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Membrane biofouling is a major stumbling block in membrane technology and particularly in the water treatment industry. Biofouling, in particular, is a serious concern because it is irreversible and thus cuts the lifespan of the polymeric membranes. This review, therefore, explores the fundamentals of biofouling development and the factors that promote biofilm growth in polymeric membrane systems. In this pursuit, we discuss avenues through which antibiofouling polymeric membranes have been fabricated using inorganic and carbon-based nanomaterials as membrane nanofillers to enhance the hydrophilicity and antibiofilm properties of the resultant composite membranes without significantly compromising the membrane filtering abilities. We further elucidate the chemistry by which the membrane nanofillers mitigate or inhibit the formation and growth of the undesirable biofilms on the surface and pores of the membranes. In achieving this, recent works on polymeric membrane biofouling are reviewed, with a particular focus on the correlation between the membrane performance and the physicochemical properties of the filler nanomaterials. The merits and demerits of inorganic and carbon-based nanomaterials as fillers to confer an antibacterial effect to the membranes are presented and perspectives and opinions on the future direction of biofouling mitigation in membranes are outlined.

The application of plant extracts in the green synthesis of silver nanoparticles (AgNPs) has attracted significant attention owing to their eco-friendliness and cost-effective features. However, nanoparticles synthesized from plant materials may also display unique physicochemical properties. This study described an improved synthesis process for silver nanoparticles (AgNPs) from the peel of the Citrus unshiufruit, an agricultural waste product. In addition to evaluating the produced AgNPs' physico-chemical characteristics, the research also examines their antibacterial and cytotoxic/anticancer capabilities. The color change from yellow to dark brown was observed immediately when 20 ml of Citrus unshiufruit peel extract was added to 0.5 g of silver nitrate. A surface plasmon resonance band at 424 nm revealed by ultra-violet spectroscopy was used as additional confirmation that AgNP had formed. The scanning electron microscope (SEM), and the transmission electron microscope (TEM), revealed spherical-shaped NPs with a mean size of 23 nm. Furthermore, X-ray diffraction (XRD) confirmed the high crystallinity of the obtained NPs while Fourier transform infrared spectroscopy (FTIR) confirmed the bioreducing capacity of the Citrus unshiufruit peel extract. The minimum inhibitory concentration (MIC) (31.25 μg/mL) of AgNPs significantly revealed a strong dose-dependent antibacterial effect on Staphylococcus aureusand Bacillus cereus. In contrast, their impact on gram-negative bacteria, such as Escherichia coliand Salmonella typhimurium, displayed an MIC of 250 μg/mL. The assessment of cytotoxicity on human embryonic kidney cells (HEK293) and lung cancer cells (A549) through a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide assay revealed no detectable cytotoxic effects. The IC50values were determined as 37.73 ± 0.34 μg/mL for HEK293 and 56.37 ± 0.73 μg/mL for A549, indicating the absence of significant adverse impacts on these cell lines. The anticancer drug doxorubicin was used as a reference standard, and had an IC50value of 1.22 ± 0.09 and 0.76 ± 0.12 μg/mL against HEK293 and A549 cells, respectively. The results show that AgNPs synthesized from Citrus unshiufruit peel could serve as antibacterial agents that may in the future be optimized for us in for example nanofiltration systems.

A new hyperbranched polyamidoamine polymer functionalized with cucurbituril (HBPA@Cucurbituril) was fabricated to enhance the antifouling properties of polyethersulfone (PES) membrane to remove dye pollutants and heavy metal ions (e.g., As3+and Hg2+). ATR-FTIR, TGA, SEM, zeta potential, AFM, water contact angle (WCA), and SEM analyses were used to investigate the morphology of modified membranes. The WCA evaluations indicated that the 0.5 wt% HBPA@cucurbituril membranes showed the best hydrophilicity improvement compared to the bare membrane (decrement from 66.6° to 37.9°). In the best case, the optimally modified membrane (0.5 wt%) indicated the best permeability (8.5 L/m2.h.bar), fouling resistance (flux recovery ratio of 92.42 %), dye rejection (Direct Red 16: 98.7 %, Reactive Blue 19: 99.8 %, Crystal Violet: 97.3 % and Methylene Blue: 98.4 %) and heavy metal removal of (As3+: 99.7 % and Hg2+: 99.2 %). This study offers a clear perspective on the treatment of industrial effluents.

