The Elmosa 3-Component Seawater Intake System

1. The InvisiHead

Intake Diffuser Both safely anchored to the seafloor	Starting at the upstream and downstream ends with the InvisiHead intake and outfall respectively. It is a hydraulically invisible seawater intake velocity cap system fitted to the upstream end of the intake pipeline. The offshore distance depends on the site conditions and the requirements of the user. The depth of the upstream end of the intake and downstream end of the outfall where the InvisiHead intake and diffuser are to be located should be deep enough to keep it submerged at all times, but the deeper is the better. It is safely fitted to the intake and diffuser pipes and safely anchored to the seafloor. Entrance and discharge velocities are 0.09 m/s max(< 0.3 fps). The approach velocity in the intake and dispersion velocities are extremely slow. The InvisiHead entrance and exist sections are hydraulically fine-tuned in lab to optimize system hydraulics. The entrance dimensions are not arbitrarily selected but hydraulically calculated in a multi dimensional approach. Each dimension is a function of the steady flow velocity. Eddies through this approach and dispersal are totally eliminated. The InvisiHead intake system can be supplied with a built-in anti biofouling dispensing system. The InvisiHead is extremely site-specific. There are no two sites identical even if located in the same neighborhood.  Each InvisiHead is hyperbolically and paraboloidaly tailored to fit and match site characteristics and operation conditions. We collect site and operation data to get them integrated during the design and fabrication phases into the InvisiHead. We are actually implanting the site DNA-like characteristics in the InvisiHead to enable its site recognition capability. As soon as it receives seawater pump pulses, it recognizes the site and manages the flow accordingly. The site-oriented hyperbolic/paraboloidal shaping of the InvisiHead structure enables it to fine-tune and locate the sea floor takeoff points of the lowermost flow streamline bundles and control and reduce floor community disturbance and prevent fine-sediment pickup; that is why it is ideal for SWRO desalination since it is low on SDI and requires less pretreatment and professional disperses, mixes, and dilutes the RO concentrate. LEARN MORE
2. The Intake Pipeline	The pipeline connects the InvisiHead-the upstream end located offshore with the downstream end the NatSep separation basin located onshore. It can be of steel, steel lined with polyethylene, concrete, GRP, or high-density polyethylene (HDPE) pipe. We apply the Elmosa Velocity Envelop  (EVE) during intake pipe configuration to maximize system stability and operation flexibility and sustain self-cleansing to prevent sediment settlement and marine growth inside the pipe.
3. The NatSep Separation Basin	The NatSep is where whatever sand and debris that may flow into the InvisiHead get naturally separated to settle at the NatSep intake basin remain in the sediment storage zone. The flow reaching the pumps is clean and free of sand and debris. Cleaning of the NatSep basin is done as frequent as needed but may never be needed. Elmosa has discontinued the use of all screening systems including stationary and traveling screens. The NatSep patented design helped eliminate standard screening processes. The Elmosa default target sediment is very fine sand (125 µm) or larger. The NatSep can be configured to remove finer sediment then the default size if required. The flow through the InvisiHead combined with the NatSep  lowers the SDI and reduces pretreatment efforts in SWRO plants.

                                                                                                                                                                                                                                                                                                                                         .    *    

Starting January 2013 the InvisiHead flow transition through the sequential 4 flow phases was upgraded to further improve flow quality and drastically reduce or eliminate flow of sediments or seaweed  if present in the water column; InvisiHead flow velocities:

1. approach is 0.002m/s (0.0066 fps),
2.  inlet is 0.09m/s (0.295 fps) max,
3.  outlet is 0.11-0.12m/s (0.36-0.39 fps),
4.  InvisiHead/intake pipe interface velocity ranges between 0.9 and 2.9m/s or (2.95-9.5fps).

• No environmental adverse impacts are associated with cooling water or RO concentrate discharges.
• Site and application recognition enables the InvisiHead to fine-tune its flow-management operation.

The 4 Zero Zone of Diversion

                                                        Elmosa InvisiHead intake and diffuser system with net positive impact on the Environment and on the Economy

NO MORE TROUBLES: Just turn-on the seawater pumps at the pump house and relax.

