Operation of an Anammox SBR in the presence of two broad-spectrum antibiotics

The feasibility of the anaerobic ammonium oxidation (Anammox) process to treat wastewaters containing antibiotics was studied in this work. Concentrations ranging from 100 to 1000 mg L^?1 for tetracycline hydrochloride and from 250 to 1000 mg L^?1 for chloramphenicol were tested in batch assays. A strong inhibitory effect was observed for both antibiotics.A concentration of 20 mg L^?1 of chloramphenicol was continuously added to an Anammox Sequential Batch Reactor (SBR) system, causing a decrease of the nitrogen removal efficiency of 25%. The Specific Anammox Activity (SAA) of the biomass also decreased from 0.25 to 0.05 g N (g VSS d)^?1. Similar effects were observed when 50 mg L^?1 of tetracycline hydrochloride were continuously fed. Both antibiotics did not cause any changes in the physical properties of the biomass. A previous degradation step could be necessary in order to treat wastewaters containing inhibitory concentrations of antibiotics by the Anammox process.     

Operation of partial nitrification to nitrite of landfill leachate and its performance with respect to different oxygen conditions

The coupled system of partial nitrification and anaerobic ammonium oxidation (Anammox) is efficient in nitrogen removal from wastewater. In this study, the effect of different oxygen concentrations on partial nitrification performance with a sequencing batch reactor (SBR) was investigated. Results indicate that, partial nitrification of landfill leachate could be successfully achieved under the 1.0–2.0 mg L⁻¹ dissolved oxygen (DO) condition after 118 d long-term operation, and that the effluent is suitable for an Anammox reactor. Further decreasing or increasing the DO concentration, however, would lead to a decay of nitrification performance. Additionally, the MLSS concentration in the reactor increased with increasing DO concentration. Respirometric assays suggest that low DO conditions (<2 mg L⁻¹) favor the ammonia-oxidizing bacteria (AOB) and significantly inhibit nitrite oxidizing bacteria (NOB) and aerobic heterotrophic bacteria (AHB); whereas high DO conditions (>3 mg L⁻¹) allow AHB to dominate and significantly inhibit AOB. Therefore, the optimal condition for partial nitrification of landfill leachate is 1.0–2.0 mg L⁻¹ DO concentration.     

Two ways to achieve an anammox influent from real reject water treatment at lab-scale: Partial SBR nitrification and SHARON process

A comparative study to produce the correct influent for Anammox process from anaerobic sludge reject water (700–800 mg NH₄⁺-N L⁻¹) was considered here. The influent for the Anammox process must be composed of NH₄⁺-N and NO₂⁻-N in a ratio 1:1 and therefore only a partial nitrification of ammonium to nitrite is required. The modifications of parameters (temperature, ammonium concentration, pH and solid retention time) allows to achieve this partial nitrification with a final effluent only composed by NH₄⁺-N and NO₂⁻-N at the right stoichiometric ratio. The equal ratio of HCO₃⁻/NH₄⁺ in reject water results in a natural pH decrease when approximately 50% of NH₄⁺ is oxidised. A Sequencing batch reactor (SBR) and a chemostat type of reactor (single-reactor high activity ammonia removal over nitrite (SHARON) process) were studied to obtain the required Anammox influent. At steady state conditions, both systems had a specific conversion rate around 40 mg NH₄⁺-N g⁻¹ volatile suspended solids (VSS) h⁻¹, but in terms of absolute nitrogen removal the SBR conversion was 1.1 kg N day⁻¹ m⁻³, whereas in the SHARON chemostat was 0.35 kg N day⁻¹ m⁻³ due to the different hydraulic retention time (HRT) used. Both systems are compared from operational (including starvation experiments) and kinetic point of view and their advantages/disadvantages are discussed.     

