Retrofitting a full-scale multistage landfill leachate treatment plant by introducing coagulation/flocculation/sedimentation and ultrafiltration process steps.

Considering that landfilling still remains among the most commonly used methods for the confrontation of solid wastes, effective methods should be applied to treat the leachate generated, due to its recalcitrant nature. In this work, a full-scale system consisting of two SBRs operating in parallel (350 m3 each) and two activated carbon (AC) columns operating in series (3 m3 each) was retrofitted by introducing a coagulation/flocculation/sedimentation (C/F/S) unit of 7.8 m3 and an ultrafiltration (UF) membrane of 100 m2 to effectively treat landfill leachate. The raw leachate was characterized by high COD and NH4+-N concentration, i.e., 3095 ± 706 mg/L and 1054 ± 141 mg/L respectively, a BOD/COD ratio of 0.22, and high concentrations of certain heavy metals. Leachate processing in this retrofitted multistage treatment system resulted in total COD removal efficiency of 89.84%, with biological treatment, C/F, UF, and AC contributing 46.31%, 4.68%, 15.98%, and 22.87% to the overall organic content removal. The retrofitted scheme achieved an overall NH4+-N and TKN removal of 92.03% and 91.75% respectively, attributed mostly to the activity of an effective nitrifying community. Color number (CN) was reduced by 26.96%, 10.29%, 15.94%, and 5.39% after the activated sludge, the C/F, the UF, and the AC adsorption process respectively, corresponding to a 58.91% overall decrease. Regarding heavy metal removal, all elements examined, apart from Ni, i.e., effluent As, Cd, Co, Cr, Cu, Hg, Mg, Mn, and Pb, were below the legislative limits set by the national authorities for restricted or unrestricted irrigation. Lastly, total operating expenses (OPEX) were estimated as equal to 72,687 €/year or 6.64 €/m3.

Evaluation of electrochemical and O3/UV/H2O2 methods at various combinations during treatment of mature landfill leachate.

In this study, electrochemical treatment and application of O3/UV/H2O2 in various combinations were evaluated in respect to their efficiency to depurate mature landfill leachate. Based on preliminary experiments, electrochemical treatment using stainless-steel electrodes at 2 cm gap was performed optimally at 50 mA/cm2 and pH 6, while application of O3 at 120 L/h, UV at 991 J/cm2 and H2O2 concentration of 1 g/L was carried out. Electrochemical treatment and O3/UV/H2O2 under optimal conditions were applied as follows: I) electrochemical treatment, followed by O3/UV/H2O2 and solids precipitation, II) electrochemical treatment, followed by precipitation and then by O3/UV/H2O2 treatment, and III) O3/UV/H2O2, followed by electrochemical treatment. A low performance was observed when O3/UV/H2O2 preceding electrochemical treatment. Solids, TKN and total COD (tCON) removal was primarily achieved through electrocoagulation, whereas color and soluble COD (sCOD) reduction was mainly attributed to electrochemical oxidation. Experimental setup I was the most efficient treatment scheme, resulting in tCOD, sCOD, TKN, TSS, SACUV254nm and color number reduction of 73%, 80%, 76%, 79%, 94% and 98%, respectively. Indeed, O3/UV/H2O2 step could be omitted since its effectiveness was restricted during landfill leachate treatment. In conclusion, electrochemical treatment followed by precipitation could result in effective reduction of nutrients and color.

Biochemical and nutritional characterization of the medfly gut symbiont Enterobacter sp. AA26 for its use as probiotics in sterile insect technique applications.