• No more clogging.
  
• No more pressure drop.
  
• No more alarms.
  
• No more backwash or air bursting.
• No more dead fish or any of the aquatic life.
  
• No more marine growth or sediments settling in the intake pipe.
  
• Simply, no more worries, and
• no more operation or maintenance.

  All remain in DAY 1 condition for decades to pass.

THE INVISIHEAD'S TWO BREAKTHROUGHS:

BREAKTHROUGH I: Environmental: Coexistence;

BREAKTHROUGH II: Economic:  Low Capital Expenditure-CAPEX, No Operational Expenses-OpeX:

BREAKTHROUGH I:
Environmental: Coexistence;the InvisiHead serves as a habitat for marine life and biomass demonstrating peaceful coexistence at its best. It, however, delivers the full
design capacity under all site conditions. This InvisiHead was installed in 2006. It never needed any care or required any operational or maintenance services ever since it was installed. It really defines what proction is: It is acting in advance to deal with an expected difficulty.



BREAKTHROUGH  II
Economic:  Low Capital  Expenditure-CAPEX, No Operational Expenses-OpeX: The InvisiHead makes money through the savings of OpeX. The savings accumulate throughout the years. It ends up paying off the CAPEX in a few years down the road.

Milestone dates:

• 1981/1982 Tthe InvisiHead was conceived, researched and developed at the reputed St. Anthony Falls Hydraulic Lab of the University of Minnesota https://www.safl.umn.edu/;
• 2002 The InvisiHead has become a BTA as per the US EPA designation;
• 2005 The structural integrity of the InvisiHead has been also reinforced to stand up to Cat5 hurricane force,
  
• 2009 Australian EPA endorsed the InvisiHead as an intak and outfall;
  
• The IH systems are made of high grade thick stainless steel plates to preserve structural integrity of the systems and remain in full operation throughout the structure's lifetime.
• In 2012 AES updated and enhanced the flow streamlining of the InvisiHead Intake and outfall systems and improved the hydraulic tuning of the flow streamlines within the approach, entrance, and outlet phases in order to increase the degree of exclusion of marine life, sediment and debris by deciding the sea floor take off location of the lowermost streamline bundle and redusing the takeoff velocity to be lower than the target sediment grain terminal velocity in order to not to disturb the local neighborhood;
  
•  Avoidance: The change in flow pattern created by the InvisiHead triggers more avoidance response mechanisms in fish both juvenile and adult, thereby avoiding their inflow;
  
• 2013 The InvisiHead had site and application recognition integrated and was more fine-tuned to better improve flow management; 
  
• 2014_water_enters_InvisiHead at 0.09m/s or lower and leaves it at 0.11-0.12m/s to allow supremacy to marine currents to flush out any fish, sediments, or seaweeds if found,
• 2020 The InvisiHead spread-out type is made to be sandwiched and inserted under ice sheets with an entrance velocity of 0.003m/s (0.01 fps).

Testimonials

Testimonials made by international authorities since 2002 about the Elmosa Seawater Intake and Outfall Systems especially the InvisiHead regarding the engineering, environmental, and economic viabilities. The testimonials displayed below may look a bit too long but they are all keywords to the three viabilities addressed by intake and outfall industry regulators. We are quoting here some of what consulting engineers, university professors, and environmental authorities had to say about the Elmosa intake and outfall systems

US EPA BTA Technology Candidate

http://www.amecosys.com/elmosa/From%20Sunda%20John,%20SAIC,%2007.08.2002.pdf
     

                                                                                                                                                                                                                                                                                                                                       07/08/2002

US EPA

Technical Development
Document for the Final Section
316(b) Phase III Rule

Research on velocity cap vendors identified only one vendor, which is located in Canada. (A possible reason for this scarcity in vendors is that many velocity caps are designed and fabricated on a site-specific basis, often called “intake cribs”.) This vendor manufactures a velocity cap called the “Invisihead,” and was contacted for cost information (Elarbash 2002a and 2002b). The Invisihead is designed with a final entrance velocity of 0.3 feet per second and has a curved cross section that gradually increases the velocity as water is drawn farther into the head. The manufacturer states the gradual increase in velocity though the velocity cap minimizes entrainment of sediment and suspended matter and minimizes inlet pressure losses (Elmosa 2002). All costs presented below are in July 2002 dollars   .

