Enrichment and characterization of a bilge microbial consortium with oil in water-emulsions breaking ability for oily wastewater treatment

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.

Exploring polyhydroxyalkanoates biosynthesis using hydrocarbons as carbon source: a comprehensive review

Environmental pollution caused by petrochemical hydrocarbons (HC) and plastic waste is a pressing global challenge. However, there is a promising solution in the form of bacteria that possess the ability to degrade HC, making them valuable tools for remediating contaminated environments and effluents. Moreover, some of these bacteria offer far-reaching potential beyond bioremediation, as they can also be utilized to produce polyhydroxyalkanoates (PHAs), a common type of bioplastics. The accumulation of PHAs in bacterial cells is facilitated in environments with high C/N or C/P ratio, which are often found in HC-contaminated environments and effluents. Consequently, some HC-degrading bacteria can be employed to simultaneously produce PHAs and conduct biodegradation processes. Although bacterial bioplastic production has been thoroughly studied, production costs are still too high compared to petroleum-derived plastics. This article aims to provide a comprehensive review of recent scientific advancements concerning the capacity of HC-degrading bacteria to produce PHAs. It will delve into the microbial strains involved and the types of bioplastics generated, as well as the primary pathways for HC biodegradation and PHAs production. In essence, we propose the potential utilization of HC-degrading bacteria as a versatile tool to tackle two major environmental challenges: HC pollution and the accumulation of plastic waste. Through a comprehensive analysis of strengths and weaknesses in this aspect, this review aims to pave the way for future research in this area, with the goal of facilitating and promoting investigation in a field where obtaining PHAs from HC remains a costly and challenging process.

Oily bilge water treatment using indigenous soil bacteria: Implications for recycling the treated sludge in vegetable farming

Hydrocarbon contamination from motorized vessels operating on seas threaten marine ecosystems and need to treated efficiently. A bilge wastewater treatment using indigenous bacteria isolated from oil contaminated soil was studied. Five bacterial isolates (Acinetobacter baumanni, Klebsiella aerogenes, Pseudomonas fluorescence, Bacillus subtilis and Brevibacterium linens) were isolated from port soil and used in the bilge water treatment. Their crude oil degradation abilities were first confirmed experimentally. The single species and the consortia of each two species were compared in an experiment where the conditions were first optimized. The optimized conditions were 40 °C, carbon source glucose, nitrogen source ammonium chloride, pH 8, and salinity 25%. Each of the species and each combination was able to degrade oil. K. aerogenes and P. fluorescence were the most efficient in reducing the crude oil concentration. The crude oil concentration was reduced from 290 mg/L to 23 mg/L and 21 mg/L, respectively. The respective values for the loss in turbidity were from 320 NTU to 29 mg/L and 27 NTU and for BOD loss from 210 mg/L to 18 mg/L and 16 mg/L. Mn was reduced from 25.4 mg/L to 1.2 mg/L and 1.0 mg/L, Cu from 26.8 mg/L to 2.9 mg/L and 2.4 mg/L, and Pb from 29.8 mg/L to 1.5 mg/L and 1.8 mg/L. The consortium of K. aerogenes and P. fluorescence in the bilge wastewater treatment reduced the crude oil concentration to 11 mg/L. After the treatment, the water was removed and the sludge was composted with palm molasses and cow dung. After 60 days of composting and inoculation with different bacterial consortia, the final product was used as a seedbed for vegetables. The compost with the consortium K. aerogenes and P. fluorescence promoted vegetable plant growth most and could be used in farming.

Identification of bilge oil with lubricant: Recent oil spill case studies

Oil spills have many adverse effects on the marine environment. Bilge oil spills occur frequently in the sea as a result of maritime accidents or illegal discharge. It is difficult to unambiguously identify the specific sources of such spills because bilge oil contains a mixture of fuel oil and lubricant. In this study, bilge oils with different fuel oil/lubricant ratios were prepared and analyzed using a modified version of the CEN/TR methodology (European Committee for Standardization, 2012). As the lubricant content of bilge oil increased, the intensity of the C20-C24 group, which is the commonly-used normalization compound group for fuel oil in the percentage weathering (PW) plot, also changed. Therefore, the mean area of the C15-C18 group, which was affected by the lubricant content, was used instead. Although heavy fuel oil is usually normalized to a hopane, bilge oil with a high lubricant content cannot be analyzed based on a mass spectrometry (MS)-PW plot; thus, heavy fuel oil-based bilge oil was normalized to a phytane in this study. Although hopanes and styrenes are unsuitable comparison compounds for heavy fuel oil-based bilge oil analysis, for light fuel oil-based bilge oil, hopanes and steranes could be applied as diagnostic ratio comparisons when the lubricant peak was clearly detected in the chromatograms of the spilled and suspected oil samples. By applying the CEN/TR methodology according to this approach, the similarities between spilled and suspected oil samples were more easily revealed. In addition, the field applicability of the proposed method was tested for four actual oil spills.

