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Total emission of an urban area considering the interaction between drainage system and treatment plant
~
Pergamon PH: S0273-1223(97)00632-X
Wat.ScL Tech. Vol.36. No. 8-9. pp. 71-76.1997. CC> 1997IAWQ.Published by ElsevierScienceLId All rightsreserved. Printedin Great Britain. 0273-1223197 S17·OO +0-00
TOTAL EMISSION OF AN URBAN AREA CONSIDERING THE INTERACTION BETWEEN DRAINAGE SYSTEM AND
TREATMENT PLANT Susanne Deyda Institutefor WaterResources. University ofHannover. Appelstr. 9A, D-30167Hannover, Germany
ABSTRACf Continuous longterm calculations of quantity and quality processes on the catchment surface. the sewerage system and the treatment plant of the City of Hildesheim have to be carried out in order to estimate the effect of the urban area on the receiving water. The calculations are performed with a pollutant-load-calculation model including a coupled hydrologic-hydrodynamic runoff-transportation module. The achievement of the developed model is shown in the example of two different subcatchments of the City of Hildesheim. With the help of this concept. it is possible to consider the existing transport, storage and treatment capacity more flexible and to find optimal rehabilitaion concepts concerning the emission loads just like the resulting costs. @ 1997 IAWQ. Published by Elsevier Science Ltd
KEYWORDS Case study; comprehensive view; continuous longterm simulation; total emission; treatment plant.
INTRODUCTION In uran hdrology, progress in computer techniques has allowed the development of numerical models for simulating hydrological processes in UDS. Depending on the investigated problem, one or more of the models are used. For a comprehensiveview, as the basis for a masterplan or similar, the effect of the sewerage system and the treatment plant on the receiving waters has to be investigated. Such an integrated simulation consists of sub models for the quantitative and qualitative calculation of surface-runoff, runoff transportation within sewerage systems, processes in treatment plants and finally within the receiving waters. Since 1993 the government of the Federal Republic has been financing a two year research programme with the interaction between drainage systems and treatment plants (Sieker and Deyda, 1996). In the investigation, continuous longterm calculations of quantity and quality processes on the catchment surface, the sewerage system and the treatment plant of the City of Hildesheim have to be carried out in order to estimate the effect of the urban area on the receiving water, the river Innerste. The continuous longterm calculations are performed with a pollutant-load-calculation model including a coupled hydrologic71
S. DEYDA
72
hydrodynamic runoff-transportation module. Regarding the water quality, relevant pollutants such as suspended Solids, BODS' COD, Ammonia, Nitrate and Phosphate (soluble and total) are considered. The parameters of the simulation model are calibrated and validated based on field measurements in the sewerage system and the treatment plant of Hildesheim. CASE STUDY HILDESHEIM The City of Hildesheim is partly drained by a separate sewerage system and partly by a combined sewerage system. The collection of necessary input and measured data for the calibration process has been carried out in the following manner: the spatial precipitation ditribution has been recorded with 6 rain gauges in the catchment and the hydraulic behaviour of the sewer system structures has been determined with the help of continuous water level measurements (see Fig. I). The investigated pollutants have been determined by taking samples at three different checkpoints in the sewerage system (rain water system left side of the Innerste, inflow into one storm water tank as the final section of one subcatchment of the combined sewer system on the right side of the Innerste and interceptor upstream of the treatment plant at the end of the main part of the combined sewer system on the right side of the Innerste) and additionally at three checkpoints at the treatment plant (upstream and downstream of the aeration tank and at the inlet of the waste water lagoon).
N
I~ Hm
<:
separate scwcr system
o
~ co mbined scwcr system
Gil CSO •
retention lank
o
rainwater inlet
~ t rc:lt mc nl plant min gauge - . measur ing slation
Figure I. Catchment of Hildesheim.
