Pyrosequencing reveals the inhibitory impact of chronic exposure to erythromycin on activated sludge bacterial community structure

The study investigated changes in the microbial population structure sustained at two different sludge ages of 10 d and 2 d under chronic impact of erythromycin. It intended to observe the experimental correlation between variable process kinetics and changes in the composition of the microbial community induced by erythromycin. Samples from two fill/draw reactors operated with continuous erythromycin dosing of 50 mg/L were collected for the analysis of microbial population structure using high-throughput sequencing of 16SrRNA gene. Significant changes were observed in the composition of microbial community during the exposure period. Richness analysis for slower growing culture indicated that most microbial fractions were inactivated and eliminated in favor of fewer more resistant species in different phyla. Sludge age appeared to control the impact of erythromycin on microbial composition. At a sludge age of 2 d, erythromycin appeared to generate richer community with faster growing and more compatible species. For slower growing culture, elimination of vulnerable species was supported by decrease in the number of shared level OTUs. For faster growing culture, shared species level OTUs also decreased significantly upon exposure to erythromycin, suggesting rapid washout and replacement by more resistant species. Resistance gene analysis yielded positive results for mph(A) gene indicating presence of erythromycin-resistant components in the microbial community.     

Biodegradation of naphthalene in the oil refinery wastewater by enriched activated sludge

The main purpose of this paper is to study naphthalene (NAP) biodegradation by acclimated activated sludge, employing the culture-enrichment method in a continuous flow bioreactor of the wastewater treatment process. The effects of various COD loadings and influent flow rates of an artificial wastewater containing 15 mg l⁻¹ NAP on the biodegradation rates of the activated sludge will be investigated, in order to determine the biodegradation kinetics and minimum mean cell residence time of the activated sludge. From the experimental results, it was found that the resulting enriched activated sludge follows the growth rate of the Monod type and can biodegrade those COD and NAP loadings in the influents efficiently, and its bio-treatment efficiency on NAPs increases with the decrease of influent flow rate. The sludge volume index (SVI) of the resulting enriched activated sludge meets the design value required by the convectional activated sludge process for the treatment of wastewater.     

Validity of Monod kinetics at different sludge ages – Peptone biodegradation under aerobic conditions

The study presented an evaluation of the effect of culture history (sludge age) on the growth kinetics of a mixed culture grown under aerobic conditions. It involved an experimental setup where a lab-scale sequencing batch reactor was operated at steady-state at two different sludge ages (θ_X) of 2 and 10 days. The system sustained a mixed culture fed with a synthetic substrate mainly consisting of peptone. The initial concentration of substrate COD was selected around 500 mg COD/L. Polyhydroxyalkanoate (PHA) storage occurred to a limited extent, around 30 mg COD/L for θ_X = 10 days and 15 mg COD/L for θ_X = 2 days. Evaluation of the experimental data based on calibration of two different models provided consistent and reliable evidence for a variable Monod kinetics where the maximum specific growth rate, was assessed as 6.1/day for θ_X = 2 days and 4.1/day for θ_X = 10 days. A similar variability was also applicable for the hydrolysis and storage kinetics. The rate of storage was significantly lower than the levels reported in the literature, exhibiting the ability of the microorganisms to regulate their metabolic mechanisms for adjusting the rate of microbial growth and storage competing for the same substrate. This adjustment evidently resulted in case-specific, variable kinetics both for microbial growth and substrate storage.     

Active heterotrophic biomass and sludge retention time (SRT) as determining factors for biodegradation kinetics of pharmaceuticals in activated sludge

The present study investigates the biodegradation of pharmaceutically active compounds (PhACs) by active biomass in activated sludge. Active heterotrophs (X_bh) which are known to govern COD removal are suggested as a determining factor for biological PhAC removal as well. Biodegradation kinetics of five polar PhACs were determined in activated sludge of two wastewater treatment plants which differed in size, layout and sludge retention time (SRT).Results showed that active fractions of the total suspended solids (TSS) differed significantly between the two sludges, indicating that TSS does not reveal information about heterotrophic activity. Furthermore, PhAC removal was significantly faster in the presence of high numbers of heterotrophs and a low SRT. Pseudo first-order kinetics were modified to include X_bh and used to describe decreasing PhAC elimination with increasing SRT.     

