Biodegradation, decolourisation and detoxification of textile wastewater enhanced by advanced oxidation processes

Recently, an increasing application of so called advanced oxidation processes (AOPs) to industrial wastewater has been observed. In particular, an integrated approach of biological and chemical treatment of wastewater is advantageous conceptually. The subject of our study was synthetic wastewater, simulating effluents from knitting industry. The wastewater contained components that are very often used in Polish textile industry: an anionic detergent Awiwaz KG conc., a softening agent Tetrapol CLB and an anthraquinone dyestuff-Acid Blue 40, CI 2125. The toxicity of the detergents and the dye was determined in terms of effective concentration EC50 using mixed cultures of activated sludge as well as pure culture of luminescent bacteria Vibrio fischerii NRRLB-11177. The dye did not undergo biodegradation without AOPs pretreatment, therefore a degree of its removal (decolourisation) by the AOPs has been determined and its bio-sorption properties on the flocks of activated sludge have been studied. The dye adsorption onto flocks of activated sludge was described by Henry's isotherm. Our investigations focussed on the influence of various oxidants like O3, H2O2 and UV light on biodegradation of single components aqueous solution as well as of the whole textile wastewater. The results of kinetic measurements of the biodegradation (by means of acclimated activated sludge) was described by Monod type of kinetic equation. The experimental evidence of the positive effect of chemical oxidation pretreatment on the biodegradation of recalcitrant compounds was quantified by estimation of the kinetic parameters of the Monod equation. Due to the AOPs pretreatment a decrease of the Monod constant and an increase of maximal specific growth rate was observed. The activity of degradative enzymes of activated sludge was assayed by the methods of 2-[4-iodophenyl]-3-[4-nitrophenyl]-5-phenyltetrazolium chloride test.     

Application of the OECD 301F respirometric test for the biodegradability assessment of various potential endocrine disrupting chemicals

The biodegradability of several potential endocrine disrupting compounds, namely 4-n-nonylphenol (4-n-NP), nonylphenol monoethoxylate (NP1EO), nonylphenol diethoxylate (NP2EO), bisphenol A (BPA), triclosan (TCS), di-(2-ethylhexyl)-phthalate (DEHP), perfluorooctanoate (PFOA) and perfluorononanoate (PFNA) was evaluated in this study, using OECD method 301F (manometric respirometry test) and activated sludge as inoculum. According to the results, 4-n-NP and BPA meet the strict definition of ready biodegradability and they are not expected to be persistent during the activated sludge process. Partial biodegradation was observed for DEHP (58.7+/-5.7%, n=3), TCS (52.1+/-8.5%, n=3) and NP1EO (25.9+/-8.1%, n=3), indicating their possible biodegradation in wastewater treatment systems, while no biodegradation was observed for NP2EO, PFOA and PFNA. Experiments in the co-presence of a readily biodegradable compound showed the absence of co-metabolic phenomena during 4-n-NP, BPA and TCS biodegradation. Using first order kinetics to describe biodegradation of the target compounds, half-lives of 4.3+/-0.6, 1.3+/-0.2, 1.8+/-0.5, 6.9+/-2.6 days were calculated for 4-n-NP, BPA, TCS and DEHP, respectively. Toxicity tests using marine bacterium Vibrio fischeri showed that biodegradation of 4-n-NP, NP1EO, BPA and TCS is a simultaneous detoxification process, while possible abiotic or biotic transformations of NP2EO, DEHP, PFOA and PFNA during respirometric test resulted to significant increase of their toxicities.     

Microalgae-based processes for the biodegradation of pretreated piggery wastewaters

The potential and limitations of photosynthetic oxygenation on carbon and nitrogen removal from swine slurry were investigated in batch experiments using Chlorella sorokiniana and an acclimated activated sludge as model microorganisms. While algal-bacterial systems exhibited similar performance than aerated activated sludge in tests supplied with four and eight times diluted slurry, a severe inhibition of the biodegradation process was recorded in undiluted and two times diluted wastewater. Daily pH adjustment to 7 in enclosed algal-bacterial tests at several swine slurry dilutions allowed the treatment of up to two times diluted slurries (containing up to 1,180 mg N-NH(4) (+) l(-1)). The combination of high pH levels and high NH(4) (+) concentrations was thus identified as the main inhibitory factor governing the efficiency of photosynthetically oxygenated processes treating swine slurry. Measurements of soluble total organic carbon (TOC) and volatile fatty acids (VFA) present in the slurry suggested that VFA degradation (mainly acetic and propionic acid) accounted for most of the soluble TOC removal, especially during the initial stages of the biodegradation process. On the other hand, assimilation into biomass and nitrification to NO(2) (-) constituted the main NH(4) (+) removal processes in enclosed algal-bacterial systems.     

