The tsunami caused by the Great East Japan Earthquake hit the coast of Eastern Japan. The outflow conditions of 37 bridges were evaluated using β (the ratio of resistance to the tsunami force). β was found effective in judging the girder outflow. Moreover, two analytical approaches (video and numerical analyses) were conducted to evaluate the tsunami characteristics and outflow mechanisms of girders. In Shizugawa town, based on video analysis, the tsunami height and velocity variations were estimated. Besides, two mechanisms on the bridge girder at Shizugawa were analyzed (One, as the tsunami hit the girder but did not submerge it; the other, as the tsunami submerged the girder totally). It was noted that in both two mechanisms, the girder was strong enough to resist the tsunami. In Utatsu Bridge, by video and numerical analyses, the wave height was observed to rise slowly, which indicated that the wave shape was not a bore wave. Moreover, it was found that when the girders of Utatsu Bridge were flooded, due to effect of buoyancy, the resistance of the girders was insufficient to resist the tsunami force.
Various forms of damage to the bridge foundation structure in the revetment along riverbanks and sea coasts caused by liquefaction had been observed during past earthquakes. Several studies on liquefaction using physical model tests and numerical analysis have been conducted in recent years. However, few studies have investigated the seismic behavior of the foundation in a revetment with a slope. In strong earthquakes, the sloped ground is expected to be unstable, and lateral spreading of the ground may occur simultaneously with the loss of soil strength in the liquefaction layer. Moreover, in the seismic design specification (JRA-2002) of the bridge, the liquefaction verification of the foundation is stipulated for a flat ground but not for a sloped ground. Therefore, the effect of the lateral pressure of the liquefaction layer on the foundation in the revetment must be investigated further. This study aims to investigate the dynamic behavior of a steel pipe sheet pile (SPSP) foundation of a cable-stayed bridge and its effect on the performance of the superstructure in the revetment with a slope. A 1-G shaking table test with a scale of 1:60 was conducted on a flat model and a slope model of 15°. In addition, 2-D numerical modeling was applied in an effective stress analysis method that was used on a multi-spring model and cocktail glass model. The differences in the dynamic responses between the two models clearly illustrate the significant effect of the ground slope on the seismic behavior of the SPSP foundation and superstructure.
This paper proposes meta-modeling as a methodology for constructing a model that is consistent with continuum mechanics. Consistency means solving a Lagrangian of continuum mechanics by using a particular subset of continuum mechanics' function space, so that a solution of a consistent model is rigorously converted to a solution of continuum mechanics or vice versa. This conversion enables us to make smart use of solid and structure element analysis. Meta-modeling is applied to beam and plate problems, and it is shown that Rayleigh beam and Kirchhoff-Love plate are consistent with continuum mechanics.
Recently, externally bonded patch plates have been widely used for the repair or strengthening of steel members due to their ease of application. When the traffic loads are applied on the steel members strengthened with patch plates, shear and normal stresses are introduced to the adhesive layer especially in the vicinity of the patch plate end. Due to the higher shear and normal stresses at the end of the patch plate, the debonding of the patch plate from the steel member could occur before the yielding of steel member or patch plate. To prevent debonding of the patch plate, the shear and normal stresses in adhesive have been studied using theoretical, numerical, and Finite Element analyses. Meanwhile, the failure criterion for debonding has not been clarified. In this study, to develop the verification method for debonding, some failure criteria were compared. The compatibility of each failure criterion was validated from the debonding test.
On November 26, 2011, the Kutai-Kartanegara Suspension Bridge in Indonesia collapsed. The collapse was triggered by failure of the clamp of cable band that connects the hanger with the main cable in the middle of the centerspan. The national investigation team report cited the failure as a result of stress accumulation on the clamps that have been weakened by fatigue, initial fracture and corrosion. In this paper, we investigated in more detail the possibility of shear brittle fracture of the clamp's pin from the viewpoint of linear fracture mechanics by utilizing the measured Charpy absorbed energy. Several possible scenarios of defect sizes and combined stress conditions were assumed. The analysis shows that the shear brittle fracture could occur even under low shear stress level when several unfavorable conditions occur simultaneously.
