Optimum design of n continuous stirred-tank bioreactors in series for fermentation processes based on simultaneous substrate and product inhibition

Optimization of the continuous fermentation process is important for increasing efficiency and decreasing cost, especially for complicated biochemical processes described by substrate and product inhibition. The optimum design (minimum volume) of CSTRs in series assuming substrate and product inhibition was determined in this study. The effect of operating parameters on the optimum design was investigated. The optimum substrate concentration in the feed to the first reactor was determined for N reactors in series. The nonlinear, constrained optimization problem was solved using the MATLAB function “fmincon”. It was found that the optimum design is more beneficial at high substrate conversion and at a medium level of feed substrate concentration. The best number of reactors is two to three for optimum arrangements and two for equal-size arrangements. The presence of biomass in the feed to the first reactor reduces the reactor volume, while the presence of product in the feed slightly increases the required total volume. The percentage reduction in the total volume using the optimum design compared to equal-volume design (R%) was determined as a function of substrate conversion and substrate concentration in the feed to the first reactor. The obtained R% values agree with experimental data available in the literature for ethanol fermentation

Effect of the organic load on salt removal efficiency of microbial desalination cell

Microbial desalination cell presents a novel concept for wastewater treatment, salt removal and bioelectricity generation in a single system. In this study, the effect of organic load on salt removal in air-cathode up-flow microbial desalination cell (UMDC) was investigated in batch mode. Four different organic concentrations were fed to the anodic chamber of microbial desalination cell. The initial chemical oxygen demand in the anodic chamber was 2,024; 4,048; 6,074 and 8,096 mg/L. Real seawater was used in the desalination chamber of UMDC. The obtained results showed that the organic load 3 (initial COD of 6,074 mg/L) produced a maximum percentage of salt removal compared with other organic loads tested. The maximum power density production (1,769 mW/m2), the maximum percentage COD removal (95%) occurred with 48% salt removal in the microbial desalination cell using the organic load of 6,074 mg/L. The obtained results showed that microbial desalination cell is a unique system that provide wastewater treatment and salt removal in a single system. Organic load is a very important factor for the operation of UMDC, there is an optimum value that achieves the best performance of the UMDC system. - 2018 Desalination Publications. All rights reserved.This work was made possible by NPRP grant # 6-289-2-125 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors.Scopu

Improved salt removal and power generation in a cascade of two hydraulically connected up-flow microbial desalination cells

A novel two chamber up-flow microbial desalination cell (UMDC) was designed for evaluating desalination of real seawater with simultaneous wastewater treatment and energy generation. Two UMDCs were hydraulically connected in continuous flow mode (cascade mode) and operated at ten different hydraulic retention times (HRTs) [120 h to 12 h] and salt retention times (SRTs) [40 h to 4 h] for improved performance of chemical oxygen demand (COD) and salt removal. These UMDCs were operated at different combinations of high power (higher external resistance) and high current (low external resistance) mode to find the most suitable conditions for obtaining higher COD removal, salt removal, power production and current generation. The optimum HRT and SRT were 60 h and 40 h, respectively. The highest salt removal achieved was 72% at SRT of 40, while the highest COD removal was 83% at a HRT of 60 h. A maximum current density of 2.375 A/m2 was obtained, while the maximum power density was 5.879 W/m2. The obtained results give an overlook for the scale up of UMDCs in the future. In the entire system, membrane fouling is still a major problem. As the operation time increases, this resulted in low power generation and low salt removal efficiency. The UMDCs can function as sustainable and alternative solution for real wastewater treatment and seawater desalination with resource recovery and power production.This publication was made possible by NPRP Grant # 6-289-2-125 from the Qatar National Research Fund (a member of Qatar Foundation).Scopu

Improved petroleum refinery wastewater treatment and seawater desalination performance by combining osmotic microbial fuel cell and up-flow microbial desalination cell

