Characteristic and Relative Environmental Risk of Disinfection by Products Associated with Simple Glucose or Naturally Occurring Algal Organic Matter as Tested in Ballast Water Treatment System

Abstract

To prevent the invasion of alien species, the International Maritime Organization and the United States Costal Guard require that a ballast water management system (BWMS) be installed on ships to treat the ballast water before discharging it. BWMS technologies use active substances, which create disinfection by-products (DBPs) during ballast water treatment. This study compared the characteristics of DBPs generated in the treatment of commercial glucose with those of algal organic matter (AOM) derived from field-collected phytoplankton using NaOCl as the active substance. During the treatment of AOM, a greater variety and higher concentrations of DBPs were generated than for glucose. For AOM in freshwater, bromoform and dibromoacetic acid were dominant because of the bromine ions present in the phytoplankton. During the treatment of glucose, the ratio of the predicted environmental concentration to the predicted no-effect concentration of dibromoacetonitrile and chloropicrin exceeded 1, indicating a potential environmental risk. Whole effluent toxicity (WET) testing showed that the chronic toxicity of phytoplankton and the total DBP concentration were highest in marine water with AOM. In addition, the results of WET testing suggested that the concentrations of haloacetic acids (HAAs) and haloacetonitriles (HANs) were important indicators for the evaluation of environmental risk. Therefore, to evaluate the risk of DBPs in international ports where phytoplankton outbreaks frequently occur, it is important to monitor not only the total DBP concentration but also the total HAA and HAN concentrations.

Simulated Testing of the Characteristics and Environmental Impacts of Disinfection By-Products Generated by Ballast Water Management Systems in Ports during Phytoplankton Blooms

“…THMs are formed in greater quantities compared to HAAs, which can be attributed to the structural propensity of DOM precursors to more readily bond with THMs and their more stable formation in reactions with oxidants. Studies on BWMS using AS also predominantly showed that the predominant compounds were in the order of THMs > HAAs > HANs [3,7,15,17]. The proportion of HAAs tended to increase with higher average TRO concentrations in each group (Figure S1).…”

“…The DOC concentration in ballast water may increase due to the input of new DOM because of the enhanced organic matter decomposition by the TRO, or it may decrease as a carbon source for the growth of heterotrophic bacteria. Furthermore, when the TRO is high, the growth of heterotrophic bacteria is inhibited, which means that a decrease in DOM concentration by microbial consumption is inhibited [3,31,32]. Therefore, we speculate that, in Group A, the consumption of DOC by heterotrophic bacteria was high on Day 1 because of the lower TRO concentration compared to Group B.…”

“…Research on disinfection by-products (DBPs) in drinking water treated with active substances (AS) has been conducted since the 1970s; however, interest in AS in seawater has increased since the 2000s because of developments in seawater desalination and ship ballast water management systems (BWMSs) [1][2][3]. In particular, a ship's ballast water is a pathway for the transfer of invasive species, which led the International Maritime Organization (IMO) to establish the Ballast Water Management Convention in 2004.…”

“…The types of DBPs formed can vary depending on the characteristics of DOM, and the toxicity of these DBPs can vary depending on the individual substances. Generally, the toxicity of Br-DBPs is higher than that of C-DBPs, and among Br-DBPs, Br-halonitromethanes (Br-HANs) are highly toxic even at low concentrations [1, 3,7,8,[14][15][16][17]. Therefore, environmental hazards could increase when ballast water is treated with BWMS using AS in seawater with high bromide concentrations.…”

“…Therefore, environmental hazards could increase when ballast water is treated with BWMS using AS in seawater with high bromide concentrations. In addition, the efficiency of BWMS using electrolytic devices is influenced by factors such as the salinity, pH, and water temperature of ship ballast water [3,8,11,17]. Cha et al reported that when the pH drops to around 6, the proportion of HOCl or HOBr increases by about 7%, and these compounds have stronger sterilizing powers than OCland/or OBr - [10].…”