Waterworks Bureau Research Articles

Strengthening the Emergency Water Supply System Utilizing Emergency Medical Information System at the Kurashiki City Waterworks Bureau

Strengthening the Emergency Water Supply System Utilizing Emergency Medical Information System at the Kurashiki City Waterworks Bureau

Efficient maintenance method for water supply facilities focused on the carbonation of concrete

Abstract In water supply facilities such as distribution reservoirs, the inner surface of reinforced concrete (RC) tanks is often coated with resin paint or the concrete cover depth is increased to protect the concrete from surface deterioration. However, there is little published research on carbonation – one of the main causes of concrete deterioration – in relation to RC tanks, leaving room for improvement with regard to methods for preventing surface deterioration. This study discusses the impact of surface coating and environmental conditions on the carbonation rate of concrete based on a survey of the present state of RC tanks of the Sapporo Waterworks Bureau. Coating was found to have an inhibitory effect on carbonation. Because the carbonation rate of concrete used for the inside and outside of RC tanks was slow, the sufficient concrete cover depth to protect rebar from carbonation while in service was found to be 75 mm for RC tanks without coating.

Initiatives for utilizing renewable energy in water supply treatment

Maintaining a safe and reliable public water supply uses massive amounts of energy, prompting calls for energy saving measures. The Yokohama Water Works Bureau has established the goal of building a water supply system that is environmentally friendly by implementing a variety of initiatives, starting with efforts in renewable energy. These efforts have featured installing solar power and micro hydropower generation facilities at our purification plants and distribution reservoirs. The Yokohama water treatment facilities include purification plants based on gravity systems (Nishiya and Kawai plants) and pumped systems (Kosuzume plant). As the purification plants employing gravity systems place a smaller load on the environment, we use them as effectively as we can. When it was time to refurbish the distribution pumps, we reviewed the pump control system and identified initiatives for reducing pumped system power consumption.

Fracture behavior of wasted activated carbon powder composites

At the Waterworks Bureau (Tokyo Metropolitan Government), activated carbon has been used for filtering water. After being used for the filtering process, it is normally disposed or burned for thermal recycling. However, CO2 emissions occur during the thermal recycling. This work focuses on the identification of mechanical behavior of recycled wasted activated carbon (WAC) in order to elaborate smart materials having mechanical–electrical functions. Acoustic emission technique (AE) was used intensively as characterization support in which sensors were attached to detect microdamage during bending tests. At first, the resonant frequencies of the specimens were measured using the through-transmission test. The resonant frequencies of the specimens containing low weight fractions of WAC powder were less in comparison to the frequencies of the specimens with higher volume fraction. The frequency analysis was carried out with the projected wavelet transform on the signals detected during bending tests. Obtained data showed that, typically, the first major peaks showed the resonant frequency of the sensors, while the second major peaks exhibited signals indicative of resin cracking. The surfaces of the fractured specimens were analyzed by optical microscopy in order to visualize the crack formation and propagation on the activated carbon composite under flexural stresses. Consequently, fractographic and AE analyses provide better understanding of the failure mechanisms involved.

Effect of Viscoelastic Behavior on Electroconductivity of Recycled Activated Carbon Composites

In the Waterworks Bureau, the activated carbon has been used for filtering water. After the life service of activated carbon, it is normally disposed. This work focuses on the processing of a composite material in order to recycle these wasted carbon particles. These activated carbons were used for the filler of composite materials, and a composite with carbon contents of 10% ~ 60% was manufactured and characterized. They exhibited electroconductive behavior because of the carbon particles used as fillers. The electroconductivity have an intimate relationship with the strain of the material. However, because of the composite viscoelasticity, the electroconductivity presented changes by their stress relaxation behavior with the same strain. In this study, it was revealed the relationship between the viscoelasticity and the electroconductivity of recycled activated carbon composites.

119206 使用済活性炭強化ポリプロピレン複合材料の変形特性と導電性に関する研究(OS06 高分子材料および高分子系複合材料,オーガナイズド・セッション)

In the Waterworks Bureau, the activated carbon was used for filtering the water. After use the activated carbon, they were disposed. In this work, we tried to make that composite to recycle these carbons. These wasted activated carbons were used for the filler of composite materials, and we got the composite with the carbon contents of 10%〜60%. To evaluate of mechanical behavior of these composites, tensile test and stress relaxation test were carried out. The results show the powder contents dependency on tensile strength and Young's modulus. As seen in the results of stress relaxation test, the effect of powder contents on stress relaxation was revealed. To evaluate the electric property, the electric resistance was measured by 4-terminal method during tensile test and stress relaxation test. By the measurement of electric resistance, these composites can be used as smart materials.

