Recent progress and challenges facing ballast water treatment - A review

Impacts of salinity stress induced by ballast water discharge on the ecosystem of shanghai port, China

Large quantities of marine ballast water discharged by ocean-going vessels can cause salinity increases in freshwater ports, which in turn negatively affects indigenous plankton in the ports. In this study, we investigated the impacts of marine ballast water discharge on the plankton community in a freshwater wharf through field surveys. It was found that salinity stress caused reductions in community indicators such as plankton community composition, abundance and diversity, thus threatening the structure and function of the plankton community in the wharf. In terms of the impact range, the salinity stress had a significant effect on all plankton in the waters near the discharge point and the phytoplankton in the waters 50 m from the discharge point, but had no significant effect on the plankton in the waters further away. Ballast water discharge also caused a significant decrease in the alpha diversity and richness of the plankton community but had no significant effect on the evenness of the plankton community. Moreover, phytoplankton were more tolerant of salinity changes than zooplankton in our study. This study provides an ecological reference for the scientific management of marine ballast water discharge and the risk of exogenous nutrient inputs to freshwater ecosystems.

Sustainability in maritime transport: Selecting ballast water treatment for a bulk carrier

The study provides a comprehensive assessment of ballast water treatment systems (BWTS) selection regarding crucial parameters such as energy efficiency, fuel consumption, and CO2 emissions. The focus of the study is investigating the environmental impacts of BWTS and how these impacts can be considered in decision-making processes. In this context, it comprehensively analyzes the importance of decision-making parameters and the environmental consequences of BWTS applications. The potential impacts of the system on the sustainability of the maritime industry are highlighted. In this context, seven different BWTSs for a bulk carrier of 83,000 deadweight tonnes are evaluated using Analytical Hierarchy Process (AHP) and Preference Ranking Technique by Similarity to Ideal Solution (TOPSIS). According to the analysis, Operational Expenditure (0.314508), Capital Expenditure (0.249515), and Capacity (0.159952) are the most critical factors. Among the seven systems analysed, product G (0.8561137) emerges as the most suitable option. The analysis represents 3% of total emissions (456.5 tonnes CO2) and highlights the impact of BWTS on CO2 emissions. The results underline the need for innovative approaches aimed at ensuring the long-term sustainability of the maritime industry.

Rapid detection of microalgae cells based on upconversion nanoprobes

The quantification of microalgae cells is crucial for the treatment of ships' ballast water. However, achieving rapid detection of microalgae cells remains a substantial challenge. Here, we develop a new method for rapid and effective detection of microalgae concentration by utilizing upconversion nanoprobes (UCNPs) of NaYF4:Er3+,Tm3+. Three ligands, carboxylated methoxypolyethylene glycols with 5000 and 2000 molecular weights (mPEG-COOH-5, mPEG-COOH-2) and D-gluconic acid sodium salt (DGAS), were used to convert hydrophobic UCNPs into a hydrophilic state through modification. The results show that the mPEG-COOH-5 modified UCNPs present the highest stability in an aqueous solution. Fourier Transform Infrared Spectroscopy (FTIR) measurements reveal the presence of a significant number of -COOH functional groups on UCNPs after the mPEG-COOH-5 modification. These -COOH groups enhance the hydrophilicity and biocompatibility of UCNPs. The soluble UCNPs were directly mixed with microalgae, and the upconversion luminescence (UCL) spectra of the UCNPs were recorded immediately after thorough shaking. This greatly reduces the measurement time and could realize rapid onboard detection. In this sensing procedure, the UCNPs with red UCL functioned as energy donors, while microalgae with red absorption served as an energy acceptor. The UCL gradually diminishes with an increase in microalgae concentration based on the inner filter effect, thus establishing a relationship between UCL and microalgae concentration. The accuracy of the detection is further validated through the traditional microscope counting method. These findings pave the way for a novel rapid strategy to assess microalgae concentration using UCNPs.

Advances on electrochemical disinfection research: Mechanisms, influencing factors and applications

Disinfection, a vital barrier against pathogenic microorganisms, is crucial in halting the spread of waterborne diseases. Electrochemical methods have been extensively researched and implemented for the inactivation of pathogenic microorganisms from water and wastewater, primarily owing to their simplicity, efficiency, and eco-friendliness. This review succinctly outlined the core mechanisms of electrochemical disinfection (ED) and systematically examined the factors influencing its efficacy, including anode materials, system conditions, and target species. Additionally, the practical application of ED in water and wastewater treatment was comprehensively reviewed. Case studies involving various scenarios such as drinking water, hospital wastewater, black water, rainwater, and ballast water provided concrete instances of the expansive utility of ED. Finally, coupling ED with other technologies and the resulting synergies were introduced as pivotal foundations for subsequent engineering advancements.

