Softening Effect Of Water Research Articles

Evaluation of biological treatment for decreasing water hardness

Abstract Water in which the hardness is too high causes scale buildup in household appliances, and is known to decrease the efficiency of soap. This study investigates the effectiveness of biological treatment for water softening as opposed to the conventional method with chemical reagents. The water softening effect of biological treatment, which was prepared by circulating well water in a plastic container containing water tank pebbles for 3 months, was evaluated by introducing sample water containing a high hardness under various light irradiation conditions (continuous light irradiation, continuous shading, and intermittent light irradiation). Water hardness was decreased by 82% following 72 h of light exposure. Additionally, when exposed to intermittent light irradiation, water hardness was decreased markedly only during the light irradiation. The grown algae in the biological treatment tank were identified as Aphanochaete magnum, which inhabit widespread freshwater areas, by using 18S rRNA sequencing. Our data demonstrate that raw water can be softened using a biological treatment under various lightning conditions. It shows that the photosynthesis of naturally occurring algae plays a major role in the water softening effect. Our data suggest that biological treatment could be a novel method to soften water rather than the conventional chemical treatment.

Experimental study on the dynamic response and stability of bedding rock slopes with weak interlayers under heavy rainfall

Rainfall-induced landslides are notable geological hazards that occur frequently in the mountainous areas of Southwest China. Heavy rainfall in the wet season often causes landslides in mountainous areas, posing a threat to the infrastructure and human safety. For rock slopes, the sliding surface often occurs along a weak interlayer which plays a key role in controlling the mechanism of slope failure during the wet season. Typical bedding rock slope in the Maoergai reservoir was taken as the prototype to determine the physical modeling test materials and parameters, and a three-layered slope model was used to simulate a rock slope with a weak interlayer. A series of laboratory tests were carried out to study the dynamic response and stability of the bedding rock slope with a weak interlayer under heavy rainfall. The experimental results showed that the shear strength of the weak interlayer decreased due to a water softening effect. The changes of pore water pressure and rainfall erosion were the two dominant dynamic factors inducing the gradual decrease of shear resistance of the weak interlayer. In addition, the limit equilibrium method (Janbu’s method) was used to analyze the stability of the slope model and investigate the relationship between shear strength and slope stability. The obtained correlation between shear parameters and the safety factor indicated that the safety factor of the slope model decreased with the softening of the weak interlayer, and its internal friction angle was the key parameter influencing slope stability.

Investigation of engineering characteristics of calcareous soils from fringing reef

Engineering characteristics of calcareous soils are more peculiar due to the grain geometries, hardness and intraparticle voids. In the fringing reef in Sanya, calcareous soils were mixed with some terrestrial deposits, such as quartz sand and clay. In this paper, a series of laboratory and in-situ tests are conducted on calcareous soils to investigate the engineering characteristics and the effect of water saturation: laboratory large-scale direct shear tests, large-scale oedometer tests, X-Ray diffraction experiments, in-situ Plate Load Tests (PLTs) and Dynamic Cone Penetration Tests (DCPTs). The results showed that: (i) apparent cohesion of calcareous soils is quite higher than that of quartz sand but decreases significantly due to the softening effect of water; (ii) the bearing capacity decreases by 43% and deformation modulus decreases by 31% at the presence of 20% clay minerals; (iii) deformation modulus reduces 80% in saturated condition compared to dry condition; (iv) the relationship between N63.5 and bearing capacity of calcareous soils was established; therefore, engineers can decrease the amount of PLTs and increase DCPTs in the site exploration of fringing coral reef according to the testing results.

Hard water softening effect of a baby cleanser.

BackgroundHard water is associated with atopic dermatitis (eczema). We wanted to determine if a baby cleanser and its individual components altered free ionized calcium (Ca2+) in a simulated hard water baby bath. For these studies, an in vitro determination of free Ca2+ in a simulated hard water baby bath, and an in vivo exploratory study of free Ca2+ absorption into skin from hard water were performed.MethodsFree Ca2+ was measured with an ion-sensitive electrode in vitro in hard water (100–500 ppm, Ca2+) before and after addition of the cleanser and/or its components. In an exploratory study, absorption of Ca2+ into skin from hard water was determined in three female participants (aged 21–29 years).ResultsAt an in-use dilution of 1%, the test cleanser reduced free Ca2+ from ~500 ppm to <200 ppm; a 10% in-use dilution bound virtually all free Ca2+. The anionic surfactant component contributed the most to this effect. In the exploratory in vivo study, we measured a reduction of ~15% in free Ca2+ from simulated hard water over 10 minutes.ConclusionBaby cleansers can bind free Ca2+ and reduce the effective water hardness of bath water. Reducing the amount of free Ca2+ in the water will reduce the availability of the ion for binding to the skin. Altering or reducing free Ca2+ concentrations in bath water may be an important parameter in creating the ideal baby bath.