Effective Measures for CO2 Reduction Harnessing the Potential Water Energy Present in the Water Service Industry

Sapporo Waterworks Bureau's (SWB's) measures for CO2 reduction started in 1982 with a hydropower project at the Moiwa Water Purification Plant (MWPP) (cap. 155,000 m3/day). Operation of the generator was temporarily discontinued in 2001 for full-scale reconstruction of the water purification plant (WPP); after the completion of the reconstruction, the power generation equipment was renewed, and the operation resumed as a joint project with a private company in 2007. Power generation is on-site since the hydropower generator within the MWPP area provides energy consumed at the MWPP and the adjoining Waterworks Museum. This power generation is expected to create an energy saving effect equivalent to 1,500 tons of CO2 and over 10 million yen of annual net benefit. In order to increase the usage rate of low-cost, clean energy like hydropower at the WPP, SWB has made a series of adjustments to the operating methods of the plant. Then, as a result, the generation covers 97% of the energy used on-site at present. Furthermore, SWB is considering introducing other hydropower facilities of this kind that harness water transmission energy from the Shiraikawa WPP (cap. 650,000 m3/day) to the major distribution reservoirs.

The Investigated Result on the Leakage Accident at the Sasage Pump Facility of Yokohama Waterworks Bureau

The Investigated Result on the Leakage Accident at the Sasage Pump Facility of Yokohama Waterworks Bureau

Influence of water-related appliances on projected domestic water use in Tokyo

In this study, the amount of domestic water use was quantified by estimating the usage rates of various water-related appliances. Tokyo Metropolis was selected as a case study because it was relatively easy to obtain detailed data from Tokyo Waterworks Bureau. In the analysis, the calculations for domestic water use reproduced actual usage figures from 1998 to 2006. From the maximum domestic water use per capita in 1997 the projected reduction was estimated to be 9% by 2025 and 10% by 2050. In addition, our results indicate that water use for both bath and toilet is expected to remain high in the future. We performed a simulation assuming that a 6 L-type toilet is installed by all consumers, with the results suggesting that domestic water use per capita per day could reduce to around 200 L. It was therefore concluded that the replacement of a conventional toilet with a water-saving-type toilet is one of the most effective solutions for reducing domestic water use.

A STUDY ON THE DESIGN OF NAGASAWA FILTRATION PLANT BY MAMORU YAMADA

In order to identify a taste of Yamada Mamoru's view of architecture in the Nagasawa Filtration Plant, which was designed by him in 1957, it is the aesthetic characteristics of the Nagasawa Filtration Plant are analyzed in this paper. Based on the documents obtained from the Waterworks Bureau as well as the literature on Yamada's work, the circumstances leading to the construction of the Nagasawa Filtration Plant as well as the context within which Yamada designed it are understood. The features of the architectural design of the building are identified from the original drawings, e.g. the site plan, the floor plans, the section plans and the elevation plans. Also the methods for deciding the curves shown in the columns and the openings are calculated from the original diagrams which detail the shape of the columns.

A Supply Promotion Program of Yokohama Water Works Bureau for Safe and Tasty Drinking Water(Dependability of Social Systems)

A Supply Promotion Program of Yokohama Water Works Bureau for Safe and Tasty Drinking Water(Dependability of Social Systems)

Report of BAC Replacement in Osaka City

An advanced water treatment system was introduced at the Osaka Municipal Water Works Bureau in March 2000. This system incorporates ozonation and a granular activated carbon (GAC) process into conventional treatment processes, improving tap water quality. The GAC process is the last stage of the process, and it can effectively remove trihalomethane precursors and other toxic organic substances. GAC treats water through a physical adsorption effect inherent in the GAC itself, and an effect by the microorganisms in the GAC layer (called the biological activated carbon (BAC) effect). Sparse reports on long-term changes in the BAC effect make it very difficult to determine the replacement period for BAC. A long-term study of BAC water treatment performance, physical characteristics, and other factors was conducted in Osaka City in order to decide upon BAC replacement standards. 48 water quality items were checked at a demonstration plant and with an experimental device. Three patterns of deterioration in BAC water treatment performance were identified. Physical properties of BAC (5 items including adsorption capacity and hardness) were also studied, and no significant correlation with water treatment performance was found. An optimal BAC replacement standard was decided upon from this and other factors (costs, environmental influence, etc.).

