Glossary

Definitions for the most common terms our customers and chemists use across water treatment, boiler & cooling chemistry, surface treatment, and fuel additives.

Water Quality Parameters

Alkalinity: The capacity of water to neutralize acid, contributed mainly by bicarbonate (HCO₃⁻), carbonate (CO₃²⁻), and hydroxide (OH⁻) ions. Reported as mg/L CaCO₃. Sufficient alkalinity buffers pH against changes during chemical dosing — critical for stable coagulation.
BODBiochemical Oxygen Demand: The amount of dissolved oxygen consumed by microorganisms while they break down organic matter in water, measured over 5 days at 20°C (BOD₅). High BOD indicates heavy organic pollution typical of food, beverage, and sewage effluents. Reported in mg O₂ / L.
CODChemical Oxygen Demand: The total oxygen required to chemically oxidize all organic and inorganic oxidizable matter in a water sample, typically using potassium dichromate. COD is faster to measure than BOD (~2 hours vs 5 days) and captures non-biodegradable pollution that BOD misses. The COD/BOD ratio hints at biodegradability.
Hardness: Concentration of multivalent cations (mainly Ca²⁺ and Mg²⁺) in water, expressed as mg/L CaCO₃. Hard water (> 180 mg/L) causes scale in pipes, boilers, and heat exchangers, and reduces detergent efficiency. Removed via softening (ion exchange) or scale inhibitors.
ORPOxidation-Reduction Potential: Voltage-based measurement (mV) of a water sample's tendency to oxidize or reduce other substances. Commonly used to monitor disinfection: ORP > 650 mV indicates effective free-chlorine disinfection in pools and drinking water.
pH: Logarithmic measure of hydrogen ion activity in water on a 0–14 scale. pH 7 is neutral; below 7 acidic, above 7 basic. Drinking water typically pH 6.5–8.5. pH directly affects coagulant dose, disinfection efficiency, and corrosion rate of distribution piping.
TDSTotal Dissolved Solids: The combined concentration of all inorganic and organic substances dissolved in water — primarily salts (sodium, calcium, magnesium, chloride, sulfate, bicarbonate). Measured in mg/L or ppm. WHO drinking-water guideline: < 1000 mg/L. High TDS causes scaling, bitter taste, and reduces RO membrane lifespan.
TSSTotal Suspended Solids: Solid particles suspended in water that are large enough (> 2 µm) to be trapped by a 1.5 µm glass-fiber filter. Includes silt, clay, organic debris, and microorganisms. Measured by filtering, drying at 105°C, and weighing. Critical metric for wastewater discharge permits.
Turbidity (NTU): The cloudiness of water caused by suspended particles, measured by light scattering in Nephelometric Turbidity Units (NTU). WHO drinking water target: < 1 NTU at point of use. Turbidity is the primary control parameter for coagulation/flocculation jar tests.

Treatment Processes

Coagulation: The first step in conventional water treatment: a coagulant (typically a metal salt like ferric chloride or polyaluminum chloride) is rapidly mixed into water to neutralize the negative surface charge of suspended particles. This destabilizes the colloid and allows particles to begin clumping.
Dewatering: Mechanical removal of water from sludge to reduce volume and disposal cost. Typical methods: belt filter press, centrifuge, plate-and-frame filter press, screw press. Cationic polyacrylamide is dosed upstream to flocculate sludge solids and improve dewaterability — typically reaching 18–35% dry solids.
Disinfection: Inactivation of pathogenic microorganisms in water, typically via chlorine (free or combined), chloramine, ozone, UV light, or chlorine dioxide. Maintaining a residual disinfectant in the distribution system prevents regrowth before water reaches the tap.
Filtration: Removal of remaining suspended particles by passing water through a media bed (rapid sand, dual-media, multi-media, or membrane filter). Reduces turbidity from settled water (~1–5 NTU) to drinking-water target (< 0.3 NTU). Backwashing periodically removes captured solids.
Flocculation: The second step after coagulation: gentle mixing causes destabilized particles to collide and bind into larger 'flocs' that can settle out. Often aided by a flocculant polymer (anionic or cationic polyacrylamide) that bridges particles into denser, more settleable aggregates.
Sedimentation: Gravity-driven separation step where flocs settle to the bottom of a tank (clarifier) under quiet conditions. Typical surface loading rate: 1–3 m³/m²·h for conventional clarifiers, 5–15 m³/m²·h for lamella plate clarifiers.

