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REVERSE OSMOSIS

What is Reverse Osmosis?

Osmosis is a process found in all biological systems and results in water from a diluted solution passing spontaneously through a semi-permeable membrane toward a more concentrated solution, releasing energy in the process. This is counterproductive to the requirements of desalination where in fact the reverse needs to occur, i.e. we need fresh water to pass out of the concentrated solution and accumulate on the other side of the membrane where it can be collected and utilized. A reversed process of this type requires the input of energy. This mechanism, for obvious reasons, is called Reverse Osmosis, commonly abbreviated to RO.

Reverse Osmosis is the most economical means to purify any form of saline water, be it sea, surface or bore water.

Saline water is categorized as:

  • Brackish - TDS < 20,000 ppm
  • Salt water – TDS > 20,000 ppm

 

What’s Needed?

Alternate Water Solutions specialises in all aspects of reverse osmosis systems and offering varying sized units to suit varied requirements:

  • Domestic/Commercial standard units: process 3,000 – 24,000 litres per day
  • Custom built skid mounted or containerized: process 24,000 litres – 1,000,000 litres per day

Chemical

AWS exclusively uses Genesys International range of products. We utilizes Genesys programming to accurately prescribe the best products required for the specific RO system that ensures longevity and maximum production. These products include antiscalants, flocculants, biocides and cleaning chemicals.

CIP Cleaning

Preventative maintenance to remove the fouling must occur periodically to the membranes to ensure their performance and longevity. The major scaling that will occur in your RO plant will be that of Calcium Carbonate and Silica. Removal is performed by what is termed a CIP (Clean in Process) function which uses an alkaline and acid wash and rinse to remove scale and fouling from the membrane wall.

its small and large CIP skid units to all prospective clients at a minimal rental providing they use AWS range of Genesys Chemicals with the clean. Assistance for the first clean is provided and the CIP units left with the customer for subsequent cleans.

The Detailed Reverse Osmosis (RO) Process

Pretreatment of the supply water feeding the RO plant is the key to a successful system and depending on the water supply quality, various pretreatment systems are utilized ranging from filter media, sediment filters, or chemical.

Our RO systems are purposely built to:

  • Maximize plant longevity while keeping running costs at a minimum
  • Utilize state of the art instrumentation to interface with the user
  • Membranes from the world’s leading membrane manufacturers
  • Designed to achieve the highest levels of productivity and water recovery

After appropriate pretreatment (to remove heavy metals, suspended particles, organics, etc.) the raw water is forced through the membrane wall with high pressure utilizing a booster pump. The membrane wall prevents the passage of dissolved salts in the water (Na, Cl, Mg, Ca, SO4, CO3, etc.) from passing through. Depending on the salt in the water, membranes with different reject capabilities are utilized.  The treated water (permeate) is stripped of nearly all the dissolved salts. Only a certain percentage of the raw water entering the RO plant is converted to permeate (recovery). You cannot obtain 100% recovery as a percentage of the raw water is needed to flush out the left-over salts from the membrane wall (concentrate), which is sent to waste.

The RO process is the effective removal of all the dissolved salts in the water. These are primarily Sodium, Magnesium, Calcium, Chloride, Nitrate, Sulphate and Potassium salts. Other trace elements present will cause scaling. These include the salts of Barium, Calcium, Strontium and Silica. Due to the membranes preventing these salts from passing through, their concentrations build up on the reject side of the membrane wall. There needs to be a certain amount of reject water to continually flush these salts away, but due to their high concentrations and the pressure exerted at the membranes wall, these salts will form scale compounds at the membrane wall. To minimize this scaling, antiscalant is dosed into the feed water flow.

AWS offers a full range of antiscalant and membrane cleaners to ensure longevity and maximum production from the RO Plant.  We use Genesys exclusively who manufacture their own range of specialty RO membrane chemicals. This include antiscalants, flocculants, biocides and cleaning chemicals. Genesys specialise in producing chemicals that allow reverse osmosis (RO) plants to operate efficiently in areas where feed waters are challenging. This might include high levels of Silica, Phosphate or Sulphate. Genesys have also developed products that take into account the different size and configuration of membrane plants. AWS utilizes a Genesys computer program to accurately prescribe the best antiscalant for the specific RO plant at the most efficient dose rate. The report provided outlines

  • Scaling issues
  • Recommend which antiscalant to use
  • What dosage is required to minimize scaling

The object is to reduce their scaling tendency to fewer than 100%. This will prolong the life of the membranes be preventing fouling and scaling, and thereby reducing the need for frequent CIP cleans. We try to extend the life of the membranes for as long as possible before replacing them.

Although utilizing an antiscalant enables scaling saturation to be reduced to under 100% for each scaling compound, scaling is not completely removed from occurring in the RO plant. From the first day of operation, fouling of the membranes will occur as organic or inorganic scaling or fouling. Preventative maintenance to remove the fouling must occur periodically to the membranes to ensure their performance and longevity.

The major scaling that will occur in your RO plant will be that of Calcium Carbonate and Silica. Removal is performed by what is termed a CIP (Clean in Process) function, which uses an alkaline and acid wash to rinse and remove scale and fouling from the membrane wall. This should occur periodically and equivalent to 6 to 8 month intervals of continuous work, as well as prior to long idle times.

The CIP process is not difficult or complex, just time consuming as the membranes are required to be soaked for several hours. In low salt feed water the use of a good antiscalant dosing regimen extends the life of the membranes so that the cost of a CIP clean versus the longevity of the membranes, and eventual replacement, is a more economical option. As such, the membranes are replaced when required, but with careful management and a good antiscalant process in place, we are finding membranes to last 2-3 years.

Due to most existing RO plants not having their own built in CIP cleaners, AWS has designed specific CIP units. These stand-alone CIP units vary in size and can be purchased or rented.

For existing RO systems with no CIP cleaners, AWS makes available its small and large CIP to rent to all prospective clients at a minimal cost providing they use AWS range of Genesys Chemicals with the clean.

Assistance for the first clean is provided and the CIP unit is left with the customer for subsequent cleans.

Our CIP units are skid mounted with independent heaters, electrical panels, storage tanks, pH and temperature monitors, VSD Pumps, flow meter and hoses.

Alternatively, AWS can build to purpose your own tried and proven performance CIP unit.

DOMESTIC / COMMERCIAL STANDARD UNITS
SIZE DIMENSIONS MATERIAL RATE OF FILTRATION LITRES/DAY
3KLD 500W X 600D X 1200H STAINLESS STEEL SUS304 UP TO 3,000L
6KLD 500W X 600D X 1600H STAINLESS STEEL SUS304 UP TO 6,000L
12KLD 500W X 600D X 1600H STAINLESS STEEL SUS304 UP TO 12,000L
24KLD 700W X 750D X 1600H STAINLESS STEEL SUS304 UP TO 24,000L

RO STANDARD UNIT 6KLD

RO STANDARD UNIT 12KLD

RO STANDARD UNIT 24KLD

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