Study on hydrodynamics associated with quality of water in water distribution system

Journal of Harbin Institute of Technology( New Series), Vol.9 ,No. 1 ,2002Study on hydrodynamics associated with quality of waterin water distribution systemLI Xin'，GU Da-ming'，ZHAO Hong-bin2，YUAN Yi-xing2李欣，顾大明,赵洪宾,袁一星( 1. Dept of Chemistry ,Harbin Institute of Technology , Harbin 150001 ,China ;2. School of Civil Engineering , Harbin Institute of Technology , Harbin 150001 ,China )Abstract : The quality of water in water distribution system may vary with both location and time. W ater qualitymodels were used to predict spatial and temporal variation of water quality throughout the water system. Beforeanalyzing the variations of water quality ,it is necessary to determine the hydrodynamics in water distributionsystem. Analytical methods for the flow path from water sources to the observed point and water age of every ob-served node are proposed. This paper makes a further study on water supply route of multi - sources water sup-ply network system. These studies have been applied to an actual water distribution system.Key words : water quality ; water distribution system ; flow path ; water ageCLC number :TU991.21Document code :AArticle ID : 1005-9113( 2002 )01-0029-030 INTRODUCTION→④Finished water may undergo substantial change in-⑥➢⑦quality during transport through the distribution systeminflowto the consumer. Water quality models were used to⑧品outlowpredict the spatial and temporal variation of water quali-ty throughout the water system. A significant aspect ofFig.1 The network consists of 14 pipesusing water quality models heavily depends on accuratehydraulic models of distribution system2I. This arti-cle describes a study that was primarily conducted toanalyse the hydrodynamic behavior related to waterquality in water distribution system.1 ANALYSIS OF FLOW PATHS IN A NET-⑨WORK①⑤∞⑦❻The loop network is different from single pipe and⑦0010parallel pipe , and how many paths of water flow fromwater sources to the observed point is concern with theamount of loop. The network is consists of 14 pipes asin Fig. 1. the water flow from 1 ( start point )to 101( end point ) along 8 paths. The analytic method of thewater paths in the loop network is as Fig. 2.Fig. 2 Analysis of flow pathMake the variable MP of the network to quadraticmatrix. The input and output are marked as startingThe analytical algorithm is as follows ( see thepoint and ending point , and then change the networkFig.3 ):into structure like tree and find the paths. In addition中国煤化工oint and the end pointwhen there are paths the MP is marked as one anarethe datum analyzed ;there is no any path the MP is zero. According to abovefYHCNMHGandtheendpointofamethod , the amount of branch is determined.network and choose essential factor of flow from start toReceived 2001 -04 - 10Sponsored by the National Natural Science Fund of China( Grant No. 59678018 )Journal of Harbin Institute of Technology( New Series), Vol.9 ,No. 1 ,2002| STARTv =-tq(2) .πD'(READ)-| inputπD2 L| DATA(3 )4q1 FAULWhere :D is pipe diameter ,L is pipe length ,q is pipeBI)≠0 二> +( WRITE)- + outputDATAflow and 0 is velocity .TRUEBy using Hazen-Williams equation to set up thef=f+1ENDrelationship between t and h( head loss ) :t = 2.08C-0.76q0.24L-+4h-0.4( m/sec) (4 )=1In Fig.4 ,the water age at point C is given :tc=tsB+tgc(5)In Fig.5 , the water age at point B is given :MP= i91t + 9212tg =( 6)91+92K=K+1In loop network , the water age at a specified node mayPS(K)=LP(i)be defined as :PE(K)=j↓TRUESqPE(K)=EX(7)2;| B()=B()+1Where :t; is water age of point i ;n is road number of| SN(B()=jwater transfer from start point to nodei :qy is the flow to .t i=B(f-1) tpoint i on free water road it; is retention time to point ion free water road ;Q; is the outflow at point I.| LP(h)=SN(h) |一↓B IucFig. 