Totalemission of an urban area
73
THE POLLUTANT-LOAD-CALCULATION MODEL The sewerage system of Hildesheim consists of steep parts and flat parts, in which sedimentation and erosion processes can be observed. For that reason, hydrological methods for the calculation of runoff transport are not suitable. The developed PLCM consists of the following submodules: Quantitative calculation of the catchment surface: runoff formation process (limited method, infiltration model) runoff concentration process (unit hydrograph) Qualitative calculation of the catchment surface: accumulation and removal on the surface, separately for each pollutant and dependent on the prehistory and the process of the runoff events Quantitative calculation of the sewerage system: coupled hydrologic-hydrodynamic runoff transportation model Qualitative calculation of the sewerage system: mixing rate THE COUPLED HYDROLOGIC·HYDRODYNAMIC RUNOFF MODEL For detailed computation of runoff transportation within sewerage systems two methods prove to be suitable. The first method implemented in the hydrodynamic flow routing model EXTRAN (Fuchs et al., 1989) takes into account gradually varied, one-dimensional, non-uniform and unsteady flow within sewerage systems. EXTRAN solves the St. Venant equations by the explicit, modified Euler procedure, which enables the model in combination with boundary considerations to simulate complex systems under sub-critical, supercritical, surcharged or backwater conditions. One disadvantage of the explicit solving method is the constraint due to the stability condition. It is formulated in the Courant condition which often leads to small time steps and a great amount of computation time. Another disadvantage caused by the theoretical derivation of the model equations and the assumption of shallow channels is the occurence of model instabilities resulting in oscillations at hydrographs of sewer pipes with steep slopes. One representative of the second method is the hydrological runoff model KMROUT (Deyda, 1992) which is based on the Kalinin-Miljukov Method for the approximation of the wave runoff in open channels (Rosemann and Vedral, 1970) and which has been modified for the calculation of runoff transportation within sewerage systems. The basis of this model is the continuity equation and the volume-runoff definite relation at stationary flow. The major idea of the Kalinin-Miljukov Method is that this definite relation is valid for a channel section even under non-stationary flow conditions. In comparision with the hYdrodynamicmodel EXTRAN the model KMROUT produces nearly identical results in parts of sewerage systems which are not surcharged but stable results in parts with a steep bed slope. The robust method calculates stable results independent of the chosen time step which leads to short computation time. On the other hand, KMROUT is not able to simulate backwater or reversal of flow. In summary, the strength of the first method is the weakness of the second one and vice versa. Coupling hYdrodynamicand hydrological methods constitutes an obvious conclusion to exploit the advantages of both methods. The main algorithm of the coupled model is to start with the hydrological runoff model and to Switchconduit by conduit to the hydrodynamic model if critical flow conditions appear and fmally to switch back to the hydrological model. As critical flow conditions in most cases occur in particular parts of the
74
S.DEYDA
sewerage system (main sewer, in front of control structures), the coupled model uses the hydrodynamic method permanently in these critical parts of the sewerage system and the hydrological method especially in parts with a steep bed slope. The achievement of the developed model is shown in the example of two different subcatchments of the City of Hildesheim (Tab. I). Fig. 2 shows discharge and water level hydrographs calculated with the coupled model. The time saving (Tab.2) depends on the percentage of hydrodynamic calculated conduits and on the magnitude of the rain event. Table I. System data of the investigated subcatchments Sewerage System
Drainage procedure
Population
Connected surface (ha)
Impervious surface (ha)
Total length (m)
Marienburger Hohe
Seperate sewer system Combined sewer system
8433
112,78
69,85
22192
2,22
.
25200
285,28
164,90
40793
0,98
Retention tank
Schiitzenallee
Middle Special slope structure
(%)
Table 2. Time saving of the coupled model Sewerage System
Marlenburger Hohe Schiitzenalle
Number of conduits
Number of Percentage of conduits calculated conduits calculated hydrodynamocally hydrologically (%)
Timesaving
(%)
380
59
18
51-57
863
125
14
43-52
FINAL WORK The developed pollutant-load-calculation model is able to perform continuous longtenn calculations of quantity and quality processes on the urban catchment surface, the sewerage system and the treatment plant as one interacting system. The total emissions of different rehabilitation concepts will be compared and analyzed under the objective to find the optimal solution in terms of the minimization of the total emission load. With the help of this concept, it is possible to consider the existing transport, storage and treatment capacity more flexible and to find optimal rehabilitation concepts concerning the emission loads just like the resulting costs.
