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Page 1Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
- Introduction: P- and N-Removal in Multistage Processes
- WWTP Ratzeburg: Step-feed Denitrification
- WWTP Lübeck: Combined Treatment with Biofiltration
All Topics: Description of Process Features,
Remarks on Loads and Effluent Values
- WWTP Flensburg:
Trickling Filter and Upflow Sludge Bed Reactor
Multistage Biological Wastewater Treatmentin Northern Germany
Dr.-Ing. Jörn Einfeldt
Dr.-Ing. H.-O. Günter / Dr.-Ing. A. Silem(Privatinstitut für Klärtechnik GmbH, 23611 Bad Schwartau, Germany)
Page 2Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Biotests and chemicalinvestigations
• Consulting
• Field investigationsand data collection
• Process design anddevelopment
• Facilities start up
• Expert‘s report
• Optimization
• Support
Introduction
Page 3Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water ManagementIntroduction
Tallinn
Schleswig-Holstein
Page 4Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Flensburg
Lübeck
Ratzeburg
Introduction
2
Page 5Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
WWTP Flensburg, 224.000 PE
WWTP Lübeck, 640.000 PE
WWTP Ratzeburg, 25.000 PE
Introduction
Page 6Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Biological Treatment:
Carbon Removal (Activated Sludge)
InletEffluent
Return sludge Excesssludge
Primary settlement tank Aeration tank Clarifier
Introduction
+ further stages for advanced treatment
Page 7Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Removal of Phosphorus
Introduction
biological
*
*
/ chemical
Page 8Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Removal of Phosphorus
Introduction
Why combining different precipitation stages ?
- Early relief of the following process stages
- Economical use of chemicals
- Reducing flushing frequency of the filtration unit
3
Page 9Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Return sludge
Aeration tank Clarifier
Excesssludge
NH4
NO3
NH4
NC
Introduction
Biological Nitrogen Removal
Page 10Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Biological Nitrogen Removal
Return sludge
Aeration tank Clarifier
Excesssludge
Recirculation
NH4
NO3
NH4NO3
N2
NDN
Recirculation = 3 to 4 times inlet quantity
Introduction
Page 11Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water ManagementIntroduction
Page 12Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water ManagementIntroduction
4
Page 13Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water ManagementIntroduction
1. Stage of Treatment
? ?
2. Stage3. Stage
Page 14Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Examples:
Different Processes for N-Removal / Integration of P-Removal
- WWTP Ratzeburg: Step-feed Denitrification
- WWTP Lübeck: Combined Treatment with Biofiltration
- WWTP Flensburg: Post-Denitrification with an
Upflow Sludge Bed Reactor
Introduction
Page 15Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
WWTP Ratzeburg (2005): 25.000 PE
WWTP Ratzeburg
Page 16Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Design CapacityPopulation Equivalents 25.000 PEB60
(34.000 PEB60)
Hydraulic Load 4.700 m³/d
470 m³/h
(500 m³/h, 275 m³/h equalized)
COD 3.240 kg/d
Nges 350 kg/d
WWTP Ratzeburg
5
Page 17Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Equalization Tank
Inlet Effluent Fill Level
WWTP Ratzeburg
Page 18Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
(Bio)-Filtration
Equalization tankSubstrate feeding
Mechanicalpretreatment
(Screen, grit chamber, primary settlement tank)
Biological treatment
DigesterBiogastank
Combinedheat and power unit
Sludgedewatering
1. Flow line
2. Flow line
Effluent
WWTP Ratzeburg
Dosing of precipitant
Page 19Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water ManagementWWTP Ratzeburg
Page 20Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Activated Sludge Stage
WWTP Ratzeburg
6
Page 21Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
DN
DN
N
NDN
N
N
Step-feed Denitrification
DN
DN
N
N
DN
DN/N
N
- No recirculation
- Higher MLSSin the upper tanks
WWTP Ratzeburg
Page 22Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Technical Specifications:
Sludge Age tSS,Dim T = 8°C 11 d
Activated Sludge Volume 3.360 m³
Biofiltration:
1st Stage, Nitrification 4 FBR each A = 5 m²
2nd Stage, Denitrification 6 Grit Filter each A = 5 m²
Digester 1.200 m³
WWTP Ratzeburg
Page 23Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Effluent Demands:
