Sewage enhanced bioelectrochemical degradation of petroleum hydrocarbons in soil environment through bioelectro-stimulation

The impact of readily biodegradable substrates (sewage and acetate) in bioelectroremediation of hydrocarbons (PW) was evaluated in a bench-scale soil-based hybrid bioelectrochemical system. Addition of bioelectro-stimulants evidenced efficient degradation than control operation. Acetate and sewage were exhibited power density of 1126 mW/m2 and 1145 mW/m2, respectively, which is almost 15 % higher than control (without stimulant, 974 mW/m2). Increased electrochemical activity was correlated well with total petroleum hydrocarbons (TPH) degradation through addition of acetate (TPHR, 525 mg/L, 67.4 %) and sewage (TPHR, 560 mg/L,71.8 %) compared to the control operation (TPHR, 503 mg/L, 64.5 %). Similarly, chemical oxygen demand (COD) reduction was also enhanced from 69.0 % (control) to 72.1 % and 74.6 % with acetate and sewage, respectively. Sewage and acetate also showed a positive role in sulfates removal, which enhanced from 56.0 % (control) to 62.9 % (acetate) and 72.6 % (sewage). This study signifies the superior function of sewage as biostimulant compared to acetate for the bioelectroremediation of hydrocarbons in contaminated soils

Integrating electrochemical and bioelectrochemical systems for energetically sustainable treatment of produced water

Pollutants present in produced water (PW) are recalcitrant in nature and difficult to treat with simple processes. Energetically sustainable and novel approach was developed by integrating electrochemical cell (EC, Primary process) and microbial fuel cell (MFC, secondary process) to treat PW. Five different current densities (26, 36, 48, 59 and 71 mA/cm2) were applied in independent EC experiments (4 h). The effluents from each EC operation was further treated by MFC (10 h), to harness bioelectricity. Operational variations were maintained only in EC phase and kept MFC phase similar. This integration revealed that the extent of bioelectricity generation depends on the electrochemical oxidation of EC process. Overall, maximum power generation of 2.74 mW was registered with EC-effluent from 48 mA/cm2. The integration also showed highest TPH removal efficiency of 89% (EC, 305 mg/L; MFC, 317 mg/L) and COD removal efficiency of 89.6% (EC, 2160 mg/L; MFC, 1960 mg/L) at 71 mA/cm2. Other pollutants of PW, such as sulfates and TDS also removed efficiently (sulfates, 42.6%; TDS, 34.3%). Cyclic voltammetric (CV) and derivative analysis of the anodic biofilm were correlated well with MFC performance during different EC-effluents as substrate, indicating NADH involvement in bioanodic electron transfer. The balance between energy utilization in EC and bioelectricity generation by MFC was depicted that the integration of EC and MFC results in net positive energy. Maximum net power generation of 565 mWh (350 mL of anode volume) was resulted by integration. This integration depicts its potential to generate 1615 Whm−3 from the treatment of 1KL PW

AN INVESTIGATION OF THE PHASE BEHAVIOR OF AN AQUEOUS SYSTEM THAT CONTAINS A POLYAMPHOLYTE AND POLY(ETHYLENE GLYCOL)

The phase behavior of aqueous two-phase polymer system containing poly(ethylene glycol) and a synthetic polyampholyte in 0.1 N KCl was studied as a function of pH. The top phase was poly(ethylene glycol)-rich and the bottom phase was polyampholyte-rich. The binodal curve was found to move towards lower concentrations of polymers with increasing pH as a result of decreased solubility of the polyampholyte. Phase compositions were correlated using a model based on Flory- Huggins theory. Also, a model based on excluded volume theory was used to correlate the binodal curve

Sustainable bioelectrochemical systems for bioenergy generation via waste treatment from petroleum industries

Petroleum industries are large water consumers and generate a lot of wastewater at various stages of industrial operations. Wastewater from the petroleum industries contain recalcitrant pollutants such as hydrocarbons that are present in high concentrations, dissolved solids and sulfur compounds that can pose potential environmental threat. Bioelectrochemical systems (BESs) are known to be sustainable processes to treat the various kinds of wastewaters such as petroleum wastewater, while simultaneously generating the bioelectricity and value-added chemicals. This review focuses on various applications of BESs such as microbial fuel cells (MFC), microbial electrolysis cells (MEC), and microbial desalination cells (MDC) using diverse types of wastewaters (petroleum sludge, produced water, formation water, and petroleum refinery wastewater) from the petroleum industries. Overall, a hybrid type BES with hydrocarbon wastewater achieved a 98% of columbic efficiency, 96.5% of chemical oxygen demand (COD), 99% of phenanthrene, 94% of pyrene and 80% of TDS removal which are superior to single and dual chamber BES performances. The review also compares the existing biological processes with BESs in terms of the treatment of hydrocarbons and process sustainability. Treatment efficiency of petroleum wastes via the BES can be further improved by integrating the biological and electrochemical processes to develop a sustainable approach to bio-refinery route

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

Recycling of hospital laundry wastewater using membrane technology

The laundry wastewater from a Qatari hospital has been characterized and its membrane filtration behavior studied. 1,800-2,500 L or wastewater per cycle for washing a laundry load of 40-50 kg was determined, with the wastewater shown to be sufficiently polluted to require treatment prior to discharge. Two treatment approaches were adopted, the first being a single membrane technology employing a “tight” ultrafiltration (UF) membrane of 5 kDa molecular weight cut-off (MWCO) and the second a combination of coarser UF of 75 kDa MWCO followed by a nominally 200 Da nanofiltration (NF) membrane. Both approaches were found to be acceptable in terms of pollutant rejection (more than 87%), with the statutory wastewater discharge limit being met. Fluxes of (29-42, 72-100 and 27-54 LMH were determined for the 5 kDa UF the 75 kDa UF and UF-pretreated NF). However, only the dual technology (combination of UF-NF) was able to remove the dissolved solids as evident by the reduction in wastewater conductivity. Results demonstrated that the hospital wastewater can be successfully treated at a pressure of 2.5 bar, temperature 25°C and a crossflow rate of 1 L/min, with rejection and flux being sensitive only to temperature within the range of 25°C-45°C

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/m 2 ; dual chamber - 1089 mW/m 2 ), 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/m 3 -day (COD removal efficiency, 54.7%); dual chamber - 0.33 kg COD/m 3 -day (COD removal efficiency, 60.2%)). Evaluated polarization behavior of both MFCs were also evidenced the effective response of the electroactive anodic biofilm. 2019 Elsevier B.V.This publication was made possible by NPRP grant # NPRP9-093-1-021 from the Qatar National Research Fund (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of the authors.Scopu