When it comes to innovative technology, MECO has a history of being at the forefront. Case in point: Reverse osmosis. When the technology first became commercially viable in the early 1970s, MECO was one of the few companies developing plants that utilized this innovative process. Today, MECO RO plants are a mainstay throughout the offshore marine industry. These units are the choice worldwide for their proven reliability, design simplicity and responsive service support.
MECO RO units incorporate all of the components and instrumentation required for operation, as well as the versatility to adapt to specific customer requirements. Technical parameters such as cross flowrates and membrane flux are among the most conservative in the industry. When membrane fouling does occur, or there is a need for routine maintenance, you will find MECO's MASTERsupport™ service capabilities to be the most comprehensive in the industry. MECO RO units are also available in the MASTERpak™ series, a system that incorporates Pretreatment, RO, and EDI all on a single packaged skid.
Side entry piping on RO pressure vessels allows for easier cleaning and removal of membranes when the need arises.
Productwater sample ports facilitate troubleshooting and allow probing of pressure vessels to isolate membrane problems.
Cross flow exceeds manufacturers recommended [25 - 32 GPM/pressure vessels]
Conservative fluxes of 12 - 16 GPD
The Reverse Osmosis Process
Two solutions made up of a solvent (water) and a solute (salt) with different concentrations have a tendency to equalize their concentrations when separated by a semi-permeable membrane. The water will tend to flow across the membrane to the more concentrated solution. This phenomenon is termed osmosis. If an external pressure is applied to the solution of higher concentration, the solvent will be separated from the solute and flow across the membrane via reverse osmosis.
MECO MASTERedge™ Membranes
Spiral wound membrane elements are the primary configuration used today in water treatment applications. Two layers of the semi-permeable membrane are glued on three sides to create an envelope around a porous permeate collector fabric. The open end of several envelopes are glued to a perforated permeate tube in a configuration that allows permeate in the permeate collector fabric to flow into the tube. These envelopes, with a layer of plastic netting between each to maintain the feed stream spacing, are wrapped around the tube in a spiral arrangement.
The pressurized feedwater flow enters at the end of the spiral and flows axially through the channels created by the plastic netting. Some of the feedwater passes through the membrane - the majority of the dissolved solids being rejected - and into the permeate collector fabric, flowing along the spiral path into the permeate tube. The concentration of dissolved solids increases as the feed flow progresses through the length of the element and exits the other end.
Multiple elements in series and/or parallel arrangements, called arrays, are utilized to meet the requirements of a particular system.
MECO MASTERedge™ Membrane Flux
The amount of membrane area employed for a given output determines a vitally important design element known as the flux rate. The flux rate is defined as the "gallons-per-day" of permeate which passes through one square foot of membrane area (GFD). A high flux rate translates to less membrane area and a lower capital cost. However, a higher flux rate results in increased fouling of the membrane and higher operating pressure. Hence, a higher cost of operation due to both energy and the maintenance associated with more frequent cleanings and, most likely, shorter membrane life.
MECO MASTERedge™ Membrane Cross Flow
The flow of the feedwater stream across the membranes surface is called the cross flow. The lowest cross flow for each element occurs at the reject end of the element. The lowest cross flow for each series of elements occurs at the reject end of the last element. The cross flow design parameter is therefore the reject flow from the last element in each series. Higher reject flow provides higher cross flow.
Proper cross flow rates impart a shearing force and turbulence across the membrane surface, which aids in the effort to reduce fouling and cleaning. Higher cross flow rates often result in a system having more pressure vessels, additional piping and a pump with a higher flowing rate, i.e. higher capital cost. The advantage, however, is reduced maintenance associated with less frequent cleanings and, most likely, improved membrane life.
Q: Why should I consider RO over the alternative waste heat or vapor compression technologies?
A: In many cases, there is no waste heat available. As such, an all-electric means of producing potable water is required. Reverse osmosis can be a cheap means of producing potable water if a relatively constant supply of clean feedwater is available.
Q: Can RO be customized for my application?
A: Absolutely. In fact, each application should be carefully reviewed to ensure that the pretreatment and components are specifically suited for it.