Effect of a static magnetic field on formaldehyde biodegradation in wastewater by activated sludge

The aim of this study was to determine the impact of a static magnetic field (MF) of 7 mT on formaldehyde (FA) biodegradation by activated sludge in synthetic wastewater. The MF had a positive effect on activated sludge biomass growth and dehydrogenase activity. The influence of the MF on the degradation process was observed with a FA concentration of 2400-2880 mg/l. Decreases in FA concentration and chemical oxygen demand (COD) were greater, by 30% and 26% respectively, than those in the control sample. At initial FA concentrations in raw wastewater of 2400 and 2880 mg/l, a decrease in the wastewater biodegradation efficiency was observed. This resulted in an increase of the ecotoxicity of the effluent to Daphnia magna. The value of the sludge biotic index (SBI) was dependent on the FA concentration in raw wastewater and the induction of the MF.     

Characterization of microbial traits associated with glyphosate biodegradation in industrial activated sludge

Summary The microorganisms from two industrial (I1, I2) activated sludges that treat glyphosate (N-phosphonomethyl glycine) wastes and one domestic (D1) sludge were enumerated by microscopic examination and by the use of eight selective media. I1 and I2 had higher total counts but fewer pseudomonads and no yeasts. The enumerations correlated directly with traditional biological performance measurements. A total of 393 microbial strains were isolated from the sludges to correlate the occurrence and relationship of glyphosate-degrading activity (GDA) to 155 biochemical and morphological characteristics. Each activated sludge contained unique bacterial populations with the microbes treating industrial wastes, capable of utilizing a wide range of carbohydrates. Numerical taxonomy (arithmetic average linkage) using simple matching and Jaccard coefficients confirmed that there were five (D1), three (I1), and 12 (I2) clusters. GDA was found in only a small portion of the industrial clusters and did not correlate with any other characteristic tested, even though the GDA strains had a large phenotypic diversity. This suggests that GDA is not a universal trait and its expression requires enrichment through specific selective pressures.     

Characterization of dewatering process of activated sludge assisted by cationic surfactants

In this work, the dewatering of activated sludge assisted by cationic surfactants was investigated. Dose of dodecyl trimethyl ammonium bromide (DTAB) and cetyl trimethyl ammonium bromide (CTAB) resulted in the release of extracellular polymeric substances (EPS) from sludge and decrease in sludge negative charge. The surfactants significantly promoted sludge dewaterability, as reflected by decreased specific resistance of filtration (SRF) and water content in sludge cakes. The treated sludge were analyzed by combined use of differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) analysis. CTAB was found more effective in releasing bound water from sludge than DTAB, due to its superior surface activity and strong adsorption/bridge capacities with sludge. The specific surface area and pore size of sludge cakes declined after surfactant treatment, indicating an enhanced compressibility. With these results, the surfactant-assisted dewatering mechanism could be attributed to the integrated effects of electrostatic neutralization, enhanced compaction and release of EPS and bound water. Our study clearly characterizes the accelerated dewatering process assisted by cationic surfactants, and demonstrates that cationic surfactants could be used as a potential agent for sludge dewatering.     

Growth kinetics of EDTA biodegradation by Burkholderia cepacia

A pure culture of an EDTA-degrading strain was isolated from the Taiwan environment. It was identified as Burkholderia cepacia, an aerobic bacterium, elliptically shaped with a length of 5–15 m. The degradation assay showed that the degradation efficiency of Fe-EDTA by B. cepacia was approximately 91%. Evaluation of kinetic parameters showed that Fe-EDTA degradation followed substrate inhibition kinetics. This is evident from the decrease in specific growth rate with an increase in the initial substrate concentration greater than 500 mg/l. To estimate the kinetic parameters – _max, K_S and K_I, five substrate–inhibition models were used. From the results of non-linear regression, the value of _max ranged from 0.150 to 0.206 d^–1, K_S from 74 to 87 mg/l, and K_I from 890 to 2289 mg/l. The five models were found to underestimate the maximum specific growth rate by 1.5–3.7. Therefore, predictions based on these models would result in lower predicted value than those from the experimental kinetic data.     

