K.P. Manikandan, Mohammad A. Qurban, T.V. Joydas, M. Wafar and

K.P. Manikandan, Mohammad A. Qurban,
T.V. Joydas, M. Wafar and P.K. Krishnakumar
10th April 2012
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Slide # 1
Introduction
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Desalination is being used in 150 countries around the world, providing some or all the daily water needs of an
estimated 300 million people
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There are now 16,000 desalination plants worldwide
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Total production = 77.4 million cubic meters per day (m3/d) (24th IDA Worldwide Desalting Plant Inventory, 2012)
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Slide # 2
Introduction
Mediterranean
Sea
17%
Arabian Gulf
76% 45%
Red Sea
14%
 76% from three Seas
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Slide # 3
Production in Arabian Gulf
 45% of the global capacity
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Slide # 4
Production in Red sea
 14% of the global capacity
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Slide # 5
Introduction
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Most desalination plants draw/pump water from the coastal waters
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Coastal waters are the biologically productive zone
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This is the zone where most marine animals prefer to lay eggs
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As most marine larvae are passive swimmers (at the mercy of water currents) they are vulnerable to suction during the intake
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Every year there is a huge loss of billions of aquatic organisms, including fishes, fish larvae and eggs, crustaceans, shellfish,
and many other forms of aquatic life from the coastal ecosystems.
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This huge loss will reflect on the declining fish landing and ultimately to the revenues generated by Fishery.
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Slide # 6
Definitions
Impingement:
Potential injuries or loss of marine organisms retained on the
intake screens. (as per USEPA > 9.5mm)
Adult fishes
Entrainment:
Loss of marine organisms which enter the desalination plant with
the source
Seawater (as per USEPA < 9.5mm)
Fish and invertebrate
larvae
Entrapment:
impacts associated with offshore intake
structures connected to an on-shore intake screen and pump
station via long conveyance pipeline ‟ Trapped
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Slide # 7
Typical Larval Cycle
One Female
99.9%
100,000 larvae
100 juveniles
98%
2 ADULTS
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Slide # 8
An example from Florida
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Florida’s - Tampa Electric Company (TECO) Big Bend station, situated on
Tampa Bay, at Apollo Beach.
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Annually, impingement resulted in the loss of 419,286
fish, and 11,113
pounds of fishery yield
“age 1” equivalent
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Entrainment was far more lethal: 7.71 billion-age 1 equivalent
were being decimated; 22.8 million pounds of lost fishery yield.
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Most heavily hit were bay anchovies
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Stone crabs, pink shrimp, sea trout, herring and black drum were also affected.
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fish
Slide # 9
Region-wise losses
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Slide # 10
Loss due to Impingement & Entrainment
in Arabian Gulf & Red Sea ‟ Unknown ?
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Slide # 11
Objectives
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To identify the methodology for quantifying the loss of marine organisms due to entrainment and impingement
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To recommend mitigation measures by way of alternative modes of seawater intake
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Slide # 12
Assessment- Methodology
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What to sample?
• Limited to only large and late stage larvae (Fish & Crabs)
• Phytoplankton to be ignored
 Short generation times
 Overly Abundant (bloom) can be a problem in quantification
• Small Invertebrate Larvae & Fish Eggs ignored ‟ Cannot be Enumerated

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Slide # 13
Assessment- Methodology
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Sampling Locations:
• From the Intake Screens (for Impingement)
• In front of the Intake and at Water Body Locations
using 300-μ mesh Plankton net (for Entrainment)
• Two replicate tows were taken with a minimum target
sample volume of 30 to 40 m3 for each net on the bongo
frame.
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Sampling Frequency:
• 12 to 18 Consecutive Months
• Weekly ‟ i.e., minimum of 52 Samples
• 24-hr Sample Collection for Impingement
• Day/Night Samples for Entrainment.
• Four times per 24-hr period†once every six hours.