Gram-staining characterisation of activated sludge filamentous bacteria by automated colour analysis

An automated image analysis method has been developed for the monitoring of the Gram-staining characteristics of filamentous bacteria in activated sludge. The binary method of pixel classification agreed with manual estimation (level of correlation of 0.9 for Gram-positive bacteria). Its robustness has been assessed by repeatability tests. Population shifts in terms of Gram-staining characteristics have been monitored in laboratory-scale experiments with two feeding schedules using this technique.Revisions requested 22 September 2004; Revisions received 11 October 2004     

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.     

Determination of biodegradation products from sulfonated dyes by <Emphasis Type="Italic">Pleurotus ostreatus</Emphasis>using capillary electrophoresis coupled with mass spectrometry

Microbial treatment of environmental pollutants including dyes with white rot fungi has received wide attention as a potential alternative for conventional methods in wastewater treatment. The degradation products from dyes and mechanism underlying fungal degradation of dyes is desirable to be understood. Capillary electrophoresis coupled with mass spectrometry (CE-MS) was used in this study to determine biodegradation products of 4-[(4-hydroxyphenyl)azo]-benzenesulfonic acid, sodium salt (4HABA) and Acid Orange 7 (C.I. 15510), produced by a white rot fungus, Pleurotus ostreatus. Two major degradation products, benzenesulfonic acid and 4-hydroxy-benzenesulfonic acid, from both sulfonated compounds, were identified and their kinetic profiles in biodegradation were followed by CE-MS. Another product, 1,2-naphthoquinone, from Acid Orange 7 was identified using HPLC. Formation of these products in fungal degradation is discussed.Revisions requested 8 October 2004; Revision received 12 November 2004     

Biodegradation kinetic constants and sorption coefficients of micropollutants in membrane bioreactors

In order to elucidate the capability of biomass developed in membrane bioreactors (MBR) to degrade and sorb emerging micropollutants, biodegradation (k_biol) and sorption (k_sor) kinetic constants as well as solid–liquid partition coefficients (K_d) of 13 selected pharmaceutical and personal care products (PPCPs) were determined with MBR heterotrophic biomass adding a pulse (100 ppb of each compound) and following the liquid and solid phase concentrations over time. The results obtained were compared to literature data referring to conventional activated sludge (CAS) systems. Two experiments were performed: one in the MBR itself and the second one in a batch reactor with the same type and concentration of biomass as in the MBR. Overall, both biodegradation and sorption coefficients were in the same range as previously reported by other studies in CAS systems, indicating that MBR biomass does not show better capabilities for the biological degradation and/or sorption of PPCPs compared to the biomass developed in CAS reactors. Therefore, the higher PPCPs removal efficiencies found in MBRs are explained by the high biomass concentrations obtained at the long sludge retention times at which this type of reactors are usually operated.     

Estimation of Biodegradation Potential of Xenobiotic Organic Chemicals

A method is described to estimate the biodegradation potential of soluble, insoluble, and unknown organic chemicals. The method consists of two stages: (i) generation of a microbial inoculum in a bench scale semicontinuous activated sludge system during which microorganisms are acclimated to test material and the removal of dissolved organic carbon is monitored and (ii) biodegradability testing (CO₂ evolution) in a defined minimal medium containing the test material as the sole carbon and energy source and a dilute bacterial inoculum obtained from the supernatant of homogenized activated sludge generated in the semicontinuous activated sludge system. Removal and biodegradation are measured using nonspecific methods, at initial concentrations of 5 to 10 mg of dissolved organic carbon per liter. Biodegradability data are accurately described by a nonlinear computer model which allows the rate and extent of biodegradation for different compounds to be compared and statistically examined. The evaluation of data generated in the combined removability-biodegradability system allows the biodegradation potential of a variety of xenobiotic organic chemicals to be estimated.     

