Activated Sludge Consortium Research Articles

Role of quorum sensing-based regulation in development of anaerobic ammonium oxidation process

Shortage of anaerobic ammonium oxidation (anammox) sludge greatly limits the extensive full-scale application of anammox-based processes. Although numerous start-up strategies have been proposed, the interaction among microbial consortia and corresponding mechanism during the process development remain unknown. In this study, three reactors were established based on different seed sludges. After 27 days, the anammox process inoculated with anammox granules and activated sludge (1:5) was firstly achieved, and the highest nitrogen removal rate was 1.17 kg N m−3 d−1. Correspondingly, the anammox activity and abundances of related functional genes increased. Notably, the dominant anammox bacteria shifted from Candidatus Kuenenia to Candidatus Brocadia. Metagenomic analysis indicated that quorum sensing-based regulation mainly contributed to the proliferation and accumulation of anammox bacteria. This work provides an insight into the quorum sensing (QS)-regulated microbial interactions in the anammox and activated sludge consortia during the process development.

How heavy metal stress promotes dissemination of antibiotic resistance genes in the activated sludge process

Heavy metals have been recently revealed as promoters to antibiotic resistance gene (ARG) dissemination in water environment, but their influence on ARG transfer in the activated sludge process has not been clear. In this study, a set of sequencing batch reactors (SBRs) and micro-scale microfluidic chips were established to quantify the impacts of heavy metals (0.5 mM of Pb, 0.1 mM of As, and 0.005 mM of Hg) on the ARG spreading in the activated sludge consortium. Under heavy metal stress, transfer frequencies were 1.7–3.6 folds increase compared to the control. Gram-negative bacteria increased significantly after heavy metal added, which were more prone to receiving resistant plasmid from donors. Meanwhile, the relative expression of genes related to conjugation changed in activated sludge, especially the expression of outer membrane protein and oxidative stress regulatory genes increased by 2.9–7.4 folds and 7.8–13.1 folds, respectively. Furthermore, using microfluidic chips, the dynamics of ARG transfer was observed at single cell level under heavy metal pressure. Heavy metals firstly promoted conjugation and then vertical gene transfer played an important part for ARG spreading. The results provided in-depth understanding of the influence of heavy metals on ARG behavior in the environment.

Assessment of toxicity and kinetic effects of erythromycin on activated sludge consortium by fast respirometry method

Background: The present study aimed to assess the acute impact of erythromycin (ERY) as an inhibitor on peptone mixture utilization of activated sludge (AS) consortium. Methods: For this purpose, the inhibition of oxygen consumption was used based on the ISO 8192:2007 procedure. In this method, the AS consortium (10-day age) was extracted from lab-scale membrane bioreactor, then, percentage inhibition for total, heterotrophic, and nitrifying microorganisms, in separate batch respirometric tests were calculated in the absence and presence of N-allylthiourea (ATU) as a specific Nitrification inhibitor. Results: The obtained data showed that the height of oxygen uptake rate (OUR) profiles and amount of oxygen consumption reduced with increasing ERY dose. The half-maximal effective concentration (EC50) of ERY for heterotrophic and nitrifier microorganisms were 269.4 and 1243.1 mg/L, respectively. In Run 1, the kinetic coefficients bH, fA,H, YH, and µH were calculated as 2.61 d-1, 0.44, 0.4945 mg VSS/mg COD, and 0.047 d-1, respectively. Also, for maximum ERY concentration (1000 mg/L), the kinetic coefficients bH., fA,H, YH, and µH were calculated as 2.27 d-1, 0.3, 0.4983 mg VSS/mg COD, and 0.0049 d-1, respectively. Conclusion: The findings showed that the inhibitory impact of ERY was observed as a decrease in the amount of oxygen consumption by OUR profiles in rapid respirometric method (ISO 8192), which offered a novel insight for the acute inhibitory impact of this antibiotic. Also, chemical oxygen demand (COD) as an overall substrate parameter is most helpful in interpreting the behavior and the metabolic functions of AS systems.

