Operating an Effluent Treatment Plant (ETP), Sewage Treatment Plant (STP), or Water Treatment Plant (WTP) in Kolkata requires a reliable supply of the right chemicals at the right concentration, dosed at the right rate. Under-dosing leads to WBPCB compliance failures and environmental penalties. Over-dosing wastes money and can create secondary pollution problems like excess sludge or residual chlorine.
Yet most chemical suppliers in Kolkata are traders who sell by the drum without understanding the process behind the dosing. They cannot tell you whether your wastewater needs PAC at 200 mg/L or ferric chloride at 150 mg/L. They cannot optimize your polyelectrolyte grade to reduce sludge volume. They certainly cannot run a jar test or calculate your monthly consumption based on flow and inlet COD.
ZEXCORP is different. We are an environmental engineering company that also supplies chemicals — not a chemical trader pretending to understand wastewater. Every chemical we supply comes with dosing recommendations based on your actual wastewater characteristics, free jar testing for new customers, and ongoing process support from engineers who design and operate ETP and STP plants across Kolkata and West Bengal.
Why buy chemicals from an engineering company? Because the chemical is only as effective as the dosing strategy. ZEXCORP provides the chemical AND the knowledge to use it optimally — reducing your cost per kilolitre of treated water while ensuring WBPCB compliance.
Complete Range of Water Treatment Chemicals
ZEXCORP supplies the full spectrum of chemicals needed for industrial and municipal wastewater treatment in Kolkata. Every product is sourced from verified manufacturers and supplied with a Certificate of Analysis (CoA), Material Safety Data Sheet (MSDS), and recommended dosing range for your specific application.
1. Coagulants — Primary Treatment Chemicals
Coagulants neutralize the electrical charge on colloidal particles in wastewater, allowing them to aggregate and settle. They are the first chemical addition in most physico-chemical treatment trains.
Poly Aluminium Chloride (PAC)
The most widely used coagulant for industrial ETPs in Kolkata. Works across pH 5.5–8.5 with faster floc formation and lower sludge volume than conventional alum. Available in powder (28–30% Al₂O₃) and liquid (10–18% Al₂O₃) grades.
Best for: Textile, food processing, pharmaceutical, chemical industries
Typical dose: 100–500 mg/L depending on TSS and COD
Indicative price: ₹30–45/kg (powder grade)
Aluminium Sulphate (Alum)
The traditional coagulant, still cost-effective for low to moderate turbidity applications. Works best at pH 6.0–7.5. Produces more sludge than PAC but costs significantly less. Available in lump, powder, and granular forms.
Best for: Drinking water treatment, STP tertiary polishing, low-COD waste streams
Typical dose: 100–400 mg/L
Indicative price: ₹12–18/kg
Ferric Chloride (FeCl₃)
Highly effective for phosphorus removal, heavy metal precipitation, and high-COD wastewater. Works across a wider pH range (4.0–11.0) than aluminium-based coagulants. Available as 40% liquid solution or anhydrous powder.
Best for: Electroplating, tannery, heavy metal-laden effluents, phosphorus removal
Typical dose: 50–300 mg/L
Indicative price: ₹18–32/kg (liquid basis)
Ferrous Sulphate (FeSO₄)
Cost-effective coagulant for specific applications. Particularly useful as a co-coagulant with lime in high-pH treatment systems. Also used for chromium reduction in electroplating waste. Available as heptahydrate crystals.
Best for: Chrome reduction, co-coagulation with lime, phosphorus removal
Typical dose: 100–500 mg/L
Indicative price: ₹8–14/kg
2. Flocculants — Settling and Dewatering Aids
Flocculants bridge the micro-flocs formed by coagulants into large, dense, rapidly settling macro-flocs. The right flocculant selection can dramatically improve clarifier performance and reduce sludge dewatering costs.
Anionic Polyelectrolyte
Long-chain polymer with negative charge. Works synergistically with metal-salt coagulants (PAC, alum, ferric chloride) to produce large, dense flocs. The workhorse flocculant for most ETP clarifiers. Available in powder form, various molecular weights and charge densities.
