Environmental impact, treatment technology and monitoring system of ship domestic sewage: A review

Characterization of microplastic distribution, sources and potential ecological risk assessment of domestic sewage from ships

Shipboard domestic sewage, encompassing both black water and gray water, has the potential to transport significant quantities of environmentally harmful microplastics, a concern that has garnered increasing global attention. In this study, Fourier infrared (FTIR) detection was used to detect microplastics in marine domestic wastewater. The primary objective was to evaluate the abundance and characteristics of microplastics present in ship domestic sewage, investigate potential sources and influencing factors, and assess the ecological risks associated with ship sewage through analyses of microplastic abundance and hazard indices. The findings revealed that the mean abundance of microplastics in ship domestic sewage are 50.82 particles per liter(n/L), with gray water exhibiting significantly higher levels at 167 n/L compared to black water at 36.96 n/L and mixed sewage at 46.57 n/L. Fiber microplastics constituted a predominant 95% of all samples collected from ships, followed by film microplastics. In terms of color distribution, transparent and blue microplastics were the most prevalent, with the majority measuring between 100 and 1000 μm in size. Polyethylene terephthalate (PET) emerged as the most common polymer type, followed by polypropylene (PP). The risk assessment highlighted that microplastics in domestic wastewater pose significant ecological risks to aquatic organisms, with pollution load indices consistently reaching Class IV levels. Correlation analyses between microplastic abundance and the physicochemical properties of sewage demonstrated a significant relationship between microplastic levels and the concentration of suspended solids in ship sewage. This study provides essential data to inform the development of regulatory policies aimed at managing the discharge of black water and gray water discharges from both domestic and international vessels.

The Environmental Hazards and Treatment of Ship's Domestic Sewage

With the rapid development of the modern shipping field, the damage caused by ship pollution to the global inland waterways and marine ecosystems has attracted extensive attention from the international community. However, there are fewer reviews on the environmental hazards of domestic ship sewage and its treatment, and a systematic summary of the environmental hazards posed by ship domestic sewage and its treatment is lacking. Based on summarizing the various environmental hazards brought about by a ship's domestic sewage and the corresponding treatment methods, this study elaborates, in detail, on the specific hazards of the main toxic and hazardous substances contained in a ship's domestic sewage on the environment and organisms, and the treatment methods of the ship's domestic sewage and their treatment effects, such as membrane bioreactor (MBR). It is also pointed out that MBR has great potential in the direction of ship domestic sewage treatment, and the solution of its membrane pollution and other problems as well as the exploration of the combination of MBR and other treatment methods will become the focus of future research. A theoretical reference is provided for the study of environmental problems caused by domestic sewage from ships and their treatment options.

Use of wastewater from passenger ships to assess the movement of COVID-19 and other pathogenic viruses across maritime international boundaries

Objective

The worldwide spread of SARS-CoV-2 and the resulting COVID-19 pandemic has been driven by international travel. This has led to the desire to develop surveillance approaches which can estimate the rate of import of pathogenic organisms across international borders. The aim of this study was to investigate the use of wastewater-based approaches for the surveillance of viral pathogens on commercial short-haul (3.5 h transit time) roll-on/roll-off passenger/freight ferries operating between the UK and the Republic of Ireland.

Methods

Samples of toilet-derived wastewater (blackwater) were collected from two commercial ships over a 4-week period and analysed for SARS-CoV-2, influenza, enterovirus, norovirus, the faecal-marker virus crAssphage and a range of physical and chemical indicators of wastewater quality.

Results

A small proportion of the wastewater samples were positive for SARS-CoV-2 (8% of the total), consistent with theoretical predictions of detection frequency (4%-15% of the total) based on the national COVID-19 Infection Survey and defecation behaviour. In addition, norovirus was detected in wastewater at low frequency. No influenza A/B viruses, enterovirus or enterovirus D68 were detected throughout the study period.

