Desalination FAQ's

1. WHAT IS THE CHARACTERISTICS OF WATER? 2. WHAT IS CONDUCTIVITY/RESISTIVITY? 3. WHAT IS MICROBIAL CONTAMINATION? 4. WHAT IS PH? 5. WHAT IS REVERSE OSMOSIS 6. HOW IS OUR MUNICIPAL WATER TREATED? 7. HOW MUCH POWER IS NEEDED TO PRODUCE A KILOLITRE OF DESALINATED WATER AND WHAT IS THE COST OF CAPITAL FOR A KILOLITRE?
8. IS IT POSSIBLE TO RUN A DESALINATION PLANT ON SOLAR ENERGY? 9. WHAT CAN BE REMOVED FROM WATER BY MEMBRANES?

Other:

Reverse Osmosis

Do you think South Africa should be looking at new technology such as desalination or be tackling the roots of our water shortage problems such as unsustainable agriculture and urban use of water. Is desalination just another quick fix? After all is appears that every time humans alter a natural system other problems arise?

What happens to the excess salt produced by desalination? Is it useful or just a waste product? If it is a waste product is it dumped out to sea where it can potentially harm marine life?

In its pure state water is one of the most aggressive solvents known to man.
Called the universal solvent, water to a certain degree, will dissolve virtually everything to which it is exposed.
Pure water has a very high energy state, and like everything else in nature, seems to reach energy equilibrium with its surroundings.
It will dissolve the quantity of material available until the solution reaches saturation, the point at which no higher level of solids can be dissolved.
Contaminants found in water include: Natural gases, minerals, organic materials (some natural, some man- made) plus any materials used to transport or store water.
The molecular weight of water can be calculated as such:
(MW): The weight of 602,200,000,000,000,000, 000, 000 (6.022X10²³) molecules of a substance. Calculated by adding up the individual atomic weights (AW) of the atoms comprising a molecule. BACK

Ions conduct electricity. Because water contains few ions, it has a high resistance to electrical current. The measurement of water’s conductivity or Resistivity provides an assessment of total ionic concentration.
Conductivity is described in micro Siemens/cm (μS), and measured with a Conductivity meter. Resistivity is described megohm/cm, and is the inverse of conductivity, and measured by Resistivity meter. BACK

There are two types of this contamination namely, viable, and non-viable.
Viable can reproduce an proliferate.
Non Viable cannot reproduce or multiply
Types of Microbiological Contamination are:

- Bacterial Contamination
- Pyrogenic Contamination
- Total Organic Carbon (TOC)
- Biochemical Oxygen Demand (BOD)
- Chemical Oxygen Demand (COD) BACK

The relative acidic or basic level of a solution is measured by pH.
The Ph is a measure of Hydrogen Ion concentration in water, specifically the negative logarithm (log) of the hydrogen ion concentration.
The measurement of pH lies in the scale of 0 – 14, with a pH of 7.0 being neutral. This means that the water is neither acidic, nor basic. It also bears equal numbers of hydroxyl (OH-) and hydrogen (H+) ions.
A pH of less than 7.0 is acidic, and more than 7.0 is basic. BACK

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

More acidic Neutral More Basic

WHAT IS REVERSE OSMOSIS?

What is osmosis? It is the phenomenon of water flow through a semi permeable membrane that blocks the transport of salts or other solutes through it. Osmosis is a fundamental effect in all biological systems. It is applied to water purification and desalination, waste material treatment, and many other chemical and biochemical laboratory and industrial processes.

When two water (or other solvent) volumes are separated by a semi permeable membrane, water will flow from the side of low solute concentration, to the side of high solute concentration. The flow may be stopped, or even reversed by applying external pressure on the side of higher concentration. In such a case the phenomenon is called reverse osmosis.

If there are solute molecules only in one side of the system, then the pressure that stops the flow is called the osmotic pressure.

Reverse Osmosis (RO) was invented in 1959 by Prof Reid of the University of Florida, and was put into practical use by Sidney Loeb and Srinivasa Sourirajan.

It is a process which removes both dissolved organics and salts.
Feedwater is pressurized and flows across a membrane, with a portion of the feed permeating the membrane. The balance of the feed sweeps parallel to the surface of the membrane to exit the system without being filtered. The filtered stream is the permeate, because it has permeated the membrane. The second stream is the concentrate because it carries off the concentrated contaminants, rejected by the membrane.
Because the feed and concentrate flow parallel to the membrane and not perpendicular to it, the process is called “cross flow filtration”.

