Water-Treatment Chemistry Glossary
The terminology Pakistani chemical engineers, plant operators, and procurement teams use when evaluating water-treatment vendors — defined plainly, with how each term maps to the AAS catalog (PAC, CPAM, UN-307, UN-611, AD-401, AD-303, AD-402).
33 terms · alphabetical · last reviewed 2026-05-12
- ANSI/NSF 60 — Drinking-Water Treatment Chemicals
- The American National Standards Institute / NSF International certification for chemicals added directly to municipal drinking water. Sets allowable impurity ceilings (heavy metals, nitrosamines) at the dose specified by the manufacturer.
- Antiscalant
- A polymer or phosphonate dosed sub-stoichiometrically to prevent the precipitation of sparingly soluble salts (CaCO₃, CaSO₄, silica, BaSO₄). Works by threshold inhibition, lattice distortion, and dispersion — not by stoichiometric sequestration.
- Biofouling
- Accumulation of biofilm — bacteria, EPS, sometimes algae — on RO membranes, heat-exchanger tubes, and cooling-tower fill. Manifests as rising differential pressure on RO trains, falling heat-transfer coefficient on coolers, and elevated planktonic counts in recirculating water.
- BOD / COD — Biochemical & Chemical Oxygen Demand
- BOD measures the oxygen biological communities consume metabolising organics over 5 days at 20 °C. COD is the oxygen equivalent of all chemically oxidisable matter measured in 2 hours by dichromate digestion. COD ≥ BOD always; the BOD/COD ratio is a proxy for biodegradability.
- Boiler blowdown
- Periodic or continuous discharge from a boiler drum to control total dissolved solids, alkalinity, and sludge buildup. ASME and IBR limit cycles of concentration in the boiler water; blowdown rate sets the makeup-feedwater rate that the chemistry programme must support.
- Brackish water
- Water with total dissolved solids between roughly 500 and 30,000 ppm — between fresh (≤500 ppm) and seawater (≈35,000 ppm). Most Pakistani inland groundwater used for RO sits in this band; the dominant scalants are CaCO₃, CaSO₄, and silica.
- ClO₂ — Chlorine dioxide
- A neutral-molecule oxidising biocide that does not produce trihalomethanes and remains effective across pH 4–10. Usually generated on site from sodium chlorite plus an activator; residual is measured by amperometric titration or DPD with a glycine masking agent.
- CPAM — Cationic Polyacrylamide
- A high-molecular-weight cationic polymer used as a flocculant downstream of a coagulant (typically PAC) for sludge dewatering, oily-water clarification, and paper-machine retention. Charge density and molecular weight are the two specification levers — both selected against the substrate-charge state.
- CT — Cycles of Concentration
- Ratio of dissolved solids in the cooling-tower recirculating water to those in the makeup. Higher cycles cut makeup and blowdown water cost but raise scaling and corrosion driving force; the chemistry programme is what lets the operator push cycles up without losing the asset.
- DBNPA — 2,2-dibromo-3-nitrilopropionamide
- A fast-kill, fast-degrading non-oxidising biocide widely used for shock dosing RO feed and pulp-mill white water. Hydrolyses within hours, leaves no persistent residue — useful when downstream discharge limits restrict cumulative biocide load.
- Dechlorination
- Removing free and combined chlorine ahead of polyamide RO membranes, which are oxidised by even trace chlorine. Two routes: chemical scavenging via sodium metabisulfite (SMBS), or sorption on granular activated carbon. SMBS is dosed at roughly 1.5–2.0 ppm per ppm of free chlorine.
- EDTA — Ethylenediaminetetraacetic acid
- A hexadentate chelating agent that binds polyvalent metal cations (Ca²⁺, Mg²⁺, Fe³⁺) into soluble complexes. Used in alkaline RO clean-in-place formulations, boiler internal-treatment programmes, and steam-condensate work.
- EPDM — Ethylene Propylene Diene Monomer
- The standard elastomer for RO membrane element O-rings, vessel end-cap gaskets, and chemical-feed line fittings. Excellent steam and chemical resistance but oxidised by free chlorine — another reason dechlorination at the RO inlet is non-negotiable.
- GMP — Good Manufacturing Practice
- The pharmaceutical and food-grade manufacturing framework (US FDA 21 CFR 210/211, EU GMP, WHO TRS) that governs water-system design, qualification, and ongoing monitoring. For pharma utilities the implications are documented IQ/OQ/PQ, validated sanitisation cycles, and recorded conductivity / TOC / bioburden.
- HEDP / ATMP / PBTC — Phosphonates
- Three workhorse phosphonate families: HEDP (1-hydroxyethylidene-1,1-diphosphonic acid), ATMP (amino-tris(methylene phosphonic acid)), and PBTC (2-phosphonobutane-1,2,4-tricarboxylic acid). Each shows different chlorine tolerance, calcium-tolerance, and corrosion-inhibition pairing — programme selection is matched to feed-water analysis.
- Hydrazine — N₂H₄
- A volatile, ammonia-forming oxygen scavenger historically used in high-pressure utility boilers. Now superseded in many specifications by carbohydrazide and DEHA (diethylhydroxylamine) on toxicity and condensate-amine grounds — though it still appears in legacy refinery and IPP specifications.