Combined anaerobic-aerobic bioreactors offer considerable potential for treating different industrial wastewaters. However, difficulty in maintaining a stable coexistence of anaerobic, anoxic, and aerobic microbial communities and the necessity of space-consuming external settlers remain as crucial drawbacks associated with these systems. In this study, an innovative single stage combined airlift bioreactor (CALBR) comprising multiple bioreactors (anaerobic/anoxic/aerobic) and an internal settler (a rotating spiral separator for in-situ separation of biomass) was exploited to achieve simultaneous carbon and nitrogen removal from milk processing wastewater (MPW). Results demonstrated that the anaerobic pre-treatment zone made a substantial contribution towards COD and TN removal. Successful biomass separation and high effluent quality revealed that the rotating spiral separator can be used as a coupled clarifier to sustain higher biomass concentration through boosting the sludge compressibility and settleability which further upgrades the overall treatment bioprocess. sCOD removal, TN removal, SVI, and effluent turbidity of ˃96%, ˃75%, ˂90 mL/g, and ˂10 NTU were reached, respectively under optimum condition. The outcomes suggested that the novel CALBR is a promising technology which has a great potential to be transferred into practical implementation for high-rate combined biological wastewater treatment and sludge separation.

In this research, the application of mesoporous carbon CMK-3 and modified CMK-3 (M-CMK-3) to improve antifouling and rejection rate of polyethersulfone nanofiltration (NF) membrane was assessed. CMK-3 was modified with H-acid to increase hydrophilic characteristics of CMK-3. The synthesized CMK-3 and M-CMK-3 membranes revealed high values of pure water flux and flux recovery ratio (up to 95%) compared to bare NF membrane. Also, the performances of the membranes with optimum additive loading (0.1 wt%) of CMK-3 and M-CMK-3 in terms of rejecting different salts and dyes were compared. From the obtained results, the membrane embedded with M-CMK-3 showed higher rejection rate rather than bare NF membrane (up to 95% for Na2SO4and 64% for CaCl2). As a result, the flux permeability was increased from 6.44 kg/m2h for bare NF membrane to 20.11 kg/m2h for the membrane embedded with M-CMK-3 with optimum additive loading. A higher rejection data for different dyes under different pH conditions (up to 90%) were reported for the synthesized membrane embedded with M-CMK-3. After all, from the obtained data, M-CMK-3 with higher negative surface charge presented a higher performance to remove salts and dyes rather than CMK-3. Therefore, M-CMK-3 could be a proper proposed additive to develop cost-effective NF membranes with high antifouling properties and super high filtration capacity for removing dyes and salts from wastewaters.

In this study, a polyamide membrane (NF-CSM 4040 commercial membrane) was examined in the treatment of baker’s yeast wastewater (BYW). The response surface methodology (RSM) used in the present study was a face-centered central composite design (CCFD). The nanofiltration process was analyzed and modeled with three numerical independent factors, namely concentration of feed chemical oxygen demand (COD) (1000–5000 mg/L), pH (3–9) and operating pressure (3–6 bar) using RSM. In order to analyze the process, two dependent parameters (flux and rejection) were studied as the process responses. Concentration of feed COD had a reverse impact on flux and rejection, while pH did not show a significant effect on the responses. The operating pressure showed a sharp increasing effect on flux. Maximum flux was found to be about 37 kg/m2.h, at a concentration of feed COD of 1000 mg/L, an operating pressure of 6 bar and a pH of 6. Maximum rejection (91%) was obtained at a COD of 5000 mg/L, a pH of 6 and an operating pressure of 3 bar. Consequently, the membrane technology could be a promising approach to the removal of natural dye from BYW.