Carbonaceous Hibiscus cannabinus L. for treatment of oil- and metal-contaminated water

The potential of carbonaceous Hibiscus cannabinus L. plant for use in the treatment of oil- and heavy metal-contaminated water is explored. The results from this work demonstrated that the material from this source was capable of sequestering oil and metal ions from the aqueous solutions. The maximum sorption to saturation capacities for diesel and cooking oil were 35 and 30 g g⁻¹, respectively, well above that of the commercial adsorbent. The carbonaceous material was also effective for sequestering Mn²⁺, Cu²⁺ and Fe²⁺. The equilibrium of metal ions adsorption was attained after 30 min for Mn²⁺ and Cu²⁺, and 60 min for Fe²⁺ solutions. The sorption of the metal ions was in the order of Mn²⁺ > Cu²⁺ > Fe²⁺, increased with increase in the dosage in the range between 60% and 92% removal, depending on the dosage amount. The quantitative removal of Mn²⁺, Cu²⁺, and Fe²⁺ at pH 4.5, 50 mg L⁻¹ initial concentration after 150 min equilibration time was 91.2%, 86.0% and 81.0%, respectively.     

Kinetics of the biodegradation of phenol in wastewaters from the chemical industry by covalently immobilized <Emphasis Type="Italic">Trichosporon cutaneum</Emphasis> cells

A simple method for the preparation of the biocatalyst with whole cells is presented, and the applicability of the technique for biodegradation of phenol in wastewater from the chemical industries using the basidomycetes yeast Trichosporon cutaneum is explored. Kinetic studies of the influence of other compounds contained in wastewater as naphthalene, benzene, toluene and pyridine indicate that apart from oil fraction, which is removed, the phenol concentration is the only major factor limiting the growth of immobilized cells. Mathematical models are applied to describe the kinetic behavior of immobilized yeast cells. From the analysis of the experimental curves was shown that the obtained values for the apparent rate parameters vary depending on the substrate concentration (μ_maxapp from 0.35 to 0.09 h⁻¹ and K _sapp from 0.037 to 0.4 g dm⁻³). The inhibitory effect of the phenol on the obtained yield coefficients was investigated too. It has been shown that covalent immobilization of T. cutaneum whole cells to plastic carrier beads is possible, and that cell viability and phenol degrading activity are maintained after the chemical modification of cell walls during the binding procedure. The results obtained indicate a possible future application of immobilized T. cutaneum for destroying phenol in industrial wastewaters.     

Biological removal of pharmaceutical and personal care products by a mixed microbial culture: Sorption,desorption and biodegradation

The performance of a mixed-culture on the removal of caffeine (CFN), sulfamethoxazole (SMX), ranitidine (RNT), carbamazepine (CZP) and ibuprofen (IBP) in a suspended growth reactor has been studied. The sorption and biodegradation of these compounds were examined when they were individually or simultaneously tested. The sorption of individual compounds was significantly low except from RNT (K_d = 0.42 L/g). In contrast, the sorption of SMX and CFN increased in detriment of RNT when all the pharmaceutical compounds were simultaneously present. The biodegradation removal also exhibited significant differences. Thus, the simultaneous treatment showed higher biodegradation rates (K_b up to 97.55 × 10⁻⁶ L/mg h) than the individual treatment (K_b up to 8.13 × 10⁻⁶ L/mg h) of the pharmaceuticals. In general, the simultaneous treatment leads to increased sorption distribution coefficients and biodegradation rates. Results seem to reveal that the enhanced biomass efficiency on the simultaneous elimination process was due to the synergistic effects of pharmaceutical compounds onto mixed-culture. During the simultaneous removal, CFN, SMX and CZP were removed consistently (5.3 ± 4.4%, 73.2 ± 21.3% and 4.2 ± 2.3%, respectively), whereas RNT and IBP showed an unsteady removal over time. Finally, a kinetic model capable of describing the influence of biomass growth and nutrients utilization on the sorption and biodegradation of the pollutants was successfully demonstrated.     

