This work describes the removal of 6 quinolone antibiotics from wastewaters under different redox conditions (aerobic, nitrifying and anoxic) through batch experiments in laboratory scale activated ...sludge reactors using mixed liquor from a membrane bioreactor pilot plant (MBR). The main removal pathways for antibiotics from wastewaters involved in each treatment are described. Mass balances indicated that sorption on sludge played a dominating role in the elimination of antibiotics. Sorption potential depended on the redox conditions, being lower in nitrifying (Kd, 414–876 L kg−1) and anoxic (Kd, 471–930 L kg−1) sludge in comparison with aerobic sludge (Kd, 534–1137 L kg−1). Kd was higher for piperazinylic quinolones. Redox conditions also influenced biodegradation, a secondary pathway, which followed first-order kinetics with degradation rates constants ranging from 1.8·10−3 to 8.2·10−3 h−1. Biodegradation rates under anoxic conditions were negligible. The experimental results have also demonstrated much higher removal efficiency by biodegradation (36.2–60.0%) under nitrifying conditions in comparison with aerobic conditions (14.9–43.8%). The addition of allylthiourea, an ammonia monooxygenase inhibitor, inhibited nitrification completely and reduced significantly the biodegradation of target antibiotics (16.5–29.3%). The residual biodegradation in the presence of allylthiourea may be due to the activity of heterotrophs in the enriched nitrifier culture. The removal of the selected antibiotics under the studied redox conditions depended significantly on the bacteria composition of the sludge. These results suggest that despite the known persistence of this group of antibiotics it is possible to enhance their degradation using nitrifying conditions, which at adequate working conditions as high SRT, typical in MBR, become a promising alternative for improving quinolones removal from environment.
► Sorption and biodegradation are the main pathways for quinolone removal. ► The nitrifying conditions improve biodegradation and reduce sorption potential. ► Biodegradation does not significantly occur under anoxic conditions. ► The inhibition of nitrification reduces the removal of antibiotics by biodegradation. ► Removal of target antibiotics depends on the composition of bacterial populations.
A partial-nitritation bench-scale submerged biofilter was used for the treatment of synthetic wastewater containing a high concentration of ammonium in order to study the influence of the antibiotic ...ciprofloxacin on the partial-nitritation process and biodiversity of the bacterial community structure. The influence of ciprofloxacin was evaluated in four partial-nitritation bioreactors working in parallel, which received sterile synthetic wastewater amended with 350ng/L of ciprofloxacin (Experiment 1), synthetic wastewater without ciprofloxacin (Experiment 2), synthetic wastewater amended with 100ng/L of ciprofloxacin (Experiment 3) and synthetic wastewater amended with 350ng/L of ciprofloxacin (Experiment 4). The concentration of 100ng/L of antibiotics demonstrated that the partial-nitritation process, microbial biomass and bacterial structure generated by tag-pyrosequencing adapted progressively to the conditions in the bioreactor. However, high concentrations of ciprofloxacin (350ng/L) induced a decay of the partial-nitritation process, while the total microbial biomass was increased. Within the same experiment, the bacterial community experienced sequential shifts with a clear reduction of the ammonium oxidation bacteria (AOB) and an evident increase of Commamonas sp., which have been previously reported to be ciprofloxacin-resistant. Our study suggests the need for careful monitoring of the concentration of antibiotics such as ciprofloxacin in partial-nitritation bioreactors, in order to choose and maintain the most appropriate conditions for the proper operation of the system.
•The study was done in 4 bench-scale partial-nitrification submerged bed bioreactors.•Changes in performance were studied under different antibiotic concentrations.•We focused the study on the influence of ciprofloxacin on the microbial population.•Ciprofloxacin effect in partial-nitritation was tested by multivariate analysis.
The protection and conservation of natural resources is one of the main priorities of modern society. Water is perhaps our most valuable resource, and thus should be recycled. Many of the current ...recycling techniques for polluted water only concentrate the pollutant without degrading it or eliminating it. In this sense, advanced oxidation processes are possibly one of the most effective methods for the treatment of wastewater containing organic products (effluents from chemical and agrochemical industries, the textile industry, paints, dyes, etc.). More conventional techniques cannot be used to treat such compounds because of their high chemical stability and/or low biodegradability. This article describes, classifies, and analyzes different types of advanced oxidation processes and their application to the treatment of polluted wastewater.
•Comparison of systems combining moving bed biofilm reactor with membrane bioreactor and membrane bioreactor configuration.•Kinetic parameters which characterised the moving bed biofilm reactor and ...the membrane bioreactor processes were analysed.•Not statistically significant differences between the experimental plants regarding the organic matter and nutrients removal.•Improvement of nitrogen and phosphorus removal of the MBBR-MBR system which contained carriers only in the aerobic zone.•MBR had a better performance from the point of view of the kinetic parameters.