Best for: ETP clarifiers with inorganic coagulation, mineral processing, paper mill effluent
Typical dose: 0.5–3 mg/L (prepared as 0.1% solution)
Indicative price: ₹180–280/kg
Cationic Polyelectrolyte
Positively charged polymer, ideal for conditioning biological sludge before dewatering. Also used as a primary coagulant for direct flocculation of negatively charged organic colloids. Critical for filter press and centrifuge performance.
Best for: Sludge dewatering (filter press, belt press, centrifuge), biological sludge conditioning
Typical dose: 2–8 kg per tonne of dry solids
Indicative price: ₹200–350/kg
Non-ionic Polyelectrolyte
Neutral polymer used in specialized applications where charge sensitivity is an issue. Effective in very low pH conditions where anionic polymers lose effectiveness. Less common but important for specific waste streams.
Best for: Acidic waste streams, mineral beneficiation, specific food processing applications
Typical dose: 1–5 mg/L
Indicative price: ₹160–250/kg
3. pH Adjustment Chemicals
Maintaining optimal pH is critical for both chemical treatment effectiveness and biological process health. Most biological processes operate best between pH 6.5–8.5. WBPCB discharge standards require pH 5.5–9.0 for inland surface water discharge.
Caustic Soda (NaOH)
The most common alkali for pH elevation in ETPs. Available as flakes (98%), pearls (99%), and liquid (48% lye). Fast-acting and highly effective. Handle with care — generates heat when dissolved in water.
Use: Raising pH of acidic effluent, neutralization of acid wash water
Indicative price: ₹45–55/kg (flakes)
Hydrochloric Acid (HCl)
Standard mineral acid for pH reduction. Available as 30–35% commercial grade. Essential for plants treating alkaline waste from textile, brewery, and food processing industries. Store in acid-resistant tanks with secondary containment.
Use: Lowering pH of alkaline effluent, acid cleaning of membranes and equipment
Indicative price: ₹8–14/litre (commercial grade)
Lime (CaO / Ca(OH)₂)
Cost-effective alkali for bulk pH adjustment and precipitation. Quicklime (CaO) or hydrated lime (Ca(OH)₂). Ideal for high-volume neutralization. Also precipitates heavy metals as insoluble hydroxides. Produces more sludge than NaOH.
Use: Bulk neutralization, heavy metal precipitation, softening
Indicative price: ₹8–12/kg (hydrated lime)
Soda Ash (Na₂CO₃)
Mild alkali for gentle pH adjustment without rapid pH spikes. Useful where pH control precision is critical. Also provides alkalinity buffer for biological processes. Does not generate as much heat as NaOH.
Use: Alkalinity supplementation, mild pH adjustment, water softening
Indicative price: ₹22–30/kg
4. Disinfectants — Final Treatment Chemicals
Sodium Hypochlorite (NaOCl)
The most widely used disinfectant for STP treated water. Available as 5–12% solution. Effective against bacteria, viruses, and most pathogens. Residual chlorine provides ongoing protection. Degrades with heat and light — use within 30 days of delivery.
Typical dose: 5–15 mg/L as available chlorine, contact time 30 minutes
Indicative price: ₹18–28/litre (10% grade)
Chlorine Dioxide (ClO₂)
Advanced oxidant with superior disinfection capability and no harmful THM (trihalomethane) formation. Generated on-site from sodium chlorite and HCl. Higher capital cost but better performance than NaOCl for sensitive applications.
Best for: Potable water treatment, food processing water reuse, legionella control
On-site generation — contact for system pricing
5. Specialty Chemicals
Anti-scalants
Prevent scale formation in RO membranes and cooling systems. Phosphonate-based and polymer-based formulations available. Critical for plants with high hardness or silica in feed water.
Indicative price: ₹120–200/litre
Biocides
Non-oxidizing biocides for cooling tower water treatment and process water systems. Control algae, bacteria, and biofilm. Glutaraldehyde, isothiazolone, and DBNPA formulations available.
Indicative price: ₹200–450/litre
Activated Carbon
Granular (GAC) and powdered (PAC) activated carbon for colour and odour removal. Essential for tertiary treatment and meeting stringent discharge or reuse standards. Coconut shell and coal-based grades available.
