Biogenic substrate benefits activated sludge in acclimation to a xenobiotic

Biodegradation of the sulfonamide antibiotic sulfamethoxazole by sulfamethoxazole acclimatized cultures in microbial fuel cells

Microbial fuel cells (MFCs) are known for their ability to enhance the removal rate of toxins while generating power. This research presents a performance assessment of MFCs for power generation and sulfamethoxazole (SMX) degradation using SMX acclimatized cultures. Experiments were performed in MFC batch mode using different SMX concentrations in synthetic wastewater. The experimental results showed that voltage generation was >400mV up to the SMX concentration of 0.20mM (at 400Ω external resistance). Control experiments supported the inference that biodegradation was the main process for SMX removal compared to sorption by SMX acclimatized cultures and that the process results in efficient removal of SMX in MFC mode. The specific removal rates of SMX in MFC with SMX acclimatized sludge were 0.67, 1.37, 3.43, 7.32, and 13.36μm/h at initial SMX concentrations of 0.04, 0.08, 0.20, 0.39, and 0.79mM, respectively. Moreover, the MFC was able to remove >90% of the TOC from the wastewater up to SMX concentrations of 0.08mM. However, this TOC removal produces negative effects at higher SMX concentrations due to toxic intermediates. Microbial community analysis revealed large changes in bacterial communities at the phylum, class, and genus levels after SMX acclimatization and MFC operation. Thauera, a well-known aromatic-degrading bacteria, was the most dominant genus present in post-acclimatized conditions. In summary, this study showed that acclimatized sludge can play an important role in the biodegradation of SMX in MFCs.

Effect of operational strategies on activated sludge's acclimation to phenol, subsequent aerobic granulation, and accumulation of polyhydoxyalkanoates

Aerobic granules, a relative novel form of microbial aggregate, are capable of degrading many toxic organic pollutants. Appropriate strategy is needed to acclimate seed sludge to the toxic compounds for successful granulation. In this study, two distinct strategies, i.e. mixed or single carbon sources, were experimented to obtain phenol-acclimated sludge. Their effects on reactor performance, biomass characteristics, microbial population and the granulation process were analyzed. Sludge fed with phenol alone exhibited faster acclimation and earlier appearance of granules, but possibly lower microbial diversity and reactor stability. Using a mixture of acetate and phenol in the acclimation stage, on the other hand, led to a reactor with slower phenol degradation and granulation, but eventual formation of strong and stable aerobic granules. In addition, the content of intracellular polyhydoxyakanoates (PHA) was also monitored, and significant accumulation was observed during the pre-granulation stage, where PHA >50% of dry weight was observed in both reactors.

Effect of acclimation and nutrient supply on 5-tolyltriazole biodegradation with activated sludge communities

The corrosion inhibitor 5-tolyltriazole (5-TTri) can have a detrimental impact on aquatic systems thus implying an acute need to reduce the effluent concentrations of 5-TTri. In this study, 5-TTri biodegradation was enhanced through acclimation and nutrient supply. Activated sludge communities (ASC) were setup in nine subsequent ASC generations. While generation two showed a lag phase of five days without biodegradation, generations four to nine utilized 5-TTri right after inoculation, with biodegradation rates from 3.3 to 5.2 mg L(-1)d(-1). Additionally, centrifuged AS supernatant was used to simulate the nutrient conditions in wastewater. This sludge supernatant (SS) significantly enhanced biodegradation, resulting in removal rates ranging from 3.2 to 5.0 mg L(-1)d(-1) without acclimation while the control groups without SS observed lower rates of ⩽ 2.2 mg L(-1)d(-1).

Propionate addition enhances the biodegradation of the xenobiotic herbicide propanil and its metabolite

This study investigated ways of stimulating the biodegradation rates of the commonly applied herbicide, 3,4-dichloropropionanilide (propanil), and its metabolite, 3,4-dichloroaniline (DCA), as well as the growth rate of propanil- and DCA-degrading organisms in a mixed culture. Propionate, the other metabolite of propanil, stimulated the specific degradation rates of both propanil and DCA after a brief acclimation period. A metabolic model developed to characterise the metabolism of propanil and DCA biodegradation showed that the efficiency of oxidative phosphorylation (i.e. P/O ratio), which measures the metabolic efficiency, increased over time by 6- to 10-fold. This increase was accompanied by a 5- to 10-fold increase in the propanil and DCA biodegradation degradation rates. The biodegradation rates of the culture were unaffected when using an irrigation water matrix (Tejo river, Portugal), highlighting the utility of the culture for bioaugmentation purposes.

Production of xenobiotic degrader for potential application in bioaugmentation

Continuous-flow chemostats were operated at different mean-cell-residence-times (θc) and influent concentrations of a xenobiotic (2,4-D) and biogenic substrates. Steady state chemostat biomasses' performances in 2,4-D degradation were analyzed with a mathematical model to determine the quantities of degrader the biomasses contained. The qualification for microbial cells to become degraders is a high grade of degradation kinetics. This qualification uniformly applies to all biomasses. The quantities of degraders vary inversely with the chemostats'θc. Biogenic substrates increase degrader yield such that a high biogenic and a high xenobiotic influent optimize degrader mass output. Economics evaluation performed around the optima finds the influent containing 5-25% 2,4-D carbon (TOC) in approximately 900 mg/l biogenic TOC, and the θc of 2-5d, are suitable operating conditions for a degrader producing bioreactor that may serve as a selector of biomass for bioaugmentation purposes.