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Slide # 14
Assessment- Methodology
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For Impingement Assessment - Adult & Juvenile Species trapped on the plant Screens are:
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•
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Identified/Classified
Counted and
Weighed
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For Entrainment Assessment ‟ Larval Species Collected on the 300-μ nets in front of the screens & in various areas of the
Potential Impact Zone are:
• Identified to the lowest taxonomic classification possible (e.g., genus or family level) and
• Counted
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Data Sets to be collected:
• For Each sample day, Larval Counts & densities (No. per Unit Volume) at the Intake & in Water Body.
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Actual Intake flows are measured at the time of sample collection.
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Slide # 15
Assessment- Methodology
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Once species are identified and enumerated ‟ the population and community levels effects caused by the removal needs to be
estimated
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Long term data not typically available
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Models have to be used to estimate the potential effects of larval removal
• Estimating the Larval mortality due to entrainment
Calculate the volume of water entering the intake (V)
Measure the concentration of larvae (no. per volume) that are entrained (N)
(assume 100% mortality)
Estimate Entrainment mortality = N x V
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Slide # 16
Assessment- Methodology
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Models ‟ two categories
Those that require life history data and those that do not
Demographic Models
„ Adult Equivalent Loss (AEL)
„ Fecundity Hindcasting (FH)
„ Habitat Production Foregone (HPF)
„ Empirical Transport Model (ETM)
Conditional
Mortality Models
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Slide # 17
Assessment- Methodology
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Requirements for demographic models
• Fecundity
• Age at first maturity
• Longevity
• Survival data for eggs, larvae and other stages through adults
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Adult Equivalent Loss
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Uses entrainment mortality in conjunction with larval sizes ( proxies for age) and natural mortality rates and
estimate the Adult Equivalent loss
Fecundity Hindcasting
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Uses entrainment mortality and back calculates the number of adult females that were lost (assuming 1:1 sex
ratio or any other from literature)
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Slide # 18
Assessment- Methodology
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Slide # 19
Assessment- Methodology
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Estimation of Habitat Production Foregone or Area Production Foregone
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HPF = Proportional mortality (PM) x Source water body (SWB)
An example from Carlsbad Desalination study
Entrained Species
Proportional mortality
(PM)
Source water body (SWB)
HPF = Proportional
mortality (PM) x Source
water body (SWB)
Gobies
21.56
302 acres
65.11
Blennies
8.63
302 acres
26.06
Hypsopops
6.48
302 acres
19.57
Average
12.22
302
36.93 (37 acres)
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So, HPF = 37 acres for 304 Million gallons per day in Carlsburg
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Slide # 20
Assessment- Methodology
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37 acres of new bay habitat if restored to the system will reduce the impacts caused due to impingement and entrainmentassuming that new bay habitat was a comparable mixture of habitats to that in source water body
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Scale and context of HPF are very important
Two fishes have estimated entrainment losses (PM) of 1%
‟ Case 1: northern anchovy has estimated source water of 1,000 km2, results in
HPF =10 km2 ‟ meaningless in a context as no habitat dependency for anchovy
spawning
‟ Case 2: kelp bass occupying kelp habitat around intake of 1 km2, results in
HPF = 0.01 km2 ‟ could be of greater concern if kelp habitat limited in area of intakes
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Mitigation could be by way of creating a coastal habitat similar to that of source water body, which will provide measurable long
term environmental benefits
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Slide # 21
Mitigation measures
Sand Filtration
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Slide # 22
Mitigation measures
Wedge Screens
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Slide # 23
Mitigation measures
Subsurface intakes
Vertical beach well
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Radial intake well
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Slide # 24
Mitigation measures
Slant wells
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Slide # 25
Mitigation measures
Horizontally directed drains (HDD) wells
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Slide # 26
Mitigation measures
Marine Life Exclusion System
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Slide # 27
Conclusion
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The current US EPA standard requires that the best available technology should be used in order to achieve
impingement reduction of 85-95% and entrainment reduction of 60-90%
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Middle east has the maximum number of desalination plants, but unfortunately, no estimate of loss due to entrainment
and impingement in the Middle east
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There is an immediate need to assess the impacts of entrainment and impingement in the Middle east
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Only by quantifying the impact, measures could be taken to minimize the loss
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Slide # 28
Thank You
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Slide # 29