Indicative price: ₹80–150/kg (coconut shell GAC)
Nutrients (Urea & DAP)
Supplementary nitrogen and phosphorus for biological treatment processes. Essential when wastewater lacks sufficient nutrients for microbial growth. Typical BOD:N:P ratio of 100:5:1 must be maintained for healthy biomass.
Indicative price: ₹18–25/kg
How to Conduct a Jar Test — Step-by-Step Guide
The jar test is the single most important procedure for optimizing chemical dosing in your ETP or STP. It simulates the coagulation-flocculation-settling process at bench scale using your actual wastewater. ZEXCORP provides free jar testing for all customers, but understanding the methodology helps plant operators make better daily decisions.
- Collect a representative sample — Take 6 litres of raw (equalized) wastewater from your ETP inlet. Record pH, temperature, turbidity, and if possible, COD/TSS.
- Prepare chemical solutions — Make 1% stock solutions of the coagulants to be tested (e.g., 1 g PAC in 100 mL distilled water). Prepare 0.1% polyelectrolyte solution (dissolve 0.1 g in 100 mL water, stir for 30 minutes).
- Fill jar test beakers — Pour 1 litre of wastewater into each of 6 beakers. Place on the jar test apparatus (flocculator).
- Add coagulant at varying doses — Add increasing doses across the 6 beakers (e.g., 100, 200, 300, 400, 500, 600 mg/L of PAC). Mix rapidly at 150–200 RPM for 2 minutes.
- Add flocculant — Add a constant low dose of polyelectrolyte (e.g., 1 mg/L anionic) to all beakers. Reduce mixing to 30–40 RPM for 15 minutes (slow mixing / flocculation).
- Allow settling — Stop mixing and let flocs settle for 30 minutes undisturbed. Observe floc size, settling speed, and supernatant clarity at each dose.
- Measure results — Carefully withdraw supernatant from each beaker using a pipette (from 2 cm below surface). Measure turbidity, colour, and if possible, COD. Record the pH of each beaker.
- Determine optimum dose — Plot dose vs. residual turbidity/COD. The optimum is the dose giving acceptable effluent quality at the lowest chemical cost. Factor in sludge volume — higher doses produce more sludge.
Pro tip from ZEXCORP engineers: Always test at least 2 different coagulant types (e.g., PAC vs. ferric chloride) before committing to bulk purchase. The cheapest chemical per kg is not always the cheapest per kilolitre treated — a higher-grade coagulant at lower dose often beats a cheaper one at high dose when you factor in sludge disposal costs.
Chemical Consumption Calculation
Accurate chemical consumption estimation prevents stockouts and over-procurement. Use these formulas to calculate your monthly requirements:
= Optimum dose (mg/L) × Daily flow (m³/day) ÷ 1,000,000 × 1,000
= Optimum dose (mg/L) × Daily flow (m³/day) ÷ 1,000
Example:
PAC dose = 300 mg/L, Plant flow = 100 m³/day
Daily PAC consumption = 300 × 100 ÷ 1,000 = 30 kg/day
Monthly consumption = 30 × 30 = 900 kg/month
Monthly cost at ₹40/kg = ₹36,000/month
Required chlorine dose = 5–10 mg/L (as available chlorine)
NaOCl solution strength = 10% (100 g/L available chlorine)
Volume of NaOCl (litres/day):
= Required dose (mg/L) × Flow (m³/day) ÷ Solution strength (g/L)
= 8 × 50 ÷ 100 = 4 litres/day for a 50 KLD STP
Chemical Price Guide — Kolkata 2026
Indicative prices for common water treatment chemicals in Kolkata. Prices vary with purity, order volume, and market conditions. Contact ZEXCORP for current quotes.
