A Complete Expert Guide

Effluent Treatment Plants (ETPs) use a combination of physical, chemical, and biological processes to remove pollutants.
But the backbone of chemical treatment lies in selecting the right set of treatment chemicals, based on effluent characteristics.

From our on-ground experience at Varuna Eco Solutions, chemical selection depends on:

• pH imbalance
• TDS levels
• Oil & grease content
• Heavy metals
• COD/BOD load
• Colour & turbidity
• Type of industrial discharge (textile, pharma, chemical, food, automobile, etc.)

Below is a complete breakdown.

What Chemicals Are Used in ETP Plants?

(With Practical Examples)

ETPs typically use the following groups of chemicals:

1. Coagulants

Used to destabilize suspended particles.
Common examples:

• Alum (Aluminium Sulphate)
• Ferric Chloride (FeCl₃)
• PAC – Poly Aluminium Chloride

When we use them:
Industries with high turbidity, colour, or colloidal solids (textile, dyeing, chemical plants).

2. Flocculants

Used to bind small particles into larger flocs.
Common examples:

• Anionic Poly Electrolyte
• Cationic Poly Electrolyte
• Non-Ionic Polymers

When we use them:
After coagulation to increase settling speed and reduce sludge carry-over.

3. pH Neutralizers

Used to adjust pH before and after treatment.
Common examples:

• Caustic Soda (NaOH) – Increase pH
• Lime (CaCO₃ / CaO) – pH correction
• Sulfuric Acid (H₂SO₄) – Decrease pH
• Hydrochloric Acid (HCl) – Strong acid dosing

Our observation:

Industries often overdose caustic or acid, which destabilizes biological systems. Controlled dosing is critical.

4. Oxidizing Agents

Used for reducing COD, colour, odour, and toxicity.
Common examples:

• Hydrogen Peroxide (H₂O₂)
• Sodium Hypochlorite (NaOCl)
• Ozone (O₃) – Advanced oxidation
• Potassium Permanganate (KMnO₄)

5. Reducing Agents

Neutralize certain oxidants or remove heavy metals.
Common examples:

• Sodium Bisulfite (NaHSO₃)
• Ferrous Sulphate (FeSO₄)

6. Anti-Scalants

Used in RO-based ETP/ZLD systems to prevent scaling.
Examples:

• Polyphosphates
• Dispersants

7. Disinfectants

Used before final discharge.
Examples:

• Chlorine
• UV Disinfection (non-chemical)

What Is the Chemical Name for ETP?

There is no single chemical called “ETP chemical.”

Instead, ETPs use a combination of:

• Coagulants
• Flocculants
• Neutralizers
• Oxidants
• Sludge conditioners
• Defoamers
• Bioculture (microbial consortia)

So when someone says “ETP chemical,” they usually mean:
Coagulants & flocculants used for wastewater clarification.

What Are the Dosing Chemicals for an ETP Plant?

Typical dosing chemicals include:

Primary Treatment Dosing

• PAC / Alum
• Ferric Chloride
• Lime
• Polymer

Secondary Treatment Dosing

• Bio-culture (for MBBR/ASP systems)
• Urea & DAP (nutrients for microorganisms)
• Anti-foaming agents

Tertiary Treatment Dosing

• Activated Carbon
• Oxidants (H₂O₂, NaOCl)
• pH adjusters
• Coagulants for polishing

RO / ZLD Dosing

• Anti-scalants
• Membrane cleaners (Alkaline & Acidic)

What Is an ETP Chemical?

In industry language, an ETP Chemical typically refers to:

• Coagulant (PAC, Alum, Ferric)
• Flocculant (Polyelectrolytes)
• Neutralizer (Acid/Alkali)

In advanced systems, it may also refer to:

• COD reducers
• Biological culture
• Odour control chemicals

What Are the 7 Major Types of Water Pollutants?

Based on CPCB and global classification, the major pollutants are:

1. Organic Pollutants (BOD, COD, food waste, effluents)
2. Inorganic Pollutants (metals, salts, acids, alkalis)
3. Suspended Solids (sand, grit, silt, industrial particles)
4. Nutrients (Nitrates, Phosphates → cause eutrophication)
5. Pathogens (bacteria, viruses, protozoa)
6. Toxic Chemicals (pesticides, solvents, phenols)
7. Oil & Grease (hydrocarbons, lubricants)

These guide the treatment strategy and chemical selection.

What Are the Top 5 Industrial Chemicals?

Across major industries, the most widely used chemicals are:

1. Sulfuric Acid (H₂SO₄) – Manufacturing, batteries, fertilizers
2. Ethylene – Plastics and polymers
3. Sodium Hydroxide (NaOH) – Industrial processing, ETPs, textiles
4. Ammonia (NH₃) – Fertilizers, refrigeration
5. Chlorine (Cl₂) – Disinfection, chemical manufacturing, PVC

Within wastewater & ETP applications specifically, the top chemicals are:

• PAC
• Alum
• Caustic Soda
• Ferric Chloride
• Polymer