NOB suppression and adaptation strategies in the partial nitrification–Anammox process for a poultry manure anaerobic digester

Poultry manure contains high levels of ammonia, which result in a suboptimal bioconversion to methane in anaerobic digesters (AD). A simultaneous process of nitrification, Anammox and denitrification (SNAD) in a continuous granular bubble column reactor to treat the anaerobically digested poultry manure was implemented. Thus, two strategies to achieve high efficiencies were proposed in this study: (1) ammonia overload to suppress nitrite oxidizing bacteria (NOB) and (2) gradual adaptation of the partial nitrification–Anammox (PN–A) biomass to organic matter. During the NOB-suppression stage, microbial and physical biomass characterizations were performed and the NOB abundance decreased from 31.3% to 3.3%. During the adaptation stage, with a nitrogen loading rate of 0.34 g L⁻¹ d⁻¹, a hydraulic retention time of 1.24 d and an influent COD/N ratio of 2.63 ± 0.02, a maximum ammonia and total nitrogen removal of 100% and 91.68% were achieved, respectively. The relative abundances of the aerobic and the anaerobic ammonia-oxidizing bacteria were greater than 35% and 40% respectively, during the study. These strategies provided useful design tools for the efficient removal of nitrogen species in the presence of organic matter.     

Nitrite inhibition and intermediates effects on Anammox bacteria: A batch-scale experimental study

A batch test procedure, based on manometric measurements, was used to study the Anammox process, in particular the inhibition due to nitrite and the effects of hydroxylamine and hydrazine, indicated as possible intermediates of the process. The maximum nitrite removal rate (MNRR) was measured. The method showed good reliability with a standard error of 4.5 ± 3.3% (n: 41). All the tests were carried out on samples taken from a pilot plant with Anammox suspended biomass. The tests were used also to monitor the reactor activity. By testing different spiked additions of nitrite (10–75 mg NO₂⁻-N L⁻¹), a short-term inhibition, with more than 25% MNRR decrease, was found at concentrations higher than 60 mg NO₂⁻-N L⁻¹. Repeated additions of nitrite higher than 30 mg NO₂⁻-N L⁻¹ caused losses of activity. After a complete loss of activity, spiked additions of hydroxylamine (30 mg N L⁻¹ in total) determined a 20% permanent recovery. Low amounts of the intermediates (1–3 mg N L⁻¹) applied on partially inhibited samples and uninhibited samples produced temporary increases in activity up to 50% and 30%, respectively.     

The investigation of dairy industry wastewater treatment in a biological high performance membrane system

The dairy industry is generally considered to be the largest source of food processing wastewater in many countries. The highly variable nature of dairy wastewaters in terms of volumes and flowrates and in terms of high organic materials contents such as COD 921–9004 mg L⁻¹, BOD 483–6080 mg L⁻¹, TN of 8–230 mg L⁻¹ and SS of 134–804 mg L⁻¹ makes the choice of an effective wastewater treatment regime difficult. A high performance bioreactor, an aerobic jet loop reactor, combined with a ceramic membrane filtration unit, was used to investigate its suitability for the treatment of the dairy processing wastewater. The oxygen transfer rates of the bioreactor were found to be very high (100–285 h⁻¹) on the operating conditions. A loading rate of 53 kg COD m⁻³ d⁻¹ resulted in 97–98% COD removal efficiencies under 3 h hydraulic retention time. The high MLSS concentrations could be retained in the system (up to 38,000 mg L⁻¹) with the contribution of UF (ultrafiltration) unit. During the filtration of activated sludge, the fluxes decreased with increasing MLSS. Cake formation fouling was determined as dominant fouling mechanisms. The results demonstrate that jet loop membrane bioreactor system was a suitable and effective treatment choice for treating dairy industry wastewater.     

Operation of a bioelectrochemical system as a polishing stage for the effluent from a two-stage biohydrogen and biomethane production process

Anaerobic bioenergy production processes including fermentative biohydrogen (BioH₂), anaerobic digestion (AD) and bioelectrochemical system have been investigated for converting municipal waste or various biomass feedstock to useful energy carriers. However, the performance of a microbial fuel cell (MFC) fed on the effluent from a two-stage biogas production process has not yet been investigated extensively in continuous reactor operation on complex substrates. In this study we have investigated the extent to which a microbial fuel cell (MFC) can reduce COD and recover further energy from the effluent of a two-stage biohydrogen and biomethane system. The performance of a four-module tubular MFC was determined at six different organic loadings (0.036–6.149 g sCOD L⁻¹ d⁻¹) in terms of power generation, COD removal efficiency, coulombic efficiency (CE) and energy conversion efficiency (ECE). A power density of 3.1 W m⁻³ was observed at the OLR = 0.572 g sCOD L⁻¹ d⁻¹, which resulted in the highest CE (60%) and ECE (0.8%), but the COD removal efficiency decreased at higher organic loading rates (35.1–4.4%). The energy recovery was 92.95 J L⁻¹ and the energy conversion efficiency, based on total influent COD was found to be 0.48–0.81% at 0.572 g sCOD L⁻¹ d⁻¹. However, the energy recovery by the MFC is only reported for a four-module reactor and improved performance can be expected with an extended module count, as chemical energy remained available for further electrogenesis.     

