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In this paper, the flocculation effect of single flocculants and compound flocculants on emulsified wastewater under different conditions was studied. The effect of flocculant type, dose, settling time and composite ratio of flocculant on the treatment of emulsified wastewater were investigated through single-factor condition tests, and then the optimal conditions of flocculants for treating emulsified wastewater were obtained. The results showed that the single inorganic flocculant could break the stable state of the emulsion when the pH was adjusted to 7 and formed tiny flocs, but it took a long time to settle down. The single organic flocculant had no flocculation effect. The inorganic–organic composite flocculants could effectively solve the problem of emulsion breaking and flocculation, and could form large flocs and alum flower formations at the same time, with mud and water effectively separated. The best conditions for the composite flocculants were as follows: under the condition of room temperature and pH 7, the dose of PFC was 2250 mg/L and APAM was 5 mg, the homogeneous stirring time was 10 min, and the settling time was 0.5 h. The removal rate of COD and turbidity reached 84.75% and 99.86%. The study could provide a new treatment idea and method for the pretreatment of stabilized high-turbidity wastewater. [ABSTRACT FROM AUTHOR]

Membrane Distillation (MD) is an emerging separation technology that has gained considerable interest in wastewater treatment. In this work, surface-modified poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) electrospun nanofibrous membranes were investigated for their potential to recover water from emulsified wastewater in direct contact membrane distillation (DCMD) mode. The modified electrospun membranes displayed a water contact angle of 130.5 ± 2° and water flux of 4.67 LMH with 99.9% rejection even when challenged with a 25000 ppm NaCl solution. However, membrane fouling and subsequent loss of permeate quality were observed within 120 minutes when emulsified wastewater (oil: surfactant-1:10 and 1000 ppm NaCl) was used as feed. Low-pressure nanofiltration (6 bar) was reported as a pre-treatment technology with thin-film nanocomposite (TFN) membranes incorporating Nickel-Aluminum Layered Double Hydroxide (Ni-Al LDH) nanoparticle on the polyamide layer. The TFN membranes were extensively characterized, and membrane N2 (0.01 wt.% Ni-Al LDH) exhibited a pure water permeance of 2.21 LMH/bar, 68% NaCl rejection, and 97% oil rejection. The integrated NF-MD process proved to be a robust technology and could remove 100% NaCl and 98.2% TOC for up to 300 minutes of operation. The proposed integrated technology holds the further potential to be investigated further. [ABSTRACT FROM AUTHOR]

Investigations on membrane materials for membrane distillation (MD) and its applications have been ongoing since the 1990s. However, a lack of materials that produce robustly stable and up-to-the-mark membranes for MD for different industrial applications remains an ongoing problem. This paper provides an overview of materials developed for MD applications. Although key aspects of published articles reviewed in this paper pertain to MD membranes synthesized for desalination, future MD can also be applied to organic wastewater containing surfactants with inorganic compounds, either with the help of hybrid treatment processes or with customized membrane materials. Many industrial discharges produce effluents at a very high temperature, which is an available driving force for MD. However, there remains a lack of cost-effective membrane materials. Amphiphobic and omniphobic membranes have recently been developed for treating emulsified and shale gas produced water, but the problem of organic fouling and pore wetting remains a major challenge, especially when NaCl and other inorganic impurities are present, which further deteriorate separation performance. Therefore, further advancements in materials are required for the treatment of emulsified industrial wastewater containing surfactants, salts, and for oil or shale gas wastewater for its commercialized reuse. Integrated MD systems, however, may represent a major change in shale gas wastewater and emulsified wastewater that are difficult to treat. • Advancements in materials for membrane distillation • Coating materials and surface modification technologies • Shale gas produced water and challenges in wastewater treatment • Superhydrophobic, Amphiphobic and Omniphobic membranes • Integrated MD processes with other technologies and advancement needed [ABSTRACT FROM AUTHOR]