COD ≤ 60 mg/l
BOD5 ≤ 15 mg/l
NH4-N ≤ 3 mg/l
Nges ≤ 10 mg/l
Pges* ≤ 0,3 mg/l
Susp. Sol. ≤ 5,0 mg/l
GK 4
90 mg/l
20 mg/l
10 mg/l
18 mg/l
2,0 mg/l
--
WWTP Ratzeburg
* T > 15°C
Page 24Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Operational results: COD
WWTP Ratzeburg
7
Page 25Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Operational results: Phosphorus
WWTP Ratzeburg
Page 26Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Operational results: Nitrogen
WWTP Ratzeburg
Page 27Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Summary: Special Features WWTP Ratzeburg
- Step-feed Denitrification(no mixed liquor recirculation)
- Upgradable by diverse extra modules,according to future requirements
- Very strict effluent demands
WWTP Ratzeburg
Page 28Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
WWTP Flensburg (1997 - 2005): 224.000 PE
WWTP Flensburg
8
Page 29Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Design CapacityPopulation Equivalents 224.000 PEB60
Hydraulic Load 55.000 m³/d
3.190 m³/h
COD 28.300 kg/d
Nges 2.125 kg/d
WWTP Flensburg
WWTP Flensburg
Page 30Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Inlet (frommechanical
treatment)
1st Lane
2nd Lane
3 Clarifiers
Effluent
Situation in 1985
WWTP Flensburg
Page 31Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Flow Scheme, Concept 1997
High loaded biology
Low loaded biology
Clarifier
Clarifier
?
Effluent
TF 2 USBR 2
USBR 1TF 1
TF 3 ?
Inlet (frommechanical
treatment)
SS as Substrate
WWTP Flensburg
Page 32Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
since Large-scale pilot operation and optimisation1999 (by PIK together with TU Hamburg-Harburg)
1997 Start of construction for nutrient removal:Existing studies by the TU Hamburg-Harburg, butlack of large-scale experience� Process survey and adjustment in parallel with
stepwise upgrading the plant
2001 Verification of the dimensioning of TF 1 and USBR 1prior to start of construction of TF 2 and USBR 2
2004 Start of operation TF 2
2005 Start of operation USBR 2 and filtration unit
1988-95 Extension of carbon-removal facilities,simultaneous phosphorus-precipitation
WWTP Flensburg
9
Page 33Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water ManagementWWTP Flensburg
Page 34Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Details high loaded lane
TF USBR FBR FF
Effluent
3rd biological stage(2-stage-filtration)
2nd biological stage
Act. sludge(HL)PT Clar.
1st biological stage
Me
SS
WWTP Flensburg
Dosing of precipitant
Page 35Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Upflow Sludge Bed Reactor (Moving Bed Reactor)
WWTP Flensburg
Page 36Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water ManagementWWTP Flensburg
Upflow Sludge Bed Reactor (Moving Bed Reactor)
Bubbling of N2
10
Page 37Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
• Inlet cylinder, diverting theflow
• Submerged outlet pipe
• Floating sludge removal
WWTP Flensburg
Page 38Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
• Two of a total of fourpaddle agitators per USBR
• Scraper for settled sludge
WWTP Flensburg
Page 39Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Kläranlage Flensburg
Hydraulikversuch 14 vom 14.09.05: Erhöhung Beschickung SBtR 2 von
900 m³/h auf 1.400 m³/h, RW=20 Hz
0
1
2
3
4
5
6
7
8
5:00 7:00 9:00 11:00 13:00 15:00 17:00 19:00 21:00
Tie
fe in
m
0
400
800
1.200
1.600
2.000
2.400
2.800
3.200
Schlammspiegel innen Schlammspiegel aussen Beschickung
Be
sch
icku
ng
in
m³/
h
Anhebung 1,02 m
Operating behaviour USBR:Inlet increase from 900 m³/h to 1.400 m³/h
Sludge rising 1 m, stable sludge bed
WWTP Flensburg
Page 40Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Technical Specifications:
Sludge Age tSS,Dim T = 12°C 9,5 d (LL)T = 12°C 1,5 - 2,0 d (HL)
Activated Sludge Volume 4.670 m³ (LL)2.700 m³ (HL)
Trickling Filter 2 TF each 4.900 m³
Upflow Sludge Bed Reactor 2 USBR each 3.350 m³
hm = 7,40 m
Biofiltration:
1st Stage, Nitrification 8 FBR each A = 40 m²
(therefrom 2 for nitrification of sludge liquor)
2nd Stage, Denitrification 8 FBR each A = 40 m²
WWTP Flensburg
11
Page 41Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Effluent Demands:
COD ≤ 60 mg/l
BOD5 ≤ 15 mg/l
NH4-N ≤ 10 mg/l
Nges ≤ 10 mg/l
Pges ≤ 0,5 mg/l
Susp. Sol. ≤ 5,0 mg/l
GK 5
75 mg/l
15 mg/l
10 mg/l
13 mg/l
1,0 mg/l
--
WWTP Flensburg
Page 42Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Operational results: Phosphorus(German limit values are based on grab samples!)
