Application of a GAC-coated hollow fiber module to couple enzymatic degradation of dye on membrane to whole cell biodegradation within a membrane bioreactor

Comparison of high-concentration azo dye removal by long HRT in MSBRs' bioaugmented with GAC and sponge media

The present study assessed the performance and fouling of adding granular activated carbon (GAC) and sponge (BioCube), as two different media, to a membrane sequencing batch reactor (MSBR) system in wastewater treatment containing Acid Red 18 (AR 18). Anaerobic phase, aerobic phase, and hydraulic retention times (HRTs) of 24 h, 12 h, and 72 h were considered for 500 mg/L AR 18 removal at a sludge retention time (SRT) of 20 days by separately adding up to 35% BioCube volume and 8 g/L GAC to the reactors. Based on the kinetic study, 63 mg/L (87% removal) and 115 mg/L (77% removal) remaining dye were reported in the GAC and BioCube membrane sequencing batch reactors (GAC-MSBR and BioCube-MSBR), respectively. A gradual oxidation-reduction potential decline toward -416 mV confirmed better dye removal in GAC-MSBR than BioCube-MSBR, observing a sudden drop to -354 mV. The morphology can explain better biological treatment in GAC-MSBR in addition to the adsorption process. Soluble microbial products (SMPs) of 126.92 mg/L and 395.18 mg/L were obtained for GAC-MSBR and BioCube-MSBR, respectively. Chemical oxygen demand (COD) and SMP indicated that the GAC-MSBR water quality is better than that of the other reactor.

Methylene blue removal using raw and modified biomass Plumeria alba (white frangipani) in batch mode: isotherm, kinetics, and thermodynamic studies

Hazardous dyes used in textile industries are considered high-risk pollutants to the environment. The raw as well as acid-treated Plumeria alba (white frangipani) leaf powder (WFLP and SWFLP) were used for the adsorption of methylene blue (MB) that is available in industrial wastewaters following the batch adsorption technique. The characterizations of adsorbents were done by FTIR, SEM, EDX, TGA, and zeta potential parameters. The adsorption was considered for the effects of temperature, initial dye concentration, solution pH, adsorbent dosage, and contact time. The experimental results obtained in the adsorption of MB were examined by nonlinear error functions like chi-square (χ²), ARE, and MPSD for three isotherm models: Langmuir, Freundlich, and Temkin. The maximum monolayer adsorption capacity, q_max (mg/g), was 45.45 mg/g for raw WFLP and 250 mg/g for SWFLP. The adsorbents fitted to the pseudo-second-order kinetic model (R² = 0.99) using the experimental data of batch adsorption. The thermodynamic studies explained the spontaneity and nature of adsorption for raw and acid-treated adsorbents. The batch experimental results and characterizations of the adsorbents revealed that the selected adsorbents would be the best adsorbents for the removal of MB from the wastewater solution.

Survival and growth of saprotrophic and mycorrhizal fungi in recalcitrant amine, amide and ammonium containing media

The elimination of hazardous compounds in chemical wastes can be a complex and technically demanding task. In the search for environmental-friendly technologies, fungal mediated remediation and removal procedures are of concern. In this study, we investigated whether there are fungal species that can survive and grow on solely amine-containing compounds. One compound containing a primary amine group; 2-diethylaminoethanol, one compound with a primary amide group; 2,6-dichlorobenzamide (BAM), and a third compound containing a quaternary ammonium group; N3-trimethyl(2-oxiranyl)methanaminium chloride, were selected. The choice of these compounds was motivated by their excessive use in large scale manufacturing of protein separation media (2-diethylaminoethanol and the quaternary amine). 2,6-dichlorobenzamide, the degradation product of the herbicide 2,6-dichlorobenzonitrile (dichlobenil), was chosen since it is an extremely recalcitrant compound. Utilising part of the large fungal diversity in Northern European forests, a screening study using 48 fungal isolates from 42 fungal species, including saprotrophic and mycorrhizal fungi, was performed to test for growth responses to the chosen compounds. The ericoid (ERM) mycorrhizal fungus Rhizoscyphus ericae showed the best overall growth on 2-diethylaminoethanol and BAM in the 1-20 g L-1 concentration range, with a 35-fold and 4.5-fold increase in biomass, respectively. For N3-trimethyl(2-oxiranyl)methanaminium chloride, the peak growth occurred at 1 g L-1. In a second experiment, including three of the most promising fungi (Laccaria laccata, Hygrophorus camarophyllus and Rhizoscyphus ericae) from the screening experiment, a simulated process water containing 1.9% (w/v) 2-diethylaminoethanol and 0.8% (w/v) N3-trimethyl(2-oxiranyl)methanaminium chloride was used. Laccaria laccata showed the best biomass increase (380%) relative to a control, while the accumulation for Rhizoscyphus ericae and Hygrophorus camarophyllus were 292% and 136% respectively, indicating that mycorrhizal fungi can use amine- and amide-containing substrates as nutrients. These results show the potential of certain fungal species to be used in alternative green wastewater treatment procedures.

