Effect of Phosphate and Hydrogen Peroxide on Bacterial Community and Removal Efficiency of Biological Activated Carbon (BAC) Process for Enhanced Biofiltration

Abstract

Objectives:The correlation between the organic material removal ability of the enhanced BAC process injected by the phosphate (PO4-P) and/or hydrogen peroxide (H2O2) and attached bacterial community was evaluated.Methods:As pilot plant for the purification of raw water downstream of Nakdong river, 4 acrylic columns with an inner diameter of 20 cm and a height of 250 cm were operated at an empty bed contact time of 20 minutes. The four BAC columns are as followed; conventional BAC (control-BAC), enhanced BAC with phosphorus (PO4-P+BAC), enhanced BAC with hydrogen peroxide (H2O2+BAC), and enhanced BAC with phosphorus and hydrogen peroxide (PO4-P+H2O2+BAC). 0.01 mg/L of PO4-P and 1 mg/L of H2O2 were added in influent in the enhanced BAC, respectively. After 18 months of operation, activated carbon was collected from the top of each BAC column and 16S rRNA amplicon sequence analysis was performed.Results and Discussion:The long-term addition of PO4-P and H2O2 contributes the increase of biomass and activity of attached bacteria, respectively. In the attached bacterial community of conventional and enhanced process, Proteobacteria phylum is the most dominant specie and both α-Proteobacteria class and β-Proteobacteria class are also highly present. Each enhanced BAC exhibits very high bacterial community similarity based on the composition of various genera but it is completely different with conventional BAC. In particular, Bradyrhizobium, Sphingomonas, Methylobacterium, Sphingobium, Belnapia, Burkholderia, Polaromonas, and Desulfuromonas, which have excellent metabolism functions for a wide range of organic substrates, are highly dominated in the enhanced BAC process. The concentration of Biodegradable Dissolved Organic Carbon (BDOC) is obtained close to 0.15 mg/L for conventional BAC and less than 0.15 mg/L for enhanced BAC process, respectively. In general, the higher BDOC concentration can result in reducing biostability in water supply and distribution system when the residual chlorine concentration does not meet requirements. As result, less than 0.15 mg/L BDOC accomplished by PO4-P and H2O2 enhances the biostability.Conclusions:Compared to the conventional BAC process, the biomass and activity of attached bacteria and the ratio of the organization composition of the bacteria insides (genus) are considerably higher in the enhanced BAC process. These results achieve higher water quality and improve biostability.