An approach to residual aluminium control at Nisiya purification plant, Water Works Bureau, Yokohama

In Yokohama Water Works Bureau, the target value for aluminium control in purified water is set to 0.05 mg/L. In this study, we examined the effects of pH and water temperature on the water solubility of aluminium during purification processes, and obtained a solubility curve of aluminium in water based on these parameters. The result indicated that the water solubility of aluminium increases as water temperature or pH increases. In addition, it was calculated from this solubility curve of aluminium in water, that the level of residual aluminium in purified water can be controlled at approx. 0.04–0.05 mg/L by adjusting pH of coagulated water to approx. 7.1–7.4 depending on water temperature. Furthermore, as a result of pH control according to actual coagulated water temperatures based on this assumption, it was demonstrated that the target value for aluminium control in purified water, (0.05 mg/L) is achievable.

Study on deterioration of water treatment capability of granular activated carbon (GAC) in Osaka City

To supply safe, good-quality tap water, Osaka Municipal Waterworks Bureau (OMWW) introduced an advanced water treatment system that incorporates ozonation and granular activated carbon (GAC) treatment into conventional treatment processes. By March 2000, all water purification plants in Osaka City were equipped with advanced water treatment facilities. This new treatment system has successfully removed odours and flavor and reduced trihalomethane. GAC treatment, the last stage of the water treatment, plays a vital role in removing organic matter in water, in conjunction with ozonation. However, GAC performance changes over time. To optimize the GAC effect, it is essential to conduct proper GAC management based on a thorough grasp of the change patterns of GAC performance. To determine GAC's water treatment capability, we analyzed data on 69 water quality items; obtained from past plant tests and chemical substance addition experiments using GAC actually used in the purification plants. Analysis revealed the deterioration patterns and time of GAC performance. By considering physical properties and economic factors as well as deterioration patterns of GAC performance, it is possible to establish an optimal GAC management system. This paper describes the findings obtained from the study on GAC water treatment performance conducted by OMWW.

Bussiness concerning IT Promotion in Hadano Waterworks Bureau

Bussiness concerning IT Promotion in Hadano Waterworks Bureau

Integrated water quality management for drinking water of good quality

The Nagoya Waterworks and Sewerage Bureau has developed original supporting tools for the systematic and cost-effective management of problem solving. An environmental information map and prediction of pollutant reaching are used for rapid and appropriate proper countermeasures against water quality accidents in the source area. In disinfection byproduct control a method for estimating trihalomethane (THM) contents was effective for the complement of their observations. Surrogate indicators such as turbidity and conductivity that could be measured continuously also could complement water quality items measured monthly. A processing tool of voluminous data was practical for rapid judgment of water quality. Systematic monitoring was established for stricter turbidity control for measures against Cryptosporidium and keeping residual chlorine stable in the service area.

Off-flavor problem in drinking water of Tokyo arising from the occurrence of musty odor in a downstream tributary

The Misato Purification Plant, Waterworks Bureau of Tokyo Metropolitan Government, in 1992 encountered an off-flavor problem due to the formation of 2-methylisoborneol (MIB) in a small tributary. This tributary had become polluted by rapid urbanization of the basin. However, it is situated at a point lower than the Plant and does not discharge directly into the main river. MIB produced in the downstream tributary was transported by a back current and via a Conveyance Pipe to the main river. The causative blue-green algae in the tributary water was determined through chemical and biological analysis of field samples as well as cultured materials. MIB production by one species of Oscillatoria isolated from the field samples was demonstrated. The strong MIB production potential of this species was also shown by a comparison of MIB production per unit length of trichome (16 pg/500μm) between this and other species reported previously. It was found that the presence of only one filament of this species in 1 ml of water could result in MIB levels above the threshold concentration of MIB for Japanese people. Results of this study revealed the importance of monitoring causative organisms and hydraulic conditions in tributary rivers.

Off-flavor problem in drinking water of tokyo arising from the occurrence of musty odor in a downstream tributary

The Misato Purification Plant, Waterworks Bureau of Tokyo Metropolitan Government, in 1992 encountered an off-flavor problem due to the formation of 2-methylisobomeol (MIB) in a small tributary. This tributary had become polluted by rapid urbanization of the basin. However, it is situated at a point lower than the Plant and does not discharge directly into the main river. MIB produced in the downstream tributary was transported by a back current and via a Conveyance Pipe to the main river. The causative blue-green algae in the tributary water was determined through chemical and biological analysis of field samples as well as cultured materials. MIB production by one species of Oscillatoria isolated from the field samples was demonstrated. The strong MIB production potential of this species was also shown by a comparison of MIB production per unit length of trichome (16 pg/500µm) between this and other species reported previously. It was found that the presence of only one filament of this species in 1 ml of water could result in MIB levels above the threshold concentration of MIB for Japanese people. Results of this study revealed the importance of monitoring causative organisms and hydraulic conditions in tributary rivers.