Division B: Hydraulic, Coastal and Environmental Engineering
Numerous cases of hazardous flooding attributed to irrigation tank overflows under concentrated downpours have recently been reported. Using a hydrograph to predict overflows is an important countermeasure against hazardous flooding in downstream areas. However, many studies have considered only the peak flow discharge without a hydrograph timescale when predicting runoff characteristics due to irrigation tank overflows. This paper uses numerical simulation to emphasize the importance of runoff characteristics and proposes a new hydrographic index to evaluate flooding risks in downstream areas. The proposed index includes both the peak flow discharge and the hydrograph timescale. The applicability of this two-dimensional numerical simulation model is examined by comparing examples of actual damage with the results of in situ experimentation carried out in a narrow channel located at a mountainous site.
In recent years, disasters caused by typhoons, localized downpours, and other phenomena have occurred frequently, and concern over the risk of large-scale water damage caused by river flooding has risen. Although damage resulting from levee breach is particularly serious, there is a lack of technical data on the mechanism behind that phenomenon. Accordingly, this mechanism needs to be clarified to reduce the risk of flood damage. We examined the relationship between the quantification of the levee breach volume and hydraulic parameters. In the widening stage of levee breach, the breach phenomenon can be described in terms of the traction of soil masses from the levee body as a result of flood flow. It was also found that the relationship between the extent of dimensionless levee collapse and dimensionless traction force around the mouth of the breach can be expressed in a form similar to that of the bed load formula.
Momentum transfer of open-channel flows in the lateral direction is important in sediment transport, flood control, environmental issues, etc. in rivers. The lateral transfer of the streamwise momentum is known to be caused by three different mechanisms: a cross-sectional secondary current due to turbulence anisotropy (secondary current of the second kind), turbulence mixing with shear instability (K–H instability), and mass transfer from the rough-bottomed to the smooth-bottomed lane due to flow redistribution. Furthermore, Vermaas et al. (2011)1) have shown experimentally that the relative contribution of each mechanism to the momentum transfer is closely affected by depth. Thus, to elucidate the fundamental characteristics of the lateral momentum transfer, we performed three-dimensional (3-D) computations of shallow open-channel flows in two parallel lanes with beds of different roughness. We simulated the momentum transfer on roughness transition using a 3-D RANS (Reynolds Averaged Navier Stokes) type κ–ε turbulence model, which has significantly greater computational efficiency than DNS (Direct Numerical Simulation) or LES (Large Eddy Simulation). Two types of computations, focusing on either the well-developed or the developing process, were performed separately. The present numerical results show that although the linear κ–ε model completely fails to capture the fundamental characteristics of the flows, a second-order non-linear κ–ε model could estimate excellently each effect on the momentum transfer, including the dependence on flow depth.
Dike failures due to overtopping flows have recently occurred during floods. It is of great importance to understand the mechanism of dike failure processes and to predict dike erosion accurately for disaster mitigation. In this study, a numerical model to simulate dike breaching is developed based on a three-dimensional flow model in porous media and density function methods, and a non-equilibrium sediment transport model. Infiltration into a dike is also considered in the simulation. First, a numerical model is applied to flows over a solid embankment in order to validate the flow model. Then, dike erosion processes are simulated. Compared with the previous experimental results, it is shown that the numerical model can reproduce overflows and dike failure processes reasonably.
Knowledge of tide level is essential for safe navigation of ships in harbor, disposal and movement of sediments, environmental observations, explorations, and many more coastal and ocean engineering applications. Traditional methods such as harmonic analysis, least mean squares method, and hydrodynamic models have disadvantages in that they require excessive data, are time consuming, and are tedious to carry out. Artificial Neural Network (ANN) has been widely applied in the coastal engineering field in the last two decades for solving various problems related to time series forecasting of waves and tides; predicting sea-bed liquefaction and scour depth; and estimating design parameters of coastal engineering structures. Its ability to learn highly complex interrelationship based on provided data sets with the help of a learning algorithm, along with built-in error tolerance and less amount of data requirement, makes it a powerful modeling tool in the research community. In the present study, an attempt was made to predict tides at Karwar, located at the west coast of India, using a type of network called Non-linear Auto Regressive eXogenous input (NARX). It has an advantage in that the generated output is fed back to the network creating a loop. Conceptually, it differs in the fact that it uses the target given to it also as an input. Predictions were carried out for various durations using the weekly and monthly data sets. It was found that at Karwar, one year's prediction can be successfully carried out using one month data as an input with correlation coefficient (‘r’) greater than 0.97. The developed model was further applied to predict tides at New Mangalore Port Trust, Panambore, along the west coast of India, which is 260 kms south of Karwar. Results obtained were encouraging with ‘r’ value greater than 0.96.