Due to the rather large opening, Invisihead performance is not affected by the attachment of Zebra mussels, so no special materials of construction are required where Zebra mussels are present.

https://www.epa.gov/sites/production/files/2015-04/documents/cooling-water_phase-3_tdd_2006.pdf

                                                                                                                                                                                                                                                                                                                                         P. 3-79

PUBLIC UTILITIES COMMISSION, STATE OF CALIFORNIA
8. Draft EIR/EIS Comments and Responses
CalAm Monterey Peninsula Water Supply Project 8.7-1 ESA / 205335.01
Final EIR/EIS March 2018
8.7 Individual(s) Comments and Responses

 

Seawater intake screening is being improved. The data cited in this DEIR/EIS from 2013 are  out of date for open ocean intake screening. Rotating and traveling screens with intake  velocity of less than 0.3 ft./sec. to mitigate impingement and entrapment, are now available, e.g.  Invisihead by Elmosa Seawater Intake and Outfall Systems; “Water particles start to move toward the Intake Head from all directions with a velocity of about 0.0027 m/s (0.009 fps) max. 5 meters (15 ft) away from the Head entrance. It rises to 0.03 m/s (0.1 fps) max. one meter (3 ft.) away. The final entrance velocity is 0.09 m/s (0.3 fps) max. .                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  P. 4   8.7-135

https://nmsmontereybay.blob.core.windows.net/montereybay-prod/media/resourcepro/resmanissues/desal_projects/pdf/180323calam-mpwsp_feireis_ch8.7-index.pdf

Balmoral South Iron Ore Project Public Environmental Review EPA Assessment No 1677, International Minerals Pty Ltd, Australia,
Volume 1 – Main Report and Appendix A
February 2009, B A L M O R A L S O U T H I R O N O R E P R O J E C T P U B L I C E N V I R O N M E N T A L
R E V I E W

Invitation to Make a Submission, URS

Invitation
The Environmental Protection Authority (EPA) invites people to make a submission on this proposal

1. Elmosa Seawater Intake and Outfall System

The seawater is transported on-shore via a buried HDPE pipeline under natural head pressure. Subject to final design, the seawater intake system and components will resemble Figure 7-6: Typical Seawater Intake System and is described more fully in Sub-section 2.11 of Section 2 - Project Description.
The flow streamlines will be controlled so that the takeoff velocities of the extreme bottom and the extreme top streamlines into the InvisiHead™ would have no suction effect on the floor and top sediments. At maximum plant capacity, the maximum entrance velocity is 0.091 m/s rising from a maximum approach velocity of 0.0025 m/s. The InvisiHead™ technology surpasses the principles of Integrated Pollution Prevention and Control (detailed in European Union Reference Document on the application of Best Available Techniques (BAT) to Industrial Cooling Systems: Dec 2001) for the selection, design and operation of cooling water systems and effluent discharge. The brine discharge system will be similar, except with outflow. An outfall pipeline is proposed to carry concentrated brine and filter backflush water to a discharge diffuser located approximately 1,600 m northeast of Cape Preston, in 7 m of water at Lowest Astronomical Tide. (Figure 2-10)                                                                        URS   P.7-34

 

        2. The NatSep

The NatSep™ acts as a gravity flow controller and provides passive removal of coarse sediment and debris from the flow. A traveling screen will be installed at the upstream end of the sedimentation zone of the basin.

The depth of the basin will include the calculated head loss in the intake pipeline, the standard tide variation of 4 metres, the 6.5 metre storm surge, plus 2 metres as a margin of safety. The NatSep basin will be installed onshore within the area allocated for the Desalination Plant.

