The effect of additives on the treatment of oil-in-water emulsions by vacuum evaporation

Ultrasonic assisted ultrafiltration process for emulsification of oil field produced water treatment

Ultrafiltration has been proven to be very effective in the treatment of oil-in-water emulsions, since no chemical additives are required. However, ultrafiltration has its limitations, the main limits are concentration polarization resulting to permeate flux decline with time. Adsorption, accumulation of oil and particles on the membrane surface which causes fouling of the membrane. Studies have shown that the ultrasonic is effective in cleaning of fouled membrane and enhancing membrane filtration performance. But the effectiveness also, depends on the selection of appropriate membrane material, membrane geometry, ultrasonic module design, operational and processing condition. In this study, a hollow and flat-sheet polyurethane (PU) membranes synthesized with different additives and solvent were used and their performance evaluated with oil-in-water emulsion. The steady-state permeate flux and the rejection of oil in percentage (%) at two different modes were determined. A dry/wet spinning technique was used to fabricate the flat-sheet and hollow fibre membrane (HFMs) using Polyethersulfone (PES) polymer base, Polyvinylpyrrolidone (PVP) additive and N, N-Dimethylacetamide (DMAc) solvent. Ultrasonic assisted cross-flow ultrafiltration module was built to avoid loss of ultrasonic to the surrounding. The polyurethane (PU) was synthesized by polymerization and sulphonation to have an anionic group (-OH; -COOH; and -SO₃H) on the membrane surface. Changes in morphological properties of the membrane had a significant effect on the permeate flow rate and oil removal. Generation of cavitation and Brownian motion by the ultrasonic were the dominant mechanisms responsible for ultrafiltration by cracking the cake layers and reducing concentration polarization at the membrane surface. The percentage of oil after ultrafiltration process with ultrasonic is about 90% compared to 49% without ultrasonic. Ultrasonic is effective in enhancing the membrane permeate flux and controlling membrane fouling.

Investigation of the disruption of algal biomass with chlorine

BACKGROUND

Algal biofuel has a potential for reducing dependence on fossil fuel while curbing CO₂ emissions. Despite these potential benefits, a scalable, sustainable, and commercially viable system has not yet been developed. One of the key barriers is the lack of viable methods for disrupting algal biomass for the separation and extraction of bioproducts. This study experimentally investigated the feasibility of using chlorine as an agent for algal biomass disruption.

RESULTS

Chlorine was an effective agent for disrupting algal cell, as demonstrated with cell viability and SEM analyses. For disruption studies conducted using algal suspension at 0.02% solids (0.2 g/L), 90% of the algal cells were disrupted in 6 min at 10 mg/L chlorine dose. Moreover, the results demonstrated that the estimated specific energy requirement, specific cost, and GWP for chlorine were lower than those of the existing methods. The energy requirement for chlorine was 3.73 MJ/ kg of dry algae disrupted, while the requirements for the existing methods ranged from 33 to 860 MJ/ kg of dry algae. The GWP for chlorine was 0.3 kg CO₂-eq./kg dry algae, while for the existing methods it varied from 5.9 to 369.8 CO₂-eq./kg dry algae. Despite these advantages, it was observed that residual chlorine reacted with and mineralized the cell contents, which is undesirable.

CONCLUSIONS

Future research efforts must be focused on eliminating or reducing the reaction of residual chlorine with cell contents. If this challenge is addressed, chlorine has a potential to be developed into an energy-efficient, cost-effective, and sustainable method for algal biomass disruption. This will in turn will overcome one of the technical bottlenecks, and ultimately increase algal biofuel production and reduce dependence on fossil fuel and curb CO₂ emissions.

Process optimization via response surface methodology in the treatment of metal working industry wastewater with electrocoagulation

In this study, process parameters in chemical oxygen demand (COD) and turbidity removal from metal working industry (MWI) wastewater were optimized by electrocoagulation (EC) using aluminum, iron and steel electrodes. The effects of process variables on COD and turbidity were investigated by developing a mathematical model using central composite design method, which is one of the response surface methodologies. Variance analysis was conducted to identify the interaction between process variables and model responses and the optimum conditions for the COD and turbidity removal. Second-order regression models were developed via the Statgraphics Centurion XVI.I software program to predict COD and turbidity removal efficiencies. Under the optimum conditions, removal efficiencies obtained from aluminum electrodes were found to be 76.72% for COD and 99.97% for turbidity, while the removal efficiencies obtained from iron electrodes were found to be 76.55% for COD and 99.9% for turbidity and the removal efficiencies obtained from steel electrodes were found to be 65.75% for COD and 99.25% for turbidity. Operational costs at optimum conditions were found to be 4.83, 1.91 and 2.91 €/m³ for aluminum, iron and steel electrodes, respectively. Iron electrode was found to be more suitable for MWI wastewater treatment in terms of operational cost and treatment efficiency.