In this study, simple equations for calculating ice sheet thickness were developed on the basis of an ice sheet thickness simulation model that used heat flux. In an array of equations, the coefficients α and β represented the effects of both snow cover and frazil ice and the effects of river ice melting, respectively. The air temperature, the water temperature, and the effective water depth were represented by independent variables. A method for calculating the ice sheet thickness on the basis of data on the air temperature alone was established. In this method, water temperatures were calculated by using air temperatures and simple equations, and a constant value was given to the effective water depth. The ice sheet thickness in a river was successfully determined by using a non-contact measuring technique. The values measured by this technique were reproduced by the values calculated by simple equations that used the air temperature as the sole input value. The simple equation using the sole input value of air temperature for calculating the ice sheet thickness was also used for retrospectively predicting the day when river water began to freeze and the day when river ice began to break for the past nine years on an actual river. The mean absolute errors in the prediction of the day of ice formation and the day of ice breakup on the basis of calculated values were 6 days and 2 days, respectively, in comparison with the predictions based on the measured values. This suggests that the simple equation is useful for accurate prediction of the days of ice formation and ice breakup.
Failure of coastal buildings under tsunami impact has caused numerous problems in past events. With the availability of advance computational capabilities, numerical simulation of such complex physical phenomena as tsunami-structure interaction has become a possibility. At the same time, a reliable simulation can be useful in understanding the tsunami-structure interaction mechanism and developing design techiques and guidelines for future constructions. In the study, three-dimensional numerical simulation was carried out to assess the failure of a reinforced concrete wall under tsunami loading, using the finite element modeling code LS-DYNA. The validity of the computational model was confirmed by comparing with the experiment results. Numerical simulation reproduced the failure and damage to the reinforced concrete wall significantly well, confirming the applicability of the simulation. Further analysis was carried out to assess the tsunami force on a lateral wall in an enclosed building and the results are discussed.
The application of negative water pressure by vacuum in pumping wells results in a drawdown of groundwater table at excavation sites. Due to the vacuum, negative water pressure will propagate around the pumping well. As a result, a large potential gradient is induced and groundwater drawdown is enhanced. In the present paper, a numerical model for three-dimensional unconfined groundwater flow towards a pumping well (Deep Well, hereafter DW) is developed and evaluated. First, the accuracy of the model is confirmed by comparing the pumping rates at steady state given by the DW formula. Second, the numerical model for negative water pressure (hereafter, NWP) is described. The model can be used in practical applications together with the water balance equation to describe groundwater inflow and pumping rate in a pumping well so that time-dependent boundary conditions are considered with the three-dimensional groundwater flow equation. How the saturated-negative pressure zone develops around the pumping well is shown. Detailed relationships between water level, pumping rate, and propagation of the negative pressure zone are described and analyzed. The analyses show that the model results can be used to operate air and water pumps more efficiently for water balance and groundwater drawdown.
This paper introduces a liquefaction mitigation method that uses log piles as environmentally friendly and practical solution for strengthening civil engineering structures. The liquefaction mitigation measure explored in this paper can be used to increase the earthquake resistance of loose sands by improving the density of soil. During the Tohoku Pacific earthquake in 2011, liquefaction was pervasive in large portions of the region, especially in Tokyo Bay and the city of Urayasu. Extensive liquefaction caused extensive damage to residential properties, electricity, water, sewage networks, and bridges. The mitigation of global warming is an important issue that requires immediate attention. Because the use of wood can be effective for preventing global warming, the authors have considered it to mitigate liquefaction damage. A series of large-scale shaking table tests was performed to investigate the effect of liquefaction mitigation by log piling into sandy ground. The results indicate that the method of log piling is an effective liquefaction mitigation compared with methods for increasing density, such as the densification method. Portable dynamic cone penetration (PDCP), Swedish weight sounding (SWS), automatic ram sounding (ARS), piezo drive cone (PDC), and flat dilatometer (FDM) tests, as well as field tests, were performed in the city of Urayasu. These tests were performed to confirm the effectiveness of log piling on liquefaction mitigation.