Chemicals & Polymers

Anionic Polymer: Polyacrylamide variant with negatively-charged carboxylate groups, used to flocculate positively-charged or neutral inorganic particles. Common in mineral processing (mining tailings), drinking-water clarification, and primary sedimentation tanks.
Cationic Polymer: Polyacrylamide variant with positively-charged quaternary ammonium groups. Workhorse polymer for sludge dewatering on belt presses and centrifuges, since municipal sludge particles carry net negative charge. Typical dose: 4–10 kg active polymer per ton of dry solids.
Corrosion Inhibitor: Chemical that, in low concentrations, dramatically reduces the corrosion rate of metals in contact with a fluid. Mechanism varies: anodic (passivation, e.g., chromate, molybdate), cathodic (zinc, polyphosphate), or film-forming (organic amines, imidazolines). Critical in cooling water, oil-and-gas pipelines, and acid pickling baths.
Ferric ChlorideFeCl₃: Iron(III) chloride, a primary inorganic coagulant for water and wastewater treatment. Sold as a 40% liquid solution (density ~1.42 g/cm³). Effective across a wide pH range (4.5–11), removes phosphorus, sulfides, and turbidity. NSF/ANSI 60-certified grades are used for municipal drinking water. CHIMI ART manufactures CHIMIFLOC FR 4011 (NSF + REACH).
Filming Amine: Long-chain amine (octadecylamine, ODA) that adsorbs onto metal surfaces to form a thin, hydrophobic protective film. Used in steam systems where oxygen ingress or geometry makes neutralizing amines insufficient. Forms a barrier against both oxygen and acid attack.
Neutralizing Amine: Volatile amine (morpholine, cyclohexylamine, DEAE) dosed into steam to neutralize carbonic acid (CO₂ + H₂O) that forms in steam condensate, preventing acidic corrosion of return-line piping. Each amine has a different distribution ratio between vapor and liquid phases — chosen by system geometry.
Oxygen Scavenger: Chemical (sodium sulfite, hydrazine, DEHA, carbohydrazide, erythorbic acid) added to boiler feedwater to remove the last traces of dissolved oxygen after mechanical deaeration. Prevents pitting corrosion of boiler tubes. Catalyzed sulfite is most common in low-pressure boilers.
PolyacrylamidePAM: Synthetic high-molecular-weight polymer used as a flocculant. Available in three charge types: anionic (negative, for mineral and inorganic flocs), cationic (positive, for organic sludge dewatering and biological floc), and nonionic. Dosed at 0.1–10 mg/L depending on application.
Polyaluminum ChloridePAC, PACl: Pre-hydrolyzed aluminum-based coagulant with formula Aln(OH)mCl(3n−m). Higher basicity (typically 30–60%) means lower alkalinity consumption and less pH drop than alum or ferric chloride — critical when treating low-alkalinity surface waters. Effective at lower doses; produces less sludge.

Methods & Tests

Breakpoint Chlorination: The chlorine dose at which all ammonia in the water is oxidized away and free residual chlorine begins to accumulate. Typically 7.6 mg Cl₂ per mg NH₃-N. Operating beyond breakpoint guarantees free chlorine residual rather than the weaker chloramines.
Jar Test: Bench-scale screening of coagulant/flocculant doses using 6 stirred 1-liter jars in parallel. Standard procedure: rapid mix 1 min @ 100–300 rpm, slow mix 15–20 min @ 20–50 rpm, settle 30 min, measure residual turbidity. Identifies optimal dose, pH, and chemical combination before plant-scale trials.
Zeta Potential: Measure (mV) of the electrostatic charge at the slipping plane of a particle in suspension. Stable colloids typically have zeta potential below −30 mV; effective coagulation pulls it close to zero (between −10 and +10 mV) so particles can collide and agglomerate.

