filtration glossary

a b c d e f g h i j k l m n o p q r s t u v w x y z

a

ABS
Copolymer comprising three constituents: acrylonitrile, butadiene and styrene

Alkali
Family of products derived from alkali metals, including compounds such as sodium carbonate and caustic soda.

Ammonia
NH3 gas formed by combining nitrogen with hydrogen; a very important intermediate throughout the chemical industry.

Ammonium Hydroxide
Aqueous solution of ammonia

b

BAT
Best Available Techniques describe the most effective technology and methods designed to prevent and where is not practicable, to reduce emissions and their impacts on the environment. These techniques must be already developed under economically and technically viable conditions.

Bentonite Clay
Soft stone formed mainly of aluminum silicate with a high capacity for absorption and decolorisation

Biorientation
Additional processing technique which greatly improves the mechanical resistance of plastic parts (PVC bottles and sheets); drawing the material in two directions (transversally and longitudinally) rearranges the molecular chains, thereby increasing cohesion

Brine
Mixture of salt and water

c

Calendering
Technique for processing plastics into sheets or film: the material is heated and mixed to obtain a viscous paste, which is passed through a series of rollers until it forms a continuous sheet, and gradually cooled before being wound into a roll.

Caprolactone
Intramolecular ester of 6-hexanolactone; a cyclic compound in which the ring opens during polymerisation to produce polycaprolactone, a biodegradable polyester.

Caro's acid
Common name for peroxysulfuric acid (H2SO5); can be produced from hydrogen peroxide

Caustic Soda
NaOH, sodium hydroxide; important intermediate in the chemical industry owing to its properties as a base

Certification
Recognition by an external body; certification can only apply to instruments; instruments are nor accredited but they may be certified

Chlorofluorocarbons (CFCs)
Family of fluorocarbons, composed of carbon (C), chlorine (Cl) and fluorine (F); production is being phased out in all the signatory countries to the Montreal protocol (1987)

Coating
Plastics processing technique whereby a polymerised coating is spread over a material (textile, paper, non-woven fabric) to produce leatherette, wall coverings, etc

Coextrusion
Plastics processing technique to produce multi-layered objects; co-extrusion is used in the production of pipes, films, gas tanks, bottles, etc

Compound
Plastics preparations in the form of granules, pellets, etc. ready for use in processing machines; depending on the intended use, stabilisers, fillers, pigments, reinforcing agents, etc. can be added to the basic resin

Concentrate
Raw water (or liquid) that does not pass through the membrane barrier. The concentrate stream contains higher total dissolved solids or suspended solids than the feed stream.

Concentration polarisation
The accumulation of ionics species within the boundary layer at the surface of crossflow membranes. The concentration of ions is greater at the surface of the membrane than in the bulk feed stream.

Control of emission
Techniques which are used to limit, to reduce, to minimise or to prevent emissions

Copolymer
Polymer whose chain contains a series of dissimilar monomers

Crossflow
A type of membrane filtration where the pressurised feed stream flows parallel to the membrane surface to continuously wash concentrated contaminants away from the membrane surface.

Cyanisation
Process of extracting gold from its ore by attacking the latter with sodium cyanide (NaCN) in the presence of oxygen (O2), hydrogen peroxide (H2O2) or Caro's acid (H2SO5); the effluents remaining once the gold has been separated contain toxic cyanide salts, which are oxidised by the hydrogen peroxide or Caro's acid into non-toxic, decomposable cyanates

d

Dichloroethane
Molecule derived from ethane (CH3-CH3), in which two chlorine atoms replace the hydrogen atoms

Diffuse emission
Emission arising from direct contact of volatile or light dusty substances with the environment (atmosphere, under normal operating circumstances. Examples of diffuse emissions: opening of a filter or a vessel; diffusion through an open surface; volatile compounds emissions from sewers, loading/unloading operations without capture of vented vapours; dust from bulk storage, ...

Dioxins and Furans
Family of aromatic molecules composed of carbon, hydrogen, oxygen and chlorine. They are produced in numerous combustion processes and may be destroyed at high temperatures .

e

Ecobalance or life cycle analysis
Analysis and measurement of the environmental impact of a product or process throughout its life cycle, from the production of the raw materials and energy to waste and recycling

ECVM
European Council of Vinyls Manufacturer, all western European PVC producers are represented in this organisation, which is leading member of Vinyl2010, the body managing the Voluntary Commitment of the industry chain

EDC
Ethylene Dichloride: C2H4Cl2 raw material used to produce VCM through thermal cracking

Effluent
Physical fluid (air or water together with contaminants) forming an emission