Three-dimensional (3D) finite element analysis programs are widely used for numerical simulation of tunneling with different degrees of approximation and various approaches. This study deals with the effects of earth pressure balanced (EPB) tunneling on the stress path and drainage condition of the soil during tunnel advancement. First, by using the Mohr-Coulomb criterion, the 3D stress distribution of the area near the crown and spring line of the tunnel is investigated, after which the tunnel stress path with respect to the Mohr-Coulomb yielding surface is presented. It was concluded that in the case of EPB shield tunneling, the soil around the cutter head tended to be in the elastic domain. Next, the effect of EPB tunneling on the drained and undrained behavior of the soil is examined. By taking into account the three significant factors of a) advance rate of the tunnel face, b) consolidation coefficient of the soil, and c) overburden depth of the tunnel, a parametric study is conducted and a numerical experimental equation proposed for determining drained or undrained soil condition during shield tunnel advancement. Finally, a case study of EPB tunneling is introduced. By using the case study data and results of EPB tunneling on stress path analyses, the proposed equation is verified.
Division D: Infrastructure Planning and Management
The main structure of timber arch bridges in China consists of two longitudinal polygonal arch systems made of straight logs. According to their present situation, location, and structural details, these timber arch bridges can be further divided into two types: one is exemplified by the non-extant ancient Bianhe rainbow bridge, and the other by the extant Min-zhe timber arch bridge. However, the historical origin of these two bridges is not clear and is still being argued. In this paper, the two types of timber arch bridges are structurally and historically analyzed and compared to determine which one is the pioneer from the technological development viewpoint. Results of our research indicate that, compared with the Bianhe rainbow bridge, the Min-zhe timber arch bridge has better traffic performance and can provide additional service performance. The spandrel structure, X-bracings as well as inserted wood blocks among logs in the Min-zhe timber arch bridge play important parts in carrying loads and enhancing the integrity and stability of its main structure, while the covering house adds dead load to the main structure to improve its resisting capacity against uplift loads. Therefore, from a reasonable consideration of technological development, the authors support the opinion that the Bianhe rainbow bridge is the origin of the Chinese timber arch bridges.
In showing the richness and diversity of the ground-based views with a lot of ambiguous dichotomy such as here/there, longitudinal/vertical, figure/ground, thing/field, the body/field bi-polar opposition was considered to be the most basic. The landscape is believed to float over the framework composed of these bi-polar opposition systems with the body/field in its center. The body of the self is incorporated into the landscape. Especially, the concept of the ego-field derived from body/field is proved to be of practical importance. After discussing some distinguished relevant previous works, we come to understand that the landscape can be effectively discussed in the body/field paradigm. Some practical design cases showed appropriateness of the body-involved theory and also suggest the needs of social theory for landscape. Thus, the concept of landscape is suggested to shift from the traditional view point/object paradigm to the body/field paradigm. To conclude, a schematic summary of the concept of landscape is shown based on the body/field paradigm.
Division E: Materials, Concrete Structures and Pavements
The paper represents the experimental work of strengthening prestressed concrete (PC) beams having strands ruptured at the midspan using externally bonded carbon fiber reinforced polymer (CFRP) sheets. The effects of different parameters as the sheet lengths, number of the bonded sheets and attaching schemes on the flexural performance were investigated. The flexural capacity of the strengthened beam having 50% ruptured strands was enhanced up to 167.3% compared to that of the undamaged PC beam. The outcomes exhibited that both the number of layers and the lengths of CFRP sheets affected the failure behaviors as well as the flexural capacity of the strengthened PC beams. The increase in the number of sheets resulted in the reduction of tensile stress resisted by the remaining prestressing strands. However, the increase in the number of sheets with insufficient sheet lengths did not provide a higher flexural strength because the failure mode was transformed from the debonding induced by the flexural cracks in the constant moment region to the debonding from the sheet ends. The increase in the sheet lengths not only prevented the latter failure but also significantly improved the beam stiffness. More importantly, the debonding of the sheets was avoided by wrapping the transverse sheets for the whole beam span. The prediction of the flexural strength of the strengthened PC beams based on the guidelines of ACI, JSCE and fib exhibited a good agreement with small total thickness of the bonded sheets. However, the equations in the guidelines were conservative when the total thickness of the bonded sheets was large.
The effects of shear reinforcement quantity on the shear capacity of Polypropylene Engineered Cementitious Composites (PP-ECC) beams were investigated in this study. A RC control beam was prepared with a shear reinforcement ratio of 0.42%. Five additional PP-ECC beams were fabricated with shear reinforcement ratios ranging from zero to 0.42%. One additional RC beam without shear reinforcement was also prepared for comparison. The experimental results showed that the shear carried by the PP-ECC decreased as the shear reinforcement ratio was increased. This was caused by the sliding on the critical crack surface that damaged the PP fibers bridging on the crack. If the reduction of shear carried by the fibers due to the increase in shear reinforcement was not considered, there could be overestimation of shear strength for PP-ECC structural members.
