High Buffering Capacity Research Articles

The enhancement of synthesized wastewater on non-uniform electrokinetic remediation of a Cd-spiked natural clayey soil.

It is usually very difficult to achieve satisfactory extraction efficiencies in electrokinetic remediation of heavy metal-contaminated soils of high acid/base buffer capacity. Enhancement agent is often required. In this study, synthesized citric acid industrial wastewater (CAIW) is used as the enhancement agent to remediate cadmium-spiked natural clayey soil from Shanghai, China. Four electrokinetic extraction experiments were carried out to evaluate the enhancement effects of CAIW on the remediation of metal-spiked clayed soil of high buffer capacity and the effects of treatment time and initial cadmium concentration on the migration of cadmium in the specimen. The results of electrokinetic experiments indicated that CAIW can efficiently enhance the transport of cadmium in comparison with HNO3 of the same pH. Cadmium mobilization was enhanced with prolonged treatment time from 104 to 261.2h, but the average cadmium removal efficiency was not significantly enhanced. A non-uniform cadmium distribution in the specimen was observed after the enhanced electrokinetic experiments due to the localized electrical gradients with an electrical gradient of approximately 1V/cm and a ratio of the distance between electrodes of the same polarity to the outer diameter of electrode of 2.8 (50:18mm).

Synthesis of europium-doped VSOP, customized enhancer solution and improved microscopy fluorescence methodology for unambiguous histological detection

BackgroundIntrinsic iron in biological tissues frequently precludes unambiguous the identification of iron oxide nanoparticles when iron-based detection methods are used. Here we report the full methodology for synthesizing very small iron oxide nanoparticles (VSOP) doped with europium (Eu) in their iron oxide core (Eu-VSOP) and their unambiguous qualitative and quantitative detection by fluorescence.Methods and resultsThe resulting Eu-VSOP contained 0.7 to 2.7% Eu relative to iron, which was sufficient for fluorescent detection while not altering other important particle parameters such as size, surface charge, or relaxivity. A customized enhancer solution with high buffer capacity and nearly neutral pH was developed to provide an antenna system that allowed fluorescent detection of Eu-VSOP in cells and histologic tissue slices as well as in solutions even under acidic conditions as frequently obtained from dissolved organic material. This enhancer solution allowed detection of Eu-VSOP using a standard fluorescence spectrophotometer and a fluorescence microscope equipped with a custom filter set with an excitation wavelength (λex) of 338 nm and an emission wavelength (λem) of 616 nm.ConclusionThe fluorescent detection of Eu-doped very small iron oxide nanoparticles (Eu-VSOP) provides a straightforward tool to unambiguously characterize VSOP biodistribution and toxicology at tissue, and cellular levels, providing a sensitive analytical tool to detect Eu-doped IONP in dissolved organ tissue and biological fluids with fluorescence instruments.

Design and performance assessment of building counter-walls integrating Moisture Buffering “active” devices

The use of building materials with high moisture buffering capacity is a well-recognized strategy to moderate the variation of indoor moisture loads. Many researchers investigated the ability and potential of finishing materials and furniture for the reduction of the amplitudes of indoor relative humidity by characterising their Moisture Buffering Value. Nevertheless, the recent and widespread building practice, which is increasingly trying to reduce the air permeability and thermal transmittance of the envelope, is likely to even worsening indoor humidity conditions, with consequences for durability of materials and inhabitants’ comfort and health. Very performing materials are then needed to act as buffering and quickly dampen high moisture loads.This paper proposes the design of a building internal counter wall equipped with an "active" moisture buffering device. This is able to measure the indoor relative humidity and consequently increase the adsorbing capacity of a porous material through an air-flow. Experimental activities were carried out on different prototypes with the combination of granular Sepiolite with two different pore structures and nonwoven fabrics.The devices effectiveness in terms of MBV has been dynamically tested in a climate chamber according to the DTU Nordtest method. Different “activation” times against several humidity levels were set in order to assess the best solution in different scenarios.

