Aerobic Mixed Culture Research Articles

Triclosan biodegradation performance of adapted mixed cultures in batch and continuous operating systems at high-concentration levels

Pollutants like triclosan (TCS) of medium to high logKow value tend to be mainly adsorbed and poorly biodegraded during waste water treatment, complicating removal after release. Complete mineralization of TCS is crucial, since transformation products may be even more toxic, but has been proven only in a few cases. In this study, the performance of different batch (cultivation flask, TCSmix100) and continuous operating systems (submerged biotrickling filter, TCSmix100; biomembrane reactor, TCSmix200) was tested with two pre-adapted mixed cultures named TCSmix100 and TCSmix200, and compared to non-adapted cultures in a biotrickling filter and a sand filter as reference systems. Mineralization rates up to 172 mg TCS/L/d were observed during batch conditions for TCSmix100 at 1.45 g TCS/L as initial concentration. Triclosan was completely mineralized by both cultures, as shown by stoichiometric release of chloride at conversion rates of 5,7–11.4 mg TCS/L/d (biotrickling filter) and 0.72–1.45 mg TCS/L/d (biomembrane reactor) at 20 and 7.5–15 mg TCS/L as influent concentrations. In TCSmix100, Achromobacter sp. was identified as the relevant strain in TCS biodegradation. Community analysis of TCSmix200 revealed Nitrosomonas europaea, Nitrospira moscoviensis, Nitrosospira multiformis , and Rhodanobacter lindaniclasticus as the predominant strains. In contrast, chloride formation and triclosan elimination in the non-adapted biotrickling filter was less than 12% of the expected chloride concentration at hydraulic retention times up to 60 d. In the reference sand filter, TCS abatement was 42.8% in average with neither formation of chloride nor increase in biofilm density, indicating mostly sorptive or precipitative effects for elimination. With mineralization levels surpassing those of comparable references by a factor of 3–11, both adapted fixed-biomass reactor systems proved highly suitable for treatment of effluents containing high concentrations of TCS as they occur in industrial discharges or concentrates of membrane-based wastewater treatment plants. • Two aerobic mixed cultures were enriched able to completely mineralize triclosan (TCS) • Mixed cultures were dominated by Achromobacter sp. or nitrifying bacteria • Turnover rates were up to two orders higher than in literature (172 mg TCS L −1 d −1 ) • Fixed biomass systems showed stable performance during 110 d and 137 d of operation • TCS was solely eliminated by sorptive effects in a sand filter as reference system

Investigation on the turbidity reduction from wastewater using electroflocculation process and aerobic mixed microbial culture: Modelling and pathway analysis

Contamination of natural water resources by industrial activites is a serious problem that appears in worldwide. The key purpose of the work is to explore the treatment of food wastewater using aerobic mixed microbial culture (AMC) and electroflocculation (EF) process. Box-Behnken design (BBD) incorporated in Response surface methodology (RSM) was used to analysis and model the each process. The effects of inoculum concentration (IC), mixing intensity and temperature has been examined over the turbidity reduction (Y1) in AMC process; where as current density, pH, treatment time and polymer (Polyethyleneimine) dose has been examined over the turbidity reduction (Y2) in EF process. The response models developed explained >97% variability for turbidity reduction. The numerical optimization was used to find out the optimal setting and both the process significantly reduce the >70% of turbidity. UV/Vis spectrophometer confirms the efficiency of each process for turbidity reduction. The operating cost of AMC and EF found to be 1.08 US $/m3 and 4.55 US $/m3, respectively were detemined in optimal conditions. 95% of organic matters was found in sediment of AMC which can be used as outstanding organic fertilizer.

