The Pros and Cons of Reverse Osmosis Systems

Reverse osmosis systems is just one type of many water filtration systems that are available on the market today. Water filtration pushes water through a filter that traps contaminant molecules and releases pure water molecules. There are many health benefits that can be had from the use of water filtration systems including reverse osmosis systems.

membrane keypad

The first benefit is clean and safe water to drink, bathe, or cook in. Exposure to contaminants is greatly reduced or virtually eliminated. This results in fewer occurrences of diseases including cancer and skin irritations/disorders. With lead content being eliminated or reduced there will likely be many fewer occurrences of learning disabilities in children that currently occur at over 400,000 in the United States yearly. Skin and hair become softer and more properly hydrated.

MEMBRANE

Osmosis is a process whereby a solution is pushed through a semi-permeable membrane with the lesser concentrated solution moving through the membrane to the greater concentration until the solutions become equalized. Reverse osmosis is where water is pushed through a semi-permeable membrane and pressure is applied to stop osmosis and then reverse it. It is a slow process and the result is pure water. The contaminants are trapped in the membrane which is an extremely fine membrane.

The pros of using reverse osmosis systems is that pure water will result. It is a popular seller. The same health benefits mentioned previously can result from using these systems. Although slow they are effective in removing contaminants.

The cons of using these systems lie in the fact that though they remove contaminants they also remove important minerals including magnesium, calcium, potassium, and many others. Depending on need and budget these systems will still be a good option for many consumers to consider for purchase.

The Pros and Cons of Reverse Osmosis Systems

MEMBRANE

The Truth About Reverse Osmosis Systems

The dictionary definition of osmosis is a "slow change in concentration: the diffusion of a solvent through a semipermeable membrane from a dilute to a more concentrated solution."
The definition of Reverse Osmosis, also known as RO, is "the production of pure liquids: a process of purifying water or other liquids such as fruit juices by passing them through a semipermeable membrane that filters out unwanted substances". Osmosis is the reason why drinking salty water is deadly. If you were to you drink salty water and have it go into your stomach, the osmotic pressure begins to draw the water out of your body to try to dilute the salt in your stomach and eventually you start to dehydrate and could possibly die.

membrane keyboard

The purified or pure water is collected from the clean side, or permeate side, of the membrane and on the other side is the water containing the concentrated contaminants which is flushed down the drain. The most common reverse osmosis system has a sediment/chlorine pre-filter, the reverse-osmosis membrane, a storage tank and an activated carbon post filter.

MEMBRANE

The reverse osmosis system removes salt and most inorganic materials that are present in the water. For this reason it is used in places where you find brackish or salty type water that contains nitrates or other dissolved minerals which are difficult to remove by other methods. It also removes the minerals from the water.

De-mineralized water contains more hydrogen and therefore, it is an acid solution where the pH is below seven. Consuming this acid substance causes our body to pull minerals from other sources, such as our teeth and bones to produce bicarbonate in an effort to neutralize the acid. This can be very negative. It has been proven that the production of free radicals goes up when body fluids are more acid than alkaline and this increases our risks for cancer.

All of our fresh water contains traces of minerals such as calcium, magnesium and potassium. I am not aware of any location on this planet earth where we can locate naturally occurring de-mineralization in the water. This makes me believe that we are meant to have these minerals. There are several studies and books written from a scientific view, that consumption of de-mineralized water can be dangerous over a long term and can result in multiple mineral deficiencies.

Many companies began marketing these reverse osmosis systems because of increased popularity and demand for water filtration products for the home. They advertised these systems as "state of the art" or "new" which is just not the case. The reverse osmosis system is often demonstrated using a device that measures the total dissolved solids or TDS or conductivity of the water. This tends to imply that this measurement shows the effectiveness of this reverse osmosis system to remove contaminants. But TDS meters measure the dissolved minerals in the water and have nothing, or very little, to do with the purity or the water or the contaminant levels.

I believe it is easy to determine which water filter system or reverse osmosis system is best for you if you take your time to compare each of the home water purifier systems data, performance, cost and ongoing cost per gallon.