Depending on the size of the pores engineered into the membrane, cross flow filters are effective in the classes of separation known as Reverse Osmosis, nano filtration, ultra filtration and micro filtration.

See “Filtration spectrum”

Cross flow membrane filtration allows continuous removal of contaminants which in normal flow filtration would blind (plug) the membrane pores rapidly, in conventional systems. (GrahamTek changed this technique successfully)

* Crossflow vs Dead end filtration discussed later in this document

RO removes most organic compounds and up to 99% of all ions.
A selection of RO membranes can be used to treat different feedwater scenarios.

It can meet almost all water standards with a single pass system and all water standards with a double pass system. The process achieves rejections of 99.9% of viruses, bacteria and pyrogens. Pressure in the range of 3.4 – 70 Bar is the driving force of the RO purification process.
It is much cheaper than most conventional treatment systems today, and with GrahamTek Proprietary technology, removes the need for pre-treatment chemicals.

There are a few types or methods of Reverse Osmosis:

- Nano Filtration (NF)

Removes organic compounds, and rejects some salts with low pressures being applied. It is the process normally used for mildly salty tasting water, or as a water softening technique.

- Ultra filtration (UF) BACK

Similar to RO and NF, but does not reject ions. It operates at low pressures (0.7-6.9 Bar). It removes larger organics, colloids, bacteria and pyrogens while allowing most ions and small organics such as sucrose to permeate the porous structure.

- Micro filtration (MF)

Micro filter membranes are absolute cut-off filters rated in the 0.1-3.0 micron range.

ADSORPTION: Adsorption is the binding of a molecule to a surface (solid or liquid) by non-specific physical forces. For example, the removal of free chlorine and chloramines by activated carbon is through the mechanism of adsorption.

AERATION: A process in which air is intimately mixed with water to remove undesirable gases, such as carbon dioxide and hydrogen sulfide. Carbon dioxide can be more economically removed from water by aeration than by chemical precipitation or by the use of ion exchange resins.

ALKALINITY: Capacity of water to accept acid, ordinarily because of its bicarbonate content. In some cases a part of the alkalinity in water may be do to carbonate, hydroxide, phosphate, or silicate. It is expressed in terms of mg/l of calcium carbonate. Total alkalinity is determined by titration with acid to a pH of 4.3. Methyl orange indicator is frequently used as the end point, but potentiometric titration is preferable.
If the pH of the water is greater than 8.3, it is probable that carbonate is present. Carbonate alkalinity is determined by titration with acid to pH 8.3 (phenolphthalein indicator).

ANION: A particle of matter dissolved in water that has a negative charge. In each system of matter the number of anions is equal to the number of cations (positively charged ions). BACK

BACTERIA: Bacteria are single cell microorganisms capable of replicating on their own. They can be divided into two broad categories: aerobic (requiring oxygen) and anaerobic (not requiring oxygen). Bacteria can live in a very broad range of habitats. Some, for example pseudomonads, can thrive in environments containing very low level of nutrients. These bacteria are frequently slime producers and are a major problem in water treatment systems. Other bacteria, which adhere to surfaces, secret gelatinous material which serves to protect the bacteria from chemical disinfectants. This combination of bacteria and their protective coating is sometimes referred to as biofilm. The concentration of bacteria in water is commonly given in terms of colony forming units (cfu) per ml. A colony forming unit is a viable bacterium able to replicate to form a whole colony when incubated in a given environment.

BICARBONATE: Bicarbonate is formed in water by the reaction of carbon dioxide with mineral matter, such as limestone or dolomite. The carbon dioxide is absorbed from air or from decaying organic matter, and the bicarbonate that is formed imparts alkalinity to water. See Alkalinity. Calcium and magnesium bicarbonate do not exist in solid form. When water is removed from solutions of these salts, they lose carbon dioxide and form calcium and magnesium carbonate.

BLOWDOWN: Discharge of water containing concentrated dissolved solids that is replaced by water containing less concentrated dissolved solids. It is conventionally used in connection with the operation of boilers and cooling towers. It is also sometimes used as a term for the concentrate from the reverse osmosis process.

BOD: Abbreviation for Biochemical Oxygen Demand. It is an emperical test used on wastewater in which organisms capable of oxidizing organic matter are introduced. The test is not precise. See COD.

BOUNDARY LAYER: A very thin liquid layer immediately adjacent to the rejecting surface of reverse osmosis membranes in which the concentration of dissolved solids is higher than it is in the main body of the water being processed. The phenomenon is known as concentration polarization.

