Coagulants play a critical role in water and wastewater treatment, as they are responsible for removing suspended solids, colloidal particles, organic matter, and color from raw water. Efficient coagulation is essential for producing clear, safe water that meets industrial, municipal, and environmental discharge standards. Without effective coagulants, downstream filtration and disinfection processes become inefficient and costly.
Among the various coagulants used globally, Poly Aluminium Chloride (PAC) and Aluminium Sulphate (Alum) are the most widely adopted. These two products are often compared because they serve the same core purpose—coagulation and flocculation—yet differ significantly in performance efficiency, dosage requirement, sludge generation, and operational flexibility.
For bulk buyers such as water treatment plants, industrial effluent units, and municipal corporations, efficiency, dosage optimization, and cost per treated kilolitre are decisive factors. Choosing the right coagulant directly impacts treatment effectiveness, chemical consumption, sludge handling costs, and overall operating expenses, making a clear comparison between PAC and Aluminium Sulphate essential.
Poly Aluminium Chloride (PAC) is a pre-hydrolyzed inorganic polymer coagulant widely used in modern water and wastewater treatment systems. Unlike conventional alum, PAC contains polymerized aluminum species that provide faster and more efficient coagulation across a wider range of water conditions.
PAC is chemically represented as Alₙ(OH)ₘCl₍₃ₙ₋ₘ₎, where the aluminum is partially neutralized, resulting in higher charge density and improved destabilization of suspended particles. This structure makes PAC more effective at lower dosages compared to traditional coagulants.
Aluminium Sulphate, commonly referred to as Alum, is one of the oldest and most widely used coagulants in water treatment. It has been traditionally used for municipal drinking water, wastewater treatment, and industrial effluent clarification due to its availability and low initial cost.
Chemically, aluminium sulphate is represented as Al₂(SO₄)₃·18H₂O. When added to water, it reacts to form aluminum hydroxide flocs that trap suspended impurities. However, this reaction is highly dependent on water alkalinity and pH.
| Technical Parameter | Poly Aluminium Chloride (PAC) | Aluminium Sulphate (Alum) |
|---|---|---|
| Chemical Nature | Pre-hydrolyzed inorganic polymer coagulant | Conventional inorganic aluminum salt |
| Typical Chemical Formula | Alₙ(OH)ₘCl₍₃ₙ₋ₘ₎ | Al₂(SO₄)₃·18H₂O |
| Working pH Range | 5.0 – 9.0 (wide operational window) | 6.0 – 7.5 (narrow range) |
| pH Impact on Treated Water | pH drop typically 0.1–0.3 units | pH drop typically 0.5–1.5 units |
| Alkalinity Consumption | Low alkalinity consumption | High alkalinity consumption |
| Need for Alkali Dosing | Usually not required | Often required to correct pH |
| Solubility & Reaction Speed | Instantly soluble, rapid floc formation | Slower hydrolysis and floc formation |
| Floc Characteristics | Dense, compact, fast-settling flocs | Light, bulky flocs |
| Sludge Volume Generated | 20–40% less sludge | Higher sludge volume |
| Residual Aluminum Risk | Lower residual Al due to better coagulation | Higher residual Al if overdosed |
| Performance in Cold Water | Stable performance even below 10 °C | Efficiency drops significantly |
| Dosage Requirement | 20–40% lower dosage | Higher dosage required |
Typical dosage range for PAC: PAC generally requires a lower dosage because it is a pre-polymerized coagulant with higher charge density. In most surface water and wastewater applications, the effective dosage typically ranges between 5–15 mg/L, depending on turbidity, organic load, and alkalinity. For industrial effluent and high-color water, dosage may extend up to 20 mg/L, but still remains lower than alum for similar performance.
Typical dosage range for Aluminium Sulphate: Aluminium Sulphate usually requires a higher dosage as it must first hydrolyze in water to form active aluminum species. Typical operational dosages range from 15–30 mg/L, and in high turbidity or colored water, this can increase further. The need for higher dosing directly increases chemical consumption.
How dosage impacts operational cost: Lower dosage requirements reduce overall chemical consumption, sludge volume, and handling costs. Although PAC may have a higher per-kg price, its lower dosage often results in lower cost per cubic meter of treated water compared to Aluminium Sulphate.