Biodegradation of hydrocarbon cuts used for diesel oil formulation

The biodegradability of various types of diesel oil (DO), such as straight-run DO, light-cycle DO, hydrocracking DO, Fischer–Tropsch DO and commercial DO, was investigated in biodegradation tests performed in closed-batch systems using two microflorae. The first microflora was an activated sludge from an urban wastewater treatment plant as commonly used in biodegradability tests of commercial products and the second was a microflora from a hydrocarbon-polluted soil with possible specific capacities for hydrocarbon degradation. Kinetics of CO₂ production and extent of DO biodegradation were obtained by chromatographic procedures. Under optimised conditions, the polluted-soil microflora was found to extensively degrade all the DO types tested, the degradation efficiencies being higher than 88%. For all the DOs tested, the biodegradation capacities of the soil microflora were significantly higher than those of the activated sludge. Using both microflora, the extent of biodegradation was highly dependent upon the type of DO used, especially its hydrocarbon composition. Linear alkanes were completely degraded in each test, whereas identifiable branched alkanes such as farnesane, pristane or phytane were degraded to variable extents. Among the aromatics, substituted mono-aromatics were also variably biodegraded.     

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.     

Mutation of Candida tropicalis by irradiation with a He-Ne laser to increase its ability to degrade phenol

Candida tropicalis isolated from acclimated activated sludge was used in this study. Cell suspensions with 5 x 10(7) cells ml(-1) were irradiated by using a He-Ne laser. After mutagenesis, the irradiated cell suspension was diluted and plated on yeast extract-peptone-dextrose (YEPD) medium. Plates with approximately 20 individual colonies were selected, and all individual colonies were harvested for phenol biodegradation. The phenol biodegradation stabilities for 70 phenol biodegradation-positive mutants, mutant strains CTM 1 to 70, ranked according to their original phenol biodegradation potentials, were tested continuously during transfers. Finally, mutant strain CTM 2, which degraded 2,600 mg liter(-1) phenol within 70.5 h, was obtained on the basis of its capacity and hereditary stability for phenol biodegradation. The phenol hydroxylase gene sequences were cloned in wild and mutant strains. The results showed that four amino acids were mutated by irradiation with a laser. In order to compare the activity of phenol hydroxylase in wild and mutant strains, their genes were expressed in Escherichia coli BL21(DE3) and enzyme activities were spectrophotometrically determined. It was clear that the activity of phenol hydroxylase was promoted after irradiation with a He-Ne laser. In addition, the cell growth and intrinsic phenol biodegradation kinetics of mutant strain CTM 2 in batch cultures were also described by Haldane's kinetic equation with a wide range of initial phenol concentrations from 0 to 2,600 mg liter(-1). The specific growth and degradation rates further demonstrated that the CTM 2 mutant strain possessed a higher capacity to resist phenol toxicity than wild C. tropicalis did.     

Substrate uptake tests and quantitative FISH show differences in kinetic growth of bulking and non-bulking activated sludge

The competition between filaments and floc formers in activated sludge has been historically described using kinetic selection. However, recent studies have suggested that bacterial storage may also be an important factor in microbial selection, since the dynamic nature of substrate flows into wastewater treatment plants elicit transient responses from microorganisms. Respirometry-based kinetic selection should thus be reevaluated by considering cell storage, and a more reliable method should be developed to include bacterial storage in the analysis of growth of filaments and floc formers in activated sludge. In this study, we applied substrate uptake tests combined with metabolic modeling to determine the growth rates, yields and maintenance coefficients of bulking and non-bulking activated sludge developed in lab scale reactors under feast and famine conditions. The results of quantitative fluorescence in situ hybridization (FISH) showed that the filaments Eikelboom Type 1851, Type 021N, and Thiothrix nivea were dominant in bulking sludge, comprising 42.0 % of mixed liquor volatile suspended solids (MLVSS), with 61.6% of the total filament length extending from flocs into bulk solution. Only low levels of Type 1851 filament length (4.9% of MLVSS) occurred in non-bulking sludge, 83.0% of which grew inside the flocs. The kinetic parameters determined from the substrate uptake tests were consistent with those from respirometry and showed that filamentous bulking sludge had lower growth rates and maintenance coefficients than non-bulking sludge. These results provide support for growth kinetic differences in explaining the competitive strategy of filamentous bacteria.     