Investigation on the formation and kinetics of glucose-fed aerobic granular sludge

Aerobic granular sludge was cultivated in a glass sequencing batch reactor (SBR) with glucose synthetic wastewater. The spherical shaped granules were observed on 4th day with the mean diameter of 0.1 mm. With the increase of chemical oxygen demand (COD) concentration of the influent, aerobic granules grew matured, the size of which ranged from 1.2 to 1.9 mm. The aerobic granular sludge could sustain high organic loading rate (about 4.0 g COD L⁻¹ d⁻¹), with good settling ability (settling velocity 36 m/h) and high biomass concentration (MLSS 6.7 ±0.2 g/L). Experimental data indicated that the substrate utilization and biomass growth kinetics followed Monod's kinetics model approximately. The corresponding kinetic coefficients of maximum specific substrate utilization rate (k), half velocity coefficient (K_s), growth yield coefficient (Y) and decay coefficient (K_d) were 13.2 d⁻¹, 275.8 mg/L, 0.183–0.250 mg MLSS/mg COD and 0.023–0.075 d⁻¹, respectively, which made aerobic granules have short setup period, high rate of substrate utilization and little surplus sludge.     

Biological treatment of low-salinity shrimp aquaculture wastewater using sequencing batch reactor

In order to improve the water quality in shrimp aquaculture operated under low-salinity conditions, a sequencing batch reactor (SBR) was tested for treatment of the wastewater. This water from the backwash of a single-bead filter from the Waddell Mariculture Center, South Carolina, contained high concentrations of carbon and nitrogen and was successfully treated using the SBR. By operating the reactor sequentially in aerobic, anoxic and aerobic modes, nitrification and denitrification were achieved, as well as removal of carbon. Specifically, the initial chemical oxygen demand (COD) concentration of 1201 mg l⁻¹ was reduced to 32 mg l⁻¹ within 8 days of reactor operation. Ammonia in the sludge was nitrified within 3 days. The denitrification of nitrate was achieved by the anoxic process and total removal of nitrate was observed.     

Synthesis of S-licarbazepine by asymmetric reduction of oxcarbazepine with Saccharomyces cerevisiae CGMCC No. 2266

S-licarbazepine was synthesized by asymmetric reduction of oxcarbazepine with CGMCC No. 2266. The optimum batch reduction conditions were found to consist of a reaction time of 36 h, temperature of 30 °C, and initial pH value of 7.0. The optimum concentration of the glucose co-substrate was found to be 0.3 mol L⁻¹. The addition of glucose contributed to in situ regeneration of NADPH in cells and improved conversion. Conversion increased with the addition of more biomass and with a decrease in the initial concentration of substrate. Within the membrane reactor, a continuous reduction process was used to improve production efficiency and reduce the inhibition of high-concentration substrate upon reduction. The optimum flux was found to be 20 ml h⁻¹. S-licarbazepine yield was 3.7678 mmol L⁻¹ d⁻¹ in continuous reduction over four days. The enantiometric excess of S-licarbazepine was 100% for both batch and continuous reduction processes.     

Cultivation of Chlorella vulgaris in tubular photobioreactors: A lipid source for biodiesel production

Chlorella vulgaris was cultivated in two different 2.0 L-helicoidal and horizontal photobioreactors at 5 klux using the bicarbonate contained in the medium and ambient air as the main CO₂ sources. The influence of bicarbonate concentration on biomass growth as well as lipid content and profile was first investigated in shake flasks, where the stationary phase was achieved in about one half the time required by the control. The best NaHCO₃ concentration (0.2 g L⁻¹) was then used in both photobioreactors. While the fed-batch run performed in the helicoidal photobioreactor provided the best result in terms of biomass productivity, which was (84.8 mg L⁻¹ d⁻¹) about 2.5-fold that of the batch run, the horizontal configuration ensured the highest lipid productivity (10.3 mg L⁻¹ d⁻¹) because of a higher lipid content of biomass (22.8%). These preliminary results suggest that the photobioreactor configuration is a key factor either for the growth or the composition of this microalga. The lipid quality of C. vulgaris biomass grown in both photobioreactors is expected to meet the standards for biodiesel, especially in the case of the helicoidal configuration, provided that further efforts will be made to optimize the conditions for its production as a biodiesel source.     

