What factors affect the service life of activated carbon?

1. Raw water quality

1. Free residual chlorine: Activated carbon dechlorination is a chemical reaction. The higher the residual chlorine, the faster the carbon consumption and the shorter the lifespan.

2. Organic matter (TOC, humic acid, color): The more organic matter, the faster the adsorption saturation.

3. Inlet turbidity, suspended solids: Suspended solids cover the surface of the carbon particles and block the micropores; they also accelerate the wear and pulverization of the carbon particles. The pre-multiple media filter has poor effect and the lifespan of the activated carbon becomes shorter.

4. Iron, manganese oxides: They will deposit on the surface of the carbon, blocking the micropores and reducing the adsorption capacity.

2. Quality of activated carbon itself

1. Material: Coconut shell activated carbon has well-developed micropores and a high iodine value (≥1000mg/g), with a lifespan longer than fruit shell activated carbon and coal-based column-shaped activated carbon.

2. Iodine adsorption value: The higher the iodine value, the greater the adsorption capacity and the longer the lifespan.

3. Mechanical strength: Activated carbon with low strength is prone to fragmentation and pulverization, causing a rapid increase in pressure difference and premature failure.

3. Equipment design parameters

1. Bed contact time (EBCT): EBCT ≥ 2 to 5 minutes. The water and carbon particles have sufficient contact, resulting in high carbon utilization and longer lifespan; if the filtration speed is too high or the EBCT is insufficient, early penetration is likely to occur.

2. Carbon layer thickness: The higher the carbon layer, the greater the total adsorption capacity and the longer the service life.

4. Operating conditions

1. Filtration speed: The higher the filtration speed, the greater the water shear force, and the carbon is more likely to be worn; at the same time, the residence time is shorter, and organic matter and residual chlorine are more likely to penetrate.

2. Water temperature: High water temperature accelerates the diffusion of organic matter, reducing the adsorption capacity; high temperature is also more likely to breed microorganisms and form a biofilm covering the micropores.

3. pH: In alkaline conditions, the adsorption effect of some organic matter is worse, reducing the adsorption capacity of the carbon.

5. Microorganisms and maintenance management

1. Biofilm growth: Activated carbon is very suitable for microbial attachment. The biofilm wraps around the carbon particles, blocking the micropores, and at the same time increasing the risk of biological contamination in the subsequent RO process.

2. Backwashing operation

- Appropriate backwashing cycle and moderate intensity: Remove suspended solids and extend the lifespan of the carbon;

- Long-term no backwashing: Accumulated dirt blocks the carbon layer;

- Excessive backwashing intensity: Scrubbing and crushing the carbon particles, increasing the amount of carbon powder.