Alkalinized sewage sludge application improves fertility of acid soils

ABSTRACT Although it is known that alkalinized sewage sludge raises the pH of acid soils, there is limited knowledge regarding its effects on other soil fertility indicators, such as P and K availability and soil organic C content. Thus, the goal of this study was to evaluate how the application of alkalinized sewage sludge affects the fertility of acid soil. Twenty sewage treatment plants were selected throughout Paraná State (Brazil), and samples of alkalinized sewage sludge and samples of the most representative agricultural soil of the region were collected (covering soils with medium, clayey or very clayey texture). Each soil was incubated for 60 days with doses of sewage sludge (0, 10, 20, 40, and 80 Mg ha-1) from its region and equivalent doses of limestone. The alkalinized sewage sludge was superior to limestone in the correction of soil acidity (pH, Al3+, and H + Al3+) and P and Ca2+ availability. The sludge also increased Mg2+ availability in all soils, K+ in seven soils and organic C in three soils. The very clayey soils (higher buffering capacity) supported higher sludge doses than did clayey and medium texture soils. The alkalinized sewage sludge application in acid soils proved to be an interesting alternative to recycling this type of waste, because it improved soil fertility and could reduce costs associated with soil management and crop fertilization.

Heavy Metal Uptake by Herbs. V. Metal Accumulation and Physiological Effects Induced by Thiuram in Ocimum basilicum L.

Basil (Ocimum basilicum L.) is extensively cultivated as either an important spice and food additive or a source of essential oil crucial for the production of natural phenylpropanoids and terpenoids. It is frequently attacked by fungal diseases. The aim of the study was to estimate the impact of thiuram contact time on the uptake of manganese, cobalt, nickel, copper, zinc, cadmium, and lead by Ocimum basilicum L. The relevant plant physiological parameters were also investigated. Two farmland soils typical for the Polish rural environment were used. Studies involved soil analyses, bioavailable, and total forms for all investigated metals, chlorophyll content, and gas exchange. Atomic absorption spectrometry was used to determine concentration of all elements. Analysis of variance proved hypothesis that thiuram treatment of basil significantly influences metal transfer from soil and their concentration in roots and aboveground parts. This effect is mostly visible on the 14th day after the fungicide administration. Thiuram modifies mycoflora in the rhizosphere zone and subsequently affects either metal uptake from the soil environment or their further migration within the basil plant. Notable, those changes are more evident for basil planted in mineral soil as compared to organic soil with higher buffering capacity.

Origin and Geochemistry of Mine Water and its Impact on the Groundwater and Surface Running Water in Post-mining Environments: Zlatna Gold Mining Area (Romania)

In application at the Zlatna gold mining area (Apuseni Mountains, Romania), the correlation of water isotopes and geochemical data were successfully used to assess the genetic relationships between surface running water, groundwater and mine water, as well as to evaluate the mining effects on the surrounding environment after the cessation of mining operations. The majority of mine water sources display pH values between 4 and 5, i.e. acid mine water. The mine water characterized by slightly higher pH values (~6) interacts with ophiolitic rocks which have high pH buffering capacity. The neutral mine water (pH ~ 7) does not come into direct contact with reactive minerals, either because it is discharged from an exploration adit or because of the complete leaching of pyrite and other sulphides in old abandoned mining works. The later also shows low levels of heavy metals concentrations. Calcium is the dominant cation in mine water and in the majority of surface running water and groundwater sources, indicating the same mechanisms of mineralization. All mine water sources are $$\text{SO}_{4}^{2 - }$$ type and show very high $$\text{SO}_{4}^{2 - }$$ concentrations (6539 mg/l mean value). Surface and groundwater sources are classified either as $$\text{SO}_{4}^{2 - }$$ or as $$\text{HCO}_{3}^{ - }$$ type water. Linear correlation between δD and δ18O values indicates that all water sources belong to the meteoric cycle. Low δD and δ18O values of mine water (δD < −70‰; δ18O < −10‰) suggest snow melt and high-altitude precipitations as the main source of recharge. The mine water is less affected by the seasonal variation of temperature. In most cases, the variations in isotopic composition are within narrow limits (less than 1‰ for both δD and δ18O), and this result suggests well-mixed underground systems. Elevated concentration of sulphates, Zn and Fe in mine waters are the main issues of concern. For the study area, no relevant contamination of springs or phreatic water by mine water was revealed. On the contrary, surface running water is contaminated by mine water, and the negative effects of acid mine drainage occur mainly in the summer months when the flow of the surface running water decreases.