The NatSep basin will remove any sediment 160 microns (0.16 mm) or larger from the flow, including fine sand, seaweed, and debris, which will settle in the sediment storage zone at the bottom of the basin. The basin is made of two bays; each 100% of the capacity, so that the intake system remains in full operation during clean up of the sediment storage area.

The basin is divided into 5 distinctive zones: The inlet zone or the stabilisation and energy dissipation zone located upstream of the basin, three zones located at the middle of the basin including the flow through zone, the sedimentation zone, the sediment storage zone, and the outlet zone.                                                  
                                                                                                                                                                                                                                                                                                                                    URS   P. 2.41

19 Conclusion
The aim of this project was to determine if a desalination plant could be cost effective and sustainable whilst minimising the environmental impact and protecting Sydney‟s natural water supplies. This was achieved by designing a sea water reverse osmosis desalination plant with the capacity to supply up to half of Sydney‟s daily water demand (9.9x105m3/day). The key components of this design are as follows.

The plant will utilise a split partial second pass reverse osmosis treatment process with an energy recovery system. This is combined with micro screening and ultra-filtration membrane pretreatment and a re-mineralisation with disinfection post-treatment. This process has been designed to utilise the most energy efficient technologies currently available whilst minimising running costs.

The inlet has been designed with the main aim of limiting ecological disruption to the Tasman Sea. This is achieved by using a passive system that keeps surrounding deep sea currents to a minimum. This will be done using Elmosa‟s InvisiHead system which has been approved by the Australian Ministry of the Environment and the Environment Public Authority.

The outlet will use a revolutionary out fall where by the effluent is transported back into the sea under gravity, thus negating the need for a pressurised pipe network. This also makes use of Elmosa‟s InvisiHead system to minimise the mixing zone surrounding the outlet.

The delivery system into the Sydney drinking water network made maximum use of existing infrastructure by utilising the existing distribution pipe constructed for the original desalination plant. This resulted in reduced costs and impact on the environment and local community, as only a single pipeline had to be laid to accommodate the increase in possible water production compared to the original plant.

To reduce the amount of spoil having to be transported off site, it was decided to raise the ground level of the site, using the spoil from the pipeline construction processes, to 6.25m above sea level. This had the added advantage of protecting the site from the effects of projected sea level rise. It was deemed that piling was the most suitable foundation method to support the weight of the main plant buildings. Secant piled walls were utilised where excavations went below the sea level to achieve a water tight seal around the construction site.

The main plant building that houses the desalination treatment process will be constructed using a number of portal frames to cover the large spans. To simplify the construction process the same portal frame design was used to construct the reception building. The pump stations were all constructed with a masonry wall with piers, supporting a flat reinforced concrete roof. By utilizing simple construction processes the cost of building the plant is kept to a minimum, thus making the project more cost effective.

Section 19                                                                   Author: Group                                                    P. 147

8. Draft EIR/EIS Comments and Responses
CalAm Monterey Peninsula Water Supply Project 8.7-1 ESA / 205335.01
Final EIR/EIS March 2018
8.7 Individual(s) Comments and Responses

 

Seawater intake screening is being improved. The data cited in this DEIR/EIS from 2013 are  out of date for open ocean intake screening. Rotating and traveling screens with intake  velocity of less than .3 ft/sec. to mitigate impingement and entrapment, are now available, eg. nvisihead by Elmosa Seawater Intake and Outfall Systems; “Water particles start to move
toward the Intake Head from all directions with a velocity of about 0.0027 m/s (0.009 fps) max. 5 meters (15 ft) away from the Head entrance. It rises to 0.03 m/s (0.1 fps) max. one meter (3 ft) away. The final entrance velocity is 0.09 m/s (0.3 fps) max.

https://nmsmontereybay.blob.core.windows.net/montereybay-prod/media/resourcepro/resmanissues/desal_projects/pdf/180323calam-mpwsp_feireis_ch8.7-index.pdf

4
8.7-135

Comparison

Conventional Linear Diffusion vs. the Round Surround InvisiHead Diffusion

 

MINERALOGY PTY. LTD

Balmoral South Iron Ore Project
Response to Public Submissions
Assessment No.1677
Mineralogy Pty Ltd
Document BSP-780-EN-REP-0110.1
Australia, June 2009

 

Response to Public Submissions

http://www.amecosys.com/elmosa/BSP-780-EN-REP-0110.pdf

Vol. I.

