ENERGY
From intake to outfall,
from environment to environment
Reduction environmental impact in large scale sea water
outfalls through optimised fouling control
Maarten Bruijs (DNV GL) & Robin Morelissen (Deltares)
April 14, 2014
International Conference on Desalination, Environment and Marine Outfall Systems
Muscat, Oman, April 13 – 16 2016
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DNV GL © 2013
April 14, 2014
SAFER, SMARTER, GREENER
From intake to outfall / from environment to environment
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April 14, 2014
Impingement mortality
 Design intake as ‘fish-friendly’ as possible
– consider far/near-field hydraulic conditions, velocities, location, configuration,
lay out, fish recovery & return, ecology (monitor fish population + habitat), etc
 Impingement & entrainment (I&E) mortality reduction during operation
– Reduce ingress of fish: proper design and apply fish deterrence systems
– Increase survival of impinged fish: apply Fish Recovery & Return system
va
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April 14, 2014
Macrofouling
Cooling Water Systems provide an ideal environment for macrofouling because:
 Water turbulence inside the CWS that facilitates settlements of larvae
 Continuous supply of nutrition and oxygen that stimulates growth
 Absence of predators that cannot pass the sieves
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April 14, 2014
Macrofouling development
 Fouling layer thickness development, if nothing is done…
Head loss calculation:
 Macrofouling mainly effects the head loss over the intake pipes
– Layer thickness independent of pipe diameter → larger additional losses in
smaller pipes
– Wall roughness location depended
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April 14, 2014
The cost of fouling
Macro Fouling
Micro Fouling
Tube clogging
Tube scaling and fouling
Narrowing of tube cross-sections
Erosion at tube inlet
Technical
+ erosion at overall tube
Increased flow resistance / head loss
+ corrosion
Impediment to heat transfer loss
of efficiency
Tube damage
Load reduction and shutdown of plants for
Ecologic
Reduction
of output
Additional
requirement of
water chemistry
Additional emission
water: chemicals
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Profit loss by lost
output
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April 14, 2014
Unscheduled
maintenance & cleaning
Domination of
leakage + repairs
Reduced
system life
Additional emission
air: Nox, SO2, CO2
Increased operational
expenditure
Economic
Profit loss
Additional
requirement of
primary energy
Loss of availability
Increased maintenance
expenditure
Increased overall cost
Increased depreciation
requirement
Costs
Output
Chlorination
 Chlorination
– worldwide still most applied method
to combat macro-fouling in once-through
cooling water systems
 Discharge of Chlorination By-Products
– Legislator: continuous strive to discharge
less residual chlorine
– Measured concentrations in the field (µg/L)
are much lower than the acute toxicity levels (mg/L)
 Dosing methods
– low level continuous dosing: not effective
– intermittent shock dosing: bivalves recover easily
– intermittent dosing (Pulse-Chlorination): intense effect
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April 14, 2014
Optimised chlorine dosing: Pulse-Chlorination®
 Behaviour of bivalves
absolute opening
550
500
450
400
350
300
time
 Dosing kinetics in SCWS
1.75
1
1.50
3
2
4
TRO/FO (mg/L)
1.25
1.00
1
2
0.75
0.50
4
3
1
2
0.25
0.00
9:00
4
3
9:14
9:28
9:43
9:57
10:12
10:26
10:40
10:55
11:09
11:24
11:38
11:52
time
INLET
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INLET
HE
April 14, 2014
HE
OUTLET
OUTLET
Mixing Zone issues
 Variability: discharge mass flux, concentration, receiving water flow (tide), wind?
 Instantaneous /cumulative /average exceedence EQS?
 Reference location: where to apply field monitoring to get sufficient insight?
– extensive monitoring and costly analyses! (seasonal + complex chemistry)
 Determining low residual chlorine [FRC] in the mixing zone (e.g. 100 m) in a
reliable way is practically not feasible
  Modelling can provide this information
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Effects of cooling water discharges – integral modelling approach
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Effects of cooling water discharges – integral modelling approach
Hydrodynamic and water
quality modelling of the
intake and outfall design
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April 14, 2014
Effects of cooling water discharges – integral modelling approach
Stress
1
Suitability
Modelling of the (potential) habitat
suitability
Stress
0
No
seagrass
Species
shifts
lower
threshold
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April 14, 2014
Morphological and physiological
response
optimum
Species
shifts
upper
threshold
No
seagrass
Conclusions
 Legislation and regulation (permitting)
– increasingly strict on CW intakes and outfalls: I&E, discharges + EQS
– EIA: more scientific information + insight in the effects of the CWS design
(intake & outfalls) on the receiving environment (discharges T and chemicals)
 Real time effects in the field
– I&E: dependent on location and hydraulic conditions
– effects of FRC and CBP discharge could be limited!?
 Chlorination procedures must be optimised, to reach cost-effective and highly
reliable mitigation effectiveness: Pulse-Chlorination
 Integral 3D modeling required tool to predict effects of intake and outfalls
– optimal design in relation to operation and environmental permit requirements
– distribution of temperature and chemical discharges
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Recommendation: Best Available Approach for new initiatives
 Optimal design:
– required cooling capacity and accompanying CW flows
– optimised fouling control
– ecology: fish populations (spawning/nursery habitat + migration route) and
other relevant flora/fauna
– near/far-field hydraulic conditions, theoretic mixing zone, location/position +
configuration of the intake and outfall (minimal recirculation)
– evaluate discharge: temperature, residual chlorine, CBPs and brine for
compliance with (local) legislation and permit requirements (ecology)
– assess discharges against site-specific, ecologically relevant criteria, including
cumulative effects, which need to be developed
With proper integral design, CAPEX, OPEX and environmental impacts
can be kept as low as possible
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“Managing environmental risks with cost
beneficial operation of intake and outfall
systems”
Invitation for a Round Table Discussion
Tuesday April 15, ~17:00
Sultan Qaboos University, Al Faham hall
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April 14, 2014
Thank you for
your attention
Maarten Bruijs
maarten.bruijs@dnvgl.com
www.dnvgl.com
SAFER, SMARTER, GREENER
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April 14, 2014