Molecular structure and biodegradation kinetics of linear alkylbenzene sulphonates in sea water

The present paper describes the results of the application of the biodegradation test proposed by the United States Environmental Protection Agency (USEPA) “Biodegradability in sea water” Office of Prevention, Pesticides, and Toxic Substances (OPPTS) 835.3160, to Linear Alkylbenzene Sulphonate (LAS), the synthetic surfactant with the highest consumption volume on a world-wide basis. High performance liquid chromatography (HPLC) has been employed for the separation and quantification of the different homologues and isomers of the surfactant. Water from the Bay of Cádiz (South–West of the Iberian peninsula) has been used as test medium. The results indicate how both lag and t ₅₀ time shows a significant linear relationship with the length of the alkyl chain of the homologue; the effect of this is that the homologues of longer chain length not only begin to degrade first but also degrade at a faster rate. Regarding the isomeric composition, it is observed that as the percentage of biodegradation increases, there is an increase in the proportion of internal isomers, in comparison with the isomeric relationships of the original test substance     

Biodegradation of wastewater pollutants by activated sludge encapsulated inside calcium-alginate beads in a tubular packed bed reactor

The wastewater treatment plants produce large quantities of biomass (sludge) that require about one-third of the total inversion and operation plant costs for their treatment. By the microorganisms immobilization it is possible to handle high cell concentration in the reactor, increasing its efficiency, reducing the loss of biomass and the wash out is avoided. Moreover, there is no cell growth then the sludge production is reduced. In this study, the COD removal and VSS variation were modeled in a tubular reactor with activated sludge immobilized in Ca-alginate. Moreover, two aspects that are commonly not considered in the performance of the actual reactors of this kind were introduced; the performance in non-steady state and the dispersion effect. The model was calibrated with an actual wastewater taken out from a Mexican wastewater treatment plant. The results of the performance of the tubular bioreactor at different scenarios (i.e., different residence time and VSS in the reactor) are presented. With longer residence times and higher VSS concentration in the Ca-alginate beads in the tubular bioreactor it is possible to increase the time operation of the bioreactor and to treat higher volumes of wastewater. During the process, the sludge generation was drastically reduced and it is possible to remove nitrogen form the wastewater making this process more attractive.     

Contribution of sludge adsorption and biodegradation to the removal of five pharmaceuticals in a submerged membrane bioreactor

A submerged membrane bioreactor was set up to investigate the removal efficiencies of five pharmaceuticals from synthetic domestic wastewater. Batch experiments were conducted with sterilized sludge and activated sludge to explore the contributions of sludge adsorption and biodegradation for those pharmaceuticals. Notable difference of those pharmaceuticals removal efficiencies was observed, at about 92.2, 90.0, 55.4, 38.5 and 3.2% for acetaminophen, 17β-estradiol, naproxen, diclofenac sodium, and carbamazepine, respectively. Results of batch adsorption experiments via sterilized sludge showed that the removal efficiencies of five pharmaceuticals by sludge adsorption were 7.9, 68.2, 60.1, 40.1 and 71.5%, respectively, which were positively correlated with their octanol–water partition coefficients. Results of batch experiments via activated sludge showed that 83.4% of acetaminophen, 98.0% of 17β-estradiol, and 46.8% of naproxen were removed through the combination of sludge adsorption and biodegradation, while adsorption accumulation in sludge phase was only 1.8, 1.3 and 7.0%. This implies that the removals of these three drugs were mainly achieved by biodegradation. The total removal efficiency of diclofenac sodium was 19.7%, and the contributions of sludge adsorption and biodegradation were 14.9 and 4.8%, which indicated that the removal of diclofenac sodium was mainly achieved by sludge adsorption. The total removal efficiency of carbamazepine was only 8.9% and this implies that neither sludge adsorption nor biodegradation is effective for its removal.     