Emission
Release of a quantity of substance, energy or vibration, into the environment (air, water, soil, ...); the emission can be expressed as a total quantity in absolute or as a rate per a defined period of time. IPPC definition: direct or indirect of substances, vibration, heat or noise form individual or diffuse sources in the installation into the air, water or land EPER definition: direct release of a pollutant to air or water as well as the indirect release by transfer to an off-site wastewater treatment plan

Emission factor
Direct relation or fixed ratio between measured data or physical parameters and a quantitative emission value, based on operational experience or previous numerous measurements, and defined within some context and within boundary conditions, expressed as specific emission

Emission limit value
Mass, expressed in terms of certain specific parameters, concentration and/or level of an emission, which may not be exceeded during one or more periods of time; ELVs may also be laid down for certain groups, families or categories of substances, in particular those list in annex III of the IPPC directive

Epichlorohydrin Epoxide
Compound with the formula CH2Cl-(CH-CH2)O, the raw material for epoxy resins

Extrusion
Plastics processing technique to produce films, pipes and smooth or corrugated sheeting. The plastic is forced through a flat or perforated annular die, which gives the object its definitive shape

Extrusion blow moulding
Plastics processing technique whereby an intermediate product, a parison obtained by extrusion, is placed in a mould; a gas, generally air, is then blown in to force it to take the shape of the mould. This technique is used to produce hollow objects such as barrels, bottles and tanks

f

Feed
Raw water (or liquid) input to a membrane array.

Feedwater spacer
A netting or similar material that separates adjacent leaves and allows feedwater to flow freely across the membrane surface.

Flue gas purification
Technique of reducing the pollutant contents of a gaseous effluent (mostly smoke): may concern dust (solid particles), acid components, heavy metals, organic micropollutants (dioxins, furans); is generally severely regulated by official emission limits (e.g. European Directives)

Fluorinated polymers
Products produced by polymerisation of fluorine containing starting material being used for surface treatment of paper and textiles creating water resistant layers

Fluorination
Technique used in the production of fuel tanks, for example; a fluorinated gas chemically modifies the surface of the plastic to increase the tank's impermeability to petrol fumes

Flux
Substance which promotes the fusing of solids by reorganising their crystal networks

Flux
Mass or volume rate of transfer through membrane surface.

Fortuitous monitoring
Monitoring achieved without any preliminary sampling plan during an anomaly or upset or unexpected conditions

Fouling
Deposition of solid material in the element from the feed stream of the membrane.

Fugitive emission
Emissions into the environment resulting from a gradual loss of tightness from an equipment designed to contain an enclosed fluid (gaseous or liquid) and supposed to be tight, basically caused by a difference of pressure and a resulting leak; examples of fugitive emissions are: leak from a flange, a pump, a sealed or tightened equipment... Fugitive emissions are a subset of diffuse emissions

Furans
see "Dioxins"

g

GLP
Good laboratory practice: set of principles that provides a framework within which laboratory studies are planned, monitored, recorded, reported and archived.

Good practice
Approach which provides a defined framework to the given activity; it does not preclude other approaches which may be more appropriate for a given requirement

Green Paper (PVC)
In 1996 the EU Commission started the "horizontal study on PVC", consisting of 5 individual studies. The outcome of these together with other information is the body of the "green paper on PVC" issued in 2000

Greenhouse gases
A basket of 6 gases, Carbondioxide (CO2), Methane (CH4), Dinitrogenoxide (N2O), HFCs, PFCs and Sulfurhexafluoride (SF6) which have a Global Warming Potential (GWP) and therefore have an impact on Climate Change

h

H2O2
See "Hydrogen Peroxide"

HCFC
Fluorine and chlorine containing hydrocarbons

HDPE
High-density polyethylene, see "Polyethylene"

HFC
Fluorine containing hydrocarbons which have no negative impact on the ozone and are mainly used for refrigeration, air-conditioning and insulation applications; they have replaced ozone depleting chlorinated hydrocarbons

Homopolymer
Polymer obtained from a single molecular radical

Hydrochlorofluorocarbons (HCFCs)
Composed of carbon (C), chlorine (Cl) and fluorine (F), with at least one hydrogen (H) atom. The first generation of CFC substitutes; they decompose in the troposphere and have little chance of reaching the stratosphere

Hydrofluorocarbons (HFCs)
Composed of hydrogen (H), carbon (C) and fluorine (F). The second generation of CFC substitutes, containing no chlorine atoms at all

Hydrogen Peroxide
H2O2, aqueous solutions of hydrogen peroxide, more commonly known as peroxide bleach, are used for their oxidising properties in the bleaching of paper and textiles, in the treatment of effluents, in pharmacology, and as an intermediate in the chemical industry. Hydrogen peroxide is broken down into water and oxygen in an alkaline environment or in the presence of metallic derivatives

Hygrometry
The measurement of air humidity

i

Injection (moulding)
Plastics processing technique to produce solid parts with a high degree of precision. The material is injected into a mould by a plunger; a press keeps the mould closed while the material cools. At the end of the process the mould is opened and the part ejected

ISO
Standards published by the International Organisation for Standardisation; the 9000 series defines quality assurance models for all companies in the industrial and service sectors; certification indicates compliance with certain formalised working procedures

Isotacticity
Quality of a polymer having a molecular chain with a regular structure

j

k

Kidney dialysis
Technique of filtering blood through a microporous membrane.

l

LDPE
Low-density polyethylene, see "Polyethylene"

Leaf
Two sheets of membrane enclosing the permeate spacer to form a leak-free envelope.

