Seawater Desalination – A need forEnvironmental Impact Assessment (EIA) and Best Available Techniques (BAT)

Global seawater desalination capacity

Lattemann and Höpner (2009), primary data from IDA (2007). Map includes all plants that are presumed online or in construction and all sites with a capacity > 1,000 m3/day.Lattemann & Höpner (2009), primary data from IDA (2007). Map includes all plants that are presumed online or in construction and all sites with a capacity > 1,000 m3/day.

Ashkelon (330,000 m3/day)

Projected growth

Australian SWRO projects

Perth144,000 m3/dAdditional projects: 144,000 m3/d (2011)?450,000 m3/d (2020)?

Gold Coast:133,000 m3/d

Sydney:250,000 m3/dExtension: 250,000 m3/d?

Résumé of the introduction

Energy demand

Energy use and CO2 emissions

Energy demand in perspective — Sydney

Is energy demand significant?

Desalination using renewable energyno large desalination plant directly driven by RE, only used as a compensation measuremostly small stand-alone systems directly driven by RE:

ED RO

Wind / Tidal

Radiation (PV)

Electricity

Mechanical (turbine)

MD MSFMEDTVC

Non-concentrating- flat plate or tube designfor domestic purposes

Concentrating- parabolic trough / dish- flat mirrors (Fresnel)- power tower

Solar energy

Heat (collector)Solarstill

Parabolic systemDishTrough

Planar mirrorsTowerFresnel

Concentrating solar thermal collectors

Linear receivers Point receivers

National Initiative for Solar Desalination

King Abdulaziz City for Science and Technology, Riyadh:

Initial phase (3 years): • Energy: 10 MW produced by solar energy• Water: 30,000 m3/d in Al Khafji

Second phase (3 years): • building a 300,000 m3/d solar-powered desalination plant

Third phase (3 years): • implementation of solar desalination plants

in several parts of the country

Spanish approach

30

35

40

45

50

55

60

65

70

75

80

Australian approachWhole effluent toxicity (WET) tests

Whole effluent toxicity testsSWRO Plant Species

protectionlevel

No. of speciesused in

WET tests

Species protectiontrigger value

(safe dilution ratio)

Gold Coast 95% * 6 species 9 : 1Perth 95% * 5 species 12 : 1 Sydney 95% * 5 species 30 : 1 Olympic Dam 99%** 15 species 45 : 1

Ecosystems: * slightly to moderately disturbed** high conservation value 0.7 psu above ambient in

300 m in 90% of time 1100 m in 99% of time

Desalination – a green technology?

Sustainable projects | green technologies

UNEP Guidance on EIA for desalination projects (2008)

www.unep.org.bh/Publications/Type7.asp

Extensive EIA and monitoring studies in progress for several desalination projects worldwide

internationally accepted BAT standards for desalination plants are still missing

U.S. EPA announced new rulemaking on drinking water treatment effluents including “facilities that discharge […]desalination concentrates […]”

Conclusions

Resource-intensive process with significant impacts

need for project- and site-specific EIA studies

need for technology standards (BAT)

Mitigation measures exist for all significant impacts

sustainable desalination is technically feasible,

even with existing technologies

three examples

Mitigating energy use & GHG emissionsMinimization:

• energy use minimized to reduce costs in most projectsby using state of the art technology

Compensation: of energy use if considered significant environmental impact

• most countries entered an international agreementto reduce GHGs (Kyoto Protocol)!

• Australia: all SWRO projects use indirect renewable energy

• Carlsbad project, Southern California: Climate Action Plan at an estimated US$ 76 million imposed on the project

Mitigating salinity impactsRegulatory mixing zones:• define the spatial & temporal distribution limit

of the concentrate plume

Whole effluent toxicity (WET) tests:• determine the safe dilution ratio of the concentrate• to be met at the edge of the regulatory mixing zone

Modeling studies: • determine the best diffuser location and design

to achieve the safe dilution ratio

Field monitoring studies• to detect possible ecological impacts using a

before-after, control-impact (BACI) approach

Mitigating chemical use

Treatment: of all intermittent wastes• pretreatment backwash (media filters, UF/MF) • cleaning solutions (SWRO, UF/MF membranes)

Substitution: of harmful chemicals where possible

• Tampa Bay (Florida), London (UK), Jumeirah (UAE): chlorine replaced by chlorine dioxide (ClO2) due to elevated chlorination by product formation

• 2 plants in the Middle East: offline use of DBNPA (U.S. EPA approved biocide) to control regrowth of biofouling organisms

Conclusions

Resource-intensive process with significant impactsneed for project- and site-specific EIA studies

need for technology standards (BAT)

Mitigation measures exist for all significant impactssustainable desalination is technically feasible,

even with existing technologies

Compensation measures, advanced technology, andextensive environmental studies increase water costs

BUT: sustainable desalination is still economically viable