Water Treatment Plants In Taiwan Research Articles

Ti-containing NPs in raw water and their removal with conventional treatments in four water treatment plants in Taiwan.

The ingestion of Ti-containing nanoparticles from drinking water has emerged as a concern in recent years. This study therefore aimed to characterize Ti-containing nanoparticles in water samples collected from four water treatment plants in Taiwan and to explore the challenges associated with measuring them at low levels using single particle-inductively coupled plasma mass spectrometry. Additionally, the study sought to identify the most effective processes for the removal of Ti-containing nanoparticles. For each water treatment plant, two water samples were collected from raw water, sedimentation effluent, filtration effluent, and finished water, respectively. Results revealed that Ti-containing nanoparticles in raw water, with levels at 8.69μg/L and 296.8 × 103 particles/L, were removed by approximately 35% and 98%, respectively, in terms of mass concentration and particle number concentration, primarily through flocculation and sedimentation processes. The largest most frequent nanoparticle size in raw water (112.0 ± 2.8nm) was effectively reduced to 62.0 ± 0.7nm in finished water, while nanoparticles in the size range of 50-70nm showed limited changes. Anthracite was identified as a necessary component in the filter beds to further improve removal efficiency at the filtration unit. Moreover, the most frequent sizes of Ti-containing nanoparticles were found to be influenced by salinity. Insights into the challenges associated with measuring low-level Ti-containing nanoparticles in aqueous samples provide valuable information for future research and management of water treatment processes, thereby safeguarding human health.

Research on the Feasibility of Concrete Incorporating Water Purification Sludge

This study aims to develop the mix proportion of concrete incorporating water purification sludge (WPS), as parts of fine aggregate and consequently investigate its mechanical properties and durability. The experiments involve three sludges from Da-Nan, Lin-Nei and Nan-Hua water treatment plants in Taiwan. In addition to the control mixture without WPS, four replacement levels of 20%, 40%, 60% and 80% of fine aggregate were selected for preparing the concrete mixture. The concretes tested were designed to have three target compressive strengths of 14MPa, 18MPa and 21MPa. Test results show that the compressive strengths of the Da-Nan and Lin-Nei WPS concretes meet the design requirements, and the strength of the Nan-Hua WPS concrete is lower to be only suitable for application in low strength concretes. The shrinkage deformation of the Da-Nan and Lin-Nei WPS concretes increase with the increase of sludge replacement level, however, the shrinkage deformation decreases with the increase of the compressive strength of concrete. If the sludge replacement ratio is less than 40%, its effect on the compressive strength of the Da-Nan and Lin-Nei WPSs concrete is limited whether they are cured in water or in the air.

N-nitrosamines in drinking water and beer: Detection and risk assessment

Occurrence and risk related to nitrosamines, a group of carcinogenic compounds found in some drinking waters and beer, are studied. An analytical method using a solid-phase micro-extraction (SPME) along with gas chromatography (GC) and mass spectrometry (MS) was developed to determine seven N-nitrosamines in drinking water and beer, including N-nitrosomethylamine (NMEA), N-nitrosodiethylamine (NDEA), N-nitrosodimethylamine (NDMA), N-nitrosodi-n-propylamine (NDPA), N-nitrosopyrrolidine (NPyr), N-nitrosopiperidine (NPip), and N-nitrosodinbutylamine (NDBA). The analysis can be completed in 70 min, and only a 4 mL sample is required, with a detection limit of 0.1–0.8 ng/L for the seven nitrosamines in water and 6–15.7 ng/L in beer. The method was applied to analyze water samples collected from 11 reservoirs and their associated drinking water treatment plants in Taiwan and 10 beer samples from 6 brands with factories located in 6 countries. In the drinking water samples, all seven N-nitrosamines were detected, with NDMA having the highest level at 10.2 ng/L. In the beer samples, NDMA was detected at much lower concentrations (0.12–0.23 μg/L) than the 5 μg/L US standard, while NPip was detected at much higher concentrations (4.1–5.3 μg/L) compared to NDMA. The risk assessment indicates that the risk associated with NDMA is the highest among the studied N-nitrosamines in Taiwan's drinking water, with an average cancer risk of 6.4 × 10−06. For other nitrosamines, the risks are all below 10−6. For the risks associated with N-nitrosamines in beer, NDMA, NDEA, NDPA, and NPip are in the range of 1.5 × 10−05 to 4.6 × 10−04, while that for other nitrosamines are much lower. As for beer, no information for NPip and no modern information for NDEA and NDPA have previously been available, more studies about nitrosamines in beer are suggested for better estimation and control of the risks associated with consumption of beer.

