Efficiency of Pre-chlorination/Powdered Carbon Process in Controlling Algal Risks in Raw Water

Abstract:

Five powdered activated carbons （PACs） were selected to carry out the study on the preference of powdered activated carbons for use in conjunction with pre-chlorination. The results show that all five powdered activated carbons can effectively adsorb trichloromethane， and the changes of adsorption rate are in accordance with the proposed second-order kinetic law， and the regression correlation coefficients are all greater than 0.99， with the best adsorption effect of wood activated carbon （k=0.419 12） and coconut shell activated carbon Ⅰ （k=0.386 93）. The presence of residual chlorine decreased the rate of adsorption of trichloromethane by powdered charcoal， but it did not change the order of superiority of the adsorption effect of each powdered activated carbon. In raw water background， coconut shell activated carbon I and wood activated carbon had more than 60% removal efficiency for 2-methylisopropanol（2-MIB）， more than 90% for Geosmin （GSM），and the highest adsorption efficiency for trihalomethanes （28±5%）. In the combined chlorine-powdered activated carbon process， the order of the advantages and disadvantages of the different activated carbon types did not change， with wood activated carbon and coconut shell activated carbon I remaining the most effective， and coal activated carbon performing poorly. Correlation analysis of powder carbon properties with the removal performance of trichloromethane and olfactory substances found that the correlation of average pore size， iodine value， methylene blue value and total pore volume was more significant， and the correlation coefficient of average pore size was the highest， and the average pore size can be taken as an important reference factor in the comparison of high-quality powdered activated carbon.

Key words:raw water;pre-chlorination;powered activated carbon;odorous substances;disinfection by-products