Evaluate the compliance of ballast water management system on various types of operational vessels based on the D-2 standard

The transfer of ship ballast water poses significant risks to the aquatic ecosystem and human health. To mitigate the influences of non-native species, ballast water management systems (BWMS) have been installed on international ships to ensure proper treatment of ballast water before discharge. This study investigates whether ballast water discharges managed by BWMS meet the requirements of the D-2 standard for organisms in different size classes. Representative ballast water samples were collected from 28 ships (a total of 20 different BWMS) arriving in Shanghai during the period 2020-2022. Results have shown that two samples (7.1 %) exceeded the D-2 Standard. The compliance rates varied among different vessel types, with cargo vessels achieving a compliance rate of 81.8 %, while LNG vessels and container vessels achieved 100 % compliance. The potential to achieve higher levels of ballast water management will increase as crews improve their skills in operating BWMS and BWMS is further developed.

Toxicity evaluation of chlorinated natural water using Photobacterium phosphoreum: Implications for ballast water management

Chlorination of ballast water could produce harmful disinfection by-products (DBPs) and total residual oxidants. The International Maritime Organization calls for toxicity testing of discharged ballast water with fish, crustacea and algae to reduce the risk, but it is difficult to evaluate the toxicity of treated ballast water in a short time. Therefore, the purpose of this study was to analyze the applicability of luminescent bacteria to the assessment of residual toxicity of chlorinated ballast water. The toxicity unit for all treated samples were higher for Photobacterium phosphoreum than for microalgae (Selenastrum capricornutum and Chlorella pyrenoidosa), after adding neutralizer, all samples showed little effect on the luminescent bacteria and microalgae. For the DBPs, except for 2,4,6-Tribromophenol, Photobacterium phosphoreum could produce more sensitive and rapid test results than other species, the results in Photobacterium phosphoreum showed that the toxicity of DBPs in order of: 2,4-Dibromophenol > 2,6-Dibromophenol > 2,4,6-Tribromophenol > Monobromoacetic acid > Dibromoacetic acid > Tribromoacetic acid, and most binary mixtures (aromatic DBPs and aliphatic DBPs) presented synergistic effects based on the CA model. The aromatic DBPs in ballast water deserve more attention. In general, for ballast water management, the use of luminescent bacteria to evaluate the toxicity of treated ballast water and DBPs is desirable, this study could provide beneficial information for enhancing ballast water management.

An Eco-Friendly Adsorbent Based on Bacterial Cellulose and Vermiculite Composite for Efficient Removal of Methylene Blue and Sulfanilamide

In this work, a novel composite of bacterial cellulose (BC) and expanded vermiculite (EVMT) composite was used to adsorb dyes and antibiotics. The pure BC and BC/EVMT composite were characterized using SEM, FTIR, XRD, XPS and TGA. The BC/EVMT composite exhibited a microporous structure, providing abundant adsorption sites for target pollutants. The adsorption performance of the BC/EVMT composite was investigated for the removal of methylene blue (MB) and sulfanilamide (SA) from an aqueous solution. The adsorption capacity of BC/ENVMT for MB increased with increasing pH, while the adsorption capacity for SA decreased with increasing pH. The equilibrium data were analyzed using the Langmuir and Freundlich isotherms. As a result, the adsorption of MB and SA by the BC/EVMT composite was found to follow the Langmuir isotherm well, indicating a monolayer adsorption process on a homogeneous surface. The maximum adsorption capacity of the BC/EVMT composite was found to be 92.16 mg/g for MB and 71.53 mg/g for SA, respectively. The adsorption kinetics of both MB and SA on the BC/EVMT composite showed significant characteristics of a pseudo-second-order model. Considering the low cost and high efficiency of BC/EVMT, it is expected to be a promising adsorbent for the removal of dyes and antibiotics from wastewater. Thus, it can serve as a valuable tool in sewage treatment to improve water quality and reduce environmental pollution.

