Open Water Systems
Elmosa Offshore Intake System
.... Steady State
Outfalls and Wastewater Disposal
More system improvement and sediment inflow protection.
In the light of the increasing pollutants reaching the shores of the seas around the world the state of the ecosystem has changed a great deal over the last four decades. It has become unsafe to install onshore open intake systems without investing heavily in equipment to safeguard an uninterrupted flow. Going offshore and drawing the water from hundreds of meters away from the shoreline has become a sound alternative. Wave action effects onshore are more pronounced than in offshore deep water locations. However, inferior designs of the upstream inlet of the intake pipelines can lead to creating high negative pressures at and around the inlet, which will result in the suction of sand, fish, seaweed and other debris as well as aquatic life impingement and resulting in an elevated mortality rate.
The inlet has to be proactive in design and not in reactive. Wedge wire screens for example do not reflect a system that is specifically made for seawater intakes. They are reactive and need a great deal of a backup effort to remain in operation. They are operation and maintenance-intensive. They have to be frequently backwashed and air purged to push away the impinging marine life and debris. Most of the backwashed and purged material returns to the screens along with fresh supplies soon after the backwash pumps and air purging compressors are turned off. The backwashed and purged material is not drained away but all or a large part of it would comes back under the effects of screen suction and local marine currents.
The AES Elmosa proactive technologies work in concert to eliminate sediment, debris, and marine life inflow including:
type of intake system used to be the most common, usually located on
shore of a water body. This kind of intake system is usually made of a
conveying concrete channel. Simple and complex mechanical screening
are always included in these types of intake systems. The size of the
system depends on the quantity and type of the suspended matter present
in the water. This type of system works with an acceptable degree of
when small loads of debris are present. It becomes ineffective when the
water gets saturated with large loads of debris and sediments such as
and sand. The open channel system is going under a phase out on a
scale in favor of the more advanced and effective offshore system. The
Open channel systems are becoming obsolete and are being
The offshore type of intake system is common where shallow water and concentrations of weeds are present near the shoreline. The controlling factors of how far should the offshore distance be are:
The problems involved with offshore systems are similar to those of the open channel, but with less severity and lower frequency. Traveling screens in settling basins onshore are still required and intake head cleaning has to be performed regularly. Large quantities of marine life including fish, fish larvae and other organisms are harmed in the process of the intake system operation and maintenance. The proactive InvisiHead was conceived in 1982 to put an end to marine life spoilage. The InvisiHead has been going through frequent improvements ever since.
There has been a wide range of submerged intake designs and layouts, all aimed at reducing approach flow velocities to help control and reduce the inflow of debris and marine life but suffer from excessive level losses and reduced flow rates caused by seaweed, and Zebra Mussels which stick and impinge to wedge wire screen tees and sections in large numbers. Very few systems are designed to limit the impingement of fish, seaweed or lake vegetation, sand, and other suspended matter inflow, which are the main concern among others of the Elmosa Intake System.
Elmosa Offshore Seawater Intake systems consist of:
After many years of research and development the InvisiHead system has been designed, optimized and produced. The system is adjustable and virtually hydraulically invisible to suspended mater including fish, fish larvae, sea floor sand, seaweed, and debris. It is engineered to control and drastically reduce the inflow of debris, the ingress of fish, and the impingement of mussels and other marine life and entrained air. It is ideal to be also installed in areas designated as fragile and critical such as spawning grounds or special habitats. By utilizing the continuity equation and the potential flow theory we developed this system. These two hydraulic principles have been used as the main tools for flow calculations and system design optimization. The system also makes use of the natural laws in its operation. Gravity is the only driving force of the flow into the InvisiHead Intake Head System. The InvisiHead structure is robust and stable. It is made of relatively thick plates of Duplex or 316 stainless steel. It is anchored to the sea floor via sturdy support legs that keep it stable and in full operation even under hurricane G5 force conditions.
The system's added costs are marginal, and it is usually less expensive and more economical than the conventional systems. Unlike the O&M-intensive wedge wire screens, the InvisiHead is self-operating and self-maintaining. It requires no backwash or air bursting. No pumps, compressors or sensors during operation. Zebra Mussels have no effect on the operation of the Intake Head when they attach to it.
The InvisiHead can also serve as a superb industrial effluent outlet by which the effluent flow can be dispersed in a way that it inhibits the fluid from sinking to the floor such as the case in RO brine discharges or rising to the surface such as in power plant cooling water discharge or municipal sewage or fresh water releases.
