Application of Ice Pigging in a Drinking Water Distribution System:Impacts on Pipes and Bulk Water Quality

Ice pigging is an emerging technique for pipe cleaning in drinking water distribution systems.However,substantial confusion and controversy exist on the potential impacts of ice pigging on bulk water quality.This study monitored the microstructural features and composition of sediments and microbial community structures in bulk water in eight multimaterial Chinese networks.Chloride concentration analysis demonstrated that separate cleaning of pipes with different materials in complex networks could mitigate the risk of losing ice pigs and degrading water quality.The microstructural and trace element characterization results showed that ice pigs would scarcely disturb the inner surfaces of long-used pipes.The bacterial richness and diversity of bulk water decreased significantly after ice pigging.Furthermore,correlations were established between pipe service age,temperature,and chloride and total iron concentrations,and the 15 most abundant taxa in bulk water,which could be used to guide practical ice pigging operations.

Application of Dynamic Programming Method in Optimization of Water Distribution Pipe Network

With a water-supply network by dynamic programming. The minimal as an example, the network was optimized annual discounted costs were taken as an objective function and node pressure etc. as constraint conditions. The alternative pipe diameters were optimized as per enumeration method and the group allowing objective function with the least values would be the optimized one. It is proved the optimized pipe network reduced by 11.49% in terms of cost and the optimized ben- efits proved much significant.

STUDY ON OPTIMAL CONTROL OF MUNICIPAL WATER DISTRIBUTION NETWORK

A systematic investigation is made on the problems which are related to the optimal control of the municipal water distribution network.A mathematical model of forecasting the water short term demand is proposed using the time series trigonometric function analysis method;the service discharge based macroscopic model of network performance is established using the network structuring method;a relatively satisfactory mathematical model for the optimal control of water distribution network is put forward in view of security and economy,and solved by the constrained mixed discrete variable complex arithmetic.The model is applied in many examples and the results are satisfactory.

Modeling of residual chlorine in water distribution system

Water quality within water distribution system may vary with both location and time. Water quality models are used to predict the spatial and temporal variation of water quality throughout water system. A model of residual chlorine decay in water pipe has been developed, given the consumption of chlorine in reactions with chemicals in bulk water, bio films on pipe wall, in corrosion process, and the mass transport of chlorine from bulk water to pipe wall. Analytical methods of the flow path from water sources to the observed point and the water age of every observed node were proposed. Model is used to predict the decay of residual chlorine in an actual distribution system. Good agreement between calculated and measured values was obtained.

Online location of seismic damage to a water distribution system

As one of the most important urban lifeline systems,a water distribution system can be damaged under a strong earthquake,and the damage cannot easily be located,especially immediately after the event.This often causes tremendous difficulties to post-earthquake emergency response and recovery activities.This paper proposes a methodology to locate seismic damage to a water distribution system by monitoring water head online at some nodes in the water distribution system.An artificial neural network-based inverse analysis method is developed to estimate the water head variations at all nodes that are not monitored based on the water head variations at the nodes that are monitored.The methodology provides a quick,effective,and practical way to locate seismic damage to a water distribution system.

Use of two-stage dough mixing process in improving water distribution of dough and qualities of bread made from wheat–potato flour

The two-stage dough mixing process was innovated to improve the qualities of bread made from potato flour(PF) and wheat flour at a ratio of 1:1(w/w). The final dough was first prepared from wheat flour before being added with PF. The effects of the method on enhancing the dough qualities were verified, and the distribution of water in gluten-gelatinized starch matrix of the doughs was investigated. We observed that the bread qualities were improved, as reflected by the increase of specific volume from 2.26 to 2.96 m L g^–1 and the decrease of crumb hardness from 417.93 to 255.57 g. The results from rheofermentometric measurements showed that the dough mixed using the developed mixing method had higher maximum dough height value, time of dough porosity appearance, and gas retention coefficient, as well as enhanced gluten matrix formation compared to that mixed by the traditional mixing method. The results from low-field nuclear magnetic resonance confirmed that the competitive water absorption between gluten and gelatinized starch could restrict the formation of gluten network in the dough mixed using the traditional mixing process. Using the novel mixing method, gluten could be sufficiently hydrated in stage 1, which could then weaken the competitive water absorption caused by gelatinized starch in stage 2;this could also be indicated by the greater mobility of proton in PF and better development of gluten network during mixing.

Identification of contamination source in water distribution network based on consumer complaints

A new methodology was proposed for contamination source identification using information provided by consumer complaints from a probabilistic view.Due to the high uncertainties of information derived from users,the objective of the proposed methodology doesn't aim to capture a unique solution,but to minimize the number of possible contamination sources.In the proposed methodology,all the possible pollution nodes are identified through the CSA methodology firstly.And then based on the principle of total probability formula,the probability of each possible contamination node is obtained through a series of calculation.According to magnitude of the probability,the number of possible pollution nodes is minimized.The effectiveness and feasibility of the methodology is demonstrated through an application to a real case of ZJ City.Four scenarios were designed to investigate the influence of different uncertainties on the results in this case.The results show that pollutant concentration,injection duration,the number of consumer complaints nodes used for calculation and the prior probability with which consumers would complaint have no particular effect on the identification of contamination source.Three nodes were selected as the most possible pollution sources in water pipe network of ZJ City which includes more than 3 000 nodes.The results show the potential of the proposed method to identify contamination source through consumer complaints.