The hidden diversity of microbes in ballast water and sediments revealed by metagenomic sequencing

With the rapid globalization of trade, the worldwide spread of pathogens through ballast water is becoming a major concern. Although the international maritime organization (IMO) convention has been adopted to prevent the spread of harmful pathogens, the limited species resolution of the current microbe-monitoring methods challenged the ballast water and sediments management (BWSM). In this study, we explored metagenomic sequencing to investigate the species composition of microbial communities in four international vessels for BWSM. Our results showed the largest species diversity (14,403) in ballast water and sediments, including bacteria (11,710), eukaryotes (1007), archaea (829), and viruses (790). A total of 129 phyla were detected, among which the Proteobacteria, followed by Bacteroidetes, and Actinobacteria were the most abundant. Notably, 422 pathogens that are potentially harmful to marine environments and aquaculture were identified. The co-occurrence network analysis showed that most of these pathogens were positively correlated with the commonly used indicator bacteria Vibrio cholerae, Escherichia coli, and intestinal Enterococci species, validating the D-2 standard in BWSM. The functional profile showed prominent pathways of methane and sulfur metabolism, indicating that the microbial community in the severe tank environment still utilizes the energy to sustain such a high level of microbe diversity. In conclusion, metagenomic sequencing provides novel information for BWSM.

Study on the effectiveness of membrane separation + N2 deoxidation process for the treatment of bacteria in ballast water

Effects of the membrane separation + N₂ deoxidation process on the abundance and activity of bacteria were examined under two salinity conditions at Yangshan Port, Shanghai, China. Sequencing of 16S rRNA gene amplicons demonstrated a decrease in the diversity and activity of bacteria in fresh water and marine water, with a total removal rate of approximately 63 % and 69 %, respectively. Indicator bacteria decreased to 10 CFU·100 mL^-1, which met the IMO D-2 standard. A total of 13 potential pathogens were detected after treatment, indicating that there is still a risk of pathogenic bacteria invasion in the discharge water, particularly marine bacteria, and that the D-2 standard may be insufficient as a preventive measure against pathogenic bacteria transfer. The results will provide reference for government supervision, and will also be important for monitoring foreign bacteria and technology development.

Probabilistic human health risk assessment of trace elements in ballast water treated by reverse osmosis desalination plants

Very few studies have paid attention to the transport of heavy and toxic metals via ballast water coming from different countries of the world. In the present study, ballast water samples (n = 83) were collected from ships, tankers and vessels of 21 different origins arriving at the two main ports of Qatar. Besides the basic physical parameters of pH, electrical conductivity (EC), and total organic carbon (TOC), concentrations of 24 elements (As, Sb, Al, Cd, Pb, Si, V, Ag, Zn, Cr, Mn, Ba, Co, Ni, Sr, Be, Cu, Tl, B, Fe, Se, Sn, Mo and U) were determined. In addition, the potential human health risks of drinking water treated by reverse osmosis (RO) were assessed using Monte Carlo simulations. Two scenarios were used to assess the risks to the general population, namely, seawater (baseline) and ballast water (worst-case scenario). Our results show significant differences among the tested elements, depending on the origin of the ballast water. The human health assessment showed that all hazardous quotients (HQs) were below the safety limits. However, for the ballast water scenario, thallium (Tl) HQs were 10 % above the safety level. Ballast water in Qatar does not pose risks for human health through drinking water, but ballast water discharges should take into consideration seawater catchments and potential toxic elements, especially Tl. Regular monitoring campaigns need to be performed.

A study on treatment efficacy of ballast water treatment system applying filtration + membrane separation + deoxygenation technology during shipboard testing

The efficacy of a BWMS with filtration + membrane separation + deoxygenation technology in treating ballast water was investigated under marine operational circumstances in five shipboard tests. The shipboard tests were carried out between August 2020 and March 2021 onboard a bulk carrier JIN HAI HUA, which sailed between Mawei, Qinhuangdao and Caofeidian in China throughout spring, summer, and fall season. The discharge results in all five tests met the D-2 standard in IMO BWMS Code, with the shortest holding time of less than three days. The BWMS does not involve application of chemicals or generation of by-products, and is considered to be an appropriate choice for certain types of ships.