The Truth About Reverse Osmosis Systems

MEMBRANE

Membrane Diffuser Solutions For Wastewater Treatment Systems

In the aeration basin of a typical wastewater treatment plant there are both organic and inorganic matter that can impair the function of fine bubble diffusers. Eventually this requires either additional energy to overcome high membrane headloss, or reducing the oxygen mass transfer to the process.

waterproof membrane

The rate and type of fouling depends on whether the plant is treating industrial or municipal wastewater, as well as on the process. Typically diffuser types foul more rapidly in low MCRT plants such as non nitrifying conventional processes than in high MCRT plants such as in nutrient removal processes like oxidation ditch, BNR and SBR.

MEMBRANE

Diffuser media which have been readily available in the market include porous types such as aluminum oxide, porcelain, ABS and Polyethylene, and non-porous types EPDM, Silicone and Polyurethane.

Most diffuser manufacturers have taken a targeted rather than blanket approach to diffuser fouling problems. For example, in a dairy WWTP, it is expected that there will be significant calcium fouling, therefore it is common to use a flexible membrane diffuser rather than a hard porous type which may prove more difficult to keep clean.

In some cases manufacturers have recommended lower roughness coefficient materials such as PU rather than EPDM in such applications to reduce surface adhesion of calcium, gypsum, and silicas to the membrane. However, there have always been trade-offs in the selection of a diffuser media other than porous types or EPDM. For example PU and Silicone formulations that have been used often have a relatively high headloss and lower SOTE than EPDM. Silicone is also prone to tear propagation, add most PU is resistant to only 40 C. Only EPDM provides desirable physical properties and bubble sizes consistent with high SOTE. It should be noted that any result above 7% SOTE/m is considered high, and these tests were conducted at a diffuser submergence of 4.7m.

PTFE layered EPDM membranes were introduced in late 2004 and were installed throughout the course of 2005 in two dairies, one paper mill, one post aeration basin, a brewery, a landfill leachate treatment plant, and a number of municipal sewage treatment plants. In most of the cases, PTFE layered EPDM was selected due to the failure of previous technologies to avoid fouling to a sufficient degree that the plant could operate efficiently.

Rosso and Stenstrom (in their paper Economics of Fine Pore Diffuser Aging) have empirically studied the extent of fouling and cleaning intervals of various diffuser media in a wide array of municipal sewage treatment plants and have found that aF rates between cleanings of membranes even in municipal plants are much greater than common perception, dropping from an average alpha in a low MCRT plant of 0.50 to less than 0.40 after up to 2 years and stabilizing to less than 0.35 thereafter. At this time specifically in low MCRT plants they have found that the difference in aF between porous and non-porous fine bubble media do not vary significantly.

Stamford Scientific has recorded case studies where diffusers did not require cleaning, however, it was the operator's curiosity to look at the diffusers that drove them to drain the tanks and inspect them. In both cases, the surface bubble pattern was consistent with new and clean diffusers, the dissolved oxygen concentrations had not changed from new, and the diffuser headloss appeared not to have changed significantly.

There are tests and evidence that shows little to no change in a between a new PTFE and an aged PTFE membrane in a typical municipal plant setting. This also includes evidence that there is little to no change in DP, with the help of independent research and the addition of further empirical examples. If this can be proven, wastewater plants of all sorts that install PTFE layered membranes will be looking at energy savings over the operating life of the plant of 30 to 40% with the added benefit of reduced maintenance and perhaps less frequent replacement requirements.