The petroleum refinery wastewater which is a product of petroleum refinery has a high organic content. This study explores the utilization of petroleum refinery wastewater collected from petroleum refinery as a resource for bioelectricity generation and using this energy for salt removal from seawater in a hydraulically connected osmotic microbial fuel cell (OsMFC) and up flow microbial desalination cell (UMDC). Anaerobic mixed sludge was used in the anodic chamber of OsMFC and UMDC. Petroleum refinery wastewater was fed first into the OsMFC and then transferred to the UMDC. The OsMFC and UMDC were connected to 1000 and 100 external resistance respectively. Experimental results showed that the combined system could remove 93% of chemical oxygen demand (COD) from the petroleum refinery wastewater whilst 48% salts were removed from the seawater. Experimental results showed that this complex wastewater can be treated and produce bioelectricity, with COD removal and salt removal. The hydraulically connected OsMFC and up flow MDC provide a suitable platform for wastewater treatment and seawater desalination.This publication was made possible by NPRP grant # 6-289-2-125 from the Qatar National Research Fund (a member of Qatar Foundation).Scopu

Boron removal from saline water by a microbial desalination cell integrated with donnan dialysis

Boron has toxic effects on plant growth and thus its removal is necessary from desalinated saline water for irrigation application. Microbial desalination cells (MDCs) are a new approach for effective desalination but boron removal has not been addressed before. Herein, MDCs were studied for boron removal with aid of Donnan Dialysis (DD). The alkaline solution generated by the MDC cathode was used to ionize boric acid to facilitate boron removal. An MDC system with DD pretreatment removed 60 or 52% of boron with the initial boron concentration of 5 or 20mgL-1. In the absence of DD, direct cathodic alkalinization of boron in an MDC was not effective in terms of boron removal and had a serious issue of salt accumulation. The MDC with DD post-treatment could reduce the boron concentration below 2mgL-1, although the high pH of its final effluent needs to be further addressed. Further investigation will consider an MDC system with both DD pre-treatment and post-treatment for improving boron removal.NPRP grant # 6-289-2-125 from the Qatar National Research Fund (a member of Qatar Foundation)Scopu

Biological anodic oxidation and cathodic reduction reactions for improved bioelectrochemical treatment of petroleum refinery wastewater

Bioelectrochemical systems (BESs) were evaluated for the bioelectrochemical treatment (BET) of petroleum refinery wastewater (PRW) by applying mild electrochemical potential in the range of 400?1000 mV on a single chamber membrane-less BES configured with anodic and cathodic biofilms. After four days of cycle operation in batch mode, BES achieved a maximum current density of 278 mA/m2 and a power density of 222 mW/m2 using applied potential of 800 mV. This system also achieved COD degradation rate of 0.364 kg COD/m3-day. Diesel range organics (DROs) exhibited more than 90% degradation, which is 15 times higher than the abiotic control. Electrochemically active bioanode and biocathode contributed to the degradation of PRW through both oxidation and reduction reactions with mild applied potentials. This also resulted in a 30% improvement in COD removal compared to MFC with biocatalyst only on the anode. The function of improved bioelectrochemical treatment was also exhibited by redox current values of cyclic voltammograms. ? 2018 Elsevier LtdThis publication was made possible by NPRP grant # 6-289-2-125 from the Qatar national research fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors. The Authors would like to acknowledge the Environmental Science Centre (ESC) , Qatar University for the support in evaluating the samples for diesel range organics (DROs).Scopu

Induced bioelectrochemical metabolism for bioremediation of petroleum refinery wastewater: Optimization of applied potential and flow of wastewater

Hybrid based bioelectrochemical system (BES) configured with embedded anode and cathode electrodes in soil was tested for the bioelectrochemical degradation of petroleum refinery wastewater (PRW). Four applied potentials were studied to optimize under batch mode operation, among which 2 V resulted in higher COD degradation (69.2%) and power density (725 mW/m2) during 7 days of operation. Further studies with continuous mode of operation at optimized potential (2 V) showed that hydraulic retention time (HRT) of 19 h achieved the highest COD removal (37%) and highest power density (561 mW/m2). BES function with respect to treatment efficiencies of other pollutants of PRW was also identified with respect to oil and grease (batch mode, 91%; continuous mode, 34%), total dissolved salts (batch mode, 53%; continuous mode, 24%) and sulfates (batch mode, 59%; continuous mode, 42%). Soil microenvironment in association with BES forms complex processes, providing suitable conditions for efficient treatment of PRW. ? 2018 Elsevier LtdThis publication was made possible by NPRP grant # 8-594-2-244 from the Qatar National Research Fund , Qatar (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of the authors