Total emission of an urban area
Sewerage system Schotzenallee 05.08.1994 Retention tank: Waterlewl 80 79 78
Sewerage system Schotzenallee 05.08.1994 Retention tank: Inlet
4000 3500
3000 _2500
rr
--Inlet: Hydrodynamlcal
~ 76
•.••••• Inlet:Coupled
~2ooo
+ 75
.E. 74
o 1500
:I:
1000
500
73 72
+-'++=+=+~;:=;=+=t=::;::::::;::=+=+~~
71 -+I 70
o-l-4-+-+-+-+-A:=:poo'l-t'""!"'"'t"-'I"'"'t-!""'+'''''I-
gggggggggggggggggg
gggggggggggggggggg
~~~~~~~~88EE~~88!!
~~~~~~~~88EE~~88!!
Time [hI
Time[hI
Sewerage system Schotzenallee 05.08.1994
Sewerage system Schotzenallee 05.08.1994 Owrflow
700
600 500
_E 1
I--Overflow: t\tdrodynarrical! ....... Overflow: Qlupled
Ul400
- - Retention tank: Hydrodynamlcal •.••••• Retention tank: Coupled
Outlet
~2oo
~
0 300 200
0150
100
50
[ --Outlet t\tdrodynarricall ....... Outlet Coupled
100 I
O ......-...-+l+-I----+.......-l-+-+......._+_+-+-+-+-+_
O+-l-+--+-t-+-+-+-I~-+-t-t-+--+-f-+-+-
gggggggggggggggggg
~~~~~~~~~~~~~~~~~~
~~~~~~~~88EE~~88!!
~~NN~~~~ggoo~~88~~ Time [hI
1400
Time[h]
Sewerage system Marienburger H
J
1200
- - Outlet:t\tdrodynenica
1000
...... , Outlet:Coupled
----
76,8 76,7
j
Sewerage system Marienburger HOhe 24.07.1991 Outlet
z76.6
'iii'8oo
Z76,5
0600
.E. 76,4
~
+
:I:
400
76,3
- - Outlet t\tdrodynarrical I I ....... Outlet Couple~
76,2
200 0-+--f4---+-~~"'I""'-~-+-..,..J--.i--t-=~
~~~~~~~~~~~~~~~ ""'UlUlCO co co co en
C\lC\IC')C')"", ~
lime[h]
. . . . . . . . . . . . 'PI"
..
76,1
I
I
I
I
I
I
I
I
I
I
I
I
I
I
~~~~~~~~~~~~~~~
.......... .,.. ... '-1ime[h)-- ...............
Figure 2. Comparision of hydrodynamic and coupled calculated hydrographs.
76
S.DEYDA
REFERENCES Deyda, S. (1992). Das hydrologische Transponmodell KMROUT. Institute of Water Resources. University of Hannover, unpublished. Fuchs. L. Harms, R. Scheffer and C. Yerworn, H.-R. (1989). Mikrocomputer in der Stadtentwllsserung. course material and program documentation, ITWH Hannover. unpublished. Rosemann, H.-J. and Yedral, J. (1970). Das Kalinin-Miljukov-Verfahren zur Berechnung von Hochwasserwellen, Schriftenreihe der bayrischen Landesreihe fUrGewllsserkunde. Heft 6. Sieker, F. and Deyda, S. (1996). Bilanzierung der Gesamtemissionen aus einem stlidtischen Einzugsgebiet unter der BerUcksichtigungder gegenseitigen EinfluBnahme von Entwllsserungssystem und Klaranlage, final report of the BMBFproject 02WA93271O.
