PAC Water Treatment: Standard Usage Guide for Loc Thien Nationwide

In industrial water and wastewater treatment systems, PAC (Poly Aluminum Chloride) PAC is currently the most widely used coagulant chemical — from urban water supply stations, textile and dyeing factories, paper mills, and aquaculture to domestic wastewater treatment plants. Its superior advantages over traditional aluminum sulfate in terms of flocculation speed, operating pH range, and sludge production have made PAC the default choice in many new projects.

However, PAC cannot be used indiscriminately — too low a dose will result in unclear water, while too high a dose will increase costs and may cause the solution's pH to deviate from the operating range. Based on Loc Thien's practical experience in treating textile and paper wastewater, most poor coagulation problems stem from two causes: incorrect dilution concentration or skipping the Jar Test step before adding it to the actual system.

This article provides a comprehensive overview: what PAC is, how to mix it, recommended dosages for different water sources, technical specifications to check when purchasing, and safety precautions — enough data for operations engineers and B2B purchasing teams to start working immediately.

What is PAC for water treatment?

PAC is Poly Aluminum Chloride

PAC—an abbreviation for Poly Aluminium Chloride—is an inorganic polymerized aluminum salt with the general formula [Al₂(OH)ₙCl₆₋ₙ]ₘ. Compared to alum (aluminum sulfate), PAC has a higher degree of polymerization, giving it a stronger positive charge when dissolved in water, thereby accelerating the neutralization of negatively charged colloids and forming larger flocs in a shorter time. PAC is produced in two main forms: powder and liquid, with alkalinity typically ranging from 70–90% depending on the manufacturer and target application.

In Vietnam, PAC is managed by Circular 49/2020/TT-BCT Regarding the PAC quality technical standards, this is an important legal basis when purchasing materials for public water supply projects or wastewater treatment plants according to state standards.

What is the difference between PAC powder and PAC liquid?

The two most common forms of PAC on the market have significantly different operating characteristics. Powdered PAC typically has a higher Al₂O₃ content (usually ≥ 28–32%), is easy to transport, comes in 25 kg bags, and is suitable for remote projects or limited storage space. Liquid PAC has a lower Al₂O₃ content (typically around 10–11%), is ready to be added directly to the system without mixing, and is suitable for stations with automatic dosing tanks.

• PAC powder: Al₂O₃ ≥ 28–32%, packaged in 25 kg bags, requires dilution to a 5–10% solution before use, easy to store if kept dry.
• Liquid PAC: Al₂O₃ at approximately 10–11%, for direct use or dilution, suitable for automated systems, concentration should be checked batch by batch (COA/MSDS).
• Note: All specific parameters for each batch must be compared with the COA (Certificate of Analysis) and MSDS provided by the manufacturer.

The coagulation and flocculation mechanism of PAC

When PAC dissolves in water, the highly positively charged Al³⁺ ions and aluminum polymer attract and neutralize the negatively charged suspended colloidal particles (clay, organic matter, bacteria, pigments). After neutralization, the colloidal particles lose their electrostatic repulsion and begin to collide and clump together—a process called "flocculation." The resulting flocs settle (or float if combined with dissolved gases), and are then separated from the water using sedimentation or flotation tanks.

The effectiveness of this mechanism depends directly on pH, temperature, stirring speed, and PAC dose — this is why the Jar Test cannot be overlooked before putting it into actual operation.

Advantages of PAC over traditional aluminum sulfate

Operates over a wide pH range.

Aluminum sulfate Traditional coagulants perform best within a narrow pH range of approximately 6,5–7,5; outside this range, coagulation efficiency decreases sharply and the amount of sediment increases. PAC, thanks to its polymer structure and higher alkalinity (basicity 70–90%), allows for stable operation over a significantly wider pH range, making it suitable for various water sources with pH fluctuations depending on the season or industrial wastewater load.

Produces less sludge, settles quickly.

The floc produced by PAC is typically denser, larger, and settles faster than that produced by aluminum sulfate floc. This means less sludge volume is generated, saving sludge treatment costs and reducing the frequency of sludge removal from settling tanks. In the practical operation of textile dyeing wastewater treatment systems in Binh Duong and Dong Nai provinces, which Loc Thien has advised on, the amount of dry sludge after pressing decreased by approximately 15–25% when switching from aluminum sulfate to PAC (actual results vary depending on the system and are not guaranteed values).

Save operating costs

Thanks to its higher coagulation efficiency per unit Al₂O₃, the required PAC dose is typically lower than that of an equivalent aluminum sulfate dose. When calculating the total cost including chemicals, sludge treatment, and stirring energy, PAC usually results in a lower overall operating cost (OPEX). However, this is a qualitative estimate—actual results require Jar Test and system-specific cost analysis.

