA) that can share common elimination transporters. A monocentric, prospective, open cohort pilot study was performed on 108 patients undergoing dialysis treatment. Results: The positive effect of residual diuresis on the reduction of IS levels was confirmed (p = 0.005). Also, an increase in IS depending on the dietary protein intake was confirmed (p = 0.040). No significant correlation between ABC gene polymorphisms was observed either, suggesting the negligible role of ABCG2 and ABCC2 in the elimination of IS in small bowel. The significant difference was observed for UA where ABCG2 421C>A (rs72552713) gene polymorphism was higher (505.3 μmol/L) in comparison with a wild-type genotype (360.5 μmol/L). Conclusion: No evidence of bowel elimination pathway via ABCC2 and ABCG2 transporters was found in renal replacement therapy patients.

Ultrafiltration as a pre-treatment technology to improve vinasse biomethanation

Vinasse is a residue that remains after the fractional distillation of fermented juice to obtain ethanol. Intended to extend the opportunities for by-product recovery, vinasse could be used as feedstock for biomethane production, departing from the linear focus of vinasse production, treatment, and disposal, to vinasse production and reuse. However, the high concentrations of sulfate and its inhibitory effect on biological activity could lower the yield of biomethane production. To overcome that, it was studied the potential of ultrafiltration membranes to alleviate the concentrations of sulfate from vinasse and concentrate the organic matter, intended to enhance the biomethane production potential. Raw vinasse, ultrafiltration concentrate, and ultrafiltration permeate were subjected to anaerobic digestion experiments and the cumulative biomethane yield was monitored over 70 days. The ultrafiltration concentrate presented the highest degradation rate (μm: 2.83 ± 0.24 mL/g-VS.d.mL-sample) and longest lag-phase time (λ: 12.31 ± 0.83 d) compared with raw sugarcane vinasse (μm: 1.44 ± 0.11 mL/g-VS.d.mL-sample; λ: 6.57 ± 0.93 d) and ultrafiltration permeate (μm: 1.14 ± 0.04 mL/g-VS.d.mL-sample; λ: 2.92 ± 0.74 d). The potential for biomethane recovery was complemented by an energetic analysis involved in biomethane production and processing. The biomethane recovery from ultrafiltration concentrate presented the lowest specific energy consumption (3.34 MJ/Nm³-CH4), followed by raw sugarcane vinasse (3.51 MJ/Nm³-CH4) and ultrafiltration permeate (3.64 MJ/Nm³-CH4). The remaining digested streams could still be potentially applied to soils for better use of their nutrients, however without an excessive load of organic matter already consumed during anaerobic digestion. Overall, the study demonstrated an effective alternative to salinity relief in raw sugarcane vinasse by ultrafiltration membranes and an alternative of higher vinasse valorization.

Sensitivity of Pathogenic Bacteria Strains to Treated Mine Water

Mine water as a result of meteoric and/or underground water's contact with tailings and underground workings could have an elevated content of metals associated with sulfate, often acidic, due to the bio-oxidation of sulfides. When entering aquatic ecosystems, the mine water can cause significant changes in the species' trophic levels, therefore a treatment is required to adjust the alkalinity and to remove the heavy metals and metalloids. The conventional mine water treatment removes metals, but in many cases it does not reduce the sulfate content. This paper aimed to predict the impact of conventionally treated mine water on the receiving river by assessing the genotoxic activity on an engineered Escherichia coli and by evaluating the toxic effects generated on two Gram-negative bacterial strains, Pseudomonas aeruginosa and Escherichia coli. Although the main chemical impact is the severe increases of calcium and sulfate concentrations, no significant genotoxic characteristics were detected on the Escherichia coli strain and on the cell-viability with a positive survival rate higher than 80%. Pseudomonas aeruginosa was more resistant than Escherichia coli in the presence of 1890 mg SO42-/L. This paper reveals different sensitivities and adaptabilities of pathogenic bacteria to high concentrations of sulfates in mine waters.

Deterioration of Mortar Bars Using Binary and Ternary Mixtures Immersed in Sodium Sulfate Solutions

In this study, the performance of several binary and ternary mixtures containing high-calcium fly ash and other pozzolans, such as Class F fly ash and silica fume, were investigated for their sulfate resistance using different sodium sulfate solutions. The mortar bars were placed in a similar sulfate solution as per modified ASTM C 1012/1012M (33,800 ppm SO42−) with a less severe sulfate solution (6000 ppm SO42−) has been tested to resemble actual field performance for a duration of 18 months. The phase composition of the mortar samples was investigated using X-ray diffraction and scanning electron microscope coupled with energy dispersive spectroscopy (SEM/EDS). Results show that the mortar bars placed in the moderate sulfate concentration experience less expansion and deterioration than the same bars placed in the higher sulfate concentration. Storage in sodium sulfate solutions resulted in the formation of ettringite and gypsum in both sulfate concentrations. Replacement of cement by high-calcium fly ash showed significantly higher amounts of ettringite formation, especially for the mortar bars stored in the higher sulfate concentration. SEM analysis revealed ettringite to be the primary cause of disruption and deterioration observed in the mortar bars.