Lemna minor tolerance to metal-working fluid residues: implications for rhizoremediation

For the first time in the literature, duckweed (Lemna minor) tolerance (alone or in combination with a consortium of bacteria) to spent metal-working fluid (MWF) was assessed, together with its capacity to reduce the chemical oxygen demand (COD) of this residue. In a preliminary study, L. minor response to pre-treated MWF residue (ptMWF) and vacuum-distilled MWF water (MWFw) was tested. Plants were able to grow in both residues at different COD levels tested (up to 2300 mg·l(-1) ), showing few toxicity symptoms (mainly growth inhibition). Plant response to MWFw was more regular and dose responsive than when exposed to ptMWF. Moreover, COD reduction was less significant in ptMWF. Thus, based on these preliminary results, a second study was conducted using MWFw to test the effectiveness of inoculation with a bacterial consortium isolated from a membrane bioreactor fed with the same residue. After 5 days of exposure, COD in solutions containing inoculated plants was significantly lower than in non-inoculated ones. Moreover, inoculation reduced β+γ-tocopherol levels in MWFw-exposed plants, suggesting pollutant imposed stress was reduced. We therefore conclude from that L. minor is highly tolerant to spent MWF residues and that this species can be very useful, together with the appropriate bacterial consortium, in reducing COD of this residue under local legislation limits and thus minimise its potential environmental impact. Interestingly, the lipophilic antioxidant tocopherol (especially the sum of β+γ isomers) proved to be an effective plant biomarker of pollution.

Feasibility of spent metalworking fluids as co-substrate for anaerobic co-digestion

In this paper, anaerobic co-digestion of spent metalworking fluids (SMWF) and pig manure (PM) was evaluated. Three SMWF:PM ratios were tested in order to find the highest process efficiency. The best results (COD removal efficiencies of 74%) were achieved co-digesting a mixture with a SMWF:PM ratio of 1:99, w/w(1) (corresponding to 3.75mL SMWF/Lreactor week), which indicates that SMWF did not affect negatively PM degradation. Furthermore, two different weekly SMWF pulse-frequencies were performed (one reactor received 1 pulse of 3.75mL/Lreactor and the other 3 pulses of 1.25mL/Lreactor) and no differences in COD removal efficiency were observed. Microbiology analysis confirmed that Pseudomonas was the predominant genus when treating anaerobically SMWF and the presence of a higher fraction of Archaea was indicative of good digester performance. This study confirms the feasibility of anaerobic co-digestion as an appropriate technology for treating and valorising SMWF.

Quantitative structure-retention relationship for retention behavior of organic pollutants in textile wastewaters and landfill leachate in LC-APCI-MS

INTRODUCTION

A quantitative structure-retention relation (QSRR) study was conducted on the retention times of organic pollutants in textile wastewaters and landfill leachate which was obtained by liquid chromatography-reversed phase-atmospheric pressure chemical ionization-mass spectrometry.

METHODS

The genetic algorithm was used as descriptor selection and model development method. Modeling of the relationship between selected molecular descriptors and retention time was achieved by linear (partial least square) and nonlinear (Levenberg-Marquardt artificial neural network, L-M ANN) methods. Linear and nonlinear models provide good results whereas more accurate results were obtained by the L-M ANN model.

CONCLUSION

This is the first research on the QSRR of the organic pollutants in textile wastewaters and landfill leachate against the retention time.

Treatment of a waste oil-in-water emulsion from a copper-rolling process by ultrafiltration and vacuum evaporation

A process is proposed for the treatment of a waste oil-in-water (O/W) emulsion generated in an industrial copper-rolling operation. The use of demulsifier agents improves the subsequent treatment by techniques such as ultrafiltration (UF) or evaporation. The effluent COD is reduced up to 50% when the O/W emulsion is treated by UF using a flat 30 nm TiO(2) ceramic membrane (ΔP = 0.1 MPa) and up to 70% when it is treated by vacuum evaporation, after an emulsion destabilization pretreatment in both cases. Increases in the UF permeate flux and in the evaporation rate are observed when a chemical demulsifier is used in the pretreatment step. A combined process consisting of destabilization/settling, UF, and vacuum evaporation can yield a very high-quality aqueous effluent that could be used for process cooling or emulsion reformulation.