WWTP Flensburg
Page 43Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Operational results and simulation study USBR:
WWTP Flensburg
Page 44Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Operational results:
High loaded biology
Low loaded biology
Clarifier
Clarifier TF 2 USBR 2
USBR 1TF 1
Inlet (frommechanical
treatment)
99 % N
50–80 % DN
0 % N
< 1 mgNH4-N/l
< 10 mgNO3-N/l
Ca. 5-6 mgNO3-N/l
< 1 mgNH4-N/l
< 8 mgNO3-N/l
2-s
tag
e-b
iofi
ltra
tio
n w
ith
nit
rifi
cati
on
an
d -
den
itri
ficati
on
WWTP Flensburg
12
Page 45Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Summary: Special Features WWTP Flensburg
- Biological process, 3 stages(no MLSS recirculation for denitrification):
- Strict effluent demands
1) Carbon removal: Activated Sludge System2a) Nitrification: Trickling Filter2b) Post-Denitrification: Upflow Sludge Bed3) Biofiltration: 1st stage subsidiary nitrification
2nd stage denitrification
WWTP Flensburg
Page 46Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
WWTP Lübeck (2009): 640.000 PE
WWTP Lübeck
Page 47Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Design CapacityPopulation Equivalents 640.000 PEB40
(Outlet primary treatment)
Hydraulic Load 90.000 m³/d
15.100 m³/h
Inlet biological treatment: 5.500 m³/h
BOD < 25.650 kg/d
BOD / Nges < 4,0
WWTP Lübeck
Page 48Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
WWTP Lübeck:1967-2007
- 1990 / 1991 Pilot Plant
- 1967 Mechanical-biological Treatment1982 Aeration with refined oxygen
1990 New mechanical treatment
- 1992 Approval Planning (641.000 PE)
- 1996 Official Approval
WWTP Lübeck
13
Page 49Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Filtration: a) Higher MLSS in aeration tank: then NH4-N < 8 mgN/l
FBR used for denitrification
1. Stage: 2-stage step-feed denitrification,
SVI 150 ml/g, actual suspended solids (2007) too low
b) Alternative, needs a longer period for putting into
operation: FBR for Nitrification, FF for Denitrification
Concept
WWTP Lübeck
Page 50Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
RecintRecint
Recext
Inlet from mechanical pretreatment
2-s
tag
e-b
iofi
ltra
tio
n
Effluent
5
Clar.
RS
VKB
K MWB 2
MWB1
C C
C
ANDN
50% QZu
50% QZu DN DNN N
MWB: Combined Wastewater Equalisation Tank
WWTP Lübeck
Dosing of precipitant
Page 51Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
RecintRecint
Recext
Inlet from mechanical pretreatment
2-s
tag
e-b
iofi
ltra
tio
n
Effluent
5
Clar.