Q: How reliable will an RO be for me?
A: The reliability of any RO installation is dependant upon a number of things. First, the quality of the feedwater supplied to the unit and the unit's ability to handle that supply. Clean seawater is best. However, as the water quality varies or diminishes with increases in turbidity, pollutants or other issues, operations may become more troublesome. The reliability is also dependant upon the design of the unit relative to the quality of the water supplied. Proper pretreatment of a given water source is imperative for proper membrane operation. Thorough operator training, routine monitoring and regular maintenance are also important to successful operation.
Q: What kind of operational issues and maintenance should I expect to have?
A: RO units need a good bit of attention. The RO unit should be monitored on a daily basis and records should be kept on pressures, flowrates, and water quality. This helps determine when the RO unit is experiencing problems with scaling, biofouling, membrane degradation, etc. Since problems with RO units are usually not associated with catastrophic failures, having the ability to trend data makes diagnosing a problem much easier.
Membrane cleaning is a task that will have to be performed on a regular basis. Cleaning of the membranes is required for removal of scale and biofouling. Depending on the size of the RO unit, it should be noted that cleaning may be a very time consuming task and the RO unit must be shutdown.
Even with proper care, RO membranes will have to be replaced. The average life of one is about three years. Replacement will require a full shutdown of the RO unit. Depending on the number of membranes in the system, this can be an expensive maintenance cost that should not be overlooked.
Conservative Flux Rate
MECO designs all of its MASTERedge™ RO units with flux rates from 12-16 GFD. Having a lower flux rate means that scale formation will be reduced, membrane life is extended, and maintenance costs will be lowered. Higher flux rates may give you more flow at a cheaper capital cost, but long-term maintenance costs will exceed those initial capital cost savings in the long run.
Sanitary Permeate Line
All MECO MASTERedge™ RO units come with permeate lines that meet or exceed current sanitary requirements. This includes two forged, pneumatically actuated diaphragm valves that can be mounted on your permeate tank. Sanitary hoses with tri-clamp connections are used on the permeate outlet connection of the RO vessels to connect to the permeate manifold. This will make the chore of replacing membranes easier, faster and will become a feature that maintenance staffs will come to appreciate.
High Cross Flow
Cross flows are set to meet or exceed manufacturer’s minimum requirements for scale prevention. MECO RO units come standard with recycle lines and flow meters, within skid limits, to ensure that membrane cross flows are set at the proper rate and that RO recovery can remain at 75% or higher.
All RO units come standard with a comprehensive control, Operator Interface Terminal (OIT) and instrumentation package.This control package is completely preprogrammed with a full set of alarms and safety features to guard your RO against possible damage. These measures ensure worry-free operation of your RO even when no one is present.
Standout Features Include:
System is automatically flushed with fresh water at shutdown
No pre-treatment chemicals are required
High quality materials of construction (904L SS high pressure piping)
Utilizes commercially available membranes
Integral cleaning system with pump, tank and instrumentation.
A low RPM positive displacement high-pressure pump is utilized.
Conservatively sized filtration (media and cartridge filter)
Packaged for easy installation
Membranes are housed in side port entry pressure vessels.
24 hours, 7 days a week access to effectively manage your water system.
Real Time Access to:
Purchase spare parts online
Track status of outstanding orders
Review shipping information
Review invoice/payment history
Review online maintenance records
Request technical information
Online electronic manuals
Remote system monitoring capabilities
MECO understands the importance of providing our customers with the parts and services required to maintain systems operating at optimum capacity. Our online service center - MECO MASTERsupport™ -is a good example of that. It enables you to monitor your system remotely, place orders, access service records and view your system's manuals when it's convenient for you. Anytime. Anywhere.
With a simple point and click, our entire parts inventory is available to you. Through the online service center, you also get real-time access to invoices, orders, shipping status, system manuals and service trip reports. Everything you need to know to effectively manage and maintain your treatment plant is right at your fingertips.
It's another example of MECO's commitment to providing the highest quality spare parts and cost effective support throughout the life-cycle of the product.
» Launch MASTERsupport™ Online