Potential biotransformation pathways and efficiencies of ciprofloxacin and norfloxacin by an activated sludge consortium

Fluoroquinolones (FQs), such as ciprofloxacin (CIP) and norfloxacin (NOR), are types of emerging trace pollutants that have attracted great attention. In this study, an activated sludge (AS) consortium with high bio-removal capability to CIP and NOR was obtained by acclimating with CIP and NOR for 10 d. Meanwhile, a CIP- and NOR- transforming bacterial strain (S5), which is highly homologous to the 16S rRNA gene sequence of Enterobacter sp., was isolated from the acclimated AS. The bio-removal efficiency of CIP under the acclimated AS consortium was better than that under the pure culture of Enterobacter sp. S5 (93.1% vs. 89.3%), while the bio-removal efficiency of NOR under the acclimated AS consortium was lower than that under the pure culture of Enterobacter sp. S5 (83.9% vs. 89.8%). The biotransformation and bio-adsorption were two main ways to bio-remove CIP and NOR. However, the CIP and NOR biotransformation efficiencies of the acclimated AS were higher than under the pure culture of Enterobacter sp. S5, while the CIP and NOR adsorption of acclimated AS were lower than that under the pure culture of Enterobacter sp. S5. The N-acetylciprofloxacin and N-acetylnorfloxacin were the main biotransformation products of CIP and NOR. It is possible that acetyltransferase may be involved in the biotransformation process. Whether under the pure culture or AS consortium, the cytotoxicity of CIP and NOR transformation products to gram-negative bacteria was alleviated. Therefore, the acclimated AS and Enterobacter sp. S5 might provide a new strategy for removing contaminants and alleviating of FQs resistance.

Biohydrogen production by vermihumus-associated microorganisms using agro industrial wastes as substrate

Typically dark fermentation is performed using activated sludge consortia and there are not studies on hydrogen production using vermihumus-associated microorganisms documented. Microorganisms from Eisenia foetida casting have proven an efficient anti-recalcitrant activity. We have evaluated hydrogen production by Eisenia foetida lixiviated earthworm as inoculum using agro industrial wastes as substrate. Experiments were performed in 120 ml serological bottles under anaerobic conditions at 40 °C by triplicate. The results showed a hydrogen production of 1571.81, 1246.36 and 232.72 mlH2L−1 from molasses, bagasse and vinasse, respectively. Butyric and acetic acids were the main metabolites produced reaching up to 6.0 and 1.26 gL−1, respectively. Butanol and ethanol were also produced, but the maximum concentrations attained were 1.7 and 0.28 gL−1, respectively. Interestingly, the bagasse did not require a pretreatment. The results demonstrated that vermihumus-associated microorganisms are capable of producing hydrogen from the recalcitrant raw materials such as the sugarcane bagasse.

Structural and Kinetic Characteristics of 1,4-Dioxane-Degrading Bacterial Consortia Containing the Phylum TM7.

1,4-Dioxane-degrading bacterial consortia were enriched from forest soil (FS) and activated sludge (AS) using a defined medium containing 1,4-dioxane as the sole carbon source. These two enrichments cultures appeared to have inducible tetrahydrofuran/dioxane and propane degradation enzymes. According to qPCR results on the 16S rRNA and soluble di-iron monooxygenase genes, the relative abundances of 1,4-dioxane-degrading bacteria to total bacteria in FS and AS were 29.4% and 57.8%, respectively. For FS, the cell growth yields (Y), maximum specific degradation rate (Vmax), and half-saturation concentration (Km) were 0.58 mg-protein/mg-dioxane, 0.037 mg-dioxane/mg-protein∙h, and 93.9 mg/l, respectively. For AS, Y, Vmax, and Km were 0.34 mg-protein/mg-dioxane, 0.078 mg-dioxane/mg-protein∙h, and 181.3 mg/l, respectively. These kinetics data of FS and AS were similar to previously reported values. Based on bacterial community analysis on 16S rRNA gene sequences of the two enrichment cultures, the FS consortium was identified to contain 38.3% of Mycobacterium and 10.6% of Afipia, similar to previously reported literature. Meanwhile, 49.5% of the AS consortium belonged to the candidate division TM7, which has never been reported to be involved in 1,4-dioxane biodegradation. However, recent studies suggested that TM7 bacteria were associated with degradation of non-biodegradable and hazardous materials. Therefore, our results showed that previously unknown 1,4-dioxane-degrading bacteria might play an important role in enriched AS. Although the metabolic capability and ecophysiological significance of the predominant TM7 bacteria in AS enrichment culture remain unclear, our data reveal hidden characteristics of the TM7 phylum and provide a perspective for studying this previously uncultured phylotype.