Biological Treatment

Activated Sludge: Biological wastewater treatment process where a flocculent suspension of aerobic microorganisms is mixed with raw wastewater in an aeration tank, then settled in a secondary clarifier. The settled biomass (return activated sludge, RAS) is recycled to maintain the microbial population.
Aerobic: Biological process requiring molecular oxygen. Aerobic wastewater treatment is faster and produces less odor than anaerobic, but consumes substantial energy for aeration (typically 0.4–0.7 kWh per m³ treated).
Anaerobic: Biological process operating without oxygen. Used for high-strength industrial wastewater (food, beverage, pulp). Produces biogas (50–70% methane) as a byproduct, but slower than aerobic and more sensitive to temperature, pH, and toxic shock.
Denitrification: Anoxic biological reduction of nitrate (NO₃⁻) to nitrogen gas (N₂), which escapes harmlessly to the atmosphere. Requires an organic carbon source (often a slipstream of raw wastewater or methanol) and zero dissolved oxygen but presence of nitrate.
Nitrification: Two-step microbial oxidation of ammonia (NH₃) to nitrite (NO₂⁻) by Nitrosomonas and then to nitrate (NO₃⁻) by Nitrobacter. Requires aerobic conditions, alkalinity (~7.1 mg CaCO₃ per mg NH₃-N), and SRT > 5–10 days at 20°C.
Phosphorus Removal: Removal of phosphorus from wastewater either chemically (precipitation with ferric chloride, alum, or lime to form FePO₄/AlPO₄) or biologically (Enhanced Biological Phosphorus Removal — EBPR — where polyphosphate-accumulating organisms store P intracellularly under alternating anaerobic/aerobic conditions).
Sulfide Control: Mitigation of hydrogen sulfide (H₂S) generation in collection systems and anaerobic environments. Methods: chemical oxidation (chlorine, hydrogen peroxide), iron salt precipitation (ferric chloride forms FeS), nitrate addition (suppresses sulfate-reducing bacteria), or pH elevation (Mg(OH)₂).

Boiler & Cooling Water

Boiler Feedwater: Treated water entering a steam boiler. Quality requirements scale with operating pressure: low-pressure (< 30 bar) tolerates moderate hardness with internal treatment; high-pressure (> 60 bar) demands demineralized water (< 0.2 µS/cm) plus oxygen scavenger plus pH-control amine.
Cooling Tower Water: Recirculating water in evaporative cooling towers. Concentrates dissolved solids as evaporation occurs (cycles of concentration, COC, typically 3–6). Requires scale inhibitor (phosphonate), corrosion inhibitor (zinc/molybdate), biocide (oxidizing + non-oxidizing), and dispersant (polymer).
Demineralization: Removal of dissolved ionic species to produce ultra-pure water (conductivity < 10 µS/cm, often < 1). Achieved via mixed-bed ion exchange (cation + anion resin), reverse osmosis followed by EDI, or distillation. Required for high-pressure boilers, semiconductor processes, and pharmaceutical water.
Ion Exchange: Removal/replacement of dissolved ions by passing water through a resin bed. Cation exchange (e.g., softening: Ca²⁺/Mg²⁺ → Na⁺) regenerated with brine. Anion exchange (e.g., dealkalization: HCO₃⁻ → Cl⁻). Mixed beds combine both for full demineralization. Periodic regeneration with acid/caustic restores capacity.
Reverse OsmosisRO: Pressure-driven membrane separation that removes 95–99% of dissolved salts. Requires pretreatment: cartridge filtration to < 5 µm, antiscalant dosing, and pH adjustment. Typical recovery 50–85%, energy 3–6 kWh/m³ for seawater, 0.5–1 kWh/m³ for brackish water.

