ALGAL TOXICITY AND FORMATION OF HALOGENATED ORGANIC COMPOUNDS IN BALLAST WATER AFTER OXIDATIVE TREATMENT
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Ballast water plays a vital role in the stabilization and operations of modern ships, and it is estimated that 3 to 5 billion tons of ballast water are transferred around the world each year. However, the discharge of ballast water has led to the release of non-indigenous species, and costly and ecologically damaging biological invasions. To combat this serious problem, ballast water discharge is now regulated and ballast water management systems (BWMS) have been developed to meet required discharge limits for the release of live organisms. The most common BWMS rely on chlorination of ballast water to kill planktonic organisms but also result in the formation of disinfection by-products (DBPs) and the potential for aquatic toxicity. The research in this thesis was conducted to advance the understanding of treated ballast water toxicity, and to document the formation of higher molecular weight DBPs using ultrahigh resolution mass spectrometry. Research was conducted with commercial BWMS that were based on either direct chlorination (Ch. 2 & 3) or in-situ electrochlorination (Ch. 2 & 4). Ballast water treatment was conducted in estuarine waters of the Port of Baltimore (Patapsco River, Maryland). In Chapter 2, I tested the algal toxicity of discharged ballast water from four BWMS at the time of discharge and monthly thereafter, showing the longevity of the toxic effect of treated water on micro algae. In Chapters 3 and 4, I used ultrahigh resolution mass spectrometry to identify the molecular composition of dissolved organic matter (DOM) and halogenated DBPs after oxidative treatment of ballast water. By comparing samples before and after direct chlorination, I was able to document the changes in dissolved organic matter and the formation of numerous halogenated DBPs (Ch. 3). In Chapter 4, I was able to document the change in brominated DBPs after a period of 92 days, showing the relative persistence of dibrominated compounds. This work together demonstrates that use of traditional water treatment to solve one environmental problem may, in fact, cause other unintended consequences to aquatic ecosystems.