Application of a crustacean bioassay to evaluate a multi-contaminated (metal, PAH, PCB) harbor sediment before and after electrokinetic remediation using eco-friendly enhancing agents

Electrokinetic (EK) remediation can be a suitable technology for treating contaminated dredged harbor sediment, stored on terrestrial disposal sites. Citric acid (CA) and biosurfactants (rhamnolipids and saponin) were chosen as enhancing agents for simultaneous metal (Cd, Cr, Cu, Pb, Zn) and PAH/PCB removal by EK because of their potential low toxicity with a view to site restoration. Three EK runs were performed using a periodic voltage (1Vcm−1) and various concentrations of agents. The best combination of CA (0.2molL−1) and saponin (0.85gL−1) did not remove high amounts of metals (4.4–15.8%) and provided only slightly better results for PAH and PCB removal (29.2% and 38.2%, respectively). The harbor sediment was highly resistant to metal and organics mobilization and transport because of an aged contamination, a high buffering capacity, a very low hydraulic permeability and a high organic matter content. The efficiency of the EK process was also assessed by measuring the acute toxicity of the EK-treated sediment on E. affinis copepods exposed to sediment elutriates. Fortunately, the use of CA and biosurfactants did not significantly impact on sediment toxicity. Some treated sediment sections, particularly those near the anode compartment, were statistically more toxic than the raw sediment. More particularly, E. affinis copepods were significantly sensitive to low pH values and oxidative conditions, to Cu, and to a lesser extent to Pb amounts. The speciation of these metals probably changed in these pH and redox conditions so that they became more easily leachable and bioavailable. In contrast, toxicity was negatively correlated to PAH and PCB amounts after EK treatment, probably due to the production of oxidized metabolites of PAHs and PCBs.

Effects of organic composition on the anaerobic biodegradability of food waste

This work investigated the influence of carbohydrates, proteins and lipids on the anaerobic digestion of food waste (FW) and the relationship between the parameters characterising digestion. Increasing the concentrations of proteins and lipids, and decreasing carbohydrate content in FW, led to high buffering capacity, reduction of proteins (52.7–65.0%) and lipids (57.4–88.2%), and methane production (385–627 mLCH4/g volatile solid), while achieving a short retention time. There were no significant correlations between the reduction of organics, hydrolysis rate constant (0.25–0.66d−1) and composition of organics. Principal Component Analysis revealed that lipid, C, and N contents as well as the C/N ratio were the principal components for digestion. In addition, methane yield, the final concentrations of total ammonia nitrogen and free ammonia nitrogen, final pH values, and the reduction of proteins and lipids could be predicted by a second-order polynomial model, in terms of the protein and lipid weight fraction.

Development of a Salmonella Typhimurium challenge model in weaned pigs to evaluate effects of water and feed interventions on fecal shedding and growth performance.