BRACKISH WATER: Water containing between 1,000 mg/l and 15,000 mg/l of dissolved solids is generally considered to be brackish.
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BRINE: Another term for concentrate.

BRINE SEAL: A U-cup of synthetic rubber attached to the upstream end of a membrane element. It is activated by water pressure to form a joint with the inner surface of the pressure vessel in which the module is placed to prevent water from bypassing around the module.

BUFFER: A substance or combination of substances that resist a change in pH when an acid or an alkali is added to water in which they are dissolved.

BUFFER SOLUTION: A solution of salts that is used to calibrate pH meters. Different combinations of salts are used to prepare buffer solutions with different pH values.

FLOW VELOCITY: The flow of fluid at any point in a water treatment system may be expressed quantitatively in two ways, either in terms of the volume of fluid passing the point in a given time (volumetric flow rate) or in terms of the velocity with which fluid passes the point (flow velocity). The flow velocity (V) depends on the geometry of the conduit through which the fluid flows and is related to the volumetric flow (Q) by:
V = Q/A
Where: A is the cross-sectional area of the conduit. As an example, Table F.1 shows the volumetric flow rate as a function of flow velocity in PVC schedule 80 pipes of different diameters. (The values in Table F.1 are based on actual, rather than nominal, pipe diameters.) Note that for such calculations, it is essential that consistent units be employed. Thus, the term Q would be expressed as ft³/sec and A as ft² to yield V as ft/sec.

FLUIDIZATION: A flowing liquid impinging on a bed of particles imparts some of its momentum to each particle. The imparted momentum is in the direction of the fluid flow. The particles are held to the floor of their container by gravity and to each other by adhesive forces. If the fluid flow is upward through the bed of particles, and if the transfer of momentum from the fluid to the particles is sufficient to overcome both the gravitational and the adhesive forces, the particles become suspended, of fluidized, in the fluid stream.

FLUX: A term that is commonly used for the flow rate of water through reverse osmosis membranes.

FOULING: Deposition of solid substances on the surface of the reverse osmosis membrane or in ion exchange resin particles. Fouling can be due to the presence of suspended solids, sparingly soluble salts, or biological growth. Fouling reverse osmosis membranes causes a decrease in both the amount of water produced and the quality of the water. The performance of fouled membranes can usually be restored by appropriate cleaning procedures. Fouling of Ion Exchange resins causes a loss of efficiency and sometimes necessitates replacement of the resins in the beds.

FRENCH DEGREE: Sometimes used as a unit of measure for any dissolved substance, but it is most frequently used as a measure of hardness. It is usually abbreviated as °F, and it is equivalent to 10 mg/l of calcium carbonate. See Hardness.

GERMAN DEGREE: Sometimes used as a unit of measure for any dissolved substance, but it is most frequently used as a measure of hardness. It is usually abbreviated as °d, and it is equivalent to 17.9 mg/l of calcium carbonate. "See Hardness".
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GRAINS OF HARDNESS: Although the theoretical hardness of water is the sum of the concentrations of all metallic ions, other than the alkali metals, it is commonly expressed as the equivalent concentration of calcium carbonate in grains. Ionic concentrations can be expressed in terms of their combining potential (Eq/L), the number of moles present (mol/L), or their masses in any of several conventions. In the English system masses are expressed in terms of pounds (avoirdupois) which contains 7000 grains each. Although considered outdated in most of the world, the U.S. water purification industry continues to express hardness in units of grains/gal expressed as calcium carbonate. Grains/gal expressed as calcium carbonate can be converted into metric units (mg/L) by multiplying the former by 17.1. Grains/gal expressed as calcium carbonate can also be converted into mEq/L of a univalent ion, such as sodium (Na+) by multiplying by 0.342.

GREENSAND: Manganese Zeolite. A bed of greensand granules used for the removal of iron and manganese from water. The greensand is a naturally occurring mineral that has cation exchange properties. The bed is first treated with manganous chloride to convert it to the manganese form and then it is activated (and subsequently regenerated in repetitive cycles) with potassium permanganate. In use, soluble iron and manganese in water precipitate on the granules, and these solids are backwashed out of the bed at the end of each cycle.