Comparison of different cultures and culturing conditions for the biological deterioration of organic load from real saline bilge wastewater: microbial diversity insights and ecotoxicity assessment

Bilge wastewater is a high strength, typically saline wastewater, originating from operation of ships. In this study, the treatment of real bilge wastewater was tested using pure isolated aerobic strains and mixed cultures (aerobic and anaerobic). The Chemical Oxygen Demand (COD) and ecotoxicity decrease were monitored over time, while the microbial dynamics alterations in mixed cultures were also recorded. The isolated strains Pseudodonghicola xiamenensis, Halomonas alkaliphila and Vibrio antiquaries were shown to significantly biodegrade bilge wastewater. Reasonable COD removal rates were achieved by aerobic mixed cultures (59%, 9 days), while anaerobic mixed cultures showed lower performance (34%, 51 days). The genus Pseudodonghicola was identified as dominant under aerobic conditions both in the mixed cultures and in the control sample (raw wastewater), after exposure to bilge wastewater, demonstrating natural proliferation of the genus and potential contribution to COD reduction. Biodegradation rates were higher when initial organic load was high, while the toxicity of raw wastewater partially decreased after treatment.

Biodegradability of carbon nanotube/polymer nanocomposites under aerobic mixed culture conditions

The properties and commercial viability of biodegradable polymers can be significantly enhanced by the incorporation of carbon nanotubes (CNTs). The environmental impact and persistence of these carbon nanotube/polymer nanocomposites (CNT/PNCs) after disposal will be strongly influenced by their microbial interactions, including their biodegradation rates. At the end of consumer use, CNT/PNCs will encounter diverse communities of microorganisms in landfills, surface waters, and wastewater treatment plants. To explore CNT/PNC biodegradation under realistic environmental conditions, the effect of multi-wall CNT (MWCNT) incorporation on the biodegradation of polyhydroxyalkanoates (PHA) was investigated using a mixed culture of microorganisms from wastewater. Relative to unfilled PHA (0% w/w), the MWCNT loading (0.5–10% w/w) had no statistically significant effect on the rate of PHA matrix biodegradation. Independent of the MWCNT loading, the extent of CNT/PNC mass remaining closely corresponded to the initial mass of CNTs in the matrix suggesting a lack of CNT release. CNT/PNC biodegradation was complete in approximately 20 days and resulted in the formation of a compressed CNT mat that retained the shape of the initial CNT/PNC. This study suggests that although CNTs have been shown to be cytotoxic towards a range of different microorganisms, this does not necessarily impact the biodegradation of the surrounding polymer matrix in mixed culture, particularly in situations where the polymer type and/or microbial population favor rapid polymer biodegradation.

Growth of Leptospirillum ferriphilum in sulfur medium in co-culture with Acidithiobacillus caldus

Leptospirillum ferriphilum and Acidithiobacillus caldus are both thermotolerant acidophilic bacteria that frequently co-exist in natural and man-made environments, such as biomining sites. Both are aerobic chemolithotrophs; L. ferriphilum is known only to use ferrous iron as electron donor, while A. caldus can use zero-valent and reduced sulfur, and also hydrogen, as electron donors. It has recently been demonstrated that A. caldus reduces ferric iron to ferrous when grown aerobically on sulfur. Experiments were carried out which demonstrated that this allowed L. ferriphilum to be sustained for protracted periods in media containing very little soluble iron, implying that dynamic cycling of iron occurred in aerobic mixed cultures of these two bacteria. In contrast, numbers of viable L. ferriphilum rapidly declined in mixed cultures that did not contain sulfur. Data also indicated that growth of A. caldus was partially inhibited in the presence of L. ferriphilum. This was shown to be due to greater sensitivity of the sulfur-oxidizer to ferric than to ferrous iron, and to highly positive redox potentials, which are characteristic of cultures containing Leptospirillum spp. The implications of these results in the microbial ecology of extremely acidic environments and in commercial bioprocessing applications are discussed.

Modelling aerobic biodegradation of atrazine and 2,4-dichlorophenoxy acetic acid by mixed-cultures

The aim of this work was to study and to model the biodegradation of atrazine and 2,4-dichlorophenoxy acetic acid by aerobic mixed cultures. Slow removal rates were observed when biodegrading atrazine, in spite of the initial concentrations. However, high removal rates were obtained when biodegrading 2,4-D, removing up to 100mg/L in about 2months. Regarding the 2,4-D it must be highlighted that a lag phase appears, being its length proportional to the initial 2,4-D concentration. The biodegradation trends were fitted to a Monod based model and the value of the main parameters determined. In the case of atrazine they were µmax: 0.011 1/d and Y: 0.53g/g and in the case of 2,4-D µmax: 0.071 1/d and Y: 0.44g/g, indicating the higher persistence of atrazine. Once finished the experiments the microbial population was characterized being the major genus Pseudomonas when treating atrazine and Rhodococcus when treating 2,4-D.