Characterization of titanium dioxide nanoparticle removal in simulated drinking water treatment processes

This study characterized the fate of nano-TiO2 in both powder (TiO2(P)) and suspension (TiO2(S)) forms in simulated drinking water treatments. Nano-TiO2 solutions of 0.1, 1.0, and 10mg/L were prepared with deionized water and raw waters from the Changxing and Fengshan Water Treatment Plants in Taiwan to assess the effects of water matrices on nano-TiO2 behavior during water treatment. After the laboratory simulated water treatment, including pre-chlorination, coagulation, sedimentation, filtration and post-chlorination, the residual Ti concentration ranged from 2.7 to 47.4% in different treatment units and overall removal efficiency was between 52.6% and 97.3% in all cases except for nano-TiO2 at concentration of 0.1mg/L. Overall removal efficiency for the TiO2 at 10mg/L concentration ranged from 9.3 to 53.5%. Sedimentation (after coagulation) and filtration were the most important processes for removing nano-TiO2 due in part to particle agglomeration, which was confirmed by size distribution and zeta potential measurements. The size of nano-TiO2 increased from 21–36nm to 4490nm in the supernatant after sedimentation, and subsequent filtration treatment further removed all agglomerates at size >1μm. Zeta potential revealed interactions between nano-TiO2 particles and anionic functional groups or negatively-charged natural organic matters, leading to a decrease in surface charge. After sedimentation and filtration, the zeta potential of supernatants and filtrates were close to zero, meaning the absence of nanoparticles. The highest Ti removal after sedimentation occurred in Fengshan raw water due to higher ionic strength and coagulant dosage applied. On the other hand, the surfactant additives in TiO2(S) promoted dispersion of nano-TiO2 particles, which in turn led to lower particle removal. SEM images of nanoparticles after chlorination or coagulation revealed the coverage of nano-TiO2 particles by viscous substances and formation of colloidal structures.

Application of water treatment sludge in the manufacturing of lightweight aggregate

This study assesses the possible use of water treatment sludge for the production of lightweight aggregate (LWA), and focuses on the engineering properties of concrete made from this LWA. The experiments in this study involve 10 sludges from ten water treatment plants in Taiwan. All sludges can be used to manufacture LWAs in the laboratory, and exhibit a particle density (ρa) of 0.65–2.05g/cm3 and water absorption of 0.5–15%. Five sludges are suitable for manufacturing both structural LWA (ρa=1.2–1.8g/cm3) and non-structural LWA (ρa<1.0g/cm3), and the other five sludges are only suitable for manufacturing structural LWA. The sludge collected from the Hsing-Zu plant was successfully used to produce both structural and non-structural LWA on a large scale using a commercial rotary kiln. The resulting aggregates possessed a particle density of 1.35g/cm3 or 0.98g/cm3 and a bulk density of 726kg/m3 or 518kg/m3 for the structural LWA and non-structural LWA, respectively. The structural LWA meets the ASTM C330 requirements, with a bulk density less than 880kg/m3 for light coarse aggregate, and is a suitable LWA for structural concrete. The engineering properties of the concrete made from the structural LWA comply with the requirements of structural lightweight concrete.