Pergamon PH: S0273-1223(97)00632-X
Wat.ScL Tech. Vol.36. No. 8-9. pp. 71-76.1997. CC> 1997IAWQ.Published by ElsevierScienceLId All rightsreserved. Printedin Great Britain. 0273-1223197 S17·OO +0-00
TOTAL EMISSION OF AN URBAN AREA CONSIDERING THE INTERACTION BETWEEN DRAINAGE SYSTEM AND
TREATMENT PLANT Susanne Deyda Institutefor WaterResources. University ofHannover. Appelstr. 9A, D-30167Hannover, Germany
ABSTRACf Continuous longterm calculations of quantity and quality processes on the catchment surface. the sewerage system and the treatment plant of the City of Hildesheim have to be carried out in order to estimate the effect of the urban area on the receiving water. The calculations are performed with a pollutant-load-calculation model including a coupled hydrologic-hydrodynamic runoff-transportation module. The achievement of the developed model is shown in the example of two different subcatchments of the City of Hildesheim. With the help of this concept. it is possible to consider the existing transport, storage and treatment capacity more flexible and to find optimal rehabilitaion concepts concerning the emission loads just like the resulting costs. @ 1997 IAWQ. Published by Elsevier Science Ltd
KEYWORDS Case study; comprehensive view; continuous longterm simulation; total emission; treatment plant.
INTRODUCTION In uran hdrology, progress in computer techniques has allowed the development of numerical models for simulating hydrological processes in UDS. Depending on the investigated problem, one or more of the models are used. For a comprehensiveview, as the basis for a masterplan or similar, the effect of the sewerage system and the treatment plant on the receiving waters has to be investigated. Such an integrated simulation consists of sub models for the quantitative and qualitative calculation of surface-runoff, runoff transportation within sewerage systems, processes in treatment plants and finally within the receiving waters. Since 1993 the government of the Federal Republic has been financing a two year research programme with the interaction between drainage systems and treatment plants (Sieker and Deyda, 1996). In the investigation, continuous longterm calculations of quantity and quality processes on the catchment surface, the sewerage system and the treatment plant of the City of Hildesheim have to be carried out in order to estimate the effect of the urban area on the receiving water, the river Innerste. The continuous longterm calculations are performed with a pollutant-load-calculation model including a coupled hydrologic71
S. DEYDA
72
hydrodynamic runoff-transportation module. Regarding the water quality, relevant pollutants such as suspended Solids, BODS' COD, Ammonia, Nitrate and Phosphate (soluble and total) are considered. The parameters of the simulation model are calibrated and validated based on field measurements in the sewerage system and the treatment plant of Hildesheim. CASE STUDY HILDESHEIM The City of Hildesheim is partly drained by a separate sewerage system and partly by a combined sewerage system. The collection of necessary input and measured data for the calibration process has been carried out in the following manner: the spatial precipitation ditribution has been recorded with 6 rain gauges in the catchment and the hydraulic behaviour of the sewer system structures has been determined with the help of continuous water level measurements (see Fig. I). The investigated pollutants have been determined by taking samples at three different checkpoints in the sewerage system (rain water system left side of the Innerste, inflow into one storm water tank as the final section of one subcatchment of the combined sewer system on the right side of the Innerste and interceptor upstream of the treatment plant at the end of the main part of the combined sewer system on the right side of the Innerste) and additionally at three checkpoints at the treatment plant (upstream and downstream of the aeration tank and at the inlet of the waste water lagoon).
N
I~ Hm
<:
separate scwcr system
o
~ co mbined scwcr system
Gil CSO •
retention lank
o
rainwater inlet
~ t rc:lt mc nl plant min gauge - . measur ing slation
Figure I. Catchment of Hildesheim.