BACKGROUND: Enterobacter sp. AA26 was recently isolated from the midgut of Ceratitis capitata (Wiedemann) and it was shown to have positive effects in rearing efficiency when used as larval probiotics. In this study, biomass production was carried out in bench-scale bioreactors to elucidate the biokinetic properties of Enterobacter sp. AA26 and its nutritional value. RESULTS: Strain AA26 is a psychrotolerant, halotolerant, facultatively anaerobic bacterium with broad pH range for growth (pH 4 to 10.2), which possessed the typical biochemical profile of Enterobacter spp. The specific oxygen uptake rate (SOUR) was calculated as 63.2 ± 1.26 and 121 ± 1.73 mg O2 g- 1 VSS h- 1, with the yield coefficients in acetate and glucose being equal to 0.62 ± 0.03 and 0.67 ± 0.003 g biomass produced/g substrate consumed, respectively. The maximum specific growth rate (µmax) of strain AA26 grown in fill-and-draw bioreactors at 20 °C and 35 °C was 0.035 and 0.069 h- 1, respectively. Strain AA26 grew effectively in agro-industrial wastewaters, i.e. cheese whey wastewater (CWW), as alternative substrate for replacing yeast-based media. Biomass of strain AA26 could provide all the essential amino acids and vitamins for the artificial rearing of C. capitata. Greater intracellular α- and ß-glucosidase activities were observed during growth of strain AA26 in CWW than in yeast-based substrate, although the opposite pattern was observed for the respective extracellular activities (p < 0.01). Low protease activity was exhibited in cells grown in yeast-based medium, while no lipase activities were detected. CONCLUSIONS: The ability of strain AA26 to grow in agro-industrial wastes and to provide all the essential nutrients can minimize the cost of commercial media used for mass rearing and large scale sterile insect technique applications.

Combined chemically enhanced primary sedimentation and biofiltration process for low cost municipal wastewater treatment.

The main objective of wastewater treatment is to remove carbon and other nutrients from municipal and industrial effluents in order to protect the environment and human health. Typical wastewater treatment is usually achieved by a combination of physical, chemical and biological methods. In this work, municipal wastewater was depurated using chemically enhanced primary treatment (CEPT) in combination with a pilot-scale trickling filter. Lab scale experiments (Jar-tests) were carried out in order to determine the optimum dosage of chemicals. Selection criteria were the organic load removal efficiency and the low operational cost. Coagulation-flocculation process was conducted through polyaluminium chloride (PAC) and the cationic polyelectrolyte (Zetag 8180) addition. By combining CEPT and trickling filter, tCOD (total Chemical Oxygen Demand), sCOD (soluble Chemical Oxygen Demand), BOD5 (5-day Biochemical Oxygen Demand), NH4+-N, TSS (Total Suspended Solids), VSS (Volatile Suspended Solids) and PO43--P removal efficiencies were estimated to be 89, 82, 93, 60, 96, 96 and 78%, respectively. It is concluded that biological filtration contributed significantly in nutrients removal processes. Moreover, the obtained effluent was low in carbon and rich in nitrogen, which can be applied for restricted irrigation after disinfection, complying with the discharge limits set in the Greek Joint Ministerial Decree 145116/2011.

Optimization aspects of the biological nitrogen removal process in a full-scale twin sequencing batch reactor (SBR) system in series treating landfill leachate.

Despite the fact that biological nitrogen removal (BNR) process has been studied in detail in laboratory- and pilot-scale sequencing batch reactor (SBR) systems treating landfill leachate, a limited number of research works have been performed in full-scale SBR plants regarding nitrification and denitrification. In the current study, a full-scale twin SBR system in series of 700 m3 (350 m3 each) treating medium-age landfill leachate was evaluated in terms of its carbon and nitrogen removal efficiency in the absence and presence of external carbon source, i.e., glycerol from biodiesel production. Both biodegradable organic carbon and ammonia were highly oxidized [biochemical oxygen demand (BOD5) and total Kjehldahl nitrogen (TKN) removal efficiencies above 90%], whereas chemical oxygen demand (COD) removal efficiency was slightly above 40%, which is within the range reported in the literature for pilot-scale SBRs. As the consequence of the high recalcitrant organic fraction of the landfill leachate, dissimilatory nitrate reduction was restricted in the absence of crude glycerol, although denitrification was improved by electron donor addition, resulting in TN removal efficiencies above 70%. Experimental data revealed that the second SBR negligibly contributed to BNR process, since carbon and ammonia oxidation completion was achieved in the first SBR. On the other hand, the low VSS/SS ratio, due to the lack of primary sedimentation, highly improved sludge settleability, resulting in sludge volume indices (SVI) below 30 mL g-1.

Microbiological and physicochemical evaluation of the effluent quality in a membrane bioreactor system to meet the legislative limits for wastewater reuse.