Effects of Al-coagulant sludge characteristics on the efficiency of coagulants recovery by acidification

This study evaluated the effects of Al-coagulant sludge characteristics on the efficiency of coagulant recovery by acidification with H2SO4. Two sludge characteristics were studied: types of coagulant and textures of the suspended solid in raw water. The coagulant types are aluminium sulphate and polyaluminium chloride (PACl); the textures of the suspended solid are sand-based and clay-based. Efficiency of aluminium recovery at a pH of 2 was compared for different sludges obtained from water treatment plants in Taiwan. The results showed that efficiency of aluminium recovery from sludge containing clayey particles was higher than that from sludge containing sandy particles. As for the effect of coagulant types, the aluminium recovery efficiency for sludge using PACl ranged between 77% and 100%, whereas it ranged between 65% and 72% for sludge using aluminium sulphate as the coagulant. This means using PACl as the coagulant could result in higher recovery efficiency of coagulant and be beneficial for water treatment plants where renewable materials and waste reduction as the factors for making decisions regarding plant operations. However, other metals, such as manganese, could be released with aluminium during the acidification process and limit the use of the recovered coagulants. It is suggested that the recovered coagulants be used in wastewater treatment processes.

Occurrence of diarrheagenic Escherichia coli genes in raw water of water treatment plants

The high incidences of waterborne diseases are frequently associated with diarrheagenic Escherichia coli (DEC). DEC may pose a health risk to people who contact surface water for recreation or domestic use. However, there is no published report on the monitoring of DEC in drinking water sources in Taiwan. In this study, the occurrence of DEC genes in raw water for water treatment plants in Taiwan was investigated. Raw water samples were taken from water treatment plants adjacent to the Kaoping River in southern Taiwan. Each water sample was treated with membrane filtration followed by DNA extraction from the concentrate and concentrate enrichment, respectively. The target genes for various DEC strains of genes were identified, including enteroaggregative E. coli (EAEC), enterohemorrhagic E. coli (EHEC), enteroinvasive E. coli (EIEC), enteropathogenic E. coli (EPEC), and enterotoxigenic E. coli (ETEC). Among 55 water samples analyzed, DEC genes were detected in 16 (29.1%) samples. Strain-specific genes for EAEC, EHEC, EIEC, and EPEC were found in the percentages of 3.6%, 10.9%, 9.1%, and 9.1%, respectively. The specific gene for ETEC is not detected in the study. By looking at the presence/absence of specific genes and water sample characteristics, water temperature was found to differ significantly between samples with and without EHEC gene. In addition, pH levels differed significantly for EHEC and EPEC presence/absence genes, and turbidity was significantly different for water with and without EPEC genes. DEC genes were detected in 29.1% of the raw water samples in the study location. The potential health threat may be increased if the treatment efficiencies are not properly maintained. Routine monitoring of DEC in drinking water sources should be considered.

The on-site feasibility study of iron and manganese removal from groundwater by hollow-fiber microfiltration

The aim of this research was to investigate the removal of iron and manganese from groundwater by aeration, chlorine oxidation and microfiltration (MF). Pilot-scale experiments were performed at the Chang-Hua Water Treatment Plant in Taiwan. The raw waters contained soluble iron (0.4 mg/L) and manganese (0.5 mg/L) which were oxidized by chlorine and then filtered by hollow-fiber PTFE-MF. The oxidized particles on membranes under appropriate backwash were also investigated. The particle size and quality of treated water were examined. The experimental results indicated that the concentration of the residual manganese remained greater than 0.1 mg/L in treated water during the initial operation period. However, it decreased to below 0.01 mg/L after 2 weeks processing time. The scanning electron microscopy (SEM) energy dispersive spectroscopy analysis of oxidized metal particles under each process illustrated that the particles accumulated on membrane enhanced removal of iron and manganese, through autocatalytic activity in the accumulated layer on membrane. Moreover, the membrane operation pressure over 120 kPa was suggested for the active backwash process, where no structural damage on membrane was confirmed by SEM analysis.

