Selecting Bacteria Candidates for the Bioaugmentation of Activated Sludge to Improve the Aerobic Treatment of Landfill Leachate

Abstract

In this study, a multifaceted approach for selecting the suitable candidates for bioaugmentation of activated sludge (AS) that supports leachate treatment was used. To determine the exploitation of 10 bacterial strains isolated from the various matrices for inoculating the AS contaminated with the Kalina pond leachate (KPL), their degradative potential was analyzed along with their aptitude to synthesize compounds improving remediation of pollutants in wastewater and ability to incorporate into the AS flocs. Based on their capability to degrade aromatic compounds (primarily catechol, phenol, and cresols) at a concentration of 1 mg/mL and survive in 12.5% of the KPL, Pseudomonas putida OR45a and P. putida KB3 can be considered to be the best candidates for bioaugmentation of the AS among all of the bacteria tested. Genomic analyses of these two strains revealed the presence of the genes encoding enzymes related to the metabolism of aromatic compounds. Additionally, both microorganisms exhibited a high hydrophobic propensity (above 50%) and an ability to produce biosurfactants as well as high resistance to ammonium (above 600 µg/mL) and heavy metals (especially chromium). These properties enable the exploitation of both bacterial strains in the bioremediation of the AS contaminated with the KPL.

Analysis of the Bioaugmentation Potential of Pseudomonas putida OR45a and Pseudomonas putida KB3 in the Sequencing Batch Reactors Fed with the Phenolic Landfill Leachate

“…It is worth emphasizing that the bioaugmentation improved the settling properties and quality of the AS in the SBRs. This can be explained by good coaggregation abilities exhibited by the bioaugmentation candidates [26]. The improvement of the AS settling properties via the bioaugmentation with Halobacter halobium was also described by Kargi et al [60].…”

“…The landfill leachate is often characterized by the high strengths of ammonia nitrogen, which toxicity may inhibit the growth and activity of microorganisms in the AS and thus suppress the biodegradation process [46]. As previously described, P. putida OR45a and P. putida KB3 withstood high concentrations of the ammonia up to 600 mg/L and 900 mg/L, respectively [26]. Herein, the removal of N-NH 3 (88-91%) was much more improved in the bioreactors L OR45a , L KB3 , and L OR45a+KB3 as compared to the noninoculated bioreactor L (64%).…”

“…In the previous study, we described P. putida OR45a and P. putida KB3 strains as suitable candidates for the bioremediation of wastewater spiked with the landfill leachate [26]. Herein, these bacterial strains introduced into the SBRs fed with the phenolic landfill leachate significantly improved the removal efficiency of contaminants by over 30%.…”

“…Two bacterial strains used in this study, Pseudomonas putida OR45a (GenBank SPUU00000000.1) and Pseudomonas putida KB3 (GenBank SPUT00000000.1), have previously been described as able to degrade high concentrations of phenol and its derivatives [26]. Before the inoculation of the AS, pure colonies of bacterial strains were cultivated separately in the mineral salts medium [26] containing 300 mg/L of phenol (Merck, Darmstadt, Germany) as the sole carbon and energy source at 23 ± 2 • C with agitation at 130 rpm for 72 h under the proviso that every 24 h a new dose of phenol was applied. Subsequently, the cells were harvested by centrifugation at 4 • C for 15 min at 5.000× g and rinsed three times with sterile mineral salts medium before they were used in the bioaugmentation experiment.…”

Mycoremediation of Old and Intermediate Landfill Leachates with an Ascomycete Fungal Isolate, Lambertella sp.

“…While conventional biological treatments, such as activated sludge, aerated lagoons, sequencing batch reactors, up-flow anaerobic sludge blanket, membrane bioreactors, are widely and often used successfully to treat young leachates [8,9], biological treatments are hampered by the toxicity and recalcitrance of intermediate and old leachates [10]. That is why strategies adopted to reduce the organic and inorganic loads in LFLs are generally chemical-physical processes, which might be expensive and not always effective in removing all the toxic and recalcitrant compounds.…”