Integrating granular activated carbon (GAC) to gravity-driven membrane (GDM) to improve its flux stabilization: Respective roles of adsorption and biodegradation by GAC

As a low-maintenance and cost-effective process, gravity-driven membrane (GDM) filtration is a promising alternative for decentralized drinking water supply, while the low flux impedes its extensive application. In order to address such issue, an integrated process consisting of granular activated carbon (GAC) layer and GDM was developed. The performance of virgin (fresh GAC) or preloaded GAC (saturated GAC) was compared. Flux stabilization was observed both in the fresh and saturated GAC/GDM process during long-term filtration and their stable fluxes were both improved by approximately 50% relative to the GDM control. Moreover, integrating GAC with GDM contributed to efficient removals for dissolved organic compounds (DOC), assimilable organic carbon (AOC) and low molecular weight substances both in fresh and saturated GAC/GDM filtration. Compared to GDM control, coupling GAC to GDM could significantly reduce the concentrations of extracellular polymeric substances (EPS) and total cell counts (TCC) within the biofouling layer, and engineer highly heterogeneous structures of biofouling layer on the membrane surface. In the fresh GAC/GDM process, the improved flux obtained was mainly related to less coverage of biofouling layer and lower EPS concentrations due to efficient removals of membrane foulants by GAC adsorption. The achieved higher stable flux can be maintained during long-term filtration (after GAC saturation) owing to the combined effects of EPS reduction and formation of highly heterogeneous structures of biofouling layer in the saturated GAC/GDM system. Overall, the integrated GAC/GDM process can hopefully facilitate improvements both in the stabilized flux and permeate quality, with practical relevance for GDM applications in decentralized drinking water supply.

A Novel Approach in Crude Enzyme Laccase Production and Application in Emerging Contaminant Bioremediation

Laccase enzyme from white-rot fungi is a potential biocatalyst for the oxidation of emerging contaminants (ECs), such as pesticides, pharmaceuticals and steroid hormones. This study aims to develop a three-step platform to treat ECs: (i) enzyme production, (ii) enzyme concentration and (iii) enzyme application. In the first step, solid culture and liquid culture were compared. The solid culture produced significantly more laccase than the liquid culture (447 vs. 74 µM/min after eight days), demonstrating that white rot fungi thrived on a solid medium. In the second step, the enzyme was concentrated 6.6 times using an ultrafiltration (UF) process, resulting in laccase activity of 2980 µM/min. No enzymatic loss due to filtration and membrane adsorption was observed, suggesting the feasibility of the UF membrane for enzyme concentration. In the third step, concentrated crude enzyme was applied in an enzymatic membrane reactor (EMR) to remove a diverse set of ECs (31 compounds in six groups). The EMR effectively removed of steroid hormones, phytoestrogen, ultraviolet (UV) filters and industrial chemical (above 90%). However, it had low removal of pesticides and pharmaceuticals.

Recent advancements in bioremediation of dye: Current status and challenges

The rampant industrialization and unchecked growth of modern textile production facilities coupled with the lack of proper treatment facilities have proliferated the discharge of effluents enriched with toxic, baleful, and carcinogenic pollutants including dyes, heavy metals, volatile organic compounds, odorants, and other hazardous materials. Therefore, the development of cost-effective and efficient control measures against such pollution is imperative to safeguard ecosystems and natural resources. In this regard, recent advances in biotechnology and microbiology have propelled bioremediation as a prospective alternative to traditional treatment methods. This review was organized to address bioremediation as a practical option for the treatment of dyes by evaluating its performance and typical attributes. It further highlights the current hurdles and future prospects for the abatement of dyes via biotechnology-based remediation techniques.

