Application of Enhanced BAC Process for Improving Drinking Water Treatment Efficiency
Authors: Son Heejong , Jung Eun-Young , Yoom Hoon-Sik , Kim Sang-Goo , Maeng Sung Kyu 
Published: July 2020

Objectives:In this study, we compared the properties of the attached biofilm with the ability to remove biodegradable dissolved organic carbon (BDOC) in the conventional BAC (biologically activated carbon) process and the enhanced BAC process with phosphorus and hydrogen peroxide added. The enhanced BAC process was designed to increase the operational efficiency of the old O<sub>3</sub>/BAC process by evaluating the applicability of large-scale water treatment facilities located downstream of the Nakdong River.Methods:The granular activated carbon which was used for 2 years in the O<sub>3</sub>/BAC process in the water treatment plant located downstream of the Nakdong River was used in this experiment. During the experiment period, the ozone dosage was fixed at 1 mg･O<sub>3</sub>/mg･DOC. Four acrylic columns with an inner diameter of 20 cm and a height of 250 cm were prepared. Empty bed contact time (EBCT) was fixed at 20 minutes and backwash was performed once a week. The four BAC columns are conventional BAC (control-BAC), enhanced BAC with hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>+BAC), enhanced BAC with phosphorus (PO<sub>4</sub>-P+BAC), and enhanced BAC with phosphorus and hydrogen peroxide together (PO<sub>4</sub>-P+H<sub>2</sub>O<sub>2</sub>+BAC). In the case of enhanced BAC with PO<sub>4</sub>-P added, PO<sub>4</sub>-P was added with a concentration of 0.010 mg/L in the influent, and in BAC with H<sub>2</sub>O<sub>2</sub>, H<sub>2</sub>O<sub>2</sub> was added with a concentration of 1 mg/L to the influent.Results and Discussion:As a result of evaluating the recovery ability of the damaged biofilm, there was no difference in the biomass recovery rate in the H<sub>2</sub>O<sub>2</sub>+BAC compared to the control-BAC, but the biomass was rapidly recovered in the PO<sub>4</sub>-P+BAC. Considered the biomass and activity of the attached biofilm after the ability to remove organic substances reached a steady state, the biomass and activity in the entire filter layer of the PO<sub>4</sub>-P+BAC increased by 20 to 86% and 7 to 14%, respectively, compared to the control-BAC. In the H<sub>2</sub>O<sub>2</sub>+BAC, only the activity increased by 3~11% and In the PO<sub>4</sub>-P+H<sub>2</sub>O<sub>2</sub>+BAC, biomass and activity were high, about 27 to 87% and 8 to 20%, respectively. In the H<sub>2</sub>O<sub>2</sub>+BAC, the BDOC removal rate was higher than the control-BAC by 20%, and in the PO<sub>4</sub>-P+BAC, the BDOC removal rate increased by more than 100%. Detached total cell counts (TCC) in the control-BAC effluent was 41.7×10<sup>6</sup> cells/mL on average, and in the H<sub>2</sub>O<sub>2</sub>+BAC, TCC was reduced by 49% compared to control-BAC and decreased by 67% and 85% in the PO<sub>4</sub>-P+BAC and the PO<sub>4</sub>-P+H<sub>2</sub>O<sub>2</sub>+BAC effluent. It means the biofilm of the enhanced BAC process was evaluated more stably than control-BAC.Conclusions:The biomass and the activity of the attached biofilm in the BAC process, are one of the important factors that determine the ability to remove contaminants. The enhanced BAC process combined PO<sub>4</sub>-P with H<sub>2</sub>O<sub>2</sub> was very effective in enhancing the biomass and the activity of the attached biofilm. The PO<sub>4</sub>-P added enhanced BAC was more effective in terms of biomass, BDOC removal rate, and biofilm stability than the H<sub>2</sub>O<sub>2</sub> added enhanced BAC. The enhanced BAC combined PO<sub>4</sub>-P with H<sub>2</sub>O<sub>2</sub> showed a slight increase additional efficiency compared to the PO<sub>4</sub>-P added BAC.