Integrated liquid chromatography method in enantioselective studies: Biodegradation of ofloxacin by an activated sludge consortium.

Ofloxacin is a chiral fluoroquinolone commercialized as racemate and as its enantiomerically pure form levofloxacin. This work presents an integrated liquid chromatography (LC) method with fluorescence detection (FD) and exact mass spectrometry (EMS) developed to assess the enantiomeric biodegradation of ofloxacin and levofloxacin in laboratory-scale microcosms. The optimized enantioseparation conditions were achieved using a macrocyclic antibiotic ristocetin A-bonded CSP (150×2.1mm i.d.; particle size 5μm) under reversed-phase elution mode. The method was validated using a mineral salts medium as matrix and presented selectivity and linearity over a concentration range from 5μgL(-1) (quantification limit) to 350μgL(-1) for each enantiomer. The method was successfully applied to evaluate biodegradation of ofloxacin enantiomers at 250μgL(-1) by an activated sludge inoculum. Ofloxacin (racemic mixture) and (S)-enantiomer (levofloxacin) were degraded up to 58 and 52%, respectively. An additional degradable carbon source, acetate, enhanced biodegradation up to 23%. (S)-enantiomer presented the highest extent of degradation (66.8%) when ofloxacin was supplied along with acetate. Results indicated slightly higher biodegradation extents for the (S)-enantiomer when supplementation was done with ofloxacin. Degradation occurred faster in the first 3days and proceeded slowly until the end of the assays. The chromatographic results from LC-FD suggested the formation of the (R)-enantiomer during levofloxacin biodegradation which was confirmed by LC-MS with a LTQ Orbitrap XL.

Cometabolic degradation of organic wastewater micropollutants by activated sludge and sludge-inherent microorganisms.

Municipal wastewaters contain a multitude of organic trace pollutants. Often, their biodegradability by activated sludge microorganisms is decisive for their elimination during wastewater treatment. Since the amounts of micropollutants seem too low to serve as growth substrate, cometabolism is supposed to be the dominating biodegradation process. Nevertheless, as many biodegradation studies were performed without the intention to discriminate between metabolic and cometabolic processes, the specific contribution of the latter to substance transformations is often not clarified. This minireview summarizes current knowledge about the cometabolic degradation of organic trace pollutants by activated sludge and sludge-inherent microorganisms. Due to their relevance for communal wastewater contamination, the focus is laid on pharmaceuticals, personal care products, antibiotics, estrogens, and nonylphenols. Wherever possible, reference is made to the molecular process level, i.e., cometabolic pathways, involved enzymes, and formed transformation products. Particular cometabolic capabilities of different activated sludge consortia and various microbial species are highlighted. Process conditions favoring cometabolic activities are emphasized. Finally, knowledge gaps are identified, and research perspectives are outlined.

Enantioselective HPLC analysis and biodegradation of atenolol, metoprolol and fluoxetine

The accurate quantification of enantiomers is crucial for assessing the biodegradation of chiral pharmaceuticals in the environment. Methods to quantify enantiomers in environmental matrices are scarce. Here, we used an enantioselective method, high-performance liquid chromatography with fluorescence detection (HPLC-FD), to analyze two beta-blockers, metoprolol and atenolol, and the antidepressant fluoxetine in an activated sludge consortium from a wastewater treatment plant. The vancomycin-based chiral stationary phase was used under polar ionic mode to achieve the enantioseparation of target chiral pharmaceuticals in a single chromatographic run. The method was successfully validated over a concentration range of 20–800 ng/mL for each enantiomer of both beta-blockers and of 50–800 ng/mL for fluoxetine enantiomers. The limits of detection were between 5 and 20 ng/mL and the limits of quantification were between 20 and 50 ng/mL, for all enantiomers. The intra- and inter-batch precision was lower than 5.66 and 8.37 %, respectively. Accuracy values were between 103.03 and 117.92 %, and recovery rates were in the range of 88.48–116.62 %. Furthermore, the enantioselective biodegradation of atenolol, metoprolol and fluoxetine was followed during 15 days. The (S)-enantiomeric form of metoprolol was degraded at higher extents, whereas the degradation of atenolol and fluoxetine did not show enantioselectivity under the applied conditions.

