Pilot-scale adsorption of pharmaceuticals from municipal wastewater effluent using low-cost magnetite-pine bark: regeneration/enumeration of viable bacteria with a study on their biotoxicity.

A low-cost and renewable magnetite-pine bark (MPB) sorbent was evaluated in continuous-flow systems for the removal of various pharmaceuticals from municipal wastewater effluent following membrane bioreactor (MBR) treatment. A 33-day small-scale column test (bed volume: 791 cm) was conducted using duplicate columns of biochar (BC, Novocarbo) and activated carbon (AC, ColorSorb) as reference for two columns of BC and MPB in order to compare the efficiency of AC and MPB. After the small-scale column test, the pharmaceutical concentrations were generally below the detection limit. In the next stage, a four-month pilot-scale adsorption test was performed using a large column (bed volume: 21 L) filled with BC and MPB. A variety of compounds were removed after the pilot-scale column, including trimethoprim (99.7%), hydrochlorothiazide (81.8%), candesartan (26.0%), carbamazepine (86.1%), ketoprofen (89.4%), clindamycin (86.6%), oxazepam (91.3%), sulfadiazine (38.6%), sulfamethoxazole (58.3%), tramadol (88.9%), zopiclone (73.5%), venlafaxine (93.7%), furosemide (93.5%), fexofenadine (91.6%) and losartan (81.2%). The enumeration of viable bacteria in the pilot-scale column samples revealed that regenerating the BC-MPB bed with NaOH increased bacterial counts in the treated water due to the desorption of adsorbed bacteria from the bed. A biotoxicity study using the Nitrosomonas europaea bioreporter strain indicated that the wastewater was generally non-toxic to this nitrifying bacterium and regeneration of pilot-scale column samples caused short-time toxicity immediately after regeneration. The study confirms that MPB is efficient for the adsorption of pharmaceuticals and can be applied in column mode with a support material such as BC. Therefore, MPB is a viable alternative for AC for the remediation of pharmaceutical-contaminated wastewaters.