The prevalence of potential pathogens in ballast water and sediments of oceangoing vessels and implications for management

Ballast water and sediments can serve as prominent vectors for the widespread dispersal of pathogens between geographically distant areas. However, information regarding the diversity and distribution of the bacterial pathogens in ballast water and sediments is highly limited. In this study, using high-throughput sequencing and quantitative PCR, we investigated the composition and abundance of potential pathogens, and their associations with indicator microorganisms. We accordingly detected 48 potential bacterial pathogens in the assessed ballast water and sediments, among which there were significant differences in the compositions and abundances of pathogenic bacterial communities characterizing ballast water and sediments. Rhodococcus erythropolis, Bacteroides vulgatus, and Vibrio campbellii were identified as predominant pathogens in ballast water, whereas Pseudomonas stutzeri, Mycobacterium paragordonae, and Bacillus anthracis predominated in ballast sediments. Bacteroidetes, Vibrio alginolyticus, Vibrio parahaemolyticus, and Escherichia coli were generally detected with median values of 8.54 × 10³-1.22 × 10⁷ gene copies (GC)/100 mL and 1.16 × 10⁷-3.97 × 10⁹ GC/100 g in ballast water and sediments, respectively. Notably, the concentrations of Shigella sp., Staphylococcus aureus, and V. alginolyticus were significantly higher in ballast sediments than in the water. In addition, our findings tend to confirm that the indicator species specified by the International Maritime Organization (IMO) might underestimate the pathogen risk in the ballast water and sediments, as these bacteria were unable to predict some potential pathogens assessed in this study. In summary, this study provides a comprehensive insight into the spectrum of the potential pathogens that transferred by ship ballast tanks and emphasizes the need for the implementation of IMO convention on ballast sediment management.

Bacterial communities in ballast tanks of cargo vessels - Shaped by salinity, treatment and the point of origin of the water but "hatch" its typical microbiome

Ballast water is a main vector of introduction of potentially harmful or pathogenic aquatic organisms. The development of genetic tools for ballast water monitoring has been underway and highlighted as a source for accurate and reliable data for decision making. We used 16S rRNA gene amplicon sequencing to analyze the microbial communities found in the ballast water of fifteen commercial ships routed through two Estonian ports. In parallel, samples from the port area were collected at the same time each ship visited. Fluorescence microscopy was utilized to assess the effectiveness of the treatment applied to ballast water. In addition, supplemental samples were collected from Hamburg Port (Germany) and a ballast tank decontamination system used at this port. The composition and diversity of bacterial communities varied greatly between obtained samples. The application of UV treatment did not demonstrate significant reduction in species richness estimates. The composition of microbial communities was significantly influenced by salinity, treatment (mainly untreated or UV treated) and the point of origin of the ballast water. Over a hundred potentially pathogenic bacterial taxa were found in relatively high abundance, including in ballast water that had received UV treatment. These shortcomings of stand-alone UV treatment of ballast water, especially when weak treatment is applied insufficiently, highlight the danger of possible harmful effects arising over time and the need for genetic tools for ballast water monitoring and management.

Novel electro-oxidation unit for electro-disinfection of E. coli and some waterborne pathogens during wastewater treatment: batch and continuous experiments

The prime objective of the current investigation is to evaluate a promising alternative method for disinfection wastewater using a novel electro-oxidation unit. The study focused on determining the best-operating conditions from a techno-economic point of view to be applied to continuous flow simulating actual disinfection modules. The treatment unit consisted of a Plexiglas container with a 3 L volume containing nine cylindrical shape electrodes (6 graphite as anode and 3 stainless steel as a cathode) connected to a variable DC power supply. Determination of the best operating parameters was investigated in batch mode on synthetic wastewater by studying the effect of contact time, current density (CD), total dissolved solids concentration (TDS), and bacterial density. Moreover, the continuous mode experiment was considered on real wastewater from an agricultural drain and the secondary wastewater treatment plant effluent before chlorination. The batch mode results revealed that the best applicable operational conditions that achieved the complete removal of E. coli were at a contact time of less than 5 min, TDS of 2000 mg/L, and CD of 4 mA/cm². Application of these conditions on the continuous mode experiment indicated the complete removal of all bacterial indicators after 5 min in the drainage wastewater and after 3 min in the secondary treated wastewater. Physico-chemical characterization also suggested that no chlorine by-products displaying the hydroxide ion formed due to water electrolysis is the main reason for prohibiting the growth of pathogenic microbes. The electrical consumption was calculated in the continuous mode and found to be 0.5 kWh/m³ with an operational cost of about 0.06 $/m³, including the cost of adding chemicals to increase the TDS. The results proved that this novel electro-oxidation unit is a robust and affordable disinfection method for complete bacterial removal from wastewater and is more environmentally benign than other conventional disinfection methods.