HARDNESS: Hardness was originally defined as a measure of the ability of water to precipitate soaps made from fatty carboxylic acids. These "soaps" precipitated in the presence of calcium and/or magnesium ions. Today, hardness is used to describe the total concentration of calcium and magnesium, expressed as mg/L of calcium carbonate. It is generally calculated from measurement of calcium and magnesium in ion concentrations using:

Hardness (mg CaCO3/L) =2.497 x Ca (mg/L) + 4.118 x Mg (mg/L)

HYDROGEN SULFIDE: A gas which is more toxic than hydrogen cyanide. it has an offensive rotten egg odor, and it is present in some ground waters as a result of microbial action on organic matter under anaerobic conditions. Its odor can be detected at concentrations of a few tenths in an mg/l in water.

HYDROLYSIS: Chemical degradation of a substance by water that is usually accelerated by acids or alkalis.

ION: A charged particle of matter. In each system of matter, the number of positive ions (cations, such as sodium) is equal to the number of negative ions (anions, such as chloride).
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ION EXCHANGE: Ion exchange is based on the principle of electro neutrality, that is, charged species are stable only when they exist as balanced pairs of positive and negative charges. Ion exchange resins, the materials used to carry out the process of ion exchange, are particles which contain fixed charges on their surface. To maintain electro neutrality, each of these charges has an ion of equal and opposite charge held to it; these ions are called counter ions. The counter ions are mobile and can leave the fixed charge if some other counter ion is available to replace it. The replacement ion must be of the same charge as the initial counter ion in order to maintain electro neutrality. The initial counter ion is established by washing the resin with a concentrated solution of the desired counter ion. For example, softener resins are cation exchangers containing carboxylic acids on their surfaces. If these resins are washed with strong NaCl solutions, the predominant cation solution is Na+ and it will become the counter ion. In use, the perfusing water will provide competing counter ions, such as Ca2+. Because of the preference of carboxylic acids for Ca2+ over the Na+ in dilute solutions, the water will be depleted of the Ca2+ in exchange for the Na+ initially present.

IONIC STRENGTH: Some properties of dissolved solids, such as the solubility of calcium sulfate and calcium carbonate, are affected by ionic strength.

LANGELIER SATURATION INDEX: The precipitation of calcium and magnesium carbonates in water purification systems is a serious cause of system failure. The insolubility of these compounds is a complex function of the pH of the water, the dissolved carbon dioxide content, the carbonate content, the presence of other salts, and the temperature. The Langelier Saturation Index is a method of predicting whether or not carbonate deposits will form under given conditions. Calculation of the Langelier Saturation Index is complex and will not normally be done by hemodialysis personnel. Reverse Osmosis vendors may use the index in determining the maximum recovery and rejection rates that can be obtained from a reverse osmosis system before carbonate deposits will seriously reduce water quality and recovery.
Note: It should be noted that the utility of such determinations is limited to those situations in which a softener is not used as part of the pre-treatment scheme for reverse osmosis.

MATERIALS BALANCE: The amount of dissolved substances in the permeate plus the amount in the concentrate must equal the amount of the feedwater. Since the volume of the permeate is a fraction corresponding to the recovery of the feedwater volume rate and the volume of the concentrate is a fraction corresponding to one minus the recovery rate, materials balance is calculated from the equation: Materials

Balance = RCp + Cc (1-r)
^{_______________}
Cf BACK

OSMOSIS: A natural phenomenon in which water diffuses through a membrane from a less concentrated solution of salts to a more concentrated solution of salts.

OSMOTIC PRESSURE: When a solution, such as salt water, is separated from pure water by a membrane which is impermeable to the salt, a flow of water will occur from the pure water to the salt solution. The driving force for this flow is called the osmotic pressure and its magnitude depends on the number of salt particles in the solution.

Note that the osmotic pressure depends on the number of particles and not on the total mass of particles. For example, 1 g/L of a small solute, such as sodium chloride, will exert a greater osmotic pressure than 1 g/L of a large solute, such as protein. For water to flow from the salt solution to the pure water this solution must be exposed to a hydrostatic pressure greater than its osmotic pressure. This is the principle of reverse osmosis

POTENTIOMETRIC TITRATION: A titration in which a rapid change in pH is used to measure the end point.

PRESSURE, APPLIED: The pressure in the feedwater supplied by the high pressure pump.