Simulation of combined anaerobic/aerobic bioremediation of tetrachloroethylene in groundwater by a column system

Chlorinated aliphatic hydrocarbons generally cannot be used as the carbon source or energy source for microorganism growth; these compounds are more difficult to be biodegraded by microorganisms in groundwater. The objective of this study was to explore the growth and degradation capability of aerobic mixed culture in a sand column simulating a PCE and DEC-contaminated aquifer. Results of the biostimulation study indicated that DCE removal rate was 60% after the operation of 56 days. With the bioaugmentation of aerobic mixed culture, DCE removal rate could be enhanced by 100% in the upstream of a simulated aerobic aquifer after the operation of 105 days. Bioremediation was conducted by addition of mixed aerobic bacteria that can degrade dichloroethylene to investigate the biodegradation of dichloroethylene in a simulated anaerobic and aerobic groundwater system. The results of column tests show that the pollutants in the downstream of the simulated anaerobic aquifer mainly comprised dichloroethylene, vinyl chloride, and methane. Fourteen days after mixed aerobic bacteria were added to the simulated aerobic aquifer, the removal efficiency of most intermediates generated from the anaerobic biodegradation process reached approximately 99%, indicating that the combined anaerobic-aerobic system accelerated the degradation of tetrachloroethylene and dichloroethylene.

Application of a hybrid biofilter column for the removal of Cr(VI) from aqueous solution using an indigenous bacterial strain Pseudomonas taiwanensis

ABSTRACTIn the present study, a laboratory-scale biofilter column was designed and fabricated. It was packed with a mixture of coal and compost as a packing medium. The column was enriched with an indigenous bacterial strain Pseudomonas taiwanensis isolated from aerobic mixed culture of Sewage Treatment Plant, BITS-Pilani, Pilani campus. The removal of hexavalent chromium [Cr(VI)] from aqueous solution was investigated in the biofilter column. The entire biofiltration operation was divided into five phases (I to V) for a period of 63 days. Biofilter column was subjected to shock loading conditions for 20 days immediately after 63 days of operation. The maximum removal efficiency of 89.4% was obtained during phase V for Cr(VI) inlet concentration of 40 mg L−1. During shock loading, maximum removal efficiency was obtained as 90% for 48.5–50 mg L−1 of initial Cr(VI) concentration. Kinetic parameters of biofiltration process for Cr(VI) removal were also determined by fitting Michaelis-Menten kinetic model with experimental data. The Michaelis-Menten kinetic constants were obtained as 0.258 mg L−1 min−1 and 26.83 mg L−1. It was found that Ottengraf-Van den Oever model with zero-order diffusion limitation fit the experimental data quite well for phases III, IV, and V with coefficient of determination (R2) values .97, .99, and .984, respectively. A possible method for safe disposal of packing medium was also presented in this study.

Biodegradation of 2,4-Dichlorophenol by Mixed Culture in an Aerobic Fixed-Biofilm Process—Kinetic Model and Reactor Performance

Abstract A mathematical model system for the kinetics of 2,4-dichlorophenol (2,4-DCP) was derived in a fixed-biofilm reactor using ceramic particles composed of dewatered sludge and fly ash as supporting media. Mechanisms in the kinetic model system included biodegradation of 2,4-DCP by attached and suspended biomasses as well as mass transport diffusion of 2,4-DCP. Batch kinetic tests were independently performed to determine biokinetic parameters of aerobic mixed culture. Molecular diffusion in biofilm (Df), film transfer coefficient (kf), and biofilm shear-loss coefficient (bs) were determined from the literature. Laboratory-scale column tests were conducted to validate the kinetic model system. In a steady-state condition, the removal efficiency for 2,4-DCP was ∼89%. Furthermore, the increase of the 2,4-DCP loading rate from 15 to 41 mg/(L·h) led to a constant removal efficiency of ∼90%. The model-predicted biofilm thickness reached up to 622 μm whereas suspended biomass in the effluent was 35 mg/L. E...