| Chemical | Grade / Form | Price Range (₹) | Unit | MOQ |
|---|---|---|---|---|
| PAC (Poly Aluminium Chloride) | Powder, 28–30% Al₂O₃ | 30–45 | per kg | 50 kg |
| Alum (Aluminium Sulphate) | Lump / Powder | 12–18 | per kg | 50 kg |
| Ferric Chloride | 40% Liquid | 18–32 | per kg | 50 kg |
| Ferrous Sulphate | Heptahydrate crystals | 8–14 | per kg | 50 kg |
| Anionic Polyelectrolyte | Powder, various MW | 180–280 | per kg | 25 kg |
| Cationic Polyelectrolyte | Powder / Emulsion | 200–350 | per kg | 25 kg |
| Caustic Soda (NaOH) | Flakes, 98% | 45–55 | per kg | 50 kg |
| Hydrochloric Acid (HCl) | Commercial, 30–35% | 8–14 | per litre | 35 litres |
| Lime (Ca(OH)₂) | Hydrated, powder | 8–12 | per kg | 50 kg |
| Soda Ash (Na₂CO₃) | Light / Dense | 22–30 | per kg | 50 kg |
| Sodium Hypochlorite (NaOCl) | Liquid, 10–12% | 18–28 | per litre | 35 litres |
| Activated Carbon (GAC) | Coconut shell, 1000+ IV | 80–150 | per kg | 25 kg |
| Anti-scalant | RO grade, liquid | 120–200 | per litre | 25 litres |
| Urea (nutrient) | Agricultural grade | 18–25 | per kg | 50 kg |
Note: Prices are indicative as of November 2026 and subject to market fluctuations, GST, and transport. Bulk discounts available for orders above 1 tonne. Contact ZEXCORP for current pricing and volume-based quotes.
Chemical Storage & Handling Safety
Proper chemical storage is not optional — it is a WBPCB compliance requirement and a critical safety measure. Mishandled chemicals cause accidents, environmental spills, and regulatory penalties.
General Storage Rules
- Segregation: Store acids (HCl, H₂SO₄) and alkalis (NaOH, lime) separately with at least 3 metres spacing or physical barrier between them
- Containment: All liquid chemical storage areas must have impervious bunding capable of holding 110% of the largest container volume
- Ventilation: Chemical storage rooms must have forced ventilation — minimum 6 air changes per hour for acid/alkali storage
- Labelling: Every container must display chemical name, hazard symbols, concentration, date of receipt, and expiry (for NaOCl)
- MSDS availability: Material Safety Data Sheets must be posted at the storage location and accessible to all operators
Chemical-Specific Precautions
- NaOCl: Store below 25°C, away from sunlight. Loses 1–2% available chlorine per week at ambient temperature. Use FIFO (first in, first out). Do not mix with acids — releases toxic chlorine gas
- NaOH: Absorbs moisture rapidly — keep bags sealed until use. Generates significant heat when dissolved. Always add NaOH to water, never water to NaOH. Use rubber-lined or PE tanks for solution storage
- HCl: Store in PVC or HDPE tanks only. Extremely corrosive to metals. Fumes are corrosive — ensure ventilation. Keep away from NaOCl (produces chlorine gas)
- Polyelectrolyte: Store powder in dry conditions. Once dissolved, use within 48 hours as solution degrades. Extremely slippery when spilled — clean spills immediately
How to Select the Right Chemical for Your ETP/STP
Selecting the correct chemical is not a guessing game. Follow this decision framework:
| Wastewater Type | Primary Coagulant | Flocculant | pH Chemical | Other |
|---|---|---|---|---|
| Textile (dyeing) | PAC + FeCl₃ | Anionic PE | NaOH / HCl | Activated carbon for colour |
| Brewery / Distillery | PAC | Anionic PE | NaOH | Nutrients (urea, DAP) |
| Food Processing | PAC / Alum | Anionic PE | NaOH / Lime | Anti-foaming agent |
| Pharmaceutical | FeCl₃ | Anionic PE | NaOH / HCl | Activated carbon, H₂O₂ |
| Electroplating | FeSO₄ + Lime | Anionic PE | Lime / NaOH | Na₂S for Cr(VI) reduction |
| Residential STP | Usually not needed | Cationic PE (dewatering) | NaOH if needed | NaOCl for disinfection |
| Hotel / Hospital STP | PAC for tertiary | Anionic PE | NaOH | NaOCl, anti-foaming agent |
Not sure which chemicals you need? Send ZEXCORP a sample of your wastewater (1 litre in a clean container). Our engineers will conduct jar tests, recommend the optimum chemical regime, and provide a detailed dosing protocol — free of charge for new customers.