In the present study, the interactive effects of two numerical variables, viz. feed to biomass concentration (F/M) ratio and dissolved oxygen (DO) concentration, and a categorical variable (type of carbon sources) on polyhydroxyalkanoate (PHA) production by activated sludge generated from an airlift bioreactor were evaluated. Three different carbon sources including acetate, soft drink industrial wastewater, and Faraman industrial wastewater (industrial estate in Kermanshah, Iran) were used as single feed to accumulation bioreactor. The yield of PHA on substrate, specific PHA production rate, and specific substrate uptake rate were evaluated as responses. The maximum PHA content was obtained around 34.2, 4.8, and 11.3% (mg PHA/mg VSS) using acetate, soft drink industrial wastewater, and Faraman industrial wastewater as carbon sources, respectively, at the optimum condition with F/Mratio of 3.5 mg COD-S/mg VSS and a DO concentration of 2 mg/L. The PHA content was mainly poly (3-hydroxybutyrate) (PHB) when acetate and soft drink industrial wastewater were used as a solo carbon source, while Faraman industrial wastewater resulted in the production of copolymer P(3HB-co-3HV).

Biological reactors are the most energy-consuming facilities of conventional wastewater treatment plant (WWTP). Therefore, adjustment of aerators installation angles inside the aeration tank seems to be an effective way to ensure efficient biological performance. In this work, the biological treatment performance of Kermanshah’s municipal WWTP (Kermanshah, Iran) was surveyed via varying angles of the aerators installation relative to the perpendicular. Two different aeration configurations in terms of installation angles of aerators, 30° and 45°, were considered. Effect of the aerators installation angles on variations of some operating and process parameters such as dissolved oxygen (DO), oxidation reduction potential (ORP), nitrogenous compounds, and phosphorus were pursued. From results, more DO and ORP amounts were found at the 30° angle compared to the 45° angle. However, changes trends in the DO and ORP amounts were similar at both angles. As the main conclusion, no prominent effect on remediation of carbon, nitrogenous compounds, and phosphorus was reported in these two angles. These results were justified by low influent organic loading, and also not to have appropriate conditions for nitrogen and phosphorus removal. In addition, in this study kinetic evaluation was conducted, and obtained findings were in a good agreement with literature.

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This work is a study of the performance and effect of operational parameters on biohydrogen production from palm oil mill effluent by dark fermentation in batch mode. The tests were conducted with samples prepared in 150 mL bottles using a shaker at 150 rpm. Response surface methodology was applied to investigate the influence of the four significant independent parameters viz. pH (5, 5.5, and 6), temperature (30°C, 35°C, and 40°C), substrate concentration (5,000, 12,500, and 20,000 mg L–1) and inoculum–substrate ratios of 2, 0.8, and 0.5 (expressed as volatile suspended solid (VSS) basis) with the inoculum concentration of 10 g L–1VSS on biohydrogen production. All the experiments were analyzed at the incubation time of 8, 16, and 24 h. Upon seeing each interval, the results were compared. The highest chemical oxygen demand (COD) removal, the hydrogen content in the biogas as hydrogen percentage (H2%), and hydrogen yield (HY) were obtained 58.3%, 80%, and 3.63 mol H2mol–1glucose, respectively, at 24 h incubation time. An overlay study was done to find an overall optimization of the parameters. The optimized conditions were COD removal 49%, HY 3.2 mol H2mol–1glucose, and hydrogen percentage 80%. Also, the Monod model was studied to calculate the kinetics constants of the maximum substrate utilization rate (Umax) and half-velocity Kswhich are found to be 0.261 g L–1d–1and 0.349 mg L–1, respectively.

In practice, established operation of activated sludge treatment system with high biomass concentration is restricted because of difficulty in settling the sludge in clarifiers. Membrane bioreactor is a modified form of activated sludge, and despite the superior advantages, its widespread application is restricted by the membrane fouling. Therefore, in this research, to improve the sludge sedimentation at high biomass concentration in the activated sludge system, high-frequency ultrasound (1.7 MHz) was exerted in clarifier of activated sludge system and its performance was compared with a bioreactor followed by an antifouling ultrafiltration membrane. The antifouling ability of NH2-functionalized multiwall carbon nanotubes (NH2-MWCNTs)-modified nanocomposite UF membrane during filtration of mixed liquor-activated sludge was investigated. Hydraulic retention time (HRT) (8–44 h) and mixed liquor suspended solids (MLSS) (6000–14,000 mg/L) were chosen as the operating variables to analyze the process. The biological process showed high COD removal efficiency throughout the experiments (> 96%). The membrane and high-frequency ultrasound had no effect on the system performance in terms of COD, TKN, TN, TP removal. However, the HRT and MLSS indicated an increasing impact on flux. The effect of ultrasound on the sludge properties, i.e., sludge volume index, sludge settling velocity and height of sludge at high MLSS concentration (14,000 mg/L), was not considerable. It was concluded at MLSS of below 10,000 mg/L, about 40% water recovery was obtained. As a result, activated sludge equipped with ultrasound showed a promising performance; however, its industrial development needs further examinations to attain the design criteria.