Degradation of phenolics, nitrogen-heterocyclics and polynuclear aromatic hydrocarbons in a rotating biological contactor

The degradation of phenolics, heterocyclics and polynuclear aromatic hydrocarbons (PAHs) in a synthetic biomass gasifier wastewater with average COD of 1388mg/L was studied in a three stage rotating biological contactor (RBC) using the pyrene degrader, Exiguobacterium aurantiacum and activated sludge consortia (1:3v/v). As the organic loading rate (OLR) was varied from 3.3 to 14g/m2/d, the COD removal ranged from 63.3% to 92.6%. Complete removal of all the constituents was observed at the lowest OLR of 3.3g/m2/d. At 24h hydraulic retention time (HRT) and OLR of 6.6g/m2/d complete removal of pyridine, quinoline and benzene and 85–96% removal of phenol, naphthalene, phenanthrene, fluoranthene and pyrene was observed. E. aurantiacum was found to be the dominant bacteria in the biofilm. Clark’s model provided good fits to data for all the three stages of the RBC.

Simultaneous nutrients and carbon removal during pretreated swine slurry degradation in a tubular biofilm photobioreactor

The biodegradation potential of an innovative enclosed tubular biofilm photobioreactor inoculated with a Chlorella sorokiniana strain and an acclimated activated sludge consortium was evaluated under continuous illumination and increasing pretreated (centrifuged) swine slurry loading rates. This photobioreactor configuration provided simultaneous and efficient carbon, nitrogen, and phosphorous treatment in a single-stage process at sustained nitrogen and phosphorous removals efficiencies ranging from 94% to 100% and 70-90%, respectively. Maximum total organic carbon (TOC), NH(4) (+), and PO(4) (3-) removal rates of 80 +/- 5 g C m(r) (-3) day(-1), 89 +/- 5 g N m(r) (-3) day(-1), and 13 +/- 3 g P m(r) (-3) day(-1), respectively, were recorded at the highest swine slurry loadings (TOC of 1,247 +/- 62 mg L(-1), N-NH(4) (+) of 656 +/- 37 mg L(-1), P-PO(4) (3+) of 117 +/- 19 mg L(-1), and 7 days of hydraulic retention time). The unusual substrates diffusional pathways established within the phototrophic biofilm (photosynthetic O(2) and TOC/NH(4) (+) diffusing from opposite sides of the biofilm) allowed both the occurrence of a simultaneous denitrification/nitrification process at the highest swine slurry loading rate and the protection of microalgae from any potential inhibitory effect mediated by the combination of high pH and high NH(3) concentrations. In addition, this biofilm-based photobioreactor supported efficient biomass retention (>92% of the biomass generated during the pretreated swine slurry biodegradation).

Biodegradation of acetonitrile by adapted biofilm in a membrane-aerated biofilm reactor