In this study, several techniques such as acoustic emission (AE), physical and mechanical tests, and scanning electron microscopy (SEM) were applied to investigate the effectiveness of high alite cement (HAC) to control microcracking in slag concrete subjected to a temperature regime simulating steam curing in early ages. The results revealed the capacity of HAC in improving resistance against microcracking of slag concrete. The mechanism for this large cracking resistance was clarified by AE analysis. The large microcrack resistance of HAC mortar might be partly due to the role of calcium hydroxide crystals as a kind of buffer preventing the propagation of microcracks. High bond strength between aggregate and HAC mortar contributed significantly to larger tensile strength.
A laboratory experiment on strain change with time in asphalt mixture under dynamic load was carried out in 2010 as previously reported, using composite specimens of asphalt mixture and a steel plate. The results revealed that tensile strain could occur in asphalt mixture under positive bending condition in many cases, depending on the pavement structure, test temperature, or loading time. The current study aimed at reproducing the strain behavior observed during the previous experiment by using linear visco-elastic analysis. The analysis verified that there could be many cases where tensile strain was induced in the asphalt mixture on a steel plate even under positive bending condition, successfully reproducing the strain behavior, which was irreproducible by elastic analysis. strain recovery increased in the steel plate with the decrease in load from the maximum level, the strain in the asphalt mixture changed from compressive to tensile, with larger tensile strain induced closer to the surface of the asphalt mixture. The strain behavior after the maximum load was irreproducible by elastic analysis.
The experimental results and predictive equation for shear capacity of Perfobond strip (PBL) joint connection with cast-in-place UFC to develop UFC-PC hybrid girders are presented in this paper. The UFC-PC bridge consists of PC segment at both ends and UFC segment at the middle of the span. Push-out test of twelve specimens was conducted. The experimental parameters were thickness of PBL, diameter of the hole of PBL, diameter of transverse rebar, prestressing stress on connection part, and the ratio of spacing to diameter of PBL. The experimental results indicated that PBL with cast-in-place UFC connection was sufficient to transfer the shear forces between the two segments. The contributions to shear capacity in each term were clarified. In addition, the shear resisting mechanisms were investigated. By inducing prestressing stress on the connection part, the shear capacity drastically increased due to the friction resistance. Finally, the shear capacity equation for PBL with cast-in-place UFC connection was proposed. The proposed calculation method can provide a reasonable agreement with the experimental results.
In today's socio-economic situations, as pavement infrastructures have aged, road agencies are obliged to monitor their pavements frequently and effectively. This study examines an automatic detection method of surface distress due to frost heaving on expressways. The result shows that an accelerometer-based profilometer can accurately detect the distress in the roughness profile by the lifting wavelet filters developed on the basis of lifting scheme theory. The filters especially respond to the severe distress similar to the distress learned for the lifting scheme that needs careful monitoring. Therefore, we conclude that the automatic distress detection method based on the lifting scheme theory improves the ability of acceleration-based profilometer that contribute to daily monitoring activities by road agencies.
This paper first illustrates briefly the possibility of fatigue failure of hydraulic, graded iron and steel slag base-course based on a follow-up on-site investigation on a trial asphalt pavement. Then, its fatigue failure criterion is derived based on repeated bending fatigue tests on the beam specimens prepared in the experimental yard. This failure criterion is implemented into the design flow of the Japanese mechanistic-empirical structural design method of asphalt pavement and an example analysis is presented. It is shown that the thickness of the base-course required for the designated design life can be reduced roughly by half with this modification of the current design flow.
Division F: Construction Engineering and Management
This study explores possibility of alleviating some of the problems in the current bidding system for public works projects. For the purpose of this study, resident involvement in the bidding procedure was conducted. The “bidding procedure with resident involvement” is one approach to encouraging public discussion concerning various issues of the current bidding system. In the practice conducted in this study, local people took part in the bidding procedure for a project to improve an intersection on a national highway in a downtown area. It was thought that local residents would easily understand the details of such a small-scale project and would regard a public works project in their area as something that relates directly to them. A questionnaire survey shows that, in selecting a contractor, the residents participating in the procedure place importance on the quality of works and the reliability of execution management. They value cost-effectiveness less. In other words, the survey found that the residents' requirements were the same as the conditions required by the party placing an order for public works construction. It was also found that resident participation in the public procurement procedure helped make bidding and contracting more transparent. A questionnaire survey was also conducted on building contractors with a main office or branch offices in Hokkaido, to understand their views on resident participation in bidding. The corporate characteristics of these contractors were classified into four groups according to their firm size and attitude toward resident involvement. These characteristics were used to examine the problems inherent in the bidding system incorporating resident participation.
