Application Of Activated Carbon Adsorption Technology For Removing Trihalomethanes From Water

Trihalomethanes (THMs) are common disinfection byproducts (DBPs) formed during the final stage of water treatment using free chlorine for disinfection. This research was conducted to evaluate the effectiveness of activated carbon (AC) adsorption technology for removing the THMs from water. The LLE-GC-ECD method was first developed for accurate measurements of THM species in aqueous samples. Extentsive equilibrium adsorptive capacity (isotherm) experiments were then performed on up to 11 granular and powdered AC samples to compare their THM capacities and the four adsorptive capacity indicators. Series of continuous flow adsorption breakthrough experiments were conducted employing the efficient micro column rapid breakthrough (MCRB) method to confirm the isotherms results for chloroform and bromoform.The isotherm results the order of AC samples'capacities for THMs are in general agreement of the order of their phenol numbers; for example, Coconut ACs having the highest phenol numbers had higher capacities for chloroform, followed by Bamboo ACs while the Coal AC was the worst. The chloroform MCRB data showing that the Bamboo1, Fruit 1 adsorbers were effective for the longest treatment time and that Bamboo1 and Coal 1 accomplished higher capacity utilization than others have confirmed the relative capacity of the isotherm runs and the faster adsorption rate of AC samples with high tannic acid number. The two beds in series treatment mode is desirable to increase the capacity utilization especially when Coconut AC is employed; the Coconut1 capacity for chloroform would increase from 18% to 51% when the discharge limit was relax from c/c0=0.05 to 0.5 which is the common practice for adsorption treatment employing two serial adsorbers. With proper design and operation of the adsorption system, Coconut Carbon and Bamboo Carbon are likely to be more attractive for removing the THMs in the water treatment plant.The AC's adsorption capacity increased from chloroform, bromodichloromethane, bromochloroacetonitrile to bromoform due primarily to the lower water solubility of the THMs. The nitic acid treatment increased the number of oxygenated groups on the surface of AC particles resulting in lower capacities for THMs.