The aim of this study was to develop a Typhimurium (ST) challenge model in weaned pigs suitable to evaluate effects of water and feed interventions on fecal shedding and growth performance. Two studies were performed. In Exp. 1 weaned pigs were fed either a standard diet (CON) or a diet with a high buffer capacity (HB) and challenged for either 3 or 7 consecutive days in a Latin square design with 4 × 8 individually housed pigs. In Exp. 2, the CON 7-d challenge method was chosen for further model development and validation. Thirty-two individually housed weaned pigs were divided over 4 treatments: a nonchallenged control group (NCON), a challenged positive control group (PCON), a challenged intervention group with acidified water (WATER), and a challenged intervention group with acidified feed (FEED). Pigs were orally challenged once daily on d 7 to 9 or d 7 to 13 after weaning (d 0) with 1 ×10 cfu ST. From d 0 to 28, rectal temperature and occurrence of diarrhea were recorded daily, and BW and feed intake were measured weekly. Fecal samples were collected on d 0, 2, 7, 9, 13, 16, 20, 23, and 27 in Exp. 1 and d 0, 2, 7, 8, 9, 13, 15, and 27 in Exp. 2 for quantification. The results of both experiments showed quantifiable fecal shedding (average peak shedding of approximately 3.5 log and 5.5 log cfu/g, respectively), accompanied by a transient 0.5°C increase in rectal temperature and an increase in occurrence of diarrhea. In Exp. 2 during the week of challenge (i.e., d 7 to 14), a reduction in growth performance (ADG: -157 to 200 g/d and G:F: -0.22 to 0.25 g/d; < 0.01) in PCON and FEED was observed compared to NCON, with WATER showing an intermediate response. The WATER treatment also showed a numerically lower peak shedding (difference of -1.3 to 1.4 log cfu/g) compared to PCON and FEED. To conclude, we repeatedly infected weaned pigs successfully with 1 × 10 cfu of ST for 7 consecutive days, resulting in detectable and quantifiable fecal shedding. This ST challenge model may be suitable for evaluation of effects of water and feed interventions on peak fecal shedding and growth performance.

Nickel removal from low permeable kaolin soil under unenhanced and EDTA-enhanced electrokinetic process

This paper represents a set of experimental tests on remediation of nickel-contaminated kaolin by Electrokinetic method. For this purpose, we conducted unenhanced and EDTA-enhanced Electrokinetic tests in one, three, and five days of treatment. In unenhanced tests, we used deionized water as an electrolyte in the anode and the cathode compartments. In the EDTA-enhance tests, we used ethylenediaaminetetra acetic acid 0.1 Molar in the cathode and sodium hydroxide 0.1 Molar in the anode. The average nickel removal for unenhanced tests after three and five days of treatment was 19 and 23 percent, respectively. High buffer capacity of the soil is responsible for low removal efficiency in the unenhanced tests, which maintained pH close to the initial amount that restrained nickel as an adsorbed or precipitated forms. The average nickel removal for EDTA-unenhanced tests after three and five days of treatment was 22 and 12 percent, respectively. Lower ionic mobility of EDTA-Ni complex in comparison with Ni+2, which is the main transportation mechanism for this complex, could be responsible for less removal efficiency in EDTA-enhanced test.

Moisture buffering phenomenon and its impact on building energy consumption

Moisture buffering is the ability of surface materials in the indoor environment to moderate the indoor humidity variations through adsorption or desorption. Materials with high moisture buffering capacity could be used to passively control the indoor moisture condition and consequently improve the indoor environmental quality and reduce the latent heat load of buildings. In order to characterize the moisture buffering ability of materials, the basic concept of moisture buffer value (MBV) is adopted. The paper first proposes a new mathematical expression of basic MBV, and then introduces a theoretical correction factor that could be used together with the MBV to calculate the moisture uptake/release by hygroscopic materials exposed to different types of humidity variations. Secondly, a simplified two-bottle test method is proposed to measure the MBV in the present study. The impact of moisture buffering on building energy consumption in different climate conditions is assessed by using numerical simulations. The results show that the potential energy saving rate could be up to 25–30% when using proper hygroscopic materials in the test building in temperate climates and semi-arid climates. Finally, the relationship between MBV and potential energy saving rate is also discussed.

Phytoplankton composition and biomass in tropical soda Lake Shala: seasonal changes in response to environmental drivers

