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Sulfate reduction by carbon monoxide (CO) utilizing anaerobic biomass from a large scale upflow anaerobic sludge blanket reactor was studied. Anaerobic mixed microbial consortia from five different sources were initially examined for their biological CO conversion potential. Among the different biomass, the biomass from an upflow anaerobic sludge blanket reactor treating domestic wastewater, located in Kavoor, Karnataka, India, showed a maximum CO conversion efficiency. The effect of three main culture parameters, i.e. inoculum volume, initial CO concentration and temperature on simultaneous CO conversion and sulfate reduction was assessed employing the Taguchi experimental design technique. A maximum CO conversion of 85.62% and a maximum sulfate reduction of 50.65% were achieved. Furthermore, the experimental data was fitted to substrate inhibition models reported in the literature. Among the different models, Monods and Haldane kinetic models were found most suitable to describe the kinetics of biomass growth and CO removal by the anaerobic biomass., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

An acclimatized mixed microbial culture, predominantly Pseudomonas sp., was enriched from a sewage treatment plant, and its potential to simultaneously degrade mixtures of phenol and m-cresol was investigated during its growth in batch shake flasks. A 2(2) full factorial design with the two substrates at two different levels and different initial concentration ranges (low and high), was employed to carry out the biodegradation experiments. The substrates phenol and m-cresol were completely utilized within 21 h when present at low concentrations of 100 mg/L for each, and at high concentration of 600 mg/L for each, a maximum time of 187 h was observed for their removal. The biodegradation results also showed that the presence of phenol in low concentration range (100-300 mg/L) did not inhibit m-cresol biodegradation. Whereas the presence of m-cresol inhibited phenol biodegradation by the culture. Moreover, irrespective of the concentrations used, phenol was degraded preferentially and earlier than m-cresol. A sum kinetics model was used to describe the variation in the substrate specific degradation rates, which gave a high coefficient of determination value (R2 > 0.98) at the low concentration range of the substrates. From the estimated interaction parameter values obtained from this model, the inhibitory effect of phenol on m-cresol degradation by the culture was found to be more pronounced compared to that of m-cresol on phenol. This study showed a good potential of the indigenous mixed culture in degrading mixed substrate of phenolics.

Endocrine-disrupting phthalates (EDPs) are widely used as plasticizers for the manufacture of different plastics and polyvinyl chloride by providing flexibility and mechanical strength. On the other hand, they are categorized under priority pollutants list due to their threat to human health and the environment. This study examined biodegradation of a mixture of dimethyl, diethyl, dibutyl, benzyl butyl, di-2-ethylhexyl, and di-n-octyl phthalates using a CSTB (continuous stirred tank bioreactor) operated under batch, fed-batch, continuous, and continuous with biomass recycle operation modes. For operating the CSTB under biomass recycle mode, microfiltration using an indigenous tubular ceramic membrane was employed. Ecotoxicity assessment of the treated water was carried out to evaluate the toxicity removal efficiency by the integrated bioreactor system. From the batch experiments, the EDPs cumulative degradation values were 90 and 75% at 1250 and 1500 mg/L total initial concentration of the mixture, respectively, whereas complete degradation was achieved at 750 mg/L. In the fed-batch study, 93% degradation was achieved at 1500 mg/L total initial concentration of the mixture. In continuous operation mode, 94 and 85% degradation efficiency values were achieved at 43.72 and 52.08 mg/L⋅h inlet loading rate of phthalate mixture. However, continuous feeding with 100% biomass recycle revealed complete degradation at 41.67 mg/L⋅h inlet loading rate within the 84 h operation period. High seed germination index and low mortality percentage of brine shrimps observed with phthalate degraded water from the integrated bioreactor system revealed its excellent potential in the treatment and toxicity removal of phthalates contaminated environment. [ABSTRACT FROM AUTHOR]