In this work, cinnamon extract/ coupling modified polyether sulfone (CiE/CPES) mixed matrix membrane with excellent anti-fouling and antibacterial properties was synthesized by the phase inversion method. To characterize the modified membrane, SEM, AFM, ATR – FTIR, EDX, WCA and porosity measurements were performed. SEM images showed the wider finger-like pores compared to the unfilled-CPES membrane. AFM images exhibited that with the addition of CiE to the polymer matrix the surface of CiE/CPES membranes has been significantly smoothed. BSA was used as a foulant to evaluate the anti-fouling properties and the results showed excellent flux recovery ratio (more than 95%) in all weight percentages of CiE, which indicates the significant improvement of self-cleaning property of fabricated membranes. To confirm the antibacterial properties of CiE, agar diffusion test was performed. A clear large halo around the CiE was observed for both model bacteria. The average halo radius was 41.63 mm for E. coli and 47.25 mm for S. aureus, which showed better performance compared to other routine studies. Also, the bacteria suspension immersion test and SEM analysis were investigated. The results showed a significant reduction of bacteria on the membrane surface compared to the control sample, which confirmed the excellent performance of CiE in the membrane. Besides, to measure the separation performance of the membranes, the biologically treated soft drink industrial wastewater (BTW) rejection was evaluated. The results provided very good efficiency in BTW purification. For further study, the desalination performance of the membranes was evaluated by examining the rejection of different salt solutions, and the order of rejection in all prepared membranes followed MgSO4> MgCl2> NaCl.

Zero-valent iron-modified Degussa P25-TiO2/ZnO nanocomposites (denoted as P25/Fe0/ZnO) were designed and prepared via Fe0impregnation of P25-TiO2/ZnO and then were employed in the visible-light photocatalytic degradation of p-nitrophenol (PNP) in the presence of [K2S2O8]. Central composite design was applied for response surface modeling (RSM) to understand the influence of selected factors (pH, [Fe0] wt% and [K2S2O8] concentration) on the degradation of PNP and to determine the interaction between the factors. The maximal PNP degradation efficiency (86.9%) was obtained with P25/1.5 wt% Fe0/ZnO at 3 mg/L of [K2S2O8] concentration and pH 7.5. In addition, the RSM showed a satisfactory correlation between the experimental and predicted values of PNP degradation. The P25/Fe0/ZnO photocatalyst performance was also examined degrading methyl orange and phenol and high degradation efficiency, 82 and 99%, was achieved, respectively. The structure, morphology, light absorption and photocatalytic properties of as-prepared P25/Fe0/ZnO were studied using TEM, BET, XRD, FTIR and DRS.

Aerobic granular sludge process, as an effective biotechnological process, was increasingly drawing the interest of researchers in the area of biological wastewater treatment. In this research, laboratory experiments were conducted to investigate the effect of feeding regime on the granulation process in a sequencing batch reactor (SBR) and continuous feed and intermittent discharge (CFID) bioreactor treating soft drink wastewater. To have a proper comparison between batch and CFID regimes, both bioreactors were operated under the same conditions with the initial chemical oxygen demand (COD) concentrations of 300 and 500 mg/L and cycle time of 4 h. From the results, contrasting to CFID regime, the batch regime was capable to form granular sludge at the applied conditions. To investigate the aerobic granulation process in the CFID bioreactor, hydraulic retention time (HRT) values of 8 and 12 h with idling times of 60 and 90 min, respectively, were examined. In the CFID bioreactor, at HRT of 8 h (CODinof 500 mg/L), the aerobic granules started to be appeared. By increasing HRT to 12 h (CODinof 1,000 mg/L), the aerobic granules were enlarged with more stability. As a conclusion, the higher values of HRT favored the granulation process in the CFID bioreactor. In addition, from the scanning electron microscopic images, the granules formed in the SBR and CFID bioreactor showed different structures.

