1. Consultative Workshop on Desalination and Renewable Energy Environmental Implications of Desalination: Concentrate Management Dr. Fulya Verdier, Dr. Rudolf Baten Fichtner GmbH & Co.KG Muscat, Oman February 2011
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2. Table of Contents Need for Concentrate Management
Characteristics of Concentrate
Potential Environmental Impacts
Impact Mitigation Measures
Concentrate Management Options
Conclusions
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3. Concentrate Management
There is increasing need, because of:
Increasing number and size of desalination plants
Increasing accumulation of desalination plants in certain regions
Increasing concentrate volumes
Limited available disposal options
More strict environmental regulations (e.g. groundwater protection)
Increasing public awareness and environmental concerns
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4. Characteristics of Concentrate
Typically there are three types of desalination plant discharges:
Brackish water concentrate
Seawater concentrate
Process effluents
Salinity level of concentrate highly depends on feed water salinity and recovery
Volume of concentrate is much greater than volume of process effluents
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5. Characteristics of Concentrate
Overview on the relevant discharge flows
Desalination Technology
Relevant Discharge Flow
Content
RO / MED / MSF
Seawater concentrate
Salt Content & Heat
Biocide (Chlorine)
Chemical
Anti-scalants RO
Filter backwash waste water
Suspended Solids
Sodium bisulfite (SBS)
Coagulants
Flocculants
MED / MSF
Corrosion inhibitors
Anti-foam agents
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6. Potential Impacts of Concentrate
Physio-chemical Impacts
Increased salinity, temperature and density of concentrate relative to receiving environment
Contaminants
Biocides (e.g. NaOCl or Cl2)
Dechlorination using SBS (sodium bisulfite)
Antiscalants (polymeric substances)
Cleaning chemicals (acid, base, detergents)
Coagulants from RO plants (e.g.FeCl3) causing reddish color
Antifoaming agents from thermal plants (polyethylene, polypropylene)
Traces of heavy metals if there is corrosion of plant equipment
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7. Cause - Impact Assessment
“Cause Impact Assessment” is difficult to determine since
there is no direct link
the receiving eco-system is complex
thorough investigations and analysis with adeaquate replication on annual basis are required to establish
statistical analysis of results
comparative analysis of trends
Even if some cause and effect relationships are not fully established scientifically, “precautionary measures” should be considered
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8. Environmental Impact Mitigation of Concentrate
The approaches are two-fold:
Environmental Impact Mitigation of Concentrate
Process
Effluent
Treatment
Concentrate
Management
Options:
Concentrate Disposal
&
Volume Reduction
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9. Impact Mitigation Measures
Waste water treatment plant (WWTP) including sludge treatment
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10. Impact Mitigation Measures
Measures to reduce the extent of impacts i.e. diffusers for enhanced mixing and dispersion of concentrate
Surface Water Discharge
Source: Bleninger (2007)
Source: Wilf (2007)
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11. Impact Mitigation Measures
“Best practice” desalination plant
Minimization of plant wastes (liquid, solid)
Process optimization in order to minimize the discharge flow quantity and contamination
Involvement of waste water treatment plants (WWTP) including sludge treatment
Neutralization of chemicals prior to discharge (~ pH=7)
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12. Further Measures Relevant Legislations and Guidelines
Generally subject to national water framework
MENA countries like Saudi Arabia, Oman, Israel and Egypt have introduced discharge limits for selected effluent pollutants and mixing zone regulations
e.g. Omani discharge requirements limit parameters in the concentrate
Temperature, Suspended solids, Total chlorine, Copper, Nickel, Molybdenum, Iron
Besides the discharge limits, a mixing zone of 300 m in diameter around the outfall is specified. Within the mixing zone, no marine life at the seabed may be destroyed.
Beyond the mixing zone
the ambient water temperature must not be increased by more than 1 °C (weekly average)
the average ambient salinity must not be changed by more than 2 g/l
the average dissolved oxygen level should not be reduced by more than 10%
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13. Further Measures Appropriate Site Selection
Data collection and evaluation including installed desalination plants in the vicinity of plant
Semi-closed areas such as Red Sea and Arabian Gulf can be more susceptiple to cumulative impacts due to limited flushing
Impact modeling and assessment (EIA) prior to environmental permit
Measures for Permit Granting
Evaluation on case-by-case basis
Establishment of discharge quality standards
Definition of minimum requirements for outfall structure
Prohibition of discharge at coast
Appropriate Monitoring
Before-After/ Control-Impact Monitoring
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14. Further Measures Additional (international) environmental requirements
Equator Principles
World Bank Standards
Measures for Institutional Water Authorities
Preparation of master plans for water bodies
Integrated, multi-scale water resources planning
Development of local, regional, national water regulations
Conducting studies to promote national water program
Assessment of desalination guidelines
Establishment of incentives, task forces
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15. Concentrate Management Options
There is no universal concentrate disposal solution for all plants and sites
Surface water discharge (oceans, seas, rivers) is the most economic and common option for large concentrate volumes
Sewer disposal may require fees and permit by local sewage agency
Deep well injection requires highly permeable, unusable saline aquifer nearby. Its feasibility depends on hydro-geological conditions
Evaporation pond is land intensive and thus rather applicable for smaller volumes
Zero liquid discharge means no liquid discharge across plant boundary. It is more applied by industry by using thermal evaporators and processing to solids
Selective salt recovery needs market development in the long term
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16. Concentrate Management Options & Costs
Options & Benchmark
Indicative Costs (1)
[US$/m³]
Critical factors
Concentrate disposal options
Surface Water
Sewer
Deep Well Injection
Evaporation Pond
Zero Liquid Discharge
Benchmark
Membrane replacement
Chemicals
Piping, pumping and outfall construction
Disposal rate, salinity, sewer capacities, fees
Tubing diameter and depth, injection rate, chemical costs
Pond size and depth, salt concentration, evaporation rate, disposal rate, pond liner cost
Disposal rate, energy costs, salinity
(1) Costs include CAPEX and OPEX costs after Greenlee et al., 2009
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17. Conclusions
Pioneer installations are operated for backwash water treatment (e.g. Perth SWRO, Sydney SWRO, planned for Raz Azzour hybrid plant), the related costs are not significant
Eco-toxicity and chemical dosing rates has been reduced
Measures to mitigate concentrate impacts are state-of-the-art
Concentrate minimization is not yet established. Currently limiting factors are related to economics rather than technical feasibility
Today’s best practice is expected to become minimum requirement for future desalination plants
MENA countries can provide a suitable platform to establish a common consensus
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18. Concentrate Management
Thank you!
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