Why Choose ZEXCORP for Water Treatment Chemicals in Kolkata
- Engineering-backed supply: Every chemical recommendation is validated by jar testing on your actual wastewater. We do not guess — we test.
- Complete range: One supplier for all your ETP/STP chemical needs — no more coordinating with 5 different vendors.
- Process support: Our engineers visit your plant quarterly to review dosing efficiency, identify optimization opportunities, and update protocols based on seasonal variation.
- Reliable delivery: Buffer stock maintained for critical chemicals. Free delivery across Kolkata metro for orders above 500 kg.
- WBPCB compliance: We understand discharge standards because we design the plants. If your treated effluent quality deteriorates, we troubleshoot the process — not just sell more chemical.
- Competitive pricing: Direct sourcing from manufacturers means competitive rates without middleman markups. Volume discounts for annual contracts.
- Documentation: CoA and MSDS provided with every delivery. Chemical consumption reports and cost-per-KL analysis available for AMC customers.
Delivery Areas in Kolkata & West Bengal
ZEXCORP supplies water treatment chemicals across Kolkata and all industrial zones in West Bengal:
- Kolkata Metro: Salt Lake, New Town, Rajarhat, Bidhannagar, Howrah, Dumdum, Behala, Jadavpur, Tollygunge, Park Street, Barrackpore, Baranagar
- Industrial Belts: Durgapur, Asansol, Haldia, Kalyani, Bantala (leather complex), Falta SEZ, Uluberia, Serampore, Dankuni
- North Bengal: Siliguri, Jalpaiguri, Darjeeling (on request)
- South Bengal: Kharagpur, Midnapore, Diamond Harbour
Frequently Asked Questions
A typical ETP requires coagulants (PAC or alum), flocculants (polyelectrolyte), pH adjustment chemicals (NaOH or HCl), nutrients (urea, DAP) for biological treatment, anti-foaming agents, and disinfectants (NaOCl) for final treated water. The exact combination depends on the industry type, wastewater characteristics, and discharge standards.
Indicative prices (2026): PAC ₹30–45/kg, alum ₹12–18/kg, polyelectrolyte ₹180–280/kg, NaOH flakes ₹45–55/kg, HCl ₹8–14/litre, NaOCl ₹18–28/litre, lime ₹8–12/kg. Prices depend on purity grade, order volume, and current market conditions. Contact ZEXCORP for the latest pricing.
Chemical dosing is determined through jar testing on your actual wastewater. Add varying doses of coagulant to samples, observe floc formation and settling, and select the dose giving the best clarity at lowest cost. Daily consumption = optimum dose (mg/L) × daily flow (m³/day) ÷ 1,000. Always validate with jar tests before scaling up. ZEXCORP offers free jar testing for customers.
Anionic polyelectrolyte has a negative charge and works best with metal-salt coagulants for inorganic sludges. Cationic polyelectrolyte has a positive charge and is preferred for biological sludge dewatering and direct flocculation. Selection depends on your wastewater chemistry — a simple jar test determines which performs better for your application.
Store chemicals in a cool, dry, ventilated area. Keep acids and alkalis separated by at least 3 metres. Use chemical-resistant containment bunds for liquids. NaOCl degrades in heat — store below 25°C and use within 30 days. Maintain MSDS sheets for all chemicals and train operators on PPE requirements and spill response.
Yes. ZEXCORP supplies the full range of STP chemicals: NaOCl for disinfection, polyelectrolyte for sludge dewatering, nutrients (urea, DAP), anti-foaming agents, and bio-culture for process start-up. We provide dosing system design, jar testing, and ongoing technical support for STPs across Kolkata and West Bengal.
A jar test simulates coagulation-flocculation at bench scale to determine the best chemical type, dose, and pH for your wastewater. Without it, plants over-dose or under-dose, wasting money or failing compliance. ZEXCORP offers free jar testing with every new chemical supply contract.
Yes. ZEXCORP delivers across Kolkata, Howrah, Hooghly, North & South 24 Parganas, Durgapur, Asansol, Haldia, Siliguri, and all West Bengal industrial zones. Orders above 500 kg within Kolkata metro qualify for free delivery. We maintain buffer stock for critical chemicals to prevent supply interruptions.
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