Iron stability in drinking water distribution systems in a city of China

A field study on the estimation and analysis of iron stability in drinking water distribution system was carried out in a city of China. The stability of iron ion was estimated by pC-pH figure. It was found that iron ion was unstable, with a high Fe （OH）3 precipitation tendency and obvious increase in turbidity. The outer layer of the corrosion scale was compact, while the inner core was porous. The main composition of the scale was iron, and the possible compound constitutes of the outer scale were α-FeOH, γ-FeOOH, α-Fe2O3, γ-F2O3, FeCl3, while the inner were Fe3O4, FeCl2, FeCO3. According to the characteristics of the corrosion scale, it was thought that the main reason for iron instability was iron release from corrosion scale. Many factors such as pipe materials, dissolved oxygen and chlorine residual affect iron release. Generally, higher iron release occurred with lower dissolved oxygen or chlorine residual concentration, while lower iron release occurred with higher dissolved oxygen or chlorine residual concentration. The reason was considered that the passivated out layer of scale of ferric oxide was broken down by reductive reaction in a condition of low oxidants concentration, which would result more rapid corrosion of the nine and red water phenomenon.

Optimal operation of water distribution networks under local pipe failures

The optimal operation of water distribution networks under local pipe failures, such as water main breaks, was proposed. Based on a hydraulic analysis and a simulation of water distribution networks, a macroscopic model for a network under a local pipe failure was established by the statistical regression. After the operation objectives under a local pipe failure were determined, the optimal operation model was developed and solved by the genetic algorithm. The program was developed and examined by a city distribution network. The optimal operation alternative shows that the electricity cost is saved approximately 11%, the income of the water corporation is increased approximately 5%, and the pressure in the water distribution network is distributed evenly to ensure the network safe operation. Therefore, the proposed method for optimal operation under local pipe failure is feasible and cost-effective.

Seismic Reliability and Rehabilitation Decision of Water Distribution System

In order to evaluate the seismic reliability of water distribution system and make rehabilitation decisions correspondingly, it is necessary to assess pipelines damage states and conduct functional analysis based on pipe leakage model. When an earthquake occurred, the water distribution system kept serving with leakage. By adding a virtual node at the centre of the pipeline with leakage, an efficient approach to pressure-driven analysis was developed for simulating a variety of low relative scenarios, and a hydraulic leakage model was also built to perform hydraulic analysis of the water supply network with seismic damage. Then the mean-first-order-second-moment method was used to analyse the seismic serviceability of the water distribution system. According to the assessment analysis, pipes that were destroyed or in heavy leakage were isolated and repaired emergently, which improved the water supply capability of the network and would constitute the basis for enhancing seismic reliability of the system. The proposed approach to seismic reliability and rehabilitation decision analysis on water distribution system is demonstrated effective through a case study.

Water Distribution and Removal along the Flow Channel in Proton Exchange Membrane Fuel Cells

Distribution expressions of total gas pressure and partial water vapor pressure along the channel direction were established based on lumped model by analyzing pressure loss in the channel and gas diffusion in the layer. The mechanism of droplet formation in the flow channel was also analyzed. Effects of the relative humidity, working temperature and stoichiometry on liquid water formation were discussed in detail. Moreover, the force equilibrium equation of the droplet in the flow channel was deduced, and the critical flow velocity for the water droplet removal was also addressed. The experimental results show that the threshold position of the liquid droplet is far from the inlet with the increase of temperature, and it decreases with the increase of the inlet total pressure. The critical flow velocity decreases with the increase of the radius and the working pressure.

Seismic reliability analysis of urban water distribution network

An approach to analyze the seismic reliability of water distribution networks by combining a hydraulic analysis with a first-order reliability method （FORM）, is proposed in this paper. The hydraulic analysis method for normal conditions is modified to accommodate the special conditions necessary to perform a seismic hydraulic analysis. In order to calculate the leakage area and leaking flow of the pipelines in the hydraulic analysis method, a new leakage model established from the seismic response analysis of buried pipelines is presented. To validate the proposed approach, a network with 17 nodes and 24 pipelines is investigated in detail. The approach is also applied to an actual project consisting of 463 nodes and 767 pipelines. The results show that the proposed approach achieves satisfactory results in analyzing the seismic reliability of large-scale water distribution networks.

Leak Detection in Water Distribution Systems Using Bayesian Theory and Fisher’s Law

A leak detection method based on Bayesian theory and Fisher’s law was developed for water distribution systems. A hydraulic model was associated with the parameters of leaks (location, extent). The randomness of parameter values was quantified by probability density function and updated by Bayesian theory. Values of the parameters were estimated based on Fisher’s law. The amount of leaks was estimated by back propagation neural network. Based on flow characteristics in water distribution systems, the location of leaks can be estimated. The effectiveness of the proposed method was illustrated by simulated leak data of node pressure head and flow rate of pipelines in a test pipe network, and the leaks were spotted accurately and renovated on time.

