Bilge water separation by membrane distillation

Advancements in bilge wastewater treatment: A review for current and future trends

Bilge wastewater (BW) from ships poses a significant threat to coastal ecosystems due to its recalcitrant nature. BW is mainly composed of organic hydrocarbons and oils together with surfactants, heavy metals, and other organic compounds but oil is the sole compound regulated by international law with a discharge limit of 15 mg/L. Therefore, BW treatment is a crucial aspect of marine pollution control and environmental protection. In this sense, BW must be treated on board or shipped to treatment plants on land. While conventional methods like gravity separation and adsorption have been used to treat BW, their inability to effectively treat complex mixtures has encouraged researchers to investigate advanced alternatives. Thus, new, cost-efficient, and sustainable technologies to treat BW are required such as those based on biological approaches. Moreover, integrating bio-based methods with existing technologies can provide comprehensive and eco-friendly treatment solutions. This review compiles various documents published regarding the treatment of BW, pointing out the necessity of developing new cost-efficient and environmentally friendly approaches to treat it. To the best knowledge of the authors this is the first comprehensive review on this very latest topic. Therefore, this review will be a significant contribution to the literature in terms of conservation of the environment, reduction in water pollution, and protection of the marine ecosystems.

Innovative Membrane Technologies for the Treatment of Wastewater Polluted with Heavy Metals: Perspective of the Potential of Electrodialysis, Membrane Distillation, and Forward Osmosis from a Bibliometric Analysis

A bibliometric analysis, using the Scopus database as a source, was carried out in order to study the scientific documents published up to 2021 regarding the use of electrodialysis, membrane distillation, and forward osmosis for the removal of heavy metals from wastewater. A total of 362 documents that fulfilled the search criteria were found, and the results from the corresponding analysis revealed that the number of documents greatly increased after the year 2010, although the first document was published in 1956. The exponential evolution of the scientific production related to these innovative membrane technologies confirmed an increasing interest from the scientific community. The most prolific country was Denmark, which contributed 19.3% of the published documents, followed by the two main current scientific superpowers: China and the USA (with 17.4% and 7.5% contributions, respectively). Environmental Science was the most common subject (55.0% of contributions), followed by Chemical Engineering (37.3% of contributions) and Chemistry (36.5% of contribution). The prevalence of electrodialysis over the other two technologies was clear in terms of relative frequency of the keywords. An analysis of the main hot topics identified the main advantages and drawbacks of each technology, and revealed that examples of their successful implementation beyond the lab scale are still scarce. Therefore, complete techno-economic evaluation of the treatment of wastewater polluted with heavy metals via these innovative membrane technologies must be encouraged.

Membrane Distillation Crystallizer Applied for Separation of NaCl Solutions Contaminated with Oil

In the present study, the membrane crystallizer was used to separate a saturated NaCl solution contaminated with an oil emulsion. The crystallizer was connected via a mesh separator with a feed tank in which capillary submerged modules were assembled. The effect of scaling and oil sorption on the wetting of polypropylene (PP) membranes has been investigated during the long-term studies. It has been found that cooling the solution in the crystallizer by 15 K below the feed temperature resulted in intensive NaCl crystallization in the zone below the mesh separator. A result, the salt crystallization on the membrane surface was eliminated. Contamination of saturated brines with oil in the concentration exceeding 100 mg/L caused the oil penetration into the membrane pores. The application of a PP net assembled on the capillary membranes surface reduced the intensity of wetting phenomenon caused by scaling and the oil sorption, which provides a stable membrane module performance during 1300 h test.

The Impact of Operational Parameters on Polypropylene Membrane Performance during the Separation of Oily Saline Wastewaters by the Membrane Distillation Process

In the present study, membrane distillation (MD) was applied for the treatment of oily saline wastewaters produced on ships sailing the Baltic Sea. For comparison purposes, experiments were also carried out with model NaCl solutions, the Baltic Seawater and oil in water emulsions. The commercial Accurel PP V8/2 membranes (Membrana GmbH, Germany) were used. In order to investigate the impact of the operational parameters on the process performance, the experiments were conducted under various values of the feed flow velocity (from 0.03 to 0.12 m/s) and the feed temperature (from 323 to 343 K). The obtained results highlight the potential of PP membranes application for a stable and reliable long-term treatment of oily wastewater. It was demonstrated that the permeate flux increased significantly with increasing feed temperature. However, the lower temperature ensured the limited scaling phenomenon during the treatment of oily wastewaters. Likewise, increasing the feed flow velocity was beneficial to the increase in the flux. Moreover, it was found that performing a cyclic rinsing of the module with a 3% HCl solution is an effective method to maintain a satisfactory module performance. The present study sheds light on improving the MD for the treatment of oily wastewaters.

Functionalized electrospun nanofiber membranes for water treatment: A review

Electrospun nanofiber membranes (ENMs) have high porosity, high specific surface area and unique interconnected structure. It has huge advantages and potential in the treatment and recycling of wastewater. In addition, ENMs can be easily functionalized by combining multifunctional materials to achieve different water treatment effects. Based on this, this review summarizes the preparation of functionalized ENMs and its detailed application in the field of water treatment. First, the process and influence factors of electrospinning process are introduced. ENMs with high porosity, thin and small fiber diameter have better performance. Secondly, the modification methods of ENMs are analyzed. Pre-electrospinning and post-electrospinning modification technology can prepare specific functionalized ENMs. Subsequently, functionalized ENMs show water treatment capabilities such as separation, adsorption, photocatalysis, and antimicrobial. Subsequently, the application of functionalized ENMs in water treatment capabilities such as separation, adsorption, photocatalysis, and antimicrobial capabilities were listed. Finally, we also made some predictions about the future development direction of ENMs in water treatment, and hope this article can provide some clues and guidance for the research of ENMs in water treatment.