P. 4.1

Site selection investigations were based on three key elements in order to meet the
proposal’s objectives.
These being:
• that the brine discharge mixing zone be limited to an area of four hectares or less,
• that sensitive habitats are protected from the operation of the outfall pipeline and diffuser, and
• that the diffuser and outfall pipeline can be adequately stabilised to protect against cyclone damage”.

The investigations by GEMS into the selection of the outfall site (PER Appendix F, sub-Appendix C, Section
1.1, page 8) identified two possible locations for the outfall that met the criteria listed above. The final site selection for the BSIOP brine outfall is “Location B”, which meets all criteria listed above.
• Near Field modelling of the proposed diffuser design is used to predict initial mixing and the efficiency of the outfall diffuser, expressed as number of dilutions at the edge of the near firld mixing zone. In common practice this modelling is used to inform the design of the diffuser and the location of the outlet. Modelling is also used to calculate an appropriate size and dimension for the LEPA. Design of diffuser: No near-field modelling is provided in the PER to describe the expected performance of the diffuser. Modelling of discharge is based on a conventional jetted diffuser 150m long. The PER proposes an “InvisiHead” diffuser installation.

Modelling of the BSIOP brine outfall diffusion was based upon a conventional jetted diffuser design to cater for the inherent restrictions associated with the USEPA PLUMES computer model used to calculate nearfield diffuser performance. The PLUMES model will only address the near-field distribution of a linear conventional jetted diffuser, and not the preferred multi-direction low-velocity installation proposed within the BSIOP PER.

Far-field distribution has been calculated using the PLUME3D model. PLUME3D is a lagrangian random walk far-field plume dispersion model which obtains oceanic conditions from GCOM3D (described below) and includes 3D plume dispersion algorithms for modelling the far-field behaviour of a wide variety of discharge materials including sediments, sewerage, thermal discharges, oils and chemicals, accounting for processes such as dispersion and dissolution, under defined release conditions (quantity, rate etc).

GEMS 3-D Coastal Ocean Model (GCOM3D) is an advanced, fully three-dimensional, ocean-circulation model that determines horizontal and vertical hydrodynamic circulation due to wind stress, atmospheric pressure gradients, astronomical tides, quadratic bottom friction and ocean thermal structure. GCOM3D is fully functional anywhere in the world using tidal constituent and bathymetric data derived from global, regional and local databases.

GEMS have confirmed that the design of the diffuser does not impact upon the far-field results generated by the PLUME3D computer model. Remodelling of the BSIOP brine outfall plume using the Invisihead design has been commissioned by Mineralogy to confirm this using the parameters listed below (Table 3-11). Results of the modelling show that the far-field plume behaviour and distribution is unaffected by the diffuser design (see Appendix D of this report).                                                                                                                                                                                                                        P. 51 of 79

                                                                                                              

Australian EPA and EU Environmernt described it as BAT

Balmoral South Iron Ore Project, Australia
Public Environmental Review
EPA Assessment No 1677

What the Australian EPA said about the InvisiHead: The IH technology surpasses the principles of Integrated Pollution Prevention and Control (detailed in European Union Reference Document on the application of Best Available
Techniques (BAT) to Industrial Cooling Systems: Dec 2001) for the selection, design and operation of cooling water systems and effluent discharge

http://www.epa.wa.gov.au/sites/default/files/PER_documentation/A1677_R1340_PER_PER_Rev1_090227.pdf 

                                                                                                                                                                                                                                                                                                                   URS 2-40, 41, 6-8, 7-34

Comparison

Conventional Linear Diffusion vs. the Round Surround InvisiHead Diffusion

 

MINERALOGY PTY. LTD

Balmoral South Iron Ore Project
Response to Public Submissions
Assessment No.1677
Mineralogy Pty Ltd
Document BSP-780-EN-REP-0110.1
Australia, June 2009

 

Response to Public Submissions

http://www.amecosys.com/elmosa/BSP-780-EN-REP-0110.pdf

4.2

Modelling of the BSIOP brine outfall diffusion was based upon a conventional jetted diffuser design to cater for the inherent restrictions associated with the USEPA PLUMES computer model used to calculate nearfield diffuser performance. The PLUMES model will only address the near-field distribution of a linear conventional jetted diffuser, and not the preferred multi-direction low-velocity installation proposed within the BSIOP PER.