Partitioning of Water Distribution Network into District Metered Areas Using Existing Valves

Water distribution network(WDN)leakage management has received increased attention in recent years.One of the most successful leakage-control strategies is to divide the network into District Metered Areas(DMAs).As a multi-staged technique,the generation of DMAs is a difficult task in design and implementation(i.e.,clustering,sectorization,and performance evaluation).Previous studies on DMAs implementation did not consider the potential use of existing valves in achieving the objective.In this work,a methodology is proposed for detecting clusters and reducing the cost of additional valves and DMA sectorization by considering existing valves as much as possible.The procedure of DMAs identification has been divided into three stages,i.e.,a)clusters identification;b)sectorization or boundaries optimization and c)performance evaluation of the partitioned network.The proposed methodology is evaluated on a simple network and a real-world water network with the findings provided and compared to the DMAs,established for a raw water network with no existing valves.It is found that there is an adequate difference in cost of strategy implementation in both the cases for the network under consideration and the existing valve system achieved better network performance in terms of resilience index.

Partial Least Squares Regression Model to Predict Water Quality in Urban Water Distribution Systems

The water distribution system of one residential district in Tianjin is taken as an example to analyze the changes of water quality.Partial least squares(PLS) regression model,in which the turbidity and Fe are regarded as control objectives,is used to establish the statistical model.The experimental results indicate that the PLS regression model has good predicted results of water quality compared with the monitored data.The percentages of absolute relative error(below 15%,20%,30%) are 44.4%,66.7%,100%(turbidity) and 33.3%,44.4%,77.8%(Fe) on the 4th sampling point;77.8%,88.9%,88.9%(turbidity) and 44.4%,55.6%,66.7%(Fe) on the 5th sampling point.

Variability of micropollutants and microorganisms in water distribution system

The variation of water quality in water distribution system was investigated with assimilable organic carbon (AOC)and trihalomethanes(THMs) used as assessment indexes. Bacterium was identified in water distribution. The result showed that there were pathogenic parasites in water distribution system. The variation of AOC is related to chlorine residual and bacterium activity, and AOC concentration decreased first and then increased with the extension of water distribution system. The formation of THMs was related to the consumption of chlorine inside the distribution system, and THMs concentration increased with the extension of water pipe line.

Assessment on reliability of water quality in water distribution systems

Water leaving the treatment works is usually of a high quality but its properties change during the transportation stage. Increasing awareness of the quality of the service provided within the water industry today and assessing the reliability of the water quality in a distribution system has become a major significance for decision on system operation based on water quality in distribution networks. Using together a water age model, a chlorine decay model and a model of acceptable maximum water age can assess the reliability of the water quality in a distribution system. First, the nodal water age values in a certain complex distribution system can be calculated by the water age model. Then, the acceptable maximum water age value in the distribution system is obtained based on the chlorine decay model. The nodes at which the water age values are below the maximum value are regarded as reliable nodes. Finally, the reliability index on the percentile weighted by the nodal demands reflects the reliability of the water quality in the distribution system. The approach has been applied in a real water distribution network. The contour plot based on the water age values determines a surface of the reliability of the water quality. At any time, this surface is used to locate high water age but poor reliability areas, which identify parts of the network that may be of poor water quality. As a result, the contour water age provides a valuable aid for a straight insight into the water quality in the distribution system.

Kinetics of Chlorine Decay in Water Distribution Systems

A combined first and second-order model, which includes bulk decay and wall decay, was developed to describe chlorine decay in water distribution systems. In the model the bulk decay has complex relationships with total organic carbon (TOC), the initial chlorine concentration and the temperature. Except for the initial stages they can be simplified into a linear increase with TOC, a linear decrease with initial chlorine concentration and an exponential relationship with the temperature. The model also explains why chlorine decays rapidly in the initial stages. The parameters of model are determined by deriving the best fitness with experimental data. And the accuracy of model has been verified by using the experimental data and the monitoring data in a distribution system.

Bacterial Communities Associated with An Occurrence of Colored Water in An Urban Drinking Water Distribution System

This study aimed to investigate bacterial community in an urban drinking water distribution system （DWDS） during an occurrence of colored water. Variation in the bacterial community diversity and structure was observed among the different waters, with the predominance of Proteobacteria. While Verrucomicrobia was also a major phylum group in colored water. Limnobacter was the major genus group in colored water, but Undibacterium predominated in normal tap water. The coexistence of Limnobacter as well as Sediminibacterium and Aquobocterium might contribute to the formation of colored water.

Review Study on the Accumulation and Release of Trace Metal Elements on Aluminum Containing Sediments in Drinking Water Distribution System

Accumulation and releasing of trace metal elements on aluminum containing sediments of inner drinking water pipe is discussed,as studied from five variations effecting:raw water quality,chemical reagents,solution pH and drinking water flow condition.In order to decrease the release of trace metal elements,and to ensure the pipe operation and human safety,water quality adjustment is suggested to avoid aluminum containing sediments formation in drinking distribution system.The maximum amounts of accumulation of common trace metal elements are given.Future trends of development in this field are also proposed.