Toxic effects of ship exhaust gas closed-loop scrubber wash water.

To meet the strict requirements of reducing sulfur emissions, an increasing number of commercial ships have installed exhaust gas cleaning systems (EGCSs). However, wash water produced during the cleaning process is discharged back to the marine environment. We investigated the effects of closed-loop scrubber (natrium-alkali method) wash water on three trophic species. Severe toxic effects were found when Dunaliella salina, Mysidopsis bahia, and Mugilogobius chulae were exposed to 0.63-6.25, 0.63-10, and 1.25-20% concentrations of wash water, respectively. The 50% effective concentration in 96 h (EC50-96 h) for D. salina was 2.48%, and the corresponding total polycyclic aromatic hydrocarbons (PAHs) and heavy metals were 22.81 and 23.67 µg L-1. The 50% lethal concentration in 7 d (LC50-7 d) values for M. bahia and M. chulae were 3.57% and 20.50%, respectively. The lowest observed effect concentration (LOEC) values for M. bahia and M. chulae were 1.25% and 2.5%, respectively, and the corresponding total PAHs and heavy metals were 11.50 and 11.93 and 22.99 and 23.86 µg L-1. M. bahia's body weight was negatively correlated with the amount of wash water. Low concentrations of wash water (0-5%) had no significant effect on the reproduction of M. bahia. Although concentrations of 16 PAHs and 8 heavy metals are known, different compounds might react with each other and form more unknown toxic substances, and the measured toxicity comes from synergistic effects between various pollutants. Therefore, future work is needed to clarify other more toxic contaminants in wash water. We highly recommend that wash water be treated before being discharged to the marine environment.

Magnetic seeds promoted high-density sulfonic acid-based hydrochar derived from sugar-rich wastewater for removal of methylene blue.

Methylene blue (MB) removal from dyeing wastewater using low-cost bio-derived adsorbent is a significant and challenging field. Herein, magnetic sugar hydrochar (MGHC) precursors derived from sugar-rich wastewater with small particle size and rich oxygen-containing functional groups (OCFGs) are prepared from sugar-rich aqueous solution via Fe salt-modified hydrothermal procedure. The role of Fe3O4 nanoparticles formed during the sugar carbonization is to provide numerous magnetic seeds to generate MGHC with core-shell structure, which reduces the particle size of hydrochar. This increases the amount of OCFGs on the surface of MGHC for bonding the sulfonic acid groups. Therefore, sulfonic acid-modified MGHC-SA shows the rapid MB adsorption rate and excellent adsorption capacity. The highest MB capacity is 869.6 mg/g at pH = 11.0 and 298 K. Additionally, the MGHC-SA can be easily recovery by magnet. And the stability of MGHC-SA was also evaluated, no degradation of adsorption performance was observed, even the adsorbent was regenerated 10 times. This study puts forward a promising way to acquire functional groups rich and easy recovery hydrochar from sugar wastewater for MB removal.

Dehydrogenation of Cyclohexanones to Phenols: A Mini Review.

BACKGROUND: Phenol and its derivatives are important intermediates in the chemical industry, especially the pharmaceutical and electronic industries. The synthesis of phenols has attracted the attention of scientists due to their importance. Dehydrogenation of cyclohexanones is one of the promising aromatization strategies for phenols manufacture because the raw materials are low cost and stable. In recent years, some efficient and green methods with the use of H2, O2 and air, alkene, H2 and O2-free are described. OBJECTIVE: This mini-review will summarize some recent developments relating to the dehydrogenation of cyclohexanones to phenols, along with their interesting mechanism aspects. The challenges and future trends of the transformation will be prospected. CONCLUSION: The synthesis of phenols from the dehydrogenation of cyclohexanones has recently attracted much attention. Some synthetic methods have been established, and interesting mechanisms have been proposed in some cases. Lots of catalysts were developed for the transformation to afford the corresponding product. Although the present methods still have drawbacks and limitations, it is supposed that many novel methods would probably be developed in the near future.

Formation of emerging iodinated disinfection by-products during ballast water treatment based on ozonation processes.

Disinfection by-products (DBPs) generated by ballast water treatment pose a potential threat to marine environment which aroused widespread concern. In recent years, emerging iodinated DBPs have attracted widespread attention because of their stronger cytotoxicity and genotoxicity than brominated/chlorinated DBPs. In this study, the effects of different natural organic matter species, total residual oxidant (TRO) concentrations, storage time, temperature, pH, bromide and iodide concentrations on the generation of iodinated trihalomethanes (I-THMs) during ozonation process of ballast water were investigated. The results showed that bromochloroiodomethane and diiodochloromethane (DICM) were not detected under all conditions during ozonation of humaic acid (HA). Different kinds of precursors had a significantly effect on the formation of I-THMs. For algal cells as precursor, DICM were detected (1.22 µg/L), while DICM were not detected from oxidation of 1,3-etonedicarboxylic acid, fulvic acid (FA), phenol, resorcinol, hydroquinone and HA as precursors. The yields of I-THMs from oxidation of algal cells, FA and phenol were higher than other precursors. Linear relationships were observed between the formation of I-THMs and TRO concentrations. The yields of I-THMs reached a peak at 48 h (180 µg/L) after ozonation treatment of ballast water, and then decreased with storage time extension. An increase in temperature enhanced the formation of dibromoiodomethane and bromodiiodomethane, while wakened the formation of iodoform and dichloroiodomethane. The formation of I-THMs was complicatedly affected by different pH values in the range from 4 to 9. The more bromide concentrations, the more brominated I-THMs were formed. The concentrations of I-THMs increased with increasing iodide concentrations, and low concentrations of iodide had greater effect on the production of I-THMs than high concentrations of iodide.

