Activated Carbon Filter

Activated Carbon Filter

1 Introduction

A tank-type filtration device, typically with a stainless steel or fiberglass shell, filled with activated carbon to filter free substances, microorganisms, and some heavy metal ions from water, effectively reducing water color.

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Activated carbon filters are commonly used water treatment equipment. As pretreatment in desalination systems, they adsorb residual chlorine that previous filtration cannot remove, effectively extending the lifespan of downstream equipment, improving water quality, preventing pollution—especially protecting reverse osmosis membranes and ion exchange resins from free chlorine poisoning—and adsorbing small organic molecules and other pollutants that leak from previous stages. They significantly remove odors, colloids, pigments, heavy metal ions, and reduce COD. They further lower the SDI value of RO feed water, ensuring SDI < 5 and TOC < 2.0 ppm.

2 Equipment Selection

Design parameters for activated carbon filters should be based on influent water quality, treatment requirements, and the type of activated carbon, referencing operational experience from similar power plants or through testing, adhering to the following principles:

1. Select activated carbon with good mechanical strength, fast adsorption speed, and high adsorption capacity.

2. Filtration rates for activated carbon filters can refer to the table below.

When placed after hydrogen ion exchangers, the filtration rate can be appropriately increased.

3. Activated carbon filters should undergo regular backwashing.

3 Application Range

Widely applicable in industries such as food, pharmaceuticals, electronics, chemicals, and industrial wastewater.

1. Meets the filtration accuracy requirements of hydraulic systems, blocking certain impurities from entering the system.

2. Filter elements should have sufficient strength to avoid damage under pressure.

3. High flow capacity with low pressure loss.

4. Easy to clean and replace. Installation points:

4 Precautions

1. Suction oil coarse filter at the pump inlet.

2. High-pressure oil filter on the pump outlet line.

3. Low-pressure oil filter on the system return line.

4. Bypass filtration system installed outside the system.

5. Since the adsorption capacity of activated carbon has a saturation point, when saturation is reached, the adsorption function significantly declines. Therefore, monitor adsorption capacity and replace activated carbon or restore it via high-pressure steam disinfection.

Notably, during initial use (or after replacement), fine powdered activated carbon may enter the reverse osmosis equipment system with water flow, clogging the RO membrane channels, increasing operating pressure, reducing water production, and raising system pressure drop. This damage is hard to reverse with常规清洗. Thus, activated carbon must be thoroughly rinsed to remove fine powder before sending filtered water to the subsequent RO system.

5 Features

Product

1. High efficiency: Operates continuously for 24 hours without停机反冲洗.

2. Low operating cost: No need for high-head, large-flow backwash pumps.

3. Low maintenance cost:除了石英砂滤料外, no moving parts, low failure rate,节省维护费用.

4. Low initial investment: No separate coagulation or clarification tanks needed, nor backwash pumps or electric/pneumatic valves, reducing engineering and initial investment.

5. Low head loss: Single filter media with timely cleaning ensures head loss ≤0.5m.

6. Lenient influent quality: Can handle 150 mg/L SS long-term and 300 mg/L SS short-term冲击 without affecting effluent quality.

7. Stable effluent quality and good filtration: Timely media cleaning ensures high-quality, stable output without periodic fluctuations.

8. Easy expansion: Modular design allows flexible addition or reduction of filters based on water volume changes.

9. Small footprint, aesthetic appearance: Integrates traditional three-stage再生水 treatment into one unit, saving 70-80% space; compact and visually appealing.

6 Principle

Working Principle

Activated carbon adsorption works by forming an equilibrium surface concentration on its particles. Particle size affects adsorption: smaller particles have larger surface area, so powdered carbon has the best adsorption but is hard to control and rarely used. Granular carbon, being less mobile, doesn’t clog easily, has strong adsorption, and is easy to replace.

Adsorption capacity is proportional to contact time; longer contact improves water quality. Note: Water should flow slowly through the filter layer. New carbon must be washed before first use to avoid black water output. Add 2-3 cm sponge layers at top and bottom to block large impurities like algae. Replace carbon every 2-3 months if efficiency drops, and change sponge periodically.

Activated carbon filter pressure vessels contain coarse quartz sand support layers and high-quality activated carbon.

Initially, adsorption is high as organic impurities are adsorbed into the carbon pores. Over time, adsorption capacity declines. If water is turbid with high organic content, carbon loses function quickly, so regular cleaning or replacement is needed.

Adsorption Principle

Activated carbon consists of fine particles with large surface area and tiny pores—capillaries—that provide strong adsorption. The large surface area allows full contact with gases (impurities), which are adsorbed upon encountering capillaries, purifying the substance. BET method is essential for accurate surface area measurement; direct comparison methods are less reliable. BET is the standard internationally and per Chinese GB/T 19587-2004 for gas adsorption-based surface area determination. Testing can be time-consuming; automation reduces human error and improves precision. The F-Sorb 2400 is a fully automated, intelligent device for BET testing, offering high consistency and stability.

Designed based on user feedback, this product improves water inflow and drainage directions for better purification, widely welcomed. It is essential for treating drinking and food water.清水 with turbidity <5 mg/L becomes clear, tasteless, non-toxic, sterile, odorless, and drinkable directly, meeting national drinking water standards.