Estimation of asbestos exposure among workers repairing asbestos cement pipes used for conduits

Asbestos cement pipes (ACPs) containing 15 to 20% chrysotile or crocidolite have been used for underground conduits. Even today 16.2% of all conduits in Japan are ACPs, though the production of ACPs was suspended in 1985. When such a conduit is accidentally damaged the workers belonging to the Waterworks Bureau of a local government cut off the damaged conduit using a high-speed disk cutter and replace it with a new conduit. This operation develops a cloud of dust and the workers involved run the risk of asbestos exposure. It was the aim of the present study to estimate asbestos exposure levels among these workers. First, in the experiment, we established the typical working conditions and requested an experienced worker to cut an ACP using a high-speed disc cutter in a hole dug in the ground as he routinely does. The experiment was repeated three times. During a bout of each experiment, dust was sampled at several points both inside and outside the hole. Second, a self-administered questionnaire survey was conducted to obtain information from the workers regarding their working conditions in cutting ACPs. The subjects of the survey were 1,048 men belonging to conduit repair sections of the Waterworks Bureau of 119 local governments. The results obtained can be summarized as follows. 1) Each bout of cutting ACPs required about five minutes. The concentration of asbestos fibers longer than 5 microns with 3:1 aspect ratio ranged from 48 to 170 fibers/ml (92 fibers/ml on an average) inside and 1.7 to 15 fibers/ml outside the hole. The concentration inside the hole exceeded the ceiling limit (10 fibers/ml) recommended for asbestos by the Japanese Association of Industrial Health. A concentration of 92 fibers/ml is equivalent to 0.96 fibers/ml as 8-h time-weighted average. 2) The number of subjects with experience of cutting ACPs was 849 (81.0%). The average length of service in conduit repair section was 14.2 yr. Based on the information obtained from each subject regarding the average working days per yr for each decade from 1946, the cumulative days to date expended in cutting ACPs was estimated to average 235 d, that is, 17 d per yr. Only 18.1% of the subjects used a protective respiratory device.(ABSTRACT TRUNCATED AT 400 WORDS)

Occupational dust exposure and prevalence of respiratory symptoms among conduit repair workers

The amount of water supply in Japan was 16 billion ton as of 1989. Water from rivers and other sources is purified, sterilized and then supplied to the residents through conduits. When conduits are accidentally damaged, they must be repaired by the workers of the Waterworks Bureau of the local government. In this task, the workers are exposed to airborne dust which develops while digging and filling the ground and cutting the conduit and the concrete covering the road. The purpose of the present study was to estimate the airborne dust exposure level among the workers and to investigate its effect on their respiratory organs. First, we measured the total dust exposure concentration of 20 conduit repair workers and the total dust concentration in 10 office rooms. Second, we conducted a self-administered questionnaire survey to estimate the prevalence of respiratory symptoms among the employees of 119 Waterworks Bureaus. The subjects of the analysis were 322 conduit repair workers and as their controls 345 clerical/engineering workers. The results can be summarized as follows: 1) The average daily total dust exposure while repairing conduits ranged from 0.27 to 5.05 mg/m3 (mean = 0.91 mg/m3), while that while exchanging water meters from 0.23 to 0.52 mg/m3 (mean 0.41 mg/m3). These values were 4.6 and 2.1 fold higher than the total dust concentration in office rooms (mean = 0.20 mg/m3). 2) With the use of fluorescent X-ray method, iron and aluminum were detected in all samples collected while repairing conduits and the intensity of X-ray increased with increase in weight of collected dust. Iron exposure concentration ranged from 0.006 to 0.095 mg/m3, which is much higher than the levels in the air in urban areas. Iron and aluminum could not be detected by fluorescent X-ray method in most of the samples collected in office rooms. These findings indicate that the main element in the dust collected while repairing conduits is soil, while that in office rooms is tobacco smoke. 3) Among the smokers, the prevalence of cough and phlegm was significantly higher in conduit repair workers than in clerical/engineering workers. A similar tendency was observed among ex-smokers and non-smokers, but the difference was not significant.