Risk assessment of human health from exposure to the discharged ballast water after full-scale electrolysis treatment.

The presence of disinfection by-products (DBPs) releasing from ballast water management systems (BWMS) can cause a possible adverse effects on humans. The objectives of this study were to compute the Derived No Effect Levels (DNELs) for different exposure scenarios and to compare these levels with the exposure levels from the measured DBPs in treated ballast water. The risk assessment showed that when using animal toxicity data, all the DNELs values were approximately 10(3)-10(12) times higher than the exposure levels of occupational and general public exposure scenarios, indicating the level of risk was low (risk characterization ratios (RCRs) < 1). However, when using human data, the RCRs were higher than 1 for dichlorobromomethane and trichloromethane, indicating that the risk of adverse effects on human were significant. This implies that there are apparent discrepancies between risk characterization from animal and human data, which may affect the overall results. We therefore recommend that when appropriate, human data should be used in risk assessment as much as possible, although human data are very limited. Moreover, more appropriate assessment factors can be considered to be employed in estimating the DNELs for human when the animal data is selected as the dose descriptors.

Risk assessment of marine environments from ballast water discharges with laboratory-scale hydroxyl radicals treatment in Tianjin Harbor, China.

For the majority of ballast water treatment system (BWTS) that employ active substances (e.g., oxidative compounds), relevant chemicals (RCs) formation is an issue owing to their potential adverse effects on aquatic organisms. Accordingly, BWTS must be approved by the International Maritime Organization (IMO), and the approval procedure requires environmental risk assessment. The most commonly employed harbor used to calculate predicted environmental concentrations (PECs) for RCs in treated ballast water is the GESAMP-BWWG (Group of Experts on Scientific Aspects of Marine Environmental Protection-Ballast Water Working Group) model harbor. However, there is very little assessment data available regarding the associated environmental impacts in ports and harbors of China. Therefore, in this study the concentration of fifteen RCs from the existing laboratory-scale BWTS using hydroxyl radicals was obtained and input into the MAMPEC (Marine Antifoulant Model to Predict Environmental Concentrations) model to compute PECs in Tianjin Harbor, China. The potential risks to the aquatic environment posed by treated ballast water in Tianjin Harbor were further assessed based on the calculated ratio of PECs and predicted no effect concentrations (PNECs). Only monochloroacetic acid and dichloroacetic acid were found to have potential risks, and the ratios of PECs and PNECs to the other measured RCs were less than 1, indicating that the environmental risk posed by treated ballast water discharged into Tianjin Harbor is of little concern. The concentration of total residual oxidant recommended by the IMO (<0.2 mg/L) in treated ballast water at discharge was found to be at levels that may pose a risk to the aquatic environment in Tianjin Harbor.

Evaluation of the ecotoxicity and biological efficacy of ship's ballast water treatment based on hydroxyl radicals technique.

Ballast water has been identified as one of the key pathways for the movement of species between different ecosystems. The purpose of this study is to evaluate the biological efficacy and the potential toxicological impact of a proposed ballast water treatment using hydroxyl radicals as the main active substances. Living biomass of organisms kept in treated water for 2 days met the requirement stated in the International Maritime Organization (IMO) Ballast Water Convention (Regulation D-2), and no re-growth was observed over a period of 5 days. Aquatic toxicity tests of three trophic levels for the treated ballast water were performed. The results indicated that the toxicological risk of the discharge water to the receiving environment was not significant.

[Studies for killing the oceanic harmful organisms in ship's ballast water using hydroxyl radicals].

With a physical method of strong electric-field discharge, O2 in air and H2O at gas state are ionized and dissociated into a number of activated particles such as *OH, O2+, H2O+, etc, which are injected into a part of ballast water to form the dissolved *OH. High concentration of *OH solution was injected into the main pipe of discharge ballast water to effectively and fast kill the oceanic harmful organisms and bacteria in the course of conveying ship's ballast water. In the 10 t x h(-1) experimental system of ship's ballast water, the experiments were carried out for killing the plankton and bacteria using *OH radicals. The *OH concentration is 0.65 mg x L(-1) for 100% killing efficiency. At the same time, cell morphology changes of Chaetoceros muelleri and Nitzschia closterium were observed by a microscope. The cells of algae in their cellular wall, cellular membrane or cell protoplasm were greatly destroyed using *OH radicals.