Owing to the high demand of petroleum and petrochemical products, refineries, among the many industries that are set up worldwide, are of special importance. Wastewater generated from such industrial activities, however, contains toxic compounds that are of environmental concern. Due to the presence of highly recalcitrant organics present in refinery wastewater, treatment prior to its discharge into the environment and water bodies in order to meet certain acceptable discharge limits is imperative. Petroleum refineries unavoidably discharge a large volume of wastewater mainly with high chemical oxygen demand (COD). Low‐cost biological wastewater treatment methods are reported to show excellent COD removal efficiency from wastewater but have their own drawbacks. Hence, advanced integrated approaches are of new interest in this field. This review focuses on emerging technologies, in particular bioreactor configurations for petroleum wastewater treatment. It further discusses some future perspective in hybrid/integrated systems for treating PRWW. [ABSTRACT FROM AUTHOR]

In this study, biogenic copper nanoparticles from metallic wastewater were examined for the synthesis of triazoles by a click reaction. The size of the copper nanoparticles obtained by biogenic sulfate reduction of synthetic wastewater using sulphate-reducing bacteria was in the range of 5–10 nm. Copper nanoparticles immobilized in polyvinyl alcohol and sodium alginate (PVA-SA-CuNPs) were prepared and then characterized by field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), field emission transmission electron microscopy (FETEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and UV-vis spectroscopy. The catalytic activity of PVA-SA-CuNPs was assessed in the three-component click synthesis of 1,2,3-triazoles in water under low catalyst loading and mild reaction conditions. The nanocatalysts can be recycled and reused up to 5 times without significant loss of their catalytic activity. [ABSTRACT FROM AUTHOR]

Refinery wastewater treatment was performed using a novel submerged tubular ceramic membrane bioreactor (STMBR) with the oleaginous hydrocarbonoclastic bacterium Rhodococcus opacus. A membrane‐based flux study with the STMBR was carried out to assess the performance of the tubular ceramic membrane. Continuous experiments with the STMBR achieved a maximum chemical oxygen demand (COD) removal of 84 %, with an average flux of 0.4 × 10−3 m3m−2s−1. To further enhance the COD removal efficiency, two STMBR were operated under the optimum conditions. Complete COD removal along with 2.98 g L−1 biomass growth was achieved during two‐stage STMBR operation. Furthermore, a toxicity assessment of the permeate water established its reuse potential. [ABSTRACT FROM AUTHOR]

A novel adsorbent based on metal sulfide nanoparticles (MeSNPs) was biologically synthesized from metallic wastewater and examined for azo dyes removal from aqueous solution in batch and continuous systems. The size of the MeSNPs was in the range of 8–10 nm, with an average specific surface area of 120.4 m2/g. Batch adsorption study was then carried out using Direct Red 80 (DR 80) and Mordant Blue 9 (MB 9) as the model azo dyes by varying MeSNPs dosage, contact time, pH, and initial dye concentration. More than 99% removal efficiency of both the dyes was achieved by using MeSNPs at the following optimum conditions: 200 mg dosage, pH 2, 6 min contact time, and 100 mg L−1 initial dye concentration. The batch sorption isotherm results were described using the Sips model, with the maximum predicted capacity values of 143.7 and 198.3 mg of dye per gram of adsorbent for DR 80 and MB 9, respectively. Besides, the sorption kinetic data for both the dyes followed the pseudo-second-order rate. Furthermore, maximum desorption efficiency values of 93% for DR 80 and 97% for MB 9 were achieved using an aqueous solution of pH 12, thus indicating that the adsorbent can be regenerated and reused further. Dynamic adsorption of the dyes was studied using a fixed-bed column with the MeSNPs as a function of liquid flow rates. The results showed an increase in breakthrough time with a decline in the flow rates for both DR 80 and MB 9 and the breakthrough behavior was explained using Thomas, Clark, and Yoon-Nelson models. [ABSTRACT FROM AUTHOR]