The aim of this study was to assess the efficacy and effluent quality of a pilot-scale intermittently aerated and fed, externally submerged membrane bioreactor (MBRes) treating municipal wastewater. The effluent quality of the MBRes was evaluated regarding system ability to comply with the Greek legislative limits for restricted and unrestricted wastewater reuse. The average permeate flux was 13.9 L m-2 h-1, while the transmembrane pressure remained above the level of -110 mbar. Experimental data showed that biochemical oxygen demand, chemical oxygen demand, total nitrogen, PO43-- P and total suspended solids removal efficiencies were 97.8, 93.1, 89.6, 93.2 and 100%, respectively, whereas turbidity was reduced by 94.1%. Total coliforms and Escherichia coli were fully eliminated by ultrafiltration and disinfection methods, such as chlorination and ultraviolet radiation. In agreement with the Greek legislation (Joint Ministerial Decree 145116/11) and the guidelines recommended for the Mediterranean countries, the disinfected effluent of the MBRes system can be safely reused directly for urban purposes.

Novel hydrolytic extremely halotolerant alkaliphiles from mature landfill leachate with key involvement in maturation process.

Mature landfill leachate is a heavily-polluted wastewater due to its recalcitrant nature of organic matter, and high ammonia and salt content. Despite the moderate saline and alkaline nature of this habitat, no attention has been paid to the isolation and functional role of extremophiles in such environment. In this work, a total of 73 and 29 bacterial strains were isolated by using alkaline and saline media, respectively, while bacteria from mature landfill leachate growing in these media were enumerated as 1.5 ± 0.1 (×108) and 5.8 ± 0.9 (×108) cfu/L. Based on their pH and salt ranges and optima for growth, all bacterial isolates were halotolerant alkaliphiles (either facultative or obligate), with the majority of them being extremely halotolerant bacteria. These halotolerant alkaliphiles were classified into 14 operational taxonomic units (OTUs). Of these, 12 are placed within known halophilic and alkaliphilic species of the genera Dietzia, Glycocaulis, Halomonas, Marinobacter, Piscibacillus and Rhodobacter, while the remaining OTUs represented two novel phylogenetic linkages among the families Cyclobacteriaceae and Rhodobacteraceae. Examination of their hydrolytic ability through the performance of lipase, protease and ß-glucosidase assays using landfill leachate as the growth substrate revealed that all halotolerant alkaliphiles isolated exhibited extremely high lipolytic activities (up to 78,800 U g-1 protein), indicating a key involvement of extremophilic microbiota at the late landfill maturation stage. The wide extremely lipolytic halotolerant alkaliphilic community identified also makes mature landfill leachate an ideal microbial pool for the isolation of novel extremophiles of biotechnological interest.

Dominance of rumen microorganisms during cheese whey acidification: acidogenesis can be governed by a rare Selenomonas lacticifex-type fermentation.

The microbial basis of acidification process during spontaneous cheese whey wastewater fermentation was decrypted by implementing both culture-dependent and culture-independent techniques. Lac tobacillus and Bifidobacterium were the predominant taxa among the microbiota growing on MRS (deMan, Rogosa, and Sharpe), while Kazachstania unispora and Dekkera anomala yeast species were also isolated. Almost all Lactobacillus isolates were heterofermentative that could ferment glucose and lactose, with most of them being related to Lactobacillus hilgardii (99.0-100 % similarity). By employing fluorescence techniques, the dominance of long crescent-shaped bacteria in the acidogenic sludge was observed. Temperature gradient gel electrophoresis (TGGE), clone library, and next-generation sequencing techniques revealed the dominance of Selenomonas lacticifex. Based on Illumina data, Selenomonas in the continuous stirred-tank reactor (CSTR) represented 70.13 ± 4.64 % of the bacterial reads, while other Veillonellaceae taxa (Megasphaera and Pectinatus) represented a notable proportion (6.54 %). Prevotella was only detected by Illumina sequencing as an important constituent of the microbial population (14.97 ± 1.71 %). Budding yeasts represented 97 % of the fungal population in the CSTR, with Yarrowia strains representing 88.85 ± 5.52 % of the fungal reads. Spontaneous cheese whey acidification can favor the dominance of rumen bacteria and here was driven by the rarely reported S. lacticifex-type fermentation, which should be taken into consideration during evaluation of acidogenesis in process simulation and modelling. Moreover, the important nervonic acid content detected indicates that acidogenic sludge can be used as a source for the production of high value-added biomedical substrates.

Performance and metabolic aspects of a novel enhanced biological phosphorus removal system with intermittent feeding and alternate aeration.