AbstractThis study investigated the microbial diversity in a laboratory-scale upflow aerobic/anoxic sequential bioreactor (UAASB) with an alternate aeration. A bacteriological study was carried out, as a cultural-based technique, detecting dominant bacteria in the aerobic/anoxic conditions. Central composite design and response surface methodology were applied to investigate the effects of two operating parameters, namely hydraulic retention time (HRT) and aeration time (AT), on the performance of the UAASB. The HRT range of 12–36 h, and the AT range of 40–60 min/constant time of anaerobic conditions (1 h), were examined on the diversity and capability of system. Results of biological investigation showed that HRT and AT have significant effects on bacterial population and diversity, which also is function of organic loading value.

This study investigated the microbial diversity in a laboratory-scale upflow aerobic/anoxic sequential bioreactor (UAASB) with an alternate aeration. A bacteriological study was carried out, as a cultural-based technique, detecting dominant bacteria in the aerobic/anoxic conditions. Central composite design and response surface methodology were applied to investigate the effects of two operating parameters, namely hydraulic retention time (HRT) and aeration time (AT), on the performance of the UAASB. The HRT range of 12–36 h, and the AT range of 40–60 min/constant time of anaerobic conditions (1 h), were examined on the diversity and capability of system. Results of biological investigation showed that HRT and AT have significant effects on bacterial population and diversity, which also is function of organic loading value.

AbstractIn this study, an immobilized nanoTiO2photocatalyst was developed for the degradation of Tire Cord manufacturing wastewater with low BOD5/COD ratio (0.1–0.2). The interactive effects of three numerical independent factors (initial COD concentration, initial pH, and reaction time) on the process performance were studied. The process performance was evaluated by monitoring three process responses including COD removal efficiency, specific COD removal rate and BOD5/COD ratio after treatment. The process was modeled and analyzed using response surface methodology. Maximum COD removal efficiency and BOD5/COD ratio were modeled to be 38% and 0.5, respectively, at CODinof 350 mg/l and initial pH of 11. The photocatalytic process induced by O3and O3/H2O2showed a remarkable improvement in the process responses studied. Photocatalytic process with sequence regeneration with ozonation could achieve higher COD removal efficiency and BOD5/COD ratio relative to that obtained from regeneration by aeration.

In this study, an immobilized nanoTiO2photocatalyst was developed for the degradation of Tire Cord manufacturing wastewater with low BOD5/COD ratio (0.1–0.2). The interactive effects of three numerical independent factors (initial COD concentration, initial pH, and reaction time) on the process performance were studied. The process performance was evaluated by monitoring three process responses including COD removal efficiency, specific COD removal rate and BOD5/COD ratio after treatment. The process was modeled and analyzed using response surface methodology. Maximum COD removal efficiency and BOD5/COD ratio were modeled to be 38% and 0.5, respectively, at CODinof 350 mg/l and initial pH of 11. The photocatalytic process induced by O3and O3/H2O2showed a remarkable improvement in the process responses studied. Photocatalytic process with sequence regeneration with ozonation could achieve higher COD removal efficiency and BOD5/COD ratio relative to that obtained from regeneration by aeration.

In this study, the FSM-16 and FSM-16 modified by metformin (FSM-16-met) additives were applied as modifiers for polyethersulfone-based membranes. The modified membranes were evaluated in terms of morphology, surface roughness, hydrophilicity, pure water flux, pore size and porosity, and resistance ability. The obtained experimental data indicated promising enhancement in permeated flux and hydrophilicity after introducing the FSM-16-met nanomaterials into the membrane texture. In the case assessment of the fabricated membranes, dye removal capability was performed using the direct red-16 and methyl orange (30 mg/L). The modified membranes showed significantly higher dye rejection ability (> 97% for direct red-16 and 95% for methyl orange) compared to the bare membrane (76% for direct red-16 and 74% for methyl orange). The antifouling evaluations were run for milk powder (1000 mg/L) filtration and the best performance was obtained for the modified membrane with 0.1wt.% FSM-16-met (FRR = 95.55 ± 1.91%, Rir= 4.45 ± 0.089%). Also, the effect of the feed pH and concentration, temperature, and membrane driving force was considered on the membrane behavior. High stability in long-term performance was also observed for the modified membrane after 25 h re-running.