New technologies regarding wastewater treatment have been developed. Among these technologies, the moving bed biofilm reactor combined with membrane bioreactor (MBBR-MBR) is a recent solution alternative to conventional processes. This paper presents the results obtained from three wastewater treatment plants working in parallel. The first wastewater treatment plant consisted of a membrane bioreactor (MBR), the second one was a MBBR-MBR system containing carriers both in anoxic and aerobic zones, and the last one consisted of a MBBR-MBR system which contained carriers only in the aerobic zone. The reactors operated with a hydraulic retention time of 26.47h. During the study, the difference between the experimental plants was not statistically significant concerning organic matter and nutrients removal. However, different tendencies regarding nutrients removal are shown by the three wastewater treatment plants. In this sense, the performances in terms of nitrogen and phosphorus removal of the MBBR-MBR system which contained carriers only in the aerobic zone (67.34±11.22% and 50.65±11.13%, respectively) were slightly better than those obtained from another experimental plants. As a whole, the pilot plant which consisted of a MBR showed better performance from the point of view of the kinetics of the heterotrophic and autotrophic biomass with values of μm,H=0.00858h−1, μm,A=0.07646h−1, KM=2.37mgO2L−1 and KNH=1.31mgNL−1.
•Conventional MBR, hybrid MBBR–MBR and pure MBBR–MBR were compared.•Pure MBBR–MBR has the highest potential of nitrogen removal.•Pure MBBR–MBR shows the best kinetic performance.•Hybrid MBBR–MBR has ...the highest performance of COD and BOD5 removal.•Attached biomass enhances the process of wastewater treatment.
The moving bed biofilm reactor–membrane bioreactor (MBBR–MBR) is a novel solution to conventional processes. In this study, a conventional membrane bioreactor (MBR), a hybrid MBBR–MBR and a pure MBBR–MBR were compared. The hybrid MBBR–MBR contained suspended and attached biomass, while the pure MBBR–MBR mainly had attached biomass. The reactors operated with a hydraulic retention time of 9.5h. The pure MBBR–MBR had the highest efficiency of nitrogen removal with a value of 71.91±16.04%. As a whole, the pure MBBR–MBR showed the best performance from the point of view of the kinetics of the heterotrophic and autotrophic biomass with values of μm,H=0.018h−1, μm,A=0.751h−1, KM=2.679mgO2L−1 and KNH=2.191mgNL−1. The presence of the attached biomass improved the organic matter and nitrogen removal in a pure MBBR–MBR system.
The effectiveness of three selected carbon sources (sucrose, ethanol and methanol) on submerged filters for the removal of nitrate from contaminated groundwater (100
mg NO
3
−/litre), was studied. ...Process yields, nitrite accumulation, biomass production and growth of denitrifying bacteria were compared. Process yields, represented as ratio C/N were 2.5, 1.08 and 1.1 for sucrose, ethanol and methanol assays, respectively, making sucrose the least efficient carbon source. Nitrite accumulation in treated groundwater was more notable for sucrose assays, reaching values of 5
mg NO
2
−/l. However, when ethanol or methanol were used as carbon sources, nitrite accumulation in treated water was practically zero during the experiments. On the other hand, a greater biomass production was observed in these assays with sucrose, causing clogging of the filter. Higher density of denitrifying bacteria in the biofilm, observed when ethanol and methanol were amended to the influent, suggested that these carbon sources increased the denitrification activity compared with the experiments performed with sucrose. Since methanol is toxic, ethanol is considered the most suitable carbon source out of the three tested, under the experimental conditions.
•The study was done in 2 bench scale partial-nitrification Submerged bed bioreactors.•Nitrifying bacteria were studied using Nxra and CTO genes by PCR-TGGE fingerprinting.•We focused the study in the ...influence of the hydraulic retention time (HRT).•The HRT effect in the microbial communities was confirmed by multivariate analysis.•In the supplementary data denitrifying bacteria were studied using nosZ gen.
The present study focused on the technical and biological characteristics of a bench-scale partial-nitritation bioreactor and established its operating parameters. In this manner 2 bench-scale submerged-bed bioreactor of 3L were operated under identical conditions of pH, oxygen concentration and temperature but under different hydraulic retention time (9 and 12h). This made it possible to study the influence of the hydraulic retention time (HRT) on the nitrification processes and on the nitrifying microbiota of the biofilms. Moreover, specific bacterial groups involved in the nitrification process, such as ammonium oxidizing (CTO) and nitrite oxidizing (nxrA) were investigated using a cultivation-independent approach based on PCR-TGGE fingerprinting. The results showed that the HRT may affect the nitrification processes of a partial-nitritation bioreactor using a synthetic wastewater containing 600mg/L of ammonia. It was found that HRT of 12h transformed 100% of the ammonium to nitrite. However, when the HRT was 9h there was a significant reduction (35%) in ammonia converted. Cluster analysis of PCR-TGGE fingerprints showed significant differences in the profiles depending on the different HRT applied, especially on the ammonia oxidizing bacteria. The importance of this factor was confirmed by multivariate analysis. Phylogenetic analysis of bands sequences showed that CTO and nxrA sequences presented similarity to those present in the database and grouped in specific clusters. Our results suggested that changes in HRT can affect significantly the nitrifying microbial community and the performance of the partial nitritation system.