Totalemission of an urban area
73
THE POLLUTANT-LOAD-CALCULATION MODEL The sewerage system of Hildesheim consists of steep parts and flat parts, in which sedimentation and erosion processes can be observed. For that reason, hydrological methods for the calculation of runoff transport are not suitable. The developed PLCM consists of the following submodules: Quantitative calculation of the catchment surface: runoff formation process (limited method, infiltration model) runoff concentration process (unit hydrograph) Qualitative calculation of the catchment surface: accumulation and removal on the surface, separately for each pollutant and dependent on the prehistory and the process of the runoff events Quantitative calculation of the sewerage system: coupled hydrologic-hydrodynamic runoff transportation model Qualitative calculation of the sewerage system: mixing rate THE COUPLED HYDROLOGIC·HYDRODYNAMIC RUNOFF MODEL For detailed computation of runoff transportation within sewerage systems two methods prove to be suitable. The first method implemented in the hydrodynamic flow routing model EXTRAN (Fuchs et al., 1989) takes into account gradually varied, one-dimensional, non-uniform and unsteady flow within sewerage systems. EXTRAN solves the St. Venant equations by the explicit, modified Euler procedure, which enables the model in combination with boundary considerations to simulate complex systems under sub-critical, supercritical, surcharged or backwater conditions. One disadvantage of the explicit solving method is the constraint due to the stability condition. It is formulated in the Courant condition which often leads to small time steps and a great amount of computation time. Another disadvantage caused by the theoretical derivation of the model equations and the assumption of shallow channels is the occurence of model instabilities resulting in oscillations at hydrographs of sewer pipes with steep slopes. One representative of the second method is the hydrological runoff model KMROUT (Deyda, 1992) which is based on the Kalinin-Miljukov Method for the approximation of the wave runoff in open channels (Rosemann and Vedral, 1970) and which has been modified for the calculation of runoff transportation within sewerage systems. The basis of this model is the continuity equation and the volume-runoff definite relation at stationary flow. The major idea of the Kalinin-Miljukov Method is that this definite relation is valid for a channel section even under non-stationary flow conditions. In comparision with the hYdrodynamicmodel EXTRAN the model KMROUT produces nearly identical results in parts of sewerage systems which are not surcharged but stable results in parts with a steep bed slope. The robust method calculates stable results independent of the chosen time step which leads to short computation time. On the other hand, KMROUT is not able to simulate backwater or reversal of flow. In summary, the strength of the first method is the weakness of the second one and vice versa. Coupling hYdrodynamicand hydrological methods constitutes an obvious conclusion to exploit the advantages of both methods. The main algorithm of the coupled model is to start with the hydrological runoff model and to Switchconduit by conduit to the hydrodynamic model if critical flow conditions appear and fmally to switch back to the hydrological model. As critical flow conditions in most cases occur in particular parts of the
74
S.DEYDA
sewerage system (main sewer, in front of control structures), the coupled model uses the hydrodynamic method permanently in these critical parts of the sewerage system and the hydrological method especially in parts with a steep bed slope. The achievement of the developed model is shown in the example of two different subcatchments of the City of Hildesheim (Tab. I). Fig. 2 shows discharge and water level hydrographs calculated with the coupled model. The time saving (Tab.2) depends on the percentage of hydrodynamic calculated conduits and on the magnitude of the rain event. Table I. System data of the investigated subcatchments Sewerage System
Drainage procedure
Population
Connected surface (ha)
Impervious surface (ha)
Total length (m)
Marienburger Hohe
Seperate sewer system Combined sewer system
8433
112,78
69,85
22192
2,22
.
25200
285,28
164,90
40793
0,98
Retention tank
Schiitzenallee
Middle Special slope structure
(%)
Table 2. Time saving of the coupled model Sewerage System
Marlenburger Hohe Schiitzenalle
Number of conduits
Number of Percentage of conduits calculated conduits calculated hydrodynamocally hydrologically (%)
Timesaving
(%)
380
59
18
51-57
863
125
14
43-52
FINAL WORK The developed pollutant-load-calculation model is able to perform continuous longtenn calculations of quantity and quality processes on the urban catchment surface, the sewerage system and the treatment plant as one interacting system. The total emissions of different rehabilitation concepts will be compared and analyzed under the objective to find the optimal solution in terms of the minimization of the total emission load. With the help of this concept, it is possible to consider the existing transport, storage and treatment capacity more flexible and to find optimal rehabilitation concepts concerning the emission loads just like the resulting costs.