Conclusion

We conclude that testing of wastewater from ships that cross international maritime boundaries may provide a cost-effective and relatively unbiased method to estimate the flow of infected individuals between countries. The approach is also readily applicable for the surveillance of other disease-causing agents.

A comprehensive study on anaerobic digestion of organic solid waste: A review on configurations, operating parameters, techno-economic analysis and current trends

The excessive discharge and accumulation of solid organic waste into the environment is of severe concern across the globe. Thus, an efficient waste management system is important to mitigate health risks to humans, minimize harmful impacts on the environment, and ensure a sustainable ecosystem. The organic waste is converted into value-added products either using microorganisms or heat energy; these methods are commonly known as biochemical and thermochemical techniques. The biochemical process has the advantage of higher selectivity of the products and lower processing temperatures. The principal conversion processes of this category are fermentation and anaerobic digestion (AD). This review article focuses on AD, a potential method for treating organic waste and creating a variety of products with added value. Here we present the digestibility of various organic wastes, the role of microorganisms, the decomposition process, co-substrates, digester designs, biogas yields, by-products, environmental impacts, and overall techno-economical effectiveness of the process. Further, this review offers insights into new directions for AD for waste treatment and future research without compromising the overall feasibility and environmental sustainability.

High nutrient availability modulates photosynthetic performance and biochemical components of the economically important marine macroalga Kappaphycus alvarezii (Rhodophyta) in response to ocean acidification

Increased atmospheric CO2 concentrations not only change the components of inorganic carbon system in seawater, resulting in ocean acidification, but also lead to decreased seawater pH, resulting in ocean acidification. Consequently, increased inorganic carbon concentrations in seawater provide a sufficient carbon source for macroalgal photosynthesis and growth. Increased domestic sewage and industrial wastewater discharge into coastal areas has led to nutrient accumulation in coastal seawaters. Combined with elevated pCO2 (1200 ppmv), increased nutrient availability always stimulates the growth of non-calcifying macroalgae, such as red economical macroalga Gracilariopsis lemaneiformis. Here, we evaluated the interactive effects of nutrients with elevated pCO2 on the economically important marine macroalga Kappaphycus alvarezii (Rhodophyta) in a factorial 21-day coupling experiment. The effects of increased nutrient availability on photosynthesis and photosynthetic pigments of K. alvarezii were greater than those of pCO2 concentration. The highest Fv/Fm values (0.660 ± 0.019 and 0.666 ± 0.030, respectively) were obtained at 2 μmol L-1 of NO3-N at two pCO2 levels. Under the elevated pCO2 condition, the Chl-a content was lowest (0.007 ± 0.004 mg g-1) at 2 μmol L-1 of NO3-N and highest (0.024 ± 0.002 mg g-1) at 50 μmol L-1 of NO3-N. The phycocyanin content was highest (0.052 ± 0.012 mg g-1) at 150 μmol L-1 of NO3-N under elevated pCO2 condition. The malondialdehyde content declined from 32.025 ± 4.558 nmol g-1 to 26.660 ± 3.124 nmol g-1 with the increased nutrients at under low pCO2. To modulate suitable adjustments, soluble biochemical components such as soluble carbohydrate, soluble protein, free amino acids, and proline were abundantly secreted and were likely to protect the integrity of cellular structures under elevated nutrient availability. Our findings can serve as a reference for cultivation and bioremediation methods under future environmental conditions.

The X-Press Pearl disaster underscores gross neglect in the environmental management of shipping: Review of future data needs

The X-Press Pearl disaster has the unfortunate hallmarks of other global container ship disasters that are becoming increasingly common and will continue to cause future environmental damage. Port container throughput is ~830 million twenty-foot equivalents (TEUs), projected to grow for the next four decades at minimum, and industry experts predict that ship sizes will continue to grow to 50,000 TEU. Misdeclared content, poor packing, inadequate stowage/lashing, ship-board fires, climate-change-driven intensity of storms, and increasing ship size all ensure increasing environmental damage from container ship maritime disasters. Industry consensus is that the number of containers lost at sea is conspicuously undercounted, and the impact of lost containers is unstudied. This paper reviews specific aspects of the container ship industry that contribute to environmental damage, and then addresses needs for risk, impact assessment and environmental management as pertains to industry operations and container ship disasters such as the X-Press Pearl.

