Removal of Contaminants of Emerging Concern (CECs) from Secondary Biologically Treated Wastewater Effluent Using Biofilters of Granular Activated Carbon (GAC)

This study investigated the removal of the three contaminants of emerging concerns (CECs) using two bench-scale biofilters of granular activated carbon (GAC) fed with the secondary effluent samples and the ozonated secondary effluent samples (ozone residuals 0.35-0.55 mg/L), respectively. The biofilters were set up and kept being operated, sampled, tested and monitored for almost nine (9) months (8/25/2017 to 6/1/2018) with a flow rate of 0.5 mL/min, and the empty bed contact time (EBCT) of 106 min. In this study, the seven (7) classical WW constituents: NH3-N, NO3--N, TKN, TP, BOD5, COD, and DOC, and the three target CECs of bisphenol A, naproxen, and ibuprofen were tested. The NH3-N and NO3--N removal by both biofilters were moderate to satisfactory, about 50-71% and 90-96%, respectively, where ozonation could remove NO3--N about 7% at some point. Moreover, average BOD5 removal ranged from 45-50% by both biofilters. The removal of COD was 48-55% and 55-65% by Biofilters #1 and #2, respectively while ozonation removed 30% of COD. DOC removal by both biofilters were not that significant but removed a certain range of 20-25% and 25-30% by Biofilters #1 and #2, respectively, while the removal by ozonation was not much (2-5%). The ozone oxidized the target CECs with moderate amounts, i.e for bisphenol A was 80% removal and for naproxen removal was 50% and ibuprofen was 50%. Moreover, the overall removal efficiency by ozonation and Biofilter #2 was 85-90% and 70-75%, 55-60% for bisphenol, naproxen and ibuprofen respectively. However, the Biofilter #1 itself could remove satisfactory quantities i.e 50%, 35-40% and 45% of bisphenol A, naproxen and ibuprofen respectively. Statistical analysis for the three target CECs’ graphs of Biofilter #1 showed significant removals of bisphenol A and ibuprofen, and non-significant removal of naproxen, while those of Biofilter #2 showed significant removals of all three target CECs. Overall, the performance of the two biofilters for removing seven classical constituents and three target CECs was satisfactory, and biofilters of GAC is an innovative, biological/green, and cost-effective treatment process, which can be used to remove CECs from secondary effluent for direct/indirect portable water reuse