RS
VKB
K MWB 2
MWB1
C C
C
ANDN
50% QZu
50% QZu DN N N
MWB: Combined Wastewater Equalisation Tank
WWTP Lübeck
Dosing of precipitant
DN
Page 52Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
- 1997 Start of overall completion
- 1996 / 1997 Verification of inlet data
- 2000 Start of operation 5 new clarifiers
- 2001 Verification of inlet data
- 2003 Start of operation of new activated sludge stage, design biofiltration
WWTP Lübeck:1967-2007
- 2008 Start of operation biofiltration (in progress)
- 2006 Verification of inlet data: declining biological load 370.000 PE,but disadvantageous CSB/BSB ratio 3,0 at weekends
WWTP Lübeck
14
Page 53Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Inlet Filtration (Effluent Secondary Clarifier)
PO4-P ≤ 1,5 mg/l
Ntot ≤ 20 mg/l
Suspended Solids ≤ 75 mg/l
Construction:
1.Stage: Upflow granular fixed bed reactor (FBR)
Fill: expanded clay
2.Stage: Sandfilter (FF)
Fill: anthracite / siliceous sand
WWTP Lübeck
Page 54Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Dosing Point Substrate, Precipitant
C
12 x FBR 12 x FF
Fe
3 x 2 RF
vom Pumpwerk
Filtration
zur Trave from pump station
Outletchannel
WWTP Lübeck
Page 55Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Prinzipskizze der 2-Stufen-Filtration
FF =
FBR = Festbettreaktor ( gefüllt mit Blähbeton )
= Verlauf des Wasserweges vom Quellschacht
Feinfilter ( gefüllt mit Sand )
FRB FF Ablauf zur Reinwasserkammer
Quellschacht
Quellschacht = Wasserverteilung
Prozeßluftgebläse
Schlammwasserkanal
RK1 RK2 RK3
RK = Rohrkanal 1, 2, 3
Schlammwasserkanal
vorh. Rohrkanal
Ablaufkanal zur Trave
FBR FF FBR FF
Flow path filtration
Inlet chamber: water distribution
FBR: upflow granular fixed bed reactor
FF: sandfilter
RK: pipe channel 1, 2, 3
Inlet chamber
WWTP Lübeck
Page 56Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
15
Page 57Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Page 58Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
„Pipe channel“
Page 59Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Upflow granular fixed bed reactor,filled with Liaperl Ø 4-8 mm (expanded clay)
height 5,00m
Page 60Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Fine filter, filled with anthracite (1,4-2,5 mm, height 1,5 m) and siliceous sand (0,7 - 1,2 mm, height 0,5 m)
16
Page 61Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Page 62Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Technical Specifications:
Sludge Age tSS,Dim T = 12°C 12 - 16 d
Activated Sludge Volume 22.400 m³ + 17.340 m³
Biofiltration (main function: removal of suspended solids):
1st Stage 12 FBR each A = 36 m²
(Denitrification, optional nitrification)
2nd Stage 12 FBR each A = 36 m²
(P-removal, optional denitrification)
WWTP Lübeck
Page 63Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Effluent Demands:
COD ≤ 60 mg/l
BOD5 ≤ 15 mg/l
NH4-N ≤ 8 mg/l
Nges ≤ 10 mg/l
Pges ≤ 0,5 mg/l
Susp. Sol. ≤ 5,0 mg/l
GK 5
75 mg/l
15 mg/l
10 mg/l
13 mg/l
1,0 mg/l
--
WWTP Lübeck
Page 64Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
KLint.KLint.
KLext.
Inlet from primary treatment
2-s
tag
e-b
iofi
ltra
tio
n
Effluent
5
Clar.
RS
VKB
K MWB 2
MWB1
ANDN
50% QZu
50% QZu DN DNN N
C C
C
99 % N
50–80 % DN< 20 mgNO3-N/l
WWTP Lübeck
< 5 mgNO3-N/l
17
Page 65Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Operational results, 2-stage-biofiltration: Phosphorus
WWTP Lübeck
Page 66Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Operational results, 2-stage-biofiltration: Phosphorus
WWTP Lübeck
?
Page 67Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Operational results, 2-stage-biofiltration: Phosphorus
WWTP Lübeck2-s
tag
e-b
iofi
ltra
tio
n
Effluent
50% QZu
50% QZu DN DNN N5
Clar.
RS
from PT
FeSO4
FeCl32) Stormwater flow: values up to 0,3 mgP/l
3) Dosing into activated sludge tank improves SVI
4) … reduces H2S-formation in digester
5) … reduces flushing frequency (energy, hydraulic backcharge)
1) FeSO4 cheaper than FeCl3
Page 68Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Operational results, 2-stage-biofiltration: Nitrogen
WWTP Lübeck
18
Page 69Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Operational results, 2-stage-biofiltration: Nitrogen
WWTP Lübeck
Page 70Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Summary: Special Features WWTP Lübeck
- Biological process, 2 stagesCombined treatment
- Strict effluent demands
1) Carbon removal, nitrification,partial denitrification:Activated Sludge System
2) Biofiltration: 1st stage denitrification2nd stage fine filter (SS)
WWTP Lübeck
Page 71Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water ManagementSummary
- Strict effluent demands,based on grab samples
- Different process designs proved to be applicable
- Different framework conditionsrequire matched process designs
- New technologies may produce newoperating challenges
- Take advantage from other operatorsexperiences
Page 72Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management
Thank you foryour attention !
Page 72Multistage Biological Wastewater Treatment in Northern Germany / Tallinn 16.03.2011
German Experts on Water Management