Bibliography: pages 112-138. / The large volume of seawater used for cooling at Koeberg Nuclear Power Station contains many planktonic organisms which are exposed to heat, chlorine and physical stress during their passage through the system. Phytoplankton biomass, measured as chlorophyll a, was reduced by an average of 55.32% due to entrainment, and productivity was decreased by 38.30% on average, mainly due to chlorination. Zooplankton mortality averaged 22.34% for all species and 30.52% for copepods, the dominant group. The copepod Paracartia africana was used in laboratory experiments designed to simulate entrainment. Latent mortality was monitored up to 60 hours after a 30-minute application of stress factors (physical stress was not simulated), and approximately 75% of the total mortality occurred within the 30-minute period. Male Paracartia experienced higher mortalities than females. Extrapolation of these results predicts an overall entrainment mortality (including latent mortality) of 40% for copepods and 29.04% for total zooplankton, although the latter cannot be substantiated. Plankton entrainment at Koeberg was not considered to be overly detrimental to the marine environment because of the very localised area affected, rapid dispersion of heat and chlorine, rapid regeneration times of phytoplankton and some zooplankton, low abundance of commercially important species and potential recruitment from the surrounding productive Benguela upwelling region.

The removal of microbial populations from potable water has been a practice with great importance towards public health, as it has resulted in the reduction of literally millions of cases of infectious disease. In the United States, pathogenic organisms are most commonly removed from drinking water through the application of chlorine. Ninety-nine per cent of all U.S. potable water treatment facilities that disinfect, rely on chlorine as their sole or primary disinfectant, and over 175,000,000 Americans regularly consume chlorinated water. In 1974, Rook and Bellar et al. published studies which indicated that chlorine reacted with organic matter in water during treatment to produce a wide-range of halogenated by-products. Since that time, numerous analyses have been performed to isolate and identify the by-products of chlorination. Toxicologic and epidemiologic studies have been performed, some of which suggest that the use of chlorine as a disinfectant may be contributing to the incidence of chronic disease in the United States. Because of the concern that the use of chlorine for potable water disinfection may be contributing to chronic disease, Amendments to the Safe Drinking Water Act (SDWA) have been promulgated which strictly regulate disinfectants and disinfection by-products. Future disinfectant and disinfectant by-product regulations (1992) will have a major impact on the purveyors of potable water in the U.S.. Probably the largest challenge U.S. water treatment utilities now face is in the attempt to control for disinfectants and disinfectant by-products while maintaining the microbiological integrity of the water supply. The SDWA Amendments and their supporting regulations will result in major changes in the way water quality parameters are measured, and the way disinfection and treatment strategies are practiced. This thesis looks closely at the role of chlorine as a disinfectant, the by-products arising from chlorine reacting with organic matter, as well as the rationale behind the disinfectant and disinfectant by-product regulations. After examining the chemical, toxicologic and epidemiologic evidence which fueled the new SDWA regulations, available treatment strategies for meeting the new regulations will be detailed and examined. A water treatment strategy which best appears to maximize the reduction of waterborne disease and minimize the risk of chronic disease will then be offered. / Graduation date: 1992