Removes color, odor, mercury, lead, cadmium, zinc, iron, manganese, chromium, and other heavy metals, as well as arsenic, cyanides, sulfides, residual chlorine, and radioactive substances like strontium and radium. Kills bacteria and E. coli. Ideal for drinking water, food, beverages, pharmaceuticals, and chemicals. Simple structure, easy operation. Suitable for high-water-quality needs in food,饮料,化工, enterprises, hotels, military, stations, ports, as industrial and domestic water supply equipment.

7 Filtration Process

Inside the adsorber, the bottom is filled with 0.15~0.4m quartz sand as support (20-40mm grains), topped with 1.0-1.5m granular activated carbon as the filter layer, typically 1000–2000mm thick.

Before filling, test quartz sand for stability by soaking for 24 hours: total solids increase ≤20mg/L, oxygen demand increase ≤10mg/L, silica increase ≤10mg/L in alkaline medium.

After cleaning, load quartz sand and rinse从上到下, dirty water discharged from bottom until clear. Then load activated carbon and rinse从下到上, dirty water from top.

Mainly removes macromolecular organics, iron oxides, and residual chlorine, which can poison ion exchange resins and damage membranes, leading to RO failure.

8 Usage

Works via the carbon bed. Activated carbon particles have numerous micropores and huge surface area, providing strong physical adsorption. Water passes through, and organic pollutants are effectively adsorbed. Oxygen-containing functional groups on the carbon surface enhance adsorption of organic pollutants.

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Main factors affecting adsorption and lifespan: type and concentration of pollutants, residence time in filter material, air temperature, and humidity.

Select filter type and carbon based on pollutant种类, concentration, and air volume.

Install efficient dust filters upstream (≥F7) to prevent dust clogging carbon, and downstream to trap carbon dust.

Appearance Diagram

9 Adopted Process

Mainly removes organic matter, colloidal silicon, residual chlorine (Cl₂), with strong adsorption of odors, color, and heavy metal ions. In beverages, improves taste.

Used in mineral water, pure water processes, swimming pools, for purification, deodorizing, dechlorination. Shell made of stainless steel or carbon steel, filled with water purification activated carbon.

Comes in tank type (with carbon granules and quartz sand, high efficiency but harder regeneration) and tube type (carbon with binder, sintered, easy use and regeneration).

10 Function

Operates via carbon bed. Particles with microporous structure and large surface area provide strong physical adsorption. Adsorbs organic pollutants from water. Oxygen functional groups aid adsorption. As pretreatment in desalination, protects downstream equipment, improves water quality, prevents pollution, especially free chlorine damage to RO membranes and ion exchange resins.

11 Influencing Factors

Main factors affecting adsorption:

① Properties of activated carbon: Larger surface area increases adsorption; non-polar, adsorbs non-polar or low-polar adsorbates; particle size, pore structure, and surface chemistry matter.

② Properties of adsorbate: Depends on solubility, surface free energy, polarity, molecular size, unsaturation, and concentration.

③ Wastewater pH: Adsorption is generally higher in acidic than alkaline solutions. pH affects adsorbate state and solubility, influencing adsorption.

12 Selection Tips

For high humidity/temperature environments, choose filters with heat-/moisture-resistant paper, separators, and frame materials. In biological/medical clean rooms, use metal frames to prevent bacterial growth; avoid wooden frames.

Usage Instructions:

1. Equipment Selection: Determine system name, influent/effluent quality, pressure, automation level.

2. Installation: ① Install water collection system, open top cover. ② Remove water distribution system. ③ Load washed large then small gravel (support layer). ④ Load washed activated carbon (filter layer). ⑤ Install top cover with seals, tighten. ⑥ Connect piping. Ensure seals are properly placed to prevent leaks.

3. Operation: ① Power on, check inlet valve and pump, ensure inlet tank at medium level. ② Run: a. Open upper inlet V2, lower drain V5, and inlet V1. b. Start pump. When V5 outputs water, adjust flow to rated value. When water is clear, open outlet V7, close V5, supply to next equipment. ③ Backwash: When pressure difference increases by 0.05–0.07 MPa, backwash: a. Open lower inlet V4, inlet V1, upper drain V3. b. Start pump, maximize flow. Backwash 20–45 min. Stop pump, close valves. ④ Rinse: After backwash, rinse: a. Open upper inlet V2, inlet V1, lower drain V5. b. Start pump, control flow to normal rate. Rinse 15–30 min until drain water is clear. Stop pump, close valves.

Main technical parameters:

Working pressure: 0.05 MPa–0.6 MPa

Working temperature: 5°C–40°C (custom for special temperatures)

Flow rate: 0.5 m³/h –125 m³/h

Operation: Manual or automatic control

Specifications: Ø173–Ø3500

Filtration speed: 5 m/h–12 m/h, max 15 m/h

Material: 304, 316L, Q235 rubber-lined or epoxy-coated

Rinse for about 15–30 minutes until the lower drain water is clear. Then turn off the pump and close all valves.