Bureau of Reclamation Banner
\
Advanced Water Treatment Research

Saline Water Category

Higher salt content increases the density of water, thus adding to the potential for suspended sediments. The table below summarizes different categories of saline water.


General Categories of Saline Water

Freshwater less than 1,000 mg/l

Brackish Slightly saline water from 1,000 to 3,000 mg/l

Moderately saline water from 3,000 to 10,000 mg/l

Seawater Highly saline water from 10,000 to 35,000 mg/l

Terms

Acre-foot (AF): A unit for measuring the volume of water. One acre-foot equals 325,851 gallons (the volume of water that will cover one acre to a depth of one foot). One million gallons equals 3.07 acre-feet.

Alkalinity: The acid consuming property of a solution, usually attributed to hydroxide, carbonate, and bicarbonate ions.

Anion: A negatively charged ion resulting from the dissociation of salts, minerals, or acids in water.

Anode: A positively charged electrode by which electrons leave an electrical device.

Antiscalant: A chemical agent added to water that raises the solubility limit and inhibits chemical precipitation.

Aquifers: water-bearing formations capable of yielding water in sufficient quantity to constitute a usable supply for people's uses. They are underground layers of porous rock or sand that allows the movement of water between layers of non-porous rock (sandstone, gravel, or fractured limestone or granite).

AWT: Advanced Water Treatment.

Bacteria: A diverse group of microorganism all of which consist of only a single cell that lacks a distinct nuclear membrane and has a cell wall of unique composition.

Blending: Mixing desalted water with undesalted water to obtain the following advantages: the addition of hardness and alkalinity from undesalted water reduces the corrosivity of the product water; and the amount of post treatment chemical and the water treatment plant size are reduced, thereby lowering capital and operating costs.

Brine: Water containing a high concentration of salt.

Cathode: A negatively charged electrode, as of an electrolytic cell, a storage battery, or an electron tube.

Cation: A positively charged ion resulting from the dissociation of salts, minerals, or acids in water.

Cellulose Acetate: An acetic acid ester of cellulose which when compounded with suitable plasticizer forms a tough thermoplastic material which may be manufactured as semipermeable membrane.

Clathrate: A lattice like structure in which molecules of one substance are enclosed within the crystal structure of another substance.

Clarification: is a separation process which utilizes gravity to remove the flocs formed by coagulation and flocculation.

Coagulation: The destabilization of colloids and initial aggregation of colloidal and finely divided suspended solids.

Concentrate: The waste stream (concentrated ions) produced as a byproduct of membrane treatment. Also called brine or reject.

Conventional wastewater treatment: consists of a combination of physical, chemical, and biological processes and operations to remove solids, organic matter and, sometimes, nutrients from wastewater.

Desalting or Desalination:A process that removes salts from water.

Distillation: The process of heating water to evaporation and its subsequent condensation to purify the water.

Electrocoagulation: use of electricity to remove contaminants instead of chemicals. It is an effective method of pretreatment for integrated membrane systems.

Electrodialysis: A process in which ions are transferred through membranes from a less concentrated to a more concentrated solution as a result of the passage of direct current electrical potential.

Electrodialysis Reversal: An automatic operating feature of some ED units that reverses the electrical potential applied to the two electrodes about every 15 minutes to promote cleaning of the unit.

Entrainment: Small marine organisms passing through tan intake system's screen mesh.

Evaporation ponds: Solar ponds trap heat due to the salinity gradient of the stratified water.

Feed Water: The input solution to any water treatment process.

Flocculation : The gathering of particles, by slow stirring, in water to bind them into larger aggregates to form a rapidly settling floc.

Flow rate: The amount of fluid that flows in a given time.

Forward Osmosis (FO): uses a draw solution such as sugar and nutrient solutions as a driving force.

Fouling: The gradual accumulation of contaminants on a membrane surface or within a porous membrane structure that inhibits the passage of water, thus decreasing permeability.

GPD: Gallons per day.

Groundwater: Subsurface water from an underground lake or river.

Hydrophobic: Repelling, tending not to combine with, or

Impingement: Sufficiently large organisms are trapped against the intake screen by water suction

Ion: An electrically charged atom, radical, or molecule formed by the loss or gain of one or more electrons.

Ion Exchange: A chemical process where certain unwanted ions of a given electrical charge are absorbed on to resin, removed from solution, and replaced by wanted ions of a like charge.

Kilowatt (kW) : A thousand watts. The watt is a measure of power used by electricity generating plants. One watt is equivalent to 1 Joule/second or 3.4127 Btu/hour.

Media filtration: A physical process that removes suspended solids

Megawatt (MW): A million watts.

MGD: Million Gallons per day.

Membrane: A thin layer of material that can separate materials as a function of their chemical or physical properties when a driving force is applied.

Microfiltration (MF): The low pressure membrane filtration through a coherent medium with a nominal pore size range from slightly below 0.1 μm to slightly above 1.5 μm.

Microfiltration membranes: They can be used in place of conventional activated sludge processes for wastewater treatment.

Microorganisms: A plant or animal of microscopic size.

Nanofiltration (NF): A membrane process capable of filtering down to 0.001 micron. NF has a lower rejection rate for monovalent ions than multivalent ions and can operate at significantly lower operating pressures than RO membranes.

Natural Organic Matter (NOM): Substances that come from animal or plant sources, and always contain carbon.

Oxidation: The addition of oxygen, removal of hydrogen, or the removal of electrons from an element or compound.

Pathogens: Disease causing organisms.

PH: Measurement of acidity (<7) or alkalinity (>7). The logarithm of the reciprocal of hydrogen ion concentration in an aqueous solution.

Phytoplankton: Small, usually microscopic plants (such as algae) found in lakes, reservoirs, or other bodies of water.

Polymer: Any of numerous natural and synthetic compounds of usually high

Pretreatment: Treatment units located upstream of the main treatment process which are necessary to remove compounds that are detrimental to the main treatment process.

Product / Permeate: The product water from a desalting process.

Raw Water: Water in its natural state, prior to any treatment. Usually the water entering the first treatment process of a treatment plant.

Recovery: The amount of permeate water attainable, expressed as a percent of the feed flow.

Rejection: The process where certain ions are not allowed to pass through a semipermeable membrane.

Reverse Osmosis (RO): A process of desalination where pressure is applied continuously to the feedwater, forcing water molecules through a semipermeable membrane. Water that passes through the membrane leaves the unit as product water; most of the dissolved impurities remain behind and are discharged in a waste stream.

Scaling: A process where precipitation or crystallation of salt compounds or solids form a coating on working surfaces of a system.

Sedimentation: A process in which solid particles settle out of the water being treated in a clarifier or sedimentation basin.

Semipermeable: The ability to allow some molecules from a mixture to pass through but not all.

Thermodynamics: A science dealing with the mechanical action or relation of heat.

Total dissolved solids (TDS): The quantity of minerals (salts) in solution in water, usually expressed in milligrams per liter (mg/L) or parts per million (ppm).

Turbidity: The cloudy appearance of water caused by the presence of suspended particles and colloidal matter, which interferes with the passage of light through the water.

Ultrafiltration (UF): The low pressure membrane filtration through a coherent medium with a nominal pore sizes range from 0.01 to 0.1 micron.

Viruses: Viruses are a major class of microorganisms but lack many of the attributes of cells. Only when a virus infects a cell does it acquire the ability to reproduce.