Abstract Marine sources especially crustaceans have been extensively used worldwide for the production of chitosan. However, limited availability as well as variations in the properties of the derived chitosan is a serious drawback of utilizing marine sources for chitosan production. This study investigated sustainable and green approach of fungal chitosan production using paper mill wastewater as a cheap and easily available substrate. The fungus Penicillium citrinum IITG_KP1 used in this study was initially isolated from an infected bamboo shoot. Addition of acetic acid at low levels led to a 150% increase in the yield of chitosan from 95 g/kg to 138 g/kg of dry fungal biomass. This result correlated well with an increase in xylose uptake rate due to acetic acid addition that was confirmed by enhanced activity of xylose reductase (XR) and xylitol dehydrogenase (XDH) enzymes in the presence of acetic acid. Very high COD removal efficiency (75%) along with 70% phenolic reduction and 84% decolourization efficiency of the raw paper mill wastewater without any prior pre-treatment was further achieved by carrying out the fungal fermentation using a bioreactor under batch mode of operation. The fungal chitosan showed properties comparable with those of a commercially available standard. Graphical abstract Image 1059 Highlights • Acetic acid induced chitosan production by P. citrinum biomass. • A novel method of fungal chitosan production using industrial wastewater is reported. • Batch mode of bioreactor operation is highly efficient for wastewater COD removal and chitosan production. • The fungal chitosan produced has properties comparable with those of the commercially available standards. [ABSTRACT FROM AUTHOR]

This study examined the valorization of dairy wastewater in the production of lipids by Rhodococcus opacus for biodiesel application. Using synthetic media based on dextrose and ammonium nitrate as the carbon and nitrogen source, respectively, the bacterium accumulated 71% (w/w) of lipids. Using only the raw dairy wastewater, the bacterium accumulated 14.28% w/w lipid and reduced the initial wastewater chemical oxygen demand (COD) by 30%. These values were, however, enhanced to 30–33% w/w and 62%, respectively, by supplementing the dairy wastewater with mineral salt media in the ratio 1:3. Bioreactor experiments were further performed using raw dairy wastewater and mineral salt medium in 1:3 ratio under both uncontrolled and controlled temperature and pH conditions. Interestingly biomass growth, lipid accumulation in the bioreactor experiments were found to be lower as compared to those in the shake flask experiments, whereas the wastewater COD removal was much higher in the bioreactor study. 1 H nuclear magnetic resonance (NMR) spectroscopy of the fatty acids accumulated by the bacteria using dairy wastewater based media revealed that it contained more saturated fatty acids than unsaturated fatty acids. Gas chromatography (GC) analysis of the biodiesel produced by either ex-situ or in-situ transesterification of the bacterial lipids further revealed the presence of methyl palmitate (34.90%), methyl stearate (35.48%) methyl myristate (29.79%), methyl linoleate (27.87%), and methyl palmitate (25.85) as the main esters. The estimated properties of the transesterified product indicated its potential for biodiesel applications. [ABSTRACT FROM AUTHOR]

Wastewater from biomass gasification chiefly contains monocyclic (MAHs) and polycyclic aromatic hydrocarbons (PAHs) that are generated by wet scrubbing process of raw synthetic gas during its cleaning process. These MAHs and PAHs are well-known as toxic, mutagenic, and carcinogenic agents which need to be removed prior to their release into the environment. The present study evaluated the potential of an up-flow packed bed bioreactor (UFPBBR) with immobilized Rhodococcus opacus onto biochar loaded polyurethane foam (PUF) as the packing material for treating biomass gasification wastewater (BGWW). Initially, the bioreactor was operated utilizing only PUF as the support material and a maximum COD removal of 81 ± 2.65% was achieved with 1820 mg L−1 of influent COD concentration and 24 h of HRT. Using biochar loaded PUF as the support material; more than 95 ± 1.27% of COD removal was attained under the same COD loading condition and HRT. Furthermore, the wastewater was detoxified to 96.2% demonstrating the ability of UFPBBR system using the novel biochar based bio-support material for biomass gasification wastewater treatment. Image 1 • Continuous treatment of biomass gasification wastewater using R. opacus is reported. • Biochar loaded polyurethane foam is an excellent bio-support material. • More than 99% toxicity removal from the wastewater could be achieved. • Stable performance is achieved even at low inlet loading and shock loading conditions. [ABSTRACT FROM AUTHOR]