The direct discharge of industrial emulsified wastewater critically threatens the environment and human health. Emulsified wastewater must be demulsified before discharge. Inspired by the applications of microchannels in oil-in-water (O/W) emulsion separation and patterned wettable surfaces to manipulate droplet formation, an arrow-shaped patterned microchannel (APM) was designed to enhance the droplet coalescence and demulsification of O/W emulsions with high oil content. The APM demulsification efficiency with 15 arrows of 5 patterns attained 70 % within 4.5 s when handling the O/W emulsion of 40 % (v / v) oil content. The experimental and simulation results revealed that the arrow-shaped patterns provided a series of inducing effects for dispersed droplets, enabling the coalesced droplets to form "oil-droplet-string flows". These positive inductions improved the efficiency of droplet coalescence and phase separation, thereby markedly enhancing the demulsification effect. By introducing the arrow-shaped wettable patterns, APM achieves the highest single demulsification efficiency of 70 % known at present for surfactant stabilized O/W emulsion with high oil content. This study provides a new technical approach for the treatment of industrial emulsified wastewater with high oil content. [Display omitted] • Arrow-shaped patterns enhance droplet coalescence efficiency and induce droplets to form "oil-droplet string flows". • Demulsification efficiency of O/W emulsion with 40 % (v / v) oil content attains 70 % in 4.5 s. • The demulsification efficiency of 5@15APM increases by 200 % compared to that of SHLM. • Numerical simulation explores the coalesce of droplets in microchannels of different wettabilities and heights. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Destabilization of emulsified wastewater from petroleum-industry using chitosan. • Optimization using surface response methodology and desirability function. • Sodium dodecyl sulfate and chitosan were combined for an efficient destabilization. • Turbidity, chemical oxygen demand, zeta-potential, clarified volume were optimized. • Coagulation/flocculation kinetics was modelled using static light dispersion. Abstract The presence of emulsified oils in wastewater from the petroleum and petrochemical industry causes a significant environmental concern. The effect of chitosan (CH) and sodium dodecyl sulfate (SDS) doses on the destabilization of emulsified wastewater was analyzed based on key parameters such as: residual turbidity (% RT), relative length of the clarified zone (CL), chemical oxygen demand (% COD) and zeta potential (ZP). A response surface methodology and central composite design were applied for optimizating the influence of CH and SDS doses, on the performance of the demulsification process. A desirability test allowed to calculate the optimal doses of CH and SDS to produce: i) minimum values of% RT and ZP and ii) maximum values of CL and % COD removal. A novel kinetic model based on first order equations for both stages: coagulation/flocculation and settling of the flocs was proposed to describe clarification using measurements of static dispersion of light and back scattering profiles (BS). The proposed model is a useful tool for predicting clarification times and to analyze the governing mechanisms of the process. Coagulation/flocculation occurs in less than 3 h reaching very low turbidity values in the clarified zone (<11% RT). Additionally, the BS profiles after 3 h showed that at the optimal dosage of CH and SDS 70% of the total volume was clarified with a total hydrocarbon removal of 98.61%. This study demonstrates that CH constitutes a potent flocculating/coagulating agent in waste-water emulsified systems from petroleum industry. [ABSTRACT FROM AUTHOR]

The highly concentrated emulsified wastewater containing non-ionic surfactant is hardly biodegradable, and few cost-effective techniques of treatment are available. In this paper a systematic study on its wet air oxidation (WAO) and the related decrease efficiency of COD, TOC, influencing factors, characteristics of the kinetics was performed in a 2-l high-pressure batch autoclave. The result indicated that the application of WAO had a good performance in the treatment of emulsified wastewater and the operation conditions such as temperature, partial pressure of oxygen, concentration of input wastewater have influence on the oxidation efficiency to different extent. And the temperature is the key influential factor: COD of the wastewater (initial COD: 48 000 mg/l) was reduced by 86.4% after 2 h oxidation at 220 °C, with the supply of oxygen 1.25 times more than its theoretical value. A general kinetic model can be used to explain the WAO process with sufficient oxygen supply, and an exponential model was developed. [Copyright &y& Elsevier]