Search

The removals of emerging contaminants (EC) through adsorption and biodegradation by Alcaligenes faecalis no.4 (A. faecalis no.4) and its combination with heterotrophic microorganisms presented in acclimated activated sludge were evaluated. The studied EC included bisphenols (BPA), di-n-butyl phthalate (DBP), and bis-2-ethyl hexyl phthalate (DEHP). Improved removals of those compounds under the presence of A. faecalis no.4 were observed. Batch experiments carried out in the absence of autotrophic nitrifying activities revealed that heterotrophic nitrification significantly contributed to the compound degradation process. Integration of mixed sludge was found effectively applied to leachate in which A. faecalis no.4 posed a higher growth rate than other acclimated heterotrophic bacteria.

The effect of Alcaligenes faecalis no.4 (A. faecalis no.4) in two-stage sequencing batch reactor (SBR) treatment of endocrine disrupting compounds (EDCs), i.e., bisphenol A (BPA), di-n-butyl phthalate (DBP) and bis-2-ethyl hexyl phthalate (DEHP) containing in landfill leachate was investigated. Two aerobic SBRs were operated without (C-SBR) and with A. faecalis no.4 bio-augmentation (B-SBR) at a hydraulic retention time (HRT) and solid retention time (SRT) of 3 and 30 days over 280 days. The removals of BPA, DBP, and DEHP were significantly improved to 91.1%, 84.5%, and 80.9% from their average influent concentrations of 185, 244, and 532 μg/l under the presence of A. faecalis no.4 through their enhanced biodegradation. The A. faecalis no.4 bio-augmentation helped promote a strong consortium of bacterial genera reported as BPA, DBP, and DEHP degraders in microbial sludge. This study demonstrated the technical feasibility of applying SBR with A. faecalis no.4 in landfill leachate treatment with effective EDC removals.

Methane (CH4) and nitrous oxide (N2O) emissions from two-stage membrane bioreactor (MBR) bio-augmented by Alcaligenes faecalis no. 4 during municipal solid waste leachate treatment were investigated. The system was operated at hydraulic retention time (HRT) of 2.5 and 1 days in each reactor under the presence and absence of sludge recirculation. Alcaligenes faecalis no. 4 bioaugmentation helped improving organic carbon and nitrogen removals while reducing CH4 and N2O emissions. CH4 and N2O emissions were decreased by 46% and 85% when A. faecalis no. 4 was introduced at HRT of 2.5 days. Under the presence of A. faecalis no. 4, the operation of twostage MBR with sludge recirculation could reduce CH4 and N2O emissions by 51% and 54% as compared to its operation without sludge recirculation. An operation under short HRT of 1 day also yielded high organic carbon and nitrogen removals of more than 85% while emitting lower CH4 and N2O emission of 6.7% C and 0.04% N when operated with sludge recirculation. Implications: A two-stage membrane bioreactor was effectively applied to the treatment of concentrated leachate (BOD~20,000 mg/L) at a short hydraulic retention time of 2.5 days and 1 day. About 80% of CH4 and N2O was emitted from the anaerobic and aerobic reactors, respectively. Introduction of Alcaligenes faecalis no. 4 reduced CH4 and N2O emissions in both reactors as it became the predominant microorganism under an elevated pH condition. Lower CH4 and N2O emissions were achieved under a sludge recirculation operation, as Alcaligenes faecalis no. 4 could suppress methanogenic activities in the anaerobic reactor and converted a majority of nitrogen into its cell mass, thus reducing N2O production through a biological nitrification-denitrification pathway. [ABSTRACT FROM AUTHOR]