Urban Water最新文献

The aim of this paper is to study the performance of a combined waste stabilisation pond after three years of functioning and the reuse of treated wastewater for irrigating potatoes and lettuce culture. The combined ponds showed good functioning conditions and excellent performances either for organic load (90%), faecal coliform (6 log units) or helminth eggs (100%) and produced a high and perennial effluent quality. The effluent could be used for non-restrictive irrigation, with a clear improvement of culture production and hygienic quality for both fruits and soil.

The objective of the paper is to investigate the attitudes and preferences of the residential water users of the city of Thessaloniki, in order to evaluate the demand management aspects of the urban water policy. A field survey has been conducted in the city of Thessaloniki and investigated among others the reliability of the utility’s services and infrastructure, the acceptability of various water demand options, the willingness to pay of the consumers and the level of public awareness. Straightforward comparisons with the results of a similar survey five years ago help extract useful remarks and conclusions concerning the shift of the urban water policy towards integrated and therefore more sustainable directions.

The economic and social costs associated with pipe bursts and associated leakage problems in modern water supply systems are rapidly rising to unacceptably high levels.

Pipe burst risks depend on a number of factors which are extremely difficult to characterise. A part of the problem is that water supply assets are mainly situated underground, and therefore not visible and under influence of various highly unpredictable forces. This paper proposes the use of advanced data mining methods in order to determine the risks of pipe bursts. For example, analysis of the database of already occurred bursts events can be used to establish a risk model as a function of associated characteristics of bursting pipe (its age, diameter, material of which it is built, etc.), soil type in which a pipe is laid, climatological factors (such as temperature), traffic loading, etc.

In addition to the immediate aid with the the choice of pipes to be replaced, the outlined approach opens completely new avenues in asset management: the one of asset modeling. The condition of an asset such as a water supply network deteriorates with age. With reliable risk models, addressing the evolution of risk with aging asset, it is now possible to plan optimal rehabilitation strategies in advance, before the burst actually occurs.

An understanding of pollutant characteristics on impervious surfaces is essential to estimate pollutant washoff characteristics and to design methods to minimise the impacts of pollutants on the environment. This paper presents data on surface pollutant characteristics on an urban road surface in Melbourne, Australia, from samples collected over a 36 day period. The data indicate that buildup over the dry days occurs relatively quickly after a rain event, but slows down after several days as redistribution occurs. The surface pollutant also becomes finer over the dry days as it is disintegrated. The washoff of surface pollutant is dependent on the rainfall and runoff characteristics, but the results here show that common storms only remove a small proportion of the total surface pollutant load. The data also show that street sweeping may have an adverse impact on pollutant washoff because the street sweeper releases the finer material but only removes some of them, making the fine sediment available for washoff by the next storm. The data also show that most of the nutrients are attached to the finer sediments, and to effectively reduce nutrient loads in particulates, treatment facilities must be able to remove the finer particles (down to 50 μm for TP and down to 10 μm for TN), and not just the total sediment or suspended solid load.

Modern methodologies for planning and design of urban drainage systems are based on the idea of minimising the receiving water pollution. However, in order to implement this concept of ambient water quality standards in practice, there is a need for simple tools that can establish a clear cause––effect relation between the drainage measures and the impact on the receiving water ecosystem. REBEKA is a software tool that has been developed to provide such a tool for a particular type of receiving waters––small, alpine and pre-alpine streams. The software has been launched among Swiss practitioners in the summer of 2000 and it is already widely applied. In this paper we outline the background of the methodology.

Owing to development pressure for land bordering the Vaal river, in South Africa. Rand Water are revising their development policy. Restrictions were in place to avoid flooding and obstructing the flood flow of the river. Relaxation of the regulations will permit controlled development along the river. A flood hazard-risk index was developed to indicate where development could be permitted. An economic comparison of costs and benefits supports the relaxation.

Based on previous observations of the 45° junction manhole for supercritical flow in the main and lateral branches, the hydraulics of the more common 90° junction manhole were explored. Using a selected manhole geometry involving: (1) a short straight piece in the lateral branch to inhibit full development of the bend wave, and (2) the addition of the junction extension as used in previous designs for the bend manhole, the present study gives results that are in basic agreement with those collected in the 45° junction manhole. This surprising result thus allows for a design basis independent of the junction angle.

The present paper defines three waves that may occur in a junction manhole, i.e. bend wave, junction wave and the swell at the manhole outlet into the downstream pipe. In addition, the position of the determining junction wave was established. Important for the junction design is the discharge capacity for which supercritical flow can be maintained across the manhole. It was found that the lateral branch flow depth and the pipe diameter have an important effect on this capacity, for both branches or only one of the branches in operation.

Arsenic occurs in both inorganic and organic forms in water. Although various methods have been adopted to remove inorganic species of arsenic from drinking water, not much emphasis has been given to the removal of organic species of arsenic. In the present study column studies were conducted using manganese greensand (MGS), iron oxide-coated sand (IOCS-1 and IOCS-2) and ion exchange resin in Fe³⁺ form, to examine the removal of organic arsenic (dimethylarsinate) spiked to required concentrations in tap water. Batch studies were conducted with IOCS-2, and the results showed that the organic arsenic adsorption capacity was 8 μg/g IOCS-2. Higher bed volumes (585 BV) and high arsenic removal capacity (5.7 μg/cm³) were achieved by the ion exchange resin among all the media studied. Poor performance was observed with MGS and IOCS-1.

Source control measures include rainwater tanks, infiltration trenches, grassed swales, detention basins and constructed wetlands that can be used in housing allotments and subdivisions. A methodology for evaluating the regional economic benefits due to implementation of source control measures is presented and illustrated for two case studies in the Lower Hunter and Central Coast regions of New South Wales, Australia. It is demonstrated that use of rainwater tanks to supplement mains water supply for toilet, hot water and outdoor uses can very significantly reduce demand on mains water supply. Reductions in regional water demand will enable deferment of water supply headworks augmentation, while reductions in peak mains water demand will extend the life of water supply distribution infrastructure. In addition, substantial reduction of stormwater discharge from allotments can be realised. For the Lower Hunter region with an urban population of about 450,000 it is shown that construction of new water supply headworks infrastructure can be delayed by up to 34 years. Compared with the traditional provision of mains water and stormwater disposal, the use of rainwater tanks along with other source control measures can produce present worth savings to the Lower Hunter region conservatively estimated to be up to $67 million. Similar results were found for the Central Coast region.