Investigation on the properties and kinetics of glucose-fed aerobic granular sludge

Aerobic granulation is a process in which suspended biomass aggregate and form discrete well-defined granules in aerobic systems. To investigate the properties and kinetics of aerobic granular sludge, aerobic granules were cultivated with glucose synthetic wastewater in a series of sequencing batch reactors (SBR). The spherical shaped granules were observed on 8th day with the mean diameter of 0.1 mm. With the organic loading rate (OLR) being increased to 4.0 g COD L⁻¹ d⁻¹, aerobic granules grew matured with spherical shape. The size of granules ranged from 1.2 to 1.8 mm, and the corresponding settling velocity of individual granule was 24.2–36.4 m h⁻¹. The oxygen utilization rate (OUR) of mature granules was 41.90 g O₂ kg MLSS⁻¹ h⁻¹, which was two times higher than that of activated sludge (18.32 g O₂ kg MLSS⁻¹ h⁻¹). The experimental data indicated that the substrate utilization and biomass growth kinetics generally followed Monod's kinetics model. The corresponding kinetic coefficients of k (maximum specific substrate utilization rate), K_s (half velocity coefficient), Y (growth yield coefficient) and K_d (decay coefficient) were determined as follows, k_c = 23.65 d⁻¹, K_c = 3367.05 mg L⁻¹, K_N = 0.038 d⁻¹, K_N = 29.65 mg L⁻¹, Y = 0.1927–0.2022 mg MMLS (mg COD)⁻¹ and K_d = 0.00845–0.0135 d⁻¹, respectively. Those properties of aerobic granules made aerobic granules system had a short setup period, high substrate utilization rate and low sludge production.     

Tween 80 influences the production of intracellular lipase by Schizochytrium S31 in a stirred tank reactor

Marine microorganisms are a potential source of enzymes with structural stability, high activity at low temperature and unique substrate selectivity. Thraustochytrids are marine heterotrophic microbes, well known for the production of omega-3 fatty acids. In this study the effect of Tween 80 as a carbon source was investigated with regard to biomass, lipase and lipid productivity in Schizochytrium sp. S31. Tween 80 (1%) and 120 h of incubation were the optimum condition period for biomass, lipid and lipase productivity in a stirred tank reactor. The yields obtained were 0.9 g L⁻¹ of biomass, 300 mg g⁻¹ of lipid and 39 U/g of lipase activity. Sonication was optimised in terms of time and acoustic power to maximise the yield of extracted lipase. The extracted lipase from Schizochytrium S31 was observed to hydrolyse long chain polyunsaturated fatty acids DHA and EPA.     

Dual purpose system that treats anaerobic effluents from pig waste and produce Neochloris oleoabundans as lipid rich biomass

Dual purpose systems that treat wastewater and produce lipid rich microalgae biomass have been indicated as an option with great potential for production of biodiesel at a competitive cost. The aim of the present work was to develop a dual purpose system for the treatment of the anaerobic effluents from pig waste utilizing Neochloris oleoabundans and to evaluate its growth, lipid content and lipid profile of the harvested biomass and the removal of nutrients from the media. Cultures of N. oleoabundans were established in 4 L flat plate photobioreactors using diluted effluents from two different types of anaerobic filters, one packed with ceramic material (D1) and another one packed with volcanic gravel (D2). Maximum biomass concentration in D1 was 0.63 g L⁻¹ which was significantly higher than the one found in D2 (0.55 g L⁻¹). Cultures were very efficient at nutrient removal: 98% for NNH₄⁺ and 98% for PO₄³⁻. Regarding total lipid content, diluted eflluents from D2 promoted a biomass containing 27.4% (dry weight) and D1 a biomass containing 22.4% (dry weight). Maximum lipid productivity was also higher in D2 compared to D1 (6.27 ± 0.62 mg L⁻¹ d⁻¹ vs. 5.12 ± 0.12 mg L⁻¹ d⁻¹). Concerning the FAMEs profile in diluted effluents, the most abundant one was C18:1, followed by C18:2 and C16:0. The profile in D2 contained less C18:3 (linolenic acid) than the one in D1 (4.37% vs. 5.55%). In conclusion, this is the first report demonstrating that cultures of N. oleoabundans treating anaerobic effluents from pig waste are very efficient at nutrient removal and a biomass rich in lipids can be recovered. The maximum total lipid content and the most convenient FAMEs profile were obtained using effluents from a digester packed with volcanic gravel.     