Lumen
A hollow fibre.

m

Mass transfer coefficient (MTC)
Mass or volume unit transfer through membrane based on a driving force.

Melted core injection
Plastics processing technique to produce hollow objects of complex geometry such as automotive engine parts. A metal core is placed in an injection molding press and the plastic injected around it. The core is an alloy with a lower melting point than the plastic, and can therefore be melted selectively at the end of the process. This gives the inner wall of the part produced an excellent surface finish

Membrane Filtration
Membrane filtration is the separation of the components of a pressurised fluid, effected by polymeric or inorganic membranes. The openings in the membrane material (pores) are so small that a significant fluid pressure is required to drive the liquid through them; the pressure required varies inversely with the size of the pores (basically classical orifice theory). There are now four commonly accepted categories or "classes" of membrane, defined based on the size of the material they will remove from the carrier liquid. Moving from the smallest to largest pore size, these are Reverse Osmosis (RO), Nanofiltration (NF), Ultrafiltration (UF), and Microfiltration (MF).

Method of detection limit
Minimum signal level required to identify qualitatively a determined that can be measured, with a 99% confidence limit that the true value is greater than 0

Molecular weight cutoff (MWCO)
The molecular weight of a molecule is the sum of the atomic weights of all the atoms in the molecule. The MWCO of a membrane is the molecular weight value where 90 percent of the feed stream solutes greater than the MWCO will be rejected.

Monitoring
Process intended to assess or to determine the actual value and the variations of an emission, based on procedures of systematic, periodic or spot surveillance, inspection, sampling and measurement or other assessment methods intended to provide information about emitted quantities and/or trends for emitted pollutants

Monomer
Repeating unit in a polymer chain

Moxonidine
Molecule which produces an antihypertensive effect

n

Net driving pressure
The available pressure to drive the feedwater through the membrane minus the permeate and osmotic backpressure.

o

Osmosis
Diffusion of water through a semi-permeable membrane from a region of low salt concentration to a region of higher salt concentration to equalise solution strength.

Ozone layer
A naturally occurring layer of gas (O3) which protects our planet surface from harmful ultraviolet radiation and makes life on earth possible

p

PA
See "Polyamide"

Passivate
To remove surface impurities from ferrous metals and alloys, e.g. prior to painting them.

PE
See "Polyethylene"

Perchloroethylene
Molecule derived from ethylene in which all hydrogen atoms are replaced by chlorine atoms; used as a degreasing solvent.

Permeate
Water that has passed through the membrane barrier and contains lower TDS or suspended solids than the feed stream.

Physiological salt solute
Saline solution isotonic with blood, i.e. where the solute concentration is equivalent overall to that of blood; used in intravenous rehydration.

Plastisol
Viscous paste formed by mixing PVC resin with a plasticiser; applied by dipping, coating, spraying, etc.

Pollutant
EPER: individual substance or group of substance listed [into a specific selection of substances or category of substances][which can harm or affect the environment]; a potentially harmful agent that occurs in the environment as a result of human action

Polyamide
Polymer, usually produced by condensing a diacid and a diamine or by polymerising cyclic lactam. Common name is Nylon®.

Polyarylamide
Aromatic polyamide in which at least one monomer contains a benzene ring, giving it improved mechanical, thermal and chemical resistance.

Polycaprolactone
Polyester obtained by the polymerisation of caprolactone.

Polycarbonates
Family of polymers with a carbonate group (O-CO-O) in the chain.

Polyether
Polymer or organic molecule composed of several C-O-C ether groups.

Polyethylene (PE)
Plastic polymer composed of carbon and hydrogen atoms with the formula -(CH2-CH2)n-, obtained by polymerising ethylene using high- or low-pressure processes. Depending on the polymerisation process used, the density of the polymer may vary widely. Low-density PE is generally used for flexible applications (films). High-density PE is used in rigid applications, such as pipes, fuel tanks, barrels, bottles, etc.

Polyol
Polymer or organic compound containing several -OH alcohol groups. Polyurethanes are manufactured using either polyether polyols or polyester polyols.

Polyolefin
Generic name for polymers obtained from olefins; e.g. polyethylene and polypropylene.