PRESSURE DROP: Expenditure of a certain amount of energy is required for a fluid to flow through any channel, such as a pipe, particle bed, or membrane. The pressure at any point is a measurement of the energy content of the fluid at that point. Since some of this energy is expended in flowing to a second point downstream, the pressure at the downstream point is less than at the original point. The amount of energy expended, and hence the decrease in pressure (or pressure drop), is dependent on the flow rate and viscosity of the fluid, and the size and shape of the channel. Pressure drops are usually expressed in terms of lb/in2 or psi, or in the SI system, kPa (kilopascals). Pressure drop is sometimes referred to colloquially as "delta P".

PRESSURE, NET: Net applied pressure minus average osmotic pressure.

PRESSURE, NET APPLIED: The average of the pressure in the feedwater and the pressure in the concentrate upstream from the pressure control valve. BACK

PRESSURE, EFFECT ON OUTPUT: RO output varies directly with Net Pressure

RECOVERY RATE: The percentage of water being processed by reverse osmosis that is produced as permeate.

REJECTION RATE: When hydraulic pressure is applied to water in contact with reverse osmosis membranes, water diffuses through the membranes and the dissolved solids that were in the water are repelled. The degree to which they are repelled is the rejection rate. The rejection rate decreases as the feedwater flows through a reverse osmosis unit because the dissolved solids in it are becoming progressively more concentrated. The net result is that the overall rejection rate depends upon the average concentration of dissolved solids in the entire unit.

RESISTIVITY: Resistivity is a measure of the ability of a substance, such as water, to carry an electric current. It is expressed in units of ohm-cm and is the reciprocal of conductivity. Resistivity measurements are commonly used to asses the quality of water produced by deionizers. Like conductivity, Resistivity is temperature dependent and should be measured with a temperature-compensated meter. The usual reference temperature is 25ºC.

SILT DENSITY INDEX: The silt density index (SDI) is a measure of the ability of water to foul a membrane or plug a filter. SDI is measured suing an apparatus which typically consists of an inlet pressure regulator and pressure gauge followed by a filter holder containing a 0.45 µm micro porous membrane filter. Commercial test kits, complete with instructions on how to calculate the index, are available. BACK

TOTAL ORGANIC CARBON: Organic compounds dissolved in water are characterized by their carbon content. Total organic carbon is the mass of carbon present in a water sample, excluding the carbon present as CO2 and/or carbonates. The values are determined by catalytically oxidizing (burning) all dissolved carbon (after CO2/CO3= removal by acidification) to CO2. The resulting CO2 may be measured directly by infra-red absorption, or it may be reduced in a furnace with hydrogen to form methane, which is measured by flame ionization detectors.

TURBIDITY: Turbidity is a measure of the presence of colloidal matter in the water that remains suspended. Suspended matter in a water sample, such as clay, silt, or finely divided organic and/or inorganic matter will scatter the light from an incident light beam. The extent of scattering is expressed in Jackson or Nephelometric turbidity units (JTU and NTU, respectively). BACK

HOW IS OUR WATER TREATED IN SOUTH AFRICA

The water treatment process used in South Africa is based on the use of chlorine as the disinfectant. The water intake to the treatment plant is from dams and rivers and it first passes through wire screens that remove any solid objects. Typically the water would then be pre-treated with chlorine to inactivate disease-causing pathogens. This is then followed by a mixing, coagulation and flocculation process, where a chemical coagulant is used to enable the microscopic dirt particles to coagulate into larger flocs, which then sink to the bottom of the sedimentation tank. The clear water is decanted from the top of these sedimentation plants and is passed through large filters made of sand and gravel that remove all the suspended matter. Finally, chlorine is added to kill any remaining germs and the treated water is tested to make sure it is safe for drinking before being pumped to reservoir tanks from which it is transferred as drinking water through a network of pipes to the consumer. Chlorine remains active in the water for some six to eight hours and Rand Water adds another chemical, namely monochloramine (a mixture of chlorine and ammonia) to the water at its booster pumping stations. Although less active than chlorine, the monochloramine protects the water against bacteria for up to eight days.

HOW MUCH POWER IS NEEDED TO PRODUCE A KILOLITRE OF DESALINATED WATER AND WHAT IS THE COST OF CAPITAL FOR A KILOLITRE?

Typically these days the energy required is about 3 kWh per kilolitre. There is a demonstration project underway in the U.S. where they anticipate dropping energy to 1.7 kWh. The typical cost range for large plant is 0.5 to 0.65 $US per kilolitre (i.e. less than 0.8 $A). The costs have dropped by a factor of three in the last 10 years.

