Combinations of Activated Carbon with Different Treatment Methods
Activated carbon can effectively remove many pollutants in water, but its microporous structure is not conducive to the removal of macromolecular organic pollutants. So, combinations of activated carbon adsorption with other water treatment technologies are often used to produce better treatment effects. The following will introduce several common activated carbon adsorption combined processes.
Ozone and activated carbon combined process
As a strong oxidant, ozone can decompose macromolecular organic matter in water into small molecular organic matter, increase the possibility of organic matter entering the micropores of activated carbon, give full play to the adsorption surface of activated carbon, and extend the life of activated carbon. At the same time, ozone also plays a bactericidal effect that activated carbon does not have. The activated carbon can effectively adsorb a large number of intermediate products produced by ozone in the oxidation process, including trihalomethanes (THMs) and their precursors that can not be removed by ozone, and ensure the biological stability of the effluent. Therefore, the ozone-activated carbon combined process has been widely used in the world since its use in 1961.
Potassium permanganate (KMnO4) and activated carbon combined process
Potassium permanganate is also a strong oxidant, which can degrade organic matter and inhibit the growth of algae. As the dosage and the contact time increase, its water treatment effect is more ideal. Powdered activated carbon has a good adsorption effect on small molecular organics (molecular weight smaller than 3000) in water, which is beneficial to remove color and smell in the water purification process. The combination of the two is often used in the conventional water purification process.
Biological activated carbon process
Biological activated carbon technology uses granular activated carbon as a carrier to form a biofilm on the surface of activated carbon by enrichment or immobilization of microorganisms, and uses the adsorption of activated carbon and the biodegradation of the biofilm to jointly remove pollutants in the water. Compared with ordinary biological methods, pollutants stay longer under the same hydraulic retention time (HRT), so the treatment effect is better. Meanwhile, the degradation of microorganisms can also regenerate activated carbon, with the regeneration rate as high as about 20%. The activated carbon can also reduce the impact of harmful substances in wastewater on microorganisms, thereby eliminating the adverse effects of biodegradation. However, prechlorination treatment should be avoided when using this technology for advanced drinking water treatment, otherwise, microorganisms cannot grow on activated carbon.
Powdered activated carbon and activated sludge combined process
The process is to add powdered activated carbon to the activated sludge aeration tank to form biological activated carbon, and use the synergistic effect of adsorption and degradation to remove organic pollutants. On the one hand, it can remove the organic matter that is difficult to remove by the activated sludge method and improve the removal efficiency of activated sludge; on the other hand, it can make the activated sludge have excellent compactness, thereby overcoming sludge expansion.
Activated carbon and ultrafiltration combined process
The remarkable advantage of the ultrafiltration process is that it can effectively remove pathogenic bacteria in water, but its thorny problem is membrane blockage and membrane fouling. The combined process of activated carbon-ultrafiltration membrane overcomes the weakness of the single treatment method. In the combined process, the use of activated carbon for pre-treatment of the water can remove various organic compounds, most of the turbidity and color in the water, which greatly alleviates the blockage and fouling problems in the subsequent ultrafiltration process, and prolong the service life of the membrane, thereby the post-treatment with membrane can solve the problem of bacteria and ensure the quality of the effluent.
Electrolysis with activated carbon
Electrolysis with activated carbon method uses the conductivity of activated carbon as an electrode. The activated carbon first adsorbs pollutants, and then undergoes oxidative degradation to remove impurities in the water. It is a process that combines flocculation and free radical reactions. The strong adsorption capacity of activated carbon can greatly improve the utilization efficiency of oxidizing products. Under the same conditions, activated carbon fixed-bed electrolyzers can save 30%-40% of power consumption compared with conventional electrolyzers.