Polyphenylene Sulfide (PPS)
Thermoplastic whose chain contains a sulphur atom between two phenylene groups (-C6H4-S-C6H4-); properties include high mechanical and thermal resistance.

Polypropylene (PP)
Thermoplastic compound composed of carbon and hydrogen atoms, obtained by the polymerisation of propylene (C H3-CH=CH2). The catalysts used in polymerisation determine the stereochemical structure of the polymer, yielding a wide product range with highly diverse applications.

Polystyrene (PS)
Thermoplastic obtained by the polymerisation of styrene (C6H5-CH=CH2).

Polyurethane
Polymer containing the urethane group, generally obtained through the polycondensation of a polyol and a diisocyanate.

Polyvinyl Chloride (PVC)
Plastic polymer composed of carbon and hydrogen atoms, with the formula -(CH2-CHCl)n-; its monomer is vinyl chloride; PVC is a thermoplastic suitable for processing using most techniques.

Polyvinylidene Chloride (PVDC)
Copolymer with the monomer vinylidene chloride (CH2=CCl2); a thermoplastic barrier resin, highly impermeable to oxygen, CO2 and water vapour.

Polyvinylidene Fluoride (PVDF)
Polymer with the monomer vinylidene fluoride (CH2=CF2); a thermoplastic with remarkable chemical inertia and heat resistance properties.

PP
See "Polypropylene"

PPS
See "Polyphenylene Sulfide"

Premix
Plastics formulation in powder form, containing, in addition to the base resin, the main additives, fillers and pigments, in appropriate proportions.

PVC
See "Polyvinyl Chloride"

PVDC
See "Polyvinylidene Chloride"

PVDF
See "Polyvinylidene Fluoride (PVDF)"

q

r

Recovery
Percent of raw water (or liquid) converted to permeate.

Reject
Raw water (or liquid) that does not pass through the membrane barrier. The concentrate stream contains higher total dissolved solids or suspended solids than the feed stream.

Release
Actual discharge (on a routine or unusual or accidental base) and dispersion of an emission into the environment

Resin
In polymer chemistry, plastics in an intermediate solid or semi-solid state.

Reverse osmosis (RO)
Applied pressure in excess of osmotic pressure forces water through a semi-permeable membrane from a region of high salt concentration to a region of lower salt concentration.

s

Salt flux
Rate of salt or ionics species flow through a semi-permeable membrane. Rate of salt flow is proportional to the concentration differential across the membrane and is independent of applied pressure.

Salt passage
The ratio of salt concentration on the permeate side of the membrane to the average salt concentration in the feed stream. Generally expressed in terms of percent salt rejection or percent of salt passage.

Solute
Dissolved solids in raw, feed, permeate, and concentrate streams.

Specific emission
Emission related to a reference basis, like production capacity, or actual production (eg: g per tonne or per unit produced like: n of equipments, m2 of material produced)

Standardisation (gauging)
Set of all operations that are establishing, in specified conditions, the relations between values of the sizes reported by a measuring device or a measuring system, or the value represented by a measure or by a reference material, and the corresponding value of the size achieved by standards

Substance
EPER definition: any chemical element and its compounds, with the exception of radioactive substance

Sulfur Hexafluoride
SF6, molecule composed of one sulphur atom and six fluorine atoms; used chiefly in the synthesis of electrical insulators.

Surfactant
Substance which when dissolved in a liquid, even in very small quantities, greatly reduces surface tension; surfactants used in detergents are part lipophile and part hydrophile, enabling the suspension of fat in water.

t

Thermoplastic
Said of plastics with long chains joined only by weak bonds, enabling repeated heating and remodelling.

Thermosetting
Said of plastics which harden when their polymer chains reticulate in response to heat, radiation and/or a reagent. The chemical bonds thus formed make the material insoluble, more rigid and more temperature-resistant. After reticulation, thermosetting polymers cannot be softened or mechanically recycled without first being broken down.

u

v

Vinyl 2010 Voluntary Commitment
The first commitment of an industry sector having measurable targets and a transparent reporting system about progress of this industry towards more sustainability.

Vinyl Chloride (VC)
H2C=CHCl monomer; polymerised to give PVC.

w

White Paper on Chemicals Policy
With the publication of its "White Paper on EU chemicals policy", the European Commission proposed a major review of its legislation on chemicals. A single regulatory framework called REACH (Registration, Evaluation and Authorisation of CHemicals) to replace the current dual system for assessing risks of "existing" (placed on market before 1981) and new substances

x

y

z

Zeolite
Family of hydrated silicates which occur as porous mineral crystals; used for their absorptive properties, as catalysts, separating agents, sequestrants in washing powders, etc.

Ziegler
Said of a type of polymerisation catalyst, after its inventor.