Continuous succinic acid production by Actinobacillus succinogenes in a biofilm reactor: Steady-state metabolic flux variation

Continuous anaerobic fermentations were performed in a novel external-recycle, biofilm reactor using d-glucose and CO₂ as carbon substrates. Succinic acid (SA) yields were found to be an increasing function of glucose consumption with the succinic acid to acetic acid ratio increasing from 2.4 g g⁻¹ at a glucose consumption of 10 g L⁻¹, to 5.7 g g⁻¹ at a glucose consumption of 50 g L⁻¹. The formic acid to acetic acid ratio decreased from an equimolar value (0.77 g g⁻¹) at a glucose consumption of 10 g L⁻¹ to a value close to zero at 50 g L⁻¹. The highest SA yield on glucose and highest SA titre obtained were 0.91 g g⁻¹ and 48.5 g L⁻¹ respectively. Metabolic flux analysis based on the established C₃ and C₄ metabolic pathways of Actinobacillus succinogenes revealed that the increase in the succinate to acetate ratio could not be attributed to the decrease in formic acid and that an additional source of NADH was present. The fraction of unaccounted NADH increased with glucose consumption, suggesting that additional reducing power is present in the medium or is provided by the activation of an alternative metabolic pathway.     

Optimization of biomass production with enhanced glucan and dietary fibres content by Pleurotus ostreatus ATHUM 4438 under submerged culture

This work was aimed at optimizing biomass production by the edible basidiomycete Pleurotus ostreatus ATHUM 4438 in a submerged process with enhanced glucan and dietary fibres content. β-Glucan from Pleurotus sp. (pleuran) has been used as food supplements due to its immunosuppressive activity. Like other dietary fibre components, oyster mushroom polysaccharides can stimulate the growth of colon microorganisms (probiotics), i.e. act as prebiotics. We used the FF MicroPlate for substrate utilization and growth monitoring. The pattern of substrate catabolism forms a substrate assimilation fingerprint which is useful in selecting media components for media optimization of maximum biomass production. Different carbon sources (95) were used and then 8 of them were tested in shake flask cultures. The effect of various organic and complex nitrogen sources on biomass production was also examined and response surface methodology based on central composite design was applied to explore the optimal medium composition. When the optimized culture medium was tested in a 20-L stirred tank bioreactor, using 57 g L⁻¹ xylose and 37 g L⁻¹ corn steep liquor, high yields (39.2 g L⁻¹) of dry biomass was obtained. The yield coefficients for total glucan and dietary fibres on mycelial biomass formed were 140 ± 4 and 625 ± 9 mg g⁻¹ mycelium dry weight, respectively.     

Optimization of fermentation parameters for the biomass and DHA production of Schizochytrium limacinum OUC88 using response surface methodology

Fermentation parameters for biomass and DHA production of Schizochytrium limacinum OUC88 in a fermenter (working volume 7 L) were optimized using Plackett–Burman and central composite rotatable design. Out of 10 factors studied by Plackett–Burman design, 4 influenced the biomass production significantly. Central composite rotatable design was used to optimize the significant factors and response surface plots were generated. Using these response surface plots and point prediction, optimized values of the factors were determined as follows temperature (°C) 23 °C, aeration rate 1.48 L min⁻¹ L⁻¹, agitation 250 rpm and inoculum cells in mid-exponential phase, the maximum yield of DCW and DHA were 24.1 and 4.7 g L⁻¹, respectively. These predicted values were also verified by validation experiments.     