3 Scheme of analytical algorithm for the flow pathA十Cend , and then find the amount of branch in everyFig.4 A single pipenodes ;( 3 )Find the next nodes forward sequentially ;( 4 )Decide the every nodes by the different fromA“amount of branch and examine the nodes for finding thepaths ;path 2path 1( 5 )According to the datum from ,( 1 ) to(4 )should be calculated repeatedly. When a path reachesthe end , need to calculate once more.口92\BThe data should be marked with amount of paths ,number of every paths and nodes.Fig.5 Parallel pipeIn the Fig. 3 , every symbols are presented as fol-lows :MP(i i): variable of path ; MP( input , out-put ) ;K : times of calculation if : number of branch ;3 ANALYSIS OF THE WATER FLOW PATHSPS( K): the start point ; B(f): the amount of theOF MULTI - SOURCESbranch.In order to determine the quality of water from2 WATER AGEmulti-sources , it is important to analyze the paths ofthe network. Let it be supposed that the water enteringIn water distribution system , the travel time of wa-a junction node mixes completely. The water flowter from source to a particular node is called as watercoming from different sources is in proportion at a nodeage. It is an important parameter to quantify the varia-and中国煤化工& when the water flowtion of water quality.fromis called distributionThe water age may be calculated by the followingfacto;YHC N M H Gng that the water comingrelationships :from each source is in proportion to the node. If the DFL(1)of water source S for node i is expressed as C,; ,and theDF of water source S for pipe ij is expressed C,，, therelation is as follows :30-Journal of Harbin Insiute of Technology( New Series ),Vol.9 ,No. 1 ,2002C = Q,;/Q;C,j = 9./q,;4 APPLICATION IN FIELD TESTThe relation between the distribution factors is asfollow :The service area had 40. 000 residential , averageC,=C,water use was 21.000 mi /day. The water came from aThe DF of any sourceS is the same and it is to anywater distribution tank which has capacity of 8. 000DF of nodes and pipes.m' /day. The distribution system is composed of pipeThe sum of DF of each source to whichever nodediameter from 0.075 m to0. 7 m , and the total lengthequals 1. It is supposed that there are m sources ,nof pipe is 49 km. The pipes are cement - mortar liningnodes andp pipes in a network ,the DF of each sourceductile iron pipes. Sampling was conducted at the nineto node and pipes could be calculated. The analyticallocations throughout the service area. Fig. 7 illustratesalgorithm is as Fig. 6.the water distribution system subjected for our studyand the flow directions obtained by our analytic meth-od. Table 1 shows the number of paths and the waterInput of outflow and pipe flowage of each observation point.-自Table 1 Water age and number of pathsObservationWaterNumber of| Assuming the staring values of distributionpointagepath|factor at any node is zeroStarting point Starting point↓3.98r=3.705.683.97i=167. 909.05CI,10.825911. 388:=C,-C-1Distribution-Tanki=i+1口: observationYFig.7 Flow directions and observation point in objective[r=r+1}max 8water distribution system5 CONCLUSION| Distribution factor of watersources at n pipeThe hydraulic factors are studied to address the_problem of water quality in potable water distributionDistribution factor of watersystem. Analytical methods for the flow path from watersources to the observed point and water age of everyobserved node are proposed. This paper makes a fur-8=s+1ther study on water supply route of multi-sources watersupply network system. These studies have been ap-plied to actual water distribution system. The result of↓Nthese studies may be input to a water quality model forDistrit， factor of m sosubsequent analysis.urces at n node and on p pipeReferences :The flow path of each source[1]中国煤化Ieasuring and modeling varin water distribution systermMHCNMHGNatler quali[J] JAWWA.Fig. 6 Scheme of analytical algorithm for the flow path in[2 ]" CLARK R M. Modelling water quality changes and conta-monant propagation in drinking water distribution systemmulti-sources water distribution system[J] J Water SRT- Aqua ,1994( 3 ):133 ~ 143.