A novel enhanced biological phosphorus removal (EBPR) system, which combined the intermittent feeding design with an anaerobic selector, was examined using on-line oxidation reduction potential (ORP), nitrate and ammonium probes. Two experimental periods were investigated: the aerobic and anoxic phases were set at 40 and 20 minutes respectively for period I, and set at 30 and 30 minutes for period II. Chemical oxygen demand (COD), biochemical oxygen demand (BOD5) and P removal were measured as high as 87%, 96% and 93% respectively, while total Kjeldahl nitrogen (TKN) and NH4(+) removal averaged 85% and 91%. Two specific denitrification rates (SDNRs), which corresponded to the consumption of the readily biodegradable and slowly biodegradable COD, were determined. SDNR-1 and SDNR-2 during period I were 0.235 and 0.059 g N g(-1) volatile suspended solids (VSS) d(-1) respectively, while the respective rates during period II were 0.105 and 0.042 g N g(-1) VSS d(-1). The specific nitrate formation and ammonium oxidizing rates were 0.076 and 0.064 g N g(-1) VSS d(-1) for period I and 0.065 and 0.081 g N g(-1) VSS d(-1) for period II respectively. The specific P release rates were 2.79 and 4.02 mg P g(-1) VSS h(-1) during period I and II, while the respective anoxic/aerobic uptake rates were 0.42 and 0.55 mg P g(-1) VSS h(-1). This is the first report on an EBPR scheme using the intermittent feeding strategy.

Intermittent operation of low pressure UF membranes for sewage reuse at household level.

A household-scale wastewater treatment system was operated with domestic sewage. The system could recover gardening/irrigation water from raw sewage or secondary effluent by low pressure ultrafiltration (UF). The UF membranes (surface area = 3.5 m(2), pore size = 0.04 µm) were operated at constant transmembrane pressure (0.13 bar). The proposed technology was examined for approximately 2 months without membrane cleaning. Membrane operation was performed periodically (one or two times per week), simulating water usage for gardening irrigation. During raw sewage filtration (chemical oxygen demand (COD) total = 242 ± 71 mg L(-1), COD soluble = 105 ± 51 mg L(-1), suspended solids = 188 ± 58 mg L(-1)), low permeate COD was achieved (52 ± 25 mg L(-1)), whereas nitrogen and phosphorus were recovered in the permeate. The water recovered during 1 h of operation displayed a gradual decrease from 42 to 22 L m(-2)h(-1) during the 50-d time period. For the secondary effluent filtration, the UF module achieved consistently a recovery rate of 39.6 ± 8.0 L m(-2)h(-1), with an average permeate COD of 37 mg L(-1). In this case, the fouling layer (cake layer) was completely reversible after the relaxation period, rendering the process suitable for unattended household applications.

Biotreatment efficiency, degradation mechanism and bacterial community structure in an immobilized cell bioreactor treating triclosan-rich wastewater.

Biotreatment of triclosan is mainly performed in conventional activated sludge systems, which, however, are not capable of completely removing this antibacterial agent. As a consequence, triclosan ends up in surface and groundwater, constituting an environmental threat, due to its toxicity to aquatic life. However, little is known regarding the diversity and mechanism of action of microbiota capable of degrading triclosan. In this work, an immobilized cell bioreactor was setup to treat triclosan-rich wastewater. Bioreactor operation resulted in high triclosan removal efficiency, even greater than 99.5%. Nitrogen assimilation was mainly occurred in immobilized biomass, although nitrification was inhibited. Based on Illumina sequencing, Bradyrhizobiaceae, followed by Ferruginibacter, Thermomonas, Lysobacter and Gordonia, were the dominant genera in the bioreactor, representing 38.40 ± 0.62% of the total reads. However, a broad number of taxa (15 genera), mainly members of Xanthomonadaceae, Bradyrhizobiaceae and Chitinophagaceae, showed relative abundances between 1% and 3%. Liquid Chromatography coupled to Quadrupole Time-Of-Flight Mass Spectrometry (LC-QTOF-MS) resulted in the identification of catabolic routes of triclosan in the immobilized cell bioreactor. Seven intermediates of triclosan were detected, with 2,4-dichlorophenol, 4-chlorocatechol and 2-chlorohydroquinone being the key breakdown products of triclosan. Thus, the immobilized cell bioreactor accommodated a diverse bacterial community capable of degrading triclosan.