In this study, two sets of superior hydrophilic nanofiltration membranes, i.e., mixed matrix membranes and UV-grafted membranes by using L-Lysine (C, N codoped)-TiO2/WO3(LTW) novel photocatalytic nanocomposite were prepared to amelioration the membrane performance and its antifouling properties. The structural and chemical characteristic, filtration performance, antifouling feature and photocatalytic behavior, and filtration reusability of the fabricated membranes were evaluated. All modified membranes showed better performance compared to the pristine ones. The LTW modified membranes via the UV-grafting method represented considerable enhancement in surface hydrophilicity and filtration performance (contact angle of 42.6º and flux of 49.65 kg/m2.h for optimal membrane). A significant improvement in flux recovery ratio (FRR, 96.96%) and other fouling resistance parameters after fouling was indicative of great antifouling property for these membranes. Also, the modified photocatalytic membrane exhibited excellent rejection of methyl red dye under visible light irradiation (99.01% for optimal UV-grafted membrane). The selected membrane demonstrated high self-cleaning behavior for dye photodegradation. Based on the findings of this study, UV-grafted photocatalytic membranes are expected to have a great potential for practical application in water treatment.

•A high frequency ultrasound-augmented SBR treating dairy wastewater was developed.•The performance of two SBRs (with and without ultrasound) were compared.•Effect of high frequency ultrasound on biological activity of biomass was studied.•Effect of high frequency ultrasound on physical properties of sludge was studied.•Response surface methodology was applied to model the biological systems.

Recent research proclivity is about supplying water for drinking, urban and industrial applications which is recognized as one of the most significant challenges that threaten humanity. Giving its simplicity and high efficient yield, membrane technology has been preferred compared to other separation technologies for water and wastewater treatment. In the present research, KIT-6 (KIT: Korea Advanced Institute of Science and Technology) was functionalized by H-acid to improve hydrophilic functional groups on KIT-6 surface. Different characterization tests were performed to prove the insertion of H-acid on KIT-6 (H-KIT-6), e.g., FT-IR, XRD, zeta potential and FESEM analysis. Also, the effects of different loading of KIT-6 and H-KIT-6 on the morphology, characteristics and performance of Polysulfone (PSf) nanofiltration (NF) membranes were investigated. The maximum pure water flux (30.2 kg/m2h), the lowest irreversible fouling ratio (3.96%) and the highest flux recovery ratio (96.04%) were obtained for the membrane embedded with 0.1 wt.% H-KIT-6 (optimum membrane). Also, the performance of the synthesized membranes was evaluated by rejection of four different salts (K2SO4, MgSO4, KCl and NaCl) and heavy metal ions (As3+and Hg2+). The NF membrane embedded with 0.1 wt.% H-KIT-6 also presented the highest rejection of different salts and heavy metal ions (As3+= 99.85% and Hg2+= 99.27%) compared to the others. Finally, the performance of the optimum membrane to treat a real case of Gachsaran brackish water was assessed. As a result, by applying the optimum membrane, 565 mg/l, 28 mg/l and 27 mg/l of Ca2+, SO42−and Mg2+were rejected, respectively.

In this study, performance of an industrial estate wastewater treatment plant (WWTP) (Faraman's Industrial Estate, Kermanshah, Iran) was investigated by varying effective operating variables in order to explore the optimum operating conditions. Two independent effective variables i.e. mixed liquor volatile suspended solids (MLVSS) (2000, 4500 and 7000mg/l) and number of working aerators (NA) (2, 4 and 6) was studied. The experimental runs were designed using Design Expert Software (DOE) (Stat-Ease Inc., version 7.0). From the results, it was found that COD and BOD removal efficiencies were increased with an increase in MLVSS and NA. This study showed that varying the arrangement of the aerators was a key factor affecting the system's performance.