A membrane-aerated biofilm reactor (MABR) was developed to degrade acetonitrile (ACN) in aqueous solutions. The reactor was seeded with an adapted activated sludge consortium as the inoculum and operated under step increases in ACN loading rate through increasing ACN concentrations in the influent. Initially, the MABR started at a moderate selection pressure, with a hydraulic retention time of 16 h, a recirculation rate of 8 cm/s and a starting ACN concentration of 250 mg/l to boost the growth of the biofilm mass on the membrane and to avoid its loss by hydraulic washout. The step increase in the influent ACN concentration was implemented once ACN concentration in the effluent showed almost complete removal in each stage. The specific ACN degradation rate achieved the highest at the loading rate of 101.1 mg ACN/g-VSS h (VSS, volatile suspended solids) and then declined with the further increases in the influent ACN concentration, attributed to the substrate inhibition effect. The adapted membrane-aerated biofilm was capable of completely removing ACN at the removal capacity of up to 21.1 g ACN/m(2) day, and generated negligible amount of suspended sludge in the effluent. Batch incubation experiments also demonstrated that the ACN-degrading biofilm can degrade other organonitriles, such as acrylonitrile and benzonitrile as well. Denaturing gradient gel electrophoresis studies showed that the ACN-degrading biofilms contained a stable microbial population with a low diversity of sequence of community 16S rRNA gene fragments. Specific oxygen utilization rates were found to increase with the increases in the biofilm thickness, suggesting that the biofilm formation process can enhance the metabolic degradation efficiency towards ACN in the MABR. The study contributes to a better understanding in microbial adaptation in a MABR for biodegradation of ACN. It also highlights the potential benefits in using MABRs for biodegradation of organonitrile contaminants in industrial wastewater.

Enzyme Activities and Shifts in Microbial Populations Associated with Activated Sludge Treatment of Textile Effluents

ABSTRACTThe enzyme studies on an activated sludge (AS) were aimed at providing information about adaptive response of microbial community during four significant alterations in textile wastewater treatment plant behavior associated with: shock loading with azo compounds; recovery after the xenobiotic shock; building up additional aerobic reactor; breakdown of facility exploitation for 5 months. The activity of several enzymes associated with target biodegradation processes was assessed. Induction of catechol 1,2—dioxygenase (C12DO), catechol 2,3—dioxygenase (C23DO), protocatechate 3,4—dioxygenase (P34DO) occurred under aerobic and notably under anoxic/microaerobic conditions, depending on the control point. Key microbial groups in the AS consortium were determined by cultivation-based-methods. The densities of bacteria from g. Pseudomonas (Ps) and Acinetobacter (Acin) were increased during the toxic shock. Aerobic heterotrophs (AH) and g. Acinetobacter decreased after pause of facility exploitation. The numbers of denitrifying bacteria (Dn) in denitrifying reactor were significantly decreased after each of the critical events.

Biodegradation of pyridine by an isolated bacterial consortium/strain and bio-augmentation of strain into activated sludge to enhance pyridine biodegradation

Pyridine and pyridine based products are of major concern as environmental pollutants due to their recalcitrant, persistent, toxic and teratogenic nature. In this study, we describe biodegradation of pyridine by an isolated consortium/strain under aerobic condition. Batch experiment results reveal that at lower initial pyridine concentrations (1-20 mg l(-1)), almost complete degradation was observed whereas at higher concentration (30-50 mg l(-1)), the degradation efficiency was dropped significantly. This may be due to inhibitory effect of pyridine at higher concentrations. The value of decay and yield coefficient was also determined. Furthermore, the bio-augmentation of isolated consortium/strain into the activated sludge consortium in different quantity has been also done and the effect of bio-augmentation on degradation has been studied. The results reveal that as the quantity of bio-augmentation increases, the degradation of pyridine increases. At 25% bio-augmentation, complete degradation of 20 mg l(-1) of pyridine can be achieved within 96 h of incubation. Thus, the study concluded that the bio-augmentation of the isolated consortium/strain into the sludge enhances the pyridine degradation efficiency of the biomass.

Biodegradation of organonitriles by adapted activated sludge consortium with acetonitrile-degrading microorganisms

A microbial process for the degradation of three types of structurally distinct organonitriles (i.e., saturated and unsaturated aliphatic nitrile and aromatic nitrile) was studied. Microorganisms were enriched from the activated sludge of a pharmaceutical wastewater treatment plant and adapted through providing acetonitrile as the sole carbon and nitrogen source for their growth. The adapted mixed culture was then examined for their capability of degrading acetonitrile, acrylonitrile and benzonitrile under various operational conditions. The performance of biodegradation and the metabolic intermediate- and end-products in the process were monitored. The results show that an average removal rate of 0.083 g acetonitrile g −1-VSS h −1, 0.0074 g acrylonitrile g −1-VSS h −1 or 0.0029 g benzonitrile g −1-VSS h −1 was achieved in the batch bioreactor under the common operational condition of 25 °C and pH 7. The biodegradation of acetonitrile and acrylonitrile showed a two-step pathway, with the generation of acetamide followed by acetic acid and ammonia for acetonitrile or acrylamide followed by acrylic acid and ammonia for acrylonitrile. However, the biodegradation of benzonitrile appeared to have only one step, with the direct production of benzoic acid and ammonia, but without benzamide being detected in the process. The results suggest that, depending on the substrates, the adapted mixed culture can develop very different degradation pathways, such as nitrile hydratase plus amidase for acetonitrile or acrylonitrile and nitrilase for benzonitrile. Therefore, the adapted mixed culture has a great potential and flexibility for actual applications in biodegradation of various organonitrile compounds.