Bioprocess performance, transformation pathway, and bacterial community dynamics in an immobilized cell bioreactor treating fludioxonil-contaminated wastewater under microaerophilic conditions.

Fludioxonil is a post-harvest fungicide contained in effluents produced by fruit packaging plants, which should be treated prior to environmental dispersal. We developed and evaluated an immobilized cell bioreactor, operating under microaerophilic conditions and gradually reduced hydraulic retention times (HRTs) from 10 to 3.9 days, for the biotreatment of fludioxonil-rich wastewater. Fludioxonil removal efficiency was consistently above 96%, even at the shortest HRT applied. A total of 12 transformation products were tentatively identified during fludioxonil degradation by using liquid chromatography coupled to quadrupole time-of-flight Mass spectrometry (LC-QTOF-MS). Fludioxonil degradation pathway was initiated by successive hydroxylation and carbonylation of the pyrrole moiety and disruption of the oxidized cyanopyrrole ring at the NH-C bond. The detection of 2,2-difluoro-2H-1,3-benzodioxole-4-carboxylic acid verified the decyanation and deamination of the molecule, whereas its conversion to the tentatively identified compound 2,3-dihydroxybenzoic acid indicated its defluorination. High-throughput amplicon sequencing revealed that HRT shortening led to reduced α-diversity, significant changes in the ß-diversity, and a shift in the bacterial community composition from an initial activated sludge system typical community to a community composed of bacterial taxa like Clostridium, Oligotropha, Pseudomonas, and Terrimonas capable of performing advanced degradation and/or aerobic denitrification. Overall, the immobilized cell bioreactor operation under microaerophilic conditions, which minimizes the cost for aeration, can provide a sustainable solution for the depuration of fludioxonil-contaminated agro-industrial effluents.

NH4+-N versus pH and ORP versus NO3--N sensors during online monitoring of an intermittently aerated and fed membrane bioreactor.

Online sensors, which monitor the ammonia oxidation and the dissimilatory nitrate reduction process, can optimize aerobic and anoxic phase duration. The purpose of this study was to comparatively evaluate the effectiveness of online sensors that were in situ-located in an intermittently aerated and fed membrane bioreactor (IAF-MBR) system. Ammonium and nitrate nitrogen sensors equipped with ion-selective electrodes as well as pH and oxidation-reduction potential (ORP) sensors were employed to online monitoring and optimizing of ammonia oxidation and nitrate reduction processes. The "ammonia valley" or pH bending point, which is indicative of ammonia depletion, was effectively and repeatedly detected by measuring the pH profile, while the "nitrate knee" point, which indicates the completion of the denitrification process, was online-detected by obtaining the ORP profile. The "ammonia valley" and "nitrate knee" were detected at pH and ORP values of 6.47 ± 0.02 and - 162 ± 39 mV, respectively. The ORP and pH first derivatives (dORP/dt and dpH/dt) were found to be more suitable than the untransformed ORP and pH values in detecting pH and ORP inflection points and controlling the shift from the anoxic to the aeration phase. Specifically, the ORP and pH bending points were detected at dORP/dt and dpH/dt values of 1.64 ± 0.82 mV min-1 and 0.005 ± 0.001 min-1, respectively. Moreover, the ORP first derivative has appeared earlier than the ORP bending point.

Biotreatment efficiency, hydrolytic potential and bacterial community dynamics in an immobilized cell bioreactor treating caper processing wastewater under highly saline conditions.

Although caper processing wastewaters (CPW) are characterized by high organic content and salt concentration, no attempt has been made to treat these effluents. In this study, an immobilized cell bioreactor efficiently treated CPW even at hypersaline conditions (100 g/L salinity). Nitrogen was mainly assimilated during biotreatment, as nitrification was inhibited at elevated salinities. The hydrolytic potential was assessed by determining glucanase, xylanase, glucosidase, lipase and protease activities, which were negatively affected above 20 g/L salinity as the consequence of the inhibition of non-halotolerant microbiota. Succession of non-halotolerant taxa by the slightly halotolerant bacteria Defluviimonas, Amaricoccus, Arenibacter, Formosa and Muricauda, and then by the moderately/extremely halotolerant genera Halomonas, Roseovarius and Idiomarina occurred over salinity increase. Diversity indices were reduced during transition from moderately saline to hypersaline conditions. A distinct network was formed at hypersaline conditions, consisting of the halotolerant genera Halomonas, Idiomarina, Saliterribacillus and Gracilibacillus.