Estimation of Kinetic Parameters for Bioremediation of Cr(VI) from Wastewater Using Pseudomonas taiwanensis, an Isolated Strain from Enriched Mixed Culture

ABSTRACTAn aerobic mixed culture collected in the form of activated sludge was enriched for Cr(VI) reduction. An indigenous microorganism was isolated from the enriched aerobic mixed culture and identified as Pseudomonas taiwanensis. Bioremediation studies were carried out for treating Cr(VI)-contaminated wastewater using the indigenous microorganism. The kinetic studies were carried out for initial Cr(VI) concentrations ranging from 20 to 200 mg L−1. The maximum consumption of Cr(VI) obtained was 108.3 mg L−1 for an initial Cr(VI) concentration of 150 mg L−1 at a solution pH of 7.0. The effect of nutrient dosage and pH were studied to get their optimum values. The same isolated bacterial strain was also used to treat Cr(VI)-contaminated industrial wastewater collected from a local plating industry. Various growth kinetic models, such as Monod, Powell, Haldane, Luong, and Edward models, were fitted with the obtained experimental data. The obtained results for different growth kinetic models indicate that the growth kinetics of Pseudomonas taiwanensis for bioremediation of Cr(VI) can be better understood by the Luong model (R2 = .913). The rate kinetic analysis was performed using zero-order and three-half-order kinetic models. The three-half-order kinetic model was found to be suitable for the present bioremediation study.

Polyhydroxyalkanoates production by aerobic mixed microbial cultures using crude glycerol

Polyhydroxyalkanoates production by aerobic mixed microbial cultures using crude glycerol

Crude glycerol as feedstock for polyhydroxyalkanoates production by mixed microbial cultures

The increase in global biodiesel production makes imperative the development of sustainable processes for the use of its main by-product, crude glycerol. In this study the feasibility of polyhydroxyalkanoates (PHA) production by a mixed microbial community using crude glycerol as feedstock was investigated. The selected culture had the ability to consume both glycerol and methanol fraction present in the crude. However, glycerol seemed to be the only carbon source contributing for the two biopolymers stored: poly-3-hydroxybutyrate (PHB) and glucose biopolymer (GB). In this work the culture reached a maximum PHB content of 47% (cdw) and a productivity of 0.27 g X/L.d, with an aerobic mixed cultures and a real waste substrate with non-volatile fatty acids (VFA) organic matter. The overall PHA yield on total substrate obtained was in the middle range of those reported in literature. The fact that crude glycerol can be used to produce PHA without any pre-treatment step, makes the overall production process economically more competitive, reducing polymer final cost.

Effect of Cycle Time on Polyhydroxybutyrate (PHB) Production in Aerobic Mixed Cultures

The aim of this study was to investigate the effect of cycle time on polyhydroxybutyrate (PHB) production under aerobic dynamic feeding system. The acetate-fed feast and famine sequencing batch reactor was used to enrich PHB accumulating microorganism. Sequencing batch reactor (SBR) was operated in four different cycle times (12, 8, 4, and 2 h) fed with a synthetic wastewater. The system performance was determined by monitoring total dissolved organic carbon, dissolved oxygen, oxidation-reduction potential, and PHB concentration. In this study, under steady-state conditions, the feast period of the SBR was found to allow the PHB storage while a certain part of stored PHB was used for continued growth in famine period. The percentage PHB storages by aerobic microorganism were at 16, 18, 42, and 55% for the 12, 8, 4, and 2-h cycle times, respectively. The PHB storage was increased as the length of the cycle time was decreased, and the ratio of the feast compared to the total cycle length was increased from around 13 to 33% for the 12 and 2-h cycle times, respectively.