The use of fungal species to remove organic and inorganic pollutants from wastewater has shown to be a good alternative to traditional wastewater treatment technologies. Fungal pellets are well settling aggregates formed by self-immobilization. Their use in bioreactors is promising as it avoids the practical and technical difficulties usually encountered with dispersed mycelium. This review presents the mechanisms involved in the formation and growth of fungal pellets as well as the different factors that influence the stability of the pellets. The various types of fungal pelleted bioreactors that are used for wastewater treatment, their configuration, design and performance are reviewed. A summary of the different organic and inorganic pollutants that have been treated using fungal pelleted reactors, from dyes to emergent pollutants such as pharmaceuticals, is discussed from an application view-point. The operational issues such as bacterial contamination and longevity of this bioprocess under non-sterile conditions, as well as the reuse of fungal pellets are also encompassed in this review. [ABSTRACT FROM AUTHOR]

Biological sulfide precipitation by sulfate reducing bacteria (SRB) is an emerging technique for the recovery of heavy metals from metal contaminated wastewater. Advantages of this technique include low capital cost, ability to form highly insoluble salts, and capability to remove and recover heavy metals even at very low concentrations. Therefore, sulfate reduction under anaerobic conditions has become a suitable alternative for the treatment of wastewaters that contain metals. However, bioreactor configurations for recovery of metals from sulfate rich metallic wastewater have not been explored widely. Moreover, the recovered metal sulfide nanoparticles could be applied in various fields such as solar cells, dye degradation, electroplating, etc. Hence, metal recovery in the form of nanoparticles from wastewater could serve as an incentive for industries. The simultaneous metal removal and recovery can be achieved in either a single-stage or multistage systems. This paper aims to present an overview of the different bioreactor configurations for the treatment of wastewater containing sulfate and metal along with their advantages and drawbacks for metal recovery. Currently followed biological strategies to mitigate sulfate and metal rich wastewater are evaluated in detail in this review. • Metal recovery using single and multi-stage systems is reported. • Metallic wastewater is an excellent source for metal biorecovery. • Very high metal recovery can be achieved using inverse fluidized bed reactor. • Recovered metals in the form of nanoparticles find diverse industrial applications. [ABSTRACT FROM AUTHOR]

This study investigated utilization of refinery wastewater containing complex hydrocarbons as the sole substrate for lipid-rich biomass production by Rhodococcus opacus in batch system followed by its kinetic modeling. The effect of different initial chemical oxygen demand (COD) concentrations of the wastewater in the range 2.5–4.5 g L−1 was examined on biomass growth, COD utilization and lipid production by R. opacus. Almost complete utilization (96.8%) of COD present in the wastewater was achieved for an initial COD concentration of 2.5 g L−1 and the value decreased to 90% and 75% for 3.5 g L−1and 4.5 g L−1COD concentrations, respectively. Moreover, a maximum lipid production of 1.3 g L−1 was obtained for an initial COD concentration of 3.5 g L−1. The results of COD utilization by the bacterium were further fitted to substrate utilization kinetic models reported in the literature, which matched well with the Logistic model. Modified Gompertz model best fitted the kinetic data on biomass growth and lipid production by the bacterium. Whereas R. opacus biomass specific growth was found to be inhibited at a high COD concentration of the wastewater, Haldane model predicted the experimental specific growth rate values with a very high determination of coefficient (R2) value of more than 0.99. All these results suggest that refinery wastewater can serve as the sole substrate for lipid-rich biomass production by R. opacus , thereby adding value to the wastewater treatment process. Image 1 • Kinetics of refinery wastewater utilization and lipid-rich biomass production by Rhodococcus opacus are reported. • High concentration of organics inhibited biomass growth and lipid production. • Modified Gompertz model accurately described the biomass growth. • Experimental specific COD utilization rates are close to the Haldane model predicted values. • Estimated values of bio-kinetic model parameters indicate scale up potential of the process. [ABSTRACT FROM AUTHOR]

