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Water treatment terms, short and clear
The Today Arıtım technical glossary gives short, clear definitions of 37 terms used in water analysis reports and quotes: TDS, conductivity, water hardness, reverse osmosis, antiscalant, regeneration and more. Each term has its own page with a detailed explanation.
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A
- Activated Carbon Filter A filter that adsorbs free chlorine, chloramine, taste and odour, and organic compounds with porous carbon media. Pretreatment and filtration
- Alkalinity The capacity of water to neutralise acid; it comes mainly from bicarbonate, carbonate and hydroxide ions and is expressed in mg/L CaCO₃. Water quality and measurement
- Antiscalant A chemical dosed into the feed water to prevent calcium carbonate, sulphate and silica from precipitating on RO membranes. Membrane technologies
B
- Bed Volume (BV) A way of expressing flow relative to the volume of resin or filter media; for example, 25 BV/h means water equal to 25 times the resin volume passes per hour. Ion exchange and softening
- Blowdown Deliberately draining water from a boiler or cooling tower to keep the salt concentration within limits. Boiler, cooling and process
- Boiler Feed Water Water fed to a steam boiler that has been softened or demineralised and chemically conditioned to prevent scaling and corrosion. Boiler, cooling and process
C
- Chlorine and Chloramine Oxidising agents used to disinfect mains water that cause taste and odour problems and damage RO membranes. Disinfection
- CIP (Clean-in-Place) Cleaning a membrane or piece of equipment by recirculating acidic/alkaline chemical solutions without dismantling it. Membrane technologies
- Conductivity (EC) The capacity of water to conduct an electric current; a quick indicator of the amount of dissolved ions, measured in µS/cm. Water quality and measurement
- Cycles of Concentration The ratio of cooling tower water TDS to make-up water TDS in a cooling tower; it shows how many times the water has been concentrated. Boiler, cooling and process
D
E
F
G
I
- Ion Exchange A treatment method based on the principle that ions on a resin swap places with unwanted ions in the water; the basis of softening and demineralisation. Ion exchange and softening
- Iron and Manganese Removal The process of oxidising the dissolved iron (Fe²⁺) and manganese (Mn²⁺) in well water and retaining them with a filter. Pretreatment and filtration
L
M
- Membrane A selectively permeable thin barrier that blocks particles or ions above a certain size in water treatment. Membrane technologies
- Micron (µm) Filtration A classification that states, in micrometres, the particle size retained by sediment cartridge filters. Pretreatment and filtration
- Multimedia (Sand) Filter A deep-bed filter made up of layers of sand, anthracite and gravel of different sizes and densities that retains suspended solids and turbidity. Pretreatment and filtration
N
O
P
R
- Recovery Rate The ratio of product water to feed water in an RO system; at 70% recovery, 100 litres of feed water yield 70 litres of product and 30 litres of concentrate. Membrane technologies
- Regeneration The process of restoring exhausted ion exchange resin to working order by rinsing it with brine. Ion exchange and softening
- Remineralisation The controlled addition of minerals such as calcium and magnesium back into water that has been over-purified by RO. Membrane technologies
- Resin (Ion Exchanger) Softener and demineralisation media in the form of spherical polymer beads that carry exchangeable ions on their surface. Ion exchange and softening
- Reverse Osmosis (RO) A treatment method that separates 95–99% of dissolved salts by forcing water through a semi-permeable membrane at high pressure. Membrane technologies
S
- Salt Rejection The performance value showing what percentage of the dissolved salts in the feed water an RO membrane retains. Membrane technologies
- SDI (Silt Density Index) A fouling index that measures the tendency of water to clog a membrane; for RO feed, SDI₁₅ should be < 5, preferably < 3. Water quality and measurement
- Simplex / Duplex Softener A simplex softener has a single tank and supplies no soft water during regeneration; a duplex softener has two tanks and supplies soft water without interruption. Ion exchange and softening
T
- TDS (Total Dissolved Solids) The total amount of all minerals, salts and organic substances dissolved in water; expressed in mg/L or ppm. Water quality and measurement
- Temporary and Permanent Hardness Temporary (carbonate) hardness precipitates on boiling; permanent (non-carbonate) hardness cannot be removed by heating and requires softening. Water quality and measurement
- Turbidity (NTU) A measure of clarity based on the scattering of light by particles suspended in water; expressed in NTU. Water quality and measurement
U
- Ultrafiltration (UF) Filtration with hollow-fibre membranes of about 0.01 micron pore size that retains suspended solids, turbidity, bacteria and viruses while letting dissolved salts through. Membrane technologies
- UV Disinfection A method that disinfects without chemicals by disrupting the DNA of bacteria, viruses and protozoa with ultraviolet light at a wavelength of 254 nm. Disinfection
W
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