What types of water is PAC used for?

Water supply, domestic water

PAC is the preferred coagulant in urban and rural water treatment plants due to its high efficiency in removing turbidity, color, and bacteria. For domestic water, PAC must meet the standards for use in drinking water treatment — suppliers must be required to present the relevant licenses and certifications as stipulated by the Ministry of Health.

Typical dosages for feedwater range from 1–10 g/m³ depending on the turbidity of the water source, and must be confirmed by a Jar Test with actual source water before being applied to the system.

Industrial wastewater

This application accounts for the largest share in the B2B sector. Wastewater treatment Textile dyeing, paper, food, brewing, or industrial wastewater treatment can all utilize PAC in the coagulation-flocculation stage. The dosage in industrial wastewater is usually much higher than in tap water, ranging from 20 to several hundred g/m³ depending on the pollution load. Combined with... cationic polymer Using anions to increase sedimentation efficiency is a common practice in operation.

Swimming pool water, pond water, aquatic life

PAC is also used to clarify swimming pool water (in combination with chlorination), treat ornamental pond water, and improve water quality in aquaculture. The quality and dosage requirements of PAC vary depending on the application. Technical consultation is necessary before application, especially in fish and shrimp ponds where incorrect dosage can negatively impact aquatic organisms.

Instructions on how to properly mix PAC

Prepare the water and equipment.

Use clean water (not seawater or contaminated water) for mixing. Containers should be HDPE plastic containers or acid-resistant stainless steel; avoid galvanized or aluminum containers as PAC is slightly acidic and can corrode them. A stirring rod or slow-to-medium speed mixer is required. Before mixing, read the product label and MSDS to understand the hazard levels and necessary protective equipment.

Dilute powdered PAC at a concentration of 5–10% or 10–20% depending on the purpose.

To prepare a 10% PAC solution from powder: weigh 1 kg of PAC powder, slowly pour it into 9 liters of clean water (do not pour it in reverse – i.e., do not pour water into the powder), and stir until completely dissolved. For a 5% solution, use 0,5 kg of powder mixed in 9,5 liters of water. Higher concentrations (15–20%) are suitable for low-flow metering systems; lower concentrations allow for more even dispersion in rapid-stirring tanks.

1. Pour clean water into the mixing container first.
2. Weigh the powdered PAC according to the target ratio.
3. Slowly pour the PAC powder into the container of water, stirring constantly.
4. Stir continuously for about 5–10 minutes until the solution is homogeneous, clear, or pale yellow.
5. Allow to settle if any undissolved sediment remains before pumping into the system.

Add the chemicals and stir.

PAC should be injected at a point with high mixing speed (rapid mix tank) to ensure even dispersion before the solution moves to the slow mixing tank (flocculation). The mixing speed in the flocculation tank needs to be adjusted appropriately: excessive mixing will break up the flocs that are forming. Peristaltic metering pumps or diaphragm pumps are common choices for precise flow control.

Jar Test to determine the optimal dose

Jar testing is an essential step before actual operation or when changing the input water source. The basic procedure is as follows: prepare six 1-liter beakers, fill with the water to be treated, add PAC in increasing increments (e.g., 2 / 4 / 6 / 8 / 10 / 12 mg/L), stir quickly for 2 minutes → stir slowly for 15 minutes → let settle for 30 minutes, then measure turbidity and observe the floc. The PAC dose that produces the lowest turbidity and best floc is the optimal dose for practical application.

Recommended PAC dosage varies depending on the water source.

The values ​​below are Reference dose Based on practical experience and technical documentation. Optimal dosage for each specific system. Must be verified by Jar Test with actual water samples.

Low, medium, and high turbidity levels.

For water supply, the PAC dosage depends primarily on turbidity (NTU) and organic matter content. Low turbidity water (<50 NTU) typically requires 1–4 g/m³; medium turbidity water (50–200 NTU) requires 5–6 g/m³; high turbidity water (>200 NTU, during flood season) may require 7–10 g/m³ or higher. Water with high organic matter content (high color, high DOC) requires higher doses because PAC is partially consumed by dissolved organic matter.

Domestic and industrial wastewater

Domestic wastewater typically requires 20–50 g/m³; industrial wastewater (textile dyeing, paper, food) may require 50–200 g/m³ or more depending on the influent SS and COD loads. In practice, Loc Thien often recommends combining PAC with flocculant (polymer) to increase cotton size and reduce the total PAC dose required.

When should the dose be increased/decreased?

