Urban Water最新文献

A contaminant balance for urban residential water systems has been performed for 12 pollutants. The characteristics of the residential site were based on Ellenbrook, a suburb of Perth, Australia. The sources of contaminants were identified and characterised using published literature values. A water balance was used to estimated flow data, and these results were used in conjunction with the contaminant source characteristics to calculate contaminant loads. The contaminants examined were total nitrogen, ammonia, total phosphorus, copper, zinc, lead, cadmium, suspended solids, dissolved solids, chemical oxygen demand, polycyclic aromatic hydrocarbons and oil and grease. Diagrams of contaminant flows through the water, wastewater and stormwater systems are presented. By identifying the sources of contaminants, the diagrams are a useful reference when considering the fate of contaminants in alternative urban water system configurations or how to better handle or reduce these contaminants.

Combined sewer overflows (CSO) are part of common combined drainage systems. Due to the improvement achieved in the efficiency of wastewater treatment plants, the discharge of such CSO became the focus of discussion regarding the quality of the natural water bodies. Thus operation of combined sewer systems and especially of existing detention facilities aims at an extensive avoidance of combined sewer discharge. To fulfil this task, real-time control may be one of the possible solutions. In Germany many communities already made the first step towards real-time control, i.e. data logging and supervision of the sewerage condition. The experience in application of real-time control and the achieved results are described regarding to case studies of existing real-time control systems.

The aim of this study was to evaluate the potential of different separation techniques for local recovery of faecal nutrients. Separation by Aquatron, filtration, flotation and sedimentation was tested in the laboratory. Only the separation of faecal matter from flushwater was investigated. For efficient nutrient capture, the system has to be combined with urine-diverting toilets.

In this study we found that the extraction of nutrients from the faeces to the liquid occurred rapidly. Therefore, to effectively separate the faecal nutrients and particles from the flushwater, the separation has to be performed locally, preferably at house level.

The Aquatron and the filtration gave a fraction of separated solids with 10% dry matter, which contained 70–80% of the incoming plant nutrients nitrogen, phosphorus and potassium. The other two methods investigated did not prove effective for local separation of faeces.

Using urine-diverting toilets, where all the urine is diverted, and collected and 70% of the faecal nutrients are separated locally, the potential for local nutrient recovery from the household wastewater is 88% for nitrogen, 75% for phosphorus and 55% for potassium, mainly in the form of directly plant available nutrients.

In real-time control (RTC) of combined urban and rural water systems the so-called centralised control requires information from different locations in the water system and hence sensitive to the communication network breakdown during extreme storm runoff events. Optimisation algorithms used in advanced forms of centralised control require considerable computing times and thus may be impractical for RTC. To overcome these problems, the application of machine learning methods is proposed, using artificial neural networks and fuzzy adaptive systems. Results obtained in a realistic case study show that the trained controllers, can replicate centralised control behaviour quite accurately and rapidly, while using only local data sources.

The city of Santiago de Compostela in north-west Spain (population about 100,000) has a combined sewer system that feeds to a grossly under-sized wastewater treatment plant. This problem is compounded by the very high rainfall (1600 mm per annum) and the age and poor repair of the sewer system (so that estimated groundwater input is about 13.4 Hm³ per annum). Combined sewer overflow (CSO) events are thus frequent, and have severe pollutant effects on the receiving watercourse, the River Sar. CSOs were monitored daily over a 40-month period, and determined the hydrographs and pollutographs for seven representative moderate-magnitude CSO events occurring during this period. Event total contaminant loads, often discharged to the river over a very short period, were in many cases very high: up to 9500 kg of suspended solids, 900 kg of total Kjeldahl N, and 3.62 kg of Zn. In most events, most contaminants showed a “first flush”, though variability was high and in many cases the pollutograph did not meet the stricter of the various criteria that have been proposed for definition of the first flush. That these stricter criteria were not met may be attributable to the dilution effect of the large volumes of groundwater that are continually entering the system.

Waste stabilization ponds are frequently considered as being effective for the removal of intestinal parasites while conventional wastewater treatment processes are not. Over a 24-month period, grab samples from a pilot stabilization pond system in Marrakech were analyzed for the presence of Giardia cysts and Ascaris eggs. Giardia was isolated with an average of 2.8×10³ cysts/l, while Ascaris eggs were detected with a mean number of 1.7 eggs/l. The data also suggest seasonal differences in Giardia cyst and Ascaris egg concentrations in raw wastewater, recording high monthly mean numbers during dry period (Spring and Summer). At the outlet of the system, neither Giardia cysts nor Ascaris eggs were found in treated wastewater. Enumeration of Giardia cysts and Ascaris eggs in the sediment at the entrance of the system resulted in average numbers of 1.3×10³ cysts/g and 29.6 eggs/g dry weight of sediment. These concentrations decreased towards the outlet of the ponds where the sediment was free of Giardia cysts and Ascaris eggs.

Stormwater samples were collected from Chollas Creek, a highly urbanized watershed in San Diego, California, that discharges directly to San Diego Bay and tested using one freshwater species (Ceriodaphnia, water flea) and two marine species (Strongylocentrotus purpuratus, purple sea urchin; and Mysidopsis bahia, mysid shrimp). No two species responded similarly after exposure to urban wet weather discharges. Strongylocentrotus was extremely sensitive to stormwater, exhibiting responses during every storm at concentrations as low as 6–12% stormwater. In contrast, Mysidopsis, exhibited no response to stormwater for any of the storms sampled. Ceriodaphnia exhibited intermediate toxic responses; two of three samples were toxic at relatively high concentrations of 50–100% stormwater. Toxicity identification evaluations (TIEs) were conducted on each species to determine the toxic constituent(s). Organophosphate pesticides, most likely diazinon and chlorpyrifos, were responsible for the toxicity observed in Ceriodaphnia. Trace metals, most likely zinc and copper, were responsible for the toxicity observed to the sea urchin.

The porous pavement of industrial and commercial areas is a form of sustainable urban drainage (SUD) system which has been developed to reduce runoff flow rates and volumes. This study reports on the modelling of the 20-month-old porous pavement at the Royal Bank of Scotland Headquarters in Edinburgh. A hydraulic model was developed using the Stormwater Modelling Program Erwin. Fifteen events were available for use in the calibration and verification procedure. The modelling results have shown an excellent prediction of the outflow behaviour of the site investigated.

In this paper, we propose a hydraulic reliability index for sewage pumping stations (SPS). This hydraulic reliability index is a measure of the ability of an SPS to fulfill its function in the future in conditions where its pump units (PUs) will be put out of operation occasionally. The reliability index is defined as the ratio of the expected volume of sewage that will not be pumped by SPS, due to possible PU failures, to the expected volume of sewage that will enter the pumping station inlet over the same prediction time. The calculation of the expected volume of unpumped sewage is based on the assumption that the processes leading to PU failures are stochastic and mutually independent. The simple example is used to demonstrate the proposed methodology.

The effect of employing demand and pressure management techniques on the cost of water reticulation systems is analysed in this paper. The analysis is based on the cost of supplying a cluster of 4000 households serving a range of hourly demands using pipes of various pressure classes. Demand management reduces costs by 25–45% and pressure management increases savings by a further 20–55%. For demands below 50 l per household per hour there is a cost shift from reticulation infrastructure, to properties, to cover the costs of water storage and fire sprinkler systems. The analysis highlighted the hidden cost within water supply infrastructure to provide fire protection based on street hydrants.