Many intake systems have either proven to be very costly to build, operate, and maintain; or have involved a great deal of guesswork that produced less than optimal results. Offshore intake systems can be upgraded and highly improved by installing the InvisiHead, a balanced and well-designed intake head system, which fully utilizes the potential flow principle in guiding water particles into it in the form of smooth, uniform streamlines. The flow into the InvisiHead system goes through four flow phases:
Super smooth flow transition from one phase to the next leads the flow through into the pipeline upstream end. Such a process made the head virtually invisible in hydraulic terms to suspended matter. There where the InvisiHead borrowed its name.
particles start to move
Intake Head from all directions surrounding it at a velocity of about
fps) max. 5 meters (15 ft) away from the Head entrance. The velocity
m/s (0.1 fps) max. one meter (3 ft) away. The final entrance velocity
0.09 m/s (0.3 fps) max. Natural currents, generated by
density differentials, tend to have velocities much higher than these
and entrance velocities. The controlling velocities at the ambient
are those of the marine currents and not those initiated by
the InvisiHead flow effects. The
pressure drop around the InvisiHead due to the suction
caused by the head deferential at the intake settling basin located
is thus negligible, and does not disturb debris or cause it to travel
the InvisiHead. This makes makes the InvisiHead virtually nonexistent
as a sink point,
thus it becomes hydraulically invisible to suspended matter.
expands from the point
outer tip of the entrance to where the flow velocity becomes 2.4 times
the entrance velocity-the perforated area of the guiding vanes. In this
phase water particles move freely through
the entrance ports of the InvisiHead. In this phase multi
of the flow overwhelms the radial flow due to providing unlimited
access to marine currents. This fact in turn enhances flow flexibility
and stability. Access for flow streams created by wind, thermal, and
differentials is permitted through the upstream part of the InvisiHead.
This provides more security against the flow of debris into
and smoothly divides and
directs the water to the InvisiHead outlet and into the intake pipe
or fish that enter the InvisiHead flow get flushed out through
the opposite end into
the ambient again and will not flow down into the intake since the flow
velocity at the InvisiHead outlet is much lower than that is naturally
extends from the down-stream
end of the guiding vanes to the inlet of the intake pipe. In
phase the flow proceeds smoothly toward the inlet and accelerates to
steady state, that is
ultimate velocity of the flow prevailing inside the intake
pipe. The phase-to-phase transition velocities are lab tested and
predetermined to provide
smooth flow transition and to eliminate any potential for
eddies or vortices, thus reducing pressure losses and in turn allowing
the use of smaller intake pipes and shallower onshore pump intake basin
since the depth needed for the settling basin
onshore would also be reduced due to the reduction of the differential
head required at the settling basin to drive the needed flow
This phase begins at the downstream point of the InvisiHead and ends at the downstream end of the intake pipeline at the settling basin onshore. In this phase steady flow regime prevails.
The InvisiHead intake head dimensions are all based on the average steady flow velocity, thus a flow-tuned intake head designs and construction were made possible. In standard practice, a reasonable entrance velocity is usually chosen with a known flow rate. The area of the intake head opening is thus calculated using the continuity equation. Either the height or the diameter/width is assumed and then the other dimension is calculated. In the flow-tuned InvisiHead no assumptions are made during the design and sizing of the IH. All values are calculated since they are all interdependent.
The InvisiHead is designed to take either individual or multiple forms. This is always decided on individual basis. The InvisiHead can be retrofitted to existing intake pipelines.
The InvisiHead works as an efficient heat transfer system when used as a power plant cooling water outfall. It ensures adequate mixing and efficient heat dispersion to reach equilibrium a few meters away from the release point. The heat plume does not reach the surface and it is confined to the area close to the point source. Heat, TDS, or sewage sensors installed a few meters away from the outfall diffuser will register no change in their readings. Linear outfalls are no longer a necessity.
The InvisiHead is a hydraulically balanced simple system, free of any operating or maintenance needs and requirements or any spare parts. It contains no moving parts. This makes the AES Elmosa intake systems including the InvisiHead, intake pipeline, and the NatSep highly feasible and attractive. The system components function by positively utilizing the natural forces. In doing so, sediment flow is drastically reduced and pressure losses are minimized. System features include:
American Eco Systems will be very glad to share their experience with their prospective customers. We at AES have the ability to solve your intake problems. The American Eco Systems Elmosa offshore intake systems and the Infiltration are designed to serve the world over. The systems are environmental friendly, help biodiversity, and protect the ecosystem. Keeping a healthy environment is a top priority at AES.
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