Acute impact of tetracycline and erythromycin on the storage mechanism of polyhydroxyalkanoates

The study investigated acute impact of tetracycline and erythromycin on substrate storage under aerobic conditions. A fill and draw reactor fed with peptone mixture was maintained at steady-state at a sludge age of 10 days; the acclimated biomass was used in a series of batch runs. The first run served as control reactor with organic substrate alone and the others were started with antibiotic doses of 50 mg/L and 200 mg/L for assessing intracellular storage. Parallel batch reactors were also conducted for recording oxygen uptake rate profiles. Both antibiotics enhanced substrate storage, leading to higher levels of polyhydroxyalkanoates incorporated into biomass, but they impaired its internal utilization for microbial growth. The observed decrease in oxygen consumption under the acute effect of antibiotics could partially be related to substrate storage – except for 50 mg/L of erythromycin dosing – suggesting an additional substrate binding mechanism by antibiotics, leading to residual biodegradable substrate.     

The effect of long-term treatment with erythromycin on Th1 and Th2 cytokines in diffuse panbronchiolitis

Diffuse panbronchiolitis (DPB) is a chronic progressive disease of the respiratory bronchioles, and has been improved by low-dose, long-term erythromycin (EMC) treatment. The therapeutic benefits may be derived from its anti-inflammatory and immunomodulatory properties rather than antimicrobial effect. However, there are few studies about the mechanism of immunomodulation by EMC treatment for patient with DPB. In this study, we quantified the changes of Th1 and Th2 cytokines in the bronchoalveolar lavage (BAL) fluid from patients with DPB after long term treatment with EMC. After the EMC treatment, a significant reduction in the number of lymphocytes was observed, and the CD4/CD8 ratio was elevated as well. The IL-2 and IFN-gamma levels in the BAL fluid were significantly decreased and the IL-4, IL-5, and IL-13 levels were significantly increased after EMC treatment. Our results suggest that the therapeutic benefits of long-term EMC treatment may be partially due to the immune system's shift from Th1 to Th2 cytokine production.     

Studies on the effect of inoculation of activated sludge with bacteria actively degrading hydrocarbons on the biodegradation of petroleum products

Eighteen strains of bacteria were isolated from activated sludge purifying petroleum-refining wastewaters. These strains were plated on solidified mineral medium supplemented with oil fraction in concentration 1000 mg/l. Four of the strains that grew best in the presence of oil were selected for further studies. The strains were identified based on Bonde's scheme and microscopic observations. Three of them belonged to the genus Arthrobacter and one to the genus Micrococcus. Stationary cultures of single strains and their mixtures were set up in mineral medium containing oil (sterile and non-sterile) as sole carbon source in concentration 1000 mg/l. The oils were found to be removed the most efficiently by a mixture of the strains. After 14 days of culture the amount of oil was utilized by from 63 to 95%. In the next stage of the studies the bacteria were used to inoculate activated sludge. Stationary cultures of the activated sludge were set up in mineral medium with oil. The utilisation of petroleum products by non-inoculated activated sludge (control), activated sludge inoculated with a single strain or a mixture of all four strains was examined. In both inoculated activated sludge cultures approximately 80% of the oils were removed, compared to 60% in the control activated sludge. Therefore, inoculated activated sludge showed 20% higher effectiveness of removal of petroleum derivatives.     

Degradation of 4-chloro-2-methylphenol by an activated sludge isolate and its taxonomic description

The Gram-negative strain S1, isolated from activated sludge, metabolized 4-chloro-2-methylphenol by an inducible pathway via a modifiedortho-cleavage route as indicated by a transiently secreted intermediate, identified as 2-methyl-4-carboxymethylenebut-2-en-4-olide by gas chromatography/mass spectrometry. Beside 4-chloro-2-methylphenol only 2,4-dichlorophenol and 4-chlorophenol were totally degraded, without an accumulation of intermediates. The chlorinated phenols tested induced activities of 2,4-dichlorophenol hydroxylase and catechol 1,2-dioxygenase type II. Phenol itself appeared to be degraded more efficiently via a separate, inducibleortho-cleavage pathway. The strain was characterized with respect to its physiological and chemotaxonomic properties. The fatty acid profile, the presence of spermidine as main polyamine, and of ubiquinone Q-10 allowed the allocation of the strain into the -2 subclass of theProteobacteria. Ochrobactrum anthropi was indicated by fatty acid analysis as the most similar organism, however, differences in a number of physiological features (e.g. absence of nitrate reduction) and pattern of soluble proteins distinguished strain S1 from this species.