Bio-oil upgrading strategies to improve PHA production from selected aerobic mixed cultures

Recent research on polyhydroxyalkanoates (PHAs) has focused on developing cost-effective production processes using low-value or industrial waste/surplus as substrate. One of such substrates is the liquid fraction resulting from pyrolysis processes, bio-oil. In this study, valorisation of bio-oil through PHA production was investigated. The impact of the complex bio-oil matrix on PHA production by an enriched mixed culture was examined. The performance of the direct utilization of pure bio-oil was compared with the utilization of three defined substrates contained in this bio-oil: acetate, glucose and xylose. When compared with acetate, bio-oil revealed lower capacity for polymer production as a result of a lower polymer yield on substrate and a lower PHA cell content. Two strategies for bio-oil upgrade were performed, anaerobic fermentation and vacuum distillation, and the resulting liquid streams were tested for polymer production. The first one was enriched in volatile fatty acids and the second one mainly on phenolic and long-chain fatty acids. PHA accumulation assays using the upgraded bio-oils attained polymer yields on substrate similar or higher than the one achieved with acetate, although with a lower PHA content. The capacity to use the enriched fractions for polymer production has yet to be optimized. The anaerobic digestion of bio-oil could also open-up the possibility to use the fermented bio-oil directly in the enrichment process of the mixed culture. This would increase the selective pressure toward an optimized PHA accumulating culture selection.

Atrazine removal from aqueous solutions using submerged biological aerated filter

Atrazine is widely used in the agriculture as an herbicide. Due to its high mobility, Atrazine leaks into the groundwaters, surface waters, and drinking water wells. Many physical and chemical methods have been suggested for removing Atrazine from aquatic environments. However, these methods are very costly, have many performance problems, produce a lot of toxic intermediates which are very harmful and dangerous, and cannot completely mineralize Atrazine. In this study, biodegradation of Atrazine by microbial consortium was evaluated in the aquatic environment. In order to assess the Atrazine removal from the aquatic environment, submerged biological aerated filter (SBAF) was fed with synthetic wastewater based on sucrose and Atrazine at different hydraulic retention times (HRTs). The maximum efficiencies for Atrazine and Soluble Chemical Oxygen Demand (SCOD) removal were 97.9% and 98.9%, respectively. The study findings showed that Stover-Kincannon model had very good fitness (R2 > 99%) in loading Atrazine in the biofilter and by increasing the initial concentration of Atrazine, the removal efficiency increased. Aerobic mixed biofilm culture was observed to be suitable for the treatment of Atrazine from aquatic environment. There was no significant inhibition effect on mixed aerobic microbial consortia. Atrazine degradation depended on the strength of wastewater and the amount of Atrazine in the influent.

Biodegradation of decabromodiphenyl ether (BDE-209) by bacterial mixed cultures in a soil/water system

Decabromodiphenyl ether (DBDE) is a brominated flame retardant that is commonly used in many commercial products. Sorption of DBDE within a soil/water system can result in serious bioaccumulation within the ecological system and be a threat to human health. Little is known about aerobic DBDE biodegradation, and the influence of the UV light radiation on DBDE biodegradation has not been considered. This study, for the first time, isolates DBDE biodegrading aerobic mixed bacterial cultures from DBDE-contaminated soil/water systems in Taiwan. The aerobic biodegradation of DBDE as a sole carbon source in the presence of 365 nm UVA irradiation over 10 months was investigated using a clay/water system. The rate constants for DBDE degradation gave values ranging from 0.0121 to 0.0134 day−1 in the presence of UV irradiation, which were significantly higher than the 0.0092–0.0102 day−1 values obtained in complete darkness. The aerobic metabolites: 2′,3′-dihydroxy-4-bromodiphenyl ether and 2′,3′-dihydroxy-diphenyl ether were identified by GC–MS. Debromination was ascribed to UV irradiation and biodegradation by facultative aerobic bacteria in the micro-anaerobic environment of the clay/water system. The products of debromination included 12 PBDE congeners (tri- to hexa-BDEs) and their concentrations ranged from 34.28 to 83.80 mg l−1. Specific bacteria capable of degrading PBDEs and carrying out nitrification/denitrification were identified. The present findings suggest that systems using a novel combination of photolysis and biodegradation could be developed to carry out DBDE remediation in the future.