Experimental study on mechanical properties of weathered rock covered by loess

Based on dynamic triaxial test, the mechanical properties of the weathered rock covered by loess were studied. The cohesion value of weathered mudstone is far below that of the weathered sandstone, while the internal friction angle values are basically equivalent, about 30°. Compared with the undisturbed sample, the cohesion value of remodeling weathered rock sample decreases significantly. With the increase of moisture content, the strength of weathered mudstone is obviously decreased due to the influence of the water softening effect. This results illustrate that the bearing stratum is not easily affected by external disturbance in comparison to weathered mudstone. In the engineering, in order to ensure the good mechanical properties of the soil, more attention should be paid to keeping the water content constant, even to reducing the water content. The experiments show that the relations between shear stress and strain of weathered rock were nonlinear and the behavior of weathered rock can be expressed by the hyperbolic model. The initial modulus of undisturbed weathered rock, under the same consolidation conditions, is much greater than that of remodeling samples. Meanwhile, the initial dynamic elastic modulus of sandstone is also greater than that of the mudstone. The dynamic shear modulus ratios of the undisturbed sandstone, the undisturbed mudstone, as well as the remodeling mudstone have the normalization characteristics with the increase of dynamic shear strain. The damping ratio of mudstone is larger than that of the sandstone, and the damping ratio of remolding sample is also greater than that of the undisturbed mudstone. The mudstone has the bad mechanical properties as bearing stratum.

Study on the Effect of Hydraulic Immersion on the Strength and Deformation Characteristics of Sandstone

During the hydraulic structure design, the stability of abutment slope is critical to the normal operation of hydraulic structure. Through the tests, the effects of different hydraulic pressure on the strength and deformation characteristics of sandstone were studied, and the variation characteristics of rock masses with joints under secondary loading after excavation damage were analyzed as well. Test results show that: 1. When the samples without immersion secondly load until complete failure, ultimate strain increases slightly than the first loading, of which the increasing value is 7.5%; elastic modulus has a relatively large reduction than the first, which reduces 22.8%; deformation modulus has a less reduction, which is about 3.3%; 2. When considering the softening action of different hydraulic pressure on samples, ultimate strain increases by about 23% than that without consideration of immersion effect; elastic modulus reduces about 53%; deformation modulus reduces about 39%; 3. With the increment of immersion pressure, sample strength decreases greater, so does the softening effect of water on rock samples. With the increment of pressure, the strength of rock with joints has a relatively large reduction, which is from 27% to 41%, and the increasing value of intact rock mass isn't great, which is only from 25% to 27%. Jointed rock masses are more sensitive to the softening effect of water, and mechanical properties weaken obviously after long-term immersion with unstable problem.

Elastic moduli of dry and water-saturated carbonates — Effect of depositional texture, porosity, and permeability

Elastic moduli of water-saturated sedimentary rocks are in some cases different from moduli derived using Gassmann fluid substitution on data for rocks in the dry state. To address this discrepancy, we use a data set representing 115 carbonate samples from different depositional settings and a wide range of porosity and permeability. Depositional texture is reflected in the effect of water on elastic moduli and in the porosity-permeability relationship. Depositional texture is taken into account when porosity and permeability are combined in the effective specific surface of pores, which is related for a given pore fluid to the reference frequency as defined by Biot. For a given frequency of elastic waves, we obtain Biot’s frequency ratio between measured ultrasonic wave frequency and Biot reference frequency. For mostsamples with a frequency ratio above 10, elastic moduli in the water-saturated case are higher than predicted from elastic moduli in the dry case by Gassmann fluid substitution. This stiffening effect of water in some cases may be described by Biot’s high-frequency model, although in heterogeneous samples, a squirt mechanism is more probable. For data representing frequency ratios of 0.01 to 1, Gassmann fluid substitution works well. For samples with frequency ratios below 0.001, elastic moduli in the water-saturated case are lower than would be expected according to Gassmann’s equations or to Biot’s theory. This water-softening effect becomes stronger with decreasing frequency ratio. Water softening or stiffening of elastic moduli may be addressed by effective-medium modeling. In this study, we used the isoframe model to quantify water softening as a function of frequency ratio.

Quantification of water in different states of interaction with wood pulp fibres

The state of water in wet pulps was studied over a wide moisture range, reflecting the conditions on the paper machine from the press section to the reel. Two methods were used: water retention value (WRV) and differential scanning calorimetry (DSC). To increase the measuring accuracy, a modification to the WRV procedure was introduced. The results were directly compared by plotting the values over the observed moisture range. Different types of water were defined from DSC data: free water, freezing bound and non-freezing bound water. The water types were plotted in water distribution charts against the solids content. These charts were compared with the WRV data. For all pulps, the three water fractions were found to be interdependent while the free water removal rate decreased. Water removal did not take place as an independent water fraction removal sequence. The presence of fines and pulp recycling were found to influence the amount of freezing bound water, but not non-freezing bound water. The results showed an irreversible decrease in WRV (hornification) for all investigated pulps in the range of 20–75% solids content. This pattern corresponded to the relative amount of free water present. Freezing bound water disappeared at a solids content of over 80–85%. With the absence of free water, no further hornification occurred. It was concluded that the WRV appears to be reduced by a closure of large voids by adhesion of the cellulosic pore walls. The softening effect of water is required to cause ‘wet hornification’ of the structure.