An integrated process for struvite recovery and nutrient removal from ship domestic sewage

Marine pollution caused by the untreated and substandard discharge of ship domestic sewage has received widespread attention. A novel integrated process for struvite recovery and nutrient removal from ship domestic sewage (SRNR-SDS) based on seawater magnesium source was developed in this study. Removal efficiencies of the total nitrogen (TN) and total phosphorus (TP) for the activated sludge unit in SRNR-SDS process were approximately 67.61% and 41.35%, respectively, under the salinity of 7.85 g/L. The coupling-induced struvite crystallization unit significantly improved the removal efficiency of TN and TP, and the scanning electron microscopy and X-ray diffraction demonstrated that magnesium ammonium phosphate (MAP) crystals were successfully formed on the surface of zeolite. The SRNR-SDS process had an ideal performance for pollutant removal and MAP recovery under the optimal hydraulic retention time of 20 h. The effluent concentrations of COD, NH₄⁺-N, TN and TP in SRNR-SDS process were approximately 34.73 mg/L, 4.31 mg/L, 10.07 mg/L and 0.23 mg/L, respectively, which meet the Chinese and international ship sewage discharge standards. SRNR-SDS process has obvious environmental, social and economic benefits, which could save 6.20%∼57.14% of the operation cost of ship domestic sewage treatment via MAP recovery. The results could provide theoretical and technical support for the development and application of ship sewage treatment process with the functions of pollutant removal and resource recovery.

Green finance and corporate environmental violations: a test from the perspective of illegal pollution discharge behaviors

Green finance aims to intervene in investment and financing behaviors through financial means, so as to promote upgrading of heavily polluting industries. Whether it can reduce illegal pollution discharge behaviors is the focus of this paper. This paper is to explore the impact of green finance on illegal emissions of heavy polluting firms. Taking green finance pilot zones (GFPZ) in 2017 as a quasi-natural experiment, the paper measures illegal emission behaviors based on day-night difference of PM_2.5 at the nearest atmospheric monitoring points and tests the impact of GFPZ on illegal emissions based on triple difference model (DDD). The results show that GFPZ inhibits illegal emissions. Influence path result shows that GFPZ reduces illegal emissions by increasing financing constraint, green innovation, and fulfilling social responsibility. At the same time, this paper also notes that regulatory distance has an interference effect on GFPZ. GFPZ aggravates illegal emission as heavy polluting firms - financial institution's distance is more than 40 km. GFPZ curbs illegal pollution more significantly as heavy polluting firms - environmental protection bureau distance is within 30 km. This paper aims to reveal the guiding effect of green finance on emission behavior of polluting firms and provide policy references for reducing emission and promoting green finance.

The Impact of Alternative Fuels on Ship Engine Emissions and Aftertreatment Systems: A Review

Marine engines often use diesel as an alternative fuel to improve the economy. In recent years, waste oil, biodiesel and alcohol fuel are the most famous research directions among the alternative fuels for diesel. With the rapid development of the shipping industry, the air of coastal areas is becoming increasingly polluted. It is now necessary to reduce the emission of marine engines to meet the strict emission regulations. There are many types of alternative fuels for diesel oil and the difference of the fuel may interfere with the engine emissions; however, PM, HC, CO and other emissions will have a negative impact on SCR catalyst. This paper reviews the alternative fuels such as alcohols, waste oils, biodiesel made from vegetable oil and animal oil, and then summarizes and analyzes the influence of different alternative fuels on engine emissions and pollutant formation mechanism. In addition, this paper also summarizes the methods that can effectively reduce the emissions of marine engines; it can provide a reference for the study of diesel alternative fuel and the reduction of marine engine emissions.