RO and Antiscalant Glossary

The grouping of smaller particles or crystals into larger clusters.

The acid-neutralising capacity of water, commonly associated with bicarbonate, carbonate and hydroxide.

The reporting basis and units must be stated.

A chemical used to inhibit or delay the precipitation and growth of mineral scale in water-treatment systems. Antiscalants vary in chemistry, scale-control coverage and application range.

The arrangement of pressure vessels within an RO stage, often written as a ratio showing the number of vessels in successive stages.

A low-solubility sulfate deposit formed from barium and sulfate under favourable concentration conditions.

Water with salinity between typical freshwater and seawater ranges.

The term alone does not define the full chemistry.

A mineral deposit influenced by calcium, alkalinity, pH, temperature and concentration conditions.

A document reporting selected quality results for a batch or lot.

Availability and reported parameters depend on the product and supplier process.

Cleaning equipment and procedures used to circulate cleaning solutions through a membrane system without removing the membrane elements.

Deposition involving very small suspended particles that remain dispersed and are not fully described by dissolved-ion analysis.

The RO stream containing salts and other constituents rejected and concentrated by the membrane.

It may also be called reject or brine in some contexts.

A representation of how much a constituent becomes concentrated as a result of water recovery, subject to system and membrane-rejection assumptions.

A measure related to the ability of water to conduct electrical current.

It is commonly used as an indicator of ionic content.

The pressure difference across a stage, pressure vessel or section of a system.

An increase can indicate flow restriction but does not by itself identify the deposit mechanism.

The quantity of chemical applied to the water, commonly expressed as mg/L or ppm. Antiscalant dosage is established from the selected product, water chemistry, RO recovery and operating conditions.

Water entering the RO system or a defined pretreatment stage.

Accumulation of material that impairs membrane-system performance.

Fouling can include:

• particles;
• colloids;
• organics;
• biological material;
• metal-related deposits;
• mineral scale.

A measure primarily associated with calcium and magnesium.

The report should state whether the value represents total hardness, calcium hardness or another basis.

Standard trade terms published by the International Chamber of Commerce that allocate selected delivery obligations, costs and risks between buyer and seller.

A quoted Incoterm should be accompanied by a named place.

A quality check comparing the electrical-charge contribution of measured cations and anions in a water analysis.

The time required to complete defined supply steps.

Lead time is not final until confirmed for the:

• product;
• quantity;
• documentation;
• destination;
• shipping arrangement.

The suitability of a chemical for use with defined membrane materials and operating limits.

Compatibility must not be assumed universally.

The smallest quantity accepted under a defined supply arrangement.

MOQ may depend on:

• product;
• packaging;
• destination;
• commercial conditions.

A pressure-driven membrane process with selectivity different from reverse osmosis.

It is often used for partial softening or selective solute removal.

Adjustment of operating data to account for variables such as pressure, temperature and feed concentration so that performance trends can be compared more meaningfully.

The initial formation of stable crystal sites from which scale may grow.

Water that passes through the membrane.

A logarithmic measure related to hydrogen-ion activity.

pH influences carbonate chemistry and other precipitation and chemical behaviour.

Physical or chemical treatment applied before the RO membranes to control particles, chlorine, scale-forming conditions and other risks.

The fraction or percentage of feedwater converted to permeate.

Higher recovery generally increases concentration in the reject stream, subject to system design and membrane performance.

See Concentrate.

A formal or structured request for price and commercial terms based on a defined requirement.

A pressure-driven membrane process used to separate water from many dissolved constituents.

A standard safety document covering hazards, handling, storage and emergency information for a specific product.

The proportion of dissolved salt passing through the membrane relative to feed concentration, expressed under a defined calculation basis.

A condition related to the equilibrium solubility of a mineral.

Supersaturation can create the potential for precipitation, but kinetics and inhibition also matter.

A mineral deposit formed by precipitation from water.

An empirical test used to indicate particulate fouling potential under specified test conditions.

Silicon-containing species reported in water analysis, commonly as SiO₂ or another stated basis.

Dissolved and colloidal forms may behave differently.

A group of RO pressure vessels receiving either:

• the feed stream in the first stage; or
• concentrate from the preceding stage.

A low-solubility sulfate deposit formed under favourable strontium and sulfate concentration conditions.

A document describing selected technical properties, applications and instructions for a product.

In water analysis, TDS can also mean Total Dissolved Solids.

Write the term in full when ambiguity is possible.

An estimate or measurement of dissolved material in water, reported under a defined analytical or calculation method.

An optical measure of water cloudiness caused by suspended or colloidal material.

A report of measured water characteristics.

Its usefulness depends on:

• representative sampling;
• stated units;
• appropriate analytical methods;
• sample date;
• sampling location;
• system context.