Coarse filter
Retains coarse particles at the very start of the line.
Retains coarse particles at the very start of the line. Self-cleaning types prevent shutdowns on continuously operating lines.
On well water with a high sand and sediment load, a separator filter separates heavy particles by centrifugal action.
Sand filter
Removal of suspended solids and turbidity.
Removal of suspended solids and turbidity. The most common first stage in treatment lines; a graded sand–gravel bed provides depth filtration.
When the bed becomes saturated it is cleaned by backwashing and returned to service.
Iron–manganese filter
Oxidation and retention of dissolved iron and manganese in well water.
Oxidation and retention of dissolved iron and manganese in well water. The principal remedy for red–brown colour and sediment complaints.
Activated carbon filter
Removal of free chlorine, taste, odour and organic matter.
Removal of free chlorine, taste, odour and organic matter. The most common way to remove chlorine ahead of reverse osmosis — membranes have a low tolerance to chlorine.
Water softening
Removal of the calcium and magnesium that cause hardness, using resin.
It is the pretreatment stage most often used on boiler feed lines, in cooling systems and ahead of reverse osmosis.
When the resin becomes saturated it is regenerated with a salt solution; the regeneration setting directly determines how long the resin lasts.
Ultrafiltration (UF)
Retains suspended solids, colloids and bacteria without altering the chemistry of the water.
Membrane filtration operating at low pressure; it retains suspended solids, colloids and bacteria without altering the chemistry of the water.
Ultrafiltration retains particles and microorganisms and passes dissolved salt — which means it does not lower the conductivity of the water.
Antiscalant dosing
Delays scale and silica precipitation on the membrane surface.
Delays scale and silica precipitation on the membrane surface. The most decisive parameters in selection are hardness and silica; the right product only becomes clear after a detailed analysis and projection.
Cartridge filter
The last safety stage ahead of the membrane.
Fine filtration with replaceable cartridges. Widely used as the last safety stage ahead of a membrane; options of 1 micron and below are also effective against colloidal silica.
Nanofiltration (NF)
Removal of hardness, colour and organic load, at lower pressure than RO.
Nanofiltration offers a selectivity between ultrafiltration and reverse osmosis. It retains multivalent ions (calcium, magnesium, sulfate) to a large extent while letting some of the monovalent ions through.
In applications where the water does not need to be fully demineralised but hardness, colour and organic load do need to come down, it delivers the result with less energy than reverse osmosis.
Reverse osmosis (RO)
Removal of dissolved salts; water of low conductivity.
It is used in every industrial process that needs water of low conductivity.
Reverse osmosis retains dissolved salt too, and therefore demands higher pressure and more energy.
Double-pass reverse osmosis
Passing the permeate of the first pass through a second membrane pass.
The permeate of the first pass is fed to a second membrane pass; used when a conductivity lower than a single pass can reach is targeted.
[TECHNICAL TEXT FROM THE COMPANY: the conditions under which double-pass osmosis is preferred and how it differs from a single pass]
Sea water reverse osmosis (SWRO)
Production of fresh water from sea water.
[TECHNICAL TEXT FROM THE COMPANY: sea water treatment — operating pressure class, energy recovery, membrane selection and pretreatment arrangement]
Degasser
Removal of dissolved gases from the water.
[TECHNICAL TEXT FROM THE COMPANY: degasser — on which lines it is required, and its relationship with the ion exchange stage]
Electrodeionization (EDI)
Continuous high-purity water without chemical regeneration.
By combining resin and selective membranes with an electric field it produces continuous high-purity water without chemical regeneration.
EDI is fed with water from a reverse osmosis outlet; it does not work without that stage.
A mixed bed requires chemical regeneration; EDI runs continuously on electricity and needs no regeneration chemicals.
Electrodialysis reversal (EDR)
Ion removal with an electric field; operates with polarity reversal.
[TECHNICAL TEXT FROM THE COMPANY: EDR — operating principle, where it stands against reverse osmosis and EDI, and on which raw water profile it is preferred]
Demineralization / mixed bed
Full demineralization with ion exchange resins.
Full demineralization with ion exchange resins; for boilers and processes that require high purity.
Mostly used as a polishing stage after reverse osmosis; silica removal takes place in the anion stage.
If outlet quality no longer holds despite regeneration and the cycle length has shortened noticeably, the resin is replaced.
Dolomite filter
Raising the pH of acidic water and correcting its hardness balance.
Used to raise the pH of acidic water and correct its hardness balance. Particularly useful for stabilising the aggressive water leaving a reverse osmosis unit.
UV disinfection
Destroys the ability of microorganisms to reproduce using ultraviolet light.
Ultraviolet light destroys the ability of microorganisms to reproduce. It uses no chemicals and alters neither the taste nor the chemistry of the water; in return it provides no lasting protection in the network and its effectiveness depends on the clarity of the water.
However powerful the UV lamp, there is no disinfection if the light cannot pass through the water. That is why UV is always positioned after the filtration stages.
Ozone contact system
Disinfection and oxidation with a powerful oxidant.
Disinfection and oxidation with ozone, a powerful oxidant. Also effective on colour, odour and organic matter; ozone is generated on site and never stored.
Chemical dosing
Controlled chemical feed where a residual disinfectant is needed in the network.
Controlled chemical feed with a dosing pump, solution tank and measuring equipment. Preferred where a residual disinfectant is needed in the distribution network.
If no residual disinfectant is required, UV is sufficient and uses no chemicals. If there is a risk of recontamination on a long distribution line, a method that leaves a residual is needed.
Treated water tank
Storage of the treated water and pumping it into the line.
Treated water is stored ready to be pumped to the point of use. The tank volume and the booster set arrangement are determined by the plant’s consumption profile.
Bottom-sweep manifold
Continuous removal of the sediment accumulating in the cooling tower basin.
A bottom-sweep manifold and filtration line for cooling tower basins; the sediment accumulating at the basin floor is removed continuously.
In cooling water it is usually unnecessary to filter the full flow; filtering a portion of the circulating water continuously is enough.