Selenite (Se4+) is the most toxic of all the oxyanion forms of selenium. In this study, a feed forward back propagation (BP) based artificial neural network (ANN) model was developed for a fungal pelleted airlift bioreactor (ALR) system treating selenite-laden wastewater. The performance of the bioreactor, i.e., selenite removal efficiency (RE selenite) (%) was predicted through two input parameters, namely, the influent selenite concentration (IC selenite) (10 mg/L – 60 mg/L) and hydraulic retention time (HRT) (24 h – 72 h). After training and testing with 96 sets of data points using the Levenberg-Marquardt algorithm, a multi-layer perceptron model (2-10-1) was established. High values of the correlation coefficient (0.96 ≤ R ≤ 0.98), along with low root mean square error (1.72 ≤ RMSE ≤ 2.81) and mean absolute percentage error (1.67 ≤ MAPE ≤ 2.67), clearly demonstrate the accuracy of the ANN model (> 96%) when compared to the experimental data. To ensure an efficient and economically feasible operation of the ALR, the process parameters were optimized using the particle swarm optimization (PSO) algorithm coupled with the neural model. The RE selenite was maximized while minimizing the HRT for a preferably higher range of IC selenite. Thus, the most favourable optimum conditions were suggested as: IC selenite – 50.45 mg/L and HRT – 24 h, resulting in RE selenite of 69.4%. Overall, it can be inferred that ANN models can successfully substitute knowledge-based models to predict the RE selenite in an ALR, and the process parameters can be effectively optimized using PSO. [Display omitted] • Selenite removal from wastewater was modelled using artificial neural networks. • The mechanism of selenite biodegradation by fungi has been discussed. • Selenite removals were predicted using retention time and inlet concentration as the inputs. • Neural model was coupled to PSO to optimize selenite removal and retention time. [ABSTRACT FROM AUTHOR]

Occurrence of selenium oxyanions and different heavy metals as co-pollutants in various waste streams is common from industries such as mining, coal burning, thermal power plants, petrochemical refinery, etc. Among the available technologies to treat such wastewater, biological removal using anaerobic microbes is one of the most advantageous. This study examined simultaneous removal and recovery of selenite and heavy metals using an inverse fluidized bed bioreactor (IFBR). The effect of commonly occurring heavy metals namely Zn, Cu and Cd on selenite removal was evaluated at 24 h hydraulic retention time (HRT). The maximum selenite removal of 93.9% was obtained in the absence of any heavy metals. The presence of heavy metals negatively impacted the selenite removal (45.8–85.3%), and the inhibitory effect due to Cu was the most significant among the three metals at 50 mg/L of influent concentration (47% lower). The heavy metal removal efficiency values were more than 70%, except in the case of Cd at 50 mg/L. The recovery values of selenium and heavy metals using the continuous bioreactor were in the range 45.1–73.9% and 59.2–69.8%, respectively, under different experimental conditions. Elemental selenium nanoparticles were formed inside the bioreactor due to selenite bioreduction and the nanoparticle size ranged from 50 to 300 nm. Furthermore, formation of small sized (<10 nm) metal selenide nanoparticles of the respective metals were detected during the bioreactor operation. Overall, this study clearly demonstrated the potential of the IFBR system for the removal of selenite and heavy metals from wastewater as well as their recovery as elemental selenium and metal selenide nanoparticles, respectively. [Display omitted] • Simultaneous recovery of selenium and heavy metal is reported. • High selenite and heavy metals removal achieved in inverse fluidized bed reactor. • Inverse fluidized bed reactor is ideal for metal recovery. • Copper showed the most significant effect on the selenite bioreduction. [ABSTRACT FROM AUTHOR]