Licorice processing industry produces a characteristic wastewater with a high chemical oxygen demand (COD), high turbidity, and intense color. Direct disposal of untreated licorice processing wastewater into water bodies can pose a serious risk to the human health and environment. The main objective of this study is to evaluate the performance of a novel laboratory scale continuous electrocoagulation (EC) reactor using iron (Fe) rod electrodes (anode and cathode) for treating a real licorice processing wastewater. Response surface methodology (RSM) was employed to investigate the effects of important parameters such as: current density (CD), electrolysis time, mixing intensity, and NaCl concentration for Fe rod electrodes on the removal efficiency of color, soluble COD (sCOD), and turbidity. In order to evaluate the effect of reactor design on the overall process performance, the results were compared with our previous study in which Fe plate electrodes were employed in an identical system. The process exhibited better performance in terms of turbidity removal for Fe rod electrodes with an average value of 59.35% in contrast to Fe plate electrodes (47.88%). Color and sCOD removal efficiencies of 94.6% and 90.1% were achieved, respectively for the EC system using Fe rod electrodes under optimum conditions: electrolysis time (71.8 min), CD (28 mA/cm2), mixing intensity (45 rpm). While in the EC reactor using Fe plate electrodes, the optimum (electrolysis time of 81.8 min, current density of 35 A/cm2, and mixing intensity of 45 rpm) color and sCOD removal were obtained 90.1% and 89.4%, respectively. Analysis and comparison of the data revealed that Fe rod electrodes delivered a better treatment performance than Fe plate electrodes, taking into account that the optimum electrolysis time and applied current density were considerably lower for the Fe rod electrodes. Overall, these results confirmed that the novel EC reactor using Fe rod electrodes can reduce the operating cost and be proposed as a pragmatic approach to remove high amount of color, COD, and suspended solids from licorice processing wastewater.

Mixed matrix membrane (MMM) is a known and useful method for the incorporation of nanomaterials to fabricate efficient membranes for water purification. The compatibility of filler (i.e., nanomaterials) and the polymeric matrix is challenging in the design of composite membranes. This study elucidates the performance of polyethersulfone-based membrane (i.e., permeation flux, oil-water emulsion filtration, and membrane stability) with the incorporation of hydrophilic porous nanomaterials, e.g., FSM-16 and metformin-modified FSM-16 (noted as FSM-16-Met). The membranes with modified FSM-16 exhibited significant improvements in physical stability (thermal and mechanical) and surface hydrophilicity (78.98–41.37º for optimal membrane). A considerable enhancement in pure water flux (29.18–132.7 kg/m2h for optimal membrane) and remarkable antifouling improvement (FRR: 43.94–96.74% for optimal membrane) were observed for the membranes incorporated with FSM-16-Met, compared to those with FSM-16, in the oily wastewater separation in different conditions (oil concentration: 100, 300, and 500 ppm; temperature: 30–90 °C; and pressure: 3–6 bar).

The aim of this study was to remove non-biodegradable colored compounds from biologically treated baker's yeast effluent using an antifouling membrane in order to facilitate reuse of the wastewater. To get this purpose, in a facile effort, a new nanofiller, citric acid functionalized tannic acid (CA-f-TA), was synthesized by employing a simple, economical and green method. The produced nanofiller was used in the fabrication of polyethersulfone (PES) nanofiltration (NF) membranes. The influence of CA-f-TA on the cross section morphology, pore size, porosity, water content, hydrophilic properties, and roughness of the modified PES/NF membrane was evaluated. The performance of the fabricated membranes was analyzed as pure water flux (PWF), antifouling and dye rejection capacity. Based on obtained results, incorporation of the CA-f-TA nanofiller resulted in an increase in the PWF from 23.5 to 23.6 and 34.4 kg m−2h−1for the membranes blended with CA-f-TA-1, CA-f-TA-0.5 and CA-f-TA-0.1, respectively, in contrast to 16.4 kg m−2h−1for the reference membrane. The antifouling characteristics of the prepared membranes dramatically raised owing to improvement in smoothness and hydrophilicity of membrane surface. The synthesized NF membrane with 1 wt% CA-f-TA nanofiller had the highest flux recovery ratio (FRR, 93.2%) and dye rejection (95.7% for Direct Red 16 (DR 16) and 97% for biologically treated baker's yeast wastewater), and the lowest irreversible fouling resistance (6.8%). Furthermore, PWF of 34 kg m−2h−1, FRR of 97%, TSS and turbidity removal efficiencies of 100%, and COD removal efficiency of 80% were obtained using the 1 wt% CA-f-TA membrane after filtration of a field sample i.e. biologically treated baker's yeast wastewater over a 1-h filtration.