Biotreatment and bacterial succession in an upflow immobilized cell bioreactor fed with fludioxonil wastewater.

The large quantities and the persistent nature of fungicide wastewaters have increased the efforts towards a sustainable technological solution. In this context, fludioxonil-contaminated wastewater was treated in an upflow immobilized cell bioreactor, resulting in chemical oxygen demand (COD) removal efficiency even higher than 80%, whereas the electrical conductivity (EC) of the effluent was gradually increased. Organic-F was mineralized by 94.0 ± 5.2%, which was in accordance with the high fludioxonil removal efficiency (95.4 ± 4.0%). In addition, effluent total Kjeldahl nitrogen (TKN) concentration reduced significantly during bioprocessing. A strong relationship among COD removal, TKN/total nitrogen removal, and effluent EC increase (p < 0.01) was identified. Despite the adequate aeration provided, effluent nitrite and nitrate concentrations were negligible. Illumina sequencing revealed a reduction in the relative abundances of Betaproteobacteria, Chloroflexi, Planctomycetes, and Firmicutes and an increase in the proportion of Alphaproteobacteria and Actinobacteria. A shift in bacterial communities occurred during fludioxonil treatment, resulting in the significant increase of the relative abundances of Empedobacter, Sphingopyxis, and Rhodopseudomonas (from 0.67 ± 0.13% at the start-up to 34.34 ± 1.60% at the end of biotreatment). In conclusion, the immobilized cell bioreactor permitted the proliferation of specialized activated sludge microbiota with an active role in the depuration of postharvest fungicides.

Effect of Chlorination on Microbiological Quality of Effluent of a Full-Scale Wastewater Treatment Plant.

The evaluation of effluent wastewater quality mainly relies on the assessment of conventional bacterial indicators, such as fecal coliforms and enterococci; however, little is known about opportunistic pathogens, which can resist chlorination and may be transmitted in aquatic environments. In contrast to conventional microbiological methods, high-throughput molecular techniques can provide an accurate evaluation of effluent quality, although a limited number of studies have been performed in this direction. In this work, high-throughput amplicon sequencing was employed to assess the effectiveness of chlorination as a disinfection method for secondary effluents. Common inhabitants of the intestinal tract, such as Bacteroides, Arcobacter and Clostridium, and activated sludge denitrifiers capable of forming biofilms, such as Acidovorax, Pseudomonas and Thauera, were identified in the chlorinated effluent. Chloroflexi with dechlorination capability and the bacteria involved in enhanced biological phosphorus removal, i.e., Candidatus Accumulibacter and Candidatus Competibacter, were also found to resist chlorination. No detection of Escherichia indicates the lack of fecal coliform contamination. Mycobacterium spp. were absent in the chlorinated effluent, whereas toxin-producing cyanobacteria of the genera Anabaena and Microcystis were identified in low abundances. Chlorination significantly affected the filamentous bacteria Nocardioides and Gordonia, whereas Zoogloea proliferated in the disinfected effluent. Moreover, perchlorate/chlorate- and organochlorine-reducing bacteria resisted chlorination.

Intermittent feeding of wastewater in combination with alternating aeration for complete denitrification and control of filaments.

In the present study, a laboratory scale system, consisting of a primary settling tank, a continuous stirred tank reactor and a clarifier were constructed and operated, using wastewater from the municipal wastewater treatment plant in Xanthi, Greece. The system operated under intermittent aeration in aerobic/anoxic conditions and feeding of the wastewater once in every cycle. The unit was inoculated with sludge, which originated from the recirculation stream of the local wastewater treatment plant. The wastewater was processed with hydraulic retention time (HRT) of 12 h, in which various experimental states were studied regarding the combination of aerobic and anoxic intervals. The wastewater was fed in limited time once in every cycle of aerobic/anoxic conditions at the beginning of the anoxic period. The two states that exhibited highest performance in nitrification and total nitrogen removal were, then, repeated with HRT of 10 h. The results show that, regarding the nitrification stage and the organic load removal, the intermittent system achieved optimum efficiency, with an overall removal of biological oxygen demand (BOD(5)) and ammonium nitrogen in the range of 93-96% and 91-95% respectively. As far as the total nitrogen removal is concerned, and if the stage of the denitrification is taken into account, the performance of the intermittent system surpassed other methods, as it is shown by the total Kjeldahl nitrogen (TKN) removal efficiency of 85-87%. These operating conditions suppressed the growth of filamentous organisms, a fact reflected at the SVI values, which were lower than 150 ml/g.