Residual aluminum levels
Effect on water taste and clarity
pH stability after treatment
Sludge handling and disposal impact
| Performance Factor | Poly Aluminium Chloride (PAC) | Aluminium Sulphate (Alum) |
|---|---|---|
| Coagulation & Flocculation Speed | Very fast coagulation due to pre-polymerized aluminum species (Al₁₃). Flocs form within seconds to 1–2 minutes. | Slower floc formation because alum must first hydrolyze in water. Flocs typically form in 3–5 minutes. |
| Floc Strength & Settling | Forms dense, heavy flocs that settle quickly, improving clarifier efficiency. | Forms lighter, bulky flocs that settle slower and may break during agitation. |
| Turbidity Removal Efficiency | Achieves >90–95% turbidity removal even at low dosages (5–15 mg/L). | Achieves 85–90% turbidity removal, usually at higher dosages (15–30 mg/L). |
| Color Removal Performance | Excellent removal of organic color (humic substances), typically 80–95% color reduction. | Moderate to good color removal, typically 60–80%, depending on dosage. |
| Performance in High Turbidity Water (>500 NTU) | Performs consistently without major dosage increase due to strong charge neutralization. | Effective but requires significant dosage increase, increasing sludge volume. |
| Residual Aluminum Control | Lower residual aluminum due to better floc capture and settling. | Higher risk of residual aluminum if overdosed or poorly mixed. |
| Sludge Handling Impact | Produces 20–40% less sludge, easier dewatering. | Produces more sludge with higher moisture content. |
How to choose the right coagulant
Selection depends on water quality variability, treatment objectives, operational cost targets, and infrastructure capability.
Based on raw water quality
For highly variable, cold, or low-turbidity water, PAC performs more reliably. Alum is better suited for stable raw water with predictable characteristics.
Based on plant capacity and design
High-capacity plants with limited settling time benefit from PAC’s fast floc formation, while older plants designed for alum may continue using Aluminium Sulphate.
Based on operating cost and efficiency
PAC offers lower total treatment cost when sludge disposal, chemical dosing, and pH correction are considered. Alum may appear cheaper initially but increases downstream costs.
Based on availability and handling ease
PAC (especially liquid form) is easier to dose and handle with less dust and safety risk. Alum requires careful handling and additional chemicals for pH control.
In India’s industrial chemical markets, Poly Aluminium Chloride (PAC) and Aluminium Sulphate (Alum) are traded widely in bulk quantities for municipal, industrial effluent, and drinking water treatment. Price trends fluctuate with raw material costs, energy prices, and seasonal demand, but recent wholesale ranges provide a useful benchmark for bulk buyers.
For PAC (liquid form) — widely used due to ease of dosing and minimal handling risk — typical wholesale prices in 2025–2026 for bulk orders (5 MT and above) range between ₹90 to ₹130 per kg (bulk tankers or drums). Liquid PAC commands a slight premium due to manufacturing complexity and logistics.
In PAC powder form, which is lighter to transport but requires on-site dissolution, wholesale rates generally range from ₹70 to ₹110 per kg for large contracts across India. Powder PAC offers cost advantages where on-site formulation and storage infrastructure exist.
For Aluminium Sulphate (Alum), a more traditional coagulant, current bulk prices (2025–2026) typically fall in the range of ₹28 to ₹45 per kg, depending on grade (technical grade vs water treatment grade), region, and order volume. Because Alum is manufactured and distributed at scale in India, it retains a relatively lower base price.
Reasons for price fluctuations include raw material costs (bauxite, sulfuric acid, energy/fuel), transportation and logistics (road and rail freight), seasonal demand from public utilities, and variations in manufacturing capacity. Market-wide demand spikes during summer and monsoon post-harvest periods often push prices upward due to higher consumption in water treatment and industrial reuse applications.
Shiv Chemicals has emerged as a trusted partner for bulk procurement of water treatment chemicals, including Poly Aluminium Chloride (PAC) and Aluminium Sulphate, by aligning quality, reliability, and service. With a robust manufacturing and distribution framework, Shiv Chemicals ensures that buyers receive consistent product formulations tailored to municipal, industrial, and effluent treatment requirements. This reliability extends from batch-based quality testing to timely dispatch and delivery coordination across India’s major industrial hubs.
One of the key strengths of Shiv Chemicals lies in its consistent quality control and adherence to regulatory and technical standards. Each shipment is backed by comprehensive laboratory documentation that confirms active aluminum content, solubility characteristics, and compliance with BIS and environmental norms. Bulk buyers, particularly large water utilities and industrial treatment plants, benefit from predictable performance that minimizes process disruptions and supports operational targets.
In addition to quality and reliability, Shiv Chemicals offers competitive wholesale pricing optimized for large-volume contracts. These pricing structures, combined with flexible packaging and supply options, help buyers manage treatment costs effectively. Supported by a dedicated technical team and supply chain professionals, Shiv Chemicals delivers end-to-end support.