Aerobic degradation of phenolics and aromatic hydrocarbons in presence of cyanide

Present study focused on the degradation of a mixture of phenol, cresol, xylenol, quinoline, and indole along with cyanide, commonly found in coke oven wastewater, using aerobic mixed culture. It was found that xylenol and indole were difficult to degrade, when the concentrations were above 250mg/L. It was observed that free cyanide (2.5mg/L and above) has the potency to holdup the oxidation of organics (250mg/L) until the cyanide concentration drops to a minimum level. Final TOC in the mixed pollutant system was less than 4mg/L, indicating the absence of other organic byproducts. Experimental results highlight effect of free cyanide on removal of organics and the combined toxic influence of cyanide and organics on the microbes treating coking wastewater. The proposed mathematical model was able to predict the biodegradation of mixed pollutant system satisfactorily.

Influence of aerobic and anoxic microenvironments on polyhydroxyalkanoates (PHA) production from food waste and acidogenic effluents using aerobic consortia

The functional role of aerobic and anoxic microenvironments on polyhydroxyalkanoates (PHA) production using food waste (UFW) and effluents from acidogenic biohydrogen production process (FFW) were studied employing aerobic mixed culture as biocatalyst. Anoxic microenvironment documented higher PHA production, while aerobic microenvironment showed higher substrate degradation. FFW showed higher PHA accumulation (39.6%) than UFW (35.6%) due to ready availability of precursors (fatty acids). Higher fraction of poly-3-hydroxy butyrate (PHB) was observed compared to poly-3-hydroxy valerate (PHV) in the accumulated PHA in the form of co-polymer [P3(HB-co-HV)]. Dehydrogenase, phosphatase and protease enzymatic activities were monitored during process operation. Integration with fermentative biohydrogen production yielded additional substrate degradation under both aerobic (78%) and anoxic (72%) microenvironments apart from PHA production. Microbial community analysis documented the presence of aerobic and facultative organisms capable of producing PHA. Integration strategy showed feasibility of producing hydrogen along with PHA by consuming fatty acids generated during acidogenic process in association with increased treatment efficiency.

Biodegradation of Chlorinated and Non-chlorinated VOCs from Pharmaceutical Industries

Biodegradation studies were conducted for major organic solvents such as methanol, ethanol, isopropanol, acetone, acetonitrile, toluene, chloroform, and carbon tetrachloride commonly used in pharmaceutical industries. Various microbial isolates were enriched and screened for their biodegradation potential. An aerobic mixed culture that had been previously enriched for biodegradation of mixed pesticides was found to be the most effective. All the organic solvents except chloroform and carbon tetrachloride were consumed as primary substrates by this mixed culture. Biodegradation rates of methanol, ethanol, isopropanol, acetone, acetonitrile, and toluene were measured individually in batch systems. Haldane model was found to best fit the kinetics of biodegradation. Biokinetic parameters estimated from single-substrate experiments were utilized to simulate the kinetics of biodegradation of mixture of substrates. Among the various models available for simulating the kinetics of biodegradation of multi-substrate systems, competitive inhibition model performed the best. Performance of the models was evaluated statistically using the dimensionless modified coefficient of efficiency (E). This model was used for simulating the kinetics of biodegradation in binary, ternary, and quaternary substrate systems. This study also reports batch experiments on co-metabolic biodegradation of chloroform, with acetone and toluene as primary substrates. The Haldane model, modified for inhibition due to chloroform, could satisfactorily predict the biodegradation of primary substrate, chloroform, and the microbial growth.

Phenol degradation kinetics of an aerobic mixed culture

Biodegradation of 0.25–7.0 mmol l −1 phenol with a mixed bacterial consortium at a temperature of 25 ± 2 °C and a pH of 7.2 was studied in batch aerobic reactors. Substrate inhibition was calculated from experimental growth parameters using the Haldane equation. Kinetic parameters were derived by non-linear regression with a correlation factor ( R 2) of 0.987. The values for Haldane constants μ max, K s and K i were 0.3095 h −1, 0.7933 mmol l −1 and 6.887 mmol l −1, respectively. The value of K i is one of the highest values obtained for mixed cultures degrading phenol under batch conditions. The yield factor (units A 578 mmol −1 phenol) ranged from 0.10 to 0.16. The biokinetic parameters were used to predict the biodegradation profile, which agreed well with the experimental data. The results obtained from this study could be useful for an estimation of the relationship between growth rate and substrate utilization, which may be used to evaluate mass balance for a phenol containing wastewater treatment system involving mixed culture as the “biocatalysts”.