The main aim of the present study is to determine the optimum operating conditions for different feed compositions with less irreversible membrane fouling in an activated sludge followed by membrane process (AS-MP). In this regard, three different wastewaters with different BOD5/COD ratios (0.83 for soft drink, 0.63 for pineapple fruit juice and 0.36 for amoxicillin) as an index of biodegradability were selected. The AS-MP system was operated with biomass concentration of 7000–8000 mg/l and different hydraulic retention times (HRTs) in the range of 4–20 h. The optimal HRT was decreased as BOD5/COD ratio was increased. In order to investigate fouling behavior of membranes in the AS-MP, a commercial polyvinylidene fluoride (PVDF) microfiltration (MF) membrane and high-performance synthetic ZnFe2O4/SiO2embedded polyether sulfone (PES) ultrafiltration (UF) membrane were applied. As a result, the UF membrane indicated the highest flux recovery ratio (FRR) for pineapple fruit juice wastewater relative to the other wastewaters. Soft drink wastewater had the maximum permeability and FRR for MF membrane due to low turbidity of the feed and low interaction with MF membrane composition, whereas this wastewater showed a lower permeability and FRR in the UF membrane, implying an effective interaction between the residual soluble microbial products and the UF membrane composition. Both membranes showed almost the same performance for amoxicillin wastewater.

•Polyhydroxyalkonate (PHA) production in mixed microbial culture was investigated.•The possibility of PHA production under short-term biomass enrichment was assessed.•The potential of different strategies to produce PHA was assessed.

In this work, a multistage flexible fibre biofilm reactor (MS-FFBR) composed of four equal-size compartments was used successfully to treat milk processing wastewater (MPW). Response surface methodology (RSM) was also used to evaluate, model, and optimize the performance of the MS-FFBR. The effect of variation of two process variables (CODin and HRT) on the system performance was evaluated by measuring different responses (TCOD, SCOD, TBOD5, SBOD5, TSS removal efficiency, turbidity, pH, SRT and U). From findings, the maximum removal efficiency in terms of TCOD, SCOD, TBOD and SBOD was achieved at 12 h HRT and 1590 mg L−1CODin, whereas the lowest removal efficiencies were observed at 8 h HRT and 5869 CODin. The minimum TSS removal efficiency was obtained at 8 h HRT and 3750 mg L−1. More importantly, the MS-FFBR indicated good buffering capacity throughout the experiments. The optimum region was found at HRT less than 8 h and 1500 mg L−1 < CODin < 2635 mg L−1. The experimental findings were in close agreement with the model prediction.

Recently, membrane bioreactors (MBRs) have received extensive attention as an innovative wastewater treatment technology. Nevertheless, membrane fouling as a serious barrier has avoided the widespread application of the MBRs. In the present study, two polyethersulfone (PES) antifouling ultrafiltration membranes entrapped by 0.1 wt. % of NH2functionalized multiwalled carbon nanotubes (NH2-MWCNTs) and of O-carboxymethyl chitosan modified Fe3O4(OCMCS- Fe3O4) nanoparticles were employed in an MBR. The effect of both modified membranes on the fouling characteristics and biological performance of bioreactor was investigated. Experimental design was conducted using central composite design (CCD) of response surface methodology (RSM). The process performance of the bioreactor treating milk processing wastewater (MPW) was analyzed at different hydraulic retention times (HRTs) and mixed liquor suspended solids (MLSS). Five dependent process and operating parameters; TKN, NO3−, TN, TP removal efficiency and flux, were measured as response for both membranes. Independent increment of the variables gave rise to an increase in the process parameters. While, simultaneous increase in the variables led to the increase in flux. The Fe3O4−OCMCS embedded membrane indicated slightly higher flux than that of NH2-MWCNTs modified membrane. The optimum region was enclosed by high MLSS (≥12,000 mg/l) at any HRT studied.