Optimal Design of Water Treatment Facilities Under Nonlinear Conditions with Uncertainty Based on Flexible Tolerance Concept

The nonlinear programming (NLP) model is often encountered when developing an optimal model for design of water treatment. In recent years, researchers have studied numerous NLP solutions. However, some solutions are convergent but nonoptimal whereas others that are convergent and optimal are time consuming and costly to solve, because more than half of the calculations are for satisfying the constraints. Hence, a new concept of flexible tolerance is proposed in this research by allowing a tolerance for each constraint. In the process of calculations, the tolerance is reduced gradually so that it approaches zero when the optimal solution is reached. Therefore, many pull-in operations will become unnecessary, thus leading to more efficient and cost-effective solutions. For practical application, a stochastic optimal water treatment plant design model was developed using the hydrological and water quality data of an existing water treatment plant in Taiwan. A proposed new method for solving NLP problems is applied to solve for the optimal solution; results are then verified by comparing with the field data. Due to the limitation of article length, sensitivity analysis is not included in this article. Research results can be used by policy makers to develop a highly reliable water treatment systems under conditions of uncertain water quality.

Analysis of polychlorinated dibenzo-p-dioxins and furans in various aqueous samples in Taiwan

Twenty-one fresh water samples were taken from reservoirs, wells and drinking water treatment plants in Taiwan for measurement of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) concentrations. Due to low concentration of PCDD/Fs, water samples (400–1000 L) were collected by using the on-site large volume pre-concentration system and analyzed by high resolution gas chromatography (HRGC)/high resolution mass spectrometer (HRMS). Different characteristics of dioxin profiles in surface water and groundwater are observed. The PCDD/F concentrations in fresh water samples varied from 0.001 to 0.265 pg WHO 98-TEQ/L which are lower than the standard (12 pg WHO 98-TEQ/L) set by the Taiwan Environmental Protection Administration (TEPA) for drinking water. Only a small fraction (<5%) of the total PCDD/F concentration in fresh water samples was water-soluble. As a result of their hydrophobicity, PCDD/Fs are effectively removed along with suspended solid via the water treatment process (average 98% removal efficiency).

Establishment and Implementation of Source Water Implementation Plan for Water Treatment Plants in Taiwan

In accordance with the source water implementation plan rule (SWIPR) in Taiwan, water treatment plants (WTPs) with source water parameters exceeding the source water quality standards are required to submit a source water implementation plan to improve the source water and drinking water quality. In this study, the SWIPR was analyzed, and the concept of comprehensive performance evaluation (CPE) was applied for upgrading the performance of WTPs. Three WTPs [Da-Nan WTP (Type 1), Liu-Du WTP (Type 2), and Chen-Chin-Lake WTP (Type 3)] were selected as demonstration projects. A CPE team was established to evaluate the operations of these WTPs and make recommendations for improving the performance of the WTPs to achieve the drinking water standards. This paper describes the analysis and recommendations of the CPE team.