Biodegradation aspects of ibuprofen and identification of ibuprofen-degrading microbiota in an immobilized cell bioreactor.

An enrichment process was employed by applying high ibuprofen concentration in an immobilized cell bioreactor in order to favor the ibuprofen-degrading community present in activated sludge. Experimental data showed the ability of the immobilized cell bioreactor to achieve high ibuprofen removal efficiencies (98.4 ± 0.3%), the tendency of the enriched biomass to acidify the treated liquor, and the inhibition of the nitrification process. Illumina sequencing revealed a massive increase in the relative abundance of Alphaproteobacteria and Gammaproteobacteria (from 29.1 to 80.8%) and a dramatic decrease in the proportion of Bacteroidetes, Planctomycetes, and Verrucomicrobia (from 42.7 to 2.1%) when pure ibuprofen served as the sole carbonaceous feeding substrate. This shift in the feeding conditions resulted in the predominance of Novosphingobium and Rhodanobacter (25.5 ± 10.8% and 25.2 ± 3.0%, respectively) and demonstrated a specialized ibuprofen-degrading bacterial community in activated sludge, which possessed the selective advantage to cope with its degradation. To the best of our knowledge, this bioreactor system was capable of effectively treating the highest ibuprofen concentration applied in wastewater treatment plants.

Protozoan indicators and extracellular polymeric substances alterations in an intermittently aerated membrane bioreactor treating mature landfill leachate.

A membrane bioreactor was operated under intermittent aeration and various organic loading rates (OLR: 0.070, 0.159 and 0.291 g COD L-1 d-1) to remove carbon and nitrogen from mature landfill leachate, where external carbon source (glycerol) addition resulted in effective nitrate removal. A relative increase in soluble microbial product (SMP) over extracellular polymeric substances (EPS) was observed at the highest OLR and glycerol addition, whereas no membrane biofouling occurred. SMP (proteins and carbohydrates) and carbohydrate EPS correlated positively and negatively, respectively, with suspended solids and transmembrane pressure (TMP). Moreover, proteinous SMP significantly correlated with carbon and nitrogen load. Principal component analysis also revealed the influence of leachate organic and nitrogen content on biomass production, TMP and sessile ciliate densities. Although filamentous index (FI) was sustained at high levels (3-4), with Haliscomenobacter hydrossis being the main filamentous bacterium identified, no bulking phenomena occurred. High glycerol addition resulted in a rapid increase in sessile ciliate population. Increased Epistylis and Vorticella microstoma population was detected by microscopic examination during high glycerol addition, while a remarkable Rhogostoma population (supergroup Rhizaria) was identified by molecular techniques. The contribution of Rhizaria in nitrogen processes may lead to the dominance of Rhogostoma during landfill leachate treatment.

Dominance of candidate Saccharibacteria in a membrane bioreactor treating medium age landfill leachate: Effects of organic load on microbial communities, hydrolytic potential and extracellular polymeric substances.

A membrane bioreactor (MBR), accomplishing high nitrogen removal efficiencies, was evaluated under various landfill leachate concentrations (50, 75 and 100% v/v). Proteinous and carbohydrate extracellular polymeric substances (EPS) and soluble microbial product (SMP) were strongly correlated (p<0.01) with organic load, salinity and NH4+-N. Exceptionally high ß-glucosidase activities (6700-10,100Ug-1) were determined during MBR operation with 50% v/v leachate, as a result of the low organic carbon availability that extendedly induced ß-glucosidases to breakdown the least biodegradable organic fraction. Illumina sequencing revealed that candidate Saccharibacteria were dominant, independently of the leachate concentration applied, whereas other microbiota (21.2% of total reads) disappeared when undiluted leachate was used. Fungal taxa shifted from a Saccharomyces- to a newly-described Cryptomycota-based community with increasing leachate concentration. Indeed, this is the first report on the dominance of candidate Saccharibacteria and on the examination of their metabolic behavior in a bioreactor treating real wastewater.