Preparation, Antimicrobial Properties under Different Light Sources, Mechanisms and Applications of TiO2: A Review

Traditional antimicrobial methods, such as antibiotics and disinfectants, may cause adverse effects, such as bacterial resistance and allergic reactions. Photocatalysts based on titanium dioxide (TiO₂) have shown great potential in the field of antimicrobials because of their high efficiency, lack of pollution, and lack of side effects. This paper focuses on the antimicrobial activity of TiO₂ under different light sources. To improve the photocatalytic efficiency of TiO₂, we can reduce electron-hole recombination and extend the photocatalytic activity to the visible light region by doping with different ions or compounds and compounding with polymers. We can also improve the surface properties of materials, increase the contact area with microorganisms, and further enhance the resistance to microorganisms. In addition, we also reviewed their main synthesis methods, related mechanisms, and main application fields to provide new ideas for the enhancement of photocatalytic microorganism performance and application popularization in the future.

Exploring Ballast Water Management in Taiwan Using the PSR Conceptual Model Based on Stakeholders’ Perspectives

Accidental introduction of nonindigenous aquatic species (NIAS) is usually mediated by shipping through ballast water. Ballast water management plans are being developed and implemented around the world to prevent the spread of NIAS. However, for marine environmental management, incorporating stakeholders’ perceptions into designing and formulating management plans is key to achieving successful implementation. This study used qualitative interviews and grounded theory to induce the influencing factors and conceptual model of stakeholders’ perceptions on ballast water management (BWM) issues. The interplay of the pressure–state–response conceptual model based on grounded theory was established to elaborate on stakeholders’ perceptions. The study results indicated that local ballast water management required comprehensive port state control (PSC) and technical competency development. Second, an international commercial port can be used as a demonstration area to demonstrate the effectiveness and the potential benefits of BWM implementation due to its potential to link with international networks. Moreover, legislation, surveying/monitoring, institutional capacity and outreach/education are the four fundamentals to marine bio-invasion management. Initiating ballast water management measures as part of port environmental management aims to enhance marine pollution management capacity, especially in the field of marine bio-invasion management.

Ecological impacts of ballast water loading and discharge: insight into the toxicity and accumulation of disinfection by-products

Since the implementation of the International Maritime Organization 2004 regulation, most ships have been equipped with on-dock ballast water treatment. While this method is effective in solving the invasive alien species problem, concerns are raised due to the potential release of disinfection by-products (DBPs) as the result of the chemical treatment. This review paper aims to summarize the history of ballast water management (BWM) and the currently used on-dock technology. Chlorination, oxidation, and ozonation are highlighted as the most currently applied methods to treat ballast water on-dock. This paper then focuses on the potential release of toxic DBPs as the result of the selected corresponding treatment methods. Tri-halo methane, haloacetic acid, and several acetic acid-related compounds are emphasized as toxic DBPs with concentrations reaching more than 10 μg/L. The potential toxicities of DBPs, including acute toxicity, carcinogenicity, genotoxicity, and mutagenicity, to aquatic organisms, are then discussed in detail. Future research directions related to the advanced treatment of DBPs before final discharge and analysis of DBPs in coastal sediments, which are barely studied at present, are suggested to enhance the current knowledge on the fate and the ecological impact of BWM.

Electrochemical Disinfection of Simulated Ballast Water Using RuO2-TiO2/Ti Electrode

The present work investigated the treatment of ballast water via electrochemical disinfection using a RuO₂-TiO₂/Ti electrode. Batch tests were conducted with simulated ballast water containing Escherichia coli as an indicator organism. The effect of varying NaCl concentrations (1%, 2%, and 3%; w/v) and current densities (0.3, 1.0, 2.0, and 3.0 mA/cm²) on the inactivation of E. coli was examined. Results showed higher disinfection efficiency of E. coli was obtained at higher NaCl concentration and current density. Complete inactivation of E. coli was attained within 2 and 1 min at 0.3 and 1 mA/cm², respectively, under 3% NaCl concentration. Meanwhile, complete disinfection at 1 and 2% NaCl concentrations was observed in 6 and 2 min, respectively, using a current density of 0.3 mA/cm². The 100% inactivation of E. coli was achieved with an energy consumption in the range of 2.8 to 2.9 Wh/m³ under the NaCl concentrations at 1 mA/cm² and 1 min of electrolysis time. The complete disinfection attained within 1 min meets the D-2 standard (<250 CFU E. coli/100 mL) of ballast water under the International Maritime Organization. The values of energy consumption of the present work are lower than previous reports on the inactivation of E. coli from simulated ballast water.