Removal of pharmaceutical compounds in water and wastewater using fungal oxidoreductase enzymes

Due to recalcitrance of some pharmaceutically active compounds (PhACs), conventional wastewater treatment is not able to remove them effectively. Therefore, their occurrence in surface water and potential environmental impact has raised serious global concern. Biological transformation of these contaminants using white-rot fungi (WRF) and their oxidoreductase enzymes has been proposed as a low cost and environmentally friendly solution for water treatment. The removal performance of PhACs by a fungal culture is dependent on several factors, such as fungal species, the secreted enzymes, molecular structure of target compounds, culture medium composition, etc. In recent 20 years, numerous researchers tried to elucidate the removal mechanisms and the effects of important operational parameters such as temperature and pH on the enzymatic treatment of PhACs. This review summarizes and analyzes the studies performed on PhACs removal from spiked pure water and real wastewaters using oxidoreductase enzymes and the data related to degradation efficiencies of the most studied compounds. The review also offers an insight into enzymes immobilization, fungal reactors, mediators, degradation mechanisms and transformation products (TPs) of PhACs. In brief, higher hydrophobicity and having electron-donating groups, such as amine and hydroxyl in molecular structure leads to more effective degradation of PhACs by fungal cultures. For recalcitrant compounds, using redox mediators, such as syringaldehyde increases the degradation efficiency, however they may cause toxicity in the effluent and deactivate the enzyme. Immobilization of enzymes on supports can enhance the performance of enzyme in terms of reusability and stability. However, the immobilization strategy should be carefully selected to reduce the cost and enable regeneration. Still, further studies are needed to elucidate the mechanisms involved in enzymatic degradation and the toxicity levels of TPs and also to optimize the whole treatment strategy to have economical and technical competitiveness.

Efficient degradation of triclosan by an endophytic fungus Penicillium oxalicum B4

Triclosan (TCS), a widely used antimicrobial and preservative agent, is an emerging contaminant in aqueous and soil environment. Microbial degradation of TCS has not been reported frequently because of its inhibition of microbe growth. To explore the new microbial resources for TCS biodegradation, fungal endophytes were isolated and screened for the degradation potential. The endophytic strain B4 isolated from Artemisia annua L. showed higher degradation efficiency and was identified as Penicillium oxalicum based on its morphology and ITS sequences of ribosomal DNA. In both medium and synthetic wastewater, TCS (5 mg/L) was almost completely degraded within 2 h by the strain B4. The high capacity of TCS uptake (127.60 ± 8.57 mg/g dry weight, DW) of fungal mycelium was observed during the first 10 min after TCS addition. B4 rapidly reduced initial content (5.00 mg/L) of TCS to 0.41 mg/L in medium in 10 min. Then, the accumulation of TCS in mycelium was degraded from 0.45 to 0.05 mg/g DW after 1-h treatment. The degradation metabolites including 2-chlorohydroquinone, 2, 4-dichloropheno, and hydroquinone were found to be restrained in mycelia. The end products of the biodegradation in medium showed no toxicity to Escherichia coli. The new characteristics of high adsorption, fast degradation, and low residual toxicity highlight the potential of endophytic P. oxalicum B4 in TCS bioremediation.

Improvement of activated sludge resistance to shock loading by fungal enzyme addition during textile wastewater treatment

The effects of the additions of the fungal enzymatic extract were investigated in relation to the treatment of real textile wastewater (RTW) by the activated sludge process (ASP). The used enzyme cocktail was produced by a new isolated fungal Chaetomium globosum IMA1. The system that was operated with enzyme addition showed a better chemical oxygen demand (COD) removal efficiency (95%) compared to the control system (75%). In addition, the improvement of color removal (OD₆₂₀) efficiencies was around 15%, when the newly consortium fungal enzymes was added. As the organic loading rate (OLR) increased from 0.33 g to 0.66 g COD L^-1 d^-1, a decrease in the performance of the two reactors was observed by monitoring the quality of treated effluents. However, the ASP working with enzyme addition showed a strong resistance to shock loadings and restored after few days compared to the control system, which was strongly inhibited. In fact, the enzyme addition improved the sludge volume index (SVI) and the activity of microorganisms. A high activity of laccase (300 U.L^-1) enzyme was observed throughout the decolorization process in the improved system.