Far-field distribution has been calculated using the PLUME3D model. PLUME3D is a lagrangian random walk far-field plume dispersion model which obtains oceanic conditions from GCOM3D (described below) and includes 3D plume dispersion algorithms for modelling the far-field behaviour of a wide variety of discharge materials including sediments, sewerage, thermal discharges, oils and chemicals, accounting for processes such as dispersion and dissolution, under defined release conditions (quantity, rate etc).

GEMS 3-D Coastal Ocean Model (GCOM3D) is an advanced, fully three-dimensional, ocean-circulation model that determines horizontal and vertical hydrodynamic circulation due to wind stress, atmospheric pressure gradients, astronomical tides, quadratic bottom friction and ocean thermal structure. GCOM3D is fully functional anywhere in the world using tidal constituent and bathymetric data derived from global, regional and local databases. GEMS have confirmed that the design of the diffuser does not impact upon the far-field results generated by the PLUME3D computer model. Remodelling of the BSIOP brine outfall plume using the Invisihead design has been commissioned by Mineralogy. Results of the modelling show that the far-field plume behaviour and distribution is unaffected by the diffuser design (see Appendix D of this report).                                                                                                                                   

P. 54 of 79

 

4.3

GEMS testimonial start in the same pdf following P. 79 of MINERALOGY PTY. LTD version

GEMS
G L O B A L E N V I R O N M E N T A L M O D E L L I N G S Y S T E M S
G L O B A L E N V I R O N M E N T A L M O N I T O R I N G S Y S T E M S

CAPE PRESTON
DESALINATION PLANT BRINE DISCHARGE MODELLING STUDY
on behalf of International Minerals P/L

June 2009

Vol. II

http://www.amecosys.com/elmosa/BSP-780-EN-REP-0110.pdf

 

Figure 2 Proposed Cape Preston port design and the IM and CPMM brine outfall locations (IM1
and IM2 are the two proposed “Invisihead” diffusers.                                                                                                                                                                                                                                                P. 27

4.4

5.3 IM DIFFUSER DESIGN
The proposed IM outfall diffuser is very different to the CPMM diffuser. Instead of utilizing a traditional linear port design with ports spaced evenly down the diffuser pipe, IM plans to install two “Invisihead” diffusers 50 metres apart along the outfall pipe. These diffusers operate differently to a diffuser with a line of ports across the dominant flow direction as the “Invisihead” diffuser head is circular with a continuous horizontal opening divided into 10 separate ports equally spaced around the head (Figure 19).                                                                                                                                                                                                                                                                                                                                                                                                                                                      P. 27

4.5

Figure 19 A single “Invisihead” outfall diffuser
The following quotation from the manufacturer concerning the installation of an “Invisihead” intake and outfall configuration in offshore conditions provides further details concerning this type of diffuser:
“The InvisiHead outfall would have the same intake criteria except that it works in reverse. The brine plume dispersion would be evenly and super slowly funneled out of the outfall so as to attain ambient conditions within a few meters from the outlet point source. The InvisiHead outfall meets and exceeds all the international environmental codes. The outfall should be constructed close to the sea floor and may terminate at the 6 meter depth. The outfall should be located at the leeside of the most dominant submarine currents. However, due to excellent properties of 3- D omni directional plume dispersion performed by the InvisiHead outfall, recirculation of effluent is highly unlikely especially if the InvisiHead outfall diffuser is installed about 100 meters away from the InvisiHead intake head.