Advanced Oxidation of Commercial Textile Biocides in Aqueous Solution: Effects on Acute Toxicity and Biomass Inhibition

In the present study, the decomposition of two biocides used in the textile finishing process with Advanced Oxidation Processes (AOPs) has been studied. Different AOPs, i.e O3/OH-, TiO2/UV-A and Fe2+/H2O2 have been used representing mutually combined components of the chemically and photochemically driven advanced oxidation systems. The course of reaction was examined by changes in chemical oxygen demand (COD), total organic carbon (TOC) and acute toxicity towards the water flea Daphnia magna (assessed in terms of the effective dilution ratio LD50). Particular attention has been paid to determine the inhibitory effect of raw and ozonated biocides on biological activated sludge consortium at concentrations typically encountered in textile finishing effluents. Significant oxidation and mineralization of both biocides could be achieved employing ozonation at pH = 11.5 and heterogeneous photocatalysis (TiO2/UV-A) at pH = 5.0, whereas Fenton's reagent appeared to be less effective in COD and acute toxicity abatement.

Reclamation of an activated-sludge microbial consortium by selective biostimulation.

Our previous study showed that an activated-sludge process broke down at the phenol-loading rate of 1.5 g l(-1) day(-1), when non-flocculating bacteria (called R6T and R10) overgrew the sludge, resulting in a sludge washout. In this study, we attempted to circumvent this breakdown problem by reclaiming the consortium structure. Activated sludge was fed phenol, and the phenol-loading rate was increased stepwise from 0.5 g l(-1) day(-1) to 1.0 g l(-1) day(-1) and then to 1.5 g l(-1) day(-1). Either galactose or glucose (at 0.5 g l(-1) day(-1)) was also supplied to the activated sludge from the phenol-loading rate of 1.0 g l(-1) day(-1). Pure culture experiments have suggested galactose to be a preferential substrate for a floc-forming bacterium (R6F) that predominantly degrades phenol under low phenol-loading conditions. Supplying galactose allowed sustainment of the R6F population and suppression of the overgrowth of R6T and R10 at the phenol-loading rate of 1.5 g l(-1) day(-1). This measure allowed the activated-sludge process to treat phenol at a phenol-loading rate up to 1.5 g l(-1) day(-1), although it broke down at 2.0 g l(-1) day(-1). In contrast, supplying glucose reduced the R6F population and allowed the activated-sludge process to break down at the phenol-loading rate of 1.0 g l(-1) day(-1). This study demonstrated that reclamation of the activated-sludge consortium by selective biostimulation of the floc-forming population improved the phenol-treating ability of the process.

Detrimental effects of high molecular-mass polyphenols on olive mill wastewater biotreatment

Research was undertaken to investigate whether low, medium or high molecular-mass polyphenolics were the most problematic compounds for olive mill wastewater (OMW) biotreatments. For this reason, three polyphenolic fractions were isolated by ultrafiltration of crude OMW and characterized by GC/MS and gel filtration analysis. When P. chrysosporium was cultivated in the presence of F1 polyphenolic fraction (F1<8 kDa), the decolorization/depolymerization was high. However, a very weak decolorization/depolymerization of the F3 fraction (F3>60 kDa) was observed. Lignin peroxidase (LiP) was detected as traces for the F1 fraction and undetected in the case of F3 one. Moreover, increasing the molecular-mass of aromatics led to decreases in levels of depolymerization and COD removal by P. chrysosporium cultures. The use of a lignin peroxidase induction medium has a positive effect on the high molecular-mass fraction decolorization and a high degree of decolorization paralleled the appearance of LiP activity in the extracellular fluid. By comparison to the synthetic medium used, LiP production was delayed in the presence of F1 fraction but strongly inhibited (80% loss) in the presence of F3 fraction. The F1 fraction was well degraded aerobically by P. putida DSM3932 (pWWO) and A. eutrophus DSM 4057 (pJP3) or an activated sludge consortium while F3 resisted degradation by the OMW-acclimated activated sludge. Moreover, continuous anaerobic biomethanization experiments conducted in parallel with the different fractions showed that at the same hydraulic retention time (26 days), the F1 fraction was bioconverted into methane at high yield while F3 fraction was poorly biodegraded.