Trace organic contaminants in biosolids: Impact of conventional wastewater and sludge processing technologies and emerging alternatives

This paper critically reviews the fate of trace organic contaminants (TrOCs) in biosolids, with emphasis on identifying operation conditions that impact the accumulation of TrOCs in sludge during conventional wastewater and sludge treatment and assessing the technologies available for TrOC removal from biosolids. The fate of TrOCs during sludge thickening, stabilisation (e.g. aerobic digestion, anaerobic digestion, alkaline stabilisation, and composting), conditioning, and dewatering is elucidated. Operation pH, sludge retention time (SRT), and temperature have significant impact on the sorption and biodegradation of TrOCs in activated sludge that ends up in the sludge treatment line. Anaerobic digestion may exacerbate the estrogenicity of sludge due to bioconversion to more potent metabolites. Application of advanced oxidation or thermal pre-treatment may minimise TrOCs in biosolids by increasing the bioavailability of TrOCs, converting TrOCs into more biodegradable products, or inducing complete mineralisation of TrOCs. Treatment of sludge by bioaugmentation using various bacteria, yeast, or fungus has the potential to reduce TrOC levels in biosolids.

Enhanced removal of naproxen and carbamazepine from wastewater using a novel countercurrent seepage bioreactor immobilized with Phanerochaete chrysosporium under non-sterile conditions

A countercurrent seepage bioreactor immobilized with Phanerochaete chrysosporium was continuously operated under non-sterile conditions to treat a synthetic wastewater spiked with naproxen and carbamazepine (1000μg/L each) for 165days. There were no serious bacterial contaminations occurred during the operational period. Naproxen was always removed to the undetectable level regardless of the experimental conditions, while the average removal efficiency for carbamazepine, a well-known recalcitrant pharmaceutically active compound, reached around 80%. The excellent removal performance was mainly attributed to the application of countercurrent seepage mode and the cardhouse fabric of the carriers, which provided the high efficiency in the transfer of oxygen and nutrients inside the bioreactor. From the fungal immobilization combined with the temperature adjustment, the fungal activity including the enzyme production was protected as well as the bacterial contamination inside the reactor was suppressed effectively.

Impact of hazardous events on the removal of nutrients and trace organic contaminants by an anoxic-aerobic membrane bioreactor receiving real wastewater

The impacts of four simulated hazardous events, namely, aeration failure, power loss, and chemical shocks (ammonia or bleach) on the performance of an anoxic-aerobic membrane bioreactor (MBR) receiving real wastewater were investigated. Hazardous events could alter pH and/or oxidation reduction potential of the mixed liquor and inhibit biomass growth, thus affecting the removal of bulk organics, nutrients and trace organic contaminants (TrOC). Chemical shocks generally exerted greater impact on MBR performance than aeration/power failure events, with ammonia shock exerting the greatest impact. Compared to total organic carbon, nutrient removal was more severely affected. Removal of the hydrophilic TrOCs that are resistant and/or occur at high concentrations in wastewater was notably affected. The MBR effectively reduced estrogenicity and toxicity from wastewater, but chemical shocks could temporarily increase the endocrine activity of the effluent. Depending on the chemical shock-dose and the membrane flux, hazardous events can exacerbate membrane fouling.

The effect of activated carbon addition on membrane bioreactor processes for wastewater treatment and reclamation - A critical review

This review concentrates on the effect of activated carbon (AC) addition to membrane bioreactors (MBRs) treating wastewaters. Use of AC-assisted MBRs combines adsorption, biodegradation and membrane filtration. This can lead to advanced removal of recalcitrant pollutants and mitigation of membrane fouling. The relative contribution of adsorption and biodegradation to overall removal achieved by an AC-assisted MBR process can vary, and "biological AC" may not fully develop due to competition of target pollutants with bulk organics in wastewater. Thus periodic replenishment of spent AC is necessary. Sludge retention time (SRT) governs the frequency of spent AC withdrawal and addition of fresh AC, and is an important parameter that significantly influences the performance of AC-assisted MBRs. Of utmost importance is AC dosage because AC overdose may aggravate membrane fouling, increase sludge viscosity, impair mass transfer and reduce sludge dewaterability.

Recent advances in new generation dye removal technologies: novel search for approaches to reprocess wastewater

In order to control the negative impacts of dyes on living organisms, several techniques and methodologies have been developed for their removal from industry effluents and other water bodies.