 

4.6
2 InvisiHead intake head systems should be installed to deliver 110,000m3/d of seawater, and the same for outfall discharge. Each unit is about 4.5 meters in diameter. The maximum entrance velocity is 0.091m/s. The maximum velocity allowed by the Clean Water Act of the US Environmental Protection Agency is 0.15 m/s. It is the lowest enforced regulation worldwide. The future expansion of the desalination plant will be dealt with separately.

Due to the extreme weather conditions existing at the region of operations, the InvisiHead systems should be well anchored to the sea bottom. The support legs built in the InvisiHead should be bolted to a heavy concrete block or piles in order for the structure to remain stable and to maintain the delivery of the design capacity. The system should be designed to remain in full operation during severe weather conditions.

The structural integrity of the IH will not be affected by the severe weather conditions including the cyclonic actions and the high waves. The InvisiHead is made of thick stainless steel plates.”

 

For the IM discharge simulations, PLUME3D was configured to represent this circular discharge port arrangement for the two “Invisihead” diffusers. The basic parameters used to setup the diffusers within
PLUME3D are summarised in Table 3.                                                                                                                                                                                                                                                                                  P. 28

 

4.7

5.5.2 STUDIES OF INITIAL DILUTION OF THE IM BRINE DISCHARGE WITH THE USEPA PLUMES MODEL Logically similar studies should be carried out for the IM diffuser configuration in order to compare the results with those obtained for the CPMM diffuser. Unfortunately this was not possible as the USEPA Plumes Model does not enable a representation of a circular diffuser head such as the “Invisihead” diffuser.

The GEMS PLUME3D model was able to be modified to represent the “Invisihead” diffuser but the USEPA Plumes Model is a “black box” and cannot be changed by the user.                                           P.33

4.8

6              CONCLUSIONS 

 

This study has examined the behavior of the brine discharge from the International Minerals desalination plant at Cape Preston. With the desalination plant working at maximum capacity the brine will be discharged at 8500 m3/hour with an expected salinity of 79 ppt into receiving waters with an average salinity of 37 ppt. The operation of the discharge has been simulated with the CPMM desalination plant discharging simultaneously to investigate whether there are any cumulative outcomes.

The criteria adopted to define the mixing zone for the IM brine discharge in these studies was the same as that applied, via Ministerial Statement 635, to the CPMM brine discharge. These criteria were that
the region within which the plume is diluted at least 22 times for 99% of the time and that this region must not exceed 4 hectares in area. To be conservative, the number of dilutions modelled in this study
was doubled to 45.

The proposed IM outfall diffuser is very different to the CPMM diffuser. Instead of utilizing a traditional linear port design with ports spaced evenly down the diffuser pipe (22 x 2.4m apart in the case of
CPMM), IM plans to install two “Invisihead” diffusers 50 metres apart along the outfall pipe. These diffusers operate differently to a diffuser with a line of ports across the dominant flow direction as the “Invisihead” diffuser head is circular with a continuous horizontal opening divided into 10 separate ports equally spaced around the head.

The US EPA PLUMES model is unable to provide information on the near-field dilution characteristics of the “Invisihead” diffuser due to design configuration. To investigate the near- and far-field dispersion of the IM brine discharge the GEMS PLUME3D model was configure with 2 diffusers, 50m apart, representing the characteristics of the “Invisihead” diffuser.

Given that the currents in the region of the diffuser are highly bi-directional, and that the diffuser extends approximately 50 metres across the flow, the maximum mixing zone dimensions allowed (4 Ha)
would be expected to be something like 100 x 400 metres. The major results of modelling 12 months of both the IM and CPMM desalination plants discharging brine into the waters off Cape Preston were:

• After the IM brine plume is discharged from the “Invisihead” diffuser it sinks to the bottom within a radius of 20m and enters the far-field hovering near the seabed;
• Analysis of the 12 months of operation indicates that the adopted conservative (45 dilutions) mixing zone area is approximately 3.7 hectares;
• Finally, due to the prevailing (quite different) current flow directions across the IM and CPMM diffusers, and to the level of mixing being achieved within 20 metres of the diffuser, there is no chance that waters with elevated salinity from one outfall will impact on the mixing zone of the other outfall                                                                                                                                                                            Page  | 39

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