- Prof Tony Fane, Director, UNESCO Centre for Membrane Science and Technology
The current power consumption for seawater desalination is less than 3 kWh/m3, which is a 90% reduction in energy use over the past 40 years. This is because of improvements in membrane technology and energy recovery systems. The cost of desalting seawater has also reduced in recent years, with the newest reverse osmosis plants in Israel and Singapore producing water for about $US 0.50 per metre cubed.

This price can vary significantly depending on whether it has the distribution costs included or not. For Perth, about half the capital cost is associated with distribution of the treated water rather than the desalination process. However, the energy use is still about four times greater than the thermodynamic minimum energy required for separating salt from seawater (0.8 kWhr/m3).

For desalination of wastewaters and groundwaters, the energy required is significantly less and the cost is usually less than 50% of that for seawater desalination and maybe as low as $A 0.20 per metre cubed for blended potable water from groundwater. This leads us to then consider using reverse osmosis for wastewater such as tertiary treated sewage. Perhaps as community attitudes and trust in our technologies improve we will be able to “close the loop” – that is fully recycle water directly.

- Colin Creighton, Director, Water for a Healthy Country, CSIRO

GrahamTek has reduced the cost even more further refining the process with the addition of flow distributors on our membranes, and the use of Electro magnetic field devices on saline water treatment systems. BACK

IS IT POSSIBLE TO RUN A DESALINATION PLANT ON SOLAR ENERGY?

It is possible to run a desalination plant on solar energy alone, but at a much smaller scale.

Solar energy is in the form of heat. Photovoltaic cells transfer this heat energy into electrical energy, and this is then transferred into mechanical and heat energy again. So it is not a terribly efficient solar energy source to use. There are other types of solar energy, for example solar ponds, that don’t use photovoltaic cells and can be incorporated into desalination plants. Photovoltaic cells are very expensive as well.

Other sources of energy can be used, for example wind energy, or waste heat produced in various industries such as the mineral processing industry or especially in power generation industry where only 60 to 70% of the heat energy is used. There is also the possibility of coupling solar energy with other energy sources or using it as a supplementary source of energy, and this is being looked at around the world. BACK

A lot of people are asking this question. There is no one solution to the problem. I think desalination should be one of a number of strategies looked at by people in a variety of disciplines in order to make sure we make the best use of water and all our resources.

Desalination produces fresh water from saline water – essentially separating salt from water. The saline water used could be seawater, but it could also be water from leachate, or saline wastewater. Many people are looking at desalination as a method to inject fresh water back into saline rivers or aquifers to reduce damages done to the water.

The issue for human beings is to learn from Mother Nature to do it correctly. After all, nature desalinates seawater in the evaporation of water from the oceans to produce rain.

To design a desalination plant you need to assess the technology you are using, how you can maximise the efficiency of the plant, and look at where the water comes from, what type and quality of water you are dealing with, where it goes to and what purpose it is required for, as well as how you use the concentrate produced.

Many things need to be taken into account so we can benefit from desalination in addition to using water efficiently. BACK

What happens to the excess salt produced by desalination? Is it useful or just a waste product? If it is a waste product is it dumped out to sea where it can potentially harm marine life?

The salt is usually a waste product from desalination. It is possible to make salt products, such as Epsom salts etc, from the brine, but because the market for these products is small and the price is cheap, it is usually not economic to make products from the brine.
When seawater is desalinated, the brine is returned to the sea. This means that the desalination process can operate with lower recoveries – you are not recovering all of the water, but some of the water – leaving you with fresh water and brine rather than water and salt, and so you use less energy per metres cubed for the water produced. The brine is usually discharged to in a location that allows it to be quickly dispersed, so its effect on the environment can be minimised.
The mixing functions in the ocean are such that it does not harm marine life unless there was no mixing at the release point, and that is avoided.
The brine generated as a wastewater during desalination is heavier than seawater, so if incorrectly discharged to the ocean would sink to the bottom. In addition, the brine is devoid of dissolved oxygen as a result of the desalination process.
If it is released into calm water it can sink to the bottom as a plume of salty water that can kill organisms on the sea bed from a lack of oxygen.
It's important to model the release of water to enable the design of appropriate brine mixing and dispersion, so avoiding plume build-up on the sea bed.
The salt, especially because of the lack of oxygen in the plume, must be well mixed and released, preferably by a high energy coastline.

GrahamTek does not use chemical agents in the treatment of seawater, and therefore the brine reject portion of our process is in a natural concentrated state. We have don various studies with institutions and Universities to prove that our brine reject has no effect on Aqua marine life.