AbstractAlthough soda lakes are valuable, sensitive aquatic resources where phytoplankton play a decisive role for the entire ecological functions, they are among the least‐studied ecosystems. Seasonal variations in phytoplankton composition, abundance and biomass in relation to some environmental parameters of the little known, deep, large, volcanic and saline–alkaline Lake Shala were investigated over an annual cycle. The lake phytoplankton community consisted of relatively diverse taxa (23) belonging to Bacillariophyceae, Cryptophyta, Cyanoprokaryota and Dinophyta. Bacillariophyceae and Cryptophyta were the dominant groups throughout the annual cycle, accounting for about 57% and 22% of the total number of species, and 28% and 69% of the total abundance of the phytoplankton community, respectively. Cryptomonas spp. were most abundant throughout nearly all months, contributing about 59%–95% of total phytoplankton abundance, followed by Thalassiosira sp. (1%–35%). The chlorophyll‐a concentration, as a proxy for algal biomass, was generally low (mean 17 μg L−1), exhibiting only small seasonal variation. The strong, inverse relation of chlorophyll‐a with water transparency (r = −0.69; n = 11) and the persistent dominance of species adapted to low‐light conditions and mixing suggest the overriding importance of these factors in controlling the lake's phytoplankton. The results of the present study generally suggest the phytoplankton composition and biomass in Lake Shala exhibited muted seasonal changes, despite the environmental perturbations, probably because of the lake's high buffering capacity against allochthonous impacts because of its voluminous nature.

Ensilage of seaweeds from an integrated multi-trophic aquaculture system

This study aimed to evaluate the feasibility of ensiling preservation of three seaweed species (Gracilaria vermiculophylla, Ulva rigida and Saccharina latissima) produced in an integrated multi-trophic aquaculture system without or with a lactic acid bacteria inoculant after 24–48hours wilting. The course of silage fermentation for a storage period up to nine weeks was also studied. The characteristics of fresh seaweeds suggested ensiling to be challenging. Overall, seaweeds presented a pH above 7.0, low dry matter (DM) content, and a non-structural polysaccharides content (DM basis) ranging from 14% (U. rigida) to 43% (S. latissima). The highest buffering capacity was recorded for U. rigida while the fermentation coefficient was higher for S. latissima, lower for U. rigida, and intermediate for G. vermiculophylla. The ensiling of S. latissima resulted in a pronounced lactic acid formation and a lower pH in comparison to the red and green seaweed silages. The ensilage of U. rigida and of G. vermiculophylla failed to decrease pH below 5.0 up to nine weeks, fermentation products suggesting the occurrence of a heterolactic fermentation or the promotion of heterofermentative bacteria and clostridia growth, respectively. The use of a lactic acid bacteria inoculant prior to ensiling had only minor effects on fermentation. Composition of seaweeds was generally preserved by ensilage, but in vitro digestibility of G. vermiculophylla was severely reduced. More research is needed to test different inoculants and dosages, and to assess the effects of seaweed silages on animal feed intake and performance.

Lactic acid fermentation of human urine to improve its fertilizing value and reduce odour emissions

During storage of urine, urea is biologically decomposed to ammonia, which can be lost through volatilization and in turn causes significant unpleasant smell. In response, lactic acid fermentation of urine is a cost-effective technique to decrease nitrogen volatilization and reduce odour emissions. Fresh urine (pH = 5.2–5.3 and NH4+-N = 1.2–1.3 g L−1) was lacto-fermented for 36 days in closed glass jars with a lactic acid bacterial inoculum from sauerkraut juice and compared to untreated, stored urine. In the lacto-fermented urine, the pH was reduced to 3.8–4.7 and the ammonium content by 22–30%, while the pH of the untreated urine rose to 6.1 and its ammonium content increased by 32% due to urea hydrolysis. The concentration of lactic acid bacteria in lacto-fermented urine was 7.3 CFU ml−1, suggesting that urine is a suitable growth medium for lactic acid bacteria. The odour of the stored urine was subjectively perceived by four people to be twice as strong as that of lacto-fermented samples. Lacto-fermented urine induced increased radish germination compared to stored urine (74–86% versus 2–31%). Adding a lactic acid bacterial inoculum to one week old urine in the storage tanks in a urine-diverting dry toilet reduced the pH from 8.9 to 7.7 after one month, while the ammonium content increased by 35%, probably due to the high initial pH of the urine. Given that the hydrolyzed stale urine has a high buffering capacity, the lactic acid bacterial inoculum should be added to the urine storage tank of a UDDT before urine starts to accumulate there to increase the efficiency of the lactic acid fermentation.