Continuous Acid Blue 45 decolorization by using a novel open fungal reactor system with ozone as the bactericide

To maintain long-term lignin-degrading enzyme production under non-sterile conditions was a key to the technical application of white rot fungi in wastewater treatment. In this work, a novel open fungal reactor system with ozone as the bactericide, and using immobilized Phanerochaete chrysosporium, was built and operated continuously to produce the manganese peroxidase and decolorize the Acid Blue 45. The results showed that an average of 84% Acid Blue 45 decolorization, the manganese peroxidase production with its activity ranging from 63 U L⁻¹ to 5 U L⁻¹, was achieved during about 25 days system continuous operation. The contaminating bacteria in the reactor can be controlled at a level of 4.65 × 10⁴ CFU ml⁻¹ that did not adversely affect the fungal activity. The result of this study provides a new practical way for future design and operation of white-rot fungi reactor under non-sterile conditions.     

Urine nitrification with a synthetic microbial community

During long-term extra-terrestrial missions, food is limited and waste is generated. By recycling valuable nutrients from this waste via regenerative life support systems, food can be produced in space. Astronauts’ urine can, for instance, be nitrified by micro-organisms into a liquid nitrate fertilizer for plant growth in space. Due to stringent conditions in space, microbial communities need to be be defined (gnotobiotic); therefore, synthetic rather than mixed microbial communities are preferred. For urine nitrification, synthetic communities face challenges, such as from salinity, ureolysis, and organics.In this study, a synthetic microbial community containing an AOB (Nitrosomonas europaea), NOB (Nitrobacter winogradskyi), and three ureolytic heterotrophs (Pseudomonas fluorescens, Acidovorax delafieldii, and Delftia acidovorans) was compiled and evaluated for these challenges. In reactor 1, salt adaptation of the ammonium-fed AOB and NOB co-culture was possible up to 45 mS cm⁻¹, which resembled undiluted nitrified urine, while maintaining a 44 ± 10 mg NH₄⁺–N L⁻¹ d⁻¹ removal rate. In reactor 2, the nitrifiers and ureolytic heterotrophs were fed with urine and achieved a 15 ± 6 mg NO₃⁻–N L⁻¹ d⁻¹ production rate for 1% and 10% synthetic and fresh real urine, respectively. Batch activity tests with this community using fresh real urine even reached 29 ± 3 mg N L⁻¹ d⁻¹. Organics removal in the reactor (69 ± 15%) should be optimized to generate a nitrate fertilizer for future space applications.     

Effect of the aeration rate and agitation speed on β-carotene production and morphology of Blakeslea trispora in a stirred tank reactor: mathematical modeling

The effect of aeration rate and agitation speed on β-carotene production and morphology of Blakeslea trispora in a stirred tank reactor was investigated. B. trispora formed hyphae, zygophores and zygospores during the fermentation. The zygospores were the morphological form responsible for β-carotene production. Both aeration and agitation significantly affected β-carotene concentration, productivity, biomass and the volumetric mass transfer coefficient (K_La). The highest β-carotene concentration (1.5 kg m⁻³) and the highest productivity (0.08 kg m⁻³ per day) were obtained at low impeller speed (150 rpm) and high aeration rate (1.5 vvm). Also, maximum productivity (0.08 kg m⁻³ per day) and biomass dry weight (26.4 kg m⁻³) were achieved at high agitation speed (500 rpm) and moderate aeration rate (1.0 vvm). Conversely, the highest value of K_La (0.33 s⁻¹) was observed at high agitation speed (500 rpm) and high aeration rate (1.5 vvm). The experiments were arranged according to a central composite statistical design. Response surface methodology was used to describe the effect of impeller speed and aeration rate on the most important fermentation parameters. In all cases, the fit of the model was found to be good. All fermentation parameters (except biomass concentration) were strongly affected by the interactions among the operation variables. β-Carotene concentration and productivity were significantly influenced by the aeration, agitation, and by the positive or negative quadratic effect of the aeration rate. Biomass concentration was principally related to the aeration rate, agitation speed, and the positive or negative quadratic effect of the impeller speed and aeration rate, respectively. Finally, the volumetric mass transfer coefficient was characterized by the significant effect of the agitation speed, while the aeration rate had a small effect on K_La.