- Isothiazolone — MIT / CMIT
- Methylisothiazolinone and chloro-methylisothiazolinone — broad-spectrum non-oxidising biocides effective at low ppm. Often used on rotation with a quaternary ammonium chemistry or an oxidiser to delay microbial resistance.
- LSI — Langelier Saturation Index
- LSI = pH − pHs, where pHs is the pH at which the water is in equilibrium with calcium carbonate. Positive LSI indicates a tendency to deposit CaCO₃ scale; negative LSI indicates a tendency to dissolve protective films and corrode mild steel.
- MEA / DEA / cyclohexylamine — Neutralising amines
- Volatile alkaline amines fed to boiler systems to raise condensate-line pH and suppress carbonic-acid corrosion. Distribution ratio (vapour vs. liquid) drives dose strategy — cyclohexylamine concentrates further down the condensate line than morpholine.
- MSDS / SDS — Safety Data Sheet
- The 16-section GHS-formatted document required for any industrial chemical shipment, covering identification, hazards, composition, first aid, handling, exposure controls, physical properties, stability, toxicology, ecology, disposal, transport, and regulatory information.
- Oxygen scavenger
- Chemistry that reduces dissolved oxygen in boiler feedwater after deaerator polish — typically below 7 ppb — to prevent pitting corrosion in the economiser and steam-drum metallurgy. Modern options: carbohydrazide, DEHA, erythorbate; legacy: hydrazine, sulfite.
- PAC — Poly-Aluminium Chloride
- A pre-hydrolysed inorganic coagulant with general formula [Al₂(OH)ₙCl₆₋ₙ]ₘ, expressed by Al₂O₃ content and basicity. Outperforms alum across a wider pH range, leaves less residual aluminium in treated water, and produces a more compact sludge.
- PAM — Polyacrylamide (Anionic / Cationic / Non-ionic)
- The high-molecular-weight polyacrylamide flocculant family. Charge selection follows substrate charge state — anionic PAM for mineral-processing slurries, cationic PAM (CPAM) for sludge dewatering and paper retention, non-ionic for neutral suspensions. Dose typically 0.5–5 ppm, depending on solids load.
- Permeate
- The treated, low-TDS water that passes through an RO membrane. Recovery (permeate / feed) is the operating lever; typical brackish-water RO recovery runs 75–85%, with the balance leaving as concentrate (reject / brine) carrying the rejected salts.
- PW / WFI — Purified Water & Water for Injection
- The two principal pharmacopoeial water grades for pharmaceutical manufacturing. PW is produced by RO + EDI or RO + ion exchange; WFI is produced by distillation or reverse-osmosis-with-ultrafiltration per current USP / EP / IP. Both require conductivity, TOC, and bioburden monitoring under a validated programme.
- Reverse osmosis (RO)
- A pressure-driven membrane separation that rejects dissolved salts, organics, and microorganisms by forcing feedwater against a semipermeable polyamide thin-film composite. Operating pressure scales with feed TDS — roughly 10–17 bar for brackish-water, 55–80 bar for seawater.
- RSI — Ryznar Stability Index
- RSI = 2·pHs − pH. An empirical complement to LSI: values below 6 trend strongly scaling, between 6 and 7 are stable, above 7 trend corrosive, above 9 highly corrosive. Useful as a secondary check on cooling-water programme calls.
- Scaling
- Precipitation of sparingly soluble salts on heat-transfer or membrane surfaces. The Pakistani scale-spectrum is dominated by CaCO₃ (high-alkalinity groundwater), CaSO₄ (gypsum-bearing sources), and reactive silica (volcanic-derived sources in some inland aquifers). Each requires a different threshold-inhibitor chemistry.
- SMBS — Sodium Metabisulfite
- Na₂S₂O₅. The standard reducing agent for dechlorinating RO feedwater. Dose is roughly 1.5–2.0 ppm of SMBS per ppm of free chlorine; over-dose feeds sulfate-reducing bacteria, so the right answer is metered injection against an inline ORP target.
- TDS — Total Dissolved Solids
- Aggregate concentration of dissolved minerals in mg/L (ppm). The headline parameter for RO and cooling-water design — it sets membrane pressure requirement, achievable recovery, blowdown rate, and antiscalant choice. Field proxy: conductivity × 0.5–0.7 for natural waters.
- THM — Trihalomethanes
- Chloroform, bromoform, dibromochloromethane, and bromodichloromethane — the four regulated disinfection by-products formed when free chlorine reacts with natural organic matter. WHO guideline values: 300, 100, 100, and 60 µg/L respectively, summed as the "THM ratio".
- WHO Drinking-Water Quality Guidelines
- The World Health Organization's Guidelines for Drinking-water Quality — the international reference national regulators adapt locally. The current edition tabulates health-based guideline values for microbial, chemical, radiological, and aesthetic parameters.
- ZLD — Zero Liquid Discharge
- A treatment train that recovers all wastewater as condensate and ships only solid residue offsite. Typically RO + brine concentrator + crystalliser, with thermal evaporation on the final concentrate. Capital-intensive — adopted under regulatory pressure (textile dyeing in particular) and where industrial water is scarce.