Cylindrical graphite based microbial fuel cell for the treatment of industrial wastewaters and bioenergy generation

Cylindrical graphite microbial fuel cell (MFC) configuration designed by eliminating distinct casing and membrane was evaluated for bioelectrogenesis and treatment of real-field wastewaters. Both petroleum refinery wastewater (PRW) and Labanah whey wastewater (LW) were used as substrates, and investigated for electricity generation and organic removal under batch mode operation. PRW showed higher bioelectricity generation (current and power generation of 3.35 mA and 1.12 mW at 100 ) compared to LW (3.2 mA and 1.02 mW). On the contrary, higher substrate degradation efficiency was achieved using LW (72.76%) compared to PRW (45.06%). Superior function of MFC operation in terms of volumetric power density (PRW, 28.27 W/m3; LW, 23.23 W/m3) suggesting the feasibility of using these wastewaters for bioelectricity generation. Large sources of wastewater that generating in the Middle-East countries have potential to produce renewable energy from the treatment, which helps for the sustainable wastewater management and simultaneous renewable energy production.This publication was made possible by NPRP grant # 6-289-2-125 from the Qatar National Research Fund (a member of Qatar Foundation).Scopu

Removal of petroleum hydrocarbons and sulfates from produced water using different bioelectrochemical reactor configurations

Produced water (PW) is a wastewater generated in large quantities from the extraction of oil and gas. PW found to have high amounts of dissolved solids (TDS) and residual petroleum hydrocarbons causing considerable damage to the environment. PW also contains sulfates in significant amounts, due to which treating this wastewater is essential prior to discharge. The present study was aimed for bioelectrochemical treatment of PW and simultaneous bioelectrogenesis in the two most studied configurations viz., single and dual chamber microbial fuel cells (MFCs). The study evidenced treatment of recalcitrant pollutants of PW. Both MFCs were operated by keeping similar operating conditions such as anode chamber volume, hydraulic retention time (HRT) for batch mode of operation, electrode materials, inlet characteristics of PW and ambient temperature. Among both configurations, dual chamber MFC showed higher efficiency with respect to bioelectrogenesis (single chamber - 789 mW/m2; dual chamber – 1089 mW/m2), sulfates removal (single chamber – 79.6%; dual chamber – 93.9%), total petroleum hydrocarbons removal (TPH, single chamber – 47.6%; dual chamber – 53.1%) and chemical oxygen demand degradation (COD, single chamber – 0.30 kg COD/m3-day (COD removal efficiency, 54.7%); dual chamber – 0.33 kg COD/m3-day (COD removal efficiency, 60.2%)). Evaluated polarization behavior of both MFCs were also evidenced the effective response of the electroactive anodic biofilm.This publication was made possible by NPRP grant # NPRP9-093-1-021 from the Qatar National Research Fund (a member of Qatar Foundation).Scopu

Utilization of residual organics of Labaneh whey for renewable energy generation through bioelectrochemical processes: Strategies for enhanced substrate conversion and energy generation

Labaneh whey (LW)that is rich in residual organics was evaluated for bioelectricity generation using microbial fuel cell (MFC)in two different configurations namely single chamber (MFC-SC)and dual chamber (MFC-DC)MFCs. The whole study was executed in three stages: The first stage evidenced promising amount of bioelectricity generation (DC, 643 mV; SC, 545 mV)along with chemical oxygen demand removal (CODr: DC, 60.63%; SC, CODr: 55.25%). In the second phase, activity of anodic electrogenic microbes was improved with short time poising at potentials of 400, 600 and 800 mV, among which 800 mV evidenced 2.24 (DC)and 1.60 (SC)fold enhancement in power generation along with significant improvement in substrate degradation. The third phase was solely focused on bioelectrochemical treatment of LW through applied potentials for extended period. This phase achieved 89 and 94% chemical oxygen demand (COD)degradation using SC and DC configurations, respectively at 800 mV. - 2019 Elsevier LtdThis publication was made possible by NPRP grant # 6-289-2-125 from the Qatar national research fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors. Appendix AScopu