Surface Treatment

Fluxing: Pre-galvanizing dip in a zinc-ammonium-chloride solution (typical 30% ZnCl₂ + 60% NH₄Cl by weight, balance water). Coats the steel with a thin protective film that prevents reoxidation between pickling and galvanizing, and reacts with the molten zinc to clean the steel surface at the moment of immersion.
Hot-Dip Galvanizing: Coating steel with zinc by dipping clean parts into a bath of molten zinc (~450°C). Forms an iron-zinc alloy layer plus a pure zinc top layer. Provides 50–100+ years corrosion protection in atmospheric exposure. Pre-treatment sequence: degrease → pickle (HCl) → flux → galvanize.
Pickling: Acid cleaning of steel surfaces (typically 10–20% HCl at 20–40°C, or H₂SO₄) to remove iron oxide scale and rust before downstream coating or galvanizing. Pickle inhibitors are added to slow base-metal attack while maintaining oxide removal rate.

Fuel & Combustion

HFOHeavy Fuel Oil: High-viscosity residual fuel from petroleum distillation. Contains 1–4% sulfur, 50–500 ppm vanadium, 20–200 ppm sodium, 50–500 ppm asphaltenes. Used in marine engines, large industrial boilers, and power plants where low fuel cost outweighs the need for a clean burn.
High-Temperature Corrosion: Accelerated metal degradation above ~500°C due to molten salt fluxing, sulfidation, and oxidation. Characteristic of waste incinerators, biomass boilers, and HFO-fired plants. Counteracted by fuel additives, refractory coatings, and material selection (Inconel, stainless 310, ceramic).
Vanadium Corrosion: Hot-end corrosion of boiler superheaters, gas turbine blades, and heavy-fuel-oil-fired engines caused by vanadium pentoxide (V₂O₅) condensing as a low-melting eutectic with sodium sulfate. Mitigated by dosing magnesium-based fuel additives that raise the melt temperature of the ash.

Documents & Compliance

CAS NumberChemical Abstracts Service Number: Unique numerical identifier (e.g., 7705-08-0 for ferric chloride) assigned to every chemical substance by the American Chemical Society's Chemical Abstracts Service. Allows unambiguous identification regardless of language, trade name, or formula notation. Required on TDS, SDS, and most regulatory submissions.
ISO 9001: International standard for quality management systems. Certifies that an organization has documented procedures, monitors process outputs, and continually improves. Most B2B contracts in MENA and EU markets require ISO 9001 certification of the supplier. Audited annually by a notified body.
NSF/ANSI 60: American national standard certifying that a chemical added to drinking water (coagulant, disinfectant, scale inhibitor) does not introduce contaminants above safe levels. Mandatory for sale to municipal water utilities in the US, Canada, and many MENA jurisdictions. CHIMI ART's CHIMIFLOC FR 4011 ferric chloride is NSF/ANSI 60-certified.
REACHRegistration, Evaluation, Authorisation and Restriction of Chemicals: EU regulation (EC 1907/2006) requiring registration of every chemical substance manufactured in or imported into the EU above 1 ton/year. Importers must demonstrate safe use across the supply chain. CHIMI ART's flagship products carry valid REACH registrations enabling EU export.
SDS (Safety Data Sheet): 16-section regulatory document (per GHS) describing hazards, handling precautions, first aid, fire-fighting, spill response, exposure controls, and disposal for a chemical product. Required by OSHA, REACH, and most national chemical safety laws. Must be current and accessible to all workers handling the product.
TDS (Technical Data Sheet): Document summarizing a chemical product's physical and chemical properties (appearance, density, concentration, pH, solubility), recommended uses, dosing rates, storage conditions, and packaging options. Provided to customers before purchase to confirm fit-for-purpose.