The effects of mediator and granular activated carbon addition on degradation of trace organic contaminants by an enzymatic membrane reactor

The removal of four recalcitrant trace organic contaminants (TrOCs), namely carbamazepine, diclofenac, sulfamethoxazole and atrazine by laccase in an enzymatic membrane reactor (EMR) was studied. Laccases are not effective for degrading non-phenolic compounds; nevertheless, 22-55% removal of these four TrOCs was achieved by the laccase EMR. Addition of the redox-mediator syringaldehyde (SA) to the EMR resulted in a notable dose-dependent improvement (15-45%) of TrOC removal affected by inherent TrOC properties and loading rates. However, SA addition resulted in a concomitant increase in the toxicity of the treated effluent. A further 14-25% improvement in aqueous phase removal of the TrOCs was consistently observed following a one-off dosing of 3g/L granular activated carbon (GAC). Mass balance analysis reveals that this improvement was not due solely to adsorption but also enhanced biodegradation. GAC addition also reduced membrane fouling and the SA-induced toxicity of the effluent.

Removal of trace organic contaminants by an MBR comprising a mixed culture of bacteria and white-rot fungi

The degradation of 30 trace organic contaminants (TrOC) by a white-rot fungus-augmented membrane bioreactor (MBR) was investigated. The results show that white-rot fungal enzyme (laccase), coupled with a redox mediator (1-hydroxy benzotriazole, HBT), could degrade TrOC that are resistant to bacterial degradation (e.g. diclofenac, triclosan, naproxen and atrazine) but achieved low removal of compounds (e.g. ibuprofen, gemfibrozil and amitriptyline) that are well removed by conventional activated sludge treatment. Overall, the fungus-augmented MBR showed better TrOC removal compared to a system containing conventional activated sludge. The major role of biodegradation in removal by the MBR was noted. Continuous mediator dosing to MBR may potentially enhance its performance, although not as effectively as for mediator-enhanced batch laccase systems. A ToxScreen3 assay revealed no significant increase in the toxicity of the effluent during MBR treatment of the synthetic wastewater comprising TrOC, confirming that no toxic by-products were produced.

Understanding the factors controlling the removal of trace organic contaminants by white-rot fungi and their lignin modifying enzymes: a critical review

White-rot fungi (WRF) and their lignin modifying enzymes (LME) can degrade a wide range of trace organic contaminants (TrOC), which are suspected to cause adverse health effects in humans and other biota. Recent studies have successfully applied either whole-cell WRF or their extracellular culture extract to remove TrOC from the aqueous phase. TrOC removal by a WRF system is dependent on a range of factors including molecular structure of the TrOC, fungal species and their specific LME, culture medium composition, and methods to enhance fungal degradation capacity; however, the specific relationships between these factors have not been systematically delineated. The aim of this review paper is to fill this important gap in the literature by critically analysing the ability of WRF and their LME specifically to remove TrOC. Mechanisms and factors governing the degradation of TrOC by WRF and their LME are reviewed and discussed.

Degradation of azo dye acid orange 7 in a membrane bioreactor by pellets and attached growth of Coriolus versicolour

The aim of this study was to systematically compare the degradation of azo dye acid orange 7 by spongy pellets and attached biofilm of Coriolus versicolour (NBRC 9791) in a membrane bioreactor (MBR) under non-sterile conditions. Mild stirring (35 rpm) resulted in spherical (φ=0.5 cm), spongy pellets and concomitantly triggered high enzymatic activity of the fungus, allowing for excellent decolouration (>99%) of a synthetic wastewater containing the dye. However, bacterial contamination eventually damaged the fungus pellets, leading to decreased decolouration efficiency. Promotion of attached growth on a plastic support along with formation of spherical spongy pellets allowed maintenance of high enzymatic activity and decolouration/degradation for an extended period. Hydraulic retention time (HRT) could influence the level of enzymatic activity and decolouration; however, even at the shortest HRT (1 day) examined, the MBR could accomplish >95% decolouration.

Optimization of membrane bioreactors by the addition of powdered activated carbon

It was found that with replenishment, powdered activated carbon (PAC) in the membrane bioreactor (MBR) would develop biologically activated carbon (BAC) which could enhance filtration performance of a conventional MBR. This paper addresses two issues (i) effect of PAC size on MBR (BAC) performance; and (ii) effect of sludge retention time (SRT) on the MBR performance with and without PAC. To interpret the trends, particle/floc size, concentration of mixed liquor suspended solid (MLSS), total organic carbon (TOC), short-term filtration properties and transmembrane pressure (TMP) versus time are measured. The results showed improved fouling control with fine, rather than coarse, PAC provided the flux did not exceed the deposition flux for the fine PAC. Without PAC, the longer SRT operation gave lower fouling at modest fluxes. With PAC addition, the shorter SRT gave better fouling control, possibly due to greater replenishment of the fresh PAC.