The activated carbon wastewater treatment method is one of the adsorption-based wastewater treatment approaches. It involves using activated carbon's properties—such as physical adsorption, chemical adsorption, oxidation, catalytic oxidation, and reduction—to remove various pollutants from wastewater.

For example, the powdered activated carbon treatment method, also known as the biological-physical treatment method or the dosing-aeration method, involves adding powdered activated carbon into the aeration tank. This approach not only maximizes the use of existing wastewater treatment equipment but also enhances treatment efficiency.

The removal of pollutants through this method is generally attributed to the synergistic effects of adsorption and microbial oxidation. The abundant micropores of activated carbon adsorb organic matter and oxygen from the wastewater, providing a high-concentration nutrient source for the growth and reproduction of microbial communities. Enzymes and coenzymes produced during microbial metabolism are, in turn, adsorbed and enriched within the micropores of the activated carbon. Additionally, the prolonged contact time between microorganisms and organic matter on the carbon surface allows even hard-to-degrade organic compounds to be decomposed through biological oxidation.

I. The powdered activated carbon treatment method generally involves three steps:

1. Vigorous mixing to rapidly disperse the carbon into the wastewater;

2. Contact adsorption and oxidation, where the carbon remains suspended in the wastewater for mixed adsorption and oxidation;

3. Liquid-solid separation, where the carbon is separated from the wastewater and subsequently regenerated.

II. The advantages of this method include:

• Effective and relatively stable treatment results;

• Enhanced microbial resistance to organic toxins and heavy metals;

• Formation of cohesive carbon and microbial aggregates, leading to robust and dense sludge, which improves the operational conditions of the activated sludge process;

• Adsorption of surfactants by activated carbon, resolving foam issues in the aeration tank;

• Applicability to treating wastewater with complex compositions and variable concentrations and volumes;

• Low cost of powdered carbon.

However, due to the difficulty in regenerating powdered carbon, its practical application has been limited. In 1972, the successful regeneration of powdered activated carbon using a fluidized bed regeneration furnace provided conditions for its broader application.

The technology of using powdered activated carbon for wastewater treatment employs a single-stage contact system, where mixing, contact reaction, and gravity sedimentation are completed within the same equipment. The carbon remains in the equipment for 2 to 5 days, which facilitates microbial activity and enhances treatment efficiency.

Adding a certain amount of powdered activated carbon to sludge digesters accelerates sludge sedimentation, purifies the supernatant returned to the water treatment system, and improves the efficiency of the water treatment system. Additionally, it promotes the decomposition of solid sludge, eliminates odors, and increases the production capacity of the equipment.