The photocatalytic degradation of textile wastewater containing Reactive Black 5 (RB5) azo dye was investigated by using immobilized TiO2 nanofiber-nanoparticle composite catalyst on glass plates. The process was studied by monitoring the change in RB5 concentration, depletion in total organic carbon (TOC) and by determining the intermediate products using UV-visible spectrophotometry and gas chromatography-mass spectrometry (GC-MS) techniques. After immobilization, the composite shows higher photocatalytic activity for degradation of RB5 than that of nanoparticle thin-film layer under UV irradia-ion. Complete decolorization was achieved in 120 min, corresponding to organic degradation with a reduction in TOC after 300 min of UV irradiation by 91%. The photocatalytic degradation mechanism of RB5 was proposed based on the identified compounds by GC-MS technique, showing the destruction of the azo dye structure, which became smaller molecular mass compounds. The degradation slightly decreased after multiple reuse of composite catalyst during photocatalytic treatment. The recovery of its photocatalytic performance was obtained through reannealing.
To elucidate the air pollution, its features, its sources, and the influence of yellow sand (kosa) in Tsu City, the ion components and trace metals in precipitation at Mie University were measured along with their temporal changes. From the obtained correlation coefficients and the results of the principal component analysis, the ions and the trace metals in the precipitation were classified into three groups: the SSI group (the ions of Cl-, Na+, K+, Mg2+, ss-SO42- and ss-Ca2+, of which the main sources were sea salt); the ASI group (the ions of F-, NO3-, NH4+, nss-SO42- and nss-Ca2+, of which the main sources were anthropogenic pollution and soil); and the ASM group (trace metals of Al, Fe, Mn, Pb, and Zn, of which the main sources were anthropogenic pollution and soil). The concentrations of the SSI group tended to be higher with increased wind velocity. Results suggest that seawater was raised into the atmosphere in proportion to the wind velocity, and that the sea salt ions were transported and increased in the precipitation. The effects of long-range transport and local pollution on the pollutants and the soil elements in the precipitation were discussed from measurements of the concentration ratios of Pb and Zn (Pb/Zn) and backward trajectory analysis. The concentrations of ion components and trace metals during the rain events in Tsu City, Mie generally decreased over time. The condensed pollutants in the air are regarded as removed in the initial period of the rain events. We can confirm that the concentration ratios (Pb/Zn ratios) are almost identical to reported values for rain clouds through Japan. Only one day showed high rates of pollutants, but it is presumed to be not the effect of kosa but of the industrial zone to the north east of Tsu City.
Some diseases in Myanmar during the rainy season are related to the water environment and the water quality. In order to contribute to ensuring safe water supply, we collected and analyzed water samples in Myanmar in September 2011. Early research had already reported that coliform and E. Coli were detected in all the survey areas. We examined the water quality, especially chemical components harmful for health, and classified the sample waters into water quality-types in order to identify the sources and contamination. We obtained the following results: (1) Some tube well, dug well, and filtered waters were estimated to be contaminated and unsuitable for drinking and domestic water. (2) Waters at elevation less than about 10 m were more likely to be polluted. (3) The chemical components beyond the drinking water guideline values of World Health Organization (WHO) for health were NO2-, NO3-, Pb2+, and Mn2+. (4) For the taps with longer direct distance from the pumping station and lower elevation, there were several cases in which the tube well water geographically close to the tap intruded into the tap of filtered water. Then, we suggested some recommendations for water treatment based on WHO guidelines, and we also suggested the desirable improvements to the water supply systems. The first potential approach to treatment of drinking water supplies is to dilute the contaminated water with a low-contaminated source (e.g., high-elevation reservoirs). The desirable improvement to the water supply systems are as follows: (a) piping routes from reservoir to user places should be maintained as sanitary and clean, and (b) tube well water systems should be improved to prevent the intrusion of contaminants.
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