Single-step disruption and protein recovery from Chlorella vulgaris using ultrasonication and ionic liquid buffer aqueous solutions as extractive solvents

Microalgae are natural renewable sources providing attractive high-value products such as proteins. Due to the high costs incurred during drying processes, wet extraction from fresh microalgae biomass can be a promising approach. In this work, a single process step integrating cell disruption and protein recovery from wet Chlorella vulgaris by using ultrasonication and aqueous solutions of ionic liquids (ILs) as extractive solvents was proposed. The ILs assessed belong to the group of Good’s buffer ionic liquids (GBILs), and were prepared by a combination of Good’s buffer-based anions, namely 2-hydroxy-3-morpholinopropanesulfonate and 2-[bis(2-hydroxyethyl)amino]ethanesulfonate, and tetrabutylammonium, tetrabutylphosphonium and cholinium cations. These GBILs possess high biocompatibility and buffering capacity at neutral pH region. The protein recovery capabilities of the aqueous solutions of GBILs were compared with conventional buffers, using the same cell disruption approach. After the proper selection of the buffer solution with higher capability to extract microalgal proteins, alternative disruption techniques such as freeze-thaw, non-ionic detergent-based lysis using Triton X-100 and the combined methods were studied. The most efficient strategy, namely ultrasonication-assisted extraction, was further investigated for the effects of the process variables such as the buffer concentration, the addition of NaCl, the biomass concentration, and the ultrasonic time and power.

Quality of Biochars Made from Eucalyptus Tree Bark and Corncob Using a Pilot-Scale Retort Kiln

In many developing countries, traditional earth-mound kilns are still the principal technology for biochar production. The present study focused on the production and characterization of two biochars from common agricultural and forestry residues in Cameroon: corncob and eucalyptus tree bark. A pilot-scale retort kiln, made from local material, was constructed for biochar production. Its production efficiency varied between 33 and 68%, compared to the 10–22% obtained with traditional biochar production systems. Both biochars exhibited good agronomic properties and fulfilled key quality criteria for soil carbon sequestration, as described by the European Biochar Certificate (EBC) and the International Biochar Initiative (IBI). Organic carbon (Corg) > 50%, H/Corg < 0.7, and potential toxic elements far below environmental threshold values. Both biochars passed seed germination and worm inhibition toxicity tests. They were characterized by similar physical properties, apart from greater water absorption observed for corncob biochar (CCB). Chemical properties differed; CCB had higher buffer capacity, and was richer in soluble potassium (5473 ppm) and in graphitic like carbon (37.7%) compared to eucalyptus bark biochar (EB) (897 ppm and 24.9%). The latter was less alkaline (pH 8.1 vs. 9.3 for CCB), had more than twice its electrical conductivity (0.68 vs. 0.25 dS m−1 for CCB) and ash content (10.1 vs. 5.3%); EB had higher sum of cations. Our results demonstrated that the constructed pyrolyser could be a current and feasible alternative to be used by farmers in Cameroon, to produce a quality biochar product from common residues.

Optimization of Bioelectricity Generation in Constructed Wetland-Coupled Microbial Fuel Cell Systems

Constructed wetland-coupled microbial fuel cell systems (CW-MFCs) incorporate an aerobic zone and an anaerobic zone to generate electricity that achieves the oxidative degradation of contaminants. However, there are few reports on the performance of such coupled systems. In this study, we determined the optimal configuration of CW-MFCs to characterize their electricity generation performance. Based on the results using different levels of dissolved oxygen among the CW-MFCs, we concluded that a 20-cm distance between the anode and cathode produced an optimal removal of chemical oxygen demand (COD) of 94.90% with a 0.15 W/m3 power density, 339.80 Ω internal resistance, and 0.31% coulombic efficiency. In addition, a COD of 200 mg/L provided greater electricity generation (741 mV open circuit voltage, 0.20 W/m3 power density, 339.80 Ω internal resistance, and 0.49 mA current) and purification ability (90.45% COD removal) to meet system COD loading limitations than did higher COD values. By adding 50 mM phosphate buffer solution to synthetic wastewater, relatively high conductivity and buffer capacity were achieved, resulting in improvement in electricity generation. These findings highlight important aspects of bioelectricity generation in CW-MFCs.