Membrane Diffuser Solutions For Wastewater Treatment Systems

MEMBRANE

Industrial Brackish Water Reverse Osmosis Systems

b>Introduction
In December 2008, Pure Aqua successfully supplied a skid-mounted Industrial Brackish Water Reverse Osmosis (BWRO) system to produce 50m3/hr product at 77°F using (42) 8"x40" FILMTEC LE-440i membrane elements, (6) FRP pressure vessels 7 elements per each vessel, SS multistage pump, PLC based controls and a digital conductivity and ORP read out, 380V/3ph/50Hz.

filmtec membrane

Systems and Process
Feed water to the system is from bore-well with raw water TDS of about 2451 PPM. The system design was based on high rejection TFC spiral wound membranes. The Brackish Water Reverse Osmosis system was selected from our RO-500 Series, model number BW-320K-6780-3. The Brackish Water Reverse Osmosis (BWRO) unit consists of 5-micron cartridge filters to reduce feed water Silt Density Index (SDI) and to limit the SS to 5-micron size and advanced PLC control panel with touch panel screen. Pre-treatment and post-treatment includes the following:

FILMTEC MEMBRANE

*Antiscalant dosing to minimize the precipitation of sparingly soluble sulfate
*Multimedia filters to remove suspended solids and reduce turbidity
*Carbon filters
*Cartridge filter with 0.2 micron cartridges
*Filter feed and backwash pumps
*Post UV system

Plant Design Summary
*Application: Bottling
*Total Plant Design Capacity: 1200 m3/day
*Product TDS: General Use = less than 240PPM
*Chemical Treatments: Antiscalant
*Feed TDS: 2451 PPM
*Maximum Pressure: 300psi
*System Recovery: 65%
*Feed SDI: Less than 3

Performance
From a feed TDS of about 2451 PPM at a temperature range of 19°C and 28°C, the BWRO skid produces 50 m3/hour of drinking water with TDS less than 240 PPM matching WHO standard for drinking water.

==> Dubai Sports City
Industrial Reverse Osmosis Waste and Processed Water

Introduction
In the Middle East, fresh water is becoming more and more difficult and expensive to obtain. As a result countries are investing in alternatives in water pufication such as reverse osmosis and desalination. In May 2007, Pure Aqua successfully supplied a water treatment package consisting of a Reverse Osmosis System to produce 200 gpm of product from 250 gpm feed, antiscalant chemical dosing, prechlorination chemical dosing, acid injection dosing, and dechlorination dosing systems.

Systems and Process
Feed water to the system is processed water with raw water TDS of about 1,500 PPM. The system design was based on high rejection TFC spiral wound low fouling membranes. The Reverse Osmosis system was selected from our RO-500 Series, model number BW-360K-8680-3. It produces 200 gpm of drinking water with TDS less than 100 mg/L. The Reverse Osmosis unit consists of 5-micron cartridge filters to reduce feed water Silt Density Index (SDI) and to limit the SS to 5-micron size. TFC spiral wound membranes have a recovery rate of 80% with an advanced microprocessor control panel and cleaning system.

Performance
From a feed TDS of about 1,500 mg/L at temperature range of 27°C, the system produces 200gpm of high quality water at less than 100 ppm. The water produced will be used in the water park area of the Sports Center in boating areas, pools and water slides.

==> Salam, Dubai UAE
Industrial Brackish Water Reverse Osmosis System

Introduction
The Industrial Brackish Water Reverse Osmosis Unit was manufactured and supplied by Pure Aqua in January 2008 for a major water treatment company in Dubai. The BWRO Unit is capacity of 90,000GPD product water.

Systems and Process
Feed water to the system is processed water with raw water TDS of about 2450 PPM. The system design was based on high rejection TFC spiral wound low fouling membranes. The Reverse Osmosis Unit was selected from our RO-400 Series, model number BW-87K-2680. It produces 63 gpm of drinking water with TDS less than 50mg/L. The BWRO Unit consists of 8"x40" Hydranautics ESPA2 membrane elements, Codeline 8" diameter FRP side ported pressure vessels, controlled by microprocessor with digital TDS read out, hi/low tank level switches, hi/low pressure switches, SS multistage pump and inlet shut off valve.

Performance
From a feed TDS of about 2,450mg/L at temperature range of 25 °C, the system produces 90,000gpd of high quality water at less than 50ppm. Since the time of its start-up in January 2008, the plant has been running smoothly with minimal troubleshooting.

Industrial Brackish Water Reverse Osmosis Systems

FILMTEC MEMBRANE