Bioremediation by oil degrading marine bacteria: An overview of supplements and pathways in key processes

Oil spillage is one of the most common pollutants which brings greater economic loss and damage to the environment. The intensity and amount of the damage may vary depending on factors such as the type of oil, the location of the spill, and the climatic parameters in the area. As for any pollution management, the guidelines are Reduce, Re-use, Recover and Disposal. Amongst the other remediation processes, Bioremediation is amongst the most significant environmentally friendly and cost-effective approaches for marine biological restoration because it allows complex petroleum hydrocarbons in spilt oil to decompose completely into harmless compounds. Mainly, the necessity and essence of bioremediation were talked about. This review discussed the bacteria identified which are capable of degrading various oil related pollutants and their components. Also, it covered the various media components used for screening and growing the oil degrading bacteria and the pathways that are associated with oil degradation. This article also reviewed the recent research carried out related to the oil degrading bacteria.

Investigations on influences of MWCNT composite membranes in oil refineries waste water treatment with Taguchi route

Most of the 'oil refineries' severally pollutes the water resources by depleting their untreated waste water like cooling water, storm water and unsanitary sewage water. These wastewaters are to be treated with high care to protect the human, pebbles, plants, fish and other water animals and from harmful effects. The present study focused to treat the oil refinery wastewater by means of Multi wall carbon nanotube (MWCNT) coated Polyvinylidene Fluoride (PVDF) membrane. The main objectives are: to increases the life of filter, reduce the percolation flux and reduce the formation of antifouling in the filter by using MWCNT composite membrane in it. Different process parameters of the proposed water treatment process, like diameter of MWCNT (15 nm, 20 nm, 25 nm and 30 nm), operating pressure (3 bar, 4 bar, 5 bar and 6 bar), pH value (3, 5, 7 and 9) and temperature (25 °C, 30 °C, 35 °C and 40 °C) temperature. Taguchi statistical technique is employed for designing experiments and for optimizing the process parameters of wastewater treatment process of an oil refinery. The proposed filter for wastewater treatment exhibited appreciable performance in removal rate of Percolation flux, percentage of chemical oxygen demand removal and percentage of total carbolic rejection as 27.2 kg/m²h, 78.51% and 95.33% respectively.

Assessment of Bilge Water Degradation by Isolated Citrobacter sp. and Two Indigenous Strains and Identification of Organic Content by GC-MS

Bilge water is oily saline wastewater accumulated on the hull at the bottom of a vessel, generated from leakage from pipes and engines and wash-down freshwater containing cleaning solvents. The present study focused on isolating microorganisms from oil-contaminated sites and indigenous species from raw bilge water and assessment of their ability to biodegrade bilge water. Using phenanthrene as a carbon source Citrobacter species was isolated from oil-contaminated sites and its optimum growth condition was found. The results indicated significant tolerance of the bacterium which presented great biodegradation ability for the tested carbon source. At high salinity (33 g L−1 of NaCl), sufficient phenathrene removal was achieved (81%), whereas variation of pH from 5 to 10 did not affected the survival of the microorganism. Regarding the effect of temperature and nutrients, Citrobacter sp. was better adapted at 30 °C, while lack of nutrients presented a negative impact on its growth. Halomonas and Exiguobacterium sp. were isolated from real bilge water using phenanthrene and phenol as a carbon source. The isolated strains independently exposed to high and low range bilge water pointed out around 83% and 53% chemical oxygen demand (COD) removal, respectively. Analysis of untreated bilge water by gas chromatography-mass spectrometry (GC-MS) was carried out, and the results confirmed the presence of organic compounds having a high similarity with Heptane, N-hexadecanoic acid, Methyl isobutyl Ketone and 1-butoxy-2-propanol. Chromatographic analysis of treated bilge water after exposure to isolated strains indicated the existence of new compounds. These metabolites presented high similarity with N-hexadecanoic, methyl ester, N-hexadecanoic and Octadecanoic acid methyl ester.

Comparison of different cultures and culturing conditions for the biological deterioration of organic load from real saline bilge wastewater: microbial diversity insights and ecotoxicity assessment

Bilge wastewater is a high strength, typically saline wastewater, originating from operation of ships. In this study, the treatment of real bilge wastewater was tested using pure isolated aerobic strains and mixed cultures (aerobic and anaerobic). The Chemical Oxygen Demand (COD) and ecotoxicity decrease were monitored over time, while the microbial dynamics alterations in mixed cultures were also recorded. The isolated strains Pseudodonghicola xiamenensis, Halomonas alkaliphila and Vibrio antiquaries were shown to significantly biodegrade bilge wastewater. Reasonable COD removal rates were achieved by aerobic mixed cultures (59%, 9 days), while anaerobic mixed cultures showed lower performance (34%, 51 days). The genus Pseudodonghicola was identified as dominant under aerobic conditions both in the mixed cultures and in the control sample (raw wastewater), after exposure to bilge wastewater, demonstrating natural proliferation of the genus and potential contribution to COD reduction. Biodegradation rates were higher when initial organic load was high, while the toxicity of raw wastewater partially decreased after treatment.