How adaptation and mass transfer control the biodegradation of linear alkylbenzene sulfonate by activated sludge

We use a nonsteady-state model to evaluate the effects of community adaptation and sorption kinetics on the fate of linear alkylbenzene sulfonate (LAS) in batch experiments conducted with activated sludge that was continuously fed different concentrations of LAS. We observed a sharp decrease in the biodegradation rate between 30 and 60 minutes and the presence of an LAS residual at the end of the batch experiments. The modeling analysis indicates that these phenomena were caused by relatively slow inter-phase mass transport of LAS. The modeling analyses also showed that the amount of LAS-degrading biomass increased when the continuous activated sludge was fed a higher LAS concentration. Although community adaptation to LAS involved accumulation of more LAS degraders, the increase was not proportional to the feed concentration of LAS, which supports the concept that LAS degraders also utilized portions of the general biochemical oxygen demand (BOD) fed to the continuous activated sludge systems.     

Monitoring the biodegradability of bisphenol A and its metabolic intermediates by manometric respirometry tests

As a result of its wide usage in the production of polycarbonate plastics and epoxy resins, bisphenol A (BPA) is commonly detected in wastewaters. Recently, BPA became a major concern because its adverse effects as an endocrine disruptor. In this work, the biodegradation kinetics of BPA and its metabolic intermediates 4-hydroxyacetophenone (4HAP), 4-hydroxybenzaldehyde (4HB) and 4-hydroxybenzoic acid (4HBA) by BPA-acclimated activated sludge was studied using manometric respirometry (BOD) tests. For all the tested compounds, BOD curves exhibited two phases. In the first one, a fast increase of the oxygen consumption (OC) due to the active oxidation of the substrate was obtained. Then, when the substrate was exhausted, the endogenous respiration produced a slower increase of OC. A standard Monod-model with biomass growth was used to represent the OC profiles as a function of time. For all the tested compounds, a good agreement between the proposed model and the experimental data was obtained. According to their biodegradation rates, the tested compounds can be ordered as follows: BPA < 4HAP ? 4HB < 4HBA. Because the oxidation rate of BPA by BPA-acclimated activated sludge limits the rate of the whole biodegradation pathway, the accumulation of metabolic intermediates 4HAP, 4HB, and 4HBA would be negligible. To calculate the dissolved oxygen (DO) concentration (C) during the BOD tests, the oxygen transfer coefficient (k_La) of the BOD bottles was obtained using the sulfite method. Finally, a simple procedure to calculate the minimum DO concentration (C_min) based on BOD data was developed. Calculation results demonstrated that under the tested conditions, C values were high enough as not to be the limiting substrate for the microbial growth.     

Biodegradation by activated sludge and toxicity of tetracycline into a semi-industrial membrane bioreactor

Much attention has been devoted recently to the fate of pharmaceutically active compounds such as tetracycline antibiotics in soil and water. Tetracycline (TC) biodegradability by activated sludge derived from membrane bioreactor (MBR) treating swine wastewater via CO₂-evolution was evaluated by means of modified Sturm test, which was also used to evaluate its toxicity on carbon degradation. The impact of tetracycline on a semi-industrial MBR process was also examined and confronted to lab-scale experiments. After tetracycline injection in the pilot, no disturbance was detected on the elimination of organic matters and ammonium (nitrification), reaching after injection 88% and 99% respectively; only denitrification was slightly affected. Confirming the ruggedness and the superiority of membrane bioreactors over conventional bioreactors, no toxicity was observed at the considered level of TC in the pilot (20 mg TOC L⁻¹), while at lab-scale sodium benzoate biodegradation was completely inhibited from 10 mg TOC L⁻¹ TC. The origin of the activated sludge showed a significant impact on the performances, since the ultimate biodegradation was in the range −50% to −53% for TC concentrations in the range 10–20 mg TOC L⁻¹ with conventional bioreactor sludge and increased to 18% for 40 mg TOC L⁻¹ of TC with activated sludge derived from the MBR pilot. This confirmed the higher resistance of activated sludge arising from membrane bioreactor.     

