Scientific approaches to assess impacts associated with seawater desalination
This presentation is the property of its rightful owner.
Sponsored Links
1 / 25

Scientific Approaches to Assess Impacts Associated with Seawater Desalination PowerPoint PPT Presentation


  • 84 Views
  • Uploaded on
  • Presentation posted in: General

Scientific Approaches to Assess Impacts Associated with Seawater Desalination. Desal Conference October 5, 2006. Susan C. Paulsen, Ph.D., P.E. Vice President and Senior Scientist. Outline. Scientific Approaches to Address Key Management Issues: Source Water Quality Issues

Download Presentation

Scientific Approaches to Assess Impacts Associated with Seawater Desalination

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Scientific approaches to assess impacts associated with seawater desalination

Scientific Approaches to Assess Impacts Associated with Seawater Desalination

Desal Conference

October 5, 2006

Susan C. Paulsen, Ph.D., P.E.

Vice President and Senior Scientist


Scientific approaches to assess impacts associated with seawater desalination

Outline

  • Scientific Approaches to Address Key Management Issues:

    • Source Water Quality Issues

    • Entrainment/Impingement Issues

    • Receiving Water Quality Issues

  • Evaluation of Impacts Through Modeling


Evaluation of possible desal configurations

Evaluation of Possible Desal Configurations

  • Intake

    • Co-located with power plant

    • Separate intake

    • Beach or subsurface wells

  • Discharge

    • With power plant effluent

    • With treated wastewater

    • Surface discharge

    • Diffuser discharge

  • Dynamics are well understood, and can be accurately modeled


Flow schematic co location

Flow Schematic – Co-Location

Source

Water

Heated

Water with

Concentrate

Heated

Water

To Receiving

Water Body

100-800 MGD

Power

Plant

50-750 MGD

100 MGD

Desalination

Plant

Brine

Concentrate

50 MGD

Drinking

Water

50 MGD


Intake issues source water

Intake Issues: Source Water

  • Contaminants may enter the plant and may or may not be removed by the desalination processes

    • Bacteria

    • Heavy metals

    • Etc.

  • Sources of Contamination

    • Wastewater treatment plant discharges

    • Storm flows, urban runoff

    • Recirculation

    • Other

  • Sanitary Surveys & Source Water Analyses are Conducted

  • DHS Approval is Required


Intake impingement and entrainment

Intake: Impingement and Entrainment

  • Function of velocity, volume, location

  • Biology!

    • Time of year

    • Duration

    • Local Dynamics

  • Effects can be quantified, including cumulative impacts (studies by others – MBC, Tenera)


Alternatives to ocean intakes test slant well section

Alternatives to Ocean IntakesTest Slant Well - Section

Drill Rig

Ocean Surface

Land Surface

23o

350 feet ±

Ocean Bottom

Main Aquifer

40 to 130 feet ±

Infiltration

Fresh Water

Salt Water

Test Slant Well

200 to 250 feet ±

Thanks to MWDOC


Slant well intake system concept

Slant Well Intake System Concept

Desalination Plant Site

Subsurface Slant Wells & Buried Collector Intake System

SOCWA Outfall

Thanks to MWDOC


Receiving water issues

Receiving Water Issues

  • Typically, desalination of seawater yields 50% brine (68 ppt)

  • Mixing in ocean is a function of density (temperature, salinity)

  • Unless diluted, the brine may cause an environmental impact

  • Besides a few added chemicals, brine is concentrated seawater

Seawater

Brine

Residue

Desalination

Plant

To Disposal

Fresh

Water


Use of modeling to assess impacts

Use of modeling to assess impacts

  • Model must evaluate

    • Near-field mixing

    • Far-field mixing

    • Stratification

    • Meteorological and oceanic processes

  • Validate model against existing data

  • Apply model to predict future conditions

  • Used ELCOM (Estuary and Lake Computer Model) to evaluate Encina discharge


Case study encina power station regional seawater desalination project

Located at Cabrillo Power Plant

SDCWA is seeking to produce 50 MGD

Work done in conjunction with RBF Consulting

SDCWA is not pursuing project

Case Study: Encina Power Station – Regional Seawater Desalination Project


Southern california bight region

Southern California Bight Region


Regional seawater desalination project elcom 328 ft 100 m computational grid

Regional Seawater Desalination ProjectELCOM 328 ft (100 m) Computational Grid


Model application

Model Application

  • Encina Desalination Plant

Movie 1: Temperature

Movie 2: Salinity


Conclusions

Conclusions

  • Source and receiving water issues must be quantified

  • Multiple configurations can be simulated

  • Modeling needs to consider all relevant physical processes

  • Analysis must consider hydrodynamic (physical), chemical, and biological processes

  • Science can and should be used to quantify impacts


Extra slides

Extra Slides


Inflow intrusion

Inflow Intrusion

Source: Textbook “Mixing in Inland and Coastal Waters” by N.H. Brooks, Hugo

Fischer,Bob Koh, Jorg Imberger, and John List. Pergamon Press 1979.

Entrainment flow arrows added to original.


Receiving water regulations

Receiving Water Regulations

  • Temperature: Thermal plan for new coastal discharges says that a plume cannot exceed 4o F at the shoreline, the surface of any ocean substrate (including bottom) or 1,000 ft away on sea surface for more than 50% of any tidal cycle. Older plants generally have exceptions, but not all.

  • Salinity: There are no clear regulations for salinity. However, there are some concerns:

    • If maximum salinity outside of the immediate area of the discharge exceeds a ppt in the low to mid 40s, then there may be biological concerns if the exposure time is in the range of hours to days.

    • If the maximum possible increase is about 37 to about 40 ppt, then there may be biological concerns if the exposure is in the range of days to a week.

How do we evaluate and quantify these potential impacts?


Evaluating water quality model overview

Evaluating Water Quality: Model Overview

  • Used Estuary and Lake Computer Model (ELCOM)

    • Developed at Centre for Water Research at University of Western Australia

    • In use in 60 countries

    • State-of-the-art code with continuous development

    • Applied in both research and practical applications

    • 3-Dimensional

    • Solves approximate flow equations in stratified environments

    • Included tides, meteorological forcing, and currents


Scientific approaches to assess impacts associated with seawater desalination

Regional Seawater Desalination Project Calibration Fall 2004Comparison of Simulated to Observed Water Temperature


Elcom calibration temperature profiles

ELCOM Calibration: Temperature Profiles


  • Login