Total emission of an urban area
Sewerage system Schotzenallee 05.08.1994 Retention tank: Waterlewl 80 79 78
Sewerage system Schotzenallee 05.08.1994 Retention tank: Inlet
4000 3500
3000 _2500
rr
--Inlet: Hydrodynamlcal
~ 76
•.••••• Inlet:Coupled
~2ooo
+ 75
.E. 74
o 1500
:I:
1000
500
73 72
+-'++=+=+~;:=;=+=t=::;::::::;::=+=+~~
71 -+I 70
o-l-4-+-+-+-+-A:=:poo'l-t'""!"'"'t"-'I"'"'t-!""'+'''''I-
gggggggggggggggggg
gggggggggggggggggg
~~~~~~~~88EE~~88!!
~~~~~~~~88EE~~88!!
Time [hI
Time[hI
Sewerage system Schotzenallee 05.08.1994
Sewerage system Schotzenallee 05.08.1994 Owrflow
700
600 500
_E 1
I--Overflow: t\tdrodynarrical! ....... Overflow: Qlupled
Ul400
- - Retention tank: Hydrodynamlcal •.••••• Retention tank: Coupled
Outlet
~2oo
~
0 300 200
0150
100
50
[ --Outlet t\tdrodynarricall ....... Outlet Coupled
100 I
O ......-...-+l+-I----+.......-l-+-+......._+_+-+-+-+-+_
O+-l-+--+-t-+-+-+-I~-+-t-t-+--+-f-+-+-
gggggggggggggggggg
~~~~~~~~~~~~~~~~~~
~~~~~~~~88EE~~88!!
~~NN~~~~ggoo~~88~~ Time [hI
1400
Time[h]
Sewerage system Marienburger H
J
1200
- - Outlet:t\tdrodynenica
1000
...... , Outlet:Coupled
----
76,8 76,7
j
Sewerage system Marienburger HOhe 24.07.1991 Outlet
z76.6
'iii'8oo
Z76,5
0600
.E. 76,4
~
+
:I:
400
76,3
- - Outlet t\tdrodynarrical I I ....... Outlet Couple~
76,2
200 0-+--f4---+-~~"'I""'-~-+-..,..J--.i--t-=~
~~~~~~~~~~~~~~~ ""'UlUlCO co co co en
C\lC\IC')C')"", ~
lime[h]
. . . . . . . . . . . . 'PI"
..
76,1
I
I
I
I
I
I
I
I
I
I
I
I
I
I
~~~~~~~~~~~~~~~
.......... .,.. ... '-1ime[h)-- ...............
Figure 2. Comparision of hydrodynamic and coupled calculated hydrographs.
76
S.DEYDA
REFERENCES Deyda, S. (1992). Das hydrologische Transponmodell KMROUT. Institute of Water Resources. University of Hannover, unpublished. Fuchs. L. Harms, R. Scheffer and C. Yerworn, H.-R. (1989). Mikrocomputer in der Stadtentwllsserung. course material and program documentation, ITWH Hannover. unpublished. Rosemann, H.-J. and Yedral, J. (1970). Das Kalinin-Miljukov-Verfahren zur Berechnung von Hochwasserwellen, Schriftenreihe der bayrischen Landesreihe fUrGewllsserkunde. Heft 6. Sieker, F. and Deyda, S. (1996). Bilanzierung der Gesamtemissionen aus einem stlidtischen Einzugsgebiet unter der BerUcksichtigungder gegenseitigen EinfluBnahme von Entwllsserungssystem und Klaranlage, final report of the BMBFproject 02WA93271O.