Automated fast filtration and on‐filter quenching improve the intracellular metabolite analysis of microorganisms

To reliably determine intracellular metabolite concentrations in microorganisms, accurate sampling and sample inactivation strategies are crucial. Here, we present a method for automated fast filtration and on‐filter quenching of microbial samples to overcome metabolite leakage induced by cold shock and significantly reduce the sampling and treatment time compared to manual filtration methods. The whole process of sampling, sample filtration, filter wash, and quenching of the filter with liquid nitrogen was finished in less than 6–15 s, depending on the experimental setup. By integration into an automated fast sampling device, we compared our method to the conventional methanol quenching method and showed that intracellular amino acid contents in Escherichia coli were significantly increased (≥75%) with our fast filtration and on‐filter quenching method. Furthermore, we investigated different filter types for the fast filtration and the efficiency of metabolite extraction from cells held on filters. Additionally, we found that the fast filtration behaves considerably different during exponential and nonexponential growth, probably due to variations of cell morphologies. Overall, we demonstrated that the automation of the fast filtration method significantly reduces the time for filtration and quenching and hence enlarge the number of metabolites that can be quantified with this leakage‐free sampling method.     

Biodegradation potential and bacterial diversity of a petrochemical wastewater treatment plant in Iran

An activated sludge treatment was evaluated for its effectiveness in cleaning up a petrochemical wastewater in Iran. For assessing biodegradation potential of activated sludge, seven characteristics of wastewater (temperature, pH, dissolved oxygen, chemical oxygen demand, concentrations of ethylene dichloride, vinyl chloride, and total hydrocarbons) were monitored during six months. It was shown that dominant pollutants in order of magnitude were normal-alkanes (C(10)-C(21)), aromatics, and polycyclic hydrocarbons. The activated sludge treatment revealed maximum reduction of 89%, 99%, 92%, and 80% in COD, ethylene dichloride, vinyl chloride and total hydrocarbons concentrations, respectively. Preliminary screening of culturable petrochemical-degrading microorganisms of the activated sludge resulted in the collection of 67 bacterial and one mold species. Bacterial strains mainly belonged to Pseudomonas, Flavobacterium, Comamonas, Cytophaga, Acidovorax, Sphingomonas, Bacillus and Acinetobacter genera. The isolated mold was identified as Trichoderma sp.     

Biodegradation kinetics of linear alkylbenzene sulphonates in sea water

This article reports the primary biodegradation kinetics of linear alkylbenzene sulphonates (LAS) in sea water from the Bay of Cadiz (South West of the Iberian Peninsula). The authors used the biodegradation test guideline proposed by the Office of Prevention, Pesticides, and Toxic Substances of the United States Environmental Protection Agency; 835.3160 “Biodegradability in sea water” in its shake flask variant. High performance liquid chromatography (HPLC) has been employed for the analysis of the surfactant material. The surfactant shows a primary biodegradation kinetic in accordance with a logistic model, the kinetic parameters t ₅₀ and lag time were calculated by means of a easy quantitative procedure introduced. Mean values of 6.15 ± 0.45 and 6.67 ± 0.6 days were obtained for t ₅₀ and lag time, respectively. These results indicate that although LAS has a high primary biodegradation rate in sea water, it biodegrades slower than in similar tests conducted in river water.     

Biodegradability of tannin-containing wastewater from leather industry

Tannins occur commonly in the wastewaters from forestry, plant medicine, paper and leather industries. The treatment of this kind of wastewaters, including settling and biodegradation, is usually difficult because tannins are highly soluble in water and would inhibit the growth of microorganisms in activated sludge. The objective of this study is to investigate biodegradability of tannin-containing wastewaters, so as to characterize the pollution properties of such wastewaters and provide a reference for their biological treatment in wastewater treatment plants. The research was typified by using the wastewater collected from vegetable tanning process in leather industry. A model was developed to describe the activated sludge process, and the biodegradation kinetics of vegetable tanning wastewater (VET wastewater) was studied. It was found that the biodegradability of tannin-containing wastewater varies heavily with the content of tannins in wastewater. The biodegradation of VET wastewater with tannin content around 4,900 mg/l occurred inefficiently due to the inhibition of tannins to the activated sludge process, and only 34.7% of biodegradation extent was reached in 14 days of incubation. The optimal biodegradability of VET wastewater was observed when its tannin content was diluted to 490 mg/l, where the COD and tannin removals reached 51.3% and 45.1% respectively in 6 days. Hence, it is suggested that a proper control of tannin content is necessary to achieve an effective biodegradation of tannin-containing wastewaters in wastewater treatment plants.     

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.