A pilot scale submerged ultra-filtration membrane bioreactor (MBR) was used for the aerobic treatment of domestic wastewater over 9 months of year 2006 (28th March to 21st December). The MBR was ...installed at a municipal wastewater facility (EMASAGRA, Granada, Spain) and was fed with real wastewater. The experimental work was divided in 4 stages run under different sets of operation conditions. Operation parameters (total and volatile suspended solids, dissolved oxygen concentration) and environmental variables (temperature, pH, COD and BOD
5 of influent water) were daily monitored. In all the experiments conducted, the MBR generated an effluent of optimal quality complying with the requirements of the European Law (91/271/CEE 1991). A cultivation-independent approach (polymerase chain reaction-temperature gradient gel electrophoresis, PCR-TGGE) was used to analyze changes in the structure of the bacterial communities in the sludge. Cluster analysis of TGGE profiles demonstrated significant differences in community structure related to variations of the operation parameters and environmental factors. Canonical correspondence analysis (CCA) suggested that temperature, hydraulic retention time and concentration of volatile suspended solids were the factors mostly influencing community structure. 23 prominent TGGE bands were successfully reamplified and sequenced, allowing gaining insight into the identities of predominantly present bacterial populations in the sludge. Retrieved partial 16S-rRNA gene sequences were mostly related to the α-Proteobacteria, β-Proteobacteria and γ-Proteobacteria classes. The community established in the MBR in each of the four stages of operation significantly differed in species composition and the sludge generated displayed dissimilar rates of mineralization, but these differences did not influence the performance of the bioreactor (quality of the permeate). These data indicate that the flexibility of the bacterial community in the sludge and its ability to get adapted to environmental changes play an important role for the stable performance of MBRs.
A hybrid moving bed biofilm reactor–membrane bioreactor (hybrid MBBR–MBR) system has been tested in this study at two scales to analyse the scale-up effect. Two municipal wastewater treatment plants ...were used, one at laboratory scale (hybrid MBBR–MBRL) with a reactor working volume of 24 l and one at pilot scale (hybrid MBBR–MBRP) with a reactor working volume of 358 l. Hybrid MBBR–MBRL and hybrid MBBR–MBRP showed that the hybrid MBBR–MBR systems used in this research were reliable for organic matter removal with COD removal percentages of 90.97±2.55% and 95.56±2.01% for hybrid MBBR–MBRL and hybrid MBBR–MBRP, respectively. In hybrid MBBR–MBRL, the sludge retention time was higher but the biofilm density was lower due to the wall effect, so the two effects cancelled one another out and the COD removal efficiencies were found to be similar. The study identified the most influential variables and their effects on the process. Hybrid MBBR–MBRL and hybrid MBBR–MBRP were influenced by the attached and suspended biomass and temperature, while the influent loading rate only affected hybrid MBBR–MBRP. On the whole, hybrid MBBR–MBRP showed a better performance from the point of view of the kinetics of the heterotrophic biomass, with values of YH=0.6130mgVSSmgCOD−1, μm,H=0.0146h−1, KS=9.8852mgO2L−1, and bH=0.0031h−1.
•Hybrid MBBR–MBR was reliable for COD removal (higher than 90.97±2.55%).•Hybrid MBBR presents a better kinetic behaviour and higher removal rate in pilot scale.•Variations of organic loading and temperature are two effects of the scale up.•The scale of working affects the sludge retention time and attached biomass.
A cultivation independent approach (PCR–TGGE) was used to evaluate the occurrence of Archaea in four wastewater treatments based on technologies other than activated sludge, and to comparatively ...analyze their community structure. TGGE fingerprints (based on partial archaeal 16S-rRNA amplicons) were obtained from sludge samples taken from a pilot-scale aerated MBR fed with urban wastewater and operated under two different sets of conditions (MBR1 and MBR2 treatments), and also from biofilms sampled from two pilot-scale submerged biofilters (SBs) consisting of one aerated and one anoxic column each, fed with urban (USB treatment) or industrial (ISB treatment) wastewater, respectively. Analysis of TGGE fingerprints revealed clear and significant differences of the community structure of Archaea between the wastewater treatments studied, primarily according to wastewater origin and the type of technology. Thirty-two different band classes were detected among the 23 sludge and biofilm samples analyzed, from which five were selected as dominant or distinctive of the four treatments studied. Sixteen predominant TGGE bands were identified, revealing that all of them were related to methanogenic Archaea. Neither other
Euryarchaeota groups nor
Crenarchaeota members were identified amongst the 16S-rRNA fragments sequenced from separated TGGE bands.