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This study characterized the fate of nano-TiO2 in both powder (TiO2(P)) and suspension (TiO2(S)) forms in simulated drinking water treatments. Nano-TiO2 solutions of 0.1, 1.0, and 10 mg/L were prepared with deionized water and raw waters from the Changxing and Fengshan Water Treatment Plants in Taiwan to assess the effects of water matrices on nano-TiO2 behavior during water treatment. After the laboratory simulated water treatment, including pre-chlorination, coagulation, sedimentation, filtration and post-chlorination, the residual Ti concentration ranged from 2.7 to 47.4% in different treatment units and overall removal efficiency was between 52.6% and 97.3% in all cases except for nano-TiO2 at concentration of 0.1 mg/L. Overall removal efficiency for the TiO2 at 10 mg/L concentration ranged from 9.3 to 53.5%. Sedimentation (after coagulation) and filtration were the most important processes for removing nano-TiO2 due in part to particle agglomeration, which was confirmed by size distribution and zeta potential measurements. The size of nano-TiO2 increased from 21–36 nm to 4490 nm in the supernatant after sedimentation, and subsequent filtration treatment further removed all agglomerates at size > 1 μm. Zeta potential revealed interactions between nano-TiO2 particles and anionic functional groups or negatively-charged natural organic matters, leading to a decrease in surface charge. After sedimentation and filtration, the zeta potential of supernatants and filtrates were close to zero, meaning the absence of nanoparticles. The highest Ti removal after sedimentation occurred in Fengshan raw water due to higher ionic strength and coagulant dosage applied. On the other hand, the surfactant additives in TiO2(S) promoted dispersion of nano-TiO2 particles, which in turn led to lower particle removal. SEM images of nanoparticles after chlorination or coagulation revealed the coverage of nano-TiO2 particles by viscous substances and formation of colloidal structures.

Mixing Water Treatment Residual with Excavation Waste Soil in Brick and Artificial Aggregate Making

A large quantity of water treatment residual is generated each year from fresh water treatment plants in Taiwan. Landfill disposal of the nonhazardous sludge is impractical because of the high cost of transportation and an increasing scarcity of landfill sites in Taiwan. The water treatment residual was characterized; the ceramic bodies were prepared and sintered to formulate into building bricks and artificial aggregates. The sintering temperature requirement by the water treatment residual was higher than normally practiced in brick works due to the higher Al2 O3 and lower Si O2 content. The excavation waste soil, practically clay, was blended with water treatment residual to improve the brick quality. Under the commonly practiced brick-making condition, up to 15% of water treatment residual could be added to produce first grade brick specified by the National Science Council (NSC). Test results of specific gravity, water absorption, and compressive strength of the artificial aggregates confirmed its ap...

Adsorption of divalent manganese ion on manganese-coated sand

Locally available manganese-coated sand, from packing and a by-product of the filtration process for water treatment plants in Taiwan, was found to be a low cost and promising adsorbent for the removal of Mn2+ from raw water. In this work, adsorption and desorption of Mn2+ in water have been studied by using batch techniques. The equilibrium adsorption level was determined to be a function of the solution pH, contact time and adsorbate concentration. The equilibrium adsorption capacity of Mn2+ was obtained by using a pseudo-Langmuir isotherm. Ion exchange is probably one of the major adsorption mechanisms for binding divalent manganese ions to the coated sand. The results provide a feasible hypothesis of adsorption mechanisms. This study also supplies significant plant operation capacity data for engineering design.

Characteristics of manganese-coated sand using SEM and EDAX analysis

“Manganese-coated sand” is a type of silica medium coated with manganese oxides, formed from the sorption of manganese oxides during long-term filtration via the process of rapid sand filtration, followed by aeration in a water treatment plant. Locally available manganese-coated sand, both for packing and as a byproduct of filtration processes for water treatment plants in Taiwan, was found to be a low-cost and promising adsorbent for removal of Mn 2+ from raw water. This study was conducted to build the basic data for coating hydrated manganese oxide on the sand surface to utilize the adsorbent properties of the coating and the filtration properties of the sand. In this study, gas adsorption porosimetry and scanning electron microscopy analyses were used to investigate the surface properties of the coated layer. An energy dispersive X-ray (EDAX) technique of analysis was used to characterize metal adsorption sites on a manganese-coated sand surface. Results indicated that manganese-coated sand had more micropores and higher specific surface area, owing to attachment of manganese sand. Manganese ions penetrated into the micropores and mesopores of manganese oxide on a sandy surface; regeneration of manganese-coated sand could be achieved by soaking with pH<2.0 acid solution. Results of EDAX analysis showed that the interfacial layer constructed the interface of manganese-coated sand. Acid and alkali resistance tests interpret a wide application range of pH for manganese-coated sand, and general temperature conditions do not affect the performance of this sand. Manganese-coated sand is potentially suitable for application as a packed bed for treatment of heavy metals from water. The results of this study can also benefit plant operational capacity data for engineering design.