Competitive Substrate Biodegradation during Surfactant-Enhanced Remediation

The impact of synthetic surfactants on the aqueous phase biodegradation of benzene, toluene, and p-xylene (BTpX) was studied using two anionic surfactants, sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS), and two nonionic surfactants, POE(20) sorbitan monooleate (T-maz-80) and octylphenolpoly(ethyleneoxy) ethanol (CA-620). Batch biodegradation experiments were performed to evaluate surfactant biodegradability using two different microbial cultures. Of the four surfactants used in this study, SDS and T-maz-80 were readily degraded by a microbial consortium obtained from an activated sludge treatment system, whereas only SDS was degraded by a microbial culture that was acclimated to BTpX. Biodegradation kinetic parameters associated with SDS and T-maz-80 degradation by the activated sludge consortium were estimated using respirometric data in conjunction with a nonlinear parameter estimation technique as μmax = 0.93 h−1, Ks = 96.18 mg/L and μmax = 0.41 h−1, Ks = 31.92 mg/L, respectively. When both BTpX and surfactant were present in the reactor along with BTpX-acclimated microorganisms, two distinct biodegradation patterns were seen. SDS was preferentially utilized inhibiting hydrocarbon biodegradation, whereas the other three surfactants had no impact on BTpX biodegradation. None of the four surfactants were toxic to the microbial cultures used in this study. Readily biodegradable surfactants are not very effective for subsurface remediation applications as they are rapidly consumed, and also because of their potential inhibitory effects on intrinsic hydrocarbon biodegradation. This greatly increases treatment costs as surfactant recovery and reuse are adversely affected.

P4F137 - Recovery capacity of a polluted urban river: A preliminary experimental simulation study with tadpoles as test organism

Phenolic composition, toxicity and biodegradability of three different phenolic leachates/samples was studied. Samples A and C were the leachates from the oil-shale industry spent shale dumps at Kohtla-Järve, Estonia. Sample B was a laboratory-prepared synthetic mixture of 7 phenolic compounds mimicking the phenolic composition of the leachate A. Toxicity of these 3 samples was analyzed using two photobacterial test (BioTox™ and Microtox™), Daphnia test (DAPHTOXKIT F™ pulex) and rotifiers' test (ROTOXKIT F™). All the LC50 values were in the range of 1–10%, leachate A being the most toxic.The growth and detoxifying potential (toxicity of the growth medium was measured using photobacterial tests) of 3 different phenol-utilizing bacteria and acclimated activated sludes was studied in shake-flask cultures. 30% leachate A (altogether 0.6 mM total phenolic compounds) was too toxic to rhodococci and they did not grow. Cell number of Kurthia sp. and Pseudomonas sp. in 30% leachate A increased by 2 orders of magnitude but despite of the growth of bacteria the tocicity of the leachate did not decrease even by 7 weeks of cultivation. However, if the activated sludge was used instead of pure bacterial cultures the toxicity of the 30% leachate A was eliminated already after 3 days of incubation 30% samples B and C were detoxified by activated sludge even more rapidly, within 2 days. As the biodegradable part of samples A and B should be identical, the detoxification of leachate A compared to that of sample B was most probably inhibited by inorganic (e.g., sulphuric) compounds present in the leachate A. Also, the presence of toxic recalcitrant organic compounds in the leachate A (missed by chemical analysis) that were not readily biodegradable even by activated sludge consortium should not be excluded.