AAS sources PAC variants certified to ANSI/NSF 60 for Pakistani municipal-water customers on request; certificate of conformance shared at sample stage. See PAC product page and municipal-water case study.
AAS supplies UN-307 RO antiscalant and AD-401 cooling-tower antiscalant ex-Karachi stock. See UN-307 and selection guide.
AAS pairs UN-611 (non-oxidising biocide) with a rotation oxidiser on cooling-water programmes to suppress biofilm without triggering polyamide-membrane damage. See biocide selection.
Textile and paper-mill wastewater customers track COD removal as the headline KPI for PAC and CPAM programmes. See paper-mill CPAM case study and textile-wastewater post.
AAS sizes oxygen-scavenger and phosphate / amine dosing programmes around customer blowdown rates and IBR-class boiler limits. See boiler chemistry guide.
UN-307 antiscalant is dosed across AAS's brackish-water RO references; the exact dose is set against an LSI / S&DSI projection on the source-water analysis.
AAS specifies ClO₂ on cooling-water programmes where THM formation, ammonia in the makeup, or high-pH operation make hypochlorite unsuitable.
AAS imports CPAM in multiple charge densities (10–55 mol%) and grades direct from Shaanxi Ande Technology. See CPAM product page and PAM family selection guide.
An AAS reference at a Karachi power utility took a 12,000 m³/h tower from 3.2 to 5.1 cycles on the AD-401 / AD-303 programme. See cooling-tower case study.
AAS specifies DBNPA for RO shock-dose programmes when polyamide-compatibility and short half-life are both required.
AAS supplies SMBS-grade chemistry and engineers pre-treatment trains for refining, power-plant, and pharma RO systems. See UN-307 refining case study.
EDTA is a recurring component in the alkaline-stage CIP chemistries AAS specifies for fouled RO trains.
AAS confirms EPDM grade and o-ring count on every RO commissioning visit before turnover.
AAS engineering visits for pharma customers carry the documentation pattern (validation protocols, change-control trail) that the QA function expects. See pharma UN-307 case study.
AAS's UN-307 and AD-401 programmes are formulated around phosphonate blends with site-tuned dose ranges; details on the relevant RO and cooling product pages.
AAS supplies both legacy hydrazine programmes and modern carbohydrazide / DEHA replacements; selection follows the boiler OEM specification and customer EHS policy. See boiler-chemistry post.
UN-611 is AAS's non-oxidising biocide alongside oxidiser rotation for cooling-tower programmes. See food-processing UN-611 case study.
AAS runs the LSI on every cooling-water and RO feed before specifying programme dose; for high-LSI waters, antiscalant choice and cycles target are set in the same calculation.
AAS sizes amine programmes against the customer's condensate-network length and the corrosion KPIs the engineering team is tracking.
AAS ships an English-language SDS with every drum and provides Urdu summary handouts for plant-floor staff on request.
AAS selects oxygen-scavenger chemistry against boiler OEM specification and customer EHS posture. See boiler chemistry guide.
AAS stocks PAC in liquid (≥10% Al₂O₃) and solid (≥30% Al₂O₃) grades direct from Shaanxi Ande Technology. See PAC product and case studies in Lahore municipal, Sialkot paper, and Faisalabad textile.
AAS imports the full PAM family from Shaanxi Ande Technology; CPAM is the highest-volume grade through Karachi. See PAM family selection guide.
AAS sizes antiscalant dose against the projected concentrate-side LSI, S&DSI, and silica saturation at the design recovery.
AAS supports pharma utilities in Karachi and beyond with chemistry, system design, and qualification documentation. See WFI/PW post.
AAS supplies the full RO chemistry stack — antiscalant (UN-307), membrane biocide (UN-611), SMBS dechlorination, and alkaline / acid CIP — for refining, power, pharma, and beverage operators.
AAS cross-checks LSI and RSI on every cooling-water programme proposal; both indices appear in the written dosing programme delivered to the customer.
AAS's antiscalant programme calls are made against the dominant scalant in the customer's source-water analysis — not against a generic recipe.
AAS engineers SMBS injection on every polyamide-membrane RO commissioning where the feed contains residual chlorine.
AAS asks for source-water TDS on every quote — without it the chemistry programme is a guess.
AAS specifies ClO₂ in place of hypochlorite on cooling and process-water systems where THM formation potential is the operating constraint.
AAS's municipal-water programmes (PAC coagulation, post-treatment dosing) are sized to land treated-water parameters inside the WHO band as a baseline.
AAS supplies antiscalant and biocide chemistry for the membrane-stage of textile-mill ZLD trains in Faisalabad and beyond. See textile-wastewater post.
Need the dosing programme for one of these terms?
Send your source-water analysis and the unit you're trying to protect (RO, cooling tower, boiler, clarifier). We come back the same Karachi business day with a programme call, a dose range, and the relevant CoAs / SDS attached.
Karachi office · Est. 1994 · Sole Pakistan agent · Shaanxi Ande & Innovative Water