If the flocs are small, settle slowly, and the water after settling remains turbid: increase the PAC dose or check the pH, and consider adding more polymer. If the water after settling has a white film, the pH drops abnormally, or there is too much sludge and the water still does not meet the requirements: recheck the COA PAC (is the Al₂O₃ content correct?), check the dosing point and stirring regime. Note the seasonal change: water in the rainy season is usually turbider, so the dose needs to be adjusted upwards compared to the dry season.

Technical specifications of PAC need to be checked before purchase.

Al₂O₃ content

This is a key indicator determining the effectiveness of coagulation and the actual cost per unit of Al₂O₃. Powdered PAC for water supply/wastewater typically has Al₂O₃ ≥ 28–30% (according to current standards and market practices); some high-grade types reach 31–32%. However, the specific content for each production batch needs to be confirmed through a COA/MSDS provided by the manufacturer — one should not rely solely on the supplier's quoted parameters without accompanying certification.

Insolubility, pH of solution

Low insolubility is a sign of good quality PAC, which is less likely to clog dosing pumps. The pH of the diluted solution (5–10%) is usually between 3,5–5 depending on the type—a slightly acidic environment, so caution is needed when in contact with skin and eyes. Water treated with PAC may have a slightly lowered pH; if the system requires a tightly controlled effluent pH (e.g., according to QCVN 40:2011/BTNMT), monitoring and neutralization steps are necessary.

Color, moisture content, packaging specifications

High-quality PAC powder is typically lemon yellow to light yellow in color and free of lumps. Dark brown, dull colors or large lumps indicate poor storage or stale stock. High moisture content reduces the actual Al₂O₃ content. Standard PAC powder is usually packaged in 25 kg bags with an inner PE liner to protect against moisture; check that the packaging is intact and has complete labels before accepting the goods.

PAC technical specifications table for reference:

Safety precautions, storage, and chemical combinations.

PPE and safe handling

PAC is a mild acid chemical that can irritate skin and eyes upon direct contact. When mixing and dispensing PAC powder, wear safety glasses, chemical-resistant gloves, and a dust mask (PAC powder can irritate the respiratory tract if inhaled). In case of skin or eye contact, rinse immediately with plenty of clean water and refer to the MSDS. Do not inhale or blow PAC powder by mouth.

Mixing equipment, dosing pumps, and piping in contact with PAC should be made of acid-resistant materials such as HDPE, PVC, or 316L stainless steel. Absolutely avoid using aluminum tanks or galvanized sheet metal equipment that are not acid-resistant.

Store in a cool, dry place away from sunlight.

PAC powder is highly hygroscopic—leaving the bag exposed to humidity for just a few hours will cause it to clump. Store in a cool, dry place, with pallets at least 10 cm off the floor, and avoid direct sunlight. After each use, seal the bag tightly with a clip or secure tie. The typical shelf life is 12–24 months from the date of manufacture if stored properly (confirmed by lot label).

Combine polymers when increased efficiency is needed.

In many industrial wastewater applications, using PAC alone is insufficient to meet effluent standards for SS and turbidity, especially when pollutant loads are high or sludge needs to be dewatered quickly. A common solution is to add PAC. cationic polymer After rapid stirring in the tank, increase floc size and settling speed. The PAC:polymer ratio and the order of dosing should be determined through experimentation — do not add PAC and polymer at the same point as they may neutralize each other.

Where can I buy PAC for water treatment, and does it come with a Certificate of Origin (CO), Certificate of Quality (CQ), and VAT?

When purchasing PAC for construction projects, factories, or other projects, there are three crucial B2B factors to ensure in addition to product quality: complete quality documentation, valid VAT invoices, and on-time delivery service. Loc Thien — the operating unit. hoachatcoban.net — We supply PAC powder and liquid to customers nationwide.

Support nationwide delivery

Loc Thien offers nationwide delivery, from the southern provinces to the central and northern regions. Typical delivery times are 1-5 business days, depending on the province and order quantity. For large projects or those with construction schedules, customers should finalize a specific delivery date when placing a deposit to avoid delays.

Quality records and invoices

For each shipment, Loc Thien provides complete COA (Certificate of Analysis), MSDS (Material Safety Data Sheet), CO (Certificate of Origin), and CQ (Certificate of Quality) as requested. Valid electronic VAT invoices are issued for each transaction. This is a basic requirement when accepting chemicals in public investment projects or projects requiring audits of purchase documents.

Consulting on selecting PACs by industry

Loc Thien's technical team provides consulting services to select the appropriate PAC (powder/liquid, Al₂O₃ content, origin) for each specific application: domestic water treatment, industrial water treatment, textile dyeing wastewater, paper mill wastewater, food processing wastewater, or pond water treatment. For the first order or when changing the input water source, the technical team is ready to assist in designing a test jar and advising on the initial dosing dosage.

Frequently Asked Questions about PAC for Water Treatment