Estimation of Potential Lifetime Cancer Risks for Trihalomethanes from Consuming Chlorinated Drinking Water in Taiwan

Data on concentrations of trihalomethanes (THMs) in raw and chlorinated water collected from three water treatment plants in Taiwan and estimates of the lifetime cancer risk for THMs from drinking water, using age-adjusted factors and volatilization terms, are presented. Data on THM levels in drinking water were obtained from the annual reports of the Environmental Protection Administration (EPA) of Taiwan. The methodology for estimation of lifetime cancer risks was taken from the USEPA. Chloroform was the major species of THMs, especially in the water plant of south Taiwan. Chloroform contributed the majority of the lifetime cancer risks (range: 87.5–92.5%) of total risks from the three water supply areas. All lifetime cancer risks for CHCl3, CHBrCl2, CHBr2Cl, and CHBr3 from consuming tap water in the three water supply areas were higher than 10−6. The sum of lifetime cancer risks for CHCl3, CHBrCl2, CHBr2Cl, and CHBr3 was highest (total risk for total THMs<1.94×10−4) for tap water from south Taiwan.

THE PREVALENCE OF GIARDIA AND CRYPTOSPORIDIUM IN TAIWAN WATER SUPPLIES

Giardia and Cryptosporidium have emerged as waterborne pathogens of concern. Thirty-one water samples were collected from nine potable water treatment plants in Taiwan and investigated for the presence of Giardia cysts and Cryptosporidium oocysts. The immunofluorescence assay was used for the simultaneous detection of cysts and oocysts. The frequency of occurrence of cysts was 77.8% for Giardia and 72.2% for Cryptosporidium in 18 raw water samples. Ten out of 13 samples collected from treated water samples showed the presence of cysts, while in 5 out of 13 treated water samples oocysts were detected. The risk assessment for adverse human effects arising from the presence of cysts and oocysts indicates the possibility of waterborne transmission of Giardia and Cryptosporidium infection in Taiwan if water is not adequately treated.

Development of surrogate organic contaminant parameters for source water quality standards in Taiwan, ROC

The objective of this research was to develop a rationale for selecting representative water quality parameters for organic contaminants and microorganisms and determining their respective contaminant level (or regulated value) for the source water quality standards in Taiwan. It was observed that chemical oxygen demand (COD) and total organic carbon (TOC) have strong correlation with UV 254 in spite of the raw water which suggests, TOC and COD should be regarded as the surrogate parameters for water quality concerns. It was also proposed to implement 4.0 mg/L of TOC as a source water criteria at the present time and to adopt a more stringent value (2. 0 mg/L of TOC) in the next phase (at 2002). The total coliform regulated from 10,000 to 20,000 most probable number (MPN)/100m1 level appears to be the most economic and logical way to control trihalomethanes (TI-IIM) formation and disinfection efficiency at the water treatment plant in Taiwan.

System Analysis of Water Treatment Plant in Taiwan

This paper presents an application of a system analysis tool to evaluate the design and operation of a water treatment plant in Taiwan. The optimal design and operation problem is posted as a nonlinear programming problem in which the decision variables are the capacities of the treatment components and the alum and chlorine feed rates used in the treatment process. The solutions to this nonlinear programming problem are obtained from a modified Hestenes' method. Application of the model to the reevaluation of an existing treatment plant in Taiwan revealed that, with the exception of the rapid mixing basin, the optimal capacities determined by the proposed model came fairly close to the original design. Optimal alum and chlorine feed rates and the optimal construction and operation costs for the plant can be estimated from the model. The results of this study suggest that the proposed tool can be used to evaluate water treatment plant design and operation in the future.