Influence of nitrogen-rich substrates on biogas production and on the methanogenic community under mesophilic and thermophilic conditions

Grass silage was evaluated as a possible substrate in anaerobic digestion for generation of biogas in mesophilic and thermophilic long-term operation. Furthermore, the molecular biological parameter Metabolic Quotient (MQ) was evaluated as early warning system to predict process disturbance. Since this substrate is rich in nitrogen, high ammonia concentration of up to 2.2 g * kgFM−1 emerged. The high buffer capacity of the ammonium/ammonia system can disguise upcoming process acidification. At organic loading rates (OLR) below 1.0 kgVS * m−3 * d−1 (VS: volatile solids) for thermophilic and below 1.5 kgVS * m−3 * d−1 for mesophilic reactors, stable processes were established. With increasing OLR, the process was stressed until it broke down in the thermophilic reactors at an OLR of 3.5 kgVS * m−3 * d−1 or was stopped at an OLR of 4.5 kgVS * m−3 * d−1 in the mesophilic reactors. Mainly propionic acid accumulated in concentrations of up to 6.5 g * kgFM−1. Due to the high buffer capacity of the reactor sludge, the chemical parameter TVA/TIC (ratio of total volatile acids to total inorganic carbon) did not clearly indicate process disturbance in advance. In contrast, the MQ indicated metabolic stress of the methanogens before process breakdown and thus showed its potential as early warning system for process breakdown. During the whole experiment, hydrogenotrophic methanogens dominated. In the thermophilic reactors, Methanoculleus IIA-2 sp. 2 and Methanothermobacter wolfeii were dominant during stable process conditions and were displaced by Methanobacterium III sp. 4, a possible new bioindicator for disturbances at these conditions. In the mesophilic reactors, mainly Methanobacterium III sp. 4 was dominant at stable, stressed and acidified processes. A hitherto uncultivated genospecies, Methanobacteriaceae genus IV(B) sp. 3 was determined as possible new bioindicator for mesophilic process disturbance.

Red mud-based geopolymers with tailored alkali diffusion properties and pH buffering ability

This study develop novel porous red mud (RM) based geopolymers and evaluates their potential to ensure prolonged pH control. Several properties of the novel geopolymers were examined including buffering ability, alkalis leaching behaviour, mineralogical composition, microstructure and physical properties. Two experimental plans were defined to evaluate the influence of porosity and RM content on those properties. The pH values of the eluted water and geopolymers OH− ions leaching have been determined over time showing that total OH− ions and the leaching rate can be tailored by controlling the geopolymers porous structure and the availability of free alkaline species. The lower pH gradient over 28th d (1.64 pH units) was achieved by combining a 0.025 wt% pore forming agent (aluminium powder) with 45 wt% MK replacement by red mud.A high and prolonged buffer capacity was accomplished, proving that red mud-based geopolymers have potential to be applied as pH buffering material.

Water chemistry of the southern Tibetan Plateau: an assessment of the Yarlung Tsangpo river basin

The Yarlung Tsangpo is the largest river draining the southern Tibetan Plateau along the Himalayan ranges. In this paper, the ions and elements in the water of the Yarlung Tsangpo were studied. In general, the water of the Yarlung Tsangpo had a fairly high buffering capacity (pH ~8.8) and oxidation environment (ORP ~190 mv). Total dissolved solids averaged approximately 157 mg L−1, which is higher than that of the global mean level. Under the dominant rock weathering due to the abundant carbonates around the river basin, the ionic chemistry of the Yarlung Tsangpo was mainly composed of Ca2+ and HCO3 −. In addition, with a large amount water discharged into the river, groundwater (e.g., numerous chloride-rich hot springs) is another potentially important source of ions that affect the water chemistry in the Yarlung Tsangpo basin. Although watercourses on the Tibetan Plateau can generally be considered pristine, concentrations of some toxic elements (i.e., Cd and Pb) were found to be higher than the WHO guideline for drinking water due to increasing influence from anthropogenic activities (e.g., tourism, mining operations and municipal wastewater discharge), which constitute a risk to human livelihoods in both local and surrounding regions.